Coated ternary positive electrode material for solid-state lithium battery as well as preparation method and application of coated ternary positive electrode material

Abstract

The invention provides a coated ternary positive electrode material for a solid-state lithium battery as well as a preparation method and application of the coated ternary positive electrode material. The coated ternary positive electrode material for the solid-state lithium battery comprises a ternary positive electrode material and a composite coating layer on the surface, ru nano-particles in the composite coating layer material are deposited on the surface of Ti3C2Tx; and Tx is any one or a combination of at least two of-O-,-OH or-F on the surface of Ti < 3 > C < 2 > Tx. A composite coating layer material comprising ruthenium nanoparticles and two-dimensional titanium carbide is adopted, the two-dimensional titanium carbide serving as two-dimensional transition metal carbide has excellent electronic conductivity and rich surface functional groups, and the layered structure of the two-dimensional titanium carbide also provides a channel for ion transmission and shows huge potential in a battery electrode material; ruthenium nanoparticles have high catalytic activity and good conductivity, can promote a charge transfer reaction, and make up for the problems of limited capacity, poor cycle performance and the like when two-dimensional titanium carbide is used as a positive electrode material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ternary positive electrode materials for solid-state batteries, in particular to a coated ternary positive electrode material for solid-state lithium batteries and a preparation method and application thereof. BACKGROUND

[0002] With the increasing demand for energy and the emphasis on environmental protection, solid-state batteries, as a new type of battery with high energy density, long cycle life and high safety, have become a research hotspot. The positive electrode material is a key component of the solid-state battery, and its performance directly affects the overall performance of the battery. Currently, the solid-state battery positive electrode material faces many challenges, such as low ionic conductivity, which leads to slow ion transport during battery charging and discharging, affecting the rate performance; insufficient electronic conduction efficiency, which limits the electrode reaction rate; at the same time, the interface impedance between the positive electrode and the solid-state electrolyte is large, which easily causes the battery capacity to decay quickly and the cycle stability to be poor.

[0003] In the prior art, various methods have been tried to solve these problems, including element doping, structure optimization of traditional positive electrode materials, and development of new solid-state electrolytes. However, the above methods still have certain limitations in improving the performance of the positive electrode material. For example, simple element doping may not effectively improve the coordinated transport of electrons and ions, and the interface compatibility problem between the new solid-state electrolyte and the positive electrode material is still prominent.

[0004] Therefore, the purpose of the present application is to provide a ternary positive electrode material that can overcome the defects of low ionic conductivity, poor electron transport and large interface impedance of the existing solid-state battery positive electrode, to improve the electrochemical performance of the solid-state battery, which is a technical problem that needs to be solved at present. SUMMARY

[0005] To solve the above technical problems, the present application provides a coated ternary positive electrode material for solid-state lithium batteries and a preparation method and application thereof. The coated ternary positive electrode material for solid-state lithium batteries provided by the present application adopts a composite coating layer material including Ru nanoparticles and Ti3C2T x The Ru nanoparticles are deposited on the surface of the Ti3C2T x As a new type of two-dimensional transition metal carbide, it has excellent electronic conductivity and abundant surface functional groups (-OH, -O-, -F), and its unique layered structure also provides a channel for ion transport, showing great potential in battery electrode materials; Ru nanoparticles have high catalytic activity and good conductivity, which can promote charge transfer reactions, making up for the problems of limited capacity and poor cycle performance faced by Ti3C2T x as a positive electrode material. Therefore, the Ti3C2T x is coated with Ru nanoparticles to form a composite coating layer material, which not only improves the electronic conductivity of the Ti3C2T xThe ternary positive electrode material is coated with the Ru nanoparticle composite material, which has the effects of synergistically improving electron conduction and ion transmission and improving interface impedance, thereby improving the electrochemical performance of the obtained solid-state battery.

[0006] To achieve this purpose, the application adopts the following technical solutions:

[0007] In a first aspect, the application provides a coated ternary positive electrode material for a solid-state lithium battery, which comprises a ternary positive electrode material and a composite coating layer on the surface of the ternary positive electrode material.

[0008] The composite coating layer material comprises Ru nanoparticles and Ti3C2T x The Ru nanoparticles are deposited on the surface of the Ti3C2T x .

[0009] T x is any one or a combination of at least two of -O-, -OH or -F on the surface of the Ti3C2T x .

[0010] The application uses the synergistic design of two-dimensional titanium carbide Ti3C2T x and Ru nanoparticles as the material of the composite coating layer on the surface of the ternary positive electrode material. Ti3C2T x has a graphene-like layered structure, high specific surface area and excellent electrical conductivity. Its porous structure not only provides high active site anchoring space for Ru nanoparticles, but also buffers the volume expansion of the ternary positive electrode material during charging and discharging, thereby improving the structural stability. The Ru nanoparticles are uniformly loaded on the surface of the Ti3C2T x , which reduces the interface impedance through electron confinement effect and accelerates the lithium / oxygen reaction kinetics as a catalyst. Ru can also promote the oxygen reduction reaction (ORR) on the surface of the ternary positive electrode material and inhibit side reactions, thereby improving the rate performance and cycle life of the battery. The high electrical conductivity of Ti3C2T x complements the catalytic activity of Ru, and the two work synergistically. Ti3C2T x provides a high-speed channel for electron transmission, and Ru improves ion migration efficiency by reducing reaction activation energy. The heterojunction effect at the interface of the two further optimizes charge separation efficiency, reducing the interface impedance of the composite coating layer material.

