A method for injecting liquid into a soft package cylindrical battery

Abstract

The application discloses a kind of soft package cylindrical battery's injection method, comprising the following steps: S1, battery roll core is soaked in electrolyte in vacuum environment;S2, after soaking, battery roll core is taken out from electrolyte, and it is stationary in vacuum environment;S3, after stationary, battery roll core is loaded into soft package shell, and sealing forms battery;S4, electrolyte is injected into battery interior;S5, after injection, battery is extracted vacuum treatment, vacuum degree is-85KPa~-95KPa, keep the vacuum degree under 5s~15s;S6, after extraction, battery is pressurized treatment, pressurization intensity is 750KPa~850KPa, and pressure maintaining 250s~350s;S7, periodically circulates and carries out step S5-S6 multiple times, stationary, obtains injection soft package cylindrical battery.Compared with prior art, the application can effectively solve the problem that soft package cylindrical battery roll core is difficult to infiltrate, battery roll core is poor in wettability and low in infiltration efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary battery preparation, and particularly relates to a liquid injection method for a soft-pack cylindrical battery. BACKGROUND

[0002] In the current widespread application of lithium-ion batteries, soft-pack cylindrical batteries have attracted much attention due to their excellent energy density and flexible shape design. However, as the market demand for high-performance batteries continues to increase, soft-pack cylindrical batteries face new challenges in the production process, especially in the electrolyte injection process. Traditional injection methods often show some shortcomings when faced with the special structure of soft-pack cylindrical batteries, mainly in terms of difficult liquid penetration, poor cell wettability, and low wettability efficiency.

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

[0004] Secondly, the poor wettability of the cell directly affects the performance and life of the battery. The uniform distribution of electrolyte is crucial for ion conduction in the battery, and uneven distribution of electrolyte can lead to excessive local current density, causing local overheating and accelerated aging of the battery. In addition, due to poor wettability, the battery may experience capacity loss during the first 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 require a long time to ensure sufficient wettability of the electrolyte, which not only prolongs the production cycle but also may increase production costs. At the same time, bubbles and voids that are easily generated during the injection process can further affect the quality and reliability of the battery.

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

[0007] The purpose of the present application is to overcome the shortcomings of the prior art and provide a liquid injection method for a soft-pack cylindrical battery, which can effectively solve the problems of difficult liquid penetration, poor cell wettability, and low wettability efficiency of soft-pack cylindrical cells.

[0008] To achieve the above object, the present application provides the following technical solutions.

[0009] A liquid injection method of a soft-pack cylindrical battery, comprising the following steps:

[0010] S1, soaking the battery roll core in electrolyte under vacuum environment, the vacuum degree is not less than-80KPa, and the soaking time is 30-60min;

[0011] S2, taking out the soaked battery roll core from the electrolyte and standing for 10-30min under vacuum environment, so that the excess electrolyte flows out naturally;

[0012] S3, loading the battery roll core after standing into a soft-pack shell and sealing to form a battery;

[0013] S4, injecting electrolyte into the battery, and the injection amount is 30%-60% of the internal gap volume of the soft-pack shell;

[0014] S5, vacuumizing the battery after injection, the vacuum degree is-85KPa--95KPa, and the vacuum degree is maintained for 5s-15s;

[0015] S6, pressurizing the battery after vacuumizing, the pressurizing strength is 750KPa-850KPa, and the pressure is maintained for 250s-350s;

[0016] S7, periodically and cyclically performing steps S5-S6 multiple times, standing, and obtaining a liquid injection soft-pack cylindrical battery.

[0017] Preferably, the steps S1-S7 are all performed in an ultra-low humidity environment with a dew point lower than-40℃.

[0018] Preferably, in step S1, the soaking time of the battery roll core is 40-50min, and the amount of electrolyte for soaking is 1.5-3 times the volume of the battery roll core.

[0019] Preferably, in step S2, the standing time of the battery roll core is 15-25min.

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

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

[0022] Preferably, in step S1, the electrolyte for soaking is heat-treated electrolyte, and the temperature of the electrolyte is 45-55℃.

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

[0024] Preferably, step S8 is further included, which is ultrasonic treatment of the battery, the ultrasonic frequency is 40kHz-60kHz, the ultrasonic power is 100W-300W, and the ultrasonic time is 20min-40min.

[0025] Preferably, step S9 is further included, which is heat treatment of the battery after ultrasonic treatment, the heat treatment temperature is 50℃-60℃, and the heat treatment time is 1-3h.

