4218 results about "Cyclic stability" patented technology

The invention belongs to the fields of material synthesis and energy technology, and especially relates to a graphene/metal oxide composite cathode material for lithium ion batteries and a preparation method thereof. Grapheme is dispersed into various metal oxide precursor salt solutions; a graphene/metal oxide compound is obtained directly by a hydrothermal method, or an graphene/metal oxide compound is obtained by a liquid in-situ polymerization method or a coprecipitation process; and the graphene/metal oxide compound is obtained by heat treatment or hydrothermal treatment. In the invention, the novel three-dimensional composite cathode material of graphene-coated metal oxide or graphene-anchored metal oxide is prepared by carrying metal oxide particles with graphene as a carrier. The obtained composite material can be used as a lithium ion battery cathode, which has a high specific capacity, excellent cycle stability and rate capability, and is expected to be used as a lithium ion battery cathode material with a high energy density and a high power density.

The invention discloses an electrode material of composite lithium titanate and its preparation method, which is secondary particles with spherical or similar spherical shape and porous nanometer channels, which is made from lithium titanate particles, nano-carbon coated materials and doped modifier. The preparation method includes: milling the inorganic lithium salt, titanium dioxide, nano-carbon coated material or doped modifier, scattering them into the organic solvent for further drying, processing heat treatment, and cooling. Comparing with the existing technologies, this electrode material has the high-rate performance, highly reversible electrochemical capacity, and smaller surface area to enhance its first Coulomb efficiency and cycle stability, applying to rechargeable and once-use lithium-ion battery.

The invention provides a multi-element composite nano-material for a super capacitor, and a preparation method of the nano-material. The nano-material comprises a carbon material, metal oxide and conducting polymer, and components of the nano-material can be two or more than two materials. By the aid of the characteristics such as fine electrical conductivity, long cycle life and high specific surface area of the carbon material, high pseudo-capacitance of the metal oxide and low internal resistance, low cost and high operating voltage of the conducting polymer, different types of electrode materials generate synergistic effects, advantages are mutually combined, shortcomings are mutually weakened, the energy storage characteristics of an electric double-layer capacitor and a pseudo-capacitor are simultaneously made full use of, a composite electrode material with high power density, fine circulating stability and higher energy density is prepared, and the multi-element composite nano-material is excellent in comprehensive performance when used for an electrode of the super capacitor, has the advantages of simple preparation process, short cycle, low cost and the like, and is suitable for large-scale industrial production.

The subject of the invention is an anode material of the silicon-carbon composite type, for a lithium cell, having a high mass capacity and good cycling stability. This material is obtained by a preparation method comprising the steps consisting of:

• • a) providing a silicon powder obtained by the plasma-enhanced chemical vapour deposition (PECVD) technique or by CO₂ laser, the size of the silicon particles being less than 100 nm; b) mixing the silicon powder with a carbon-containing polymer, and c) carrying out the pyrolysis of the mixture. The invention also proposes a lithium cell containing at least one anode the material of which contains the nanocomposite material produced by this method.

The invention discloses a grapheme/silicon composite material for a lithium ion battery cathode material and a preparation method thereof, belonging to the fields of electrochemistry and new energy materials. The method comprises the following steps of: using graphite as a raw material; oxidizing the graphite into oxidized graphite by adopting oxidants of concentrated sulfuric acid and potassium permanganate; then, ultrasonically stripping the oxidized graphite to prepare oxidized graphene; mixing oxidized graphene in different proportions with nano silicon powder; ultrasonically dispersing, filtering or directly drying into a cake/film; and roasting under a reduction atmosphere to prepare self-support graphene/silicon composite film materials in different proportions. Proved by electrochemistry tests, the graphene/silicon composite film material prepared by the method has higher specific capacity and cycle stability, simple preparation method and easy mass production and consequently is an ideal high-energy lithium ion battery cathode material.

