303results about How to "Improve fast charging performance" patented technology

The invention discloses a lithium iron phosphate battery. The lithium iron phosphate battery comprises a positive electrode, a negative electrode, an isolating membrane and an electrolyte, a main material of the positive electrode comprises lithium iron phosphate, and a main material of the negative electrode comprises graphite and a silicon-based material; the surface density of the positive electrode is greater than or equal to 23mg / cm < 2 >, and the surface density of the negative electrode is greater than or equal to 7.8 mg The electrolyte comprises a lithium salt, a solvent and an additive, the solvent mainly comprises ethylene carbonate and a micromolecular linear solvent, the additive comprises FEC and a negative electrode film-forming additive, and a negative electrode film-forming agent comprises vinylene carbonate and a lithium salt additive; the mass fraction of the micromolecular linear solvent is 35%-60%, the mass fraction of the fluoroethylene carbonate is M, the mass fraction of the silicon element in the negative electrode layer is W1, M is greater than or equal to 2% and less than or equal to 2 * W1, and the mass fraction of the negative electrode film-forming agent is 4%-6%. The energy density of the battery cell can be improved and the cycle life and the quick charge capacity of the battery cell are both considered by doping a silicon-based material into the negative electrode, designing a thick electrode and adjusting an electrolyte formula.

The invention provides a preparation method of a lithium iron phosphate material, a lithium ion battery and electric equipment, and relates to the technical field of batteries. The method comprises the following steps: mixing raw materials of an iron source, a lithium source and a phosphorus source with a reagent serving as a reducing agent and a carbon source, and grinding to obtain precursor powder; wherein the molar ratio of the lithium source to the iron source is 1.03-1.05, and the molar ratio of the iron source to the phosphorus source is 0.965-0.99; carrying out high-temperature treatment on the precursor powder in an inert atmosphere to obtain a lithium iron phosphate base material; and crushing the lithium iron phosphate base material to obtain the lithium iron phosphate material meeting the particle size requirement. The high-capacity and high-compaction lithium iron phosphate material is obtained by accurately controlling key indexes such as the iron-phosphorus ratio, the carbon content, the graphitization degree and the particle size and combining an optimized processing technology, so that the fast charging performance of a lithium ion battery is improved, and the effect of not reducing the electric quantity while the fast charging requirement is met is achieved.

The invention relates to the technical field of electrochemistry, and particularly discloses a positive pole piece, an electrochemical device comprising the positive pole piece and an electric device. The positive pole piece comprises a first active material with a particle size of 4-20 [mu] m and a second active material with a particle size of 200-600 nm, the first active material comprises lithium manganese iron phosphate with the manganese content of m%, the second active material comprises lithium manganese iron phosphate and / or lithium iron phosphate with the manganese content of n%, and m and n meet the condition that m-n is larger than or equal to 15 and smaller than or equal to 85. According to the invention, by controlling the particle size distribution in the positive electrode active material and the manganese content relationship, the electrochemical device containing the positive electrode plate has excellent fast charging performance and energy density.

The invention relates to the technical field of lithium batteries, in particular to a composite binder aqueous solution, a silicon-based negative pole piece and a preparation method and application of the silicon-based negative pole piece. The preparation method of the composite binder aqueous solution comprises the following steps: dissolving a water-based polymer binder and a micromolecular physical crosslinking agent in water, adding pyrrole, stirring, adding an initiator, and mixing to obtain the composite binder aqueous solution. A small molecule physical cross-linking agent is introduced into the water-based polymer binder, and a large number of hydrogen bond binding sites are increased, so that the mechanical property of the binder is remarkably enhanced, and the machinability of the pole piece is further improved. Meanwhile, polypyrrole can be generated in the binder through in-situ polymerization, and the polypyrrole can be tightly coated on the surfaces of the silicon particles through strong interaction between the binder and the silicon particles to form a stable conductive network, so that the charge transfer capability of the electrode is remarkably improved. In addition, the composite binder is also beneficial to formation of a solid electrolyte layer rich in Li-N and participates in formation of a solid electrolyte interface layer, so that the lithium ion transmission capability of the composite binder is further improved.

