Sodium ion battery repair method and sodium ion battery

Abstract

The present invention proposes a sodium ion battery repair method and a sodium ion battery, which relates to the technical field of batteries. The sodium ion battery repair method comprises the following steps: a high current discharge step, comprising discharging the battery with a first current I1 at a constant current; a high temperature standing step, comprising heating the sodium ion battery and then keeping it at a temperature T1; a low current cyclic charge and discharge step, comprising at least cyclically charging and discharging the sodium ion battery with a second current I2; wherein the current intensity of the sodium ion battery during one hour of full discharge is 1C, 2C≤I1≤4C, 1 / 20C≤I2≤1C, and 40℃≤T1≤70℃. The technical solution of the present invention can activate a large number of precipitated sodium dendrites by performing high current discharge and high temperature standing aging treatment on the sodium precipitating battery cell, so that the precipitated sodium dendrites are re-ionized; and then a low current charge and discharge treatment is performed to ionize the re-electrically connected sodium dendrites, thereby increasing the deintercalation rate of sodium ions participating in the reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a sodium ion battery repair method and a sodium ion battery. Background Art

[0002] With the rapid development of sodium-ion batteries and their increasing popularity in application terminals such as new energy vehicles and energy storage base stations, the risk of failure and the damage caused by failure are becoming more and more serious. In fact, the failure mechanism and form of batteries are very complex, and each reaction process of each component has different effects on the failure of the battery. In particular, sodium-ion batteries have the risk of sodium precipitation during the charging process.

[0003] When sodium-ion batteries are charged rapidly with high current or at low temperatures, the rate at which sodium ions are embedded in the negative electrode is slower than the rate at which sodium ions are conducted to the negative electrode active material, causing the precipitation of metallic sodium on the surface of the negative electrode, which in turn causes irreversible loss of sodium ion stock. When metallic sodium precipitates, dendritic metallic sodium crystals are usually formed, referred to as sodium dendrites. The presence of sodium dendrites greatly increases the risk of side reactions with the electrolyte, thereby generating large amounts of gas and heat. At the same time, the rampant growth of sodium dendrites may puncture the isolation membrane, causing the sodium-ion battery to short-circuit or even burn and explode.

[0004] To address the sodium precipitation phenomenon in sodium-ion batteries, existing technologies mainly include: 1) battery structure optimization, such as multi-electrode design to balance the current density distribution and inhibit local sodium precipitation; 2) negative electrode material optimization, improving or synthesizing materials with intrinsic parameters that are easier to improve the sodium insertion kinetics to inhibit the sodium precipitation reaction; 3) diaphragm design and optimization, electrochemical or mechanical modification of the diaphragm to improve its performance and prevent puncture short circuits; 4) electrolyte optimization, by adding additives to improve the quality of the SEI film to avoid sodium precipitation as much as possible.

[0005] In summary, most existing technologies only consider how to improve the performance of sodium-ion batteries in suppressing the precipitation of sodium ions in the early stages of manufacturing. However, common factors that trigger sodium precipitation failure are not only defects in battery design / process manufacturing, but also improper battery charging and discharging strategies or harsh actual battery application environments. In the life cycle of commercial sodium-ion batteries, the precipitation of sodium dendrites is almost an inevitable phenomenon.

[0006] At present, the latest technical solutions have begun to improve the charging and discharging strategies, and have improved the sodium dendrite problem throughout the battery life cycle through technologies such as ambient temperature and electrochemical activation. However, the technical solutions are relatively simple, the improvement effects are limited, and they are not effective for batteries in any state. Summary of the invention

[0007] The main purpose of the present invention is to provide a sodium ion battery repair method and a sodium ion battery, aiming to reduce sodium dendrites in the sodium ion battery.

[0008] To achieve the above object, the present invention provides a sodium ion battery repair method, comprising the following steps:

[0009] A high current discharge step includes discharging the battery at a constant current with a first current I1;

[0010] A high temperature standing step comprises heating the sodium ion battery and then keeping it at a temperature T1;

[0011] The low current cyclic charging and discharging step at least comprises cyclically charging and discharging the sodium ion battery with a second current I2;

[0012] The current intensity of the sodium ion battery during one-hour full discharge is 1C, 2C≤I1≤4C, 1 / 20C≤I2≤1C, and 40°C≤T1≤70°C.

