Method for rapidly recovering capacity of secondary battery

Abstract

The invention belongs to the technical field of batteries. The invention particularly relates to a secondary battery capacity rapid recovery method. The method comprises the following steps: performing low-rate discharge on a circulated secondary battery to lower limit cutoff voltage, and standing at normal temperature to obtain a discharged battery; and reversely connecting the positive electrode and the negative electrode of the discharged battery, charging by adopting reverse pulse, and standing at normal temperature after charging to obtain the capacity recovery battery. According to the charging mode, battery capacity recovery can be realized in a short time, active ions which cannot be normally de-embedded in the negative electrode can be effectively returned to the positive electrode through forced pulse charging at the negative electrode, the overall capacity and energy density of the battery are improved, equipment does not need to be purchased again, the process is simple, and large-scale application is expected to be realized.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and mainly relates to a method for rapid recovery of secondary battery capacity. Background Technology

[0002] With the development of the new energy economy, especially the rapid growth of power batteries and 3C consumer rechargeable batteries, higher demands are being placed on the low-temperature performance of batteries as application markets shift. For example, the transportation sector requires batteries to provide stable energy output at -40°C, the military defense sector requires batteries that can operate at -40°C for communication equipment, the polar scientific research sector requires batteries that can operate at -80°C, and the extraterrestrial exploration sector requires batteries that can withstand extremely cold conditions of -100°C or even lower.

[0003] During low-temperature use, the health, lifespan, and energy density of rechargeable batteries decrease significantly with prolonged use and increased charge-discharge cycles. Besides crack growth and lattice slip in the positive electrode material, the low ionic and electronic conductivity and poor system kinetics at low temperatures, along with the growth of the passivation film in the negative electrode material and the inability of active ions to properly intercalate and deintercalate, are also significant causes of battery capacity loss. Therefore, there is an urgent need for a safe, quick, simple, and low-cost method for restoring the capacity of rechargeable batteries after low-temperature cycling, enabling their reactivation. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the capacity loss of secondary batteries after cycling under low-temperature conditions, and to provide a method for capacity recovery after low-temperature cycling conditions that is safe, quick, simple, low-cost, and suitable for practical application.

[0005] To achieve the above objectives, this invention provides a method for rapid capacity recovery of a secondary battery, employing low-rate discharge combined with high-temperature pulse reverse charging to achieve rapid capacity recovery in a short time, comprising the following steps: S1. Discharge the cycled secondary battery at a low rate to the lower cutoff voltage and then let it stand at room temperature to obtain the discharged battery. S2. Reverse the positive and negative terminals of the discharged battery and use reverse pulse charging. After charging, allow it to stand at room temperature to obtain a capacity-recovered battery.

[0006] In a specific implementation, the discharge rate range of the low-rate process in step S1 is 0.01C to 0.05C.

[0007] In a specific implementation, the process conditions for reverse pulse charging in step S2 are as follows: The temperature is 45~65℃; The charging rate range is 0.05C~0.1C, and the charging time is 5~10 minutes.

[0008] In a specific implementation, the process conditions for standing at room temperature in steps S1 and S2 are as follows: The temperature is 25~30℃; Let it stand for 30 to 60 minutes.

[0009] In a specific embodiment, the secondary battery is any one of a sodium-ion battery, a lithium-ion battery, or a zinc-ion battery.

[0010] In a specific embodiment, the method further includes: cycling the capacity recovery battery at a set rate.

[0011] In a specific implementation, the set multiplier is any one of 0.5C / 0.5C cycle, 0.1C / 0.1C cycle, or 0.1C / 1C cycle.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs high-temperature pulse reverse charging for 5-10 minutes. Using an external charging and discharging device, the positive and negative electrodes are reversed during charging. This re-excites the inactive elements, such as the metal plating and dendrites, that have formed on the surface of the negative electrode after long cycles into an ionic state. Under the influence of the electric field, these ionic elements are transferred back to the positive electrode. Simultaneously, the localized high temperature generated by the reverse charging melts the metal dendrites, eliminating micro-short circuits within the electric field. The high-temperature conditions and pulse charging further enhance these steps, improving the electric field energy density and cycle life. This method is quick, requires no new equipment purchase, and has a simple process, making it promising for large-scale application. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 A flowchart of a method for rapidly restoring the capacity of a secondary battery provided in an embodiment of the present invention; Figure 2 The electrical performance diagram of the capacity recovery cycle to 60 cycles after 50 cycles at -20℃ provided in Embodiment 1 of the present invention is shown. Figure 3 The electrical performance diagram provided in Embodiment 2 of the present invention shows the capacity recovery cycle to 1100 cycles after 1000 cycles at room temperature. Figure 4The diagram shows the electrical performance of the circuit after 50 cycles at -20°C, as provided in Comparative Example 1 of this invention, where the capacity recovers to 60 cycles. Detailed Implementation

[0015] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0016] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0017] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0018] As attached Figure 1 As shown, this invention provides a method for rapidly restoring the capacity of a secondary battery, specifically including the following steps: S1. After cycling, the secondary battery is discharged at a low rate of 0.01C to 0.05C to the lower cutoff voltage, and then left to stand at room temperature for 30 to 60 minutes at 25 to 30°C to obtain the discharged battery. The secondary battery can be any one of sodium-ion, lithium-ion, or zinc-ion batteries. This discharge process pushes sodium that cannot be properly removed from the negative electrode back to the positive electrode, achieving partial capacity recovery.

