A mechanical vibration-based lithium ion battery infiltration process optimization method

Abstract

The application provides a lithium ion battery infiltration process optimization method based on mechanical vibration. The application fixes the battery after injection on a vibration platform, applies controlled mechanical vibration, uses the dynamic pressure effect of the periodic acceleration field to drive the electrolyte to overcome the capillary resistance to penetrate the deep layer of the pole piece and remove residual bubbles, determines the wetting state by monitoring the open circuit voltage change rate or the ultrasonic image, and stops after reaching the standard. The application can significantly shorten the infiltration time, greatly improve the uniformity of electrolyte distribution and liquid retention, reduce the internal resistance of the battery and improve the cycle stability. The process has high integration and low energy consumption, effectively solving the technical problems of slow infiltration and dry area residue of high energy density batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, and in particular to an optimization method for lithium-ion battery wetting process based on mechanical vibration. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage systems, lithium-ion batteries, as core energy storage units, have become a key focus of the industry in terms of manufacturing consistency and performance stability. The electrolyte impregnation process is one of the crucial steps in lithium-ion battery production, and its quality directly affects the cell's ion conductivity, impedance characteristics, and cycle life. After electrolyte injection, the electrolyte needs to gradually penetrate into the microporous structure of the electrodes and separator through capillary action to form continuous and stable ion conduction channels.

[0003] However, with the increase in cell energy density and the densification of electrode structure, the natural penetration rate of electrolyte has decreased significantly. Conventional natural static wetting methods have problems such as long wetting time, uneven penetration, bubble retention and insufficient liquid retention, which lead to increased cell internal resistance and reduced consistency. In severe cases, it may also affect the safety performance of the cell.

[0004] Currently, the industry commonly uses methods such as high-temperature settling, vacuum-assisted impregnation, or pressure wetting to accelerate electrolyte penetration. However, these methods suffer from problems such as complex equipment, high energy consumption, and narrow process windows, making it difficult to achieve high efficiency and stability in mass production. Some studies have attempted to utilize external fields such as electric fields and acoustic fields to improve the wetting effect, but their system construction is complex and their control precision is low, which is not conducive to large-scale promotion and application.

[0005] Therefore, how to effectively improve the wetting rate and uniformity of the electrolyte and enhance the electrolyte retention capacity of the battery cell while ensuring the simplicity, controllability and mass production of the process has become an urgent technical problem to be solved in the field of lithium-ion battery manufacturing. Summary of the Invention

[0006] The purpose of this invention is to propose an optimization method for the lithium-ion battery wetting process based on mechanical vibration. By applying controlled mechanical vibration energy to the outside of the cell, the flow dynamics of the electrolyte inside the porous electrode and separator are changed by using a periodic acceleration field, thereby shortening the production cycle and improving the consistency of electrolyte distribution inside the cell.

[0007] To achieve the above objectives, this invention proposes an optimization method for the lithium-ion battery wetting process based on mechanical vibration, comprising the following steps: S1. Clamping preparation stage: The lithium-ion battery cell with electrolyte injection and sealing completed is placed on the vibration platform and the lithium-ion battery cell is fixed by the battery cell clamp. S2, Vibration Immersion Stage: The vibration platform is activated to apply mechanical vibration to the lithium-ion cell, and the mechanical vibration generates a periodic acceleration field inside the lithium-ion cell; S3. Status Monitoring and Process Termination Stage: During the vibration process, the wetting state parameters of the lithium-ion battery cell are collected by the monitoring device; the collected wetting state parameters are compared with the preset process indicators; when the monitoring data reaches the preset wetting threshold, the operation of the vibration platform is stopped and the fixed constraint of the battery cell fixture is released.

[0008] Furthermore, the mechanical vibration may be generated by piezoelectric, electromagnetic, or mechanical eccentric wheels; the mechanical vibration may be linear, torsional, or a combination of vibrations, and the vibration frequency, amplitude, and duration may be adjusted according to the cell structure, electrolyte properties, or wetting stage.

[0009] Furthermore, the frequency parameter of the mechanical vibration is from 10Hz to 2000Hz, and the amplitude parameter is from 0.01mm to 5mm.

[0010] Furthermore, the frequency of the mechanical vibration is set to 175Hz, the amplitude is set to 0.2mm, and the vibration waveform adopts a sinusoidal perturbation waveform.

[0011] Furthermore, the mechanical vibration is applied in a longitudinal direction along the stacking direction of the lithium-ion cell electrode sheets.