The present invention discloses a method for preparing a lithium battery high energy density and fast charging graphite negative electrode material, comprising the following steps: mixing, briquetting, and graphitization. The modified graphene is evenly distributed in the graphite phase, and the two have good contact performance, which greatly enhances the conductivity of the graphite material and its coating layer. The amount of conductive agent added can be reduced in the manufacturing process, so that more active substances can be placed in a limited battery space, increasing the energy density of the battery; secondly, catalytic graphitization can increase the capacity of graphite to more than 360 mAh / g, further improving the energy density of the battery; the synergistic effect brought about by graphene modification and catalyst pore formation improves the fast charging performance, and graphene forms a rich conductive network between graphite and granulated coating layers, reducing system impedance and battery polarization, improving conductivity, and enhancing the rate characteristics of the battery. The catalyst volatilization will leave abundant pores, providing a convenient path for the diffusion of lithium ions, and improving the fast charging performance.

The invention relates to the field of batteries, in particular to a negative plate and a battery comprising the negative plate. The negative plate comprises a negative current collector, a bottom coating and a negative active material layer, the bottom coating and the negative active material layer are positioned on one side or two sides of the negative current collector, the bottom coating is positioned between the negative current collector and the negative active material layer, the bottom coating comprises a three-dimensional structure formed by a first conductive binder, the first conductive binder comprises a first carbon nano tube, and the first carbon nano tube comprises a second carbon nano tube. The negative plate meets the following relational expression: 1.2 < = B / K < = 3.4, B is the length-diameter ratio of the first carbon nanotube, and K is the tensile strength of the negative current collector. According to the negative plate, the thickness of the priming coat can be greatly reduced, and the energy density of the battery is increased; the binding power between the negative electrode current collector and the negative electrode active material layer can be enhanced, the structural stability of the active material layer can be improved, the pole piece deformation and powder falling in pole piece processing and battery circulation can be improved, and the circulation expansion can be inhibited; the conductivity of the pole piece is improved and the fast charging performance of the battery is improved.

The invention relates to a silicon-carbon composite material, a preparation method thereof and a lithium ion battery. The preparation method comprises the following steps: adding porous carbon into a fluidized bed, heating and introducing alkaline mixed gas to obtain amino porous carbon; transferring the amino porous carbon into fluidized bed equipment, vacuumizing, heating, and introducing hydroxyl silane gas for nano silicon deposition; after deposition, introducing ultraviolet light for polymerization and oxidation to obtain a modified silicon-carbon precursor material; transferring the modified silicon-carbon precursor material into a tubular furnace, introducing inert gas to discharge air in the tube, and performing first carbonization to obtain a silicon-carbon material; and adding the resin into an organic solvent, adding the fast ion conductor and the silicon carbon material to be uniformly dispersed, performing spray drying, and performing secondary carbonization to obtain the fast ion conductor coated silicon carbon composite material. The preparation method provided by the invention is simple and efficient, and the prepared silicon-carbon composite material can improve the fast charging performance and is suitable for a negative electrode material of a high-energy-density lithium ion battery.

The invention provides positive electrode slurry, a positive electrode plate, a lithium ion battery and a power utilization device, a positive electrode lithium supplement agent comprises a lithium iron phosphate main material, a binder, a conductive agent and a porous additive, the conductive agent comprises conductive carbon black with a high specific surface area, and the specific surface area of the conductive carbon black is greater than or equal to 130 m < 2 > / g. The space between the lithium iron phosphate particles in the positive electrode slurry provided by the invention is filled with the porous additive with the medium aperture and the conductive carbon black with the small aperture and the high specific surface area, so that a positive electrode plate applying the positive electrode slurry not only is small in internal pore spacing, but also forms gradient pore structure matching capable of reducing tortuosity of lithium ion transmission, and the lithium ion transmission efficiency is improved. And the technical effects of improving the electrolyte wettability of the electrode, improving the quick charge capacity, the cycle life, the low-temperature discharge capacity and the like of the battery are achieved.

