JP5023541B2 - Manufacturing method of secondary battery - Google Patents

Description

  The present invention relates to a secondary battery. In particular, the present invention relates to an improvement for further improving the capacity characteristics of a secondary battery.

  In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide has been strongly desired. In the automobile industry, there is a great expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV), and the development of secondary batteries for motor drive that holds the key to commercialization of these is thriving. Has been done.

  As a secondary battery for driving a motor, a lithium ion secondary battery having the highest theoretical energy among all the batteries is attracting attention, and is currently being developed rapidly. Generally, a lithium ion secondary battery includes a positive electrode in which a positive electrode active material or the like is applied to both surfaces of a positive electrode current collector using a binder, and a negative electrode in which a negative electrode active material or the like is applied to both surfaces of a negative electrode current collector using a binder. However, it has the structure connected through an electrolyte layer and accommodated in a battery case.

  In order to improve characteristics such as capacity characteristics and output characteristics of the lithium ion secondary battery, selection of the active material constituting each active material layer is extremely important.

Here, conventionally, as a candidate for a positive electrode active material of a lithium ion secondary battery, xLi [Mn _1/2 Ni _1/2 ] O ₂ .yLiCoO ₂ .zLi [Li _1/3 ] which is a pseudo ternary solid solution. Mn _2/3 ] O ₂ (x + y + z = 1, 0 <x <1, 0 ≦ y <0.5, 0 <z <1) has been proposed (for example, see Non-Patent Document 1). Since this active material has a high discharge capacity of 200 mAh / g and is excellent in cycle durability and thermal stability, it is a promising candidate for a positive electrode active material.
Journal of Electrochemical Society, 152 (9) A1879-A1889 (2005)

  However, the present inventors have found that when the above-described quasi-ternary solid solution is used as a positive electrode active material, there is a problem that irreversible capacity is large and initial charge / discharge loss occurs. That is, when the pseudo ternary solid solution is used as a positive electrode active material, a certain ratio (for example, about 20%) cannot be used for charge / discharge with respect to the theoretical capacity that can be originally exhibited, resulting in a loss. The cause of the occurrence of such initial charge / discharge loss is not completely clear, but since the initial charge / discharge loss increases as the z value in the above general formula increases, Mn is present in the pseudo-ternary solid solution. Presumably due to inclusion.

  By the way, the electric capacity utilized at the time of the discharge after a full charge is equal between each active material which comprises each electrode active material layer of a lithium ion secondary battery. Therefore, even when each active material is used in an amount having the same theoretical capacity, if the initial charge / discharge loss as described above occurs in the positive electrode active material, the negative electrode active material that is the counterpart is at the time of discharge after full charge. The theoretical capacity of the material is not fully utilized, and the capacity corresponding to the initial charge / discharge loss of the positive electrode active material is wasted. This phenomenon is noticeably manifested when an active material (for example, graphite) having almost no initial charge / discharge loss is used as the negative electrode active material, and the energy density of the battery is reduced.

  Accordingly, an object of the present invention is to provide means capable of preventing a decrease in capacity characteristics of the entire battery due to an initial charge / discharge loss of the positive electrode active material in a secondary battery employing a predetermined positive electrode active material. .

  The present inventors have intensively studied to solve the above problems. As a result, when the pseudo ternary solid solution is used as the positive electrode active material, by adopting a compound capable of generating the same initial charge / discharge loss as the negative electrode active material, the generated losses are canceled, and the positive electrode active material The present inventors have found that the reversible capacities of both the negative electrode active material and the negative electrode active material can be used effectively, thereby completing the present invention.

That is, the present invention comprises a positive electrode active material layer containing a positive electrode active material formed on the surface of a current collector,
A secondary battery having a battery element including at least one unit cell in which an electrolyte layer and a negative electrode active material layer including a negative electrode active material formed on the surface of a current collector are laminated in this order, The positive electrode active material is xLi [Mn _1/2 Ni _1/2 ] O ₂ .yLiCoO ₂ .zLi [Li _{1 /
3} Mn _2/3 ] O ₂ (x + y + z = 1, 0 <x <1, 0 ≦ y <0.5, 0 <z <1), and the initial charge / discharge loss capacity of the negative electrode active material is reversible electric capacity It is a manufacturing method of a secondary battery characterized by being 10% or more. And the said manufacturing method is a battery element preparation process which produces a battery element,
Injecting an electrolyte containing no redox shuttle into the battery element;
Performing a first charge / discharge treatment until the battery voltage is 4.5 V or higher;
Adding a redox shuttle to the electrolyte ;
A degassing step of extracting the gas generated during the first charge / discharge treatment from the battery element;
A sealing step for sealing the battery element;
Have

  According to the present invention, in a secondary battery employing a predetermined positive electrode active material, it is possible to effectively prevent a decrease in capacity characteristics of the entire battery due to an initial charge / discharge loss of the positive electrode active material.

  Embodiments of the present invention will be described below.

The present invention includes a positive electrode active material layer including a positive electrode active material formed on the surface of a current collector, an electrolyte layer, and a negative electrode active material layer including a negative electrode active material formed on the surface of the current collector, Is a secondary battery having a battery element including at least one single battery stacked in this order, wherein the positive electrode active material is xLi [Mn _1/2 Ni _1/2 ] O ₂ .yLiCoO ₂ .zLi [Li _1/3 Mn _2/3 ] O ₂ (x + y + z = 1, 0 <x <1, 0 ≦ y <0.5, 0 <z <1), the initial charge / discharge loss capacity of the negative electrode active material is reversible It is a secondary battery characterized by being 10% or more of electric capacity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention should be determined based on the description of the scope of claims, and is not limited to the following embodiments. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

(First embodiment)
(Constitution)
FIG. 1 is a cross-sectional view showing an outline of the secondary battery of the present embodiment, which is a bipolar lithium ion secondary battery (hereinafter also referred to as “bipolar battery”). In the present specification, a bipolar battery will be described in detail as an example, but the technical scope of the present invention is not limited to such a form.

  The bipolar battery 10 of this embodiment shown in FIG. 1 has a structure in which a substantially rectangular battery element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is an exterior.

