Method for improving lithium supplement battery formation
By employing a formation method controlled by gradient pressure and temperature, the problems of poor electrolyte wetting and SEI film instability caused by gas generation during the formation process of lithium-ion batteries have been solved, thereby improving the cycle performance of the cells.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-03-13
AI Technical Summary
Existing lithium-ion battery formation methods are prone to gas generation, which affects electrolyte wetting and SEI film stability, leading to a decline in cell cycle performance.
A gradient pressure and temperature controlled formation method is adopted, including room temperature initial formation, standing and high temperature re-formation, combined with slow current charging, to ensure that the electrolyte is fully wetted and the SEI film is densely formed, eliminating the influence of gas generation.
It improves the electrolyte retention and ion transport efficiency of the battery cell, enhances the stability of the SEI film, and extends the cycle life of the battery.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a method for improving the formation of lithium-ion batteries. Background Technology
[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.
[0003] Lithium-ion batteries are widely used in electric vehicles, portable electronic devices, and other fields due to their high energy density and long cycle life. Generally, during the first charge, a solid electrolyte interphase (SEI) film forms on the negative electrode surface, permanently consuming lithium ions and reducing usable lithium. Lithium replenishment agents pre-embed lithium sources before the battery operates, directly compensating for this loss. During subsequent charge and discharge processes, the negative electrode continuously consumes lithium ions (e.g., the volume expansion and rupture of silicon-based negative electrodes leads to SEI film reconstruction). The lithium stored in the negative electrode by the replenishment agent can dynamically compensate for later cycle losses, extending battery life. However, replenishment agent materials (such as lithium-rich ferric oxide (LFO)) are prone to oxidation, increasing process complexity, and the replenishment agent may generate gas during later cell cycles, especially if the formation method is improper.
[0004] When generated gas is not discharged in time, it will form gaps between the electrodes, hindering the electrolyte from fully wetting the electrodes and affecting the electrolyte retention and ion transport efficiency. The gas will also damage the stability of the negative electrode SEI film, which may lead to the continuous consumption of lithium ions during SEI film reconstruction, resulting in a decrease in the cell's cycle capacity retention rate. Gas accumulation will increase the internal pressure of the cell, which may lead to structural problems such as electrode deformation and separator damage, further aggravating performance degradation. The gas generation process is often accompanied by electrolyte decomposition or lithium replenishment side reactions, which will consume additional available lithium sources and reduce the actual capacity of the battery. Summary of the Invention
[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an improved method for the formation of lithium batteries.
[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: A method for improving the formation of lithium-ion batteries includes the following steps: The battery cell with lithium added to the positive and / or negative electrodes is left to stand for the first time to allow the electrodes to be fully wetted; Formation is carried out using a current of 0.02-0.05C, a pressure of 200-400kg, and a temperature of 22-28℃ until the voltage reaches 3-3.2V; Adjust the pressure to 500-800 kg and continue to convert to 3.3-3.5 V; After the battery cell has been formed, let it rest for the second time, then continue to form it to 4-4.1V.
[0007] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: Gradient pressure formation can not only avoid the formation gas from not being discharged in time, which would lead to poor wetting areas between electrodes, but also effectively promote electrolyte wetting through the physical and chemical forces of the internal micro-regions during the formation process, thereby increasing the electrolyte retention.
[0008] Conventional high-temperature formation of SEI films results in rapid formation, but the structure is relatively loose, potentially leading to continuous electrolyte decomposition and increased irreversible lithium loss. In contrast, room-temperature formation produces dense and stable SEI films that effectively suppress side reactions. Post-formation settling eliminates physical and chemical polarization, improving film stability.
[0009] In addition, lithium-rich iron acid and other lithium replenishing agents release oxygen during the high-temperature delithiation process. Experiments show that the oxygen release rate of LFO at 60°C is more than 5 times higher than that at room temperature. Therefore, using higher temperature formation can ensure that the lithium replenishing agent completely generates gas to the greatest extent and prevent gas generation during later cell cycling.
