Method for improving cycle performance of silicon-based negative electrode lithium ion battery by using pulse current training

Abstract

The application provides a method for improving the cycle performance of a silicon-based negative electrode lithium ion battery by pulse current training, and belongs to the technical field of lithium ion batteries. The method comprises the following steps: performing formation on the assembled silicon-based negative electrode lithium ion battery according to a preset process, so that the battery forms a preliminarily stable interface state; the battery is left to stand for a period of time after the formation is completed; the phase transition characteristic peak potential interval in the lithiation process of the silicon-based negative electrode lithium ion battery is determined according to the electrochemical data of the silicon-based negative electrode lithium ion battery collected in the formation stage in the formation and standing steps; after the silicon-based negative electrode lithium ion battery is adjusted to the vicinity of the phase transition characteristic potential interval in the lithiation process, pulse current training is applied before entering the conventional cycle; the pulse current ratio used in the pulse current training is 1C-5C, so that a mechanical pre-damage structure can be introduced into the silicon-based active layer, thereby reducing the overall apparent stiffness of the electrode system and improving the cycle stability and capacity retention performance of the silicon-based negative electrode lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulsed current training. Background Technology

[0002] A lithium-ion battery is a rechargeable battery, mainly composed of a positive electrode material capable of reversibly inserting and deintercalating lithium ions, a negative electrode material, an electrolyte, a separator, and an outer packaging structure. The positive and negative electrodes are collectively referred to as electrodes, which are typically formed by coating an electrode slurry containing active materials, conductive agents, binders, and solvents onto a metal current collector and then drying it. The dried electrode active layer is usually a porous composite structure; its pores are used to contain the electrolyte and transport lithium ions, while the conductive network formed by the conductive agent and binder is connected to the current collector for electron transport.

[0003] Lithium-ion batteries, due to their high specific energy, long cycle life, and good environmental adaptability, have been widely used in new energy vehicles, energy storage systems, aerospace, and other fields. With the development of electric vehicles and new energy storage technologies, higher demands are being placed on the energy density, cycle life, and charge / discharge performance of power batteries. Existing lithium-ion battery systems are gradually approaching their theoretical limits in terms of energy density, necessitating improvements in materials, structural design, or operating methods to enhance performance.

[0004] Among the key components of lithium-ion batteries, the anode material has a significant impact on battery capacity and cycle stability. Currently, commercially available anode materials are mainly graphite-based carbon materials, which have limited theoretical specific capacity and cannot meet the development requirements of higher energy density batteries. Silicon-based anode materials have a theoretical specific capacity far exceeding that of graphite and have significant potential in improving battery energy density, making them important candidate anode materials for next-generation high-energy-density lithium-ion batteries.

[0005] However, silicon undergoes alloying reactions during lithium insertion and extraction, resulting in significant volume expansion and contraction, with volume changes exceeding 300%. This volume effect generates tensile and shear stresses within the electrode, along with cyclic fluctuations, leading to silicon particle cracking and pulverization, active layer structure degradation, conductive network disruption, and delamination between the active layer and the current collector interface. Furthermore, repeated volume changes cause continuous evolution of the electrode-electrolyte interface, resulting in repeated rupture and thickening of the solid electrolyte interfacial film, thereby reducing battery coulombic efficiency and cycle life. This mechanochemical coupling degradation, caused by electrochemical reactions, volume deformation, and mechanical failure, is a significant factor limiting the practical application of silicon-based anodes.

[0006] To address the aforementioned issues, existing technologies primarily focus on improvements through material modification and electrode structure design. These improvements include methods such as surface coating, porous structures, core-shell structures, nano-processing, or gradient electrode structures to mitigate the volume effect of silicon materials and improve ion and electron transport. However, these methods typically require adjustments to material preparation or electrode manufacturing processes, resulting in complex processes, high production costs, and difficulties in large-scale application.

[0007] In contrast, from the perspective of battery operation and charge / discharge control strategies, actively adjusting the stress evolution and structural state inside the silicon-based anode by rationally designing the current loading method is a technical approach that does not change the material system and is easy to implement in engineering. Therefore, there is an urgent need to propose a pulsed current training method with a clear implementation path that is compatible with existing battery production and testing processes. This method, without altering the silicon-based anode material composition, electrode structure, or manufacturing process, introduces controlled mechanical pre-damage by applying current pulses within the phase transition characteristic potential range after formation, thereby improving the cycle performance of silicon-based anode lithium-ion batteries. Summary of the Invention

[0008] This invention was made to solve the above-mentioned problems, and its purpose is to provide a method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulsed current training.

