Lithium metal negative plate, preparation method thereof and lithium ion battery

Abstract

The invention provides a lithium metal negative plate, a preparation method thereof and a lithium ion battery. The preparation method comprises the following steps: step S1, sequentially dropwise adding a lithium salt solution and overlapping a diaphragm and a conductive substrate layer on the surface of one side of a solid electrolyte layer to form a prepared electrode; s2, immersing the surface of the other side, far away from the conductive substrate layer, of the solid electrolyte layer in the prepared electrode into the liquid lithium ore, and placing the counter electrode in the liquid lithium ore for electro-deposition to form a lithium metal deposition layer on the surface of the conductive substrate layer so as to obtain a lithium metal negative plate; the liquid lithium ore is not in contact with the lithium salt solution, and the current density of electro-deposition is 0.05-0.5 mA. Cm <-2 >. Lithium is directly extracted through the liquid lithium ore, lithium metal is deposited on the conductive substrate material, a high-temperature melting step is not needed, and the preparation process of the negative electrode is simplified. The lithium metal negative electrode plate prepared by the preparation method disclosed by the invention has relatively high cycling stability.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium metal negative electrode sheet and a preparation method thereof, and a lithium ion battery. Background Art

[0002] With the continuous development of modern science and technology, lithium batteries, as a high-performance secondary battery, have been widely used in mobile communications, electric vehicles, energy storage systems and other fields, becoming a key energy storage technology to promote social progress. With the rapid development of electric vehicles and renewable energy, the requirements for battery performance are also increasing. As the current mainstream battery technology, lithium-ion batteries usually use carbon materials for their negative electrodes, but the capacity of carbon materials is relatively low and cannot meet the needs of high energy density in the future. In contrast, lithium metal negative electrodes have a higher theoretical specific capacity (3860mAh·g -1 ), and is therefore considered to have greater potential.

[0003] At present, there are two main common methods for preparing lithium metal negative electrodes: one is to directly cut lithium metal sheets from metallic lithium, and the other is to reduce and deposit lithium metal from a lithium salt solution by electrochemical deposition. Traditional metallic lithium deposition methods usually use lithium salts in organic solvents as lithium sources, and the production of lithium salts depends on ore resources. The mining and refining process is usually complicated and costly. In addition, the mining and extraction of ores often cause irreversible damage to the ecological environment. Therefore, there is an urgent need for a simpler and more environmentally friendly way to extract high-purity metallic lithium from liquid lithium ore.

[0004] In addition, existing metal lithium negative electrode materials have problems such as uneven deposition, lithium dendrite formation, short cycle life and unstable battery performance. The growth of lithium dendrites can cause short circuits and even form dead lithium areas, reducing the effective capacity and cycle life of the battery. The volume change of the negative electrode material can also cause mechanical damage, further affecting the stability of the negative electrode. Therefore, it is urgent to develop a new, efficient, energy-saving and environmentally friendly method for preparing metal lithium negative electrodes. Summary of the invention

[0005] The main purpose of the present invention is to provide a lithium metal negative electrode sheet and a preparation method thereof and a lithium ion battery, so as to solve the problem of poor cycle stability of lithium metal negative electrode sheets in the prior art.

[0006] In order to achieve the above-mentioned object, according to one aspect of the present invention, a method for preparing a lithium metal negative electrode sheet is provided, and the preparation method comprises the following steps: step S1, dripping a lithium salt solution, stacking a diaphragm and a conductive substrate layer on one side surface of a solid electrolyte layer in sequence to form a preliminary electrode; step S2, immersing the other side surface of the solid electrolyte layer in the preliminary electrode away from the conductive substrate layer into liquid lithium ore, and placing a counter electrode in the liquid lithium ore for electrodeposition to form a lithium metal deposition layer on the surface of the conductive substrate layer, thereby obtaining a lithium metal negative electrode sheet; the liquid lithium ore is not in contact with the lithium salt solution, and the current density of the electrodeposition is 0.05-0.5 mA·cm -2 .

[0007] Furthermore, the current density of the above-mentioned electrodeposition is 0.1-0.2 mA·cm -2 ; and / or, the electrodeposition time is 24 to 72 hours.

