Lithium metal battery service life prolonging method based on bidirectional pulse charging strategy

Abstract

The invention relates to the technical field of lithium battery charging application, and discloses a lithium metal battery service life prolonging method based on a bidirectional pulse charging strategy. According to the method for prolonging the service life of the lithium metal battery based on the bidirectional pulse charging strategy, the deposition of a lithium metal negative electrode in the charging and discharging process of the battery is more uniform and compact by adjusting the frequency, duty ratio, forward and reverse amplitude and the like of the bidirectional pulse charging current, so that the polarization in the battery is improved, the irreversible capacity of the battery is reduced, and the service life of the battery is prolonged. The bidirectional pulse charging method can effectively improve the lithium dendrite precipitation phenomenon of the negative electrode, reduces the internal impedance and irreversible capacity loss of the battery, can improve the cycling stability and safety of the battery, and prolongs the service life of the lithium metal battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery charging applications, and specifically to a method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy. Background Art

[0002] The technology of new energy vehicles has witnessed a booming development. However, along with it, people are anxious about aspects such as its cruising range and battery safety. However, the energy density of traditional lithium-ion batteries has already approached its theoretical energy density and cannot meet the requirements of practical applications and future development. Therefore, lithium metal batteries have been put back on the research process again. The energy density of lithium metal batteries (LMB) is nearly 10 times higher than that of current lithium-ion batteries (LIB), so it is considered to be one of the potential storage systems in the future. However, lithium metal batteries have certain safety hazards and cannot be used for fast charging applications. Uncontrolled dendrite formation will lead to overheating and battery short circuit, which is one of the key challenges in its development process.

[0003] Regarding the common problems of easy dendrite formation and easy pulverization of lithium metal batteries, methods such as modifying the separator with graphite derivatives, constructing an artificial solid electrolyte interface, and applying mechanical stress are often used. This means will lead to uneven deposition of lithium ions during the charging process of metal batteries, severe internal polarization, and other potential safety risk problems. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] In view of the deficiencies of the prior art, the present invention provides a method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy, which effectively alleviates defects such as uneven deposition of lithium ions, severe internal polarization, and other potential safety risks during the charging process of lithium metal batteries, and solves the above problems.

[0006] (II) Technical Solutions

[0007] To achieve the above object, the present invention provides the following technical solution: A method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy, comprising the following steps:

[0008] S1. Apply a clamping force of 0.8 N / M - 1.5 N / M to the lithium metal battery using a torque wrench;

[0009] S2. Improve the initial performance and cycle stability of the lithium metal battery through constant volume charge and discharge;

[0010] S3. Evaluate the internal impedance of the lithium metal battery in different states, and select the best charging frequency as the frequency of the battery two-way pulse current for charging the lithium metal battery;

[0011] S4. Set the duty cycle of the pulsed current, and calculate the charging time corresponding to the duty cycle and the discharging time corresponding to the duty cycle;

[0012] S5. Set the forward pulsed current amplitude and the reverse pulsed current amplitude for reducing the internal impedance of the lithium metal battery, and calculate the influence coefficient of the current amplitude on the performance of the lithium metal battery;

[0013] S6. Select the characteristic waveform, record the impedance values under different waveforms, and select the pulsed waveform with the minimum internal impedance as the characteristic waveform;

[0014] S7. Conduct a charging experiment in combination with the steps of S1 - S6, and evaluate the performance improvement effect of the lithium metal battery according to the experimental data.

[0015] Preferably, in S2, select a charge - discharge device with a charge - discharge current between 0.2C - 0.5C, and conduct a charge - discharge process for 3 - 5 cycles.

[0016] Preferably, in S3, evaluate the internal impedance of the battery under different states. Conduct an electrochemical impedance spectroscopy test on the lithium metal battery during charging at states of 20%, 40%, 60%, and 80%, and record the minimum internal impedance and the corresponding frequency during charging at each state.

[0017] Preferably, the duty cycle of the pulsed current in S4 is set between 1% - 30%.

[0018] Preferably, the calculation formula for the charging time corresponding to the duty cycle is as follows:

[0019] t charge = D * T

[0020] In the formula, t charge represents the charging time corresponding to the duty cycle, D represents the duty cycle, and T represents the pulse period, that is, the total time of charging and discharging.