[0012] Furthermore, the wetting state parameters in step S3 are obtained through an electrical signal monitoring scheme: the open-circuit voltage data of the lithium-ion cell is recorded using a voltage acquisition module and the rate of change of the open-circuit voltage over time is calculated; when the absolute value of the rate of change is less than 0.1mV / h for 30 consecutive minutes, the lithium-ion cell is determined to have reached the wetting equilibrium state.

[0013] Furthermore, the wetting state parameters in step S3 are obtained through a physical detection scheme: an ultrasonic C-scan image of the inside of the lithium-ion battery cell is obtained using an ultrasonic scanning device, and the pixel area ratio of the unwetted area in the image is calculated; when the pixel area ratio drops below 1%, a vibration stop command is executed.

[0014] Compared with the prior art, the advantages of the present invention are: 1. Significantly improves electrolyte wetting efficiency. This invention introduces an external mechanical vibration field, providing the electrolyte with additional kinetic energy under normal pressure, forcing it to overcome the capillary resistance inside the porous electrode in a very short time. Using the vibration process described in this invention, the time required for traditional static wetting can be greatly shortened, significantly improving the output efficiency of lithium-ion battery production lines.

[0015] 2. Significantly improved uniformity and consistency of wetting. The periodic stress waves generated by mechanical vibration can reach the dead zones inside the electrode. This all-round penetration mechanism promotes the continuous distribution of electrolyte in the positive and negative electrode active materials and the pores of the separator, eliminates local dry areas, thereby reducing the DC internal resistance (DCR) of the cell and improving the capacity retention and rate performance of the cell in subsequent charge and discharge cycles.

[0016] 3. This invention effectively eliminates internal trapped air bubbles. During the liquid injection and natural wetting process, tiny air bubbles often remain in the pores of the electrode, occupying active sites and hindering ion transport. This invention utilizes the pressure gradient and shearing effect generated by vibration to promote the aggregation of tiny bubbles and their discharge to the outside of the electrode assembly, thereby increasing the effective electrochemical reaction area, reducing local polarization, fundamentally reducing the risk of lithium plating, and enhancing the safety performance of the battery.

[0017] 4. Enhanced electrolyte retention capacity of the battery cell. Through the forced penetration effect of mechanical vibration, the electrolyte can penetrate deeper into the micropores of the active material and be firmly adsorbed by the material surface. Compared with natural wetting, the battery cell after vibration-assisted wetting exhibits superior electrolyte retention characteristics during long-term cycling, reducing the loss of free electrolyte and extending the battery's lifespan.

[0018] 5. This invention combines OCV monitoring and ultrasonic scanning technology with vibration processing to achieve closed-loop control of the impregnation process. This real-time feedback-based process adjustment method eliminates the influence of environmental temperature changes, electrolyte batch differences, or fluctuations in electrode physical parameters on the impregnation effect, ensuring the consistency of impregnation quality for each cell leaving the factory, and providing technical support for the large-scale manufacturing of high-performance lithium-ion batteries. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of an optimization method for lithium-ion battery wetting process based on mechanical vibration according to the present invention. Figure 2 This is a comparison curve of the open circuit voltage (OCV) over time between the mechanical vibration-assisted immersion group and the conventional static group in this embodiment of the invention. Figure 3 This is a comparison curve of the voltage change rate (dU / dt) over time between the mechanical vibration-assisted immersion group and the conventional static group in an embodiment of the present invention. Figure 4 This is an ultrasonic C-scan image of the mechanical vibration-assisted immersion group after 12 hours of immersion in an embodiment of the present invention; Figure 5 The image shows the ultrasound C-scan image of the conventional static group in the comparative example after 12 hours of immersion. Figure 6This is an ultrasonic C-scan image of the mechanical vibration-assisted immersion group after 24 hours of immersion in an embodiment of the present invention; Figure 7 The image shows the ultrasound C-scan image of the conventional static group after 24 hours of immersion in the comparative example. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be further described below.

[0021] This invention discloses an optimization method for the wetting process of lithium-ion batteries based on mechanical vibration. The aim is to improve the permeation kinetics of the electrolyte within the porous medium of the lithium-ion cell by introducing an externally controlled mechanical stress field. In the manufacturing process of lithium-ion batteries, the wetting quality of the electrolyte directly determines the utilization rate of the active material and the consistency of the battery.

[0022] like Figure 1 As shown, the optimization method described in this invention is mainly divided into three core stages: clamping preparation stage S1, vibration immersion stage S2, and condition monitoring and process termination stage S3.