[0008] Furthermore, the concentration of lithium ions in the above-mentioned liquid lithium ore is 0.01-5 mol / L; preferably, the liquid lithium ore is salt lake brine and / or seawater.

[0009] Furthermore, the material of the solid electrolyte layer is a ceramic electrolyte and / or a polymer electrolyte; preferably, the material of the solid electrolyte layer is a ceramic electrolyte; further preferably, the ceramic electrolyte is selected from Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 Electrolyte, Li 1.3 Al 0.3 Ti 1.7 Electrolyte and Li 0.33 La 0.56 TiO 3 Any one or more of the electrolytes.

[0010] Furthermore, the amount of the lithium salt solution added to one side of the solid electrolyte layer is 0.3 to 0.5 μL / mm 2 ; Preferably, the concentration of lithium salt in the lithium salt solution is 0.5-1.5 mol / L; further preferably, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide and lithium nitrate; and / or, the solvent in the lithium salt solution is selected from any one or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, fluorinated ethylene carbonate, 1,3-dioxolane; preferably, the solvent contains at least ethylene carbonate and dimethyl carbonate, and the volume ratio of ethylene carbonate to dimethyl carbonate is (0.5-1.5):(0.5-1.5).

[0011] Furthermore, the conductive substrate layer is selected from any one or more of copper foil, nickel foil, aluminum foil, foam metal layer, carbon cloth and metal-organic skeleton layer.

[0012] Furthermore, the above-mentioned separator is selected from any one or more of polypropylene membrane, glass fiber membrane, cellulose membrane and polytetrafluoroethylene membrane.

[0013] Furthermore, the counter electrode is selected from any one or more of a copper electrode, a zinc electrode, a silver electrode and an aluminum electrode.

[0014] According to another aspect of the present invention, a lithium metal negative electrode sheet is provided. The lithium metal negative electrode sheet is prepared by the aforementioned preparation method.

[0015] According to another aspect of the present invention, a lithium-ion battery is provided, comprising a positive electrode sheet, an electrolyte and a negative electrode sheet, wherein the negative electrode sheet is the aforementioned lithium metal negative electrode sheet.

[0016] By applying the technical solution of the present invention, compared with the traditional method for preparing lithium metal negative electrode sheets, the present application directly extracts lithium from liquid lithium ore and deposits lithium metal on a conductive substrate material, without the need for a high-temperature melting step, thereby simplifying the negative electrode preparation process. Using liquid lithium ore as a lithium source has lower raw material costs and less environmental pollution than traditional lithium salt extraction methods. Electrodeposition technology allows lithium metal to be directly deposited on a conductive substrate material at a lower temperature, which greatly improves the preparation efficiency compared to methods such as high-temperature melting, while also avoiding the degradation of material properties that may be caused by high temperatures. Controlling the current density of electrodeposition within the above range helps to improve the dispersion uniformity of lithium metal deposition and reduce the formation of lithium dendrites, thereby helping to improve the structural stability and cycle stability of the lithium metal negative electrode sheet, and helps to improve the deposition selectivity of lithium ions, thereby helping to improve the purity of lithium metal in the lithium metal negative electrode sheet. Adding a lithium salt solution dropwise on one side of the solid electrolyte helps to further improve the transmission efficiency of lithium ions and the uniformity of the distribution of metallic lithium on the surface of the conductive substrate material. The lithium metal negative electrode sheet prepared by the preparation method of the present application can be directly used as the negative electrode of the battery, which helps to further reduce the preparation cost of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 The XRD diagram of the lithium metal negative electrode sheet in Example 1 of the present application is shown;

[0019] Figure 2 The charge and discharge curve of the battery at 0.1C in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] As analyzed in the background technology of this application, the prior art lithium metal negative electrode sheet has the problem of poor cycle stability. In order to solve the above problem, this application provides a lithium metal negative electrode sheet and a preparation method thereof and a lithium ion battery.

[0022] In a typical embodiment of the present application, a method for preparing a lithium metal negative electrode sheet is provided, and the preparation method comprises the following steps: step S1, sequentially adding a lithium salt solution, stacking a diaphragm and a conductive substrate layer on a surface of one side of a solid electrolyte layer to form a preliminary electrode; step S2, immersing the other side of the solid electrolyte layer in the preliminary electrode away from the conductive substrate layer into liquid lithium ore, and placing a counter electrode in the liquid lithium ore for electrodeposition to form a lithium metal deposition layer on the surface of the conductive substrate layer, thereby obtaining a lithium metal negative electrode sheet; the liquid lithium ore is not in contact with the lithium salt solution, and the current density of the electrodeposition is 0.05 to 0.5 mA cm -2 .

