Lithium metal battery formation method

Abstract

The invention provides a lithium metal battery formation method. The lithium metal battery formation method specifically comprises the following steps: S1, injecting liquid into a lithium metal battery, sealing and standing; s2, performing constant-current charging on the lithium metal battery with a first current C1, wherein the charging time is T1; s3, the battery subjected to constant-current charging is subjected to standing for the standing time T2; S4, the battery subjected to standing in the step S3 is continuously charged with second current C2 for the charging time T3, and the second current C2 is larger than the first current C1; and S5, carrying out third current C3 discharge on the battery processed in the step S4 to cut-off voltage. According to the formation method of the lithium metal battery, the electrochemical performance of the battery is improved, and the formation time of the lithium metal battery is shortened, so that the formation efficiency of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a lithium metal battery formation method. Background Art

[0002] Lithium metal batteries can provide higher energy density than existing lithium-ion batteries due to their extremely high theoretical specific capacity (3860mAh g-1) and low electrochemical potential (-3.04V relative to standard hydrogen electrode), which is crucial for electric vehicles and portable electronic devices that require long driving range.

[0003] Lithium metal battery formation is a key step in the battery manufacturing process. Its purpose is to activate the active substances in lithium metal batteries and form a stable solid electrolyte interface film (SEI film). SEI film is crucial for lithium metal batteries. Currently, lithium metal batteries often use small currents for pre-cycling during the production process to grow SEI in a slow way, but there is still room for improvement in formation efficiency. Summary of the invention

[0004] In order to improve the formation efficiency of a lithium metal battery, the present invention provides a formation method for a lithium metal battery, which specifically includes the following steps: S1, injecting liquid into the lithium metal battery, sealing it and then letting it stand; S2, charging the lithium metal battery with a first current C1 at a constant current, and the charging time is T1; S3, letting the battery after constant current charging stand for a time of T2; S4, continuing to charge the battery after standing in step S3 with a second current C2, and the charging time is T3, wherein the second current C2 is greater than the first current C1; S5, discharging the battery after step S4 with a third current C3 to a cut-off voltage.

[0005] Furthermore, the standing time in step S1 ranges from 3 hours to 24 hours.

[0006] Furthermore, the first current C1 in step S2 ranges from 0.005C to 0.1C.

[0007] Furthermore, the charging time T1 in step S2 is 1 min to 60 min.

[0008] Furthermore, the standing time T2 of step S3 ranges from 1 h to 3 h.

[0009] Furthermore, the second current C2 in step S4 is in a range of 0.2C to 1C.

[0010] Furthermore, the charging time T3 in step S4 ranges from 1 hour to 3 hours.

[0011] Furthermore, the third current C3 in step S5 is set to 0.5C.

[0012] Furthermore, the negative electrode active material of the battery is a combination of one or more of pure lithium sheets, lithium zinc alloys, lithium magnesium alloys, lithium silver alloys, lithium indium alloys, lithium aluminum alloy materials, and the like.

[0013] Furthermore, the positive electrode active material of the battery is a combination of one or more of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium vanadate, lithium manganate, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, etc.

[0014] The formation method of the lithium metal battery of the present invention first charges the lithium metal battery with a small current for a short time in the early stage of formation, which promotes the formation of the SEI film of the lithium metal negative electrode and increases the infiltration rate of the positive electrode sheet of the battery cell, which is beneficial to the improvement of the internal resistance of the lithium metal battery. Therefore, the formation method of the lithium metal battery of the present invention not only improves the electrochemical performance of the battery, but also shortens the formation time of the lithium metal battery, thereby improving the formation efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, 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 drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 The present invention is a flow chart of the lithium metal battery formation method. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0018] Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0019] The present invention provides a formation method for a lithium metal battery, comprising the following steps:

[0020] S1: Prepare a lithium metal battery and inject liquid into the lithium metal battery, seal it, and then let it stand. Specifically, a positive electrode sheet with a nickel-cobalt-manganese oxide ternary material as the positive electrode active material and a negative electrode sheet with a lithium-zinc alloy as the negative electrode active material are used, and a separator is used to separate the positive electrode sheet and the negative electrode sheet. The copper electrode tab of the lithium-zinc alloy negative electrode sheet is realized by pressing, and a base film stack is used to form a bare battery cell, which is encapsulated with an aluminum-plastic film, and the aluminum electrode tab and the copper-plated nickel electrode tab are respectively led out. After the electrolyte is injected, it is sealed and left to stand for a period of time to obtain a 2.6Ah soft-pack battery, recorded as C, waiting for formation.

[0021] The electrolyte injected in this process can be a combination of one or more lithium salts such as lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl imide), bis(trifluoromethanesulfonyl imide), etc.; in this embodiment, the injected electrolyte also needs to have an electrolyte additive, and the electrolyte additive is a combination of one or more of lithium difluorooxalate borate, vinylene carbonate, lithium nitrate, fluoroethylene carbonate, etc. After the lithium metal battery after injection is sealed, it is preferably placed on hold. Of course, the subsequent formation step can be performed directly without the placement step. The formation time and formation efficiency mentioned later in the present invention do not include the placement time before the formation starts after injection.

