Liquid injection method of soft package cylindrical battery

Abstract

The invention discloses a liquid injection method of a soft package cylindrical battery. The liquid injection method comprises the following steps: S1, soaking a battery roll core in an electrolyte in a vacuum environment; s2, taking out the soaked battery roll core from the electrolyte, and standing in a vacuum environment; s3, loading the battery roll core after standing into a soft package shell, and sealing to form a battery; s4, injecting an electrolyte into the battery; s5, the battery after liquid injection is subjected to vacuumizing treatment, the vacuum degree ranges from-85 KPa to-95 KPa, and the vacuum degree is kept for 5 s to 15 s; s6, carrying out pressurization treatment on the vacuumized battery at the pressurization strength of 750 to 850 KPa, and maintaining the pressure for 250 to 350 seconds; and S7, cyclically carrying out the steps S5-S6 for multiple times, and standing to obtain the liquid injection soft package cylindrical battery. Compared with the prior art, the invention can effectively solve the problems of difficult liquid seepage, poor cell wettability and low infiltration efficiency of the soft package cylindrical cell.

Description

Technical Field

[0001] The invention belongs to the technical field of secondary battery preparation, and in particular relates to a liquid injection method for a soft-package cylindrical battery. Background Art

[0002] Among the current widespread applications of lithium-ion batteries, soft-pack cylindrical batteries have attracted much attention due to their excellent energy density and flexible shape design. However, with the increasing market demand for high-performance batteries, soft-pack cylindrical batteries have encountered new challenges in the production process, especially in the electrolyte injection process. Traditional injection methods often show some shortcomings when facing the special structure of soft-pack cylindrical batteries, mainly reflected in the difficulty of liquid penetration, poor cell wettability and low wettability efficiency.

[0003] First, the structural characteristics of soft-pack cylindrical batteries make it difficult for the electrolyte to be evenly distributed inside the battery cell. Since soft-pack batteries use aluminum-plastic film as the outer packaging material, although this material can effectively reduce the weight and thickness of the battery, it also puts higher requirements on the permeability of the electrolyte. After the battery cell is wound, the close arrangement of the electrode sheets further aggravates the difficulty of the electrolyte to penetrate into the battery, making it difficult for the electrolyte to quickly and evenly infiltrate the electrode active material.

[0004] Secondly, the problem of poor cell wettability directly affects the performance and life of the battery. The uniform distribution of electrolyte is crucial for the ion conduction of the battery. Uneven electrolyte distribution may lead to excessive local current density, thus causing local overheating and accelerated aging of the battery. In addition, due to poor wettability, the battery may experience capacity loss during the initial charge and discharge, reducing the overall performance of the battery.

[0005] Finally, the existing injection process also has certain limitations in terms of efficiency. Traditional injection methods often take a long time to ensure sufficient electrolyte infiltration, which not only prolongs the production cycle but may also lead to increased production costs. At the same time, bubbles and voids that are easily generated during the injection process will further affect the quality and reliability of the battery.

[0006] In summary, the existing technology has problems such as difficult liquid penetration, poor wettability and low efficiency in the liquid injection process of soft-pack cylindrical batteries, which seriously restrict the widespread application and marketization of soft-pack cylindrical batteries. Therefore, an improved liquid injection method is urgently needed to improve the permeability and wettability of the electrolyte, thereby improving the overall performance and production efficiency of the battery. Summary of the invention

[0007] The purpose of the present invention is to provide a liquid injection method for a soft-pack cylindrical battery in view of the deficiencies in the prior art, which can effectively solve the problems of difficult liquid penetration of soft-pack cylindrical batteries, poor wettability of batteries and low wettability.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for injecting liquid into a soft-pack cylindrical battery comprises the following steps:

[0010] S1. Immerse the battery core in the electrolyte under vacuum, with the vacuum degree not less than -80KPa, and the immersion time is 30 to 60 minutes;

[0011] S2. Take out the soaked battery coil from the electrolyte and place it in a vacuum environment for 10 to 30 minutes to allow excess electrolyte to flow out naturally;

[0012] S3, placing the rested battery roll core into a soft-pack shell, and sealing it to form a battery;

[0013] S4, injecting electrolyte into the battery, the injection amount is 30% to 60% of the internal void volume of the soft package shell;

[0014] S5. The battery after liquid injection is subjected to vacuum treatment, the vacuum degree is -85KPa to -95KPa, and the vacuum degree is maintained for 5s to 15s;

[0015] S6. Pressurize the vacuumed battery at a pressure of 750 KPa to 850 KPa for 250 s to 350 s.