[0010] After re-forming and allowing the cells to stand, polarization is eliminated, improving cell stability and increasing cycle life. After standing, a low-current cycle for three weeks eliminates potential problems such as black spots and poor wetting of the electrodes caused by gas generation, further increasing cell cycle life.
[0011] Energy density and cycle life are the most important parameters of lithium-ion batteries. Cycle failure is also one of the failure modes of lithium-ion batteries. Currently, using lithium replenishment agents to increase capacity and improve cycling is a common method. However, improper formation methods for lithium replenishment cells can actually lead to faster cell failure. Therefore, this invention can effectively improve the formation method of lithium replenishment cells and enhance cell cycle life. Detailed Implementation
[0012] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0013] To address the technical problems mentioned in the background section, this invention provides a method for improving the formation of lithium-ion batteries, comprising the following steps: The battery cell with lithium added to the positive and / or negative electrodes is left to stand for the first time to allow the electrodes to be fully wetted; Formation is carried out using a current of 0.02-0.05C, a pressure of 200-400kg, and a temperature of 22-28℃ until the voltage reaches 3-3.2V; Adjust the pressure to 500-800 kg and continue to convert to 3.3-3.5 V; After the cells have been formed, they are left to stand for a second time and then formed to 4-4.1V.
[0014] The formation process at room temperature (22-28℃) results in a denser and more stable SEI film compared to high-temperature formation, effectively suppressing side reactions and reducing irreversible lithium loss. An initial gradient pressure of 200-400 kg prevents the formation gas from failing to dissipate in time, thus avoiding poor wetting areas between electrodes, while also promoting electrolyte wetting and increasing electrolyte retention. Room temperature conditions slow down the oxygen release rate of the lithium replenishing agent (such as lithium-rich iron acid), preventing excessively rapid initial gas production and subsequent high-temperature steps to promote complete gas production from the lithium replenishing agent, preventing gas production during later cell cycling. Formation at a slow current of 0.02-0.05C to 3-3.2V helps to uniformly form the SEI film and stabilize the initial state of the cell.
[0015] By increasing the pressure to 500-800 kg, the gases generated during the formation process are further expelled in a timely manner, preventing gas accumulation between the electrodes and the formation of voids, thus preventing gas generation during later cycles from affecting performance. The higher pressure enhances the tight contact between the electrodes, promoting the full penetration of the electrolyte into the electrodes through internal physical forces, increasing electrolyte retention, and ensuring ion transport efficiency. During the SEI film improvement stage at a voltage of 3.3-3.5V, the higher pressure helps the SEI film form a more uniform and dense structure, reducing subsequent side reactions and irreversible lithium loss. It also provides a stable cell state for subsequent higher voltage (up to 4.05V) formation steps, ensuring performance consistency and improving cycle life.
[0016] The second settling process eliminates cell polarization, further stabilizes the SEI film structure, and improves the overall stability of the cell. Continuing formation to 4-4.1V further improves the SEI film, ensuring full utilization of the cell capacity. At the same time, by controlling gradient pressure and temperature, the efficiency of electrolyte wetting and ion transport is optimized, increasing electrolyte retention. This step lays a stable foundation for subsequent cell cycling, reduces irreversible lithium loss, and significantly improves cycle capacity retention.
[0017] In some embodiments, the positive electrode of the battery cell is lithium supplemented, and the content ratio of positive electrode active material, conductive agent, binder and lithium supplementing agent in the positive electrode is 96-98:0.5-1.5:1.5-3:0.5-3.
[0018] Preferably, the lithium supplement is selected from at least one of lithium ferrite, lithium nickelate, or lithium oxide.
[0019] In some embodiments, the positive electrode active material is at least one of lithium iron phosphate, lithium manganese iron phosphate, ternary lithium, lithium manganese oxide, etc., the conductive agent is conductive carbon black or a combination of conductive carbon black and carbon nanotubes, and the binder is PVDF.
[0020] The positive and negative electrode sheets and the separator are stacked to obtain the stacked core; then, through processes such as packaging, baking, and electrolyte injection, a soft-pack battery cell is obtained.
