Interface protection layer material, preparation method and application thereof

Abstract

The application discloses an interface protection layer material and a preparation method and application thereof. The interface protection layer material is composed of a heteroatom-doped carbon material, MXene and C3N4. The heteroatom-doped carbon material / MXene / C3N4 composite material, i.e. the interface protection layer material, is prepared by first freezing and drying a water solution of a heteroatom source and MXene, then pyrolyzing at high temperature, and then freezing and drying a water solution of C3N4. The heteroatom-doped carbon material / MXene / C3N4 composite material can be used as an interface protection material for a lithium metal negative electrode, has good lithium affinity, can effectively reduce the local current density on the surface of the lithium metal negative electrode, can relieve the generation of "dead lithium" of the lithium metal negative electrode in long cycle, can inhibit the growth of lithium dendrites, and can improve the cycle stability and coulombic efficiency of the lithium metal battery.

Description

Technical Field

[0001] This invention relates to an interface protective layer material, its preparation method and application, specifically to a heteroatom-doped carbon / MXene / C3N4 composite material, belonging to the field of lithium metal battery technology. Background Technology

[0002] With societal development, current lithium-ion batteries using graphite as the negative electrode can no longer meet the demand for high energy density. To address this issue, a negative electrode material with higher specific capacity is needed to replace graphite. Lithium metal possesses an extremely high theoretical specific capacity (3860 mAh g⁻¹). -1 With its low redox potential (-3.04V vs. standard hydrogen electrode), lithium metal anodes are currently the most promising and ideal anode material. However, during charge-discharge cycles, lithium dendrite growth and severe volume expansion occur, leading to low coulombic efficiency, short cycle life, and even safety issues, thus limiting their development and application. Therefore, suppressing lithium dendrite growth and mitigating the volume expansion effect of lithium metal anodes is currently a hot research topic in academia.

[0003] Guiding the orderly deposition of lithium metal and suppressing the growth of lithium dendrites and volume expansion during lithium deposition-desorption are crucial for maintaining the cycle stability of lithium metal batteries. In recent years, loading lithiophilic materials onto interface protective layer materials has been widely used in lithium metal anodes. On the one hand, the high specific surface area of ​​the interface protective layer material can effectively reduce the local current density of the electrode, thereby promoting uniform lithium metal deposition; on the other hand, the porous structure provides sufficient space to store lithium, suppressing battery volume expansion. Furthermore, the lithiophilic materials distributed within the interface protective layer material can guide the uniform nucleation of lithium metal within the layer.

[0004] In conclusion, interface protective layer materials have broad application prospects in the future development of lithium metal battery energy storage. Further exploration of interface protective layer materials that can regulate the uniform deposition of lithium ions, inhibit the growth of lithium dendrites, and alleviate the volume expansion effect of lithium metal is of great significance for promoting the commercial application of lithium metal anodes. Summary of the Invention

[0005] The main objective of this invention is to provide an interface protective layer material to overcome the shortcomings of the prior art.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] This invention provides an interface protective layer material, characterized in that the interface protective layer material is a heteroatom-doped carbon material / MXene / C3N4 composite material, comprising: carbon material, MXene, and C3N4; the carbon skeleton of the carbon material is doped with heteroatoms, the heteroatoms including any one or a combination of two or more of nitrogen, sulfur, and phosphorus; the MXene includes any one or a combination of two or more of Ti3C2, Ti2C, Nb3C2, Ti4N3, and Ta4C3; the solvent includes any one or a combination of two or more of deionized water, anhydrous ethanol, and ethylene glycol.

[0008] Another object of the present invention is to provide a method for preparing the aforementioned interface protective layer material, comprising:

[0009] The carbon source, heteroatom source and MXene were dissolved in a solvent and freeze-dried to obtain the precursor material;

[0010] The precursor material was subjected to high-temperature pyrolysis to obtain a heteroatom-doped carbon material / MXene composite structure;

[0011] The heteroatom-doped carbon material / MXene composite structure and C3N4 are dissolved in a solvent and freeze-dried to obtain a heteroatom-doped carbon material / MXene / C3N4 composite material, namely the interface protective layer material.