[0009] This invention provides a method for improving the cycle performance of silicon-based lithium-ion anode batteries using pulsed current training. The method includes: a formation and resting step, in which the assembled silicon-based lithium-ion anode battery is formed according to a preset process to achieve a preliminary stable interface state, and then the battery is rested for a period of time after formation; a pulse potential confirmation step, in which the phase transition characteristic peak potential range during lithiation is determined based on the electrochemical data of the silicon-based lithium-ion anode battery itself collected during the formation stage of the formation and resting step; and a pulse training loading step, in which the silicon-based lithium-ion anode battery is adjusted to near the lithiation phase transition characteristic potential range, and pulsed current training is applied before entering normal cycling, wherein the pulsed current rate used for pulsed current training is 1C~5C.

[0010] The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulse current training provided by the present invention may also have the following feature: wherein, in the formation and resting steps, formation according to the preset process means cycling at a rate of 0.1C for 2 to 5 cycles for a period of 6 to 24 hours.

[0011] The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training provided by the present invention may also have the following features: wherein the electrochemical data is capacity-voltage data, and the pulse potential confirmation step further includes calculating the dQ / dV curve based on the capacity-voltage data, then determining the phase transition characteristic peak potential during the lithiation process based on the dQ / dV curve, and taking the phase transition characteristic peak potential ±0.05 V as the phase transition characteristic peak potential range.

[0012] The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulse current training provided by the present invention may also have the following feature: wherein the phase transition characteristic peak potential range is 0.2~0.3 V.

[0013] The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulse current training provided by the present invention may also have the following features: in the pulse training loading step, the pulse width used in the pulse current training is 1~5 s, and the number of training rounds is 10~200 rounds.

[0014] The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulse current training provided by the present invention may also have the following feature: wherein, in the pulse training loading step, the pulse form of the pulse current training is a unidirectional pulse or an alternating positive and negative pulse.

[0015] The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulse current training provided by the present invention may also have the following features: wherein the pulse form of the pulse current training is an alternating positive and negative pulse, and no rest time or a short rest time is set between adjacent positive and negative pulses.

[0016] The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulsed current training provided by the present invention may also have the following feature: wherein the pulsed training loading step can reduce the apparent electrode stiffness and subsequent cycle stress level of the silicon-based negative electrode lithium-ion battery through controlled pre-damage.

[0017] The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulse current training provided by the present invention may also include the following feature: a conventional cycling step, in which the silicon-based negative electrode lithium-ion battery after pulse current training is transferred to a preset conventional cycling test, and its performance indicators are tested and evaluated.

[0018] The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries by using pulse current training provided by the present invention may also have the following features: wherein the conventional cycle test is a constant current charge-discharge cycle or a rate cycle, and the performance indicators include cycle capacity, capacity retention rate, median voltage, and dQ / dV curve.

[0019] Compared with existing technologies, the advantages and effects of the method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training in this invention include:

[0020] 1. Phase transition characteristic potential selection mechanism: The phase transition characteristic potential range during the lithiation process of silicon-based anode lithium-ion battery (i.e., the battery to be trained) is determined by the electrochemical data (dQ / dV curve or capacity-voltage curve) obtained during the formation stage. Pulse current loading is applied near this potential range so that the training process corresponds to the stage where the phase transition and stress evolution of silicon-based materials are relatively concentrated.

[0021] 2. High-rate short-pulse loading method: A short-time pulsed current with a higher rate than the conventional cycling rate is applied within the phase transition characteristic potential range. The pulse rate, pulse width, pulse direction, and number of training cycles can be set according to the battery system to create controllable transient stress fluctuations within the electrodes, promoting the early release of local strain energy through limited plastic deformation or interface adjustment. This method helps avoid the continuous accumulation of stress in locally weak areas during conventional constant current cycling and improves the overall stress distribution through microstructural adjustments.

[0022] 3. Mechanical pre-damage introduction mechanism: Through multiple rounds of pulse loading, limited local plastic deformation, microcrack initiation, or interface slip are introduced into the silicon-based active layer to form a diffusely distributed limited pre-damage structure. This controlled pre-damage process can reduce the effective modulus and overall apparent stiffness of the electrode system, thereby reducing the internal stress level caused by the same volume expansion during subsequent long cycles, thus reducing the risk of further particle cracking and structural failure.

