JP2018147565A - Method for manufacturing power storage element and power storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage element which is superior in cycle life characteristic and coulomb efficiency.SOLUTION: A method for manufacturing a power storage element according to an embodiment of the present invention comprises pressing a housing case which contains an electrode body arranged by laminating positive and negative electrode plates with a separator interposed therebetween, and an electrolyte solution. When A is an air impermeability of the separator before the pressing, and B is an air impermeability of the separator after the pressing, the relation between A and B is given by: A/B≤0.89. A power storage element according to another embodiment of the invention comprises an electrode body arranged by laminating positive and negative electrode plates with a separator interposed therebetween; and a housing case which contains the electrode body. The separator has: opposed portions opposed to the positive electrode plate and the negative electrode plate; and unopposed portions not opposed to the positive electrode plate and/or the negative electrode plate. When B is an air impermeability of the separator in the opposed portions and A is an air impermeability of the separator in the unopposed portions, the relation between A and B is given by: A/B≤0.89.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a power storage element and a power storage element.

  Various power storage elements are used in which an electrode body in which a positive electrode plate and a negative electrode plate are laminated via a separator is accommodated in a case. Attempts have been made to reduce the thickness of the separator in order to improve the energy density (amount of electricity stored per volume) of the electricity storage element.

  For example, it is proposed to manufacture a power storage device having a relatively large energy density by pressing an electrode body in which a positive electrode plate, a negative electrode plate, and a separator (porous material) are stacked, thereby compressing the separator and reducing its thickness. (Japanese Patent Laid-Open No. 2005-93375). In the method for manufacturing an electricity storage device described in this publication, by heating the electrode body, a part of the polymer of the separator is eluted in the electrolytic solution to generate a gap, and the gap is crushed by compressing the separator. It is said.

JP 2005-93375 A

  In a power storage element, an electrolyte solution needs to be infiltrated into a separator. However, when the porosity of the separator is small, it takes time to inject the electrolyte into the separator. Moreover, when using an electrical storage element, it is necessary for electrolyte solution to fill the hole of a separator, but electrolyte solution will be electrochemically reacted and consumed by repetition of charging / discharging. When the porosity of the separator is large, the amount of electrolyte necessary to fill the separator holes increases, so that when the electrolyte is consumed by repeated charge and discharge, the electrolyte necessary to fill the separator holes As a result, the cycle life characteristics and the Coulomb efficiency of the electricity storage element deteriorate.

  In the method for manufacturing an electricity storage device described in the above-mentioned publication, since the separator is compressed while elution of a part of the polymer by heating, process management is complicated and it is not easy to stabilize the porosity of the separator.

  In view of the above disadvantages, the present invention relates to a method for manufacturing a power storage device that can manufacture a power storage device having excellent cycle life characteristics and coulomb efficiency relatively easily, and a power storage device that is relatively easy to manufacture and that has high cycle life characteristics and coulomb efficiency. It is an issue to provide.

  The method for manufacturing a power storage device according to one aspect of the present invention includes pressing an electrode body in which a positive electrode plate and a negative electrode plate are stacked via a separator, and a case in which an electrolytic solution is contained, The relationship between A and B is A / B ≦ 0.89, where A [s] is the air permeability resistance of the separator before and B [s] is the air resistance of the separator after the pressing. .

  An electricity storage device according to another aspect of the present invention includes an electrode body in which a positive electrode plate and a negative electrode plate are stacked via a separator, and a case that houses the electrode body, and the separator includes the positive electrode plate and the negative electrode plate. And a non-facing portion that does not face the positive electrode plate and / or the negative electrode plate, the air resistance at the facing portion of the separator is B [s], and the non-facing portion of the separator Assuming that the air resistance in A is [s], the relationship between A and B is A / B ≦ 0.89.

  With the method for manufacturing a power storage element according to one embodiment of the present invention, a power storage element having excellent cycle life characteristics and Coulomb efficiency can be manufactured relatively easily. In addition, the electricity storage device according to another aspect of the present invention is relatively easy to manufacture and has excellent cycle life characteristics and coulomb efficiency.

It is typical sectional drawing which shows the electrical storage element of one Embodiment of this invention. It is an external appearance perspective view which shows the nonaqueous electrolyte secondary battery which concerns on one Embodiment of the electrical storage element of this invention. It is the schematic which shows the electrical storage apparatus comprised by collecting the nonaqueous electrolyte secondary battery which concerns on one Embodiment of the electrical storage element of this invention.

  One aspect of the present invention includes pressing an electrode body in which a positive electrode plate and a negative electrode plate are stacked via a separator and a case in which an electrolytic solution is housed, and air permeability of the separator before the pressing This is a method of manufacturing a storage element in which the relationship between A and B is A / B ≦ 0.89, where A [s] is the resistance and B [s] is the air resistance of the separator after pressing. .

  According to the method for manufacturing the power storage element, a power storage element having a relatively large energy density can be manufactured by compressing the separator by pressing a case in which the electrode body and the electrolytic solution are housed. In addition, since the relationship between A and B satisfies the relationship, the electrolytic solution can be infiltrated (injected) into the separator before pressing relatively easily. Can be manufactured. Furthermore, since the relationship between A and B is A / B ≦ 0.89, the amount of electrolyte required for impregnating the separator after pressing is reduced. It is possible to manufacture a high-quality power storage element that is less likely to occur and has excellent cycle life characteristics and coulomb efficiency.

  The relationship between A and B is preferably A / B ≦ 0.40. This further improves the performance of the storage battery.

  When the porosity of the separator before pressing is C [%] and the porosity of the separator after pressing is D [%], the relationship between C and D may be C> D. As a result, the amount of the electrolyte present in the separator of the obtained electricity storage device can be reduced, so that the cycle life characteristics and the Coulomb efficiency of the electricity storage device can be improved.

  The relationship between C and D is preferably D / C ≦ 0.95. As a result, the performance of the obtained power storage element can be reliably improved.