[0021] In some embodiments, the temperature of the first settling period is 42-48°C, and the settling time is 40-50 hours, so that the electrode is completely wetted.
[0022] In some embodiments, the temperature for the second settling period is 42-48°C, and the settling time is 40-50 hours.
[0023] In some embodiments, the method for further forming the battery cell to 4.05V after a second settling is as follows: at 42-48°C, charge to 3-3.5V with a clamping force of 200-400kg and a current of 0.1-0.3C; after settling for a set time, adjust the temperature to 57-63°C, adjust the pressure to 800-1000kg, and then charge to 4-4.1V with 0.015-0.025C. After allowing it to stand for the set time, charge it to 4-4.1V at 0.005-0.015C.
[0024] Charging and allowing the cell to stand at 42-48℃ eliminates cell polarization, further stabilizing the uniformity and density of the SEI film and improving the overall stability of the cell. Adjusting the temperature to 57-63℃ significantly accelerates the oxygen release rate of the lithium replenishing agent (such as lithium-rich iron acid), allowing it to completely release gas and preventing gas generation during later cycles from damaging cell performance. Increasing the pressure to 800-1000 kg promotes the timely discharge of gas generated during the formation process through gradient pressure, preventing the formation of voids between electrodes. At the same time, it enhances the tight contact between electrodes, promotes full electrolyte penetration, and improves electrolyte retention and ion transport efficiency. Using a slow current of 0.015-0.025C to charge to 4-4.1V helps the SEI film to form uniformly and densely, reducing side reactions and ensuring that the cell capacity is fully utilized.
[0025] Charging to 4-4.1V with an extremely low current of 0.005-0.015C helps the SEI film grow uniformly in a near-fully charged state, forming a denser and more stable structure, reducing side reactions and irreversible lithium loss in subsequent cycles; slow current charging allows the active materials of the cell to fully participate in the reaction, ensuring maximum capacity release, avoiding polarization or incomplete capacity activation caused by high current charging, optimizing the ion distribution and interface state inside the cell, and helping to improve cycle capacity retention.
[0026] Preferably, the voltage is charged to 3.3-3.5V at 42-48℃ with a clamping force of 250-350kg and a current of 0.15-0.25C.
[0027] Further preferably, the voltage is charged to 3.5V at 42-48℃ with a clamping force of 300kg and a current of 0.2C.
[0028] Preferably, after standing for 8-10 minutes, adjust the temperature to 57-63℃.
[0029] Preferably, after standing for 8-10 minutes, charge to 4-4.1V at 0.01C.
[0030] In some embodiments, the battery cells, after being converted to 4-4.1V, are cycled for 2-4 weeks under a current of 0.15-0.25C and a clamping force of 800-1000kg, and then subjected to secondary sealing and capacity testing.
[0031] Cycling with a low current (0.15-0.25C) for 2-4 weeks can eliminate problems such as black spots on the electrodes and poor wetting that may be caused by gas generation during the formation process, thus improving the internal interface state of the cell. Cycling under a high-voltage clamp force of 800-1000kg further promotes the discharge of residual gas inside the cell, preventing gas accumulation during later cycles from damaging the electrode or separator structure. At the same time, it enhances the tight contact between electrodes, ensuring ion transport efficiency. The cycling process can stabilize the SEI film structure, reduce side reactions and irreversible lithium loss in subsequent use, and significantly improve the cycle capacity retention rate of the cell. Through this cycling step, the reaction uniformity of the active materials inside the cell can be optimized, individual differences can be reduced, and the performance stability of mass production can be improved.
[0032] The present invention will be further described below with reference to the embodiments.
[0033] Example 1 In this embodiment, the dimensions of the soft-pack lithium-ion battery are 7mm × 65mm × 115mm. 1. Place the above-mentioned battery cells in a high-temperature warehouse (45℃) and let them stand for 48 hours; 2. Using a variable pressure and temperature formation method, the above-mentioned battery cell is formed at a current of 0.04C at room temperature (25℃) with a clamping force of 300kg until the voltage is 3.2V. The pressure is then adjusted to 500kg, and the battery is further formed to 3.4V.
