JP2022086223A - Method for manufacturing non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a method for manufacturing a non-aqueous electrolyte secondary battery having an excellent battery performance and capable of effectively removing a gas generated when a film is formed.SOLUTION: A method for manufacturing a non-aqueous electrolyte secondary battery includes a housing step (S10), a constructing step (S20), a first charging step (S30), a sealing step (S40), and a second charging step (S50). The housing step houses an electrode body 20 including a positive electrode 50 including a positive electrode active material layer 54, a negative electrode 60 including a negative electrode active material layer 64, a first separator 71, and a second separator 72 in a battery case 30 in which a liquid injection hole 37 is formed. The constructing step constructs a battery assembly 100A by injecting a non-aqueous electrolyte 10 into the battery case 30. The first charging step arranges a battery assembly 100A in which the liquid injection hole 37 is opened inside a chamber 90 and charges the battery assembly 100A with a first pressure inside the chamber 90 being lower than a second pressure inside the battery case 30. The sealing step seals the liquid injection hole 37. The second charging step further charges the battery assembly 100A in which the liquid injection hole 37 is sealed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery.

Generally, in a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, a part of the non-aqueous electrolyte is decomposed at the time of initial charging, and a film (that is, a film) containing the decomposed product is formed on the surface of the negative electrode active material layer. A Solid Electrolyte Interface film, hereinafter referred to as an SEI film) is formed. The SEI film plays a role of protecting the negative electrode active material layer, stabilizes the interface between the negative electrode active material layer and the non-aqueous electrolytic solution, and can improve the battery performance (for example, cycle characteristics).

By the way, when the film is formed on the surface of the negative electrode active material layer, a part of the non-aqueous electrolytic solution is decomposed at the same time to generate gas. The generated gas may remain inside the electrode body. If the gas remains inside the electrode body, it means that the non-aqueous electrolytic solution does not exist in such a portion, and there is a possibility that a film will not be formed in the portion. As a result, there may be a problem that the battery performance is deteriorated.

Patent Document 1 and Patent Document 2 are examples of conventional techniques for removing gas generated during film formation. Patent Document 1 discloses a technique of discharging the gas accumulated in the accommodation space in which the power generation element is accommodated after the initial charge to the outside, and further evacuating the accommodation space. Further, Patent Document 2 describes a technique of discharging the generated gas from the non-aqueous electrolytic solution to the outside by performing precharging in a state where the battery element is arranged in the non-aqueous electrolytic solution filled in the vacuum chamber. Is disclosed. Further, in Patent Document 3, a heat-shrinkable member having been cut is provided between the electrode winding body and the cylindrical can to secure a gas flow path between the electrode winding body and the battery can. The technology for the purpose of is disclosed.

Japanese Unexamined Patent Publication No. 2001-283923 Japanese Unexamined Patent Publication No. 11-31531 Japanese Unexamined Patent Publication No. 2012-114006

However, the technique described in Patent Document 1 cannot effectively remove the gas remaining inside the electrode body, and cannot suppress the deterioration of the battery performance. That is, since the non-aqueous electrolytic solution hardly impregnates the portion of the negative electrode active material layer that is in contact with the gas, there is a possibility that the SEI film is not sufficiently formed during the initial charging.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a non-aqueous electrolytic solution secondary battery having excellent battery performance by effectively removing a gas generated during film formation.

INDUSTRIAL APPLICABILITY According to the present invention, an accommodating step of accommodating an electrode body including a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and a separator in a battery case having a liquid injection hole, and a non-water-free battery case. The construction process of injecting an electrolytic solution to construct a battery assembly and the battery assembly having an open injection hole are arranged inside the chamber, and the first pressure inside the chamber is the battery case. A first charging step of charging the battery assembly in a state of being lower than the second pressure inside, a sealing step of sealing the injection hole, and the battery assembly in which the injection hole is sealed. A method for manufacturing a non-aqueous electrolyte secondary battery, comprising a second charging step of further charging.

