P and S co-doped carbon material loaded LTO-Li-Rich positive electrode material and preparation method thereof

Abstract

The invention provides a P and S co-doped carbon material loaded LTO-Li-Rich positive electrode material and a preparation method thereof, and relates to the technical field of solid-state batteries. According to the preparation method provided by the invention, a sol-gel reaction is carried out to form a lithium-rich manganese precursor, then a high-temperature reaction is carried out in an inert gas to form a high-purity phase lithium-rich manganese material, and then a rigid framework LTO with high ionic conductivity is introduced to the surface of the lithium-rich manganese material, so that the volume change of lithium-rich manganese in the charging and discharging process is relieved; meanwhile, a titanate coupling agent is adopted for surface grafting, functional groups are further introduced, meanwhile, a polymer net structure containing P and S elements is introduced, a P and S co-doped carbon material is loaded on the surface of the modified material, migration of electrons on the surface of the active material is improved, and the performance of the material is improved. The first-circle coulombic efficiency of the prepared positive electrode material is high, and the cycle life is greatly prolonged, so that the application requirements are better met.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and more specifically, to a P, S co-doped carbon material-supported LTO@Li-Rich cathode material and its preparation method. Background Technology

[0002] Lithium-rich manganese-based layered oxides (LLOs, molecular formula: xLi2MnO3·(1−x)LiMO2 (M=Ni, Co, Mn)) have achieved >250 mAh·g as cathode materials for all-solid-state batteries by leveraging the synergistic effect of anionic and cationic redox reactions. -1 With its ultra-high theoretical discharge specific capacity, high manganese abundance in the Earth's crust (approximately 0.1% of the crust's composition), and cost only 1 / 20th that of cobalt, manganese combines high energy density with environmental friendliness, making it a suitable candidate for sulfide all-solid-state batteries (with ionic conductivity reaching 10⁻³ S·cm). -1 As a core candidate material, LLOs have shown irreplaceable application prospects in fields with extremely stringent requirements for battery energy density, such as electric vehicles and large-scale energy storage.

[0003] Compared to traditional ternary (NCM) and lithium iron phosphate (LFP) cathode materials, the layered crystal structure of lithium ion intercalation and deintercalation (Li⁺) is theoretically more conducive to the process. However, in the practical application of LLOs in sulfide all-solid-state batteries and the construction of a composite cathode of "active material-sulfide electrolyte-carbon additive", three major technical bottlenecks are still faced. These bottlenecks severely restrict the cycle stability and full utilization of energy density of the battery:

[0004] a) Bulk structure degradation: During battery cycling, the activation of the Li2MnO3 phase is accompanied by the release of lattice oxygen and the migration of transition metal ions, which in turn triggers the transformation of the layered structure into spinel or rock salt phase, resulting in a significant decrease in battery voltage and capacity.

[0005] b) Interface instability: Active oxygen in LLOs easily oxidizes sulfide electrolytes, generating byproducts with poor conductivity. At the same time, the enrichment of lithium ions will form a space charge layer. In addition, the volume change (5%-8%) of LLOs during charging and discharging will cause electrolyte cracking, and the interfacial impedance will increase sharply.

[0006] c) Kinetic hysteresis: LLOs materials themselves have low electronic and ionic conductivity, and rely on carbon additives to improve their conductivity, but carbon additives will catalyze the decomposition of sulfide electrolytes.

[0007] In addition, the activation energy barrier of Li2MnO3 is relatively high, resulting in a first-cycle coulombic efficiency of only 60%-70% and poor high-rate performance.

[0008] Although existing modification methods (such as oxide coating, bulk doping, carbon coating, etc.) can improve the performance of LLOs to some extent, they all have limitations and cannot simultaneously solve the three major problems faced by LLOs in sulfide all-solid-state batteries: "bulk structure degradation, interface impedance surge, and kinetic lag". Therefore, it is difficult to achieve the synergistic optimization of composite cathodes in terms of "high capacity, long cycle life, and high rate".

[0009] Therefore, this application aims to provide a P, S co-doped carbon material-supported LTO@Li-Rich cathode material and its preparation method, so as to better solve the above-mentioned technical problems. Summary of the Invention

[0010] The purpose of this application is to provide a P, S co-doped carbon material-supported LTO@Li-Rich cathode material and its preparation method, which can solve the technical problems of simultaneously stabilizing the bulk structure of LLOs, suppressing side reactions at the sulfide electrolyte interface, and improving electron / ion conduction efficiency.

[0011] This application provides a method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon material, including the following steps:

[0012] S1. In a first solvent, lithium salt, nickel salt, cobalt salt, and manganese salt are used as reactants and undergo a sol-gel reaction in the presence of ammonia. This is followed by high-temperature calcination under an inert gas atmosphere to obtain a lithium-rich manganese cathode material, Li. 1.26 Ni x Co y Mn z O2, where x, y, and z are mole fractions, and satisfy x + y + z = 0.741, 0.0693 ≤ x ≤ 0.0781, 0.0693 ≤ y ≤ 0.0781, and 0.567 ≤ z ≤ 0.617;

[0013] The first reaction performed in this step is to obtain a uniform lithium-rich manganese precursor;

[0014] In this step, high-temperature calcination is divided into two stages: pre-calcination and high-temperature calcination. The main purpose of the pre-calcination stage (430-470℃) is to remove organic matter and water of crystallization from the gel and form an amorphous precursor; the high-temperature calcination stage (780-820℃) promotes the formation and growth of layered oxide crystal phases to obtain lithium-rich manganese cathode material with high crystallinity.

[0015] Specifically, in this step, the reaction time of the pre-calcination stage is 4-6 hours, preferably 4.5-5.5 hours. The reaction time of the high-temperature calcination stage is 9-11 hours, preferably 9.5-10.5 hours.

