Pouch lithium ion battery electrolyte infiltration method and application thereof

Abstract

The application belongs to the technical field of batteries, and particularly relates to a soft package lithium ion battery electrolyte infiltration method and application thereof, the method comprising the following steps: (1) placing a dry battery into an aluminum plastic film, heat-sealing three sides of the aluminum plastic film, leaving a gas bag at one end, and taking the opening at the gas bag end as an injection port; (2) injecting electrolyte after vacuum drying the battery; (3) performing vacuum operation on the battery injection port after battery injection, maintaining a vacuum degree for 0.5-10 min, and standing at normal pressure for 1-10 min; (4) clamping the battery main body, performing vacuum operation on the battery injection port, maintaining a vacuum degree for 0.5-10 min, and standing at normal pressure for 1-10 min; (5) repeating steps (3) and (4) for several times to complete the infiltration. The application is simple, easy and convenient to operate. Through multi-stage vacuum negative pressure and clamping operation, the flowability of electrolyte between the electrode plate and the diaphragm is increased, the wettability between the electrolyte and the electrode and the diaphragm is improved, thereby shortening the infiltration time and quickly achieving good infiltration effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to the technical field of lithium electronic power battery production, and specifically to a soft-pack lithium ion battery electrolyte infiltration method and application thereof. BACKGROUND

[0002] The electrolyte in a lithium ion battery is a lithium ion migration channel between the positive and negative electrodes, and is responsible for the back-and-forth transmission of lithium ions between the positive and negative electrodes during the charging and discharging process of the battery. During the production process of a lithium ion battery, a dry battery cell needs to be subjected to a liquid injection process, and after the liquid injection operation, a long period of standing is required to allow the electrolyte to fully infiltrate the positive and negative active materials and the separator inside the lithium ion battery. If the standing time after liquid injection is insufficient, the electrolyte infiltration inside the battery may not be ideal, which will make the lithium ion transmission path difficult and hinder the transmission of lithium ions between the positive and negative electrodes during the charging and discharging process of the battery. Moreover, the electrode sheets that are not infiltrated with electrolyte cannot participate in the electrochemical reactions inside the battery, and a stable solid electrolyte interphase (SEI) film cannot be formed on the surface of the electrode active material of the battery. At the same time, the battery interface impedance increases, affecting the rate capability, cycle performance, and safety performance of the battery. If the standing time after liquid injection is too long, although the electrolyte infiltration can be improved to some extent, it will directly affect the production efficiency of the lithium ion battery.

[0003] In order to solve the problem of electrolyte infiltration in lithium ion batteries in the prior art, generally, the lithium ion battery will be subjected to a long standing time (20-50 h) after the liquid injection process by increasing the room temperature infiltration time. The method of increasing the infiltration temperature can be used for infiltration, but long-term high-temperature standing will cause an increase in electrolyte side reactions and deteriorate the performance of the battery. Chinese Invention Patent CN110247121A discloses a method for electrolyte infiltration of a lithium ion battery, which uses vacuum negative pressure standing for 6-10 h after liquid injection to increase the contact opportunities between the electrolyte and the electrodes and the separator. However, this method generally has a complex process, and the battery is in an open state for a long time, which will increase the water absorption rate and the evaporation rate of the electrolyte, causing adverse effects. In addition, there are methods such as vibration-vacuum standing (for example, Chinese Invention Patent CN111403819A) or rotating the battery cell (for example, Chinese Invention Patent CN111540957A) to increase the electrolyte infiltration effect, but the vibration force or centrifugal force of these methods can cause damage to the position of the electrode sheet or the electrode sheet itself inside the battery, which may cause safety problems later.

[0004] Therefore, it is of great significance to develop a method that is simple in steps, easy to operate, can greatly shorten the electrolyte infiltration time of a soft-pack lithium ion battery while ensuring good infiltration effect, and is suitable for the processing and production of soft-pack lithium ion batteries. SUMMARY

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present application is to provide a soft package lithium ion battery electrolyte infiltration method and its application, which is used to solve the problems of long infiltration time of the electrolyte infiltration method of the soft package lithium ion battery in the prior art, or adverse effects on battery performance and safety, etc.