[0012] The present invention also provides the application of the heteroatom-doped carbon material / MXene / C3N4 composite material in lithium metal battery anode materials.

[0013] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0014] 1) The use of heteroatom doping in the interface protective layer material provided by the present invention can effectively improve the lithiophilicity of carbon materials and promote the uniform deposition of lithium metal on the entire material surface.

[0015] 2) The interface protective layer material provided by the present invention is a heteroatom-doped carbon material / MXene / C3N4 composite material. Its three-dimensional porous structure can accommodate a large amount of lithium metal, thereby slowing down the volume change of the lithium metal anode during the charging and discharging process and obtaining a volume-stable lithium metal anode.

[0016] 3) The interface protective layer material provided by this invention is used as a negative electrode protective layer for lithium metal batteries. The specific surface area of ​​the entire electrode material is very large, which reduces the effective current density of the electrode, thereby effectively suppressing the generation of lithium dendrites. The battery has longer cycle stability and coulombic efficiency, thus improving the cycle stability and coulombic efficiency of lithium metal batteries. Attached Figure Description

[0017] Figure 1The figures show the cycle curves of stacked batteries made according to Embodiment 3 of the present invention, using heteroatom-doped carbon material / Nb3C2 / C3N4 composite material as a protective layer and Comparative Example 1, using lithium metal anode material without a protective layer. Detailed Implementation

[0018] In view of the deficiencies of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below, which is mainly an interface protective layer material, its preparation method and application.

[0019] As one aspect of the present invention, it relates to an interface protective layer material, including carbon materials, MXene and C3N4;

[0020] The carbon skeleton of the carbon material is doped with heteroatoms, which include any one or a combination of two or more of nitrogen, sulfur, and phosphorus.

[0021] The mass ratio of the carbon material, MXene, and C3N4 is 20-30:35-40:35-40.

[0022] Heteroatom (nitrogen, sulfur, phosphorus, etc.) doped carbon materials have the characteristics of good lithium affinity, good conductivity and light weight, and have great potential as lithium metal hosts. At the same time, they form composite structures with MXene and C3N4. The large specific surface area and porous structure can reduce the local current density, thereby promoting uniform lithium metal deposition, providing enough space to store lithium metal and suppressing the volume expansion problem of the battery during charging and discharging.

[0023] Another aspect of the present invention relates to a method for preparing an interface protective layer material, comprising:

[0024] The carbon source, heteroatom source and MXene were dissolved in a solvent and freeze-dried to obtain the precursor material;

[0025] The precursor material was subjected to high-temperature pyrolysis to obtain a heteroatom-doped carbon material / MXene composite structure;

[0026] The heteroatom-doped carbon material / MXene composite structure and C3N4 are dissolved in a solvent and freeze-dried to obtain a heteroatom-doped carbon material / MXene / C3N4 composite material, namely the interface protective layer material.

[0027] In some specific embodiments, the carbon source includes any one or a combination of two or more of sodium citrate, glucose, polydopamine, starch, pitch, and lignin.

[0028] Furthermore, the heteroatom source includes any one or a combination of two or more of urea, thiourea, ammonium dihydrogen phosphate, melamine, ammonium persulfate, and diamine hydrogen phosphate.

[0029] Furthermore, the MXene includes any one or a combination of two or more of Ti3C2, Ti2C, Nb3C2, Ti4N3, and Ta4C3.

[0030] Furthermore, the solvent includes any one or a combination of two or more of deionized water, anhydrous ethanol, and ethylene glycol.

[0031] Furthermore, the mass ratio of the carbon source, heteroatom source, MXene, and C3N4 is 1-2:1-4:1-2:1-2.

