JP2015133178A - Electrode, and battery having electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode which allows for enhancement of cycle characteristics, by suppressing elution of an adhesive upon occurrence of potential change of an active material during charge and discharge, thereby minimizing reduction in the ion conductivity of an electrolyte, and to provide a battery having the electrode.SOLUTION: A positive electrode 20 as an electrode 10 has a collector 21, an active material layer 22 formed on the collector so as to leave a partial exposed part 21b of the collector, and an insulation member 50 covering a boundary 23 of the active material layer and the exposed part. The insulation member 50 is provided, on the surface facing the collector, with an adhesive region 50a formed of an adhesive material 51, and a non-adhesive region 50b not containing the adhesive material. The non-adhesive region is located on the active material layer side.

Description

  The present invention relates to an electrode and a battery having the electrode.

  In recent years, in the fields of the automobile industry and the advanced electronics industry, the demand for batteries for automobiles and batteries for electronic devices is increasing, and in particular, there is a demand for miniaturization, thinning, and high capacity. Among these, nonaqueous electrolyte secondary batteries that have a higher energy density than other batteries have attracted attention.

  The nonaqueous electrolyte secondary battery includes a negative electrode in which a negative electrode active material layer is applied on a current collector, a positive electrode in which a positive electrode active material layer is applied on a current collector, and a separator disposed between the negative electrode and the positive electrode And have. In order to suppress an internal short circuit caused by a deviation between the positive electrode and the negative electrode when a battery is formed by laminating a positive electrode, a separator, and a negative electrode, an insulating coating material (insulating member) is provided at the end of the active material layer of the positive electrode. Has been proposed (see, for example, Patent Document 1).

JP 2004-259625 A

  By the way, as shown in Patent Document 1, such an insulating member is generally provided from the active material layer on the current collector of the electrode to the exposed portion. An adhesive is applied to the entire surface of the insulating member. For this reason, the adhesive is on the active material layer of the electrode at the end of the insulating member. Therefore, in the non-aqueous electrolyte secondary battery, there is a problem that when the potential change of the active material occurs during charging / discharging, the adhesive is eluted and the ionic conductivity of the electrolyte is lowered, and as a result, the cycle characteristics are lowered. .

  The present invention has been made to solve the problems associated with the above-described conventional technology, and suppresses the elution of the adhesive when the potential change of the active material occurs during charging and discharging, thereby reducing the ionic conductivity of the electrolyte. An object of the present invention is to provide an electrode that can be suppressed and improved in cycle characteristics, and a battery having the electrode.

  The electrode according to the present invention that achieves the above object includes a current collector, an active material layer formed on the current collector so as to leave an exposed portion that exposes a part of the current collector, and the active material. And an insulating member that covers a boundary portion between the material layer and the exposed portion. The insulating member includes a bonding region formed by an adhesive and a non-bonding region not including the adhesive on a surface facing the current collector. The non-bonding region is located on the active material layer side.

  The battery according to the present invention that achieves the above object has a laminated body in which the above electrodes are laminated via a separator, and the laminated body is sealed by an exterior body.

  According to the electrode of the present invention configured as described above and the battery having the electrode, the insulating member has a non-adhesive region that does not include an adhesive on the active material layer side. The elution of the adhesive when the potential change of the material layer occurs can be suppressed. Thereby, a decrease in the ionic conductivity of the electrolyte can be suppressed, and as a result, the cycle characteristics can be improved.

It is sectional drawing which shows the structure of the battery which concerns on embodiment. It is sectional drawing which shows the structure of the positive electrode and negative electrode in the battery of FIG. 6 is a cross-sectional view showing the configuration of a positive electrode and a negative electrode according to Modification 1. FIG. FIG. 6 is a cross-sectional view showing a configuration of a positive electrode and a negative electrode according to Modification 2. FIG. 10 is a cross-sectional view showing a configuration of a positive electrode and a negative electrode according to Modification 3.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. The size and ratio of each member in the drawings are exaggerated for convenience of explanation and may be different from the actual size and ratio. The battery 100 according to the embodiment is used, for example, as a driving power source or auxiliary power source for motors of vehicles such as electric vehicles, fuel cell vehicles, and hybrid electric vehicles. In the present embodiment, a nonaqueous electrolyte secondary battery will be described as an example of the battery 100.

<Embodiment>
A battery 100 according to an embodiment will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a cross-sectional view illustrating a configuration of a battery 100 according to the embodiment. FIG. 2 is a cross-sectional view showing the configuration of the positive electrode and the negative electrode in the battery of FIG.

  A battery 100 shown in FIG. 1 is a non-aqueous electrolyte lithium ion secondary battery (hereinafter simply referred to as “battery”) that is not a flat (stacked) bipolar type. The battery 100 includes a power generation element 70 (corresponding to a stacked body) in which the positive electrode 20 and the negative electrode 30 are stacked with a separator 40 interposed therebetween, and an exterior body 80 that seals the power generation element 70.

  In the battery 100, a substantially rectangular power generation element 70 in which a charge / discharge reaction proceeds is sealed inside a laminate sheet that is an exterior body 80. The adjacent positive electrode 20, separator 40, and negative electrode 30 form one single cell layer 90. The power generation element 70 has a configuration in which a plurality of unit cell layers 90 are stacked and electrically connected in parallel. The battery 100 may be arranged such that the positive electrode 20 and the negative electrode 30 of the battery 100 shown in FIG.

  The battery 100 has a rectangular flat shape, and draws out a positive electrode tab 24 and a negative electrode tab 34 for extracting electric power from opposite ends. The power generation element 70 is sealed in a state where the positive electrode tab 24 and the negative electrode tab 34 are pulled out by thermally welding the periphery of the outer package 80.

  The positive electrode 20 has a current collector 21 and an active material layer 22, and the negative electrode 30 has a current collector 31 and an active material layer 32. The active material layers 22 and 32 are formed on the current collectors 21 and 31 so that exposed portions 21b and 31b in which a part of the current collectors 21 and 31 are exposed remain. The positive electrode 20 of the present embodiment further includes an insulating member 50 that covers the boundary portion 23 between the active material layer 22 and the exposed portion 21b. The insulating member 50 includes a bonding region 50 a formed by the adhesive 51 and a non-bonding region 50 b that does not include an adhesive on the surface facing the current collector 21. The non-bonding region 50b is located on the active material layer 22 side.

