Lithium-rich manganese-based solid-state battery positive electrode material as well as preparation method and application thereof

Abstract

The invention provides a lithium-rich manganese-based solid-state battery positive electrode material as well as a preparation method and application thereof, and relates to the technical field of solid-state battery positive electrode materials, the lithium-rich manganese-based solid-state battery positive electrode material comprises a lithium-rich manganese-based positive electrode material body and a composite coating layer of a fast ion conductor layer and an electronic conductor layer, and the composite coating layer coats the surface of the lithium-rich manganese-based positive electrode material body. Aiming at the problems of poor interface contact between a lithium-rich manganese base and a sulfide solid electrolyte in an all-solid-state battery, difficulty in ion transmission and unstable structure in a circulation process, the invention provides a lithium-rich manganese-based positive electrode material which can simultaneously realize high interface ion / electron conduction, excellent interface stability and effective inhibition of bulk phase structure degradation. Therefore, the electrochemical performance of the material in a solid-state battery is obviously improved.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery cathode material technology, and in particular to a lithium-rich manganese-based solid-state battery cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-rich manganese-based cathode materials have become one of the key materials for realizing the next generation of high-energy-density batteries due to their high reversible specific capacity.

[0003] However, when lithium-rich manganese-based cathode materials are combined with solid electrolytes to construct all-solid-state batteries, especially when matched with sulfide-based solid electrolytes, they exhibit serious interfacial compatibility and bulk structure stability issues during cycling. This severely affects the rate performance and cycle performance of solid-state batteries, thus restricting the practical application of lithium-rich manganese-based materials in high-energy-density solid-state batteries.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] One objective of this invention is to provide a lithium-rich manganese-based solid-state battery cathode material to at least address one of the technical problems existing in the prior art. This invention addresses the issues of poor interfacial contact between lithium-rich manganese-based electrolytes and sulfide solid electrolytes, difficulties in ion transport, and structural instability during cycling in all-solid-state batteries. It provides a lithium-rich manganese-based cathode material that simultaneously achieves high interfacial ion / electron conductivity, excellent interfacial stability, and effective suppression of bulk structural degradation, thereby significantly improving its electrochemical performance in solid-state batteries.

[0006] The second objective of this invention is to provide a method for preparing a lithium-rich manganese-based solid-state battery cathode material.

[0007] The third objective of this invention is to provide an application of the lithium-rich manganese-based solid-state battery cathode material prepared by the aforementioned method in the preparation of solid-state batteries.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a lithium-rich manganese-based solid-state battery cathode material, comprising: a lithium-rich manganese-based cathode material body and a composite coating layer of a fast ion conductor layer and an electronic conductor layer coated on the surface of the lithium-rich manganese-based cathode material body.

[0009] Furthermore, the electronic conductor layer and the fast ion conductor layer are interwoven or stacked to form a composite coating layer.

[0010] Furthermore, the bulk chemical formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, wherein M includes at least one of Mn, Ni, Co, Al, Zr, and Ti, and 0 <x<1。

[0011] Furthermore, the fast ion conductor layer includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, Li2ZrO3, Li3PO4, LiPON, Li3BO3, Li2SiO3, LiAlO2, Li3PS4 and their dopants or derivatives.

[0012] Furthermore, the electronic conductor layer comprises at least one of conductive carbon, conductive polymer, and metal nanoparticles; Preferably, the conductive carbon includes at least one of Super P, acetylene black, Ketjen black, graphene, and carbon nanotubes; Preferably, the conductive polymer comprises at least one of PEDOT:PSS and polyaniline; Preferably, the metal nanoparticles include at least one of Ag and Cu.

[0013] Furthermore, the total mass of the composite coating layer accounts for 0.5% to 15% of the total mass of the cathode material; Preferably, the total mass of the composite coating layer accounts for 1% to 10% of the total mass of the cathode material; Preferably, the thickness of the composite coating layer is 2 nm to 50 nm.

[0014] Secondly, the present invention provides a method for preparing a lithium-rich manganese-based solid-state battery cathode material, comprising the following steps: (a) Provides an intermediate product, the intermediate product being a lithium-rich manganese-based cathode material body with a fast ion conductor precursor and an electronic conductor loaded on its surface, wherein the fast ion conductor precursor forms a precursor coating layer on the material surface. (b) The intermediate product is subjected to heat treatment, and the fast ion conductor precursor is transformed into a crystalline or amorphous fast ion conductor, which is then combined with the electronic conductor on the material surface to form a composite coating layer, thereby obtaining the lithium-rich manganese-based cathode material.