  As shown in FIG. 1, the battery element 21 of the bipolar battery 10 of this embodiment has a positive electrode active material layer 13 formed on one surface of a current collector 11 and a negative electrode active material layer 15 formed on the other surface. A plurality of bipolar electrodes. Each bipolar electrode is laminated via an electrolyte layer 17 to form a battery element 21. At this time, each bipolar type is formed such that the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode face each other through the electrolyte layer 17. An electrode and an electrolyte layer 17 are laminated.

  The adjacent positive electrode active material layer 13, electrolyte layer 17, and negative electrode active material layer 15 constitute one unit cell layer 19. Therefore, it can be said that the bipolar battery 10 has a configuration in which the single battery layers 19 are stacked and electrically connected in series. In addition, an insulating layer 31 for insulating adjacent current collectors 11 is provided on the outer periphery of the unit cell layer 19. The current collector (outermost layer current collector) (11a, 11b) located in the outermost layer of the battery element 21 has a positive electrode active material layer 13 (positive electrode side outermost layer current collector 11a) or a negative electrode only on one side. One of the active material layers 15 (negative electrode side outermost layer current collector 11b) is formed.

  Furthermore, in the bipolar battery 10 shown in FIG. 1, the positive electrode side outermost layer current collector 11a is extended to form a positive electrode tab 25, which is led out from a laminate sheet 29 which is an exterior. On the other hand, the negative electrode side outermost layer current collector 11 b is extended to form a negative electrode tab 27, which is similarly derived from the laminate sheet 29.

  Hereinafter, a characteristic configuration of the present embodiment will be described in detail.

First, the bipolar battery 10 of the present embodiment includes, as a positive electrode active material, xLi [Mn _1/2 Ni _1/2 ] O ₂ .yLiCoO ₂ .zLi [Li _1/3 Mn, which is a pseudo ternary solid solution. _2/3 ] It is characterized in that it contains O ₂ .

  In the above general formula representing the positive electrode active material that is an essential component in the positive electrode active material layer of the bipolar battery of the present embodiment, 0 <x <1, 0 ≦ y <0.5, and 0 <z <1. And x + y + z = 1.

  As the predetermined positive electrode active material described above, when a product is commercially available, the product may be purchased and used, or an active material prepared by itself may be used. When the active material is prepared by itself, for example, the description of Non-Patent Document 1 (Journal of Electrochemical Society, 152 (9) A1879-A1889 (2005)) can be referred to.

In addition, the positive electrode active material layer of the secondary battery of this embodiment may include other positive electrode active materials in addition to the predetermined positive electrode active material described above. The specific form of the other positive electrode active material is not particularly limited, and conventionally known knowledge can be referred to as appropriate. Examples of other positive electrode active materials include lithium-transition metal composite oxides such as Li—Mn composite oxides such as LiMn ₂ O ₄ and Li—Ni composite oxides such as LiNiO ₂ . As for these positive electrode active materials, only 1 type may be used independently and 2 or more types may be used together.

  Here, from the viewpoint of sufficiently exerting the effects of the present invention, the content of the predetermined positive electrode active material described above is 30 to 100% by mass with respect to the total amount of the positive electrode active material contained in the positive electrode active material layer. It is preferable that However, it goes without saying that forms outside these ranges may be employed.

  Second, the bipolar battery 10 of the present embodiment is characterized in that the initial charge / discharge loss capacity of the negative electrode active material is 10% or more of the reversible electric capacity. Thus, by setting the initial charge / discharge loss capacity of the negative electrode active material to be increased to some extent, the initial charge / discharge loss capacity is reduced to the initial charge / discharge loss generated in the predetermined positive electrode active material described above during the initial charge / discharge. Can correspond. As a result, the initial charge / discharge losses that occur in both the positive electrode active material and the negative electrode active material cancel each other, and the occurrence of problems such as a decrease in the overall battery capacity due to the initial charge / discharge loss in the positive electrode active material is effectively suppressed. Can be done.

  In the present embodiment, the initial charge / discharge loss capacity of the negative electrode active material may be 10% or more of the reversible electric capacity of the negative electrode active material, preferably 10 to 50%, more preferably 10 to 30%. It is. When the initial charge / discharge loss capacity of the negative electrode active material is within such a range, the effect of the present invention can be sufficiently exhibited while maintaining the absolute value of the reversible electric capacity of the negative electrode active material at a high value. Is possible. The ratio of the initial charge / discharge loss capacity to the reversible electric capacity of the negative electrode active material can be measured by charging / discharging at a low rate of about 0.1 C using lithium metal as a counter electrode.

  The specific form of the negative electrode active material in which the ratio of the initial charge / discharge loss capacity becomes a value within the above-described range is not particularly limited, and conventionally known knowledge can be appropriately referred to. Further, a newly developed negative electrode active material may be used. Specific examples of the negative electrode active material that can be used in the present embodiment include, for example, hard carbon (ratio of initial charge / discharge loss capacity to reversible electric capacity = about 15 to 30%) and soft carbon (initial charge / discharge to reversible electric capacity). Amorphous carbon such as a ratio of loss capacity = about 15 to 30%). Among these, hard carbon can be preferably used from the viewpoint that the absolute value of the reversible electric capacity is large.

  Note that the negative electrode active material layer of the secondary battery of the present embodiment may include other negative electrode active materials in addition to the predetermined negative electrode active material described above. The specific form of the other negative electrode active material is not particularly limited, and conventionally known knowledge can be referred to as appropriate. Examples of other negative electrode active materials include alloys that can occlude and release lithium by charge / discharge of graphite, silicon, tin, germanium, aluminum, and lead, and composites thereof. As for these negative electrode active materials, only 1 type may be used independently and 2 or more types may be used together. When two or more kinds of negative electrode active materials are used in combination, the mass average value of all negative electrode active materials included in the negative electrode active material layer 15 is used as the value of “ratio of initial charge / discharge loss capacity to reversible electric capacity”. Shall be adopted.

  Here, from the viewpoint of sufficiently exerting the effects of the present invention, the content of the predetermined negative electrode active material described above is 30 to 100% by mass with respect to the total amount of the negative electrode active material contained in the negative electrode active material layer. It is preferable that However, it goes without saying that forms outside these ranges may be employed.

  Also about the negative electrode active material mentioned above, when goods are marketed, the goods may be purchased and used, and the active material prepared by itself may be used.

  Hereinafter, the mechanism by which the effect of the present invention described above can be obtained will be described with reference to the drawings.

