A method for improving voltage consistency in a silicone system

Abstract

The application discloses a method for improving voltage consistency of a silicon-oxygen system, comprising the following steps: selecting a battery cell with a determined silicon-oxygen ratio; selecting different cut-off voltages according to a discharge curve, and performing constant-current and constant-voltage charging and discharging to corresponding potentials on a blue cabinet; collecting voltage data after 24 hours of standing, and calculating voltage drop; determining a cut-off voltage with stable and small voltage drop; and performing small-batch testing after combining the cut-off voltage with delivery voltage requirements. The voltage range of the application can be reduced to at least 5 mV, the individual differences of the battery cell are reduced, the voltage consistency is improved, the long-term storage power consumption is small, the battery cell overcharging is prevented, the battery cell aging is delayed, the cycle performance is improved, and the long-term storage power consumption is small.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a method for improving the voltage uniformity of silicon-oxygen systems. Background Technology

[0002] Lithium-ion batteries exhibit inherent differences between individual cells after production. These differences widen with increasing charge-discharge cycles, eventually leading to some cells being undercharged while others are overcharged. Therefore, lithium batteries must undergo equalization before leaving the factory to ensure consistent intrinsic characteristics among individual cells. Voltage is one of the battery's intrinsic parameters, and equalization manifests as voltage balancing, which improves system capacity, alters DOC depth, and enhances battery efficiency. However, existing lithium-ion batteries, after normal sorting, exhibit significant voltage variations, failing to meet requirements. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving the voltage consistency of silicon-oxygen systems by reducing individual cell differences and improving voltage consistency.

[0004] The objective of this invention is achieved through the following technical solution: a method for improving voltage uniformity in silicon-oxygen systems, comprising the following steps.

[0005] 1) Assemble battery cells with different silicon-oxygen ratios;

[0006] 2) Select negative electrode materials with a determined silicon-oxygen ratio, assemble them into coin cells, and discharge them on a battery testing system to obtain discharge curves;

[0007] 3) Perform a three-electrode test to determine the negative electrode potential corresponding to the production line cutoff voltage when the full battery is charged;

[0008] 4) Select the battery cell with the silicon-oxygen ratio determined in step 2;

[0009] 5) Select different cutoff voltages based on the button discharge curve and its corresponding negative electrode potential, and perform constant current and constant voltage charging and discharging on the blue power cabinet until the corresponding potential is reached;

[0010] 6) Collect voltage data after 24 hours of settling and calculate the voltage drop;

[0011] 7) Determine the cutoff voltage with a stable and small voltage drop;

[0012] 8) After taking into account the outbound voltage requirements, conduct a small-batch test on the cutoff voltage in step 7.

[0013] Preferably, in step 5, the selected cutoff voltages are spaced at the same potential interval.

[0014] Preferably, in step 5, the charging and discharging process on the blue battery cabinet is as follows: discharge at 0.8C to 2.5V and let stand for 5 minutes; charge at 0.5C to the cutoff voltage and let stand for 24 hours.

[0015] The present invention has the following advantages: the voltage difference can be reduced to at least 5mV, reducing individual differences in battery cells, improving voltage consistency, helping to prevent overcharging of battery cells, delaying battery cell aging, improving cycle performance, and having low power loss during long-term storage. It is suitable for silicon-oxygen-containing anode materials, and the experiment is simple with obvious effects. Attached Figure Description

[0016] Figure 1 These are graphs showing silicon-oxygen discharge curves at different scales;

[0017] Figure 2 This is a graph showing the voltage drop data over 24 hours at different charging cutoff voltages;

[0018] Figure 3 This is a histogram of the cutoff voltage of 3630mV;

[0019] Figure 4 This is a histogram of the cutoff voltage of 3670mV. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the specific embodiments will be described clearly and completely below.

[0021] A method for improving voltage uniformity in silicon-oxygen systems includes the following steps:

[0022] Taking a cylindrical 18650 battery as an example, with a capacity of 3.35Ah, the negative electrode ratio is: C72:KY100:SP:O2HO17:MAC500:B9 = 91:9:0.5:12.5:1.2:2.6.

