A high reaction kinetics lithium sulfide nanocomposite cathode material and a preparation method and application thereof

Abstract

The application belongs to the technical field of all-solid-state lithium-sulfur battery materials, and relates to a lithium sulfide nano composite positive electrode material with high reaction kinetics and a preparation method and application thereof. The application aims to solve the deficiencies of the lithium sulfide positive electrode material in ion and electron conductivity, reduce the activation barrier of the lithium sulfide positive electrode material, improve the battery redox kinetics, and further improve the rate performance and cycle capacity of the battery. The lithium sulfide nano composite positive electrode material is prepared by using an in-situ synthesis method, the obtained composite material has rich metal atom crystals embedded in the lithium sulfide matrix, and a layer of amorphous carbon is uniformly coated on the surface. The finally obtained lithium sulfide nano composite positive electrode material exhibits high reversible capacity and excellent rate performance. The application has the characteristics of uniform coating and simple process, is suitable for large-scale production, and has a wide application prospect in the field of all-solid-state lithium-sulfur batteries.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state lithium-sulfur battery materials technology, specifically to a method for preparing lithium sulfide nanocomposite cathode materials with high reaction kinetics and their applications. Background Technology

[0002] In recent years, lithium-ion batteries have become very mature with continuous development. However, to meet the increasing demands of the electric vehicle industry in terms of energy density and safety, the development of rechargeable batteries with higher specific energy is of paramount importance.

[0003] All-solid-state lithium-sulfur batteries boast a capacity of up to 2600Wh / kg. -1 With its theoretical energy density and intrinsic safety advantages, the all-solid-state lithium-sulfur battery is considered one of the most promising directions for next-generation energy storage systems. Compared to traditional liquid lithium-sulfur batteries, the all-solid-state system, through the application of solid electrolytes, can fundamentally solve two core problems: First, the dissolution of polysulfides during discharge leads to a "shuttle effect," which significantly reduces coulombic efficiency and causes rapid capacity decay; second, the replacement of flammable organic electrolytes with solid electrolytes effectively improves the thermal stability of the battery system, completely eliminating the safety hazards of liquid systems. However, the use of sulfur cathode materials in all-solid-state lithium-sulfur batteries still leads to structural collapse during charging and discharging due to volume expansion of up to 80%, and elemental sulfur materials also have problems such as low conductivity, which seriously affect the rate performance of the battery.

[0004] The use of lithium sulfide (Li₂S) as the cathode material provides a new approach for the development of all-solid-state lithium-sulfur batteries. Compared to elemental sulfur, Li₂S has a higher mAh / g capacity. -1 Lithium sulfide's high theoretical specific capacity and melting point of 938℃ facilitate diverse chemical modification methods at high temperatures. As a cathode material, lithium sulfide can also mitigate the problem of cathode volume expansion during charging and discharging, thereby improving mechanical stability. Furthermore, lithium sulfide itself can provide lithium ions, making it compatible with lithium-free anodes such as graphite and silicon-carbon, fundamentally avoiding the dendrite growth risk of metallic lithium anodes. However, lithium sulfide materials still have many problems. For example, lithium sulfide has low electronic conductivity, with a conductivity of only 10 at room temperature. -13 S cm -1 This hinders electron conduction between lithium sulfide and the current collector, thereby reducing the electrochemical reaction rate. Secondly, lithium sulfide ions also have poor conductivity, making them difficult to activate during the first charge and requiring overcoming a high activation barrier.

[0005] To address the aforementioned problems with lithium sulfide cathodes, researchers have proposed various strategies, including nanostructure design, core-shell encapsulation, and redox media catalysis, achieving some progress in these areas. Patent CN118359172A describes a process involving material purification, nanoscale wet milling, homogeneous reaction, and ball milling to obtain high-purity nanoscale lithium sulfide material. Patent CN115714169A describes the preparation of lithium sulfate microspheres via spray drying, followed by thorough mixing with a carbon source precursor and in-situ redox reactions to obtain carbon-coated hollow lithium sulfide spheres. However, single modifications cannot completely solve the problems of lithium sulfide cathodes. Therefore, this invention proposes an in-situ synthesized lithium sulfide nanocomposite cathode material with high reaction kinetics and its preparation method. Summary of the Invention

[0006] To address the shortcomings of existing lithium sulfide cathode materials in terms of ionic and electronic conductivity, as well as high activation energy barriers, this invention provides a lithium sulfide nanocomposite cathode material with high reaction kinetics, its preparation method, and its application in all-solid-state lithium-sulfur batteries.

[0007] This invention first involves an in-situ reaction of a lithium source, a metal sulfide, and carbon disulfide, followed by an in-situ electrochemical reduction reaction, thereby obtaining a lithium sulfide nanocomposite cathode material with a shell structure containing a metal atom catalyst.

