A method for repairing and regenerating a lithium metal battery lithium negative electrode failure

Abstract

The application discloses a kind of lithium metal battery lithium negative electrode failure repair regeneration method, by analyzing the charge-discharge cycle curve of lithium metal battery after cycle, judge whether there is " burr lithium-3 " in current lithium metal battery lithium negative electrode, if " burr lithium-3 " exists, analyze the highest critical safety temperature that current lithium metal battery can bear, heat current lithium metal battery to critical safety temperature, and after incubation and standing for a set time, in critical safety temperature environment, constant current small current is used to discharge current lithium metal battery voltage to set voltage. So that " burr lithium-3 " is repaired in situ, so it can continue to participate in the reaction, effectively improve the utilization rate of limited lithium source in lithium metal battery, so that lithium metal battery recovers charge-discharge cycle, and then effectively prolongs the continuation of lithium metal battery, long cycle performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium battery repair and regeneration, and particularly relates to a method for repairing and regenerating lithium metal battery lithium negative electrode failure. BACKGROUND

[0002] In the prior art, lithium metal has high theoretical specific capacity (3860 mAh / g), extremely low negative potential (−3.04 V) and very light mass density (0.534 g / cm 3 ), and can greatly improve the battery energy density to more than 500 Wh / kg, and is therefore considered as an ideal negative electrode material for the next generation of high-energy-density batteries. Lithium metal negative electrode is prone to form lithium dendrites in the electrochemical "nucleation-deposition-growth" process, which induces the rupture of the solid-state electrolyte interface (SEI) film. After repeated deposition and stripping, a large number of lithium metal particles wrapped by SEI are generated, causing rapid pulverization and rapid volume expansion of the lithium negative electrode, increasing the battery resistance and polarization, and ultimately leading to the capacity attenuation of the battery. Especially under high energy density conditions, high load of the positive electrode means that a large amount of electric capacity flows through the battery during each charge and discharge, and the proportion of lithium negative electrode participating in the reaction is high, the interface side reaction between lithium and electrolyte will accelerate, and the consumption between the two will accelerate, ultimately leading to the rapid capacity attenuation of the lithium metal battery. After the lithium metal battery is cycled, the lithium negative electrode contains "true dead lithium" (lithium-containing compounds such as LiF, Li2CO3, Li2O, ROCO2Li, etc., mainly existing in the SEI layer) generated by the irreversible reaction between lithium and electrolyte. Related technical personnel have also begun to focus on the repair work of the cycled lithium negative electrode, including applying short and intermittent large current pulses during battery use, or building a stable surface passivation layer to inhibit the corrosion of electrolyte to lithium and promote uniform deposition, or building an exogenous conductive network in the dead lithium to re-establish the electronic path between the dead lithium and the electrode, so that the dead lithium can be reused. However, the average cycle performance of the repaired battery obtained by using these methods is still lower than that of the continuously cycled battery, and the cycle maintenance time is short, which cannot effectively be applied on a large scale, and thus the lithium dendrite problem is difficult to be completely solved.

[0003] The inventors found that after the lithium metal battery is cycled, the lithium negative electrode contains not only "true dead lithium" generated by the irreversible reaction of lithium and electrolyte, but also a large amount of "false dead lithium" that temporarily loses electron conduction or ion transport and cannot continue to participate in the charge-discharge reaction. The "false dead lithium" includes "false dead lithium-1", "false dead lithium-2", "false dead lithium-3" and other unknown forms of "false dead lithium". The "false dead lithium-1" is lithium temporarily losing electron transport path wrapped by the SEI insulation layer; the "false dead lithium-2" is lithium temporarily losing ion transport at the newly exposed reaction interface without being infiltrated by electrolyte in time; and the "false dead lithium-3" is lithium dendrite penetrating the surface of the lithium negative electrode but not completely piercing the separator to cause micro-short circuit. Since the "false dead lithium" still contains bulk lithium, it may still have electrochemical activity. The amount of these "false dead lithium" generated is much larger than that of "true dead lithium", which has become the main source of battery capacity loss. If an effective method can be found to activate these temporarily inactive "false dead lithium" again and make them participate in electrochemical reactions, the utilization rate of limited lithium in the battery will be greatly improved, thereby effectively prolonging the endurance and long cycle performance of the lithium metal battery. This is particularly critical in the current situation where lithium dendrite problems are difficult to be completely solved.