  As shown in FIG. 2, in the present embodiment, the case where the insulating member 50 is provided on the positive electrode 20 as the electrode 10 will be described as an example. Therefore, in the present embodiment, the current collector and the active material layer on the side where the insulating member 50 is provided are the current collector 21 and the active material layer 22 for the positive electrode 20.

  The structure of the battery 100 may be a known material used for a general nonaqueous electrolyte secondary battery, and is not particularly limited. The current collector 21 and active material layer 22 of the positive electrode 20 that can be used in the battery 100, the current collector 31 and active material layer 32 of the negative electrode 30, the separator 40, the insulating member 50, the outer package 80, and the like will be described.

  As a material constituting the current collector 21 of the positive electrode 20, a member conventionally used as a battery current collector can be appropriately adopted. For example, aluminum, nickel, iron, stainless steel (SUS), titanium, or copper may be used. Among these, aluminum is preferable as the current collector 21 of the positive electrode 20 from the viewpoint of electronic conductivity and battery operating potential. However, without being particularly limited thereto, for example, an aluminum foil, a nickel-aluminum clad material, a copper-aluminum clad material, or a plating material of a combination of these metals can be used. The thickness of the positive electrode current collector is not particularly limited, and is set in consideration of the intended use of the battery.

A material constituting the active material layer 22 of the positive electrode 20 is, for example, LiMn ₂ 0 ₄ . However, it is not particularly limited to this. Note that it is preferable to use a lithium-transition metal composite oxide from the viewpoint of capacity and output characteristics. The positive electrode 20 has active material layers 22 formed on both surfaces of a current collector 21.

  The material of the current collector 31 of the negative electrode 30 is the same as the material of the current collector 21 of the positive electrode 20. Among these, copper is preferable as the current collector 31 of the negative electrode 30 from the viewpoint of electronic conductivity and battery operating potential. The thickness of the current collector 31 of the negative electrode 30 is not particularly limited, as is the thickness of the current collector 21 of the positive electrode 20, and is set in consideration of the intended use of the battery.

  The active material layer 32 of the negative electrode 30 is, for example, hard carbon (non-graphitizable carbon material). However, without being particularly limited to this, for example, a graphite-based carbon material or a lithium-transition metal composite oxide can be used. In particular, a negative electrode active material composed of carbon and a lithium-transition metal composite oxide is preferable from the viewpoints of capacity and output characteristics. The negative electrode 30 has active material layers 32 formed on both surfaces of a current collector 31.

  The separator 40 has a porous shape and has air permeability. The separator 40 constitutes an electrolyte layer by being impregnated with the electrolyte. The material of the separator 40 that is the electrolyte layer is, for example, porous PE (polyethylene) having air permeability that can penetrate the electrolyte. However, the present invention is not particularly limited to this, and other polyolefins such as PP (polypropylene), laminates having a three-layer structure of PP / PE / PP, polyamide, polyimide, aramid, and non-woven fabric can also be used. is there. Nonwoven fabrics are, for example, cotton, rayon, acetate, nylon, and polyester.

  The electrolyte host polymer is, for example, PVDF-HFP (polyvinylidene fluoride / hexafluoropropylene copolymer) containing 10% of HFP (hexafluoropropylene) copolymer. However, the present invention is not particularly limited to this, and other polymers that do not have lithium ion conductivity or polymers that have ion conductivity (solid polymer electrolyte) can also be applied. Other polymers having no lithium ion conductivity are, for example, PAN (polyacrylonitrile) and PMMA (polymethyl methacrylate). Examples of the polymer having ion conductivity include PEO (polyethylene oxide) and PPO (polypropylene oxide).

The electrolyte solution held by the host polymer contains, for example, an organic solvent composed of PC (propylene carbonate) and EC (ethylene carbonate), and a lithium salt (LiPF ₆ ) as a supporting salt. The organic solvent is not particularly limited to PC and EC, and other cyclic carbonates, chain carbonates such as dimethyl carbonate, and ethers such as tetrahydrofuran can be applied. The lithium salt is not particularly limited to LiPF ₆ , and other inorganic acid anion salts and organic acid anion salts such as LiCF ₃ SO ₃ can be applied.

  The battery 100 is a lithium ion secondary battery, and the active material layer 32 for the negative electrode 30 is larger than the active material layer 22 for the positive electrode 20 in plan view. This is for preventing dendrite precipitation of lithium metal in the negative electrode 30 due to current concentration at the end of the negative electrode 30. In the battery 100, there is a portion where the exposed portion 21 b in the current collector 21 of the positive electrode 20 and the active material layer 32 of the negative electrode 30 face each other with the separator 40 interposed therebetween. In order to prevent an internal short circuit in this portion, the insulating member 50 is provided so as to cover the boundary portion 23 between the active material layer 22 and the exposed portion 21b.

  In the present embodiment, of the four sides of the outer peripheral edge of the active material layer 22, one side that is connected to the positive electrode tab 24 is used as the boundary portion 23. This boundary portion 23 is covered with an insulating member 50. The boundary portion 23 covered by the insulating member 50 is not limited to one side. A plurality of sides of the outer peripheral edge of the active material layer 22 may be covered with the insulating member 50, or all sides of the outer peripheral edge may be covered with the insulating member 50.

  The material of the base material of the insulating member 50 is a thermoplastic resin. The base material of the insulating member 50 is, for example, polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyvinyl acetate (PVAc), polytetrafluoroethylene (PTFE), acrylonitrile butadiene styrene resin. (ABS resin), acrylonitrile styrene resin (AS resin), acrylic resin (PMMA), polyamide (PA), polyacetal (POM), polycarbonate (PC), polyphenylene ether (PPE), polybutylene terephthalate (PBT), polyethylene terephthalate ( PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cyclic polyolefin (COP), polyphenylene sulfide (PPS), polysulfone (PSF), polyether resin Phone (PES), amorphous polyarylate (PAR), liquid crystal polymer (LCP), polyether ether ketone (PEEK), thermoplastic polyimide (PI), polyamide-imide (PAI) and the like.

