Method for quickly formulating battery quick charging system

Abstract

The invention provides a method for rapidly formulating a battery rapid charging system, and belongs to the technical field of secondary batteries. The method comprises the following steps: S1, implanting a reference electrode into a battery needing to formulate a fast charging system to obtain three electrodes; s2, monitoring the change of positive and negative electrode potentials in the charge and discharge test process of different charge rates through the three electrodes; and S3, determining the relationship between the charging rate and the negative electrode potential when the battery is charged to different SOCs according to the data obtained in the step S2, and further determining the maximum charging rate under different SOCs, so as to formulate a battery fast charging system. The method can quickly formulate the battery fast charging system, and is simple to operate and high in applicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and in particular relates to a method for quickly formulating a battery fast charging system. Background Art

[0002] With the rapid development of new energy, various electrical equipment are constantly being updated and iterated, from electronic watches to electric cars. The performance of core components such as batteries is also constantly being optimized and improved, among which fast charging performance is urgently needed. However, unreasonable fast charging systems often cause metal dendrites in batteries, which in turn bring safety hazards; therefore, it is very important to quickly find a fast charging system suitable for the battery.

[0003] The fast charging performance of the battery is not only related to the electrode material, but also closely related to factors such as the cell structure and structural component design. In the initial research and development stage of a new battery, it often involves many aspects of design and verification. At this time, the fast charging performance of the battery and how to quickly formulate a reasonable fast charging system are particularly important. If the fast charging performance is confirmed only by testing the electrode status of a large number of cells at different charging rates, the efficiency is low. Conventional fast charging modes are mostly step charging, but there is no systematic method for quickly evaluating the battery fast charging system. Therefore, it is particularly important to quickly and simply evaluate the battery fast charging strategy.

[0004] Patent application CN117236200A discloses a method for optimizing the fast-charging strategy of flying car batteries based on a data-driven reduced-order model. This method generates a fast-charging strategy for batteries by establishing a multi-physics coupling model for batteries, and then establishing a reduced-order model based on the ant colony optimization-GRU fusion algorithm. This method requires the establishment of various mathematical models, which is difficult to calculate. It is difficult to establish models for various variables encountered in the development of new batteries, and it is difficult to operate, so it cannot be widely applied.

[0005] Patent application document CN115021359A discloses a method for formulating a temperature-controlled fast-charging strategy without lithium precipitation. By establishing a digital twin model of the battery, the real-time maximum temperature, minimum temperature and SOC value of the battery are obtained; then, by judging whether the SOC reaches the target value, if not, the battery is charged, and the temperature-controlled current and the current value without lithium precipitation are obtained according to the maximum and minimum temperatures; the fast-charging curve is obtained by repeated simulation, and then the fast-charging strategy is obtained. This method also obtains data through multiple tests and then simulates the fast-charging strategy. The operation is somewhat difficult and difficult to be generally applicable.

[0006] In general, the existing fast charging systems are mostly obtained through relatively complex or difficult-to-implement methods such as establishing mathematical models and simulation models, and are not universally applicable. Summary of the invention

[0007] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, an embodiment of the present invention proposes a method for quickly formulating a battery fast charging system.

[0008] The embodiment of the present invention provides a method for quickly formulating a battery fast charging system, comprising the following steps:

[0009] S1. Implant a reference electrode in a battery that needs to develop a fast charging system to obtain three electrodes;

[0010] S2. Monitoring the changes in the positive and negative electrode potentials during the charge and discharge test at different charge rates by the three electrodes;

[0011] S3. Determine the relationship between the charging rate and the negative electrode potential at different SOCs through the data obtained in step S2, and then determine the maximum charging rate at different SOCs, so as to formulate a battery fast charging system.

[0012] The advantages and technical effects brought by the method of the embodiment of the present invention are as follows:

[0013] (1) The method of the embodiment of the present invention takes a very short time, only one or two days, and a battery fast charging system can be quickly established.

[0014] (2) The method of the embodiment of the present invention is simple to operate. It only requires making three electrodes, then performing several cycles of charge and discharge tests, monitoring the changes in the positive and negative electrode potentials during the test, and then performing data processing.

[0015] (3) The method of the embodiment of the present invention is not limited to battery systems (such as lithium batteries, sodium batteries, etc.) and battery structures (such as soft packs, cylindrical and square structures, etc.), and has strong applicability.