[0016] S7, cycle through steps S5-S6 for multiple times, let stand, and obtain a liquid-filled soft-pack cylindrical battery.

[0017] Preferably, the above steps S1 to S7 are all performed in an ultra-low humidity environment with a dew point below -40°C.

[0018] Preferably, in step S1, the battery core is immersed for 40 to 50 minutes, and the amount of the electrolyte used is 1.5 to 3 times the volume of the battery core.

[0019] Preferably, in step S2, the battery roll core is left to stand for 15 to 25 minutes.

[0020] Preferably, in step S4, the injection amount is controlled to be 40% to 50% of the internal void volume of the soft package shell.

[0021] Preferably, in step S6, the gas used for the pressurization treatment is any one of nitrogen and argon.

[0022] Preferably, in step S1, the electrolyte for immersion is a heat-treated electrolyte, and the temperature of the electrolyte is 45-55°C.

[0023] Preferably, in step S4, the injected electrolyte is a heat-treated electrolyte, and the temperature of the electrolyte is 45-55°C.

[0024] Preferably, the method further comprises step S8, performing ultrasonic treatment on the battery, wherein the ultrasonic frequency is 40kHz to 60kHz, the ultrasonic power is 100W to 300W, and the ultrasonic time is 20min to 40min.

[0025] Preferably, the method further comprises step S9, heat treating the battery after ultrasonic treatment, wherein the heat treatment temperature is 50° C. to 60° C., and the heat treatment time is 1 to 3 hours.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] 1) The battery core is immersed in the electrolyte under a high vacuum environment, and the air inside the battery core is removed by the vacuum environment. At the same time, the contact time between the electrolyte and the battery cell is prolonged in the presence of a large amount of electrolyte. Therefore, the vacuum pre-immersion significantly improves the adsorption capacity of the battery core to the electrolyte, allowing the electrolyte to quickly penetrate into the core, greatly improving the wettability of the core.

[0028] 2) The soaked battery coil is placed in a vacuum environment to dehydrate, and the vacuum environment is used to accelerate the natural outflow of excess electrolyte, which can effectively prevent too much electrolyte from being brought into the battery and affecting the subsequent injection accuracy. Therefore, by combining static dehydration and quantitative injection, the amount of electrolyte in the battery can be accurately controlled to prevent excessive or insufficient electrolyte from affecting battery performance.

[0029] 3) Inject an appropriate amount of electrolyte into the packaged battery, and then repeatedly cycle through vacuum (-85~-95KPa) and pressurization (750~850KPa) to promote the rapid penetration and uniform distribution of the electrolyte inside the battery cell; vacuuming can remove residual bubbles inside the battery cell, and pressurization can increase the driving force for the electrolyte to penetrate into the battery cell. The combination of the two cycles can greatly improve the wetting efficiency and uniformity of the battery cell.

[0030] Therefore, the soft-pack cylindrical battery injection method provided by the present invention effectively solves the problems of difficult liquid penetration of soft-pack cylindrical batteries, poor wettability of batteries and low wettability efficiency through a series of optimized process steps such as vacuum pre-soaking, static dehydration, quantitative injection, vacuum infiltration, and pressurized liquid equalization. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present application provides a method for injecting liquid into a soft-pack cylindrical battery, comprising the following steps:

[0033] S1. Place the battery core in a vacuum immersion device, which includes a vacuum chamber, an electrolyte storage tank and a vacuum pump; immerse the core in the electrolyte, evacuate to no less than -80KPa, and maintain for 30 to 60 minutes; this step can effectively remove the gas inside the core and promote electrolyte penetration.

[0034] S2. Take out the soaked core and place it in a vacuum drying oven, maintain the vacuum degree not less than -80KPa, and let it stand for 10 to 30 minutes; this step allows the excess electrolyte to flow out naturally to avoid electrolyte overflow during the subsequent packaging process.

[0035] S3. Use automated packaging equipment to load the roll core into a pre-prepared soft-pack shell and perform heat sealing to form a battery.

[0036] S4. Use a liquid injection machine to inject electrolyte into the packaged battery; the injection amount is controlled to be 30% to 60% of the void volume inside the soft package shell. The injection process should be carried out slowly to ensure that the electrolyte is evenly distributed.

[0037] S5. The battery after liquid injection is evacuated to a vacuum degree of -85 KPa to -95 KPa, and the vacuum degree is maintained for 5s to 15s.

[0038] S6. The vacuumed battery is pressurized at a pressure of 750 KPa to 850 KPa for 250 s to 350 s.

[0039] S7, cycle steps S5-S6 for multiple times, the specific number of times can be adjusted according to the battery capacity, usually 3 to 5 times, let it stand, and obtain a liquid-filled soft-pack cylindrical battery.