  FIG. 2 is a schematic diagram for explaining a mechanism by which the effect of the present invention can be obtained. Each figure of FIG. 2 is a figure which shows the state in each time of charging / discharging of the battery of this embodiment. The vertical axis indicates the capacity density (dQ / dE) of each active material, and the horizontal axis indicates the potential. Further, the straight line P indicates the potential of the positive electrode, and the straight line N indicates the potential of the negative electrode. Therefore, the distance between the straight line P and the straight line N indicates the battery voltage. The shaded portion indicates the chargeable capacity (reversible capacity), and the shaded area indicates the non-dischargeable charge capacity (irreversible capacity).

  Fig.2 (a) is a figure which shows the state immediately after battery preparation. Immediately after manufacturing the battery and before charging, the potential of each electrode is about ± 0.5 V, and the battery voltage is about 1 V. The reason why a potential is generated in the electrode immediately before charging immediately after the battery is produced and a constant battery voltage is generated is not completely clear, but it is considered that a very small amount of impurities are involved.

  When charging is started, a charging reaction proceeds in the active material. FIG.2 (b) is a figure which shows the state in the middle of initial stage charge / discharge. At this time, in the bipolar battery of this embodiment, as shown in FIG. 2B, a certain ratio of the charged positive electrode active material and negative electrode active material is an irreversible capacity.

  When the charging is further continued, the charging reaction proceeds in both the positive electrode active material and the negative electrode active material, and the charging is completed when at least one of the positive electrode active material and the negative electrode active material is completely charged. FIG.2 (c) is a figure which shows the state (full charge state) in which charge was completed.

  On the other hand, when the discharge is started, the discharge corresponding to the reversible capacity proceeds in both the positive electrode active material and the negative electrode active material, and the discharge corresponding to the irreversible capacity is not performed.

  Here, FIG. 3 employs the above-described predetermined quasi-ternary solid solution as the positive electrode active material, and has almost no initial charge / discharge loss (ratio of initial charge / discharge loss capacity to reversible electric capacity = about 4.6%). It is a figure which shows the state which the discharge in the battery which employ | adopted as a negative electrode active material was completed. Thus, when the predetermined solid solution described above is used as the positive electrode active material, if graphite or the like is used as the negative electrode active material, the same amount of irreversible capacity as that generated in the positive electrode active material is generated in the negative electrode active material. Will also occur. When the irreversible capacity as shown in the figure is generated in the negative electrode active material, the capacity characteristics of the entire battery are deteriorated.

  FIG. 2D is a diagram illustrating a state in which the discharge in the battery of the present embodiment has been completed. In the present embodiment, an active material having an initial charge / discharge loss of a certain ratio or more is used as the negative electrode active material. As a result, as shown in FIG. 2D, an irreversible capacity derived from the initial charge / discharge loss of the predetermined positive electrode active material used in the present embodiment was generated in the negative electrode active material used in the present embodiment as well. It will be canceled by the initial charge / discharge loss. As a result, during the subsequent charge / discharge, the charge / discharge reaction proceeds at a portion corresponding to the reversible capacity shown in FIG. 2 (d), and the active material can be used efficiently. However, the technical scope of the present invention is not limited only to the form in which the initial charge / discharge loss generated in the positive electrode active material is completely canceled by the initial charge / discharge loss in the negative electrode active material. The capacity of the negative electrode may be excessive with respect to the positive electrode so that no abnormal reaction occurs at the negative electrode even under severe use conditions.

  As described above, according to the battery of the present embodiment, problems such as a decrease in discharge capacity in the negative electrode active material and a decrease in capacity characteristics of the entire battery due to this can be solved. Note that the above mechanism is merely an estimate, and the technical scope of the present invention is not affected at all even if the capacity characteristics of the battery are improved by other mechanisms.

  Hereinafter, although the member which comprises the bipolar battery 10 of this embodiment is demonstrated easily, it is not restrict | limited only to the following form, A conventionally well-known form can be employ | adopted similarly.

[Current collector (including outermost layer current collector)]
The current collector 11 and the outermost layer current collector (11a, 11b) are made of a conductive material such as an aluminum foil, a copper foil, or a stainless steel (SUS) foil. The general thickness of the current collector is 1 to 30 μm. However, a current collector having a thickness outside this range may be used.

  The size of the current collector 11 is determined according to the intended use of the bipolar battery 10. If a large electrode used for a large battery is manufactured, a current collector having a large area is used. If a small electrode is produced, a current collector with a small area is used.

[Active material layer]
The active material layer contains an active material, and further contains other additives as necessary.

  The positive electrode active material layer 13 includes a predetermined pseudo ternary solid solution as a positive electrode active material. Note that since the specific structure of the active material is as described above, the description thereof is omitted here. Further, as described above, the positive electrode active material layer 13 may contain an active material other than the above.

  The negative electrode active material layer 15 includes a negative electrode active material having a ratio of initial charge / discharge loss to reversible electric capacity of 10% or more. Note that since the specific structure of the active material is as described above, the description thereof is omitted here. Further, as described above, the negative electrode active material layer 15 may contain an active material other than the above.

  The average particle diameter of each active material contained in each active material layer (13, 15) is not particularly limited, and can be appropriately adjusted with reference to conventionally known knowledge. Preferably, the average particle diameter of the active material is about 1 to 30 μm. However, it is of course possible to use an active material having a particle size outside this range.

  Each active material layer (13, 15) may contain other materials if necessary. For example, a binder, a conductive additive, a lithium salt (supporting electrolyte), an ion conductive polymer, and the like can be included. When an ion conductive polymer is included, a polymerization initiator for polymerizing the polymer may be included.

  Examples of the binder include polyvinylidene fluoride (PVdF) and a synthetic rubber binder.

  A conductive support agent means the additive mix | blended in order to improve the electroconductivity of an active material layer (13,15). Examples of the conductive auxiliary agent include acetylene black.

As a lithium salt (supporting electrolyte), LiBETI (lithium bis (perfluoroethylenesulfonylimide); Li (C ₂ F ₅ SO ₂ ) ₂ N), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ Etc.

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers. Here, the ion conductive polymer may be the same as or different from the ion conductive polymer used as the electrolyte in the electrolyte layer 17 of the bipolar battery 10, but is preferably the same.