[0023] 4. Subsequent Cyclic Stress Reduction Mechanism: Since the electrode has completed a certain degree of structural pre-adjustment during the training phase, the stress peak and stress level caused by the same volume change are reduced during subsequent long cycles. This helps to slow down crack propagation, particle pulverization and interface failure, maintain a relatively stable interface state and reduce cyclic polarization, thereby improving the cycle stability and capacity retention performance of silicon-based anode lithium-ion batteries.

[0024] 5. Engineering Implementation Compatibility: This invention does not require changes to the composition of silicon-based electrode materials, coating process, or battery structure. It can be implemented simply by adjusting the charge and discharge control strategy, making it easy to integrate with existing battery testing processes or battery management systems. Attached Figure Description

[0025] Figure 1 This is the dQ / dV curve of the third cycle in the battery formation stage of Embodiment 1 of the present invention.

[0026] Figure 2 This is a schematic diagram of the pulse current application interval in Embodiment 1 of the present invention.

[0027] Figure 3 This is a schematic diagram of the alternating positive and negative pulse current form of 1C in Embodiments 1 and 2 of the present invention.

[0028] Figure 4 This is a schematic diagram of the 2C alternating positive and negative pulse current form in embodiments 3 and 4 of the present invention.

[0029] Figure 5 The results show the capacity decay comparison of Examples 1-6 of the present invention under 0.1C cycling test.

[0030] Figure 6 The results show the comparison of median voltage changes in Embodiments 1-6 of the present invention under 0.1C cyclic testing.

[0031] Figure 7 This is a graph showing the evolution trend of dQ / dV during the 0.1C cycle test process in Embodiment 4 of the present invention. Detailed Implementation

[0032] This application provides a method for improving the cycle performance of silicon-based lithium-ion batteries using pulsed current training, including:

[0033] (1) Formation and resting steps: The assembled silicon-based negative electrode lithium-ion battery is cyclically cycled at 0.1C for 2 to 5 cycles to form a preliminary stable interface state. After the formation is completed, the battery is rested for 6 to 24 hours.

[0034] (2) Pulse potential confirmation step: dQ / dV curve is calculated based on the capacity-voltage data of the silicon-based negative electrode lithium-ion battery itself collected during the formation and resting steps. Then, the phase transition characteristic peak potential of the silicon-based negative electrode lithium-ion battery during the lithiation process is determined based on the dQ / dV curve, and the phase transition characteristic peak potential ±0.05 V is taken as its phase transition characteristic peak potential range.

[0035] (3) Pulse training loading step: After adjusting the silicon-based negative electrode lithium-ion battery to the characteristic potential range of lithiation phase transition, pulse current training is applied before entering the normal cycle. The pulse current ratio used in the pulse current training is 1C~5C, the pulse width is 1~5s, and the number of training rounds is 10~200 rounds. The pulse form is unidirectional pulse or alternating positive and negative pulse, preferably alternating positive and negative pulse. No rest time is set between adjacent positive and negative pulses or a short rest time is set.

[0036] (4) Routine Cycling Steps: After the pulse current training is completed, the silicon-based negative electrode lithium-ion battery is transferred to the preset routine cycle test, and its performance indicators are tested and evaluated. Among them, the routine cycle test is a routine constant current charge-discharge cycle or rate cycle or other working modes. Performance indicators include cycle capacity, capacity retention rate, median voltage, and dQ / dV curve.

[0037] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the method of improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training.

[0038] Example 1

[0039] This embodiment provides a method for improving the cycle performance of silicon-based lithium-ion batteries using pulsed current training, including:

[0040] (1) Formation and resting steps: The assembled silicon-based negative electrode lithium-ion battery is cyclically cycled at 0.1C for 3 cycles to form a preliminary stable interface state. After the formation is completed, the battery is rested for 12 hours.

[0041] (2) Pulse potential confirmation step: Calculate the dQ / dV curve based on the capacity-voltage data collected during the formation and resting stages. Then, determine the phase transition characteristic peak potential during lithiation based on the dQ / dV curve, and take ±0.05 V of this phase transition characteristic peak potential as its phase transition characteristic peak potential range. In this embodiment, the phase transition characteristic peak potential is 0.25 V during the lithiation stage, and the phase transition characteristic peak potential range is 0.2~0.3 V.