  The relationship between C and D is preferably D / C ≦ 0.83. Thereby, the performance of the obtained electricity storage device can be further improved.

  The positive electrode plate may have a composite layer, and the porosity of the composite layer may be 20% or more and 35% or less.

  The viscosity of the electrolytic solution is preferably 0.01 cP or more and 5 cP or less. This makes it easier to inject the electrolyte.

  Another aspect of the present invention includes an electrode body in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween, and a case that houses the electrode body, and the separator faces the positive electrode plate and the negative electrode plate. A non-opposing portion that does not oppose the positive electrode plate and / or the negative electrode plate, and the air resistance at the non-opposing portion of the separator is B [s]. A storage element in which the relationship between A and B is A / B ≦ 0.89 when the resistance is A [s].

  In the electricity storage device, the air permeability resistance of the facing portion of the separator, that is, the portion where the separator is compressed between the electrode plates, is the non-opposing portion of the separator, that is, the portion of the separator that is not compressed. Greater than air resistance. Therefore, the power storage element has a cycle life characteristic and a structure in which the electrolyte solution is relatively easily infiltrated into a separator having a low air permeability resistance before compression, and then the electrode body is pressed to compress the separator between the electrode plates. Coulomb efficiency can be improved.

  The “air permeability resistance” is a value measured according to JIS-P8117 (2009), and is an average value obtained by measuring 10 or more different positions. The “porosity” is a value measured by the “mercury intrusion method” based on JIS-R1655 (2003), and is an average value obtained by measuring three or more different positions. Each value of “after pressing” or “opposing part” is a value measured in a state where elastic strain is removed, and the value of “non-opposing part” is not compressed by the positive electrode plate and / or the negative electrode plate. The value measured in the part. The “viscosity” is a value measured by a “single cylindrical rotational viscometer” in accordance with JIS-Z8803 (2011).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[Storage element]
A power storage device according to an embodiment of the present invention shown in FIG. 1 includes an electrode body 1 and a case 2 that accommodates the electrode body 1. Further, the power storage element is filled with an electrolyte in the case 2.

(Electrode body)
The electrode body 1 is formed by laminating a positive electrode plate 3 and a negative electrode plate 4 with a separator 5 interposed therebetween. Specifically, as shown in the figure, the electrode body 1 is formed by winding a long laminate of a first separator 5, a positive electrode plate 3, a second separator 5, and a negative electrode plate 4 in an elliptical shape in cross section. It is formed by turning. That is, the electrode body 1 has a portion in which the positive electrode plate 3, the negative electrode plate 4, and the separator 5 extend in a planar shape and a portion that connects these planar portions.

<Positive electrode plate>
The positive electrode plate 3 has a conductive foil-shaped or sheet-shaped positive electrode current collector, and a porous positive electrode mixture layer laminated on both surfaces of the positive electrode current collector. More specifically, the positive electrode plate 3 includes an electrode part in which a positive electrode mixture layer is laminated on both surfaces of the positive electrode current collector, a connection part that protrudes from the electrode part and is electrically connected to a connection terminal of the power storage element. Have

(Positive electrode current collector)
As a material of the positive electrode current collector, a metal such as aluminum, copper, iron, nickel, or an alloy thereof is used. Among these, aluminum, an aluminum alloy, copper, and a copper alloy are preferable from the balance between high conductivity and cost, and aluminum and an aluminum alloy are more preferable. Moreover, as a shape of a positive electrode electrical power collector, foil, a vapor deposition film, etc. are mentioned, A foil is preferable from the surface of cost. That is, an aluminum foil is preferable as the positive electrode current collector. Examples of aluminum or aluminum alloy include A1085P and A3003P defined in JIS-H4000 (2014).

  The lower limit of the average thickness of the positive electrode current collector is preferably 5 μm, more preferably 10 μm. On the other hand, the upper limit of the average thickness of the positive electrode current collector is preferably 50 μm, more preferably 40 μm. By setting the average thickness of the positive electrode current collector to be equal to or more than the lower limit, the positive electrode current collector has sufficient strength. Moreover, the energy density of the said electrical storage element can be made comparatively large by making average thickness of a positive electrode electrical power collector below the said upper limit.

(Positive electrode mixture layer)
The positive electrode mixture layer is a porous layer formed from a so-called mixture containing a positive electrode active material. Moreover, the composite material which forms a positive electrode composite material layer contains arbitrary components, such as a electrically conductive agent, a binder (binder), a thickener, and a filler, as needed.

  The lower limit of the porosity of the positive electrode mixture layer is preferably 15%, more preferably 20%. On the other hand, the upper limit of the porosity of the positive electrode mixture layer is preferably 35%, more preferably 30%. By setting the porosity of the positive electrode mixture layer to be equal to or higher than the lower limit, the electrolytic solution can be sufficiently infiltrated to cause a sufficient positive electrode reaction. Moreover, since the positive electrode composite material layer can be made relatively thin by setting the porosity of the positive electrode composite material layer to be equal to or less than the above upper limit, the energy density of the power storage element can be increased.

Examples of the positive electrode active material include complex oxides (Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _x ) represented by Li _x MO _y (M represents at least one transition metal). _{MnO 3, Li x Ni α Co} (1-α) O 2, Li x Ni α Mn β Co (1-α-β) O 2, Li x Ni α Mn (2-α) O 4 , etc.), Li _w A polyanion compound (LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ ) represented by Me _x (XO _y ) _z (Me represents at least one transition metal, and X represents, for example, P, Si, B, V, etc.) Li ₃ V ₂ (PO ₄ ) ₃ , Li ₂ MnSiO ₄ , Li ₂ CoPO ₄ F, etc.). The elements or polyanions in these compounds may be partially substituted with other elements or anion species. In the positive electrode mixture layer, one kind of these compounds may be used alone, or two or more kinds may be mixed and used. The crystal structure of the positive electrode active material is preferably a layered structure or a spinel structure.

