A battery formation method
By quantifying the gas generation voltage range and gas generation amount of different film-forming additives during the lithium-ion battery formation process, and by adopting stepped rate charging and formation pressure adjustment, the problem of large electrolyte loss was solved, the electrolyte loss was effectively reduced and the SEI film was optimized, thereby improving battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEFEI GUOXUAN HIGH TECH POWER ENERGY
- Filing Date
- 2026-03-13
- Publication Date
- 2026-06-05
AI Technical Summary
In existing lithium-ion battery formation processes, especially the negative pressure formation process for lithium iron phosphate prismatic batteries, there is a large loss of electrolyte, which affects the formation quality of the SEI film and battery performance. Furthermore, the gas generation rate and amount of different electrolyte additives have not been effectively adjusted.
By conducting charge-discharge tests on unformed batteries, the gas generation voltage range and gas generation amount of different film-forming additives were quantified. A stepped rate charging method and formation pressure adjustment were adopted, and constant current charging was carried out in stages to optimize the formation process and reduce electrolyte loss.
It effectively reduces electrolyte loss, forms a dense and thermally stable SEI film, and improves battery performance.
Smart Images
Figure CN122158770A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery manufacturing technology, specifically relating to a battery formation method. Background Technology
[0002] In the production of lithium-ion batteries, the formation process is a crucial step in forming a stable solid electrolyte interphase (SEI) film, directly affecting the battery's cycle life, capacity retention, and other performance characteristics. However, existing formation processes, especially the negative pressure formation process for lithium iron phosphate prismatic batteries, have many defects, resulting in significant electrolyte loss.
[0003] In existing negative pressure formation processes for lithium iron phosphate (LFP) prismatic batteries, a single high-negative-pressure gas extraction mode is often used during formation. In carbonate electrolytes, this method results in relatively low electrolyte loss. However, due to the increasing demand for fast charging in lithium-ion batteries, large amounts of carboxylic acid ester solvents (such as EA and EP) are increasingly used in electrolytes. Furthermore, because carboxylic acid ester electrolytes have poor high-temperature stability, various electrolyte additives are often introduced to improve their high-temperature performance. Due to their high volatility, carboxylic acid ester electrolytes are easily extracted in large quantities during formation. Simultaneously, during negative pressure formation, different electrolyte additives exhibit varying gas production rates and quantities at different charging rates. For additives with high gas production rates and quantities, using a high charging rate often leads to violent reactions, resulting in excessively high internal battery pressure, exacerbating electrolyte spraying, and causing electrolyte loss rates exceeding 15%. Existing formation processes fail to make targeted adjustments for different electrolytes, which not only affects the formation quality of the SEI film but also exacerbates electrolyte volatilization and loss.
[0004] Therefore, a formation method that can specifically reduce electrolyte loss is needed to solve the problems existing in the prior art.
[0005] Chinese patent application CN106058326A discloses a lithium-ion battery formation method that can optimize the performance of the SEI film. The method first measures the film formation potential of a sample battery, and then sets a sinusoidal alternating current at all film formation potentials to perform periodic charging and discharging, and repeats this process multiple times. In the potential range where film formation does not occur, a larger current can be selected for charging. However, the patent does not mention improvements to the electrolyte loss problem, so further improvements are needed. Summary of the Invention
[0006] The technical problem to be solved by this invention is how to solve the problem of large electrolyte loss during the battery formation process.
