Diaphragm lithium supplement laminated soft-package battery with high cycle stability and preparation method of diaphragm lithium supplement laminated soft-package battery
By coating the separator with LFO and LNO materials in a 3:7 ratio and combining it with a high-temperature and high-pressure formation process, the problem of active lithium loss during lithium battery cycling is solved, resulting in a soft-pack battery with high cycle stability and safety, suitable for application scenarios with stringent requirements for lifespan and safety.
Patent Information
- Application Number
- CN202511730416.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-24
- Publication Date
- 2026-02-17
AI Technical Summary
Existing lithium batteries suffer capacity decay during cycling due to the loss of active lithium in the SEI film. Furthermore, existing lithium replenishment materials such as lithium iron ferrite and lithium nickel oxide have problems with poor stability or low specific capacity during cycling and high-temperature storage.
A 3:7 mixture of LFO and LNO is coated onto the separator, and combined with a specific high-temperature and high-pressure formation process, including gradient current charge and discharge and multi-stage resting, the lithium-ion intercalation efficiency is optimized through JK step cycling to form a stable SEI film and eliminate gas hazards.
It achieves 100% capacity retention after 1000 battery cycles, maintains a stable negative electrode interface, avoids safety hazards such as electrode black spots and lithium plating, and improves the cycle stability and safety of the battery.
Smart Images
Figure CN121546178A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of secondary battery technology, and more specifically, to a membrane-replenished lithium-coated pouch cell with high cycle stability and its preparation method. Background Technology
[0002] In today's technological age, batteries have become an indispensable energy source for numerous devices, from everyday mobile phones and laptops to large-scale equipment such as electric vehicles and energy storage systems. Battery cycle life, as a key indicator of battery performance, directly relates to battery lifespan and economic efficiency, and has a crucial impact on its performance in various application scenarios. With the rise of the energy storage industry, the requirements for lithium battery performance are becoming increasingly stringent, especially the demand for long-life lithium batteries.
[0003] However, existing lithium batteries have the following problems when in use: During the use of lithium batteries, the solid electrolyte interphase (SEI) membrane is damaged and repaired with each charge and discharge cycle. This process leads to the continuous loss of active lithium, which is a major cause of lithium battery capacity decay. Coating the separator with lithium-rich compounds can effectively compensate for the loss of active lithium during battery cycling. However, lithium ferrite (LFO) has a high specific capacity but poor stability and is prone to decomposition and gas generation during cycling and high-temperature storage. Lithium nickel oxide (LNO) has a high lithium release voltage window and is less prone to gas generation during cycling and high-temperature storage, but its specific capacity is relatively low.
[0004] This invention uses a 3:7 ratio of LFO to LNO separator for lithium replenishment, combined with a specific high-temperature and high-pressure formation process, to stably replenish the lithium source, optimize lithium-ion intercalation efficiency, and guide the battery to complete gas generation and discharge of residual gas, avoiding potential problems such as electrode black spots and lithium plating, so that the battery can maintain 100% capacity after 1000 cycles, balancing cycle stability and safety. Summary of the Invention
[0005] The present invention aims to solve the technical problems mentioned in the background art and provide a membrane-replenished lithium-layer pouch cell with high cycle stability and its preparation method.
