JP5261961B2 - Secondary battery positive electrode, secondary battery negative electrode, secondary battery, and vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery having an excellent output characteristic, and also having an excellent cycle life characteristic; and a vehicle equipped with a power source having an excellent output characteristic, and also having an excellent cycle life characteristic. <P>SOLUTION: In this secondary battery 100, a positive electrode 160 includes a positive electrode collector plate 161, and a plurality of positive electrode mix layers stacked on the positive electrode collector plate 161, and each containing positive electrode material powder 165 and a positive electrode binder 166. The percentage content (wt.%) of the positive electrode binder 166 related to the innermost positive electrode mix layer (first positive electrode mix layer 163) positioned most adjacently to the positive electrode collector plate 161 within the plurality of positive electrode mix layers is set higher than that of another positive electrode mix layer (the second positive electrode mix layer 164), and set to 4-7 wt.%. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a secondary battery and a vehicle including the same.

  Secondary batteries (for example, lithium ion secondary batteries) are attracting attention as power sources for portable devices and portable devices, and as power sources for vehicles such as electric vehicles and hybrid vehicles. In this secondary battery, an electrode mixture layer formed by mixing an electrode raw material powder such as an active material and a binder is laminated on the surface of a current collector plate to form an electrode (positive electrode and negative electrode). In recent years, various electrodes have been proposed in order to improve the characteristics of secondary batteries (see, for example, Patent Document 1 and Patent Document 2).

JP-A-10-270013 Japanese Patent Laid-Open No. 11-3699

  Patent Document 1 proposes an electrode for a secondary battery in which the concentration of the binder in the electrode mixture layer is increased near the current collector plate. Specifically, it has two electrode mixture layers laminated in order from the surface of the current collector plate toward the outside in the thickness direction of the current collector plate, and the binder concentration of the lower layer located on the current collector plate side is set to the outside. An electrode for a secondary battery having a higher binder concentration than the upper layer positioned is disclosed. Specifically, a negative electrode is disclosed in which the lower layer binder concentration is 10 wt% and the upper layer binder concentration is adjusted to 4 to 9 wt% as the negative electrode. Further, as a positive electrode, a positive electrode is disclosed in which the lower layer binder concentration is 8 wt% and the upper layer binder concentration is adjusted to 3 to 7.2 wt%.

  Thus, it is described that the adhesiveness between the current collector plate and the electrode mixture layer is increased by increasing the binder concentration in the lower layer located on the current collector plate side (in contact with the current collector plate). Moreover, since the binder concentration of the upper layer is lowered, the binder concentration can be suppressed in the entire electrode mixture layer. Thus, it is described that the charge / discharge characteristics and life of the secondary battery can be improved.

Patent Document 2 discloses that a negative electrode mixture layer (coating layer) containing a carbon material has two or more layers, and the specific surface area is 2 m ² / g as a carbon material contained in the negative electrode mixture layer (lower layer) in contact with the current collector. A negative electrode for a lithium ion secondary battery is disclosed in which the following carbon material is used and the thickness of the negative electrode mixture layer is in the range of 20 to 100 μm.
Thus, the binder adsorbed on the surface of the carbon material can be suppressed by containing the carbon material having a specific surface area of 2 m ² / g or less in the lower layer. Accordingly, it is described that a binder effective for adhesion between the carbon material and the current collector can be sufficiently present, so that a negative electrode plate having excellent adhesion between the current collector and the carbon material can be provided. Further, it is described that a negative electrode plate having a high discharge capacity can be obtained by laminating a negative electrode mixture layer containing a carbon material having a large specific surface area and a high discharge capacity on the upper layer.

By the way, in recent years, a secondary battery having good output characteristics and good cycle life characteristics has been demanded. In particular, there is an increasing demand for such secondary batteries as power sources for vehicles such as electric vehicles and hybrid vehicles.
In contrast, by using the secondary battery electrode proposed in Patent Document 1 and Patent Document 2, the discharge capacity of the secondary battery can be increased, but the output characteristics and cycle life characteristics can be improved. There wasn't. In particular, the output characteristics and cycle life characteristics required as a power source for vehicles such as electric vehicles and hybrid vehicles are high and cannot be satisfied.

The present invention has been made in view of the current situation, and the secondary battery positive electrode, the secondary battery negative electrode, and the output characteristics that can improve the output characteristics and cycle life characteristics of the secondary battery are good. Another object of the present invention is to provide a secondary battery having good cycle life characteristics and a vehicle equipped with a power source having good output characteristics and good cycle life characteristics.

The solution is a secondary battery comprising a positive electrode and a negative electrode, wherein the positive electrode is stacked on the positive electrode current collector plate and the positive electrode current collector plate, and includes a plurality of positive electrode mixture materials including a positive electrode raw material powder and a positive electrode binder. The positive electrode binder content (wt%) of the innermost positive electrode mixture layer located closest to the positive electrode current collector plate among the plurality of positive electrode mixture layers is determined as another positive electrode mixture layer. and higher than that, and, possess a positive-electrode mixture layer formed as less than 6 wt% 7 wt%, and the thickness of the innermost positive electrode material layer laminated above positive-electrode mixture layer total thickness 1 / 10 or more and ½ or less, and the negative electrode is a negative electrode current collector plate and a plurality of negative electrode mixture layers laminated on the negative electrode current collector plate and including a negative electrode raw material powder and a negative electrode binder. Among the negative electrode composite layers, the innermost negative electrode mixture layer located closest to the negative electrode current collector plate A negative electrode mixture layer having a content (wt%) of the negative electrode binder higher than that of other negative electrode mixture layers and 3 wt% or more and 4 wt% or less, and the innermost negative electrode mixture It is a secondary battery whose layer thickness is 1/20 or more and 1/2 or less of the thickness of the whole laminated negative electrode mixture layer .

In a secondary battery, charge and discharge are performed by exchange of ions through an electrolytic solution between a positive electrode mixture layer (such as a positive electrode active material) and a negative electrode mixture layer (such as a negative electrode active material). For example, in a lithium ion secondary battery, charging / discharging is performed by exchange of Li ions through an electrolytic solution between a positive electrode mixture layer (positive electrode active material) and a negative electrode mixture layer (negative electrode active material). Therefore, when ions are exchanged between the positive electrode active material and the electrolyte solution in accordance with charge / discharge, the fewer the positive electrode binder in the positive electrode mixture layer, the faster the ions are exchanged and the better the output characteristics. Become.
On the other hand, if the positive electrode binder in the positive electrode mixture layer is reduced too much, the binding force between the positive electrode mixture layer and the positive electrode current collector plate becomes low, and the positive electrode mixture layer peels off from the positive electrode current collector plate with long-term use. There is a risk of it.

  On the other hand, the secondary battery of the present invention includes a plurality of positive electrode mixture layers laminated on the positive electrode current collector plate, and is the innermost positive electrode located closest to the positive electrode current collector plate among the plurality of positive electrode mixture layers. About the composite material layer, the content rate (wt%) of a positive electrode binder is made higher than other positive electrode composite material layers. That is, for the innermost positive electrode mixture layer (the positive electrode mixture layer directly bonded to the positive electrode current collector plate), the binding force with the positive electrode current collector plate can be increased by increasing the content of the positive electrode binder. On the other hand, the content of the positive electrode binder layer as a whole of the positive electrode mixture layer is lower than the innermost positive electrode mixture layer for the other positive electrode mixture layers that are not directly bonded to the positive electrode current collector plate. Therefore, the output characteristics of the battery as a whole can be improved.

In particular, in the secondary battery of the present invention, the content of the positive electrode binder in the innermost positive electrode mixture layer is 6 wt% or more and 7 wt% or less.
By setting the content of the positive electrode binder in the innermost positive electrode composite material layer to 6 wt% or more, the positive electrode composite material layer and the positive electrode current collector plate can be firmly bonded. Bonding between the composite material layer and the positive electrode current collector plate can be maintained. Thereby, cycle life characteristics become favorable.

  By the way, as the content of the positive electrode binder in the innermost positive electrode mixture layer is increased, the positive electrode mixture layer and the positive electrode current collector plate can be strongly bonded. However, if the content of the positive electrode binder is too high, Since the movement of ions in the material layer is hindered, the output characteristics of the battery as a whole are lowered, and the cycle life characteristics are also lowered.

On the other hand, in the secondary battery of the present invention, the content of the positive electrode binder is suppressed to 7 wt% or less for the innermost positive electrode mixture layer. As a result, while firmly bonding the positive electrode mixture layer and the positive electrode current collector plate, the movement of ions can be smoothly performed in the innermost positive electrode mixture layer together with other positive electrode mixture layers, so that the output characteristics and cycle can be improved. Any of the life characteristics can be improved.
In addition, as a positive electrode raw material powder, a positive electrode active material, a electrically conductive material, etc. can be mentioned, for example.

By the way, even if the content of the positive electrode binder in the innermost positive electrode mixture layer directly bonded to the positive electrode current collector plate is increased to 6 wt% or more, the ratio of the thickness of the innermost positive electrode mixture layer to the total thickness of the positive electrode mixture layer Is low, the thickness of the innermost positive electrode mixture layer contributing to the fixation of the entire positive electrode mixture layer is too thin, and the entire positive electrode mixture layer cannot be firmly bonded to the positive electrode current collector plate.