  The lower limit of the content of the positive electrode active material in the positive electrode mixture layer is preferably 50% by mass, more preferably 70% by mass, and still more preferably 80% by mass. On the other hand, as an upper limit of content of a positive electrode active material, 99 mass% is preferable and 94 mass% is more preferable. By setting the content of the positive electrode active material in the above range, the energy density of the power storage element can be increased.

  The conductive agent is not particularly limited as long as it is a conductive material that does not adversely affect battery performance. Examples of such a conductive agent include carbon black such as natural or artificial graphite, furnace black, acetylene black, and ketjen black, metals, and conductive ceramics. Examples of the shape of the conductive agent include powder and fiber.

  The lower limit of the content of the conductive agent in the positive electrode mixture layer is preferably 0.1% by mass, and more preferably 0.5% by mass. On the other hand, as an upper limit of content of a electrically conductive agent, 10 mass% is preferable and 5 mass% is more preferable. By setting the content of the conductive agent in the above range, the energy density of the power storage element can be increased.

  Examples of the binder include thermoplastic resins such as fluororesin (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyimide; ethylene-propylene-diene rubber (EPDM), sulfonated EPDM. , Elastomers such as styrene butadiene rubber (SBR) and fluororubber; polysaccharide polymers and the like.

  The lower limit of the binder content in the positive electrode mixture layer is preferably 1% by mass, and more preferably 2% by mass. On the other hand, as an upper limit of content of a binder, 10 mass% is preferable and 5 mass% is more preferable. By setting the content of the binder in the above range, the positive electrode active material can be stably held.

  Examples of the thickener include polysaccharide polymers such as carboxymethylcellulose (CMC) and methylcellulose. When the thickener has a functional group that reacts with lithium, it is preferable to deactivate this functional group in advance by methylation or the like.

  The filler is not particularly limited as long as it does not adversely affect battery performance. Examples of the main component of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, and carbon. The “main component” means a component having the largest mass content.

<Negative electrode plate>
The negative electrode plate 4 includes a conductive foil-like or sheet-like negative electrode current collector and a porous negative electrode mixture layer laminated on both surfaces of the negative electrode current collector. More specifically, the negative electrode plate 4 includes an electrode part in which a negative electrode mixture layer is laminated on both surfaces of the negative electrode current collector, a connection part that protrudes from the electrode part and is electrically connected to a connection terminal of the power storage element. Have

  The negative electrode plate 4 preferably has a winding axial width equal to or larger than the positive electrode plate 3 width. In other words, in the electrode body 1, the positive electrode plate 3 is preferably arranged so as not to protrude from the negative electrode plate 4 in the axial direction of winding. Thereby, it can prevent that reaction becomes excessive in the edge part of the negative electrode plate 4, and electrodeposition is promoted.

(Negative electrode current collector)
The negative electrode current collector can have the same shape as the positive electrode current collector described above, but the material is preferably copper or a copper alloy. That is, the negative electrode current collector of the negative electrode plate 4 is preferably a copper foil. Examples of the copper foil include a rolled copper foil and an electrolytic copper foil.

(Negative electrode mixture layer)
The negative electrode composite material layer is formed from a so-called composite material containing a negative electrode active material. Moreover, the composite material which forms a negative electrode composite material layer is a porous layer containing arbitrary components, such as a electrically conductive agent, a binder (binder), a thickener, and a filler, as needed. Arbitrary components such as a conductive agent, a binder, a thickener, and a filler can be the same as those for the positive electrode mixture layer.

  The lower limit of the porosity of the negative electrode mixture layer is preferably 20%, and more preferably 25%. On the other hand, the upper limit of the porosity of the negative electrode mixture layer is preferably 40%, more preferably 30%. By setting the porosity of the negative electrode mixture layer to be equal to or higher than the lower limit, the electrolytic solution can be sufficiently infiltrated to cause a sufficient positive electrode reaction. Moreover, since the negative electrode composite material layer can be made relatively thin by setting the porosity of the negative electrode composite material layer to be equal to or lower than the above upper limit, the energy density of the power storage element can be increased.

  As the negative electrode active material, a material capable of inserting and extracting lithium ions is preferably used. Specific examples of the negative electrode active material include metals such as lithium and lithium alloys; metal oxides; polyphosphate compounds; carbon materials such as graphite and amorphous carbon (easily graphitizable carbon or non-graphitizable carbon). Can be mentioned.

  Among the negative electrode active materials, Si, Si oxide, Sn, Sn oxide, or a combination thereof is used from the viewpoint of setting the discharge capacity per unit facing area between the positive electrode plate 3 and the negative electrode plate 4 to a suitable range. It is preferable to use Si oxide. Si and Sn can have a discharge capacity about three times that of graphite when they are made into oxides.

When Si oxide is used as the negative electrode active material, the ratio of the number of atoms of O to Si contained in the Si oxide is preferably more than 0 and less than 2. That is, as the Si oxide, a compound represented by SiO _x (0 <x <2) is preferable. The ratio of the number of atoms is more preferably 0.5 or more and 1.5 or less.

  As the negative electrode active material, those described above may be used singly or in combination of two or more. For example, by using a mixture of Si oxide and another negative electrode active material, the discharge capacity per unit facing area between the positive electrode plate 3 and the negative electrode plate 4 and the mass of the negative electrode active material described later with respect to the mass of the negative electrode active material described later. Both of the mass ratios can be adjusted to be suitable values. Other negative electrode active materials used in combination with Si oxide include carbon materials such as graphite, hard carbon, soft carbon, coke, acetylene black, ketjen black, vapor grown carbon fiber, fullerene, activated carbon and the like. . Only one kind of these carbon materials may be mixed with Si oxide, or two or more kinds may be mixed with Si oxide in an arbitrary combination and ratio. Among these other negative electrode active materials, graphite having a relatively low charge / discharge potential is preferable, and a secondary battery element having a high energy density can be obtained by using graphite. Examples of graphite used by mixing with Si oxide include flaky graphite, spherical graphite, artificial graphite, and natural graphite. Among these, scaly graphite that can easily maintain contact with the surface of the Si oxide particles even after repeated charge and discharge is preferable.