[0013] In one embodiment, before the high current discharge step, the method further includes:

[0014] Obtaining a sodium precipitation coefficient of a sodium ion battery, and determining whether the sodium ion battery has repair value according to the sodium precipitation coefficient of the sodium ion battery;

[0015] If yes, a high current discharge step is performed;

[0016] Wherein, the sodium precipitation coefficient formula is:

[0017] ,

[0018] Among them, ζ is the sodium precipitation coefficient of the sodium ion battery, α1 is the temperature induction coefficient, α2 is the resistance induction coefficient, and α3 is the electrochemical induction coefficient;

[0019] α1, α2, and α3 are calculated according to the following formulas:

[0020] ,

[0021] ,

[0022] ,

[0023] Among them, ΔT is the temperature rise of the battery during charging, T0 is the charging and discharging ambient temperature, R ohm is the ohmic resistance of the battery, Z ω is the sodium ion diffusion impedance, C 理 is the theoretical capacity of the battery, J is the charge and discharge current of the battery, ΔCE is the coulombic efficiency of the battery, τ 弛 It is the relaxation time of the high voltage platform of battery discharge.

[0024] In one embodiment, in the high current discharge step, the discharge time is t1, 60 s≤t1≤90 s.

[0025] In one embodiment, in the high temperature standing step, the insulation time is t2, 24 h≤t2≤36 h.

[0026] In one embodiment, in the low current cyclic charge and discharge step, the temperature of the sodium ion battery is T2, 30°C≤T2≤60°C, and T2≤T1.

[0027] In one embodiment, the low current cyclic charge and discharge step includes the following steps:

[0028] Cyclic charging and discharging of the sodium ion battery with a second current I2;

[0029] Cyclic charging and discharging of the sodium ion battery with a third current I3;

[0030] Among them, 1 / 2C≤I2≤1C, 1 / 20C≤I3≤1 / 10C.

[0031] In one embodiment, in the step of cyclically charging and discharging the sodium ion battery with the second current I2, the number of cycles of cyclic charging and discharging is n, 2≤n≤3; and / or,

[0032] In the step of cyclically charging and discharging the sodium ion battery with the third current I3, the number of cycles of cyclic charging and discharging is m, and 2≤m≤5.

[0033] In one embodiment, before the high current discharge step, the following steps are also included:

[0034] The sodium ion battery is charged with a constant current using the fourth current I4 until the charging voltage reaches an upper charging limit voltage.

[0035] In one embodiment, 1 / 3C≤I4≤1 / 2C.

[0036] In one embodiment, in step S12 of performing constant current charging on the sodium ion battery with the fourth current I4, the temperature of the sodium ion battery is T3, 25°C≤T3≤30°C.

[0037] The technical solution of the present invention can activate a large number of precipitated sodium dendrites by subjecting the sodium-precipitating battery cell to high-current discharge and high-temperature static aging treatment, so that the precipitated sodium dendrites can be re-ionized, and the relative position of the "dead sodium" can be promoted to approach the negative terminal, and the isolated "dead sodium" can be promoted to re-establish electrical connection with the electrode, so as to promote the re-ionization of the sodium dendrites to participate in the de-embedding reaction, thereby eliminating the sodium dendrites; by high-temperature static treatment, on the one hand, the sodium dendrites can be thermally "melted", and on the other hand, the particle diffusion performance and reaction kinetics performance after high-current activation and ionization can be improved, so that more sodium ions can be promoted to return to the sodium ion de-embedding reaction, thereby promoting the elimination of sodium dendrites; by The low-current charge-discharge treatment ionizes the sodium dendrites that have been "electrically connected" again, reduces the influence of adverse factors such as concentration polarization and electrochemical polarization caused by the current, increases the number of lattices participating in charge transport in the material, improves the deintercalation rate of sodium ions participating in the reaction, inhibits the sodium precipitation reaction, turns defects into energy, and turns waste into treasure; through the high-temperature standing step, the sodium dendrites that have been electrically connected and ionized in the high-current discharge step are accelerated to diffuse and participate in the reaction; through the low-current cyclic charge-discharge step, the polarization can be reduced, and the sodium ions activated by the high-current discharge step and the high-temperature standing step can play a greater role, so that the effect of inhibiting and eliminating dendrites is optimal. ; By adjusting the first current I1 to 2C~4C, the sodium dendrites can be quickly activated and the sodium precipitates can be re-ionized. If the discharge current I1 is too large, the charge transfer speed and ion diffusion speed do not match the internal electric field strength, and the sodium dendrite ionization process is not complete. If the discharge current I1 is too small, the activation effect is limited, the sodium precipitate ionization process is slow, and the repair effect is poor; by adjusting the static temperature T1 to 40℃~70℃, the sodium dendrites can be effectively "melted", the sodium precipitates that are not dissolved in the high current discharge step can be re-ionized, and the ionized sodium ions can be diffused outward to avoid the accumulation of sodium ions, which leads to a slowdown in the "melting" process of the sodium dendrites. If the static temperature T1 is too low, the heat " The effects of "melting" and promoting diffusion are not obvious. If the static temperature T1 is too high, it is easy to induce an internal chain exothermic reaction to trigger thermal runaway of the battery cell. Through low-rate current charge and discharge treatment, the influence of adverse factors such as concentration polarization and electrochemical polarization brought by the current can be reduced, so that more sodium ions can participate in the charging and discharging process of the battery, thereby completely eliminating sodium dendrites. In addition, the technical solution of the present invention is not limited to the development stage, and can perform non-destructive repair within the full life cycle of the sodium ion battery. It supports flexible determination of the repair conditions, cycles or frequencies based on the actual use data of the battery cell, and achieves a significant improvement in the service life of the battery cell and the safety during service at a low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 It is a schematic diagram of the process of the sodium ion battery repair method in the prior art;