[0016] S2. In a fluidized bed, the lithium-rich manganese cathode material obtained in step S1 is reacted with a second solvent, and the LTO precursor solution is uniformly coated on the surface of the lithium-rich manganese particles by atomization spraying, followed by heat treatment to obtain LTO@Li-Rich material.

[0017] In this step, LTO(Li4Ti5O) 12 The coating is achieved through a fluidized bed process. Fluidized bed technology ensures that the Li-Rich particles are in a fluidized state within the cavity, allowing the LTO precursor solution (an anhydrous ethanol solution of lithium ethoxide and titanium ethoxide) to be uniformly sprayed onto the particle surface through an atomizing nozzle, thus achieving a nanoscale uniform coating of LTO.

[0018] S3. The LTO@Li-Rich material obtained in step S2 is reacted with a titanate coupling agent to graft the coupling agent onto the surface of the LTO@Li-Rich material and release active groups C=C, thereby obtaining the modified LTO@Li-Rich material.

[0019] In this step, the titanate coupling agent used is at least one of neoalkoxytris(dioctylpyrophosphoryloxy) titanate, neoalkoxytris(dioctylphosphoryloxy) titanate, and neoalkoxytris(tridodecylbenzenesulfonyloxy) titanate; all titanate coupling agents can introduce the functional group C=C on the LTO@Li-Rich surface, which is beneficial for the introduction of heteroatoms.

[0020] According to the present invention, the amount of titanate coupling agent used is 1.1-1.3g relative to 50g of LTO@Li-Rich material. According to the present invention, the coupling agent grafting reaction is carried out in a high-speed mixer, the reaction temperature is controlled at 90-110℃, and the reaction time is 0.3-1.5 h. High-speed stirring (1100-1300 rpm) is beneficial to the dispersion and reaction of the coupling agent on the particle surface.

[0021] S4. In the presence of an emulsifier, the modified LTO@Li-Rich material obtained in step S3 is polymerized with allyl phosphonate and vinyl sulfonate in a third solvent. After the reaction is completed, carbonization is carried out under an inert gas atmosphere to obtain P and S co-doped carbon material loaded with LTO@Li-Rich cathode material.

[0022] In this step, the PS co-doped carbon layer is formed by in-situ polymerization of allyl phosphonate (phosphorus source) and vinyl sulfonate (sulfur source) on the surface of the modified LTO@Li-Rich material and subsequent carbonization.

[0023] Further, in step S1, the first solvent is an aqueous system, and the molar ratio of lithium salt, nickel salt, cobalt salt and manganese salt is 1:(0.055-0.062):(0.055-0.062):(0.45-0.49), preferably 1:(0.058-0.059):(0.058-0.059):(0.47-0.48).

[0024] Specifically, in step S1:

[0025] The lithium salt is any one of lithium acetate, lithium nitrate, and lithium carbonate;

[0026] The nickel salt is any one of nickel acetate tetrahydrate, nickel nitrate, and nickel sulfate;

[0027] The cobalt salt is any one of cobalt acetate tetrahydrate, cobalt nitrate, and cobalt chloride.

[0028] The manganese salt is any one of manganese acetate tetrahydrate, manganese nitrate, and manganese sulfate.

[0029] Furthermore, in step S1, during the sol-gel reaction, citric acid is added as a complexing agent. After stirring and dissolving, the pH value is adjusted to 9-12, preferably 10-11, by adding ammonia dropwise.

[0030] In this step, the amount of citric acid added is crucial for forming a stable sol-gel structure. The molar ratio of total metal ions to citric acid is controlled within the range of 1.1-1.3, preferably 1.2-1.25. At this ratio, the citric acid can adequately complex the metal ions to prevent segregation.

[0031] The dropping rate and final pH value of the ammonia solution have a significant impact on the morphology and particle size distribution of the precursor. Slow dropping (e.g., 1 drop / second) and controlling the pH within the range of 9-12 (preferably 10-11) are beneficial for forming precursor materials with a concentrated particle size distribution.

[0032] In this step, the temperature and time parameters of the sol-gel process directly affect the structure of the precursor. The sol formation stage is controlled at 70-72℃ with stirring for 1.5-2.5 hours; the gel aging stage is controlled at 78-82℃ with standing for 10-14 hours. These mild reaction conditions are conducive to the formation of a dense, defect-free dry gel.

[0033] Further, in step S2, the molar ratio of lithium ethoxide to titanium ethoxide in the LTO coating solution is 0.04:(0.05-0.08), preferably 0.04:0.05-0.06, to ensure the formation of a lithium titanate interface layer.

[0034] Specifically, relative to 100g of lithium-rich manganese cathode material, the amount of lithium ethanol added is 0.03-0.05 mol, preferably 0.035-0.045 mol.

[0035] Furthermore, in step S2, the bed temperature in the fluidized bed process is controlled at 180-220℃, preferably 200-210℃, and the spraying rate is 0.8-1.2 mL / min, preferably 1-1.1 mL / min.

[0036] In step S2, the fluidized bed process parameters are crucial to the coating effect. Controlling the bed temperature at 180-220℃ (preferably 200-210℃) facilitates rapid solvent evaporation and allows the LTO precursor to decompose and undergo a preliminary reaction on the Li-Rich surface. Controlling the spraying rate at 0.8-1.2 mL / min (preferably 1-1.1 mL / min) ensures uniform and dense coating, avoiding localized excessive thickness or incomplete coating.

[0037] In step S2, the subsequent heat treatment process (680-720℃) is to crystallize the amorphous LTO coating layer to form a crystal with a spinel structure. This structure, as a "rigid framework", can effectively suppress the volume change of lithium-rich manganese materials during cycling and provide lithium-ion migration channels.