In the above configuration, the liquid injection hole of the battery case of the battery assembly arranged inside the chamber is open. That is, the inside of the chamber and the inside of the battery case (that is, the electrode body) are in a state of communicating with each other through the liquid injection holes. Here, in the first charging step, since the battery assembly is charged in a state where the first pressure inside the chamber is lower than the second pressure inside the battery case, it is generated by the decomposition of the non-aqueous electrolytic solution inside the battery case. The resulting gas moves into the lower pressure chamber. That is, the gas generated inside the battery case is discharged to the inside of the chamber shortly after staying inside the electrode body. As a result, the non-aqueous electrolytic solution infiltrates the entire negative electrode active material layer, so that a film can be suitably formed over the entire negative electrode active material layer during the first charging step. Therefore, it is possible to manufacture a non-aqueous electrolytic solution secondary battery having excellent battery performance.

In a preferred embodiment of the manufacturing method disclosed herein, in the first charging step, the battery assembly is evacuated while the inside of the chamber is evacuated so that the first pressure inside the chamber becomes a negative pressure. To charge. As a result, it is possible to more reliably prevent the gas generated by the decomposition of the non-aqueous electrolytic solution from remaining inside the electrode body.

In a preferred embodiment of the manufacturing method disclosed herein, in the first charging step, the battery assembly is charged until the SOC reaches 10% to 20%. Most of the gas generated by the decomposition of the non-aqueous electrolyte is generated between 10% and 20% SOC. Therefore, in the first charging step, by charging the battery assembly until the SOC reaches 10% to 20%, most of the gas can be removed, and the gas that may remain inside the electrode body is reduced. be able to.

In a preferred embodiment of the production method disclosed herein, the positive electrode active material layer contains a lithium transition metal oxide as the positive electrode active material, and the non-aqueous electrolyte solution contains a lithium salt as an electrolyte and the lithium salt. Includes a soluble carbonate-based solvent. According to such a configuration, the decomposition of the non-aqueous electrolytic solution may proceed more and more gas may be generated. Therefore, according to the above manufacturing method, more gas generated can be removed more reliably.

It is a flowchart which shows each process of the manufacturing method of the lithium ion secondary electric | cylinder which concerns on one Embodiment. It is a schematic diagram which shows the state which the battery assembly is arranged in the chamber which concerns on one Embodiment. It is sectional drawing of the lithium ion secondary battery which concerns on one Embodiment.

Hereinafter, preferred embodiments of the techniques disclosed herein will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention (for example, general configurations and manufacturing processes of batteries that do not characterize the present invention) are in the art. It can be grasped as a design matter of a person skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed in the present specification and the common general technical knowledge in the art.

In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged. The non-aqueous electrolyte secondary battery refers to a secondary battery that uses electrolyte ions contained in a non-aqueous electrolyte as a charge carrier. Hereinafter, the present technology will be described by taking as an example a method for manufacturing a lithium ion secondary battery as an example of a method for manufacturing a non-aqueous electrolyte secondary battery. In the present specification, the "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and realizes charge / discharge by the transfer of charges accompanying the lithium ions between the positive and negative electrodes.

As shown in FIG. 1, the method for manufacturing a lithium ion secondary battery (non-aqueous electrolyte secondary battery) 100 according to the present embodiment includes a housing step S10 in which the electrode body 20 is housed in the battery case 30 and a battery assembly. It includes a construction step S20 for constructing 100A, a first charging step S30 for charging the battery assembly 100A, a sealing step S40, and a second charging step S50 for further charging the battery assembly 100A.

First, the accommodating step S10 will be described. In the accommodating step S10, a liquid injection hole 37 is formed in the electrode body 20 including the positive electrode 50 including the positive electrode active material layer 54, the negative electrode 60 including the negative electrode active material layer 64, the first separator 71, and the second separator 72. It is housed in the battery case 30.

