Electroplating solution composition for lithium metal and use thereof

Abstract

The application discloses a kind of electroplating solution compositions for lithium metal and its application, it is made of lithium salt, solvent and leveling agent, the concentration of lithium salt is 1-10M, the addition amount of leveling agent is 1-10wt%.The application can prepare 0.0-20.0um within any thickness of lithium metal electrode by changing component and electroplating condition, SEI layer is spontaneously formed in the process of electroplating, and the consumption of active lithium in battery activation process is effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery production technology, specifically relating to a lithium metal electroplating solution composition and its application. Background Technology

[0002] Lithium-ion batteries have demonstrated wide applications in powering portable power sources, electric vehicles, and renewable energy storage. Currently, the graphite anodes used in commercial lithium-ion batteries are approaching their capacity limits. As the demand for high-energy lithium-ion batteries becomes increasingly urgent, existing commercial anode materials are no longer sufficient to meet this growing need.

[0003] Lithium metal, with its high theoretical capacity of 3862 mAh / g and low standard electrode potential (3.04 (relative to SHE)), is an ideal material for the anode of high-energy-density lithium secondary batteries. However, the formation of lithium dendrites during charging and discharging can lead to safety issues such as short circuits, hindering the practical application of lithium metal anode materials.

[0004] Furthermore, during the charging and discharging process of lithium metal secondary batteries, when lithium ions are reduced on the lithium metal surface, the solvent and salt of the electrolyte form a solid electrolyte interphase (SEI) layer on the lithium surface due to side reactions. This leads to the irreversible loss of active lithium. When the SEI layer is unstable, side reactions between the electrolyte and lithium metal will continue to occur, resulting in a continuous loss of active lithium and a rapid decline in the capacity of the lithium metal battery.

[0005] Furthermore, lithium metal electrodes fabricated by rolling lithium metal onto a current collector exhibit poor adhesion, and it is difficult to control the lithium layer thickness of the rolled lithium metal electrode to within 20 μm. Moreover, the rolled lithium metal anode cannot form a stable SEI layer, requiring the consumption of active lithium during battery activation to form the SEI layer.

[0006] In view of the above, when using lithium metal to manufacture electrodes, it is necessary to develop lithium metal electrode manufacturing technology that can control the thickness of the lithium metal layer, ensure uniform thickness, smooth surface, and form a stable SEI layer. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of the prior art and provide a lithium metal electroplating solution composition.

[0008] Another object of the present invention is to provide the application of the above-described lithium metal electroplating solution composition in the electroplating manufacture of lithium metal electrodes.

[0009] The technical solution of the present invention is as follows:

[0010] A lithium metal electroplating solution composition comprises a lithium salt, a solvent, and a leveling agent, wherein the concentration of the lithium salt is 1-10 M and the amount of the leveling agent added is 1-10 wt%.

[0011] The lithium salt is at least one of LiFSI, LiTFSI, LiPF6, LiPO2F2, LiBOB, LiDFOB, LiCl, LiBr, LiI, LiNO3, LiClO4, LiBF4 and CF3SO3Li;

[0012] The solvent is a mixed solvent composed of DME and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, or a mixed solvent composed of EC, DMC and 2,2,2-trifluoroethyl ether;

[0013] The leveling agent is at least one of the following: acid anhydride compounds, crown ether compounds, thiourea compounds, nitrile compounds, ethylene ester compounds, bis(trifluoromethanesulfonyl)imide salt compounds, and organic polymers.

[0014] In a preferred embodiment of the present invention, the acid anhydride compound is succinic anhydride, oxalic anhydride, difluoroacetic anhydride, heptafluorobutyric anhydride, or pentafluoropropionic anhydride.

[0015] In a preferred embodiment of the present invention, the crown ether compound is 12-crown-4, 15-crown-5, or 18-crown-6.

[0016] In a preferred embodiment of the present invention, the thiourea compound is thiourea, ether thiourea, N-methylthiourea, tetramethylthiourea, or 2,5-dithiourea.

[0017] In a preferred embodiment of the present invention, the nitrile compound is succinic acid, adiponitrile, or acetonitrile.

[0018] In a preferred embodiment of the present invention, the ethylene ester compound is fluoroethylene carbonate (FEC), vinylene carbonate (VC), or ethylene sulfate (DTD).

[0019] In a preferred embodiment of the present invention, the bis(trifluoromethanesulfonyl)imide salt compound is magnesium bis(trifluoromethanesulfonyl)imide, zinc bis(trifluoromethanesulfonyl)imide, or aluminum bis(trifluoromethanesulfonyl)imide.