[0032] In some specific embodiments, the freeze-drying specifically includes freeze drying and vacuum drying.

[0033] Preferably, the freezing temperature is -35 to -50°C, and the freezing time is 10-15 hours.

[0034] Preferably, the vacuum degree of the vacuum drying is 1-30 Pa, and the drying time is 48-54 h.

[0035] In some specific embodiments, the high-temperature pyrolysis temperature is 700-900℃, and the high-temperature pyrolysis time is 60-180min.

[0036] Furthermore, the high-temperature pyrolysis is carried out under an inert protective atmosphere.

[0037] In some more specific embodiments, the preparation method of the heteroatom-doped carbon material / MXene / C3N4 composite material includes:

[0038] A mixed solution is obtained by dissolving a carbon source, a nitrogen / sulfur / phosphorus source and MXene in a solvent;

[0039] The resulting mixed solution was freeze-dried to obtain the precursor material;

[0040] The precursor powder is pyrolyzed at high temperature to carbonize the carbon source, and nitrogen / sulfur / phosphorus atoms from the nitrogen / sulfur / phosphorus source are doped into the carbon material framework.

[0041] Excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / MXene composite structure.

[0042] Heteroatom-doped carbon material / MXene and C3N4 were dissolved in a solvent to obtain a mixed solution;

[0043] The resulting mixed solution was freeze-dried to obtain the final product, a heteroatom-doped carbon / MXene / C3N4 composite material, which is the interface protective layer material.

[0044] In summary, the interface protective layer material is composed of heteroatom-doped carbon material, MXene, and C3N4. The preparation method includes the following steps: dissolving a carbon source, a nitrogen / sulfur / phosphorus source, and MXene in a solvent to obtain a mixed solution; freeze-drying the obtained mixed solution to obtain a precursor powder; pyrolyzing the precursor powder at high temperature to carbonize the carbon source, and doping nitrogen / sulfur / phosphorus atoms from the nitrogen / sulfur / phosphorus source into the carbon material framework; washing away excess impurities from the carbonized material to obtain a heteroatom-doped carbon material / MXene composite structure; dissolving the heteroatom-doped carbon material / MXene and C3N4 in a solvent to obtain a mixed solution; and freeze-drying the obtained mixed solution to obtain the final product, a heteroatom-doped carbon material / MXene / C3N4 composite material. This invention obtains a precursor powder with perfect morphology through freeze drying, then carbonizes the carbon source through high-temperature pyrolysis, incorporating heteroatoms into the carbon material framework, and then washes away excess impurities. At the same time, it forms a composite structure with MXene and C3N4, forming a three-dimensional porous structure, which further improves the performance of the material.

[0045] This invention also provides the application of the interface protective layer material in lithium metal battery anode materials.

[0046] The slurry of the heteroatom-doped carbon material / MXene / C3N4 composite material is uniformly coated on the surface of copper foil. After drying, it is used to make a lithium copper battery. At the same time, after drying, the negative electrode protective layer on the surface of the copper foil is also pressed onto the lithium foil. After the operation is completed, a lithium metal negative electrode material with a protective layer can be obtained.

[0047] Using the heteroatom-doped carbon / MXene / C3N4 composite material as the interface protective layer material for lithium metal anodes can effectively suppress the formation of lithium dendrites during lithium metal deposition and desorption, as well as the problem of lithium metal deposition volume expansion and the further formation of dead lithium causing battery capacity decay. This can effectively improve the coulombic efficiency and cycle stability of the battery. The process is simple, low-cost, and suitable for industrial production.

[0048] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention, and do not constitute any limitation thereof. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the manufacturer.

[0049] Example 1

[0050] Preparation of heteroatom-doped carbon materials / Ti3C2 / C3N4 composite materials

[0051] 5g sodium citrate, 10g urea, and 5g Ti3C2 were added to 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ti3C2 composite material. The obtained heteroatom-doped carbon material / Ti3C2 and 5g C3N4 were dissolved in 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ti3C2 / C3N4 composite material.