[0016] In some embodiments, step S2 comprises the following steps:

[0017] S2-1. First, the three electrodes are charged to a cut-off voltage by a current with a small charging rate, and the positive and negative electrode potentials are monitored in intervals;

[0018] S2-2. Then, the three electrodes are discharged at a constant current by a current of a small discharge rate, and then the charge rate is slightly increased to charge the three electrodes at a constant current to a cut-off voltage, and the positive and negative electrode potentials are monitored in intervals;

[0019] S2-3. Repeat step S2-2 until the negative electrode potential is less than or equal to 0 V when the SOC is charged below 50% at a certain charging rate, and then stop the test.

[0020] In some embodiments, in step S2-1, the charging rate is 0.33-0.6C.

[0021] In some embodiments, in step S2-2, the interval between two adjacent charging rates is 0.4-0.6C.

[0022] In some embodiments, step S3 includes the following steps:

[0023] S3-1. Based on the data obtained in step S2, a scatter plot of the charge rate and the negative electrode potential at different SOCs is plotted, with the charge rate as the x-axis and the negative electrode potential as the y-axis; a linear fit is then performed on the scatter plot of the charge rate and the negative electrode potential at different SOCs, and the fitting formula is y=kx+b, to obtain a linear relationship diagram of the charge rate and the negative electrode potential at different SOCs;

[0024] S3-2. In the linear relationship diagram between the charge rate and the negative electrode potential at different SOCs, let y = 0 of the linear fitting curve y = kx + b at different SOCs, and obtain x = -b / k corresponding to the linear fitting curve y = kx + b at different SOCs, where x = -b / k is the charge rate when the metal potential is deposited at the negative electrode, and is also the maximum charge rate at the SOC; then, a scatter plot of the SOC and the maximum charge rate is drawn with the maximum charge rate as the X-axis and the SOC as the Y-axis; then, a polynomial fitting is performed on the scatter plot of the SOC and the maximum charge rate, and the fitting formula is Y = aX 2 +bX+c, to obtain the fitting relationship diagram between SOC and maximum charging rate;

[0025] S3-3. A battery fast charging system is formulated based on the fitting relationship diagram between the SOC and the maximum charging rate, wherein the charging rate adopted at different SOCs in the battery fast charging system is less than or equal to the maximum charging rate, and greater than or equal to 0.9-0.95 times the maximum charging rate.

[0026] In some embodiments, in step S3-1, the SOC ranges from 10% to 90%.

[0027] In some embodiments, in step S3-1, the interval between two adjacent SOCs is 0.5-12%.

[0028] In some embodiments, in step S3, after formulating the battery fast charging system, the following steps are also included: verifying the battery fast charging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart of the method of Example 1;

[0030] Figure 2 is a linear relationship diagram between the charge rate and the negative electrode potential at different SOCs in the method of Example 1;

[0031] Figure 3is a fitting relationship diagram of SOC and maximum charging rate in the method of Example 1;

[0032] Figure 4 This is a relationship diagram between the positive and negative electrode potentials and the charging rate during the step charging scheme verification process in the method of Example 1;

[0033] Figure 5 This is a photo of the negative electrode sheet disassembled after the step charging scheme verification in the method of Example 1. DETAILED DESCRIPTION

[0034] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0035] The main challenge of fast charging of batteries comes from metal precipitation. Since the difference between the metal embedding potential and the metal deposition potential of graphite is too small, during the fast charging process, the larger polarization of the graphite negative electrode will cause the negative electrode potential to drop below 0V, resulting in metal precipitation on the graphite surface. The precipitated metal easily reacts with the electrolyte to form high-resistance inorganic salts, resulting in the loss of limited metal sources, increase in battery internal resistance, capacity decay, etc. At the same time, the precipitated metal forms dendritic crystals and grows perpendicular to the surface of the electrode. Once the dendrites pierce the diaphragm and reach the positive electrode, it will cause a short circuit inside the battery and generate heat rapidly, thereby triggering side reactions inside the battery.

[0036] The embodiment of the present invention provides a method for quickly formulating a battery fast charging system, comprising the following steps:

[0037] S1. Implant a reference electrode in a battery that needs to develop a fast charging system to obtain three electrodes;

[0038] S2. Monitoring the changes in the positive and negative electrode potentials during the charge and discharge test at different charge rates by the three electrodes;

[0039] S3. Determine the relationship between the charging rate and the negative electrode potential at different SOCs through the data obtained in step S2, and then determine the maximum charging rate at different SOCs, so as to formulate a battery fast charging system.