On the other hand, in the secondary battery of the present invention, the thickness of the innermost positive electrode mixture layer in which the positive electrode binder content is 6 wt% or more and 7 wt% or less is 1/10 or more of the total thickness of the positive electrode mixture layer. . As a result, the thickness of the innermost positive electrode mixture layer that contributes to the fixation of the entire positive electrode mixture layer can be secured sufficiently, so that the entire positive electrode mixture layer is firmly bonded to the positive electrode current collector plate by the innermost positive electrode mixture layer. can do. Therefore, the secondary battery of the present invention has good cycle life characteristics.

  On the contrary, if the ratio of the thickness of the innermost positive electrode mixture layer to the total thickness of the positive electrode mixture layer is too high, the absolute amount of the positive electrode binder in the entire positive electrode mixture layer is too large, In this case, the movement of ions is largely hindered by the positive electrode binder.

In contrast, in the secondary battery of the present invention, the thickness of the innermost positive electrode mixture layer in which the positive electrode binder content is 6 wt% or more and 7 wt% or less is suppressed to ½ or less of the total thickness of the positive electrode mixture layer. doing. Thereby, since the absolute amount of the positive electrode binder in the whole positive electrode mixture layer can be suppressed and the movement of ions in the positive electrode mixture layer during charging and discharging can be made smooth, the output characteristics are also improved.
Furthermore, the secondary battery of the present invention includes a plurality of negative electrode mixture layers laminated on the negative electrode current collector plate, and is an innermost negative electrode mixture material that is located closest to the negative electrode current collector plate among the plurality of negative electrode mixture layers. About the layer, the content rate (wt%) of the negative electrode binder is made higher than the other negative electrode mixture layers. That is, for the innermost negative electrode mixture layer (negative electrode mixture layer directly bonded to the negative electrode current collector plate), the binding force with the negative electrode current collector plate can be increased by increasing the content of the negative electrode binder. On the other hand, for the other negative electrode mixture layers that are not directly bonded to the negative electrode current collector plate, the content of the negative electrode binder as a whole of the negative electrode mixture layer is reduced by lowering the negative electrode binder content than the innermost negative electrode mixture layer. Since it can suppress, the output characteristic as a whole battery can be made favorable.
In particular, in the secondary battery of the present invention, the content of the negative electrode binder in the innermost negative electrode mixture layer is 3 wt% or more and 4 wt% or less.
By setting the content of the negative electrode binder in the innermost negative electrode mixture layer to 3 wt% or more, the negative electrode mixture layer and the negative electrode current collector plate can be firmly bonded. Bonding between the composite layer and the negative electrode current collector plate can be maintained. Thereby, cycle life characteristics become favorable. In particular, in the secondary battery in which the content of the positive electrode binder in the innermost positive electrode mixture layer is 4 wt% or more and the content of the negative electrode binder in the innermost negative electrode mixture layer is 3 wt% or more, the cycle life is further increased. Good characteristics.
By the way, as the content of the negative electrode binder in the innermost positive electrode mixture layer is increased, the negative electrode mixture layer and the negative electrode current collector plate can be strongly bonded. However, if the content of the negative electrode binder is too high, Since the movement of ions in the material layer is hindered, the output characteristics of the battery as a whole are lowered and the cycle life characteristics are also lowered.
On the other hand, in the secondary battery of the present invention, the content of the negative electrode binder is suppressed to 4 wt% or less for the innermost negative electrode mixture layer. As a result, the negative electrode mixture layer and the negative electrode current collector plate are firmly bonded, and the movement of ions can be smoothly performed in the innermost negative electrode mixture layer together with the other negative electrode mixture layers, so that the output characteristics and cycle life are increased. Any of the characteristics can be improved. In particular, in a secondary battery in which the content of the positive electrode binder in the innermost positive electrode mixture layer is suppressed to 7 wt% or less and the content of the negative electrode binder in the innermost negative electrode mixture layer is suppressed to 4 wt% or less, the output characteristics And cycle life characteristics can be made even better.
In addition, as negative electrode raw material powder, a negative electrode active material, a hydrogen storage alloy, a electrically conductive material etc. can be mentioned, for example.
Furthermore, in the secondary battery of the present invention, the thickness of the innermost negative electrode mixture layer in which the content of the negative electrode binder is 3 wt% or more and 4 wt% or less is 1/20 or more of the total thickness of the negative electrode mixture layer. As a result, the thickness of the innermost negative electrode mixture layer that contributes to the fixation of the entire negative electrode mixture layer can be sufficiently secured, so that the entire negative electrode mixture layer is firmly bonded to the negative electrode current collector plate by the innermost negative electrode mixture layer. can do. Therefore, the secondary battery of the present invention has good cycle life characteristics.
Furthermore, in the secondary battery of the present invention, the thickness of the innermost negative electrode mixture layer in which the content of the negative electrode binder is 3 wt% or more and 4 wt% or less is suppressed to ½ or less of the total thickness of the negative electrode mixture layer. Yes. Thereby, the absolute amount of the negative electrode binder in the entire negative electrode mixture layer can be suppressed, and the movement of ions in the negative electrode mixture layer during charge / discharge can be made smooth, so that the output characteristics are also improved.

  Furthermore, it is preferable that the secondary battery be any one of the above-described secondary batteries, in which the thickness of the stacked positive electrode mixture layer as a whole is 50 μm or less.

  In the secondary battery of the present invention, the entire thickness of the positive electrode mixture layer is 50 μm or less. By reducing the thickness of the entire positive electrode mixture layer to 50 μm or less, the movement of ions between the positive electrode mixture layer and the electrolytic solution becomes extremely quick during charging and discharging. Therefore, the secondary battery of the present invention is a high output secondary battery. The secondary battery of the present invention can be sufficiently used as a power source for, for example, a hybrid vehicle or an electric vehicle.

  Furthermore, in the secondary battery according to any one of the above, the outermost positive electrode mixture layer located on the outermost side among the plurality of positive electrode mixture layers has a secondary binder content of 2 wt% or less. Use batteries.

  During charge / discharge, the exchange of ions between the positive electrode mixture layer and the electrolyte is most actively performed in the outermost positive electrode mixture layer located on the outermost side among the plurality of positive electrode mixture layers. Therefore, in particular, by reducing the content of the positive electrode binder in the outermost positive electrode mixture layer in the entire positive electrode mixture layer, the output characteristics can be drastically improved. In the secondary battery of the present invention, since the content of the positive electrode binder is extremely low at 2 wt% or less in the outermost positive electrode mixture layer, the output characteristics are remarkably improved, resulting in a high output secondary battery. .

  Furthermore, any of the above secondary batteries may be a secondary battery in which the thickness of the laminated negative electrode mixture layer as a whole is 50 μm or less.

  In the secondary battery of the present invention, the entire thickness of the negative electrode mixture layer is 50 μm or less. By reducing the thickness of the entire negative electrode mixture layer to 50 μm or less, the movement of ions between the negative electrode mixture layer and the electrolytic solution becomes extremely rapid during charging and discharging. Therefore, the secondary battery of the present invention is a high output secondary battery. The secondary battery of the present invention can be sufficiently used as a power source for, for example, a hybrid vehicle or an electric vehicle.

  Furthermore, in the secondary battery according to any one of the above, the outermost negative electrode mixture layer located on the outermost side among the plurality of negative electrode mixture layers has a secondary binder content of 2 wt% or less. Use batteries.

  During charging / discharging, the exchange of ions between the negative electrode mixture layer and the electrolytic solution is most actively performed in the outermost negative electrode mixture layer located on the outermost side among the plurality of negative electrode mixture layers. Therefore, in particular, by reducing the content of the negative electrode binder in the outermost negative electrode mixture layer in the entire negative electrode mixture layer, the output characteristics can be dramatically improved. In the secondary battery of the present invention, since the content of the negative electrode binder is extremely low at 2 wt% or less in the outermost negative electrode mixture layer, the output characteristics are remarkably improved, resulting in a high output secondary battery. .

Further, any of the secondary batteries described above, wherein the secondary battery is preferably a secondary battery that is a lithium ion secondary battery.
By applying the present invention to a lithium ion secondary battery, it is possible to appropriately obtain a lithium ion secondary battery having good output characteristics and good cycle life characteristics.

  Another solution is a vehicle on which any of the above secondary batteries is mounted.