[0052] Performance testing

[0053] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0054] Example 2

[0055] Preparation of heteroatom-doped carbon materials / Ti2C / C3N4 composite materials

[0056] 5g sodium citrate, 10g thiourea, and 5g Ti₂C were added to 100g anhydrous ethanol and stirred for 2 hours. The resulting mixture was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain a dry, fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ti₂C composite material. The obtained heteroatom-doped carbon material / Ti₂C and 5g C₃N₄ were dissolved in 100g anhydrous ethanol and stirred for 2 hours. The resulting mixture was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ti₂C / C₃N₄ composite material.

[0057] Performance testing

[0058] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0059] Example 3

[0060] Preparation of heteroatom-doped carbon materials / Nb3C2 / C3N4 composite materials

[0061] 5g sodium citrate, 10g ammonium dihydrogen phosphate, and 5g Nb3C2 were added to 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1-30 Pa for 48 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Nb3C2 composite material. The obtained heteroatom-doped carbon material / Nb3C2 and 5g C3N4 were dissolved in 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1-30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Nb3C2 / C3N4 composite material.

[0062] Performance testing

[0063] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0064] Example 4

[0065] Preparation of heteroatom-doped carbon materials / Ti4N3 / C3N4 composite materials

[0066] 5g glucose, 10g melamine, and 5g Ti4N3 were added to 100g ethylene glycol and stirred for 2 hours. The resulting mixture was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ti4N3 composite material. The obtained heteroatom-doped carbon material / Ti4N3 and 5g C3N4 were dissolved in 100g ethylene glycol and stirred for 2 hours. The resulting mixture was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ti4N3 / C3N4 composite material.

[0067] Performance testing

[0068] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0069] Example 5

[0070] Preparation of heteroatom-doped carbon materials / Ta4C3 / C3N4 composite materials

[0071] 5g starch, 10g ammonium persulfate, and 5g Ta4C3 were added to 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1-30 Pa for 48 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ta4C3 composite material. The obtained heteroatom-doped carbon material / Ta4C3 and 5g C3N4 were dissolved in 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1-30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ta4C3 / C3N4 composite material.

[0072] Performance testing

[0073] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0074] Example 6

[0075] Preparation of heteroatom-doped carbon materials / Ti3C2 / C3N4 composite materials

[0076] 5g of asphalt, 10g of diammonium hydrogen phosphate, and 5g of Ti3C2 were added to 100g of anhydrous ethanol and stirred for 2 hours. The resulting mixture was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ti3C2 composite material. The obtained heteroatom-doped carbon material / Ti3C2 and 5g of C3N4 were dissolved in 100g of anhydrous ethanol and stirred for 2 hours. The resulting mixture was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ti3C2 / C3N4 composite material.

[0077] Performance testing

[0078] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0079] Example 7

[0080] Preparation of heteroatom-doped carbon materials / Ti2C / C3N4 composite materials

[0081] 5g of polydopamine, 10g of thiourea, and 5g of Ti₂C were added to 100g of ethylene glycol and stirred for 2 hours. The resulting mixture was frozen at -40°C for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain a dry, fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800°C for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ti₂C composite material. The obtained heteroatom-doped carbon material / Ti₂C and 5g of C₃N₄ were dissolved in 100g of ethylene glycol and stirred for 2 hours. The resulting mixture was frozen at -40°C for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ti₂C / C₃N₄ composite material.

[0082] Performance testing

[0083] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0084] Example 8

[0085] Preparation of heteroatom-doped carbon materials / Nb3C2 / C3N4 composite materials

[0086] 5g of lignin, 5g of ammonium dihydrogen phosphate, and 5g of Nb3C2 were added to 100g of deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen protective atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Nb3C2 composite material. The obtained heteroatom-doped carbon material / Nb3C2 and 5g of C3N4 were dissolved in 100g of deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Nb3C2 / C3N4 composite material.