  As a minimum of content of Si oxide in a negative electrode active material, 30 mass% is preferred, 50 mass% is more preferred, and 70 mass% is still more preferred. On the other hand, the upper limit of the content of Si oxide is usually 100% by mass, and preferably 90% by mass.

  Further, the negative electrode mixture layer includes a small amount of typical nonmetallic elements such as B, N, P, F, Cl, Br, and I, Li, Na, Mg, Al, K, Ca, Zn, Typical metal elements such as Ga and Ge, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W may be contained.

As the Si oxide (substance represented by the general formula SiO _x ), it is preferable to use a material containing both phases of SiO ₂ and Si. Such Si oxide has a small volume change and excellent charge / discharge cycle characteristics because lithium is occluded and released from Si in the SiO ₂ matrix.

  The average particle size of the Si oxide is preferably 1 μm or more and 15 μm or less. By setting the average particle diameter of the Si oxide to the upper limit or less, the charge / discharge cycle characteristics of the power storage element can be improved.

  The Si oxide can be used from highly crystalline to amorphous. Further, as the Si oxide, one washed with an acid such as hydrogen fluoride or sulfuric acid or one reduced with hydrogen may be used.

  The lower limit of the content of the negative electrode active material in the negative electrode mixture layer is preferably 60% by mass, more preferably 80% by mass, and still more preferably 90% by mass. On the other hand, as an upper limit of content of a negative electrode active material, 99 mass% is preferable and 98 mass% is more preferable. By making content of a negative electrode active material into the said range, the energy density of an electrical storage element can be raised.

  As a minimum of content of a binder in a negative electrode compound-material layer, 1 mass% is preferable and 5 mass% is more preferable. On the other hand, as an upper limit of content of a binder, 20 mass% is preferable and 15 mass% is more preferable. By setting the content of the binder in the above range, the negative electrode active material can be stably held.

<Separator>
The separator 5 is formed from a porous sheet-like or film-like resin and is infiltrated with an electrolytic solution. The separator 5 separates the positive electrode plate 3 and the negative electrode plate 4 and holds an electrolytic solution between the positive electrode plate 3 and the negative electrode plate 4.

  Examples of the main component of the separator 5 include polyolefins such as polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and chlorinated polyethylene. Derivatives, polyolefins such as ethylene-propylene copolymers, and polyesters such as polyethylene terephthalate and copolymerized polyesters can be employed. Among these, as the main component of the separator 5, polyethylene and polypropylene excellent in electrolytic solution resistance, durability, and weldability are preferably used.

  As a minimum of average thickness of separator 5, 5 micrometers is preferred and 10 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the separator 5 is preferably 50 μm and more preferably 30 μm. By setting the average thickness of the separator 5 to the lower limit or more, a short circuit between the positive electrode plate 3 and the negative electrode plate 4 can be more reliably prevented. Moreover, the energy density of the said electrical storage element can be enlarged by making the average thickness of the separator 5 below the said upper limit. The separator is preferably an inorganic coating separator from the viewpoint of wettability.

  Moreover, as a minimum of the piercing strength of the separator 5, 200 gf is preferable and 300 gf is more preferable. On the other hand, the upper limit of the piercing strength of the separator 5 is preferably 1000 gf, more preferably 800 gf. By setting the puncture strength of the separator 5 to be equal to or higher than the lower limit, for example, metal deposits formed by electrodeposition such as lithium dendrite can break through the separator 5 and short-circuit the positive electrode plate 3 and the negative electrode plate 4 more reliably. Can be prevented. Moreover, the processing of the separator 5 becomes comparatively easy by making the puncture strength of the separator 5 below the upper limit. The “puncture strength” is a value measured according to JIS-Z1707 (1997).

  Further, the separator 5 has a facing portion that faces the positive electrode plate 3 and the negative electrode plate 4 and a non-facing portion that does not face the positive electrode plate 3 or the negative electrode plate 4. In other words, the separator 5 is sandwiched between the positive electrode plate 3 and the negative electrode plate 4 and pressed (compressed) in the thickness direction, and the positive electrode 3 protrudes from the positive electrode plate 3 or the negative electrode plate 4 in the winding axial direction. A non-opposing portion that is not sandwiched and pressed (compressed) between the plate 3 and the negative electrode plate 4.

  When the air permeation resistance at the non-opposing part of the separator 5 is A [s] and the air permeation resistance at the opposing part is B [s], A / B (the air permeation resistance at the non-opposing part of the opposing part The lower limit of the ratio to the air resistance is preferably 0.20, more preferably 0.25, and still more preferably 0.30. On the other hand, the upper limit of A / B is 0.89, preferably 0.40, and more preferably 0.35. By setting A / B to be equal to or higher than the lower limit, a sufficient electrolyte can be held in the separator 5, and the separator 5 can be compressed and thus the storage element can be manufactured relatively easily. In addition, by setting A / B to be equal to or less than the above upper limit, the liquid injection property at the time of manufacture is improved, and the porosity at the facing portion of the separator 5 is sufficiently reduced so that the cycle life characteristics and the Coulomb efficiency of the power storage element are increased. Can be improved.

  As a minimum of air permeability resistance A in a non-opposition part of separator 5, 30s is preferred, 50s is more preferred, and 60s is still more preferred. On the other hand, the upper limit of the air resistance A at the non-opposing portion of the separator 5 is preferably 250 s, more preferably 150 s, and even more preferably 100 s. By setting the air permeation resistance A at the non-facing portion of the separator 5 to be equal to or higher than the lower limit, the porosity at the facing portion of the separator 5 is sufficiently reduced, and the cycle life characteristics and the Coulomb efficiency of the power storage element are improved. be able to. Moreover, since the electrolyte solution can be rapidly infiltrated at the time of manufacture by setting the air permeability resistance A at the non-opposing portion of the separator 5 to be equal to or less than the upper limit, the manufacturing efficiency of the power storage element is improved.

