Methods for evaluating the wetting effect of battery electrolyte

Abstract

This invention belongs to the field of battery testing, specifically relating to a method for evaluating the wetting effect of battery electrolyte. The evaluation method involves injecting electrolyte into the battery, sealing it, and then charging and discharging the battery to evaluate the wetting effect of the electrolyte. The method includes the following steps: First, the battery is charged with a constant current I, and then placed in a dormant state after charging. The battery voltage V1 at the end of charging is recorded. After a certain dormant period tr1, the battery voltage V2 at the end of dormant state is recorded. Then, the relaxation impedance R of the battery after charging is calculated according to Ohm's law. s = (V1-V2) / I; Discharge the battery with the same current I for the same duration tc, and then allow it to rest for the same duration tr1 after discharge; Third, set the rest period tr2 after discharge and rest period; Plot the curve of battery relaxation impedance changing with immersion time; When the relaxation impedance tends to stabilize, it indicates that the battery has been sufficiently wetted. This method is simple to operate and is a non-destructive testing method.

Description

Technical Field

[0001] This invention belongs to the field of battery testing, specifically relating to a method for evaluating the wetting effect of battery electrolyte. Background Technology

[0002] After electrolyte is injected into the battery, it needs to stand for a period of time to allow the electrolyte to fully penetrate. However, in the current technology, it is difficult to determine the penetration time of the battery after electrolyte injection. If the penetration time is too short, the penetration will be insufficient. If electrical performance testing is carried out at this time, some electrodes will not be able to participate in the battery electrochemical reaction, which will affect the battery performance, and the capacity will not meet the design requirements. The battery will also be scrapped, resulting in waste. If the battery is left to stand for too long after electrolyte injection, the storage time will be too long, which will affect the production efficiency.

[0003] Currently, the common method for testing electrolyte wettability after battery filling is to observe it through subsequent battery disassembly. This involves adding dye to the electrolyte, wetting the cells, and then disassembling the corresponding electrodes and separators to determine the wetting effect by observing the staining. However, this method only characterizes the electrolyte wetting on the surface of the electrode materials and cannot determine the wetting effect along the thickness of the electrode materials. Furthermore, disassembly causes irreversible damage to the battery. Additionally, this method cannot be used on-site in production to promptly assess the electrolyte wetting effect. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for evaluating the wetting effect of battery electrolyte.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] One method for evaluating the wetting effect of battery electrolyte involves injecting electrolyte into the battery, sealing it, charging and discharging the battery, and then evaluating the wetting effect of the electrolyte.

[0007] Specifically, the steps include: First, charge the battery with a constant current I for a certain time tc, and then allow it to rest for a certain time tr after charging. Calculate the battery voltage V1 at the end of charging, and the voltage V2 at the end of rest after the resting period tr1. Then, calculate the relaxation impedance R of the battery after charging according to Ohm's law. s = (V1-V2) / I and record it;

[0008] The second step is to use a symmetrical charging and discharging method. After the first step of charging and dormancy is completed, the battery is discharged with the same current I for the same time tc. After the discharge is completed, the battery is dormant for the same time tr1.

[0009] The third step is to set the hibernation tr2 after the discharge and hibernation are completed, so that the battery can be further wetted;

[0010] Fourth step: Repeat steps one through three to obtain the relaxation impedance of the battery electrolyte after different immersion times;

[0011] Fifth, plot the battery relaxation impedance as a function of immersion time, with the battery electrolyte immersion time t as the abscissa and the battery relaxation impedance Rs measured at that time as the ordinate. Use the curve to evaluate the wetting effect of the battery electrolyte.

[0012] When the relaxation impedance tends to stabilize, it indicates that the battery has been fully wetted by the electrolyte.