[0007] The present invention solves the above-mentioned technical problems through the following technical means:
[0008] This invention provides a battery formation method, comprising the following steps: (1) Charge and discharge tests were performed on the unformed battery to obtain the voltage range of gas generation for each film-forming additive and the amount and rate of gas generation of different additives in the range. According to the order of film formation potential, the film-forming additives were recorded as V1, V2, V3...Vn in order from low to high, where n is a positive integer and n≥2. The gas generation start voltage of film-forming additive V1 was recorded as V1-1 and the gas generation end voltage was recorded as V1-2. The gas generation start voltage of film-forming additive V2 was recorded as V2-1 and the gas generation end voltage was recorded as V2-2. The gas generation start voltage of film-forming additive V3 was recorded as V3-1 and the gas generation end voltage was recorded as V3-2. And so on. The gas generation start voltage of film-forming additive Vn was recorded as Vn-1 and the gas generation end voltage was recorded as Vn-2. (2) After the battery is injected with liquid, the first stage of formation is carried out and the constant current is charged until the battery voltage reaches V1-1. During this stage, negative pressure evacuation is not performed. (3) Perform the second stage of formation and charge the battery at a constant current until the battery voltage reaches V1-2; (4) Perform the third stage of formation and charge the battery at a constant current until the battery voltage reaches V2-1; (5) Perform the fourth stage of formation, charge the battery at a constant current until the battery voltage reaches V2-2, and then repeat steps (4) and (5) until all film-forming additives have reacted. (6) Perform the fifth stage of formation and constant current charging.
[0009] This invention quantifies the gas generation voltage and gas generation amount of electrolyte additives through charge-discharge tests. Based on the results, the negative pressure and charging rate during the formation process are adjusted according to the different gas generation amounts of different additives in steps (2)-(6) to effectively reduce the amount of electrolyte loss.
[0010] Based on the gas production and gas production rate of different additives at different rates obtained in step (1), the charging rate and formation pressure of the reaction voltage range of different additives are repeatedly adjusted between steps (2) and (6) until the liquid loss of the battery cell reaches the required liquid loss range.
[0011] In a further preferred embodiment, in step (1), n is 3.
[0012] In a further preferred embodiment, step (3) also includes adjusting the formation pressure to -30~-50 kPa.
[0013] In a further preferred embodiment, step (4) also includes adjusting the formation pressure to -30~-50 kPa.
[0014] In a further preferred embodiment, step (5) also includes adjusting the formation pressure to -30~-50 kPa.
[0015] In a further preferred embodiment, step (6) also includes adjusting the formation pressure to -30~-50 kPa.
[0016] Preferably, in step (1), the charge-discharge test method is to use an in-situ gas generation analyzer.
[0017] Preferably, in step (1), the charge-discharge test conditions are 0.1-0.5C and 0.02-0.05C at 35-55°C.
[0018] Preferably, in step (2), the formation conditions are a temperature of 35 to 55°C and constant current charging with a current of 0.1 to 0.5C.
[0019] Preferably, in step (3), the formation conditions are to maintain the temperature at 35-55°C and continue constant current charging with a current of 0.02-0.05C.
[0020] Preferably, in step (4), the formation conditions are a temperature maintained at 35-55°C and a current of 0.1C.
[0021] Preferably, in step (5), the formation conditions are a temperature maintained at 35-55°C and a current of 0.02-0.05C.
[0022] Preferably, in step (6), the formation conditions are to maintain the temperature at 35-55°C and charge the device with constant current until the state of charge (SOC) is cut off.
[0023] More preferably, in step (6), the battery is charged to 30% SOC using a constant current of 0.5C.
[0024] The beneficial effects of this invention are as follows: 1. This invention provides a battery formation method. First, based on the specific battery system and electrolyte formulation, the film-forming gas generation is measured to determine the film-forming gas generation voltage range. Then, based on the film-forming gas generation voltage range, a stepped rate charging method is used for precise control. This can slow down the reaction rate and reduce electrolyte loss. At the same time, the slow reaction of additives can more effectively form a dense and thermally stable SEI film. The above battery formation method can effectively reduce the electrolyte loss rate by 12.67%.
[0025] 2. This invention provides a battery formation method. This method optimizes the charging mode during the formation process by quantifying the gas generation voltage range and corresponding gas generation amount of different electrolyte additives, effectively reducing electrolyte loss during the formation process, while ensuring the formation quality of the SEI film and guaranteeing battery performance.