The invention discloses a method for preparing graphene aerogel and graphene/ metallic oxide aerogel. The method is characterized in that graphite oxide aqueous solution serves as a raw material, alcohol serves as a cross-linking agent, a precursor solution is obtained through the simple mixing and dispersing processes, the hydrothermal method is adopted, the freeze drying method or a supercritical drying method is adopted, and then the graphene aerogel is obtained . The graphene/ metallic oxide aerogel can be prepared by adding metallic oxide into the polymeric precursor solution. On one hand, the graphene vinyl aerogel material has the characteristic of the graphene aerogel, and on the other hand, the graphene vinyl aerogel material can have the physicochemical characteristic of the metallic oxide. In addition, the aerogel material has a large specific surface and good electrical conductivity, can directly serve as a supercapacitor electrode, and has large specific capacity, good rate capability and cycling stability. The materials used in the method are low in cost, the industrial process is simple, and the method is friendly to the environment.

A preparation method of a high power capacity lithium ion battery cathode material uses natural spherical graphite to serve as raw materials, uses concentrated sulfuric acid to serve as an inserting layer agent, uses potassium permanganate to serve as an oxidizing agent, conducts expansion treatment at high temperature to obtain micro-expanded graphite, then enables the micro-expanded graphite in different proportions to be mixed with nanometer ganister sand, conducts ultrasonic dispersion, suction filtration and dying to obtain the micro-expanded graphite with the nanometer ganister sand inserted in layers, enables the micro-expanded graphite to be mixed and coated with carbon source carbon source according to certain proportion, and finally conducts carburizing sintering under inert gas shielding to prepare completely coated silicon carbon composite cathode material with sufficient obligated obligate inside. Electrochemistry shows that the silicon carbon composite material prepared by the preparation method has high specific capacity and cycling stability and is the ideal high power capacity lithium ion battery cathode material.

The invention relates to a lithium battery with a polymer-coated sulfur/carbon composite material as an anode. According to the invention, sublimed sulfur or sulfur powder and a conductive carbon material are mixed according to a mass ratio of 3:7-8:2; the mixture is subject to ball milling, such that a sulfur/carbon composite material is obtained; the composite material is dispersed in a solution, and a polymer monomer is added to the solution; under a low temperature and the protection of inert gas, an oxidizing agent is added for initiating polymerization; the material is centrifuged, washed, and dried; the obtained polymer-coated elemental sulfur/carbon composite material, acetylene black and PTFE are mixed; a dispersant is added to the mixture, and the mixture is sufficiently mixed by stirring; the mixture is rolled into a sheet, and is vacuum-dried under a temperature of 55 DEG C, such that an electrode sheet is obtained. The prepared electrode sheet is adopted as an anode, metal lithium is adopted as a cathode, and a solvent type organic solution system containing 0.2mol/L of a waterless lithium nitrate additive is adopted as electrolyte, and a battery is assembled. With the electrode material, the assembled lithium battery is advantaged in high specific capacity, good circulation stability, and excellent heavy-current charge/discharge performances. The preparation method is advantaged in simple process, low cost, and good repeatability.

The invention relates to the technical field of energy storage material, in particular to inorganic phase change energy storage material. The material comprises the following components by mass: 70 to 99.5 % of energy storage material, 0.25-20 % of nucleating agent, 0.1-15 % of modifying agent and 0.1-15 % of water. The bases hydrate or crystalline hydrous salt, especially the bases hydrate is adopted as energy storage material; the nucleating agent adopts carbonate; and the modifying agent is dispersant. According to the inorganic phase change energy storage material, by selecting proper nucleating agent and the ration of the nucleating agent, material phase separation can be effectively solved, especially the phase change energy storage material prepared by adding the dispersant into a system has good cycling stability, and simultaneously the potential heat value does not change after circulation for thousands of times.

There are provided an anode for a lithium metal polymer secondary battery comprising an anodic current collector having a surface on which a plurality of recesses having a predetermined shape are formed and a method of preparing the same. The plurality of recesses are formed on a surface of the anodic current collector using a physical method or a chemical method. In a lithium metal polymer secondary battery employing the anode, oxidation/reduction of lithium and the formation of dendrite occur only in the recesses formed by surface patterning of the anodic current collector. Thus, expanding and shrinking of a battery due to a change in the thickness of the lithium anode can be prevented and cycling stability and the lifespan of a battery can be improved.