[0040] The method of the embodiment of the present invention formulates a fast charging system by first monitoring the changes in the positive and negative electrode potentials of the battery during the charge and discharge test at different charge rates through three electrodes. Then, based on the relationship between the charging rate and the negative electrode potential when charged to different SOCs, the maximum charging rate at different SOCs is determined, thereby formulating a safe battery fast charging system. The charging rate used in each charging stage is less than the maximum charging rate in that stage, which can ensure that there is no risk of metal precipitation during the rapid charging of the battery at each stage, and thus there will be no significant capacity degradation due to metal precipitation during the battery cycle.

[0041] In some embodiments, step S2 comprises the following steps:

[0042] S2-1. First, the three electrodes are charged to a cut-off voltage by a current with a small charging rate, and the positive and negative electrode potentials are monitored in intervals;

[0043] S2-2. Then, the three electrodes are discharged at a constant current by a current of a small discharge rate, and then the charge rate is slightly increased to charge the three electrodes at a constant current to a cut-off voltage, and the positive and negative electrode potentials are monitored in intervals;

[0044] S2-3. Repeat step S2-2 until the negative electrode potential is less than or equal to 0 V when the SOC is charged below 50% at a certain charging rate, and then stop the test.

[0045] In step S2 of the method of the embodiment of the present invention, the three electrodes are first charged with a current of a small charging rate. If the negative electrode potential is greater than 0V when charged to less than 50% SOC, the charging rate is gradually increased to charge the three electrodes with a constant current. If the negative electrode potential is less than 0V when charged to less than 50% SOC, it indicates that metal is precipitated at the negative electrode, and the test is terminated. In step S2-3, the negative electrode potential is preferably less than or equal to 0V when charged to 50% SOC at a certain charging rate, and the test is stopped, because when the SOC used in this step is too small, the test cycle is too long, which is not conducive to improving the efficiency of the method of the embodiment of the present invention.

[0046] In some embodiments, in step S2-1, the charging rate is 0.33-0.6C, such as 0.33C, 0.4C, 0.42C, 0.44C, 0.46C, 0.48C, 0.5C, 0.52C, 0.54C, 0.56C, 0.58C, 0.6C, etc. In some embodiments, in step S2-2, the interval between two adjacent charging rates is 0.4-0.6C, such as 0.4C, 0.42C, 0.44C, 0.46C, 0.48C, 0.5C, 0.52C, 0.54C, 0.56C, 0.58C, 0.6C, etc. First, the three electrodes are charged with a constant current by a current of a small charging rate, and then the charging rate is gradually increased by a small amplitude to charge the three electrodes with a constant current, which helps to improve the accuracy of the relationship between the charging rate and the negative electrode potential under different SOCs. If the first charging rate is too large or the interval between two adjacent charging rates is too small, too few numerical points can be selected, and the accuracy of the relationship between the charging rate and the negative electrode potential under different SOCs may be too low.

[0047] In some embodiments, step S3 includes the following steps:

[0048] S3-1. Based on the data obtained in step S2, a scatter plot of the charge rate and the negative electrode potential at different SOCs is plotted, with the charge rate as the x-axis and the negative electrode potential as the y-axis; a linear fit is then performed on the scatter plot of the charge rate and the negative electrode potential at different SOCs, and the fitting formula is y=kx+b, to obtain a linear relationship diagram of the charge rate and the negative electrode potential at different SOCs;

[0049] S3-2. In the linear relationship diagram between the charge rate and the negative electrode potential at different SOCs, let y = 0 of the linear fitting curve y = kx + b at different SOCs, and obtain x = -b / k corresponding to the linear fitting curve y = kx + b at different SOCs, where x = -b / k is the charge rate when the metal potential is deposited at the negative electrode, and is also the maximum charge rate at the SOC; then, a scatter plot of the SOC and the maximum charge rate is drawn with the maximum charge rate as the X-axis and the SOC as the Y-axis; then, a polynomial fitting is performed on the scatter plot of the SOC and the maximum charge rate, and the fitting formula is Y = aX 2 +bX+c, to obtain the fitting relationship diagram between SOC and maximum charging rate;

[0050] S3-3. A battery fast charging system is formulated based on the fitting relationship diagram between the SOC and the maximum charging rate, wherein the charging rate adopted at different SOCs in the battery fast charging system is less than or equal to the maximum charging rate, and greater than or equal to 0.9-0.95 times the maximum charging rate.