[0040] In one embodiment of the present application, the above steps S1 to S7 are all performed in an ultra-low humidity environment with a dew point below -40°C. This can be achieved by using a drying box or a dedicated low-humidity workshop; the ultra-low humidity environment can minimize the impact of moisture on battery performance and improve the safety and long-term stability of the battery.

[0041] In one embodiment of the present application, in step S1, the battery core is immersed for 40 to 50 minutes, and the amount of electrolyte immersed is 1.5 to 3 times the volume of the battery core. This optimization can ensure sufficient infiltration while avoiding the falling off of the electrode material due to excessive immersion.

[0042] In one embodiment of the present application, in step S2, the battery core is left standing for 15 to 25 minutes, which is sufficient to allow excess electrolyte to flow out without causing excessive volatilization of the electrolyte that has been soaked.

[0043] In one embodiment of the present application, in step S4, the injection amount is controlled to be 40% to 50% of the internal void volume of the soft pack shell. Accurately controlling the injection amount can prevent insufficient electrolyte from affecting the performance of the battery cell, and prevent excessive injection from causing the electrolyte to squeeze, deform the soft pack or leak.

[0044] In one embodiment of the present application, in step S6, the gas used for the pressurization treatment is any one of nitrogen and argon. Inert gas can reduce the risk of electrolyte contact with air, prevent oxidative decomposition of electrolyte, and improve the safety and stability of the battery.

[0045] In one embodiment of the present application, in step S1, the electrolyte used for immersion is a heat-treated electrolyte, and the temperature of the electrolyte is 45-55° C. Heat treatment can reduce the viscosity of the electrolyte and improve its fluidity, thereby promoting the electrolyte to penetrate more evenly into the core.

[0046] In one embodiment of the present application, in step S4, the injected electrolyte is a heat-treated electrolyte, and the temperature of the electrolyte is 45-55° C. Heat treatment can reduce the viscosity of the electrolyte and improve its fluidity, thereby promoting the electrolyte to penetrate more evenly into the core.

[0047] In one embodiment of the present application, step S8 is further included, using an ultrasonic processor to perform ultrasonic treatment on the battery, with an ultrasonic frequency of 40kHz to 60kHz, an ultrasonic power of 100W to 300W, and an ultrasonic time of 20min to 40min. Ultrasonic treatment can further promote uniform distribution of the electrolyte in the winding core and eliminate tiny bubbles.

[0048] In one embodiment of the present application, step S9 is further included, wherein the battery after ultrasonic treatment is subjected to heat treatment at a temperature of 50° C. to 60° C. for a time of 1 to 3 hours. Heat treatment can promote the interaction between the electrolyte and the electrode material, form a stable SEI film, and improve the initial performance and cycle stability of the battery.

[0049] The implementation and advantages of this application will be further explained below in conjunction with specific embodiments.

[0050] Example 1

[0051] A method for injecting liquid into a soft-pack cylindrical battery comprises the following steps:

[0052] S1. Immerse the battery core in the electrolyte under vacuum, the vacuum degree is -80Kpa, and the immersion time is 45min; the battery core is wound with a positive electrode sheet made of NCM811 positive electrode material, a negative electrode sheet made of graphite negative electrode material and a PE separator, and the electrolyte is 1.0M LiPF 6 EC / EMC / DMC (volume ratio 1:1:1) solution, the amount of electrolyte soaked is twice the volume of the battery core;

[0053] S2. Take out the soaked battery coil from the electrolyte and place it in a vacuum environment for 20 minutes to allow excess electrolyte to flow out naturally;

[0054] S3, placing the rested battery roll core into an aluminum-plastic composite film soft-package shell, and sealing the soft-package edge by heat sealing to form a battery; the inner cavity of the soft-package shell matches the shape of the battery roll core;

[0055] S4, inject electrolyte into the battery cell through the injection port, the injection amount is 45% of the internal void volume of the soft pack shell;

[0056] S5. The battery cell after liquid injection is subjected to vacuum treatment, the vacuum degree is -90Kpa, and the vacuum degree is maintained for 10s;

[0057] S6. The vacuumized battery cell is subjected to nitrogen pressurization treatment with a pressurization intensity of 800Kpa and the pressure is maintained for 300s;

[0058] S7, repeat steps S5 and S6 for 3 cycles, let stand for 30 minutes, and obtain a finished liquid-filled battery.

[0059] Wherein, steps S1 to S7 are all performed in an ultra-low humidity clean room with a dew point of -45°C and a humidity of 0.5%.

