Operation maintenance method suitable for lithium metal secondary battery

Abstract

The invention provides an operation maintenance method suitable for a lithium metal secondary battery. The operation maintenance method comprises the following steps: performing charge-discharge maintenance on the lithium metal secondary battery; and the charging and discharging maintenance comprises the following steps: after the lithium metal secondary battery is circularly used every 60 times, carrying out 0.1 C constant-current charging to 4.35 V, standing for 10 minutes, carrying out 1.0 C constant-current discharging with the discharging capacity of 2.5 Ah, and standing for 10 minutes again. The method has the beneficial effects that through targeted charging and discharging maintenance, uncontrollable growth of lithium dendrites in the service process of the lithium metal secondary battery is effectively inhibited, rapid generation of an irreversible SEI film and accumulation of dead lithium are slowed down, and use safety of the battery in the whole life cycle is guaranteed; maintenance operation is periodically executed in the normal use period of the lithium metal battery, the electrode interface state can be actively optimized, invalid consumption of active lithium is reduced, rapid increase of internal resistance of the battery and irreversible expansion of thickness are avoided, the cycle life of the battery is further prolonged, and the capacity retention ratio under the same use period is improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium metal battery safety technology, and in particular relates to an operation and maintenance method suitable for lithium metal secondary batteries. Background Technology

[0002] Lithium metal secondary batteries, as the core technology direction of the next generation of high energy density energy storage systems, can significantly break through the energy density bottleneck compared with traditional graphite anode batteries, and have become a key choice to meet the stringent requirements of electric vehicles, large-scale grid energy storage, high-end portable electronic devices and other scenarios.

[0003] In recent years, the energy density and basic cycle stability of lithium metal rechargeable batteries have been improved synergistically. However, their commercialization is still limited by inherent technical defects during service. On the one hand, lithium metal anodes are prone to uncontrollable growth of lithium dendrites during cycling, which may puncture the separator and cause internal short circuits. At the same time, the solid electrolyte interphase (SEI) film at the electrode interface will continuously consume active lithium and generate "dead lithium" due to repeated rupture and regeneration during charging and discharging, which can easily lead to rapid capacity decay and shorten battery life. On the other hand, some technologies (such as electrolyte additives and anode nanocoatings) can locally suppress lithium dendrites or optimize the SEI film, but they cannot eliminate the dynamic degradation problem during battery service and may even introduce new risks such as additive decomposition and gas generation. Other related technologies (such as the porous conductive monitoring network early warning scheme proposed in CN111710927A) require modification of the internal physical structure of the battery, increasing the complexity and cost of the production process. Moreover, they only focus on "passive early warning intervention" for short circuit risks and cannot actively optimize the electrode interface state to alleviate capacity decay and shortened life.

[0004] In summary, the current lithium metal secondary battery field urgently needs an operation and maintenance method that can solve the above problems. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an operation and maintenance method suitable for lithium metal secondary batteries, particularly suitable for extending the service life of lithium metal secondary batteries.

[0006] The technical solution adopted in this invention is: to provide an operation and maintenance method suitable for lithium metal secondary batteries, comprising the following steps:

[0007] Perform charge-discharge maintenance on the lithium metal secondary battery;

[0008] The charge and discharge maintenance includes charging the lithium metal secondary battery at a constant current of 0.1C to 4.35V after every 60 use cycles, letting it stand for 10 minutes, discharging it at a constant current of 1.0C with a discharge capacity of 2.5Ah, and then letting it stand for another 10 minutes.

[0009] Furthermore, the cycle procedure includes charging the battery at a constant current of 0.33C to 4.35V, letting it stand for 10 minutes, discharging it at a constant current of 0.33C to 3V, and then letting it stand for another 10 minutes.

[0010] Furthermore, the charge and discharge maintenance also includes: after the lithium metal secondary battery has undergone the usage cycle every 20 times, it is charged at a constant voltage of 5V for 5 seconds, left to stand for 10 minutes, and then charged at a constant current of 0.2C until it reaches 4.35V. After being left to stand for another 10 minutes, it is discharged at a constant current of 0.5C with a discharge capacity of 1.5Ah, and then left to stand for another 10 minutes.