[0042] (3) Pulse training loading step: Adjust the silicon-based negative electrode lithium-ion battery to the phase transition characteristic peak potential range of the lithiation stage (e.g., Figure 2 After (as shown), pulse current training is applied before entering the regular cycle. The pulse current training uses a pulse current multiplier of 1 C, a pulse width of 1 s, and an alternating positive and negative pulse pattern, with no rest time set between adjacent positive and negative pulses (e.g., Figure 3 (As shown); the training rounds were 80. The final result was a silicon-based lithium-ion negative electrode battery after pulse current training.

[0043] Example 2

[0044] This embodiment provides a method for improving the cycle performance of silicon-based lithium-ion anode batteries using pulsed current training. The only difference between this method and Embodiment 1 is the pulsed current training conditions in the pulsed training loading step. The remaining steps are identical and will not be described again here.

[0045] The pulse current training conditions used in this embodiment are as follows: pulse current multiplier is 1 C, pulse width is 1 s, pulse form is alternating positive and negative pulses, and no rest time is set between adjacent positive and negative pulses (e.g., Figure 3 (As shown); the number of training rounds is 160.

[0046] Example 3

[0047] This embodiment provides a method for improving the cycle performance of silicon-based lithium-ion anode batteries using pulsed current training. The only difference between this method and Embodiment 1 is the pulsed current training conditions in the pulsed training loading step. The remaining steps are identical and will not be described again here.

[0048] The pulse current training conditions used in this embodiment are as follows: pulse current multiplier is 2 C, pulse width is 1 s, pulse form is alternating positive and negative pulses, and no rest time is set between adjacent positive and negative pulses (e.g., Figure 4 (As shown); the number of training rounds is 40.

[0049] Example 4

[0050] This embodiment provides a method for improving the cycle performance of silicon-based lithium-ion anode batteries using pulsed current training. The only difference between this method and Embodiment 1 is the pulsed current training conditions in the pulsed training loading step. The remaining steps are identical and will not be described again here.

[0051] The pulse current training conditions used in this embodiment are as follows: pulse current multiplier is 2 C, pulse width is 1 s, pulse form is alternating positive and negative pulses, and no rest time is set between adjacent positive and negative pulses (e.g., Figure 4 (As shown); the number of training rounds is 80.

[0052] Example 5

[0053] This embodiment provides a method for improving the cycle performance of silicon-based lithium-ion anode batteries using pulsed current training. The only difference between this method and Embodiment 1 is the pulsed current training conditions in the pulsed training loading step. The remaining steps are identical and will not be described again here.

[0054] The pulse current training conditions used in this embodiment are as follows: pulse current multiplier is 2 C, pulse width is 1 s, pulse form is alternating positive and negative pulses, and no rest time is set between adjacent positive and negative pulses (e.g., Figure 4 (As shown); the number of training rounds is 160.

[0055] Example 6

[0056] This embodiment is a comparative example, and its processing of the silicon-based negative electrode lithium-ion battery only includes the following steps: formation and resting. The assembled silicon-based negative electrode lithium-ion battery is formed by cycling at a rate of 0.1C for 3 cycles to allow the battery to form a preliminary stable interface state. After formation, the battery is rested for 12 hours. No pulse current training is performed.

[0057] Example 7

[0058] This example serves as a test case, where the silicon-based negative electrode lithium-ion batteries obtained in Examples 1-6 are subjected to constant current charge-discharge cycle performance tests. The test voltage range is 0.05~1 V, and the cycle rate is 0.1C. The pulse current training effect is evaluated through capacity decay curves, median voltage changes, and dQ / dV curves. Specific results are as follows:

[0059] Figure 5 This is a comparison of capacity decay results for Examples 1-6 of the present invention under 0.1C cycling tests. Figure 5 It can be seen that during the 0.1C constant current charge-discharge cycle test, the discharge capacity of Examples 1-5 and Example 6 gradually decreased with the increase of the number of cycles. However, Examples 1-5, after pulse current training, showed better overall capacity retention. Among them, Example 4 exhibited a relatively slow capacity decay during cycling and maintained a relatively high discharge capacity at the same number of cycles, indicating that applying pulse current training at an appropriate rate and number of cycles within the lithiation phase transition characteristic potential range is beneficial to improving the capacity retention performance of the silicon-based anode in subsequent cycles. In contrast, Example 6, without pulse current training, showed a more significant capacity decay, indicating that pulse current training after formation and before conventional cycling can have a beneficial regulatory effect on the structural state of the silicon-based anode before service.