[0013] Specifically, the criterion for judging sufficient electrolyte wetting is as follows: plot the relaxation impedance change rate versus wetting time with dRs / dt as the ordinate and wetting time t as the abscissa. When the relaxation impedance change rate is less than 10mΩ / h for more than 2 consecutive recording points, the battery is judged to be sufficiently wetting. For example, when the relaxation impedance change rate is less than 10mΩ / h for more than 3, 4, 5 or even more consecutive recording points, the battery is judged to be sufficiently wetting.

[0014] The electrolyte wetting time t is the wetting time calculated from the time the electrolyte is injected into the battery and after sealing.

[0015] The current I mentioned in the first step is 0.05C-0.2C (e.g., 0.05C, 0.15C, or 0.2C). Preferably, the current I mentioned in the first step is 0.1C.

[0016] In the first step, tc is 5-50s (e.g., 5s, 20s, or 50s). Preferably, tc is 10s in the first step.

[0017] In the first step, tr1 is 20-60 min (e.g., 20 min, 40 min, or 60 min). Preferably, tr1 is 30 min.

[0018] In the third step, tr2 is 1-4h (e.g., 1h, 2h, or 4h). Preferably, tr2 is 3h in the third step.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention discloses a method for evaluating the wetting effect of battery electrolyte. The method is simple to operate. By measuring the method for evaluating the wetting effect of battery electrolyte, the electrolyte wettability of the electrode can be analyzed. Moreover, it is a non-destructive testing method, which has certain guiding significance for judging the electrolyte wetting time in the production line. Attached Figure Description

[0021] Figure 1 This is a graph showing the battery impedance-electrolyte wetting time in Example 1 of the present invention.

[0022] Figure 2 This is a graph showing the battery impedance-electrolyte wetting time in Example 2 of the present invention. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0024] Example 1: Three 2.6Ah 18650 batteries were prepared. Electrolyte was injected into the batteries, and after sealing, the batteries were charged and discharged to evaluate the wetting effect of the electrolyte. The batteries were subjected to a 0.1C constant current charging test for 10 seconds. After charging, the batteries were allowed to rest for 30 minutes. The voltage at the end of the constant current charging was V1, and the voltage at the end of the resting period was V2. The relaxation impedance of the battery after charging was calculated according to Ohm's law as Rs = (V1-V2) / I and recorded. Then, the battery was charged at 0.1C. Discharge at 1C current for 10 seconds, followed by a 30-minute sleep period. After the charge and discharge cycle, the battery is placed in sleep mode for another 1 hour. This cycle is repeated. A relaxation impedance change rate versus electrolyte wetting time curve is plotted with the initial relaxation impedance change rate dRs at each charge-sleep stage as the x-axis and the initial relaxation impedance change rate dRs at each charge-sleep stage as the y-axis. Figure 1 .

[0025] from Figure 1 As can be seen from the data, after 36 hours of electrolyte injection, the relaxation impedance change rate dRs / dt at three consecutive recording points was less than 10 mΩ / h. At this point, the relaxation impedance tended to stabilize. Therefore, we determined that the electrolyte was fully wetted after 36 hours of electrolyte injection.

[0026] The results of disassembling this series of batteries are consistent with those of this embodiment, indicating that the technical solution of this embodiment can evaluate the electrolyte wetting effect of the battery.

[0027] Example 2: Two 4.2Ah pouch batteries (model 4360143) were prepared. Electrolyte was injected into the batteries, and after sealing, the batteries were charged and discharged to observe the wetting effect of the electrolyte. A 0.1C constant current charging test was performed on the batteries for 10 seconds. After charging, the batteries were allowed to rest for 30 minutes. The voltage at the end of the constant current charging was V1, and the voltage after the resting period was V2. Then, the relaxation impedance Rs = (V1 - V2) / I of the battery after charging was calculated according to Ohm's law and recorded. Then, discharge at a current of 0.1C for 10 seconds, followed by a 30-minute sleep period. After the charge and discharge cycle, the battery is set to sleep for 1 hour. This cycle test is repeated. A relaxation impedance-electrolyte immersion time curve is plotted with the wetting time t (the wetting time of the electrolyte is calculated from the time the electrolyte is injected into the battery until it is sealed) as the x-axis and the rate of change of relaxation impedance dRs at the start of each charge-sleep phase as the y-axis, with the wetting time as the x-axis. Figure 2 .