[0015] Furthermore, the fast ion conductor precursor includes at least one selected from phosphate, titanate, lanthanum nitrate, lanthanum oxide, zirconium nitrate, germanium oxide, and boric acid; Preferably, the electronic conductor comprises at least one of carbon nanotube dispersion, graphene oxide solution, aniline monomer, and pyrrole monomer; Preferably, the intermediate product is prepared by one of the following methods: (1) The fast ion conductor precursor solution is mixed with the lithium-rich manganese-based cathode material, and a precursor coating layer is formed by solvent evaporation, precipitation or hydrothermal / solvothermal method, and then an electronic conductor is added for mixing. (2) Mix the fast ion conductor precursor, the electronic conductor and the lithium-rich manganese-based cathode material, and load them together on the surface of the material by wet or dry mixing. Preferably, step (b) is performed in a gaseous atmosphere; the gas includes at least one of nitrogen, argon and air; Preferably, the heat treatment includes annealing; Preferably, the annealing temperature is 300~700℃ and the holding time is 3~5 h.

[0016] Furthermore, the lithium-rich manganese-based cathode material is prepared through the following steps: (A) Preparation of lithium-rich manganese-based precursor: A mixed solution of nickel salt, cobalt salt, manganese salt and water, a precipitant and a complexing agent are mixed and subjected to a co-precipitation reaction. Then, the mixture is aged, centrifuged, washed and dried in sequence to obtain the lithium-rich manganese-based precursor. (B) The lithium-rich manganese-based precursor is mixed with a lithium source to obtain a mixed material; (C) The mixed material is sintered to form the lithium-rich manganese-based cathode material body; (D) Crushing and Classification: The lithium-rich manganese-based cathode material is crushed; Preferably, the nickel salt, the cobalt salt, and the manganese salt are each independently selected from their water-soluble salts; Preferably, the water-soluble salt includes at least one selected from sulfate, nitrate, chloride, and acetate; Preferably, the precipitant comprises an alkaline solution; Preferably, the alkali includes one of sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide; Preferably, the concentration of the alkaline solution is 1~10 mol / L; Preferably, the pH value of the coprecipitation reaction system is 8.0~11.0; Preferably, the complexing agent includes at least one selected from ammonia, ammonium bicarbonate, ammonium carbonate, and ammonium sulfate; Preferably, the concentration of the complexing agent is 5~15 mol / L; Preferably, the ammonia concentration in the coprecipitation reaction system is 0.1~1.5 mol / L; Preferably, the coprecipitation reaction is carried out under an inert atmosphere; the inert atmosphere includes at least one of nitrogen and argon. Preferably, the aging time is 3-5 hours; Preferably, the lithium source includes at least one of lithium hydroxide and lithium carbonate; Preferably, the sintering is carried out in a gaseous atmosphere; the gas includes at least one of oxygen and air; Preferably, the sintering includes pre-firing and main firing performed sequentially; Preferably, the pre-firing temperature is 400~600℃, the heating rate is 2~10℃ / min, and the holding time is 3~5h; Preferably, the temperature of the main firing is 800~1000℃, the heating rate is 2~10℃ / min, and the holding time is 12~15 h; Preferably, the particle size of the pulverized lithium-rich manganese-based cathode material is 2-5 μm.

[0017] Thirdly, the present invention provides an application of the lithium-rich manganese-based solid-state battery cathode material prepared by the above-described preparation method in the preparation of solid-state batteries.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The lithium-rich manganese-based solid-state battery cathode material provided by this invention effectively solves the problems of poor interfacial compatibility, slow ion / electron transport kinetics, and structural instability during cycling by constructing a composite coating layer of fast ion conductor layer and electronic conductor layer on the surface of the lithium-rich manganese-based cathode material. Among them, the fast ion conductor layer not only provides an efficient conduction channel for lithium ions and reduces interfacial impedance, but also physically isolates the cathode and electrolyte, suppresses harmful side reactions, and improves interfacial stability. The electronic conductor layer forms a three-dimensional conductive network on the surface, enhancing electron transport capability. The synergistic effect of the two achieves dual continuous transport of ions and electrons, significantly improving the rate performance and cycle stability of the material. At the same time, it helps to suppress irreversible oxygen evolution and lithium loss during the first charge, thereby comprehensively improving the electrochemical performance of the lithium-rich manganese-based cathode material in all-solid-state batteries. Detailed Implementation

[0019] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0021] The first aspect of the present invention provides a lithium-rich manganese-based solid-state battery cathode material, comprising: a lithium-rich manganese-based cathode material body and a composite coating layer of a fast ion conductor layer and an electronic conductor layer coated on the surface of the lithium-rich manganese-based cathode material body.