[0021] Preferably, the calculation formula for the duty cycle is as follows:

[0022]

[0023] In the formula, D represents the charging time corresponding to the duty cycle, t on represents the pulse - on time, and T represents the pulse period, that is, the total time of charging and discharging.

[0024] Preferably, the calculation formula for the discharging time corresponding to the duty cycle is as follows:

[0025] t discharge =(1 - D) * T

[0026] In the formula, t dischargeIt represents the discharge time corresponding to the duty cycle, D represents the charging time corresponding to the duty cycle, and T represents the pulse period, that is, the total time of charging and discharging.

[0027] Preferably, the forward pulse current amplitude is set between 0.01C and 1.5C, and the reverse pulse current amplitude is set between 0.01C and 1C.

[0028] Preferably, the calculation formula for the influence coefficient of the current amplitude on the performance of the lithium metal battery is as follows:

[0029]

[0030] In the formula, IF represents the influence coefficient of the current amplitude on the battery performance, k represents the magnitude constant for adjusting the influence coefficient, which is obtained by fitting experimental data, I represents the actual charging current applied to the lithium metal battery, and I nom represents the rated charging current of the lithium metal battery, and I threshold represents the maximum current amplitude that the lithium metal battery can withstand, and e represents the natural constant, which is 2.71828.

[0031] Preferably, the pulse waveform includes single-phase full-wave, three-phase full-wave, six-phase full-wave, and six-phase double reverse star.

[0032] Compared with the prior art, the present invention provides a method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy, having the following beneficial effects:

[0033] The present invention proposes to charge the lithium metal battery by using a two-way pulse method instead of the conventional constant current charging method. The pulse frequency is clear and can be directly applied to the charging of conventional batteries. The charging process is simple and easy to control, and is easy to implement. According to experiments, in the process of forward current charging, there will inevitably be an uneven distribution of current density. More lithium metal is deposited in the area with a large current density at the negative extreme, so it will bulge. The bulged part further makes the current concentrated here, making the metal coating here further thickened, forming a vicious cycle. Adding a negative current can dissolve the bulged part and play a role in flattening the deposition layer. According to Mas' three laws, appropriate discharging before and during charging can improve the charging acceptance ability. By applying a reverse current during the charging process, it helps to improve the polarization inside the battery, reduce the irreversible capacity of the battery. The two-way pulse charging method can effectively improve the phenomenon of lithium dendrite precipitation on the negative electrode, effectively reduce the internal impedance of the battery and the irreversible capacity loss, and can improve the cycle stability and safety of the battery and extend the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the method steps of the present invention;

[0035] Figure 2 It is the cycle life diagram of a lithium metal battery during conventional constant current charging;

[0036] Figure 3 It is the cycle life diagram of a lithium metal battery using two-way pulse charging;

[0037] Figure 4 It is the microscopic morphology diagram of the negative electrode after charge and discharge cycles of a lithium metal battery using the conventional constant current charging method;

[0038] Figure 5 It is the microscopic morphology diagram of the negative electrode after charge and discharge cycles of a lithium metal battery using the two-way pulse charging method. Specific embodiments

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] In view of the problems that the existing methods will cause uneven deposition of lithium ions, serious internal polarization and other potential safety risks during the charging process of metal batteries, a method for improving the service life of lithium metal batteries based on a two-way pulse charging strategy is proposed. Please refer to Figure 1 This method includes the following steps:

[0041] S1. Apply a clamping force of 0.8 N / M - 1.5 N / M to the lithium metal battery using a torque wrench;

[0042] During the assembly and testing of lithium metal batteries, it is crucial to apply an appropriate clamping force to ensure the stability of the internal structure of the battery and the optimization of electrochemical performance. Applying a clamping force of 0.8 N / M - 1.5 N / M to the lithium metal battery using a torque wrench can effectively control the fastening degree between battery components, thereby promoting good contact between the battery active material and the current collector. This process not only reduces the contact resistance, improves the energy conversion efficiency, but also prevents the dendritic growth of lithium metal during charging to a certain extent, reducing the short-circuit risk. In addition, the applied clamping force can maintain the sealing of the battery case during the assembly process, helping to prevent electrolyte leakage and the intrusion of external pollutants, thereby ensuring the long-term stable operation of the battery under extreme temperature and high load conditions;