  The adhesive 51 applied to the base material of the insulating member 50 is not particularly limited, for example, either an organic solvent binder (non-aqueous binder) or a water dispersion binder (aqueous binder) can be used. For example, the following materials are mentioned. Polyethylene, polypropylene, polyethylene terephthalate, polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber, isoprene rubber, butadiene rubber, ethylene Thermoplastic polymers such as propylene rubber, ethylene / propylene / diene copolymers, styrene / butadiene / styrene block copolymers and their hydrogenated products, styrene / isoprene / styrene block copolymers and their hydrogenated products, polyfluorinated Vinylidene (PVDF), polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether Copolymers, ethylene / tetrafluoroethylene copolymers, polychlorotrifluoroethylene, ethylene / chlorotrifluoroethylene copolymers, fluororesins such as polyvinyl fluoride, vinylidene fluoride-hexafluoropropylene fluororubber, vinylidene fluoride Ride-hexafluoropropylene-tetrafluoroethylene-based fluororubber, vinylidene fluoride-based fluororubber, epoxy resin and the like. Among these, polyvinylidene fluoride, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. These suitable binders are excellent in heat resistance, have low reactivity with the electrolyte, and further have excellent resistance to dissolution, and can be used by being applied on the active material layers of the positive electrode and the negative electrode. . These binders may be used alone or in combination of two.

  In the present embodiment, a case where an adhesive tape is used as the insulating member 50 will be described as an example. A non-adhesive region 50 b is formed in the insulating member 50 by applying a dry edge to a part of the surface of the adhesive tape to which the adhesive 51 is applied to remove the adhesive 51. In this manner, the insulating member 50 including the adhesion region 50a formed by the adhesive material 51 and the non-adhesion region 50b not including the adhesive material 51 is formed. However, the present invention is not limited to this, and as the base material of the insulating member 50, for example, a tape to which no adhesive is applied can be used. In the case of the above configuration, the adhesive region 51 is formed by applying the adhesive 51 to a part of the base material of the insulating member 50 made of tape. Also in this configuration, the insulating member 50 including the adhesion region 50a formed by the adhesive material 51 and the non-adhesion region 50b not including the adhesive material 51 is formed.

  The insulating member 50 has a non-adhesive region 50b that does not include the adhesive 51 on the active material layer 22 side. 2, the boundary 52 between the non-adhesion region 50b and the adhesion region 50a is located on the exposed portion 21b side with respect to the boundary portion 23.

  In this embodiment, the adhesive 51 provided on the base material of the insulating member 50 adheres only to the exposed portion 21 b on the current collector 21 of the positive electrode 20 and does not adhere to the active material layer 22. The part where the charge / discharge reaction occurs in the active material layer 22 is a part not covered with the insulating member 50. In FIG. 2, the end of the portion where the charge / discharge reaction occurs is located below the left end of the non-adhesive region 50b in the insulating member 50, and is located closer to the left side than the right end of the active material layer 22 itself in the drawing. Will do. When the potential change of the active material layer 22 occurs during charging / discharging, since the end of the portion where the charging / discharging reaction occurs is separated from the left end of the adhesive 51 in the figure, the elution of the adhesive 51 is suppressed. be able to. Thereby, a decrease in the ionic conductivity of the electrolyte can be suppressed, and as a result, the cycle characteristics can be improved.

  The non-adhesion region 50 b of the insulating member 50 is located on the active material layer 22 and is fixed by the lamination pressure after the battery 100 is configured. For this reason, even if the insulating member 50 is not bonded to the active material layer 22, there is no problem as long as the insulating member 50 is bonded to the exposed portion 21b of the current collector 21 in the bonding region 50a.

  The exterior body 80 is a member that encloses the power generation element 70 therein, and a bag-like case using a laminate film containing aluminum that can cover the power generation element 70 can be used. As the laminate film, for example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used, but is not limited thereto. A laminate film is desirable from the viewpoint that it is excellent in high output and cooling performance, and can be suitably used for a battery for large equipment for EV and HEV. Moreover, since the group pressure to the power generation element applied from the outside can be easily adjusted and the battery can be enlarged, the power generation element has a laminated structure, and the exterior body is more preferably a laminate film containing aluminum.

  The inner volume of the exterior body 80 is configured to be larger than the volume of the power generation element 70 so that the power generation element 70 can be enclosed. Here, the internal volume of the exterior body 80 refers to the volume in the exterior body 80 before vacuuming after sealing with the exterior body 80. Further, the volume of the power generation element 70 is a volume of a portion that the power generation element 70 occupies in space, and includes a hole portion in the power generation element 70. Since the internal volume of the exterior body 80 is larger than the volume of the power generation element 70, there is a space in which gas can be stored when gas is generated. Thereby, the gas release property from the power generation element 70 is improved, the generated gas is less likely to affect the battery behavior, and the battery characteristics are improved.

Moreover, in this embodiment, the value (L / V ₁ ) of the ratio of the volume L of the electrolyte injected into the exterior body 80 to the volume V ₁ of the pores of the power generation element 70 is 1.2 to ₁ . It is preferable that the range is 6. If the amount (volume L) of the electrolytic solution is large, even if the electrolytic solution is unevenly distributed on the positive electrode 20 side, a sufficient amount of the electrolytic solution is also present on the negative electrode 30 side. It is advantageous from the viewpoint of making it progress. On the other hand, if the amount (volume L) of the electrolytic solution is large, the cost of increasing the electrolytic solution is generated, and too much electrolytic solution leads to an increase in the distance between the electrodes, resulting in an increase in battery resistance. Therefore, the ratio of the liquid absorption rates of the active material layer 22 of the positive electrode 20 and the active material layer 32 of the negative electrode 30 is in an appropriate range (Tc / Ta = range of 0.6 to 1.3), and the amount of the electrolytic solution (Specifically, it is desirable that the ratio L / V ₁ of the ratio of the electrolyte volume L to the volume V ₁ of the pores of the power generation element 70) be appropriate. Thereby, it is excellent at the point which can make uniform film formation, cost, and cell resistance compatible. From this viewpoint, it is preferable the value of L / _{V 1} is configured to be in the range of 1.2 to 1.6, more preferably 1.25 to 1.55, particularly preferably 1.3 to The range is 1.5.