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

[0027] 1) The battery roll core is soaked in the electrolyte in a high-vacuum environment, the vacuum environment is used to remove air inside the battery roll core, and the contact time of the electrolyte with the battery core is extended in the presence of a large amount of electrolyte, so that the vacuum pre-soaking significantly improves the adsorption capacity of the battery roll core to the electrolyte, enables the electrolyte to quickly penetrate into the roll core, and greatly improves the roll core wettability.

[0028] 2) The soaked battery roll core is placed in a vacuum environment for liquid removal, the vacuum environment is used to accelerate the natural outflow of excess electrolyte, which can effectively avoid the excessive electrolyte from being brought into the battery to affect the subsequent liquid injection accuracy; therefore, by combining the standing liquid removal and quantitative liquid injection, the amount of electrolyte in the battery is accurately controlled, and the influence of excessive or insufficient electrolyte on the battery performance is avoided.

[0029] 3) A proper amount of electrolyte is injected into the packaged battery, and then the periodic circulation of vacuum extraction (-85 to -95KPa) and pressure treatment (750 to 850KPa) is performed to repeatedly promote the rapid penetration and uniform distribution of the electrolyte in the battery core; the vacuum extraction can remove the residual bubbles in the battery core, and the pressure treatment can improve the driving force of the electrolyte to penetrate into the battery core, and the combination of the two can greatly improve the wettability efficiency and uniformity of the battery core.

[0030] Therefore, the soft-pack cylindrical battery liquid injection method provided by the present application effectively solves the problems of difficult electrolyte penetration, poor battery core wettability, and low wettability efficiency of the soft-pack cylindrical battery core through a series of optimized process steps such as vacuum pre-soaking, standing liquid removal, quantitative liquid injection, vacuum extraction penetration, and pressure liquid distribution. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be clearly and completely described below in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0032] The application provides a liquid injection method of a soft-pack cylindrical battery, comprising the following steps:

[0033] S1, placing a battery roll core in a vacuum soaking device, the device comprising a vacuum cavity, an electrolyte storage tank and a vacuum pump; immersing the roll core in electrolyte, vacuumizing to not less than-80KPa, and maintaining for 30-60 minutes; this step can effectively remove the gas inside the roll core and promote the penetration of electrolyte.

[0034] S2, taking out the soaked roll core and placing it in a vacuum drying box, maintaining the vacuum degree to not less than-80KPa, and standing for 10-30 minutes; this step can make the excess electrolyte flow out naturally, avoiding electrolyte overflow in the subsequent packaging process.

[0035] S3, using an automatic packaging equipment to pack the roll core into a pre-prepared soft-pack shell, and performing heat sealing treatment to form a battery.

[0036] S4, using a liquid injection machine to inject electrolyte into the packaged battery; the injection amount is controlled to be 30%-60% of the internal gap volume of the soft-pack shell. The injection process should be slow to ensure uniform distribution of electrolyte.

[0037] S5, vacuumizing the battery after injection, the vacuum degree being-85KPa to-95KPa, and maintaining the vacuum degree for 5s-15s.

[0038] S6, pressurizing the battery after vacuumizing, the pressurizing strength being 750KPa-850KPa, and maintaining the pressure for 250s-350s.

[0039] S7, periodically and cyclically performing steps S5-S6 for multiple times, the specific number of times being adjusted according to the battery capacity, usually 3-5 times, and standing to obtain a liquid injection soft-pack cylindrical battery.

[0040] In an embodiment according to the present application, the above steps S1-S7 are all performed in an ultra-low humidity environment with a dew point lower than-40℃. This can be achieved by using a drying box or a special low-humidity workshop; the ultra-low humidity environment can maximize the reduction of the influence of moisture on the performance of the battery, and improve the safety and long-term stability of the battery.

[0041] In an embodiment according to the present application, in step S1, the soaking time of the battery roll core is 40-50 min, and the amount of electrolyte for soaking is 1.5-3 times the volume of the battery roll core. This optimization can ensure sufficient soaking while avoiding excessive soaking of the pole piece material, which can cause it to fall off.

[0042] In an embodiment according to the present application, in step S2, the standing time of the battery roll core is 15-25 min. This time range can allow sufficient excess electrolyte to flow out while not causing excessive evaporation of the soaked electrolyte.