[0038] Further, in step S4, the third solvent is an oil-in-water emulsion, with a volume ratio of oil phase to water phase of 1:(5-15); the emulsifier is sodium dodecylbenzenesulfonate, with an addition amount of 0.5-2.0 g; and the initiator used in the polymerization reaction is potassium persulfate, with an addition amount of 0.5-1.5 g.

[0039] The addition of sodium dodecylbenzenesulfonate as an emulsifier, relative to 100 mL of the third solvent, facilitates the formation of an oil-in-water emulsion, promotes polymerization of polymer monomers at the oil-water interface, and forms a uniform coating on the material surface. Potassium persulfate, as an initiator, is used at a dosage of 0.5-1.5 g relative to 100 mL of the third solvent. The amount of the modified LTO@Li-Rich material added relative to 100 mL of the third solvent is 3-8 g. The amount of allyl phosphonate added relative to 100 g of the modified LTO@Li-Rich material is 0.1-0.3 mol, preferably 0.15-0.25 mol. The allyl phosphonate includes one of allyl phosphonate dimethyl ester and allyl phosphonate tetrabutyl ester. The vinyl sulfonate includes one of sodium styrene sulfonate and sodium vinyl sulfonate. The molar ratio of allyl phosphonate to vinyl sulfonate is 1:(0.8-1.2), preferably 1:(0.9-1.1).

[0040] Further, in step S4, the temperature of the carbonization treatment is 650 - 750 °C, preferably 700 - 720 °C, and the carbonization time is 0.5 - 1 h; within this temperature range, the polymer coating layer can be fully carbonized to form a carbon layer with good conductivity, and at the same time, phosphorus and sulfur elements exist in the carbon skeleton in a doped form. The P, S co-doped carbon layer not only improves the electronic conductivity of the material, but the nitrogen- and sulfur-containing functional groups on its surface also help to inhibit the side reactions between the cathode material and the sulfide electrolyte, enhancing the interfacial stability; in the carbonization reaction, too long carbonization time will cause a reduction reaction between the oxide and the carbon material, while too short carbonization time will result in incomplete carbonization.

[0041] Based on the same inventive concept, the present application also provides a P, S co-doped carbon material-supported LTO@Li-Rich cathode material prepared by using the above preparation method. This cathode material uses a lithium-rich manganese-based layered oxide (LLOs) as the matrix, with a rigid lithium titanate (LTO) skeleton layer coated on the surface, and a P, S co-doped carbon material layer is further supported outside this coating layer;

[0042] Among them, the molecular formula of the lithium-rich manganese-based layered oxide is xLi2MnO3·(1−x)LiMO2, M is selected from one or more of Ni, Co, Mn, and 0 < x < 1; the P, S co-doped carbon material layer is formed by in-situ polymerization and carbonization of phosphorus- and sulfur-containing organic compounds on the surface of the LTO@Li-Rich material.

[0043] Further, the average particle size of the cathode material is 3.3 - 12.5 μm, preferably 3.3 - 6.0 μm, and the first-cycle discharge specific capacity is greater than 240 mAh·g -1 preferably greater than 260 mAh·g -1 .

[0044] Advantages of the present invention:

[0045] The method for preparing the cathode material provided by this invention includes a first reaction, a sol-gel reaction, which is beneficial for forming a lithium-rich manganese precursor; a second reaction, a high-temperature reaction in an inert gas atmosphere, which is beneficial for forming a high-purity lithium-rich manganese material; and a third reaction, which facilitates the introduction of a rigid LTO framework with high ionic conductivity onto the surface of the lithium-rich manganese material, thus mitigating the volume change of lithium-rich manganese during charge and discharge and promoting the migration of lithium ions at the lithium-rich manganese interface. Simultaneously, the titanate coupling agent used can be grafted onto the surface of the LTO@Li-Rich material and release active C=C groups, which is beneficial for further processing. In this invention, functional groups are introduced in one step. Allyl phosphonate and vinyl sulfonate react with modified LTO@Li-Rich material to introduce a polymer network structure containing P and S elements. P and S co-doped carbon materials are loaded on the surface of the modified LTO@Li-Rich material, which helps to improve the migration of electrons on the surface of the active material. This results in high first-cycle coulombic efficiency and significantly extended cycle life of the prepared cathode material. It also helps to improve the cathode stability of sulfide solid-state batteries and suppress interfacial chemical / electrochemical side reactions, thereby better meeting application requirements. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flowchart illustrating the preparation process in an embodiment of the present invention. Detailed Implementation

[0048] To facilitate understanding of the present invention, it will be described more fully below through embodiments, and preferred embodiments are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Any other implementation schemes obtained by modifying or equivalently substituting the technical solutions of the present invention without inventive step are all within the protection scope of the present invention.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0050] The numerical values ​​disclosed in the embodiments of this invention are approximate values, not definitive values. Where error or experimental conditions permit, all values ​​within the error range may be included, and the specific numerical values ​​disclosed in the embodiments of this invention are not limited to those specified.

[0051] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0052] Example 1

[0053] See Figure 1 As shown, this embodiment provides a method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon materials. The specific steps are as follows:

[0054] S1. In a 500 mL beaker, 300 mL of distilled water, 0.5 mol of lithium acetate, 0.0295 mol of nickel acetate tetrahydrate, 0.0295 mol of cobalt acetate tetrahydrate, and 0.235 mol of manganese acetate tetrahydrate were added sequentially. The mixture was stirred at 300 rpm for 1.5 h at 71 °C. Subsequently, 0.64 mol of citric acid and 15 mL of 6 mol / L ammonia solution were added sequentially, and the mixture was aged at 78 °C for 10 h to form a gel. The gel was then dried in a vacuum drying oven at 80.5 °C for 12.5 h, transferred to a tube furnace, and calcined at 455 °C for 5.2 h, followed by calcination at 805 °C for 10.2 h to obtain a lithium-rich manganese cathode material.