[0051] When y=0 of the linear fitting curve y=kx+b under different SOCs, the negative electrode potential at this time is the metal precipitation potential, and the charging rate x=-b / k corresponding to the metal precipitation potential is the charging rate when the negative electrode precipitates metal potential, which is also the maximum charging rate under the current SOC. Therefore, in the fitting relationship diagram between SOC and the maximum charging rate, the area below the SOC and the maximum charging rate fitting curve is the safe area, and the area above the SOC and the maximum charging rate fitting curve is the metal precipitation area. The charging rate used in each charging stage is less than or equal to the maximum charging rate under the current SOC, and the negative electrode potential is greater than or equal to zero, and the negative electrode will not precipitate metal. On the contrary, if the charging rate used is greater than the maximum charging rate under the current SOC, the negative electrode potential is less than zero, and the negative electrode will precipitate metal. In addition, since there is a certain error in the three-electrode monitoring of the negative electrode potential, in order to ensure that the negative electrode does not precipitate metal under this charging rate, it is recommended that the charging rate in the battery fast charging system has a 5-10% margin compared to the maximum charging rate, which can ensure safe and fast charging.

[0052] In some embodiments, in step S3-1, the range of the SOC is 10-90%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc. It is understandable that the SOC range may not be limited to the range of 10-90%, but the amount of data processing will be increased. In some embodiments, in step S3-1, the interval between two adjacent SOCs is 0.5-12%, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, etc. Selecting the above SOC numerical points or SOC intervals helps to refine the battery fast charging system, and adopts the appropriate charging rate for each charging stage when charging to different SOC stages, which helps to improve the charging efficiency.

[0053] In some embodiments, in step S3, after the battery fast charging system is formulated, the following steps are also included: verifying the battery fast charging system. After the battery fast charging system is verified, the accuracy of the determined battery fast charging system can be more effectively proved. If no metal is deposited at the negative electrode, it proves that the battery fast charging system is reasonable and effective; if metal is found to be deposited at the negative electrode, the battery fast charging system needs to be corrected.

[0054] The present invention is described in detail below with reference to the embodiments and the accompanying drawings.

[0055] Example 1

[0056] A method for quickly formulating a lithium battery fast charging system, such as Figure 1 As shown, the specific steps are as follows:

[0057] (1) Preparation of three electrodes:

[0058] In a disassembly room with humidity <10% RH, part of the enameled copper wire is soaked in concentrated sulfuric acid for 30 minutes to remove the insulating layer and oxide layer on the surface. At the same time, ultrasonic treatment is performed for 3 minutes during the soaking process to enhance the cleaning effect, so as to increase the strength of subsequent lithium plating. The treated copper wire will be used as a reference electrode. A layer of diaphragm is placed between the positive electrode sheet and the diaphragm, and the copper wire is between the two diaphragms and insulated from the positive and negative electrodes. Then the three-electrode winding core is made according to the normal battery cell production process, and then the copper wire is plated with lithium, and the three-electrode production is completed.

[0059] (2) Three-electrode test:

[0060] The prepared three electrodes were charged at a constant current of 0.5C to a cut-off voltage of 4.2V, and then discharged at a constant current of 0.33C to 0% SOC with a lower limit voltage of 2.5V; during this period, the potentials of the positive electrode and the three electrodes, and the potentials of the negative electrode and the three electrodes were monitored by multi-channel equipment.

[0061] The three electrodes were charged at a constant current of 1.0C to a cut-off voltage of 4.2V, and then discharged at a constant current of 0.33C to 0% SOC with a lower limit voltage of 2.5V; during this period, the potentials of the positive electrode and the three electrodes, and the potentials of the negative electrode and the three electrodes were monitored by multiplex equipment.

[0062] The three electrodes were charged at a constant current of 1.5C to a cut-off voltage of 4.2V, and then discharged at a constant current of 0.33C to 0% SOC with a lower limit voltage of 2.5V; during this period, the potentials of the positive electrode and the three electrodes, and the potentials of the negative electrode and the three electrodes were monitored by multiplex equipment.