[0040] Figure 2 A schematic diagram of a process flow of an embodiment of a sodium ion battery repair method provided by the present invention;

[0041] Figure 3 A schematic diagram of a process flow of another embodiment of the sodium ion battery repair method provided by the present invention;

[0042] Figure 4 A schematic flow chart of another embodiment of the sodium ion battery repair method provided by the present invention.

[0043] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0044] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0045] It should be noted that, in the embodiments, those without specifying specific conditions are carried out according to normal conditions or conditions recommended by the manufacturer. Those without specifying the manufacturer of reagents or instruments used are conventional products that can be purchased commercially. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes, and "A and / or B" is taken as an example, including schemes A, B, or A and B that meet the same time. In addition, the technical schemes between the various embodiments can be combined with each other, but must be based on the ability of ordinary technicians in the field to achieve. When the combination of the technical schemes is contradictory or cannot be achieved, it should be considered that the combination of such technical schemes does not exist, and is not within the scope of protection required by the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work, all belong to the scope of protection of the present invention.

[0046] As the global energy consumption pattern gradually shifts from fossil energy to sustainable new energy, the secondary battery industry with high energy density, long cycle life and low environmental pollution is developing rapidly, but the bottleneck of resource side such as the scarcity of lithium resources is becoming increasingly prominent. As sodium resources have the characteristics of wide distribution, rich reserves and low cost, they are gradually developing into one of the most promising energy storage battery types in the world. At the same time, sodium-ion batteries have emerged as a substitute for lithium-ion batteries and are gaining more and more attention in the battery field.

[0047] With the rapid development of sodium-ion batteries and their increasing popularity in application terminals such as new energy vehicles and energy storage base stations, the risk of failure and the damage caused by failure are becoming more and more serious. In fact, the failure mechanism and form of batteries are very complex, and each reaction process of each component has different effects on the failure of the battery. In particular, sodium-ion batteries have the risk of sodium precipitation during the charging process.

[0048] When sodium-ion batteries are charged rapidly with high current or at low temperatures, the rate at which sodium ions are embedded in the negative electrode is slower than the rate at which sodium ions are conducted to the negative electrode active material, causing the precipitation of metallic sodium on the surface of the negative electrode, which in turn causes irreversible loss of sodium ion stock. When metallic sodium precipitates, dendritic metallic sodium crystals are usually formed, referred to as sodium dendrites. The presence of sodium dendrites greatly increases the risk of side reactions with the electrolyte, thereby generating large amounts of gas and heat. At the same time, the rampant growth of sodium dendrites may puncture the isolation membrane, causing the sodium-ion battery to short-circuit or even burn and explode.