The invention discloses a preparation method of a spherical doped Al-Ni lithium cobalt oxide for lithium-ion battery. The preparation steps are that: first, sulfate, nitrate or chlorate of Al-Ni-Co react with strong alkali that is added with complex agent in liquid phase; the pH value, the temperature and the feeding speed of the reaction solution are controlled so as to produce a spherical precursor of Al-Ni-Co hydroxide; then the spherical precursor of Al-Ni-Co hydroxide is dried and evenly mixed with lithium hydroxide, lithium nitrate or lithium carbonate and dried; the obtained mixture is roasted into a spherical doped Al-Ni lithium cobalt oxide. The spherical doped Al-Ni lithium cobalt oxide has comparatively high tap density and remarkable cycle stability in the process of high-rate charge/discharge cycle, which improves over charge performance of Ni-Co substance and first obviously enhances charge/discharge efficiency; in addition, the preparation method of the spherical doped Al-Ni lithium cobalt oxide has the advantages of being simple, controllable and suitable for industrialized production with low energy consumption, high efficiency, short reaction time and low cost.

The invention discloses a transition metal oxide/graphene composite material, which consists of a nanometer transition metal oxide and graphene, wherein the transition metal oxide is MnO, Fe2O3, Cr2O3, Cu2O, CuO or V2O5. Because of the dispersing and loading effects of the graphene, the transition metal oxide in the composite material can be distributed uniformly and is small in particle size, and the stability and the cyclical stability of the transition metal oxide in the process of charging and discharging can be effectively improved. The invention also discloses a one-step low-temperature preparation method of the composite material, which has the advantages of simple process, low cost, short cycle, low energy consumption and the like, and is suitable for large-scale industrial production.

The invention discloses a preparation method of a composite lithium metal anode and belongs to the technical field of lithium metal batteries. The preparation method of the composite lithium metal anode comprises steps as follows: firstly, the surface of a framework material is modified, the framework material with the lithiophilic surface is prepared, the framework material is contacted with liquid metal lithium, so that the liquid metal lithium is injected into the framework material with the lithiophilic surface, and the composite lithium metal anode is prepared after cooling. The lithiophilic surface can be obtained through modification of various framework materials (including a conductive framework material and an insulated framework material), the framework materials are efficientlycomposited with the liquid metal lithium, and the composite lithium metal anode material is obtained. When the obtained composite lithium metal anode material is assembled in a total battery, growthof lithium dendrites can be effectively inhibited, the volume expansion effect of the anode is relieved, the pulverization phenomenon of the lithium metal anode is reduced, and the cycling stability and the safety of the lithium metal battery are substantially improved, and the cycle life of the lithium metal battery is substantially prolonged.

The invention relates to a synthesis and surface modification method of a lithium rich anode material Li1+xM1-xO2 (M is one or more of Ni, Co and Mn, and X is more than or equal to 0 and less than or equal to 1/3) for a lithium ion battery. The method comprises the following steps of: synthesizing a precursor by using a carbonate precipitation method, mixing the precursor and a lithium salt, and calcining for 2 to 20 hours at the temperature of between 800 and 1,100 EG C to obtain a lithium rich material, wherein the prepared lithium rich material has controllable particle size and higher reversible capacity; and dissolving persulfate or sulfate in an amount which is 5 to 80 mass percent of the lithium rich material into deionized water, adding the lithium rich material, stirring for 2 to 100 hours at the temperature of between 25 and 80 DEG C, heating the materials to the temperature of between 100 and 500 DEG C in a muffle furnace, calcining the materials for 2 to 20 hours, fully filtering the obtained materials, and washing off impurities to obtain the surface modified anode material Li1+x-yM1-xO2. The synthesized lithium rich material has controllable particle size; the first charge/discharge efficiency of the lithium rich material and the discharge specific capacity and the cyclical stability under high magnification can be improved; and the method is simple, low in cost, convenient for operation and suitable for industrialized production.

