JP2017174796A - Characteristic evaluation method of lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a characteristic evaluation method of a lithium ion secondary battery, by which the performance of a positive electrode active material in connection with the battery characteristic can be evaluated with high accuracy because the amount of HF retained between current collectors can be reduced.SOLUTION: The characteristic evaluation method comprises: a step S1 for producing a positive electrode having a positive electrode current collector and a positive electrode active material layer formed thereon; a step S2 for producing a negative electrode having a negative electrode current collector and a negative electrode active material layer formed thereon; a step S3 for interposing a separator between the positive and negative electrodes; a step S4 for sealing the positive and negative electrodes and the separator together with an electrolyte solution in a laminate film to assemble a laminate cell; and a step S5 for making a battery characteristic evaluation on the laminate cell in connection while pressurizing the laminate cell at 1.50×10Pa or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for evaluating characteristics of a lithium ion secondary battery and a lithium ion secondary battery.

  Since lithium ion secondary batteries have high energy density, they are widely used in portable electronic devices such as mobile phones and notebook computers that are required to be smaller and lighter in recent years. Moreover, development as a clean energy source is actively performed for automobile applications, and high performance and low cost such as small size, light weight, high capacity, and high output are required. Among them, the 5V class positive electrode active material that operates at a high potential of 4V or more has the advantage of increasing the energy density of the battery and reducing the number of batteries of the assembled battery, and as a positive electrode active material for batteries for hybrid vehicles and electric vehicles. Development is progressing.

  In order to proceed with these developments quickly and at a low cost, the evaluation means is one of the important elements, and the importance of the evaluation in the development of the positive electrode active material for the lithium ion secondary battery is increasing. As specific evaluation methods, the composition of the positive electrode active material, particle size distribution, particle shape, crystal structure, arrangement of constituent elements, etc. and battery performance by so-called analytical evaluation methods such as composition analysis and XRD, SEM EDX, XPS, etc. Although there is correlation evaluation, it is indispensable to actually make a battery and evaluate battery characteristics. However, in the characteristic evaluation of a 5V class lithium ion secondary battery, it is difficult to obtain an accurate evaluation result due to decomposition of the electrolytic solution or gas generation.

  For example, in Patent Document 1, as a reason why it is difficult to evaluate a battery of a spinel-type lithium manganese-containing composite oxide having a working potential of 4.5 V or higher (5 V class), the presence of gas generated by reaction with an electrolytic solution is present. It has been pointed out that it is disclosed that the ratio of the interatomic distance between the 16d site and the 32e site is set to a desired value in order to suppress the generation amount of gas, but an improved method is disclosed for the battery evaluation method. I'm not doing it.

JP 2015-38872 A

  By the way, the main battery characteristics include initial charge / discharge capacity characteristics, charge / discharge cycle characteristics (durability characteristics), output characteristics, thermal stability, etc. Initial charge / discharge capacity evaluation is indispensable as basic battery characteristics. If an accurate measurement value is not obtained as the initial charge / discharge capacity characteristic, the characteristic evaluation of the subsequent measurement value is also affected. For example, the capacity maintenance rate when the cycle is repeated is evaluated as a relative value with respect to the initial charge / discharge capacity. Therefore, if the measured value of the initial charge / discharge capacity is not accurate, the evaluation based on the capacity maintenance rate also lacks accuracy. Become. For this reason, the initial charge / discharge capacity is a particularly important battery characteristic.

  A non-aqueous electrolyte secondary battery is usually composed of an electrode part in which a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material are arranged opposite to each other with a separator interposed therebetween, and a non-aqueous electrolyte solution impregnated in the electrode part. ing.

The non-aqueous electrolytes used for these materials exhibit sufficient performance in 4V class positive electrode active materials such as LiCoO ₂ that are currently widely used in the market, but are not suitable for operating 5V class positive electrode active materials. When trying to evaluate the battery characteristics of a 5V class positive electrode active material using a general non-aqueous electrolyte for a lithium ion secondary battery, excess electrolyte is present at the interface between the positive electrode active material and the electrolyte during charging at a high voltage. Oxidative decomposition occurs, and CO ₂ gas and H ₂ O are generated. The generated H ₂ O reacts with LiPF ₆ that is a supporting electrolyte contained in the electrolytic solution to generate hydrofluoric acid (HF). HF, which is a strong acid, adversely affects many battery components such as elution of the positive electrode active material, corrosion of the Al current collector, separation of the Cu current collector and the negative electrode coating film, and deterioration of the separator and binder. Therefore, it is difficult to stably evaluate the 5V class positive electrode active material by evaluating the lithium ion secondary battery at a high voltage. Currently, the development of electrolytes with a wide potential window, which shows potential regions where meaningful electrochemical measurements are possible, is still underway, but the level of practical use has not yet reached the level of evaluation of 5V class positive electrode active materials. It is an evaluation that includes the reaction of and degradation due to HF.

  In addition, Patent Document 1 described above does not describe any technique for suppressing deterioration of members formed in the nonaqueous electrolyte secondary battery by reducing the retention of HF, which is a strong acid.

  In order to perform cycle evaluation of a 5V-class positive electrode active material with high accuracy and stability over a long period of time, it is important to suppress HF generated by oxidative decomposition on the surface of the positive electrode active material. For this purpose, it is preferable to use an electrolyte solution with high oxidation resistance, but the currently available electrolyte solution with high oxidation resistance has problems such as insufficient reduction resistance and decomposition at the negative electrode. To do.

  The present invention has been proposed in view of the above-described problems of the prior art, and evaluates a positive electrode active material that requires charge / discharge evaluation at a high potential, such as a positive electrode active material for a 5 V class lithium ion secondary battery. New and improved lithium ion secondary battery capable of reducing battery member deterioration due to HF, which is a strong acid generated by decomposition of non-aqueous electrolyte, and obtaining highly accurate battery characteristic evaluation results An object of the present invention is to provide a method for evaluating the characteristics and a lithium ion secondary battery.

  As a result of earnest research on the means for suppressing the HF generated due to the oxidative decomposition of the electrolyte solution on the surface of the positive electrode active material, the inventor seems to sandwich both the positive electrode and the negative electrode. To the positive electrode current collector and the negative electrode current collector, specifically, a constituent part of the "positive electrode current collector-positive electrode active material layer-separator-negative electrode active material layer-negative electrode current collector" It was also found that the amount of HF staying between the current collectors can be reduced and the deterioration of the battery components can be suppressed by reducing the gap between the current collectors.