[0006] To achieve the above objectives, the present invention provides the following technical solution: a high-cycle-stability membrane-replenished lithium-layer pouch cell and its preparation method, comprising the following steps: Step 1: Mix LFO and LNO in a certain ratio and coat them onto the membrane to a thickness of 10 micrometers; Step 2: Stack the prepared positive and negative electrode sheets with the separator to form a dry cell, and then inject electrolyte. Step 3: After electrolyte injection, the battery is placed at 45℃ for 24 hours for formation. The formation process uses high temperature and high pressure, and the specific implementation steps are as follows: A. Let it sit for 5 minutes; B. Charge at a constant current of 0.1C for 120 minutes, with a voltage limit of 3.2V, and then let it rest for 5 minutes; C. Charge at a constant current of 0.3C for 180 minutes, with a voltage limit of 3.55V; D. Charge at a constant current and constant voltage of 0.2C for 60 minutes until the voltage reaches 3.55V, with the current limited to 0.05C, and let it rest for 5 minutes; E. Charge at a constant current of 0.05C for 180 minutes, with a limiting voltage of 4.05V, and let stand for 5 minutes; F. Charge at a constant current of 0.02C for 30 minutes, with a voltage limit of 4.05V, and let stand for 5 minutes; G. Charge at a constant current of 0.01C for 30 minutes, with a voltage limit of 4.05V, and let stand for 5 minutes; H, 0.5C constant current discharge for 180 minutes, limiting voltage is 2.0V, and then rest for 5 minutes; 1. Charge at a constant current of 0.5C for 180 minutes, with a voltage limit of 3.65V, and let stand for 5 minutes; J, constant current discharge at 0.2C for 40 minutes, limiting voltage at 3.2V, then rest for 5 minutes; K, 0.2C constant current charging for 40 minutes, with a limiting voltage of 3.65V, followed by resting for 5 minutes; L. Repeat the JK process steps 3 times; Discharge at constant current of 0.5C for 72 minutes, with a limiting voltage of 2.9V, then stop.
[0007] Step 4: After formation, vent the battery and leave it at 45°C for 24 hours; Step 5: After being placed at high temperature, the battery undergoes a second venting, sealing, and capacity testing, completing the battery preparation process.
[0008] A further preferred embodiment: In step one, LFO and LNO are mixed in a ratio of 3:7 and coated onto the membrane to a thickness of 10 micrometers.
[0009] A further preferred option: In step two, the stacking is an assembly method in which the separator, positive electrode, and negative electrode are stacked alternately in sequence.
[0010] Further preferred option: In step three, all resting steps are carried out in a formation environment with a formation temperature of 45°C and a formation pressure of 0.7MPa.
[0011] Further preferred options: In steps four and five, the venting operation is a conventional pre-packaging process for removing residual gas inside the battery. Beneficial effects
[0012] 1. By setting up a lithium replenishment membrane and coating the membrane with a 3:7 ratio of LFO and LNO lithium replenishment materials, combined with a specific high-temperature and high-pressure formation process and JK cycle step, compared with Comparative Example 1, the lithium replenishment membrane effectively improves the battery cycle stability, with a capacity retention rate of 100% after 1000 cycles, far exceeding the 92.56% of Comparative Example 1. At the same time, the lithium replenishment material ratio has good compatibility with the formation process. After formation, the fully charged negative electrode has no black spots or lithium plating, and the interface state is excellent. In Example 2, after changing the mixing ratio, and in Example 3, after deleting key formation steps, interface defects appeared and the cycle performance decreased. This further confirms that the reasonable ratio of lithium replenishment materials and the synergistic effect of the complete formation process can accurately improve the negative electrode interface state and significantly extend the battery cycle life. 2. By setting different formation programs and combining gradient current charging and discharging with multi-stage resting, the reaction rhythm of lithium replenishment materials is matched. First, the battery is pretreated at 45℃ and 0.7MPa to gradually stimulate film formation with a small current, forming a good SEI film and reducing film impedance. In the intermediate stage, the voltage threshold is precisely controlled by constant current and constant voltage charging, and multiple resting stages are used to activate the lithium replenishment components and replenish the active lithium lost due to film formation. The key step is to add the JK cycle, which further promotes battery gas production through low-rate charging and discharging, eliminating potential lithium plating and black spot hazards. Comparative experiments show that the absence of this cycle or adjustment of parameters will cause interface defects, while the optimized formation program can enable the battery to complete the gas production cycle while ensuring that the electrode has no safety hazards, laying the foundation for improving cycle stability. 3. In summary, this type of high-cycle-stability membrane-replenished lithium-coated pouch battery and its preparation method, through setting membrane lithium replenishment and designing different formation processes, precisely matches the battery system requirements by adopting a 3:7 LFO and LNO mixed coating scheme for membrane lithium replenishment, providing a stable lithium source for the negative electrode and improving lithium-ion intercalation efficiency from the source. In terms of formation process design, based on a high-temperature and high-pressure environment of 45℃ and 0.7MPa, through gradient current charge and discharge, multi-stage rest, and the key JK step cycle, it effectively guides the battery to complete the gas generation cycle, completely expelling internal residual gas, and avoiding safety hazards such as black spots in the electrode gas channels and lithium plating. The synergistic effect of the two core technologies enables the battery to exhibit excellent performance: the capacity retention rate reaches 100% after 1000 cycles, far exceeding that of conventional batteries without pre-lithiation, while the negative electrode interface remains stable, balancing the battery's cycle stability, safety, and production adaptability. It provides a reliable preparation solution for high-end lithium battery products, especially suitable for application scenarios with stringent requirements for lifespan and safety. Attached Figure Description
[0013] Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation
[0014] The following will refer to the appendices in the embodiments of the present invention. Figure 1 The technical solutions in the embodiments of the present invention will be clearly and completely described.
