Battery cell formation method and lithium battery cell

Abstract

The invention discloses a battery cell formation method and a lithium battery cell, and relates to the technical field of battery cell formation, and the method comprises the steps of battery cell pretreatment, staged constant-current charging, intelligent constant-voltage charging, stepped discharging and formation post-treatment; through pretreatment of the battery cell, the influence of environmental factors on the battery cell can be reduced, the internal state of the battery cell is homogenized, and formation of the battery cell is facilitated; through staged constant-current charging, the interior of a battery cell can adapt to a reaction process, charging safety is ensured, formation quality is improved, and formation time and efficiency are optimized; through intelligent constant-voltage charging, charging safety is ensured, battery cell performance is protected, SEI film quality is ensured, and charging efficiency is improved; misjudgment caused by accidental factor interference is avoided by triggering short circuit detection and multi-dimensional reason troubleshooting when the internal resistance is suddenly changed; and qualified, unqualified or re-checked battery cells are automatically marked according to the internal resistance threshold value, manual intervention is reduced, and the sorting efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery cell formation, and in particular to a battery cell formation method and a lithium battery cell. Background Art

[0002] With the booming development of modern electronic devices and new energy, lithium batteries have become an indispensable key power source due to their outstanding advantages such as high energy density, long cycle life, and low self-discharge rate. From small portable devices such as mobile phones and laptops to large-scale application scenarios such as electric vehicles and energy storage power stations, the performance of lithium batteries directly affects the user experience and operating efficiency of related products. As the core link that determines the performance of lithium batteries, the development of cell formation technology has attracted much attention.

[0003] Traditional battery cell formation methods have exposed many problems in practical applications; in the charging process, a single current charging mode was mostly used in the early days, which failed to fully consider the reaction characteristics of the battery cell at different stages; although high-current charging can speed up the charging speed, in the early stage of battery cell formation, the active substances inside the battery cell have not yet been fully activated, and the high current will cause the electrode material to withstand too high a current density, resulting in damage to the electrode structure, such as the shedding of electrode material particles and destruction of the pore structure, which seriously affects the cycle life and charge and discharge performance of the battery; moreover, when charging with a high current, the internal heat of the battery is generated rapidly, which can easily cause the problem of excessive temperature, not only increasing the risk of thermal runaway of the battery, but also promoting the decomposition of the electrolyte and abnormal growth of the SEI film, further reducing the battery performance and safety. If a current that is too small is used for full charging, although a certain degree of safety can be guaranteed, the charging time will be greatly extended, which greatly increases the production cost and time cost in large-scale production scenarios and reduces production efficiency;

[0004] The traditional method uses fixed current segmented discharge, but in the actual process, various performance data are constantly changing. It is difficult to accurately reflect the internal state of the battery cell using a fixed pattern, and a single current discharge cannot adapt to the reaction characteristics of different battery cells, resulting in inaccurate detection of parameters such as capacity and internal resistance. Summary of the Invention

[0005] In order to solve the problems in the background technology, the present invention proposes a battery cell formation method and a lithium battery cell.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A battery cell formation method, comprising: battery cell pretreatment, staged constant current charging, intelligent constant voltage charging, step-by-step discharge and formation post-treatment; The staged constant current charging is carried out in the following manner: Phase 1: The battery cell is charged with a constant current of a small current. When the battery cell voltage reaches When the battery is fully charged, it enters the next stage; in this stage, low-current charging can gently activate the active substances inside the battery cell, avoid damage to the electrode material caused by high current, and help to initially form a relatively stable SEI film; The second stage: increase the charging current to Continue constant current charging, when the cell voltage reaches When the battery is fully charged, it enters the next stage; as the reaction inside the battery cell proceeds, increasing the current appropriately can speed up the charging process while ensuring that the battery cell reacts within a safe voltage range; Phase 3: Adoption The current is constant current charging, when the cell voltage reaches When the battery is fully charged, it enters the constant voltage charging stage; in this stage, the current is further increased to improve the formation efficiency while ensuring the safety of the battery cell; , .

[0007] Preferably, the battery cell pretreatment is to place the battery cell to be formed into a constant temperature and humidity pretreatment box, and let it stand for 2-4 hours in an environment with a temperature of 25±2°C and a humidity of 50±5%, RH, so that the temperature and humidity inside the battery cell are evenly distributed, thereby reducing the battery cell performance differences caused by environmental factors.