[0063] The three electrodes were charged at a constant current of 2.0C to a cut-off voltage of 4.2V, and then discharged at a constant current of 0.33C to 0% SOC with a lower limit voltage of 2.5V; during this period, the potentials of the positive electrode and the three electrodes, and the potentials of the negative electrode and the three electrodes were monitored by multiplex equipment.

[0064] The three electrodes were charged at a constant current of 2.5C to a cut-off voltage of 4.2V, and then discharged at a constant current of 0.33C to 0% SOC with a lower limit voltage of 2.5V; during this period, the potentials of the positive electrode and the three electrodes, and the potentials of the negative electrode and the three electrodes were monitored by multi-channel equipment.

[0065] The three electrodes were charged at a constant current of 3.0C to a cut-off voltage of 4.2V, and then discharged at a constant current of 0.33C to 0% SOC with a lower limit voltage of 2.5V; during this period, the potentials of the positive electrode and the three electrodes, and the potentials of the negative electrode and the three electrodes were monitored by multi-channel equipment.

[0066] The negative electrode potential when charged to 50% SOC at different charging rates is shown in Table 1.

[0067] Table 1. Negative electrode potential when charged to 50% SOC at different charge rates

[0068]

[0069] (3) Data processing and formulation of a step-by-step charging plan:

[0070] Through the three-electrode test data, a scatter plot of the charge rate and the negative electrode potential under different SOCs is compiled: Here, the SOC is preferably spaced at 10%, the interval is 10%-90%, and the interval of the charge rate is 0.5C; select the charge rate and negative electrode potential data points under the SOC at integer points in the range of 10%-90%, and draw a scatter plot with the negative electrode potential as the y-axis and the charge rate as the x-axis. Then a linear fit is made to the scatter plot, and the fitting formula is y=kx+b. After fitting, a linear relationship diagram of the charge rate and the negative electrode potential under different SOCs is obtained, such as Figure 2 shown. Figure 2 The fitting formula of the linear curve between the charging rate and the negative electrode potential at different SOCs is shown in Table 2.

[0071] Table 2. Fitting formula of the linear curve of charge rate and negative electrode potential at different SOC

[0072] Charging to different SOC Fitting formula 10% SOC y=-0.0343x+0.2067 20% SOC y=-0.0375x+0.1787 30% SOC y=-0.0416x+0.1638 40% SOC y=-0.0509x+0.1528 50% SOC y=-0.0487x+0.1325 60% SOC y=-0.0432x+0.0997 70% SOC y=-0.0461x+0.0968 80% SOC y=-0.0455x+0.0901 90% SOC y=-0.0443x+0.0761

[0073] Through the linear relationship diagram of charge rate and negative electrode potential under different SOC, a scatter plot of SOC and maximum charge rate is sorted out: using the linear fitting curve y=kx+b of charge rate and negative electrode potential under different SOC obtained in the previous step, let y=0, x=-b / k be the charge rate when the negative electrode potential is zero (negative electrode lithium deposition potential), that is, the maximum charge rate under this SOC. When the negative electrode potential exceeds this charge rate, it is less than zero, that is, negative electrode lithium deposition; then draw a scatter plot with the SOC data at this location as the Y axis and the maximum charge rate as the X axis. Then do a polynomial fit on the scatter plot, and the fitting formula is Y=aX 2 +bX+c, after fitting, the fitting relationship diagram between SOC and maximum charging rate is obtained, such as Figure 3 shown.

[0074] Through the fitting relationship diagram of SOC and maximum charging rate above, a step charging scheme is initially proposed, as shown in Table 3. It can be seen that the charging rates corresponding to different SOCs in Table 3 are all less than the maximum charging rates corresponding to the SOC. This is because there is a certain error in the three-electrode monitoring of the negative electrode potential. In order to ensure that the negative electrode does not precipitate lithium at this charging rate, the actual charging rate used has a margin of 5-10% relative to the maximum charging rate.

[0075] Table 3. Preliminary proposed step-by-step charging scheme

[0076] Step filling Charging rate / C Charging time / min SOC / % Cumulative SOC / % Step 1 1 6 10 10％ Step 2 2.5 9.6 40 50％ Step 3 2 4.5 15 65％ Step 4 1.5 4 10 75％ Step 5 1.2 2.5 5 80％ Step 6 0.5 ≥24(Upper voltage limit) 20 100％

[0077] The charging time in Table 3 is a theoretical calculation value and also a practical verification value.