[0008] To achieve the above-mentioned technical objectives, the present invention provides the following specific technical solution:

[0009] This invention relates to a method for preparing a lithium sulfide nanocomposite cathode material with high reaction kinetics, comprising the following steps:

[0010] (1) Mixing: The lithium source and the metal sulfide are thoroughly mixed to obtain a mixed material;

[0011] (2) Heat treatment: The mixed material obtained in step (1) is mixed with carbon disulfide (CS2) and heated. After the reaction is completed, it is dried to obtain carbon-coated lithium sulfide nanocomposite cathode material with internal metal sulfide doping.

[0012] (3) In-situ electrochemical reduction reaction: The composite cathode material obtained in step (2) is used as the active material to prepare electrode composite material, and an all-solid-state lithium-sulfur battery is assembled and electrochemically discharged. The lithium sulfide nanocomposite cathode material with internal doped single metal atoms is obtained through in-situ electrochemical reduction reaction.

[0013] By adopting the above technical solution, this invention can generate metal doping in situ during the reaction process by mixing lithium source with metal sulfide, achieving a uniform doping effect. Compared with direct metal mixing doping, this is more uniform and efficient, and the material performance is further improved. At the same time, lithium sulfide can be generated, further increasing the content of active material. Subsequently, by mixing and reacting with carbon disulfide, uniform carbon coating can be achieved in situ while generating lithium sulfide, further improving the conductivity of the material, alleviating the volume change problem, maintaining the structural stability of the cathode material, and further improving battery performance.

[0014] The following are further preferred technical solutions of the present invention:

[0015] Preferably, in step (1), the lithium source is at least one of lithium powder (Li), lithium sheet (Li), and lithium hydride (LiH);

[0016] And / or, the metal sulfide is at least one of manganese disulfide (MnS2), iron disulfide (FeS2), cobalt disulfide (CoS2), nickel disulfide (NiS2), molybdenum disulfide (MoS2), titanium disulfide (TiS2), vanadium disulfide (VS2), zinc disulfide (ZnS2), chromium disulfide (CrS2), copper sulfide (CuS), manganese sulfide (MnS), ferrous sulfide (FeS), cobalt sulfide (CoS), nickel sulfide (NiS), molybdenum sulfide (MoS), titanium sulfide (TiS), vanadium sulfide (VS), zinc sulfide (ZnS), and chromium sulfide (CrS);

[0017] And / or, the molar ratio of the lithium source to the metal sulfide is 2 to 8:1.

[0018] Preferably, in step (1), the mixture is thoroughly mixed by ball milling. The ball milling conditions are: a ball milling speed of 100–700 rpm and a ball milling time of 4–20 h; more preferably, a ball milling speed of 300–600 rpm and a ball milling time of 8–16 h. By using ball milling, the metal sulfide and lithium source can be effectively and thoroughly mixed and homogeneously. If the metal sulfide and lithium source are not mixed evenly, the reaction will be insufficient or almost non-existent, resulting in the lithium source reacting directly with carbon disulfide without reacting with the metal sulfide. This leads to uneven dispersion of dopants within the obtained material and poor electrochemical performance.

[0019] Preferably, in step (2), the solid content after mixing is 20-60%;

[0020] And / or, the heating conditions are: heating temperature of 300-700℃; holding time of 1-5h; heating rate of 2-5℃ / min; more preferably, heating temperature of 400-700℃;

[0021] And / or, the drying conditions are: heating temperature of 30-100℃; drying time of 0.5-3h.

[0022] Preferably, in step (2), the size of the composite cathode material prepared is ≤100nm and the thickness of the carbon coating layer is 1~10nm.

[0023] Preferably, in step (3), the electrode composite material includes a composite positive electrode material, a sulfide solid electrolyte, and conductive carbon.

[0024] More preferably, the sulfide solid electrolyte is Li6PS5Cl or Li7P3S 11 Li 10 GeP2S 12 At least one of;

[0025] And / or, the conductive carbon is at least one of multi-walled carbon nanotubes (WMCNTs), acetylene black (AB), and activated carbon (AC);

[0026] And / or, the mass ratio of the composite cathode material, the sulfide solid electrolyte, and the conductive carbon is (50-90):(10-40):(0-10), more preferably 5:4:1;

[0027] And / or, the composite cathode material, sulfide solid electrolyte, and conductive carbon are ball-milled and mixed to obtain an electrode composite material. The ball-milling parameters are: ball-milling speed of 100-500 rpm and ball-milling time of 2-16 h.

[0028] Preferably, in step (3), the in-situ electrochemical reduction reaction is performed by discharging the assembled battery on the battery rack with a cutoff discharge voltage of 0.5V; more preferably, the discharge is performed with a current density of 20mA / g to 100mA / g, and even more preferably, 50mA / g.

[0029] Preferably, in step (3), the elemental metal atoms include at least one of manganese, iron, cobalt, nickel, molybdenum, titanium, vanadium, zinc, chromium, and copper.

[0030] Preferably, the size of the carbon-coated metal-doped lithium sulfide nanoparticles is ≤100nm; the thickness of the carbon coating layer is 1-10nm; and the metal atom doping content accounts for 15-24wt.% of the composite cathode material.