[0008] Preferably, the intelligent constant voltage charging is in the constant voltage charging stage, and the charging cut-off voltage is set to , while monitoring the charging current and temperature of the battery cell in real time. When the charging current drops to 0.02C and remains unchanged for 10 minutes, or the battery cell temperature exceeds 45°C, charging is stopped immediately. During the charging process, the battery cell temperature is collected in real time through a temperature sensor. If the temperature rises too quickly, exceeding 1°C per minute, the charging current is automatically reduced by 10%-20%. After the temperature stabilizes, the normal charging current is gradually restored. This intelligent constant-voltage charging method can dynamically adjust the charging parameters according to the actual state of the battery cell, avoid damage to the battery cell due to overcharging or excessive temperature, and ensure the uniform formation of the SEI film.

[0009] Preferably, the step-by-step discharge is to discharge the battery cells in a step-by-step manner after charging is completed. The current discharges the cell voltage to , and then adjust the discharge current to , continue to discharge until , and finally The current discharges to Step-by-step discharge can more accurately detect performance parameters such as the capacity and internal resistance of the battery cell, while keeping the battery cell in a suitable initial state for subsequent storage and use. , .

[0010] Preferably, the cell formation is carried out by a formation device, and an intelligent control component is provided inside the control box of the formation device, and the intelligent control component includes an acquisition module, an analysis module and an execution module; The acquisition module collects the internal resistance data of the battery cell, the pressure data at the battery cell installation position, the lithium salt concentration data of the electrolyte, the flow rate data at the diaphragm position, and the image data of the electrode material, and transmits the collected data to the analysis module; The analysis module analyzes the internal resistance data transmitted by the acquisition module to determine whether the internal resistance has suddenly changed. If so, the analysis module sequentially analyzes the pressure data, lithium salt concentration data, flow rate data, and image data transmitted by the acquisition module to determine the cause of the sudden change in internal resistance, generates a corresponding signal based on the cause, and transmits the generated signal to the execution module; The execution module receives the signal transmitted by the analysis module and performs the corresponding operation; If the received signal is an electrode correction signal, a buzzer warning will be issued through the buzzer module in the intelligent control component, and the signal type and correction position will be displayed on the display screen of the control box, so that the staff can reset the electrode at the corresponding position in time: If the received signal is a concentration adjustment signal, a buzzer alarm will be issued through the buzzer module in the intelligent control component, and the signal type and concentration data will be displayed on the display screen of the control box, so that the staff can adjust the concentration of the electrolyte in time; If the received signal is a diaphragm damage signal, a buzzer warning will be issued through the buzzer module in the intelligent control component, and the signal type and mark position will be displayed on the display screen of the control box. The staff will compare the flow rate change amplitude with the preset flow rate change threshold. If it is greater than the preset flow rate change threshold, the diaphragm will be replaced; otherwise, the diaphragm will be repaired.

[0011] Preferably, the analysis module performs the following steps to analyze the internal resistance data: S1: collect the data at the same time The internal resistance data of the cells are placed in the same data set, and the mean value of the internal resistance data of the cells in the data set is and standard deviation Calculate and use the calculated mean and standard deviation The fluctuation range of the battery cell internal resistance data The setting is to mark the cell internal resistance data that is not within the fluctuation range in the corresponding data set as an outlier, and the number of outliers is Conduct statistics; S2: If , then it is determined that the internal resistance data of the battery cell is not accurate, and the internal resistance data of the battery cell is retested. is the preset proportional coefficient; otherwise, after removing the abnormal values, the average of the remaining battery cell internal resistance data is calculated. The calculation of the mean As the cell internal resistance data detected at that moment; S3: Compare the cell internal resistance data at the corresponding moment with a preset cell internal resistance threshold. If the cell internal resistance data at the corresponding moment is less than the preset cell internal resistance threshold, the internal resistance is determined to be normal, the corresponding cell is marked as "qualified", and the qualified cell is passed to the next operation step. If the cell internal resistance data at the corresponding moment is greater than the preset cell internal resistance threshold, the internal resistance is determined to have suddenly changed, the discharge is automatically suspended, and the short circuit detection is triggered. S4: After discharging is suspended, the control system triggers the short circuit detection program. By applying a specific low voltage signal to the battery cell, the current in the circuit is measured. If the ratio of the measured current data to the preset reference current value is greater than the preset ratio , it is determined that a short circuit has occurred, the corresponding battery cell will be marked as "unqualified", and the unqualified battery cell will be isolated; otherwise, it is determined that no short circuit has been detected, and the cause of the internal resistance mutation will continue to be investigated.