[0023] Compared with the traditional method for preparing lithium metal negative electrode sheets, the present application directly extracts lithium from liquid lithium ore and deposits lithium metal on a conductive substrate material, without the need for a high-temperature melting step, thereby simplifying the negative electrode preparation process. Using liquid lithium ore as a lithium source has lower raw material costs and less environmental pollution than traditional lithium salt extraction methods. Electrodeposition technology allows lithium metal to be directly deposited on a conductive substrate material at a lower temperature, which greatly improves the preparation efficiency compared to methods such as high-temperature melting, while also avoiding the degradation of material properties that may be caused by high temperatures. Controlling the current density of electrodeposition within the above range helps to improve the dispersion uniformity of lithium metal deposition and reduce the formation of lithium dendrites, thereby helping to improve the structural stability and cycle stability of the lithium metal negative electrode sheet, and helps to improve the deposition selectivity of lithium ions, thereby helping to improve the purity of lithium metal in the lithium metal negative electrode sheet. Adding a lithium salt solution dropwise on one side of the solid electrolyte helps to further improve the transmission efficiency of lithium ions and the uniformity of the distribution of metallic lithium on the surface of the conductive substrate material. The lithium metal negative electrode sheet prepared by the preparation method of the present application can be directly used as the negative electrode of the battery, which helps to further reduce the preparation cost of the battery.

[0024] In one embodiment of the present application, in the above step S1, a lithium salt solution is dripped on the surface of one side of the solid electrolyte layer, a diaphragm and a conductive substrate layer are stacked in sequence, and a polytetrafluoroethylene ring is used for pressurized sealing and fixing, so that only the side of the conductive substrate layer and the solid electrolyte layer away from the lithium salt solution is exposed to the air, thereby forming a preliminary electrode.

[0025] In one embodiment of the present application, the thickness ratio of the solid electrolyte layer to the conductive substrate layer is (1:1) to (200:1).

[0026] In one embodiment of the present application, the current density of the above-mentioned electrodeposition is 0.1-0.2 mA·cm -2 ; and / or, the electrodeposition time is 24 to 72 h, preferably 24 to 48 h, specifically 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, 48 h and a range between any two values.

[0027] Controlling the current density of the electrodeposition within the above range helps to make the reduction process of lithium ions more stable, thereby helping to deposit lithium metal evenly on the surface of the conductive substrate material, reducing the formation of lithium dendrites, and helping to further improve the deposition selectivity of lithium ions, thereby helping to further improve the purity of lithium metal in the lithium metal negative electrode sheet. Controlling the electrodeposition time within the above range helps to control the thickness of the lithium metal layer, reducing the problem of increased internal pressure and volume expansion of the battery due to excessive thickness, and insufficient capacity due to excessive thinness, and helps to provide high energy density while maintaining good structural stability and cycle stability.

[0028] In one embodiment of the present application, the concentration of lithium ions in the above-mentioned liquid lithium ore is 0.01-5 mol / L; preferably, the liquid lithium ore is salt lake brine and / or seawater.

[0029] The preparation method of the present application can be applied to the extraction of lithium from liquid lithium ore having a lithium ion concentration within the above range, which helps to reduce the preparation cost of lithium metal negative electrode sheets.

[0030] In one embodiment of the present application, the material of the solid electrolyte layer is a ceramic electrolyte and / or a polymer electrolyte; preferably, the material of the solid electrolyte layer is a ceramic electrolyte; further preferably, the ceramic electrolyte is selected from Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 Electrolyte, Li 1.3 Al 0.3 Ti 1.7 Electrolyte and Li 0.33 La 0.56TiO 3 Any one or more of the electrolytes.

[0031] Ceramic electrolytes have high lithium ion conductivity, which can effectively promote the migration of lithium ions and improve the efficiency of the electrodeposition process. Ceramic electrolytes have good chemical stability and can remain stable even at high potentials without harmful side reactions with lithium metal or electrolytes. The use of ceramic electrolytes helps to inhibit the growth of lithium dendrites because the rigid structure of ceramic materials can limit the irregular deposition of lithium metal, thereby reducing dendrite formation.

