A method for controllably constructing a carbon composite coating layer containing phosphate by polymerization and application thereof

Abstract

The application discloses a method for realizing controllable construction of a phosphate carbon composite coating layer by polymerization and application thereof. The method utilizes the coordination of polymer monomer A hexachlorocyclotriphosphazene with metal ions, and realizes the control of kinetics by means of a polymerization precipitation process, so as to promote the in-situ growth of a phosphorus and metal containing coating layer intermediate on the surface of the above-mentioned core, thereby obtaining a uniform, continuous and complete coating layer on the surface of the core structure, and the thickness of the coating layer can be adjusted by changing the concentration of the polymer monomer A, polymer monomer B, metal salt or the above-mentioned particle material as the core in the reaction system. The method is simple and easy to operate, has mild conditions, is strong in universality, and has uniform, complete and adjustable coating layer thickness. The obtained core-shell type particle can improve the cycle stability and rate performance of the material when used in a lithium ion battery, and has very high practical value and application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of materials, and particularly relates to a method for realizing controllable construction of a carbon composite coating layer containing phosphate by a polymerization method and application thereof. BACKGROUND

[0002] Phosphate is very suitable for being used as a coating layer of a lithium ion battery electrode material surface due to its stability, so as to improve the surface interface characteristics of the material, relieve the side reaction occurring when the electrode material contacts with an electrolyte during charging and discharging, reduce the interface resistance of the material, improve the ion conductivity of the material, and improve the cycle stability. The carbon material can effectively improve the electronic conductivity of the electrode material, stabilize the interface, and improve the rate performance of the material. The combination of the two can effectively play a synergistic effect, and the obtained coating layer has both electronic and ionic conduction capabilities. Therefore, the construction of a uniform and complete phosphate and carbon composite coating layer is an ideal modification method for a lithium ion battery electrode material, and has great value for systematic theoretical research and practical application.

[0003] A large amount of research work explores the construction method of the phosphate coating layer. The most direct strategy is to directly and simply adsorb phosphate particles, and it is difficult to realize uniform and controllable coating effect by this method. A small amount of work can realize the uniform coating effect of phosphate by relatively harsh reaction control, for example, the patent document CN105322158 discloses a method for realizing uniform and controllable coating by controlling the precipitation process of phosphate based on pH value. The carbon coating layer is usually realized by using some organic precursors, such as dopamine (patent CN201310537745), phenolic resin (patent CN201410205805), etc. However, it is difficult to realize the composite coating of the two, and the corresponding research is also less. How to develop a method for constructing a uniform, continuous, complete, and thickness-controllable phosphate and carbon composite coating layer becomes a difficulty in the field. SUMMARY

[0004] The purpose of the present application is to provide a method for realizing controllable construction of a carbon composite coating layer containing phosphate by a polymerization method and application thereof.

[0005] The present application provides a method for controllably constructing a carbon composite coating layer containing phosphate, which comprises:

[0006] (1) adding a coating substrate, a metal salt, and a polymerization monomer into a solvent to obtain a reaction system, and the polymerization monomer has coordination effect with metal ions in the reaction system, wherein the polymerization monomer contains at least phosphorus element;

[0007] (2) Slowly adding a polymerization initiator into the reaction system, the polymerized monomer coordinated with the metal ion in the reaction system is polymerized and precipitated, forming an intermediate of the polymer coating layer containing phosphorus and metal on the surface of the substrate-coated particles;

[0008] (3) Calcining the intermediate of the polymer coating layer prepared in step (2), carbonizing the polymer coating layer containing phosphorus and metal on the surface of the intermediate, to obtain a core-shell structure particle of the carbon composite coating layer containing phosphate.

[0009] According to an embodiment of the present application, the solvent is selected from non-aqueous solvents, preferably anhydrous organic solvents, such as anhydrous alcohol solvents and / or anhydrous ketone solvents.

[0010] Preferably, the non-aqueous solvent has a chromatographic purity level, and its water content is ≤0.1wt%.

[0011] Illustratively, the anhydrous alcohol solvent is selected from at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, propylene glycol, n-butanol, preferably methanol.

[0012] Illustratively, the anhydrous ketone solvent is selected from acetone.

[0013] According to an embodiment of the present application, the substrate-coated particles are selected from at least one of metal, non-metal, carbide, nitride, oxide, sulfide, phosphide, phosphate, lithium salt, organic particles.