[0087] Performance testing

[0088] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0089] Example 9

[0090] Preparation of heteroatom-doped carbon materials / Ti4N3 / C3N4 composite materials

[0091] 5g of lignin, 10g of ammonium dihydrogen phosphate, and 5g of Ti4N3 were added to 100g of deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ti4N3 composite material. The obtained heteroatom-doped carbon material / Ti4N3 and 5g of C3N4 were dissolved in 100g of deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ti4N3 / C3N4 composite material.

[0092] Performance testing

[0093] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0094] Example 10

[0095] Preparation of heteroatom-doped carbon materials / Ta4C3 / C3N4 composite materials

[0096] 5g of lignin, 20g of ammonium dihydrogen phosphate, and 5g of Ta4C3 were added to 100g of deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ta4C3 composite material. The obtained heteroatom-doped carbon material / Ta4C3 and 5g of C3N4 were dissolved in 100g of deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ta4C3 / C3N4 composite material.

[0097] Performance testing

[0098] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0099] Example 11

[0100] Preparation of heteroatom-doped carbon materials / Ti3C2 / C3N4 composite materials

[0101] 5g sodium citrate, 20g urea, and 5g Ti3C2 were added to 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -35℃ for 15 hours and then dried under a vacuum of 1–30 Pa for 50 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 700℃ for 3 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ti3C2 composite material. The obtained heteroatom-doped carbon material / Ti3C2 and 5g C3N4 were dissolved in 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ti3C2 / C3N4 composite material.

[0102] Example 12

[0103] 5g sodium citrate, 2.5g urea, and 5g Ti3C2 were added to 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -50℃ for 10 hours and then dried under a vacuum of 1–30 Pa for 54 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 900℃ for 1 hour under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a heteroatom-doped carbon material / Ti3C2 composite material. The obtained heteroatom-doped carbon material / Ti3C2 and 5g C3N4 were dissolved in 100g deionized water and stirred for 2 hours. The resulting mixed solution was frozen at -40℃ for 12 hours and then dried under a vacuum of 1–30 Pa for 48 hours to obtain the final product, a heteroatom-doped carbon material / Ti3C2 / C3N4 composite material.

[0104] Comparative Example 1

[0105] In contrast to the examples above, unprotected lithium metal anode materials were used to fabricate lithium-copper batteries and assembled with ternary materials into stacked batteries. The coulombic efficiency of the resulting lithium-copper batteries was recorded during charge-discharge cycle tests. Specifically, the average coulombic efficiency was calculated for every 100 charge-discharge cycles after 100 cycles. Cyclic charge-discharge tests were performed on the stacked batteries, and the cycle time was recorded.

[0106] Comparative Example 2

[0107] Preparation of heteroatom-free carbon materials / Ta4C3 / C3N4 composite materials

[0108] 5g of glucose and 5g of Ta4C3 were added to 100g of deionized water and stirred for 2 hours. The resulting mixture was frozen at -40℃ for 12 hours and then dried under a vacuum of 1-30 Pa for 48 hours to obtain a dry and fluffy precursor powder. The precursor powder was then pyrolyzed in a tube furnace at high temperature and held at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, excess impurities in the carbonized material were washed away to obtain a carbon / Ta4C3 composite material without heteroatom doping. The obtained carbon / Ta4C3 without heteroatom doping and 5g of C3N4 were dissolved in 100g of deionized water and stirred for 2 hours. The resulting mixture was frozen at -40℃ for 12 hours and then dried under a vacuum of 1-30 Pa for 48 hours to obtain the final product, a carbon / Ta4C3 / C3N4 composite material without heteroatom doping.

