Process method for secondary liquid injection of soft package battery

Abstract

The invention provides a process method for secondary liquid injection of a soft package battery, which comprises the following steps of: dividing an exhaust bag into a primary liquid injection area and a secondary liquid injection area, subsequently and sequentially performing the operation steps of secondary liquid injection sealing, primary liquid injection sealing, pre-formation, extruding to break the sealing to release liquid and standing, and uniformly extruding the area where the secondary liquid injection bag is positioned after pre-formation, a first seal of secondary heat sealing is broken, a secondary electrolyte is released to a battery main body, then the battery is vertically placed for standing for 12-24 hours, a vacuumizing and gas removing process is carried out, the exhaust bag is divided into two independent areas through secondary heat sealing, and the two independent areas are respectively used for storing a primary injection electrolyte and a secondary injection electrolyte. And meanwhile, the pre-formed gas storage function is considered, and the dual purposes of gas storage and secondary liquid injection of the exhaust bag are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery manufacturing, and in particular to a process method for secondary liquid injection of a soft package battery. BACKGROUND

[0002] With the rapid development of science and technology, lithium ion batteries have been widely used in various electronic devices and large and medium-sized electric devices due to their high specific energy, long cycle life, good storage stability, green environmental protection and other remarkable advantages. And with the continuous expansion of application scenarios, the market's requirements for its performance are increasingly stringent. As an important structure type of lithium ion batteries, soft package batteries have unique advantages such as light weight, good safety performance, strong shape plasticity, and relatively simple protection design, and their application in 3C products and power batteries is showing a rapid growth trend. In the production process of lithium ion batteries, the liquid injection link is a very critical process operation. The electrolyte plays an important role in conducting lithium ions during the charging and discharging process of the battery, and is the key guarantee for the battery to obtain excellent performance such as high voltage and high specific energy. And in the first charging activation stage of the battery, the dense, uniform and stable SEI film (solid electrolyte interface film) formed on the positive and negative electrode surfaces plays a decisive role in isolating the negative electrode electron transmission, ensuring the free shuttle of lithium ions, maintaining the stability of the negative electrode, and inhibiting the side reaction, which is directly related to the performance of the battery.

[0003] In order to improve the electrochemical performance of the battery, secondary injection of lithium ion batteries has become an effective means, and has been widely used in prismatic batteries. Due to the reserved injection hole in the shell structure of prismatic battery, it can be used for open-mouth formation during formation, which provides convenient conditions for secondary or even multiple injection.

[0004] However, due to its special structural design, the air bag position of the soft package battery cannot reserve the injection hole, and it faces many difficult problems in secondary or multiple injection. The current soft package battery assembly process is as follows: lamination (or winding) → welding → packaging → liquid injection → sealing → pre-formation → degas (vacuum extraction) → capacity distribution. If re-injection is to be carried out after the first injection, the aluminum plastic shell of the soft package battery needs to be cut open, but this method will directly expose the charged soft package battery to the air, causing impurities such as oxygen, moisture and dust to easily enter the battery, seriously polluting the inside of the battery, and thus causing the battery performance to drop significantly, and also bringing about a security risk that cannot be ignored. Even if the re-injection operation is carried out in an inert gas environment, although it can avoid the above problems to some extent, it will significantly increase the processing cost and labor cost, which undoubtedly brings great challenges to the large-scale application and cost control of soft package batteries. SUMMARY