[0031] Further preferably, the preparation method includes the following steps:

[0032] (1) Ball milling mixing: In a glove box filled with argon gas and with humidity and oxygen concentration of less than 0.01ppm, weigh a certain amount of lithium source and metal sulfide, seal the two in a ball mill jar, and ball mill them at a certain speed for several hours.

[0033] (2) Heat treatment: In a glove box, the material obtained after ball milling in step (1) is mixed with carbon disulfide and magnetically stirred for 10 minutes. Then, it is placed in a quartz tube for encapsulation and heat treatment. After the reaction is completed, it is dried to volatilize the excess carbon disulfide, thus obtaining the carbon-coated lithium sulfide nanocomposite cathode material with internal metal sulfide doping.

[0034] (3) In-situ electrochemical reduction reaction:

[0035] In a glove box, the composite cathode material obtained in step (2) was ball-milled with a sulfide solid electrolyte and conductive carbon for several hours to obtain an electrode composite material. Subsequently, carbon-coated aluminum foil, electrode composite material, sulfide solid electrolyte, and lithium sheet were sequentially cold-pressed to assemble an all-solid-state lithium-sulfur battery. Then, electrochemical discharge was performed on the battery rack, and lithium sulfide nanocomposite cathode material with internal doped elemental metal atoms was obtained through in-situ electrochemical reduction reaction.

[0036] The present invention also provides a lithium sulfide nanocomposite cathode material with high reaction kinetics prepared by the above preparation method.

[0037] This invention also provides an application of the high reaction kinetics lithium sulfide nanocomposite cathode material prepared by the above preparation method in the field of all-solid-state lithium-sulfur batteries.

[0038] Preferably, the application includes a sulfide all-solid-state lithium-sulfur battery comprising the aforementioned high-reaction-kinetic lithium-sulfur nanocomposite cathode material.

[0039] This invention aims to address the shortcomings of lithium sulfide cathode materials in terms of ionic and electronic conductivity, reduce the activation barrier of lithium sulfide cathode materials, improve battery redox kinetics, and thus improve the rate performance and cycle capacity of the battery. This invention employs an in-situ synthesis method to prepare lithium sulfide nanocomposite cathode materials. The resulting composite material has abundant metal atomic crystals embedded in a lithium sulfide matrix, and its surface is uniformly coated with a layer of amorphous carbon. The final lithium sulfide nanocomposite cathode material exhibits high reversible capacity and excellent rate performance. This invention features uniform coating and a simple process, making it suitable for large-scale production and showing broad application prospects in the field of all-solid-state lithium-sulfur batteries.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The method for preparing lithium sulfide nanocomposite cathode material with high reaction kinetics provided by this invention is entirely generated through in-situ reaction. This invention is not only simple to operate, but also produces composite materials with complete doping and uniform coating. The lithium sulfide composite cathode material generated by the reaction has nanoscale dimensions. At the same time, due to in-situ growth, the carbon coating of this invention has a more stable interface. Meanwhile, the coated carbon inhibits the volume change of lithium sulfide during charge and discharge. After cycling, the carbon coating layer remains intact and does not detach, further improving the stability.

[0042] 2. Existing technologies all involve single modifications to lithium sulfide cathode materials, including nanostructure design, core-shell encapsulation, and redox medium catalysis. This invention combines the advantages of these three strategies to synthesize lithium sulfide nanocomposite cathode materials with high reaction kinetics in situ. Furthermore, this invention does not simply combine the three strategies, but rather achieves in-situ synthesis through precise design of raw materials, successfully obtaining a fully and uniformly doped composite material with uniform coating.

[0043] 3. The modified composite material exhibits superior ionic and electronic conductivity, improving the redox reaction kinetics of the lithium sulfide cathode and resulting in better rate performance. Furthermore, the introduction of metal atoms lowers the activation energy barrier of the lithium sulfide cathode material and leads to a smaller polarization voltage during charge and discharge. Attached Figure Description

[0044] Figure 1 This is the XRD pattern of the lithium sulfide nanocomposite cathode material with high reaction kinetics in Example 1 of the present invention;

[0045] Figure 2 This is a SEM image of the lithium sulfide nanocomposite cathode material with high reaction kinetics in Example 1 of this invention;

[0046] Figure 3 This is a TEM image of the lithium sulfide nanocomposite cathode material with high reaction kinetics in Example 1 of this invention;

[0047] Figure 4 The two materials in Example 1 and Comparative Example 1 of this invention are at 100 mAg -1 Comparison of the first charge-discharge curves at current density;

[0048] Figure 5 These are cycle capacity diagrams of the two materials in Embodiment 1 and Comparative Example 1 of the present invention under different current densities;

[0049] Figure 6 The first ring of the two materials in Embodiment 1 and Comparative Example 1 of this invention has a g / m² of 50 mAg. -1 Differential capacity curve at current density. Detailed Implementation

[0050] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0051] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, and instruments used in the embodiments, unless otherwise specified, can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention can all achieve the reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0052] Example 1

[0053] (1) Ball milling and mixing

[0054] In a glove box filled with argon gas and with humidity and oxygen concentrations of less than 0.01 ppm, 0.258 g of lithium hydride (LiH) and 1 g of cobalt disulfide (CoS2) were weighed, sealed in a ball mill jar with a ball-to-material ratio of 10:1, and ball milled at 500 rpm for 12 hours.

