Method for recovering dead lithium
By charging at room temperature and using low current density discharge at low temperature, the problem of difficulty in taking into account the electric field strength and dead lithium movement time in the prior art is solved, and efficient dead lithium recovery is achieved, with a recovery rate of more than 90%.
Patent Information
- Application Number
- CN202510024942.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-08
- Publication Date
- 2025-04-15
AI Technical Summary
When the prior art improves the electric field strength to move dead lithium, it is difficult to take into account both the strong driving force and the long moving time, resulting in a low recovery rate of dead lithium.
The lithium-ion battery containing dead lithium is charged at room temperature, and then discharged at a low temperature environment using a low current density to generate a large electric field intensity by reducing the conductivity of the electrolyte.
A high recovery rate of dead lithium is achieved, taking into account strong driving force and long moving time, and the method is safe, applicable and low cost.
Smart Images
Figure CN119833797A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of batteries, and in particular to a method for recovering dead lithium. Background Art
[0002] Lithium-ion batteries have been widely used in electronic devices and electric vehicles due to their high energy density and long cycle life.
[0003] The generation of dead lithium is one of the main reasons for the attenuation of lithium-ion batteries. The appearance of dead lithium not only reduces the battery capacity, but also accelerates battery aging. Therefore, solving the problem of dead lithium is of great significance for the optimization of lithium-ion batteries.
[0004] One of the current methods to solve the dead lithium problem is to use the electric field strength in the electrolyte during the discharge process to "move" the dead lithium to the negative electrode to re-establish the electron path with the current collector (Nature, 2021, 600 (7890): 659-663.). In this method, the driving force for the "movement" of dead lithium is the electric field strength in the electrolyte. In order to establish a high electric field strength in the electrolyte, the method applies a high current density. Although increasing the current density can increase the electric field strength and enhance the driving force for moving dead lithium, increasing the current density also reduces the discharge time and reduces the time for dead lithium to move to the negative electrode. Therefore, this technical solution is caught in the dilemma of not being able to have both strong driving force and long "movement" time. Summary of the invention
[0005] The purpose of the present invention is to provide a method for recovering dead lithium, which has a higher dead lithium recovery rate.
[0006] The purpose of the present invention can be achieved by the following technical scheme: A method for recovering dead lithium comprises the following steps:
[0007] S1: Charging of lithium-ion batteries containing dead lithium at room temperature;
[0008] S2: Discharging the lithium-ion battery charged in step S1 at a low current density in a low temperature environment.
[0009] Preferably, step S1 is performed at room temperature at 4.5-5.5 mA / cm 2 The current is charged to 0.8~1.2mAh / cm 2 .
[0010] Preferably, the room temperature in step S1 is 20-30°C.
[0011] Preferably, the low current density in step S2 is 0.1 mA / cm 2 ~0.5mA / cm 2 .
[0012] Preferably, the low temperature environment in step S2 is 0°C to -20°C.
[0013] Further preferably, the low temperature environment in step S2 is -5°C to -15°C.
[0014] Preferably, the lithium-ion battery includes a variety of batteries that may have dead lithium, such as Li||Cu half-cell, LFP||graphite full cell, NMC||graphite full cell, LCO||graphite full cell, lithium metal battery or anode-free lithium metal battery.
[0015] Further preferably, the lithium-ion battery comprises a Li||Cu half-cell.
[0016] More preferably, the Li||Cu half-cell uses a lithium sheet as the positive electrode, a copper foil as the negative electrode, and the electrolyte contains LiPF6.
[0017] Preferably, the solvent in the electrolyte includes one or more of ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene glycol dimethyl ether (DME).
[0018] Preferably, the additive in the electrolyte includes one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), and propane sultone (PS).
[0019] Preferably, the recovery rate of dead lithium is above 17%.
[0020] Compared with the prior art, the present invention has the following beneficial effects:
[0021] 1. The present invention provides a method for recovering dead lithium, which has a high dead lithium recovery rate.
[0022] 2. Compared with the existing solutions for establishing high electric field strength, the technical solution of the present invention bypasses the high current and reduces the electrolyte conductivity by low temperature so that a larger electric field strength can be generated in the electrolyte at a lower current density, thereby taking into account both strong driving force and long movement time.