[0005] The technical problem to be solved by the present invention is to provide a process method for secondary electrolyte injection of soft-pack batteries.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A process for secondary electrolyte injection of a soft-pack battery includes an additional heat-sealing step with an venting bag between the packaging and electrolyte injection steps. The specific steps are as follows: (1) After the battery is first packaged, an exhaust bag is reserved on one side of the battery. The exhaust bag can provide a dedicated space to store the gas generated by the battery during the pre-formation process, so as to avoid the gas from affecting the battery performance. (2) The exhaust bag is heat-sealed a second time to form a first seal 2. One end of the first seal 2 is fully integrated with the top sealing area of ​​the battery. The first seal 2 divides the exhaust bag into two areas: a primary liquid injection bag 1 and a secondary liquid injection bag 3. (3) After the second heat sealing is completed, the liquid injection stage is entered. The liquid injection is carried out in two steps. First, the electrolyte (the electrolyte required for the second liquid injection) is injected into the second liquid injection bag 3. After the liquid injection is completed, the second liquid injection bag needs to be sealed under normal pressure to form the second seal 4. (4) After the secondary injection bag is sealed under normal pressure, the primary injection bag 1 is vacuum-filled (conventional primary injection process). After the injection is completed, the primary injection bag 1 is sealed to form the third seal 5. (5) After the battery has completed pre-formation, all the gas generated during the pre-formation process is concentrated in the primary injection bag 1. At this time, the final operation of secondary injection is completed according to the following steps: 1) Remove the pre-formed battery from the equipment and apply external force (including but not limited to manual or equipment-based methods) to uniformly squeeze the area where the secondary filling bag 3 is located, so that the first seal 2 of the secondary heat seal is opened under force; 2) After the first seal 2 is opened, the electrolyte in the secondary injection bag 3 will flow into the battery body through the rupture point, completing the electrolyte replenishment for the secondary injection. 3) After the electrolyte is poured in, place the battery upright and let it stand for 12-24 hours to ensure that the electrolyte fully wets the internal structure of the battery. 4) After the settling period is complete, the regular vacuuming and degassing process (degas process) can be started, and the entire secondary liquid injection process is now complete.

[0007] Preferably, in the above-mentioned process for secondary liquid injection of soft-pack batteries, the vent bag, after secondary heat sealing, consists of a primary liquid injection bag and a secondary liquid injection bag.

[0008] Preferably, in the above-mentioned process for secondary electrolyte filling of soft-pack batteries, the width of the vent bag is ≥20mm to ensure sufficient space for subsequent secondary electrolyte filling, thereby realizing the use of the vent bag for secondary electrolyte filling. The size design of the vent bag needs to meet the principle of "positive correlation with gas production" (generally, the gas production accounts for <2 / 3 of the total volume of the vent bag).

[0009] Preferably, in the above-mentioned process for secondary electrolyte injection of the soft-pack battery, the technical parameters of the first seal 2 are as follows: Size requirements: The width of the first seal 2 should be controlled between 0.5-10mm; Tensile strength requirement: 0 N / 10mm < first seal tensile strength ≤ 50 N / 10mm.

[0010] In the above-mentioned process for secondary electrolyte injection of soft-pack batteries, the function of the first seal 2 is required as follows: Sol effect requirements: After the seal is torn open, the sol must be evenly distributed, without any defects such as missing seals or air bubbles; Core function: Used to separate the exhaust bag. Through secondary heat sealing, the exhaust bag is divided into two independent spaces: primary injection bag 1 and secondary injection bag 3. This achieves physical isolation between the two electrolytes in primary injection bag 1 and secondary injection bag 3, preventing premature mixing. Shape and position requirements: The seal shape can be flexibly designed (it can be straight, corrugated, etc., but is not limited to this), but it must be fully integrated with the top seal area of ​​the battery to ensure the isolation and sealing of the two liquid injection areas and completely eliminate the risk of electrolyte contact.

[0011] Preferably, in the above-mentioned process for secondary electrolyte injection of the soft-pack battery, the technical parameters of the second seal 4 are as follows: Tensile strength requirement: The second seal tensile strength is ≥100N / 15mm.

[0012] In the above-mentioned process for secondary electrolyte injection of soft-pack batteries, the function of the second seal 4 is required as follows: Sol coating effect: After tearing, the sol coating is evenly distributed and there are no defects in sealing. Core purpose: To seal the secondary injection bag after it has been filled with electrolyte, ensuring the bag's airtightness and preventing electrolyte leakage or contamination.

[0013] Preferably, in the above-mentioned process for secondary electrolyte injection of the soft-pack battery, the technical parameters of the third seal 5 are as follows: Tensile strength requirement: The tensile strength of the third seal is ≥100N / 15mm.