[0055] (2) Heat treatment

[0056] The material obtained after ball milling in step (1) was mixed with carbon disulfide in a glove box, with a solid content of 40%, and magnetically stirred for 10 min. Then, it was placed in a quartz tube and sealed, and kept at 500℃ for 2 h with a heating rate of 2℃ / min. After the reaction, it was dried at 30℃ for 2 h to volatilize excess carbon disulfide, thus obtaining a lithium sulfide nanocomposite cathode material (Li2S@Co) internally doped with 23 wt.% metal sulfides. x S y -C), whose composite cathode material has a particle size of 30-70 nm;

[0057] (3) In-situ electrochemical reduction reaction

[0058] The composite cathode material (Li2S@Co) obtained in step (2) is placed in a glove box. x Sy -C) was ball-milled with sulfide solid electrolyte (Li6PS5Cl) and multi-walled carbon nanotubes (WMCNTs) at a mass ratio of 5:4:1 at 500 rpm for 12 h to obtain an electrode composite material. Subsequently, carbon-coated aluminum foil, the electrode composite material, the sulfide solid electrolyte (Li6PS5Cl), and lithium sheets were sequentially cold-pressed to assemble an all-solid-state lithium-sulfur battery. The battery was then mounted on a battery rack at 50 mAg. -1 Electrochemical discharge was performed at a current density with a cutoff discharge voltage of 0.5V. An in-situ electrochemical reduction reaction yielded a lithium sulfide nanocomposite cathode material (Li₂S@Co-C) internally doped with 15 wt.% elemental cobalt atoms. The material has a particle size of 30–70 nm and a carbon coating thickness of 3–10 nm.

[0059] Example 2

[0060] (1) Ball milling and mixing

[0061] In a glove box filled with argon gas and with humidity and oxygen concentrations of less than 0.01 ppm, 0.175 g of lithium powder (Li) and 1 g of cobalt sulfide (CoS) were weighed, sealed in a ball mill jar with a ball-to-material ratio of 10:1, and ball milled at 100 rpm for 20 h.

[0062] (2) Heat treatment

[0063] The material obtained after ball milling in step (1) was mixed with carbon disulfide in a glove box, with a solid content of 20%, and magnetically stirred for 10 min. Then, it was placed in a quartz tube and sealed, and kept at 400℃ for 5 h with a heating rate of 2℃ / min. After the reaction, it was dried at 50℃ for 1 h to volatilize excess carbon disulfide, thus obtaining a lithium sulfide nanocomposite cathode material (Li2S@Co) internally doped with 36 wt.% metal sulfides. x S y -C), whose composite cathode material has a particle size of 30-70 nm;

[0064] (3) In-situ electrochemical reduction reaction

[0065] The composite cathode material (Li2S@Co) obtained in step (2) is placed in a glove box. x S y -C) and sulfide solid electrolyte (Li7P3S) 11 The electrode composite material was obtained by ball milling acetylene black (AB) at a mass ratio of 5:4:1 at 300 rpm for 12 h. Subsequently, carbon-coated aluminum foil, the electrode composite material, and a sulfide solid electrolyte (Li7P3S) were sequentially added. 11 The lithium sheets are sequentially cold-pressed to assemble an all-solid-state lithium-sulfur battery, which is then mounted on a battery rack at 50 mAg. -1Electrochemical discharge was performed at a current density with a cutoff discharge voltage of 0.5V. An in-situ electrochemical reduction reaction yielded a lithium sulfide nanocomposite cathode material (Li₂S@Co-C) internally doped with 24 wt.% elemental cobalt atoms. The material has a particle size of 30–70 nm and a carbon coating thickness of 1–8 nm.

[0066] Example 3

[0067] (1) Ball milling and mixing

[0068] In a glove box filled with argon gas and with humidity and oxygen concentrations of less than 0.01 ppm, 0.265 g of lithium hydride (LiH) and 1 g of iron disulfide (FeS2) were weighed, sealed in a ball mill jar with a ball-to-material ratio of 10:1, and ball milled at 700 rpm for 4 hours.