In the present embodiment, the value (V ₂ / V ₁ ) of the ratio of the volume V ₂ of the surplus space 81 inside the exterior body 80 to the volume V ₁ of the pores of the power generation element 70 is 0.5 to 1. It is preferable to configure so as to be 0.0. Further, the ratio value (L / V ₂ ) of the volume L of the electrolyte injected into the exterior body 80 to the volume V ₂ of the surplus space 81 inside the exterior body 80 is 0.4 to 0.7. It is preferable to configure. As a result, it is possible to ensure that the portion of the electrolyte injected into the exterior body 80 that has not been absorbed by the binder is present in the surplus space 81. In addition, the movement of lithium ions in the battery 100 can be reliably ensured. As a result, the occurrence of a heterogeneous reaction due to the increase in the distance between the electrode plates due to the presence of an excessive amount of electrolytic solution that may be a problem when using a large amount of electrolytic solution similar to that when using a solvent-based binder such as PVdF. Is prevented. For this reason, the nonaqueous electrolyte secondary battery excellent in a long-term cycle characteristic (life characteristic) can be provided.

Here, the “hole volume (V ₁ ) of the power generation element 70” can be calculated in the form of adding all the hole volumes of the positive electrode 20, the negative electrode 30, and the separator 40. That is, it can be calculated as the total sum of the holes of the constituent members constituting the power generation element 70. In addition, the battery 100 is usually manufactured by sealing the power generation element 70 in the exterior body 80, injecting an electrolytic solution, and evacuating and sealing the interior of the exterior body 80. When gas is generated inside the exterior body 80 in this state, if there is a space in the exterior body 80 where the generated gas can be stored, the generated gas accumulates in the space and the exterior body 80 expands. . Such a herein space defined as "surplus spaces 81", the volume of the excess space when inflated maximum without outer package is ruptured was defined as V _2. As described above, the value of V ₂ / V ₁ is preferably 0.5 to 1.0, more preferably 0.6 to 0.9, and particularly preferably 0.7 to 0.8. is there.

Further, as described above, in the present invention, the ratio value between the volume of the injected electrolyte and the volume of the surplus space 81 described above is controlled to a value within a predetermined range. Specifically, the ratio value (L / V ₂ ) of the volume (L) of the electrolyte injected into the exterior body 80 to the volume V ₂ of the surplus space 81 inside the exterior body 80 is 0.4 to It is desirable to control to 0.7. The value of L / V ₂ is more preferably 0.45 to 0.65, and particularly preferably 0.5 to 0.6.

  In the present embodiment, it is preferable that the surplus space 81 present inside the exterior body 80 is disposed at least vertically above the power generation element 70. With such a configuration, the generated gas can be accumulated in the vertical upper part of the power generation element 70 in which the surplus space 81 exists. Thereby, compared with the case where the surplus space 81 exists in the side part and the lower part of the power generation element 70, the electrolyte is preferentially present in the lower part where the power generation element 70 exists in the exterior body 80. Can do. As a result, it is possible to ensure that the power generation element 70 is always immersed in a larger amount of electrolyte, and it is possible to minimize a decrease in battery performance due to liquid drainage. Although there is no particular limitation on the specific configuration for arranging the surplus space 81 vertically above the power generation element 70, for example, the material and shape of the exterior body 80 itself are changed to the side portions of the power generation element 70. It may be configured not to swell toward the lower part, or a member that prevents the outer body 80 from bulging toward the side part or the lower part may be disposed outside the outer body 80. It is done.

  In automobile applications and the like, recently, a large-sized battery is required. The effect of the battery 100 having the electrode 10 of the present invention is more effective in the case of a large area battery in which both the active material layer 22 of the positive electrode 20 and the active material layer 32 of the negative electrode 30 have large electrode areas. Demonstrated. That is, in the case of a large area battery, cohesive failure from the electrode surface due to friction between the electrode 10 (the positive electrode 20 and the negative electrode 30) and the separator 40 is further suppressed, and the battery characteristics can be maintained even when vibration is input. Excellent in terms. Therefore, in the present embodiment, it is preferable that the battery structure in which the power generation element 70 is covered with the exterior body 80 is large in the sense that the effect of the present embodiment is more exhibited. Specifically, the active material layer of the electrode 10 (the positive electrode 20 and the negative electrode 30) has a rectangular shape, and the length of the short side of the rectangle is preferably 100 mm or more. Such a large battery can be used for vehicle applications. Here, the length of the short side of the active material layer 32 of the negative electrode 30 refers to the side having the shortest length among the electrodes. The upper limit of the length of the short side of the battery structure is not particularly limited, but is usually 250 mm or less.

Further, as a viewpoint of a large-sized battery, which is different from the viewpoint of the physical size of the electrode 10 (the positive electrode 20 and the negative electrode 30), it is possible to regulate the size of the battery from the relationship between the battery area and the battery capacity. For example, in the case of a flat laminated laminate battery, the value of the ratio of the battery area to the rated capacity (projected area of the battery including the exterior body) is 5 cm ² / Ah or more, and the rated capacity is 3 Ah. That's it. In the battery, since the battery area per unit capacity is large, it is difficult to remove the gas generated between the electrodes. Due to such gas generation, if a gas retention portion exists between large electrodes, the heterogeneous reaction tends to proceed starting from that portion. For this reason, the problem of deterioration of battery performance (particularly, life characteristics after long-term cycle) in a large-sized battery using an aqueous binder such as SBR for forming an active material layer of the negative electrode is more likely to be manifested. Therefore, it is preferable that the nonaqueous electrolyte secondary battery according to the present embodiment is a battery having a large size as described above, because the merit due to the expression of the effects of the present invention is greater. Furthermore, the aspect ratio of the rectangular electrode is preferably 1 to 3, and more preferably 1 to 2. The electrode aspect ratio is defined as the aspect ratio of the active material layer of the rectangular positive electrode. By setting the aspect ratio within such a range, gas can be discharged uniformly in the surface direction.

  The rated capacity of the battery 100 is obtained as follows.

  The rated capacity of the test battery is left to stand for about 10 hours after injecting the electrolytic solution, and the initial charge is performed. Then, it measures by the following procedures 1-5 in the temperature range of 25 degreeC and the voltage range of 3.0V to 4.15V.

  Procedure 1: After reaching 4.15 V by constant current charging at 0.2 C, pause for 5 minutes.

  Procedure 2: After Procedure 1, charge for 1.5 hours by constant voltage charging and rest for 5 minutes.