The invention discloses a lithium ion battery silicon carbide composite anode material and a preparation method thereof and aims to solve the technical problem of improving the cycling stability of a silicon carbide cathode. The lithium ion battery silicon carbide composite anode material consists of the following components in percentage by mass: 85 to 75 percent of graphite and 15 to 25 percent of silica particles, wherein the nano silica particles are dispersed on a graphite carrier to form a nuclear shell structure and are 5 to 16 mum in granularity. The preparation method comprises the following steps of: preparing a graphite dispersing agent and a silicon grinding dispersing agent; adding the silicon grinding dispersing agent into the graphite dispersing agent; and performing thermal treatment. When the method is compared with the prior art, silicon atoms are dispersed on a graphite atomic nucleus by a cation-anion charge absorption method, so that the silicon atoms can uniformly wrap the surface of the graphite, the dispersity of silicon is effectively improved in a silicon carbide composite material preparing process, the initial efficiency and the cycling stability of the silicon carbide composite anode material are improved, and a battery using the material as an anode material has relatively high safety, multiplying power performance and cycle performance.

The invention relates to a high polymer-based graphene composite material with positive resistance temperature coefficient, and a preparation method of the material. The composite material comprises a base body and conductive filler; the content of conductive material is 0.01-10wt%; all components are mixed uniformly and are formed through mold-pressing or extrusion/injection molding; and the formed material is irradiated after being dried, so that the high polymer-based graphene composite material with positive resistance temperature coefficient can be obtained. Compared with the prior art, the graphene composite material and the preparation method have the advantages that the manufacturing process is simple, less influence is caused to the performance of base material, oxidation is unlikely to occur, the resistivity is more stable, the circulation stability of the material is better, and NTC (Negative Temperature Coefficient) effect is not generated easily.

The invention discloses a method for improving the cycling stability of a lithium ion battery anode material, belonging to the field of lithium ion battery anode materials. The lithium ion battery anode material comprises an anode material and metal oxides uniformly and compactly coated on the surface of the anode material, wherein the anode material comprises lithium manganate, lithium manganous silicate, lithium-nickel-cobalt-manganate and the like, and the metal oxides mainly comprise Al2O3, ZnO, TiO2, Nb2O5, ZrO2, Ta2O5 and the like. Due to the adoption of the metal oxide coating layer, lithium ions can be rapidly and better transmitted, and an electrolyte can be prevented from being in contact with the anode material in a cycling process and further the anode material is prevented from dissolving in the electrolyte, and thus the cycling stability of the anode material is improved. The method has the advantages of simplicity in operation, low cost, high efficiency, and the like; and massive and industrialized production can be easily realized.

The invention provides a method for preparing a multilevel porous carbon base composite phase change material, and belongs to the field of composite phase change materials. The method comprises the following steps: at first, preparing an organic metal skeleton material by using such methods as a solution method, a solvothermal method or a stirring synthesis method; with the organic metal skeleton material as a template, high temperature carbonizing under the protection of an inert gas, and changing the carbonizing temperature and the post treatment manner to obtain a multilevel porous carbon material with a super-large specific surface area and a super-large pore volume; selecting proper solvents according to different kinds of phase change core materials, preparing the phase change core materials to a solution, dispersing the porous carbon material into the solution, removing the solvent by such manners as heating, and meanwhile the phase change core materials are adsorbed and limited in the porous carbon material. The composite phase change material prepared by the method provided by the invention has good thermal storage property, can effectively avoid the leakage problem of the phase change core material, and has the advantages of excellent heat transfer property, good cycling stability and wide application range, and the process is simple and is suitable for large-scale production.