[0014] Preferably, the metal is selected from at least one of ruthenium, rhodium, palladium, silver, platinum, gold, germanium, tin, antimony, and alloys thereof.

[0015] Preferably, the non-metal is selected from at least one of carbon, silicon, phosphorus, sulfur, selenium.

[0016] Preferably, the carbide is selected from at least one of titanium carbide, vanadium carbide, chromium carbide, tantalum carbide, tungsten carbide, boron carbide, silicon carbide.

[0017] Preferably, the nitride is selected from at least one of titanium nitride, vanadium nitride, niobium nitride, tungsten nitride, boron nitride, silicon nitride, phosphorus nitride.

[0018] Preferably, the oxide is selected from at least one of silicon dioxide, titanium dioxide, vanadium pentoxide, manganese dioxide, trimanganese tetroxide, ferrous oxide, ferric oxide, cobalt tetroxide, nickel oxide, zirconium oxide, molybdenum oxide, indium tin oxide, tin oxide, lithium lanthanum zirconium oxide.

[0019] Preferably, the sulfide is selected from at least one of titanium disulfide, iron sulfide, cobalt sulfide, nickel sulfide, molybdenum sulfide, tin sulfide, antimony sulfide.

[0020] Preferably, the phosphide is selected from at least one of titanium phosphide, iron phosphide, cobalt phosphide, nickel phosphide, molybdenum phosphide, and tin phosphide.

[0021] Preferably, the phosphate is selected from at least one of phosphopeptide, titanium pyrophosphate, lithium phosphopeptide, lithium aluminum titanium phosphate, lithium vanadium phosphate, sodium vanadium phosphate, iron phosphate, lithium iron phosphate, lithium iron manganese phosphate, and lithium cobalt phosphate.

[0022] Preferably, the lithium salt is selected from at least one of lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium-rich lithium nickel cobalt manganese oxide.

[0023] Preferably, the organic compound is selected from at least one of phenolic resin, urea-formaldehyde resin, melamine resin, and polystyrene.

[0024] According to an embodiment of the present invention, in the reaction system, the concentration of the substrate to be coated is 0.1 to 150 g / L.

[0025] According to an embodiment of the present invention, in the reaction system, the metal ions are derived from metal salts.

[0026] According to an embodiment of the present invention, the metal salt is selected from at least one of the chloride, sulfate, nitrate, acetate and alkoxide of the corresponding metal element.

[0027] According to an embodiment of the present invention, the concentration of the metal salt in the reaction system is 0.002 to 0.02 mol / L.

[0028] According to an embodiment of the present invention, the polymeric monomers include at least phosphorus-containing polymeric monomer A and polymeric monomer B.

[0029] According to an embodiment of the present invention, the phosphorus-containing polymeric monomer A is hexachlorocyclotriphosphazene.

[0030] According to an embodiment of the present invention, the concentration of the polymeric monomer A in the reaction system is 0.004 to 0.04 mol / L.

[0031] According to an embodiment of the present invention, the polymeric monomer B is selected from one or more of 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxybiphenyl, and 4,4'-diaminobiphenyl.

[0032] According to an embodiment of the present invention, the concentration of the polymeric monomer B in the reaction system is 0.012 to 0.12 mol / L.

[0033] According to an embodiment of the present invention, the initiator is a solution of triethylamine.

[0034] According to an embodiment of the present invention, the concentration of the initiator is 0.2 to 2.0 mol / L.

[0035] According to an embodiment of the present invention, the initiator is added slowly by dripping, preferably by a peristaltic pump.

[0036] According to an embodiment of the present invention, the initiator is added slowly under stirring conditions.

[0037] According to an embodiment of the present invention, in step (2), the temperature of the polymerization reaction is 10 to 40°C, and the time of the polymerization reaction is 1 to 30 hours.

[0038] According to an embodiment of the present invention, the calcination atmosphere is at least one of air, oxygen, nitrogen, and argon.

[0039] According to an embodiment of the present invention, the calcination temperature is 400–900°C and the time is 1–10 h.

[0040] The present invention also provides a core-shell structured particle containing a phosphate carbon composite coating layer prepared by the above method, wherein the core structure is selected from the above coating substrate, the phosphate carbon composite coating layer is grown in situ on the surface of the core structure, and the phosphate carbon composite coating layer is uniform, continuous, complete, and has controllable thickness.