[0012] Preferably, the analysis module performs the following steps to troubleshoot the cause of the internal resistance mutation: K1: Obtain pressure data detected by the pressure sensor installed at the corresponding position. If the change in pressure data is greater than the preset pressure fluctuation threshold, it is determined that the electrode material is loose and the internal resistance mutation is caused by the loose electrode material. An electrode correction signal is generated and transmitted to the execution module. K2: If the electrode material is not loose, the lithium salt concentration data in the electrolyte is obtained through spectral analysis. If the change in the concentration data is greater than the preset concentration fluctuation threshold, it is determined that the change in the lithium salt concentration data of the electrolyte is abnormal. The sudden change in internal resistance is caused by the change in the lithium salt concentration of the electrolyte. A concentration adjustment signal is generated and transmitted to the execution module; K3: If the change in the lithium salt concentration of the electrolyte is in line with expectations, the flow rate change at the diaphragm position is obtained and the flow rate change values ​​at adjacent monitoring moments are compared. If the flow rate after a certain moment is greater than the standard flow rate data, the diaphragm is determined to be damaged, the flow rate change position is marked, and a diaphragm damage signal is generated and transmitted to the execution module; K4: If none of the above are abnormal, analyze the electrode material.

[0013] Preferably, the analysis module performs the following steps to analyze the electrode material: M1: Obtain diffraction pattern data through X-ray diffraction technology and record different diffraction angles Diffraction intensity under , and then according to the interplanar spacing in the crystal structure The relationship between the diffraction angle and the interplanar spacing is calculated , is the diffraction order, is the wavelength of X-rays; and the calculated interplanar spacing The recorded interplanar spacing data of the electrode material Compare them. If the two are the same, it is determined that the crystal structure has not changed; otherwise, it is determined that the crystal structure has changed, and the impact value of the crystal structure change is preset. ; M2: Obtain image data of the electrode material surface and obtain the diameter data of the particles in the electrode material through image analysis After collecting multiple particle diameter data in the image, calculate the mean of the diameter data , then estimate the surface area of ​​the particles in the electrode material , is the density data of the particles; if the mean diameter and surface area data of the particles are the same as the diameter recorded for the corresponding electrode material and surface area data If the electrode material is the same as the original material, it is determined that the electrode material has not changed in its microstructure; otherwise, it is determined that the electrode material has changed in its microstructure. The impact value of the microstructure change is , and is the preset weight coefficient; M3: Total impact ,like , it is determined that the internal resistance mutation is caused by the change of electrode material. is the preset impact threshold; otherwise, it is determined that the cause of the abnormality has not been analyzed, the corresponding battery cell is marked as "needing re-inspection", the battery cell to be re-inspected is transferred to the inspection position for storage, and then the inspection operation of the next battery cell is carried out.

[0014] Preferably, the post-formation treatment is to place the formed battery cell back into a constant temperature and humidity treatment box, and leave it for 6-8 hours in an environment with a temperature of 20-25°C and a humidity of 40-50%RH to further stabilize the chemical composition inside the battery cell and reduce the self-discharge rate of the battery cell.

