2642results about How to "Improved magnification performance" patented technology

The embodiment of the invention relates to a lithium cobalt oxide positive electrode material with a composite phase as well as a preparation method and application of the lithium cobalt oxide positive electrode material. The chemical general formula of the lithium cobalt oxide positive electrode material with the composite phase is AXCo (1-y) M (1y) O2, wherein x is more than or equal to 0.5 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 0.03, A is Li or Li and Na, and M1 is one or more of A1, Zr, Ni, Mn, Y, Nb, La, Fe, Cu, Cr, Ti, W, Mg, Mo or Yb; the composite phase of the lithium cobalt oxide positive electrode material comprises an O2 phase, a T2 phase and an O3 phase; wherein the sum of the molar ratios of the O2 phase and the T2 phase in the composite phase is greater than or equal to 90%, and the molar ratio of the O3 phase is less than or equal to 10%. By regulating and controlling the composite phase proportion of the lithium cobalt oxide positive electrode material, the rate capability, the structural stability under high voltage, the stability of a thermodynamic structure, the specific capacity, a discharge platform and other characteristics of the positive electrode material can be effectively improved, so that the lithium cobalt oxide positive electrode material with high energy density and high stability is realized.

The lithium nickel manganese oxide positive electrode material, the preparation method thereof and the electrochemical device are characterized in that the lithium nickel manganese oxide positive electrode material provided by the embodiment of the invention comprises a base material and a coating layer located on the surface of the base material, the general formula of the base material is Li (LiaNixMnyMbO4), the element M comprises at least one of Ti, Zr, Al, Nb and Mo, and a is more than or equal to 0.02 and less than or equal to 0.06; 0.45 < = x < = 0.55, 1.4 < = y < = 1.6; 0.05 < = b < = 0.55; a + x + y + b = 2, and the coating layer contains phosphate. According to the lithium nickel manganese oxide positive electrode material, through doping and coating technologies, under the condition that the capacity is not sacrificed, the gas production phenomenon is effectively reduced, the cycling stability of the lithium nickel manganese oxide positive electrode material is improved, and the service life of an electrochemical device applying the lithium nickel manganese oxide positive electrode material is prolonged.

The invention provides a high-rate and high-first-effect biomass hard carbon composite negative electrode material and a preparation method and application thereof, the hard carbon composite negative electrode material has a core-shell structure, the core-shell structure comprises a core, an inner shell and an outer shell, the core comprises biomass hard carbon containing P and graphite microcrystals, the inner shell comprises graphene, and the outer shell comprises a carbon nanotube. According to the invention, the surface of the biomass hard carbon is coated with the graphene layer, the carbon nanotubes grow on the surface of the graphene in situ, and transition metal synergistically induces the hard carbon to be arranged and grow along the graphene layer in a high-temperature carbonization process, so that the graphene coating layer is tightly coated, and the cycle performance of the material is improved; transition metal ions catalyze graphitization to generate a more regular and ordered graphite-like layer microcrystalline structure coating layer, so that the defects of graphene and carbon nanotubes are reduced, and the first coulombic efficiency is improved; in addition, the ion transmission capability is improved by phosphorus doping, the electron transmission capability is improved by graphite microcrystals generated by catalysis in hard carbon, and the rate capability is ensured by synergistic improvement of ion transmission and electron transmission.

The invention provides an asphalt-based closed-pore carbon material, a preparation method thereof and a sodium ion battery, the preparation method of the asphalt-based closed-pore carbon material comprises the following steps: S1, pre-oxidizing an asphalt-based carbon source in an oxidizing gas atmosphere at 200-350 DEG C to obtain a pre-oxidized product; s2, carrying out low-temperature carbonization on the pre-oxidized product in an inert atmosphere at 300-800 DEG C to obtain a first precursor; s3, performing gas activation on the first precursor in an activated gas atmosphere to obtain a second precursor; s4, performing chemical activation on the second precursor by adopting a chemical activating agent to obtain a porous carbon material; s5, dipping the porous carbon material in an asphalt solution, and then separating and drying to obtain a blank; and S6, carbonizing the blank under the protection of inert gas to obtain the asphalt-based closed-cell carbon material. The asphalt-based closed-cell carbon material has the advantages of high capacity, high first efficiency and high stable circularity.

The invention provides a positive electrode material and a preparation method thereof, a positive electrode plate and a battery, the positive electrode material comprises lithium manganese iron phosphate particles, a first shell layer and a second shell layer, the first shell layer and the second shell layer sequentially coat the surfaces of the lithium manganese iron phosphate particles, the material of the first shell layer comprises nanoscale SiO2 particles, and the material of the second shell layer comprises nanoscale TiO2 particles. The surfaces of the lithium manganese iron phosphate particles are sequentially coated with the SiO2 layer and the TiO2 layer, so that the contact between the lithium manganese iron phosphate particles and an electrolyte can be reduced, the side reaction between the lithium manganese iron phosphate particles and the electrolyte in the electrochemical reaction process is reduced, the cycle life attenuation of the battery is relieved, the dissolution of Mn element is reduced, and the service life of the battery is prolonged. Therefore, the battery impedance increase caused by deposition of Mn < 2 + > on the negative electrode in the circulation process is relieved.