The invention relates to a preparation method of lithium iron phosphate for the carbon cladding of a lithium ion battery. The prior lithium iron phosphate preparation technical art is complex, and has high cost. The invention has the synthetic process that: ferric oxide, phosphoric acid, simple organics and doped element compound are mixed and dried, the mol ratio of phosphate radical ion, ferric ion and doped element ion is 1:y:z, wherein, y is larger than or equal to 0.95 and smaller than or equal to 1, and y plus z is equal to 1; the mixture is added with lithium source compound, added with water to be mixed and dried, the mol ratio of lithium ion and phosphate radical ion is x:1, and x is larger than or equal to 0.95 and smaller than or equal to 1.05; the mixture which reacts for 2 to 20 hours under 500 to 800 DEG C is cooled in a furnace. The invention finally produces the precursor uniformly mixed with superfine crystal grain, and during the subsequent high temperature solid phase reaction, the end product lithium iron phosphate can be produced through shorter distance diffuseness of atoms. The end product has high purity, the crystallisation is good, the capacity is high, and the cycle stability is good.

The invention provides a preparation method of a nano porous metal oxide/carbon lithium ion battery cathode material. The preparation method comprises the following steps: firstly, weighting ferric salt or manganese salt and carboxylate organic ligands, and putting into a high-pressure reaction kettle; and after a polar solvent is added and dissolved, carrying out a hydrothermal reaction for 10-72h at 100-180 DEG C to generate a transition metal coordination polymer precursor; and after the transition metal coordination polymer precursor is washed and dried, decomposing the precursor for 0.5-6h at a temperature of 300-600 DEG C in an inert atmosphere in a tube furnace, thus obtaining a nano porous metal oxide/carbon lithium ion battery cathode material containing iron oxides or manganese oxides. According to the preparation method, since the transition metal coordination polymer precursor which is structurally designable and controllable is used as a template-type precursor, a nano porous metal oxide/carbon lithium ion battery cathode material is obtained by using an in-situ thermal decomposition method. The method is simple in process, and the obtained products have the advantages of high electrical conductivity, high specific capacity, good cycle stability, excellent high-ratio discharge performance and high energy density.

The invention discloses a carbon nano tube-containing sulfur-based composite cathode material and a preparation method thereof. The sulfur-based composite cathode material is a ternary composite material AxByCz, wherein A is a dehydrocyclization product of an acrylonitrile-itaconic acid copolymer; B is elemental sulfur; C is a carbon nano tube; x is more than or equal to 30 weight percent and less than or equal to 60 weight percent; y is more than or equal to 30 weight percent and less than or equal to 60 weight percent; and z is more than or equal to 1 weight percent and less than or equal to 20 weight percent. The preparation method comprises the following steps of: in-situ polymerizing an acrylonitrile-itaconic acid monomer on the surface of the multi-wall carbon nano tube, and performing thermal treatment on both of the acrylonitrile-itaconic acid copolymer and the elemental sulfur, so that the sulfur is uniformly dispersed in a substrate formed by the dehydrocyclization of the acrylonitrile-itaconic acid copolymer. The carbon nano tube-containing sulfur-based composite cathode material and a lithium cathode form a secondary lithium-sulfur battery which is charged and discharged at the room temperature. The carbon nano tube-containing sulfur-based composite cathode material has the reversible specific capacity of 697 mAh/g and high cyclical stability.

The invention discloses an MOFs (metal-organic frameworks) based carbon dioxide adsorbent, which includes MOFs and organic amine loaded in the pore channels and on the surface of MOFs. The mass ratio of the MOFs to the organic amine is 0.1-10:1. The MOFs based carbon dioxide adsorbent provided by the invention realizes the combined action of physical adsorption and chemical adsorption and can adsorb and store carbon dioxide at medium and low temperature, and regeneration and reutilization of the adsorbent can be realized under certain condition. The MOFs based carbon dioxide adsorbent has good adsorption capacity, high selectivity and cycling stability on carbon dioxide, and can overcome the disadvantages of easy volatilization and easy corrosion of equipment in organic amine so as to meet the industrial processing requirements. The invention also discloses a preparation method of the MOFs based carbon dioxide adsorbent and application of the adsorbent in adsorption of carbon dioxide in flue gas.