[0004] Therefore, there is a need for a new method for repairing and regenerating the failure of the lithium negative electrode of a lithium metal battery. SUMMARY

[0005] The purpose of the present application is to provide a method for repairing and regenerating the failure of the lithium negative electrode of a lithium metal battery, which solves the technical problems in the prior art that the "false dead lithium" generated after the lithium metal battery is cycled causes battery capacity loss, and the average cycle performance of the repaired lithium metal battery is lower than that of the continuously cycled lithium metal battery.

[0006] The technical scheme for solving the technical problems of the present application is as follows:

[0007] A method for repairing and regenerating the failure of the lithium negative electrode of a lithium metal battery, comprising the following steps:

[0008] S1: analyzing the charge-discharge cycle curve of the lithium metal battery after cycling to determine whether "false dead lithium-3" exists in the lithium negative electrode of the current lithium metal battery, if yes, executing step S2; if no, ending;

[0009] S2: analyzing the highest critical safety temperature that the current lithium metal battery can withstand, heating the current lithium metal battery to the critical safety temperature, and after holding for a set time, discharging the current lithium metal battery voltage to a set voltage at the critical safety temperature environment by using a constant current small current;

[0010] Wherein, the "false dead lithium-3" is lithium dendrite penetrating the surface of the lithium negative electrode but not completely piercing the separator to cause micro-short circuit.

[0011] Preferably, the highest critical safety temperature in step S2 is determined by the thermal decomposition temperature of the positive electrode material, the negative electrode material, the electrolyte salt, the solvent and additives, and the separator.

[0012] Preferably, the critical safety temperature in step S2 is 60℃-150℃.

[0013] Preferably, the time set in step S2 is 24h-36h.

[0014] Preferably, the constant current in step S2 is 0.02C-0.1C.

[0015] Preferably, the voltage in step S2 is set to 2.7V.

[0016] Preferably, the positive electrode material of the lithium metal battery is any one of lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese oxide, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and lithium cobalt phosphate, and the loading of the positive electrode material is 0.5 mg / cm³. 2 -30mg / cm 2 .

[0017] Preferably, the negative electrode material of the lithium metal battery is any one of lithium, lithium-magnesium alloy, lithium-aluminum alloy, and lithium-indium alloy, and the thickness of the negative electrode material is 20um-600um.

[0018] Preferably, the electrolyte of the lithium metal battery is any one of esters, ethers, or ionic liquids.

[0019] The beneficial effects of this invention are as follows: By analyzing the charge-discharge cycle curves of the lithium metal battery after cycling, it is determined whether "burst lithium-3" exists in the lithium anode of the current lithium metal battery. If "burst lithium-3" exists, the maximum critical safety temperature that the current lithium metal battery can withstand is analyzed. The current lithium metal battery is heated to the critical safety temperature and kept at that temperature for a set time. Then, under the critical safety temperature environment, a constant current is used to discharge the current lithium metal battery voltage to the set voltage. This allows the "burst lithium-3" to be repaired in situ, enabling it to continue participating in the reaction, effectively improving the utilization rate of the limited lithium source in the lithium metal battery, allowing the lithium metal battery to resume charge-discharge cycles, and thus effectively extending the battery's range and long-cycle performance. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the present invention;

[0021] Figure 2 It is the main form of lithium in the negative electrode after lithium metal battery cycling;

[0022] Figure 3is a repair strategy schematic diagram for "burr lithium-3" causing micro-short circuit;

[0023] Figure 4 is the charge-discharge curve of the repaired battery obtained in embodiment 1 before repair;

[0024] Figure 5 is the charge-discharge curve of the repaired battery obtained in embodiment 1 after repair;

[0025] Figure 6 is the cycle performance comparison diagram of the repaired battery obtained in embodiment 1 before and after repair;

[0026] Figure 7 is the charge-discharge curve of the repaired battery obtained in embodiment 2 before repair;

[0027] Figure 8 is the charge-discharge curve of the repaired battery obtained in embodiment 2 after repair;

[0028] Figure 9 is the cycle performance comparison diagram of the repaired battery obtained in embodiment 2 before and after repair. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application.