[0011] As a preferred technical solution of the application, in the composite coating layer, the mass ratio of the Ru nanoparticles to the Ti3C2T x is (0.02-0.08):1, for example 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1 or 0.08:1.

[0012] The mass ratio of the Ru nanoparticles to the Ti3C2T x may be (0.02-0.08):1, which can significantly reduce the cost of noble metals and also can take into account the better electrochemical performance of the coated ternary positive electrode material for solid-state lithium batteries. If the content of the Ru nanoparticles is too much, the Ru nanoparticles will be deposited on the surface of the Ti3C2T x and agglomerate to form larger particles, and the agglomerates will not only reduce the effective catalytic active sites, but also can block the Ti3C2T x The unique layered structure provides ion transmission channels, which hinder the rapid migration of lithium ions and instead increase the interface impedance; in addition, a too thick Ru layer will cover the surface of the Ti3C2T x The high-conductivity surface itself reduces the direct contact area between the ternary positive electrode material and the Ti3C2T x and affects the electron conduction; if the content of the Ru nanoparticles is too little, the catalytic active sites will be insufficient, and the sparse Ru nanoparticles cannot form a continuous and uniform composite conductive network with the Ti3C2T x The surface of the Ti3C2T x may not be effectively modified, the interface charge transport is uneven, and the side reaction between the positive electrode material and the solid-state electrolyte cannot be fully inhibited; in addition, the heterojunction effect between the Ti3C2T x and the Ru cannot be sufficiently strong, and the synergistic effects such as electron confinement and charge separation cannot be obvious, and the advantages of the composite coating layer cannot be fully played.

[0013] Preferably, the average particle size of the Ru nanoparticles is 5-20 nm, for example, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm, etc.

[0014] As a preferred technical solution of the present application, the mass of the composite coating layer accounts for 3wt%-10wt% of the mass of the coated ternary positive electrode material for solid-state lithium batteries, for example, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%, etc.

[0015] In the present application, the mass of the composite coating layer accounts for 3wt%-10wt% of the mass of the coated ternary positive electrode material for solid-state lithium batteries, which can not only effectively inhibit the side reaction between the positive electrode material and the solid-state electrolyte, but also can improve the electrochemical performance of the coated ternary positive electrode material for solid-state lithium batteries. xThe high conductivity of the coating layer compensates for the poor electron conduction of the ternary cathode material and avoids excessive occupation of active substances. If the proportion of the coating layer is too high, the energy density will be significantly reduced. The specific capacity of the composite coating layer (especially Ti3C2T x ), and a too thick coating layer will relatively reduce the proportion of active substances (ternary materials) in the unit mass of the cathode material, directly leading to a decrease in the energy density of the battery, which is contrary to the original intention of designing high-energy-density batteries. Moreover, a too thick coating layer, especially a dense accumulation, will increase the path resistance of lithium ions diffusing from the bulk electrolyte to the surface of the ternary cathode material particles, possibly forming a new ion transport bottleneck and increasing the interface impedance, which is not conducive to the rate performance. If the proportion of the coating layer is too small, the coating will be incomplete and the modification effect will be insufficient. A too small coating layer cannot form a continuous and complete coating layer on the surface of the ternary cathode material, which will cause part of the ternary material surface to be directly exposed to the solid-state electrolyte, unable to effectively inhibit side reactions (such as interface layer generation, oxygen release, etc.), and unable to fully exert the synergistic protection and catalysis of Ti3C2T x and Ru. In addition, a lack of coating layer makes it difficult to build an effective three-dimensional electron conduction network. The electronic conduction ability of the ternary material located at the particle contact points or the weakly coated area cannot be effectively improved, limiting the overall rate performance. A weak coating layer cannot provide effective mechanical support and buffering for the volume change of the ternary material during the cycling process, thus having limited effect on inhibiting particle rupture and maintaining structural stability, and thus being difficult to significantly improve the cycle life.

[0016] In a second aspect, the application also provides a preparation method of the coated ternary cathode material for solid-state lithium batteries according to the first aspect, which comprises the following steps:

[0017] (1) first mixing a ruthenium salt solution and a Ti3C2T x suspension to obtain a two-dimensional titanium carbide / ruthenium nanoparticle composite material through a reduction reaction;

[0018] wherein T x is any one or a combination of at least two of -O-, -OH, or -F on the surface of the Ti3C2T x ;

[0019] (2) second mixing a ternary precursor hydroxide, the two-dimensional titanium carbide / ruthenium nanoparticle composite material of step (1), and a lithium salt to obtain a coated ternary cathode material for solid-state lithium batteries through sintering.

[0020] As a preferred technical solution of the present application, the concentration of the ruthenium salt solution in step (1) is 0.05 mol / L to 0.2 mol / L, for example, 0.05 mol / L, 0.08 mol / L, 0.10 mol / L, 0.12 mol / L, 0.15 mol / L, 0.18 mol / L or 0.2 mol / L, etc.

[0021] Preferably, the ruthenium salt in the ruthenium salt solution in step (1) includes any one or a combination of at least two of RuCl3·H2O, RuCl3·3H2O, RuCl3, RuBr3 or Ru(NO3)3.

[0022] Preferably, the Ti3C2T x The preparation method of the suspension includes: mixing Ti3C2T x with a solvent, and performing ultrasonic treatment on the obtained mixed solution to obtain a Ti3C2T x suspension.