[0006] To achieve the above-mentioned purpose and other related purposes, the present application provides a soft package lithium ion battery electrolyte infiltration method, whose basic scheme is as follows: the method comprises the following steps:

[0007] (1) Put the dry battery cell into the aluminum plastic film, heat seal the three sides of the aluminum plastic film, and leave a gas bag at one end. The opening at the end of the gas bag is used as the liquid injection port;

[0008] (2) After vacuum drying the battery cell, inject the electrolyte;

[0009] (3) After injecting the electrolyte, perform vacuum operation on the battery liquid injection port, maintain the vacuum degree for 0.5min~10min, and stand at normal pressure for 1min~10min;

[0010] (4) Clamping the main body of the battery cell, perform vacuum operation on the battery liquid injection port, maintain the vacuum degree for 0.5min~10min, and stand at normal pressure for 1min~10min;

[0011] (5) Repeat steps (3) and (4) for several times to complete the infiltration.

[0012] Further, the method further comprises step (6): sealing the end of the battery gas bag, and pre-charging, forming, and double-sealing the battery.

[0013] Further, in steps (3) and (4), the vacuum degree is -300Kpa~-20Kpa, preferably -180Kpa~-100Kpa.

[0014] Further, in steps (3) and (4), the vacuum time is 5min~10min, i.e. maintaining the vacuum degree for 5min~10min.

[0015] Further, the vacuum degree, vacuum time, and normal pressure standing time of steps (3) and (4) are the same and / or different.

[0016] Further, in step (5), steps (3) and (4) are repeated 1~5 times to complete the infiltration.

[0017] Further, in step (1), the length of the gas bag is preferably 5~20mm.

[0018] Further, in the step (2), the vacuum degree is 100Kpa~20Kpa, the drying temperature is 80℃~100℃, and the drying time is 8h~24h.

[0019] Further, in the step (2), the battery is injected with electrolyte from the top, and the electrolyte is injected in one injection.

[0020] The application also provides application of the soft package lithium ion battery electrolyte infiltration method in the production of the soft package lithium ion battery.

[0021] As described above, the soft package lithium ion battery electrolyte infiltration method and the application thereof have the following beneficial effects:

[0022] The application provides a soft package lithium ion battery electrolyte infiltration method, which increases the flowability of electrolyte between electrode sheets and diaphragms through multi-stage vacuum negative pressure and clamping operations, improves the wettability between electrolyte and electrodes and diaphragms, and thus can better spread and quickly achieve good infiltration effect.

[0023] The method is simple and easy to implement, convenient to operate, can quickly achieve the electrolyte infiltration effect of the lithium ion battery, and greatly shortens the electrolyte infiltration time of the soft package lithium ion battery. DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described below with reference to the accompanying drawings and preferred embodiments, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure herein. The present application can also be implemented or applied by different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for illustrating the present application, but not for limiting the protection scope of the present application.

[0025] The preparation of lithium ion battery from batching to sheet, to formation and capacity, each step plays a vital role in the performance of lithium ion battery. Especially the liquid injection process, in which the electrolyte, like the "blood" of the human body, transports lithium ions to the positive and negative electrode sheets through the separator. Therefore, only the electrolyte has good contact with the positive and negative electrode sheets and the separator, and the wetting is sufficient, the battery can exhibit excellent performance. The separator of lithium ion battery is generally PE, PP or multi-layer composite aluminum plastic film, which belongs to non-polar polymer separator. It is incompatible with the battery electrode, polar cyclic carbonate solvents (such as EC, PC, etc.), which can easily lead to a larger contact angle between the electrolyte and the separator, and poor wettability, which generally requires a long time to achieve good wetting effect. In order to improve the existing electrolyte wetting method, the application provides a new soft package lithium ion battery electrolyte wetting method, the basic scheme of which is to increase the flowability of electrolyte between the electrode sheet and the separator by multi-stage vacuum negative pressure and clamping operation, so that the wettability between the electrolyte and the electrode and the separator is good, so that the electrolyte can be better spread and quickly achieve good wetting effect.

[0026] Based on the above purpose, an embodiment of the application provides a soft package lithium ion battery electrolyte wetting method, comprising the following steps:

[0027] (1) The dry battery is loaded into the aluminum plastic film, and the aluminum plastic film is heat-sealed on three sides, and one end is left as a gas bag, and the opening at the gas bag end is used as a liquid injection port;

[0028] (2) After the battery is vacuum dried, the electrolyte is injected;

[0029] (3) After the battery is injected, the battery injection port is vacuum operated, and the vacuum degree is maintained for 0.5min~10min, and the atmospheric pressure is maintained for 1min~10min;

[0030] (4) The battery injection port is vacuum operated by clamping the main body of the battery, and the vacuum degree is maintained for 0.5min~10min, and the atmospheric pressure is maintained for 1min~10min;

[0031] (5) Repeat steps (3) and (4) several times to complete the wetting.