[0015] Please see Figure 1 In this embodiment of the invention, a high-cycle-stability membrane-replenished lithium-ion stacked pouch cell and its preparation method include the following steps: Step 1: Mix LFO and LNO in a certain ratio and coat them onto the membrane to a thickness of 10 micrometers; Step 2: Stack the prepared positive and negative electrode sheets with the separator to form a dry cell, and then inject electrolyte. Step 3: After electrolyte injection, the battery is placed at 45℃ for 24 hours for formation. The formation process uses high temperature and high pressure, and the specific implementation steps are as follows: A. Let it sit for 5 minutes; B. Charge at a constant current of 0.1C for 120 minutes, with a voltage limit of 3.2V, and then let it rest for 5 minutes; C. Charge at a constant current of 0.3C for 180 minutes, with a voltage limit of 3.55V; D. Charge at a constant current and constant voltage of 0.2C for 60 minutes until the voltage reaches 3.55V, with the current limited to 0.05C, and let it rest for 5 minutes; E. Charge at a constant current of 0.05C for 180 minutes, with a limiting voltage of 4.05V, and let stand for 5 minutes; F. Charge at a constant current of 0.02C for 30 minutes, with a voltage limit of 4.05V, and let stand for 5 minutes; G. Charge at a constant current of 0.01C for 30 minutes, with a voltage limit of 4.05V, and let stand for 5 minutes; H, 0.5C constant current discharge for 180 minutes, limiting voltage is 2.0V, and then rest for 5 minutes; 1. Charge at a constant current of 0.5C for 180 minutes, with a voltage limit of 3.65V, and let stand for 5 minutes; J, constant current discharge at 0.2C for 40 minutes, limiting voltage at 3.2V, then rest for 5 minutes; K, 0.2C constant current charging for 40 minutes, with a limiting voltage of 3.65V, followed by resting for 5 minutes; L. Repeat the JK process steps 3 times; Discharge at constant current of 0.5C for 72 minutes, with a limiting voltage of 2.9V, then stop.
[0016] Step 4: After formation, vent the battery and leave it at 45°C for 24 hours; Step 5: After being placed at high temperature, the battery undergoes a second venting, sealing, and capacity testing, completing the battery preparation process.
[0017] In step one, LFO and LNO are mixed in a 3:7 ratio and coated onto a 10-micron thick separator. In step two, the stacking is an assembly method in which the separator, positive electrode, and negative electrode are stacked alternately in sequence. In step three, all resting steps are carried out in a formation environment with a formation temperature of 45°C and a formation pressure of 0.7 MPa. In steps four and five, the venting operation is a conventional pre-packaging process for removing residual gases inside the battery. Example
[0018] Based on the embodiments of the present invention, the mixing ratio of LFO and LNO is changed from 3:7 to 5:5; the remaining steps are the same as those of the present invention. Example
[0019] Based on the embodiments of the present invention, the formation process is modified as follows, while the remaining steps are the same as those of the present invention: A. Let it sit for 5 minutes; B. Charge at a constant current of 0.1C for 120 minutes, with a voltage limit of 3.2V, and then let it rest for 5 minutes; C. Charge at a constant current of 0.3C for 180 minutes, with a voltage limit of 3.55V; D. Charge at a constant current and constant voltage of 0.2C for 60 minutes until the voltage reaches 3.55V, with the current limited to 0.05C, and let it rest for 5 minutes; E. Charge at a constant current of 0.05C for 180 minutes, with a limiting voltage of 4.05V, and let stand for 5 minutes; F. Charge at a constant current of 0.02C for 30 minutes, with a limiting voltage of 4.05V, and let stand for 5 minutes; G. Charge at a constant current of 0.01C for 30 minutes, with a limiting voltage of 4.05V, and let stand for 5 minutes; H, 0.5C constant current discharge for 180 minutes, limiting voltage is 2.0V, rest for 5 minutes; 1. Charge at a constant current of 0.5C for 180 minutes, with a limiting voltage of 3.65V, and let stand for 5 minutes; J, constant current discharge at 0.2C for 40 minutes, limiting voltage at 3.2V, then rest for 5 minutes; K, 0.2C constant current charging for 40 minutes, with a limiting voltage of 3.65V, followed by resting for 5 minutes; Discharge at 0.5C for 72 minutes with a constant current of L and a limiting voltage of 2.9V, then stop.