[0023] Preferably, the solvent includes deionized water and / or an alcohol-water mixed solvent.

[0024] Preferably, the ultrasonic treatment time is 30 min to 60 min, for example, 30 min, 32 min, 35 min, 38 min, 40 min, 42 min, 45 min, 48 min, 50 min, 52 min, 55 min, 58 min or 60 min, etc.

[0025] Preferably, the first mixing in step (1) includes adding the ruthenium salt solution dropwise into the Ti3C2T x suspension, and continuously stirring during the dropwise adding process.

[0026] Preferably, the dropwise adding rate is 1 mL / min to 5 mL / min, for example, 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min or 5 mL / min, etc.

[0027] Preferably, the stirring rate is 300 rpm to 800 rpm, for example, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm or 800 rpm, etc.

[0028] Preferably, the stirring time is 30 min to 120 min, for example, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min, etc.

[0029] As a preferred technical scheme of the present application, the reducing agent used in the reduction reaction of step (1) includes any one or a combination of at least two of sodium borohydride, ascorbic acid or sodium citrate.

[0030] Preferably, the molar ratio of the reducing agent to the ruthenium salt is (3~5):1, such as 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, etc.

[0031] Preferably, the temperature of the reduction reaction of step (1) is 25℃~40℃, such as 25℃, 28℃, 30℃, 32℃, 35℃, 38℃ or 40℃, etc.

[0032] Preferably, the time of the reduction reaction of step (1) is 2h~5h, such as 2h, 3h, 4h or 5h, etc.

[0033] Preferably, the stirring rate of the reduction reaction of step (1) is 300rpm~800rpm, such as 300rpm, 400rpm, 500rpm, 600rpm, 700rpm or 800rpm, etc.

[0034] Preferably, after the reduction reaction of step (1) is completed, it further includes the steps of solid-liquid separation, washing and drying.

[0035] Preferably, the drying includes vacuum drying.

[0036] Preferably, the temperature of the vacuum drying includes 50℃~70℃, such as 50℃, 55℃, 60℃, 65℃ or 70℃, etc.

[0037] Preferably, the time of the vacuum drying includes 8h~16h, such as 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or 16h, etc.

[0038] As a preferred technical scheme of the present application, the chemical formula of the ternary precursor hydroxide of step (2) includes Ni 1－y－z Co y Mn z (OH)2, wherein 0.05≤y≤0.15, such as y can be 0.05, 0.08, 0.1, 0.12 or 0.15, etc., 0

[0039] It should be noted that the ternary precursor hydroxide in the present application is a conventional preparation method in the art, which is applicable to the present application, and the person skilled in the art can make adaptive selection and adjustment according to the actual situation, for example, the co-precipitation method can be used for preparation.

[0040] Preferably, in step (2), the molar ratio of the ternary precursor hydroxide and the lithium salt is 1:(1.03~1.06), such as 1:1.03, 1:1.04, 1:1.05 or 1:1.06, etc.

[0041] Preferably, in step (2), the lithium salt comprises any one or a combination of at least two of lithium hydroxide, lithium carbonate or lithium acetate.

[0042] As a preferred technical solution of the present application, in step (2), the second mixing comprises first mixing the ternary precursor hydroxide and the two-dimensional titanium / ruthenium carbide nanocomposite material uniformly, and then mixing with the lithium salt for ball milling.

[0043] In the present application, the mixing in step (2) adopts dry ball milling dispersion technology, and the two-dimensional titanium / ruthenium carbide nanocomposite material is uniformly attached to the surface of the ternary precursor hydroxide to form an effective composite coating layer, thereby constructing an initial "core-shell" structure precursor with the ternary precursor hydroxide as the "core" and the composite coating layer as the "shell". The dry process not only avoids the restacking problem of the two-dimensional titanium carbide in wet mixing due to the action of the solvent, but also enhances the interfacial bonding force between the composite coating layer and the ternary precursor hydroxide core through mechanical force, reduces the particle shedding in the subsequent sintering and battery charging and discharging process, and thus improves the structural stability of the coated ternary positive electrode material for solid-state lithium batteries.

[0044] Preferably, the rotation speed of the ball milling is 300rpm~600rpm, such as 300rpm, 400rpm, 500rpm or 600rpm, etc.

[0045] Preferably, the ball milling time is 30min~120min, such as 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min or 120min, etc.

[0046] Preferably, the ball milling is carried out in a protective atmosphere.

[0047] Preferably, the gas used in the protective atmosphere comprises nitrogen and / or argon.

[0048] Preferably, the ball-to-material ratio of the ball milling is (5~10):1, such as 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0049] As a preferred technical solution of the present application, in step (2), the heating rate of the sintering is 2℃ / min~5℃ / min, such as 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, etc.

[0050] Preferably, the holding temperature of the sintering in step (2) is 600-900°C, for example 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C, etc.

[0051] Preferably, the holding time of the sintering in step (2) is 12-20h, for example 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h, etc.

[0052] Preferably, the sintering in step (2) is carried out in an oxygen atmosphere.