[0109] Performance testing

[0110] First, the final product is made into a slurry and uniformly coated onto the surface of copper foil. After drying, a lithium-copper battery is formed. Simultaneously, after drying, the negative electrode protective layer on the copper foil surface is pressed onto the lithium foil. After this process, a lithium metal negative electrode material with a protective layer is obtained. Finally, it is assembled with ternary materials to form a stacked battery. The coulombic efficiency of the resulting lithium-copper battery is recorded during charge-discharge cycle testing. Specifically, 100 cycles are performed, and the average coulombic efficiency is calculated for every 10 charge-discharge cycles. Cyclic charge-discharge tests are conducted on the stacked battery, and the cycle time is recorded.

[0111] The average coulombic efficiency of the lithium copper batteries in Examples 1-12 and Comparative Examples 1-2 and the cycle time of the stacked battery charge-discharge test were recorded. The specific results are shown in Table 1.

[0112] Table 1 shows the average coulombic efficiency and number of cycles to maintain 80% capacity in Examples 1-12 and Comparative Examples 1-2.

[0113] Example 1 99.38％ 154 Example 2 99.55％ 167 Example 3 99.61％ 183 Example 4 98.56％ 130 Example 5 98.92％ 142 Example 6 98.84％ 135 Example 7 99.27％ 142 Example 8 99.32％ 146 Example 9 99.39％ 153 Example 10 99.45％ 164 Example 11 99.47％ 162 Example 12 99.23％ 140 Comparative Example 1 94.69％ 102 Comparative Example 2 97.34％ 121

[0114] As can be seen from Table 1, the average coulombic efficiency of the lithium copper batteries prepared by the method of this disclosure is higher than that of the comparative example, which shows that the negative electrode of the battery prepared by the method of this disclosure with protective layer material has stronger stability. At the same time, the number of cycles in which the stacked battery prepared by the method of this disclosure retains 80% capacity is better than that of the comparative example, which shows that the battery prepared by this disclosure with protective layer material has better cycle life.

[0115] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0116] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. The application of an interface protective layer material in lithium metal battery anode materials, the application including: The interface protective layer material is used as a protective layer for the negative electrode of a lithium metal battery and is applied to the surface of the negative electrode material of the lithium metal battery, wherein the lithium metal battery is a lithium copper battery. The interface protective layer material is a heteroatom-doped carbon material / MXene / C3N4 composite material, comprising carbon material, MXene and C3N4 in a mass ratio of 20-30:35-40:35-40; the carbon skeleton of the carbon material is doped with heteroatoms, which include any one or a combination of two or more of nitrogen, sulfur and phosphorus. Furthermore, the method for preparing the composite material includes: The carbon source, heteroatom source and MXene were dissolved in a solvent and freeze-dried to obtain the precursor material; The precursor material was subjected to high-temperature pyrolysis at 700-900℃ for 60-180 min under an inert protective atmosphere to obtain a heteroatom-doped carbon material / MXene composite structure. The heteroatom-doped carbon material / MXene composite structure and C3N4 were dissolved in a solvent, frozen at -35~-50℃ for 10-15 h, and then vacuum dried at 1-30 Pa for 48-54 h. The mass ratio of the carbon source, heteroatom source, MXene, and C3N4 is 1-2:1-4:1-2:1-2.

2. The application according to claim 1, characterized in that: The carbon source includes any one or a combination of two or more of sodium citrate, glucose, polydopamine, starch, pitch, and lignin.

3. The application according to claim 1, characterized in that: The heteroatom source includes any one or a combination of two or more of urea, thiourea, ammonium dihydrogen phosphate, melamine, ammonium persulfate, and diamine hydrogen phosphate.

4. The application according to claim 1, characterized in that: The MXene includes any one or a combination of two or more of Ti3C2, Ti2C, Nb3C2, Ti4N3, and Ta4C3.

5. The application according to claim 1, characterized in that: The solvent includes any one or a combination of two or more of deionized water, anhydrous ethanol, and ethylene glycol.

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