The invention provides a quick-charge and quick-discharge type lithium battery and a preparation method thereof, and belongs to the technical field of lithium battery preparation. The preparation process comprises the following steps: preparing a fluorinated carbon nanotube based on biomass carbon; preparing a positive electrode plate; preparing the dendritic mesoporous silicon dioxide nano particles; preparing a cerium oxide-loaded two-dimensional hierarchical porous composite material; preparing a negative electrode plate; and assembling the lithium battery. According to the preparation method, the eutectic and the carbon fluoride nanotubes are added in the preparation of the positive electrode plate, and the cerium oxide-loaded two-dimensional hierarchical porous composite material and the carbon fluoride nanotubes are added in the preparation of the negative electrode plate, so that the prepared positive electrode plate and the prepared negative electrode plate have relatively high conductivity; and moreover, the ion transmission efficiency is improved, the rapid ion transmission is beneficial to reducing the polarization phenomenon of the battery, improving the charging and discharging rate and the power performance of the battery, enhancing the structural stability of the electrode, improving the performance and the safety of the battery, and being more beneficial to rapid charging and rapid discharging.

The invention relates to a graphite negative electrode material and a preparation method thereof, a negative electrode plate and an electrochemical device. The graphite negative electrode material comprises secondary particles formed by granulating and carbonizing 20%-90% of a doped porous graphite precursor, 5%-30% of hard carbon particles and 5%-50% of a coating agent, in the secondary particles, the hard carbon particles are at least partially filled in holes of the doped porous graphite precursor, and the coating agent is at least partially filled in the holes of the doped porous graphite precursor. And after the coating agent is carbonized, at least part of the coating agent forms amorphous carbon to coat the outer layer of the doped porous graphite precursor. According to the scheme provided by the invention, the doped porous graphite precursor can be compounded with the hard carbon particles and the coating agent to obtain the graphite negative electrode material with high capacity and fast charging performance.

The invention provides a secondary battery comprising a diaphragm and a pole piece and an electronic device. The diaphragm in the secondary battery comprises a base film layer, at least one surface of the base film layer is provided with a bonding layer, the bonding layer is composed of a plurality of bonding points, and the thickness of the bonding layer is 0.5-5 [mu] m; in the bonding layer, the longest diameter of a bonding point is 10 [mu] m-400 [mu] m, and the distance between adjacent bonding points is 100 [mu] m-400 [mu] m. The pole piece of the secondary battery comprises a current collector, at least one surface of the current collector is provided with an active layer, a partial area of the surface of the active layer is recessed inwards to form a plurality of scribed grooves, and the scribed grooves are arranged along the length direction of the pole piece; the width of the scribing groove is D1 mm, and 0.2 < = D1 < = 1.5. The diaphragm and the pole piece provided by the invention have good electrolyte transmission capability and storage capability, and can enhance the cycle performance and fast charge performance of the secondary battery.

The invention discloses a battery and a power utilization device, the battery comprises a battery cell and an electrolyte, the battery cell comprises a negative plate and a diaphragm, the negative plate comprises a current collector and a negative active material layer, the negative active material layer comprises a silicon-based material, and the diaphragm comprises a base film and a coating; the mass percent of the silicon element in the negative electrode active material layer is a; the viscosity of the electrolyte is b, and the unit is cp; the percentage of the thickness of the coating to the thickness of the diaphragm is c; 0.037 < = a * b / c < = 5.625. By controlling the value of a * b / c within the range of 0.037-5.625, the infiltration effect of the electrolyte on the negative electrode and the fast charging performance of the battery can be effectively improved under the condition of ensuring the energy density of the battery.