[0026] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the in-situ gas generation measuring instrument used for charge-discharge testing in an embodiment of the present invention; Figure 2 This is the DV gas flow rate / DV voltage curve of the additive in the embodiments of the present invention. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art.
[0029] Unless otherwise specified, the test materials and reagents used in the following examples are commercially available or prepared by known methods.
[0030] Unless otherwise specified, all techniques or conditions described in the embodiments can be performed in accordance with the techniques or conditions described in the literature in this field or in the product manual. Unless otherwise specified, the quantitative experiments in the following embodiments are all repeated three times or more, and the results are averaged.
[0031] The present invention will be further described below with reference to specific embodiments.
[0032] This embodiment of the invention takes 45°C as an example: A battery to be formed (120Ah square-shell battery, electrolyte filling coefficient 3.2) is placed in... Figure 1 In the formation chamber shown, the positive electrode is lithium iron phosphate, the negative electrode is graphite, the electrolyte is EC / EA-1M LiPF6, and the film-forming additives are 2.5% VC, 1% DTD, and 0.5% LiODFB. At 45°C, a charging rate of 0.1C was used, the formation pressure was adjusted to -50 kPa, and constant current charging was performed to 30% SOC to ensure complete reaction of all additives. Based on the charging data, the DV gas flow rate / DV voltage curve was plotted as follows. Figure 2As shown, the peaks corresponding to the three additives LiODFB (lithium difluoroborate oxalate), DTD (1,3-dithiacyclopentane-2-thionone), and VC (ethylene carbonate) are peak 1, peak 2, and peak 3. The gas production initiation voltage and gas production termination voltage of LiODFB are V1-1 = 1.67V and V1-2 = 1.97V, respectively, with a gas production volume of approximately 23 ml. The gas production initiation voltage and gas production termination voltage of DTD are V2-1 = 2.28V and V2-2 = 2.41V, respectively, with a gas production volume of approximately 92 ml. The gas production initiation voltage and gas production termination voltage of VC are V3-1 = 2.52V and V3-2 = 2.72V, respectively, with a gas production volume of approximately 153 ml.
[0033] Example 1: This example provides a formation method to improve the stability of the SEI film on an electrode. The formation method includes the following steps: (1) After the battery cell has been injected and allowed to stand, it is placed in a high-temperature negative pressure formation cabinet. After the battery cell temperature rises to 45°C, it is allowed to stand for 2 hours. The formation pressure is adjusted to 0 kPa, and then it is charged at a constant current of 0.1C to V1-1 = 1.67V; (2) The formation pressure is adjusted to -30 kPa, the temperature is maintained at 45°C, and a constant current of 0.02C is used. (3) Adjust the formation pressure to -50kPa, keep the temperature at 45℃, and charge the battery with a constant current of 0.1C until the battery voltage reaches V2-1; (4) Adjust the formation pressure to -30kPa, keep the temperature at 45℃, and charge the battery with a constant current of 0.02C until the battery voltage reaches V2-2; (5) Adjust the formation pressure to -50kPa, keep the temperature at 45℃, and charge the battery with a constant current of 0.1C until the battery voltage reaches V3-1; (6) Adjust the formation pressure to -30kPa, keep the temperature at 45℃, and charge the battery with a constant current of 0.02C until the battery voltage reaches V3-2; (7) Adjust the formation pressure to -50kPa, and charge the battery with a constant current of 0.5C until 30% SOC.
[0034] Example 2: Compared with Example 1, the difference in this example is that step (2) is converted into a pressure adjustment of -50kPa; the rest is the same as Example 1.
[0035] Example 3: Compared with Example 1, this example changes step (4) to a pressure adjustment of -50 kPa; the rest is the same as Example 1.
[0036] Example 4: Compared with Example 1, this example changes step (6) to a pressure adjustment of -50 kPa; the rest is the same as Example 1.
[0037] Example 5: Compared with Example 1, the difference in this example is that the charging rate in step (2) is adjusted to 0.05C; the rest is the same as in Example 1.