[0053] As a preferred technical solution of the present application, the preparation method comprises the following steps:

[0054] (1) mixing Ti3C2T x with a solvent, and ultrasonically treating the obtained mixture for 30-60min to obtain a Ti3C2T x suspension, adding a ruthenium salt solution with a concentration of 0.05-0.2mol / L to the Ti3C2T x suspension at a rate of 1-5mL / min, continuously stirring at a stirring rate of 300-800rpm for 30-120min during the adding process, carrying out a reduction reaction at 25-40°C and a stirring rate of 300-800rpm for 2-5h, wherein the molar ratio of the reducing agent to the ruthenium salt is (3-5):1, carrying out solid-liquid separation, washing and vacuum drying at 50-70°C for 8-16h to obtain a two-dimensional titanium carbide / ruthenium nanoparticle composite material;

[0055] (2) mixing the ternary precursor hydroxide and the two-dimensional titanium carbide / ruthenium nanoparticle composite material uniformly first, then mixing with a lithium salt, carrying out ball milling under a protective atmosphere at 300-600rpm for 30-120min, with a ball-to-material ratio of (5-10):1, then increasing the temperature to 600-900°C at a temperature increasing rate of 2-5°C / min, and sintering for 12-20h to obtain a coated ternary positive electrode material for solid-state lithium batteries;

[0056] The chemical general formula of the ternary precursor hydroxide includes Ni 1－y－z Co y Mn z (OH)2, wherein 0.05≤y≤0.15 and 0

[0057] In a third aspect, the present application further provides a solid-state lithium battery comprising the coated ternary cathode material for solid-state lithium batteries according to the first aspect, or the coated ternary cathode material for solid-state lithium batteries prepared by the preparation method according to the second aspect.

[0058] Compared with the prior art, the present application has at least the following beneficial effects:

[0059] 1) The two-dimensional titanium carbide Ti3C2T x and Ru nanoparticles are used as the material of the composite coating layer on the surface of the ternary cathode material, the two-dimensional titanium carbide has high electronic conductivity and interlayer ion transmission channels, and its layered structure can increase the specific surface area and provide more active sites, providing a highly dispersed carrier for Ru nanoparticles, forming a synergistic conductive network, which can significantly improve the electronic conductivity and ion diffusion rate of the cathode; the surface functional groups can form good interfacial contact with the solid-state electrolyte, reducing the interfacial impedance.

[0060] 2) The Ru nanoparticles are uniformly loaded on the surface of the two-dimensional titanium carbide, which on the one hand promotes the charge transfer reaction at the cathode / electrolyte interface through its high catalytic activity, and on the other hand further improves the conductivity of the composite material, and synergistically optimizes the electron-ion transmission network.

[0061] 3) The preparation method of the present application is simple and controllable, and the uniform loading of Ru nanoparticles is realized by a liquid phase reduction method, without the need for high-temperature and high-pressure equipment, and the amount of ruthenium is low, significantly reducing the cost of noble metals, the process has good repeatability, and is easy to scale up. DETAILED DESCRIPTION

[0062] In order to facilitate the understanding of the present application, the present application is illustrated by the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0063] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0064] The NCM811 ternary precursor hydroxide used in the detailed description of the present application is prepared by the following method:

[0065] The ternary hydroxide precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 is prepared by a co-precipitation method.

[0066] Firstly, nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a ternary mixed sulfate solution of nickel, cobalt and manganese with a concentration of 120 g / L according to a stoichiometric ratio of 8:1:1, and then a certain amount of deionized water, a 32wt% sodium hydroxide solution and a 16wt% ammonia solution are added into the reaction kettle in a nitrogen atmosphere as a bottom liquid (pH is 11 and ammonia concentration is 6 g / L); subsequently, the ternary mixed sulfate solution of nickel, cobalt and manganese, the sodium hydroxide solution and the ammonia solution are continuously added into the bottom liquid in parallel, the temperature of the reaction system is controlled at 55°C, the pH value is controlled at 11, the ammonia concentration is controlled at 6 g / L, and the continuous stirring is carried out during the whole process to carry out the co-precipitation reaction; after the reaction is completed, the obtained precipitate is washed and dried to obtain a Ni 0.8 Co 0.1 Mn 0.1 (OH)2.

[0067] Example 1

[0068] The embodiment provides a coated ternary positive electrode material for solid-state lithium batteries and a preparation method thereof. The coated ternary positive electrode material for solid-state lithium batteries comprises a ternary positive electrode material and a composite coating layer on the surface of the ternary positive electrode material. The composite coating layer material comprises Ru nanoparticles with an average particle size of 10 nm and Ti3C2T x The Ru nanoparticles are deposited on the surface of the Ti3C2T x The mass ratio of the Ru nanoparticles to the Ti3C2T x is 0.06:1, and the mass of the composite coating layer accounts for 5wt% of the mass of the coated ternary positive electrode material for solid-state lithium batteries.

[0069] The preparation method comprises the following steps:

[0070] (1) uniformly dispersing Ti3C2T x powder in deionized water, ultrasonically treating the mixed solution for 40 min to uniformly disperse the two-dimensional titanium carbide powder, and forming a stable suspension; under a stirring speed of 500 rpm, a RuCl3 solution with a concentration of 0.1 mol / L is slowly added to the suspension at a rate of 3 mL / min, and the stirring is continuously performed for 60 min during the adding process to ensure that the RuCl3 solution is fully mixed with the suspension, so that Ru x ions are coordinated with the -O- and -OH functional groups on the surface of the two-dimensional titanium carbide through electrostatic interaction and are adsorbed on the Ti3C2T 3+ powder. xThe nanosheets were then subjected to a reduction reaction at 25°C and a stirring rate of 500 rpm, followed by the addition of a sodium borohydride solution with a molar ratio of sodium borohydride to RuCl3 of 3:1. After 3 hours of reduction reaction, the solid product was obtained by centrifugation. The solid product was washed multiple times with deionized water and ethanol to remove unreacted RuCl3, sodium borohydride and reaction byproducts. After washing, the product was dried in a vacuum environment at 70°C for 10 hours to obtain a two-dimensional titanium carbide / ruthenium nanoparticle composite material.