  Procedure 3: After reaching 3.0 V by constant current discharge of 0.2 C, discharge by constant voltage discharge for 2 hours, and then rest for 10 seconds.

  Procedure 4: After reaching 4.1 V by constant current charging at 0.2 C, charge for 2.5 hours by constant voltage charging, and then rest for 10 seconds.

  Procedure 5: After reaching 3.0 V by constant current discharge of 0.2 C, discharge by constant voltage discharge for 2 hours, and then stop for 10 seconds.

  Rated capacity: The discharge capacity (CCCV discharge capacity) in the discharge from the constant current discharge to the constant voltage discharge in the procedure 5 is defined as the rated capacity.

  The electrode 10 according to the first embodiment described above provides the following operational effects.

  The positive electrode 20 as the electrode 10 includes a current collector 21, an active material layer 22, and an insulating member 50 that covers a boundary portion 23 between the active material layer 22 and the exposed portion 21 b. The insulating member 50 includes an adhesion region 50a and a non-adhesion region 50b, and the non-adhesion region 50b is located on the active material layer 22 side.

  According to the positive electrode 20 configured in this manner, the insulating member 50 has the non-adhesive region 50b that does not include the adhesive 51 on the active material layer 22 side, so that the potential change of the active material layer 22 during charge / discharge The elution of the adhesive 51 when this occurs can be suppressed. Thereby, a decrease in the ionic conductivity of the electrolyte can be suppressed, and as a result, the cycle characteristics can be improved.

  Further, according to the present electrode 10, the boundary between the non-adhesion region 50 b and the adhesion region 50 a is located closer to the exposed portion 21 b than the boundary portion 23.

  According to the electrode 10 configured as described above, the bonding region 50a of the insulating member 50 and the active material layer 22 of the positive electrode 20 are sufficiently separated from each other, so that the potential change of the active material layer 22 occurred during charging and discharging. The elution of the adhesive material 51 can be further suppressed. As a result, a decrease in the ionic conductivity of the electrolyte can be further suppressed, and as a result, the cycle characteristics can be further improved.

  Further, the current collector and the active material layer on the side where the insulating member 50 is provided are the current collector 21 and the active material layer 22 for the positive electrode 20.

  In the battery 100 in which the active material layer 32 for the negative electrode 30 is configured larger than the active material layer 22 for the positive electrode 20, the exposed portion 21 b of the current collector 21 in the positive electrode 20 and the active material layer 32 in the negative electrode 30 form the separator 40. Thus, an internal short circuit at the portion facing each other can be suitably prevented.

  Furthermore, the battery 100 includes a power generation element 70 in which the negative electrode 30 and the positive electrode 20 as the electrode 10 are stacked via a separator 40, and an exterior body 80 that seals the power generation element 70.

  According to the battery 100 configured as described above, the elution of the adhesive 51 when the potential change of the active material layer 22 of the positive electrode 20 occurs during charging / discharging can be prevented. Therefore, in the battery 100, it is possible to suppress a decrease in the ionic conductivity of the electrolyte, and as a result, it is possible to improve cycle characteristics.

  Furthermore, in the battery 100, the active material layers 22 and 32 are rectangular, and the length of the short side of the rectangle is 100 mm or more.

  According to the battery 100 configured as described above, the positive electrode 20 active material layer 22 and the active material layer 32 of the negative electrode 30 have a rectangular shape with a short side length of 100 mm or more. Thus, since the battery 100 is a large battery, cohesive failure from the electrode surface due to friction between the electrode 10 (the positive electrode 20) and the separator 40 is further suppressed, and the battery characteristics are maintained even when vibration is input. be able to.

Furthermore, in this battery 100, the value of the ratio of the area of the battery 100 to the rated capacity (projected area including the exterior body 80 of the battery 100) is 5 cm ² / Ah or more, and the rated capacity is 3 Ah or more. is there.

  According to the battery 100 configured as described above, the enlargement of the battery 100 is defined from the relationship between the battery area and the battery capacity as the viewpoint of the enlargement battery, which is different from the viewpoint of the physical size of the electrode 10. You can also.

  Further, in the present electrode 10, the aspect ratio of the electrode 10 defined as the aspect ratio of the active material layer 22 of the rectangular positive electrode 20 is 1 to 3.

  According to the electrode 10 configured in this way, the gas can be discharged uniformly in the plane direction by setting the aspect ratio in such a range.

  Furthermore, the battery 100 is a lithium ion secondary battery, and the active material layer 32 for the negative electrode 30 is larger than the active material layer 22 for the positive electrode 20 in plan view.

  The battery 100 configured as described above is a lithium ion secondary battery in which the active material layer 32 for the negative electrode 30 is configured to be larger than the active material layer 22 for the positive electrode 20 in order to prevent dendrite precipitation of lithium metal in the negative electrode 30. Applicable. Therefore, it is possible to obtain a lithium ion secondary battery that can improve cycle characteristics while suitably preventing an internal short circuit.

<Modification 1>
Next, Modification 1 of the electrode 10 of the embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected and demonstrated to the member same as embodiment mentioned above, and the duplicate description is abbreviate | omitted.

  FIG. 3 is a cross-sectional view illustrating a configuration of the electrode 10 of the first modification.

  In the electrode 10 according to the first modification, the insulating member 50 covers the boundary portion 23 in a state where the boundary 52 between the non-bonding region 50b and the bonding region 50a is positioned so as to coincide with the boundary portion 23. That is, in the first modification, as shown in FIG. 3, the adhesive 51 formed on the base material of the insulating member 50 includes the exposed portion 21 b on the current collector 21 of the positive electrode 20 and the end portion 22 a of the active material layer 22. It is adhered to.

  Although the adhesive 51 is adhered to the end 22a of the active material layer 22, the active material layer 22 is covered with the non-adhesive region 50b of the insulating member 50, so that it adheres to the end of the portion where charge / discharge reaction occurs. It becomes a form separated from the material 51. Therefore, also in the modification 1, the elution of the adhesive 51 when the potential change of the active material layer 22 occurs during charging / discharging can be suppressed. Thereby, a decrease in the ionic conductivity of the electrolyte can be suppressed, and as a result, the cycle characteristics can be improved.