[0034] After the formed cells are left to stand at a high temperature (45℃) for 48 hours, they are placed on a forming cabinet for further high-temperature forming to 4.05V. Specifically, at 45℃, they are charged to 3.5V with a clamp force of 300kg at 0.2C. After standing for 10 minutes, the temperature is adjusted to 60℃ and the pressure to 900kg. They are then charged to 4.05V at 0.02C. After standing for 10 minutes, they are charged to 4.05V at 0.01C.
[0035] The formed battery cells are left to stand at a high temperature (45°C) for 48 hours.
[0036] 3. After the cells have been left to stand, they are cyclically rotated for 3 cycles at a current of 0.2C under a clamping force of 900kg, followed by a second sealing and capacity testing.
[0037] 4. Test and disassemble the obtained finished battery cells.
[0038] Example 2 In this embodiment, the dimensions of the soft-pack lithium-ion battery are 7mm×65mm×115mm; compared with Embodiment 1, the difference lies in the change of parameters; 1. Place the above-mentioned battery cells in a high-temperature warehouse (45℃) and let them stand for 48 hours; 2. Using a variable pressure and temperature formation method, the above-mentioned battery cell is formed at a current of 0.03C at room temperature (26℃) with a clamping force of 300kg until the voltage is 3.2V. The pressure is then adjusted to 600kg, and the battery is further formed to 3.4V.
[0039] After formation, the battery cells are left to stand at a high temperature (47℃) for 48 hours, then placed in a formation cabinet for further high-temperature formation to 4.0V. Specifically, at 47℃, the cells are charged to 3.5V with a 0.2C rate using a 300kg clamp force, left to stand for 10 minutes, then the temperature is adjusted to 62℃ and the pressure to 800kg, and then charged to 4.0V at 0.02C. After standing for 10 minutes, the cells are charged to 4.0V at 0.01C. The formed battery cells are then left to stand at a high temperature (43℃) for 48 hours.
[0040] 3. After the cells have been left to stand, they are cyclically rotated for 3 cycles at a current of 0.2C under a clamping force of 800kg, followed by a second sealing and capacity testing.
[0041] 4. Test and disassemble the obtained finished battery cells.
[0042] Example 3 In this embodiment, the dimensions of the soft-pack lithium-ion battery are 7mm × 65mm × 115mm; compared with Embodiment 1, the difference lies in the change of parameters: 1. Place the above-mentioned battery cells in a high-temperature warehouse (48℃) and let them stand for 48 hours; 2. Using a variable pressure and temperature formation method, the above-mentioned battery cell is formed at a current of 0.05C at room temperature (28℃) with a clamping force of 300kg until the voltage is 3.2V. The pressure is then adjusted to 700kg, and the battery is further formed to 3.4V.
[0043] After formation, the battery cell is left to stand at a high temperature (48℃) for 48 hours, then placed in a formation cabinet for further high-temperature formation to 4.1V. Specifically, at 48℃, it is charged to 3.5V with a 0.2C rate using a 300kg clamp force, left to stand for 10 minutes, then the temperature is adjusted to 63℃ and the pressure to 800kg, and then charged to 4.1V at 0.02C. After standing for 10 minutes, it is charged to 4.1V at 0.01C. The formed battery cell is then left to stand at a high temperature (48℃) for 48 hours.
[0044] 3. After the cells have been left to stand, they are cyclically rotated for 3 cycles at a current of 0.2C under a clamping force of 1000kg. Then, they are resealed and their capacity is tested.
[0045] 4. Test and disassemble the obtained finished battery cells.