[0023] In the clamping preparation stage S1, the lithium-ion battery cells that have been injected with electrolyte and have undergone preliminary sealing or pre-sealing need to be transferred from the electrolyte injection station to the immersion optimization station.

[0024] In this step, the vibration platform serves as the energy output source, with a specially designed cell clamp positioned on top of it. After the lithium-ion cell is placed on the vibration platform, the power mechanism is activated, causing the inner surface of the clamp to form a large-area, tight contact with the outer shell of the lithium-ion cell. For pouch cells, the control electrode assembly is placed horizontally with its large surface facing down, which helps the electrolyte migrate towards the center region of the electrode under the combined action of gravity and vibration.

[0025] In the vibration wetting stage S2, the vibration platform begins to output mechanical vibration according to the preset process formula. In this embodiment, the vibration frequency is set to 175Hz, the amplitude to 0.2mm, and the vibration waveform is selected as a sinusoidal perturbation waveform. When the vibration platform starts working, the electrolyte inside the lithium-ion cell is in a periodic acceleration field; the permeation rate of the electrolyte in the porous electrode is significantly affected by porosity, tortuosity, and liquid viscosity. The intervention of mechanical vibration provides an additional dynamic pressure source for the electrolyte.

[0026] During the specific execution of the vibration wetting stage S2, the direction of mechanical vibration can be combined in various ways. A preferred embodiment is to apply longitudinal vibration along the stacking direction of the lithium-ion cell. This vibration directly acts on the interface between the electrode and the separator, generating a pump-like effect through the expansion and contraction of tiny gaps, forcing the electrolyte into the deep micropores of the active material. Another embodiment is to apply axial vibration in conjunction with the injection direction, utilizing the inertial force of the liquid to propel the electrolyte rapidly along the length of the electrode. Furthermore, multi-degree-of-freedom composite vibration is achieved through a vibration platform, creating a complex stress field within the cell. This causes microbubbles trapped in the porous structure to deform and coalesce under shear force, ultimately being expelled from the electrode assembly under the induction of buoyancy and vibration disturbance, thus making room for electrolyte filling.

[0027] In the vibration wetting stage S2, during the first 10 minutes of wetting, the vibration platform 1 operates at a higher frequency, using high-frequency disturbances to reduce the apparent viscosity of the electrolyte, allowing it to quickly cover the electrode surface. Subsequently, the frequency is reduced to the mid-to-low frequency range, and the amplitude is increased, using larger inertial displacement to drive the electrolyte to penetrate into the high-density center of the electrode. This staged vibration control method addresses the dual requirements of surface wetting and deep penetration.

[0028] In the condition monitoring and process termination phase S3, the monitoring device begins to function as a closed-loop control system. During the vibration application process, the monitoring device acquires the open-circuit voltage (OCV) data of the lithium-ion battery cell in real time. For example... Figure 2 As shown in the figure, the OCV evolution curves of the mechanical vibration-assisted wetting group and the conventional static group are illustrated. It can be seen that the slope of the open-circuit voltage rise of the lithium-ion cell subjected to mechanical vibration is significantly higher than that of the control group in the early stage of wetting. This is because mechanical vibration accelerates the establishment of ion conduction pathways, allowing the double-layer charge on the electrode surface to reach equilibrium more quickly. Simultaneously, the steady-state OCV value of the vibration group after reaching the plateau period is also slightly higher than that of the static group, reflecting that the electrolyte retention inside the cell is improved under vibration, resulting in a more complete wetting coverage of the electrode surface.

[0029] In this embodiment, the monitoring device calculates the voltage change rate dU / dt in real time using a built-in processing chip. For example... Figure 3 As shown, the voltage change rate curve can more sensitively reflect the switching point of wetting kinetics. Under vibration process, the OCV change rate decreases significantly faster over time than under static process, indicating that the electrolyte penetration process completes the transition from kinetic control to thermodynamic equilibrium in a shorter time. When the monitoring device detects that the dU / dt value is lower than the preset stability threshold for multiple consecutive sampling cycles, it determines that the cell has reached the preset wetting level.