[0014] In the above-mentioned process for secondary electrolyte injection of soft-pack batteries, the function of the third seal 5 is required as follows: Sol coating effect: After tearing, the sol coating is evenly distributed and there are no defects in sealing. Core purpose: To seal the primary injection bag after injection, ensuring that the seal does not cover the area of ​​the secondary injection bag; Location and sealing requirements: After the third seal is applied, ensure that there is no leakage of the battery, and the seal position must not cover or fall into the secondary filling bag area to avoid affecting the release of electrolyte during subsequent secondary filling.

[0015] Preferably, in the above-mentioned process of secondary electrolyte injection for soft-pack batteries, the electrolyte used in the primary electrolyte injection contains a high-efficiency SEI film additive, thereby ensuring the basic stability of the electrode interface, and its main function is "film formation".

[0016] Preferably, in the above-mentioned process of secondary electrolyte injection for soft-pack batteries, the electrolyte used during secondary electrolyte injection contains interface stabilizing additives to compensate for formation losses and ensure final performance, with "energy replenishment" as the core.

[0017] The above-mentioned process for secondary electrolyte injection of soft-pack batteries ensures consistent ion conduction through a unified lithium salt / solvent system in both electrolytes. Differentiated additive systems (e.g., designing different formulations for electrolyte A and electrolyte B, where electrolyte A contains only film-forming additives to reduce the film-forming impedance of the SEI film during formation, and electrolyte B increases the content of vinylene carbonate in the free electrolyte, significantly improving the cycle performance of the battery, and the electrolyte formulation can be flexibly adjusted according to requirements to achieve the goal of improving battery performance) achieve the stage goals, jointly determining the cycle life, capacity, and safety of ternary lithium batteries.

[0018] Beneficial effects: The process for secondary electrolyte injection in the described soft-pack battery divides the vent bag into a primary injection area and a secondary injection area. Subsequent steps include secondary injection sealing, primary injection sealing, pre-formation, compression to break the seal and release electrolyte, and standing. After pre-formation, the area containing the secondary injection bag is uniformly compressed to break the first seal of the secondary heat seal, releasing the secondary electrolyte into the battery body. The battery is then placed vertically and left to stand for 12-24 hours, followed by a vacuum degassing process. The vent bag, divided into two independent areas by secondary heat sealing, is used to store the primary and secondary electrolytes respectively, while also serving as a pre-formation gas storage function, achieving a dual purpose of "gas storage + secondary injection" for the vent bag. Specifically: Regarding battery performance: It improves battery performance stability and cycle life, avoids performance loss due to premature mixing of electrolytes, and through the physical isolation effect of the first seal 2, the electrolytes of the first and second injections are completely independent before pre-formation. The electrolyte formula can be customized according to the different functional requirements of the two injections (such as the first injection focusing on initial activation and the second injection focusing on later replenishment), avoiding the performance superposition failure caused by the premature mixing of different functional electrolytes, and further optimizing the battery charge and discharge efficiency and rate performance.

[0019] The sealing process features a "tiered reliability design": the second seal 4 and the third seal 5, designed for different injection areas, are set with a high strength requirement of ≥100N / 15mm tensile force to ensure no electrolyte leakage after injection; while the first seal 2 is set with a low tensile force threshold of 0-10N / 10mm, which not only meets the isolation requirements before pre-formation but also allows the seal to be easily opened during subsequent extrusion, avoiding problems such as electrolyte not being able to be released due to excessively strong seals or premature leakage due to excessively weak seals, thus significantly improving the process tolerance.

[0020] In terms of manufacturing costs: No new core equipment is required. Through processes such as secondary heat sealing, regional liquid injection, and extrusion sealing, the process can be achieved by adjusting the parameters of the existing heat sealing machine and liquid injection machine in the soft-pack battery production line (such as adjusting the sealing edge width of the heat sealing machine and adding regional liquid injection stations to the liquid injection machine), without the need to invest in purchasing a brand new production line.

[0021] Flexible electrolyte adaptation: Traditional single electrolyte injection needs to take into account multiple needs such as activation and replenishment, which limits the design of electrolyte formulation; This application, through partitioned electrolyte injection, can customize solutions for different scenarios (such as adding conductive additives for secondary electrolyte injection of high-rate batteries, and optimizing antifreeze components for secondary electrolyte injection of low-temperature batteries), and can achieve differentiated upgrades of battery performance without changing the primary electrolyte injection formulation. The technology is more versatile and can be adapted to the needs of multiple fields such as consumer electronics and power batteries. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the exhaust bag before secondary heat sealing.