[0032] In one embodiment of the present application, the amount of the lithium salt solution added to one side of the solid electrolyte layer is 0.3-0.5 μL / mm 2 ; Preferably, the concentration of lithium salt in the lithium salt solution is 0.5-1.5 mol / L; further preferably, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide and lithium nitrate; and / or, the solvent in the lithium salt solution is selected from any one or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, fluorinated ethylene carbonate, 1,3-dioxolane; preferably, the solvent contains at least ethylene carbonate and dimethyl carbonate, and the volume ratio of ethylene carbonate to dimethyl carbonate is (0.5-1.5):(0.5-1.5).

[0033] The amount of lithium salt solution added to the surface of one side of the solid electrolyte layer is within the above range, which helps to cover the solid electrolyte surface with sufficient lithium salt solution to promote the effective deposition of lithium ions while reducing side reactions caused by excessive solution. Controlling the concentration of lithium salt in the lithium salt solution within the above range helps to improve the transmission efficiency of lithium ions, thereby helping to improve the deposition efficiency of metallic lithium. Controlling the type of solvent in the lithium salt solution within the above range helps to improve the stability of the lithium salt solution and the lithium ion conductivity. Controlling the volume ratio of ethylene carbonate and dimethyl carbonate within the above range helps to improve the interaction between the two, thereby helping to optimize the viscosity of the lithium salt solution and the mobility of lithium ions, improving the stability of the lithium salt solution, and reducing side reactions, thereby helping to improve the uniformity and efficiency of lithium metal deposition.

[0034] In order to further optimize the viscosity of the lithium salt solution and the mobility of lithium ions, improve the stability of the lithium salt solution, and reduce side reactions, in one embodiment of the present application, the solvent in the above-mentioned lithium salt solution is preferably a combination of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, a combination of ethylene carbonate, dimethyl carbonate and 1,3-dioxolane, or a combination of ethylene carbonate, dimethyl carbonate and ethylene glycol dimethyl ether.

[0035] In one embodiment of the present application, the above-mentioned conductive substrate layer is selected from any one or more of copper foil, nickel foil, aluminum foil, foam metal layer, carbon cloth and metal-organic skeleton layer. Preferably, the conductive substrate layer is a foam metal layer, and further preferably, the foam metal layer is a foam copper layer and / or a foam nickel layer.

[0036] Metal foam has a high specific surface area and good electrical conductivity. By depositing metallic lithium on metal foam, it helps to improve the charge and discharge specific capacity of lithium metal negative electrode sheets, and the porous structure of metal foam helps to induce uniform deposition of lithium and inhibit the growth of lithium dendrites, thereby helping to improve the cycle stability of lithium metal negative electrode sheets.

[0037] In one embodiment of the present application, the above-mentioned diaphragm is selected from any one or more of a polypropylene membrane, a glass fiber membrane, a cellulose membrane and a polytetrafluoroethylene membrane.

[0038] Controlling the type of the separator within the above range helps to improve the stability of the separator, reduce the probability of side reactions, and help improve the transmission efficiency of lithium ions, thereby helping to improve the electrodeposition efficiency of metallic lithium.

[0039] In one embodiment of the present application, the counter electrode is selected from any one or more of a copper electrode, a zinc electrode, a silver electrode and an aluminum electrode.

[0040] Controlling the type of the counter electrode within the above range helps to provide a stable current field, thereby helping to improve the deposition efficiency and purity of lithium metal.

[0041] In order to further improve the efficiency of lithium metal deposition and reduce the generation of lithium dendrites, in one embodiment of the present application, the current density of the above-mentioned electrodeposition is preferably 0.1-0.2 mA·cm -2 The electrodeposition time is 24 to 48 hours, the solid electrolyte is a ceramic electrolyte, and the conductive substrate material is foam metal.

[0042] In another typical embodiment of the present application, a lithium metal negative electrode sheet is provided, and the lithium metal negative electrode sheet is prepared by the aforementioned preparation method.

[0043] Since the lithium metal negative electrode sheet is prepared by the preparation method of the present application, the lithium metal negative electrode sheet has a higher specific capacity and cycle stability.