  As a minimum of air permeability resistance B in the portion which counters separator 5, 90s is preferred, 200s is more preferred, and 250s is still more preferred. On the other hand, the upper limit of the air permeability resistance B at the facing portion of the separator 5 is preferably 500 s, more preferably 400 s, and even more preferably 350 s. By setting the air permeability resistance B at the facing portion of the separator 5 to be equal to or higher than the lower limit, the porosity at the facing portion of the separator 5 is sufficiently reduced to improve the cycle life characteristics and the Coulomb efficiency of the power storage element. Can do. In addition, by setting the air permeability resistance B at the facing portion of the separator 5 to be equal to or less than the above upper limit, the separator 5 can be infiltrated with a sufficient amount of the electrolyte solution to promote the polar reaction. Will improve.

  When the porosity at the non-opposing part of the separator 5 is C [%] and the porosity at the opposing part is D [s], D / C (the porosity of the opposing part with respect to the porosity in the non-opposing part) The ratio is preferably smaller than 1. That is, the porosity D at the facing portion of the separator 5 is preferably smaller than the porosity C at the non-facing portion. Thereby, the injection property of the electrolyte solution at the time of manufacture, the cycle life characteristics and the Coulomb efficiency of the electric storage element can be compatible.

  As a minimum of D / C, 0.70 is preferred and 0.71 is more preferred. On the other hand, the upper limit of D / C is preferably 0.95, more preferably 0.83, and even more preferably 0.79. By setting D / C to be equal to or higher than the lower limit, a sufficient amount of the electrolytic solution can be held in the separator 5, and the separator 5 can be easily compressed, thereby improving the manufacturing efficiency of the power storage element. Further, by setting D / C to be equal to or less than the above upper limit, the liquid injection property at the time of manufacture is increased, so that the manufacturing efficiency of the power storage element is improved and the porosity of the separator 5 after the manufacturing can be decreased. The cycle life characteristics and coulomb efficiency of the device are improved.

  As a minimum of porosity C in a non-opposition part of separator 5, 40% is preferred, 50% is more preferred, and 55% is still more preferred. On the other hand, the upper limit of the porosity C at the non-opposing portion of the separator 5 is preferably 80%, more preferably 70%, and even more preferably 60%. By setting the porosity C in the non-opposing portion of the separator 5 to be equal to or higher than the lower limit, the separator 5 can hold a sufficient amount of the electrolytic solution, thereby promoting the polar reaction and improving the performance of the power storage element. it can. In addition, by setting the porosity C in the non-opposing part of the separator 5 to be equal to or less than the above upper limit, the porosity D in the opposing part of the separator 5 can be sufficiently reduced. Will improve.

  As a minimum of porosity D in the portion which counters separator 5, 35% is preferred, 38% is more preferred, and 40% is still more preferred. On the other hand, the upper limit of the porosity D at the facing portion of the separator 5 is preferably 55%, more preferably 50%, and even more preferably 45%. By setting the porosity D at the facing portion of the separator 5 to be equal to or higher than the lower limit, a sufficient amount of the battery device can be brought into contact with the positive electrode plate 3 and the negative electrode plate 4, so that the performance of the electric storage element is improved. In addition, by setting the porosity D at the facing portion of the separator 5 to be equal to or lower than the upper limit, the cycle life characteristics and the Coulomb efficiency of the power storage element are improved.

  Moreover, the separator 5 is good to have a heat resistant layer on both surfaces or one surface (preferably the surface facing the positive electrode). Thereby, damage to the separator 5 due to heat can be prevented, and a short circuit between the positive electrode plate 3 and the negative electrode plate 4 can be more reliably prevented.

(Heat resistant layer)
The heat-resistant layer of the separator 5 can include a large number of inorganic particles and a binder that connects the inorganic particles.

  As the main component of the inorganic particles, for example, oxides such as alumina, silica, zirconia, titania, magnesia, ceria, yttria, zinc oxide, iron oxide, nitrides such as silicon nitride, titanium nitride, boron nitride, silicon carbide, carbonate Calcium, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amicite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate Etc. Among these, alumina, silica and titania are particularly preferable as the main component of the inorganic particles of the heat-resistant layer.

  The lower limit of the average particle size of the inorganic particles in the heat-resistant layer is preferably 1 nm, and more preferably 7 nm. On the other hand, the upper limit of the average particle diameter of the inorganic particles is preferably 5 μm and more preferably 1 μm. By setting the average particle diameter of the inorganic particles to the above lower limit or more, the ratio of the inorganic particles and the binder in the heat-resistant layer can be optimized, and the heat resistance of the heat-resistant layer can be improved. Moreover, a uniform heat-resistant layer can be formed by setting the average particle diameter of the inorganic particles to the upper limit or less. The “average particle diameter” is a value measured according to JIS-R1670.

  As a main component of the binder of the heat-resistant layer, for example, fluororesin such as polyvinylidene fluoride and polytetrafluoroethylene, fluororubber such as vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, styrene-butadiene copolymer and Its hydride, acrylonitrile-butadiene copolymer and its hydride, acrylonitrile-butadiene-styrene copolymer and its hydride, methacrylic acid ester-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, acrylonitrile- Synthetic rubber such as acrylic ester copolymer, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), cellulose derivatives such as ammonium salt of carboxymethylcellulose, polyetherimide, polyester Polyimides such as amide imide, polyamide and precursors thereof (polyamic acid, etc.), ethylene-acrylic acid copolymers such as ethylene-ethyl acrylate copolymer, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP) , Polyvinyl acetate, polyurethane, polyphenylene ether, polysulfone, polyether sulfone, polyphenylene sulfide, polyester and the like.

  The lower limit of the average thickness of the heat-resistant layer is preferably 0.5 μm, and more preferably 1 μm. On the other hand, the upper limit of the average thickness of the heat-resistant layer is preferably 10 μm, and more preferably 6 μm. The heat resistance of the separator 5 can be improved by setting the average thickness of the heat resistant layer to the lower limit or more. Moreover, the energy density of the said electrical storage element can be enlarged more by making the average thickness of a heat-resistant layer below the said upper limit.