[0030] As shown in Figure 1 , the application discloses a repair and regeneration method for lithium metal battery lithium negative electrode failure, comprising the following steps:

[0031] S1: analyze the charge-discharge cycle curve of the lithium metal battery after cycling, determine whether there is "burr lithium-3" in the current lithium metal battery lithium negative electrode, if yes, execute step S2; if no, end;

[0032] S2: analyze the highest critical safety temperature that the current lithium metal battery can withstand, heat the current lithium metal battery to the critical safety temperature, and after holding and standing for a set time, discharge the current lithium metal battery voltage to a set voltage under the critical safety temperature environment by using constant current small current, wherein "burr lithium-3" is a lithium dendrite that causes micro-short circuit by piercing the surface of the lithium negative electrode but not completely piercing the separator. The set time is generally 24h-36h, the critical safety temperature is generally 60℃-150℃, the constant current small current is generally 0.02C-0.1C constant current, and the set voltage is 2.7V. The highest critical safety temperature is determined by the thermal decomposition temperature of the positive electrode material, the negative electrode material, the salt, the solvent and the additive of the electrolyte, and the separator.

[0033] The cathode material for lithium metal batteries is any one of the following: lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese oxide, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and lithium cobalt phosphate, with a cathode material loading of 0.5 mg / cm³. 2 -30mg / cm 2 The negative electrode material of lithium metal batteries is any one of lithium, lithium-magnesium alloy, lithium-aluminum alloy, or lithium-indium alloy, with a thickness ranging from 20µm to 600µm. The electrolyte of lithium metal batteries is any one of ester, ether, or ionic liquid types. The separator is a PP / PE / PP separator.

[0034] like Figure 3 As shown, the above-mentioned repair and regeneration method for lithium anode failure in lithium metal batteries utilizes the "burr lithium-3" morphology of the lithium anode. Initially, the "burr lithium-3" punctures the separator, causing a micro-short circuit. Through heating and increasing the temperature, lithium surface diffusion is introduced, increasing lithium fluidity and softening the burr lithium. Finally, constant current low-current discharge reconstruction allows the protruding parts on the anode surface to discharge preferentially, converting the burr lithium into lithium ions that dissolve in the electrolyte, eliminating the micro-short circuit hazard. Unlike the conventional approach of protecting the lithium metal anode before cycling, this method addresses the issue after battery cycling. Using electro / thermal physical field coupling technology and a critical high-temperature constant current discharge repair method, it repairs the "pseudo-dead lithium" in the lithium anode in situ, allowing it to re-participate in the reaction. This effectively improves the long-cycle performance of the lithium metal battery. The repair process is simple, low-cost, easy to apply in practice, environmentally friendly, and produces no additional pollution. It effectively improves the utilization rate of the limited lithium source within the lithium metal battery, thereby effectively extending the battery's range and long-cycle performance.

[0035] Example 1:

[0036] Taking the 2016-type button cell battery as an example, the specific lithium metal battery parameters are as follows: the negative electrode material is a lithium sheet with a thickness of 50μm, and the positive electrode material has a loading capacity of 20mg / cm³. 2 LiNi 0.8 Mn 0.1 Co 0.1 For O2, the positive electrode material can be of various types, including 111, 523, 622 and 811. Here, the 811 type is selected. The separator is a 20 μm thick PP / PE / PP separator, and the electrolyte volume is 100 μL.

[0037] Ideally, a lithium metal battery cycle consists of two charge-discharge cycles within a 2.7-4.4V voltage range and a charge / discharge rate of 0.1C (1C=200 mA / g), followed by two charge-discharge cycles within the same voltage range and at charge / discharge rates of 0.1C / 0.33C (1C=200 mA / g).Figure 4 As shown, generally in lithium metal batteries, the battery capacity suddenly decreases when cycled to 150 cycles, and the analysis of the charge-discharge curve shows that the battery voltage fluctuates during charging, micro-short circuit occurs, and it is determined that this "false death lithium" is "burr lithium-3". "Burr lithium-3" can cause the charging voltage of the battery to approach the cutoff voltage but always fail to reach it during charging, causing partial short circuit and capacity decay of the battery. At this time, the lithium metal battery is first placed in an oven at 60°C for 24 hours, and then discharged to 2.7V at a low rate current of 0.1C, which can complete the repair of the lithium negative electrode of the lithium metal battery. Figure 5 As shown, the charge-discharge curve of the repaired lithium metal battery returns to normal, and the capacity is also significantly improved, and the discharge specific capacity is 177.1 mAh / g when cycled to 230 cycles, and the capacity retention rate is 89%, effectively improving the cycle life of the battery. As shown, Figure 6 As shown, by comparing the cycle performance of the lithium metal battery before and after repair, it can be directly obtained that when the lithium metal battery is cycled, the "burr lithium-3" generated by the lithium negative electrode after the cycle can be effectively repaired by the high-temperature constant current discharge repair technology, thereby prolonging the cycle life of the battery.