[0041] According to embodiments of the present invention, the phosphate is selected from at least one of magnesium phosphate, aluminum phosphate, titanium phosphate, vanadium phosphate, manganese phosphate, iron phosphate, and cobalt phosphate. Exemplarily, the core-shell structured particles are selected from at least one of the following: carbon-coated silicon nanoparticles of magnesium phosphate, carbon-coated phenolic resin of aluminum phosphate, carbon-coated silica of iron phosphate, carbon-coated lithium iron phosphate of vanadium phosphate, carbon-coated lithium nickel manganese oxide of titanium phosphate, carbon-coated lithium cobalt oxide of manganese phosphate, and carbon-coated lithium nickel cobalt manganese oxide of cobalt phosphate.

[0042] According to an embodiment of the present invention, the phosphate content in the composite coating layer is 20-90 wt%, preferably 20-60 wt%, for example 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, or 70 wt%.

[0043] According to an embodiment of the present invention, the carbon content in the composite coating layer is 0-80 wt%, preferably 20-70 wt%, for example 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, or 70 wt%.

[0044] According to an embodiment of the present invention, the thickness of the carbon composite coating layer is 1–200 nm, for example, 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, or 200 nm. Preferably, the thickness of the composite coating layer is 1–20 nm.

[0045] According to an embodiment of the present invention, the average particle size of the core structure is 50 nm to 10 μm, for example, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 10 μm or any two of the above values.

[0046] The present invention also provides the application of the above-mentioned core-shell structured particles in lithium-ion batteries.

[0047] The present invention also provides a cathode material comprising the above-described core-shell structured particles.

[0048] According to an embodiment of the present invention, when the core-shell structured particles are prepared by the above method and the coating substrate is selected from the lithium salt, the cathode material is the core-shell structured coated particles.

[0049] According to an embodiment of the present invention, when the core-shell structured particles are prepared by the above method and the coating substrate is selected from a non-lithium salt, the cathode material can be obtained by lithiation treatment of the core-shell structured particles.

[0050] Preferably, the lithiation treatment can be performed using lithiation conditions commonly used in this technical field, as long as lithiation of the core-shell structured particles is achieved. Exemplarily, the lithiation treatment includes the following steps: the core-shell structured particles are mixed with lithium hydroxide or lithium carbonate and sintered. The molar ratio of the core-shell structured particles to lithium hydroxide or lithium carbonate is 1:(1-1.1), for example, 1:(1-1.08) or 1:(1.02-1.06). The sintering is carried out in an oxygen-containing atmosphere, such as air or an oxygen atmosphere. The sintering temperature is 400-1000℃, for example, 500-900℃ or 600-800℃. The sintering time is 1-10 hours, for example, 2-8 hours or 4-6 hours. The sintering can be a one-step sintering or a multi-step sintering process, where the sintering temperature and time for each step can be the same or different.

[0051] The present invention also provides a high-energy lithium storage device, wherein the high-energy lithium storage device comprises the above-mentioned core-shell structure particles or the above-mentioned positive electrode material. Preferably, the high-energy lithium storage device is a lithium-ion battery.

[0052] The beneficial effects of this invention are:

[0053] The method of the present invention can be used as a means of modifying lithium-ion batteries or positive electrode materials of lithium batteries by in-situ coating with controllable thickness.

[0054] The core-shell structured particles with phosphate-coated carbon composite layers prepared by this invention can be used as positive electrode materials for high-energy lithium storage devices (such as lithium-ion batteries or lithium batteries) by in-situ coating the surface of the substrate particles to obtain a coating layer with controllable thickness.

[0055] The phosphate carbon composite coating method of the present invention, which allows for controllable coating thickness, utilizes the coordination effect of polymeric monomer A (hexachlorocyclotriphosphazene) on metal ions. Through the precipitation process of polymerization, kinetic control is achieved, promoting the in-situ growth of phosphorus- and metal-containing coating intermediates on the core surface. This results in a uniform, continuous, and complete coating layer on the core structure surface. Furthermore, the thickness of the coating layer can be adjusted by changing the concentrations of polymeric monomer A, polymeric monomer B, metal salt, or the particulate material used as the core in the reaction system. This invention employs a liquid-phase method, providing a simple method for constructing the coating layer with mild reaction conditions and strong versatility. It also demonstrates high practicality and application prospects in the field of lithium-ion batteries.