〔Case〕
The case 2 includes a pair of pressing walls 6 facing the both sides of a laminated region in which the positive electrode plate 3, the negative electrode plate 4, and the separator 5 of the electrode body 1 housed therein extend in a planar shape, and the one pressing wall 6. It has a cylindrical portion having a pair of connection walls 7 that connect both ends.

  The pair of pressing walls 6 sandwich the electrode body 1 and compress the separator 5 in the laminated body in the thickness direction. The pair of connection walls 7 are plastically deformed to maintain the distance between the pair of pressing walls 6. That is, the power storage element extends in a planar shape of the separator 5 of the electrode body 1, and the portion facing the positive electrode plate 3 and the negative electrode plate 4 is compressed in the thickness direction by pressing the pressing wall 6 of the case. ing.

  The material of the case 2 may be any material as long as it has a sealing property that can enclose an electrolytic solution and a strength that can hold the electrode body 1, and a metal is preferably used, and stainless steel, aluminum, and the like are particularly preferable. Used. That is, as the case 2, it is preferable to use a metal case that can more reliably press and hold the electrode body 1.

[Electrolyte]
As the electrolytic solution enclosed in the case 2, known electrolytic solutions that are usually used for power storage elements can be used. For example, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or diethyl A solution in which lithium hexafluorophosphate (LiPF ₆ ) or the like is dissolved in a solvent containing a chain carbonate such as carbonate (DEC), dimethyl carbonate (DMC), or ethyl methyl carbonate (EMC) can be used.

  The lower limit of the viscosity of the electrolytic solution is preferably 0.01 cP or more and 5 cP or less. By setting the viscosity of the electrolytic solution to be equal to or higher than the lower limit, the electrolytic solution has sufficient ion conductivity, and the performance of the power storage element can be improved. Moreover, the liquid injection property of the electrolyte solution to the separator 5 at the time of manufacture is improved by setting the viscosity of the electrolyte solution to the upper limit or less.

[Method of manufacturing power storage element]
1 may be manufactured by a manufacturing method according to another embodiment of the present invention. The manufacturing method includes pressing the case 2 in which the electrode body 1 in which the positive electrode plate 3 and the negative electrode plate 4 are stacked via the separator 5 and the electrolytic solution are housed, and the pressing is performed during the pressing. The pressing amount is determined such that the relationship between the air permeability resistance A of the previous separator and the air resistance B of the separator 5 after pressing satisfies A / B ≦ 0.89.

  Various methods can be applied as the pressing method. For example, there are a method in which the case 2 is sandwiched and pressed between two flat plates and defined by a distance between the flat plates, a method in which the pressure is applied to the flat plate, and the like. Conceivable. In this case, the pressure applied to the flat plate was adjusted between 0.01 and 4.0 MPa to determine the target pressing amount.

  Moreover, in the manufacturing method of the said electrical storage element, it is preferable to charge in the state which pressed the case 2. FIG. Thereby, the gas generated at the time of charging can be discharged at the manufacturing stage, and expansion of the case 2 in use can be prevented.

  As described above, the method for manufacturing the electric storage element manages the ratio of the air permeability resistance A of the separator before pressing and the air resistance B of the separator after pressing to the separator 5 as described above. The electrolytic solution can be injected relatively easily, and the cycle life characteristics and coulombic efficiency of the obtained energy storage device can be improved.

[Other Embodiments]
The said embodiment does not limit the structure of this invention. Therefore, in the above-described embodiment, components of each part of the above-described embodiment can be omitted, replaced, or added based on the description and common general knowledge of the present specification, and they are all interpreted as belonging to the scope of the invention. Should.

  In the power storage element, the electrode body may be a stacked type in which a plurality of positive plates and negative plates are stacked via a separator.

  In the power storage element, the case may be formed of a flexible material, and may further include an exterior body that presses the case and compresses the separator of the electrode body.

  In addition, the power storage element may be one in which the separator is plastically deformed by pressing the case and compressed, and then the pressing force is removed to remove elastic strain.

  FIG. 2 shows a schematic diagram of a rectangular nonaqueous electrolyte secondary battery 10 which is an embodiment of the electricity storage device according to the present invention. In the figure, the inside of the battery container is seen through. A non-aqueous electrolyte secondary battery 10 shown in FIG. 2 includes an electrode body 11 in which a positive electrode plate and a negative electrode plate are laminated via a separator, and a case 12 that houses the electrode body 11. The electrode body 11 is formed by winding a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material via a separator. The case 12 has a positive terminal 13 and a negative terminal 14. The positive electrode of the electrode body 11 is electrically connected to the positive electrode terminal 13 via the positive electrode lead 15, and the negative electrode of the electrode body 11 is electrically connected to the negative electrode terminal 14 via the negative electrode lead 16.

  The configuration of the energy storage device according to the present invention is not particularly limited, and examples include a rectangular energy storage device (rectangular energy storage device), a flat energy storage device, and the like. The present invention can also be realized as a power storage device including a plurality of the above power storage elements. One embodiment of a power storage device is shown in FIG. In FIG. 3, the power storage device 30 includes a plurality of power storage units 20. Each power storage unit 20 includes a plurality of nonaqueous electrolyte secondary batteries 10. The power storage device 30 can be mounted as a power source for vehicles such as an electric vehicle (EV), a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), and the like.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

  By producing an electrode body in which a positive electrode plate and a negative electrode plate are laminated via a separator, and placing the electrode body in a case and injecting an electrolytic solution, batteries 1 to 4 that are prototypes of the storage element are obtained. Prototype. Also, an electrode body in which a positive electrode plate and a negative electrode plate are laminated via a separator is prepared, and the electrode body separator is pressed by placing the electrode body in a case and injecting an electrolytic solution, and then pressing the case. Batteries 5 to 10, which are prototypes of power storage elements, were manufactured by compressing in the thickness direction. In the batteries 1 to 10, the distance from the opening of the case to the center position in the axial direction of winding of the electrode body was 60 mm.

