JP7182590B2 - Manufacturing method of lithium ion battery - Google Patents

Description

The present technology relates to a method for manufacturing a lithium ion battery.

International Publication No. 2013/121563 (Patent Document 1) discloses maintaining a charged state in which the positive electrode potential is the oxidation potential of iron (Fe) or higher and the negative electrode potential is the reduction potential of iron (Fe) or higher. there is

WO2013/121563

During the manufacturing process of a lithium ion battery (which may be abbreviated as “battery” hereinafter), the positive electrode may be contaminated with copper (Cu) pieces. The Cu piece may be, for example, negative electrode cutting debris, negative electrode welding spatter, or the like. The Cu pieces mixed in the positive electrode are oxidized during charging, and can be eluted into the electrolytic solution as Cu ions. Cu ions can be reduced on the surface of the negative electrode and deposited as a solid. A minute short circuit may occur due to the growth of deposited Cu (solid) toward the positive electrode side.

An object of the present technology is to reduce the frequency of occurrence of micro short circuits.

The configuration and effects of the present technology will be described below. However, the mechanism of action of this technology includes presumption. Whether the mechanism of action is correct or not does not limit the scope of the present technology.

[1] A method for manufacturing a lithium ion battery includes the following (A) to (D).
(A) forming an electrode body including a positive electrode, a negative electrode, and a separator;
(B) The electrode body is housed in the exterior body.
(C) A lithium ion battery is formed by injecting an electrolytic solution into the package.
(D) After an interval of 3 hours or more from the injection of the electrolytic solution, the lithium ion battery is charged for the first time.
The first charge is to charge the lithium-ion battery such that the negative electrode potential of 2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li) is maintained for more than 4 hours. include.

It is considered that the Cu pieces mixed in the positive electrode are dissolved in the electrolytic solution when the positive electrode potential becomes equal to or higher than the oxidation potential of Cu. The oxidation potential of Cu is considered to be, for example, about 3.39 V (vs. Li ⁺ /Li).

In the present technology, a film can be formed on the negative electrode before the potential of the positive electrode reaches or exceeds the oxidation potential of Cu. That is, after the electrolyte is injected, when the battery is first energized (initial charge), the negative electrode potential of 2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li) exceeds 4 hours. The battery is charged so that it lasts. Thereby, a homogeneous and dense film can be formed on the surface of the negative electrode. Since the coating is homogeneous and dense, it is expected that Cu deposition will not concentrate locally but will be dispersed throughout the coating. As a result, Cu deposited on the negative electrode is less likely to grow toward the positive electrode, and it is expected that the frequency of occurrence of micro-short circuits will be reduced.

As long as it is within the range of 2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li), the negative electrode potential may be substantially constant or may vary. good.

However, the initial charging is performed after an interval of 3 hours or more from the injection of the electrolytic solution. In this specification, the interval between the injection of the electrolyte and the initial charging is also referred to as the "pre-initial charging interval". If the interval before the first charge is less than 3 hours, the penetration of the electrolytic solution into the negative electrode is insufficient, and the homogeneity and denseness of the film may decrease.

[2] The interval may be, for example, 8 hours or more and less than 75 hours. When the interval before the first charge is 8 hours or more, it is expected that, for example, the homogeneity and fineness of the film will be improved. If the interval before the first charge is 75 hours or more, for example, Cu contained in the negative electrode may be eluted.

[3] In the initial charge, the lithium ion battery is charged so that the negative electrode potential of, for example, 2.5 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li) is maintained for 12 hours or more. may include This is expected to improve, for example, the uniformity and density of the film.

[4] The positive electrode contains a positive electrode active material. The positive electrode active material may contain, for example, a layered oxide.

[5] The electrolytic solution may contain, for example, vinylene carbonate. The inclusion of vinylene carbonate (VC) in the electrolytic solution is expected to promote the formation of the film.

[6] The separator may have, for example, a multilayer structure. Since the separator has a multilayer structure, Cu ions tend to diffuse in the plane direction of the separator. As a result, the deposition of Cu is dispersed, and it is expected that Cu will be less likely to grow toward the positive electrode side.

FIG. 1 is a schematic flow chart of the manufacturing method of this embodiment. FIG. 2 is a schematic diagram showing an example of the configuration of the electrode assembly of this embodiment. FIG. 3 is a schematic diagram showing an example of the configuration of the lithium ion battery of this embodiment.