[0011] Furthermore, the charge and discharge maintenance also includes: after the lithium metal secondary battery has undergone 60 use cycles, it is charged at 0.5C for 20ms with a pulse parameter of 80% duty cycle to 4.35V, then left to stand for 10 minutes before being discharged at 4.0C for 5ms with a pulse parameter of 40% duty cycle to a discharge capacity of 2.5Ah, and then left to stand for another 10 minutes.

[0012] Furthermore, the charge and discharge maintenance also includes: after the lithium metal secondary battery has undergone 60 use cycles, it is charged at a constant power of 5W to 4.35V, left to stand for 10 minutes, and then discharged at a constant power of 20W with a discharge capacity of 2.5Ah, and left to stand for another 10 minutes.

[0013] The advantages and positive effects of this invention are as follows: By adopting the above-mentioned technical solution and through targeted charge and discharge maintenance, the uncontrollable growth of lithium dendrites during the service of lithium metal secondary batteries is effectively suppressed, the rapid formation of irreversible SEI film and the accumulation of dead lithium are slowed down, and the risk of internal short circuit caused by dendrites piercing the separator is reduced from the root, reducing the probability of safety accidents such as thermal runaway and explosion, and ensuring the safety of the battery throughout its entire life cycle; Periodic maintenance operations during the normal use cycle of the battery can actively optimize the state of the electrode interface, reduce the ineffective consumption of active lithium, avoid rapid growth of battery internal resistance and irreversible expansion of thickness, thereby extending the battery cycle life, improving the capacity retention rate under the same use cycle, and reducing the frequency and cost of frequent battery replacement; The maintenance process adopts a non-invasive design, which does not require modification of the original physical structure and packaging form of lithium metal secondary batteries, and can be directly adapted to existing lithium metal secondary batteries of different shapes (such as pouch, cylindrical, and square); Moreover, the maintenance operation is interspersed in the normal use of the battery, without interrupting the normal charge and discharge function, without the need for additional disassembly or reassembly steps, which greatly reduces maintenance costs and operational complexity, and is suitable for large-scale promotion and application. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the operation and maintenance method of a lithium metal secondary battery according to an embodiment of the present invention. Detailed Implementation

[0015] The present disclosure will now be described more fully with reference to the accompanying drawings, which illustrate exemplary embodiments of the present disclosure. The technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative effort are within the scope of protection of the present disclosure.

[0016] like Figure 1 As shown, the present invention provides an operation and maintenance method suitable for lithium metal secondary batteries, characterized by comprising the following steps:

[0017] S100, Performs charge and discharge maintenance on lithium metal secondary batteries;

[0018] During the service life of a lithium metal rechargeable battery, it is necessary to periodically monitor the battery's usage count to confirm whether it has reached the stage requiring maintenance. Once the battery has reached the required maintenance count, a charge-discharge maintenance method is used for non-destructive maintenance. The monitored usage count refers to one charge-discharge cycle for this type of battery. Whether a lithium metal battery requires maintenance is determined by parameters including whether the battery's usage count meets the corresponding requirements and standards. The maintenance methods employed include pulse charging, pulse discharging, constant current charging, constant current discharging, constant voltage charging, constant voltage discharging, constant power charging, constant power discharging, and combinations of different charging and discharging methods. The charge-discharge maintenance strategy consists of parameters such as the type of charge-discharge during the maintenance phase, the magnitude of the charge-discharge current, the depth of charge / discharge (DOD), and the maintenance cycle. The magnitude of constant current and variable current includes, but is not limited to, 0-50C. The depth of charge / discharge range includes, but is not limited to, 0-500% DOD. The maintenance cycle includes, but is not limited to, 1-5 consecutive maintenance cycles every 5-100 uses.

[0019] S200, charge and discharge maintenance includes charging the lithium metal secondary battery at a constant current of 0.1C to 4.35V after every 60 use cycles, letting it stand for 10 minutes, then discharging it at a constant current of 1.0C with a discharge capacity of 2.5Ah, and letting it stand for another 10 minutes.

[0020] Preferably, the lithium metal secondary battery undergoes a charge-discharge maintenance cycle after 20 cycles. The maintenance procedure is as follows: the battery is charged at a constant current of 0.05C (0.25A) to 4.35V, and then left to stand for 10 minutes. During the discharge process, the battery is discharged at a constant current of 0.5C (2.5A) to a discharge capacity of 1.5Ah, and then left to stand for 10 minutes.