[0055] S2. Add 51 mL of anhydrous ethanol to a 100 mL beaker, then add 0.04 mol of lithium ethoxide, 0.05 mol of titanium ethoxide, and 100 g of lithium-rich manganese cathode material sequentially. Stir at 300 rpm for 1.6 h at 31 °C. Transfer to a fluidized bed reactor, heat to 205 °C, introduce nitrogen gas, and spray at a spraying rate of 1.05 mL / min for 41 min. After the reaction is complete, transfer to a tube furnace and hold at 705 °C for 5.1 h to obtain LTO@lithium-rich manganese material, which is then passed through a 355 mesh sieve.

[0056] S3. Add 50 g LTO@lithium-rich manganese material, 1.22 g neoalkoxytris(dioctylpyrophosphoryloxy)titanate, and 15.5 mL anhydrous ethanol to a 250 mL beaker. After ultrasonic dispersion for 5 min, transfer to a high-speed mixer and stir at 1220 rpm for 5.2 min at 96 °C. Then, raise the temperature to 106 °C and continue stirring for 15.5 min (grafting C=C active groups) to obtain modified LTO@lithium-rich manganese material.

[0057] S4. Add 100 mL of deionized water and 500 mL of white oil to a 1000 mL beaker, then add 1.0 g of sodium dodecylbenzenesulfonate and stir at 300 rpm for 30 min to form an oil-in-water emulsion. Then, add 20 g of modified LTO@lithium-rich manganese material, 0.15 mol of sodium styrenesulfonate, 0.15 mol of dimethyl allylphosphonate, and 1.0 g of potassium persulfate. After deoxygenation under nitrogen for 31 min, react the mixture at 66 °C and 250 rpm for 5.1 h. Dry the product under vacuum at 80 °C for 12 h, then transfer it to a tube furnace and carbonize it at 710 °C under an inert atmosphere for 0.5 h to finally obtain P,S co-doped carbon material-supported LTO@Li-Rich cathode material.

[0058] The resulting product was named M1, with an average particle size of 3.3 μm.

[0059] Example 2

[0060] This embodiment provides a method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon materials, and the specific steps are as follows:

[0061] S1. In a 500 mL beaker, 300 mL of distilled water, 1.35 mol of lithium acetate, 0.07965 mol of nickel acetate tetrahydrate, 0.07965 mol of cobalt acetate tetrahydrate, and 0.6345 mol of manganese acetate tetrahydrate were added sequentially. The mixture was stirred at 310 rpm for 1.5 h at 72 °C. Subsequently, 1.715 mol of citric acid was added, and after stirring to dissolve, 16.5 mL of 6.5 mol / L ammonia solution was slowly added dropwise to adjust the pH to 11. The mixture was then aged at 79 °C for 11 h to form a gel. Subsequently, the gel was dried in a vacuum drying oven at 81 °C for 13 h, transferred to a tube furnace, and calcined at 460 °C for 5.5 h, followed by calcination at 810 °C for 10.5 h to obtain a lithium-rich manganese cathode material.

[0062] S2. Add 52 mL of anhydrous ethanol to a 100 mL beaker, then add 0.04 mol of lithium ethoxide, 0.05 mol of titanium ethoxide, and 100 g of lithium-rich manganese cathode material sequentially. Stir at 300 rpm for 1.8 h at 32 °C. Transfer to a fluidized bed reactor, heat to 210 °C, introduce nitrogen gas, and spray at a spraying rate of 1.1 mL / min for 42 min. After the reaction is complete, transfer to a tube furnace and hold at 710 °C for 5.2 h to obtain LTO@lithium-rich manganese material, which is then passed through a 360-mesh sieve.

[0063] S3. Add 50 g LTO@lithium-rich manganese material, 1.25 g neoalkoxytris(tridodecylbenzenesulfonyloxy)titanate, and 16 mL anhydrous ethanol to a 250 mL beaker. After ultrasonic dispersion for 5.5 min, transfer to a high-speed mixer and stir at 1250 rpm at 98 °C for 5.5 min. Then, raise the temperature to 108 °C and continue stirring for 16 min to obtain modified LTO@lithium-rich manganese material.

[0064] S4. Add 100 mL of deionized water and 600 mL of white oil to a 1000 mL beaker, then add 1.2 g of sodium dodecylbenzenesulfonate and stir at 300 rpm for 30 min to form an oil-in-water emulsion. Then, add 21 g of modified LTO@lithium-rich manganese material, 0.165 mol of sodium styrenesulfonate, 0.165 mol of tetrabutyl allylphosphonate, and 1.1 g of potassium persulfate. After deoxygenation under nitrogen for 32 min, react the mixture at 68 °C and 250 rpm for 5.2 h. Dry the product under vacuum at 80 °C for 12 h, then transfer it to a tube furnace and carbonize it at 720 °C under an inert atmosphere for 0.6 h to finally obtain P,S co-doped carbon material-supported LTO@Li-Rich cathode material.

[0065] The resulting product was named M2, with an average particle size of 5.5 μm.