[0020] Comparative Example 1 Step 1: Use a conventional separator without pre-lithiation; Step 2: Stack the prepared positive and negative electrode sheets with the separator to form a dry cell, and then inject electrolyte. Step 3: After electrolyte injection, the battery is placed at 45℃ for 24 hours for formation. The formation process uses high temperature and high pressure, with a formation temperature of 45℃ and a formation pressure of 0.7MPa. The specific implementation steps are as follows: A. Let it sit for 5 minutes; B. Charge at a constant current of 0.1C for 120 minutes, with a voltage limit of 3.2V, and then let it rest for 5 minutes; C. Charge at a constant current of 0.3C for 180 minutes, with a voltage limit of 3.55V; D. Charge at a constant current and constant voltage of 0.2C for 60 minutes until the voltage reaches 3.55V, with the current limited to 0.05C, and let it rest for 5 minutes; 1. Charge at a constant current of 0.5C for 180 minutes, with a voltage limit of 3.65V, and let stand for 5 minutes; J, constant current discharge at 0.2C for 40 minutes, limiting voltage at 3.2V, then rest for 5 minutes; K, 0.2C constant current charging for 40 minutes, with a limiting voltage of 3.65V, followed by resting for 5 minutes; Discharge at constant current of 0.5C for 72 minutes, with a limiting voltage of 2.9V, then stop.
[0021] Step 4: After formation, vent the battery and leave it at 45°C for 24 hours; Step 5: After being placed at high temperature, the battery undergoes a second venting, sealing, and capacity testing, completing the battery preparation process.
[0022] The formation time, fully charged negative electrode interface state, and cycle performance of the batteries manufactured in the above embodiments and comparative examples are recorded in the table below. Transform into time State of the fully charged negative electrode interface after formation Cyclic performance (compared to initial capacity retention %) This invention 13h No black spots, lithium plating 1000 laps (100%) Example 2 13h Black spots and electrode wrinkles 1000 laps (98.19%) Example 3 10.7 Black spots and electrode wrinkles 1000 laps (97.40%) Comparative Example 1 8.5h No black spots, lithium plating 1000 laps (92.56%) As shown in the table, the battery made by this invention has the best cycle performance, with a capacity retention rate of 100% after 1000 cycles and a good negative electrode interface state, exhibiting excellent long-cycle stability, making it suitable for high-end battery products with stringent lifespan requirements; the mixed coating ratio of LFO and LNO3:7 is adapted to the formation process, and no interface defects have appeared. The battery prepared in Example 2 had a compatibility problem with the 5:5 mixing ratio of LFO and LNO. Although the formation time was the same as that of Comparative Example 1, black spots and electrode wrinkles appeared on the negative electrode after formation. The interface defects caused the cycle performance to drop to 98.19%. This mixing ratio is not suitable for the separator modification of this battery system. The battery prepared in Example 3 had a formation time shortened to 10.7h after the J~K steps were removed. However, black spots and electrode wrinkles appeared at the negative electrode interface, and the cycle performance further decreased to 97.40%. This indicates that the J~K step cycle operation plays a key role in optimizing the negative electrode interface and improving cycle stability. Its absence will lead to interface defects and performance degradation. This mixing ratio is not suitable for the separator modification of this battery system. While the battery made in Comparative Example 1 had the shortest formation time of only 8.5 hours and a production efficiency significantly higher than the three comparative examples, and the negative electrode interface was in good condition after formation with no black spots or lithium plating problems, its cycle performance was low at only 92.56%, making it unsuitable for applications with high requirements for lithium battery life. The battery produced by this invention has good cycle performance and a good negative electrode interface, making it suitable for scenarios with extreme requirements for long cycle life. Examples 2 and 3 have interface defects or performance shortcomings and have no obvious application advantages. Their process parameters, mixing ratios, and formation steps are not recommended to be used directly, but can be used as reference benchmarks for optimization experiments, such as adjusting the LFO to LNO ratio and retaining key formation steps to balance efficiency and performance. Comparative Example 1 has poor cycle performance and is not suitable for occasions with high requirements for lithium battery life.