[0019] S2. Reverse the positive and negative terminals of the discharged battery and perform reverse pulse charging: the temperature during this process is 45~65℃; the charging rate range is 0.05C~0.1C; and the charging time is 5~10 minutes. After charging, allow the battery to stand at room temperature for 30~60 minutes at a temperature of 25~30℃ to obtain a capacity-recovered battery. During this process, reversing the positive and negative terminals during charging re-excites the inactive elements such as metal plating and dendrites generated on the surface of the negative electrode after long-term cycling into an ionic state, and under the action of the electric field, they are transferred back to the positive electrode. At the same time, the local high temperature generated by reverse charging melts the metal dendrites, and the micro-short circuits inside the electric field are eliminated. The high temperature conditions and pulse charging further enhance the above steps, thereby improving the electric field energy density and cycle life.

[0020] S3. Cycle the capacity recovery battery under any of the following conditions: 0.5C / 0.5C cycle, 0.1C / 0.1C cycle, and 0.1C / 1C cycle, and measure the capacity recovery.

[0021] The specific implementation methods of this application have been described above. In order to objectively illustrate the technical effects produced by this application, the following examples and comparative examples will be used to describe them.

[0022] Example 1 The capacity retention rate of sodium-ion batteries after cycling at -20℃ for 50 cls at 0.5C / 0.5C is less than 30%. The capacity recovery method for secondary batteries provided by this invention is used for capacity recovery, and the specific steps include: S1. After cycling the secondary battery 50 times at low temperature, discharge it to 2V at a low rate of 0.04C under the condition of -20℃. After the discharge is completed, place it in a 25℃ environment and let it stand for 30 minutes.

[0023] S2. Place the discharged battery in a high-temperature chamber, match the positive terminal of the charging and discharging cabinet to the negative terminal of the battery, and match the negative terminal of the charging and discharging cabinet to the positive terminal of the battery. Under 45℃ conditions, use a 0.05C reverse pulse charge for 10 minutes. After charging, place the battery in a 25℃ environment for 30 minutes.

[0024] S3. After charging and allowing the battery to stand, place it back into a -20°C low-temperature chamber and cycle it again under 0.5C / 0.5C, 2-4V constant current and constant voltage conditions.

[0025] The sodium-ion battery after the above capacity recovery is as follows: Figure 2 As shown, the capacity retention rate of the sodium-ion battery recovered from 25.85%@50cls to 44.22%@60cls, and the low-temperature cycling performance of the battery was effectively restored.

[0026] Example 2 The capacity retention rate of a sodium-ion battery after cycling at 25℃ for 1000 cls at 0.5C / 0.5C and 2-3.9V is less than 90%. The capacity recovery method for secondary batteries provided by this invention is used for capacity recovery, and the specific steps include: S1. After cycling 1000 times at room temperature, discharge the secondary battery to 2V using a constant current of 0.03C at room temperature. After the discharge is complete, place it in a 25℃ environment and let it stand for 30 minutes.

[0027] S2. Place the discharged battery in a high-temperature chamber, match the positive terminal of the charging and discharging cabinet to the negative terminal of the battery, and match the negative terminal of the charging and discharging cabinet to the positive terminal of the battery. Under 45°C conditions, use a 0.1C reverse pulse charge for 10 minutes. After charging, place the battery in a 25°C environment for 30 minutes.

[0028] S3. After charging and allowing the battery to stand, place it back in a normal temperature environment and cycle it again under constant current and constant voltage conditions of 0.5C / 0.5C and 2-3.9V.

[0029] The sodium-ion battery after the above capacity recovery is as follows: Figure 3 As shown, the capacity retention rate of the sodium-ion battery recovered from 94.67% to 96.61%, and after 100 cls of cycling, the capacity retention rate was still greater than 96%, indicating that the battery's room temperature cycling performance was effectively restored.

[0030] Comparative Example 1 After cycling at -20℃ for 0.5C / 0.5C for 50cls at 2-4V, the capacity retention rate of sodium-ion batteries is less than 30%. Capacity recovery is achieved using a temperature protocol, and the specific steps include: S1. After cycling the secondary battery 50 times at low temperature, discharge it to 2V at a low rate of 0.04C under the condition of -20℃. After the discharge is completed, place it in a 25℃ environment and let it stand for 30 minutes.

[0031] S2. After discharging and allowing the battery to stand, place it in a high-temperature chamber for 10 minutes, and then place it in a 25°C environment for 30 minutes.