[0038] Example 6: Compared with Example 1, the difference in this example is that the charging rate in step (4) is adjusted to 0.05C; the rest is the same as in Example 1.
[0039] Example 7: Compared with Example 1, the difference in this example is that the charging rate in step (6) is adjusted to 0.05C; the rest is the same as in Example 1.
[0040] Example 8: Take the battery to be formed and place it in the following... Figure 1 In the formation cabinet shown, after the cell temperature rises to 45°C, it is left to stand for 2 hours. (1) 0.1C constant current charging to V1-1=1.67V; (2) 0.02C constant current charging to the battery voltage reaches V1-2; (3) 0.1C constant current charging to the battery voltage reaches V2-1; (4) 0.02C constant current charging to the battery voltage reaches V2-2; (5) 0.1C constant current charging to the battery voltage reaches V3-1; (6) 0.02C constant current charging to the battery voltage reaches V3-2; (7) 0.5C constant current charging to 30% SOC. Calculate the gas production amount and gas production rate of each additive.
[0041] Example 9: Compared to Example 8, this example adjusts the charging rate in step (2) to 0.05C; the rest is the same as Example 8.
[0042] Example 10: Compared with Example 8, this example adjusts the charging rate in step (4) to 0.05C; the rest is the same as Example 8.
[0043] Example 11: Compared with Example 8, this example adjusts the charging rate of step (6) to 0.05C; the rest is the same as Example 8.
[0044] Comparative Example 1: Compared with Example 1, this comparative example does not use stepped rate charging; the battery cell after liquid injection and standing is placed in a high-temperature formation cabinet, and after the battery cell temperature rises to 45°C, it is left to stand for 2 hours. The formation pressure is adjusted to -50kPa, and then it is charged at a constant current of 0.1C to 30% SOC.
[0045] Comparative Example 2: Compared with Example 1, this comparative example does not use stepped rate charging; the battery cell after liquid injection and standing is placed in a high-temperature formation cabinet, and after the battery cell temperature rises to 45°C, it is left to stand for 2 hours. The formation pressure is adjusted to -30kPa, and then it is charged at a constant current of 0.1C to 30% SOC.
[0046] Comparative Example 3: Compared to Example 1, this comparative example converts step (2) into a pressure adjustment of -70 kPa; the rest is the same as Example 1.
[0047] Comparative Example 4: Compared to Example 1, this comparative example converts step (4) into a pressure adjustment of -70 kPa; the rest is the same as Example 1.
[0048] Comparative Example 5: Compared to Example 1, this comparative example converts step (6) into a pressure adjustment of -70 kPa; the rest is the same as Example 1.
[0049] Comparative Example 6: Compared to Example 1, the difference in this comparative example is that the charging rate in step (2) is adjusted to 0.1C; the rest is the same as in Example 1.
[0050] Comparative Example 7: Compared to Example 1, the difference in this comparative example is that the charging rate in step (4) is adjusted to 0.1C; the rest is the same as in Example 1.
[0051] Comparative Example 8: Compared to Example 1, the difference in this comparative example is that the charging rate in step (6) is adjusted to 0.1C; the rest is the same as in Example 1.
[0052] Comparative Example 9: Compared to Example 8, this comparative example adjusts the charging rate in step (2) to 0.1C; the rest is the same as Example 8.
[0053] Comparative Example 10: Compared with Example 8, the difference in this comparative example is that the charging rate in step (4) is adjusted to 0.1C; the rest is the same as Example 8.
[0054] Comparative Example 11: Compared to Example 8, this comparative example adjusts the charging rate in step (6) to 0.1C; the rest is the same as Example 8.