[0066] Example 3

[0067] This embodiment provides a method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon materials, and the specific steps are as follows:

[0068] S1. In a 500 mL beaker, 300 mL of distilled water, 1.5 mol of lithium acetate, 0.087 mol of nickel acetate tetrahydrate, 0.087 mol of cobalt acetate tetrahydrate, and 0.705 mol of manganese acetate tetrahydrate were added sequentially. The mixture was stirred at 300 rpm for 1.5 h at 70 °C. Subsequently, 1.956 mol of citric acid was added, and after stirring to dissolve, 19.5 mL of 7 mol / L ammonia solution was slowly added dropwise to adjust the pH to 10. The mixture was then aged at 78 °C for 10 h to form a gel. Subsequently, the gel was dried in a vacuum drying oven at 80 °C for 12 h, transferred to a tube furnace, and calcined at 450 °C for 5 h, followed by calcination at 800 °C for 10 h to obtain a lithium-rich manganese cathode material.

[0069] S2. Add 50 mL of anhydrous ethanol to a 100 mL beaker, then add 0.04 mol of lithium ethoxide, 0.05 mol of titanium ethoxide, and 100 g of lithium-rich manganese cathode material sequentially. Stir at 300 rpm for 1.5 h at 30 °C. Transfer to a fluidized bed reactor, heat to 200 °C, introduce nitrogen gas, and spray at a spraying rate of 1.0 mL / min for 40 min. After the reaction is complete, transfer to a tube furnace and hold at 700 °C for 5 h to obtain LTO@lithium-rich manganese material, which is then passed through a 350-mesh sieve.

[0070] S3. Add 50 g LTO@lithium-rich manganese material, 1.2 g neoalkoxytris(dioctylpyrophosphoryloxy)titanate, and 15 mL anhydrous ethanol to a 250 mL beaker. After ultrasonic dispersion for 5 min, transfer to a high-speed mixer and stir at 1200 rpm at 95 °C for 5 min. Then, raise the temperature to 105 °C and continue stirring for 15 min to obtain modified LTO@lithium-rich manganese material.

[0071] S4. Add 100 mL of deionized water and 500 mL of white oil to a 1000 mL beaker, then add 1.0 g of sodium dodecylbenzenesulfonate and stir at 300 rpm for 30 min to form an oil-in-water emulsion. Then, add 18 g of modified LTO@lithium-rich manganese material, 0.15 mol of sodium vinylsulfonate, 0.15 mol of dimethyl allylphosphonate, and 1.0 g of potassium persulfate. After deoxygenation under nitrogen for 30 min, react the mixture at 65 °C and 250 rpm for 5 h. Dry the product under vacuum at 80 °C for 12 h, then transfer it to a tube furnace and carbonize it at 700 °C under an inert atmosphere for 0.5 h to finally obtain P,S co-doped carbon material-supported LTO@Li-Rich cathode material.

[0072] The resulting product was named M3, with an average particle size of 6.0 μm.

[0073] Example 4

[0074] This embodiment provides a method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon materials, and the specific steps are as follows:

[0075] S1. In a 500 mL beaker, 300 mL of distilled water, 1.2 mol of lithium acetate, 0.066 mol of nickel acetate tetrahydrate, 0.066 mol of cobalt acetate tetrahydrate, and 0.54 mol of manganese acetate tetrahydrate were added sequentially. The mixture was stirred at 280 rpm for 1.5 h at 70 °C. Subsequently, 1.628 mol of citric acid was added, and after stirring to dissolve, 15 mL of 5 mol / L ammonia solution was slowly added dropwise to adjust the pH to 9. The mixture was then aged at 78 °C for 9 h to form a gel. Subsequently, the gel was dried in a vacuum drying oven at 75 °C for 10 h, transferred to a tube furnace, and calcined at 430 °C for 4 h, followed by calcination at 780 °C for 9 h to obtain the lithium-rich manganese cathode material.

[0076] S2. Add 45 mL of anhydrous ethanol to a 100 mL beaker, then add 0.04 mol of lithium ethoxide, 0.07 mol of titanium ethoxide, and 100 g of lithium-rich manganese cathode material sequentially. Stir at 300 rpm for 1 h at 25 °C. Transfer to a fluidized bed reactor, heat to 180 °C, introduce nitrogen gas, and spray at a spraying rate of 0.8 mL / min for 35 min. After the reaction is complete, transfer to a tube furnace and hold at 680 °C for 4.5 h to obtain LTO@lithium-rich manganese material, which is then passed through a 320-mesh sieve.

[0077] S3. Add 50 g LTO@lithium-rich manganese material, 1.1 g neoalkoxytris(dioctylpyrophosphoryloxy)titanate, and 12 mL anhydrous ethanol to a 250 mL beaker. After ultrasonic dispersion for 4 min, transfer to a high-speed mixer and stir at 1100 rpm for 4 min at 90 °C. Then, raise the temperature to 100 °C and continue stirring for 12 min to obtain modified LTO@lithium-rich manganese material.

[0078] S4. Add 100 mL of deionized water and 500 mL of kerosene to a 1000 mL beaker, then add 0.8 g of sodium dodecylbenzenesulfonate and stir at 300 rpm for 30 min to form an oil-in-water emulsion. Then, add 15 g of modified LTO@lithium-rich manganese material, 0.135 mol of sodium vinylsulfonate, 0.135 mol of dimethyl allylphosphonate, and 0.9 g of potassium persulfate. After deoxygenation under nitrogen for 25 min, react the mixture at 60 °C and 250 rpm for 4.5 h. Dry the product under vacuum at 80 °C for 12 h, then transfer it to a tube furnace and carbonize it at 650 °C under an inert atmosphere for 0.8 h to finally obtain P,S co-doped carbon material-supported LTO@Li-Rich cathode material.

[0079] The resulting product was named M4, with an average particle size of 8.7 μm.