The invention discloses a preparation method of a multi-element doped ferromanganese oxide positive electrode precursor, and belongs to the technical field of lithium ion battery positive electrode material preparation. The molar ratio of manganese to iron in the multi-element doped ferromanganese oxide positive electrode precursor is x: (1-x), 0.2 lt; xlt; and the doping element accounts for 0.1-10% of the total mole number of manganese and iron. According to the multi-element doped ferromanganese oxide positive electrode precursor prepared by the invention, the coprecipitation intermediates are manganese carbonate and ferrous carbonate, and Ksp of the manganese carbonate and the ferrous carbonate are relatively close, so that the uniformity of ferromanganese can be ensured, meanwhile, metal ion doping is carried out in a liquid phase synthesis precursor stage, and the probability that doped ions enter compound lattices is greatly improved. The multi-element doped ferromanganese oxide positive electrode precursor has relatively high stability and good conductivity, and is beneficial to improving the capacity, the cycle life and the compaction density of a lithium iron manganese phosphate positive electrode material.

The invention provides a lithium supplement diaphragm, a preparation method thereof and a lithium ion battery, and relates to the technical field of lithium ion batteries. The lithium supplementing diaphragm comprises a base membrane and a lithium supplementing coating attached to at least one face of the base membrane, and the lithium supplementing coating comprises aluminum oxide loaded cobalt, a carbon nano tube and lithium sulfide. Aluminum oxide can remarkably improve the thermal stability of the diaphragm and inhibit shrinkage of the diaphragm at high temperature, lithium sulfide serves as a lithium supplementing agent and can achieve the lithium supplementing effect, cobalt and sulfur are combined to form stable sulfide in the lithium supplementing process, accordingly, electrochemical inertia is kept after lithium supplementing is completed, stable lithium supplementing is achieved, and the carbon nano tubes have selective permeability on lithium ions, so that the lithium-ion battery diaphragm can be applied to lithium ion batteries. And as a conductive framework, rapid migration of electrons and ions can be promoted, and the rapid charging performance of the lithium ion battery can be enhanced, so that the lithium ion battery integrates the safety performance, the energy density and the rapid charging performance.

The invention relates to the technical field of batteries, in particular to a negative electrode material, a preparation method thereof, a negative electrode plate and a battery. The negative electrode material comprises a graphite inner core and a carbon coating layer coating at least part of the surface of the graphite inner core, and the carbon coating layer comprises soft carbon and hard carbon; the thickness of the carbon coating layer is H; in a Raman spectrum, the negative electrode material has a carbon characteristic peak D and a carbon characteristic peak G, and the ratio ID / IG of the peak intensity ID of the carbon characteristic peak D to the peak intensity IG of the carbon characteristic peak G is S; the OI value of the negative electrode material is DOI; the median particle size of the negative electrode material is Dv50; h, S, DOI and Dv50 meet the condition that H * S / DOI * Dv50 is larger than or equal to 0.1 and smaller than or equal to 1. The negative pole piece comprises the negative pole material. The negative electrode material disclosed by the invention has high fast charging performance and long cycle performance, and can relieve the problem that the existing graphite negative electrode material is poor in fast charging capability and cycle performance.

The invention relates to the technical field of electrochemistry, and particularly discloses a positive pole piece, an electrochemical device comprising the positive pole piece and an electric device. The positive pole piece comprises a first active material with a particle size of 4-20 [mu] m and a second active material with a particle size of 200-600 nm, the first active material comprises lithium manganese iron phosphate with the manganese content of m%, the second active material comprises lithium manganese iron phosphate and / or lithium iron phosphate with the manganese content of n%, and m and n meet the condition that m-n is larger than or equal to 15 and smaller than or equal to 85. According to the invention, by controlling the particle size distribution in the positive electrode active material and the manganese content relationship, the electrochemical device containing the positive electrode plate has excellent fast charging performance and energy density.