[0069] (2) Heat treatment

[0070] The material obtained after ball milling in step (1) was mixed with carbon disulfide in a glove box, with a solid content of 40%, and magnetically stirred for 10 min. Then, it was placed in a quartz tube and sealed, and kept at 300℃ for 5 h with a heating rate of 2℃ / min. After the reaction, it was dried at 100℃ for 3 h to volatilize the excess carbon disulfide, thus obtaining a lithium sulfide nanocomposite cathode material (Li2S@Fe) internally doped with 23 wt.% metal sulfides. x S y -C), whose composite cathode material has a particle size of 20-60 nm;

[0071] (3) In-situ electrochemical reduction reaction

[0072] The composite cathode material (Li2S@Fe) obtained in step (2) is placed in a glove box. x S y -C) was ball-milled with sulfide solid electrolyte (Li6PS5Cl) and multi-walled carbon nanotubes (WMCNTs) at a mass ratio of 5:4:1 at 100 rpm for 16 h to obtain an electrode composite material. Subsequently, carbon-coated aluminum foil, the electrode composite material, the sulfide solid electrolyte (Li6PS5Cl), and lithium sheets were sequentially cold-pressed to assemble an all-solid-state lithium-sulfur battery. The battery was then mounted on a battery rack at 50 mAg. -1 Electrochemical discharge was performed at a current density with a cutoff discharge voltage of 0.5V. An in-situ electrochemical reduction reaction yielded a lithium sulfide nanocomposite cathode material (Li₂S@Fe-C) internally doped with 16 wt.% elemental iron atoms. The material has a particle size of 20–60 nm and a carbon coating thickness of 1–8 nm.

[0073] Example 4

[0074] (1) Ball milling and mixing

[0075] In a glove box filled with argon gas and with humidity and oxygen concentrations of less than 0.01 ppm, 0.282 g of lithium hydride (LiH) and 1 g of nickel disulfide (NiS2) were weighed, sealed in a ball mill jar with a ball-to-material ratio of 10:1, and ball milled at 500 rpm for 12 hours.

[0076] (2) Heat treatment

[0077] The material obtained after ball milling in step (1) was mixed with carbon disulfide in a glove box, with a solid content of 30%, and magnetically stirred for 10 min. Then, it was placed in a quartz tube and sealed, and kept at 400℃ for 3 h with a heating rate of 2℃ / min. After the reaction, it was dried at 100℃ for 0.5 h to volatilize the excess carbon disulfide, thus obtaining a lithium sulfide nanocomposite cathode material (Li2S@Ni) internally doped with 23 wt.% metal sulfide. x S y -C), whose composite cathode material has a particle size of 30-90 nm;

[0078] (3) In-situ electrochemical reduction reaction

[0079] The composite cathode material (Li2S@Ni) obtained in step (2) is placed in a glove box. x S y -C) and sulfide solid electrolytes (Li 10 GeP2S 12 Activated carbon (AC) was ball-milled at 500 rpm for 2 hours in a mass ratio of 5:4:1 to obtain an electrode composite material. Subsequently, carbon-coated aluminum foil, the electrode composite material, and a sulfide solid electrolyte (Li) were sequentially added. 10 GeP2S 12 The lithium sheets are sequentially cold-pressed to assemble an all-solid-state lithium-sulfur battery, which is then mounted on a battery rack at 50 mAg. -1 Electrochemical discharge was performed at a current density with a cutoff discharge voltage of 0.5V. An in-situ electrochemical reduction reaction yielded a lithium sulfide nanocomposite cathode material (Li₂S@Ni-C) internally doped with 15 wt.% elemental nickel atoms. The material has a particle size of 30–90 nm and a carbon coating thickness of 4–10 nm.

[0080] Example 5

[0081] (1) Ball milling and mixing

[0082] In a glove box filled with argon gas and with humidity and oxygen concentrations of less than 0.01 ppm, 0.183 g of lithium powder (Li), 0.5 g of manganese sulfide (MnS) and 0.5 g of titanium sulfide (TiS) were weighed, sealed in a ball mill jar with a ball-to-material ratio of 10:1, and ball milled at 400 rpm for 10 h.

[0083] (2) Heat treatment

[0084] The material obtained after ball milling in step (1) was mixed with carbon disulfide in a glove box, with a solid content of 20%, and magnetically stirred for 10 min. Then, it was placed in a quartz tube and sealed, and kept at 650℃ for 2 h with a heating rate of 5℃ / min. After the reaction, it was dried at 60℃ for 2 h to volatilize excess carbon disulfide, thus obtaining a lithium sulfide nanocomposite cathode material (Li2S@Mn) internally doped with 30 wt.% metal sulfides. x S y @Ti x S y -C), whose composite cathode material has a particle size of 30-80 nm;

[0085] (3) In-situ electrochemical reduction reaction

[0086] The composite cathode material (Li2S@Mn) obtained in step (2) is placed in a glove box. x S y @Ti x S y -C) was ball-milled with sulfide solid electrolyte (Li6PS5Cl) and multi-walled carbon nanotubes (WMCNTs) at a mass ratio of 5:4:1 at 300 rpm for 8 h to obtain an electrode composite material. Subsequently, carbon-coated aluminum foil, the electrode composite material, the sulfide solid electrolyte (Li6PS5Cl), and lithium sheets were sequentially cold-pressed to assemble an all-solid-state lithium-sulfur battery. The battery was then mounted on a battery rack at 50 mAg. -1 Electrochemical discharge was performed at a current density with a cutoff discharge voltage of 0.5V. An in-situ electrochemical reduction reaction yielded a lithium sulfide nanocomposite cathode material (Li₂S@Mn@Ti-C) internally doped with 18 wt.% elemental manganese and titanium atoms. The material has a particle size of 30–80 nm and a carbon coating thickness of 3–9 nm.