[0023] Figure 2 This is a schematic diagram of the exhaust bag after secondary heat sealing.

[0024] Figure 3 This is a schematic diagram showing the exhaust bag after secondary heat sealing and atmospheric pressure sealing.

[0025] In the diagram: 1-Primary injection bag, 2-First seal, 3-Secondary injection bag, 4-Second seal, 5-Third seal, 6-Exhaust bag. Detailed Implementation

[0026] The following describes in detail a process method and implementation method for secondary electrolyte injection of a soft-pack battery according to the present invention, with reference to embodiments and accompanying drawings.

[0027] Example 1 A process for secondary electrolyte injection of a soft-pack battery includes an additional heat-sealing step with an venting bag between the packaging and electrolyte injection steps. The specific steps are as follows: (1) After the battery is first packaged, an exhaust bag 6 is reserved on one side of the battery. The exhaust bag can provide a special space to store the gas generated by the battery during the pre-formation process, so as to avoid the gas from affecting the battery performance. At the same time, the exhaust bag 6 is 20mm wide to ensure that there is enough space for subsequent secondary electrolyte filling, so as to realize the secondary electrolyte filling by using the exhaust bag. (2) The exhaust bag is heat-sealed a second time to form a straight first seal 2. The width of the first seal 2 is controlled within 8mm and the tension of the first seal 2 is within the range of 30N / 10mm. One end of the first seal 2 is fully integrated with the top sealing area of ​​the battery. The first seal 2 divides the exhaust bag into two independent areas: a primary liquid injection bag 1 and a secondary liquid injection bag 3, so as to achieve physical isolation between the two electrolytes in the primary liquid injection bag 1 and the secondary liquid injection bag 3 and avoid premature mixing. (3) After the secondary heat sealing is completed, the liquid injection stage is entered. The liquid injection is carried out in two steps. First, the electrolyte (which is electrolyte B containing 12% vinylene carbonate) is injected into the secondary liquid injection bag 3. The amount of liquid injected in the secondary injection is 10% of the total amount of liquid injected. The organic solvent of electrolyte B is 25 parts vinylene carbonate, 2.5 parts propylene carbonate, 70 parts methyl ethyl carbonate and 2.5 parts fluorobenzene by mass fraction. With the mass of electrolyte B as 100%, the amount of vinylene carbonate in electrolyte B is 2.5% and methyl methylene disulfonate is 0.25% by mass fraction. The lithium salt of electrolyte B is 1.1 mol / L LiPF6g. With the mass of electrolyte B as 100%, the amount of lithium salt is 12.5 wt% by mass fraction. After the liquid injection is completed, the secondary liquid injection bag needs to be sealed under normal pressure to form a second seal 4 with a sealing pull force of 100N / 15mm. This seal is used to seal the secondary liquid injection bag after liquid injection to ensure the sealing of the secondary liquid injection bag and prevent electrolyte leakage or contamination. (4) After the secondary injection bag is sealed under normal pressure, the primary injection bag 1 is then vacuum-filled (the conventional primary injection process injects electrolyte A containing 2.5% vinylene carbonate). The primary injection volume is 90% of the total injection volume. The solvent of electrolyte A consists of 25 parts vinylene carbonate, 2.5 parts propylene carbonate, 70 parts methyl ethyl carbonate, and 2.5 parts fluorobenzene by mass fraction, and the solvent accounts for 84.75 wt% of the mass fraction of electrolyte A. Taking the mass of electrolyte A as 100%, the additives in electrolyte A are 2.5% vinylene carbonate and 0.25% methylene disulfonate by mass fraction. The lithium salt in electrolyte A is 1.0 mol / L LiPF6g, and taking the mass of electrolyte A as 100%, the lithium salt accounts for 12.5 wt% of the mass fraction of electrolyte A. After the injection is completed, the first injection bag 1 is sealed to form the third seal 5. The sealing pull force is 100N / 15mm. It is used to seal the first injection bag after the injection. The sealing position after the first injection does not cover the area where the second injection bag is located, so as to avoid affecting the release of electrolyte in the subsequent second injection. (5) After the battery has completed pre-formation, all the gas generated during the pre-formation process is concentrated in the primary injection bag 1. At this time, the final operation of secondary injection is completed according to the following steps: 1) Remove the pre-formed battery from the equipment, apply external force through the equipment (or manually) to uniformly squeeze the area where the secondary injection bag 3 is located, so that the first seal 2 of the secondary heat seal is opened under force; 2) After the first seal 2 is opened, the electrolyte in the secondary injection bag 3 will flow into the battery body through the rupture point, completing the electrolyte replenishment for the secondary injection. 3) After the electrolyte is poured in, place the battery upright and let it stand for 20 hours to ensure that the electrolyte fully wets the internal structure of the battery. 4) After the settling period is complete, the regular vacuuming and degassing process (degas process) can be started, and the entire secondary liquid injection process is now complete.

