Modified metal lithium negative electrode material, preparation method thereof and all-solid-state lithium metal battery

Abstract

The invention provides a modified metal lithium negative electrode material, a preparation method thereof and an all-solid-state lithium metal battery, and the modified metal lithium negative electrode material comprises a negative electrode conductive substrate and an interface passivation layer formed on the surface of the negative electrode conductive substrate; the all-solid-state lithium metal battery comprises a positive electrode, a negative electrode and a solid electrolyte, wherein the negative electrode is a modified metal lithium negative electrode material. The interface passivation layer is generated on the substrate, and the interface passivation layer has good electrochemical stability and shows chemical reaction inertness on the solid electrolyte, so that the problem of interface side reaction caused by direct contact of the lithium metal negative electrode and the solid electrolyte can be effectively solved, and uniform deposition of lithium can be induced to further inhibit growth of lithium dendrites; the safety of the all-solid-state lithium ion battery is improved; the interface impedance of the solid electrolyte and the lithium metal negative electrode is effectively reduced, the coulombic efficiency and the cycling stability of the charge-discharge cycle of the all-solid-state lithium ion battery are improved, and the service life of the all-solid-state lithium metal battery is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a modified metal lithium negative electrode material, a preparation method thereof and a full-solid-state lithium metal battery. BACKGROUND

[0002] With the development of electric vehicles, the development of power grid energy storage and small energy storage equipment, it is imperative to develop batteries with wide working temperature range, high safety, high energy density and high power density. Full-solid-state lithium metal batteries are considered to be the most promising next-generation energy device candidates in the future due to their high safety and energy density, and solve many problems that cannot be solved in a short time, such as electrolyte leakage, corrosion of electrodes and flammable and explosive organic components, which exist in traditional lithium-ion batteries due to the use of liquid organic electrolyte. Sulfide solid electrolyte is considered to be the most promising solid electrolyte material due to its high ionic conductivity and good mechanical processing performance.

[0003] Lithium metal negative electrode has an anode potential of-3.04V (compared with the standard hydrogen electrode) and a theoretical capacity of up to 3860mAhg-1, and is therefore known as the holy grail of the battery energy storage industry. However, due to the influence of lithium dendrites, the commercialization is difficult.

[0004] Although solid-state batteries can theoretically well inhibit the growth and extension of lithium dendrites, due to the presence of gaps in the electrolyte and at the interface caused by the difficulty in completely suppressing and compacting, lithium dendrites still nucleate and grow at the interface and in the electrolyte, eventually leading to short circuit.

[0005] On the other hand, due to the strong chemical reaction between lithium and sulfide electrolyte, strong side reactions occur when the two are in contact, thereby causing the accumulation of by-products, which seriously hinders the transmission capacity of ions at the interface. The uneven stripping and deposition of lithium metal at the interface eventually leads to battery short circuit and failure. These problems fundamentally limit the practical application of lithium metal negative electrode in full-solid-state batteries. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a modified metal lithium negative electrode material, a preparation method thereof and a full-solid-state lithium metal battery. The present application can effectively solve the problem of interface side reaction caused by direct contact between lithium metal negative electrode and solid-state electrolyte, and can induce uniform deposition of lithium and inhibit growth of lithium dendrites, thereby improving the cycle stability of the battery and improving the safety of the full-solid-state lithium ion battery.

[0007] The technical scheme of the present application is: a modified metal lithium negative electrode material, comprising a negative electrode conductive substrate and an interface passivation layer formed on the surface of the negative electrode conductive substrate; the negative electrode conductive substrate is lithium metal with a thickness of 100 microns to 2 cm or a current collector with a single surface deposited with lithium metal with a thickness of 10 microns to 2 cm; the interface passivation layer is generated by in-situ reaction of lithium metal and an organic solution, and the thickness of the generated interface passivation layer is 1 nm to 80 microns.

[0008] Preferably, the material of the current collector is at least one of copper, boron, gold, silver, platinum, carbon, iron, titanium, nickel, and stainless steel.

[0009] Preferably, the present application further provides a preparation method of the modified metal lithium negative electrode material, comprising the following steps: S1), mixing an organic matter with a solvent for 5 seconds to 2 hours to prepare a solution with a concentration of 0.001 mol / L to 10 mol / L; S2), placing the negative electrode conductive substrate in the solution of step S1), and then placing it at room temperature for 30 seconds to 48 hours to generate an interface passivation layer with a thickness of 1 nm to 80 microns on the surface of the negative electrode conductive substrate.

[0010] Preferably, in step S1), the organic matter is one or more of thioacetamide, thioformamide, thiopropionamide, thioacetanilide, thio-benzamide, and thioacetanilide.