[0049] Regarding the sodium precipitation phenomenon in sodium ion batteries, Figure 1 As shown, the existing technical solutions mainly include: 1) battery structure optimization, such as multi-electrode design to balance the current density distribution and inhibit local sodium precipitation; 2) negative electrode material optimization, improving or synthesizing materials with intrinsic parameters that are easier to improve the sodium insertion kinetics to inhibit the sodium precipitation reaction; 3) diaphragm design and optimization, electrochemical or mechanical modification of the diaphragm to improve its performance and prevent puncture short circuit; 4) electrolyte optimization, by adding additives to improve the quality of the SEI film to avoid sodium precipitation as much as possible.

[0050] In summary, most existing technologies only consider how to improve the performance of sodium-ion batteries in suppressing the precipitation of sodium ions in the early stages of manufacturing. However, common factors that trigger sodium precipitation failure are not only defects in battery design / process manufacturing, but also improper battery charging and discharging strategies or harsh actual battery application environments. In the life cycle of commercial sodium-ion batteries, the precipitation of sodium dendrites is almost an inevitable phenomenon.

[0051] At present, the latest technical solutions have begun to improve the charging and discharging strategies, and have improved the sodium dendrite problem throughout the battery life cycle through technologies such as ambient temperature and electrochemical activation. However, the technical solutions are relatively simple, the improvement effects are limited, and they are not effective for batteries in any state.

[0052] For this reason, please see Figure 2 The present invention provides a sodium ion battery repair method, comprising the following steps:

[0053] Step S10: a high current discharge step, comprising discharging the battery at a constant current with a first current I1;

[0054] Step S20. A high temperature standing step, comprising heating the sodium ion battery and then keeping it at a temperature T1;

[0055] Step S30. A low current cyclic charge and discharge step, at least comprising cyclically charging and discharging the sodium ion battery with a second current I2;

[0056] The current intensity of the sodium ion battery during one-hour full discharge is 1C, 2C≤I1≤4C, 1 / 20C≤I2≤1C, and 40°C≤T1≤70°C.

[0057] The technical solution of the present invention can activate a large number of precipitated sodium dendrites by subjecting the sodium-precipitating battery cell to high-current discharge and high-temperature static aging treatment, so that the precipitated sodium dendrites can be re-ionized, and the relative position of the "dead sodium" can be promoted to approach the negative terminal, and the isolated "dead sodium" can be promoted to re-establish electrical connection with the electrode, so as to promote the re-ionization of the sodium dendrites to participate in the de-embedding reaction, thereby eliminating the sodium dendrites; by high-temperature static treatment, on the one hand, the sodium dendrites can be thermally "melted", and on the other hand, the particle diffusion performance and reaction kinetics performance after high-current activation and ionization can be improved, so that more sodium ions can be promoted to return to the sodium ion de-embedding reaction, thereby promoting the elimination of sodium dendrites; by The low-current charge-discharge treatment ionizes the sodium dendrites that have been "electrically connected" again, reduces the influence of adverse factors such as concentration polarization and electrochemical polarization caused by the current, increases the number of lattices participating in charge transport in the material, improves the deintercalation rate of sodium ions participating in the reaction, inhibits the sodium precipitation reaction, turns defects into energy, and turns waste into treasure; through the high-temperature standing step, the sodium dendrites that have been electrically connected and ionized in the high-current discharge step are accelerated to diffuse and participate in the reaction; through the low-current cyclic charge-discharge step, the polarization can be reduced, and the sodium ions activated by the high-current discharge step and the high-temperature standing step can play a greater role, so that the effect of inhibiting and eliminating dendrites is optimal. ; By adjusting the first current I1 to 2C~4C, the sodium dendrites can be quickly activated and the sodium precipitates can be re-ionized. If the discharge current I1 is too large, the charge transfer speed and ion diffusion speed do not match the internal electric field strength, and the sodium dendrite ionization process is not complete. If the discharge current I1 is too small, the activation effect is limited, the sodium precipitate ionization process is slow, and the repair effect is poor; by adjusting the static temperature T1 to 40℃~70℃, the sodium dendrites can be effectively "melted", the sodium precipitates that are not dissolved in the high current discharge step can be re-ionized, and the ionized sodium ions can be diffused outward to avoid the accumulation of sodium ions, which leads to a slowdown in the "melting" process of the sodium dendrites. If the static temperature T1 is too low, the heat " The effects of "melting" and promoting diffusion are not obvious. If the static temperature T1 is too high, it is easy to induce an internal chain exothermic reaction to trigger thermal runaway of the battery cell. Through low-rate current charge and discharge treatment, the influence of adverse factors such as concentration polarization and electrochemical polarization brought by the current can be reduced, so that more sodium ions can participate in the charging and discharging process of the battery, thereby completely eliminating sodium dendrites. In addition, the technical solution of the present invention is not limited to the development stage, and can perform non-destructive repair within the full life cycle of the sodium ion battery. It supports flexible determination of the repair conditions, cycles or frequencies based on the actual use data of the battery cell, and achieves a significant improvement in the service life of the battery cell and the safety during service at a low cost.