[0043] S2. Improve the initial performance and cycle stability of the lithium metal battery through constant volume charge and discharge;

[0044] To improve the initial performance and cycling stability of lithium-metal batteries, the method of constant-volume charge and discharge is an effective technical means. In this process, first, a suitable charge and discharge device is selected to ensure that the charge and discharge current remains within the set range, usually performing charge and discharge operations between 0.5C and 1C of the maximum rated capacity of the battery. This selection not only ensures fast and safe charging but also avoids thermal runaway or lithium dendrite formation caused by over-fast charging;

[0045] During the charge and discharge process, using the constant-volume operation mode can effectively control the voltage of the battery during the charging and discharging stages, ensure the full utilization of the battery's active materials, and thus improve the energy conversion efficiency. Specifically, during charging, through the constant-volume charging strategy, the current automatically adjusts with the change of the battery voltage, ensuring that the voltage of the battery rises slowly when it is close to full charge and always remains within a safe range. Similarly, during the discharge stage, the constant-volume discharge method is adopted to keep the discharge current at a stable level, thus achieving the effect of uniform discharge;

[0046] Through this series of constant-volume charge and discharge cycles, not only the initial electrochemical performance of the lithium-metal battery is significantly improved, the energy density and power output are enhanced, but also the uniform distribution of lithium ions inside the battery is promoted, and the non-uniformity of lithium metal deposition is reduced, thereby improving the cycling stability of the battery. This evidence-based method not only plays an important role in the research and development stage of the battery but also lays a solid foundation for subsequent commercial applications;

[0047] S3. Evaluate the internal impedance of the lithium-metal battery in different states and select the best charging frequency to set the frequency of the bidirectional pulse current of the battery for charging the lithium-metal battery;

[0048] When studying the charging performance of lithium-metal batteries, evaluating their internal impedance in different charging states is an important part of optimizing the charging strategy. For this reason, we will conduct systematic electrochemical impedance spectroscopy (EIS) tests and conduct in-depth analysis when the battery is charged to 20%, 40%, 60%, and 80% states respectively. This method can accurately evaluate the electrochemical behavior and its internal impedance characteristics of the battery at different charging levels;

[0049] During the experiment, use a high-precision electrochemical workstation to apply a small-amplitude alternating voltage perturbation and record the battery's response to different frequencies at the same time. The frequency range is from millihertz (mHz) to several kilohertz (kHz) to obtain rich frequency response data. This process will be able to identify the contributions of different components inside the battery (such as electrolytes, electrode materials, and their interfaces) to the conversion of electrical energy and determine key parameters such as charge transfer impedance, double-layer capacitance, and ion diffusion impedance;

[0050] Specifically, at each state of charge, we will focus on the lowest internal impedance value and its corresponding frequency. This data will help us find the optimal charging frequency for the battery in a specific state and optimize the charging settings of the bidirectional pulsed current based on these frequencies. By selecting the frequency with the lowest internal impedance at a specific state of charge for pulsed charging, the charging efficiency of the lithium metal battery can be significantly improved, energy loss can be reduced, and the risk of lithium dendrite formation can be minimized, thus effectively extending the battery's cycle life and operational safety;

[0051] S4. Set the duty cycle of the pulsed current and calculate the charging time corresponding to the duty cycle and the discharging time corresponding to the duty cycle;

[0052] In the charge and discharge management of lithium metal batteries, setting the duty cycle of the pulsed current is one of the important technical means to optimize battery performance. The duty cycle refers to the proportion of time that the pulsed signal is at a high level within one cycle, usually expressed as a percentage. By reasonably adjusting the duty cycle, the charging and discharging times of the battery can be effectively controlled, thereby improving the energy conversion efficiency and reducing heat generation;

[0053] In this experiment, we set the duty cycle of the pulsed current between 1% and 30%. For example, if we choose a cycle time of 1000 milliseconds (ms), then at a 1% duty cycle, the high-level duration is 10 ms, and at a 30% duty cycle, the high-level duration is 300 ms. This setting allows the battery to maintain an appropriate current intensity during charging and discharging, while avoiding thermal runaway and lithium dendrite formation caused by excessive current;

[0054] The formula for calculating the charging time corresponding to the duty cycle is as follows:

[0055] t charge = D * T

[0056] The calculation of this value helps to control the intensity of the current during charging, reduce heat accumulation caused by high current, lower the battery temperature, and prevent thermal runaway. In the formula, t charge represents the charging time corresponding to the duty cycle, D represents the duty cycle, and T represents the pulse period, that is, the total time of charging and discharging. By reasonably setting the duty cycle, the effective utilization of the current during charging can be ensured, overcharging or over-discharging can be avoided, and thus the charging efficiency of the battery can be improved;

[0057] The formula for calculating the discharging time corresponding to the duty cycle is as follows:

[0058] t discharge = (1 - D) * T

[0059] By reasonably setting the discharging time, the battery can maintain a stable current output during discharging, improving the discharging performance and energy release efficiency of the battery. In the formula, tdischarge Indicates the discharge time corresponding to the duty cycle, D indicates the charging time corresponding to the duty cycle, and T indicates the pulse period, that is, the total time of charging and discharging. A reasonable discharge time can reduce the voltage fluctuation of the battery during discharge, thereby reducing the aging rate of the battery and extending its service life;

[0060] S5. Set the forward pulse current amplitude and the reverse pulse current amplitude to reduce the internal impedance of the lithium metal battery and calculate the influence coefficient of the current amplitude on the performance of the lithium metal battery;

[0061] During the charge and discharge optimization of the lithium metal battery, the strategy of setting the forward pulse current amplitude and the reverse pulse current amplitude is crucial for reducing the internal impedance and improving the battery performance. Specifically, we set the forward pulse current amplitude between 0.01C and 1.0C, and the reverse pulse current amplitude between 0.01C and 5C. This design aims to effectively promote the rapid migration of lithium ions through alternating forward and reverse pulse currents, reduce the internal resistance of the battery, and thus improve the overall efficiency of the battery;

[0062] Among them, the calculation formula for the influence coefficient of the current amplitude on the performance of the lithium metal battery is as follows:

[0063]

[0064] Calculating the influence coefficient of the current amplitude on the battery performance can quantify the influence of different current intensities on key performance indicators such as the charge and discharge efficiency and capacity retention rate of the battery, providing data support for optimizing the charging strategy. In the formula, IF represents the influence coefficient of the current amplitude on the battery performance, k represents the magnitude constant for adjusting the influence coefficient, which is obtained by fitting experimental data, I represents the actual charging current applied to the lithium metal battery, I nom represents the rated charging current of the lithium metal battery, I threshold represents the maximum current amplitude that the lithium metal battery can withstand, and e represents the natural constant, which is 2.71828. By analyzing the influence of the current amplitude, a reasonable charging and discharging strategy can be formulated to ensure that the battery can obtain the best performance under different working conditions;

[0065] S6. Select the characteristic waveform, record the impedance values under different waveforms, and select the pulse waveform with the minimum internal impedance as the characteristic waveform;

[0066] In the design and optimization process of the lithium metal battery, selecting the appropriate pulse waveform is a key step in reducing the internal impedance and improving the battery performance. For this reason, we will conduct a systematic test on a variety of pulse waveforms and record the impedance values under each waveform to determine the optimal characteristic waveform. Specifically, the experiment will consider the following several pulse waveforms, including single-phase full-wave, three-phase full-wave, three-phase full-wave, six-phase full-wave, and six-phase double reverse star;

[0067] Each pulse waveform has different current characteristics. Therefore, various pulse signals need to be generated by an electrochemical workstation or a signal generator. Single-phase full-wave pulses may be suitable for simple applications, while three-phase full-wave and double-star pulses can achieve higher current output and better energy efficiency.

[0068] Under different pulse waveforms, we will use electrochemical impedance spectroscopy (EIS) technology for real-time impedance measurement. The test will cover a wide frequency range, usually from a few hertz to several kilohertz, to capture the battery's response at various frequencies. In addition, by adjusting waveform parameters such as frequency and duty cycle, further analyze their impact on the internal impedance of the battery, record the internal impedance values after each waveform is applied, and select the pulse waveform with the minimum internal impedance among all test waveforms as the characteristic waveform. This waveform selection can not only optimize the battery charging efficiency but also improve the performance of the entire battery system.

[0069] S7. Combine the steps of S1 - S6 to conduct a charging experiment and evaluate the performance improvement effect of the lithium metal battery based on the experimental data.