[0044] In another typical embodiment of the present application, a lithium-ion battery is provided, comprising a positive electrode sheet, an electrolyte and a negative electrode sheet, wherein the negative electrode sheet is the aforementioned lithium metal negative electrode sheet.

[0045] Since the lithium-ion battery contains the lithium metal negative electrode sheet prepared by the preparation method of the present application, the lithium-ion battery has higher specific capacity, cycle stability and safety.

[0046] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0047] Example 1

[0048] Using LLZTO as solid electrolyte, copper foil as conductive substrate material, salt lake brine as liquid lithium ore, the concentration of lithium ions in the salt lake brine is 0.1 mol / L, and electrodeposition is performed. The specific preparation method and materials used are as follows:

[0049] (1) The garnet-structured LLZTO (Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 ). The raw materials are LiOH·H 2 O, La 2 O 3 , ZrO 2 and Ta 2 O 5 The raw materials were weighed according to the stoichiometric ratio and placed in a polyurethane ball mill containing yttrium-stabilized zirconia at 175 r / min. -1 The mixture was dry-milled at a speed of 100 for 2 hours, sieved through a 100-mesh screen and transferred to a 250 mL alumina crucible for pre-sintering at a sintering heating rate of 5 °C min -1 , heat to 950℃ and keep it for 6 hours, then cool to room temperature with the furnace. -1 The powder was dry-milled again at a speed of 2 hours and sieved to obtain the powder. The green embryo was pressed into a 18 mm tableting mold and then placed in a magnesium oxide crucible for secondary sintering at a heating rate of 5 °C min -1 , heated to 1320°C and kept at this temperature for 10 min, then cooled to room temperature. Finally, the obtained ceramic sheet was polished with 250#, 500#, 1000# and 2500# SiC sandpapers, and then transferred to a glove box filled with argon (H 2 O<0.1ppm and O 2 <0.1ppm).

[0050] (2) 80 μL of lithium hexafluorophosphate solution was dripped onto one side of the LLZTO ceramic sheet prepared in step (1). The solvent in the lithium hexafluorophosphate solution was a combination of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, and the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate was 1:1:1. The concentration of the lithium hexafluorophosphate solution was 1 mol / L. A copper foil with a diameter of 14 mm was used as a conductive substrate material. A polypropylene diaphragm (model: Celgard2400) and copper foil were stacked on the lithium hexafluorophosphate solution in sequence, and a polytetrafluoroethylene sleeve was used for pressure sealing and fixing to form a preliminary electrode. The ratio of the thickness of the LLZTO ceramic sheet to the thickness of the copper foil was 200:1. The side of the LLZTO ceramic sheet exposed to the air was immersed in salt lake brine. A Cu electrode (2 cm×2 cm) was used as a counter electrode. The counter electrode was placed in the salt lake brine for electrodeposition at a current density of 0.1 mA·cm -2 , time is 24h, and a lithium metal negative electrode sheet is obtained.

[0051] Example 2

[0052] The difference from Example 1 is that nickel foam is used as the conductive base material to finally obtain a lithium metal negative electrode sheet.

[0053] Example 3

[0054] The difference from Example 1 is that foam copper is used as the conductive base material and the current density is 0.2 mA·cm -2 , and finally a lithium metal negative electrode sheet is obtained.

[0055] Example 4

[0056] The difference from Example 1 is that Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 It is a solid electrolyte, with carbon cloth as the conductive base material, seawater as the liquid lithium ore, and the concentration of lithium ions in seawater is 0.01 mol / L, and electrodeposition is performed. The specific preparation method and materials used are as follows:

[0057] (1) LATP powder was synthesized by solid phase reaction method. 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 Li 2 CO 3 、Al 2 O 3 、TiO 2 and NH 4 H 2 PO4 The precursor powder was ball milled in a nylon jar at 175 rpm for 6 h with isopropanol as solvent and yttrium-stabilized zirconia beads as grinding media. The viscous slurry was dried at 65 °C overnight. The dried mixture was calcined at 700 °C for 6 h. The calcined powder was ball milled at 175 rpm with ethanol as solvent for 3 h. The LATP slurry was dried at 60 °C to obtain a uniform powder. The obtained powder was mechanically pressed into a 18 mm disc green embryo at a pressure of 500 MPa. The green embryo was heated at 850 °C at 5 °C min -1 The ceramic pieces were sintered for 6 hours at a heating rate of . After sintering, the ceramic pieces were polished in air with SiC sandpaper of 500#, 1000#, 1500# and 2000# grit.

