Novel lithium battery matching method

Abstract

The invention provides a novel lithium battery matching method which comprises the following steps: performing high-temperature aging treatment on a new battery for 7 days, then storing the battery in a discharge state process for 13 days, testing the voltage, and matching the batteries with the voltage gears of 2700-2800mv and 2800-2900mv; the aging treatment comprises the following steps of: fully charging to 3.65 v at the current of 0.5 c, stopping the current of 0.05 c, discharging to 2.0 v at the current of 0.5 c, stopping discharging, standing the battery for 24 hours, testing the voltage, aging for 7 days at the temperature of 45 DEG C, standing for 24 hours, and testing the voltage. The invention also provides a novel lithium battery matching method, which comprises the following steps: carrying out capacity grading on new batteries: carrying out a 0.5 c current charge and discharge test, identifying a discharge platform according to a charge and discharge curve, and matching the batteries with the discharge platform time of 0-4 minutes. According to the invention, the difference between single batteries is small, and the grouped batteries have higher utilization efficiency.

Description

Technical Field

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

[0002] Lithium batteries are widely used in various fields as an important power source for digital products, high-end instruments, new energy vehicles and other products. When using lithium batteries, they are usually combined in multiple strings and parallels (i.e., grouping) to achieve the voltage platform and power requirements. Therefore, it is important that each single battery in a group of power supplies can achieve maximum utilization efficiency, so as to effectively ensure the actual nominal capacity and charging and discharging efficiency, and maximize the utilization efficiency of the battery pack. After the lithium battery is produced, it can be grouped. Generally, a single battery cell is grouped according to the three parameters of CRV (capacity, internal resistance, and voltage). As a result, when the module is assembled, the charging voltage difference and discharge voltage difference of a single string are often large, resulting in the battery stopping charging and discharging due to the voltage difference of the same group of batteries before reaching the maximum capacity, and the actual capacity requirements cannot be met, and the battery efficiency is not high. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a novel lithium battery assembly method, which solves the problems that may occur in battery assembly in the prior art.

[0004] According to an embodiment of the present invention, a novel lithium battery assembly method is provided, wherein the new battery is subjected to a 7-day high-temperature aging treatment, and then the battery is stored in a discharge state for 13 days and the voltage is tested, and batteries with voltage levels of 2700-2800mv and 2800-2900mv are assembled; the aging treatment comprises the steps of: fully charging to 3.65v with a 0.5c current, cutting off the current with a 0.05c current, and then discharging to 2.0v with a 0.5c current, stopping the discharge, and testing the voltage after the battery has been allowed to stand for 24 hours, and then aging at 45°C for 7 days, and testing the voltage after standing for 24 hours.

[0005] Furthermore, the average daily voltage drop of the battery during storage in the discharged state process is less than 0.75mv.

[0006] According to the embodiment, a novel lithium battery grouping method is also provided, in which new batteries are divided into different capacities: a 0.5C current charge and discharge test is performed, a discharge platform is identified according to the charge and discharge curve, and batteries with a discharge platform time of 0-4 minutes are grouped.

[0007] Furthermore, the discharge platform is 3.1V.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] Through high-temperature aging storage or capacity division, 0.5C current charge and discharge test is adopted in the process. The first method pairs the batteries with voltage range of 2700-2800mv and 2800-2900mv, and the second method pairs the electromagnetic with voltage platform time between 0-4min. Both ensure that the difference between individual batteries is small and the paired batteries have greater utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A battery curve diagram of an embodiment of the present invention;

[0011] Figure 2 A comparison diagram of discharge curves of batteries of different batches of samples according to an embodiment of the present invention;

[0012] Figure 3 It is a scatter diagram of discharge time data on different voltage platforms of an embodiment of the present invention;

[0013] Figure 4 4 groups of 8S1P module diagrams according to an embodiment of the present invention. DETAILED DESCRIPTION

[0014] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0015] The present embodiment provides a novel lithium battery assembly method, which is subjected to high-temperature aging treatment, and then the battery is stored in a discharged state (referring to the battery being discharged to a cut-off voltage of 2.0V in the last step of the charging and discharging process and then stopping discharging, and the process is ended) for 13 days, and batteries with a small daily voltage drop during the storage period are selected for configuration, specifically including batteries with voltage levels of 2700-2800mv and 2800-2900mv. In more detail, the aging treatment includes the steps of: fully charging to 3.65v with a current of 0.5c, cutting off the current of 0.05c, and then discharging to 2.0v with a current of 0.5c and then stopping discharging, the battery is left to stand for 24 hours and then the voltage is tested, and then aged at 45°C for 7 days, and the voltage is tested after standing for 24 hours.

[0016] Furthermore, the following table shows the comparison of battery voltage drops at different charged states:

[0017]

[0018] From the above table, it can be seen that the voltage drop of the battery with a voltage of 2600-2700mv in the discharge state is large during storage, but the voltage drop of the battery in this voltage range is not significantly different from that of the battery in other voltage ranges after being charged (i.e., charged state, which means that the battery undergoes the prescribed charging process after charge-discharge and then completes all processes). If the battery is stored with a certain amount of electricity and self-discharge is selected, the battery with large self-discharge in this range cannot be selected. If it is used in a combination module, there will be a great quality hazard. Therefore, it is not suitable for use in a battery combination module, that is, it is not suitable for battery matching; while the voltage ranges of 2700-2800mv and 2800-2900mv have a smaller daily average voltage drop, both less than 0.75mv. Selecting batteries with voltage ranges of 2700-2800mv and 2800-2900mv for matching can improve the efficiency of the battery.