As a method for reducing the gap between the current collectors, there are methods such as roll press and hydraulic press, and a method of increasing the density by rolling the electrodes using a compression machine. However, when these methods are used to reduce the porosity of the electrode, naturally, the amount of the electrolytic solution retained inside the electrode is reduced, and the electrolytic solution is oxidized and decomposed on the surface of the positive electrode to generate a gas such as CO _2. In the positive electrode active material, gasification causes a problem that the electrolyte in the positive electrode active material layer is depleted and the charge / discharge capacity decreases. Therefore, in the embodiment of the present invention, the HF retention amount existing between the current collectors is reduced by reducing the voids in the portion other than the positive electrode where the oxidative decomposition of the electrolytic solution does not occur, and the cycle characteristics and the like are improved.

That is, the method for evaluating the characteristics of a lithium ion secondary battery according to one embodiment of the present invention is a method for evaluating the characteristics of a lithium ion secondary battery using a laminate cell composed of at least a positive electrode, a negative electrode, a separator, and an electrolytic solution. A step of producing the positive electrode in which a positive electrode active material layer is formed on a positive electrode current collector, a step of producing the negative electrode in which a negative electrode active material layer is formed on a negative electrode current collector, the positive electrode and the A step of interposing the separator between negative electrodes; a step of sealing the positive electrode, the negative electrode, and the separator together with an electrolyte in a laminate film; and assembling a laminate cell; and 1.50 of the laminate cell. And a step of evaluating the battery characteristics of the laminate cell while applying pressure at 10 ⁴ Pa or higher.

In one embodiment of the present invention, it is preferable to pressurize the laminate cell at 7.50 × 10 ⁴ Pa or more.

  In one embodiment of the present invention, it is preferable to pressurize only the electrode portion where the positive electrode and the negative electrode are present.

  In one embodiment of the present invention, it is preferable that the laminate cell has a gap in at least a part of the non-pressurized region.

  In one embodiment of the present invention, it is preferable that the gap portion is provided on the end portion side of the laminate cell facing the electrode terminal portions of the positive electrode and the negative electrode.

  In one embodiment of the present invention, in the step of interposing the separator between the positive electrode and the negative electrode, a cellulose separator is further interposed between the separator and the positive electrode, and the cellulose separator is the laminate. It is preferable that it extends along the longitudinal direction of the cell and is longer than the positive electrode and the negative electrode.

  In one embodiment of the present invention, a slurry obtained by wet-mixing the material constituting the positive electrode active material layer together with a solvent is coated on the positive electrode current collector foil and dried, whereby the positive electrode current collector foil is It is preferable to use a positive electrode on which a positive electrode active material layer is formed.

  In one embodiment of the present invention, it is preferable to perform a conditioning treatment while pressurizing the laminate cell.

  In one embodiment of the present invention, the positive electrode active material is preferably a positive electrode active material for a 5 V class lithium ion secondary battery.

A lithium ion secondary battery according to another aspect of the present invention includes a positive electrode in which a positive electrode active material layer is formed on a positive electrode current collector, a negative electrode in which a negative electrode active material layer is formed on a negative electrode current collector, the positive electrode, A laminate cell comprising a separator interposed between the negative electrode, the positive electrode, the negative electrode, and a laminate film for sealing the separator together with an electrolyte; and a pressurizing mechanism for pressurizing the laminate cell. The pressurizing mechanism pressurizes the laminate cell at 1.50 × 10 ⁴ Pa or more.

In one embodiment of the present invention, it is preferable that the pressurizing mechanism pressurizes the laminate cell at 7.50 × 10 ⁴ Pa or more.

  In one embodiment of the present invention, it is preferable that the pressurizing mechanism pressurizes only the electrode portion where the positive electrode and the negative electrode are present.

  In one embodiment of the present invention, it is preferable that at least a gap is provided in the laminate cell.

  In one embodiment of the present invention, it is preferable that the gap is provided on the side of the laminate cell opposite to the electrode terminal portions of the positive electrode and the negative electrode.

  In one embodiment of the present invention, in addition to the separator interposed between the positive electrode and the negative electrode, a cellulose separator is interposed between the separator and the positive electrode, and the cellulose separator is in the longitudinal direction of the laminate cell. It is preferable that it extends along and is longer than the positive electrode and the negative electrode.

  In one embodiment of the present invention, a slurry obtained by wet-mixing the material constituting the positive electrode active material layer together with a solvent is coated on the positive electrode current collector foil and dried, whereby the positive electrode current collector foil is It is preferable to use a positive electrode on which a positive electrode active material layer is formed.

  In one embodiment of the present invention, the positive electrode active material is preferably a positive electrode active material for a 5 V class lithium ion secondary battery.

  According to the present invention, it is possible to reduce the amount of HF that remains between the current collectors during charge / discharge reactions, particularly during charging with a high voltage applied. Therefore, it is possible to suppress deterioration due to HF of each member to be performed, and it is possible to evaluate a stable battery characteristic of the lithium ion secondary battery. In particular, the performance of the positive electrode active material related to battery characteristics can be evaluated with high accuracy.

It is a flowchart which shows the outline of the characteristic evaluation method of the lithium ion secondary battery which concerns on embodiment of this invention. It is a figure which shows the lithium ion secondary battery used for the characteristic evaluation method of the lithium ion secondary battery which concerns on embodiment of this invention, (A) is a schematic explanatory drawing of a laminate cell, (B) is a laminate cell. It is a front view. It is a figure which shows the conventional lithium ion secondary battery, (A) is a schematic explanatory drawing of a lamination cell, (B) is a front view of a lamination cell. It is explanatory drawing of the lithium ion secondary battery which concerns on embodiment of this invention, (A) is schematic explanatory drawing of a lithium ion secondary battery, (B) is AA which shows the outline of a lithium ion secondary battery. It is sectional drawing.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are essential as means for solving the present invention. Not necessarily.