[0020] In a preferred embodiment of the present invention, the organic polymer is polyethylene oxide, polyacrylic acid, polyvinyl alcohol, or polyacrylonitrile.

[0021] In a preferred embodiment of the present invention, the solvent is a mixed solvent composed of DME and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a volume ratio of 1.2:3, or a mixed solvent composed of EC, DMC and 2,2,2-trifluoroethyl ether in a volume ratio of 1:1:1.

[0022] Another technical solution of the present invention is as follows:

[0023] The application of the above-mentioned lithium metal electroplating solution composition in the electroplating manufacturing of lithium metal electrodes.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention can prepare lithium metal electrodes of any thickness within 0.0-20.0 μm by changing the composition and electroplating conditions (deposition time and deposition current). During the electroplating process, an SEI layer will be spontaneously formed, which effectively reduces the consumption of active lithium during battery activation.

[0026] 2. The leveling agent in this invention can adsorb lithium ions, change the deposition overpotential of lithium, or adsorb and change the double layer on the surface of the current collector, inducing lithium ions to tend to deposit in a two-dimensional plane, thereby improving the smoothness of electroplated lithium. At the same time, some complexing agents also have a certain effect on improving the SEI structure.

[0027] 3. The leveling agent in this invention can form a specific solid electrolyte interface (SEI) layer, reduce the consumption of active lithium during battery activation, improve the stability of the lithium metal electrode interface, and enhance the resistance to water and oxygen corrosion in the air. Attached Figure Description

[0028] Figure 1 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 1 of the present invention.

[0029] Figure 2 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 2 of the present invention.

[0030] Figure 3 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 5 of the present invention.

[0031] Figure 4 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 7 of the present invention.

[0032] Figure 5 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 12 of the present invention.

[0033] Figure 6This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 15 of the present invention.

[0034] Figure 7 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 19 of the present invention.

[0035] Figure 8 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 22 of the present invention.

[0036] Figure 9 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 24 of the present invention.

[0037] Figure 10 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 25 of the present invention.

[0038] Figure 11 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Example 28 of the present invention.

[0039] Figure 12 This is a morphology diagram of a lithium metal electrode prepared by the lithium metal electroplating solution composition of Comparative Example 1 of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0041] Examples 1 to 32 and Comparative Example 1

[0042] The preparation method of the lithium metal electroplating solution compositions in Examples 1 to 32 and Comparative Example 1 is as follows: Lithium salt is dissolved in a solvent, and then a leveling agent is added and mixed thoroughly. The specific formulations obtained in Examples 1 to 32 and Comparative Example 1 are shown in Table 1 below:

[0043] Table 1

[0044]

[0045]

[0046]

[0047] The above-mentioned lithium metal electroplating solution composition is used for electroplating to manufacture ultra-thin lithium metal. The specific steps are as follows: using 5mA / cm 2Electroplating is performed using an electrolytic cell containing: copper foil as a current density and a negative electrode; lithium sheet as a lithium source and a positive electrode; and the aforementioned lithium metal electroplating solution composition filled between the positive and negative electrodes. When the deposition current density is controlled to be from 0.1 mA / cm² to 10 A / cm² and the electrodeposition time to be from 0.1 s to 3 h, lithium metal electrodes of any thickness within the range of 0.0-20.0 μm can be prepared. During the electroplating process, an SEI layer spontaneously forms, effectively reducing the consumption of active lithium during battery activation.

[0048] Depend on Figures 1 to 11 As can be seen, the lithium deposition is very uniform, with no obvious gaps. Although the surface is still somewhat rough, a dense and uniform dendrite-free lithium plating layer was observed. Correspondingly, such as... Figure 12 As shown in Comparative Example 1, the effect reveals uneven lithium deposition with many sharp, elongated dendritic structures.

[0049] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. An electroplating solution composition for lithium metal, characterized by: It consists of lithium salt, solvent, and leveling agent. The concentration of lithium salt is 1-10 M, and the amount of leveling agent added is 1-10 wt%. The lithium salt is at least one of LiFSI, LiTFSI, LiPF6, LiPO2F2, LiBOB, LiDFOB, LiCl, LiBr, LiI, LiNO3, LiClO4, LiBF4 and CF3SO3Li; The solvent is a mixed solvent composed of EC, DMC and 2,2,2-trifluoroethyl ether in a volume ratio of 1:1:1; The leveling agent is an acid anhydride compound, such as succinic anhydride, difluoroacetic anhydride, heptafluorobutyric anhydride, or pentafluoropropionic anhydride.

2. The use of the lithium metal electroplating solution composition according to claim 1 in the electroplating manufacture of lithium metal electrodes.

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