As shown in FIG. 2, the shape of the battery case 30 is a flat square shape. The battery case 30 includes a box-shaped main body 31 having an opening 30H on one side surface, and a plate-shaped lid 32 that closes the opening 30H of the main body 31. The lid 32 of the battery case 30 is provided with a positive electrode external terminal 42 and a negative electrode external terminal 44 for external connection, and a safety valve 36. The safety valve 36 releases the internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. Further, the lid 32 of the battery case 30 is provided with a liquid injection hole 37 for injecting the non-aqueous electrolytic solution 10 into the inside of the battery case 30. The material of the battery case 30 is preferably a material that is lightweight and has good thermal conductivity. As an example, aluminum having high thermal conductivity and appropriate rigidity is used as the material of the battery case 30 of the present embodiment. However, it is also possible to change the configuration of the battery case 30. For example, a flexible laminate may be used as the battery case 30.

The electrode body 20 is wound by superimposing a long positive electrode 50, a long first separator 71, a long negative electrode 60, and a long second separator 72. Specifically, the positive electrode 50 has a long positive electrode current collector 52 and a positive electrode active material layer 54 formed along one side or both sides (both sides in this embodiment) of the positive electrode current collector 52 along the longitudinal direction. And, including. The negative electrode 60 includes a long negative electrode current collector 62 and a negative electrode active material layer 64 formed along the longitudinal direction on one side or both sides (both sides in this embodiment) of the negative electrode current collector 62. .. The exposed portions 52A and 62A are located at both ends of the electrode body 20 in the direction of the winding axis. The exposed portion 52A is a portion where the positive electrode current collector 52 is exposed without forming the positive electrode active material layer 54. A positive electrode current collecting terminal 43 is joined to the exposed portion 52A. A positive electrode external terminal 42 is electrically connected to the positive electrode current collecting terminal 43. Further, the exposed portion 62A is a portion where the negative electrode current collector 62 is exposed without forming the negative electrode active material layer 64. A negative electrode current collector terminal 45 is joined to the exposed portion 62A. A negative electrode external terminal 44 is electrically connected to the negative electrode current collector terminal 45. The electrode body 20 may be a laminated electrode body in which a positive electrode, a negative electrode, and a separator are laminated, instead of the wound electrode body.

As the positive electrode 50 and the negative electrode 60, the same ones used in the conventional lithium ion secondary battery can be used without particular limitation. A typical aspect is shown below.

Examples of the positive electrode current collector 52 constituting the positive electrode 50 include aluminum foil and the like. Examples of the positive electrode active material contained in the positive electrode active material layer 54 include lithium transition metal oxides (eg, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , LiFeO ₂ , LiMn ₂ O). ₄ , LiNi _0.5 Mn _1.5 O ₄ , etc.), lithium transition metal phosphate compounds (eg, LiFePO ₄ , etc.) and the like. The positive electrode active material layer 54 may contain components other than the active material, such as a conductive material and a binder. As the conductive material, for example, carbon black such as acetylene black (AB) or other carbon material (eg, graphite or the like) can be preferably used. As the binder, for example, polyvinylidene fluoride (PVDF) or the like can be used.

Examples of the negative electrode current collector 62 constituting the negative electrode 60 include copper foil and the like. As the negative electrode active material contained in the negative electrode active material layer 64, a carbon material such as graphite, hard carbon, or soft carbon can be used. Of these, graphite is preferable. The graphite may be natural graphite, artificial graphite, or may be coated with an amorphous carbon material. The negative electrode active material layer 64 may contain components other than the active material, such as a binder and a thickener. As the binder, for example, styrene butadiene rubber (SBR) or the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) or the like can be used.

As the first separator 71 and the second separator 72, a porous sheet (film) made of polyolefin such as polyethylene (PE) or polypropylene (PP) can be preferably used. The porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat-resistant layer (HRL) may be provided on the surfaces of the first separator 71 and the second separator 72.