Hereinafter, embodiments of the present technology (hereinafter also referred to as “present embodiments”) will be described. However, the following description does not limit the scope of this technology.

As used herein, "comprise, include," "have," and variations thereof [e.g., "be composed of," "emcopass, involve," Descriptions of "contain", "carry, support", "hold", etc.] are open-ended. That is, it includes a configuration, but is not limited to including only that configuration. References to "consist of" are closed form. The statement "consisting essentially of" is semi-closed form. That is, the description “consisting essentially of” indicates that additional components may be included in addition to the essential components within a range that does not hinder the purpose of the present technology. For example, components normally assumed in the field to which the present technology belongs (for example, unavoidable impurities, etc.) may be included as additional components.

In this specification, any two or more steps, acts and operations involved in a method are not limited to the order in which they are presented unless specifically stated otherwise.

In this specification, singular forms (“a,” “an,” and “the”) include plural forms unless otherwise stated. For example, "particle" can include not only "one particle" but also "aggregate of particles (powder)".

In this specification, the description “V (vs. Li ⁺ /Li)” indicates a potential based on the standard electrode potential of lithium (Li).

In the present specification, numerical ranges such as "2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li)" include upper and lower limits unless otherwise specified. . For example, "2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li)" is "2.0 V (vs. Li ⁺ /Li) or more, 2.8 V (vs. Li ⁺ /Li) or less” indicates a numerical range. Also, numerical values arbitrarily selected from within the numerical range may be used as the new upper and lower limits. For example, a new numerical range may be set by arbitrarily combining the numerical values within the numerical range and the numerical values described elsewhere in this specification.

In this specification, when a compound is represented by a stoichiometric composition formula such as "LiCoO ₂ ", the stoichiometric composition formula is merely a representative example. Composition ratios may be non-stoichiometric. For example, when lithium cobalt oxide is expressed as “LiCoO ₂ ”, the composition ratio of lithium cobalt oxide is not limited to “Li/Co/O=1/1/2” unless otherwise specified. It may contain Li, Co and O in a compositional ratio.

<Method for manufacturing lithium ion battery>
FIG. 1 is a schematic flow chart of the manufacturing method of this embodiment.
The manufacturing method of the present embodiment includes "(A) formation of electrode body", "(B) accommodation", "(C) injection of electrolyte" and "(D) initial charging". The manufacturing method of the present embodiment may further include, for example, "(E) first aging", "(F) capacitance measurement", "(G) second aging", and "(H) voltage measurement". good.

<<(A) Formation of electrode body>>
FIG. 2 is a schematic diagram showing an example of the configuration of the electrode assembly of this embodiment.
The manufacturing method of this embodiment includes forming an electrode body 50 including a positive electrode 10 , a negative electrode 20 and a separator 30 .

The electrode body 50 may be of a wound type, for example. The electrode body 50 can be formed, for example, by laminating the positive electrode 10, the separator 30 and the negative electrode 20 in this order and winding them in a spiral shape. The electrode body 50 may be flattened after winding. Note that the winding type is an example. The electrode body 50 may be, for example, a stacked type. For example, the electrode body 50 may be formed by alternately stacking the positive electrode 10 and the negative electrode 20 with the separator 30 interposed therebetween.

(positive electrode)
The positive electrode 10 may be, for example, a strip-shaped sheet. Cathode 10 may be prepared by any method. For example, the cathode 10 can be prepared by forming the cathode active material layer 12 on the surface of the cathode current collector 11 . The positive electrode active material layer 12 may be formed by applying slurry, for example. The positive electrode current collector 11 may be aluminum (Al) foil or the like, for example. The positive electrode active material layer 12 may contain, for example, a positive electrode active material, a conductive material, a binder, and the like.

The positive electrode current collector 11 may have a thickness of, for example, 10 μm to 30 μm. The cathode active material layer 12 may have a thickness of, for example, 10 μm to 100 μm. The thickness of each member herein can be measured by a constant pressure thickness gauge (thickness gauge). The positive electrode active material layer 12 may have a density of, for example, 2 g/cm ³ to 4 g/cm ³ . The density of the active material layer in this specification indicates the apparent density.