[0022] The lithium-rich manganese-based cathode material provided by this invention is a highly stable lithium-rich manganese-based cathode for solid-state batteries. By introducing a unique structure of a composite coating layer of fast ion conductor and electronic conductor, the following significant beneficial effects are achieved: (1) The fast ion conductor layer of the present invention blocks the direct contact between the lithium-rich manganese-based cathode material and the solid electrolyte. Furthermore, its excellent structure and electrochemical stability can effectively stabilize the structure of the lithium-rich manganese-based material and suppress the irreversible precipitation of lattice oxygen.

[0023] (2) The present invention constructs a composite coating layer in which the fast ion conductor greatly reduces the ion transport impedance and promotes the transport of lithium ions at the solid-solid interface. The electronic conductor constructs a three-dimensional electronic conductive network on the material surface to ensure efficient electron supply. The stable composite coating layer can suppress some of the lithium consumption caused by irreversible surface oxygen evolution and violent interfacial side reactions during the first charge, thereby reducing the first irreversible capacity loss.

[0024] (3) The preparation method of the present invention is simple and conducive to industrialization. The construction of the two functional layers is integrated into a heat treatment process, avoiding the complex procedures and multiple heat treatments of the traditional step-by-step coating method. The method has a short process flow, low energy consumption, controllable conditions, and good repeatability, making it suitable for large-scale industrial production.

[0025] In some preferred embodiments, the electronic conductor layer and the fast ion conductor layer are interwoven or stacked to form a composite coating layer. The fast ion conductor and electronic conductor composite coating layer uniformly coats the outer surface of the lithium-rich manganese-based cathode material body.

[0026] In some preferred embodiments, the bulk lithium-rich manganese-based cathode material has the general chemical formula xLi₂MnO₃·(1-x)LiMO₂, wherein M includes at least one of Mn, Ni, Co, Al, Zr, and Ti, and 0 <x<1。

[0027] In some preferred embodiments, the fast ion conductor layer comprises lithium lanthanum zirconium oxide (Li7La3Zr2O) 12 LLZO), lithium lanthanum titanium oxide (Li 0.33 La 0.56 At least one of TiO3, LLTO, Li2ZrO3, Li3PO4, LiPON, Li3BO3, Li2SiO3, LiAlO2, Li3PS4 and their dopants or derivatives.

[0028] In this invention, the fast ion conductor layer is made of a material with high lithium-ion conductivity, a wide electrochemical window, and good compatibility with the solid electrolyte. Its function is to provide a fast migration channel for lithium ions from the bulk phase to the solid electrolyte and to physically isolate the positive electrode material from direct contact with the solid electrolyte, thereby suppressing side reactions.

[0029] In some preferred embodiments, the electronic conductor layer comprises at least one of conductive carbon, conductive polymer, and metal nanoparticles; preferably, the conductive carbon comprises at least one of Super P, acetylene black, Ketjen black, graphene, and carbon nanotubes; preferably, the conductive polymer comprises at least one of PEDOT:PSS and polyaniline; preferably, the metal nanoparticles comprise at least one of Ag and Cu.

[0030] In this invention, the electronic conductor layer is made of a material with good electrical conductivity. Its function is to construct an electronic conductive network, reduce the interfacial charge transfer impedance, and improve rate performance.

[0031] In some preferred embodiments, the total mass of the composite coating layer accounts for 0.5% to 15% of the total mass of the cathode material, more preferably 1% to 10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. Preferably, the thickness of the composite coating layer is 2 nm to 50 nm, for example, it can be 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc. If the coating layer is too thin, the effect will be insignificant; if it is too thick, it will hinder ion and electron transport and reduce the capacity.

[0032] A second aspect of this invention provides a method for preparing a lithium-rich manganese-based solid-state battery cathode material, comprising the following steps: (a) Provides an intermediate product, the intermediate product being a lithium-rich manganese-based cathode material body with a fast ion conductor precursor and an electronic conductor loaded on its surface, wherein the fast ion conductor precursor forms a precursor coating layer on the material surface. (b) The intermediate product is subjected to heat treatment, and the fast ion conductor precursor is transformed into a crystalline or amorphous fast ion conductor, which is then combined with the electronic conductor on the material surface to form a composite coating layer, thereby obtaining the lithium-rich manganese-based cathode material.

[0033] This invention proposes a specific structure for the composite coating layer. This structure is a tightly bonded synergistic system formed in situ during a single heat treatment process. Fast ion conductors ensure efficient interfacial transport of lithium ions and stabilize the interface, while electronic conductors construct an electron permeation network, reducing polarization. The highly stable lithium-rich manganese-based cathode material completes the reaction and film formation simultaneously through a single heat treatment. This preparation method not only simplifies the process and reduces costs but also facilitates the formation of an interwoven, tightly bonded "hybrid conductor network" on the substrate surface, rather than a simple "sandwich" structure, potentially achieving a superior ion / electron hybrid conduction path.