  The polymerization initiator is added to act on the crosslinkable group of the ion conductive polymer to advance the crosslinking reaction. Depending on the external factor for acting as an initiator, it is classified into a photopolymerization initiator, a thermal polymerization initiator and the like. Examples of the polymerization initiator include azobisisobutyronitrile (AIBN), which is a thermal polymerization initiator, and benzyl dimethyl ketal (BDK), which is a photopolymerization initiator.

  The compounding ratio of each component contained in each active material layer (13, 15) is not particularly limited. The blending ratio can be adjusted by appropriately referring to known knowledge about lithium ion secondary batteries.

[Electrolyte layer]
In general, the electrolyte constituting the electrolyte layer 17 includes a liquid electrolyte or a polymer electrolyte. In the present invention, a polymer electrolyte is preferably used. By using the polymer electrolyte, leakage of electrolyte and the like can be prevented, and the safety of the bipolar battery 10 can be improved.

  The polymer electrolyte is composed of an ion conductive polymer, and the material is not limited as long as it exhibits ion conductivity. In view of the fact that excellent mechanical strength can be expressed, a polymerized ion conductive polymer that is crosslinked by thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, or the like is preferably used. By using such a crosslinked polymer, the reliability of the battery is improved, and the bipolar battery 10 having a simple configuration and excellent output characteristics is manufactured.

  Examples of the polymer electrolyte include an intrinsic polymer electrolyte and a gel polymer electrolyte.

  The intrinsic polymer electrolyte is not particularly limited, and examples thereof include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. In such polyalkylene oxide polymers, electrolyte salts such as lithium salts can be well dissolved. In addition, these polymers can exhibit excellent mechanical strength by forming a crosslinked structure.

The gel polymer electrolyte generally refers to an electrolyte solution held in an all-solid polymer electrolyte having ion conductivity. In the present application, a gel polymer electrolyte also includes a polymer skeleton having no lithium ion conductivity and a similar electrolyte solution held therein. The kind of electrolyte solution (electrolyte salt and plasticizer) used is not particularly limited. Examples of the electrolyte salt include lithium salts such as LiBETI, LiBF ₄ , LiPF ₆ , and LiN (SO ₂ CF ₃ ) ₂ . Examples of the plasticizer include carbonates such as propylene carbonate and ethylene carbonate.

  When the electrolyte layer includes a gel polymer electrolyte, the electrolyte layer may be formed by impregnating a gel polymer raw material solution into a separator such as a nonwoven fabric and then polymerizing using the various methods described above. . By using the separator, the filling amount of the electrolytic solution can be increased, and the thermal conductivity inside the battery can be ensured.

  In a more preferred form of the present embodiment, the electrolyte layer 17 includes a redox shuttle. A “redox shuttle” is a compound having a function of preventing a potential difference (battery voltage) between positive and negative electrodes from exceeding a predetermined value (ie, overcharge) through an oxidation-reduction reaction. Specifically, the redox shuttle, which is originally a reduction type (non-ion type), is oxidized at the positive electrode to become an oxidation type (cationic type) when the battery voltage exceeds a predetermined value during charging. It is reduced and returns to the reduced type (non-ionic type) again. By repeating this cycle, overcharge is prevented, and as a result, the occurrence of problems such as a decrease in battery reliability associated therewith is prevented.

  Here, for example, as shown in FIG. 4, consider the case where three cells are connected in series. In this case, even though the battery 1 and the battery 3 shown in FIG. 4 are in a fully charged state, if the charged state of the battery 2 is not 100%, the batteries 1 to 1 are used for the purpose of putting the battery 2 in a fully charged state It is necessary to further charge the battery for all three batteries. However, if such a charging process is applied to the batteries 1 and 3 that are already fully charged, these batteries are overcharged, and the above-described problem may occur.

  On the other hand, when the electrolyte layer includes a redox shuttle as in the preferred embodiment described above, the battery voltage is increased by the action of the redox shuttle even when the battery 2 is further charged to make the battery 2 fully charged. It is prevented that the voltage exceeds a certain value (redox shuttle oxidation start potential). As a result, the battery 2 can be fully charged without making the battery 1 and the battery 3 excessively charged.

  Here, the oxidation start potential of the redox shuttle contained in the electrolyte layer is not particularly limited, but from the viewpoint of fully utilizing the battery capacity, the oxidation start potential of the redox shuttle is 4.2 V or more with respect to lithium. Preferably, it is 4.2 to 5.0V, more preferably 4.3 to 4.7V. However, it goes without saying that a redox shuttle in a form outside these ranges may be used.

There is no restriction | limiting in particular also about the specific form of a redox shuttle, The compound which can exhibit the effect mentioned above can be employ | adopted suitably. An example of the redox shuttle together with the value of the oxidation initiation potential for lithium is, for example, hexaethylbenzene (about 4.5 V), Li ₂ B ₁₂ F ₁₂ (about 4.5 V), Li ₂ B ₁₂ F ₉ H ₃ (about 4.35V). Only 1 type of these redox shuttles may be used independently, and 2 or more types may be used together.

  When a redox shuttle is contained in the electrolyte layer, the content of the redox shuttle in the electrolyte layer is not particularly limited, but is preferably 1 to 50 mol% with respect to the lithium ion concentration in the electrolyte layer. The amount to be included in the electrolyte layer is selected depending on the type of redox shuttle, the use condition of the battery, and the purpose of use of the battery. Needless to say, the redox shuttle of the lithium salt can be used as a lithium salt necessary for the electrolyte layer.

[Insulation layer]
In the bipolar battery 10, an insulating layer 31 is usually provided around each single battery layer 19. The insulating layer 31 prevents the adjacent current collectors 11 in the battery from coming into contact with each other or a short circuit caused by a slight irregularity at the end of the unit cell layer 19 in the battery element 21. Is provided. The installation of such an insulating layer 31 ensures long-term reliability and safety, and can provide a high-quality bipolar battery 10.

  The insulating layer 31 may be made of a material having insulating properties, sealing properties against falling off of the solid electrolyte, sealing properties against moisture permeation from the outside (sealing properties), heat resistance at the battery operating temperature, and the like. For example, urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber or the like can be used. Among these, polyethylene resin and polypropylene resin are preferably used as the constituent material of the insulating layer 31 from the viewpoints of corrosion resistance, chemical resistance, ease of production (film forming property), economy, and the like.