[0056] This invention utilizes coordination and polymerization-assisted methods to achieve a uniform carbon composite coating of phosphate on the surface of the cathode material of lithium-ion batteries or lithium-ion batteries. This coating can prevent side reactions between the cathode material and the electrolyte solution, and reduce the surface film impedance and charge transfer impedance of the cathode material, accelerating lithium-ion diffusion and significantly improving the cycle performance and rate performance of the cathode material. Furthermore, by controlling the thickness of the phosphate carbon composite coating, the electrochemical performance of the material can be optimized, determining the optimal thickness of the phosphate carbon composite coating and the best electrochemical performance.

[0057] This invention provides another simple, mild, universal, and uniformly controllable method. This method employs a liquid-phase approach in a non-aqueous solvent. Polymer monomer A, hexachlorocyclotriphosphazene, serves not only as a phosphorus source but also as a ligand for metal ions, coordinating with metal salts. Simultaneously, under the action of an initiator, polymer A and polymer monomer B undergo a polymerization reaction, resulting in a phosphorus- and metal-salt-containing intermediate coating layer on the surface of the substrate particles. This invention, through a liquid-phase method and coordination and polymerization reactions, achieves a uniform, continuous, complete, and controllable thickness phosphorus- and metal-containing polymer composite coating layer intermediate on the surface of the substrate particles. Calcination then yields core-shell structured particles with a phosphate carbon composite coating. Furthermore, this method allows for controllable coating on various substrate surfaces. The phosphate carbon composite coating core-shell structured particles obtained by this method exhibit excellent cycle stability when used as cathode materials for lithium-ion batteries. Attached Figure Description

[0058] Figure 1 This is a transmission electron microscope image of silicon nanoparticles with a magnesium phosphate-containing carbon composite coating, as shown in Example 1.

[0059] Figure 2 This is a transmission electron microscope image of the phenolic resin with an aluminum phosphate-containing carbon composite coating, as shown in Example 2.

[0060] Figure 3 The image shows a transmission electron microscope (TEM) image of the silicon dioxide with a carbon composite coating containing iron phosphate as described in Example 3.

[0061] Figure 4 This is a transmission electron microscope image of lithium iron phosphate with a carbon composite coating containing vanadium phosphate, as shown in Example 4.

[0062] Figure 5 This is a transmission electron microscope image of lithium nickel manganese oxide with a carbon composite coating containing titanium phosphate, as shown in Example 5.

[0063] Figure 6 The cycling performance of lithium nickel manganese oxide particles with a carbon composite coating containing titanium phosphate in Example 5 is shown at a charge-discharge current of 14.7 mA / g.

[0064] Figure 7 This is a transmission electron microscope image of lithium cobalt oxide with a carbon composite coating containing manganese phosphate, as shown in Example 6.

[0065] Figure 8 This is a transmission electron microscope image of lithium nickel cobalt manganese oxide with a carbon composite coating containing cobalt phosphate, as shown in Example 7. Detailed Implementation

[0066] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0067] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0068] Example 1

[0069] Preparation of silicon nanoparticles with a core-shell structure and a carbon composite coating containing magnesium phosphate

[0070] 1) Mix 0.1g of silicon nanoparticles with an average particle size of 50nm, 0.1g of hexachlorocyclotriphosphazene, 0.213g of 4,4'-dihydroxydiphenyl sulfone, and 0.033g of magnesium acetate in 70ml of ethanol until homogeneous;

[0071] 2) Disperse 2 ml of triethylamine in 30 ml of ethanol under stirring, and add it dropwise to the above solution. Continue the reaction at room temperature for 10 hours. After centrifugation, washing and drying, calcine the obtained particles at 500℃ under an argon atmosphere for 3 hours to obtain silicon nanoparticles with a carbon composite coating containing magnesium phosphate.

[0072] The silicon nanoparticles with a magnesium phosphate-containing carbon composite coating have a core-shell structure, as shown in the transmission electron microscope image below. Figure 1 As shown, the core is composed of silicon nanoparticles with an average particle size of 50 nm, and the shell is composed of a carbon composite layer containing magnesium phosphate with a thickness of 15 nm. The magnesium phosphate carbon composite coating layer uniformly covers the surface of the silicon nanoparticles. Energy dispersive X-ray spectroscopy analysis shows that magnesium phosphate accounts for 36% of the mass fraction of the coating layer, and the carbon content is 64%.