[0022] Example 1

[0023] The positive electrode sheet with lithium nickel cobalt manganese oxide as the active material and the negative electrode sheet with lithium zinc alloy as the active material are realized by pressing together the copper tabs of the lithium zinc alloy negative electrode. The bare battery cell is formed by using base film stacking and encapsulated with aluminum-plastic film. The aluminum tabs and copper-plated nickel tabs are respectively led out, sealed after liquid injection, and left to stand for 12 hours to wait for formation.

[0024] The cells were placed in a lithium metal battery formation cabinet in turn, the temperature was set to 25°C, the formation pressure was 1.0 MPa, and they were first placed for 15 minutes, then charged at 0.005C constant current for 60 minutes, placed for 120 minutes, and then fully charged at 0.2C constant current and constant voltage, with a cutoff current of 0.05C. After standing for 15 minutes, the battery was fully discharged at 0.5C current to complete the formation, and a 2.6Ah soft-pack battery was obtained, recorded as C1.

[0025] Example 2

[0026] The positive electrode sheet with lithium nickel cobalt manganese oxide as the positive electrode active material and the negative electrode sheet with lithium zinc alloy as the active material, the lithium zinc alloy negative electrode copper tab is realized by pressing, and the base film is stacked to form a bare battery cell, which is encapsulated with aluminum-plastic film, and the aluminum tabs and copper-plated nickel tabs are respectively led out, sealed after liquid injection, and left to stand for 18 hours to wait for formation.

[0027] The cells were placed in a lithium metal battery formation cabinet in turn, the temperature was set to 25°C, the formation pressure was 1.0 MPa, and they were first placed for 15 minutes, then charged at 0.01C constant current for 5 minutes, and placed for 60 minutes; then fully charged at 0.4C constant current and constant voltage, with a cutoff current of 0.05C, and placed for 15 minutes, and finally fully discharged at 0.5C to complete the formation, obtaining a 2.6Ah soft-pack battery, recorded as C2.

[0028] Example 3

[0029] The positive electrode sheet with lithium nickel cobalt manganese oxide as the positive electrode active material and the negative electrode sheet with lithium zinc alloy as the active material, the lithium zinc alloy negative electrode copper tab is realized by pressing, and the base film stack is used to form a bare battery cell, which is encapsulated with aluminum-plastic film, and the aluminum tabs and copper-plated nickel tabs are respectively led out, sealed after liquid injection, and wait for formation.

[0030] The cells were placed in a lithium metal battery formation cabinet in turn, the temperature was set to 25°C, the formation pressure was 1.0 MPa, and they were first placed for 15 minutes, then charged at 0.02C constant current for 5 minutes, and placed for 150 minutes; then fully charged at 0.5C constant current and constant voltage, with a cutoff current of 0.05C, and placed for 15 minutes; finally, the formation was completed with a full discharge at 0.5C current to obtain a 2.6Ah soft-pack battery, recorded as C3.

[0031] Example 4

[0032] The positive electrode sheet with lithium nickel cobalt manganese oxide as the positive electrode active material and the negative electrode sheet with lithium zinc alloy as the active material, the lithium zinc alloy negative electrode copper tab is realized by pressing, and the base film is stacked to form a bare battery cell, which is encapsulated with aluminum-plastic film, and the aluminum tabs and copper-plated nickel tabs are respectively led out, sealed after liquid injection, and left to stand for 3 hours to wait for formation.

[0033] The cells were placed in a lithium metal battery formation cabinet in turn, the temperature was set to 25°C, the formation pressure was 1.0 MPa, and they were first placed for 15 minutes, then charged at 0.04C constant current for 5 minutes, and placed for 180 minutes; then fully charged at 0.8C constant current and constant voltage, with a cutoff current of 0.05C, and placed for 15 minutes; finally, the formation was completed with a full discharge at 0.5C current to obtain a 2.6Ah soft-pack battery, recorded as C4.

[0034] Example 5

[0035] The positive electrode sheet with lithium nickel cobalt manganese oxide as the positive electrode active material and the negative electrode sheet with lithium zinc alloy as the active material, the lithium zinc alloy negative electrode copper tab is realized by pressing, and the base film is stacked to form a bare battery cell, which is encapsulated with aluminum-plastic film, and the aluminum tabs and copper-plated nickel tabs are respectively led out, sealed after liquid injection, and left to stand for 24 hours to wait for formation.

[0036] The cells were placed in a lithium metal battery formation cabinet in turn, the temperature was set to 25°C, the formation pressure was 1.0 MPa, and they were first placed for 15 minutes, then charged at 0.1C constant current for 5 minutes, and then placed for 15 minutes; then fully charged at 1C constant current and constant voltage, with a cutoff current of 0.05C, and placed for 15 minutes; finally, fully discharged at 0.5C current to complete the formation, and a 2.6Ah soft-pack battery was obtained, recorded as C5.