[0011] Preferably, in step S1), the solvent is one or more of methyl ethyl carbonate, methyl propionate, fluoroethylene carbonate, ethylene glycol dimethyl ether, vinyl carbonate, vinylene carbonate, dimethyl carbonate, propylene sulfite, and propylene carbonate.

[0012] Preferably, in step S1), the mixing time of the organic matter and the solvent is 5 seconds to 30 minutes; and the concentration of the solution is 0.64 M.

[0013] Preferably, the present application further provides an all-solid-state lithium metal battery, comprising a positive electrode, a negative electrode, and a solid-state electrolyte; the positive electrode is Li or a compound that can reversibly intercalate and deintercalate lithium ions; the solid-state electrolyte is a mixture of one or more of a polymer electrolyte, an inorganic solid electrolyte, and a composite electrolyte; and the negative electrode is a modified metal lithium negative electrode material.

[0014] Preferably, the compound that can reversibly intercalate and deintercalate lithium ions is a ternary positive electrode material.

[0015] Preferably, the mixture comprises one or more of lithium iron phosphate, lithium nickel manganese acid, lithium manganese acid, and lithium cobalt acid.

[0016] The present application has the following beneficial effects: 1. The modified lithium sheet of the present application contains an interface passivation layer of Li-X (X=F, S), which has good electrochemical stability and exhibits chemical inertness to solid-state electrolyte, can effectively solve the problem of interface side reaction caused by direct contact between lithium metal negative electrode and solid-state electrolyte, and can induce uniform deposition of lithium and inhibit the growth of lithium dendrites, thereby improving the cycle stability of the battery and improving the safety of the all-solid-state lithium ion battery; 2. The interface passivation layer of the present application has better interface affinity to solid-state electrolyte, can realize selective conduction of lithium ions, induce uniform deposition of lithium ions, effectively reduce the interface impedance between solid-state electrolyte and lithium metal negative electrode, improve the coulombic efficiency and cycle stability of the all-solid-state lithium ion battery during charge and discharge cycles, and prolong the service life of the all-solid-state lithium metal battery. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a long cycle diagram of the symmetric battery of Example 2 and Comparative Example 2 of the present application at a current density of 0.2 mA / cm2; Figure 2 is a long cycle diagram of the symmetric battery of Example 2 and Comparative Example 2 of the present application at a current density of 0.5 mA / cm2; Figure 3 is a critical current density CCD diagram of Example 2 and Comparative Example 2 of the present application; Figure 4 is a full battery long cycle comparison diagram of Example 3 and Comparative Example 3 of the present application at a rate of 0.2C; Figure 5 is a full battery long cycle comparison diagram of Example 3 and Comparative Example 3 of the present application at a rate of 0.3C; Figure 6 is a full battery rate performance diagram of Example 3 and Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0018] The specific embodiments of the present application will be further described below in conjunction with the accompanying drawings: Example 1 The present embodiment provides a preparation method of a modified metal lithium negative electrode material, comprising the following steps: S1), mixing the organic substance thioacetamide with the solvent ethylene glycol dimethyl ether (DME) for 5s-2h to prepare a 1 mol / L solution; S2), placing the lithium metal negative electrode conductive substrate in the solution of step S1), and then placing it in a glove box for normal temperature treatment for 9h, to generate an interface passivation layer containing Li-F-S on the surface of the lithium metal negative electrode conductive substrate, which has a thickness of 1nm-50µm, is electrochemically stable and has uniform morphology, and a modified lithium metal negative electrode is obtained.

[0019] Comparative Example 1 Comparative Example Compared with Example 1, the lithium metal negative electrode of the comparative example is not modified, that is, the lithium metal negative electrode does not have the Li-SF interface passivation layer.

[0020] Example 2 The modified lithium metal negative electrode prepared in Example 1 was used as the negative electrode, the non-polar solid electrolyte Li6PS5Cl was used as the solid electrolyte, and a button-type solid-state symmetrical battery was assembled using conventional technology.

[0021] Comparative Example 2 Comparative Example 2 uses the unmodified lithium metal prepared in Comparative Example 1 as the negative electrode, that is, the lithium metal negative electrode does not have the Li-SF interface passivation layer, the solid electrolyte uses the non-polar solid electrolyte Li6PS5Cl, and the button-type solid-state symmetrical battery is assembled using conventional technology.

[0022] Example 3 The modified lithium metal negative electrode prepared in Example 1 was used as the negative electrode, nickel cobalt manganese 811 was used as the positive electrode, and the inorganic solid electrolyte Li6PS5Cl was used as the solid electrolyte. A button-type all-solid-state battery was assembled using conventional technology.