  About these batteries 1-10, the initial stage discharge capacity confirmation test was done on the following charging / discharging conditions. The battery was charged to 4.35 V at a constant current of 40 A at 25 ° C., charged at a constant voltage of 4.35 V, and charged for a total of 3 hours including constant current charging and constant voltage charging. After charging, the battery was discharged at a constant current of 40 A to a discharge end voltage of 2.75 V, and this discharge capacity was defined as “initial capacity”.

  About each battery after initial stage discharge capacity measurement, the 45 degreeC cycle life test was done on condition of the following, and capacity retention and coulomb efficiency were measured.

  Charge to 4.35V at a constant current of 40A at 45 ° C, then charge at a constant voltage of 4.35V, charge for a total of 3 hours including constant current charge and constant voltage charge, then 40A at 45 ° C Discharging to 2.75 V at a constant current of 1 cycle was one cycle, and this cycle was repeated 300 cycles. After charging and discharging, a pause of 10 minutes was provided at 45 ° C. A battery that has completed 300 cycles is charged and discharged under the same conditions as the initial capacity confirmation test, and the discharge capacity at that time is defined as “capacity after cycle”, and the discharge capacity is divided by the amount of charged electricity to obtain “Coulomb efficiency”. Was calculated. Moreover, the retention rate of the discharge capacity before and after the 45 ° C. cycle life test was calculated as “capacity retention rate” by dividing “capacity after cycle” after the end of 300 cycles by “initial capacity”.

(Battery 1)
The battery 1 uses a positive electrode plate having a porosity of 25% of the active material layer, and has a heat resistance containing alumina particles having an average thickness of 16 μm as a separator, an air resistance of 300 s, and a porosity of 41%. It was prepared using a polyethylene separator having a layer on one side. In the process of making the battery 1, the time (injection time) required to inject a predetermined amount of the electrolyte into the case, that is, to infiltrate the separator with the electrolyte was 243 s. This battery 1 had a capacity retention of 71% and a Coulomb efficiency of 99.8%.

(Battery 2)
Battery 2 uses a positive electrode plate with an active material layer porosity of 25%, and has a separator having an average thickness of 16 m, an air resistance of 230 s, and a porosity of 46%, including alumina particles. It was prepared using a polyethylene separator having a layer on one side. The injection time in the production process of the battery 2 was 235 s. This battery 2 had a capacity retention of 71% and a Coulomb efficiency of 99.8%.

(Battery 3)
The battery 3 uses a positive electrode plate having a porosity of 25% of the active material layer, and has a heat resistance including alumina particles having an average thickness of 16 μm as a separator, an air resistance of 200 s, and a porosity of 48%. It was prepared using a polyethylene separator having a layer on one side. The injection time in the production process of this battery 3 was 221 s. This battery 3 had a capacity retention rate of 70% and a Coulomb efficiency of 99.8%.

(Battery 4)
The battery 4 uses a positive electrode plate with a porosity of 25% of the active material layer, and has a heat resistance containing alumina particles having an average thickness of 16 μm as a separator, an air resistance of 80 s, and a porosity of 58%. It was prepared using a polyethylene separator having a layer on one side. The injection time in the production process of the battery 4 was 85 s. This battery 4 had a capacity retention rate of 54% and a Coulomb efficiency of 92.7%.

(Battery 5)
Battery 5 uses a positive electrode plate with an active material layer porosity of 25%, an average thickness of 16 μm as a separator before lamination (before pressing), an air resistance of 80 s, and a porosity of 58%. A polyethylene separator having a heat-resistant layer containing alumina particles on one side was used, and the separator was compressed in the thickness direction by pressing the case at 0.01 MPa after injecting the electrolyte. The injection time in the production process of the battery 5 was 85 s. Further, the separator after the battery 5 was pressed had an air permeability resistance of 90 s and a porosity of 55%. The battery 5 had a capacity retention rate of 57% and a Coulomb efficiency of 93.8%.

(Battery 6)
The battery 6 uses a positive electrode plate with a porosity of 25% in the active material layer, and has an average thickness of 16 μm as a separator before lamination (before pressing), an air resistance of 80 s, and a porosity of 58%. A polyethylene separator having a heat-resistant layer containing alumina particles on one side was used, and the separator was compressed in the thickness direction by pressing the case at 0.05 MPa after injecting the electrolyte. The injection time in the production process of the battery 6 was 85 s. Further, the separator after the battery 6 was pressed had an air permeability resistance of 150 s and a porosity of 53%. The battery 6 had a capacity retention rate of 62% and a Coulomb efficiency of 96.8%.

(Battery 7)
Battery 7 uses a positive electrode plate with an active material layer porosity of 25%, an average thickness of 16 μm as a separator before lamination (before pressing), an air resistance of 80 s, and a porosity of 58%. A polyethylene separator having a heat-resistant layer containing alumina particles on one side was used, and the separator was compressed in the thickness direction by pressing the case at 1.2 MPa after pouring the electrolyte. The injection time in the production process of the battery 7 was 85 s. Further, the separator after the battery 7 was pressed had an air permeability resistance of 200 s and a porosity of 48%. The battery 7 had a capacity retention rate of 76% and a Coulomb efficiency of 99.8%.

(Battery 8)
Battery 8 uses a positive electrode plate with an active material layer porosity of 25%, an average thickness of 16 μm as a separator before lamination (before pressing), an air resistance of 80 s, and a porosity of 58%. A polyethylene separator having a heat-resistant layer containing alumina particles on one side was used, and the separator was compressed in the thickness direction by pressing the case at 2.0 MPa after injecting the electrolyte. The injection time in the production process of the battery 8 was 85 s. Further, the separator after the battery 8 was pressed had an air permeability resistance of 230 s and a porosity of 46%. The battery 8 had a capacity retention rate of 79% and a Coulomb efficiency of 99.7%.