[0070] Example 1:

[0071] In this example, a 1Ah ternary lithium metal battery is used, and a soft-pack battery test fixture is used to apply a clamping force of 1.2 N / M. The battery is formed and fixed in volume with a charge-discharge strategy of "constant current charging at 0.2C to 4.3V → constant voltage charging to the cut-off current of 0.02C → standby for 0.5h → discharge at 0.2C → standby for 0.5h".

[0072] After the above battery is fixed in volume, a cycle performance test is carried out with a charge-discharge strategy of "constant current charging at 0.5C to 4.3V voltage → constant voltage charging to the cut-off current of 0.02C → standby for 0.5h → discharge at 1C → standby for 0.5h". The test termination condition is 70% capacity retention rate.

[0073] As attached Figure 2 shown, it is the cycle performance graph of the lithium metal battery under the constant current charging method. With 70% retention rate as the cut-off for battery scrapping, this battery has cycled more than 190 times, and the Coulomb efficiency has remained at about 98%.

[0074] From the discharge capacity in the graph, it can be seen that when the battery is cycled to more than 110 times, the discharge capacity starts to decrease rapidly, the polarization inside the battery starts to increase, and the reversible capacity decreases.

[0075] As attached Figure 4As shown in the figure, when disassembling the above battery and observing the microscopic morphology of its negative electrode through an electron microscope, it is found that after cycling, the lithium metal on the negative electrode shows irregular granulation, and the generation of dendrites can be clearly observed. Such uneven deposition leads to a large-rate decrease in the capacity of the battery at the end of the cycle. The lithium dendrites generated are more likely to pierce through the separator, causing an internal short circuit of the battery and thus triggering a safety accident;

[0076] Example 2:

[0077] In this example, a 1Ah ternary lithium metal battery is used, and a soft-pack battery test fixture is used to apply a clamping force of 1.2 N / M to it. The battery is formed and its capacity is determined using a charge-discharge strategy of "constant current charging at 0.2C to 4.3V → constant voltage charging to the cut-off current of 0.02C → standby for 0.5h → discharge at 0.2C → standby for 0.5h";

[0078] After the above battery is formed and its capacity is determined, the internal resistance of the battery at different frequencies is tested by electrochemical impedance spectroscopy at the 20% Soc state of the battery. The frequency with the smallest internal resistance is selected as the characteristic frequency of the battery for this Soc segment, which is 200 Hz, the duty cycle is 8%, the forward current is 1 A, the reverse current is 1.5 A, and its pulse waveform is a sine full wave;

[0079] At the 40% Soc state of the battery, the internal resistance of the battery at different frequencies is tested by electrochemical impedance spectroscopy. The frequency with the smallest internal resistance is selected as the characteristic frequency of the battery for this Soc segment, which is 800 Hz, the duty cycle is 14%, the forward current is 1 A, the reverse current is 1.5 A, and its pulse waveform is a sine full wave;

[0080] At the 60% Soc state of the battery, the internal resistance of the battery at different frequencies is tested by electrochemical impedance spectroscopy. The frequency with the smallest internal resistance is selected as the characteristic frequency of the battery for this Soc segment, which is 1400 Hz, the duty cycle is 24%, the forward current is 1 A, the reverse current is 1.5 A, and its pulse waveform is a sine full wave;

[0081] At the 80% Soc state of the battery, the internal resistance of the battery at different frequencies is tested by electrochemical impedance spectroscopy. The frequency with the smallest internal resistance is selected as the characteristic frequency of the battery for this Soc segment, which is 2000 Hz, the duty cycle is 28%, the forward current is 0.5 A, the reverse current is 0.8 A, and its pulse waveform is a sine full wave;

[0082] As attached Figure 3 The lithium metal battery using two-way pulse charging has a cycle life exceeding 300 cycles. Compared with the lithium metal battery using the conventional constant current charging method in Example 1, its cycle life is increased by 50%, and a high Coulomb efficiency is maintained throughout the period. There is no serious internal polarization of the battery at the end of the cycle, and the dischargeable capacity does not decrease at a large rate;

[0083] As attached Figure 5As shown, by disassembling the above battery and observing the microscopic morphology of its negative electrode through an electron microscope, it is found that for the battery undergoing cyclic testing using the bidirectional pulse charging method, the lithium metal negative electrode has a uniform texture, no granulation phenomenon occurs, and no dendrites are generated. In contrast, for the lithium metal battery in Example 1 using the conventional constant current charging method, negative electrode granulation and dendrite generation occur. The bidirectional pulse current charging can effectively improve the lithium ion deposition situation during the charging process of the lithium metal battery, effectively avoid the generation of lithium dendrites, and improve the internal polarization of the battery, thereby extending the cycle life of the lithium metal battery.