[0046] Example 4 In this embodiment, the dimensions of the soft-pack lithium-ion battery are 7mm × 65mm × 115mm; compared with Embodiment 1, the difference lies in the change of parameters: 1. Place the above-mentioned battery cells in a high-temperature warehouse (42℃) and let them stand for 48 hours; 2. Using a variable pressure and temperature formation method, the above-mentioned battery cell is formed at a current of 0.02C at a high temperature (42℃) with a clamping force of 300kg until the voltage is 3.2V. The pressure is then adjusted to 800kg, and the battery is further formed to 3.4V.
[0047] After the formed cells are left to stand at a high temperature (42℃) for 48 hours, they are placed on a forming cabinet for further high-temperature forming to 4.05V. Specifically, at 42℃, they are charged to 3.5V with a clamp force of 300kg at 0.2C. After standing for 10 minutes, the temperature is adjusted to 57℃ and the pressure to 1000kg. They are then charged to 4.05V at 0.02C. After standing for 10 minutes, they are charged to 4.05V at 0.01C.
[0048] The formed battery cells were left to stand at a high temperature (47°C) for 48 hours.
[0049] 3. After the cells have been left to stand, they are cyclically rotated for 3 cycles at a current of 0.2C under a clamping force of 800kg, followed by a second sealing and capacity testing.
[0050] 4. Test and disassemble the obtained finished battery cells.
[0051] Comparative Example 1 In this comparative example, the dimensions of the pouch lithium-ion battery are 7mm × 65mm × 115mm; the difference from Example 1 lies in the method used. 1. Place the above-mentioned battery cells in a high-temperature warehouse (45℃) and let them stand for 48 hours; 2. The above-mentioned battery cells are formed at a current of 0.04C at a high temperature (45℃) with a clamping force of 300kg until the voltage reaches 4.05V: Specifically, they are charged at 0.05C to 3.0V, charged at 0.1C to 3.5V, charged at 0.02C to 4.05V, left to stand for 10 minutes, and then charged at 0.01C to 4.05V.
[0052] Then cycle at 0.33C for one more week.
[0053] The formed battery cells are left to stand at a high temperature (45°C) for 48 hours.
[0054] 3. After the cells have been left to stand, they are resealed and their capacity is tested.
[0055] 4. Test and disassemble the obtained finished battery cells.
[0056] Comparative Example 2 In this comparative example, the dimensions of the pouch lithium-ion battery are 7mm × 65mm × 115mm; the difference from Example 1 lies in the method used. 1. Place the above-mentioned battery cells in a high-temperature warehouse (45℃) and let them stand for 48 hours; 2. The above-mentioned battery cells are formed at a current of 0.04C at a high temperature (45℃) with a clamping force of 300kg until the voltage reaches 4.05V: Specifically, they are charged at 0.05C to 3.0V, charged at 0.1C to 3.5V, charged at 0.02C to 4.05V, left to stand for 10 minutes, and then charged at 0.01C to 4.05V.
[0057] Then cycle at 0.33C for one more week.
[0058] The formed battery cells were left to stand at a high temperature (45±3℃) for 48 hours.
[0059] 3. After cycling the above-mentioned battery cells for 3 cycles with a current of 0.2C and a clamping force of 900kg, perform secondary sealing and capacity testing.
[0060] 4. Test and disassemble the finished battery cells.
[0061] Comparative Example 3 In this comparative example, the dimensions of the soft-pack lithium-ion battery are 7mm × 65mm × 115mm; the difference from Example 1 is that the parameters have changed. 1. Place the above-mentioned battery cells in a high-temperature warehouse (45℃) and let them stand for 48 hours; 2. Using a variable pressure and temperature formation method, the above-mentioned battery cell is formed at a current of 0.04C at room temperature (25℃) with a clamping force of 300kg until the voltage is 3.2V. The pressure is then adjusted to 500kg, and the battery is further formed to 3.4V.
[0062] After the formed cells are left to stand at a high temperature (45°C) for 48 hours, they are placed on a forming cabinet for further high-temperature forming to 4.05V. Specifically, they are charged to 3.5V with a 0.2C charge using a 300kg clamp force, left to stand for 10 minutes, then the pressure is adjusted to 900kg, and then charged to 4.05V with a 0.02C charge. After standing for 10 minutes, they are charged to 4.05V with a 0.01C charge.