<Modification 2>
Next, Modification 2 of the electrode 10 of the embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected and demonstrated to the member same as embodiment mentioned above, and the duplicate description is abbreviate | omitted.

  FIG. 4 is a cross-sectional view showing the configuration of the electrode 10 of the second modification.

  In the electrode 10 according to the modified example 2, the insulating member 50 includes the boundary portion 23 in a state where the boundary 52 between the non-bonding region 50b and the bonding region 50a is located closer to the active material layer 22 than the boundary portion 23. Covered. That is, in Modification 2, as shown in FIG. 4, the adhesive 51 formed on the base material of the insulating member 50 is exposed to the exposed portion 21 b on the current collector 21 of the positive electrode 20 and a part 22 b of the active material layer 22. It adheres to (the part slightly extending from the end 22a).

  Although the adhesive 51 is adhered to a part 22b of the active material layer 22 (a portion slightly extending from the end 22a), the active material layer 22 is covered with the non-adhesive region 50b in the insulating member 50. The end portion of the part where the charge / discharge reaction occurs and the adhesive 51 are separated from each other. Therefore, also in the modification 2, the elution of the adhesive 51 when the potential change of the active material layer 22 occurs during charging / discharging can be suppressed. Thereby, a decrease in the ionic conductivity of the electrolyte can be suppressed, and as a result, the cycle characteristics can be improved.

<Modification 3>
Next, Modification 3 of the electrode 10 of the embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected and demonstrated to the member same as embodiment mentioned above, and the duplicate description is abbreviate | omitted.

  FIG. 5 is a cross-sectional view illustrating a configuration of the electrode 10 of the third modification.

  In the electrode 10 according to the modified example 3, the insulating member 50 includes a plurality of boundaries (boundary 52, boundary 53), and the boundary 52 closest to the active material layer 22 side among the plurality of boundaries is the boundary portion 23. The boundary portion 23 is covered in a state in which the boundary portion 23 is positioned so as to match.

  As shown in FIG. 5, in the insulating member 50 of Modification 3, the non-adhesive region 50 b is provided not only on the active material layer 22 of the positive electrode 20 but also on the exposed portion 21 b on the current collector 21. For this reason, the insulating member 50 of the modification 3 has a smaller bonding area 50a of the insulating member 50 than the insulating members 50 of the modifications 1 and 2. As in the first modification, the adhesive 51 formed on the base material of the insulating member 50 is bonded to the exposed portion 21 b on the current collector 21 of the positive electrode 20 and the end portion 22 a of the active material layer 22.

  As in the first modification, although the adhesive 51 is adhered to the end 22a of the active material layer 22, the active material layer 22 is covered by the non-adhesive region 50b in the insulating member 50. The end of the part where it occurs and the adhesive 51 are in a separated form. Therefore, also in the modification 3, the elution of the adhesive 51 when the potential change of the active material layer 22 occurs during charging / discharging can be suppressed. Thereby, a decrease in the ionic conductivity of the electrolyte can be suppressed, and as a result, the cycle characteristics can be improved.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

  First, production of the positive electrode 20 will be described. The current collector 21 of the positive electrode 20 is an Al foil having a thickness of 20 μm. The positive electrode slurry is composed of lithium nickelate powder (positive electrode active material), PVdF (polyvinylidene fluoride, binder), and carbon powder (conducting aid) at 90: 5: 5 (weight ratio), respectively, and NMP (N-methylpyrrolidone). ). Thereafter, a positive electrode slurry was applied to both surfaces of a 20 μm thick Al foil by a die coater, dried, and pressed after drying to obtain a positive electrode 20 having a thickness of 150 μm.

  Next, production of the negative electrode 30 will be described. The current collector 21 of the negative electrode 30 is a Cu foil having a thickness of 10 μm. The negative electrode slurry was prepared by dispersing Gr powder (negative electrode active material) and PVdF (polyvinylidene fluoride, binder) in NMP (N-methylpyrrolidone) at 95: 5 (weight ratio). Then, negative electrode slurry was apply | coated with the die-coater on both surfaces of 10-micrometer-thick Cu foil, it was made to dry, and it pressed after drying, and obtained 140-micrometer-thick negative electrode 30.

  Next, production of the battery 100 will be described. As the insulating member 50, a protective tape having a length of 10 mm, a width of 12 mm, and a thickness of 30 μm was used. A protective tape was applied so as to cover the boundary portion 23 between the active material layer 22 on the current collector 21 of the positive electrode 20 (hereinafter, also simply referred to as “positive electrode active material layer 22”) and the exposed portion 21b. The boundary portion 23 is one side of the four sides of the outer peripheral edge of the rectangular positive electrode active material layer 22 that is connected to the positive electrode tab. The material of the protective tape, the length of the non-adhesion region 50b, the length of the adhesion region 50a, the form to be applied, and the coating length that covers the positive electrode active material layer 22 are shown in the description of each example and comparative example described later. .

A polyethylene microporous membrane (thickness = 25 μm) was prepared as the separator 40. Further, as the _{electrolyte, 1M LiPF 6 EC: DEC =} 1: Using 1 (volume ratio).

  10 sheets of the produced positive electrode 20, 11 sheets of the negative electrode 30, and 20 sheets of the separator 40 were prepared and laminated in the order of the negative electrode 30 / the separator 40 / the positive electrode 20 / the separator 40 / the negative electrode 30. did.

  The obtained power generation element 70 was placed in a bag made of an aluminum laminate sheet having a thickness of 150 μm, which is an exterior body 80, and an electrolytic solution was injected. Under vacuum conditions, the opening of the aluminum laminate sheet bag was sealed so that the positive electrode tab 24 and the negative electrode tab 34 for current extraction connected to the positive electrode 20 and the negative electrode 30 were led out, and the test cell was completed. .

Next, evaluation of the battery 100 will be described. The produced battery 100 was sandwiched between SUS plates having a thickness of 5 mm so that the pressure applied to the battery was 100 g / cm ² , and 0.2C / 4.2V_CC / CV charging was performed at 25 ° C. for 7 hours. Next, after 10 minutes of rest, the battery was discharged to 2.5 V with 0.2 C_CC discharge. Thereafter, the cycle of 1C / 4.2V_CC / CV charge (0.015C cut) and 1C_CC discharge (2.5V voltage cut) was repeated in a 55 ° C atmosphere (cycle test), 300 cycles for the discharge capacity of the first cycle. The value of the discharge capacity at the eye was calculated as the cycle capacity maintenance rate.