[0058] In one embodiment, if Figure 3 As shown, before the high current discharge step S10, it also includes:

[0059] Step S11. Obtaining the sodium precipitation coefficient of the sodium ion battery, and determining whether the sodium ion battery has repair value according to the sodium precipitation coefficient of the sodium ion battery;

[0060] If yes, a high current discharge step is performed;

[0061] Wherein, the sodium precipitation coefficient formula is:

[0062] ,

[0063] Among them, ζ is the sodium precipitation coefficient of the sodium ion battery, α1 is the temperature induction coefficient, α2 is the resistance induction coefficient, and α3 is the electrochemical induction coefficient;

[0064] α1, α2, and α3 are calculated according to the following formulas:

[0065] ,

[0066] ,

[0067] ,

[0068] Among them, ΔT is the temperature rise of the battery during charging, T0 is the charging and discharging ambient temperature, R ohm is the ohmic resistance of the battery, Z ω is the sodium ion diffusion impedance, C 理 is the theoretical capacity of the battery, J is the charge and discharge current of the battery, ΔCE is the coulombic efficiency of the battery, τ 弛 It is the relaxation time of the high voltage platform of battery discharge.

[0069] 1. From the main differences with lithium-ion batteries:

[0070] Sodium-ion batteries have excellent rate performance because Na + The solvation energy is low and the ion diffusion performance at the interface is good, so it is easier to be put into high-rate conditions first, and the risk of sodium precipitation increases (Z ω Large, ζ large); limited by the ion radius, the insertion and extraction reactions of ions in the electrode are difficult, which is manifested as a large internal resistance of the sodium ion battery (R ohm Sodium ion batteries have a wide operating temperature range and excellent low-temperature performance, so they are often used in low-temperature scenarios. However, the risk of sodium precipitation is greatly increased when they are in low-temperature conditions for a long time (T0 is small, ζ is large). Compared with lithium ions, sodium ions have stable chemical properties and large ionic radius. Correspondingly, the electrode stress in the battery is also large, resulting in a higher temperature rise and a larger amount of dendrite precipitation, which aggravates the precipitation behavior of sodium dendrites (ΔT is large, ζ is large).

[0071] 2. From the general characteristics of alkali metal ion batteries:

[0072] The lower the initial temperature T0, the greater the amount of dendrite precipitation, temperature rise and stress (small T0, large ζ); the theoretical electrode capacity C理 High, polarization is serious at high magnification, and dendrite precipitation is more serious (C 理 Large and / or large J, large ζ); Studies have shown that the physical quantity of sodium precipitation, which needs to be accurately characterized at the microscopic level, can be mapped by macroscopic parameters that are easily measured by the battery, such as the decrease in Coulomb efficiency (large ΔCE, large ζ), the strong contraction of the EIS spectrum, and the long duration of the high-voltage platform of the low-rate discharge curve (τ 弛 big, ζ big) etc.;

[0073] Based on the above two points, the temperature induction coefficient α1, the resistance induction coefficient α2 and the electrochemical induction coefficient α3 can be summarized. By combining the three coefficients α1, α2 and α3, a quantitative evaluation of the degree of sodium precipitation in the current state of the sodium-ion battery can be obtained to effectively inhibit the precipitation and / or growth of sodium dendrites during the full life cycle of the battery; and different types of sodium-ion batteries have large differences in the degree of sodium precipitation under different usage conditions. The degree of sodium precipitation of the battery is evaluated by a variety of apparent state parameters of the battery, and the battery repair value is judged based on the evaluation of the degree of sodium precipitation, and then the key parameters of the repair technology are regulated based on each induction coefficient, so as to solve the technical problem of the inevitable sodium dendrite growth at each stage of the battery in the prior art, which leads to a reduction in the capacity of the sodium-ion battery and an increase in the safety risk, and maximize the improvement effect.