[0073] Example 2

[0074] Preparation of phenolic resin particles with a core-shell structure and coated with a carbon composite layer containing aluminum phosphate

[0075] 1) Mix 0.3g of 3-aminophenol resin particles with an average particle size of 400nm, 0.1g of hexachlorocyclotriphosphazene, 0.213g of 4,4'-dihydroxydiphenyl sulfone, and 0.052g of aluminum nitrate in 70ml of ethanol until homogeneous;

[0076] 2) Disperse 2 ml of triethylamine in 30 ml of ethanol under stirring, and slowly add it to the above solution using a peristaltic pump. Continue the reaction at room temperature for 10 hours. After centrifugation, washing, and drying, calcine the obtained particles at 500°C under an argon atmosphere for 3 hours to obtain phenolic resin particles with a carbon composite coating containing aluminum phosphate.

[0077] The phenolic resin particles with the aluminum phosphate-containing carbon composite coating have a core-shell structure, as shown in the transmission electron microscope image below. Figure 2 As shown. The core material consists of phenolic resin particles with an average particle size of 400 nm, and the shell material consists of a carbon composite coating layer of aluminum phosphate with a thickness of 10 nm. The aluminum phosphate carbon composite coating layer uniformly covers the surface of the phenolic resin particles. Energy dispersive X-ray spectroscopy analysis shows that aluminum phosphate accounts for 32% of the mass fraction of the coating layer, and the carbon content is 68%.

[0078] Example 3

[0079] Preparation of silica particles with a core-shell structure and a carbon composite coating containing iron phosphate

[0080] 1) Mix 0.3g of silica particles with an average particle size of 400nm, 0.1g of hexachlorocyclotriphosphazene, 0.213g of 4,4'-dihydroxydiphenyl sulfone, and 0.043g of ferric nitrate in 70ml of ethanol until homogeneous;

[0081] 2) Disperse 2 ml of triethylamine in 30 ml of ethanol under stirring, and slowly add it dropwise to the above solution. Continue the reaction at room temperature for 10 hours. After centrifugation, washing and drying, calcine the obtained particles at 500℃ under an argon atmosphere for 3 hours to obtain silica particles with a carbon composite coating containing iron phosphate.

[0082] The silica particles in the carbon composite coating containing iron phosphate have a core-shell structure, as shown in the transmission electron microscope image below. Figure 3 As shown. The core material is silica particles with an average particle size of 400 nm, and the shell material is a carbon composite coating layer containing iron phosphate with a thickness of 10 nm. The carbon composite coating layer containing iron phosphate uniformly covers the surface of the silica particles. Energy dispersive X-ray spectroscopy analysis shows that iron phosphate accounts for 44% of the mass fraction of the coating layer, and the carbon content is 56%.

[0083] Example 4

[0084] Preparation of lithium iron phosphate particles with a core-shell structure and a carbon composite coating containing vanadium phosphate

[0085] 1) Mix 1g of lithium iron phosphate (LiFePO4) particles (average particle size 300nm), 0.1g of hexachlorocyclotriphosphazene, 0.213g of 4,4'-dihydroxydiphenyl sulfone, and 0.035g of vanadium chloride in 70ml of ethanol until homogeneous;

[0086] 2) Disperse 2 ml of triethylamine in 30 ml of ethanol under stirring, and slowly add it to the above solution using a peristaltic pump. Continue the reaction at room temperature for 10 hours. After centrifugation, washing, and drying, calcine the obtained particles at 500°C under a nitrogen atmosphere for 1 hour to obtain lithium iron phosphate particles with a carbon composite coating containing vanadium phosphate.

[0087] The lithium iron phosphate particles with a carbon composite coating containing vanadium phosphate have a core-shell structure, as shown in the transmission electron microscope image below. Figure 4 As shown. The core material is lithium iron phosphate particles with an average particle size of 300 nm, and the shell material is a carbon composite coating layer containing vanadium phosphate with a thickness of 20 nm. The carbon composite coating layer containing vanadium phosphate uniformly covers the surface of the lithium iron phosphate particles. Energy dispersive X-ray spectroscopy analysis shows that vanadium phosphate accounts for 39% of the mass fraction of the coating layer, and the carbon content is 61%.