The vehicle of the present invention is equipped with a secondary battery having good output characteristics and good cycle life characteristics. Therefore, the vehicle of the present invention is a vehicle equipped with a power source having good output characteristics and good cycle life characteristics.
Examples of the vehicle equipped with the secondary battery include electric vehicles, hybrid vehicles, motorcycles, forklifts, electric wheelchairs, electric assist bicycles, electric scooters, railway vehicles, and the like.
Another solution is a positive electrode for a secondary battery having a positive electrode current collector plate and a plurality of positive electrode mixture layers that are stacked on the positive electrode current collector plate and include a positive electrode raw material powder and a positive electrode binder. The content rate (wt%) of the positive electrode binder applied to the innermost positive electrode composite material layer located closest to the positive electrode current collector plate among the plurality of positive electrode composite material layers is higher than other positive electrode composite material layers, And the thickness of the innermost positive electrode mixture layer is 1/10 or more and 1/2 or less of the total thickness of the laminated positive electrode mixture layer. is there.
Furthermore, it is preferable that the positive electrode for a secondary battery is a positive electrode for a secondary battery in which the thickness of the stacked positive electrode mixture layer as a whole is 50 μm or less.
Furthermore, in any one of the above-described positive electrodes for a secondary battery, the outermost positive electrode mixture layer located on the outermost side among the plurality of positive electrode mixture layers has a content of the positive electrode binder of 2 wt% or less. A positive electrode for a secondary battery is preferable.
Another solution is a negative electrode for a secondary battery having a negative electrode current collector plate and a plurality of negative electrode mixture layers laminated on the negative electrode current collector plate and including a negative electrode raw material powder and a negative electrode binder. The negative electrode binder content (wt%) of the innermost negative electrode mixture layer located closest to the negative electrode current collector plate among the plurality of negative electrode mixture layers is higher than that of the other negative electrode mixture layers. And the thickness of the innermost negative electrode mixture layer is from 1/20 to 1/2 of the total thickness of the laminated negative electrode mixture layer. It is a negative electrode.
Furthermore, it is preferable that the negative electrode for a secondary battery is the above-described negative electrode for a secondary battery in which the thickness of the laminated negative electrode mixture layer as a whole is 50 μm or less.
Furthermore, in any one of the negative electrodes for a secondary battery, the outermost negative electrode mixture layer located on the outermost side among the plurality of negative electrode mixture layers has a content of the negative electrode binder of 2 wt% or less. A negative electrode for a secondary battery is preferable.

(Embodiment 1)
Next, a first embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the vehicle 1 according to the present embodiment includes a vehicle body 2, an engine 3, a front motor 4, a rear motor 5, a cable 7, and a battery pack 6, and includes the engine 3, the front motor 4, and the rear motor 5. It is a hybrid car that is driven in combination. Specifically, the vehicle 1 is configured to be able to travel using the engine 3, the front motor 4, and the rear motor 5 by known means using the battery pack 6 as a driving power source for the front motor 4 and the rear motor 5. .

  Among these, the battery pack 6 is attached to the vehicle body 2 of the vehicle 1 and is connected to the front motor 4 and the rear motor 5 by a cable 7. As shown in FIG. 2, the battery pack 6 includes a plurality of battery modules 10 arranged in a line. Specifically, a plurality of lithium ion secondary batteries 100 (single cells) arranged in a row are electrically connected in series by a bus bar 20 to form a battery module 10, and a plurality of the battery modules (see FIG. 2, only two are shown), and the battery pack 6 is configured by being arranged in series and connected in series.

  Next, the lithium ion secondary battery 100 of this embodiment will be described. As shown in FIG. 3, the lithium ion secondary battery 100 of the present embodiment includes a storage case 110 having a rectangular shape in plan view, a positive electrode terminal 120 extending from the inside of the storage case 110 to the outside, and the interior of the storage case 110. And a negative electrode terminal 130 extending to the outside.

Further, as shown in FIG. 4, an electrode body 150 and an electrolyte solution (not shown) are accommodated in the accommodation case 110. As the electrolytic solution, for example, an organic electrolytic solution obtained by adding LiPF ₆ as a solute to a mixed organic solvent of EC (ethylene carbonate) and DEC (diethyl carbonate) can be used.

  The electrode body 150 is an oblong cross-section, and is a flat type wound body obtained by winding a sheet-like positive electrode 160, a negative electrode 170, and a separator 180. The electrode body 150 is positioned at one end (left end in FIG. 4) in the axial direction (left and right in FIG. 4), and a positive electrode connection portion 160b in which only a part of the positive electrode 160 overlaps spirally, and the other end The negative electrode connecting portion 170b is located at a portion (the right end portion in FIG. 3), and only a part of the negative electrode 170 is spirally overlapped. Among these, the positive electrode terminal 120 is welded to the positive electrode connection part 160b. Further, the negative electrode terminal 130 is welded to the negative electrode connecting portion 170b.

  Note that the positive electrode 160 includes a positive electrode mixture layer 162 (see FIG. 5) including the positive electrode raw material powder 165 at a portion other than the positive electrode connection portion 160b. Similarly, the negative electrode 170 includes a negative electrode mixture layer 172 (see FIG. 6) including a negative electrode raw material powder 175 in a portion excluding the negative electrode connection portion 170b.

  The housing case 110 is an inner resin film 111 located on the innermost side (the front side in FIG. 4) of the housing case 110, and a metal located adjacent to the outer side (the back side of the paper surface in FIG. 4) of the inner resin film 111. The film 112 is formed of a laminate film 101 in which an outer resin film 113 positioned adjacent to the outside of the metal film 112 (in addition to the back side in FIG. 4) is laminated. As shown in FIG. 4, the housing case 110 is formed by laminating the laminate film 101 in which the electrode body 150 is disposed in the housing portion 119 at a folding position 110g, and as shown in FIG. The stop part 115 (peripheral part of the housing case 110) is sealed by heat welding and formed into a rectangular shape in plan view.

  Here, the positive electrode 160 will be described in detail with reference to FIG. As shown in FIG. 5, the positive electrode 160 includes a positive electrode current collector plate 161 made of aluminum foil, and a positive electrode mixture layer 162 laminated on the surface 161 b of the positive electrode current collector plate 161.

As illustrated in FIG. 5, the positive electrode mixture layer 162 includes a first positive electrode mixture layer 163 and a second positive electrode mixture layer 164 that are stacked on the surface 161 b of the positive electrode current collector plate 161. Specifically, the positive electrode mixture layer 162 is positioned on the outer side in the thickness direction of the first positive electrode mixture layer 163 (innermost positive electrode mixture layer) positioned on the positive electrode current collector plate 161 side. A second positive electrode mixture layer 164 (outermost positive electrode mixture layer) is formed. Each of the first positive electrode mixture layer 163 and the second positive electrode mixture layer 164 includes a positive electrode raw material powder 165 (positive electrode active material, conductive material) and a positive electrode binder 166 (PVDF).
In the first embodiment, LiNi _0.8 Co _0.15 Al _0.05 O ₂ is used as the positive electrode active material, and acetylene black is used as the conductive material. The same applies to Embodiments 2 and 3 described later.

In particular, in the present embodiment, the content (wt%) of the positive electrode binder 166 in the first positive electrode mixture layer 163 is higher than the content (wt%) of the positive electrode binder 166 in the second positive electrode mixture layer 164. doing. Specifically, in the first positive electrode mixture layer 163, the content of the positive electrode binder 166 is 6 wt% or more and 7 wt% or less, whereas in the second positive electrode mixture layer 164, the content of the positive electrode binder 166 is 2 wt%. %.
In the present embodiment, the thickness T2 of the positive electrode mixture layer 162 is extremely thin, ie, 50 μm or less (specifically, about 30 μm). Furthermore, the thickness T1 of the first positive electrode mixture layer 163 is set to 1/10 or more and 1/2 or less of the thickness T2 of the entire positive electrode mixture layer 162.

As shown in FIG. 6, the negative electrode 170 includes a negative electrode current collector plate 171 made of copper foil and a negative electrode mixture layer 172 laminated on the surface 171 b of the negative electrode current collector plate 171.
The negative electrode mixture layer 172 includes a negative electrode raw material powder 175 (negative electrode active material) and a negative electrode binder 176 (SBR, CMC). Thus, in the present embodiment, unlike the positive electrode 160, the negative electrode 170 includes the negative electrode mixture layer 172 including one layer (one type) of the negative electrode mixture layer. Note that the thickness U2 of the negative electrode mixture layer 172 is very thin, 50 μm or less (specifically, about 30 μm).
In the first embodiment, graphite is used as the negative electrode active material. The same applies to Embodiments 2 and 3 described later.

  As the separator 180, for example, a resin film made of PE (polyethylene) and PP (polypropylene) can be used.

Next, the manufacturing method of the lithium ion secondary battery 100 of this embodiment is demonstrated.
(Production of positive electrode)
First, 94 to 93 wt% of the positive electrode raw material powder 165 and 6 to 7 wt% of the positive electrode binder 166 (PVDF) were mixed, and an organic solvent (NMP) was added and stirred to prepare a first positive electrode paste. . Next, the first positive electrode paste was applied onto the surface 161b of the positive electrode current collector plate 161 (aluminum foil) and dried. In this way, the first positive electrode mixture layer 163 was formed on the surface 161 b of the positive electrode current collector plate 161.

  Next, 98 wt% of the positive electrode raw material powder 165 and 2 wt% of the positive electrode binder 166 (PVDF) were mixed, and an organic solvent (NMP) was added thereto and stirred to prepare a second positive electrode paste. Next, the second positive electrode paste was applied onto the surface 163b of the first positive electrode mixture layer 163 and dried. In this way, the second positive electrode mixture layer 164 was formed on the surface 163b of the first positive electrode mixture layer 163.