[tab]
In the bipolar battery 10, a laminate sheet 29 in which the tabs (the positive electrode tab 25 and the negative electrode tab 27) electrically connected to the outermost layer current collector (11 a, 11 b) are the exterior for the purpose of taking out current outside the battery. It is taken out outside. Specifically, a positive electrode tab 25 electrically connected to the positive electrode side outermost layer current collector 11a and a negative electrode tab 27 electrically connected to the negative electrode side outermost layer current collector 11b are provided outside the exterior. It is taken out.

  The material constituting the tabs (the positive electrode tab 25 and the negative electrode tab 27) is not particularly limited, and a known material conventionally used as a tab for a bipolar battery can be used. Examples of the constituent material of the tab include aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof. The positive electrode terminal 25 and the negative electrode terminal 27 may be made of the same material or different materials. Further, as in the present embodiment, the outermost layer current collectors (11a, 11b) may be extended to form tabs (25, 27), or a separately prepared tab may be connected to the outermost layer current collector. Good.

[Exterior]
In the bipolar battery 10, the battery element 21 is preferably housed in an exterior such as a laminate sheet 29 in order to prevent external impact and environmental degradation during use. The exterior is not particularly limited, and a conventionally known exterior can be used. A polymer-metal composite laminate sheet or the like excellent in thermal conductivity can be preferably used in that heat can be efficiently transferred from a heat source of an automobile and the inside of the battery can be rapidly heated to the battery operating temperature.

(Production method)
There is no restriction | limiting in particular about the manufacturing method of the bipolar battery 10 of this embodiment, It can manufacture with reference to conventionally well-known knowledge in the manufacturing field of a battery. Hereinafter, a preferred embodiment of the bipolar battery manufacturing method of the present invention in the case where the electrolyte layer contains an electrolytic solution will be described. The technical scope of the bipolar battery of the present invention is manufactured by the following manufacturing method. It is not limited to only.

  First, a slurry containing an active material is applied to a current collector and dried to produce a bipolar electrode. Here, when preparing the slurry containing a positive electrode active material, the predetermined pseudo ternary solid solution described above is added to the slurry. On the other hand, when preparing a slurry containing a negative electrode active material, the predetermined negative electrode active material described above is added to the slurry. Moreover, you may add another active material in each slurry as needed.

  Next, the bipolar electrode prepared above and the electrolyte layer are laminated to produce a battery element (battery element production process). Since the form of the specific member which comprises a battery element is as having mentioned above, description is abbreviate | omitted here. The method for producing the electrolyte layer is not particularly limited, and can be produced by a conventionally known method. In addition, there is no restriction | limiting in particular about the number of lamination | stacking of the bipolar electrode and electrolyte layer in a battery element, What is necessary is just to determine the number of lamination | stacking in consideration of the desired battery voltage about the obtained bipolar battery.

  Subsequently, a tab to which a lead is connected is bonded to the outermost layer of the obtained battery element, and the battery element is placed in a laminate sheet so that the lead is exposed to the outside.

  Subsequently, an electrolytic solution is prepared, and the prepared electrolytic solution is injected into the battery element prepared above (electrolytic solution injection step). Since the specific form of the electrolytic solution is also as described above, the description is omitted here.

  After injection of the electrolytic solution, the laminate sheet is sealed under reduced pressure. Next, an initial charge / discharge treatment is performed on the obtained battery (initial charge / discharge step). At this time, there is no particular limitation on the charge / discharge conditions in the initial charge / discharge treatment, but in order to fully exert the effects of the present invention, that is, the initial charge / discharge loss generated in the positive electrode active material and the negative electrode active material are generated. In order to efficiently cancel the initial charging / discharging loss, it is preferable to perform the initial charging / discharging process until the battery voltage becomes 4.5V or higher. On the other hand, the upper limit value of the maximum battery voltage in the initial charge / discharge treatment is not particularly limited, but is preferably 5.0 V or less from the viewpoint of preventing deterioration of the electrolyte, and is 4.8 V or less. More preferably.

  After the completion of the first charge / discharge treatment, the laminate sheet is once sealed, and the gas generated from the battery element in the first charge / discharge process is removed (gas release process). Thereby, it is possible to suppress the generated gas from staying between the layers constituting the battery element, and it is possible to prevent the occurrence of problems such as delamination due to gas retention.

  After the degassing step, the laminate sheet is again sealed under reduced pressure conditions (sealing step). Thereby, the bipolar battery of the present invention is completed.

  Then, the preferable form of the manufacturing method of the bipolar battery of this invention in case a redox shuttle is contained in an electrolyte layer is demonstrated.

  In the above-described manufacturing method, a series of steps including bipolar electrode production / battery element production / insertion into a laminate sheet / injection of electrolyte solution / laminate sheet sealing / initial charge / discharge / gas venting / resealing Thus, a bipolar battery is manufactured.

  Here, for example, consider a case where a bipolar battery in which a redox shuttle having an oxidation start potential of 4.5 V or less with respect to lithium is included in the electrolyte layer is to be manufactured. In this case, if a bipolar battery is manufactured by adding a redox shuttle from the beginning to the electrolytic solution in the above-described manufacturing method, the redox shuttle acts from the time when the battery voltage reaches the oxidation start potential of the redox shuttle in the initial charge / discharge process. I will start. Then, the battery voltage cannot be higher than the oxidation start potential of the redox shuttle. On the other hand, in order to efficiently cancel the initial charge / discharge loss between the positive and negative electrode active materials, which is the original effect of the bipolar battery of the present invention, the battery voltage value is set to a certain value in the initial charge / discharge process. It is necessary to do it above. From the above, if the redox shuttle is already included in the electrolyte in the initial charge / discharge step, the initial charge / discharge loss between the positive and negative electrode active materials is not efficiently canceled by the action of the redox shuttle. There is a risk that.

  Therefore, when a redox shuttle is to be included in the electrolyte layer, first, an electrolyte solution that does not include a redox shuttle is prepared. Then, in accordance with the above-described steps, the electrolyte solution is injected, the laminate sheet is sealed, the initial charge / discharge is performed, the degassing is performed, and then the redox shuttle is added to the electrolyte solution before the laminate sheet is resealed do it. By manufacturing a bipolar battery by such a method, the initial charge / discharge loss between the positive and negative electrode active materials in the initial charge / discharge process is efficiently canceled, and in the subsequent charge / discharge, a redox shuttle is used. It is possible to prevent excessive overcharge by exerting the above action.