[0060] Example 2

[0061] Different from Example 1, in this example, based on Example 1, in steps S1 and S4, the electrolytes used for immersion and injection are both preheated electrolytes, and the temperature is 50° C. Proper heating of the electrolyte can reduce its viscosity, accelerate its penetration into the core, and further improve the wetting efficiency.

[0062] The rest is the same as in Example 1 and will not be described again here.

[0063] Example 3

[0064] Different from Example 2, this embodiment adds step S8 on the basis of Example 2, using an ultrasonic processor to perform ultrasonic treatment on the battery, with an ultrasonic frequency of 50 kHz, an ultrasonic power of 200 W, and an ultrasonic time of 30 min.

[0065] The rest is the same as in Example 2 and will not be described again here.

[0066] Example 4

[0067] Different from Example 3, this embodiment adds step S9 on the basis of Example 3, and performs heat treatment on the battery after ultrasonic treatment, with the heat treatment temperature being 55° C. and the heat treatment time being 2 h.

[0068] The rest is the same as in Example 3 and will not be described again here.

[0069] Comparative Example 1

[0070] Different from Example 1, the conventional liquid injection method is used to directly inject the electrolyte into the packaged battery without vacuum pre-soaking and vacuum-pressurization cycle treatment.

[0071] Comparative Example 2

[0072] Different from Example 1, a vacuum liquid injection method is adopted, but there are no pre-soaking and pressurizing treatment steps.

[0073] The following electrochemical performance tests were performed on the batteries prepared by the injection methods of the embodiment and the comparative example, respectively. The test results are shown in Table 1 below.

[0074] 1. Electrolyte wettability test:

[0075] a) After the injection is completed, place the battery in a 25°C environment for 24 hours;

[0076] b) Use precision cutting equipment to cut open the battery in the glove box and quickly remove the battery core;

[0077] c) Weigh the weight of the battery core (W1) using a precision balance (accuracy 0.1 mg);

[0078] d) Soak the battery core in DMC (dimethyl carbonate) for 2 hours to dissolve all the electrolyte;

[0079] e) taking out the battery core and vacuum drying it at 60° C. for 24 hours;

[0080] f) Weigh the weight of the dried battery core again (W2);

[0081] g) Electrolyte wetting rate = [(W1-W2) / theoretical electrolyte weight] x 100%, wherein the theoretical electrolyte weight is calculated based on the injection volume.

[0082] 2. First charge and discharge efficiency test:

[0083] a) Use Xinwei BTS4000 series battery testing equipment;

[0084] b) Test in a constant temperature box at 25±2℃;

[0085] c) First charge: 0.2C constant current charge to 4.2V, then 4.2V constant voltage charge until the current drops to 0.05C; record the charge capacity (C1);

[0086] d) let stand for 30 minutes;

[0087] e) First discharge: 0.2C constant current discharge to 3.0V; record the discharge capacity (C2);

[0088] f) Initial charge and discharge efficiency = (C2 / C1) × 100%.

[0089] 3. Cycle life test:

[0090] a) Use Xinwei BTS4000 series battery testing equipment;

[0091] b) Test in a constant temperature box at 25±2℃;

[0092] c) Charging: 1C constant current charging to 4.2V, then 4.2V constant voltage charging until the current drops to 0.05C;

[0093] d) let stand for 10 minutes;

[0094] e) Discharge: 1C constant current discharge to 3.0V;

[0095] f) Repeat the above steps 100 times;

[0096] g) Record the discharge capacity of the 1st and 100th cycles (D1 and D100);

[0097] h) Capacity retention after 100 cycles = (D100 / D1) × 100%.

[0098] 4. Rate performance test:

[0099] a) Use Xinwei BTS4000 series battery testing equipment;

[0100] b) Test in a constant temperature box at 25±2℃;

[0101] c) 0.5C rate test: charge at 0.5C to 4.2V, then keep constant voltage at 4.2V until the current drops to 0.05C; let stand for 30 minutes; discharge at 0.5C to 3.0V, and record the discharge capacity (E1);

[0102] d) let stand for 1 hour;

[0103] e) 3C rate test: charge at 0.5C to 4.2V, then keep constant voltage at 4.2V until the current drops to 0.05C; let stand for 30 minutes; discharge at 3C to 3.0V, and record the discharge capacity (E2);

[0104] f) Rate performance (3C / 0.5C capacity ratio) = (E2 / E1) × 100%.

[0105] The above test results are specifically shown in Table 1 below.