[0063] The formed battery cells are left to stand at a high temperature (45°C) for 48 hours.
[0064] 3. After the cells have been left to stand, they are cyclically rotated for 3 cycles at a current of 0.2C under a clamping force of 900kg, followed by a second sealing and capacity testing.
[0065] 4. Test and disassemble the obtained finished battery cells.
[0066] Comparative Example 4 In this comparative example, the dimensions of the soft-pack lithium-ion battery are 7mm×65mm×115mm. Compared with Example 1, the difference lies in the method: in step 2, after the battery is formed to 3.4V, the step of "setting the formed cell at high temperature (45°C) for 48 hours" is omitted.
[0067] 1. Place the above-mentioned battery cells in a high-temperature warehouse (45℃) and let them stand for 48 hours; 2. Using a variable pressure and temperature formation method, the above-mentioned battery cell is formed at a current of 0.04C at room temperature (25℃) with a clamping force of 300kg until the voltage is 3.2V. The pressure is then adjusted to 500kg, and the battery is further formed to 3.4V.
[0068] Continue to reformat the above battery to 4.05V: under (45℃) conditions, charge to 3.5V with a clamp force of 300kg at 0.2C, let stand for 10 minutes, then adjust the temperature to 60℃ and the pressure to 900kg, then charge to 4.05V at 0.02C, let stand for 10 minutes, and then charge to 4.05V at 0.01C.
[0069] The formed battery cells are left to stand at a high temperature (45°C) for 48 hours.
[0070] 3. After the cells have been left to stand, they are cyclically rotated for 3 cycles at a current of 0.2C under a clamping force of 900kg, followed by a second sealing and capacity testing.
[0071] 4. Test and disassemble the obtained finished battery cells.
[0072] Comparative Example 5 In this comparative example, the dimensions of the soft-pack lithium-ion battery are 7mm × 65mm × 115mm; the difference from Example 1 lies in the method. 1. Place the above-mentioned battery cells in a high-temperature warehouse (45℃) and let them stand for 48 hours; 2. Using a variable pressure and temperature formation method, the above-mentioned battery cell is formed at a current of 0.04C at a high temperature (45℃) with a clamping force of 300kg until the voltage is 3.2V. The pressure is then adjusted to 500kg, and the battery is further formed to 3.4V.
[0073] After the formed cells are left to stand at a high temperature (45℃) for 48 hours, they are placed on a forming cabinet for further high-temperature forming to 4.0V. Specifically, at 45℃, they are charged to 3.5V with a clamp force of 300kg at 0.2C. After standing for 10 minutes, the temperature is adjusted to 60℃ and the pressure to 900kg. Then, they are charged to 4.05V at 0.02C. After standing for 10 minutes, they are charged to 4.05V at 0.01C.
[0074] 3. After cycling the above-mentioned battery cells for 3 cycles with a current of 0.2C and a clamping force of 900kg, perform secondary sealing and capacity testing.
[0075] 4. Test and disassemble the finished battery cells.
[0076] Comparative Example 6 In this comparative example, the dimensions of the soft-pack lithium-ion battery are 7mm×65mm×115mm. Compared with Example 1, the difference lies in the method: the step of "cycling for 3 cycles with a current of 0.2C under a clamping force of 900kg" in step 3 is omitted.
[0077] 1. Place the above-mentioned battery cells in a high-temperature warehouse (45℃) and let them stand for 48 hours; 2. Using a variable pressure and temperature formation method, the above-mentioned battery cell is formed at a current of 0.04C at room temperature (25℃) with a clamping force of 300kg until the voltage is 3.2V. The pressure is then adjusted to 500kg, and the battery is further formed to 3.4V.
[0078] After the formed cells are left to stand at a high temperature (45℃) for 48 hours, they are placed on a forming cabinet for further high-temperature forming to 4.05V. Specifically, at 45℃, they are charged to 3.5V with a clamp force of 300kg at 0.2C. After standing for 10 minutes, the temperature is adjusted to 60℃ and the pressure to 900kg. They are then charged to 4.05V at 0.02C. After standing for 10 minutes, they are charged to 4.05V at 0.01C.