[0023] 1) Prepare button cells with silicon-oxygen ratios of 10%, 20%, and 30%, and discharge them using a battery testing system to obtain discharge curves. This involves using an Arbin cabinet for battery testing and plotting the discharge curves for different silicon-oxygen ratios. Figure 1 As shown, the discharge curves of silicon-oxygen ratios show that the higher the silicon-oxygen ratio, the higher the electrode potential at which the plateau appears; compared with the discharge curve of graphite, the higher the silicon-oxygen ratio, the less obvious the plateau region of the discharge curve.

[0024] 2) Three-electrode test: When the current production line cutoff voltage is 3630mV, the potential of the silicon-oxygen negative electrode is about 0.1V.

[0025] 3) The discharge curve of the silicon-oxygen negative electrode coin cell shows that there are two relatively obvious plateau regions below 0.1V. Based on this, different cutoff voltages were selected to conduct experiments to find the region where the voltage drop is stable, i.e. the plateau region.

[0026] The battery cells undergo a process of micro-charging, aging, pre-charging, high-temperature aging, room-temperature resting, capacity testing, and sorting before being stored. Cells to be tested on the production line are selected, and different cutoff voltages are chosen based on the 10% silicon-oxygen ratio and the corresponding discharge curve. The cutoff voltages range from 3620mV to 4200mV, with each cutoff voltage tested at 20mV intervals, for a total of 31 cells. These cells are then subjected to constant current and constant voltage charging and discharging to the corresponding potentials on a blue battery cabinet. Different capacity testing steps are set on the blue battery cabinet. The specific charging and discharging process is as follows: uniformly discharge at 0.8C to 2.5V, rest for 5 minutes, charge at 0.5C to the cutoff voltage of 3620mV, and rest for 24 hours. The 31 cells have different cutoff voltages, with adjacent cells differing by 20mV. The cutoff voltage of the 31st cell is 4200mV.

[0027] 4) After standing for 24 hours, collect the voltage changes during the process, calculate the voltage drop, and compile the data into a table. Figure 2 The specific calculation formula is as follows:

[0028] ΔOCV=OCV3(24h)-OCV(selected cutoff voltage)

[0029]

[0030] 5) The voltage drop curve shows that there are two plateau regions around 3660mV-3800mV and 3880mV-4100V, and the voltage drop in the plateau region is smaller than the voltage drop of 3630mV on the production line.

[0031] 6) Considering that 3660mV has reached the plateau range, and taking into account factors such as the shipment voltage, 3670mV and 3630mV were selected as cutoff voltages for small-scale testing. Data tracking was conducted on 10 trays of cells for each test. After the capacity grading was completed, the cells were left to stand for 40-70 hours, and the cell voltage values ​​were tested. Figure 3 and Figure 4 As shown in the histograms of the two schemes, the standard deviation of the cutoff voltage of 3670mV is smaller than that of the cutoff voltage of 3630mV, indicating improved voltage consistency.

Claims

1. A method for improving voltage consistency in a silicone system, comprising: The method comprises the following steps: 1) Assembling the battery cells with different silicon-oxygen ratios; 2) Selecting the negative electrode material with a certain silicon-oxygen ratio to assemble a button cell, and obtaining a discharge curve by discharging the button cell on a battery test system; 3) Performing a three-electrode test to determine the negative electrode potential corresponding to the production line cutoff voltage of the full battery; 4) Selecting the battery cell with a certain silicon-oxygen ratio in step 2); 5) Selecting different cutoff voltages in combination with the corresponding negative electrode potential, and performing constant-current constant-voltage charging and discharging to the corresponding potential on a blue cabinet; wherein the discharge curve of the button cell corresponds to an obvious platform region near the negative electrode potential, and the cutoff voltage is selected according to the platform region; wherein the charging and discharging process on the blue cabinet is as follows: 1) Discharge uniformly at 0.8C to 2.5V, and stand for 5min; 2) Charge at 0.5C to the cutoff voltage, and stand for 24h; 6) Collect the voltage data after standing for 24h, and calculate the pressure drop; 7) Determine the cutoff voltage with stable and small pressure drop; 8) After combining with the delivery voltage requirement, perform small batch test on the cutoff voltage in step 7).

2. The method of claim 1, wherein the method is characterized by: In step 5), the selected cutoff voltages are spaced at the same potential.

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