[0074] In some embodiments of the present invention, in step S11, whether the sodium ion battery has repair value is determined according to the sodium precipitation coefficient of the sodium ion battery. If the sodium precipitation coefficient ζ of the sodium ion battery is ≥80, the subsequent steps of repairing the sodium ion battery are performed.

[0075] In one embodiment, in the high current discharging step S10, the discharging time is t1, 60 s≤t1≤90 s.

[0076] The technical solution of the present invention can completely ionize the precipitated sodium dendrites by adjusting the discharge time t1 between 60 s and 90 s. If the discharge time t1 is too short, the connection between the sodium dendrites and the electrodes is weak, and it is impossible to establish an electrical connection between the isolated sodium dendrites and the electrodes; if the discharge time t1 is too long, there will be risks of battery heating, short circuit, over-discharge, etc., which will affect the battery performance and life.

[0077] In one embodiment, in the high temperature standing step S20, the insulation time is t2, 24 h≤t2≤36 h.

[0078] The technical solution of the present invention adjusts the static insulation time t2 to 24 h~36 h. If the static insulation time t2 is too short, the "melting" process of sodium precipitation is not complete, and there are still undissolved sodium dendrites, and the optimal "melting" effect cannot be achieved. The sodium precipitation ionization process is not complete and the repair effect is poor; if the static insulation time t2 is too long, it is easy to make the electrode ionization degree too large, so that the internal resistance of the battery is too large, resulting in reduced discharge performance of the sodium ion battery, reduced battery capacity, and poor repair effect.

[0079] In one embodiment, in the low current cyclic charge and discharge step S30, the temperature of the sodium ion battery is T2, 30°C≤T2≤60°C, and T2≤T1.

[0080] The technical solution of the present invention reduces the side reaction rate caused by high temperature during low current cyclic charge and discharge by adjusting the temperature T2 not higher than the static insulation temperature T1 and not higher than 60°C, thereby reducing battery aging, ensuring the capacity of the battery, and improving the repair effect; by adjusting the temperature T2 not lower than 30°C, the chemical reaction rate in the low current cyclic charge and discharge step 30 is increased, the migration of sodium ions is accelerated, and the sodium dendrites are promoted to be eliminated. Therefore, the temperature T2 described in the present invention is preferably 30°C to 60°C.

[0081] In one embodiment, the low current cyclic charge and discharge step S30 includes the following steps:

[0082] Step S31. Cyclic charging and discharging of the sodium ion battery with a second current I2;

[0083] Step S32. Cyclic charging and discharging of the sodium ion battery with a third current I3;

[0084] Among them, 1 / 2C≤I2≤1C, 1 / 20C≤I3≤1 / 10C.

[0085] The technical solution of the present invention can reduce the influence of adverse factors such as concentration polarization and electrochemical polarization caused by current through low-rate current charge and discharge treatment, so that more sodium ions can participate in the charge and discharge process of the battery, thereby completely eliminating sodium dendrites; by adopting two small current cycle charge and discharge, wherein the first cycle charge and discharge is carried out by adopting a current of 1 / 2C~1C to quickly repair and shorten the time required for repair, and the second cycle charge and discharge is carried out by adopting a current of 1 / 20C~1 / 10C to deeply repair and increase the degree of depolarization and improve the repair effect; if the currents I3 and I4 are too large, the depolarization effect will not be achieved, and if the currents are too small, the repair time is too long and the repair efficiency is low.

[0086] In one embodiment, in the step S31 of cyclically charging and discharging the sodium ion battery with the second current I2, the number of cycles of cyclic charging and discharging is n, 2≤n≤3; and / or, in the step S32 of cyclically charging and discharging the sodium ion battery with the third current I3, the number of cycles of cyclic charging and discharging is m, 2≤m≤5.

[0087] The technical solution of the present invention can repair larger electrode defects by adopting 1 / 2C~1C current for 2~3 cycles of charge and discharge, and if the number of cycles is less than 2 times, the repair effect is poor, and if the number of cycles is more than 3 times, the repair effect after 3 cycles is not obvious, which prolongs the repair time and reduces the repair efficiency; the technical solution of the present invention can repair smaller electrode defects by adopting 1 / 20C~1 / 10C current for 2~5 cycles of charge and discharge, and if the number of cycles is less than 2 times, the repair effect is poor, and if the number of cycles is more than 5 times, the repair effect after 5 cycles is not obvious, and prolongs the repair time and reduces the repair efficiency.

