A lithium battery charging method suitable for a large temperature window

Abstract

The application belongs to the technical field of lithium batteries, and relates to a lithium battery charging method suitable for a large temperature window. The lithium battery charging method comprises the following steps: performing constant-current charging on the lithium battery at a first current value to make the voltage of the lithium battery reach a first upper limit voltage value; performing constant-current charging on the lithium battery at a second current value to make the voltage of the lithium battery rise from the first upper limit voltage value to a second upper limit voltage value; and performing constant-current constant-voltage charging on the lithium battery at a third current value to make the voltage of the lithium battery rise from the second upper limit voltage value to a third upper limit voltage value, and the charging current of the lithium battery is cut off at a preset current value; wherein the first current value, the second current value, the third current value and the preset current value decrease in sequence. The application can retain the fast charging efficiency while maintaining normal charging, avoid performance deterioration of the lithium battery, and meet the charging demand of a large temperature window.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a lithium battery charging method applicable to a large temperature window. Background Technology

[0002] Lithium-ion batteries are a type of battery that uses lithium metal or lithium alloys as the positive / negative electrode materials and a non-aqueous electrolyte solution. Lithium-ion batteries are widely used in various electronic products.

[0003] The existing charging methods for lithium batteries are mainly one-step constant current and constant voltage direct charging, and multi-step charging in stages, namely stepped voltage boost fast charging.

[0004] Constant current and constant voltage direct charging generally uses a smaller charging current and takes a longer time to fully charge, typically 2-4 hours, which cannot meet the needs of fast charging.

[0005] Existing stepped-boost fast charging methods, in pursuit of higher charging efficiency, operate at high current density throughout the entire charging process. At high temperatures, the heat generated during charging becomes excessively concentrated, causing the internal temperature of the lithium battery to rise too high, which can damage the positive electrode material structure and lead to poor cycle performance. At low temperatures, the activity of the positive electrode material decreases, making it difficult for lithium ions to effectively migrate and embed into the negative electrode graphite. This results in excessive lithium ion accumulation on the graphite surface, leading to lithium plating during charging and further degrading battery performance. Therefore, different charging methods are used to charge lithium batteries in different temperature windows, such as 15–25°C, 25–35°C, and 35–45°C, to ensure normal battery use and high charging efficiency. However, the charging methods used in these temperature windows only meet the normal charging and fast charging requirements of lithium batteries within their respective temperature windows, and cannot meet the charging needs in other temperature windows. This limitation by ambient temperature makes it difficult to achieve high charging efficiency for lithium batteries in a wider temperature range. Summary of the Invention

[0006] The purpose of this invention is to provide a lithium battery charging method with a large temperature window that is less limited by ambient temperature.

[0007] To address the aforementioned technical problems, embodiments of the present invention provide a lithium battery charging method applicable to a large temperature window, employing the following technical solution:

[0008] The lithium battery charging method includes the following steps:

[0009] The lithium battery is charged at a constant current rate of the first multiple, so that the voltage of the lithium battery reaches the first upper limit voltage value.

[0010] The lithium battery is charged at a constant current value at a second rate, so that the voltage of the lithium battery rises from the first upper limit voltage value to the second upper limit voltage value.

[0011] The lithium battery is charged with constant current and constant voltage at a third rate current value, so that the voltage of the lithium battery rises from the second upper limit voltage value to the third upper limit voltage value, and the charging current of the lithium battery is cut off at a preset current value.

[0012] Among them, the first multiplier current value, the second multiplier current value, the third multiplier current value, and the preset current value decrease sequentially.

[0013] In some preferred embodiments, the first rate current value is 0.9nC to 1.1nC, where C is the capacity of the lithium battery and n is the rate.

[0014] In a preferred embodiment of some examples, the second multiplier current value is 0.65nC to 0.75nC.

[0015] In some preferred embodiments, the third rate current value is 0.45nC to 0.55nC.

[0016] In some preferred embodiments, the preset current value is 0.11nC to 0.13nC.

[0017] In a preferred embodiment of some embodiments, before the lithium battery is charged at a constant current rate to bring its voltage to a first upper limit voltage value, the lithium battery charging method further includes the following steps:

[0018] The appropriate charging current for a lithium battery is determined based on the kinetic properties of the lithium battery raw materials. Then, the first upper limit voltage and the first rate current are determined by combining the voltage and charging current at which lithium plating occurs under preset temperature and preset cycle number conditions.