[0021] By employing the above method, a synergistic mechanism of non-invasive dynamic monitoring (multiple parameters such as voltage, internal resistance, and thickness) and customized charge-discharge maintenance (current change combination, DOD regulation, and cycle optimization) achieves three breakthrough advantages: First, enhanced safety performance: actively suppressing dendrite initiation and SEI runaway, significantly reducing the probability of thermal runaway; second, extended lifespan: improving the utilization rate of active lithium, simultaneously alleviating dead lithium accumulation and thickness expansion, and extending the battery's service life; third, significantly optimized economy: eliminating the need for battery disassembly or structural modification, avoiding material loss and high labor costs, reducing operation and maintenance costs, and ensuring compatibility with large-scale power systems (strong applicability to vehicle / energy storage scenarios). This integrated "monitoring-maintenance" strategy provides an efficient and low-cost industrial-grade solution for the safe long-cycle application of lithium metal batteries. Compared with batteries that do not employ any operation and maintenance measures, batteries maintained using this invention show significantly improved capacity retention and significantly extended cycle life at the same number of cycles. The battery operation and maintenance method developed in this invention is simple, low-cost, and does not involve limitations such as industrial production and preparation conditions, making it easy to promote and use on a large scale.

[0022] In one embodiment, the cyclic procedure includes charging the battery at a constant current of 0.33C to 4.35V, letting it rest for 10 minutes, discharging it at a constant current of 0.33C to 3V, and then letting it rest for another 10 minutes.

[0023] In one embodiment, the charge-discharge maintenance further includes: performing a discharge maintenance every 20 cycles of use of the lithium metal secondary battery, charging with a constant voltage of 5V for 5 seconds, letting it stand for 10 minutes, and then charging with a constant current of 0.2C (1.0A) until it reaches 4.35V, letting it stand for 10 minutes again, discharging with a constant current of 0.5C (2.5A) to discharge with a discharge capacity of 1.5Ah, and then letting it stand for 10 minutes again.

[0024] In one embodiment, the charge-discharge maintenance further includes: performing a discharge maintenance after the lithium metal secondary battery has undergone 60 use cycles, charging with a 0.5C (2.5A) charge for 20ms and a duty cycle of 80% pulse parameters until it reaches 4.35V, then letting it rest for 10 minutes, discharging with a 4.0C (20.0A) discharge for 5ms and a duty cycle of 40% pulse parameters until the discharge capacity is 2.5Ah, and then letting it rest for another 10 minutes.

[0025] In one embodiment, the charge-discharge maintenance further includes: performing a discharge maintenance after the lithium metal secondary battery has undergone 60 use cycles, charging with a constant power of 5W to 4.35V, letting it stand for 10 minutes, discharging with a constant power of 20W to discharge with a discharge capacity of 2.5Ah, and then letting it stand for another 10 minutes.

[0026]

[0027] Table 1. Comparison of failure cycle counts of pouch cells in Examples 1-9 and Comparative Examples

[0028] As shown in Table 1, the basic physical properties of the batteries used in the experiment (such as capacity, thickness, internal resistance, open circuit potential, etc.), the test environment (such as ambient temperature, etc.), the equivalent current density during charging and discharging, and the stress on the batteries should be kept consistent. A 5Ah lithium metal secondary battery was used, and the battery cycle regime was as follows: the battery was charged at a constant current of 0.33C (1.65A) to 4.35V, and then allowed to rest for 10 minutes. The discharge process was carried out at a constant current of 0.33C (1.65A) to 3V, and then allowed to rest for 10 minutes.

[0029] The battery in Comparative Example 1 was cycled using the aforementioned cycle regime without charge / discharge maintenance. Table 1 clearly shows that performing maintenance after a certain usage cycle effectively improves battery life. The battery maintained under the maintenance regime in Example 3 cycled 103 times, while the comparative example only cycled 61 times. This demonstrates that the operation and maintenance method proposed in this invention—0.2C charging, 2.0C discharging, 50% depth of discharge, and maintenance every 60 cycles—significantly improves the cycle life of lithium metal secondary batteries. In the constant current maintenance experiments (Examples 1-3), it can be seen that low-rate charging and high-rate discharging allow lithium ions to deposit uniformly on the negative electrode, thereby improving the battery's cycle life.