[0058] (2) 80 μL of lithium hexafluorophosphate solution was dripped onto one side of the LATP ceramic sheet prepared in step (1). The solvent in the lithium hexafluorophosphate solution was a combination of ethylene carbonate, dimethyl carbonate and 1,3-dioxolane, and the volume ratio of ethylene carbonate, dimethyl carbonate and 1,3-dioxolane was 1:1:1. The concentration of the lithium hexafluorophosphate solution was 1 mol / L. A carbon cloth with a diameter of 14 mm was used as a conductive substrate material. A polypropylene diaphragm (model: Celgard2400) and a carbon cloth were stacked on the lithium hexafluorophosphate solution in sequence, and a polytetrafluoroethylene sleeve was used for pressure sealing and fixing to form a preliminary electrode. The ratio of the thickness of the LLZTO ceramic sheet to the thickness of the copper foil was 200:1. The other side of the LATP ceramic sheet was immersed in seawater. A silver electrode (2 cm×2 cm) was used as a counter electrode. The counter electrode was placed in seawater for electrodeposition at a current density of 0.2 mA cm -2 , the time is 48 hours, and a lithium metal negative electrode sheet is obtained.

[0059] Example 5

[0060] The difference from Example 1 is that Li 0.33 La 0.56 TiO 3 (LLTO) is a solid electrolyte with Ni 3 (HITP) 2 As a conductive substrate material, seawater is used as liquid lithium ore, and the concentration of lithium ions in seawater is 0.01 mol / L. Electrodeposition is performed. The specific preparation method and materials used are as follows:

[0061] (1) LLTO powder was synthesized by solid phase reaction method. 0.33 La 0.56 TiO 3 Weigh and mix LiOH·H 2 O.La 2 O 3 and TiO2 No excess LiOH·H is required 2 O. The mixture was ball milled at 175 rpm for 3 h and then sintered at 850 °C for 6 h to dehydrate. The obtained powders were mixed thoroughly and ball milled at 175 rpm for 3 h. After that, 1 g of LLTO powder was pressed into 18 mm discs at 10 MPa. The discs were sintered in a muffle furnace at 1320 °C in air for 6 h. The heating and cooling rates of the sintering process were both set to 5 °C min -1 All heat treatments were performed in magnesia crucibles and covered with magnesia lids.

[0062] (2) 120 μL of lithium bis(trifluoromethylsulfonyl)imide solution was dripped onto one side of the LLTO ceramic sheet prepared in step (1), wherein the solvent in the lithium bis(trifluoromethylsulfonyl)imide solution was a combination of ethylene carbonate, dimethyl carbonate and ethylene glycol dimethyl ether, and the volume ratio of ethylene carbonate, dimethyl carbonate and ethylene glycol dimethyl ether was 1:1:1, the concentration of the lithium bis(trifluoromethylsulfonyl)imide solution was 1 mol / L, and a Ni-270 having a diameter of 14 mm was used. 3 (HITP) 2 As the conductive substrate material, a polypropylene separator (model Celgard2400) and Ni 3 (HITP) 2 The thickness of the LLZTO ceramic sheet is 200:1 compared to the thickness of the copper foil. The side of the LLTO ceramic sheet exposed to the air is immersed in seawater. An aluminum electrode (2 cm × 2 cm) is used as a counter electrode. The counter electrode is placed in seawater for electrodeposition at a current density of 0.2 mA cm -2 , the time is 72 hours, and a lithium metal negative electrode sheet is obtained.

[0063] Example 6

[0064] The difference from Example 1 is that the current density of the electrodeposition is 0.05 mA cm -2 , and finally a lithium metal negative electrode sheet is obtained.

[0065] Example 7

[0066] The difference from Example 1 is that the current density of the electrodeposition is 0.5 mA cm -2 , and finally a lithium metal negative electrode sheet is obtained.