[0023] 3. The present invention provides a lithium-ion battery capacity recovery method with high safety, strong applicability and low cost. The dead lithium recovery rate is above 17% and can be as high as 90%. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Schematic diagram of a process for recovering dead lithium in an embodiment of the present invention;
[0025] Figure 2 A representative capacity-voltage diagram for the dead lithium accumulation process;
[0026] Figure 3 The capacity-voltage diagram of the lithium-ion battery of the present invention in the dead lithium recovery stage and the capacity-voltage diagram of the battery without dead lithium under the same cycle conditions;
[0027] Figure 4 This is a process diagram of accumulating dead lithium (4a) and recovering dead lithium (4b) according to Example 1 of the present invention;
[0028] Figure 5 This is a process diagram of accumulating dead lithium (5a) and recovering dead lithium (5b) according to Example 2 of the present invention;
[0029] Figure 6 This is a process diagram of accumulating dead lithium (6a) and recovering dead lithium (6b) according to Example 3 of the present invention;
[0030] Figure 7 This is a process diagram of accumulating dead lithium (7a) and recovering dead lithium (7b) according to Example 4 of the present invention;
[0031] Figure 8 This is a process diagram of accumulating dead lithium (8a) and recovering dead lithium (8b) in Comparative Example 1;
[0032] Fig. 9 This is a process diagram of accumulating dead lithium (9a) and recovering dead lithium (9b) in Comparative Example 2. DETAILED DESCRIPTION
[0033] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.
[0034] A method for recovering dead lithium, such as Figure 1 As shown, the following steps are included:
[0035] 1. Charge lithium-ion batteries containing dead lithium at room temperature;
[0036] 2. Discharge the lithium-ion battery using a low current density in a low temperature environment.
[0037] Specifically:
[0038] The battery manufacturing method and testing method used in the embodiments and comparative examples are as follows:
[0039] The technical solution of the present invention is described using a Li||Cu half-cell. The Li||Cu half-cell is assembled using a CR2032 button battery shell. Before assembly, the copper foil is cleaned with 0.1M hydrochloric acid, ethanol, acetone and deionized water in sequence to remove surface contaminants. A lithium sheet with a diameter of 12.5mm is used as the positive electrode, a copper foil with a diameter of 14mm is used as the negative electrode, a Celgard2320 type is used as the diaphragm, and the electrolyte formula is 1.3M LiPF6 in EC:DEC (3:7vol%) with10%FEC. The battery assembly is completed in an argon-filled glove box (O2<0.01ppm, H2O<0.01ppm), and the battery is then transferred to a CT3002A blue battery test system for testing. The battery is first tested at 0.1mA / cm 2 Ten pre-cycles were performed with a current density between 0V and -1V. These ten pre-cycles reduced the oxide on the surface of the copper foil, formed an initial SEI film, and improved the consistency of the experiment.
[0040] In order to compare the dead lithium recovery rates of different solutions, all batteries were divided into "batteries using this solution to recover dead lithium", "batteries using existing solutions to recover dead lithium" and "batteries without dead lithium" after completing the above process. For "batteries using this solution to recover dead lithium", the battery was tested at 5 mA / cm 2 The current density is 5 mAh / cm 2 The battery is discharged to -1V at the same current density to complete the accumulation of dead lithium. Then it enters the dead lithium recovery stage, that is, discharge at 5mA / cm 2 Charging current 1mAh / cm 2 Then discharge at a low current density in a low temperature environment to recover dead lithium. As for the "battery that uses the existing solution to recover dead lithium", the cycle conditions of the dead lithium accumulation process are exactly the same as the cycle conditions of the "battery that uses this solution to recover dead lithium", and the cycle conditions in the dead lithium recovery stage are the normal temperature high current density provided by the existing technical solution. The "battery that does not contain dead lithium" skips the dead lithium accumulation stage of the above two batteries, and directly uses the same cycle conditions as the dead lithium recovery stage of the above two batteries to understand the dead lithium recovery rate. The calculation formula for the dead lithium recovery rate is as follows:
[0041]
[0042] Where R is the recovery rate of dead lithium; Q r is the amount of dead lithium recovered; Q c is the amount of dead lithium accumulated. c The calculation method is to accumulate the difference between the charging capacity and the discharging capacity in the dead lithium cycle; Q r The calculation method is the difference between the discharge capacity of a battery with dead lithium and the discharge capacity of a battery without dead lithium under the same cycle conditions.
[0043] Figure 2 A representative capacity-voltage diagram of the dead lithium accumulation process is shown, showing Q c The calculation method of "battery using this scheme to recover dead lithium" and "battery using the existing scheme to recover dead lithium" both carried out this process before the dead lithium recovery stage. The battery has a charging capacity of 6.13mAh and a discharge capacity of 5.718mAh. Due to the short cycle time, the electrolyte reaction produces less lithium SEI. It can be considered that the main reason for the discharge capacity being less than the charging capacity is the generation of dead lithium, that is, Q c =6.13mAh-5.718mAh=0.412mAh.