[0015] A lithium battery cell, wherein the lithium battery cell is prepared by the method according to any one of claims 1 to 9.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. Cell pretreatment can reduce the impact of environmental factors on the cell and make the internal state of the cell uniform, which is conducive to the cell formation. Phased constant current charging can adapt the cell to the reaction process, ensure charging safety, improve formation quality and optimize formation time and efficiency. Intelligent constant voltage charging can ensure charging safety, protect cell performance, ensure SEI film quality and improve charging efficiency. 2. Real-time internal resistance data is used to eliminate outliers to ensure the accuracy of test data. Short-circuit detection and multi-dimensional cause investigation are triggered when the internal resistance changes suddenly, avoiding misjudgments caused by accidental interference. Cells are automatically marked as "qualified", "unqualified" or "need re-inspection" based on the internal resistance threshold, reducing manual intervention and improving sorting efficiency. Through historical data fitting and model prediction, potential problems are warned in advance, reducing trial and error costs and improving the accuracy of performance testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of cell formation according to an embodiment of the present invention is shown; Figure 2 A system flow chart provided according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0019] See also Figure 1-2 , the present invention provides a technical solution: A cell formation method includes cell pretreatment, staged constant-current charging, intelligent constant-voltage charging, stepped discharge, and post-formation treatment. Cell pretreatment can reduce the impact of environmental factors on the cell and make the internal state of the cell uniform, which is conducive to the formation of the cell. Staged constant-current charging can adapt the interior of the cell to the reaction process, ensure charging safety, improve formation quality, and optimize formation time and efficiency. Intelligent constant-voltage charging ensures charging safety, protects cell performance, ensures SEI film quality, and improves charging efficiency. The staged constant current charging is carried out as follows: Phase 1: The battery cell is charged with a small current to gently activate the active material, protect the electrode material and initially form a stable SEI film; when the battery cell voltage reaches When the battery is fully charged, it enters the next stage; in this stage, low-current charging can gently activate the active substances inside the battery cell, avoid damage to the electrode material caused by high current, and help to initially form a relatively stable SEI film; The second stage: increase the charging current to Continue constant current charging, when the cell voltage reaches When the battery is fully charged, it enters the next stage; as the reaction inside the battery cell proceeds, increasing the current appropriately can speed up the charging process while ensuring that the battery cell reacts within a safe voltage range; Phase 3: Adoption The current is constant current charging, when the cell voltage reaches When the battery is charged, it enters the constant voltage charging stage; in this stage, the current is further increased to improve the formation efficiency while ensuring the safety of the battery cell; in this embodiment, for the ternary system battery cell, 、 and 0.05C, 0.2C and 0.5C respectively; 、 and They are 2.5V, 3.6V and 4.0V respectively.

[0020] In the present invention, the battery cell pretreatment is to place the battery cell to be formed into a constant temperature and humidity pretreatment box, and let it stand for 2-4 hours in an environment with a temperature of 25±2°C and a humidity of 50±5%, RH, so that the temperature and humidity inside the battery cell are evenly distributed, reducing the battery cell performance differences caused by environmental factors, which is beneficial to the formation of the battery cell.

[0021] In the present invention, the intelligent constant voltage charging is in the constant voltage charging stage, and the charging cut-off voltage is set to (4.0V), while monitoring the charging current and temperature of the battery cell in real time. When the charging current drops to 0.02C and remains unchanged for 10 minutes, or the battery cell temperature exceeds 45°C, charging is stopped immediately. During the charging process, the battery cell temperature is collected in real time through a temperature sensor. If the temperature rises too quickly, exceeding 1°C per minute, the charging current is automatically reduced by 10%-20%. After the temperature stabilizes, the normal charging current is gradually restored. This intelligent constant voltage charging method can dynamically adjust the charging parameters according to the actual state of the battery cell, avoiding damage to the battery cell due to overcharging or excessive temperature, and ensuring the uniform formation of the SEI film.

[0022] In the present invention, the step-by-step discharge is to discharge the battery cell in a step-by-step manner after the charging is completed. The current discharges the cell voltage to , and then adjust the discharge current to , continue to discharge until , and finally The current discharges to ; Step-by-step discharge can more accurately detect performance parameters such as the capacity and internal resistance of the battery cell, while placing the battery cell in a suitable initial state for subsequent storage and use; In this embodiment, for the ternary system battery cell, 、 and 0.3C, 0.2C and 0.1C respectively; 、 and They are 3.8V, 3.5V and 3.0V respectively.