[0067] Example 8

[0068] The difference from Example 1 is that the electrodeposition time is 48 hours, and a lithium metal negative electrode sheet is finally obtained.

[0069] Example 9

[0070] The difference from Example 1 is that the electrodeposition time is 72 hours, and a lithium metal negative electrode sheet is finally obtained.

[0071] Example 10

[0072] The difference from Example 1 is that the electrodeposition time is 84 hours, and a lithium metal negative electrode sheet is finally obtained.

[0073] Embodiment 11

[0074] The difference from Example 1 is that PVDF / LLZTO organic-inorganic composite electrolyte is used to replace LLZTO as a solid electrolyte, and finally a lithium metal negative electrode sheet is obtained. The specific preparation method of PVDF / LLZTO organic-inorganic composite electrolyte is as follows: 1g of PVDF powder, 0.2g of LiTFSI lithium salt, 0.3g of LLZTO powder and 5mL of anhydrous acetonitrile are stirred and mixed for 6 hours to obtain a composite electrolyte slurry. The slurry is cast in a 7cm×7cm square mold with a thickness of about 2mm, and dried overnight at 40°C in a glove box to remove all solvents to obtain a PVDF / LLZTO organic-inorganic composite electrolyte.

[0075] Example 12

[0076] The difference from Example 1 is that the volume of the lithium hexafluorophosphate solution is 60 μL, and a lithium metal negative electrode sheet is finally obtained.

[0077] Example 13

[0078] The difference from Example 1 is that the concentration of the lithium hexafluorophosphate solution is 2 mol / L, and a lithium metal negative electrode sheet is finally obtained.

[0079] Embodiment 14

[0080] The difference from Example 1 is that the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is 0.5:1.5:0.5, and a lithium metal negative electrode sheet is finally obtained.

[0081] Embodiment 15

[0082] The difference from Example 1 is that the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is 0.5:2:0.5, and a lithium metal negative electrode sheet is finally obtained.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that the current density of the electrodeposition is 0.01 mA·cm -2 , and finally a lithium metal negative electrode sheet is obtained.

[0085] Comparative Example 2

[0086] The difference from Example 1 is that the current density of the electrodeposition is 1 mA·cm -2 , and finally a lithium metal negative electrode sheet is obtained.

[0087] Comparative Example 3

[0088] The difference from Example 1 is that the addition of lithium hexafluorophosphate solution is eliminated, and a lithium metal negative electrode sheet is finally obtained.

[0089] Performance Testing

[0090] The lithium metal negative electrode sheets prepared in the examples and comparative examples were placed in 20 ml of deionized water, and the concentration of lithium metal ions was measured using ICP to calculate the purity of the lithium metal.

[0091] The lithium metal negative electrode sheet prepared in the embodiment and the comparative example was used as the negative electrode and assembled into a button battery with a lithium iron phosphate positive electrode. The electrolyte was 1 mol / L LiPF 6 Solution, LiPF 6 The solvent in the solution is a combination of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, and the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is 1:1:1. The solution is charged and discharged at a capacity of 0.1C, and the first discharge capacity at 0.1C and the capacity retention rate after 500 cycles are measured.

[0092] The purity of lithium metal in the lithium metal negative electrode sheets prepared in the examples and comparative examples, the initial discharge specific capacity at 0.1C, and the capacity retention rate after 500 cycles at 0.1C are shown in Table 1.

[0093] Table 1

[0094]

[0095] Figure 1 This is the XRD diagram of the lithium metal negative electrode sheet in Example 1 of the present application. It can be seen from the figure that the peaks of the lithium metal negative electrode sheet correspond to the peaks of metallic lithium and metallic copper, indicating that metallic lithium is successfully deposited on the copper foil.

[0096] Figure 2 This is a charge and discharge curve diagram of the battery in Example 1 of the present application at 0.1C. It can be seen from the diagram that the discharge specific capacity of the battery at 0.1C is 136mAh / g, and the charge specific capacity is 140mAh / g.