  Examples 1 to 5 will be described below.

<Example 1>
As the insulating member 50, a protective tape made of polypropylene was used. Of the total length of 10 mm, a protective tape having a length of the non-adhesive region 50b of 2 mm and a length of the adhesive region 50a of 8 mm was used. The non-adhesion region 50b of the protective tape was positioned on the positive electrode active material layer 22 side to cover the boundary 23 between the positive electrode active material layer 22 and the exposed portion 21b. It coat | covered so that the coating length with respect to the positive electrode active material layer 22 of a protective tape might be set to 3 mm. Accordingly, at this time, the length of the adhesive region 50a of the protective tape facing the positive electrode active material layer 22 is 1 mm (see the state shown in FIG. 4).

The positive electrode 20 was cut out so that the size of the active material layer 22 was 190 mm × 190 mm. The negative electrode 30 was cut out so that the size of the active material layer 32 was 200 mm × 200 mm. The positive electrode 20 and the negative electrode 30 were laminated to produce a test cell.

  As a result of the cycle test, the cycle capacity retention rate was 90%.

<Example 2>
As the insulating member 50, a protective tape made of polypropylene was used. Of the total length of 10 mm, a protective tape having a length of 4 mm for the non-adhesion region 50 b and a length of 6 mm for the adhesion region 50 a was used. The non-adhesion region 50b of the protective tape was positioned on the positive electrode active material layer 22 side to cover the boundary 23 between the positive electrode active material layer 22 and the exposed portion 21b. It coat | covered so that the coating length with respect to the positive electrode active material layer 22 of a protective tape might be set to 3 mm. Therefore, at this time, the adhesive region 50a of the protective tape does not face the positive electrode active material layer 22, and the length becomes 0 (zero) mm (see the state shown in FIG. 2).

  The positive electrode 20 was cut out so that the size of the active material layer 22 was 190 mm × 190 mm. The negative electrode 30 was cut out so that the size of the active material layer 32 was 200 mm × 200 mm. The positive electrode 20 and the negative electrode 30 were laminated to produce a test cell.

  As a result of the cycle test, the cycle capacity retention rate was 95%.

<Example 3>
As the insulating member 50, a protective tape made of polypropylene was used. A protective tape provided with a non-adhesive region 50b on both sides in the longitudinal direction and an adhesive region 50a at the center was used. Of the total length of 10 mm, a protective tape was used in which the length of the non-adhesion region 50b was 3 mm, the length of the adhesion region 50a was 4 mm, and the length of the non-adhesion region 50b was 3 mm. One non-adhesion region 50b of the protective tape was positioned on the positive electrode active material layer 22 side to cover the boundary 23 between the positive electrode active material layer 22 and the exposed portion 21b. It coat | covered so that the coating length with respect to the positive electrode active material layer 22 of a protective tape might be set to 3 mm. Therefore, at this time, the adhesive region 50a of the protective tape does not face the positive electrode active material layer 22, and the length becomes 0 (zero) mm (see the state shown in FIG. 5).

  The positive electrode 20 was cut out so that the size of the active material layer 22 was 190 mm × 190 mm. The negative electrode 30 was cut out so that the size of the active material layer 32 was 200 mm × 200 mm. The positive electrode 20 and the negative electrode 30 were laminated to produce a test cell.

  As a result of the cycle test, the cycle capacity retention rate was 94%.

<Example 4>
A polyimide protective tape was used as the insulating member 50. Example 1 was performed except that the material of the protective tape was different. Of the total length of 10 mm, a protective tape having a length of the non-adhesive region 50b of 2 mm and a length of the adhesive region 50a of 8 mm was used. The non-adhesion region 50b of the protective tape was positioned on the positive electrode active material layer 22 side to cover the boundary 23 between the positive electrode active material layer 22 and the exposed portion 21b. It coat | covered so that the coating length with respect to the positive electrode active material layer 22 of a protective tape might be set to 3 mm. Accordingly, at this time, the length of the adhesive region 50a of the protective tape facing the positive electrode active material layer 22 is 1 mm (see the state shown in FIG. 4).

  The positive electrode 20 was cut out so that the size of the active material layer 22 was 190 mm × 190 mm. The negative electrode 30 was cut out so that the size of the active material layer 32 was 200 mm × 200 mm. The positive electrode 20 and the negative electrode 30 were laminated to produce a test cell.

  As a result of the cycle test, the cycle capacity retention rate was 91%.

<Example 5>
As the insulating member 50, a protective tape made of polyphenylene sulfide was used. Example 1 was performed except that the material of the protective tape was different. Of the total length of 10 mm, a protective tape having a length of the non-adhesive region 50b of 2 mm and a length of the adhesive region 50a of 8 mm was used. The non-adhesion region 50b of the protective tape was positioned on the positive electrode active material layer 22 side to cover the boundary 23 between the positive electrode active material layer 22 and the exposed portion 21b. It coat | covered so that the coating length with respect to the positive electrode active material layer 22 of a protective tape might be set to 3 mm. Accordingly, at this time, the length of the adhesive region 50a of the protective tape facing the positive electrode active material layer 22 is 1 mm (see the state shown in FIG. 4).

  The positive electrode 20 was cut out so that the size of the active material layer 22 was 190 mm × 190 mm. The negative electrode 30 was cut out so that the size of the active material layer 32 was 200 mm × 200 mm. The positive electrode 20 and the negative electrode 30 were laminated to produce a test cell.

  As a result of the cycle test, the cycle capacity retention rate was 90%.

  Hereinafter, Comparative Examples 1 and 2 will be described.

<Comparative Example 1>
As the insulating member 50, a protective tape made of polypropylene was used. A protective tape having a total length of 10 mm was the adhesive region 50a. The protective tape covered the boundary portion 23 between the positive electrode active material layer 22 and the exposed portion 21b. It coat | covered so that the coating length with respect to the positive electrode active material layer 22 of a protective tape might be set to 3 mm. Accordingly, at this time, the length of the adhesive region 50a of the protective tape facing the positive electrode active material layer 22 is 3 mm.