[0044] Figure 3 The capacity-voltage diagram of the dead lithium recovery stage of the "battery using this solution to recover dead lithium" and the capacity-voltage diagram of the "battery without dead lithium" under the same cycle conditions show the Q r The calculation method of "using this solution to restore dead lithium batteries" is as follows Figure 2 The accumulation of dead lithium is shown in Figure 5. 2 The current density is 1 mAh / cm 2 And 0.5mA / cm 2 The battery was discharged to -1V at a current density of -5℃, and the discharge capacity was 1.2712mAh. The battery without dead lithium was directly discharged at 5mA / cm 2 The current density is 1 mAh / cm 2 , and then at 0.5mA / cm 2 The current density is discharged to -1V in an environment of -5℃, and the discharge capacity is 1.1408mAh. r =1.2712-1.1408=0.1304mAh. So the dead lithium recovery rate is R=Q r ÷Q c =0.1304÷0.412=31.65%.
[0045] In order to reduce the error of the discharge capacity of the "battery without dead lithium" under different cycle conditions, the discharge capacity of three batteries was tested under different cycle conditions and the average value was taken to represent the discharge capacity (mAh) of the "battery without dead lithium" under the cycle conditions. The following table shows the average discharge capacity at different discharge current densities and different temperatures:
[0046] Table 1
[0047]
[0048] Example 1
[0049] This example shows that the battery using this solution to recover dead lithium can be used at an ambient temperature of -5°C with a current of 0.5 mA / cm 2 The dead lithium recovery rate of discharge at a current density of . Figure 4 (a) shows the dead lithium accumulation process of the battery. The charging capacity is 6.13 mAh and the discharging capacity is 5.718 mAh. c =6.13mAh-5.718mAh=0.412mAh. Figure 4 (b) shows the process of the battery recovering dead lithium, and the discharge capacity is 1.2712mAh. In Table 1, under the same cycle conditions, the average discharge capacity of the "dead lithium battery" is 1.144386mAh, so the amount of dead lithium recovered is Q r =1.2712mAh-1.144386mAh=0.126814mAh, dead lithium recovery rate R=0.126814mAh÷0.412mAh=30.78%. In order to reduce the contingency, two additional dead lithium recovery experiments were conducted under the experimental conditions, and the dead lithium recovery rates were 30.89% and 29.24% respectively.
[0050] Example 2
[0051] This example shows that the battery using this solution to recover dead lithium can be used at an ambient temperature of -10°C with a current of 0.5 mA / cm 2 The dead lithium recovery rate of discharge at a current density of . Figure 5 (a) shows the dead lithium accumulation process of the battery, the charging capacity is 6.13mAh and the discharging capacity is 5.77mAh, and Q c =6.13mAh-5.77mAh=0.36mAh. Figure 5 (b) shows the process of the battery recovering dead lithium, and the discharge capacity is 1.2178 mAh. In Table 1, the average discharge capacity of the "dead lithium battery" under the same cycle conditions is 1.146325 mAh, so the amount of dead lithium recovered is Q r =1.2178mAh-1.146325mAh=0.071475mAh, dead lithium recovery rate R=0.071475mAh÷0.36mAh=19.85%. In order to reduce the contingency, two additional dead lithium recovery experiments were conducted under the experimental conditions, and the dead lithium recovery rates were 17.69% and 21.22% respectively.
[0052] Example 3
[0053] This example shows that the battery using this solution to recover dead lithium can be used at an ambient temperature of -10°C with a current of 0.3 mA / cm 2 The dead lithium recovery rate of discharge at a current density of . Figure 6(a) shows the dead lithium accumulation process of the battery. The charging capacity is 6.13 mAh and the discharging capacity is 5.748 mAh. c =6.13mAh-5.748mAh=0.382mAh. Figure 6 (b) shows the process of the battery recovering dead lithium, and the discharge capacity is 1.256 mAh. In Table 1, the average discharge capacity of the "dead lithium battery" under the same cycle conditions is 1.144425 mAh, so the amount of dead lithium recovered is Q r =1.256mAh-1.144425mAh=0.111575mAh, dead lithium recovery rate R=0.111575mAh÷0.382mAh=29.21%. In order to reduce the contingency, two additional dead lithium recovery experiments were conducted under the experimental conditions, and the dead lithium recovery rates were 32.98% and 32.1% respectively.