[0060] Figure 6 This is a comparison of the median voltage changes under 0.1C cyclic testing in Examples 1-6 of the present invention. Figure 6 It can be seen that during the 0.1C cycle test, the median voltage of each embodiment changed to some extent with each cycle. Compared with Example 6, which did not undergo pulsed current training, some of the embodiments that underwent pulsed current training showed a smoother trend in median voltage change during the cycle, indicating that pulsed current training helps to slow down polarization growth during the cycle. In particular, Example 4 maintained a relatively high median voltage level during the cycle, indicating that the pulsed current training condition can improve the uniformity of electrode reaction and interface stability to a certain extent, thereby reducing electrochemical polarization in subsequent cycles.

[0061] Figure 7 This is a graph showing the evolution trend of dQ / dV during the 0.1C cycle test in Embodiment 4 of the present invention. Figure 7It can be seen that Example 4 still maintains relatively obvious lithiation and delithiation characteristic peaks during the 0.1C cycle test, indicating that the silicon-based anode after pulsed current training still has reversible electrochemical reaction characteristics during long-term cycling. With increasing cycle number, the characteristic peaks in the dQ / dV curve show a certain degree of peak position shift and peak intensity change. This phenomenon is related to the structural adjustment, polarization evolution, and interface state changes that occur in the silicon-based anode during long-term lithium insertion / delithiation. The characteristic peaks of Example 4 did not disappear abruptly during cycling, indicating that appropriate pulsed current training is beneficial for maintaining the continuity and stability of the silicon-based anode reaction process.

[0062] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving the cycle performance of silicon-based lithium-ion anode batteries using pulsed current training, characterized in that, include: The formation and settling steps involve forming the assembled silicon-based negative electrode lithium-ion battery according to a preset process to make the battery form a preliminary stable interface state. After the formation is completed, the battery is settling for a period of time. The pulse potential confirmation step determines the phase transition characteristic peak potential range during the lithiation process based on the electrochemical data of the silicon-based negative electrode lithium-ion battery itself collected during the formation stage in the formation and resting steps. The pulse training loading step involves adjusting the silicon-based negative electrode lithium-ion battery to the lithium phase transition characteristic potential range and applying pulse current training before entering the normal cycle. The pulse current training uses a pulse current ratio of 1C to 5C.

2. The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training according to claim 1, characterized in that: in, In the formation and settling steps, formation according to the preset procedure means cycling at a 0.1C rate for 2 to 5 times. The time period is 6 to 24 hours.

3. The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training according to claim 1, characterized in that: in, The electrochemical data are capacity-voltage data. The pulse potential confirmation step further includes calculating the dQ / dV curve based on the capacity-voltage data, then determining the phase transition characteristic peak potential during the lithiation process based on the dQ / dV curve, and using the phase transition characteristic peak potential ±0.05 V as the phase transition characteristic peak potential range.

4. The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training according to claim 3, characterized in that: in, The phase transition characteristic peak potential range is 0.2~0.3 V.

5. The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training according to claim 1, characterized in that: in, In the pulse training loading step, the pulse width used in the pulse current training is 1~5 s, and the number of training rounds is 10~200 rounds.

6. The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training according to claim 5, characterized in that: in, In the pulse training loading step, the pulse form of the pulse current training is a unidirectional pulse or an alternating positive and negative pulse.

7. The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training according to claim 6, characterized in that: in, The pulse form of the pulse current training is alternating positive and negative pulses, with no rest time or a short rest time set between adjacent positive and negative pulses.

8. The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training according to any one of claims 1-7, characterized in that: in, The pulse training loading step can reduce the apparent electrode stiffness and subsequent cyclic stress level of silicon-based negative electrode lithium-ion batteries through controlled pre-damage.

9. The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training according to claim 1, characterized in that, Also includes: The routine cycle procedure involves transferring the silicon-based negative electrode lithium-ion battery, after pulse current training, into a preset routine cycle test, and testing and evaluating its performance indicators.

10. The method for improving the cycle performance of silicon-based negative electrode lithium-ion batteries using pulsed current training according to claim 9, characterized in that: in, The conventional cyclic test is a constant current charge-discharge cycle or a rate cycle. The performance indicators include cycle capacity, capacity retention, median voltage, and dQ / dV curve.

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