  Thereafter, the first positive electrode mixture layer 163 and the second positive electrode mixture layer 164 were press-molded by press working so that their thickness T2 was about 30 μm. As a result, as shown in FIG. 5, the positive electrode 160 having the positive electrode current collector plate 161 and the positive electrode mixture layer 162 laminated on the surface 161 b of the positive electrode current collector plate 161 was obtained. The thickness T1 of the first positive electrode mixture layer 163 is 1/10 or more and 1/2 or less of the thickness T2 of the positive electrode mixture layer 162.

(Production of negative electrode)
96 wt% of negative electrode raw material powder 175 (negative electrode active material) and 4 wt% of negative electrode binder 176 (SBR, CMC) were mixed, and water was added and stirred to prepare a negative electrode paste. Next, this negative electrode paste was applied on the surface of a negative electrode current collector (copper foil) and dried. In this way, a negative electrode mixture layer was formed on the surface of the negative electrode current collector plate. Thereafter, the negative electrode mixture layer was press-molded by press working so that the thickness of the negative electrode mixture layer was about 30 μm. Thus, unlike the positive electrode 160, a negative electrode 170 having only one negative electrode mixture layer was obtained.

(Production of battery)
Next, while laminating the positive electrode 160, the negative electrode 170, and the separator 180, these were wound to form a flat wound electrode body 150. In addition, when laminating the positive electrode 160, the negative electrode 170, and the separator 180, the positive electrode 160 has an uncoated portion that is not coated with the positive electrode mixture, protruding from one end of the electrode body 150. 160 is arranged. Furthermore, the negative electrode 170 is disposed so that an uncoated portion of the negative electrode 170 that is not coated with the negative electrode mixture protrudes from the side opposite to the uncoated portion of the positive electrode 160. Thereby, the electrode body 150 (refer FIG. 4) which has the positive electrode connection part 160b and the negative electrode connection part 170b is formed.

  Next, the positive electrode connection part 160b of the electrode body 150 and the positive electrode terminal 120 are connected. Specifically, for example, the positive electrode connection portion 160b and the positive electrode terminal 120 are connected by welding (for example, ultrasonic welding or spot welding) in a state where the positive electrode connection portion 160b and the positive electrode terminal 120 are pressure-bonded. Similarly, the negative electrode connection part 170b of the electrode body 150 and the negative electrode terminal 130 are connected. Specifically, for example, the negative electrode connecting portion 170b and the negative electrode terminal 130 are connected by welding (for example, ultrasonic welding or spot welding) in a state where the negative electrode connecting portion 170b and the negative electrode terminal 130 are pressure-bonded.

  Separately, a laminate film 101 is prepared. Specifically, after laminating the inner resin film 111, the metal film 112, and the outer resin film 113, this is press-molded to obtain a laminate film 101 in which the housing portion 119 is recessed (see FIG. 4). Next, as illustrated in FIG. 4, the electrode body 150 in which the positive electrode terminal 120 and the negative electrode terminal 130 are welded is disposed in the accommodating portion 119 of the laminate film 101. Thereafter, the laminate film 101 is folded at the folding position 110g, and the electrode body 150 is accommodated therein.

  Next, as shown in FIG. 7, a portion of the welded sealing portion 115 excluding the inlet 116 into which the electrolytic solution is to be injected later (the portion marked with dots in FIG. 7) is pressurized in the thickness direction. The inner resin films 111 are heat-welded by heating. Thereby, the electrode body 150 can be accommodated inside the positive electrode terminal 120 and the negative electrode terminal 130 while extending from the inside of the housing case 110 to the outside. Next, an electrolytic solution is injected into the housing case 110 through the liquid injection port 116. Then, the container case 110 is sealed by closing the liquid injection port 116 by heat welding. Thereby, the lithium ion secondary battery 100 shown in FIG. 3 is completed.

  Note that, in the lithium ion secondary battery 100 of the present embodiment, the adhesive force is slightly weakened in the portion that is the liquid injection port 116 in the welded sealing portion 115 as compared with other portions. As a result, as shown in FIG. 3, the site that is the liquid injection port 116 can be a safety valve 118. Therefore, when the internal pressure of the battery case 110 exceeds a predetermined value, the sealing of the storage case 110 is opened at the position of the safety valve 118, and the gas in the storage case 110 can be discharged to the outside.

(Examples 1 and 2 and Reference Examples 1 and 2 )
The content of the positive electrode binder 166 of the first positive-electrode mixture layer 163 was (wt%) only the different, were manufactured 4 types of lithium ion secondary batteries (Examples 1, 2 and Reference Examples 1 and 2). Specifically, the content (wt%) of the positive electrode binder 166 of the first positive electrode mixture layer 163 is 4 wt% ( Reference Example 1 ), 5 wt% ( Reference Example 2 ), 6 wt% (Example 1 ), 7 wt. % (Example 2 ).

(Comparative Examples 1-4)
Compared with the lithium ion secondary battery 100 of the embodiment, four types of lithium ion secondary batteries (Comparative Examples 1 to 1) differing only in the content (wt%) of the positive electrode binder 166 of the first positive electrode mixture layer. 4) was produced. Specifically, the content (wt%) of the positive electrode binder 166 in the first positive electrode mixture layer is 2 wt% (Comparative Example 1), 3 wt% (Comparative Example 2), 8 wt% (Comparative Example 3), 10 wt%. Different from (Comparative Example 4).

(Charge / discharge test)
Next, charge / discharge tests were conducted on the lithium ion secondary batteries according to Examples 1 and 2, Reference Examples 1 and 2, and Comparative Examples 1 to 4.
Specifically, each lithium ion secondary battery is charged with a current of 2 C (1.4 A) under a normal temperature environment of 25 ° C. until the battery is fully charged, and then discharged until the battery is fully discharged. 500 charge / discharge cycles were performed.

  In this charge / discharge test, for each lithium ion secondary battery, first, in the first charge / discharge cycle, after charging until it reaches a fully charged state, the output (watt) per 10 seconds is measured. did. The output (watts) at this time is indicated by a circle in FIG. 8 as an “initial” output. Furthermore, in the charge / discharge cycle of the 500th cycle, when the battery was discharged until it was fully charged, the output (watt) per 10 seconds was measured. The output (watts) at this time is indicated by Δ in FIG. 8 as the output “after cycle test”.

As indicated by a circle in FIG. 8, secondary batteries (Comparative Examples 1 and 2) in which the content of the positive electrode binder 166 of the first positive electrode mixture layer is 7 wt% or less (specifically, 2 to 7 wt%). In Examples 1 and 2 and Reference Examples 1 and 2 ), the initial output was as high as about 19 W, and excellent output characteristics were exhibited. However, when the content of the positive electrode binder 166 in the first positive electrode mixture layer is larger than 7 wt% (specifically, 8 to 10 wt%), the initial output is greatly reduced.

  From this result, by making the content rate of the positive electrode binder 166 of the first positive electrode mixture layer 163 to be 7 wt% or less, the output characteristics of the secondary battery (particularly, the output characteristics under the normal temperature environment) can be improved. I can say that. This is because the content of the positive electrode binder 166 in the first positive electrode mixture layer 163 is suppressed to 7 wt% or less, so that the content of the positive electrode binder 166 is reduced (2 wt% in this embodiment). It is considered that not only the material layer 164 but also the first positive electrode mixture layer 163 can smoothly move Li ions.

Further, as indicated by Δ in FIG. 8, a secondary battery (Comparative Example 1) in which the content of the positive electrode binder 166 of the first positive electrode mixture layer is smaller than 4 wt% (specifically, 2 to 3 wt%). In 2), the output after the cycle test was reduced by about 6 to 7 W compared to the initial output, and the cycle life characteristics were not preferable. In contrast, secondary batteries (Examples 1 and 2 and Reference Examples 1 and 2 ) in which the content of the positive electrode binder 166 in the first positive electrode mixture layer is 4 wt% or more (specifically, 4 to 10 wt%) are used. In Comparative Examples 3 and 4), the output after the cycle test was only about 2 to 3 W lower than the initial output, and excellent cycle life characteristics were exhibited.

  From this result, by making the content rate of the positive electrode binder 166 of the first positive electrode mixture layer 163 to be 4 wt% or more, the cycle life characteristics of the secondary battery (particularly, the cycle life characteristics under the normal temperature environment) are improved. It can be said that it is possible. The reason for this is that by setting the content of the positive electrode binder 166 in the first positive electrode mixture layer 163 to 4 wt% or more, the positive electrode mixture layer 162 and the positive electrode current collector plate 161 can be firmly bound, This is considered to be because the bond between the positive electrode mixture layer 162 and the positive electrode current collector plate 161 can be maintained even if the period charge / discharge is repeated.

  As described above, with respect to the first positive electrode mixture layer 163 (innermost positive electrode mixture layer), the content of the positive electrode binder 166 is set to 4 wt% or more and 7 wt% or less, whereby output characteristics (particularly, output characteristics in a room temperature environment). It can be said that a secondary battery with good cycle life characteristics (especially cycle life characteristics in a room temperature environment) can be obtained.