[0055] The formula for calculating electrolyte loss is as follows: Liquid loss = Weight of battery after formation - Weight of battery before formation Electrolyte loss rate = Loss volume / Injection volume Table 1 shows a comparison of the electrolyte loss and loss rate data for the examples and comparative examples. Within the voltage range of additive gas generation, examples 1-7 significantly reduced electrolyte loss by lowering the charging rate to 0.02-0.05C, and also reduced electrolyte loss by lowering the negative pressure during additive gas generation to -30 to -50 kPa. Comparative examples 1-8, with a charging rate of 0.01C and a negative pressure during additive gas generation of -70 kPa, showed a significantly increased electrolyte loss compared to examples 1-7. This demonstrates that the charging rate range of 0.02-0.05C and the negative pressure range of -30 to -50 kPa defined in this invention are specific choices. Through extensive experiments, process parameters that can reduce electrolyte loss during battery formation were found. Arbitrarily selecting parameters will not achieve the effects of this application.
[0056] Table 2 shows a comparison of the gas production rate and production period of the additives under different steps in the examples and comparative examples. By comparing Examples 8-11 and Comparative Examples 9-11, it can be seen that reducing the charging rate during the decomposition and gas production of each additive will greatly reduce the gas production rate of the additive.
[0057] Table 1: Comparison of liquid loss between the example and comparative batteries
[0058] Table 2 compares the gas production and production rate of the additives under different production steps in the examples and comparative examples.
[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A battery formation method, characterized in that, Includes the following steps: (1) Charge and discharge tests were performed on the unformed battery to obtain the voltage range of gas generation for each film-forming additive and the amount and rate of gas generation of different additives in the range. According to the order of film formation potential, the film-forming additives were recorded as V1, V2, V3...Vn in order from low to high, where n is a positive integer and n≥2. The gas generation start voltage of film-forming additive V1 was recorded as V1-1 and the gas generation end voltage was recorded as V1-2. The gas generation start voltage of film-forming additive V2 was recorded as V2-1 and the gas generation end voltage was recorded as V2-2. The gas generation start voltage of film-forming additive V3 was recorded as V3-1 and the gas generation end voltage was recorded as V3-2. And so on. The gas generation start voltage of film-forming additive Vn was recorded as Vn-1 and the gas generation end voltage was recorded as Vn-2. (2) After the battery is injected with liquid, the first stage of formation is carried out and the constant current is charged until the battery voltage reaches V1-1. During this stage, negative pressure evacuation is not performed. (3) Perform the second stage of formation and charge the battery at a constant current until the battery voltage reaches V1-2; (4) Perform the third stage of formation and charge the battery at a constant current until the battery voltage reaches V2-1; (5) Perform the fourth stage of formation, charge the battery at a constant current until the battery voltage reaches V2-2, and then repeat steps (4) and (5) until all film-forming additives have reacted. (6) Perform the fifth stage of formation and constant current charging.
2. The battery formation method according to claim 1, characterized in that, Steps (3) and (4) also include adjusting the formation pressure to -30~-50 kPa.
3. The battery formation method according to claim 1, characterized in that, Steps (5) and (6) also include adjusting the formation pressure to -30~-50 kPa.
4. The battery formation method according to claim 1, characterized in that, In step (1), the charge-discharge test method is to use an in-situ gas generation analyzer.
5. The battery formation method according to claim 1, characterized in that, In step (1), the charge and discharge test conditions are 35-55℃, and the test conditions are 0.1-0.5C and 0.02-0.05C respectively.
6. The battery formation method according to claim 1, characterized in that, In step (2), the formation conditions are a temperature of 35 to 55°C and a constant current charging of 0.1 to 0.5C.
7. The battery formation method according to claim 1, characterized in that, In step (3), the formation conditions are to maintain the temperature at 35-55°C and continue constant current charging with a current of 0.02-0.05C.
8. The battery formation method according to claim 1, characterized in that, In step (4), the formation conditions are to maintain the temperature at 35-55°C and use a current of 0.1C.
9. The battery formation method according to claim 1, characterized in that, In step (5), the formation conditions are to maintain the temperature at 35-55°C and use a current of 0.02-0.05C.
10. The battery formation method according to claim 1, characterized in that, In step (6), the formation conditions are to maintain the temperature at 35-55°C and charge the device with constant current until the cutoff SOC.