The invention relates to a preparation method of a biomass hard carbon negative electrode material and application of the biomass hard carbon negative electrode material in the field of energy storage. The method comprises the following steps: carrying out pretreatment, crushing and pre-carbonization treatment on a biomass raw material to obtain a pre-carbonized material; mixing and stirring the pre-carbonized material and an acid solution, washing and drying to obtain an acid-treated hard carbon material; soaking the obtained acid-treated hard carbon material in an alkaline solution, heating and stirring, washing and drying to obtain an alkali-treated hard carbon material; mixing the obtained alkali-treated hard carbon material with a pore-forming agent, carrying out ball milling, carrying out solid-liquid separation, and carrying out high-temperature carbonization and grinding on the obtained solid phase to obtain a powder sample; and mixing the obtained powder sample with hydrofluoric acid, and carrying out hydrothermal treatment to obtain the biomass hard carbon negative electrode material. The sodium ion battery prepared by taking the biomass hard carbon negative electrode material as a negative electrode material has the characteristics of high initial coulombic efficiency, high low-voltage platform specific capacity and excellent cycle performance and rate capability.

The invention provides a secondary battery and electric equipment, and belongs to the technical field of new energy. According to the invention, the first positive electrode active material layer and the second positive electrode active material layer with specific position sequence and specific lithium iron phosphate particle size distribution are arranged on the positive electrode current collector, so that the bottlenecks of quick charge performance and power performance of the secondary battery are broken, and the quick charge performance, the power performance, the cycle performance and the energy density are better balanced.

The present invention belongs to the technical field of battery negative electrode materials, and specifically relates to a tin oxide-based composite negative electrode material and its preparation method and use. The in-situ synthesis method of the present invention can enhance the bonding force between SnO2 particles, porous carbon skeletons, and carbon nanotubes, making them a firmly bonded whole. The composite negative electrode material can withstand the stress generated by the volume change of tin oxide, constrain and buffer the volume change of tin oxide, reduce the volume expansion multiple of tin oxide after cyclic charge and discharge, and further prevent the pulverization of the composite negative electrode material; at the same time, it can also improve the conductivity of the composite negative electrode material and improve the electrochemical performance of the negative electrode material.

The invention discloses a battery, an electrochemical device and a power utilization device.The battery comprises a battery cell, and the battery cell comprises a pole piece and a pole lug arranged on the pole piece; the lithium ion battery is characterized in that the negative electrode active material layer of the pole piece contains silicon, the percentage content of the silicon in the negative electrode active material layer is b, and the unit is%; the longest distance between the tab and the end part of the pole piece in the length direction is d, the width of the connecting position of the tab and the pole piece is m, and the units of d and m are the same; b, d and m meet the following relation: # imgabs0 #. By comprehensively controlling the value of # imgabs1 #, not only can the battery with relatively high energy density be obtained, but also the battery can be ensured to have relatively good battery fast charging performance.

The invention relates to the technical field of batteries, in particular to a lithium ion secondary battery. The lithium ion secondary battery comprises a negative plate and a positive plate, the negative plate comprises a negative active material layer, and the negative active material layer comprises a first negative active material layer deviating from the negative current collector and a second negative active material layer close to the negative current collector which are laminated in the thickness direction of the negative plate; the liquid absorption coefficient Y of the negative plate and the vertical distance X from any point in the negative electrode active material layer to the surface of the negative electrode current collector meet the following formula: Y = eX + M-N, the liquid absorption coefficient Y is the ratio of the surface porosity of the section of the negative electrode active material layer which is parallel to the surface of the negative electrode current collector and has the vertical distance X to the average particle size of the negative electrode active material on the section, e is a natural constant, and M is a natural constant. M is 4 to 10, and N is 50 to 4000; at least one side surface of the positive plate is provided with a convex part. The lithium ion secondary battery disclosed by the invention can take both high energy density and relatively good fast charging performance into account.