In particular, in the embodiment 1, 2 and lithium ion secondary batteries of Reference Examples 1 and 2, the initial output is high as 19W, showed excellent output characteristics. This is because the total thickness of the positive electrode mixture layer 162 is very thin, 50 μm or less (specifically, about 30 μm), so that the movement of Li ions between the positive electrode mixture layer 162 and the electrolyte during charging / discharging. This is thought to be because it became extremely quick. Furthermore, the content of the positive electrode binder 166 in the second positive electrode mixture layer 164 (outermost positive electrode mixture layer) is extremely low, 2 wt% or less (2 wt% in Examples 1 and 2 and Reference Examples 1 and 2). Furthermore, it is considered that the exchange of Li ions between the second positive electrode mixture layer 164 and the electrolytic solution became particularly active, and the output characteristics could be dramatically improved.

(Examples 3 to 6 )
Next, four types of lithium ion secondary batteries 100 (Example 3 ) in which only the ratio (= T1 / T2) of the thickness T1 of the first positive electrode mixture layer 163 to the thickness T2 of the entire positive electrode mixture layer 162 was varied. To 6 ). Specifically, the value of T1 / T2 is made different from 1/10 (Example 3 ), 1/6 (Example 4 ), 1/3 (Example 5 ), and 1/2 (Example 6 ). ing. In addition, the content rate of the positive electrode binder 166 of the 1st positive electrode compound material layer 163 (innermost positive electrode compound material layer) is 6 wt% in any secondary battery.

(Comparative Examples 5 and 6)
Compared to the lithium ion secondary battery 100 of the embodiment, two types of lithium differing only in the ratio (= T1 / T2) of the thickness T1 of the first positive electrode mixture layer to the thickness T2 of the entire positive electrode mixture layer An ion secondary battery (Comparative Examples 5 and 6) was manufactured. Specifically, the value of T1 / T2 is different from 1/30 (Comparative Example 5) and 2/3 (Comparative Example 6). In addition, the content rate of the positive electrode binder 166 of the first positive electrode mixture layer (innermost positive electrode mixture layer) is set to 6 wt% in any secondary battery as in the example.

(Charge / discharge test)
Next, the lithium ion secondary batteries according to Examples 3 to 6 and Comparative Examples 5 and 6 were subjected to a charge / discharge test in a room temperature environment of 25 ° C. as in Examples 1 and 2 described above. The output (initial output) of each secondary battery in the first cycle of the charge / discharge test is indicated by a circle in FIG. Furthermore, the output (the output after the cycle test) in the 500th cycle of each secondary battery is indicated by Δ in FIG.

As shown by the circles in FIG. 9, secondary batteries (Comparative Example 5 and Examples 3-6 ) in which the value of T1 / T2 is ½ or less (specifically, 1/30 to 1/2). Then, the initial output was as high as about 19 W, and excellent output characteristics were exhibited. However, in the secondary battery (Comparative Example 6) in which the value of T1 / T2 is larger than 1/2 (specifically, 2/3), the initial output is reduced to about 16 W, and the output characteristics are deteriorated.

From this result, by setting the value of T1 / T2 to 1/2 or less, that is, the thickness of the first positive electrode mixture layer 163 (innermost positive electrode mixture layer) is set to 1 of the total thickness of the positive electrode mixture layer 162. By setting it to / 2 or less, it can be said that the output characteristics of the secondary battery (particularly, the output characteristics in a room temperature environment) can be improved. This is because the thickness of the first positive electrode mixture layer 163 (innermost positive electrode mixture layer) in which the content of the positive electrode binder 166 is 4 wt% or more and 7 wt% or less (in the examples 3 to 6 is 6 wt%) By suppressing it to 1/2 or less of the total thickness of the composite material layer 162, the absolute amount of the positive electrode binder 166 in the entire positive electrode composite material layer 162 is suppressed, and Li ions in the positive electrode composite material layer 162 at the time of charging and discharging are suppressed. It is thought that the movement can be made smooth.

Further, as indicated by Δ in FIG. 9, in the secondary battery (Comparative Example 5) in which the value of T1 / T2 is smaller than 1/10 (specifically, 1/30), the output after the cycle test is The cycle life characteristics were not preferable because the output was reduced by about 7 W compared to the initial output. On the other hand, in secondary batteries (Examples 3 to 6 and Comparative Example 6) in which the value of T1 / T2 is 1/10 or more (specifically, 1/10 to 2/3), the cycle test is performed. Only when the output was reduced by about 2 to 4 W from the initial output, good cycle life characteristics were exhibited.

  From this result, by setting the value of T1 / T2 to 1/10 or more, that is, the thickness of the first positive electrode mixture layer 163 (innermost positive electrode mixture layer) is 1 of the total thickness of the positive electrode mixture layer 162. By setting it to / 10 or more, it can be said that the cycle life characteristics of the secondary battery (particularly, the cycle life characteristics under a normal temperature environment) can be improved. This is because the thickness of the first positive electrode mixture layer 163 (innermost positive electrode mixture layer) in which the content of the positive electrode binder 166 is 4 wt% or more and 7 wt% or less (specifically, 6 wt%) By setting the thickness to 1/10 or more of the total thickness of the layer, the first positive electrode mixture layer 163 can sufficiently secure the thickness of the first positive electrode mixture layer 163 that contributes to the fixation of the entire positive electrode mixture layer 162. This is because the entire material layer 162 can be firmly bonded to the positive electrode current collector plate 161.

  From the above, the thickness of the first positive electrode mixture layer 163 (innermost positive electrode mixture layer) in which the content of the positive electrode binder 166 is 4 wt% or more and 7 wt% or less is 1/10 or more of the total thickness of the positive electrode mixture layer 162. By setting it to ½ or less, a secondary battery having good output characteristics (especially output characteristics under normal temperature environment) and good cycle life characteristics (particularly cycle life characteristics under normal temperature environment) is obtained. It can be said that it is possible.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to the drawings.
The second embodiment is different from the first embodiment only in the electrodes (positive electrode and negative electrode) of the lithium ion secondary battery, and the other parts are the same. Therefore, here, a different part from Embodiment 1 is demonstrated, and description is abbreviate | omitted or simplified about another part.

  The lithium ion secondary battery 200 of the second embodiment includes an electrode body 250 instead of the electrode body 150 as compared with the lithium ion secondary battery 100 of the first embodiment, as shown in the development view of FIG. The only difference is that The electrode body 250 is different from the electrode body 150 of the first embodiment in that a positive electrode 260 is substituted for the positive electrode 160 and a negative electrode 270 is substituted for the negative electrode 170.

  As shown in FIG. 11, the positive electrode 260 includes a positive electrode current collector plate 261 made of aluminum foil, and a positive electrode mixture layer 262 laminated on the surface 261 b of the positive electrode current collector plate 261. Unlike the positive electrode mixture layer 162 of the first embodiment, the positive electrode mixture layer 262 includes one (one type) positive electrode mixture layer. The positive electrode mixture layer 262 includes a positive electrode raw material powder 165 (positive electrode active material, conductive material) and a positive electrode binder 166 (PVDF), like the positive electrode mixture layer 162 of the first embodiment.

As shown in FIG. 12, the negative electrode 270 includes a negative electrode current collector plate 271 made of copper foil and a negative electrode mixture layer 272 laminated on the surface 271 b of the negative electrode current collector plate 271.
Unlike the negative electrode mixture layer 172 of the first embodiment, the negative electrode mixture layer 272 is laminated on the surface 271b of the negative electrode current collector plate 271, and the first negative electrode mixture layer 273 (the innermost negative electrode mixture layer) and The second negative electrode mixture layer 274 (outermost negative electrode mixture layer) is configured. Specifically, the negative electrode mixture layer 272 includes a first negative electrode mixture layer 273 located on the negative electrode current collector plate 271 side, and a second negative electrode mixture layer 274 located outside the negative electrode current collector plate 271 in the thickness direction. It is comprised by. The first negative electrode mixture layer 273 and the second negative electrode mixture layer 274 are each composed of a negative electrode raw material powder 175 (negative electrode active material) and a negative electrode binder 176 (SBR, CMC), as in the first embodiment. ing.

In particular, in the present embodiment, the content (wt%) of the negative electrode binder 176 in the first negative electrode mixture layer 273 is higher than the content (wt%) of the negative electrode binder 176 in the second negative electrode mixture layer 274. doing. Specifically, in the second positive electrode mixture layer 273, the content of the negative electrode binder 176 is 3 wt% or more and 4 wt% or less, whereas in the second negative electrode mixture layer 274, the content of the negative electrode binder 176 is 2 wt%. %.
Furthermore, in this embodiment, the thickness U1 of the second negative electrode mixture layer 273 is set to 1/20 or more and 1/2 or less of the total thickness U2 of the negative electrode mixture layer 272.