The positive electrode active material can contain any component. The positive electrode active material may contain, for example, a layered oxide. The positive electrode active material may, for example, consist essentially of a layered oxide. The layered oxide has a layered rock salt type crystal structure. The layered oxide may contain, for example, at least one selected from the group consisting of LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , Li(NiCoMn)O ₂ and Li(NiCoAl)O ₂ . Here, for example, descriptions such as “(NiCoMn)” in composition formulas such as “Li(NiCoMn)O ₂ ” indicate that the sum of the composition ratios in parentheses is one. The conductive material can contain any component. The conductive material may contain, for example, acetylene black. The blending amount of the conductive material may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The binder can contain optional ingredients. The binder may include, for example, polyvinylidene fluoride (PVdF). The blending amount of the binder may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material.

(negative electrode)
The negative electrode 20 may be, for example, a strip-shaped sheet. Anode 20 can be prepared by any method. For example, the negative electrode 20 can be prepared by forming the negative electrode active material layer 22 on the surface of the negative electrode current collector 21 . The negative electrode active material layer 22 may be formed by applying slurry, for example. The negative electrode current collector 21 may be, for example, a Cu foil or the like. The negative electrode active material layer 22 may contain, for example, a negative electrode active material, a conductive material, a binder, and the like.

The negative electrode current collector 21 may have a thickness of, for example, 5 μm to 20 μm. The negative electrode active material layer 22 may have a thickness of, for example, 10 μm to 100 μm. The negative electrode active material layer 22 may have a density of, for example, 0.8 g/cm ³ to 1.6 g/cm ³ .

The negative electrode active material can contain any component. The negative electrode active material contains, for example, at least one selected from the group consisting of graphite, soft carbon, hard carbon, Si, SiO, Si-based alloys, Sn, _SnO , Sn _- based alloys, and _Li4Ti5O12 . You can The negative electrode active material may consist essentially of graphite, for example. The binder can contain optional ingredients. The binder may contain, for example, at least one selected from the group consisting of carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR). The blending amount of the binder may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material.

(separator)
The separator 30 may be, for example, a strip-shaped sheet. At least part of the separator 30 is arranged between the positive electrode 10 and the negative electrode 20 . Separator 30 separates positive electrode 10 and negative electrode 20 . Separator 30 is porous. The separator 30 is permeable to the electrolyte. Separator 30 is electrically insulating. The separator 30 may contain, for example, polyolefin resin. The separator 30 may be substantially made of a polyolefin resin layer, for example. The polyolefin resin may contain, for example, at least one selected from the group consisting of polyethylene (PE) and polypropylene (PP).

Separator 30 may have a thickness of, for example, 10 μm to 30 μm. The separator 30 may have, for example, a single layer structure. The separator 30 may, for example, consist essentially of a PE layer. The separator 30 may have a multilayer structure, for example. Since the separator 30 has a multilayer structure, Cu ions tend to diffuse in the plane direction of the separator 30 . As a result, the deposition of Cu is dispersed, and it is expected that Cu will be less likely to grow toward the positive electrode 10 side. The separator 30 may have, for example, a three-layer structure. The separator 30 may include, for example, a PP layer, a PE layer and a PP layer. The PP layer, PE layer and PP layer may be laminated in this order. A ceramic layer may be formed on the surface of the separator 30 . The separator 30 may have, for example, a two-layer structure. Separator 30 may include, for example, a PE layer and a ceramic layer. The ceramic layer may contain, for example, ceramic particles and a binder. The ceramic particles may contain, for example, at least one selected from the group consisting of alumina, boehmite, titania, magnesia and zirconia. A ceramic layer may be arranged, for example, between the polyolefin-based resin layer and the positive electrode 10 . A ceramic layer may be formed on the surface of the positive electrode 10 .

《(B) Storage》
FIG. 3 is a schematic diagram showing an example of the configuration of the lithium ion battery of this embodiment.
The manufacturing method of this embodiment includes housing the electrode body 50 in the exterior body 90 . The exterior body 90 may be, for example, a rectangular (flat rectangular parallelepiped) container. The exterior body 90 may be substantially made of Al alloy, for example. The exterior body 90 may include, for example, an electrolytic solution injection port (not shown). The injection port may be configured to be openable and closable.

In addition, the exterior body of FIG. 3 is only an example. The exterior body 90 in this embodiment may have any configuration. The exterior body 90 may be cylindrical, for example. The exterior body 90 may be, for example, pouch-shaped. The exterior body 90 may be substantially made of an Al laminate film, for example.