  A characteristic evaluation method for a lithium ion secondary battery according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an outline of a method for evaluating characteristics of a lithium ion secondary battery. FIG. 2 is a diagram showing a configuration of a lithium ion secondary battery used in a method for evaluating the characteristics of a lithium ion secondary battery according to an embodiment of the present invention, (A) is a schematic explanatory diagram of a laminate cell, B) is a front view of the laminate cell.

As shown in FIG. 1, the method for evaluating the characteristics of a lithium ion secondary battery includes a step S1 for producing a positive electrode in which a positive electrode active material layer is formed on a positive electrode current collector, and a negative electrode active material layer is formed on the negative electrode current collector. Step S2 for producing a negative electrode, Step S3 for inserting a separator sheet impregnated with a non-aqueous electrolyte between the positive electrode and the negative electrode, and sealing the positive electrode, the negative electrode, and the separator together with the electrolyte with a laminate film Step S4 for assembling the laminate cell and a step S5 for conditioning the laminate cell while applying pressure to the laminate cell while applying pressure of 1.50 × 10 ⁴ Pa or more and evaluating the battery characteristics of the laminate cell while applying pressure to the laminate cell; Is included. Moreover, the laminate cell used for this lithium ion secondary battery is comprised from at least a positive electrode, a negative electrode, a separator, and electrolyte solution, as shown to FIG. 2 (A).

  First, in this embodiment, as shown in FIG. 2A, a positive electrode 110 in which a positive electrode active material layer (hereinafter also referred to as “positive electrode film”) is formed on a positive electrode current collector is manufactured (step S1). .

The positive electrode active material contained in the positive electrode active material layer is a layered composite oxidation such as LiCoO ₂ , LiNiO ₂ , Li (Ni, Co, Al) O ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O _2. Or a spinel positive electrode active material such as LiMn ₂ O ₄ can be used. The present invention is not limited to a 5V class positive electrode active material, but is particularly suitable for a method for evaluating a 5V class positive electrode active material represented by LiNi _0.5 Mn _1.5 O ₄ . As the positive electrode active material, those prepared according to the embodiment are used in order to express various battery characteristics. For example, the component composition, particle size, surface, and the like are considered as factors that affect the battery characteristics of the positive electrode active material.

  The positive electrode 110 includes a conductive material, a binder (binder), and the like in addition to the positive electrode active material, and these are mixed and used as a positive electrode mixture. Since battery characteristics are affected by these constituent materials, a positive electrode mixture is prepared using an appropriate material.

  The conductive material is for increasing the electrical conductivity between the positive electrode active material particles, which are semiconductors, and efficiently performing the charge / discharge reaction of the positive electrode 110, and is used in a general non-aqueous electrolyte secondary battery. Any conductive material may be used. For example, carbon materials such as graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black materials such as acetylene black and ketjen black (registered trademark) are used alone or in combination. be able to.

  The binder plays a role of connecting the positive electrode active material and the conductive material particles, and any binder used in a general non-aqueous electrolyte secondary battery may be used. For example, polytetrafluoroethylene, polyvinylidene fluoride, fluorine Fluorine-containing resins such as rubber, heat-plastic resins such as polypropylene and polyethylene, ethylene propylene diene rubber, styrene butadiene, cellulose resins, polyacrylic acid, and the like can be used.

  As a method for manufacturing the positive electrode 110, for example, a sheet method or a coating method can be used. In the sheet method, a positive electrode active material is dry-mixed together with a conductive material and a binder, and the resulting mixture is used together with a positive electrode current collector and a roll press or the like to form a sheet on which a positive electrode film is formed on a current collector such as an aluminum foil. After the production, the positive electrode 110 is obtained by punching into a desired size. The sheet method has an advantage that the positive electrode 110 can be manufactured quickly as compared with the electrode manufacturing method using a coating method.

  For example, the positive electrode 110 obtained by the sheet method is cut into a shape in which a band-like portion (terminal) having a step of 10 mm and 5 mm in width is projected at a corner of 3 cm × 5 cm. And the said positive electrode active material layer is removed from the strip | belt-shaped part, and the aluminum foil of a collector is exposed. Thus, as shown in FIG. 2A, the positive electrode 110 in which the positive electrode active material layer is formed on the positive electrode current collector is manufactured. A positive electrode terminal portion 111 is formed on the positive electrode 110.

  On the other hand, the coating method involves wet mixing the positive electrode active material with a conductive material, a binder, and a solvent, kneading to make a slurry, coating the obtained slurry on the positive electrode current collector and drying to form a positive electrode film, The positive electrode 110 is obtained by punching to the size of The coating method can reduce the coating thickness. In lithium-ion secondary batteries where the diffusion of lithium ions is rate-determined, it is possible to charge and discharge at a high rate by thinning the coating thickness and shortening the diffusion distance of lithium, enabling efficient long-term cycle evaluation. be able to.

  For dry mixing and wet mixing, a dry ball mill, a dry bead mill, a blade planetary motion mixer, a container rotation type planetary motion mixer can be used for dry mixing, and a stirrer, a homogenizer, etc. can be used for wet mixing. In particular, when a container rotation type planetary motion mixer is used, a homogeneous positive electrode film is easily obtained.

  Next, in this embodiment, as shown in FIG. 2A, a negative electrode 120 in which a negative electrode active material layer (hereinafter also referred to as “negative electrode film”) is formed on a negative electrode current collector is manufactured (step S2). ).

  The negative electrode active material contained in the negative electrode active material layer is a coke that can occlude and release lithium ions because inactive dentite is generated when metallic lithium is used and long-term cycle characteristics cannot be evaluated. , Glassy carbons, graphites, non-graphitizable carbons, and pyrolytic carbons can be used alone or in admixture of two or more.

  As a binder for accumulating them and bonding them on a metal foil current collector such as copper in a desired thickness and form, any binder may be used as long as it is used in general non-aqueous electrolyte secondary batteries. Fluorine-containing resins such as tetrafluoroethylene, polyvinylidene fluoride, and fluorine rubber, heat-plastic resins such as polypropylene and polyethylene, ethylene propylene diene rubber, styrene butadiene rubber, cellulose resin, and polyacrylic acid can be used. The powdered negative electrode active material is mixed with the above binder, added with a solvent such as N-methyl-2-pyrrolidinone (NMP), wet-mixed and kneaded into a slurry in the same manner as the positive electrode, and then a metal foil such as copper It is possible to use a material that is applied to the surface of the current collector, dried, and compressed to increase the electrode density as necessary, and cut into a desired size or punched.