(Production of negative electrode)
Next, a manufacturing method of the negative electrode 270 will be described.
First, 97 to 96 wt% of negative electrode raw material powder 175 (negative electrode active material) and 3 to 4 wt% of negative electrode binder 176 (SBR, CMC) are mixed, and water is added to this and stirred. A negative electrode paste was prepared. Next, the first negative electrode paste was applied onto the surface 271b of the negative electrode current collector plate 271 (copper foil) and dried. In this way, the first negative electrode mixture layer 273 was formed on the surface 271 b of the negative electrode current collector plate 271.

  Next, 98 wt% of negative electrode raw material powder 175 (negative electrode active material) and 2 wt% of negative electrode binder 176 (SBR, CMC) were mixed, and water was added thereto and stirred to prepare a second negative electrode paste. . Next, the second negative electrode paste was applied onto the surface 273b of the first negative electrode mixture layer 273 and dried. In this way, the second positive electrode mixture layer 274 was formed on the surface 273b of the first negative electrode mixture layer 273.

  Thereafter, the first negative electrode mixture layer 273 and the second negative electrode mixture layer 274 were press-formed by press working so that the thickness U2 thereof was about 30 μm. As a result, as shown in FIG. 12, a negative electrode 270 having a negative electrode current collector plate 271 and a negative electrode mixture layer 272 laminated on the surface 271b of the negative electrode current collector plate 271 was obtained. The thickness U1 of the first negative electrode mixture layer 273 is set to 1/20 or more and 1/2 or less of the total thickness U2 of the negative electrode mixture layer 272.

(Examples 7 to 9 and Reference Examples 3 and 4 )
The content of the negative electrode binder 176 of the first negative-electrode mixture layer 273 was (wt%) only the different, were prepared five kinds of lithium ion secondary batteries (7-9 and Reference Examples 3 and 4). Specifically, the content (wt%) of the negative electrode binder 176 in the first negative electrode mixture layer 273 is 3 wt% (Example 7 ), 3.5 wt% (Example 8 ), 4 wt% (Example 9 ). They are different from 5 wt% ( Reference Example 3 ) and 6 wt% ( Reference Example 4 ).

(Comparative Examples 7-9)
Compared with the lithium ion secondary battery 200 of the embodiment, three types of lithium ion secondary batteries (Comparative Examples 7 to 7) in which only the content (wt%) of the negative electrode binder 176 of the first negative electrode mixture layer is different. 9) was produced. Specifically, the content (wt%) of the negative electrode binder 176 in the first negative electrode mixture layer is 2 wt% (Comparative Example 7), 2.5 wt% (Comparative Example 8), and 8 wt% (Comparative Example 9). It is different.

(Charge / discharge test)
Next, charge / discharge tests were performed on the lithium ion secondary batteries according to Examples 7 to 9, Reference Examples 3 and 4, and Comparative Examples 7 to 9. Specifically, each lithium ion secondary battery is charged at a low temperature environment of −30 ° C. with a current of 2C (1.4 A) until it is fully charged, and then is fully discharged. 500 charge / discharge cycles were performed.

  In this charge / discharge test, for each lithium ion secondary battery, first, in the first charge / discharge cycle, the battery was charged until it was fully charged, and then the output (watt) per second was measured when discharging. did. The output (watt) at this time is indicated by a circle in FIG. 13 as an “initial” output. Furthermore, in the 500th charge / discharge cycle, when the battery was discharged until it was fully charged, the output (watt) per second was measured. The output (in watts) at this time is indicated by Δ in FIG. 13 as the output after “cycle test”.

As indicated by a circle in FIG. 13, secondary batteries (Comparative Examples 7 and 8 and Comparative Examples 7 and 8) in which the content of the negative electrode binder 176 of the first negative electrode mixture layer is 6 wt% or less (specifically, 2 to 6 wt%). In Examples 7 to 9 and Reference Examples 3 and 4 ), the initial output was higher than 3 W, and good output characteristics were exhibited. However, in the secondary battery (Comparative Example 9) in which the content of the negative electrode binder 176 of the first negative electrode mixture layer is larger than 6 wt% (specifically, 8 wt%), the initial output is about 2.5 W. The output characteristics were unfavorable.

  From this result, by making the content rate of the negative electrode binder 176 of the first negative electrode mixture layer 273 6 wt% or less, the output characteristics of the secondary battery (particularly, the output characteristics in a low temperature environment) can be improved. I can say that. The reason for this is that the content of the negative electrode binder 176 in the first negative electrode mixture layer 273 is set to 6 wt% or less, so that the content of the negative electrode binder 176 is reduced (2 wt% in this embodiment). This is because not only the layer 274 but also the first negative electrode mixture layer 273 can smoothly move Li ions.

Further, as shown by Δ in FIG. 13, a secondary battery in which the content of the negative electrode binder 176 in the first negative electrode mixture layer is smaller than 3 wt% (specifically, 2 to 2.5 wt%) (comparison) In Examples 7 and 8), the output after the cycle test was reduced by about 1.3 to 1.5 W compared to the initial output, and the cycle life characteristics were not preferable. On the other hand, secondary batteries (Examples 7 to 9 and Reference Examples 3 and 4 ) in which the content of the negative electrode binder 176 in the first negative electrode mixture layer is 3 wt% or more (specifically, 3 to 8 wt%) In Comparative Example 9), the output after the cycle test was only about 0.2 to 0.6 W lower than the initial output, and good cycle life characteristics were exhibited.

  From this result, by making the content rate of the negative electrode binder 176 of the first negative electrode mixture layer 273 3 wt% or more, the cycle life characteristics of the secondary battery (particularly, the cycle life characteristics in a low temperature environment) are improved. It can be said that it is possible. The reason is that the negative electrode binder layer 272 and the negative electrode current collector plate 271 can be firmly bonded by setting the content of the negative electrode binder 176 in the first negative electrode mixture layer 273 to 3 wt% or more. This is considered to be because the bond between the negative electrode mixture layer 272 and the negative electrode current collector plate 271 can be maintained even if the period charge / discharge is repeated.

  From the above, regarding the first negative electrode mixture layer 273 (innermost positive electrode mixture layer), by setting the content of the negative electrode binder 176 to 3 wt% or more and 6 wt% or less, output characteristics (particularly, output characteristics in a low temperature environment) ) With good cycle life characteristics (especially cycle life characteristics under a low temperature environment) can be obtained.

(Examples 10 to 14 )
Next, five types of lithium ion secondary batteries 200 (Example 10 ) in which only the ratio of the thickness U1 of the first negative electrode mixture layer 273 to the thickness U2 of the entire negative electrode mixture layer 272 (= U1 / U2) was varied. To 14 ). Specifically, the values of U1 / U2 are set to 1/20 (Example 10 ), 1/10 (Example 11 ), 1/5 (Example 12 ), 1/3 (Example 13 ), 1 / 2 (Example 14 ). In addition, the content rate of the negative electrode binder 176 of the 1st negative electrode composite material layer 273 (innermost negative electrode composite material layer) is 4 wt% also in any secondary battery.

(Comparative Examples 10 and 11)
Compared to the lithium ion secondary battery 200 of the embodiment, two types of lithium differing only in the ratio (= U1 / U2) of the thickness U1 of the first negative electrode mixture layer to the thickness U2 of the entire negative electrode mixture layer Ion secondary batteries (Comparative Examples 10 and 11) were manufactured. Specifically, the value of U1 / U2 is different from 1/30 (Comparative Example 10) and 2/3 (Comparative Example 11). In addition, the content rate of the negative electrode binder 176 of the first negative electrode mixture layer (innermost negative electrode mixture layer) is 4 wt% in any secondary battery as in the example.

(Charge / discharge test)
Next, the lithium ion secondary batteries according to Examples 10 to 14 and Comparative Examples 10 and 11 were subjected to a charge / discharge test in a low temperature environment (−30 ° C.) as in Examples 7 to 9 described above. The output (initial output) of each secondary battery in the first cycle of this charge / discharge test is indicated by a circle in FIG. Furthermore, the output (the output after the cycle test) at the 500th cycle of each secondary battery is indicated by Δ in FIG.

As indicated by circles in FIG. 14, secondary batteries in which the value of U1 / U2 is ½ or less (specifically, 1/30 to 1/2) (Comparative Example 10 and Examples 10 to 14 ) In either case, the initial output was higher than 3 W, and good output characteristics were exhibited. However, in the secondary battery (Comparative Example 11) in which the value of U1 / U2 is larger than 1/2 (specifically, 2/3), the initial output is reduced to about 2.6 W, and the output characteristics are reduced. It was not preferable.

From this result, the value of U1 / U2 is set to 1/2 or less, that is, the thickness of the first negative electrode mixture layer 273 (innermost negative electrode mixture layer) is set to 1 of the total thickness of the negative electrode mixture layer 272. By setting it to / 2 or less, it can be said that the output characteristics of the secondary battery (particularly, the output characteristics in a low temperature environment) can be improved. This is because the thickness of the first negative electrode mixture layer 273 (innermost negative electrode mixture layer) in which the content of the negative electrode binder 176 is 3 wt% or more and 6 wt% or less (4 wt% in Examples 10 to 14 ) By suppressing it to 1/2 or less of the total thickness of the composite material layer 272, the absolute amount of the negative electrode binder 176 in the entire negative electrode composite material layer 272 is suppressed, and Li ions in the negative electrode composite material layer 272 during charging and discharging are suppressed. It is thought that the movement can be made smooth.