[0054] Example 4
[0055] This example shows that the battery using this solution to recover dead lithium can be used at an ambient temperature of -15°C with a current of 0.1 mA / cm 2 The dead lithium recovery rate of discharge at a current density of . Figure 7 (a) shows the dead lithium accumulation process of the battery. The charging capacity is 6.13 mAh and the discharging capacity is 5.795 mAh. c =6.13mAh-5.795mAh=0.335mAh. Figure 7 (b) shows the process of the battery recovering dead lithium, and the discharge capacity is 1.21 mAh. In Table 1, the average discharge capacity of the "dead lithium battery" under the same cycle conditions is 1.14275 mAh, so the amount of dead lithium recovered is Q r =1.21mAh-1.14275mAh=0.06725mAh, dead lithium recovery rate R=0.06725mAh÷0.335mAh=20.07%. In order to reduce the contingency, two additional dead lithium recovery experiments were conducted under the experimental conditions, and the dead lithium recovery rates were 28.88% and 23.72% respectively.
[0056] Comparative Example 1
[0057] This comparative example shows that the battery using the existing solution to recover dead lithium is 5 mA / cm at room temperature (about 26 ° C). 2 The dead lithium recovery rate of discharge at a current density of . Figure 8 (a) shows the dead lithium accumulation process of the battery. The charging capacity is 6.13 mAh and the discharging capacity is 5.699 mAh. Q c =6.13mAh-5.795mAh=0.431mAh. Figure 8(b) shows the process of the battery recovering dead lithium, and the discharge capacity is 1.18 mAh. In Table 1, the average discharge capacity of the "dead lithium battery" under the same cycle conditions is 1.136763 mAh, so the amount of dead lithium recovered is Q r =1.18mAh-1.136763mAh=0.043237mAh, dead lithium recovery rate R=0.043237mAh÷0.431mAh=10.03%. In order to reduce the contingency, two additional dead lithium recovery experiments were conducted under the experimental conditions, and the dead lithium recovery rates were 5.49% and 7.38% respectively.
[0058] Comparative Example 2
[0059] This comparative example shows that the battery using the existing scheme to recover dead lithium is 4 mA / cm at room temperature (about 26 ° C). 2 The dead lithium recovery rate of discharge at a current density of . Fig. 9 (a) shows the dead lithium accumulation process of the battery. The charging capacity is 6.13 mAh and the discharging capacity is 5.731 mAh. c =6.13mAh-5.795mAh=0.399mAh. Fig. 9 (b) shows the process of the battery recovering dead lithium, and the discharge capacity is 1.188 mAh. In Table 1, the average discharge capacity of the "dead lithium battery" under the same cycle conditions is 1.142387 mAh, so the amount of dead lithium recovered is Q r =1.188mAh-1.142387mAh=0.045613mAh, dead lithium recovery rate R=0.043237mAh÷0.431mAh=11.43%. In order to reduce the contingency, two additional dead lithium recovery experiments were conducted under the experimental conditions, and the dead lithium recovery rates were 11.97% and 10.73% respectively.
[0060] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.
Claims
1. A method for recovering dead lithium, characterized in that: The following steps are involved: S1: Charging of lithium-ion batteries containing dead lithium at room temperature; S2: Discharging the lithium-ion battery charged in step S1 at a low current density in a low temperature environment.
2. The method for recovering dead lithium according to claim 1, characterized in that: Step S1: at room temperature at 4.5-5.5 mA / cm 2 The current is charged to 0.8~1.2mAh / cm 2 .
3. The method for recovering dead lithium according to claim 1, characterized in that: The room temperature in step S1 is 20-30°C.
4. The method for recovering dead lithium according to claim 1, characterized in that: The low current density in step S2 is 0.1 mA / cm 2 ~0.5mA / cm 2 .
5. The method for recovering dead lithium according to claim 1, characterized in that: The low temperature environment in step S2 is 0°C to -20°C.
6. The method for recovering dead lithium according to claim 5, characterized in that: The low temperature environment in step S2 is -5°C to -15°C.
7. The method for recovering dead lithium according to claim 1, characterized in that: The lithium-ion battery includes a Li||Cu half-cell, an LFP||graphite full cell, an NMC||graphite full cell, an LCO||graphite full cell, a lithium metal battery or an anode-free lithium metal battery.
8. The method for recovering dead lithium according to claim 7, characterized in that: The lithium-ion battery includes a Li||Cu half-cell.
9. The method for recovering dead lithium according to claim 8, characterized in that: The Li||Cu half-cell uses a lithium sheet as a positive electrode, a copper foil as a negative electrode, and the electrolyte contains a solute LiPF6.
10. The method for recovering dead lithium according to claim 9, characterized in that: The solvent in the electrolyte includes one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and ethylene glycol dimethyl ether; The additive in the electrolyte includes one or more of fluoroethylene carbonate, vinylene carbonate, and propane sultone.