[0034] In some preferred embodiments, the fast ion conductor precursor includes at least one of phosphate, titanate, lanthanum nitrate, lanthanum oxide, zirconium nitrate, germanium oxide, and boric acid; Preferably, the electronic conductor comprises at least one of carbon nanotube dispersion, graphene oxide solution, aniline monomer, and pyrrole monomer; Preferably, the intermediate product is prepared by one of the following methods: (1) The fast ion conductor precursor solution is mixed with the lithium-rich manganese-based cathode material, and a precursor coating layer is formed by solvent evaporation, precipitation or hydrothermal / solvothermal method, and then an electronic conductor is added for mixing. In this invention, this method facilitates the uniform deposition and dense coating of fast ion conductor precursors on the surface of cathode materials, while avoiding the agglomeration or uneven distribution of electronic conductors during the pretreatment process, thereby ensuring the continuity of ion conduction channels and the effective construction of electronic conduction networks in the subsequent composite coating layer.

[0035] (2) Mix the fast ion conductor precursor, the electronic conductor and the lithium-rich manganese-based cathode material, and load them together on the surface of the material by wet or dry mixing. In this invention, the method achieves the synergistic loading of fast ion conductor precursor and electronic conductor in a one-step process, which is simpler and conducive to large-scale production, while still forming a precursor coating layer with controllable structure and a uniformly distributed electronic conductive network.

[0036] This invention utilizes methods such as solvent evaporation, precipitation, or hydrothermal / solvothermal processes to deposit a fast-ion conductor precursor onto the surface of a lithium-rich manganese-based cathode material, forming a uniform precursor coating layer. The electronic conductor is then physically attached to this layer or the particle surface, together constituting an intermediate product. At this stage, a true "composite coating layer" has not yet been formed. Subsequent annealing transforms the precursor into a fast-ion conductor phase with high ionic conductivity, achieving a tight bond with the electronic conductor at the interface, thus constructing a stable composite coating layer in situ that combines ionic and electronic conduction functions.

[0037] Preferably, step (b) is performed in a gaseous atmosphere; the gas includes at least one of nitrogen, argon and air; Preferably, the heat treatment includes annealing; Preferably, the annealing temperature is 300~700℃, for example, it can be 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, etc.; the holding time is 3~5 h, for example, it can be 3h, 3.5h, 4h, 4.5h, 5h, etc.

[0038] In some preferred embodiments, the lithium-rich manganese-based cathode material bulk is prepared by the following steps: (A) Preparation of lithium-rich manganese-based precursor: A mixed solution of nickel salt, cobalt salt, manganese salt and water, a precipitant and a complexing agent are mixed and subjected to a co-precipitation reaction. Then, the mixture is aged, centrifuged, washed and dried in sequence to obtain the lithium-rich manganese-based precursor. (B) The lithium-rich manganese-based precursor is mixed with a lithium source to obtain a mixed material; (C) The mixed material is sintered to form the lithium-rich manganese-based cathode material body; (D) Crushing and Classification: The lithium-rich manganese-based cathode material is crushed; Preferably, the nickel salt, the cobalt salt, and the manganese salt are each independently selected from their water-soluble salts; Preferably, the water-soluble salt includes at least one selected from sulfate, nitrate, chloride, and acetate; Preferably, the precipitant comprises an alkaline solution; Preferably, the alkali includes one of sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide; Preferably, the concentration of the alkaline solution is 1~10 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, etc. Preferably, the complexing agent includes at least one selected from ammonia, ammonium bicarbonate, ammonium carbonate, and ammonium sulfate; Preferably, the concentration of the complexing agent is 5~15 mol / L, for example, it can be 5 mol / L, 10 mol / L, 15 mol / L, etc.; Preferably, the ammonia concentration in the coprecipitation reaction system is 0.1~1.5 mol / L, for example, it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, etc. Preferably, the pH value of the coprecipitation reaction system is 8.0~11, for example, it can be 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, etc.; Preferably, the coprecipitation reaction is carried out under an inert atmosphere; the inert atmosphere includes at least one of nitrogen and argon. Preferably, the aging time is between 3 and 5 hours, for example, 3 hours, 4 hours, 5 hours, etc. Preferably, the lithium source includes at least one of lithium hydroxide and lithium carbonate; Preferably, the sintering is carried out in a gaseous atmosphere; the gas includes at least one of oxygen and air; Preferably, the sintering includes pre-firing and main firing performed sequentially; Preferably, the preheating temperature is 400~600℃, for example, 400℃, 450℃, 500℃, 550℃, 600℃, etc., the heating rate is 2~10℃ / min, and the holding time is 3~5 h, for example, 3 h, 4 h, 5 h, etc. Preferably, the temperature of the main firing is 800~1000℃, for example, 800℃, 900℃, 1000℃, etc., the heating rate is 2~10℃ / min, and the holding time is 12~15 h, for example, 12 h, 13 h, 14 h, 15 h, etc. Preferably, the particle size of the pulverized lithium-rich manganese-based cathode material is 2-5 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, etc.