[0032] S3. After charging and allowing the battery to stand, place it back into a -20°C low-temperature chamber and cycle it again under 0.5C / 0.5C, 2-4V constant current and constant voltage conditions.

[0033] After the sodium-ion battery undergoes the aforementioned capacity recovery process, increasing the temperature can eliminate some of the polarization capacity loss caused by low temperature. Upon returning to a low-temperature environment, the capacity retention rate recovers from 26.54% to 30.25%, resulting in a temporary capacity recovery. However, as the reaction continues, the battery performance rapidly deteriorates after 10 cycles, with the capacity retention rate decreasing from 30.25% to 25.10%, indicating a poor recovery effect. Figure 4 As shown.

[0034] Comparative Example 2 Sodium-ion batteries subjected to -20℃ low-temperature 0.5C / 0.5C cycling at 2-4V for 50cls retain less than 30% of their capacity. Capacity recovery for these batteries involves the following steps: S1. After cycling the secondary battery 50 times at low temperature, discharge it to 2V at a low rate of 0.04C under the condition of -20℃. After the discharge is completed, place it in a 25℃ environment and let it stand for 30 minutes.

[0035] S2. Place the discharged battery in a high-temperature chamber, match the positive terminal of the charging and discharging cabinet to the positive terminal of the battery, and match the negative terminal of the charging and discharging cabinet to the negative terminal of the battery. Under 45℃ conditions, use a 0.1C rate pulse charge for 10 minutes. After charging, place the battery in a 25℃ environment for 30 minutes.

[0036] S3. After charging and allowing the battery to stand, place it back into a -20°C low-temperature chamber and cycle it again under 0.5C / 0.5C, 2-4V constant current and constant voltage conditions.

[0037] After the sodium ion battery was restored to its original capacity, the battery capacity increased to 32.66%. After being returned to a low-temperature environment and cycled for 10 times, the capacity decreased to 28.08%.

[0038] As can be seen from Examples 1 and 2 above, the secondary battery (sodium-ion battery) undergoes short-cycle (50cls) at low temperature and long-cycle (1000cls) at room temperature. Using the battery capacity recovery method proposed in this invention, system polarization can be effectively removed, and reversible capacity loss can be effectively recovered. Simultaneously, through the reverse charging step (reversing the positive and negative electrodes), sodium dendrites on the negative electrode surface and dead sodium in the coating are reactivated and returned to the positive electrode material, achieving effective recovery of irreversible capacity. Furthermore, this recovery method can stably recover capacity; after resetting the battery and re-cycling in a low-temperature environment, the capacity basically does not decrease. As can be seen from Examples 1 and Comparative Example 1 above, after low-temperature cycling and deep discharge followed by room temperature rest, some of the reversible capacity loss caused by polarization due to temperature changes is recovered. However, as low-temperature cycling continues, the battery capacity retention rate quickly decreases to the level before capacity recovery. As can be seen from Example 1 and Comparative Example 2 above, after low-temperature cycling and deep discharge, the battery is left to stand at room temperature and then charged forward using pulses. However, forward charging cannot bring the dead sodium of the negative electrode back to the positive electrode to achieve the transformation from irreversible loss to reversible capacity loss. As low-temperature cycling continues, the battery capacity retention rate quickly decays to the level before capacity recovery.

[0039] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. However, it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for rapidly restoring the capacity of a secondary battery, characterized in that, The method includes the following steps: S1. Discharge the cycled secondary battery at a low rate to the lower cutoff voltage and then let it stand at room temperature to obtain the discharged battery. S2. Reverse the positive and negative terminals of the discharged battery and use reverse pulse charging. After charging, allow it to stand at room temperature to obtain a capacity-recovered battery.

2. The method for rapid capacity recovery of a secondary battery according to claim 1, characterized in that, The discharge rate range in step S1 is 0.01C to 0.05C.

3. The method for rapid capacity recovery of a secondary battery according to claim 1, characterized in that, The reverse pulse charging process conditions in step S2 are as follows: The temperature is 45~65℃; The charging rate range is 0.05C~0.1C, and the charging time is 5~10 minutes.

4. The method for rapid capacity recovery of a secondary battery according to claim 1, characterized in that, The process conditions for standing at room temperature in steps S1 and S2 are as follows: The temperature is 25~30℃; the standing time is 30~60min.

5. The method for rapid capacity recovery of a secondary battery according to claim 1, characterized in that, The secondary battery is any one of a sodium-ion battery, a lithium-ion battery, or a zinc-ion battery.

6. The method for rapid capacity recovery of a secondary battery according to claim 1, characterized in that, The method further includes: cycling the capacity recovery battery at a set rate.

7. The method for rapid capacity recovery of a secondary battery according to claim 6, characterized in that, The set multiplier is any one of 0.5C / 0.5C cycle, 0.1C / 0.1C cycle, or 0.1C / 1C cycle.

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