[0019] In a preferred embodiment of some embodiments, before the lithium battery is charged at a constant current rate to raise its voltage from a first upper limit voltage value to a second upper limit voltage value, the lithium battery charging method further includes the following steps:

[0020] Based on the voltage value at which lithium plating occurs in the lithium battery under preset temperature and preset cycle number conditions, the first upper limit voltage value is increased as the second upper limit voltage value to be determined.

[0021] Based on the charging current of the lithium battery under preset temperature and preset cycle number conditions when lithium plating occurs, and combined with the second upper limit voltage value to be determined, the final second upper limit voltage value and second rate current value are adjusted and determined.

[0022] In a preferred embodiment, before the lithium battery is charged at a constant current and constant voltage rate at a third multiple of the current value, causing the lithium battery voltage to rise from a second upper limit voltage value to a third upper limit voltage value, and before the lithium battery charging current is cut off at a preset current value, the lithium battery charging method further includes the following steps:

[0023] Based on the material properties of lithium batteries and the voltage value at which lithium plating occurs under preset temperature and preset cycle number conditions, the second upper limit voltage value is adjusted upward as the third upper limit voltage value.

[0024] The third upper limit voltage value and the charging current that causes lithium plating in the lithium battery under preset temperature and preset cycle number conditions are used to determine the third rate current value and the preset current value.

[0025] In some preferred embodiments, the first upper limit voltage value is U-0.1V, the second upper limit voltage value is U, and the third upper limit voltage value is U+0.05V, where U is the rated voltage value of the lithium battery.

[0026] In some preferred embodiments, the large temperature window is 15°C to 45°C.

[0027] Compared with the prior art, the lithium battery charging method applicable to a large temperature window provided by the embodiments of the present invention has the following main advantages:

[0028] This lithium battery charging method charges the battery in stages using progressively decreasing current rates and progressively increasing upper voltage limits. The first stage uses a first-rate current to charge the lithium battery at a constant current until the voltage reaches the first upper voltage limit. The second stage uses a second-rate current to charge the lithium battery at a constant current until the voltage rises from the first upper voltage limit to the second upper voltage limit. The third stage uses a third-rate current to charge the lithium battery at a constant current and voltage until the voltage rises from the second upper voltage limit to the third upper voltage limit. The charging current is cut off at a preset current value, thus maintaining high charging efficiency while ensuring normal charging, preventing performance degradation of the lithium battery, and meeting the charging requirements across a wide temperature window. Attached Figure Description

[0029] To more clearly illustrate the solutions in this invention, a brief introduction to the accompanying drawings used in the description of the embodiments will be provided below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort. Wherein:

[0030] Figure 1 This is a flowchart of the lithium battery charging method of the present invention;

[0031] Figure 2 This is a flowchart illustrating the specific process of the lithium battery charging method of the present invention.

[0032] Figure 3 This is a chart showing the capacity retention rate of lithium batteries under existing stepped boost fast charging.

[0033] Figure 4 This is a chart showing the thickness increase rate of lithium batteries under existing stepped boost fast charging.

[0034] Figure 5 This is a graph showing the capacity retention rate of a lithium battery under the lithium battery charging method of the present invention.

[0035] Figure 6 This is a graph showing the thickness increase rate of the lithium battery under the lithium battery charging method of the present invention.

[0036] Specific implementation party

[0037] With increasingly extreme global temperatures, it has become the norm for indoor temperatures to reach 40°C in summer and drop to 20°C in winter. Due to manufacturing cost limitations, existing lithium batteries cannot be equipped with high-precision intelligent temperature sensors to regulate charging methods and thus meet the charging requirements of lithium batteries.

[0038] Therefore, this application provides a lithium battery charging method applicable to a large temperature window, which can meet the charging requirements of lithium batteries under a large temperature window, specifically, it can meet the requirements of safe and fast charging under a large temperature window of 15℃ to 45℃.

[0039] refer to Figure 1 The lithium battery charging method of this application includes the following steps:

[0040] S20. Charge the lithium battery with a constant current at a first rate current value until the lithium battery voltage reaches the first upper limit voltage value.