[0071] (2) First, NCM811 ternary precursor hydroxide and two-dimensional titanium carbide / ruthenium nanoparticle composite material are mixed evenly, and then put into a ball mill jar with lithium hydroxide at a molar ratio of 1:1.03. Under nitrogen atmosphere, the mixture is ball-milled at 600 rpm for 60 min with a ball-to-material ratio of 6:1. The temperature is raised to 800℃ at a heating rate of 4℃ / min. After sintering for 18 h, the mixture is naturally cooled to room temperature to obtain a solid-state lithium battery coated ternary cathode material.

[0072] Example 2

[0073] This embodiment provides a coated ternary cathode material for solid-state lithium batteries and its preparation method. The coated ternary cathode material for solid-state lithium batteries includes a ternary cathode material and a composite coating layer located on the surface of the ternary cathode material. The composite coating layer material includes Ru nanoparticles with an average particle size of 5 nm and Ti3C2T. x Ru nanoparticles were deposited on Ti3C2T x Surface, Ru nanoparticles and the Ti3C2T x The mass ratio is 0.02:1, and the mass of the composite coating layer accounts for 3 wt% of the mass of the coated ternary cathode material for solid-state lithium batteries.

[0074] The preparation method includes the following steps:

[0075] (1) Ti3C2T x The powder was uniformly dispersed in deionized water, and the mixture was ultrasonically treated for 30 minutes to ensure uniform dispersion of the two-dimensional titanium carbide powder and form a stable suspension. The suspension was then continuously stirred at 500 rpm, following the mixing process of Ru nanoparticles and Ti3C2T... x The powder mass ratio was 0.02:1. A 0.2 mol / L RuCl3 solution was slowly added dropwise to the suspension at a rate of 1 mL / min, with continuous stirring for 30 min during the addition process to ensure thorough mixing of the RuCl3 solution and the suspension. 3+ Ions are coordinated with the -O- and -OH functional groups on the surface of two-dimensional titanium carbide through electrostatic interactions and adsorbed on Ti3C2T xThe nanosheets were then subjected to a reduction reaction at 25°C and a stirring rate of 500 rpm, followed by the addition of a sodium borohydride solution with a molar ratio of sodium borohydride to RuCl3 of 4:1. After 2 hours of reduction reaction, the solid product was obtained by centrifugation. The solid product was washed multiple times with deionized water and ethanol to remove unreacted RuCl3, sodium borohydride and reaction byproducts. After washing, the product was dried in a vacuum environment at 70°C for 10 hours to obtain a two-dimensional titanium carbide / ruthenium nanoparticle composite material.

[0076] (2) First, NCM811 ternary precursor hydroxide and two-dimensional titanium carbide / ruthenium nanoparticle composite material are mixed evenly, and then put into a ball mill jar with lithium hydroxide at a molar ratio of 1:1.03. Under nitrogen atmosphere, the mixture is ball-milled at 300 rpm for 120 min with a ball-to-material ratio of 6:1. The temperature is raised to 600℃ at a heating rate of 2℃ / min. After sintering for 20 h, the mixture is naturally cooled to room temperature to obtain a solid-state lithium battery coated ternary cathode material.

[0077] Example 3

[0078] This embodiment provides a coated ternary cathode material for solid-state lithium batteries and its preparation method. The coated ternary cathode material for solid-state lithium batteries includes a ternary cathode material and a composite coating layer located on the surface of the ternary cathode material. The composite coating layer material includes Ru nanoparticles with an average particle size of 20 nm and Ti3C2T. x Ru nanoparticles were deposited on Ti3C2T x Surface, Ru nanoparticles and the Ti3C2T x The mass ratio is 0.08:1, and the mass of the composite coating layer accounts for 10 wt% of the mass of the coated ternary cathode material for solid-state lithium batteries.

[0079] The preparation method includes the following steps:

[0080] (1) Ti3C2T x The powder was uniformly dispersed in deionized water, and the mixture was ultrasonically treated for 60 minutes to ensure uniform dispersion of the two-dimensional titanium carbide powder, forming a stable suspension. The suspension was then continuously stirred at 500 rpm, following the mixing process of Ru nanoparticles and Ti3C2T... x The powder mass ratio was 0.08:1. A 0.05 mol / L RuCl3 solution was slowly added dropwise to the suspension at a rate of 5 mL / min, with continuous stirring for 120 min during the addition process to ensure thorough mixing of the RuCl3 solution and the suspension. 3+ Ions coordinate with the -O- and -OH functional groups on the surface of two-dimensional titanium carbide through electrostatic interactions and adsorb onto Ti3C2T xThe surface of the nanosheet is then added with a sodium borohydride solution at 25°C with a stirring speed of 500 rpm, wherein the molar ratio of sodium borohydride to RuCl3 is 5:1, and the reduction reaction is performed for 5 h, and the solid product is separated by centrifugation, and the solid product is washed with deionized water and ethanol for multiple times to remove unreacted RuCl3, sodium borohydride and reaction byproducts, and after the washing is completed, the product is dried in a vacuum environment at 70°C for 10 h to obtain a two-dimensional titanium carbide / ruthenium nanoparticle composite material;