[0080] Example 5

[0081] This embodiment provides a method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon materials, and the specific steps are as follows:

[0082] S1. In a 500 mL beaker, 300 mL of distilled water, 1.32 mol of lithium acetate, 0.07392 mol of nickel acetate tetrahydrate, 0.07392 mol of cobalt acetate tetrahydrate, and 0.6072 mol of manganese acetate tetrahydrate were added sequentially. The mixture was stirred at 290 rpm for 1.5 h at 70 °C. Subsequently, 1.78 mol of citric acid was added, and after stirring to dissolve, 16.2 mL of 5.9 mol / L ammonia solution was slowly added dropwise to adjust the pH to 9.5. The mixture was then aged at 78 °C for 10.5 h to form a gel. Subsequently, the gel was dried in a vacuum drying oven at 78 °C for 11 h, transferred to a tube furnace, and calcined at 440 °C for 4.5 h, followed by calcination at 790 °C for 9.5 h to obtain a lithium-rich manganese cathode material.

[0083] S2. Add 48 mL of anhydrous ethanol to a 100 mL beaker, then add 0.04 mol of lithium ethoxide, 0.07 mol of titanium ethoxide, and 100 g of lithium-rich manganese cathode material sequentially. Stir at 300 rpm for 1.3 h at 28 °C. Transfer to a fluidized bed reactor, heat to 190 °C, introduce nitrogen gas, and spray at a spraying rate of 0.9 mL / min for 38 min. After the reaction is complete, transfer to a tube furnace and hold at 690 °C for 4.8 h to obtain LTO@lithium-rich manganese material, which is then passed through a 340 mesh sieve.

[0084] S3. Add 50 g LTO@lithium-rich manganese material, 1.15 g neoalkoxytris(dioctylphosphoyloxy)titanate, and 14 mL anhydrous ethanol to a 250 mL beaker. After ultrasonic dispersion for 4.5 min, transfer to a high-speed mixer and stir at 1150 rpm at 92 °C for 4.5 min. Then, raise the temperature to 102 °C and continue stirring for 14 min to obtain modified LTO@lithium-rich manganese material.

[0085] S4. Add 100 mL of deionized water and 550 mL of white oil to a 1000 mL beaker, then add 0.9 g of sodium dodecylbenzenesulfonate and stir at 300 rpm for 30 min to form an oil-in-water emulsion. Then, add 16.5 g of modified LTO@lithium-rich manganese material, 0.1425 mol of sodium styrenesulfonate, 0.15675 mol of tetrabutyl allylphosphonate, and 0.95 g of potassium persulfate. After deoxygenation under nitrogen for 28 min, react the mixture at 62 °C and 250 rpm for 4.8 h. Dry the product under vacuum at 80 °C for 12 h, then transfer it to a tube furnace and carbonize it at 680 °C under an inert atmosphere for 0.85 h to finally obtain P,S co-doped carbon material-supported LTO@Li-Rich cathode material.

[0086] The resulting product was named M5, with an average particle size of 9.2 μm.

[0087] Example 6

[0088] This embodiment provides a method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon materials, and the specific steps are as follows:

[0089] S1. In a 500 mL beaker, 300 mL of distilled water, 1.8 mol of lithium acetate, 0.1116 mol of nickel acetate tetrahydrate, 0.1116 mol of cobalt acetate tetrahydrate, and 0.882 mol of manganese acetate tetrahydrate were added sequentially. The mixture was stirred at 315 rpm for 1.5 h at 70 °C. Subsequently, 2.51 mol of citric acid was added, and after stirring to dissolve, 21 mL of 8 mol / L ammonia solution was slowly added dropwise to adjust the pH to 11.5. The mixture was then aged at 82 °C for 13.5 h to form a gel. Subsequently, the gel was dried in a vacuum drying oven at 84 °C for 13.5 h, transferred to a tube furnace, and calcined at 466 °C for 5.8 h, followed by calcination at 816 °C for 10.8 h to obtain the lithium-rich manganese cathode material.

[0090] S2. Add 54 mL of anhydrous ethanol to a 100 mL beaker, then add 0.04 mol of lithium ethoxide, 0.08 mol of titanium ethoxide, and 100 g of lithium-rich manganese cathode material sequentially. Stir at 300 rpm for 1.9 h at 34 °C. Transfer to a fluidized bed reactor, heat to 215 °C, introduce nitrogen gas, and spray at a spraying rate of 1.15 mL / min for 44 min. After the reaction is complete, transfer to a tube furnace and hold at 690 °C for 5.4 h to obtain LTO@lithium-rich manganese material, which is then passed through a 370-mesh sieve.

[0091] S3. Add 50 g LTO@lithium-rich manganese material, 1.1 g neoalkoxytris(tridodecylbenzenesulfonyloxy)titanate, and 17 mL anhydrous ethanol to a 250 mL beaker. After ultrasonic dispersion for 5.8 min, transfer to a high-speed mixer and stir at 1280 rpm at 99 °C for 5.8 min. Then, raise the temperature to 109 °C and continue stirring for 17 min to obtain modified LTO@lithium-rich manganese material.

[0092] S4. Add 100 mL of deionized water and 600 mL of white oil to a 1000 mL beaker, then add 1.3 g of sodium dodecylbenzenesulfonate and stir at 300 rpm for 30 min to form an oil-in-water emulsion. Then, add 24 g of modified LTO@lithium-rich manganese material, 0.171 mol of sodium styrenesulfonate, 0.1368 mol of dimethyl allylphosphonate, and 1.2 g of potassium persulfate. After deoxygenation under nitrogen for 34 min, react the mixture at 69 °C and 250 rpm for 5.4 h. Dry the product under vacuum at 80 °C for 12 h, then transfer it to a tube furnace and carbonize it at 740 °C under an inert atmosphere for 0.95 h to finally obtain P,S co-doped carbon material-supported LTO@Li-Rich cathode material.