  In addition, in the manufacturing method mentioned above, a redox shuttle is added to the electrolyte solution which does not contain a redox shuttle, However The addition form of the redox shuttle in this case is not restrict | limited in particular. For example, a solid redox shuttle such as powder may be added to the electrolyte as it is, or an electrolyte containing a redox shuttle is prepared in advance, and the redox shuttle is added by adding the electrolyte. Also good. However, the latter method can be preferably employed from the viewpoint of uniformly dispersing the redox shuttle throughout the battery element.

(Second Embodiment)
In the second embodiment, an assembled battery is configured by connecting a plurality of the bipolar batteries of the first embodiment in parallel and / or in series.

  FIG. 5 is a perspective view showing the assembled battery of the present embodiment.

  As shown in FIG. 5, the assembled battery 40 is configured by connecting a plurality of bipolar batteries described in the first embodiment. Each bipolar battery 10 is connected by connecting the positive electrode tab 25 and the negative electrode tab 27 of each bipolar battery 10 using a bus bar. On one side surface of the assembled battery 40, electrode terminals (42, 43) are provided as electrodes of the entire assembled battery 40.

  A connection method in particular when connecting the some bipolar battery 10 which comprises the assembled battery 40 is not restrict | limited, A conventionally well-known method can be employ | adopted suitably. For example, a technique using welding such as ultrasonic welding or spot welding, or a technique of fixing using rivets, caulking, or the like can be employed. According to such a connection method, the long-term reliability of the assembled battery 40 can be improved.

  According to the assembled battery 40 of the present embodiment, an assembled battery having excellent capacity characteristics can be provided by using the bipolar battery 10 of the first embodiment as an assembled battery.

  The bipolar batteries 10 constituting the assembled battery 40 may be connected in parallel to each other, or may be connected in series, or a combination of series connection and parallel connection. May be.

(Third embodiment)
In the third embodiment, the bipolar battery 10 of the first embodiment and / or the assembled battery 40 of the second embodiment is mounted as a motor driving power source to constitute a vehicle. As a vehicle using the bipolar battery 10 or the assembled battery 40 as a motor power source, for example, a complete electric vehicle not using gasoline, a hybrid vehicle such as a series hybrid vehicle or a parallel hybrid vehicle, and a fuel cell vehicle, a wheel motor is used. A car driven by

  For reference, FIG. 6 shows a schematic diagram of an automobile 50 on which the assembled battery 40 is mounted. The assembled battery 40 mounted on the automobile 50 has the characteristics as described above. For this reason, by mounting the assembled battery 40 on the automobile 50, the output characteristics of the automobile 50 are improved, and further, the automobile 50 can be further reduced in weight and size.

  As described above, some preferred embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and various modifications, omissions, and additions can be made by those skilled in the art. . For example, in the above description, a bipolar lithium ion secondary battery (bipolar battery) has been described as an example. However, the technical scope of the battery of the present invention is not limited to a bipolar battery. A lithium ion secondary battery that is not a bipolar type may also be used.

(Fourth embodiment)
(Constitution)
FIG. 7 is a cross-sectional view showing an outline of the secondary battery of the present embodiment, which is a lithium ion secondary battery that is not a bipolar type.

  As shown in FIG. 7, in the lithium ion secondary battery 60 that is not a bipolar type according to the present embodiment, a polymer-metal composite laminate film is used for the laminate sheet 29 that is the exterior of the battery, and the entire peripheral part is thermally fused. The battery element (power generation element) 21 is housed and sealed by bonding by wearing. Here, the battery element 21 includes a negative electrode plate in which the negative electrode active material layer 15 is formed on both surfaces of the negative electrode current collector 35 (one surface for the lowermost layer and the uppermost layer of the battery element 21), the electrolyte layer 17, and the positive electrode current collector. The electric body 33 has a configuration in which a plurality of positive electrode plates each having the positive electrode active material layer 13 formed thereon are stacked. At this time, the positive electrode active material layer 13 on one side of one positive electrode plate and the negative electrode active material layer 15 on one side of one negative electrode plate adjacent to the one positive electrode plate face each other with the electrolyte layer 17 therebetween, A plurality of layers are laminated in the order of the electrolyte layer and the negative electrode plate.

  As a result, the adjacent positive electrode active material layer 13, electrolyte layer 17, and negative electrode active material layer 15 constitute one unit cell layer 19. Therefore, it can be said that the lithium ion secondary battery 60 which is not a bipolar type has a configuration in which a plurality of single battery layers 19 are stacked and electrically connected in parallel. In addition, an insulating layer (not shown; refer to FIG. 1) for insulating the adjacent current collectors 33 and 35 may be provided on the outer periphery of the unit cell layer 19. Note that the positive electrode active material layer 13 is formed on only one side of the outermost negative electrode current collector 33 a located in both outermost layers of the battery element 21. In addition, by changing the arrangement of the positive electrode plate and the negative electrode plate in FIG. 7, the outermost layer negative electrode current collector (not shown) is positioned in both outermost layers of the battery element 21, and the outermost layer negative electrode current collector In some cases, the negative electrode active material layer may be formed only on one side.

  Furthermore, the positive electrode current collector 33 and the negative electrode current collector 35 of each electrode plate are extended, and ultrasonic waves are applied to the positive electrode tab 25 and the negative electrode tab 27 so as to be electrically connected to each of the above electrode plates (positive electrode plate and negative electrode plate). It is attached by welding, resistance welding, or the like, and is sandwiched between heat-sealed portions of the laminate sheet 29. Further, a part of the positive electrode tab 25 and the negative electrode tab 27 has a structure led out from the laminate sheet 29.