  For example, the negative electrode 120 obtained by the sheet method is cut into a shape in which a strip-like portion (terminal) having a step of 10 mm and 5 mm in width is projected at a corner of 3 cm × 5 cm. And the said negative electrode active material layer is removed from the strip | belt-shaped part, and collector copper foil is exposed. Thus, as shown in FIG. 2A, the negative electrode 120 in which the negative electrode active material layer is formed on the negative electrode current collector is manufactured. The negative electrode 120 is formed with a negative electrode terminal portion 121.

  Next, in this embodiment, as shown to FIG. 2 (A), the separator 130 is inserted between the positive electrode 110 and the negative electrode 120 (process S3).

  As shown in FIG. 2A, the separator 130 is disposed between the positive electrode 110 and the negative electrode 120. The separator 130 separates the positive electrode 110 and the negative electrode 120 and retains the function of preventing the short circuit between the positive electrode 110 and the negative electrode 120 and the electrolytic solution. Examples of the separator 130 include polyethylene, polypropylene, cellulose, or polyfluoride. Examples thereof include a porous film containing vinylidene (PVDF) and a synthetic resin nonwoven fabric. They can be used alone or in combination.

  In step S3, a cellulose separator (not shown) may be further interposed between the separator 130 and the positive electrode 110. Since the cellulose separator is a separator having a particularly high porosity, it is excellent in holding the electrolytic solution and can efficiently release generated HF to the gap. However, since the cellulose separator has a low physical strength, when used alone, there is a greater risk of breakage during pressurization than other types of separators, and the cellulose separator is preferably used together with other types of separators. Further, by making the cellulose separator larger than the positive electrode and the negative electrode, the portion of the cellulose separator that is not in contact with the positive electrode and the negative electrode can function as a HF escape destination. Therefore, the cellulose separator preferably extends along the longitudinal direction of the laminate cell 100 and is longer than the positive electrode 110 and the negative electrode 120. The length of the cellulose separator is particularly preferably 1.2 times or more and 2.0 times or less than the positive electrode 110 and the negative electrode 120. If it is shorter than 1.2 times, such an effect is small, and if it is longer than 2.0 times, there is a part that is not in contact with more than necessary, so the laminate cell becomes unnecessarily large, and the capacity of the charge / discharge evaluation apparatus This is because the efficiency deteriorates.

  The electrolytic solution (non-aqueous electrolytic solution) is obtained by dissolving a lithium salt as a supporting salt in an organic solvent. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate; and tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. are used alone or in admixture of two or more. be able to.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , or a composite salt thereof can be used. Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

  Next, in this embodiment, as shown in FIG. 2A, the positive electrode 110, the negative electrode 120, and the separator 130 are sealed together with an electrolyte solution with a laminate film 140, and the laminate cell 100 shown in FIG. Assemble (step S4).

  A negative electrode having a positive electrode sheet (positive electrode 110) having a positive electrode terminal portion 111 in which a positive electrode active material layer is formed on an aluminum current collector, and a negative electrode terminal portion 121 having a negative electrode active material layer formed in a copper current collector A sheet (negative electrode 120) is used, and a separator 130 is interposed therebetween to form a laminated sheet. This laminated sheet is sandwiched between two laminated sheets (two-folded part (not shown)) laminated sheet (laminated film 140), and the positive electrode terminal part 111 and the negative electrode terminal part 121 are prepared in advance in the laminate cell 100. It accommodates so that it may be in the state which protruded from the edge of the exterior (aluminum laminate exterior).

  Then, two sides of the exterior of the laminate cell 100 are sealed by heat sealing. Next, after the inside of the exterior of the laminate cell 100 is evacuated from the opening on the remaining side, an electrolytic solution is injected, and the opening is also sealed by heat sealing, so that the laminate cell 100 is manufactured.

  Here, when the laminate cell 100 is assembled, the laminate cell 100 is preferably provided with a gap 150 in at least a part of a non-pressurized region (a region where the laminate cell is not pressurized in the subsequent step S5). . In this laminate cell 100, it is more preferable that the gap 150 is provided on the end side of the laminate cell facing the electrode terminal portions (the positive electrode terminal portion 111 and the negative electrode terminal portion 121) of the positive electrode 110 and the negative electrode 120. The void 150 is a portion that is covered with the laminate film 140 and is inside the laminate cell 100, and where the positive electrode 110 and the negative electrode 120 do not exist. As a result, the laminate cell 100 is provided with a gap 150 as shown in FIG. 2B, and HF can be transferred to the gap 150 so that HF generated between the current collectors does not stay. . Since the amount of HF in contact with the electrode member is small, corrosion deterioration of the electrode member is reduced. For this reason, measurement with little influence of HF on battery characteristics such as initial discharge capacity becomes possible, and the performance of the positive electrode active material can be measured with high accuracy. Here, the shape of the gap 150 is not particularly limited, and examples thereof include a rectangular shape and a square shape. Furthermore, the gap 150 preferably has a predetermined area or more, and in order to ensure a sufficient space for HF to escape, the area of the gap 150 is 1 to 5 times the area of the positive and negative electrodes. preferable. If the area of the gap portion 150 is about 1 time, it is enough to hold the generated HF, and even if it is larger than 5 times, the laminate cell becomes unnecessarily large and the volume efficiency of the charge / discharge evaluation apparatus deteriorates. It is.

  FIG. 3 is a view showing a conventional lithium ion secondary battery, in which (A) is a schematic explanatory view of a laminate cell, and (B) is a front view of the laminate cell. As shown in FIG. 3A, the conventional laminate cell 200 is laminated in the order of a positive electrode 210 having a positive electrode terminal portion 211 formed thereon, a separator 220, and a negative electrode 230 having a negative electrode terminal portion 231 formed thereon. The obtained laminate is covered with a laminate film 240 to produce a laminate cell 200 shown in FIG. When the configuration of the laminate cell 100 used in the present embodiment and the conventional laminate cell 200 are compared, the conventional laminate cell 200 does not have the gap 150 unlike the laminate cell 100 of FIG. For this reason, in the conventional laminate cell 200, there is no space for HF to stay in the electrode part. As a result, the battery member of the laminate cell is corroded by HF, making it difficult to evaluate the battery characteristics.