[0088] Example 5

[0089] I. Preparation of lithium nickel manganese oxide particles with a core-shell structure and a carbon composite coating containing titanium phosphate

[0090] 1) Lithium nickel manganese oxide (LiNi) 0.5 Mn 1.5 1g of O4 particles (average particle size of 300nm), 0.1g of hexachlorocyclotriphosphazene, 0.213g of 4,4'-dihydroxydiphenyl sulfone, and 0.05ml of tetrabutyl titanate were mixed evenly in 70ml of ethanol.

[0091] 2) Disperse 2 ml of triethylamine in 30 ml of ethanol under stirring, and slowly add it to the above solution using a peristaltic pump. Continue the reaction at room temperature for 10 hours. After centrifugation, washing, and drying, calcine the obtained particles at 500°C under a nitrogen atmosphere for 1 hour to obtain lithium nickel manganese oxide particles with a carbon composite coating containing titanium phosphate.

[0092] The lithium nickel manganese oxide particles with a carbon composite coating containing titanium phosphate have a core-shell structure, as shown in the transmission electron microscope image below. Figure 5 As shown, the core material consists of lithium nickel manganese oxide particles with an average particle size of 300 nm, and the shell material consists of a carbon composite coating layer containing titanium phosphate with a thickness of 15 nm. The carbon composite coating layer containing titanium phosphate uniformly covers the surface of the lithium nickel manganese oxide particles. Energy dispersive X-ray spectroscopy analysis shows that titanium phosphate accounts for 43% of the mass fraction of the coating layer, and the carbon content is 67%.

[0093] II. Preparation of lithium nickel manganese oxide electrodes with carbon composite coatings containing titanium phosphate

[0094] 0.16 g of lithium nickel manganese oxide particles with a carbon composite coating containing titanium phosphate prepared above were mixed with 0.02 g of conductive additive acetylene black, 0.4 g of PVDF binder with a mass concentration of 5%, and a small amount of solvent NMP. After slurry preparation, coating (with an aluminum sheet as the current collector), and drying, a lithium nickel manganese oxide electrode with a titanium phosphate and carbon composite coating was obtained, denoted as electrode 1.

[0095] III. Assembling the Battery

[0096] The nickel manganese oxide lithium electrode coated with titanium phosphate and carbon prepared above was used as the positive electrode and lithium metal was used as the negative electrode to assemble battery 1. The electrolyte was selected as 1M carbonate electrolyte, in which the solvent was DMC:DEC:EC = 1:1:1 (W / W / W) and the solute was LiPF6.

[0097] Furthermore, the difference between the assembled and comparative battery 1 is that the positive electrode material is uncoated lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5 The O4 positive electrode particle material is used, and the remaining steps are the same as those for battery 1.

[0098] IV. Battery Testing

[0099] The batteries were subjected to constant current charge-discharge tests using a charge-discharge apparatus. The test voltage range was 3.5–5V, and the test temperature was 25°C. Battery specific capacity and charge / discharge current were calculated based on the mass of lithium nickel manganese oxide.

[0100] Figure 6 The figure shows the cycle performance of battery 1 and control battery 1 at a charge / discharge current of 14.7 mA / g. As can be seen from the figure, the battery prepared using the coated modified cathode material of the present invention has an initial discharge specific capacity of 135 mAh / g and a discharge specific capacity of 130 mAh / g after 100 cycles, while the uncoated lithium nickel manganese oxide cathode material has a discharge specific capacity of 115 mAh / g after cycling. Therefore, the coated modified cathode material of the present invention has higher capacity retention and cycle stability.

[0101] Example 6

[0102] Preparation of lithium cobalt oxide particles with a core-shell structure and a carbon composite coating containing manganese phosphate

[0103] 1) Mix 3g of lithium cobalt oxide (LiCoO2) particles (average particle size 5μm), 0.1g of hexachlorocyclotriphosphazene, 0.213g of 4,4'-dihydroxydiphenyl sulfone, and 0.038g of manganese acetate in 70ml of ethanol until homogeneous;

[0104] 2) Disperse 2 ml of triethylamine in 30 ml of ethanol under stirring, and slowly add it to the above solution using a peristaltic pump. Continue the reaction at room temperature for 10 hours. After centrifugation, washing, and drying, calcine the obtained particles at 400°C in air atmosphere for 1 hour to obtain lithium cobalt oxide particles with a carbon composite coating containing manganese phosphate.