[0084] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy, characterized in that, It includes the following steps: S1. Apply a clamping force of 0.8 N / M - 1.5 N / M to the lithium metal battery using a torque wrench; S2. Improve the initial performance and cycle stability of the lithium metal battery through constant-volume charge and discharge; S3. Evaluate the internal impedance of the lithium metal battery in different states, select the best charging frequency, and set it as the frequency of the bidirectional pulse current for charging the lithium metal battery; S4. Set the duty cycle of the pulse current, and calculate the charging time corresponding to the duty cycle and the discharging time corresponding to the duty cycle; S5. Set the amplitude of the forward pulse current and the amplitude of the reverse pulse current to reduce the internal impedance of the lithium metal battery, and calculate the influence coefficient of the current amplitude on the performance of the lithium metal battery; S6. Select characteristic waveforms, record the impedance values under different waveforms, and select the pulse waveform with the minimum internal impedance as the characteristic waveform; S7. Combine the steps of S1 - S6 to conduct a charging experiment, and evaluate the performance improvement effect of the lithium metal battery according to the experimental data.

2. A method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy according to claim 1, characterized in that: In S2, select a charge and discharge device with a charge and discharge current between 0.2C and 0.5C, and conduct a charge and discharge process for 3 - 5 cycles.

3. A method for improving the service life of a lithium metal battery based on a bidirectional pulse charging strategy according to claim 2, wherein: In S3, evaluate the internal impedance of the battery in different states. Conduct an electrochemical impedance spectroscopy test on the lithium metal battery during charging at 20%, 40%, 60%, and 80% states, and record the minimum internal impedance and the corresponding frequency for each state during charging.

4. A method for improving the service life of a lithium metal battery based on a bidirectional pulse charging strategy according to claim 3, characterized in that: The duty cycle of the pulse current in S4 is set between 1% and 30%.

5. A method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy according to claim 4, characterized in that: The calculation formula for the charging time corresponding to the duty cycle is as follows: t charge = D * T In the formula, t charge represents the charging time corresponding to the duty cycle, D represents the duty cycle, and T represents the pulse period, that is, the total time of charging and discharging.

6. A method for improving the service life of a lithium metal battery based on a bidirectional pulse charging strategy according to claim 5, characterized in that: The calculation formula for the duty cycle is as follows: In the formula, D represents the charging time corresponding to the duty cycle, and t on represents the time when the pulse is turned on, and T represents the pulse period, that is, the total time of charging and discharging.

7. A method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy according to claim 6, characterized in that: The calculation formula for the discharging time corresponding to the duty cycle is as follows: t discharge = (1 - D) * T In the formula, t discharge represents the discharge time corresponding to the duty cycle, D represents the charge time corresponding to the duty cycle, and T represents the pulse period, that is, the total time of charge and discharge.

8. A method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy according to claim 7, characterized in that: The amplitude of the forward pulse current is set between 0.01C and 1.0C, and the amplitude of the reverse pulse current is set between 0.01C and 5C.

9. A method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy according to claim 8, characterized in that: The calculation formula for the influence coefficient of the current amplitude on the performance of the lithium metal battery is as follows: In the formula, IF represents the influence coefficient of the current amplitude on the battery performance, k represents the magnitude constant for adjusting the influence coefficient, which is obtained by fitting experimental data, I represents the actual charging current applied to the lithium metal battery, I nom represents the rated charging current of the lithium metal battery, I treshold represents the maximum current amplitude that the lithium metal battery can withstand, and e represents the natural constant, which is 2.71828.

10. A method for improving the service life of a lithium metal battery based on a two-way pulse charging strategy according to claim 9, characterized in that: The pulse waveforms include single-phase full-wave, three-phase full-wave, six-phase full-wave, and six-phase double reverse star type.

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