The invention relates to the technical field of batteries, in particular to a negative pole piece, a preparation method thereof and a battery. The negative pole piece comprises a current collector; the first negative electrode coating is arranged on the surface of at least one side of the current collector in the thickness direction, the second negative electrode coating is arranged on the surface, far away from the current collector, of the first negative electrode coating, the second negative electrode coating comprises a layered multi-element metal oxide, and the layered multi-element metal oxide comprises at least two metal elements, the layered multi-element metal oxide meets at least one of the following characteristics: the capacity of the layered multi-element metal oxide is greater than or equal to 100mAh / g; the specific surface area of the layered multi-element metal oxide is greater than or equal to 100m < 2 > / g; the layered multi-element metal oxide has a porous structure; the interlayer spacing of the layered multi-element metal oxide is greater than or equal to 0.15 nm. The ion diffusion rate of the negative pole piece can be improved, rapid transmission of sodium ions on the surface of the negative pole piece is facilitated, and the cycle stability and the rapid charging performance of the battery are further improved.

The invention discloses high-capacity fast-charging hard carbon with precise regulation and control of confinement carbonization of a monatomic composite material as well as a preparation method and application of the high-capacity fast-charging hard carbon. According to the method, micropore-rich porous carbon is used as a carrier, a metal compound and a high-molecular polymer are compounded for one-step carbon thermal reduction, monatomic metal nanoparticles are introduced into high-capacity fast-charge hard carbon, and the sodium storage capacity of the material is further improved. The micropore-rich porous carbon is coordinated with a metal compound group through a carbon-oxygen single bond and a carbon-carbon single bond, superfine metal nanoparticles are subjected to in-situ carbon thermal reduction in micropores, the metal nanoparticles have high sodium storage capacity, and the micropore structure of the porous carbon can be used as a framework material to solve the problem of poor cycle performance caused by volume expansion.

The invention discloses a pole piece, a battery and electric equipment, and relates to the technical field of batteries, at least one side of a current collector is provided with a first active material layer, and a second active material layer is arranged on the first active material layer; the first active material layer comprises a first type of active material, the second active material layer comprises a second type of active material, and the particle size distribution (D90-D10) / D50 of the first type of active material is greater than the particle size distribution (D90-D10) / D50 of the second type of active material. Therefore, the particle size distribution (D90-D10) / D50 of the first active substance is greater than the particle size distribution (D90-D10) / D50 of the second active substance, so that the second active substance with a smaller particle size in the second active substance layer is concentrated in distribution, small in tap density, small in filling density and high in porosity, Li < + > de-intercalation is facilitated, and the quick charging performance of the battery is improved; the first active substance with a large particle size in the first active substance layer can be widely distributed, the tap density is large, the filling density is large, and the energy density of the battery can be improved.

The invention relates to the technical field of lithium ion batteries, and provides a lithium ion battery. The battery comprises a positive plate, a negative plate and an electrolyte, in the thickness direction of the positive plate, the positive plate comprises a first surface and a second surface which are oppositely arranged, a plurality of first convex parts are arranged on the first surface at intervals, and a plurality of first concave parts corresponding to the first convex parts are arranged on the second surface; in the unit area of 1cm * 1cm, the ratio of the total projection area of the first lug boss on the positive plate to the unit area is recorded as m%, and m is more than or equal to 3 and less than or equal to 60; the electrolyte comprises a compound A, the mass ratio of the compound A is recorded as a% based on the total mass of the electrolyte, and a is more than or equal to 5 and less than or equal to 70; by optimizing the structure of the positive electrode and combining the use of the compound A in the electrolyte, the fast charging performance and the safety performance of the battery can be improved.