(Battery 9)
Battery 9 uses a positive electrode plate with an active material layer porosity of 25%, an average thickness of 16 μm as a separator before lamination (before pressing), an air resistance of 80 s, and a porosity of 58%. A polyethylene separator having a heat-resistant layer containing alumina particles on one side was used, and the separator was compressed in the thickness direction by pressing the case at 3.0 MPa after electrolyte injection. The injection time in the production process of the battery 9 was 85 s. Further, the separator after pressing the battery 9 had an air permeability resistance of 260 s and a porosity of 43%. This battery 9 had a capacity retention rate of 77% and a Coulomb efficiency of 99.7%.

(Battery 10)
Battery 10 uses a positive electrode plate with an active material layer porosity of 25%, an average thickness of 16 μm as a separator before lamination (before pressing), an air resistance of 80 s, and a porosity of 58%. A polyethylene separator having a heat-resistant layer containing alumina particles on one side was used, and the separator was compressed in the thickness direction by pressing the case at 4.0 MPa after electrolyte injection. The injection time in the production process of the battery 10 was 85 s. Further, the separator after the battery 10 was pressed had an air resistance of 300 s and a porosity of 41%. The battery 10 had a capacity retention rate of 75% and a Coulomb efficiency of 99.5%.

  In Table 1 below, for these batteries 1 to 10, the air permeability resistance A of the separator before lamination (before pressing), the air resistance B of the separator (after pressing) in the battery, and the ratio A / B thereof Summarize the porosity C of the separator before lamination (before pressing), the porosity D of the separator in the battery (after pressing) and their ratio D / C, the electrolyte injection time, the capacity retention, and the Coulomb efficiency. Show.

  The batteries 1 to 3 having a large air resistance (A) before pressing the separator have a long injection time required to infiltrate the electrolyte solution, whereas the batteries 4 having a small air resistance before pressing the separator are small. No. 10 is excellent in manufacturing efficiency because the injection time is short and the manufacturing efficiency is short.

  However, even if the air resistance before pressing the separator is small, the battery 4 has a large ratio (A / B) of the air resistance (A) before pressing the separator to the air resistance (B) after pressing. Has low capacity retention and coulomb efficiency. On the other hand, the air resistance before pressing the separator is small, and the ratio (A / B) of the air resistance (A) before pressing the separator to the air resistance (B) after pressing is 0. Batteries 5 to 10 which are .89 or less are excellent in capacity retention and coulomb efficiency. In particular, the batteries 7 to 10 in which the ratio (A / B) of the air permeability resistance (A) before pressing the separator to the air resistance (B) after pressing is 0.40 or less include the capacity retention ratio and coulomb. It is particularly efficient.

  Batteries 1 to 4 in which the ratio (D / C) of the porosity (D) after pressing to the porosity (C) before pressing the separator is 1 have a longer electrolyte injection time or a capacity retention rate. And the coulomb efficiency is small. For this reason, by reducing the ratio (D / C) of the porosity (D) after pressing to the porosity (C) before pressing the separator to less than 1, the capacity retention rate while shortening the injection time of the electrolytic solution In addition, the coulomb efficiency can be increased. Specifically, in the batteries 5 to 10 in which the ratio (D / C) of the porosity (D) after pressing to the porosity (C) before pressing the separator is 0.95 or less, the electrolyte injection time is Despite being short, the capacity retention rate and the coulomb efficiency are sufficiently large. In particular, the batteries 7 to 10 in which the ratio (D / C) of the porosity (D) after pressing to the porosity (C) before pressing the separator is 0.83 or less have particularly high capacity retention and Coulomb efficiency. It is a value.

  Thus, by increasing the air permeability resistance of the separator before pressing (during liquid injection), the injection time can be shortened to improve the production efficiency of the electricity storage device, and the separator is pressed after injection. Thus, it was confirmed that the capacity retention rate and the coulomb efficiency can be improved by reducing the air resistance.

  The method for manufacturing a power storage element and the power storage element according to the embodiment of the present invention can be used as a power source for various devices such as automobiles and mobile phones.

DESCRIPTION OF SYMBOLS 1 Electrode body 2 Case 3 Positive electrode plate 4 Negative electrode plate 5 Separator 6 Press wall 7 Connection wall 10 Nonaqueous electrolyte secondary battery 11 Electrode body 12 Case 13 Positive electrode terminal 14 Negative electrode terminal 15 Positive electrode lead 16 Negative electrode lead 20 Power storage unit 30 Power storage device

Claims (8)

Including pressing an electrode body in which a positive electrode plate and a negative electrode plate are laminated via a separator, and an electrolytic solution housed therein,
When the air resistance of the separator before pressing is A [s] and the air resistance of the separator after pressing is B [s], the relationship between A and B is A / B ≦ 0.89. The manufacturing method of the electrical storage element which is.   The method for manufacturing a power storage element according to claim 1, wherein the relationship between A and B is A / B ≦ 0.40.   The relationship between C and D is C> D, where C [%] is the porosity of the separator before pressing and D [%] is the porosity of the separator after pressing. The manufacturing method of the electrical storage element of Claim 2.   The method for manufacturing a power storage element according to claim 3, wherein the relationship between C and D is D / C ≦ 0.95.   The method for manufacturing a storage element according to claim 4, wherein the relationship between C and D is D / C ≦ 0.83.   The method for manufacturing a power storage element according to any one of claims 1 to 5, wherein the positive electrode plate has a composite material layer, and the porosity of the composite material layer is 20% or more and 35% or less.   The method for manufacturing a power storage element according to claim 1, wherein the electrolytic solution has a viscosity of 0.01 cP or more and 5 cP or less. An electrode body in which a positive electrode plate and a negative electrode plate are laminated via a separator, and a case for housing the electrode body,
The separator has a facing portion facing the positive electrode plate and the negative electrode plate, and a non-facing portion not facing the positive electrode plate and / or the negative electrode plate,
When the air permeation resistance at the facing part of the separator is B [s] and the air permeation resistance at the non-opposing part of the separator is A [s], the relationship between A and B is A / B ≦ 0. 89, an electricity storage device;

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