[0032] During the formation process, various gases such as C2H4 and CO are generated. In order to store these gases, a gas bag area is usually reserved on the aluminum plastic film bag for storing the generated gases, and these gas bag areas are soft and flexible. In the specific embodiment of the application, in step (1), the length of the gas bag is preferably 5~20mm.

[0033] In the detailed description of the present application, in the step (2), the vacuum degree is -100 Kpa to -20 Kpa, the drying temperature is 80℃ to 100℃, and the drying time is 8h to 24h.

[0034] In the detailed description of the present application, in the step (2), the battery injection port is upward, and the electrolyte is injected by one-time injection.

[0035] In the detailed description of the present application, in the steps (3) and (4), the vacuum degree is -300 Kpa to -20 Kpa, preferably -180 Kpa to -100 Kpa; and the vacuum time is 5min to 10min, that is, the vacuum degree is maintained for 5min to 10min.

[0036] Further, the vacuum degree, vacuum time and atmospheric pressure standing time of the steps (3) and (4) can be set to be completely the same, partially the same or completely different.

[0037] In the detailed description of the present application, in the step (5), the steps (3) and (4) are repeated 1 to 5 times to complete the infiltration.

[0038] In another embodiment of the present application, the method further comprises a step (6) of sealing the air bag end of the battery and pre-charging, formation and second sealing of the battery.

[0039] The soft package lithium ion battery electrolyte infiltration method provided in the above embodiments of the present application has simple steps and strong operability. When the method is applied in the production of soft package lithium ion batteries, the infiltration effect is good, and the electrolyte infiltration time of the soft package lithium ion battery is greatly shortened. The method has important significance for the processing and production of soft package lithium ion batteries.

[0040] It should be noted that the vacuum operation mentioned in the above embodiments of the present application is a vacuum negative pressure operation, which can be realized by using a vacuum device. The vacuum device uses common vacuum equipment in the art, and will not be described in detail. The main body of the battery cell is clamped by a clamp, which is a common method for lithium ion batteries, and will not be described in detail.

[0041] In addition, it should be noted that the lithium ion battery processing steps not described in detail in the above embodiments of the present application include: dry cell production, aluminum plastic film hot pressing packaging, injection method, pre-charging, formation, second sealing and related electrochemical performance testing, which are all produced according to the conventional production process of lithium ion batteries.

[0042] The following specific examples are used to illustrate the present application in detail. It should also be understood that the following examples are only used to illustrate the present application in detail, and cannot be understood as a limitation on the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application are within the scope of protection of the present application. The specific process parameters and the like described below are only one example in the appropriate range, i.e. those skilled in the art can make appropriate selection within the range according to the description herein, and are not limited to the specific values of the examples below.

[0043] It should be noted that in the following specific examples, all the cell systems, electrode designs, electrolyte formulations and electrolyte injection amounts are the same. In addition, the pre-charging, formation and battery test system after the completion of the battery electrolyte infiltration are also consistent.

[0044] Example 1

[0045] The electrolyte infiltration method of the soft package lithium ion battery of the present embodiment is as follows:

[0046] (1) According to the conventional production process of lithium ion battery, dry cell is produced, which is packaged in aluminum plastic film, and the aluminum plastic film 3 is heat sealed and packaged, and the aluminum plastic film is left with a gas bag at one end. The opening at the gas bag end is used as the injection port, and after drying in a vacuum oven, the electrolyte is injected into the dried cell: the vacuum degree is-20Kpa, the drying temperature is 90℃, and the drying time is 12h; The dry cell is injected with a certain amount of electrolyte by one-time injection method;

[0047] (2) After the battery is injected, the vacuum device is used to operate the battery injection port under vacuum, and the vacuum degree is set to-90Kpa, and the vacuum time is set to 1min, and then it is placed under normal pressure for 1min;

[0048] (3) The cell body is clamped using a clamp, and the vacuum device is used to operate the battery injection port under vacuum, and the vacuum degree is set to-90Kpa, and the vacuum time is set to 1min, and then it is placed under normal pressure for 1min;

[0049] (4) After the injection port is packaged, pre-charging, formation, second sealing and related electrochemical performance test are carried out.