Next, the construction step S20 will be described. In the construction step S20, the non-aqueous electrolytic solution 10 is injected into the battery case 30 to construct the battery assembly 100A. The non-aqueous electrolytic solution 10 is injected into the inside of the battery case 30 (that is, the main body 31) through the injection holes 37 formed in the lid 32 of the battery case 30. For example, the non-aqueous electrolytic solution 10 is injected in a state where the pressure inside the battery case 30 is lower than the atmospheric pressure. When the injection is completed, the pressure inside the battery case 30 is returned to a pressure equal to or higher than the atmospheric pressure. The non-aqueous electrolyte 10 usually contains an organic solvent (non-aqueous solvent) and a supporting salt.

As the non-aqueous solvent, a known one used as a non-aqueous solvent for the electrolytic solution for a lithium ion secondary battery can be used, and specific examples thereof include carbonates, ethers, esters, nitriles, and the like. Examples thereof include solvents and lactones. Of these, carbonates are preferable. Examples of carbonates (carbonate-based solvents) include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like. These can be used alone or in combination of two or more. The non-aqueous solvent dissolves the supporting salt (electrolyte).

The supporting salt is used as the main electrolyte, and for example, lithium salts such as LiPF ₆ , LiBF ₄ , and LiClO ₄ are preferably used. The content of the supporting salt is not particularly limited as long as the effect of the present invention is not significantly impaired. For example, when LiPF ₆ is used as the supporting salt, the molar content of LiPF ₆ is 0.5 mol / L to 3.0 mol / L (preferably 0.5 mol / L to 1.5 mol / L, for example, 1 mol / L). Is adjusted to. By adjusting the content of LiPF ₆ in the non-aqueous electrolytic solution in this way, the total ion content in the non-aqueous electrolytic solution and the viscosity of the electrolytic solution can be appropriately balanced, so that the ionic conductivity can be adjusted. The input / output characteristics can be improved without excessively deteriorating.

Next, the first charging step S30 will be described. In the first charging step S30, the battery assembly 100A in which the injection hole 37 is opened is arranged inside the chamber 90, and the first pressure inside the chamber 90 is lower than the second pressure inside the battery case 30. Charges the battery assembly 100A with.

As shown in FIG. 2, the chamber 90 is formed in a size capable of arranging the battery assembly 100A inside. The battery assembly 100A can be arranged inside the chamber 90 or removed from the inside of the chamber 90. An exhaust port 90H is formed in the chamber 90. A vacuum pump 92 is provided at the exhaust port 90H. The vacuum pump 92 is configured to evacuate the inside of the chamber 90. When the vacuum pump 92 is driven, the inside of the chamber 90 becomes a negative pressure (for example, low vacuum, medium vacuum, high vacuum). Further, a charging device (not shown) for charging the battery assembly 100A is provided inside the chamber 90.

Here, when the battery assembly 100A in which the injection hole 37 is opened is arranged inside the chamber 90, that is, the first pressure inside the chamber 90 before driving the vacuum pump 92 is equal to the atmospheric pressure. Further, the second pressure inside the battery case 30 before driving the vacuum pump 92 is, for example, equal to atmospheric pressure. In the first charging step S30, the vacuum pump 92 is driven to evacuate the inside of the chamber 90 so that the first pressure inside the chamber 90 becomes smaller than the second pressure inside the battery case 30. In the present embodiment, the inside of the chamber 90 is evacuated so that the first pressure inside the chamber 90 becomes a negative pressure. Then, the battery assembly 100A is charged in a state where the first pressure inside the chamber 90 is lower than the second pressure inside the battery case 30. In the first charging step S30, the battery assembly 100A is charged until the SOC reaches 10% to 20% (for example, 15%). In the first charging step S30, the battery assembly 100A is charged until it reaches, for example, 3.7V. In the first charging step S30, the battery assembly 100A is preferably charged while the inside of the chamber 90 is evacuated by the vacuum pump 92. By charging the battery assembly 100A, a part of the non-aqueous electrolytic solution 10 is decomposed to form a film (SEI film) on the negative electrode active material layer 64, and gas is generated on the electrode body 20, but it is generated. The gas is discharged to the outside of the battery case 30 by the vacuum pump 92. Gas continues to be generated during charging of the battery assembly 100A, but by continuing to evacuate the inside of the chamber 90 by the vacuum pump 92, it is suppressed that gas remains in the electrode body 20. That is, since the non-aqueous electrolytic solution 10 invades the entire electrode body 20, it is possible to suppress the occurrence of unevenness in the film formed on the negative electrode active material layer 64.