[0023] During the battery cell formation process, the formation process is controlled by the control device inside the formation equipment control box. The control box is also equipped with an intelligent control component, which includes an acquisition module, an analysis module and an execution module. A high-precision internal resistance tester is connected in series in the cell discharge circuit. The internal resistance tester establishes a communication connection with the cell formation control system to ensure stable data transmission. The internal resistance tester can achieve real-time measurement of milliohm-level internal resistance. At each stage of step-by-step discharge, the internal resistance tester collects cell internal resistance data at a set frequency and collects the data at the same time. The internal resistance data of the cells are placed in the same data set, and the mean value of the internal resistance data of the cells in the data set is and standard deviation Calculate and use the calculated mean and standard deviation The fluctuation range of the battery cell internal resistance data The setting is to mark the cell internal resistance data that is not within the fluctuation range in the corresponding data set as an outlier, and the number of outliers is Perform statistics, if , then it is determined that the internal resistance data of the battery cell is not accurate, and the internal resistance data of the battery cell is retested. is the preset proportional coefficient; otherwise, after removing the abnormal values, the average of the remaining battery cell internal resistance data is calculated. The calculation of the mean As the cell internal resistance data detected at that moment; Compare the cell internal resistance data at the corresponding moment with the preset cell internal resistance threshold. If the cell internal resistance data at the corresponding moment is less than the preset cell internal resistance threshold, the internal resistance is determined to be normal, the corresponding cell is marked as "qualified", and the qualified cell is passed to the next operation step. If the cell internal resistance data at the corresponding moment is greater than the preset cell internal resistance threshold, it is determined that the internal resistance has suddenly changed, and the discharge is automatically suspended and the short-circuit detection is triggered to prevent unqualified cells from flowing into the next process. After pausing the discharge, the control system triggers the short-circuit detection program, applies a specific low-voltage signal to the cell, measures the current in the circuit, and if the ratio of the measured current data to the preset reference current value is greater than the preset ratio , it is determined that a short circuit has occurred, the corresponding battery cell will be marked as "unqualified", and the unqualified battery cell will be isolated; otherwise, it is determined that no short circuit has been detected, and the cause of the internal resistance mutation will continue to be investigated; The pressure data detected by the pressure sensor installed at the corresponding position is obtained. If the change value of the pressure data is greater than the preset pressure fluctuation threshold, it is determined that the installation of the electrode material is loose, and the sudden change in internal resistance is caused by the loose electrode material. An electrode correction signal is generated and transmitted to the execution module; A small AC signal is applied to the battery cell, and the change in its impedance with frequency is measured. Changes in the electrolyte composition affect the ion conduction characteristics, resulting in changes in the impedance spectrum. By establishing an electrolyte composition-impedance spectrum model and analyzing the real-time impedance spectrum data, real-time lithium salt concentration information can be inferred. The specially designed battery structure allows X-rays to penetrate the battery casing and other components, reaching the electrode material and diffracting. The diffraction signal is then received by the detector, realizing X-ray diffraction technology. If the electrode material is not loose, the lithium salt concentration data in the electrolyte is obtained through spectral analysis. If the change value of the concentration data is greater than the preset concentration fluctuation threshold, it is determined that the change in the lithium salt concentration data of the electrolyte is abnormal, and the internal resistance mutation is caused by the change in the lithium salt concentration of the electrolyte. A concentration adjustment signal is generated and the concentration adjustment signal is transmitted to the execution module; if the change in the lithium salt concentration of the electrolyte is as expected, the flow velocity change at the diaphragm position is obtained, and the flow velocity change values ​​at adjacent monitoring moments are compared. If the flow velocity after a certain moment is greater than the standard flow velocity data, it is determined that the diaphragm is damaged, the flow velocity change position is marked, and a diaphragm damage signal is generated and transmitted to the execution module; if none of the above are abnormal, the electrode material is analyzed; After the execution module receives the electrode correction signal, it issues a buzzer warning through the buzzer module in the intelligent control component, and displays the signal type and correction position on the display screen of the control box, so that the staff can promptly perform the reset operation of the electrode at the corresponding position; after the execution module receives the concentration adjustment signal, it issues a buzzer warning through the buzzer module in the intelligent control component, and displays the signal type and concentration data on the display screen of the control box, so that the staff can promptly perform the electrolyte concentration adjustment operation; after the execution module receives the diaphragm damage signal, it issues a buzzer warning through the buzzer module in the intelligent control component, and displays the signal type and mark position on the display screen of the control box. The staff compares the flow rate change amplitude with the preset flow rate change threshold. If it is greater than the preset flow rate change threshold, the diaphragm is replaced; otherwise, the diaphragm is repaired. Obtain diffraction pattern data through X-ray diffraction technology and record different diffraction angles Diffraction intensity under , and then according to the interplanar spacing in the crystal structure The relationship between the diffraction angle and the interplanar spacing is calculated , is the diffraction order, is the wavelength of X-rays; and the calculated interplanar spacing The recorded interplanar spacing data of the electrode material Compare them. If the two are the same, it is determined that the crystal structure has not changed; otherwise, it is determined that the crystal structure has changed, and the impact value of the crystal structure change is preset. ; Obtain image data of the electrode material surface and obtain the diameter data of the particles in the electrode material through image analysis After collecting multiple particle diameter data in the image, calculate the mean of the diameter data , then estimate the surface area of ​​the particles in the electrode material , is the density data of the particles; if the mean diameter and surface area data of the particles are the same as the diameter recorded for the corresponding electrode material and surface area data If the electrode material is the same as the original material, it is determined that the electrode material has not changed in its microstructure; otherwise, it is determined that the electrode material has changed in its microstructure. The impact value of the microstructure change is , and is the preset weight coefficient; affects the total value ,like , it is determined that the internal resistance mutation is caused by the change of electrode material. is the preset impact threshold; otherwise, it is determined that the cause of the abnormality has not been analyzed, the corresponding battery cell is marked as "needing re-inspection", the battery cell to be re-inspected is transferred to the inspection position for storage, and then the inspection operation of the next battery cell is carried out.