  The lithium ion secondary battery that is the subject of the present invention includes a positive electrode containing a predetermined pseudo ternary solid solution as a positive electrode active material, and a negative electrode containing a negative electrode active material having an initial charge / discharge loss of a predetermined ratio or more. There are no particular restrictions on other configuration requirements. For example, when the lithium ion secondary battery is distinguished by form / structure, it can be applied to any conventionally known form / structure such as a stacked (flat) battery or a wound (cylindrical) battery. Is. In addition, when viewed in terms of electrical connection (electrode structure) in a lithium ion secondary battery, it is not a bipolar type (internal parallel connection type) battery or a bipolar type (internal series connection type) battery. It can be applied. When distinguished by the type of electrolyte (layer) in the lithium ion secondary battery, a solution electrolyte type battery using a solution electrolyte such as a non-aqueous electrolyte as the electrolyte (layer), or a polymer electrolyte as the electrolyte (layer) A polymer battery using a polymer battery (the polymer battery is a gel electrolyte battery using a polymer gel electrolyte (also simply referred to as gel electrolyte), a solid polymer using a polymer solid electrolyte (also simply referred to as polymer electrolyte) (all It can be applied to any conventionally known electrolyte (layer). Among them, polymer batteries, especially solid polymer (all solid) batteries, do not leak, so that there is no problem of liquid junction, high reliability, and a simple configuration with excellent output characteristics. It is advantageous in that it can. In addition, by adopting a laminated (flat) battery structure, long-term reliability can be secured by a sealing technique such as simple thermocompression bonding, which is advantageous in terms of cost and workability.

  As described above, with respect to each constituent requirement and manufacturing method of the lithium ion secondary battery 60 that is not a bipolar type according to the present embodiment, the first embodiment is different except that the electrical connection form (electrode structure) in the lithium ion secondary battery is different. The same manufacturing method as that of the first embodiment already described, using the same configuration as the bipolar lithium ion secondary battery 10 of the embodiment and the same components as those described in the first embodiment. Can be applied.

  Further, the non-bipolar lithium ion secondary battery 60 of the present embodiment can be used to form the positive electrode active material layer as in the second embodiment, or the assembled battery as in the third embodiment. Or the vehicle of 4th Embodiment can also be comprised. Furthermore, the assembled battery as in the third embodiment or a vehicle using the same may be configured by combining the lithium ion secondary battery 60 that is not bipolar and the bipolar lithium ion secondary battery 10.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

Example 1
An electrode was produced by the following method, and a test cell was further produced using the produced electrode.

<Preparation of positive electrode>
First, a positive electrode active material was synthesized. Specifically, Journal of Electrochemical Society, 152 ( 9) A1879-A1889 according mixed hydroxide method described in _{(2005), LiOH · 2H 2} O as the raw _{material, Ni (NO 3) 2 ·} 6H 2 O And Mn (NO ₃ ) ₂ .6H ₂ O are mixed at a predetermined molar ratio, fired (final firing temperature = 900 ° C.), and xLi [Mn _1/2 Ni _1/2 ] O _{2 as the} positive electrode active material. YLiCoO ₂ · zLi [Li _1/3 Mn _2/3 ] O ₂ was synthesized and pulverized with a ball mill. The average particle diameter of the positive electrode active material after pulverization was about 11 μm. In addition, the value of x, y, and z in the obtained positive electrode active material is shown in Table 1 below.

  Next, the positive electrode active material (86 parts by mass) synthesized above, acetylene black (7 parts by mass) as a conductive auxiliary agent, and polyvinylidene fluoride (PVdF) (7 parts by mass) as a binder are mixed, and then the slurry viscosity An appropriate amount of N-methyl-2-pyrrolidone (NMP) as a adjusting solvent was added, and the mixture was stirred and mixed with a homogenizer to prepare a positive electrode active material slurry.

  On the other hand, an aluminum foil (thickness: 20 μm) was prepared as a positive electrode current collector. The positive electrode active material slurry prepared above was applied to one side of the prepared current collector by a coater and dried. Thereafter, a press treatment is performed using a roll press machine, and the positive electrode active material layer portion is cut out so that the size is 30 mm × 50 mm, and the slurry uncoated portion to be a lead remains to some extent, and a vacuum dryer is used. It dried at 90 degreeC for 1 day, and was set as the positive electrode for a test. In addition, the thickness of the positive electrode active material layer in the obtained test positive electrode was set to 150 μm by adjusting the amount of slurry applied.

<Production of negative electrode>
Hard carbon as the negative electrode active material (average particle size: 20 μm, reversible charge / discharge capacity: 550 mAh / g, irreversible capacity during initial charge / discharge: 100 mAh / g) (90 parts by mass), and polyvinylidene fluoride (PVdF) as the binder (10 parts by mass) was mixed, and then an appropriate amount of N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent was added, followed by stirring and mixing with a homogenizer to prepare a positive electrode active material slurry.

  On the other hand, stainless steel (SUS) foil (thickness: 15 μm) was prepared as a current collector for the negative electrode. The negative electrode active material slurry prepared above was applied to one side of the prepared current collector by a coater and dried. Thereafter, a press process is performed using a roll press machine, and the negative electrode active material layer part is cut out so that the size of the negative electrode active material layer part is 35 mm × 55 mm, and the slurry uncoated part to be a lead remains to some extent, and a vacuum dryer is used. It was made to dry at 90 degreeC for 1 day, and it was set as the negative electrode for a test. The reversible capacity of the negative electrode active material included in the negative electrode active material layer was adjusted to 1.2 times the reversible capacity of the positive electrode active material included in the positive electrode active material layer by adjusting the amount of slurry applied. .

<Production of test cell>
As an electrolytic solution, a solution prepared by dissolving LiPF ₆ as a lithium salt in an equal volume mixed solution of ethylene carbonate (PC) and dimethyl carbonate (DMC) to a concentration of 1M was prepared. Moreover, the redox shuttle containing electrolyte solution was prepared by dissolving hexaethylbenzene as a redox shuttle at a concentration of 0.1 M in the electrolyte solution prepared above.

  On the other hand, a polypropylene microporous membrane (thickness: 25 μm) was prepared as a separator.

  The positive electrode, separator, and negative electrode prepared above were stacked in this order. At this time, the direction of the electrode was adjusted so that the positive electrode active material layer and the negative electrode active material layer face each other.

  Next, leads were connected to the current collectors of both the positive and negative electrodes by welding, and the laminate was placed in an aluminum laminate pack so that the leads were exposed. Then, the electrolyte solution which does not contain a redox shuttle was inject | poured using the pouring machine, and the aluminum laminate pack was sealed under pressure reduction conditions.

  After sealing, the first charge / discharge treatment was performed. At this time, charging / discharging was performed at a current of 1/24 C to a voltage of 4.8 V at CC-CV for a total of 36 hours, and then discharged to a voltage of 2.5 V at a constant current of 1/24 C. Thereafter, a part of the aluminum laminate pack was opened, degassed, and sealed again under reduced pressure conditions to complete a test cell.