[0028] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention. The construction steps of the structure of the present invention are not in any particular order. All improvements and modifications, such as structural modifications, made by those skilled in the art based on the method of the present invention or based on the method are considered to be within the scope of protection of the present invention.

Claims

1. A process for soft package battery secondary liquid injection, characterized in that: Between the packaging process and the liquid injection process, a secondary heat sealing process of the exhaust bag is added, and the specific steps are as follows: (1) After the battery completes the first packaging, an exhaust bag is reserved on one side of the battery; (2) The exhaust bag is subjected to secondary heat sealing to form a first seal, one end of the first seal is fully integrated with the top sealing area of the battery, and the first seal divides the exhaust bag into a primary liquid injection bag and a secondary liquid injection bag; (3) After the secondary heat sealing is completed, the liquid injection stage is entered, and the liquid injection is performed in two steps, first, electrolyte is injected into the secondary liquid injection bag, and after the liquid injection is completed, the secondary liquid injection bag is subjected to normal pressure sealing to form a second seal; (4) After the secondary liquid injection bag is subjected to normal pressure sealing, the primary liquid injection bag is subjected to vacuum injection, and after the liquid injection is completed, the primary liquid injection bag is sealed to form a third seal; (5) When the battery completes the pre-formation, the gas generated during the pre-formation process is all concentrated in the primary liquid injection bag, at this time, the final operation of the secondary liquid injection is completed according to the following steps: 1) The pre-formed battery is uniformly pressed on the area where the secondary liquid injection bag is located by applying external force, so that the first seal of the secondary heat sealing is stressed and opened; 2) After the first seal is opened, the electrolyte in the secondary liquid injection bag flows into the battery body through the broken position to complete the electrolyte supplement of the secondary liquid injection; 3) After the electrolyte flows in, the battery is placed vertically and statically, and the static time is controlled to be 12-24 hours; 4) After the static state is completed, the conventional vacuum degassing process is entered, and thus the entire secondary liquid injection process is completed. 2.The process method of secondary injection of the pouch battery according to claim 1, characterized in that: The exhaust bag is composed of a primary liquid injection bag and a secondary liquid injection bag after secondary heat sealing. 3.The process method of secondary injection of the pouch battery according to claim 1, characterized in that: The width of the exhaust bag is greater than or equal to 20 mm. 4.The process method of secondary injection of the pouch battery according to claim 1, characterized in that: The width of the first seal is controlled to be 0.5-10 mm, and the tensile force requirement is 0 N / 10 mm < first seal tensile force ≤ 50 N / 10 mm. 5.The process method of secondary injection of the pouch battery according to claim 1, wherein: The tensile force requirement of the second seal is second seal tensile force ≥ 100 N / 15 mm. 6.The process method of secondary injection of the pouch battery according to claim 1, wherein: The tensile force requirement of the third seal is third seal tensile force ≥ 100 N / 15 mm. 7.The process method of secondary injection of the pouch battery according to claim 1, wherein: The electrolyte used in the primary liquid injection contains a high-efficiency SEI film additive. 8.The process of claim 1, wherein: The electrolyte used in the secondary liquid injection contains an interface stabilizing additive.

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