[0023] Comparative Example 3 The unmodified lithium metal prepared in Comparative Example 1 was used as the negative electrode, that is, the lithium metal negative electrode did not have the Li-SF interface passivation layer, the positive electrode used nickel cobalt manganese 811 as the positive electrode, and the solid electrolyte used the inorganic solid electrolyte Li6PS5Cl, and the button-type all-solid-state battery was assembled using conventional technology.

[0024] Example 4 The batteries of Example 2, Example 3, Comparative Example 2, and Comparative Example 3 were tested as follows: like Figure 1 As shown, the solid-state button-type symmetrical battery cycle test was carried out at a current density of 0.2 mAh cm-1 for Example 2 and Comparative Example 2. Figure 1 It can be seen that the battery of Example 2 has a more stable cycle.

[0025] like Figure 2 As shown, the solid-state button-type symmetrical battery cycle test was carried out at a current density of 0.5 mAh cm-1 for Example 2 and Comparative Example 2. Figure 2 It can be seen that the battery of Example 2 has a more stable cycle.

[0026] like Figure 3 As shown, the critical current density diagram (CCD diagram) of Example 2 and Comparative Example 2 is shown. Figure 3 It can be seen that the battery of Example 2 has a higher CCD.

[0027] likeFigure 4 As shown, Example 3 and Comparative Example 3 were tested for long cycle stability at 0.2C rate, from Figure 4 It can be seen that the battery of Example 3 has more stable cycles.

[0028] As shown, Example 3 and Comparative Example 3 were tested for long cycle stability at 0.3C rate, from Figure 5 It can be seen that the battery of Example 3 has more stable cycles. Figure 5

[0029] As shown, Example 3 and Comparative Example 3 were tested for full cell rate performance, from Figure 6 It can be seen that the battery of Example 3 has better rate performance. Figure 6

[0030] The foregoing embodiments and description of the application only illustrate the principles of the application and the best mode of practicing it. Various changes and modifications can be suggested to those skilled in the art and it is intended that the application embrace all such changes and modifications as fall within the spirit and scope of the application.​​

Claims

1. A modified lithium metal negative electrode material, characterized in that: It includes a negative electrode conductive substrate and an interface passivation layer formed on the surface of the negative electrode conductive substrate; the negative electrode conductive substrate is lithium metal with a thickness of 100μm to 2cm or a current collector with lithium metal deposited on one side with a thickness of 10μm to 2cm; the interface passivation layer is generated by an in-situ reaction between lithium metal and an organic solution.

2. A modified metal lithium negative electrode material according to claim 1, characterized in that: The thickness of the interface passivation layer is 1 nm to 80 μm.

3. The modified metal lithium negative electrode material according to claim 1, characterized in that: The material of the current collector is at least one of copper, boron, gold, silver, platinum, carbon, iron, titanium, nickel, and stainless steel.

4. A method for preparing the modified metal lithium negative electrode material according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: S1), mixing the organic matter with the solvent for 5 seconds to 2 hours to prepare a 0.001 mol / L to 10 mol / L solution; S2), placing the negative electrode conductive substrate in the solution of step S1), and then placing it at room temperature for 30 seconds to 48 hours to form an interface passivation layer with a thickness of 1 nm to 80 μm on the surface of the negative electrode conductive substrate.

5. The method for preparing a modified metallic lithium negative electrode material according to claim 4, wherein: In step S1), the organic matter is one or more of thioacetamide, thioformamide, thiopropionamide, thioacetanilide, thiobenzamide, and thioacetanilide.

6. The method for preparing a modified metallic lithium negative electrode material according to claim 4, wherein: In step S1), the solvent is one or more of ethyl methyl carbonate, methyl propionate, fluoroethylene carbonate, ethylene glycol dimethyl ether, ethylene carbonate, vinylene carbonate, dimethyl carbonate, propylene sulfite, and propylene carbonate.

7. The method for preparing a modified metallic lithium negative electrode material according to claim 4, wherein: In step S1), the organic matter and the solvent are mixed for 5 seconds to 30 minutes; and the concentration of the solution is 0.64M.

8. An all-solid-state lithium metal battery comprising a positive electrode, a negative electrode, and a solid electrolyte; characterized in that: The positive electrode is Li or a compound that can reversibly embed and extract lithium ions; The negative electrode is the modified metal lithium negative electrode material according to any one of claims 1 to 3; The solid electrolyte is a mixture of one or more of a polymer electrolyte, an inorganic solid electrolyte, and a composite electrolyte.

9. The all-solid-state lithium metal battery according to claim 8, characterized in that: The compound that can reversibly embed and extract lithium ions is a ternary positive electrode material.

10. The all-solid-state lithium metal battery according to claim 9, characterized in that: The lithium ion battery comprises a mixture of one or more of lithium iron phosphate, lithium nickel manganese oxide, lithium manganese oxide, and lithium cobalt oxide.

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