[0039] In an optional embodiment of the present invention, a more preferred method for preparing the lithium-rich manganese-based solid-state battery cathode material includes the following steps: Step 1: Preparation of lithium-rich manganese-based precursor A mixed solution of nickel salt, cobalt salt, and manganese salt in a specific molar ratio with pure water was prepared. Simultaneously, an alkaline solution was prepared with alkali and pure water to act as a precipitant. These two materials, along with a complexing agent, were added to a reaction vessel, and a co-precipitation reaction was carried out under an inert atmosphere. After the reaction, the product was aged, centrifuged, washed, and dried to obtain a lithium-rich manganese-based precursor—a nickel-cobalt-manganese matrix.

[0040] Step 2: Preparation of the lithium-rich manganese-based cathode material bulk material S2.1 Mixing and Pretreatment: The lithium-rich manganese-based precursor obtained in step one is mixed with a lithium source in a certain molar ratio at room temperature until homogeneous. S2.2, First sintering: The mixed material obtained in S2.1 is transferred to a rotary kiln and sintered in two stages under a certain atmosphere, namely pre-sintering and main sintering, to form the lithium-rich manganese-based cathode material body; S2.3, Crushing and Classification: The obtained lithium-rich manganese-based cathode material is crushed by airflow to reduce its particle size.

[0041] Step 3: Construction of the composite coating layer The material obtained in step 2 is dispersed in a mixed solution containing a fast ion conductor precursor and an electronic conductor (prepared using the intermediate product preparation method in method (2) above). It is then uniformly mixed by stirring and sonication. The precursor is uniformly deposited on the material surface by solvent evaporation, precipitation, or hydrothermal / solvothermal methods. Annealing is performed in a specific atmosphere to transform the fast ion conductor precursor into a crystalline or amorphous fast ion conductor, which then firmly bonds with the electronic conductor, ultimately forming the composite coating layer to obtain a lithium-rich manganese-based cathode material.

[0042] The third aspect of this invention provides an application of the lithium-rich manganese-based solid-state battery cathode material prepared by the aforementioned preparation method in the preparation of solid-state batteries.

[0043] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0044] Preparation Example 1 This preparation example provides a lithium-rich manganese-based cathode material, the preparation process of which is as follows: Step 1: Preparation of lithium-rich manganese-based precursor A mixed solution was prepared by dissolving 1.0 mol / L nickel sulfate, cobalt sulfate, and manganese sulfate in pure water, wherein Ni... 2+ Co 2+ Mn 2 + The molar ratio was 0.13:0.13:0.54. Simultaneously, an alkaline solution of 2.0 mol / L sodium carbonate and pure water was prepared as a precipitant. These two materials, along with the complexing agent ammonia, were added to a reaction vessel. The reaction pH was controlled at 10.0, and a co-precipitation reaction was carried out under an inert atmosphere. After the reaction, the precursor—a nickel-cobalt-manganese matrix—was obtained through aging (4 hours), centrifugation, washing, and drying.

[0045] Step 2: Preparation of the lithium-rich manganese-based cathode material bulk material S2.1 Mixing and Pretreatment: The lithium-rich manganese-based precursor obtained in step 1 is mixed with Li2CO3 at room temperature in a stoichiometric ratio (Li / transition metal = 1.53); S2.2, First sintering: The mixture obtained in S2.1 is transferred to a rotary kiln and sintered in two stages in an air atmosphere, namely pre-firing (heating rate of 5℃ / min, pre-firing at 500℃ for 5 hours) and main firing (heating rate of 5℃ / min, sintering at 900℃ for 12 hours) to form the lithium-rich manganese-based cathode material body. S2.3, Crushing and Classification: After cooling the obtained lithium-rich manganese-based cathode material, it is crushed and sieved using airflow to obtain Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 powder is denoted as "LLO".

[0046] The lithium-rich manganese-based cathode materials used in the following examples and comparative examples are all LLOs prepared in Preparation Example 1.