Next, the present embodiment is characterized in that the characteristics of the laminate cell are evaluated while pressing the laminate cell at 1.96 × 10 ⁴ Pa (0.2 kgf / cm ² ) or more (step S5). The means for pressurizing is not particularly limited, and for example, pressing may be performed by sandwiching the laminate cell 100 by a press machine in which the pressure is adjusted. The laminate cell is pressurized by applying pressure so as to sandwich both the positive electrode and the negative electrode as described above, and specifically between the positive electrode current collector and the negative electrode current collector, specifically, “positive electrode current collector-positive electrode”. The amount of HF staying between the current collectors is reduced by reducing the voids in the constituent parts of the active material layer-separator-negative electrode active material layer-negative electrode current collector (hereinafter also referred to as “between current collectors”). In order to suppress the deterioration of the battery constituent members. Another reason for this is to efficiently escape the generated HF to the gaps of the laminate cell to suppress contact between the positive electrode, the negative electrode and the HF.

  Moreover, it is preferable to perform a conditioning process, pressing a laminate cell. This conditioning treatment is performed in order to sufficiently impregnate the positive electrode, the negative electrode, and the separator with the electrolytic solution in the produced laminate cell, and is usually performed by storing at around room temperature for 12 to 24 hours.

  Therefore, in this embodiment, it is preferable to pressurize only the electrode part in which the positive electrode 110 and the negative electrode 120 exist. In the case where only the electrode part is locally pressurized, HF staying in the electrode can be efficiently removed rather than pressurizing the entire laminate cell 100. Thereby, since there is little HF amount which contacts an electrode member, corrosion of an electrode member is reduced. For this reason, there is almost no influence of battery characteristics such as initial discharge capacity. As a result, in this embodiment, the performance of the positive electrode active material can be accurately measured with respect to the battery characteristics.

In the present embodiment, the effect of the pressure of the laminate cell becomes remarkable when pressurized with a laminate cell 1.50 × 10 4 ^Pa or more, the laminate cell preferably be pressurized with 1.50 × 10 4 ^Pa or more, It is more preferable to pressurize at 7.50 × 10 ⁴ Pa or more, and particularly preferably 8.83 × 10 ⁴ Pa or more. If a pressure of 1.50 × 10 ⁴ Pa or more is applied to the laminate cell, the effect of escaping the generated HF to the gap appears, so that the initial charge / discharge capacity can be accurately evaluated. Furthermore, since the generation of HF is remarkable in the cycle characteristics evaluation that repeats charging and discharging, it is necessary to increase the above effect by pressurizing the laminate cell at 7.50 × 10 ⁴ Pa or more. Moreover, since the separator between electrodes may be damaged when the pressurization pressure becomes extremely large, the pressurization pressure is preferably 20.0 × 10 ⁴ Pa or less.

Next, a lithium ion secondary battery according to an embodiment of the present invention will be described with reference to FIG. FIG. 4 is an explanatory diagram of a lithium ion secondary battery according to an embodiment of the present invention, FIG. 4 (A) is a schematic explanatory diagram of a lithium ion secondary battery, and FIG. 4 (B) is a lithium ion secondary battery. It is AA sectional drawing which shows the outline of a battery. As shown in FIGS. 4A and 4B, the lithium ion secondary battery 300 according to the present embodiment includes a laminate including a positive electrode 311, a negative electrode 312, and a laminate film 314 that seals the separator 313 together with an electrolytic solution. It has a cell 310 and a pressurizing mechanism that is housed in the pressurizing case 320 and pressurizes the laminate cell 310. The pressurizing mechanism pressurizes the laminate cell 310 at 1.50 × 10 ⁴ Pa or more. In addition, in this embodiment, description of the structure which overlaps in the evaluation method for lithium ion secondary batteries is omitted.

  The pressurization mechanism includes a first support member 321a that is in surface contact with the side surfaces of the electrode terminal side 311a and 312a of the laminate cell 310, and a first compression coil spring 322a that pressurizes the first support member 321a against the side surface of the laminate film 340. A second support member 321b in surface contact with the opposite side surface of the laminate cell 310 in surface contact with the first support member 321a, and a second compression coil spring that pressurizes the second support member 321b against the side surface of the laminate cell 310. 322b. The pressurizing mechanism pressurizes the laminate cell 310 so that both the positive electrode 311 and the negative electrode 312 are sandwiched between the first support member 321a and the second support member 321b. On the other hand, a non-pressurized region that does not pressurize the laminate cell 310 is generated, and the laminate cell 310 is provided with a gap 330 in at least a part of the non-pressurized region.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example and a comparative example, this invention is not limited to these Examples and a comparative example.

  In Examples 1 to 3 and Comparative Examples 1 and 2, after the laminate cells were produced by the method for evaluating the characteristics of the lithium ion secondary battery according to this embodiment, the charge capacity and the discharge capacity of the laminate cells were evaluated. Details will be described below.

Example 1
In Example 1, the negative electrode is a slurry obtained by mixing a negative electrode material for lithium ion secondary batteries (natural graphite) manufactured by Mitsubishi Chemical and PVDF (binder) so as to have a mass ratio of 90:10 and dispersing in NMP. Turned into. This slurry was applied to a copper foil (negative electrode current collector) having a thickness of 15 μm to 3.1 mg / cm ² per unit area using an applicator. Then, it dried at 120 degreeC * 30 minutes with the ventilation dryer, and the electrode after drying was rolled with the linear pressure of 390 kgf / cm using the roll press, and the negative electrode sheet was obtained. The obtained negative electrode sheet was cut into a rectangular shape having a strip portion (terminal) having a size of 3.2 cm × 5.2 cm and a corner having a width of 10 mm. And the said negative electrode active material layer was removed from the strip | belt-shaped part, copper foil was exposed, the negative electrode terminal part was formed, and the negative electrode sheet with a terminal was obtained.