[0041] S50. The lithium battery is charged at a constant current value with a second rate, so that the voltage of the lithium battery rises from the first upper limit voltage value to the second upper limit voltage value.

[0042] S80. The lithium battery is charged with constant current and constant voltage at a third rate current value, so that the voltage of the lithium battery rises from the second upper limit voltage value to the third upper limit voltage value, and the charging current of the lithium battery is cut off at a preset current value.

[0043] Among them, the first multiplier current value, the second multiplier current value, the third multiplier current value and the preset current value decrease sequentially.

[0044] The lithium battery charging method of this application charges the battery in stages using progressively decreasing current rates. In the first stage, the lithium battery is charged with a constant current at a first current rate until the voltage reaches a first upper limit voltage value. In the second stage, the lithium battery is charged with a constant current at a second current rate until the voltage rises from the first upper limit voltage value to the second upper limit voltage value. In the third stage, the lithium battery is charged with a constant current and constant voltage at a third current rate until the voltage rises from the second upper limit voltage value to the third upper limit voltage value. The charging current of the lithium battery is cut off at a preset current value, which can maintain the efficiency of fast charging while maintaining normal charging, avoiding the deterioration of lithium battery performance, and meeting the charging requirements of a wide temperature window.

[0045] refer to Figure 2 Before step S20, when the lithium battery is charged at a constant current rate to the first upper limit voltage value, the lithium battery charging method further includes the following steps:

[0046] S10. Determine the appropriate charging current for the lithium battery based on the kinetic properties of the lithium battery raw materials. Combine the voltage and charging current at which lithium plating occurs under preset temperature and preset cycle number conditions to determine the first upper limit voltage and the first rate current.

[0047] The rechargeable current of a lithium battery is determined based on the kinetic properties of its raw materials, ensuring safe charging of the subsequently determined first rate current and first upper limit voltage. Furthermore, using different charging currents may lead to lithium plating at a preset temperature, degrading the battery's performance. This application obtains the charging current at which lithium plating occurs by charging the lithium battery at a preset temperature for a preset number of cycles, and determines the first rate current value based on the aforementioned rechargeable current, enabling safe charging of the lithium battery without lithium plating.

[0048] Meanwhile, to balance the fast charging efficiency of lithium batteries, the first upper limit voltage is adjusted based on the voltage value corresponding to lithium plating when the lithium battery reaches a preset number of charging cycles at a preset temperature. The first rate current value is also adjusted accordingly to determine the final first upper limit voltage and first rate current values. This ensures that the charging performance of the lithium battery does not deteriorate at the preset temperature, meaning the charging performance is normal and a high fast charging efficiency can be achieved at that temperature. The preset temperature is selected as a temperature within a large temperature window, such as 15℃, 30℃, and 45℃ within a large temperature window of 15℃~45℃.

[0049] Specifically, the first rate current value is 0.9nC to 1.1nC, where C is the capacity of the lithium battery and n is the rate. The rate n is determined by the kinetic properties of the lithium battery raw materials. Depending on the material, the appropriate charging rate for the corresponding lithium battery material can be determined, thus determining the value of n. For example, if the lithium battery material is suitable for 2C charging, then n is 2.

[0050] Preferably, in this embodiment, the first rate current value is 1nC. The first upper limit voltage value is U-0.1V, where U is the rated voltage of the lithium battery. If the first rate current value is less than 0.9nC, the efficiency of the lithium battery will decrease. If the first rate current value is greater than 1.1nC, the charging current is too high. When the lithium battery is under high-temperature conditions within a large temperature window (e.g., a preset number of charge cycles at 45°C within a 15°C to 45°C temperature window), the charging temperature rise will be too high, affecting the performance of the lithium battery. Conversely, when the lithium battery is under low-temperature conditions within a large temperature window (e.g., a preset number of charge cycles at 15°C within a 15°C to 45°C temperature window), the ion migration rate in the lithium battery will decrease, affecting the performance of the lithium battery. Furthermore, when the corresponding first rate current value is 0.9nC to 1.1nC, if the first upper limit voltage value is lower than U-0.1V, the efficiency of the lithium battery will decrease. If it is higher than U-0.1V, the lithium battery will be under high temperature conditions in a large temperature window, such as 45℃ in the 15℃ to 45℃ temperature window, and the charging performance of the lithium battery will deteriorate after a preset number of cycles. Therefore, by using 0.9nC to 1.1nC for the first rate current value and U-0.1V for the first upper limit voltage value, the constant current charging of the lithium battery in the first stage can maintain safe and fast charging in a large temperature window while ensuring normal performance of the lithium battery.