[0105] The lithium cobalt oxide particles with a carbon composite coating containing manganese phosphate have a core-shell structure, as shown in the transmission electron microscope image below. Figure 7 As shown. The core material is lithium cobalt oxide particles with an average particle size of 5 μm, and the shell material is a carbon composite coating layer containing manganese phosphate with a thickness of 15 nm. The carbon composite coating layer containing manganese phosphate uniformly covers the surface of the lithium cobalt oxide particles. Energy dispersive X-ray spectroscopy analysis shows that manganese phosphate accounts for 66% of the mass fraction of the coating layer, and carbon content is 34%.

[0106] Example 7

[0107] Preparation of lithium nickel cobalt manganese oxide particles with a core-shell structure and a carbon composite coating containing cobalt phosphate

[0108] 1) Lithium nickel cobalt manganese oxide (LiNi) 0.6 Co 0.2 Mn 0.2 3g of O2 particles (average particle size 5μm), 0.1g of hexachlorocyclotriphosphazene, 0.213g of 4,4'-dihydroxydiphenyl sulfone, and 0.038g of cobalt acetate were mixed evenly in 70ml of ethanol.

[0109] 2) Disperse 2 ml of triethylamine in 30 ml of ethanol under stirring, and slowly add it to the above solution using a peristaltic pump. Continue the reaction at room temperature for 10 hours. After centrifugation, washing, and drying, calcine the obtained particles at 400°C in air atmosphere for 1 hour to obtain lithium nickel cobalt manganese oxide particles with a carbon composite coating containing cobalt phosphate.

[0110] The lithium nickel cobalt manganese oxide particles with a carbon composite coating containing cobalt phosphate have a core-shell structure, as shown in the transmission electron microscope image below. Figure 8 As shown, the core material consists of lithium nickel cobalt manganese oxide particles with an average particle size of 5 μm, and the shell material consists of a carbon composite coating layer containing cobalt phosphate with a thickness of 8 nm. The cobalt phosphate and carbon composite layer uniformly covers the surface of the lithium nickel cobalt manganese oxide particles. Energy dispersive X-ray spectroscopy analysis shows that cobalt phosphate accounts for 69% of the mass fraction of the coating layer, and carbon content is 31%.

[0111] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controllably constructing a carbon composite coating layer containing phosphate, characterized in that, The method includes: (1) A reaction system is obtained by adding a coating substrate, a metal salt, and a polymeric monomer to a solvent. The polymeric monomer coordinates with the metal ions in the reaction system. The polymeric monomer includes at least a phosphorus-containing polymeric monomer A and a polymeric monomer B. The phosphorus-containing polymeric monomer A is hexachlorocyclotriphosphazene. The polymeric monomer B is selected from one or more of 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxybiphenyl, and 4,4'-diaminobiphenyl. In the reaction system, the concentration of the coated substrate is 0.1~150 g / L, the concentration of the metal salt is 0.002~0.02 mol / L, the concentration of polymeric monomer A is 0.004~0.04 mol / L, and the concentration of polymeric monomer B is 0.012~0.12 mol / L. (2) A polymerization initiator is slowly added to the reaction system. The polymer monomers coordinated with metal ions in the reaction system undergo a polymerization reaction and produce a precipitate, forming an intermediate containing phosphorus and metal polymer coating on the surface of the substrate particles; the temperature of the polymerization reaction is 10~40℃ and the time of the polymerization reaction is 1~30h. (3) The intermediate of the polymer coating layer prepared in step (2) is calcined, and the phosphorus-containing and metal-containing polymer coating layer on the surface of the intermediate is carbonized to obtain core-shell structured particles of phosphate-containing carbon composite coating layer; the calcination temperature is 400~900℃ and the time is 1~10h. The carbon composite coating layer of the phosphate is grown in situ on the surface of the core structure. The carbon composite coating layer of the phosphate is uniform, continuous, complete, and has a controllable thickness. In the composite coating layer, the content of phosphate is 20~90wt% and the content of carbon is 20~80wt%. The phosphate is selected from at least one of magnesium phosphate, aluminum phosphate, titanium phosphate, vanadium phosphate, manganese phosphate, iron phosphate, and cobalt phosphate.