[0087] Example 6

[0088] (1) Ball milling and mixing

[0089] In a glove box filled with argon gas and with humidity and oxygen concentrations of less than 0.01 ppm, 0.166 g of lithium hydride (LiH), 0.5 g of copper sulfide (CuS) and 0.5 g of titanium disulfide (TiS2) were weighed, sealed in a ball mill jar with a ball-to-material ratio of 10:1, and ball-milled at 500 rpm for 10 h.

[0090] (2) Heat treatment

[0091] The material obtained after ball milling in step (1) was mixed with carbon disulfide in a glove box, with a solid content of 60%, and magnetically stirred for 10 min. Then, it was placed in a quartz tube and sealed, and kept at 700℃ for 1 h with a heating rate of 5℃ / min. After the reaction, it was dried at 60℃ for 2 h to volatilize excess carbon disulfide, thus obtaining a lithium sulfide nanocomposite cathode material (Li2S@Cu) internally doped with 30 wt.% metal sulfides. x S y @Ti x S y -C), whose composite cathode material has a particle size of 20-90 nm;

[0092] (3) In-situ electrochemical reduction reaction

[0093] The composite cathode material (Li2S@Cu) obtained in step (2) is placed in a glove box. x S y @Ti x S y -C) and sulfide solid electrolytes (Li 10 GeP2S 12 The electrode composite material was obtained by ball milling acetylene black (AB) at a mass ratio of 5:4:1 at 500 rpm for 6 hours. Subsequently, carbon-coated aluminum foil, the electrode composite material, and a sulfide solid electrolyte (Li) were sequentially added. 10 GeP2S 12 The lithium sheets are sequentially cold-pressed to assemble an all-solid-state lithium-sulfur battery, which is then mounted on a battery rack at 50 mAg. -1 Electrochemical discharge was performed at a current density with a cutoff discharge voltage of 0.5V. An in-situ electrochemical reduction reaction yielded a lithium sulfide nanocomposite cathode material (Li₂S@Cu@Ti-C) internally doped with 15 wt.% elemental copper and titanium atoms. The material has a particle size of 20–90 nm and a carbon coating thickness of 3–10 nm.

[0094] Example 7

[0095] Based on Example 1, the cobalt disulfide metal sulfide was replaced with at least one of manganese disulfide (MnS2), molybdenum disulfide (MoS2), titanium disulfide (TiS2), vanadium disulfide (VS2), zinc disulfide (ZnS2), chromium disulfide (CrS2), ferrous sulfide (FeS), nickel sulfide (NiS), molybdenum sulfide (MoS), vanadium sulfide (VS), zinc sulfide (ZnS), and chromium sulfide (CrS). The feeding relationship between the metal sulfide and the lithium source was the same as in Example 1, and other conditions were the same as in Example 1, resulting in a lithium sulfide nanocomposite cathode material internally doped with elemental metal atoms. The material particle size was 10–90 nm, and the carbon coating thickness was 1–10 nm.

[0096] Comparative Example 1

[0097] The cathode material is lithium sulfide without any treatment and has a particle size of 2-4 μm.

[0098] Comparative Example 2

[0099] Ball milling: In a glove box filled with argon gas and with humidity and oxygen concentrations less than 0.01 ppm, 0.77 g of lithium sulfide (Li2S), 0.15 g of cobalt powder (Co), and 0.08 g of acetylene black (AB) were weighed and sealed in a ball mill jar with a ball-to-material ratio of 10:1. The mixture was ball-milled at 500 rpm for 12 h to obtain a lithium sulfide composite cathode material (Li2S@Co-C) with 15 wt.% elemental cobalt atoms mixed inside. The particle size of this material was 1–2 μm.

[0100] Comparative Example 3

[0101] Heat treatment: In a glove box filled with argon, with humidity and oxygen concentration both less than 0.01 ppm, 1 g of lithium hydride (LiH) was mixed with carbon disulfide, with a solid content of 60%, and magnetically stirred for 10 min. The mixture was then placed in a quartz tube and sealed, and held at 500 °C for 2 h at a heating rate of 2 °C / min. After the reaction, the mixture was dried at 60 °C for 2 h to volatilize excess carbon disulfide, yielding carbon-coated lithium sulfide composite cathode material (Li2S-C). The material has a particle size of 0.5–1 μm and a carbon coating thickness of 1–10 nm.