[0093] The resulting product was named M6, with an average particle size of 12.50 μm.

[0094] Comparative Example 1

[0095] Prepared using the same method as in Example 1, except that step S2 is completely omitted, i.e., lithium titanate (LTO) coating is not performed.

[0096] The resulting product was labeled D1, with an average particle size of 11.8 μm.

[0097] Comparative Example 2

[0098] Prepared using the same method as in Example 1, except that step S4 is completely omitted, i.e., P and S co-doped carbon layer loading is not performed.

[0099] The resulting product was labeled D2, with an average particle size of 10.5 μm.

[0100] Comparative Example 3

[0101] Prepared in the same manner as in Example 1, except that in step S3, instead of using a titanate coupling agent, an equal amount of a silane coupling agent (octyltriethoxysilane) without active groups is used.

[0102] The resulting product was labeled D3, with an average particle size of 11.2 μm.

[0103] Comparative Example 4

[0104] The cathode material was prepared using the same method as in Example 1, except that in step S4, the carbonization temperature was changed to 550°C and the carbonization time was changed to 2 hours.

[0105] The resulting product was labeled D4 and had an average particle size of 10.8 μm.

[0106] Comparative Example 5

[0107] The cathode material was prepared using the same method as in Example 1, except that in step S2, the bed temperature of the fluidized bed was set to 250°C.

[0108] The resulting product was labeled D5 and had an average particle size of 12.1 μm.

[0109] Performance testing

[0110] The cathode materials prepared in the above embodiments and comparative examples were assembled into sulfide all-solid-state batteries for performance testing. The specific methods are as follows:

[0111] (1) Preparation of composite cathode

[0112] The cathode material, electrolyte, and VGCF conductive agent were weighed and mixed at a mass ratio of 60:40:5, placed in a ball mill jar, and ball-milled at a speed of 250 rpm for 4 cycles to obtain a uniformly mixed composite cathode material.

[0113] (2) Assembly of all-solid-state batteries

[0114] Using a 10 mm diameter mold, assemble the battery sequentially: Weigh 100 mg of LPSC powder and place it in the mold, shake it flat, apply pressure until the pointer slightly moves, and press for 1 minute to form a dense electrolyte layer. Take about 4-6 mg of the composite cathode material obtained in step (1), add 2-4% PFPE as a binder, dry roll it into a film, and cut it into a 10 mm diameter cathode sheet. Place it on one side of the electrolyte layer, apply 250 MPa pressure, and let it stand for 5 minutes to form a good interface. Finally, evenly spread a 10 mm indium sheet and 3-6 mg of cut lithium sheet on the other side of the solid electrolyte, pressurize until the pointer slightly moves, wait for 30 seconds, remove it from the pressurizing device, remove it outside the glove box, put on the outer stainless steel frame, and use a torque wrench to tighten the shell screws to 7-9 N·m to complete the battery encapsulation.

[0115] The first-cycle electrochemical performance (0.1 C) of the solid-state battery with added cathode material was tested. The test data are shown in Table 1.

[0116] Table 1. First-cycle coulombic efficiency and discharge capacity of sulfide solid-state batteries with different cathode materials.

[0117] cathode materials 0.1 C first-cycle discharge specific capacity (mAh / g) First-lap coulomb efficiency (%) cathode materials M1 268.5 91.4 M1 M2 266.8 91 M2 M3 265.2 91.4 M3 M4 252.7 88.6 M4 M5 250.3 88.3 M5 M6 248.5 88.1 M6 D1 225.8 75.6 D1 D2 235.8 78.3 D2 D3 228.4 77 D3 D4 232.6 78.9 D4 D5 230.1 78.3 D5 Commercial LLOs 232.5 75 Commercial LLOs

[0118] As shown in Table 1 above, the sulfide all-solid-state battery containing the P and S co-doped carbon material prepared in this application and loaded with LTO@Li-Rich cathode material has higher first-cycle coulombic efficiency and discharge capacity, which are much higher than those of commercial LLOs and cathode materials obtained in Comparative Examples 1-5.

[0119] Next, the capacity retention of solid-state batteries with different cathode materials was tested at a current density of 0.5 C. (The initial capacity was the discharge specific capacity at 0.5 C on the 4th cycle). The test results are shown in Table 2 below.

[0120] Table 2. Capacity retention of sulfide solid-state batteries with different cathode materials

[0121] cathode materials Specific capacity of discharge at 0.5 C, 4th cycle (mAh / g) Specific capacity of discharge at 0.5 C, 50th cycle (mAh / g) Specific capacity of discharge at 0.5 C on the 100th cycle (mAh / g) Capacity retention rate (%) M1 258.7 250.2 241.5 93.3 M2 255.2 246.8 236.8 92.8 M3 252.1 243.5 233 92.4 M4 240.5 225.8 210.7 87.6 M5 238.2 222.5 206 86.5 M6 235.8 218.3 200.1 85 D1 205.3 162.8 128 62.3 D2 220.1 185.3 165.1 75 D3 212.4 178.5 153.7 72.4 D4 218.5 180.2 158.3 72.4 D5 215.7 175.4 150.2 69.6 Commercial LLOs 218.2 170.5 135.3 62

[0122] As shown in Table 2 above, the sulfide all-solid-state battery with P and S co-doped carbon material supporting LTO@Li-Rich cathode material exhibits higher capacity retention and stability, which are far superior to those of commercial LLOs and cathode materials obtained in Comparative Examples 1-5.