[0081] (2) The NCM811 ternary precursor hydroxide and the two-dimensional titanium carbide / ruthenium nanoparticle composite material are uniformly mixed, and then are put into a ball milling tank with lithium hydroxide at a molar ratio of 1:1.03, and are ball milled at 600 rpm for 30 min under a nitrogen atmosphere, the ball-to-material ratio is 6:1, and the temperature is increased to 900°C at a temperature increasing rate of 5°C / min, and is sintered for 12 h, and is naturally cooled to room temperature to obtain a coated ternary positive electrode material for solid-state lithium batteries.

[0082] Example 4

[0083] The present embodiment provides a coated ternary positive electrode material for solid-state lithium batteries and a preparation method thereof, wherein the difference between the coated ternary positive electrode material for solid-state lithium batteries and Example 1 is that the mass of the composite coating layer accounts for 2wt% of the mass of the coated ternary positive electrode material for solid-state lithium batteries, and the rest of the structure and components remain the same as those in Example 1.

[0084] The difference between the preparation method and Example 1 is that the amount of the two-dimensional titanium carbide / ruthenium nanoparticle composite material added in step (2) is adjusted so that the mass of the composite coating layer accounts for 2wt% of the mass of the coated ternary positive electrode material for solid-state lithium batteries, and the rest of the preparation method and parameters remain the same as those in Example 1.

[0085] Example 5

[0086] The present embodiment provides a coated ternary positive electrode material for solid-state lithium batteries and a preparation method thereof, wherein the difference between the coated ternary positive electrode material for solid-state lithium batteries and Example 1 is that the mass of the composite coating layer accounts for 11wt% of the mass of the coated ternary positive electrode material for solid-state lithium batteries, and the rest of the structure and components remain the same as those in Example 1.

[0087] The difference between the preparation method and Example 1 is that the amount of the two-dimensional titanium carbide / ruthenium nanoparticle composite material added in step (2) is adjusted so that the mass of the composite coating layer accounts for 11wt% of the mass of the coated ternary positive electrode material for solid-state lithium batteries, and the rest of the preparation method and parameters remain the same as those in Example 1.

[0088] Example 6

[0089] The embodiment provides a coated ternary positive electrode material for a solid-state lithium battery and a preparation method thereof.

[0090] The preparation method is different from that in the embodiment 1 in that dry ball milling is replaced by wet ball milling in the step (2), and specifically, the NCM811 ternary precursor hydroxide and the two-dimensional titanium / ruthenium nanoparticle composite material are uniformly mixed, then the lithium hydroxide is put into a ball milling tank in a molar ratio of 1:1.03, anhydrous ethanol is added to cover the powder, ball milling is carried out at 600 rpm for 60 min under a protective atmosphere, the ball-to-material ratio is 6:1, after filtration, washing and drying, the temperature is increased to 800 DEG C at a temperature increasing rate of 4 DEG C / min, sintering is carried out for 18 h, and natural cooling is carried out to room temperature, so that the coated ternary positive electrode material for a solid-state lithium battery is obtained, and the rest of the preparation method and parameters are consistent with those in the embodiment 1.

[0091] Embodiment 7

[0092] The embodiment provides a coated ternary positive electrode material for a solid-state lithium battery and a preparation method thereof, and the structure and components of the coated ternary positive electrode material for a solid-state lithium battery are consistent with those in the embodiment 1.

[0093] The preparation method is different from that in the embodiment 1 in that the rotating speed of ball milling in the step (2) is adjusted to 200 rpm, and the rest of the preparation method and parameters are consistent with those in the embodiment 1.

[0094] Embodiment 8

[0095] The embodiment provides a coated ternary positive electrode material for a solid-state lithium battery and a preparation method thereof, and the structure and components of the coated ternary positive electrode material for a solid-state lithium battery are consistent with those in the embodiment 1.

[0096] The preparation method is different from that in the embodiment 1 in that the rotating speed of ball milling in the step (2) is adjusted to 700 rpm, and the rest of the preparation method and parameters are consistent with those in the embodiment 1.

[0097] Embodiment 9

[0098] The embodiment provides a coated ternary positive electrode material for a solid-state lithium battery and a preparation method thereof, and the coated ternary positive electrode material for a solid-state lithium battery is different from that in the embodiment 1 in that the mass ratio of Ru nanoparticles and the Ti3C2T x is 0.1:1, and the rest of the structure and components are consistent with those in the embodiment 1.

[0099] The preparation method is different from that in the embodiment 1 in that the addition amount of the RuCl3 solution in the step (1) is adjusted, so that the mass ratio of Ru nanoparticles and the Ti3C2T xThe mass ratio of the NCM811 ternary precursor hydroxide and the two-dimensional titanium carbide Ti3C2T

[0100] Comparative Example 1

[0101] The comparative example provides a coated ternary cathode material for solid-state lithium batteries and a preparation method thereof, which is different from example 1 in that the deposition of Ru nanoparticles is omitted, and the composite coating layer material only includes Ti3C2T x The mass of the composite coating layer accounts for 5wt% of the mass of the coated ternary cathode material for solid-state lithium batteries, and the rest of the structure and components remain the same as example 1.