[0106] Table 1

[0107]

[0108] From the test results in Table 1 above, we can see that:

[0109] By comparing the embodiments and comparative examples 1 to 2, it can be seen that compared with the traditional liquid injection method or the simple vacuum liquid injection method, the battery manufactured by the liquid injection method of the present invention has better electrolyte infiltration rate, initial charge and discharge efficiency, cycle performance and rate performance; it shows that the liquid injection method of the present invention can effectively solve the problems of difficult liquid infiltration, poor wettability and low wetting efficiency of soft-pack cylindrical batteries.

[0110] Comparing Examples 1 to 4, it can be seen that Example 2 is significantly improved compared to Example 1, indicating that heat treatment of the electrolyte has a significant effect on improving battery performance. Example 3 adds ultrasonic treatment on the basis of Example 2, further improving various performance indicators, especially the electrolyte wetting rate and cycle performance, indicating that ultrasonic treatment helps to uniformly distribute the electrolyte. Example 4 adds heat treatment on the basis of Example 3, achieving the optimal values ​​of all indicators, especially the first charge and discharge efficiency and rate performance are significantly improved, indicating that heat treatment helps to form a stable SEI film and improve the electrode / electrolyte interface. It can be seen that from Example 1 to Example 4, various performance indicators show a trend of gradual improvement, indicating that each optimization step proposed in the present invention has a positive effect on improving battery performance, and there is a synergistic effect between these steps.

[0111] In summary, the soft-pack cylindrical battery injection method proposed in the present invention achieves a comprehensive improvement in battery performance through a combination of multiple optimization steps; each additional optimization step brings further improvement in performance, among which Example 4 shows the best comprehensive performance, which fully demonstrates the effectiveness and superiority of the method of the present invention.

[0112] It should be noted that the contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field and will not be repeated here.

[0113] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for injecting liquid into a soft-pack cylindrical battery, characterized in that: The following steps are involved: S1. Immerse the battery core in the electrolyte under vacuum, with the vacuum degree not less than -80KPa, and the immersion time is 30 to 60 minutes; S2. Take out the soaked battery coil from the electrolyte and place it in a vacuum environment for 10 to 30 minutes to allow excess electrolyte to flow out naturally; S3, placing the rested battery roll core into a soft-pack shell, and sealing it to form a battery; S4, injecting electrolyte into the battery, the injection amount is 30% to 60% of the internal void volume of the soft package shell; S5. The battery after liquid injection is subjected to vacuum treatment, the vacuum degree is -85KPa to -95KPa, and the vacuum degree is maintained for 5s to 15s; S6. Pressurize the vacuumed battery at a pressure of 750 KPa to 850 KPa for 250 s to 350 s. S7, cycle through steps S5-S6 for multiple times, let stand, and obtain a liquid-filled soft-pack cylindrical battery.

2. The method for injecting liquid into a soft-pack cylindrical battery according to claim 1, characterized in that: in, Steps S1 to S7 are all performed in an ultra-low humidity environment with a dew point below -40°C.

3. The method for injecting liquid into a soft-pack cylindrical battery according to claim 1, characterized in that: In step S1, the battery core is immersed for 40 to 50 minutes, and the amount of the electrolyte is 1.5 to 3 times the volume of the battery core.

4. The method for injecting liquid into a soft-pack cylindrical battery according to claim 1, characterized in that: In step S2, the battery core is left to stand for 15 to 25 minutes.

5. The method for injecting liquid into a soft-pack cylindrical battery according to claim 1, characterized in that: In step S4, the injection amount is controlled to be 40% to 50% of the internal void volume of the soft package shell.

6. The method for injecting liquid into a soft-pack cylindrical battery according to claim 1, characterized in that: In step S6, the gas used for the pressurization treatment is any one of nitrogen and argon.

7. The method for injecting liquid into a soft-pack cylindrical battery according to claim 1, characterized in that: In step S1, the electrolyte used for immersion is a heat-treated electrolyte, and the temperature of the electrolyte is 45-55°C.

8. The method for injecting liquid into a soft-pack cylindrical battery according to claim 1, characterized in that: In step S4, the injected electrolyte is a heat-treated electrolyte, and the temperature of the electrolyte is 45-55°C.

9. The method for injecting liquid into a soft-pack cylindrical battery according to claim 1, characterized in that: The method further comprises step S8, performing ultrasonic treatment on the battery, wherein the ultrasonic frequency is 40kHz to 60kHz, the ultrasonic power is 100W to 300W, and the ultrasonic time is 20min to 40min.

10. The method for injecting liquid into a soft-pack cylindrical battery according to claim 9, characterized in that: The method further comprises step S9, performing heat treatment on the battery after ultrasonic treatment, wherein the heat treatment temperature is 50° C. to 60° C. and the heat treatment time is 1 to 3 hours.

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