[0123] In summary, the method for preparing the cathode material provided by this invention involves a first reaction, a sol-gel reaction, which is beneficial for forming a lithium-rich manganese precursor. The second reaction, a high-temperature reaction in an inert gas atmosphere, is beneficial for forming a high-purity lithium-rich manganese material. The third reaction facilitates the introduction of a rigid LTO framework with high ionic conductivity onto the surface of the lithium-rich manganese material, mitigating volume changes during charging and discharging and promoting lithium-ion migration at the lithium-rich manganese interface. Simultaneously, the titanate coupling agent used can be grafted onto the surface of the LTO@Li-Rich material, releasing active C=C groups, which is beneficial for further introducing functional groups. Furthermore, in this invention, allyl phosphonate and vinyl sulfonate react with the modified LTO@Li-Rich material to introduce a polymer network structure containing P and S elements, and P is loaded onto the surface of the modified LTO@Li-Rich material. S co-doping of carbon materials is beneficial for improving electron migration on the surface of active materials, resulting in high first-cycle coulombic efficiency and significantly extended cycle life of the prepared cathode material. It also helps to improve the cathode stability of sulfide solid-state batteries, suppress interfacial chemical / electrochemical side reactions, and thus better meet application requirements.

[0124] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing P, S co-doped carbon material loaded LTO@Li-rich cathode material, characterized in that: The method comprises the following steps: S1. In a first solvent, lithium salt, nickel salt, cobalt salt and manganese salt are used as reaction monomers to carry out sol-gel reaction under the action of ammonia water, followed by high-temperature calcination under inert gas atmosphere to obtain a lithium-rich manganese positive electrode material Li 1.26 Ni x Co y Mn z O2, wherein x, y, z are mole fractions, and satisfy x+y+z=0.741, 0.0693≤x≤0.0781, 0.0693≤y≤0.0781, 0.567≤z≤0.

617. S2. In a fluidized bed, the Li-rich manganese positive electrode material prepared in step S1 is reacted with a second solvent, the LTO precursor solution is uniformly coated on the surface of the Li-rich manganese particles by means of atomization spraying, and then heat treatment is performed to obtain an LTO@Li-Rich material; S3. The LTO@Li-Rich material prepared in step S2 is reacted with a titanate coupling agent, the coupling agent is grafted on the surface of the LTO@Li-Rich material and releases active groups C=C, and a modified LTO@Li-Rich material is obtained; S4. In the presence of an emulsifier, the modified LTO@Li-Rich material prepared in step S3 is subjected to a polymerization reaction with allyl phosphonate and vinyl sulfonate in a third solvent, and after the reaction is completed, carbonization treatment is performed in an inert gas atmosphere to obtain a P, S co-doped carbon material loaded LTO@Li-Rich positive electrode material.

2. The method for preparing P, S co-doped carbon material loaded LTO@Li-rich cathode material according to claim 1, characterized in that: In step S1, the first solvent is an aqueous system, and the molar ratio of lithium salt, nickel salt, cobalt salt and manganese salt is 1: (0.055-0.062): (0.055-0.062): (0.45-0.49).

3. The method for preparing P, S co-doped carbon material loaded LTO@Li-rich cathode material according to claim 2, characterized in that: In step S1: The lithium salt is any one of lithium acetate, lithium nitrate or lithium carbonate; The nickel salt is any one of nickel acetate tetrahydrate, nickel nitrate or nickel sulfate; The cobalt salt is any one of cobalt acetate tetrahydrate, cobalt nitrate or cobalt chloride; The manganese salt is any one of manganese acetate tetrahydrate, manganese nitrate or manganese sulfate.

4. The method for preparing P, S co-doped carbon material loaded LTO@Li-rich cathode material according to claim 1, characterized in that: In step S1, during the sol-gel reaction process, citric acid is added as a complexing agent, after stirring and dissolving, the pH value is adjusted to 9-12 by dropwise addition of ammonia water.

5. The method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon material according to claim 1, characterized in that: In step S2, the molar ratio of lithium ethoxide to titanium ethoxide in the LTO coating solution is 0.04: (0.05-0.08).

6. The method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon material according to claim 1, characterized in that: In step S2, the bed temperature in the fluidized bed process is controlled at 180-220℃, and the spraying rate is 0.8-1.2 mL / min.

7. The method for preparing LTO@Li-Rich cathode material supported on P and S co-doped carbon material according to claim 1, characterized in that: In step S4, the third solvent is an oil-in-water emulsion, and the volume ratio of oil phase to water phase is 1: (5-15); the emulsifier is sodium dodecyl benzene sulfonate, and the addition amount is 0.5-2.0 g; the initiator used in the polymerization reaction is potassium persulfate, and the addition amount is 0.5-1.5 g.

8. The method for preparing P, S co-doped carbon material loaded LTO@Li-rich cathode material according to claim 1, characterized in that: In step S4, the carbonization treatment temperature is 650-750℃, and the carbonization time is 0.5-1 h.

9. The P, S co-doped carbon material supported LTO@Li-rich cathode material prepared by the method of any one of claims 1-8, wherein, The positive electrode material has a lithium-rich manganese-based layered oxide (LLOs) as a substrate, a lithium titanate (LTO) rigid framework layer coated on the surface, and a P, S co-doped carbon material layer further loaded outside the coating layer. The molecular formula of the lithium-rich manganese-based layered oxide is xLi2MnO3· (1−x)LiMO2, M is selected from one or more of Ni, Co and Mn, and 0 < x < 1; the P, S co-doped carbon material layer is formed by in-situ polymerization and carbonization of phosphorus-containing and sulfur-containing organic compounds on the surface of the LTO@Li-Rich material.

10. The P, S co-doped carbon material supported LTO@Li-rich cathode material of claim 9, wherein, The average particle size of the positive electrode material is 3.3-12.5 μm.

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