The exterior body 90 may include, for example, a positive electrode terminal 91 and a negative electrode terminal 92 . The electrode body 50 and the positive electrode terminal 91 can be connected by, for example, a positive current collecting member 81 . The positive current collecting member 81 may be, for example, an Al plate. The electrode body 50 and the negative terminal 92 can be connected by, for example, a negative collector member 82 . The negative electrode current collecting member 82 may be, for example, a Cu plate or the like.

<<(C) Injection of Electrolyte>>
The manufacturing method of the present embodiment includes forming the battery 100 by injecting an electrolytic solution (not shown) into the outer package 90 . The electrode body 50 is impregnated with the electrolytic solution inside the exterior body 90 . This enables exchange of Li ions between the positive electrode 10 and the negative electrode 20 . That is, it becomes a state in which electricity can be supplied. The exterior body 90 may be sealed immediately after the electrolyte is injected. The exterior body 90 may be hermetically sealed after initial charging, which will be described later. This is because gas may be generated during the initial charge.

The injection amount of the electrolytic solution can be appropriately adjusted according to, for example, the amount of the active material. For example, the electrode assembly 50 may be impregnated with substantially all of the electrolytic solution. For example, the electrode body 50 may be impregnated with a part of the electrolytic solution. For example, part of the electrolytic solution may be stored outside the electrode body 50 (bottom portion of the exterior body 90).

The electrolyte is a liquid electrolyte. The electrolytic solution contains a solvent and a supporting electrolyte. Solvents are aprotic. The solvent can contain any component. Solvents include, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), 1,2-dimethoxyethane (DME ), methyl formate (MF), methyl acetate (MA), methyl propionate (MP), and γ-butyrolactone (GBL).

The supporting electrolyte is dissolved in the solvent. The supporting electrolyte may contain, for example, at least one selected from the group consisting of LiPF ₆ , LiBF ₄ and LiN(FSO ₂ ) ₂ . The supporting electrolyte may have a molarity of, for example, 0.5 mol/L to 2.0 mol/L. The supporting electrolyte may have a molarity of, for example, 0.8 mol/L to 1.2 mol/L.

The electrolyte may further contain optional additives. Additives are, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), propanesultone (PS), cyclohexylbenzene (CHB), biphenyl (BP) and It may contain at least one selected from the group consisting of lithium bisoxalatoborate (LiBOB). That is, the electrolytic solution may contain VC. The inclusion of VC in the electrolytic solution is expected to promote the formation of the film. The additive may have a weight concentration of, for example, 0.1% to 1%.

《(D) Initial charge》
The manufacturing method of this embodiment includes charging the battery 100 for the first time after an interval of 3 hours or more from the injection of the electrolytic solution.

If the interval before the first charge is less than 3 hours, the penetration of the electrolytic solution into the negative electrode 20 (negative electrode active material layer 22) is insufficient, and the homogeneity and denseness of the film may be reduced. The interval before the first charge may be, for example, 8 hours or more. When the interval before the first charge is 8 hours or more, it is expected that, for example, the homogeneity and fineness of the film will be improved. The interval before the first charging may be, for example, 10 hours or longer, or 12 hours or longer. The pre-first charge interval may be, for example, less than 75 hours. If the interval before the first charge is 75 hours or longer, for example, Cu contained in the negative electrode 20 (negative electrode current collector 21) may be eluted. The interval before the first charge may be, for example, 72 hours or less, 48 hours or less, or 24 hours or less.

During the pre-first charge interval, for example, operations may be performed to facilitate electrolyte penetration. For example, the interior of the exterior body 90 may be decompressed or pressurized. For example, battery 100 may be heated. For example, the attitude of battery 100 may be changed. For example, battery 100 may be rocked.

After the interval before the first charge has elapsed, the battery 100 is connected to the charging device. The ambient temperature of the battery 100 may be normal temperature (20° C.±15° C.), for example. Hereinafter, in this specification, "CC (constant current)" indicates a constant current method, "CV (constant voltage)" indicates a constant voltage method, and "CC-CV" indicates a constant current-constant voltage method. Note that the term "constant" in this specification does not indicate strict constantness. "Constant" indicates that the variation is small enough to be considered substantially constant in the field to which this technology belongs. "It" is a symbol indicating the time rate of current. For example, a current of 1 It is defined as the current at which the battery's rated capacity is discharged in 1 hour.

The initial charging may include, for example, first CC charging, CV charging, and second CC charging. The first CC charging, the CV charging and the second CC charging may be performed continuously, for example. For example, there may be a predetermined interval between each operation.