The invention relates to a layered lithium-rich anode material clad by metal fluoride, and a preparation method thereof. According to the invention, a layered lithium-rich material Li[Li(1-2x)/3MxMn(2-x)/3]O2 is prepared with a combined technology of a oxalate precipitation method and a hydro-thermal method, wherein M is Ni, Co, Cr or any two of them which coexist, and x=0 to 0.33. The lithium-rich material is impregnated in a solution of soluble salts of metals such as yttrium, magnesium and iron; a soluble fluoride solution is added to the mixture, wherein n(Me):n(F)=1:y; the solution is continuously stirred for 3-8h in a water bath with a temperature of 60-90 DEG C; the solution is subject to centrifugal washing, and is dried under a temperature of 60 DEG C in a vacuum thermostat; a material obtained after drying is roasted for 4-8h under a temperature of 400 DEG C and under the protection of argon gas, such that Li[Li(1-2x)/3NixMn(2-x)/3]O2 clad by a fluoride MeFy is prepared. The electrode material provided by the invention is advantaged in high electrochemical capacity, good cyclical stability, excellent rate performance, and the like. The preparation process is simple, the cost is low, and the reproducibility is good.

The invention relates to a phase-change energy-storage material which comprises the following components in percentage by mass: 75%-99% of an energy storage main body material, 0.1%-10% of a thickening agent, 0.2%-15% of a nucleating agent and 0.01%-8% of a reinforcing material, wherein the energy storage main body material comprises crystal water and salt; the thickening agent comprises one or more of an inorganic thickening agent, fibers, polyacrylates, polyurethanes and a natural polymer thickening agent; the nucleating agent comprises one or more of sodium pyrophosphate, sodium phosphate decahydrate, calcium sulfate dihydrate, potassium sulfate, potassium borate, barium hydroxide octahydrate, sodium phosphate dibasic dodecahydrate and sodium sulfate; the reinforcing material comprises one or more of metal and metal oxide powder, carbon materials, nanoparticles and foam materials. By selecting proper materials and ratio, the supercooling degree and the phase separation phenomenon are reduced and good circulating stability is achieved; especially the reinforcing material is added into a system to form a heat-conducting network so as to improve the heat conductivity of the material by more than two times.

The invention relates to an electrode material of a lithium ion battery, in particular to a method for pre-lithiating a cathode material. The method comprises the steps that an electrolytic cell cathode cavity is made of the electrode material such as a lithium ion cathode material and arranged in a lithium ion conductive organic electrolyte; an anode cavity is an aqueous solution containing lithium salt or an organic solution; the anode cavity is separated from the cathode cavity by a lithium ion conductor ceramic membrane or a composite membrane of lithium ion conductor ceramic and a high molecular material; an electric potential and current density are controlled by external circuit charge and discharge equipment to allow lithium ions to migrate to a cathode from an anode through the membrane; and an SEI (Solid Electrolyte Interphase) membrane is formed on the surface of the material; or the electrode material is pre-lithiated. According to the method, a cheap and safe lithium ion saline solution serves as a source of the lithium ion; the SEI membrane is generated for the cathode of the lithium ion battery in advance; or lithium is supplemented to the electrode material; the coulombic efficiency and cycling stability of the cathode material can be improved; a formation process in production of the lithium ion battery in the prior art is simplified; the electrode material and cost are saved; and the method is safe and efficient and has a large-scale application prospect.

Provided is a lithium mixed transition metal oxide having a composition represented by Formula I of Li_xM_yO₂ (M, x and y are as defined in the specification) having mixed transition metal oxide layers (“MO layers”) comprising Ni ions and lithium ions, wherein lithium ions intercalate into and deintercalate from the MO layers and a portion of MO layer-derived Ni ions are inserted into intercalation/deintercalation layers of lithium ions (“reversible lithium layers”) thereby resulting in the interconnection between the MO layers. The lithium mixed transition metal oxide of the present invention has a stable layered structure and therefore exhibits improved stability of the crystal structure upon charge/discharge. In addition, a battery comprising such a cathode active material can exhibit a high capacity and a high cycle stability. Further, such a lithium mixed transition metal oxide is substantially free of water-soluble bases, and thereby can provide excellent storage stability, decreased gas evolution and consequently superior high-temperature stability with the feasibility of low-cost mass production.