[0024] In the present invention, the post-formation treatment is to place the formed battery cell again into a constant temperature and humidity treatment box, and let it stand for 6-8 hours in an environment with a temperature of 20-25°C and a humidity of 40-50%RH, so as to further stabilize the chemical composition inside the battery cell, reduce the self-discharge rate of the battery cell, and facilitate the formation of the battery cell.

[0025] A lithium battery cell, including a positive electrode, a negative electrode, an electrolyte, a separator and other auxiliary materials; wherein the positive electrode is usually made of lithium metal oxide or other lithium-containing compounds, which can embed lithium ions during charging and release lithium ions during discharging, and the charging and discharging process of the battery is realized by the embedding and release of lithium ions, which is the electrode where oxidation reaction occurs in the lithium battery; the negative electrode is generally made of carbon materials such as graphite, and silicon-based materials or other alloy materials are also used; during the charging process, lithium ions are released from the positive electrode and embedded in the negative electrode material; during discharge, lithium ions are released from the negative electrode and return to the positive electrode; the negative electrode is the electrode where reduction reaction occurs in the lithium battery; the electrolyte is the medium for lithium ion transmission, usually composed of organic solvents and lithium salts; it plays a role in conducting lithium ions inside the battery The role of electrons enables lithium ions to move freely between the positive and negative electrodes, thereby realizing the charge and discharge function of the battery; at the same time, the electrolyte also needs to have good chemical stability, thermal stability and high ionic conductivity and other characteristics; the diaphragm is a polymer film with a microporous structure, located between the positive and negative electrodes, used to separate the positive and negative electrodes and prevent the positive and negative electrodes from direct contact and short circuit; the micropores of the diaphragm allow lithium ions to pass through while blocking electrons from passing, ensuring ion conduction and electronic insulation inside the battery; in addition, the diaphragm also needs to have high mechanical strength, good chemical stability and thermal stability to ensure that it can function stably during the use of the battery; at the same time, lithium battery cells may also include some auxiliary materials, such as current collectors, binders, conductive agents, etc. The current collector is used to collect and conduct current, usually aluminum foil is used as the positive current collector, and copper foil is used as the negative current collector; the binder is used to bond the electrode active material to the current collector to ensure the stability of the electrode structure; the conductive agent is used to improve the conductivity of the electrode and increase the charge and discharge performance of the battery.

[0026] The above description of the embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A battery cell formation method, characterized in that: include: Cell pre-treatment, staged constant current charging, intelligent constant voltage charging, stepped discharge and post-formation treatment; The staged constant current charging is carried out in the following manner: Phase 1: The battery cell is charged with a constant current of a small current. When the battery cell voltage reaches When the time comes, enter the next stage; During this stage, low-current charging can gently activate the active substances inside the battery cell, preventing damage to the electrode materials caused by high current, and at the same time helps to initially form a relatively stable SEI film. The second stage: increase the charging current to Continue constant current charging, when the cell voltage reaches When the battery is fully charged, it enters the next stage; as the reaction inside the battery cell proceeds, increasing the current appropriately can speed up the charging process while ensuring that the battery cell reacts within a safe voltage range; Phase 3: Adoption The current is constant current charging, when the cell voltage reaches When the battery is fully charged, it enters the constant voltage charging stage; in this stage, the current is further increased to improve the formation efficiency while ensuring the safety of the battery cell; , .