First, a first CC charge may be performed. In the first CC charge, the battery 100 is charged until the negative electrode potential reaches a value within the range of 2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li). When the negative electrode active material contains graphite, the battery voltage (terminal voltage) after the first CC charge can be, for example, 2.1V to 2.9V. The charging current may be, for example, 0.1 It to 1 It.

After the first CC charging, CV charging may be performed. CV charging is performed so that the negative electrode potential of 2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li) is maintained. CV charging is carried out over 4 hours. Thereby, a homogeneous and dense film can be formed on the surface of the negative electrode 20 (negative electrode active material). As a result, it is expected that micro short circuits due to Cu are reduced. CV charging may be performed such that the negative electrode potential of, for example, 2.5 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li) is maintained. The battery voltage during CV charging can be, for example, 2.1V to 2.9V.

The duration of CV charging is arbitrary as long as it exceeds 4 hours. The duration of CV charging may be, for example, 12 hours or more. Of course, an excessively long duration of CV charging can affect productivity. The duration of CV charging may be, for example, 24 hours or less, or 18 hours or less.

As long as the negative electrode potential of 2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li) can be maintained, the charging method is arbitrary. CC charging may be performed, for example, with a sufficiently low rate of current.

After CV charging, a second CC charging may be performed. In the second CC charging, battery 100 is charged until reaching a predetermined SOC (state of charge). As used herein, "SOC" refers to the percentage of current charge capacity of a battery relative to its full charge capacity. The SOC after the second CC charging may be, for example, 40% to 80% or 50% to 70%. Since a film is formed on the surface of the negative electrode 20 in CV charging, the second CC charging may be performed so that the potential of the positive electrode is equal to or higher than the oxidation potential of Cu. The battery voltage after the second CC charging may be 3.5V to 3.8V, for example.

<<(E) First Aging>>
The manufacturing method of the present embodiment may include subjecting the battery 100 to first aging. For example, the first aging may be performed after initial charging. "Aging" in this specification indicates that the battery is stored for a predetermined period of time in a temperature environment exceeding normal temperature. For example, the battery 100 may be stored under a temperature environment of 40°C to 80°C. The retention period may be, for example, from 1 hour to 72 hours.

<<(F) Capacitance measurement>>
The manufacturing method of this embodiment may include measuring the capacity of the battery 100 . For example, after the first aging, the capacity of battery 100 may be measured. For example, the discharge capacity of the battery 100 may be measured by CC-CV charging and CC-CV discharging. For example, charge/discharge cycles may be performed about 2 to 5 times.

<<(G) Second Aging>>
The manufacturing method of the present embodiment may include subjecting the battery 100 to second aging. For example, a second aging may be performed after capacity measurement. The temperature of the second aging may be higher or lower than the temperature of the first aging. The temperature of the second aging may be, for example, 60°C to 80°C. The second aging period may be longer or shorter than the first aging period. The period of second aging may be, for example, 12 to 24 hours.

<<(H) Voltage measurement>>
The manufacturing method of this embodiment may include measuring the voltage of the battery 100 . When a minute short circuit occurs during the manufacturing process, the voltage drop rate of the battery 100 increases. Therefore, a micro short circuit can be detected from the voltage measurement result. For example, the presence or absence of a minute short circuit may be determined from the amount of voltage drop before and after the second aging. In this embodiment, it is expected that the frequency of occurrence of micro short circuits will be reduced. This is because micro short-circuiting due to Cu deposition is less likely to occur.

As described above, the battery 100 of the present embodiment can be manufactured. Battery 100 can be used in any application. Battery 100 may be used, for example, in an electric vehicle as a main power source or power assist power source. A battery module or an assembled battery may be manufactured by connecting a plurality of batteries 100 .

Hereinafter, an embodiment of the present technology (hereinafter also referred to as "this embodiment") will be described. However, the following description does not limit the scope of the present technology.

<Manufacture of lithium-ion batteries>
No. in Table 1 below. 1 to No. Each battery was manufactured according to the 9 conditions. The rated capacity of the battery was 80mAh.

<<(A) Formation of electrode body>>
A positive electrode and a negative electrode were prepared. The positive electrode active material included a layered oxide. The negative electrode active material contained graphite. The positive electrode and the negative electrode had a rectangular planar shape. A lead tab was connected to the positive electrode. A lead tab was connected to the negative electrode. Cu spheres were prepared. The Cu spheres had a diameter of 40 μm. A Cu ball was placed on the surface of the positive electrode. By pressing the Cu spheres, the Cu spheres were embedded in the surface of the positive electrode.