[0030] To further verify the wetting effect accurately, this invention incorporates ultrasonic C-scan detection during the process. Please refer to [link / reference]. Figures 4 to 7 By utilizing the difference in acoustic impedance at the interface of different media, the wetting distribution within the battery cell can be clearly identified. At the 12-hour immersion stage, such as... Figure 4 As shown, the ultrasonic images of the mechanical vibration group reveal a continuous and uniform dark area, indicating that the electrolyte has been well filled. And as... Figure 5 The standard static group shown still has obvious white bright spots at the center and edges of the image. These bright spots represent dry areas or residual air bubbles that have not been wetted by the electrolyte.

[0031] As the soaking time is extended to 24 hours, such as Figure 6 As shown, the internal acoustic characteristics of the battery cell in the mechanical vibration group are completely uniform, indicating that the electrolyte distribution is highly consistent. (Comparison) Figure 7 Even after 24 hours of natural seepage, the static group still had scattered unwetted areas inside. This fully demonstrates the significant technical advantage of mechanical vibration in eliminating seepage dead zones. When the monitoring device confirms through image processing algorithms that the percentage of unwetted pixels is less than 1%, the system automatically sends a stop command to the vibration platform.

[0032] In summary, this invention introduces controlled mechanical vibration during the electrolyte wetting stage, changing the traditional static wetting process that relies solely on weak capillary forces. By utilizing the dynamic pressure effect and microfluidic effect generated by a periodic acceleration field, rapid and uniform electrolyte penetration is achieved. A closed-loop feedback mechanism combining OCV monitoring and ultrasonic scanning ensures high reliability of the wetting process. This invention not only significantly shortens the production cycle and improves production efficiency, but also enhances the overall electrochemical performance of lithium-ion batteries by optimizing the wetting state inside the cell, providing strong technical support for the large-scale manufacturing of high-quality batteries.

[0033] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A method for optimizing the wetting process of lithium-ion batteries based on mechanical vibration, characterized in that, Includes the following steps: S1. Clamping preparation stage: The lithium-ion battery cell with electrolyte injection and sealing completed is placed on the vibration platform and the lithium-ion battery cell is fixed by the battery cell clamp. S2, Vibration Immersion Stage: The vibration platform is activated to apply mechanical vibration to the lithium-ion cell, and the mechanical vibration generates a periodic acceleration field inside the lithium-ion cell; S3. Status Monitoring and Process Termination Stage: During the vibration process, the wetting state parameters of the lithium-ion battery cell are collected by the monitoring device; the collected wetting state parameters are compared with the preset process indicators; when the monitoring data reaches the preset wetting threshold, the operation of the vibration platform is stopped and the fixed constraint of the battery cell fixture is released.

2. The method for optimizing the lithium-ion battery wetting process based on mechanical vibration according to claim 1, characterized in that, The mechanical vibrations are generated by piezoelectric, electromagnetic, or mechanical eccentric wheels; the mechanical vibrations include linear vibration, torsional vibration, or a combination of vibrations, and the vibration frequency, amplitude, and duration can be adjusted according to the cell structure, electrolyte properties, or wetting stage.

3. The method for optimizing the wetting process of lithium-ion batteries based on mechanical vibration according to claim 1, characterized in that, The frequency parameter of the mechanical vibration is from 10Hz to 2000Hz, and the amplitude parameter is from 0.01mm to 5mm.

4. The method for optimizing the lithium-ion battery wetting process based on mechanical vibration according to claim 3, characterized in that, The frequency of the mechanical vibration is set to 175Hz, the amplitude is set to 0.2mm, and the vibration waveform adopts a sinusoidal perturbation waveform.

5. The method for optimizing the lithium-ion battery wetting process based on mechanical vibration according to claim 1, characterized in that, The mechanical vibration is applied in a longitudinal direction along the stacking direction of the lithium-ion cell electrode sheets.

6. The method for optimizing the lithium-ion battery wetting process based on mechanical vibration according to claim 1, characterized in that, The wetting state parameters in step S3 are obtained through an electrical signal monitoring scheme: the open-circuit voltage data of the lithium-ion cell is recorded using a voltage acquisition module and the rate of change of the open-circuit voltage over time is calculated; when the absolute value of the rate of change is less than 0.1mV / h for 30 consecutive minutes, the lithium-ion cell is determined to have reached the wetting equilibrium state.

7. The method for optimizing the lithium-ion battery wetting process based on mechanical vibration according to claim 1, characterized in that, The wetting state parameters in step S3 are obtained through a physical detection scheme: an ultrasonic C-scan image of the inside of the lithium-ion battery cell is obtained using an ultrasonic scanning device, and the pixel area ratio of the unwetted area in the image is calculated; when the pixel area ratio drops below 1%, a vibration stop command is executed.

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