[0078] (4) Verification of the step-charging scheme:

[0079] In addition, a new three-electrode prepared according to step (1) is taken, and the three-electrode is charged and discharged using the step charging scheme shown in Table 3. During the test, a multi-channel device is used to monitor the potential between the positive electrode and the three electrodes and the potential between the negative electrode and the three electrodes at different charging rates. The relationship between the positive and negative electrode potentials and the charging rate is shown in the figure below. Figure 4 As shown, it is necessary to understand that Figure 4 The blue voltage curve overlaps with the orange positive electrode curve. Then, the three electrodes after charge and discharge are disassembled, and the disassembled negative electrode sheet is as follows Figure 5 As shown. Figure 5 It can be seen that there is no lithium plating, which shows that the step-charging scheme proposed in this embodiment is reasonable and effective, and can ensure that the lithium battery can be fast charged safely and reliably.

[0080] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0081] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for quickly formulating a battery fast charging system, characterized in that: The following steps are involved: S1. Implant a reference electrode in a battery that needs to develop a fast charging system to obtain three electrodes; S2. Monitoring the changes in the positive and negative electrode potentials during the charge and discharge test at different charge rates by the three electrodes; S3. Determine the relationship between the charging rate and the negative electrode potential at different SOCs through the data obtained in step S2, and then determine the maximum charging rate at different SOCs, so as to formulate a battery fast charging system.

2. The method according to claim 1, characterized in that Step S2 includes the following steps: S2-1. First, the three electrodes are charged to a cut-off voltage by a current with a small charging rate, and the positive and negative electrode potentials are monitored in intervals; S2-2. Then, the three electrodes are discharged at a constant current by a current of a small discharge rate, and then the charge rate is slightly increased to charge the three electrodes at a constant current to a cut-off voltage, and the positive and negative electrode potentials are monitored in intervals; S2-3. Repeat step S2-2 until the negative electrode potential is less than or equal to 0 V when the SOC is charged below 50% at a certain charging rate, and then stop the test.

3. The method according to claim 2, characterized in that In step S2-1, the charging rate is 0.33-0.6C.

4. The method according to claim 2, characterized in that: In step S2-2, the interval between two adjacent charging rates is 0.4-0.6C.

5. The method according to any one of claims 1 to 4, characterized in that: Step S3 includes the following steps: S3-1. Based on the data obtained in step S2, a scatter plot of the charge rate and the negative electrode potential at different SOCs is plotted, with the charge rate as the x-axis and the negative electrode potential as the y-axis; a linear fit is then performed on the scatter plot of the charge rate and the negative electrode potential at different SOCs, and the fitting formula is y=kx+b, to obtain a linear relationship diagram of the charge rate and the negative electrode potential at different SOCs; S3-2. In the linear relationship diagram between the charge rate and the negative electrode potential at different SOCs, let y = 0 of the linear fitting curve y = kx + b at different SOCs, and obtain x = -b / k corresponding to the linear fitting curve y = kx + b at different SOCs, where x = -b / k is the charge rate when the metal potential is deposited at the negative electrode, and is also the maximum charge rate at the SOC; then, a scatter plot of the SOC and the maximum charge rate is drawn with the maximum charge rate as the X-axis and the SOC as the Y-axis; then, a polynomial fitting is performed on the scatter plot of the SOC and the maximum charge rate, and the fitting formula is Y = aX 2 +bX+c, to obtain the fitting relationship diagram between SOC and maximum charging rate; S3-3. A battery fast charging system is formulated based on the fitting relationship diagram between the SOC and the maximum charging rate, wherein the charging rate adopted at different SOCs in the battery fast charging system is less than or equal to the maximum charging rate, and greater than or equal to 0.9-0.95 times the maximum charging rate.

6. The method according to claim 5, characterized in that In step S3-1, the SOC ranges from 10% to 90%.

7. The method according to claim 5, characterized in that In step S3-1, the interval between two adjacent SOCs is 0.5-12%.

8. The method according to claim 1, characterized in that In step S3, after formulating the battery fast charging system, the following steps are also included: verifying the battery fast charging system.

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