[0028] from Figure 2 As can be seen from the data, after 40 hours of electrolyte injection, the relaxation impedance change rate dRs / dt at three consecutive recording points was less than 10 mΩ / h. At this point, the relaxation impedance tended to stabilize. Therefore, we determined that the electrolyte was fully wetted after 40 hours of electrolyte injection.

[0029] Similarly, the results of disassembling this series of batteries are consistent with those of this embodiment, indicating that the technical solution of this embodiment can evaluate the electrolyte wetting effect of the battery.

[0030] This application uses a current I of 0.05C, 0.15C, or 0.2C, tc of 5s, 20s, or 50s, tr1 of 20min, 40min, or 60min, and tr3 of 1h, 2h, or 4h for wetting, and the wetting effect of the electrolyte can be evaluated using this method.

[0031] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for evaluating the wetting effect of battery electrolyte, characterized in that, Electrolyte was injected into the battery, and after sealing, the battery was charged and discharged to evaluate the wetting effect of the electrolyte. Includes the following steps: The first step is to charge the device with a constant current I for a certain period of time tc, and then put it into a sleep state for a certain period of time tr1 after charging is completed. Given the battery voltage V1 at the end of charging, and the voltage V2 at the end of the dormant period after a certain dormant time tr1, calculate the relaxation impedance R of the battery after charging is completed using Ohm's law. s = (V1-V2) / I and record it; The second step is to use a symmetrical charging and discharging method. After the first step of charging and dormancy is completed, the battery is discharged with the same current I for the same time tc. After the discharge is completed, the battery is dormant for the same time tr1. The third step is to set the hibernation tr2 after the discharge and hibernation are completed, so that the battery can be further wetted; Fourth step: Repeat steps one through three to obtain the relaxation impedance of the electrolyte after different wetting times t; Fifth, plot the curve of battery relaxation impedance as a function of immersion time, with electrolyte immersion time t as the abscissa and the battery relaxation impedance Rs measured at that time as the ordinate. The wetting effect of the battery electrolyte is evaluated through the curve. The relaxation impedance tends to stabilize, indicating that the battery has been fully wetted by the electrolyte.

2. The method for evaluating the wetting effect of battery electrolyte according to claim 1, characterized in that, The current I mentioned in the first step is 0.05C-0.2C.

3. The method for evaluating the wetting effect of battery electrolyte according to claim 1, characterized in that, The current I mentioned in the first step is 0.1C.

4. The method for evaluating the wetting effect of battery electrolyte according to claim 1, characterized in that, In the first step, tc is 5-50s.

5. The method for evaluating the wetting effect of battery electrolyte according to claim 1, characterized in that, In the first step, tc is 10s.

6. The method for evaluating the wetting effect of battery electrolyte according to claim 1, characterized in that, In the first step, tr1 is 20-60 minutes.

7. The method for evaluating the wetting effect of battery electrolyte according to claim 1, characterized in that, tr1 is 30 minutes.

8. The method for evaluating the wetting effect of battery electrolyte according to claim 1, characterized in that, In the third step, tr2 is 1-4h.

9. The method for evaluating the wetting effect of battery electrolyte according to claim 8, characterized in that, In the third step, tr2 is 3h.

10. The method for evaluating the wetting effect of battery electrolyte according to claim 9, characterized in that, The criterion for judging whether the electrolyte is sufficiently wetted is as follows: plot the relaxation impedance change rate dRs / dt as the ordinate and the wetting time t as the abscissa, and determine the electrolyte is sufficiently wetted when the relaxation impedance change rate is less than 10mΩ / h for more than two consecutive recording points.

Images