The invention relates to a preparation method of a silicon/graphene laminar composite material for lithium ion battery cathode. The composite material adopts a laminar sandwich structure, silicon nano-particles are dispersed on each lamina of the grapheme, the laminas of the grapheme are separated from one another by the silicon nano-particles and the edges of the laminas are in lapped joint so as to constitute a laminar conductive network structure. The preparation method thereof comprises the steps of: formulating anhydrous silicon tetrachloride, surface active agent, sodium naphthalene and graphite oxide to tetrahydrofuran solution, adding the tetrahydrofuran solution into a reactor for reaction in vacuum at the temperature ranging from 380 to 400 DEG C, filtering the reactant to result in the product, and then washing, drying and heating the product to obtain the silicon/grapheme composite material. The preparation method of the invention has the advantages of simple preparation process and great easiness for industrial production; and the silicon/graphene laminar composite material prepared according to the method includes excellent conductivity, power performance, electrochemical activity and cycle stability, and is particularly suitable for manufacturing lithium ion battery cathode.

The invention belonging to a preparation method of LiFePO4 material, the LiFePO4 material is wrapped with 1-10% weight carbon material, the range of the high tap density of the composite material is 1.0-1.6g per cubic centimeter, the range of the diameter of the first particle is 0.1-3 um; the preparation method comprises a ball milling iron source, a Lithium source, a Phosphate source compound, and a dopant that are made into slurry materials; the slurry materials are dried by a spray granulating drier; after sintering and cooling, the slurry materials are ground and classified and then sieved to obtain the LiFePO4 material; as the spray granulating drier is adopted, the tap density is improved; the air inlet temperature is controlled when spray drying, thereby improving circulation stability; as the diameter and distribution of the particles are controlled, the diameter of the first particle is not more than 3um generally, so as to reduce path and resistance of lithium ion dispersion and improve rate characteristic, moreover the invention has low cost and less pollution.

A composite-coated lithium iron phosphate in a three-dimensional nanonetwork layered structure and a preparation method therefor, and a lithium ion battery, wherein a composite is prepared by compounding a conducting polymer, graphene and a carbon nano tube. The preparation method for the coated lithium iron phosphate comprises the following steps: doping the composite and anhydrous ferric phosphate in situ in the process of preparing the anhydrous ferric phosphate, serving as a lithium iron phosphate precursor, then mixing the composite in-situ doped anhydrous ferric phosphate, a lithium source, a traditional carbon material and a solvent to obtain slurry, spray drying the slurry, and calcining to obtain the composite-coated lithium iron phosphate in a three-dimensional nanonetwork layered structure. The preparation method is simple and has a wide raw material source, low cost and very broad practical application prospect. Serving as an anode material of the lithium ion battery, the coated lithium iron phosphate has higher electrical conductivity and cycling stability, and more excellent comprehensive electrochemical performance.

The invention discloses a graphene modified lithium iron phosphate/carbon composite material and its application. The graphene modified lithium iron phosphate/carbon composite material is prepared by the following steps of: using a solvent-thermal in-situ composite mode and adding a surfactant to prepare a lithium iron phosphate/graphene composite material, adding an aqueous solution of water-soluble carbon source, controlling the carbon content, carrying out drying and annealing treatments on the mixture to obtain the graphene modified lithium iron phosphate/carbon composite material. The graphene modified lithium iron phosphate/carbon composite material prepared in the invention can be used as the positive electrode active material for lithium ion cells and can be used to remarkably improve the electrochemical performance, especially the charge-discharge performance and the cycle stability of cells.