[0023] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.
Claims
1. A high-cycle-stability membrane-replenished lithium-layer pouch cell and its preparation method, characterized in that: Includes the following steps: Step 1: Mix LFO and LNO in a certain ratio and coat them onto the membrane to a thickness of 10 micrometers; Step 2: Stack the prepared positive and negative electrode sheets with the separator to form a dry cell, and then inject electrolyte. Step 3: After electrolyte injection, the battery is placed at 45℃ for 24 hours for formation. The formation process uses high temperature and high pressure, and the specific implementation steps are as follows: A. Let it sit for 5 minutes; B. Charge at a constant current of 0.1C for 120 minutes, with a voltage limit of 3.2V, and then let it rest for 5 minutes; C. Charge at a constant current of 0.3C for 180 minutes, with a voltage limit of 3.55V; D. Charge at a constant current and constant voltage of 0.2C for 60 minutes until the voltage reaches 3.55V, with the current limited to 0.05C, and let it rest for 5 minutes; E. Charge at a constant current of 0.05C for 180 minutes, with a limiting voltage of 4.05V, and let stand for 5 minutes; F. Charge at a constant current of 0.02C for 30 minutes, with a voltage limit of 4.05V, and let stand for 5 minutes; G. Charge at a constant current of 0.01C for 30 minutes, with a voltage limit of 4.05V, and let stand for 5 minutes; H, 0.5C constant current discharge for 180 minutes, limiting voltage is 2.0V, and then rest for 5 minutes; 1. Charge at a constant current of 0.5C for 180 minutes, with a voltage limit of 3.65V, and let stand for 5 minutes; J, constant current discharge at 0.2C for 40 minutes, limiting voltage at 3.2V, then rest for 5 minutes; K, 0.2C constant current charging for 40 minutes, with a limiting voltage of 3.65V, followed by resting for 5 minutes; L. Repeat the JK process steps 3 times; Discharge at constant current of 0.5C for 72 minutes, with a limiting voltage of 2.9V, then stop.
2. Fourth step: After formation, vent the battery and leave it at 45°C for 24 hours; Step 5: After being placed at high temperature, the battery undergoes a second venting, sealing, and capacity testing, completing the battery preparation process.
3. The high cycle stability membrane-replenished lithium-filled pouch cell and its preparation method according to claim 1, characterized in that: In step one, LFO and LNO are mixed in a ratio of 3:7 and coated onto the membrane to a thickness of 10 micrometers.
4. The high cycle stability membrane-replenished lithium-filled pouch cell and its preparation method according to claim 1, characterized in that: In step two, the stacking is an assembly method in which the separator, positive electrode, and negative electrode are stacked alternately in sequence.
5. The high cycle stability membrane-replenished lithium-filled pouch cell and its preparation method according to claim 1, characterized in that: In step three, all the resting steps were carried out in a formation environment with a formation temperature of 45°C and a formation pressure of 0.7 MPa.
6. The high cycle stability membrane-replenished lithium-filled pouch cell and its preparation method according to claim 1, characterized in that: In steps four and five, the venting operation is a routine pre-packaging process for removing residual gas inside the battery.