2. A battery cell formation method according to claim 1, characterized in that: The cell pretreatment is to place the cell to be formed into a constant temperature and humidity pretreatment box, and leave it for 2-4 hours in an environment with a temperature of 25±2°C and a humidity of 50±5%, RH, so that the temperature and humidity inside the cell are evenly distributed, thereby reducing the performance differences of the cell caused by environmental factors.

3. A battery cell formation method according to claim 1, characterized in that: The intelligent constant voltage charging is in the constant voltage charging stage, and the charging cut-off voltage is set to , while monitoring the charging current and temperature of the battery cell in real time. When the charging current drops to 0.02C and remains unchanged for 10 minutes, or the battery cell temperature exceeds 45°C, charging is stopped immediately. During the charging process, the battery cell temperature is collected in real time through a temperature sensor. If the temperature rises too quickly, exceeding 1°C per minute, the charging current is automatically reduced by 10%-20%. After the temperature stabilizes, the normal charging current is gradually restored. This intelligent constant-voltage charging method can dynamically adjust the charging parameters according to the actual state of the battery cell, avoid damage to the battery cell due to overcharging or excessive temperature, and ensure the uniform formation of the SEI film.

4. A battery cell formation method according to claim 1, characterized in that: The step-by-step discharge is to discharge the battery cells step by step after charging is completed. The current discharges the cell voltage to , and then adjust the discharge current to , continue to discharge until , and finally The current discharges to Step-by-step discharge can more accurately detect performance parameters such as the capacity and internal resistance of the battery cell, while keeping the battery cell in a suitable initial state for subsequent storage and use. , .

5. A battery cell formation method according to claim 4, characterized in that: The battery cell formation is carried out by the formation equipment. The control box of the formation equipment is equipped with an intelligent control component, which includes an acquisition module, an analysis module and an execution module. The acquisition module collects the internal resistance data of the battery cell, the pressure data at the battery cell installation position, the lithium salt concentration data of the electrolyte, the flow rate data at the diaphragm position, and the image data of the electrode material, and transmits the collected data to the analysis module; The analysis module analyzes the internal resistance data transmitted by the acquisition module to determine whether the internal resistance has suddenly changed. If so, the analysis module sequentially analyzes the pressure data, lithium salt concentration data, flow rate data, and image data transmitted by the acquisition module to determine the cause of the sudden change in internal resistance, generates a corresponding signal based on the cause, and transmits the generated signal to the execution module; The execution module receives the signal transmitted by the analysis module and performs the corresponding operation; If the received signal is an electrode correction signal, a buzzer warning will be issued through the buzzer module in the intelligent control component, and the signal type and correction position will be displayed on the display screen of the control box, so that the staff can reset the electrode at the corresponding position in time: If the received signal is a concentration adjustment signal, a buzzer alarm will be issued through the buzzer module in the intelligent control component, and the signal type and concentration data will be displayed on the display screen of the control box, so that the staff can adjust the concentration of the electrolyte in time; If the received signal is a diaphragm damage signal, a buzzer warning will be issued through the buzzer module in the intelligent control component, and the signal type and mark position will be displayed on the display screen of the control box. The staff will compare the flow rate change amplitude with the preset flow rate change threshold. If it is greater than the preset flow rate change threshold, the diaphragm will be replaced; otherwise, the diaphragm will be repaired.