[0051] refer to Figure 2 In step S50, the lithium battery is charged at a constant current rate of the second multiple, causing the voltage of the lithium battery to rise from the first upper limit voltage value to the second upper limit voltage value. The lithium battery charging method also includes the following steps:

[0052] S30. Based on the voltage value at which lithium plating occurs in the lithium battery under preset temperature and preset cycle number conditions, the first upper limit voltage value is increased as the second upper limit voltage value to be determined.

[0053] S40. Based on the charging current of the lithium battery under preset temperature and preset cycle number conditions when lithium plating occurs, and in conjunction with the second upper limit voltage value to be determined, adjust and determine the final second upper limit voltage value and the second rate current value.

[0054] This application uses an upward adjustment of the first upper limit voltage value as the second upper limit voltage value to be determined. At this second upper limit voltage value, the lithium battery will not undergo lithium plating under preset temperature and preset cycle number conditions. Further, by combining the charging current that causes lithium plating under the preset temperature and preset cycle number conditions, a second rate current value to be determined is obtained. The second upper limit voltage value and the second rate current value to be determined are then further adjusted to determine the final second upper limit voltage value and second rate current value. This ensures that in the second stage, the lithium battery is charged at a constant current using the second rate current value, and the lithium battery voltage rises from the first upper limit voltage value to the second upper limit voltage value. Under the preset temperature and preset cycle number conditions, lithium plating will not occur. The lithium battery can achieve high charging efficiency in the second stage while ensuring normal charging.

[0055] The heat generated during the lithium battery charging process mainly comes from physical heat generation, i.e., Q = I. 2 *R and Q represent the heat generated, I is the charging current, R is the resistance of the lithium battery, and t is the charging time. Under otherwise constant conditions, the higher the charging current, the greater the heat generated. Since the second-rate current value is lower than the first-rate current value, it is safe to use the second-rate current value for constant current charging of the lithium battery, provided that charging at the first-rate current is safe. Therefore, constant current charging of the lithium battery at the second-rate current value allows for safe charging without lithium plating.

[0056] Specifically, the second rate current value is 0.65nC to 0.75nC, where C is the capacity of the lithium battery and n is the factor. Preferably, in this embodiment, the second rate current value is 0.7nC. The second upper limit voltage value is UV, where U is the rated voltage of the lithium battery.

[0057] Specifically, if the second-rate current value is less than 0.65nC, the efficiency of the lithium battery will decrease. If the second-rate current value is higher than 0.75nC, the charging current is too high. When the lithium battery is under high-temperature conditions within a large temperature window, such as cycling at 45°C within a temperature window of 15°C to 45°C for a preset number of times, the charging temperature rise will be too high, affecting the performance of the lithium battery. When the lithium battery is under low-temperature conditions within a large temperature window, such as cycling at 15°C within a temperature window of 15°C to 45°C for a preset number of times, the ion migration rate in the lithium battery will decrease, affecting the performance of the lithium battery. Furthermore, when the corresponding second rate current value is 0.65nC to 0.75nC, if the second upper limit voltage value is lower than UV, the efficiency of the lithium battery will decrease. If it is higher than UV, the lithium battery will be under high temperature conditions in a large temperature window, such as 45°C in the 15°C to 45°C temperature window, and the charging performance of the lithium battery will deteriorate after a preset number of charge cycles. Therefore, by using the second rate current value of 0.65nC to 0.75nC and the first upper limit voltage value of UV, the second stage constant current charging of the lithium battery can maintain safe and fast charging in a large temperature window while ensuring normal lithium battery performance.

[0058] refer to Figure 2 In step S80, the lithium battery is charged at a constant current and constant voltage using a third-rate current value, causing the lithium battery voltage to rise from the second upper limit voltage value to the third upper limit voltage value, and the charging current of the lithium battery is cut off before the preset current value is reached. The lithium battery charging method also includes the following steps:

[0059] S60. Based on the material characteristics of the lithium battery and the voltage value at which lithium plating occurs under preset temperature and preset cycle number conditions, the second upper limit voltage value is increased as the third upper limit voltage value.