[0037] Comparative Example

[0038] The positive electrode sheet with lithium nickel cobalt manganese oxide as the positive electrode active material and the negative electrode sheet with lithium zinc alloy as the active material are realized by pressing. The copper pole ear of the lithium zinc alloy negative electrode is formed by laminating the base film, and the bare battery cell is encapsulated with aluminum plastic film. The aluminum pole ear and the copper nickel-plated pole ear are respectively led out, and the liquid is injected and sealed. It is left to stand for 24 hours to wait for formation. The battery cells are placed in the lithium metal battery formation cabinet in turn, the temperature is set to 25℃, the formation pressure is 1.0Mpa, and it is left for 15 minutes; first, 0.1C constant current and constant voltage are fully charged, the cut-off current is 0.05C, and then it is left for 15 minutes, 0.1C constant current discharge is fully discharged, and it is left for 15 minutes. Finally, the formation is completed to obtain a 2.6Ah soft pack battery, which is recorded as C6.

[0039] The batteries of the above-mentioned Examples 1-5 and the comparative examples were subjected to cycle tests, internal resistance tests, and DCR growth rate tests, and the relevant performance parameters obtained are shown in Table 1 below:

[0040] Table 1: Performance comparison of each group of embodiments after formation

[0041]

[0042] According to Table 1, by comparing the data of the comparative example and the experimental example, it is found that the formation time of the comparative example 0.1C constant current constant voltage full charge and 0.1C full discharge is 20 hours, the ACR internal resistance is 8.23mΩ, and the number of cycles with a capacity retention rate of 95% is 205 cycles, corresponding to a DCR growth rate of 80.1%; and the cycle performance of Experimental Examples 1-5 obtained by the formation method of the present invention is improved, and the internal resistance is low, which is mainly attributed to the formation of a thinner SEI film on the lithium metal negative electrode sheet, and the battery positive electrode sheet obtains better wettability during the process. At the same time, it is found that the low DCR growth rate indicates that the battery cell has fewer side reactions during the cycle process. This is because the SEI film formation is very stable during the formation, and the formation time required by the formation method of the present invention is much shorter than that of the comparative example.

[0043] The present invention provides a novel formation method for lithium metal batteries, which performs micro-charging on lithium metal batteries, i.e., a method for short-time charging in the form of providing a small current, including charging with a small current for a period of time after the battery is filled with liquid, promoting the lithium ions in the electrolyte molecules to move to the negative electrode side for desolvation and reduction, and using the unique low potential of the lithium metal negative electrode during the subsequent static time, the negative electrode side of the lithium metal battery continuously forms a stable SEI film, and at the same time, the potential decreases during the film formation stage, and the capillary phenomenon is used to accelerate the infiltration of the positive electrode sheet, thereby greatly improving the formation effect of the lithium metal battery. Therefore, compared with the conventional method, the novel formation method of lithium metal batteries provided by the present invention is conducive to improving the electrochemical performance of the battery cell, and can also shorten the formation time of the lithium metal battery.

[0044] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A lithium metal battery formation method, characterized in that: The specific steps include: S1. Filling the lithium metal battery with liquid, sealing it and letting it stand; S2, charging the lithium metal battery with a first current C1 at a constant current for a charging time of T1; S3. Let the battery stand after constant current charging for a period of time T2: S4, the battery after step S3 is left to stand with the second current C2 to continue charging, the charging time is T3, wherein the second current C2 is greater than the first current C1; S5, discharging the battery processed in step S4 with a third current C3 to a cut-off voltage.

2. The lithium metal battery formation method according to claim 1, characterized in that: The range of the standing time in step S1 is 3h~24h.

3. The lithium metal battery formation method according to claim 1, characterized in that: The first current C1 in the step S2 is in a range of 0.005C to 0.1C.

4. The lithium metal battery formation method according to claim 3, characterized in that: The charging time T1 in step S2 is 1 min to 60 min.

5. The lithium metal battery formation method according to claim 1, characterized in that: The range of the standing time T2 in step S3 is 1h~3h.

6. The lithium metal battery formation method according to claim 1, characterized in that: The second current C2 in step S4 is in a range of 0.2C to 1C.

7. The lithium metal battery formation method according to claim 1, characterized in that: The charging time T3 in step S4 ranges from 1 hour to 3 hours.

8. The lithium metal battery formation method according to claim 1, characterized in that: The third current C3 in step S5 is set to 0.5C.

9. The lithium metal battery formation method according to claim 1, characterized in that: The negative electrode active material of the battery is a combination of one or more of pure lithium sheet, lithium zinc alloy, lithium magnesium alloy, lithium silver alloy, lithium indium alloy, lithium aluminum alloy material and the like.

10. The lithium metal battery formation method according to claim 1, characterized in that: The positive electrode active material of the battery is a combination of one or more of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium phosphate, lithium vanadate, lithium manganate, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, etc.

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