For the positive electrode, the positive electrode active material LiNi _0.5 Mn _1.5 O ₄ is mixed with acetylene black (conductive material) and PVDF (binder) in a mass ratio of 85: 10: 5 and dispersed in NMP to form a slurry. Turned into. This slurry was applied to an aluminum foil (positive electrode current collector) having a thickness of 20 μm at a rate of 5 mg / cm ² per unit area using an applicator. Then, it dried at 120 degreeC x 30 minutes with the ventilation dryer, and rolled with the load of the linear pressure of 180 kgf / cm with the roll press, and the positive electrode sheet was obtained. The obtained positive electrode sheet was cut into a rectangular shape having a strip-like portion (terminal) having a size of 3 cm × 5 cm and a width of 10 mm. And the said positive electrode active material layer was removed from the strip | belt-shaped part, aluminum foil was exposed, the positive electrode terminal part was formed, and the positive electrode sheet with a terminal was obtained.

  As the separator, a 20 μm-thick polypropylene microporous membrane separator sheet generally used in lithium ion secondary batteries cut to 5.8 cm × 3.4 cm was used as the separator sheet on the negative electrode side. Moreover, the cellulose separator sheet cut into 6 cm x 7 cm was used for the positive electrode side.

As the non-aqueous electrolyte, an electrolyte obtained by dissolving LiPF ₆ (1 mol / L) in a mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of EC / DMC = 4: 6 was used.

  The above materials were dried under reduced pressure at 80 ° C. for 8 hours, and then brought into a dry room having a dew point of less than −60 ° C. to assemble a laminated cell type battery having an exterior size of 80 mm × 90 mm.

As a conditioning treatment, the electrode part was restrained with a load of 1.96 × 10 ⁴ Pa (0.2 kgf / cm ² ) applied in a thermostat controlled at 25 ° C. and stored for 12 hours. .

  Thereafter, using a charge / discharge test apparatus (company name: Hokuto Denko, product name: HJ1001SD8), an operation of charging up to 5 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours), The operation of discharging to 3.5 V at a rate was performed. The rest time after charging and discharging was 10 minutes.

As an initial charge / discharge capacity, charge and discharge were performed in a constant temperature bath controlled at 25 ° C. while a load of 1.96 × 10 ⁴ Pa (0.2 kgf / cm ² ) was applied to the electrode part. Using a test apparatus, an operation of charging to 4.8 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours) and an operation of discharging to 3.5 V at a rate of 0.2 C were performed. The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the initial charge / discharge capacity of the laminate cell produced in Example 1, as shown in Table 1, the charge capacity was 119.5 mAh / g and the discharge capacity was 117.9 mAh / g.

Next, as an evaluation of the charge / discharge cycle characteristics (durability characteristics), a load of 1.96 × 10 ⁴ Pa (0.2 kgf / cm ² ) was applied to the electrode portion in a thermostat controlled at 60 ° C. 200 operations including charging to 4.9 V at a rate of 2 C (current value that becomes fully charged in 30 minutes) and discharging to 3.5 V at a rate of 2 C using a charge / discharge test apparatus. Repeated 200 times (200 cyc). The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the cycle characteristics (durability characteristics) of the laminate cell produced in Example 1, as shown in Table 1, the discharge capacity after 200 cyc was 69.1 mAh / g.

(Example 2)
In Example 2, similarly to Example 1, a laminated cell type battery was produced.

As a conditioning treatment, the electrode part was restrained under a load of 3.92 × 10 ⁴ Pa (0.4 kgf / cm ² ) in a thermostat controlled at 25 ° C. and stored for 12 hours. .

  Thereafter, an operation of charging to 5 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours) and an operation of discharging to 3.5 V at a rate of 0.2 C were performed using a charge / discharge test apparatus. The rest time after charging and discharging was 10 minutes.

As an initial charge / discharge capacity, charge / discharge was performed in a constant temperature bath controlled at 25 ° C. while a load of 3.92 × 10 ⁴ Pa (0.4 kgf / cm ² ) was applied to the electrode part. Using a test apparatus, an operation of charging to 4.8 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours) and an operation of discharging to 3.5 V at a rate of 0.2 C were performed. The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the initial charge / discharge capacity of the laminate cell produced in Example 2, as shown in Table 1, the charge capacity was 121.3 mAh / g and the discharge capacity was 119.6 mAh / g.

Next, as an evaluation of charge / discharge cycle characteristics (durability characteristics), a load of 3.92 × 10 ⁴ Pa (0.4 kgf / cm ² ) was applied to the electrode part in a thermostat controlled at 60 ° C. 200 operations including charging to 4.9 V at a rate of 2 C (current value that becomes fully charged in 30 minutes) and discharging to 3.5 V at a rate of 2 C using a charge / discharge test apparatus. Repeated 200 times (200 cyc). The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the cycle characteristics (durability characteristics) of the laminate cell produced in Example 2, as shown in Table 1, the discharge capacity after 200 cyc was 68.2 mAh / g.

(Example 3)
In Example 3, similarly to Example 1, a laminated cell type battery was produced.

As a conditioning treatment, the electrode part was restrained under a load of 8.83 × 10 ⁴ Pa (0.9 kgf / cm ² ) in a thermostat controlled at 25 ° C. and stored for 12 hours. .

  Thereafter, an operation of charging to 5 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours) and an operation of discharging to 3.5 V at a rate of 0.2 C were performed using a charge / discharge test apparatus. The rest time after charging and discharging was 10 minutes.

As an initial charge / discharge capacity, charge and discharge were performed in a constant temperature bath controlled at 25 ° C. while a load of 8.83 × 10 ⁴ Pa (0.9 kgf / cm ² ) was applied to the electrode part. Using a test apparatus, an operation of charging to 4.8 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours) and an operation of discharging to 3.5 V at a rate of 0.2 C were performed. The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the initial charge / discharge capacity of the laminate cell produced in Example 3, as shown in Table 1, the charge capacity was 120.9 mAh / g and the discharge capacity was 119.3 mAh / g.

Next, as an evaluation of charge / discharge cycle characteristics (endurance characteristics), a load of 8.83 × 10 ⁴ Pa (0.9 kgf / cm ² ) was applied to the electrode part in a thermostat controlled at 60 ° C. 200 operations including charging to 4.9 V at a rate of 2 C (current value that becomes fully charged in 30 minutes) and discharging to 3.5 V at a rate of 2 C using a charge / discharge test apparatus. Repeated 200 times (200 cyc). The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the cycle characteristics (durability characteristics) of the laminate cell produced in Example 3, as shown in Table 1, the discharge capacity after 200 cyc was 79.1 mAh / g.