A separator was prepared. The separator had a multilayer structure. The separator included a polyolefin resin layer and a ceramic layer. An electrode body was formed by stacking the positive electrode, the separator, and the negative electrode such that the positive electrode and the negative electrode face each other with the separator interposed therebetween. The ceramic layer was arranged between the positive electrode and the polyolefin resin layer. The electrode assembly was compressed by a pressure of 4 MPa.

《(B) Storage》
A shell was prepared. The package was in the form of a pouch. The exterior body was made of Al laminated film. The electrode body was housed in the exterior body.

<<(C) Injection of Electrolyte>>
An electrolyte was prepared. The electrolyte contained VC. An electrolytic solution was injected into the exterior body.

《(D) Initial charge》
After the injection of the electrolyte, the interval before the first charge in Table 1 below was provided. After the interval before the first charge had elapsed, the first charge was performed. In this embodiment, the initial charging was performed in the order of "first CC charging→CV charging→second CC charging". Conditions for CV charging are shown in Table 1 below. After the first charge, the exterior body was sealed.

No. 6 and no. 7, an initial charge was performed at the time of capacity measurement. In CV charging during capacity measurement, the negative electrode potential was about 0.1 V (vs. Li ⁺ /Li).

<<(E) first aging, (F) capacitance measurement, (G) second aging>>
After the initial charge, first aging, capacity measurement and second aging were performed in this order.

<<(H) Voltage measurement>>
In this example, the voltage drop width (absolute value) was measured before and after the second aging. The average value (μ) and the standard deviation (σ) of the voltage drop width were calculated for the battery group (population) that did not contain the Cu spheres. A micro-short circuit was considered to have occurred when the voltage drop width in the target battery was "μ+4σ" or more. In the column of "micro-short circuit occurrence frequency" in Table 1 below, for example, "2/3" indicates that micro-short circuits occurred in two of the three batteries.

<Results>
In Table 1 above, when all of the following conditions are satisfied, there is a tendency for the frequency of occurrence of micro short circuits to decrease.
- The interval before the first charge is 3 hours or longer.
- The negative electrode potential in the initial charge (CV charge) is from 2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li).
- The charging time for the initial charge (CV charge) exceeds 4 hours.

This embodiment and this example are illustrative in all respects. This embodiment and this example are not restrictive. The scope of the present technology includes all changes within the meaning and range of equivalence to the description of the claims. For example, it is planned from the beginning that arbitrary configurations are extracted from this embodiment and this example and they are arbitrarily combined. When a plurality of actions and effects are described in this embodiment and this example, the scope of the present technology is not limited to the range in which all the actions and effects are exhibited.

10 positive electrode 11 positive electrode current collector 12 positive electrode active material layer 20 negative electrode 21 negative electrode current collector 22 negative electrode active material layer 30 separator 50 electrode body 81 positive electrode current collecting member 82 negative electrode current collecting member 90 exterior body, 91 positive terminal, 92 negative terminal, 100 battery (lithium ion battery).

Claims (4)

forming an electrode assembly including a positive electrode, a negative electrode, and a separator;
housing the electrode body in an exterior body;
Forming a lithium ion battery by injecting an electrolytic solution into the exterior body;
and,
Initial charging of the lithium ion battery with an interval of 3 hours or more from the injection of the electrolyte solution;
including
The electrolytic solution contains vinylene carbonate,
In the lithium ion battery, a member containing copper is housed inside the exterior body,
The first charge charges the lithium ion battery such that a negative electrode potential of 2.0 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li) is maintained for more than 4 hours. including and
The interval is 8 hours or more and less than 75 hours ,
A method for manufacturing a lithium ion battery. In the initial charge, the lithium ion battery is charged so that the negative electrode potential of 2.5 V (vs. Li ⁺ /Li) to 2.8 V (vs. Li ⁺ /Li) is maintained for 12 hours or longer. including,
A method for manufacturing a lithium ion battery according to claim 1 . the positive electrode comprises a positive electrode active material;
wherein the positive electrode active material comprises a layered oxide;
3. A method for producing a lithium ion battery according to claim 1 or 2 . The separator has a multilayer structure,
A method for manufacturing a lithium ion battery according to any one of claims 1 to 3 .

Images