[0047] Example 1 This embodiment provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: Weigh 0.15 g LiNO3, 0.26 g La(NO3)3·6H2O, and 0.21 g Zr(NO3)4·5H2O, dissolve them in 20 mL of anhydrous ethanol, and stir magnetically for 40 minutes to obtain a clear LLZO precursor solution. Weigh 5 g LLO and add it to the above solution. Transfer the beaker to a 60℃ constant temperature water bath and stir for 4 hours (400 rpm). Evaporate to dryness using a rotary evaporator in a 60℃ water bath under a vacuum of -0.095 MPa. Load the dried powder and 0.075 g carboxylated multi-walled carbon nanotubes (CNTs) into a zirconia ball mill jar, add 50 g of 5 mm zirconia grinding balls, evacuate and purge with argon three times, and ball mill at 350 rpm for 2 hours. Place the mixed powder in a tube furnace under flowing argon (200 sccm) and heat to 600℃ at 5℃ / min, hold for 4 hours. After natural cooling, the samples were passed through a 400-mesh sieve to obtain LLO@LLZO-CNTs; the mass fraction of the composite coating layer was approximately 12.0%.

[0048] Example 2 This embodiment provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: Weigh out 0.2 g CH3COOLi, 0.45 g La(NO3)3·6H2O and 0.17 g C16H 36O4Ti was dissolved in a mixed solvent of 25 mL anhydrous ethanol and 5 mL ethylene glycol methyl ether and stirred for 1 hour. 5 g of LLO was weighed and added to the above solution. The beaker was transferred to a 60°C constant temperature water bath and stirred for 6 hours (400 rpm). The mixture was then evaporated to dryness using a rotary evaporator under a 60°C water bath and a vacuum of -0.095 MPa. The dried powder was placed in a zirconia ball mill jar along with 0.1 g of graphene nanosheets (GNPs), and 50 g of 5 mm zirconia grinding balls were added. After evacuation and argon purging three times, the mixture was ball-milled at 400 rpm for 3 hours. Under an oxygen atmosphere, the temperature was increased to 700°C at 5°C / min and held for 3 hours. After natural cooling, the mixture was passed through a 400-mesh sieve to obtain LLO@LLTO-Gn; the mass fraction of the composite coating layer was approximately 10.5%.

[0049] Example 3 This embodiment provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: 5 g LLO, 0.115 g (NH4)2HPO4, 0.09 g LiNO3, and 0.1 g Ketjen Black (KB) were weighed and placed together in a zirconia ball mill jar. The mixture was dry-milled at 400 rpm for 5 hours under argon protection. The temperature was then increased to 500℃ at 5℃ / min under argon protection and held for 5 hours. After natural cooling, the mixture was passed through a 400-mesh sieve to obtain LLO@LPO-KB; the mass fraction of the composite coating was approximately 4.8%.

[0050] Example 4 This embodiment provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: Weigh 0.102 g of Al(OCH(CH3)2)3 and 0.048 g of CH3COOLi, and dissolve them in 20 mL of anhydrous ethanol. Weigh 5 g of LLO and add it to the above solution for ultrasonic dispersion. Transfer the beaker to a 60℃ constant temperature water bath and stir for 6 hours (400 rpm). Evaporate to dryness using a rotary evaporator in a 60℃ water bath under a vacuum of -0.095 MPa. Load the dried powder and 0.125 g of Super P into a zirconia ball mill jar, add 50 g of 5 mm zirconia grinding balls, evacuate and purge with argon three times, and then ball mill at 350 rpm for 2 hours. Under an argon atmosphere, heat to 500℃ at 5℃ / min and hold for 4 hours. After natural cooling, pass through a 400-mesh sieve to obtain LLO@LAO-SP; the mass fraction of the composite coating layer is approximately 4.2%.

[0051] Example 5 This embodiment provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: Weigh 0.1 g of tetraethyl orthosilicate (TEOS) and 0.06 g of LiNO3, and dissolve them in 20 mL of anhydrous ethanol. Weigh 5 g of LLO, add it to the above solution, and add 2 drops of dilute ammonia water for catalytic hydrolysis. Stir at room temperature for 12 hours, and then dry by rotary evaporation. Grind the dried powder with 0.08 g of PANI nanofibers by hand in a mortar for 30 minutes. Under an argon atmosphere, heat to 400℃ at 3℃ / min and hold for 2 hours. After natural cooling, pass through a 400-mesh sieve to obtain LLO@LSO-PANI; wherein the mass fraction of the composite coating layer is approximately 3.5%.

[0052] Example 6 This embodiment provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: Weigh 0.105 g H3BO3 and 0.095 g LiNO3, dissolve them in 15 mL deionized water, and stir until homogeneous. Weigh 5 g LLO and add it to the above solution. Transfer the beaker to an 80 ℃ constant temperature water bath and stir for 5 hours (400 rpm). Evaporate using a rotary evaporator under an 80 ℃ water bath and a vacuum of -0.095 MPa. Transfer the viscous slurry to a 120 ℃ oven and dry thoroughly. Mix the dried lumps with 0.15 g silver nanoparticle suspension (dissolved in ethanol), dry again, and then lightly ball mill (250 rpm, 1 hour) to disperse. Under argon atmosphere, heat to 500 ℃ at 3 ℃ / min and hold for 3 hours. After natural cooling, pass through a 400-mesh sieve to obtain LLO@LBO-Ag; the mass fraction of the composite coating layer is approximately 3.1%.