[0030] The battery maintained under the maintenance procedure in Example 4 can cycle 88 times, while the comparative example only cycles 61 times. This shows that the operation and maintenance method proposed in this invention, which uses constant voltage charging of 5V for 5s before constant current charging (0.2C charging), discharges at 0.5C with a depth of discharge of 70%, and performs maintenance every 20 cycles, can significantly improve the cycle life of lithium metal secondary batteries. In the constant voltage maintenance experiments (Examples 4-6), it can be seen that constant voltage charging before constant current charging can form uniform lithium deposition nucleation sites on the surface of lithium metal negative electrode, thereby improving the macroscopic uniformity of lithium ion deposition on the negative electrode and thus improving the cycle life of the battery. The battery maintained under the maintenance regime of Example 9 can cycle 9 times, while the comparative example only cycles 61 times. This shows that the operation and maintenance method proposed in this invention, which involves charging at 0.5C, 20ms, with a duty cycle of 80%, discharging at 4.0C, 5ms, with a duty cycle of 40%, and a depth of discharge of 50%, with maintenance every 60 cycles, can significantly improve the cycle life of lithium metal secondary batteries. In the pulse charge-discharge maintenance experiments (Examples 7-9), it can be seen that low-rate charging and high-rate discharging can cause lithium ions to be uniformly deposited at the negative electrode, thereby improving the cycle life of the battery. The battery maintained under the maintenance regime of Example 12 can cycle 99 times, while the comparative example only cycles 61 times. This shows that the operation and maintenance method proposed in this invention, which involves charging at 5W, discharging at 60W, with a depth of discharge of 70%, and maintenance every 20 cycles, can significantly improve the cycle life of lithium metal secondary batteries. In the constant power maintenance experiments (Examples 10-12), it can be seen that low-rate charging and high-rate discharging can cause lithium ions to be uniformly deposited at the negative electrode, thereby improving the cycle life of the battery.

[0031] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method for operation and maintenance of lithium metal secondary batteries, characterized in that, Includes the following steps: Perform charge-discharge maintenance on the lithium metal secondary battery; The charge and discharge maintenance includes charging the lithium metal secondary battery at a constant current of 0.1C to 4.35V after every 60 use cycles, letting it stand for 10 minutes, discharging it at a constant current of 1.0C with a discharge capacity of 2.5Ah, and then letting it stand for another 10 minutes.

2. The operation and maintenance method for lithium metal secondary batteries according to claim 1, characterized in that: The cycle procedure includes charging the battery at a constant current of 0.33C until it reaches 4.35V, letting it rest for 10 minutes, then discharging it at a constant current of 0.33C until it reaches 3V, and then letting it rest for another 10 minutes.

3. The operation and maintenance method for lithium metal secondary batteries according to claim 1, characterized in that, The charge and discharge maintenance also includes: after the lithium metal secondary battery has undergone the above-mentioned 20 cycles, it is charged at a constant voltage of 5V for 5 seconds, left to stand for 10 minutes, and then charged at a constant current of 0.2C until it reaches 4.35V. After being left to stand for 10 minutes again, it is discharged at a constant current of 0.5C with a discharge capacity of 1.5Ah, and then left to stand for 10 minutes again.

4. The operation and maintenance method for lithium metal secondary batteries according to claim 1, characterized in that, The charge and discharge maintenance also includes: after the lithium metal secondary battery has undergone 60 use cycles, it is charged at 0.5C for 20ms with a pulse parameter of 80% duty cycle to 4.35V, then left to stand for 10 minutes before being discharged at 4.0C for 5ms with a pulse parameter of 40% duty cycle to a discharge capacity of 2.5Ah, and then left to stand for another 10 minutes.

5. The operation and maintenance method for lithium metal secondary batteries according to claim 1, characterized in that, The charge and discharge maintenance also includes: after the lithium metal secondary battery has undergone 60 cycles of use, it is charged at a constant power of 5W to 4.35V, left to stand for 10 minutes, and then discharged at a constant power of 20W with a discharge capacity of 2.5Ah, and left to stand for another 10 minutes.

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