In order to solve the problems of acidity increase and lithium salt consumption in the cycle process of an existing lithium ion battery, the invention provides a non-aqueous electrolyte and a lithium ion battery, the non-aqueous electrolyte comprises a non-aqueous organic solvent, a first lithium salt, a second lithium salt and a first additive, the first lithium salt is lithium hexafluorophosphate, and the second lithium salt is lithium hexafluorophosphate. The second lithium salt comprises at least one of lithium bis (fluorosulfonyl) imide and lithium bis (trifluoromethylsulfonyl) imide, the first additive comprises a compound shown in a structural formula 1: # imgabs0, and the non-aqueous electrolyte meets the following conditions: 45 < = sigma * (b + c) < = 220, 0.01 < = a / c < = 0.8, 0.001 < = a < = 1, 2 < = b < = 19, 1 < = c < = 10, and 6 < = sigma < = 13. The non-aqueous electrolyte provided by the invention can keep a low-acidity state after long-term circulation, and can effectively prolong the cycle life of a lithium ion battery when being applied to the lithium ion battery.

The invention discloses an electrolyte, a secondary battery and a power utilization device, and belongs to the technical field of batteries, the electrolyte comprises a lithium salt, the molecular structure of the lithium salt contains C3-C20 alkyl ether, a sulfonic acid amine group and a fluorine element, the lithium salt has a large dipole moment and a high donor number, meanwhile, the lithium salt can be combined with Li < + >, and the lithium salt can be combined with Li < + >. A solvation structure is formed, solvent decomposition is inhibited, and the fast charging performance and the cycle performance of the secondary battery are remarkably improved.

The invention discloses a high-voltage fast-charging electrolyte and a preparation method and application thereof, the electrolyte comprises an electrolyte lithium salt, an organic solvent and an additive, the organic solvent comprises a carbonic ester organic solvent and a carboxylic ester organic solvent, and the additive comprises a film-forming additive, a resistance-reducing additive and a high-voltage additive; wherein the mass content of the film-forming additive is recorded as W1, the mass content of the resistance-reducing additive is recorded as W2, and the mass content of the carboxylic ester organic solvent is recorded as Ws by taking the electrolyte as a reference, so that W1 / Ws is more than or equal to 0.003 and less than or equal to 0.125; and / or 0.01 < = W2 / Ws < = 0.25. The formula composition and the content of the electrolyte are optimally designed, and the fast charging performance of the battery under high voltage is greatly improved through the synergistic effect of the solvent and the additive; in addition, the electrolyte is good in interface stability, and the overall performance of the battery is improved.

The invention relates to the technical field of batteries, in particular to a negative electrode material and a preparation method and application thereof. The negative electrode material comprises a base material and a composite coating layer coated on the surface of the base material, the base material comprises a compound of graphite and hard carbon, the base material has a porous structure, the composite coating layer comprises a first coating layer coated on the surface of the base material and a second coating layer coated on the surface of the first coating layer, the first coating layer includes a carbon material and a conductive agent, and the second coating layer includes a lithium-containing compound. In the negative electrode material provided by the invention, the matrix material comprises the compound of graphite and hard carbon, has abundant porous structures and defects, can increase lithium intercalation channels of lithium ions in particles, and improves the fast charging capability; the composite coating layer can effectively improve defect interface conductivity, reduce overall cross-linking impedance, improve the transmission capacity of Li < + > between carbon layers, promote Li < + > desolvation in SEI and improve the graphite fast charging performance.

The invention relates to the technical field of electrochemistry, and particularly discloses a positive pole piece, an electrochemical device comprising the positive pole piece and an electric device. The positive pole piece comprises a first active material with a particle size of 4-20 [mu] m and a second active material with a particle size of 200-600 nm, the first active material comprises lithium manganese iron phosphate with the manganese content of m%, the second active material comprises lithium manganese iron phosphate and / or lithium iron phosphate with the manganese content of n%, and m and n meet the condition that m-n is larger than or equal to 15 and smaller than or equal to 85. According to the invention, by controlling the particle size distribution in the positive electrode active material and the manganese content relationship, the electrochemical device containing the positive electrode plate has excellent fast charging performance and energy density.