[0102] Comparative Example 4

[0103] (1) Ball milling and mixing

[0104] In a glove box filled with argon gas and with humidity and oxygen concentrations of less than 0.01 ppm, 0.166 g of lithium hydride (LiH) and 0.1 g of nickel disulfide (NiS2) were weighed, sealed in a ball mill jar with a ball-to-material ratio of 10:1, and ball milled at 500 rpm for 10 h.

[0105] (2) Heat treatment

[0106] The material obtained after ball milling in step (1) was placed into a quartz tube and sealed in a glove box. It was then kept at 500℃ for 4 hours with a heating rate of 5℃ / min. This yielded a lithium sulfide composite cathode material (Li2S@Ni) internally doped with 36wt.% elemental nickel, with a particle size of 0.5–1 μm.

[0107] Comparative Example 5

[0108] (1) Grinding and mixing

[0109] In a glove box filled with argon gas and with humidity and oxygen concentrations of less than 0.01 ppm, weigh 0.166 g of lithium hydride (LiH) and 0.1 g of vanadium disulfide (VS2), mix them in a mortar, and grind for 1 hour.

[0110] (2) Heat treatment

[0111] The material obtained after grinding in step (1) was mixed with carbon disulfide in a glove box, with a solid content of 60%, and magnetically stirred for 10 min. Then, it was placed in a quartz tube and sealed, and kept at 400℃ for 2 h with a heating rate of 2℃ / min. After the reaction, it was dried at 60℃ for 2 h to volatilize excess carbon disulfide, thus obtaining a lithium sulfide composite cathode material (Li2S@V) internally doped with 23 wt.% metal sulfides. x S y -C), whose composite cathode material has a particle size of 0.5 to 1 μm;

[0112] (3) In-situ electrochemical reduction reaction

[0113] The composite cathode material (Li2S@V) obtained in step (2) is placed in a glove box. x S y -C) and sulfide solid electrolytes (Li 10 GeP2S 12 Activated carbon (AC) was ball-milled at 500 rpm for 2 hours in a mass ratio of 5:4:1 to obtain an electrode composite material. Subsequently, carbon-coated aluminum foil, the electrode composite material, and a sulfide solid electrolyte (Li) were sequentially added. 10 GeP2S 12 The lithium sheets are sequentially cold-pressed to assemble an all-solid-state lithium-sulfur battery, which is then mounted on a battery rack at 50 mAg. -1Electrochemical discharge was performed at a current density with a cutoff discharge voltage of 0.5V. An in-situ electrochemical reduction reaction yielded a lithium sulfide nanocomposite cathode material (Li2S@VS2@VC) internally doped with elemental vanadium atoms (V) and vanadium disulfide (VS2). The material has a particle size of 0.5–1 μm and a carbon coating thickness of 2–10 nm.

[0114] Test Example: Battery Assembly and Performance Testing

[0115] All-solid-state lithium-sulfur battery assembly: Electrode composite material consists of composite cathode material (Li2S@M x S y The electrode composite material, consisting of C and M (metal atoms), a sulfide solid electrolyte, and conductive carbon, was ball-milled in a mass ratio of 5:4:1. In a glove box filled with argon gas and with humidity and oxygen concentration below 0.01 ppm, 120 mg of the sulfide solid electrolyte was placed in a 12 mm diameter PTFE mold and compressed into a sheet under 20 MPa pressure. Then, 5-10 mg of the electrode composite material was uniformly coated onto a carbon-coated aluminum foil, placed on the upper surface of the mold, and subjected to 10 MPa pressure. Finally, a 10 mm diameter lithium foil was placed on the back of the mold, and the assembly was cold-pressed under 10 MPa pressure.

[0116] Place the assembled battery on the Xinwei Battery Tester. First, perform an in-situ electrochemical reduction reaction with 50 mAg. -1 The battery was discharged to 0.5V to convert the metal sulfide into elemental metal and a lithium sulfide cathode. Subsequent charge / discharge tests were conducted within a voltage range of 1.5–3.8V to activate the lithium sulfide cathode. Afterwards, tests were performed within a voltage range of 1.5–3V. The initial current density for the test was 50 mAg. -1 Activation for 3 cycles, followed by 200mAg -1 The current density was used for charge-discharge cycles. The rate test current density was 100 mAg. -1 200mA g -1 500mAg -1 1000mAg -1 100mAg -1 .

[0117] The battery was prepared and its performance was measured according to the above method. The results are shown in Table 1.

[0118] Table 1. Comparison of electrochemical performance of lithium sulfide nanocomposite cathode materials with different high reaction kinetics.

[0119]

[0120] The material was tested under the test conditions specified in the test examples, and all of them met the following requirements: at 50 mAg...-1 The initial discharge specific capacity at current density is not less than 800 mAh g. -1 The initial coulomb efficiency is no less than 90% at 200mAg. -1 The initial discharge specific capacity at current density is not less than 700 mAh g. -1 After 100 cycles, the discharge specific capacity is not less than 500mAh g. -1 The cycle capacity retention rate is no less than 80%. In contrast, the battery in the comparative test, at 50 mAg... -1 The initial discharge specific capacity at current density was below 800 mAh g. -1 The coulomb efficiency was below 85% in all cases, and also below 200 mAg. -1 The discharge specific capacity at current density is low, and the capacity retention rate is less than 70% after 100 cycles.