[0043] In an embodiment according to the present application, in step S4, the injection amount is controlled to be 40-50% of the internal gap volume of the soft package. Precise control of the injection amount can avoid insufficient electrolyte affecting the performance of the battery core, and prevent excessive injection causing electrolyte to be squeezed and deformed in the soft package or to leak.

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

[0045] In an embodiment according to the present application, in step S1, the soaked electrolyte is a heat-treated electrolyte, and the temperature of the electrolyte is 45-55℃. Heat treatment can reduce the viscosity of the electrolyte and improve its flowability, thereby promoting more uniform penetration of the electrolyte into the interior of the roll core.

[0046] In an embodiment according to the present application, in step S4, the injected electrolyte is a heat-treated electrolyte, and the temperature of the electrolyte is 45-55℃. Heat treatment can reduce the viscosity of the electrolyte and improve its flowability, thereby promoting more uniform penetration of the electrolyte into the interior of the roll core.

[0047] In an embodiment according to the present application, it further includes step S8, using an ultrasonic processor to perform ultrasonic treatment on the battery, with an ultrasonic frequency of 40-60 kHz, an ultrasonic power of 100-300 W, and an ultrasonic time of 20-40 min. Ultrasonic treatment can further promote the uniform distribution of electrolyte in the roll core and eliminate microbubbles.

[0048] In an embodiment according to the present application, it further includes step S9, performing heat treatment on the battery after ultrasonic treatment, with a heat treatment temperature of 50-60℃ and a heat treatment time of 1-3 h. 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 the present application will be further described below in conjunction with specific embodiments.

[0050] Example 1

[0051] A liquid injection method of a soft package cylindrical battery, comprising the following steps:

[0052] S1, soaking the battery roll core in electrolyte under vacuum environment, the vacuum degree is-80Kpa, the soaking time is 45min; wherein the battery roll core is made of positive electrode sheet made of NCM811 positive electrode material, negative electrode sheet made of graphite negative electrode material and PE diaphragm, the electrolyte is 1.0M LiPF6 EC / EMC / DMC(volumetric ratio 1:1:1) solution, the amount of soaking electrolyte is 2 times of the volume of battery roll core;

[0053] S2, taking out the soaked battery roll core from the electrolyte, and standing for 20min under vacuum environment, so that the excess electrolyte flows out naturally;

[0054] S3, putting the battery roll core after standing into the aluminum plastic composite film soft package shell, and sealing the soft package edge by heat sealing to form the battery; the inner cavity of the soft package shell matches the outer shape of the battery roll core;

[0055] S4, injecting electrolyte into the battery core through the liquid injection port, the injection amount is 45% of the volume of the internal gap of the soft package shell;

[0056] S5, vacuumizing the battery core after injection, the vacuum degree is-90Kpa, and the vacuum degree is maintained for 10s;

[0057] S6, nitrogen pressurizing treatment is carried out on the vacuumized battery core, the pressurizing strength is 800Kpa, and the pressure is maintained for 300s;

[0058] S7, repeating steps S5 and S6 for 3 times, standing for 30min, and obtaining the finished product injection battery.

[0059] Wherein, steps S1 to S7 are carried out in an ultra-low humidity clean room with dew point-45℃ and humidity 0.5%.

[0060] Example 2

[0061] Different from example 1, in this embodiment, on the basis of example 1, the electrolyte soaked and injected in steps S1 and S4 is preheated electrolyte, and the temperature is 50℃. Proper heating of electrolyte can reduce its viscosity and accelerate its penetration into the core, further improving the soaking efficiency.

[0062] The others are the same as example 1, which will not be repeated here.

[0063] Example 3

[0064] Different from example 2, this example adds step S8 to the 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] Other than example 2, which will not be repeated here.

[0066] Example 4

[0067] Different from example 3, this example adds step S9 to the example 3, performing heat treatment on the battery after ultrasonic treatment, with a heat treatment temperature of 55℃ and a heat treatment time of 2 h.

[0068] Other than example 3, which will not be repeated here.

[0069] Comparative example 1

[0070] Different from example 1, a conventional liquid injection method is used to directly inject 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 used, but without pre-soaking and pressurization treatment steps.

[0073] The batteries prepared by the liquid injection methods of the examples and comparative examples were subjected to the following electrochemical performance tests, and the test results are shown in Table 1 below.