Further, as indicated by Δ in FIG. 14, in the secondary battery (Comparative Example 10) in which the value of U1 / U2 is smaller than 1/20 (specifically, 1/30), the output after the cycle test is The cycle life characteristics were unfavorable because it was reduced by about 1.5 W compared to the initial output. On the other hand, in the secondary batteries (Examples 10 to 14 and Comparative Example 11 ) in which the value of U1 / U2 is 1/20 or more (specifically, 1/20 to 2/3), after the cycle test Only when the output was reduced by about 0.3 to 0.7 W from the initial output, good cycle life characteristics were exhibited.

From this result, the value of U1 / U2 is set to 1/20 or more, that is, the thickness of the first negative electrode mixture layer 273 (innermost negative electrode mixture layer) is 1 of the total thickness of the negative electrode mixture layer 272. It can be said that the cycle life characteristics of the secondary battery (particularly, the cycle life characteristics under a low temperature environment) can be improved by setting the ratio to / 20 or more. This is because the thickness of the first negative electrode mixture layer 273 (innermost negative electrode mixture layer) in which the content of the negative electrode binder 176 is 3 wt% or more and 6 wt% or less (4 wt% in Examples 10 to 14 ) Since the thickness of the first negative electrode mixture layer 273 that contributes to the fixation of the entire negative electrode mixture layer 272 can be sufficiently ensured by setting it to 1/20 or more of the total thickness of the mixture layer, the first negative electrode mixture layer 273 is secured. This is because the entire negative electrode mixture layer 272 can be firmly bonded to the negative electrode current collector plate 271.

  From the above, the thickness of the first negative electrode mixture layer 273 (innermost negative electrode mixture layer) in which the content of the negative electrode binder 176 is 3 wt% or more and 6 wt% or less is 1/20 or more of the total thickness of the negative electrode mixture layer 272. By setting it to 1/2 or less, a secondary battery having good output characteristics (particularly, output characteristics in a low temperature environment) and good cycle life characteristics (particularly, cycle life characteristics in a low temperature environment) is obtained. It can be said that it is possible.

(Embodiment 3)
Next, a third embodiment of the present invention will be described with reference to the drawings.
The third embodiment is different from the first embodiment only in the lithium ion secondary battery, and the other parts are the same. Specifically, as shown in FIG. 15, the lithium ion secondary battery 300 according to the third embodiment includes an electrode body 350 instead of the electrode body 150 as compared with the lithium ion secondary battery 100 according to the first embodiment. The only difference is the provision. This electrode body 350 is different from the electrode body 150 of the first embodiment only in that it has a negative electrode 270 (see FIG. 12) according to the second embodiment instead of the negative electrode 170.

That is, in the lithium ion secondary battery 300 according to the third embodiment, the content (wt%) of the positive electrode binder 166 applied to the first positive electrode mixture layer 163 is set to the content of the positive electrode binder 166 applied to the second positive electrode mixture layer 164. The content (wt%) of the negative electrode binder 176 applied to the first negative electrode mixture layer 273 is set to the content (wt%) of the negative electrode binder 176 applied to the second negative electrode mixture layer 274. %). Moreover, the content of the positive electrode binder 166 in the first positive electrode mixture layer 163 is 6 wt% or more and 7 wt% or less, and the content of the negative electrode binder 176 in the first negative electrode mixture layer 273 is 3 wt% or more and 4 wt% or less. I'm trying. In addition, the thickness T1 of the first positive electrode mixture layer 163 is set to 1/10 or more and 1/2 or less of the thickness T2 of the positive electrode mixture layer 162, and the thickness U1 of the first negative electrode mixture layer 273 is set to the negative electrode mixture. It is set to 1/10 or more and 1/2 or less of the thickness U2 of the whole material layer 272.

(Example 15 )
A positive electrode 160 was produced by laminating a first positive electrode mixture layer 163 with a positive electrode binder 166 content of 6 wt% and a second positive electrode mixture layer 164 with a positive electrode binder 166 content of 2 wt%. Further, a first negative electrode mixture layer 273 with a negative electrode binder 176 content of 4 wt% and a second negative electrode mixture layer 274 with a negative electrode binder 176 content of 2 wt% are stacked to produce a negative electrode 270. did. Next, a lithium ion secondary battery 300 according to Example 15 was manufactured using the positive electrode 160 and the negative electrode 270.

(Charge / discharge test)
Next, the lithium ion secondary battery 300 according to Example 19 was subjected to a charge / discharge test in a room temperature environment of 25 ° C. as in Examples 1 to 4 described above. The output (initial output) of the lithium ion secondary battery 300 in the first cycle of the charge / discharge test is shown by a white bar graph in FIG. Further, the output in the 500th cycle (output after the cycle test) is shown in FIG. 16 as a hatched bar graph.

Further, for comparison with the lithium ion secondary battery 300 of Example 15 , the initial output applied to the lithium ion secondary battery 100 of Example 1 when a charge / discharge test was performed in a room temperature environment of 25 ° C. 16 is shown by a white bar graph, and the output after the cycle test is shown by a hatched bar graph in FIG. The lithium ion secondary battery 100 of Example 1 is different from the lithium ion secondary battery 300 according to Example 15 only in the negative electrode. Specifically, in the lithium ion secondary battery 100 of Example 1 , as in Example 15 , the content (wt%) of the positive electrode binder 166 in the first positive electrode mixture layer 163 was changed to the second positive electrode compound. The positive electrode 160 is made higher than the content (wt%) of the positive electrode binder 166 in the material layer 164. On the other hand, unlike the positive electrode 160, the negative electrode has a negative electrode mixture layer 172 (see FIG. 16) composed of one layer (one type) of the negative electrode mixture layer.

As shown in the bar graph of white in FIG. 16, a lithium ion secondary battery 300 of the lithium ion secondary battery 100 and the embodiment 15 of the first embodiment, both the initial output is as high as approximately 19W, the output characteristic It was good. When examined in detail, the lithium ion secondary battery 300 of Example 15 had higher initial output and superior output characteristics than the lithium ion secondary battery 100 of Example 1 .

Further, as shown by bar graph hatching in FIG. 16, a lithium ion secondary battery 300 of the lithium ion secondary battery 100 and the embodiment 15 of the first embodiment, both the output after the cycle test is as high as approximately 17W, The cycle life characteristics were also good. When examined in detail, the lithium ion secondary battery 300 of Example 15 had higher output after the cycle test and excellent cycle life characteristics than the lithium ion secondary battery 100 of Example 1 .

The reason for this is that, in the lithium ion secondary battery 300 of Example 15 , unlike the lithium ion secondary battery 100 of Example 1 , not only the positive electrode but also the negative electrode, the first negative electrode mixture layer (innermost negative electrode) The content (wt%) of the negative electrode binder 176 related to the composite material layer) is higher than the content (wt%) of the negative electrode binder 176 related to the second negative electrode composite material layer (outermost negative electrode composite material layer); This is probably because the content of the negative electrode binder 176 in the first negative electrode mixture layer is 3 wt% or more and 6 wt% or less.

(Charge / discharge test)
Moreover, about the lithium ion secondary battery 300 concerning Example 15 , the charging / discharging test was done in -30 degreeC low temperature environment similarly to the above-mentioned Examples 7-9 . The output (initial output) of the lithium ion secondary battery 300 in the first cycle of this charge / discharge test is shown by a white bar graph in FIG. Further, the output at the 500th cycle (the output after the cycle test) is shown in a hatched bar graph in FIG.

Further, for comparison with the lithium ion secondary battery 300 of Example 15 , the initial charge applied to the lithium ion secondary battery 200 of Example 9 when the charge / discharge test was performed in a low temperature environment of −30 ° C. The output is shown by a white bar graph in FIG. 17, and the output after the cycle test is shown by a hatched bar graph in FIG. The lithium ion secondary battery 200 of Example 9 is different from the lithium ion secondary battery 300 according to Example 15 only in the positive electrode. Specifically, in the lithium ion secondary battery 200 of Example 9 , as in Example 15 , the content (wt%) of the negative electrode binder 176 in the first negative electrode mixture layer 273 was changed to the second negative electrode compound. The negative electrode 270 is made higher than the content (wt%) of the negative electrode binder 176 in the material layer 274. On the other hand, unlike the negative electrode 270, the positive electrode has a positive electrode mixture layer 262 (see FIG. 11) composed of one (one type) positive electrode mixture layer.

As shown by a white bar graph in FIG. 17, both the lithium ion secondary battery 200 of Example 9 and the lithium ion secondary battery 300 of Example 15 have an initial output as high as about 3.4 W. The characteristics were good. Furthermore, as shown by the hatched bar graph in FIG. 17, both the lithium ion secondary battery 200 of Example 9 and the lithium ion secondary battery 300 of Example 15 have a high output after the cycle test of about 3 W, The cycle life characteristics were good. When examined in detail, the lithium ion secondary battery 300 of Example 15 had higher output after the cycle test and excellent cycle life characteristics than the lithium ion secondary battery 200 of Example 9 .