[0088] In one embodiment, if Figure 4 As shown, before the high current discharge step S10, the following steps are also included:

[0089] Step S12. The sodium ion battery is charged with a fourth current I4 at a constant current until the charging voltage reaches an upper charging limit voltage; wherein 1 / 3C≤I4≤1 / 2C.

[0090] The technical solution of the present invention charges the sodium ion battery in advance so that the discharge time can be extended during the high current discharge step so that the sodium dendrites can be completely "melted"; by adjusting the range of I4 to 1 / 3C~1 / 2C, within this current range is the charging current of the battery during normal operation or the charging current in long-term use, the charging can be stably performed to improve the guarantee of sufficient power in the battery, so as to extend the discharge time during the high current discharge step so that the sodium dendrites can be completely "melted". In some embodiments of the present invention, such as Figure 4 As shown, step S12 is after step S11, judging that the sodium precipitation coefficient ζ of the sodium ion battery is ≥ 80, judging that its repair value is high, and then charging and subsequent steps are performed to complete the repair.

[0091] In one embodiment, in step S12 of performing constant current charging on the sodium ion battery with the fourth current I4, the temperature of the sodium ion battery is T3, 25°C≤T3≤30°C.

[0092] The technical solution of the present invention adjusts the temperature of the sodium ion battery to 25°C~30°C so as to charge normally at room temperature, which helps to reduce side reactions caused by overheating during charging, such as electrolyte decomposition, thereby reducing battery aging and ensuring the battery capacity.

[0093] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0094] Example 1

[0095] This embodiment provides a sodium ion battery repair method, comprising the following steps:

[0096] S1. At room temperature, the battery is charged with a constant current of 1 / 3C, and the charging voltage reaches the upper limit voltage of the charge as the cutoff condition;

[0097] S2. The battery is discharged at a constant current of 2C for 90 seconds.

[0098] S3. The sodium ion battery is heated to 40°C and allowed to stand at this temperature for 24 h;

[0099] S4. Adjust the temperature to 30°C, charge and discharge the battery twice at a relatively low rate current of 1 / 2C, and then charge and discharge the battery three times at another relatively low rate current of 1 / 20C, and record the discharge capacity of the last cycle, that is, the capacity of the battery after repair.

[0100] Example 2

[0101] This embodiment provides a sodium ion battery repair method, comprising the following steps:

[0102] S1. At room temperature, the battery is charged with a constant current of 1 / 3C, and the charging voltage reaches the upper limit voltage of the charge as the cutoff condition;

[0103] S2. The battery is discharged at a constant current of 4C for 60 s.

[0104] S3. The sodium ion battery is heated to 70°C and allowed to stand at this temperature for 36 h;

[0105] S4. Adjust the temperature to 30°C, charge and discharge the battery three times at a relatively low rate current of 1C, and then charge and discharge the battery five times at another relatively low rate current of 1 / 10C, ​​and record the discharge capacity of the last cycle, i.e. the capacity of the battery after repair.

[0106] Example 3

[0107] This embodiment provides a sodium ion battery repair method, comprising the following steps:

[0108] S1. At room temperature, the battery is charged with a constant current of 1 / 3C, and the charging voltage reaches the upper limit voltage of the charge as the cutoff condition;

[0109] S2. The battery is discharged at a constant current of 3C for 75 seconds.

[0110] S3. The sodium ion battery is heated to 55°C and allowed to stand at this temperature for 30 h;

[0111] S4. Adjust the temperature to 30°C, charge and discharge the battery three times at a relatively low rate current of 2 / 3C, and then charge and discharge the battery four times at another relatively low rate current of 2 / 30C, and record the discharge capacity of the last cycle, i.e. the capacity of the battery after repair.

[0112] Comparative Example 1

[0113] This comparative example provides a sodium ion battery repair method, comprising the following steps:

[0114] The ambient temperature is 25°C, the pulse charging current is 0.5C, the pulse time is 10s, the pulse time interval is 10s, and the charging cycle time is 3600s.

[0115] Performance Testing

[0116] A plurality of sodium ion batteries with different sodium precipitation states were obtained, and pulse current was applied to the batteries to perform capacity repair according to the sodium ion battery repair method provided in Comparative Example 1. The repair effect statistics are shown in Table 1.