(Comparative Example 1)
In Comparative Example 1, a laminated cell type battery was produced as in Example 1.

As a conditioning treatment, the electrode part was restrained with a load of 0.39 × 10 ⁴ Pa (0.04 kgf / cm ² ) in a thermostat controlled at 25 ° C. and stored for 12 hours. .

  Thereafter, an operation of charging to 5 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours) and an operation of discharging to 3.5 V at a rate of 0.2 C were performed using a charge / discharge test apparatus. The rest time after charging and discharging was 10 minutes.

As an initial charge / discharge capacity, charge and discharge were performed in a constant temperature bath controlled at 25 ° C. with a load of 0.39 × 10 ⁴ Pa (0.04 kgf / cm ² ) applied to the electrode part. Using a test apparatus, an operation of charging to 4.8 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours) and an operation of discharging to 3.5 V at a rate of 0.2 C were performed. The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the initial charge / discharge capacity of the laminate cell produced in Comparative Example 1, as shown in Table 1, the charge capacity was 106.5 mAh / g and the discharge capacity was 103.3 mAh / g.

Next, as an evaluation of charge / discharge cycle characteristics (durability characteristics), a load of 0.39 × 10 ⁴ Pa (0.04 kgf / cm ² ) was applied to the electrode part in a thermostat controlled at 60 ° C. 200 operations including charging to 4.9 V at a rate of 2 C (current value that becomes fully charged in 30 minutes) and discharging to 3.5 V at a rate of 2 C using a charge / discharge test apparatus. Repeated 200 times (200 cyc). The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the cycle characteristics (durability characteristics) of the laminate cell produced in Comparative Example 1, as shown in Table 1, the discharge capacity after 200 cyc was 52.9 mAh / g.

(Comparative Example 2)
In Comparative Example 2, a laminated cell type battery was produced as in Example 1.

As a conditioning treatment, the electrode part was restrained under a load of 0.98 × 10 ⁴ Pa (0.1 kgf / cm ² ) in a thermostat controlled at 25 ° C. and stored for 12 hours. .

  Thereafter, an operation of charging to 5 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours) and an operation of discharging to 3.5 V at a rate of 0.2 C were performed using a charge / discharge test apparatus. The rest time after charging and discharging was 10 minutes.

As an initial charge / discharge capacity, charge and discharge were performed in a constant temperature bath controlled at 25 ° C. while a load of 0.98 × 10 ⁴ Pa (0.1 kgf / cm ² ) was applied to the electrode part. Using a test apparatus, an operation of charging to 4.8 V at a rate of 0.2 C (current value that becomes fully charged in 5 hours) and an operation of discharging to 3.5 V at a rate of 0.2 C were performed. The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the initial charge / discharge capacity of the laminate cell produced in Comparative Example 2, as shown in Table 1, the charge capacity was 101.9 mAh / g and the discharge capacity was 100.1 mAh / g.

Next, as an evaluation of charge / discharge cycle characteristics (durability characteristics), a load of 0.98 × 10 ⁴ Pa (0.1 kgf / cm ² ) was applied to the electrode part in a thermostat controlled at 60 ° C. 200 operations including charging to 4.9 V at a rate of 2 C (current value that becomes fully charged in 30 minutes) and discharging to 3.5 V at a rate of 2 C using a charge / discharge test apparatus. Repeated 200 times (200 cyc). The rest time after charging and discharging was 10 minutes.

  As a result of evaluating the cycle characteristics (durability characteristics) of the laminate cell produced in Example 3, as shown in Table 1, the discharge capacity after 200 cyc was 68.5 mAh / g.

  The charge capacity and discharge capacity of the laminate cells evaluated in Examples 1 to 3 and Comparative Examples 1 to 2 and the value of the discharge capacity after 200 cyc were evaluated in three stages based on the following criteria. The obtained results are shown in Table 1.

Judgment criteria for initial charge / discharge capacity ○: When charge capacity and discharge capacity are each 110 mAh / g or more Δ: When either charge capacity or discharge capacity is 110 mAh / g or more ×: Charge capacity and discharge capacity are , Each less than 110 mAh / g

Cycle characteristics (endurance characteristics) Discharge capacity after 200 cyc Criteria ○: When the discharge capacity is 70 mAh / g or more Δ: When the discharge capacity is 60 mAh / g or more and less than 70 mAh / g ×: Discharge capacity is less than 60 mAh / g If it is

Comprehensive determination ○: When the determination of the initial charge / discharge capacity evaluation result and the determination of the cycle characteristic evaluation result are both “good”: The determination of the initial charge / discharge capacity evaluation result and the determination of the cycle characteristic evaluation result are both When there is no and either is △: When the determination of the initial charge / discharge capacity evaluation result and the determination of the cycle characteristic evaluation result are either ×

Regarding the initial charge / discharge capacity, in Examples 1 to 3, when evaluating the laminate cell, maintaining the pressure of 1.96 × 10 ⁴ Pa (0.2 kgf / cm ² ) or more in the electrode portion of the laminate cell, Both the charge capacity and discharge capacity exceeded 115 mAh / g.

  As described above, the characteristic evaluation method (initial charge / discharge capacity evaluation) of the lithium ion secondary battery according to the present embodiment is useful because the charge capacity and discharge capacity of the positive electrode active material can be observed more accurately. It was confirmed.

  On the other hand, in Comparative Examples 1-2, compared with Examples 1-3, the value with low charge / discharge capacity and discharge capacity was obtained. From this result, it was confirmed that the low binding force in the electrode part is not suitable for the initial charge / discharge capacity evaluation of the 5V class positive electrode active material.

Regarding the cycle characteristics (durability characteristics), in Example 3, when the laminate cell was evaluated, the electrode part of the laminate cell was maintained at a pressure of 8.83 × 10 ⁴ Pa (0.9 kgf / cm ² ) or more. The discharge capacity after 200 cyc exceeded 70 mAh / g.