This is because the lithium ion secondary battery 300 of Example 15 differs from the lithium ion secondary battery 200 of Example 9 in that not only the negative electrode but also the positive electrode includes the first positive electrode mixture layer (the innermost positive electrode composite layer). The content (wt%) of the positive electrode binder 166 related to the material layer) is higher than the content (wt%) of the positive electrode binder 166 related to the second positive electrode mixture layer (outermost positive electrode mixture layer), and This is presumably because the content of the positive electrode binder 166 in the first positive electrode mixture layer is 4 wt% or more and 7 wt% or less.

  From the above results, for the positive electrode, the content (wt%) of the positive electrode binder in the first positive electrode mixture layer (innermost positive electrode mixture layer) is changed to the second positive electrode mixture layer (outermost positive electrode mixture layer). The positive electrode binder content is higher than the positive electrode binder content (wt%), and the positive electrode binder content of the first positive electrode mixture layer is 4 wt% or more and 7 wt% or less. The content rate (wt%) of the negative electrode binder applied to the (innermost negative electrode composite material layer) is set higher than the content rate (wt%) of the negative electrode binder applied to the second negative electrode composite material layer (outermost negative electrode composite material layer). In addition, the secondary battery in which the content of the negative electrode binder in the first negative electrode mixture layer is 3 wt% or more and 6 wt% or less is a room temperature environment as compared with a secondary battery in which only one of the electrodes is set to the above conditions. Output characteristics and cycle life in both low and low temperature environments Sex can be said to have become more favorable.

In the above, the present invention has been described with reference to Embodiments 1 to 3 (Examples 1 to 15 ). However, the present invention is not limited to the above-described embodiments, and may be appropriately changed without departing from the gist thereof. Needless to say, this is applicable.
For example, in the first to third embodiments, the lithium ion secondary batteries 100 to 300 are exemplified as the power source of the vehicle 1, but other secondary batteries such as a nickel hydride storage battery are used instead of the lithium ion secondary battery. May be. That is, the present invention can be applied not only to lithium ion secondary batteries but also to other secondary batteries such as nickel metal hydride storage batteries.

  Moreover, in Embodiments 1-3, although the lithium ion secondary batteries 100-300 provided with the storage case 110 which consists of a laminate film 101 were illustrated, the storage case 110 is a laminate film formed by laminating a metal film and a resin film. However, the present invention is not limited to this, and it may be made of a metal, a resin, or the like formed into a rectangular parallelepiped shape or a cylindrical shape.

1 is a schematic view of a vehicle 1 according to an embodiment. It is the schematic of the battery pack 6 concerning embodiment. 1 is a plan view of a lithium ion secondary battery 100 according to an embodiment. 2 is a plan view of a lithium ion secondary battery 100 before being laminated with a laminate film 101. FIG. 2 is an enlarged cross-sectional view of a positive electrode 160 of a lithium ion secondary battery 100. FIG. 2 is an enlarged cross-sectional view of a negative electrode 170 of a lithium ion secondary battery 100. FIG. 2 is a plan view of a lithium ion secondary battery 100 having a liquid injection hole 116. FIG. It is a graph which shows the relationship between the content rate of the positive electrode binder 166, and an output. It is a graph which shows the relationship between T1 / T2 of a positive electrode compound material layer, and an output. It is an expanded view of the lithium ion secondary battery 200 concerning embodiment. 3 is an enlarged cross-sectional view of a positive electrode 260 of a lithium ion secondary battery 200. FIG. 3 is an enlarged cross-sectional view of a negative electrode 270 of a lithium ion secondary battery 200. FIG. It is a graph which shows the relationship between the content rate of the negative electrode binder 176, and an output. It is a graph which shows the relationship between U1 / U2 of a negative electrode compound-material layer, and an output. It is an expanded view of the lithium ion secondary battery 300 concerning embodiment. It is a graph which shows Example 1 and Example 15 output characteristic. It is a graph which shows the output characteristic of Example 9 and Example 15. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 6 Battery pack 10 Battery module 100,200,300 Lithium ion secondary battery 160,260 Positive electrode 161,261 Positive electrode current collecting plate 162,262 Positive electrode mixture layer 163 1st positive electrode mixture layer (innermost positive electrode mixture layer )
164 Second positive electrode mixture layer (outermost positive electrode mixture layer)
165 Positive electrode raw material powder 166 Positive electrode binder 170, 270 Negative electrode 171, 271 Negative electrode current collector plates 172, 272 Negative electrode material layer 175 Negative electrode raw material powder 176 Negative electrode binder 273 First negative electrode material layer (innermost negative electrode material layer)
274 Second negative electrode mixture layer (outermost negative electrode mixture layer)

Claims (13)

A secondary battery comprising a positive electrode and a negative electrode,
The positive electrode
A positive electrode current collector plate;
A plurality of positive electrode mixture layers laminated on the positive electrode current collector plate and including a positive electrode raw material powder and a positive electrode binder,
Of the plurality of positive electrode mixture layers, the content (wt%) of the positive electrode binder on the innermost positive electrode mixture layer located closest to the positive electrode current collector plate,
Higher than other positive electrode mixture layers, and
It possesses a positive-electrode mixture layer formed as follows 6 wt% or more 7 wt%, and
The thickness of the innermost positive electrode mixture layer is 1/10 or more and 1/2 or less of the total thickness of the laminated positive electrode mixture layer,
The negative electrode is
A negative electrode current collector plate;
A plurality of negative electrode mixture layers laminated on the negative electrode current collector plate and including a negative electrode raw material powder and a negative electrode binder,
The content (wt%) of the negative electrode binder applied to the innermost negative electrode mixture layer located closest to the negative electrode current collector plate among the plurality of negative electrode mixture layers,
Higher than other negative electrode composite layers, and
3 wt% or more and 4 wt% or less
A negative electrode mixture layer,
The secondary battery has a thickness of the innermost negative electrode mixture layer that is 1/20 or more and 1/2 or less of a total thickness of the laminated negative electrode mixture layer . The secondary battery according to claim 1 ,
A secondary battery in which the thickness of the laminated positive electrode mixture layer as a whole is 50 μm or less. The secondary battery according to claim 1 or 2 , wherein
The outermost positive electrode mixture layer located on the outermost side among the plurality of positive electrode mixture layers is a secondary battery in which the content of the positive electrode binder is 2 wt% or less. The secondary battery according to any one of claims 1 to 3 ,
A secondary battery in which the thickness of the entire laminated negative electrode mixture layer is 50 μm or less. The secondary battery according to any one of claims 1 to 4 ,
The outermost negative electrode mixture layer located on the outermost side among the plurality of negative electrode mixture layers is a secondary battery in which the content of the negative electrode binder is 2 wt% or less. A secondary battery according to any one of claims 1 to 5 ,
The secondary battery is a secondary battery that is a lithium ion secondary battery. A vehicle comprising the secondary battery according to any one of claims 1 to 6 .   A positive electrode current collector plate;
  A plurality of positive electrode mixture layers including a positive electrode raw material powder and a positive electrode binder laminated on the positive electrode current collector plate.
In the positive electrode for secondary battery,
  Of the plurality of positive electrode mixture layers, the content (wt%) of the positive electrode binder on the innermost positive electrode mixture layer located closest to the positive electrode current collector plate,
    Higher than other positive electrode mixture layers, and
    6 wt% or more and 7 wt% or less,
  The thickness of the innermost positive electrode mixture layer is 1/10 or more and 1/2 or less of the total thickness of the laminated positive electrode mixture layer.
Secondary battery positive electrode. The positive electrode for a secondary battery according to claim 8,
  The thickness of the laminated positive electrode mixture layer as a whole is 50 μm or less.
Secondary battery positive electrode. A positive electrode for a secondary battery according to claim 8 or claim 9,
  Outermost positive electrode mixture layer located on the outermost side among the plurality of positive electrode mixture layers has a content of the positive electrode binder of 2 wt% or less.
Secondary battery positive electrode.   A negative electrode current collector plate;
  A plurality of negative electrode mixture layers including a negative electrode raw material powder and a negative electrode binder laminated on the negative electrode current collector plate.
A negative electrode for a secondary battery,
  The content (wt%) of the negative electrode binder applied to the innermost negative electrode mixture layer located closest to the negative electrode current collector plate among the plurality of negative electrode mixture layers,
    Higher than other negative electrode composite layers, and
    3 wt% or more and 4 wt% or less,
  The thickness of the innermost negative electrode mixture layer is 1/20 or more and 1/2 or less of the total thickness of the laminated negative electrode mixture layer.
Negative electrode for secondary battery. The negative electrode for a secondary battery according to claim 11,
  The entire thickness of the laminated negative electrode mixture layer is 50 μm or less.
Negative electrode for secondary battery. The secondary battery negative electrode according to claim 11 or 12,
  The outermost negative electrode mixture layer located on the outermost side among the plurality of negative electrode mixture layers has a content of the negative electrode binder of 2 wt% or less.
Negative electrode for secondary battery.

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