[0053] Comparative Example 1 This comparative example provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: Place 5 g of LLO in a muffle furnace and heat it to 500°C at a rate of 5°C / min under air atmosphere, then hold for 4 hours. After natural cooling, pass the mixture through a 400-mesh sieve to obtain LLO-Bare.

[0054] Comparative Example 2 This comparative example provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: Perform the exact same steps as in Example 1, but without adding carbon nanotubes, to obtain LLO@LLZO.

[0055] Comparative Example 3 This comparative example provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: Weigh 5 g of LLO and 0.075 g of CNTs together and place them in a 100 mL zirconia ball mill jar. Add 50 g of 5 mm zirconia grinding balls, evacuate and purge with argon three times, and then ball mill at 350 rpm for 2 hours. Place the mixed powder in a tube furnace and heat to 600 °C at 5 °C / min under flowing argon (200 sccm), and hold for 4 hours. After natural cooling, pass through a 400-mesh sieve to obtain LLO@CNTs.

[0056] Comparative Example 4 This comparative example provides a lithium-rich manganese-based solid-state battery cathode material, and the preparation process is as follows: Weigh 0.15 g of Al(NO3)3·9H2O and dissolve it in 20 mL of anhydrous ethanol. Weigh 5 g of LLO and add it to the above solution. Transfer the beaker to a 60℃ constant temperature water bath and stir (400 rpm) for 4 hours. Evaporate to dryness using a rotary evaporator in a 60℃ water bath under a vacuum of -0.095 MPa. Place the dried powder and 0.075 g of CNTs into a zirconia ball mill jar, add 50 g of 5 mm zirconia grinding balls, evacuate and purge with argon three times, and ball mill at 350 rpm for 2 hours. Place the mixed powder in a tube furnace and heat to 600℃ at 5℃ / min under flowing argon (200 sccm), hold for 4 hours. After natural cooling, pass through a 400-mesh sieve to obtain LLO@Al2O3-CNTs.

[0057] Test case Battery assembly: The battery assembly method is as follows: For mold battery testing, the solid-state battery cathode material prepared in the examples and comparative examples was mixed with sulfide solid electrolyte and conductive agent vapor-grown carbon fiber (VGCF) in a ratio of 70:25:5 and ground in a mortar for 15 min to obtain the composite cathode material. Then, 100 mg of sulfide solid electrolyte, 8 mg of composite cathode material, and lithium-indium alloy were successively added to a mold and assembled under pressure to form a solid-state battery.

[0058] Battery testing methods The cutoff voltage was set to 1.9~4.2 V, and the test temperature was 60℃. The circuit was first cycled 5 times at 0.1C, then 100 times at 0.5C.

[0059] The test results are shown in Table 1.

[0060] Table 1

[0061] As shown in Table 1, all embodiments exhibit excellent electrochemical performance, significantly outperforming the comparative examples of uncoated, single-coated, and non-lithium conductor composites. This demonstrates that the composite coating of fast-ion conductors and electronic conductors in this invention can effectively construct a stable interface, significantly suppress side reactions and structural decay, and has universality and high efficiency in improving the performance of lithium-rich manganese-based materials. It is an effective solution to address the bottleneck in the application of lithium-rich materials in solid-state batteries.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium-rich manganese-based solid-state battery cathode material, characterized in that, include: A lithium-rich manganese-based cathode material body and a composite coating layer consisting of a fast ion conductor layer and an electronic conductor layer covering the surface of the lithium-rich manganese-based cathode material body.

2. The lithium-rich manganese-based solid-state battery cathode material according to claim 1, characterized in that, The electronic conductor layer and the fast ion conductor layer are interwoven or stacked to form a composite coating layer.

3. The lithium-rich manganese-based solid-state battery cathode material according to claim 1, characterized in that, The bulk chemical formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, where M includes at least one of Mn, Ni, Co, Al, Zr, and Ti, and 0 <x<1。 4. The lithium-rich manganese-based solid-state battery cathode material according to claim 1, characterized in that, The fast ion conductor layer includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, Li2ZrO3, Li3PO4, LiPON, Li3BO3, Li2SiO3, LiAlO2, Li3PS4 and their dopants or derivatives.