[0060] S70. Based on the third upper limit voltage value and the charging current at which lithium plating occurs in the lithium battery under preset temperature and preset cycle number conditions, determine the third rate current value and the preset current value.

[0061] Regarding the third upper limit voltage value, it is determined first by the rated voltage of the lithium battery based on the characteristics of its raw materials, and then by the voltage at which lithium battery does not undergo lithium plating under preset charging temperature and preset cycle numbers. When the third upper limit voltage value exceeds a certain limit, an irreversible reaction of lithium battery positive electrode structure collapse will occur. Therefore, based on the material characteristics of lithium battery and the voltage at which lithium plating occurs under preset temperature and preset cycle numbers, it can be ensured that irreversible damage and lithium plating will not occur during the charging process of the lithium battery.

[0062] Regarding the third rate current value and the preset current value, the third rate current value and the preset current value are determined by adjusting the charging current when lithium plating occurs in the lithium battery under preset temperature and preset cycle number conditions. This allows the lithium battery to have higher charging efficiency in the third stage and ensures normal charging performance.

[0063] Since the first, second, and third rate current values ​​decrease sequentially, charging the lithium battery with the third rate current value under constant current and constant voltage conditions can also ensure that the lithium battery is charged safely and without lithium plating.

[0064] In this embodiment, the lithium battery is charged with constant current and constant voltage at a third rate current value, causing the lithium battery voltage to rise from the second upper limit voltage value to the third upper limit voltage value, and the charging current of the lithium battery is cut off at a preset current value. The specific charging process is as follows: the lithium battery is charged with constant current at a third rate current value, causing the lithium battery voltage to rise from the second upper limit voltage value to the third upper limit voltage value, and the lithium battery is charged with constant voltage at the third upper limit voltage value, causing the lithium battery current to decrease to the preset charging current.

[0065] Specifically, the third rate current value is 0.45nC to 0.55nC, and the preset current value is 0.12C, where C is the capacity of the lithium battery and n is the multiple. Preferably, in this embodiment, the third rate current value is 0.5nC. The third upper limit voltage value is U + 0.05V, where U is the rated voltage of the lithium battery.

[0066] Specifically, the third upper limit voltage value is U+0.05V, and the preset current value is 0.12C. If the third rate current value is less than 0.45nC, the efficiency of the lithium battery will decrease. If the third rate current value is higher than 0.55nC, the charging current is too high. Under high-temperature conditions within a large temperature window, such as cycling at 45°C within the 15°C to 45°C temperature window for a preset number of times, the charging temperature rise will be too high, affecting the performance of the lithium battery. Under low-temperature conditions within a large temperature window, such as cycling at 15°C within the 15°C to 45°C temperature window for a preset number of times, the ion migration rate in the lithium battery decreases, affecting the performance of the lithium battery, and it is difficult to maintain normal charging under low-temperature conditions. Furthermore, with the third rate current value set at 0.45nC to 0.55nC and the preset current value at 0.12C, if the second upper limit voltage value is lower than U+0.05V, the efficiency of the lithium battery will decrease; if it is higher than U+0.05V, it will damage the structure of the lithium battery itself.

[0067] Therefore, by setting the third rate current value to 0.45nC to 0.55nC, the third upper limit voltage value to U+0.05V, and the preset current value for charging cutoff to 0.12C, the third stage constant current charging of the lithium battery can maintain safe and fast charging while ensuring normal lithium battery performance within a wide temperature window.

[0068] refer to Figure 3 and Figure 4 , Figure 3 This chart shows the capacity retention of lithium batteries after being charged using existing charging methods at 15°C for 1000 cycles. Figure 4 This chart shows the thickness increase rate of lithium batteries after being charged using existing charging methods under 1000 cycles at 15°C. Figure 5 The graph shows the capacity retention rate of the lithium battery obtained after charging it using the lithium battery charging method of this application under the condition of 1000 cycles at 15°C. Figure 6 This chart shows the thickness increase rate of lithium batteries obtained after charging them using the lithium battery charging method of this application under 1000 cycles at 15°C. As can be seen from the chart, compared to existing charging methods, the lithium battery charging method of this application results in higher capacity retention, lower thickness increase, and normal charging of the lithium battery.