[0079] The formed battery cells are left to stand at a high temperature (45°C) for 48 hours.
[0080] 3. After the cells have been left to stand, they are resealed and their capacity is tested.
[0081] 4. Test and disassemble the obtained finished battery cells.
[0082] Table 1 Fully charged disassembly status
[0083] Table 2 Performance Test and Cell Gas Generation During Cycling
[0084] As shown in Tables 1 and 2, conventional formation methods carry the risk of black spots appearing on the electrodes. Low-current cycling after formation effectively alters the electrode state and improves cell cycle life. Low-temperature film formation results in higher film stability, which is beneficial for cycling. High-temperature settling after formation eliminates cell polarization, stabilizes the SEI film, and thus increases the cell's cycle life. Higher formation temperatures promote the generation of lithium supplementation gas, effectively preventing cell cycle failure due to gas generation later on. Examples 1-3 show that when the formation voltage is low, the capacity cannot be fully utilized; when the formation voltage is too high, the cell impedance increases, affecting later cycle life.
[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for improving the formation of lithium-ion batteries, characterized in that: Includes the following steps: The battery cell with lithium added to the positive and / or negative electrodes is left to stand for the first time to allow the electrodes to be fully wetted; Formation is carried out using a current of 0.02-0.05C, a pressure of 200-400kg, and a temperature of 22-28℃ until the voltage reaches 3-3.2V; Adjust the pressure to 500-800 kg and continue to convert to 3.3-3.5 V; After the cells have been formed, they are left to stand for a second time and then formed to 4-4.1V.
2. The method for improving the formation of lithium-ion batteries according to claim 1, characterized in that: The positive electrode of the battery cell is used for lithium replenishment. In the positive electrode, the content ratio of positive electrode active material, conductive agent, binder and lithium replenishing agent is 96-98:0.5-1.5:1.5-3:0.5-3. Preferably, the lithium supplement is selected from at least one of lithium ferrite, lithium nickelate, or lithium oxide.
3. The method for improving the formation of lithium-ion batteries according to claim 1, characterized in that: The temperature for the first settling period is 42-48℃, and the settling time is 40-50 hours.
4. The method for improving the formation of lithium-ion batteries according to claim 3, characterized in that: The second settling temperature is 42-48℃, and the settling time is 40-50 hours.
5. The method for improving the formation of lithium-ion batteries according to claim 4, characterized in that: The method for further processing the battery cell to 4-4.1V after the second settling is as follows: At 42-48℃, charge to 3-3.5V with a clamping force of 200-400kg and a current of 0.1-0.3C. After settling for a set time, adjust the temperature to 57-63℃ and the pressure to 800-1000kg, and then charge to 4-4.1V with 0.015-0.025C. After allowing it to stand for the set time, charge it to 4-4.1V at 0.005-0.015C.
6. The method for improving the formation of lithium-ion batteries according to claim 5, characterized in that: Charge to 3.3-3.5V at 42-48℃ with a clamping force of 250-350kg and a current of 0.15-0.25C.
7. The method for improving the formation of lithium-ion batteries according to claim 6, characterized in that: Charge to 3.5V at 42-48℃ with a clamping force of 300kg and a current of 0.2C.
8. The method for improving the formation of lithium-ion batteries according to claim 5, characterized in that: After standing for 8-10 minutes, adjust the temperature to 57-63℃.
9. The method for improving the formation of lithium-ion batteries according to claim 5, characterized in that: After standing for 8-10 minutes, charge to 4-4.1V at 0.01C.
10. The method for improving the formation of lithium-ion batteries according to claim 5, characterized in that: After the battery cell is converted to 4.05V, it is cyclically operated for 2-4 cycles under a current of 0.15-0.25C and a clamping force of 800-1000kg, and then resealed and tested for capacity.