<Example 2>
After degassing, before resealing the aluminum laminate pack, a test cell was produced in the same manner as in Example 1 except that the redox shuttle-containing electrolyte was further added. In addition, the addition amount of the redox shuttle containing electrolyte solution was set to ½ amount of the volume of the electrolyte solution (electrolyte solution not containing the redox shuttle) contained in the pack before the addition.

<Example 3>
A test cell was produced in the same manner as in Example 1 except that the composition of the positive electrode active material (specifically, the values of x, y, and z) was changed to the form shown in Table 1 below. .

<Example 4>
After degassing, before resealing the aluminum laminate pack, a test cell was produced in the same manner as in Example 3 except that the redox shuttle-containing electrolyte was further added. In addition, the addition amount of the redox shuttle containing electrolyte solution was set to ½ amount of the volume of the electrolyte solution (electrolyte solution not containing the redox shuttle) contained in the pack before the addition.

<Example 5>
A test cell was produced in the same manner as in Example 1 except that the composition of the positive electrode active material (specifically, the values of x, y, and z) was changed to the form shown in Table 1 below. .

<Comparative example>
Example 1 except that graphite (average particle size: 26 μm, reversible charge / discharge capacity: 325 mAh / g, irreversible capacity during initial charge / discharge: 15 mAh / g) was used as the negative electrode active material instead of hard carbon. A test cell was produced in the same manner as described above.

<Evaluation of mass energy density>
About the test cell obtained by said each Example and comparative example, mass energy density was computed with the following method.

  First, after charging and discharging 5 times in the voltage range of 4.3 V to 3.0 V, the discharge curve is integrated to a voltage of 4.3 V with CC-CV at a current of 1/6 C, and the battery energy (mAh) is calculated. Calculated. The mass energy density (mAh / g) was calculated by dividing the obtained battery energy value by the total mass (g) of the used electrode, separator and electrolyte. Table 2 below shows relative values of the calculated mass energy density when the value of the comparative example is set to 100.

  From comparison between each example and comparative example, when a predetermined pseudo ternary solid solution is used as a positive electrode active material of a lithium ion secondary battery, a battery is configured by combining negative electrode active materials having a large initial charge / discharge loss to some extent This indicates that the energy density of the battery can be improved. This improvement in energy density cancels the initial charge / discharge loss that occurs in the specified pseudo-ternary solid solution during the initial charge / discharge, cancels the initial charge / discharge loss that occurs in the negative electrode active material, and the reversible capacity of both the positive and negative electrodes is wasted. It is presumed that it is due to efficient use.

<Effect of redox shuttle addition>
Next, for the purpose of showing the effect of redox shuttle addition, the test cell of Example 2 in which the redox shuttle was added to the electrolyte was charged to a high voltage.

  Specifically, after the evaluation of the mass energy density described above, the battery was charged for 12 hours in total with a current (CC) of 1/6 C exceeding a voltage of 4.3 V, and then the capacity was measured by charging and discharging. However, there is almost no deterioration of the capacity compared to the initial stage, and the redox shuttle function is exhibited during charging, and it can be seen that overcharging is prevented.

  From the above, according to the present invention, it is possible to effectively prevent a decrease in capacity characteristics of the entire battery and to provide a battery having excellent capacity characteristics.

It is sectional drawing which shows the outline | summary of the battery of 1st Embodiment which is a bipolar battery. It is a schematic diagram for demonstrating the mechanism in which the effect of this invention is acquired. Fig.2 (a) is a figure which shows the state immediately after battery preparation. FIG.2 (b) is a figure which shows the state in the middle of initial stage charge / discharge. FIG.2 (c) is a figure which shows the state (full charge state) in which charge was completed. FIG. 2D is a diagram showing a state where the discharge is completed. It is a figure which shows the state which the discharge in the battery which employ | adopted graphite as a negative electrode active material was completed. It is explanatory drawing for demonstrating the effect of the battery of 1st Embodiment when a charge condition varies in the assembled battery formed by connecting three unit cells in series. It is a perspective view which shows the assembled battery of 2nd Embodiment. It is the schematic of the motor vehicle of 3rd Embodiment carrying the assembled battery of 2nd Embodiment. It is sectional drawing which shows the outline | summary of the lithium ion secondary battery which is not a bipolar type.

Explanation of symbols

10 Bipolar battery,
11 Current collector,
11a Positive electrode side outermost layer current collector,
11b The negative electrode side outermost layer current collector,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21 battery elements,
25 positive electrode tab,
27 negative electrode tab,
29 Laminate sheet,
31 insulating layer,
33 positive electrode current collector,
35 negative electrode current collector,
35a outermost layer negative electrode current collector,
40 battery packs,
50 cars,
60 Lithium ion secondary battery that is not bipolar.

Claims (5)

A positive electrode active material layer including a positive electrode active material formed on the surface of the current collector, an electrolyte layer, and a negative electrode active material layer including a negative electrode active material formed on the surface of the current collector are stacked in this order. A battery element comprising at least one unit cell
The positive electrode active material is xLi [Mn _1/2 Ni _1/2 ] O ₂ .yLiCoO ₂ .zLi [Li _1/3 Mn _2/3 ] O ₂ (x + y + z = 1, 0 <x <1, 0 ≦ y < 0.5, 0 <z <1), the initial charge / discharge loss capacity of the negative electrode active material is 10% or more of the reversible electric capacity ,
A battery element production process for producing a battery element;
Injecting an electrolyte containing no redox shuttle into the battery element;
Performing a first charge / discharge treatment until the battery voltage is 4.5 V or higher;
Adding a redox shuttle to the electrolyte;
A degassing step of extracting the gas generated during the first charge / discharge treatment from the battery element;
A sealing step for sealing the battery element;
A method for producing a secondary battery, comprising: The method for manufacturing a secondary battery according to claim 1, wherein the electrolyte layer includes a redox shuttle having an oxidation start potential that is 4.2 V or more higher than lithium. The method for manufacturing a secondary battery according to claim 1, wherein the negative electrode active material is amorphous carbon. The method for manufacturing a secondary battery according to claim 3, wherein the amorphous carbon is hard carbon. The manufacturing method of the secondary battery of any one of Claims 1-4 which is a bipolar type lithium ion secondary battery.

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