[0097] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0098] Compared with the traditional method for preparing lithium metal negative electrode sheets, the present application directly extracts lithium from liquid lithium ore and deposits lithium metal on a conductive substrate material, without the need for a high-temperature melting step, thereby simplifying the negative electrode preparation process. Using liquid lithium ore as a lithium source has lower raw material costs and less environmental pollution than traditional lithium salt extraction methods. Electrodeposition technology allows lithium metal to be directly deposited on a conductive substrate material at a lower temperature, which greatly improves the preparation efficiency compared to methods such as high-temperature melting, while also avoiding the degradation of material properties that may be caused by high temperatures. Controlling the current density of electrodeposition within the above range helps to improve the dispersion uniformity of lithium metal deposition and reduce the formation of lithium dendrites, thereby helping to improve the structural stability and cycle stability of the lithium metal negative electrode sheet, and helps to improve the deposition selectivity of lithium ions, thereby helping to improve the purity of lithium metal in the lithium metal negative electrode sheet. Adding a lithium salt solution dropwise on one side of the solid electrolyte helps to further improve the transmission efficiency of lithium ions and the uniformity of the distribution of metallic lithium on the surface of the conductive substrate material. The lithium metal negative electrode sheet prepared by the preparation method of the present application can be directly used as the negative electrode of the battery, which helps to further reduce the preparation cost of the battery.

[0099] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a lithium metal negative electrode sheet, characterized in that: The preparation method comprises the following steps: Step S1, dripping a lithium salt solution, stacking a separator and a conductive substrate layer in sequence on one side surface of the solid electrolyte layer to form a preliminary electrode; Step S2, immersing the other side of the solid electrolyte layer in the preliminary electrode away from the conductive substrate layer into liquid lithium ore, and placing the counter electrode in the liquid lithium ore for electrodeposition to form a lithium metal deposition layer on the surface of the conductive substrate layer, thereby obtaining the lithium metal negative electrode sheet; the liquid lithium ore is not in contact with the lithium salt solution, and the current density of the electrodeposition is 0.05 to 0.5 mA cm -2 .

2. The preparation method according to claim 1, characterized in that: The current density of the electrodeposition is 0.1-0.2 mA·cm -2 ; And / or, the electrodeposition time is 24 to 72 hours.

3. The preparation method according to claim 1 or 2, characterized in that: The concentration of lithium ions in the liquid lithium ore is 0.01-5 mol / L; preferably, the liquid lithium ore is salt lake brine and / or seawater.

4. The preparation method according to any one of claims 1 to 3, characterized in that The material of the solid electrolyte layer is a ceramic electrolyte and / or a polymer electrolyte; preferably, the material of the solid electrolyte layer is a ceramic electrolyte; further preferably, the ceramic electrolyte is selected from Li 6.5 Ln3Z 1.5 Ta 0.5 O 12 Electrolyte, Li 1.3 Al 0.3 Ti 1.7 Electrolyte and Li 0.33 La 0.56 Any one or more of TiO3 electrolyte.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The amount of the lithium salt solution dripped onto the surface of one side of the solid electrolyte layer is 0.3 to 0.5 μL / mm 2 ; Preferably, the concentration of lithium salt in the lithium salt solution is 0.5 to 1.5 mol / L; Further preferably, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide and lithium nitrate; And / or, the solvent in the lithium salt solution is selected from any one or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, fluorinated ethylene carbonate, and 1,3-dioxolane; preferably, the solvent contains at least the ethylene carbonate and the dimethyl carbonate, and the volume ratio of the ethylene carbonate to the dimethyl carbonate is (0.5-1.5):(0.5-1.5).

6. The preparation method according to any one of claims 1 to 5, characterized in that The conductive substrate layer is selected from any one or more of copper foil, nickel foil, aluminum foil, foam metal layer, carbon cloth and metal-organic skeleton layer.

7. The preparation method according to any one of claims 1 to 6, characterized in that The separator is selected from any one or more of a polypropylene membrane, a glass fiber membrane, a cellulose membrane and a polytetrafluoroethylene membrane.

8. The preparation method according to any one of claims 1 to 7, characterized in that The counter electrode is selected from any one or more of a copper electrode, a zinc electrode, a silver electrode and an aluminum electrode.

9. A lithium metal negative electrode sheet, characterized in that: The lithium metal negative electrode sheet is prepared by the preparation method according to any one of claims 1 to 8.

10. A lithium ion battery comprising a positive electrode, an electrolyte and a negative electrode, characterized in that: The negative electrode sheet is the lithium metal negative electrode sheet as claimed in claim 9.

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