[0121] The lithium sulfide nanocomposite cathode material doped with elemental cobalt atoms in Example 1 at 100 mAg -1 200mAg -1 500mAg -1 The discharge specific capacity that can be achieved at the current density is 992.26 mAh g. -1 857.65mAh g -1 678.62mAh g -1 Even at 1000mAg -1 Even at high current density, the battery capacity remains as high as 511.62 mAh g. -1 The performance of Examples 2-6 shows the same trend as that of Example 1. In Comparative Example 1, the battery capacity was lower than that of the Examples at different current densities, and the coulombic efficiency was low. Comparative Examples 2-4 were also lower than the Examples in terms of capacity utilization and capacity retention.

[0122] according to Figure 6 The differential capacity curves show that the material in Comparative Example 1 has a higher polarization voltage but lower peak intensity, indicating poor reaction kinetics. In contrast, the differential capacity curve of Example 1 has a sharper peak, indicating a rapid redox reaction during cycling and higher reaction kinetics. Therefore, the carbon-coated, metal-doped lithium sulfide nanocomposite cathode material has a well-formed coating structure and uniform internal metal atom doping, significantly improving the overall conductivity of the material, enhancing the reaction kinetics of the battery composite cathode, and exhibiting excellent rate performance.

[0123] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims, and all such variations and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a lithium sulfide nanocomposite cathode material with high reaction kinetics, characterized in that, Includes the following steps: (1) Mixing: The lithium source and the metal sulfide are thoroughly mixed to obtain a mixed material; the metal sulfide is at least one of MnS2, FeS2, CoS2, NiS2, MoS2, TiS2, VS2, ZnS2, CrS2, CuS, MnS, FeS, CoS, NiS, MoS, TiS, VS, ZnS, and CrS; the mixture is thoroughly mixed by ball milling, and the ball milling conditions are: ball milling speed of 100-700 rpm and ball milling time of 4-20 h; (2) Heat treatment: The mixed material is mixed with carbon disulfide and heated. After the reaction is completed, it is dried to obtain carbon-coated lithium sulfide nanocomposite cathode material with internal metal sulfide doping. (3) In-situ electrochemical reduction reaction: Electrode composite material is prepared using composite cathode material as active material, and an all-solid-state lithium-sulfur battery is assembled. Then, electrochemical discharge is performed to obtain lithium sulfide nanocomposite cathode material with internal doped elemental metal atoms through in-situ electrochemical reduction reaction. The in-situ electrochemical reduction reaction is carried out with a cutoff discharge voltage of 0.5V and / or with a discharge density of 20mA / g to 100mA / g. The carbon coating layer thickness is 1 to 10nm, and the metal atom doping content accounts for 15 to 24wt.% of the composite cathode material.

2. The method for preparing a lithium sulfide nanocomposite cathode material with high reaction kinetics according to claim 1, characterized in that, In step (1), the lithium source is at least one of lithium and lithium hydride; And / or, the molar ratio of the lithium source to the metal sulfide is 2 to 8:

1.

3. The method for preparing a lithium sulfide nanocomposite cathode material with high reaction kinetics according to claim 1, characterized in that, The ball milling speed is 300-600 rpm, and the ball milling time is 8-16 hours.

4. The method for preparing a lithium sulfide nanocomposite cathode material with high reaction kinetics according to claim 1, characterized in that, In step (2), the solid content after mixing is 20-60%; And / or, the heating conditions are: heating temperature of 300-700℃; holding time of 1-5h; heating rate of 2-5℃ / min; And / or, the drying conditions are: heating temperature of 30-100℃; drying time of 0.5-3h.

5. The method for preparing a lithium sulfide nanocomposite cathode material with high reaction kinetics according to claim 1, characterized in that, In step (3), the electrode composite material includes a composite positive electrode material, a sulfide solid electrolyte, and conductive carbon, wherein the sulfide solid electrolyte is Li6PS5Cl or Li7P3S 11 Li 10 GeP2S 12 At least one; and / or, the conductive carbon is at least one of multi-walled carbon nanotubes, acetylene black, and activated carbon; and / or, the mass ratio of the composite cathode material, the sulfide solid electrolyte, and the conductive carbon is (50-90):(10-40):(0-10).

6. The method for preparing a lithium sulfide nanocomposite cathode material with high reaction kinetics according to claim 1, characterized in that, The obtained lithium sulfide nanoparticles have a size ≤100nm.

7. A lithium sulfide nanocomposite cathode material with high reaction kinetics prepared by the preparation method according to any one of claims 1-6.

8. The application of a high-reaction-kinetic lithium sulfide nanocomposite cathode material prepared by the preparation method according to any one of claims 1-6 in the field of all-solid-state lithium-sulfur batteries.

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