Next, the sealing step S40 will be described. In the sealing step S40, the battery assembly 100A charged in the first charging step S30 is taken out from the chamber 90. Then, the liquid injection hole 37 is sealed. In the present embodiment, the liquid injection hole 37 is sealed by welding the sealing member 38 (see FIG. 3) to the liquid injection hole 37.

Next, the second charging step S50 will be described. In the second charging step S50, the battery assembly 100A in which the injection hole 37 is sealed is further charged. The second charging step S50 is usually performed under atmospheric pressure, and is not performed inside the chamber 90. In the second charging step S50, the battery assembly 100A is charged until the SOC reaches 100%. In the second charging step S50, the battery assembly 100A is charged from, for example, 3.7V to 4.2V. As described above, as shown in FIG. 3, a sealed lithium ion secondary battery 100 including the electrode body 20, the non-aqueous electrolytic solution 10, and the battery case 30 is manufactured. Since the lithium ion secondary battery 100 manufactured by the above manufacturing method charges the battery assembly 100A while vacuuming the inside of the chamber 90 in the first charging step S30, it is generated by the decomposition of the non-aqueous electrolytic solution 10. The generated gas is removed from the inside of the battery case 30 (that is, the inside of the electrode body 20), and a film is suitably formed over the entire negative electrode active material layer 64, so that excellent battery performance can be exhibited. ..

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims are variously modified with the specific examples illustrated above.
Includes modified ones.

In the above-described embodiment, in the first charging step S30, the battery assembly 100A is charged while driving the vacuum pump 92 to evacuate the inside of the chamber 90. For example, the pressure inside the chamber 90 is sufficient. When the pressure is negative, the gas can be discharged from the battery case 30 even if the battery assembly 100A is charged without driving the vacuum pump 92.

10 Non-aqueous electrolyte 20 Electrode body 30 Battery case 37 Injection hole 50 Positive electrode 60 Negative electrode 64 Negative electrode active material layer 90 Chamber 92 Vacuum pump 100 Lithium ion secondary battery (non-aqueous electrolyte secondary battery)
100A battery assembly

Claims (4)

A storage step of accommodating a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and an electrode body including a separator in a battery case having a liquid injection hole formed therein.
The construction process of constructing a battery assembly by injecting a non-aqueous electrolyte solution into the battery case,
The battery assembly having the liquid injection hole opened is arranged inside the chamber, and the battery assembly is charged in a state where the first pressure inside the chamber is lower than the second pressure inside the battery case. The first charging process and
The sealing process for sealing the injection hole and
A method for manufacturing a non-aqueous electrolytic solution secondary battery, comprising a second charging step of further charging the battery assembly in which the injection hole is sealed. The manufacturing method according to claim 1, wherein in the first charging step, the battery assembly is charged while evacuating the inside of the chamber so that the first pressure inside the chamber becomes a negative pressure. The manufacturing method according to claim 1 or 2, wherein in the first charging step, the battery assembly is charged until the SOC reaches 10% to 20%. The positive electrode active material layer contains a lithium transition metal oxide as a positive electrode active material.
The production method according to any one of claims 1 to 3, wherein the non-aqueous electrolyte solution contains a lithium salt as an electrolyte and a carbonate-based solvent that dissolves the lithium salt.

Images