[0069] The lithium battery charging method of the present invention will be described in detail below through specific examples. Taking the charging of a lithium battery with a rated voltage of 4.4V at a 1C rate as an example, the charging method is as follows:

[0070] Phase 1: Charge the lithium battery at a constant current of 1C to raise its voltage to 4.3V.

[0071] The second stage: The lithium battery is charged at a constant current of 0.7C to increase the voltage of the lithium battery from 4.3V to 4.4V.

[0072] The third stage: The lithium battery is charged at a constant current of 0.5C to raise its voltage from 4.4V to 4.45V. Then, the lithium battery is charged at a constant voltage of 4.45V until the charging current drops to 0.12C, at which point charging stops.

[0073] Taking the charging of a lithium battery with a rated voltage of 4.45V at a 1.5C rate as an example, the charging method is as follows:

[0074] First stage: Charge the lithium battery with a constant current of 1.5C to raise the voltage of the lithium battery to 4.35V.

[0075] The second stage: The lithium battery is charged at a constant current of 1.0C to increase the voltage of the lithium battery from 4.35V to 4.45V.

[0076] The third stage: The lithium battery is charged at a constant current of 0.8C to raise its voltage from 4.45V to 4.5V. Then, it is charged at a constant voltage of 4.5V until the charging current drops to 0.12C, at which point charging stops.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A lithium battery charging method suitable for a large temperature window, characterized in that, The large temperature window is 15℃~45℃, and the lithium battery charging method includes the following steps: The lithium battery is charged at a constant current with a first rate current value to bring the lithium battery voltage to a first upper limit voltage value. The first rate current value is 0.9nC~1.1nC, where C is the capacity of the lithium battery and n is the rate. The first upper limit voltage value is U-0.1V, where U is the rated voltage value of the lithium battery. The lithium battery is charged at a constant current value at a second rate, so that the voltage of the lithium battery rises from a first upper limit voltage value to a second upper limit voltage value, wherein the second rate current value is 0.65nC~0.75nC; The lithium battery is charged with a constant current and constant voltage at a third rate current value, so that the voltage of the lithium battery rises from the second upper limit voltage value to the third upper limit voltage value, and the charging current of the lithium battery is cut off at a preset current value. The third rate current value is 0.45nC~0.55nC, the preset current value is 0.11nC~0.13nC, the second upper limit voltage value is U, and the third upper limit voltage value is U+0.05V. Among them, the first multiplier current value, the second multiplier current value, the third multiplier current value, and the preset current value decrease sequentially; The lithium battery charging method further includes the following steps before the lithium battery is charged at a constant current rate to reach a first upper limit voltage value: The appropriate charging current for a lithium battery is determined based on the kinetic properties of the lithium battery raw materials. Then, the first upper limit voltage and the first rate current are determined by combining the voltage and charging current at which lithium plating occurs under preset temperature and preset cycle number conditions.

2. The lithium battery charging method of claim 1, wherein, Before the lithium battery is charged at a constant current rate of the second multiple to raise its voltage from the first upper limit voltage value to the second upper limit voltage value, the lithium battery charging method further includes the following steps: Based on the voltage value at which lithium plating occurs in the lithium battery under preset temperature and preset cycle number conditions, the first upper limit voltage value is increased as the second upper limit voltage value to be determined. Based on the charging current of the lithium battery under preset temperature and preset cycle number conditions when lithium plating occurs, and combined with the second upper limit voltage value to be determined, the final second upper limit voltage value and second rate current value are adjusted and determined.

3. The lithium battery charging method of claim 1, wherein, The lithium battery charging method further includes the following steps: Charging the lithium battery at a constant current and constant voltage rate (third multiple of the current value) to raise the lithium battery voltage from the second upper limit voltage value to the third upper limit voltage value, and before the lithium battery charging current is cut off at a preset current value. Based on the material properties of lithium batteries and the voltage value at which lithium plating occurs under preset temperature and preset cycle number conditions, the second upper limit voltage value is adjusted upward as the third upper limit voltage value. The third upper limit voltage value and the charging current that causes lithium plating in the lithium battery under preset temperature and preset cycle number conditions are used to determine the third rate current value and the preset current value.

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