6. A battery cell formation method according to claim 5, characterized in that: The analysis module performs the following steps to analyze the internal resistance data: S1: collect the data at the same time The internal resistance data of the cells are placed in the same data set, and the mean value of the internal resistance data of the cells in the data set is and standard deviation Calculate and use the calculated mean and standard deviation The fluctuation range of the battery cell internal resistance data The setting is to mark the cell internal resistance data that is not within the fluctuation range in the corresponding data set as an outlier, and the number of outliers is Conduct statistics; S2: If , then it is determined that the internal resistance data of the battery cell is not accurate, and the internal resistance data of the battery cell is retested. is the preset proportional coefficient; otherwise, after removing the abnormal values, the average of the remaining battery cell internal resistance data is calculated. The calculation of the mean As the cell internal resistance data detected at that moment; S3: Compare the cell internal resistance data at the corresponding moment with a preset cell internal resistance threshold. If the cell internal resistance data at the corresponding moment is less than the preset cell internal resistance threshold, the internal resistance is determined to be normal, the corresponding cell is marked as "qualified", and the qualified cell is passed to the next operation step. If the cell internal resistance data at the corresponding moment is greater than the preset cell internal resistance threshold, the internal resistance is determined to have suddenly changed, the discharge is automatically suspended, and the short circuit detection is triggered. S4: After discharging is suspended, the control system triggers the short circuit detection program. By applying a specific low voltage signal to the battery cell, the current in the circuit is measured. If the ratio of the measured current data to the preset reference current value is greater than the preset ratio If the battery is not detected, it is determined that a short circuit has occurred, the corresponding battery cell will be marked as "unqualified", and the unqualified battery cell will be isolated; otherwise, it is determined that no short circuit has been detected, and the cause of the internal resistance mutation will be investigated.

7. A battery cell formation method according to claim 6, characterized in that: The steps for troubleshooting the cause of internal resistance mutation using the analysis module are as follows: K1: Obtain pressure data detected by the pressure sensor installed at the corresponding position. If the change in pressure data is greater than the preset pressure fluctuation threshold, it is determined that the electrode material is loose and the internal resistance mutation is caused by the loose electrode material. An electrode correction signal is generated and transmitted to the execution module. K2: If the electrode material is not loose, the lithium salt concentration data in the electrolyte is obtained through spectral analysis. If the change in the concentration data is greater than the preset concentration fluctuation threshold, it is determined that the change in the lithium salt concentration data of the electrolyte is abnormal. The sudden change in internal resistance is caused by the change in the lithium salt concentration of the electrolyte. A concentration adjustment signal is generated and transmitted to the execution module; K3: If the change in the lithium salt concentration of the electrolyte is in line with expectations, the flow rate change at the diaphragm position is obtained and the flow rate change values ​​at adjacent monitoring moments are compared. If the flow rate after a certain moment is greater than the standard flow rate data, the diaphragm is determined to be damaged, the flow rate change position is marked, and a diaphragm damage signal is generated and transmitted to the execution module; K4: If none of the above are abnormal, analyze the electrode material.

8. A battery cell formation method according to claim 7, characterized in that: The analysis module performs the following steps to analyze electrode materials: M1: Obtain diffraction pattern data through X-ray diffraction technology and record different diffraction angles Diffraction intensity under , and then according to the interplanar spacing in the crystal structure The relationship between the diffraction angle and the interplanar spacing is calculated , is the diffraction order, is the wavelength of X-rays; The calculated interplanar spacing The recorded interplanar spacing data of the electrode material Compare them. If the two are the same, it is determined that the crystal structure has not changed; otherwise, it is determined that the crystal structure has changed, and the impact value of the crystal structure change is preset. ; M2: Obtain image data of the electrode material surface and obtain the diameter data of the particles in the electrode material through image analysis After collecting multiple particle diameter data in the image, calculate the mean of the diameter data , then estimate the surface area of ​​the particles in the electrode material , is the density data of the particles; if the mean diameter and surface area data of the particles are the same as the diameter recorded for the corresponding electrode material and surface area data If the electrode material is the same as the original material, it is determined that the electrode material has not changed in its microstructure; otherwise, it is determined that the electrode material has changed in its microstructure. The impact value of the microstructure change is , and is the preset weight coefficient; M3: Total impact ,like , it is determined that the internal resistance mutation is caused by the change of electrode material. is the preset impact threshold; otherwise, it is determined that the cause of the abnormality has not been analyzed, the corresponding battery cell is marked as "needing re-inspection", the battery cell to be re-inspected is transferred to the inspection location for storage, and then the inspection operation of the next battery cell is carried out.

9. A battery cell formation method according to claim 1, characterized in that: The post-formation treatment is to place the formed battery cell back into a constant temperature and humidity treatment box and leave it for 6-8 hours in an environment with a temperature of 20-25°C and a humidity of 40-50%RH to further stabilize the chemical composition inside the battery cell and reduce the self-discharge rate of the battery cell.

10. A lithium battery cell, characterized in that: The lithium battery cell is prepared by the method according to any one of claims 1 to 9.

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