2. The method according to claim 1, characterized in that, The solvent is selected from anhydrous organic solvents; The anhydrous organic solvent is of chromatographic purity and has a water content ≤0.1 wt%. The coating substrate is selected from at least one of the following: metals, nonmetals, carbides, nitrides, oxides, sulfides, phosphides, phosphates, lithium salts, and organic particles. The metal is selected from at least one of ruthenium, rhodium, palladium, silver, platinum, gold, germanium, tin, antimony and their alloys; The nonmetal is selected from at least one of carbon, silicon, phosphorus, sulfur, and selenium; The carbide is selected from at least one of titanium carbide, vanadium carbide, chromium carbide, tantalum carbide, tungsten carbide, boron carbide, and silicon carbide; The nitride is selected from at least one of titanium nitride, vanadium nitride, niobium nitride, tungsten nitride, boron nitride, silicon nitride, and phosphorus nitride; The oxide is selected from at least one of silicon dioxide, titanium dioxide, vanadium pentoxide, manganese dioxide, manganese tetroxide, ferric oxide, ferric oxide, cobalt tetroxide, nickel oxide, zirconium oxide, molybdenum oxide, indium tin oxide, tin oxide, and lithium lanthanum zirconium oxide. The sulfide is selected from at least one of titanium disulfide, iron sulfide, cobalt sulfide, nickel sulfide, molybdenum sulfide, tin sulfide, and antimony sulfide; The phosphide is selected from at least one of titanium phosphide, iron phosphide, cobalt phosphide, nickel phosphide, molybdenum phosphide, and tin phosphide; The phosphate is selected from at least one of titanium phosphate, titanium pyrophosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium vanadium phosphate, sodium vanadium phosphate, iron phosphate, lithium iron phosphate, lithium iron manganese phosphate, and lithium cobalt phosphate. The lithium salt is selected from at least one of lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide. The organic compound is selected from at least one of phenolic resin, urea-formaldehyde resin, and polystyrene.

3. The method according to claim 1, characterized in that, In the reaction system, the metal ions are derived from metal salts; the metal salts are selected from at least one of the chloride, sulfate, nitrate, acetate, and alkoxide salts of the corresponding metal element.

4. The method according to claim 1, characterized in that, The initiator is a solution of triethylamine; The concentration of the initiator is 0.2~2.0 mol / L; The initiator is added slowly by dripping using a peristaltic pump; The initiator is added slowly under stirring conditions; The calcination atmosphere is at least one of air, oxygen, nitrogen, and argon.

5. A core-shell structured particle with a phosphate-containing carbon composite coating, prepared by the method according to any one of claims 1-4, wherein, The core structure is selected from the coating substrate described in claim 2, and the carbon composite coating layer of the phosphate is grown in situ on the surface of the core structure. The carbon composite coating layer of the phosphate is uniform, continuous, complete, and has a controllable thickness. The composite coating layer contains 20-90 wt% phosphate and 20-80 wt% carbon. The phosphate is selected from at least one of magnesium phosphate, aluminum phosphate, titanium phosphate, vanadium phosphate, manganese phosphate, iron phosphate, and cobalt phosphate.

6. The core-shell structured particles with a phosphate-containing carbon composite coating according to claim 5, characterized in that, The phosphate content in the composite coating layer is 20-60 wt%. The carbon content in the composite coating layer is 20-70 wt%.

7. The core-shell structured particles with a phosphate-containing carbon composite coating according to claim 5, characterized in that, The thickness of the composite coating layer is 1~200nm; The average particle size of the nuclear structure is 50 nm to 10 μm.

8. The core-shell structured particles with a phosphate-containing carbon composite coating according to claim 5, characterized in that, The thickness of the composite coating layer is 1–20 nm.

9. The core-shell structured particles with a phosphate-containing carbon composite coating according to claim 5, characterized in that, The core-shell structured particles are selected from at least one of the following: magnesium phosphate carbon composite coated silicon nanoparticles, aluminum phosphate carbon composite coated phenolic resin, iron phosphate carbon composite coated silicon dioxide, vanadium phosphate carbon composite coated lithium iron phosphate, titanium phosphate carbon composite coated lithium nickel manganese oxide, manganese phosphate carbon composite coated lithium cobalt oxide, and cobalt phosphate carbon composite coated lithium nickel cobalt manganese oxide.

10. The application of the core-shell structured particles according to any one of claims 5-9 in lithium-ion batteries.

11. A positive electrode material, characterized in that, The cathode material comprises the core-shell structured particles as described in any one of claims 5-9.

12. A high-energy lithium storage device, characterized in that, The high-energy lithium storage device comprises the core-shell structured particles as described in any one of claims 5-9 or the cathode material as described in claim 11.

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