[0038] Example 2:

[0039] Taking a 2016 type button cell as an example, the specific lithium metal battery parameters are as follows: the negative electrode material is selected to be a lithium-magnesium alloy with a thickness of 50 μm, the positive electrode material is selected to be LiNi 2 Mn 0.8 Co 0.1 O2 with a loading capacity of 20 mg / cm 0.1 , the separator is selected to be a PP / PE / PP separator with a thickness of 20 μm, and the electrolyte is used in an amount of 100 μL.

[0040] Under ideal conditions, the lithium metal battery cycle is as follows: charge and discharge cycles are performed 2 times at a voltage range of 2.7-4.4V and a charge / discharge rate of 0.1C (1C=200 mA / g), and the battery is charged and discharged at a voltage range of 2.7-4.4V and a charge / discharge rate of 0.1C / 0.33C (1C=200 mA / g). As shown, Figure 7 As shown, when the lithium metal battery is cycled to 80 cycles, the charge-discharge curve is normal, but when it is cycled to 87 cycles, the battery capacity suddenly decreases, and the analysis of the charge-discharge curve shows that the battery voltage fluctuates during charging, micro-short circuit occurs, and it is determined that this "false death lithium" is "burr lithium-3". At this time, the lithium metal battery is first placed in an oven at 60°C for 24 hours, and then discharged to 2.7V at a low rate current of 0.1C, which can complete the repair of the lithium negative electrode of the lithium metal battery. Figure 8As shown, the charge-discharge curve of the repaired lithium metal battery returns to normal, and the capacity is also significantly improved. The specific discharge capacity is 206.8 mAh / g when stably cycled to 30 cycles, and the capacity retention rate is 98%, effectively improving the cycle life of the battery. As shown in FIG. 6B, the capacity retention rate of the repaired lithium metal battery is 98% after 30 cycles, which is much higher than that of the unmodified lithium metal battery (about 60%). Figure 9 As shown in FIG. 6B, by comparing the cycle performance of the lithium metal battery before and after repair, it can be directly obtained that when the lithium metal battery is cycled, the "burr lithium-3" generated by the lithium negative electrode after cycling can be effectively repaired by the high-temperature constant-current discharge repair technology, thereby prolonging the cycle life of the battery.

[0041] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0042] Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative labor belong to the scope of protection of the present application.

Claims

1. A method for repairing and regenerating a lithium metal battery lithium anode failure, characterized in that, Comprising the following steps: S1: analyzing the charge-discharge cycle curve of the lithium metal battery after cycling, judging whether there is "burr lithium-3" in the lithium metal battery lithium negative electrode according to the voltage fluctuation at the end of charging or the characteristics of approaching the cut-off voltage infinitely, if yes, executing step S2; if no, ending; S2: analyzing the highest critical safety temperature that the current lithium metal battery can withstand, heating the current lithium metal battery to the critical safety temperature, and after holding and standing for a set time, discharging the current lithium metal battery voltage to a set voltage under the critical safety temperature environment by using a constant small current; Wherein, the highest critical safety temperature is determined by the thermal decomposition temperature of the positive material, the negative material, the salt, the solvent and the additive of the electrolyte, and the separator; the constant small current is: 0.02C-0.1C constant current; the set voltage is: 2.7V; "burr lithium-3" is the lithium dendrite that penetrates the surface of the lithium negative electrode but does not completely pierce the separator to cause micro-short circuit.

2. The method of claim 1, wherein the method is characterized by: The critical safety temperature in step S2 is: 60℃-150 ℃.

3. The method of claim 1, wherein the method is characterized by: The set time in step S2 is: 24h-36h.

4. The method of claim 1, wherein the method is characterized by: The positive electrode material of the lithium metal battery is any one of lithium nickelate, lithium manganate, lithium nickel manganate, lithium cobaltate, lithium nickel cobalt manganate, lithium-rich lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and lithium cobalt phosphate, and the loading amount of the positive electrode material is 0.5 mg / cm 2 -30 mg / cm 2 .

5. The method of claim 1, wherein the method is characterized by: The negative material of the lithium metal battery is: any one of lithium, lithium-magnesium alloy, lithium-aluminum alloy, lithium-indium alloy, and the thickness of the negative material is: 20um-600um.

6. The method of claim 1, wherein the method is characterized by: The electrolyte of the lithium metal battery is: any one of ester, ether, ionic liquid.

Images