[0050] Example 2

[0051] The electrolyte infiltration method of the soft package lithium ion battery of the present embodiment is as follows:

[0052] (1) According to the conventional production process of lithium ion battery, dry battery is produced, and is put into aluminum plastic film, and the aluminum plastic film is heat-pressed and packaged on three sides, and an air bag is left at one end of the aluminum plastic film, and the opening at the air bag end is used as a liquid injection port, and after drying in a vacuum oven, liquid injection is performed: when the battery is vacuum dried, the vacuum degree is-20 Kpa, the drying temperature is 90 DEG C, and the drying time is 12h; the dry battery is injected with a certain amount of electrolyte by one-time injection;

[0053] (2) After the battery is injected with liquid, a vacuum device is used to perform vacuum operation on the battery liquid injection port, the vacuum degree is set to-90 Kpa, and the vacuum time is set to 10 min, and then the battery is placed at normal pressure for 5 min;

[0054] (3) The battery main body is clamped by using a clamp, and a vacuum device is used to perform vacuum operation on the battery liquid injection port, the vacuum degree is set to-90 Kpa, and the vacuum time is set to 10 min, and then the battery is placed at normal pressure for 5 min;

[0055] (4) After the vacuum operation is repeated 3 times, the liquid injection port is packaged, and pre-charging, formation, second sealing and related electrochemical performance tests are performed.

[0056] Example 3

[0057] The soft package lithium ion battery electrolyte infiltration method of the embodiment is as follows:

[0058] (1) According to the conventional production process of lithium ion battery, dry battery is produced, and is put into aluminum plastic film, and the aluminum plastic film is heat-pressed and packaged on three sides, and an air bag is left at one end of the aluminum plastic film, and the opening at the air bag end is used as a liquid injection port, and after drying in a vacuum oven, liquid injection is performed: when the battery is vacuum dried, the vacuum degree is-20 Kpa, the drying temperature is 90 DEG C, and the drying time is 12h; the dry battery is injected with a certain amount of electrolyte by one-time injection;

[0059] (2) After the battery is injected with liquid, a vacuum device is used to perform vacuum operation on the battery liquid injection port, the vacuum degree is set to-200 Kpa, and the vacuum time is set to 3 min, and then the battery is placed at normal pressure for 10 min;

[0060] (3) The battery main body is clamped by using a clamp, and a vacuum device is used to perform vacuum operation on the battery liquid injection port, the vacuum degree is set to-200 Kpa, and the vacuum time is set to 3 min, and then the battery is placed at normal pressure for 10 min;

[0061] (4) After the vacuum operation is repeated 3 times, the liquid injection port is packaged, and pre-charging, formation, second sealing and related electrochemical performance tests are performed.

[0062] Example 4

[0063] The soft package lithium ion battery electrolyte infiltration method of the embodiment is as follows:

[0064] (1) According to the conventional production process of lithium ion batteries, dry cells are produced, packed into aluminum plastic films, and the three sides of the aluminum plastic film 3 are hot-pressed and packaged. The air bag is left at one end of the aluminum plastic film, and the opening at the air bag end is used as the liquid injection port. After drying in a vacuum oven, the electrolyte is injected: the vacuum degree is-20 Kpa, the drying temperature is 90°C, and the drying time is 12h; the dry cell is injected with a certain amount of electrolyte by one-time injection;

[0065] (2) After the battery is injected with liquid, a vacuum device is used to perform vacuum operation on the battery liquid injection port, and the vacuum degree is set to-200 Kpa, and the vacuum time is set to 3min, and then it is placed at normal pressure for 10min;

[0066] (3) The cell body is clamped using a clamp, and a vacuum device is used to perform vacuum operation on the battery liquid injection port, and the vacuum degree is set to-200 Kpa, and the vacuum time is set to 3min, and then it is placed at normal pressure for 10min;

[0067] (4) After repeating the vacuum operation of (2) and (3) 5 times, the liquid injection port is packaged, and pre-charging, formation, two-sealing and related electrochemical performance tests are performed.

[0068] Comparative Example 1

[0069] The electrolyte immersion method steps of the soft package lithium ion battery of the present comparative example are as follows:

[0070] (1) According to the conventional production process of lithium ion batteries, dry cells are produced, packed into aluminum plastic films, and the three sides of the aluminum plastic film 3 are hot-pressed and packaged. The air bag is left at one end of the aluminum plastic film, and the opening at the air bag end is used as the liquid injection port. After drying in a vacuum oven, the electrolyte is injected: the vacuum degree is-20 Kpa, the drying temperature is 90°C, and the drying time is 12h; the dry cell is injected with a certain amount of electrolyte by one-time injection;

[0071] (2) After the battery is injected with liquid, a vacuum device is used to perform vacuum operation on the battery liquid injection port, and the vacuum degree is set to-90 Kpa, and the vacuum time is set to 1min, and then the liquid injection port is packaged;

[0072] (3) After the battery is placed for 120min, pre-charging, formation, two-sealing and related electrochemical performance tests are performed.