[0102] The preparation method is different from example 1 in that step (1) is omitted, and the NCM811 ternary precursor hydroxide and the two-dimensional titanium carbide Ti3C2T x are mixed uniformly, and the rest of the preparation method and parameters remain the same as example 1.

[0103] Application Examples 1-9 and Comparative Application Example 1

[0104] The coated ternary cathode material for solid-state lithium batteries provided by examples 1-9 and comparative example 1 is mixed uniformly with sulfide solid-state electrolyte (Li6PS5Cl) and conductive agent VGCF according to a mass ratio of 70:25:5, and is pressed into a sheet as a positive electrode-electrolyte integrated structure, and is assembled with a negative electrode material (metal lithium sheet) to obtain a solid-state lithium battery, which corresponds to application examples 1-9 and comparative application example 1, respectively.

[0105] At ambient temperature, the following electrochemical performance tests are performed on the solid-state lithium batteries provided by application examples 1-9 and comparative application example 1:

[0106] Rate performance test: the solid-state lithium battery is charged at a rate of 0.2C (1C=200mA / g) to 4.3V, and then discharged at the same rate to 3.0V, and the discharge specific capacity is recorded. Subsequently, charge and discharge tests are carried out at rates of 0.5C, 1C, 2C and 5C, respectively, and the discharge specific capacity at each rate is recorded, and then the test is returned to 0.2C rate, and the capacity retention rate is calculated.

[0107] Cycle performance test: the battery is subjected to charge and discharge cycle test at a rate of 1C, and the discharge specific capacity of the first cycle is recorded, and then the cycle performance test is carried out at a rate of 0.2C, and the cycle number is 100 times, and the capacity retention rate of the battery at the 100th cycle is calculated. The specific test results are shown in Table 1.

[0108] Table 1

[0109]

[0110] From the test results, it can be seen that:

[0111] (1) From application examples 1-3, it can be seen that the solid-state lithium battery coated ternary positive electrode material provided by the application adopts a composite coating layer material including Ru nanoparticles and Ti3C2T x , the Ru nanoparticles are deposited on the surface of Ti3C2T x , and Ti3C2T x , as a new type of two-dimensional transition metal carbide, has excellent electronic conductivity and abundant surface functional groups (-OH, -O-, -F), and its unique layered structure also provides a channel for ion transmission, showing great potential in battery electrode materials; Ru nanoparticles have high catalytic activity and good conductivity, which can promote charge transfer reactions and make up for the problems of limited capacity and poor cycle performance of Ti3C2T x as a positive electrode material. Therefore, the Ti3C2T x and Ru nanoparticle composite material are coated on the ternary positive electrode material, which has the effect of synergistically improving electronic conduction and ion transmission and improving interface impedance, thereby improving the electrochemical performance of the obtained solid-state battery. Specifically, the capacity retention rate after 100 cycles is 94.5%-95.2%, and the 5C / 0.2C rate capacity retention rate is 83.1%-85.5%.

[0112] (2) From application examples 1 and 4-5, it can be seen that the application further regulates the mass of the composite coating layer to be 3wt%-10wt% of the mass of the solid-state lithium battery coated ternary positive electrode material, which not only makes up for the electronic conduction shortcomings of the ternary positive electrode material through the high conductivity of Ti3C2T x , but also avoids excessive occupation of active substances.

[0113] (3) Through application example 1 and application example 6, it can be seen that in the application, the mixing in the regulation step (2) adopts a dry method ball milling dispersion technology, the two-dimensional titanium carbide / ruthenium nanoparticle composite material is uniformly attached to the surface of the ternary precursor hydroxide to form an effective composite coating layer, and an initial "core-shell" structure precursor with the ternary precursor hydroxide as the "core" and the composite coating layer as the "shell" is constructed, which can not only avoid the re-stacking problem of the two-dimensional titanium carbide due to the solvent effect in the wet mixing, but also enhance the interfacial bonding force between the composite coating layer and the ternary precursor hydroxide core through mechanical force, reduce the particle shedding in the subsequent sintering and battery charging and discharging process, and thus improve the structural stability of the coated ternary positive electrode material for solid-state lithium batteries; through application example 1 and application examples 7-8, it can be seen that the application further limits the rotation speed of the ball milling to 300 rpm-600 rpm, which can ensure the uniformity of the composite coating layer, thereby ensuring the integrity and consistency of the "core-shell" precursor structure, avoiding uneven coating caused by too low rotation speed, affecting the consistency of the material, and material structure damage caused by too high rotation speed; through application example 1 and application example 9, it can be seen that the application further regulates the mass ratio of Ru nanoparticles and Ti3C2T x x is (0.02-0.08):1, which can significantly reduce the cost of noble metals, and also can take into account the better electrochemical performance of the coated ternary positive electrode material for solid-state lithium batteries.

[0114] (4) Through application example 1 and comparative application example 1, it can be seen that the application uses the synergistic design of two-dimensional titanium carbide Ti3C2T x x and Ru nanoparticles as the material of the composite coating layer on the surface of the ternary positive electrode material, the Ru nanoparticles are uniformly loaded on the surface of Ti3C2T x x, the interface impedance is reduced through electron confinement effect, and Ru also accelerates the lithium / oxygen reaction kinetics as a catalyst, Ru can also promote the oxygen reduction reaction (ORR) on the surface of the ternary positive electrode material, inhibit the side reaction, and thus improve the rate performance and cycle life of the battery, and if the loading of Ru nanoparticles is omitted, the rate performance and cycle life of the battery will be greatly reduced.