5. The lithium-rich manganese-based solid-state battery cathode material according to claim 1, characterized in that, The electronic conductor layer includes at least one of conductive carbon, conductive polymer and metal nanoparticles; Preferably, the conductive carbon includes at least one of Super P, acetylene black, Ketjen black, graphene, and carbon nanotubes; Preferably, the conductive polymer comprises at least one of PEDOT:PSS and polyaniline; Preferably, the metal nanoparticles include at least one of Ag and Cu.

6. The lithium-rich manganese-based solid-state battery cathode material according to claim 1, characterized in that, The total mass of the composite coating layer accounts for 0.5% to 15% of the total mass of the cathode material; Preferably, the total mass of the composite coating layer accounts for 1% to 10% of the total mass of the cathode material; Preferably, the thickness of the composite coating layer is 2 nm to 50 nm.

7. The method for preparing the lithium-rich manganese-based solid-state battery cathode material according to any one of claims 1-6, characterized in that, Includes the following steps: (a) Provides an intermediate product, the intermediate product being a lithium-rich manganese-based cathode material body with a fast ion conductor precursor and an electronic conductor loaded on its surface, wherein the fast ion conductor precursor forms a precursor coating layer on the material surface. (b) The intermediate product is subjected to heat treatment, and the fast ion conductor precursor is transformed into a crystalline or amorphous fast ion conductor, which is then combined with the electronic conductor on the material surface to form a composite coating layer, thereby obtaining the lithium-rich manganese-based cathode material.

8. The preparation method according to claim 7, characterized in that, The fast ion conductor precursor includes at least one of phosphate, titanate, lanthanum nitrate, lanthanum oxide, zirconium nitrate, germanium oxide, and boric acid; Preferably, the electronic conductor comprises at least one of carbon nanotube dispersion, graphene oxide solution, aniline monomer, and pyrrole monomer; Preferably, the intermediate product is prepared by one of the following methods: (1) The fast ion conductor precursor solution is mixed with the lithium-rich manganese-based cathode material, and a precursor coating layer is formed by solvent evaporation, precipitation or hydrothermal / solvothermal method, and then an electronic conductor is added for mixing. (2) Mix the fast ion conductor precursor, the electronic conductor and the lithium-rich manganese-based cathode material, and load them together on the surface of the material by wet or dry mixing. Preferably, step (b) is performed in a gaseous atmosphere; the gas includes at least one of nitrogen, argon and air; Preferably, the heat treatment includes annealing; Preferably, the annealing temperature is 300~700℃ and the holding time is 3~5 h.

9. The preparation method according to claim 7, characterized in that, The lithium-rich manganese-based cathode material bulk is prepared through the following steps: (A) Preparation of lithium-rich manganese-based precursor: A mixed solution of nickel salt, cobalt salt, manganese salt and water, a precipitant and a complexing agent are mixed and subjected to a co-precipitation reaction. Then, the mixture is aged, centrifuged, washed and dried in sequence to obtain the lithium-rich manganese-based precursor. (B) The lithium-rich manganese-based precursor is mixed with a lithium source to obtain a mixed material; (C) The mixed material is sintered to form the lithium-rich manganese-based cathode material body; (D) Crushing and Classification: The lithium-rich manganese-based cathode material is crushed; Preferably, the nickel salt, the cobalt salt, and the manganese salt are each independently selected from their water-soluble salts; Preferably, the water-soluble salt includes at least one selected from sulfate, nitrate, chloride, and acetate; Preferably, the precipitant comprises an alkaline solution; Preferably, the alkali includes one of sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide; Preferably, the concentration of the alkaline solution is 1~10 mol / L; Preferably, the pH value of the coprecipitation reaction system is 8.0~11.0; Preferably, the complexing agent includes at least one selected from ammonia, ammonium bicarbonate, ammonium carbonate, and ammonium sulfate; Preferably, the concentration of the complexing agent is 5~15 mol / L; Preferably, the coprecipitation reaction is carried out under an inert atmosphere; the inert atmosphere includes at least one of nitrogen and argon. Preferably, the aging time is 3-5 hours; Preferably, the lithium source includes at least one of lithium hydroxide and lithium carbonate; Preferably, the sintering is carried out in a gaseous atmosphere; the gas includes at least one of oxygen and air; Preferably, the sintering includes pre-firing and main firing performed sequentially; Preferably, the pre-firing temperature is 400~600℃, the heating rate is 2~10℃ / min, and the holding time is 3~5 h; Preferably, the temperature of the main firing is 800~1000℃, the heating rate is 2~10℃ / min, and the holding time is 12~15 h; Preferably, the particle size of the pulverized lithium-rich manganese-based cathode material is 2-5 μm.

10. The application of the lithium-rich manganese-based solid-state battery cathode material prepared by the preparation method according to any one of claims 7-9 in the preparation of solid-state batteries.

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