[0074] 1. Electrolyte infiltration rate test:

[0075] a) After the liquid injection is completed, the battery is placed in a 25℃ environment for 24 hours;

[0076] b) The battery is cut open in a glove box using a precision cutting device, and the battery roll core is quickly removed;

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

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

[0079] e) The battery roll core is removed and vacuum dried at 60℃ for 24 hours;

[0080] f) The weight of the dried battery roll core (W2) is measured again;

[0081] g) Electrolyte infiltration rate = [(W1-W2) / theoretical electrolyte weight] x 100%. The theoretical electrolyte weight is calculated according to the liquid injection amount.

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

[0083] a) Using new BTS4000 series battery test equipment;

[0084] b) Test in a constant temperature oven at 25±2°C;

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

[0086] d) Stand for 30 minutes;

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

[0088] f) First charge-discharge efficiency = (C2 / C1) x 100%.

[0089] 3. Cycle life test:

[0090] a) Using new BTS4000 series battery test equipment;

[0091] b) Test in a constant temperature oven at 25±2°C;

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

[0093] d) 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) x 100%.

[0098] 4. Rate performance test:

[0099] a) Using new BTS4000 series battery test equipment;

[0100] b) Test in a constant temperature oven at 25±2°C;

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

[0102] d) stand for 1 hour;

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

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

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

[0106] Table 1

[0107]

[0108] From the test results in Table 1 above, it can be seen that:

[0109] From the comparative example and Comparative Examples 1-2, it can be seen that, compared to the traditional liquid injection method or the simple vacuum liquid injection method, the battery produced by the liquid injection method of the present application has better electrolyte infiltration rate, first charge-discharge efficiency, cycle performance and rate performance; which shows that the liquid injection method of the present application can effectively solve the problems of difficult liquid penetration, poor wettability and low wettability efficiency of soft-pack cylindrical batteries.

[0110] From Comparative Examples 1-4, it can be seen that Example 2 has obvious improvement compared to Example 1, which shows that electrolyte heat treatment has a significant effect on improving battery performance. Example 3 further improves various performance indicators, especially electrolyte infiltration rate and cycle performance, on the basis of Example 2 by adding ultrasonic treatment, which shows that ultrasonic treatment helps to evenly distribute the electrolyte. Example 4 reaches the optimal value of all indicators, especially the first charge-discharge efficiency and rate performance, on the basis of Example 3 by adding heat treatment, which shows 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, the performance indicators show a gradual improvement trend, which shows that each optimization step proposed in the present application has a positive effect on improving battery performance, and there is a synergistic effect between these steps.

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

[0112] It should be noted that the contents not described in detail in the present specification belong to the existing technology known to those skilled in the art, which will not be described here.

[0113] Those skilled in the art can make various modifications and variations to the above embodiments based on the disclosure and teachings of this specification. Therefore, the present application should not be limited to the above specific embodiments, and any obvious modifications, replacements or variations made by those skilled in the art based on the present application shall fall within the scope of the present application. 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 on the present application.

Claims

1. A method for injecting electrolyte into a pouch cylindrical battery, characterized in that, Includes the following steps: S1. Immerse the battery core in electrolyte under vacuum conditions. The vacuum degree is -80KPa and the immersion time is 45min. The amount of electrolyte is twice the volume of the battery core. S2. Remove the soaked battery core from the electrolyte and let it stand in a vacuum environment for 20 minutes to allow the excess electrolyte to flow out naturally. S3. Insert the rested battery core into the soft-pack casing and seal it to form a battery; S4. Inject electrolyte into the battery, the amount of electrolyte being 45% of the internal void volume of the soft-pack outer casing; S5. Vacuum the battery after liquid injection to a vacuum degree of -90KPa and maintain this vacuum degree for 10s. S6. After vacuuming, the battery is pressurized with nitrogen at a pressure of 800 kPa and held for 300 seconds. S7. Repeat steps S5 and S6 for 3 cycles, let stand for 30 minutes to obtain liquid-filled soft-pack cylindrical batteries. S8. Perform ultrasonic treatment on the battery at a frequency of 50kHz, a power of 200W, and a duration of 30min. S9. The ultrasonically treated battery is subjected to heat treatment at a temperature of 55°C for 2 hours. In steps S1 and S4, the electrolyte used for soaking and injection is a heat-treated electrolyte with a temperature of 50°C. Steps S1 to S7 are all carried out in an ultra-low humidity environment with a dew point of -45°C and a humidity of 0.5%.

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