[0117] Table 1 Sodium precipitation coefficient and capacity repair rate of sodium ion battery repaired by the method of comparative example 1

[0118]

[0119] It can be seen from Table 1 that for batteries with a sodium precipitation coefficient value lower than 80, the repair rate of the conventional pulse charging method provided in Comparative Example 1 is less than 2%, and the repair effect is poor; while for batteries with a value exceeding 80, it can be determined to have a high value of inhibiting sodium precipitation repair. The key parameters of the repair technology are selected based on each induction factor to effectively inhibit the sodium precipitation reaction, thereby achieving rapid and lossless capacity repair of sodium ion batteries, and the repair rate can exceed 4%.

[0120] A plurality of sodium ion batteries with different sodium precipitation states were obtained, and pulse current was applied to the batteries to perform capacity repair according to the sodium ion battery repair methods provided in Examples 1 to 3. The repair effect statistics are shown in Table 2.

[0121] Table 2 Sodium precipitation coefficient and capacity repair rate of sodium ion batteries repaired by the methods of Examples 1 to 3

[0122]

[0123] It can be seen from Table 2 that for sodium ion batteries of layered and Prussian blue material systems, the sodium precipitation coefficient has an obvious positive correlation with the repair rate, and the repair rate is higher than the highest capacity repair rate described in Comparative Example 1, indicating that the capacity repair effect is significantly improved through the present technical solution.

[0124] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A sodium ion battery repair method, characterized in that: The following steps are involved: The high current discharge step includes discharging the battery at a constant current with a first current I1, and the discharge time is t1, 60 s≤t1≤90 s; The high-temperature standing step includes heating the sodium-ion battery and then keeping it at a temperature T1 for a period of time t2, 24 h≤t2≤36 h; The low current cyclic charging and discharging step at least comprises cyclically charging and discharging the sodium ion battery with a second current I2; The current intensity of the sodium ion battery during one-hour full discharge is 1C, 2C≤I1≤4C, 1 / 20C≤I2≤1C, 40℃≤T1≤70℃; Before the high current discharge step, it also includes: Obtaining a sodium precipitation coefficient of a sodium ion battery, and determining whether the sodium ion battery has repair value according to the sodium precipitation coefficient of the sodium ion battery; If yes, a high current discharge step is performed; Wherein, the sodium precipitation coefficient formula is: ， Among them, ζ is the sodium precipitation coefficient of the sodium ion battery, α1 is the temperature induction coefficient, α2 is the resistance induction coefficient, and α3 is the electrochemical induction coefficient; α1, α2, and α3 are calculated according to the following formulas: ， ， ， Among them, ΔT is the temperature rise of the battery during charging, T0 is the charging and discharging ambient temperature, R ohm is the ohmic resistance of the battery, Z ω is the sodium ion diffusion impedance, C 理 is the theoretical capacity of the battery, J is the charge and discharge current of the battery, ΔCE is the coulombic efficiency of the battery, τ 弛 It is the relaxation time of the high voltage platform of battery discharge.

2. The sodium ion battery repair method according to claim 1, characterized in that: In the low current cycle charge and discharge step, the temperature of the sodium ion battery is T2, 30°C≤T2≤60°C, and T2≤T1.

3. The sodium ion battery repair method according to claim 1, characterized in that: The low current cycle charge and discharge step includes the following steps: Cyclic charging and discharging of the sodium ion battery with a second current I2; Cyclic charging and discharging of the sodium ion battery with a third current I3; Among them, 1 / 2C≤I2≤1C, 1 / 20C≤I3≤1 / 10C.

4. The sodium ion battery repair method according to claim 3, characterized in that: in, In the step of cyclically charging and discharging the sodium ion battery with the second current I2, the number of cycles of cyclic charging and discharging is n, 2≤n≤3; and / or, In the step of cyclically charging and discharging the sodium ion battery with the third current I3, the number of cycles of cyclic charging and discharging is m, and 2≤m≤5.

5. The sodium ion battery repair method according to claim 1, characterized in that: Before the high current discharge step, the following steps are also included: The sodium ion battery is charged with a fourth current I4 at a constant current until the charging voltage reaches an upper charging limit voltage; Among them, 1 / 3C≤I4≤1 / 2C.

6. The sodium ion battery repair method according to claim 5, characterized in that: In the step of performing constant current charging on the sodium ion battery with the fourth current I4, the temperature of the sodium ion battery is T3, 25°C≤T3≤30°C.

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