[0019] In another embodiment, a novel lithium battery grouping method is provided, which uses a 0.5C current charge and discharge test for capacity division. During the battery charge and discharge process, due to differences in materials or process environment and other related aspects, the performance of each battery during the charge and discharge process is not completely consistent, which is particularly prominent during the charge and discharge process. When this difference becomes larger, it will affect the overall performance of the same group of modules, such as Figure 1 The battery charge and discharge curves are shown. Figure 1 The red vertical line in the middle is the dividing line between constant current and constant voltage charging, and the red box area is the characteristic discharge platform (during the discharge process, when the constant current discharge reaches a certain voltage, the voltage will suddenly accelerate the downward trend if the same current discharge is continued. The voltage before the acceleration is called the characteristic discharge platform). Figure 1 It can be seen that different batteries have different discharge curves. For example, if the discharge characteristic platform time is very different, then when the battery packs with different differences are charged and discharged on the same module, the voltages of different batteries will be different, resulting in a larger voltage difference between different strings. When it is large to a certain extent, it will seriously affect the performance of the module and the nominal capacity cannot be effectively discharged.

[0020] Figure 2The comparison of battery discharge curves of different batches of samples is shown (the horizontal axis unit is mv, the vertical axis unit is min). When the battery is discharged, the discharge voltage curve drops from about 3.4v (defined as V1) to 2.0v (defined as V3). The discharge curve first decreases in a steady and slow trend. After it decreases to a certain point, the voltage will show an obvious steep drop trend. At a certain point when the voltage begins to drop sharply, we define the voltage at this point as the platform voltage V2 of the battery. The time for the battery voltage to discharge from V1 to V2 is defined as the platform of the battery. First, the platform voltage of the battery is identified. After the platform voltage of the battery is determined, the discharge platform is controlled to achieve the goal of consistent battery discharge curves. In other words, the initial discharge voltage of the battery can be determined, and then the discharge time of the battery to a certain voltage can be controlled to determine the discharge curve of the battery. By controlling the consistency of this discharge time, it can be determined that the discharge curve of the battery is consistent.

[0021] Further comparison of discharge time data at different voltage platforms: From the data scatter diagram ( Figure 3 As shown in the distribution, the closer the voltage value is to 2.0v, the discharge time tends to the discharge time of the cut-off voltage. The collected discharge time data at different voltage cut-off points are compared with the discharge data. It can be seen that when the cut-off voltage is 3.0v and 2.8v, the correlation between the cut-off time and the discharge time is relatively strong. The voltage with a relatively strong correlation is used as the cut-off point, and the grading is not very meaningful. The purpose of grouping is to eliminate the differences of batteries and put battery groups with consistent performance together. According to the original intention of grouping, if 3.2v is used as the battery discharge node, it will cause excessive selection of batteries and is unnecessary. Therefore, 3.1v is a more appropriate position for the platform voltage. Therefore, in the process of using 0.5c current capacity division, the 3.1v discharge platform is a more appropriate reference point.

[0022] Furthermore, through the combination of batteries (using 8S1P) with different discharge platform times, it is verified that this structure has very high requirements for battery performance. Figure 4 Four groups of 8S1P modules are shown, 1#-4# respectively. The single-cell single-string platform discharge characteristic curve in each group of modules is shown. The four groups of modules are charged and discharged 8 times at 0.5c. The dynamic pressure difference test data between each string each time is as follows (the unit of platform time is minutes, and the unit of pressure difference is mv):

[0023]

[0024] From the test data of the above four groups of different discharge platform time combinations, it can be seen that the discharge voltage difference of the combination cells with the closest platform time is the smallest (3#, 4# combination), and the discharge voltage difference of the combination cells with large platform time difference is larger (1#, 2# combination). The determining factor of the combined module capacity is the capacity that can be discharged when the single string voltage reaches the protection voltage first and the discharge is cut off. Therefore, the smaller the dynamic voltage difference between the strings, the more each string battery can be discharged as much as possible, and the closer it is to the actual capacity of the cell, thereby improving the actual discharge efficiency.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A novel lithium battery assembly method, characterized in that: The new battery is subjected to a 7-day high-temperature aging treatment, and then the battery is stored in a discharge state for 13 days and the voltage is tested, and the batteries with voltage levels of 2700-2800mv and 2800-2900mv are grouped; the aging treatment includes the steps of: fully charging to 3.65v with a current of 0.5c, cutting off the current of 0.05c, and then discharging to 2.0v with 0.5c and stopping the discharge, the battery is left to stand for 24 hours and the voltage is tested, and then aged at 45°C for 7 days, and the voltage is tested after standing for 24 hours.

2. The novel lithium battery assembly method as described in claim 1, wherein the average daily voltage drop of the battery during storage in a discharged state is less than 0.75 mv.

3. A novel lithium battery assembly method, characterized in that: New batteries are divided into different capacities: 0.5C current charge and discharge test, the discharge platform is identified according to the charge and discharge curve, and the batteries with a discharge platform time of 0-4min are grouped.

4. The novel lithium battery assembly method as described in claim 3, wherein the discharge platform is 3.1V.

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