  The positive electrode 20 was cut out so that the size of the active material layer 22 was 190 mm × 190 mm. The negative electrode 30 was cut out so that the size of the active material layer 32 was 200 mm × 200 mm. The positive electrode 20 and the negative electrode 30 were laminated to produce a test cell.

  As a result of the cycle test, the cycle capacity retention rate was 78%.

<Comparative Example 2>
As the insulating member 50, a protective tape made of polypropylene was used. A protective tape having a total length of 10 mm was the adhesive region 50a. With this protective tape, only the exposed portion 21b was covered along the boundary portion 23 between the positive electrode active material layer 22 and the exposed portion 21b. Therefore, at this time, the adhesive region 50a of the protective tape does not face the positive electrode active material layer 22, and the length is 0 (zero) mm.

  The positive electrode 20 was cut out so that the size of the active material layer 22 was 190 mm × 190 mm. The negative electrode 30 was cut out so that the size of the active material layer 32 was 200 mm × 200 mm. The positive electrode 20 and the negative electrode 30 were laminated to produce a test cell.

  As a result of the cycle test, the cycle capacity retention rate was 85%.

  Table 1 summarizes the test results of the cycle capacity retention rates of Examples 1 to 6 and Comparative Examples 1 and 2.

<Comparison result>
In Examples 1 to 5, the cycle capacity retention rate was improved as compared with Comparative Examples 1 and 2. This is because, by providing a non-adhesive region on the active material layer side of the protective tape, it is possible to prevent the adhesive from eluting due to an increase in potential at the end of the active material layer during the cycle, and the ionic conductivity of the electrolyte. Reduction is suppressed. As a result, it is considered that the cycle characteristics are improved.

  The reason why the cycle capacity retention ratios of Examples 1 to 5 are improved as compared with Comparative Example 2 is as follows. When the adhesive region of the protective tape is attached along the outer peripheral edge of the active material layer (part where the active material is applied) as in Comparative Example 2, the active material layer having a high potential during charge / discharge Under the influence, the adhesive in the adhesive region is eluted, and the ionic conductivity of the electrolyte is lowered. As a result, cycle characteristics deteriorated. On the other hand, in Examples 1 to 5, since the outer peripheral edge of the active material layer is covered with the protective tape, the end portion of the active material layer where the charge / discharge reaction occurs (hereinafter referred to as “reaction end portion”) is It is inside the outer peripheral edge of the active material layer. In Examples 1 to 5, the distance between the reaction end portion and the adhesion region is 2 mm, 4 mm, 3 mm, 2 mm, and 2 mm in this order. In both Example 3 and Comparative Example 2, the adhesive region of the protective tape is adhered to the end portion of the active material layer. In Example 3, since the outer peripheral edge of the active material layer is covered with the protective tape, the distance between the reaction end portion and the adhesion region is 3 mm. On the other hand, in Comparative Example 2, since the outer peripheral edge of the active material layer is not covered with the protective tape, the distance between the reaction end portion and the adhesion region is 0 (zero) mm. Thus, since the reaction edge part and the adhesion | attachment area | region are spaced apart from Examples 1-5 compared with the comparative example 2, the elution of an adhesive material is suppressed and the fall of the ionic conductivity of electrolyte is suppressed. . As a result, it is considered that the cycle characteristics are improved.

  As in Examples 2 and 3, the positive electrode active material layer 22 was preferably covered with a protective tape, and the positive electrode active material layer 22 and the adhesive region 50a of the protective tape did not face each other, and the cycle characteristics were the best. .

  From Examples 4 and 5, if the material of the protective tape was an insulating material such as polyimide or polyphenylene sulfide in addition to polypropylene, the same effect was obtained.

  In the present embodiment, the power generation element 70 in which the positive electrode 20, the separator 40, and the negative electrode 30 are alternately laminated is manufactured. However, the present invention is not limited to this, and the power generation element in which the positive electrode and the negative electrode are wound via the separator is also used. It has been confirmed that similar effects can be obtained.

  In addition, the present invention can be variously modified based on the configurations described in the claims, and these are also within the scope of the present invention.

  For example, although the case where the insulating member 50 is applied to the positive electrode 20 has been described as an example, the present invention is not limited to this case. The insulating member 50 may be applied to the negative electrode 30, and the boundary portion 33 between the active material layer 32 and the exposed portion 31 b on the current collector 31 of the negative electrode 30 may be covered with the insulating member 50. Furthermore, the insulating member 50 can be applied to both the positive electrode 20 and the negative electrode 30.

10 electrodes,
20 positive electrode (electrode),
21 current collector,
21b exposed part,
22 active material layer,
22a end,
22b part,
23 border,
24 positive electrode tab,
30 negative electrode,
31 current collector,
31b exposed part,
32 active material layer,
33 border,
34 negative electrode tab,
40 separator,
50 insulation members,
50a bonding area,
50b, 50c non-adhesive area,
51 adhesives,
52, 53 border,
70 power generation element (laminate),
80 exterior body,
90 cell layer,
100 battery.

Claims (8)

A current collector,
An active material layer formed on the current collector so as to leave an exposed portion where a part of the current collector is exposed;
An insulating member that covers a boundary portion between the active material layer and the exposed portion;
The insulating member includes a bonding area formed by an adhesive on a surface facing the current collector, and a non-bonding area not including the adhesive,
The electrode, wherein the non-bonded region is located on the active material layer side.   The electrode according to claim 1, wherein a boundary between the non-bonded region and the bonded region is located closer to the exposed portion than the boundary portion.   The electrode according to claim 1, wherein the current collector and the active material layer are for a positive electrode.   The battery which has the laminated body which laminated | stacked the electrode of any one of Claims 1-3 via the separator, and the exterior body which seals the said laminated body.   The battery according to claim 4, wherein the active material layer has a rectangular shape, and a length of a short side of the rectangle is 100 mm or more. The value of the ratio of the area of the battery to the rated capacity (projected area of the battery including the exterior body) is 5 cm ² / Ah or more, and the rated capacity is 3 Ah or more. The battery according to any one of 5.   The battery according to claim 4, wherein an aspect ratio of the electrode defined as an aspect ratio of the rectangular active material layer is 1 to 3.   It is a lithium ion secondary battery, Comprising: The battery of any one of Claims 4-7 in which the said active material layer for negative electrodes is larger than the said active material layer for positive electrodes in planar view.