[0115] In summary, the coated ternary positive electrode material for solid-state lithium batteries provided by the application adopts a composite coating layer material including Ru nanoparticles and Ti3C2T x x, the Ru nanoparticles are deposited on the surface of Ti3C2T x x, and Ti3C2T xAs a new type of two-dimensional transition metal carbide, it has excellent electronic conductivity and rich surface functional groups (-OH, -O-, -F), and its unique layered structure also provides a channel for ion transmission, showing great potential in battery electrode materials; Ru nanoparticles have high catalytic activity and good conductivity, which can promote charge transfer reactions, making up for the shortcomings of Ti3C2T x As a positive electrode material, it faces problems such as limited capacity and poor cycle performance. Therefore, Ti3C2T x The composite material coated with Ru nanoparticles on the ternary positive electrode material has the effect of synergistically improving electronic conduction and ion transmission, and improving the interface impedance, thereby improving the electrochemical performance of the obtained solid-state battery.

[0116] Applicants declare that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by any person skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A coated ternary cathode material for solid-state lithium batteries, characterized in that, The solid-state lithium battery coated ternary cathode material includes a ternary cathode material and a composite coating layer located on the surface of the ternary cathode material; The composite coating material includes Ru nanoparticles and Ti3C2T. x The Ru nanoparticles are deposited on the Ti3C2T x surface; Among them, T x For the Ti3C2T x Any one or a combination of at least two of the following on the surface: -O-, -OH, or -F.

2. The coated ternary cathode material for solid-state lithium batteries according to claim 1, characterized in that, In the composite coating layer, the Ru nanoparticles and the Ti3C2T x The mass ratio is (0.02~0.08):1; Preferably, the average particle size of the Ru nanoparticles is 5 nm to 20 nm.

3. The coated ternary cathode material for solid-state lithium batteries according to claim 1 or 2, characterized in that, The mass of the composite coating layer accounts for 3wt% to 10wt% of the mass of the coated ternary cathode material for solid-state lithium batteries.

4. A method for preparing a coated ternary cathode material for solid-state lithium batteries according to any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: (1) Mix ruthenium salt solution and Ti3C2T x The suspension was first mixed and then subjected to a reduction reaction to obtain a two-dimensional titanium carbide / ruthenium nanoparticle composite material; Among them, T x For the Ti3C2T x Any one or a combination of at least two of the following: -O-, -OH, or -F on the surface; (2) The ternary precursor hydroxide, the two-dimensional titanium carbide / ruthenium nanoparticle composite material described in step (1) and the lithium salt are mixed for the second time and sintered to obtain a coated ternary cathode material for solid lithium batteries.

5. The preparation method according to claim 4, characterized in that, The concentration of the ruthenium salt solution in step (1) is 0.05 mol / L to 0.2 mol / L; Preferably, the ruthenium salt in the ruthenium salt solution in step (1) includes any one or a combination of at least two of RuCl3·H2O, RuCl3·3H2O, RuCl3, RuBr3 or Ru(NO3)3; Preferably, the Ti3C2T in step (1) x The method for preparing the suspension includes: mixing Ti3C2T x The mixture was mixed with a solvent, and the resulting mixture was ultrasonically treated to obtain Ti3C2T. x suspension; Preferably, the ultrasonic treatment time is 30 min to 60 min; Preferably, step (1) the first mixing includes adding a ruthenium salt solution dropwise to Ti3C2T x In the suspension, the mixture is continuously stirred during the dropwise addition process.

6. The preparation method according to claim 4 or 5, characterized in that, The reducing agent used in the reduction reaction in step (1) includes any one or a combination of at least two of sodium borohydride, ascorbic acid, or sodium citrate; Preferably, the molar ratio of the reducing agent to the ruthenium salt is (3~5):1; Preferably, the temperature of the reduction reaction in step (1) is 25℃~40℃; Preferably, the reduction reaction in step (1) takes 2 to 5 hours.

7. The preparation method according to any one of claims 4 to 6, characterized in that, The general chemical formula of the ternary precursor hydroxide in step (2) includes Ni 1－y－z Co y Mn z (OH)₂, where 0.05≤y≤0.15, 0≤z≤0.05; Preferably, in step (2), the molar ratio of the ternary precursor hydroxide to the lithium salt is 1:(1.03~1.06).

8. The preparation method according to any one of claims 4 to 7, characterized in that, Step (2) The second mixing includes first mixing the ternary precursor hydroxide and the two-dimensional titanium carbide / ruthenium nanoparticle composite material evenly, and then mixing it with lithium salt and ball milling it; Preferably, the rotational speed of the ball mill is 300 rpm to 600 rpm; Preferably, the ball milling time is 30 min to 120 min.

9. The preparation method according to any one of claims 4 to 8, characterized in that, The heating rate for sintering in step (2) is 2℃ / min to 5℃ / min; Preferably, the holding temperature for sintering in step (2) is 600℃~900℃; Preferably, the holding time for sintering in step (2) is 12h~20h.

10. A solid-state lithium battery, characterized in that, The solid-state lithium battery includes the coated ternary cathode material for solid-state lithium batteries as described in any one of claims 1 to 3, or the coated ternary cathode material for solid-state lithium batteries prepared by the preparation method described in any one of claims 4 to 9.

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