  From the above, the characteristic evaluation method (cycle characteristic (durability characteristic) evaluation) of the lithium ion secondary battery according to the present embodiment was useful because it was possible to observe the charge capacity and discharge capacity of the positive electrode active material more accurately. It was confirmed that.

On the other hand, in Examples 1-2 and Comparative Examples 1-2, compared with Example 3, the value with a low discharge capacity after 200 cyc was obtained. From this result, it was confirmed that the restraining force of 8.83 × 10 ⁴ Pa or more is more suitable for evaluating the cycle characteristics (durability characteristics) of the 5V class positive electrode active material.

In Examples 1 to 3, it was confirmed that maintaining the pressure of 1.96 × 10 ⁴ Pa or more is effective for evaluating the initial charge / discharge capacity. According to Example 3, it was confirmed that maintaining a pressure of 8.83 × 10 ⁴ Pa or more is more effective for evaluating cycle characteristics (durability characteristics).

  The characteristic evaluation method (initial charge / discharge capacity evaluation and cycle characteristic (durability characteristic) evaluation) of the lithium ion secondary battery according to the present embodiment is suitable as a method for evaluating characteristics related to the positive electrode active material of the secondary battery.

100 Laminate Cell, 110 Positive Electrode, 111 Positive Electrode Terminal Part, 120 Negative Electrode, 121 Negative Electrode Terminal Part, 130 Separator, 140 Laminate Film, 150 Void Part, 200 Laminate Cell, 210 Positive Electrode, 211 Positive Electrode Part, 220 Separator, 230 Negative Electrode, 231 Negative electrode terminal, 240 Laminate film, 300 Lithium ion secondary battery, 310 Laminate cell, 311 positive electrode, 311a Positive electrode terminal part, 312 Negative electrode, 312a Negative electrode terminal part, 313 Separator, 314 Laminate film, 320 Pressure case, 321a 1st Support member, 321b Second support member, 321a First compression coil spring, 322b Second compression coil spring

Claims (17)

A method for evaluating the characteristics of a lithium ion secondary battery using a laminate cell composed of at least a positive electrode, a negative electrode, a separator, and an electrolyte solution,
Producing the positive electrode in which a positive electrode active material layer is formed on a positive electrode current collector;
Producing the negative electrode having a negative electrode active material layer formed on a negative electrode current collector;
Inserting the separator between the positive electrode and the negative electrode;
Sealing the positive electrode, the negative electrode, and the separator together with an electrolyte in a laminate film, and assembling a laminate cell;
And a step of evaluating the battery characteristics of the laminate cell while pressurizing the laminate cell at 1.50 × 10 ⁴ Pa or more. 2. The method for evaluating characteristics of a lithium ion secondary battery according to claim 1, wherein the laminate cell is pressurized at 7.50 × 10 ⁴ Pa or more.   3. The method for evaluating characteristics of a lithium ion secondary battery according to claim 1, wherein only the electrode portion where the positive electrode and the negative electrode are present is pressurized.   The method for evaluating characteristics of a lithium ion secondary battery according to any one of claims 1 to 3, wherein the laminate cell is provided with a gap in at least a part of the non-pressurized region.   5. The method for evaluating characteristics of a lithium ion secondary battery according to claim 4, wherein the gap is provided on an end portion side of the laminate cell facing the electrode terminal portions of the positive electrode and the negative electrode. In the step of inserting the separator between the positive electrode and the negative electrode, a cellulose separator is further inserted between the separator and the positive electrode,
The lithium ion secondary battery according to claim 1, wherein the cellulose separator extends along a longitudinal direction of the laminate cell and is longer than the positive electrode and the negative electrode. Characterization method.   A positive electrode in which the positive electrode active material layer is formed on the positive electrode current collector foil by applying a slurry obtained by wet mixing the material constituting the positive electrode active material layer together with a solvent onto the positive electrode current collector foil and drying the slurry. The method for evaluating characteristics of a lithium ion secondary battery according to any one of claims 1 to 6, wherein:   The method for evaluating characteristics of a lithium ion secondary battery according to any one of claims 1 to 7, wherein a conditioning treatment is performed while pressurizing the laminate cell.   The method for evaluating characteristics of a lithium ion secondary battery according to any one of claims 1 to 8, wherein the positive electrode active material is a positive electrode active material for a 5V class lithium ion secondary battery. A positive electrode on which a positive electrode active material layer is formed on a positive electrode current collector, a negative electrode on which a negative electrode active material layer is formed on a negative electrode current collector, a separator interposed between the positive electrode and the negative electrode, the positive electrode, A laminate cell comprising a negative electrode and a laminate film for sealing the separator together with an electrolyte;
A pressurizing mechanism for pressurizing the laminate cell;
The lithium ion secondary battery, wherein the pressurizing mechanism pressurizes the laminate cell at 1.50 × 10 ⁴ Pa or more. The lithium ion secondary battery according to claim 10, wherein the pressurizing mechanism pressurizes the laminate cell at 7.50 × 10 ⁴ Pa or more.   The lithium ion secondary battery according to claim 10 or 11, wherein the pressurizing mechanism pressurizes only an electrode portion where the positive electrode and the negative electrode exist.   13. The lithium ion secondary battery according to claim 10, wherein the laminate cell is provided with a gap in at least a part of the non-pressurized region.   The lithium ion secondary battery according to claim 13, wherein the gap is provided on an end side of the laminate cell facing the electrode terminal portions of the positive electrode and the negative electrode.   In addition to the separator interposed between the positive electrode and the negative electrode, a cellulose separator is interposed between the separator and the positive electrode, and the cellulose separator extends along the longitudinal direction of the laminate cell, and the positive electrode 15. The lithium ion secondary battery according to claim 10, wherein the lithium ion secondary battery is longer than the negative electrode.   A positive electrode in which the positive electrode active material layer is formed on the positive electrode current collector foil by applying a slurry obtained by wet mixing the material constituting the positive electrode active material layer together with a solvent onto the positive electrode current collector foil and drying the slurry. The lithium ion secondary battery according to any one of claims 10 to 15, wherein the lithium ion secondary battery is used.   The lithium ion secondary battery according to any one of claims 10 to 16, wherein the positive electrode active material is a positive electrode active material for a 5V class lithium ion secondary battery.

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