[0073] Comparative Example 2

[0074] The electrolyte immersion method steps of the soft package lithium ion battery of the present comparative example are as follows:

[0075] (1) According to the conventional production process of lithium ion batteries, dry cells are produced, packed in aluminum plastic films, and the aluminum plastic film 3 is hot-pressed and packaged. The aluminum plastic film has a gas bag at one end, and the opening at the gas bag end is used as a liquid injection port. After drying in a vacuum oven, the cell is injected with electrolyte: when the cell is vacuum dried, the vacuum degree is-20 Kpa, the drying temperature is 90°C, and the drying time is 12h; and the dry cell is injected with a certain amount of electrolyte by one-time injection;

[0076] (2) After the battery is injected with liquid, a vacuum device is used to perform vacuum operation on the battery injection port, and the vacuum degree is set to-90 Kpa. The vacuum time is set to 1 min, and then the injection port is packaged;

[0077] (3) The battery is left to stand for 24 hours, and then pre-charged, formed, two-sealed, and related electrochemical performance tests are performed.

[0078] The electrochemical performance test results of the soft package lithium ion batteries of Examples 1-4 and Comparative Examples 1-2 are shown in Table 1.

[0079] Table 1. Electrochemical performance of batteries of Examples 1-4 and Comparative Examples 1-2

[0080]

[0081] Table 1 shows the electrochemical performance of the soft package lithium ion batteries prepared by Examples 1-4 and Comparative Examples 1-2 provided by the present application.

[0082] As can be seen from Table 1, the soft package lithium ion batteries prepared by Examples 1-4 and Comparative Examples 1-2 all have good electrochemical performance, but compared with Comparative Example 1 and Comparative Example 2 which do not perform vacuum operation on the battery after injection, the first week discharge capacity, first week charge-discharge efficiency and cycle 300 week capacity retention rate of the soft package lithium ion batteries of Examples 2-3 obtained by electrochemical performance test are higher. Moreover, the electrochemical performance of the soft package lithium ion batteries of Examples 2-3 is comparable to that of the soft package lithium ion batteries prepared after 24h standing of Comparative Example 2.

[0083] The above results show that the soft package lithium ion battery electrolyte infiltration method provided by the present application can effectively improve the infiltration effect of the lithium ion battery electrolyte, and compared with the existing infiltration method, the method provided by the present application is not only simple and easy to operate, but also can quickly realize the electrolyte infiltration effect of the lithium ion battery, greatly shortening the electrolyte infiltration time of the soft package lithium ion battery.

[0084] The above embodiments are only illustrative of the principles of the present application and its efficacy, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. A method of electrolyte impregnation of a pouch lithium-ion battery, characterized in that, The method comprises the following steps: (1) the dry battery cell is put into the aluminum plastic film, the aluminum plastic film is heat-sealed on three sides, and a gas bag is left at one end, and the opening at the end of the gas bag is used as a liquid injection port; (2) after the battery cell is vacuum dried, electrolyte is injected; (3) after the battery is injected with electrolyte, vacuum operation is performed on the liquid injection port of the battery, the vacuum degree is-300Kpa~-20Kpa, the vacuum degree is maintained for 0.5min~10min, and the battery is placed at normal pressure for 1min~10min; (4) the battery cell body is clamped, vacuum operation is performed on the liquid injection port of the battery, the vacuum degree is-300Kpa~-20Kpa, the vacuum degree is maintained for 0.5min~10min, and the battery is placed at normal pressure for 1min~10min; (5) steps (3) and (4) are repeated several times to complete the infiltration; (6) the end of the battery gas bag is sealed, and the battery is pre-charged, formed, and double-sealed.

2. The method of claim 1, wherein: In steps (3) and (4), the vacuum degree is-180Kpa~-100Kpa.

3. The method of claim 1, wherein: In steps (3) and (4), the vacuum time is 5min~10min.

4. The method of claim 1, wherein: The vacuum degree, vacuum time and normal pressure standing time of steps (3) and (4) are the same and / or different.

5. The method of claim 1, wherein: In step (5), steps (3) and (4) are repeated 1~5 times to complete the infiltration.

6. The method of claim 1, wherein: In step (2), when the battery cell is vacuum dried, the vacuum degree is-100Kpa~-20Kpa, the drying temperature is 80℃~100℃, and the drying time is 8h~24h.

7. The method of claim 1, wherein: In step (2), the liquid injection port of the battery is upward, and electrolyte is injected by one-time injection.

8. Application of the soft package lithium ion battery electrolyte infiltration method according to any one of claims 1~7 in the production of soft package lithium ion batteries.

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