The invention relates to the technical field of secondary batteries, in particular to a conductive composite current collector, a preparation method thereof and a battery. The conductive composite current collector comprises a supporting layer, a metal layer arranged on at least one surface of the supporting layer and a PTC (Positive Temperature Coefficient) bottom coating arranged on the surface, far away from the supporting layer, of the metal layer, the supporting layer comprises a polymer base membrane and conductive fibers dispersed in the polymer base membrane; the PTC undercoat layer includes a conductive polymer and a conductive agent dispersed in the conductive polymer. The conductive composite current collector provided by the invention is high in conductivity and excellent in safety, the probability of thermal runaway of the battery at a high temperature is effectively reduced, and the rate capability and the cycle performance of the battery are improved.

The invention belongs to the technical field of sodium ion battery negative electrode materials, and particularly relates to an amylocellulose composite hard carbon material as well as a preparation method and application thereof. Pre-oxidation and pre-carbonization are carried out step by step, the starch cellulose composite hard carbon material is prepared through low-temperature pre-oxidation, a ball milling method, low-temperature pre-carbonization and a high-temperature pyrolysis method in sequence, the obtained starch cellulose composite hard carbon material is used for preparing the negative electrode of the sodium-ion battery, and then the sodium-ion battery is further constructed. An electrochemical performance test result shows that the obtained sodium ion battery has excellent first-circle coulombic efficiency, cycle performance and rate capability; moreover, the preparation method of the starch cellulose composite hard carbon material is simple to operate, can perform a pre-oxidation process in an air atmosphere, does not need additional oxidation treatment, is environment-friendly, can prevent the starch cellulose composite material from melting and foaming in high-temperature pyrolysis, improves the cycling stability of the material, and is suitable for industrial production.

The invention relates to a polymer coated graphite negative electrode material and a preparation method and application thereof, the preparation method comprises the following steps: mixing polyacrylonitrile and graphite by adopting a ball milling method, then treating by adopting a liquid phase coating method to coat the surface of the graphite with a layer of polyacrylonitrile, and then carrying out low-temperature heat treatment to obtain the cyclized polyacrylonitrile coated graphite negative electrode material. The compact, flexible, high-electron and high-ion conductive coating is constructed on the surface of the graphite, so that the mechanical stability and the chemical stability of the graphite negative electrode material are effectively enhanced, the problem that a coating material is easy to break and fall off in a long-cycle process in the prior art is avoided, the interface performance of a graphite negative electrode and an electrolyte is improved, and the service life of the graphite negative electrode is prolonged. The volume expansion of the graphite negative electrode material is inhibited, the electrochemical activity of the graphite negative electrode material is enhanced, the electron transmission rate is accelerated, the rate capability and the cycle performance of the graphite negative electrode are further improved, and the preparation process is simple, green and environment-friendly, and is beneficial to industrial production and application.

The invention discloses a silicon-carbon composite material and a preparation method thereof, a pole piece and a battery. The silicon-carbon composite material comprises a cluster structure and a third carbon layer coating the cluster structure, wherein the cluster structure comprises a plurality of silicon-carbon composite particles, pores are distributed among the plurality of silicon-carbon composite particles, each silicon-carbon composite particle has a core-shell structure, each silicon-carbon composite particle comprises an inner core and an outer shell coating the inner core, each outer shell sequentially comprises a first carbon layer and a second carbon layer in the direction far away from the inner core, the first carbon layer comprises a conductive carbon material with a three-dimensional structure, an annular gap exists between the second carbon layer and the first carbon layer, and the inner core comprises porous silicon nanoparticles. The battery prepared from the silicon-carbon composite material has excellent electrochemical performance.

The invention belongs to but not limited to the technical field of electrode materials, and particularly relates to a high-tap-density lithium nickel manganese oxide positive electrode material, a preparation method and a lithium ion battery, the chemical general formula of the high-tap-density lithium nickel manganese oxide positive electrode material is LiNi < 0.5-x > Mn < 1.5-y > M < x > N < y > O < 4 >, 0.1, 0 < = y < lt >; 0.1, M and N are doping elements and comprise one or more of Mg, Co, Al, Zr, W, Sb, Ta and Ti; the material is micron-sized spherical secondary particles formed by stacking and aggregating nano-sized octahedral primary particles, and is uniformly dispersed without agglomeration; the spherical secondary particles are formed by mixing spherical secondary particles with large and small particle size distribution, and the average particle size range of the large particles is 3lt; d < 50lt >; the average particle size range of the small particles is 1lt; d < 50lt >; 2 [mu] m.

The invention discloses a carbon-coated sodium ferrous sulfate phosphate positive electrode material as well as a preparation method and application thereof. The carbon-coated sodium ferrous sulfate phosphate positive electrode material is square flaky particles formed by coating sodium ferrous sulfate phosphate with a conductive carbon material and irregular aggregates of the square flaky particles. The molecular formula of the sodium ferrous sulfate phosphate is Na (6-2x + y) Fex( SO4) (3-y) (PO4) y, x is more than 0 and less than 3, and y is more than 0 and less than or equal to 0.5. The invention also discloses a preparation method and application of the carbon-coated sodium ferrous sulfate phosphate positive electrode material. The positive electrode material has the advantages of phosphate and sulfate positive electrode materials, the voltage platform is high, the conductivity is excellent, the air stability is good, and the assembled battery has excellent chemical sodium storage performance, high discharge specific capacity, highly reversible charge-discharge reaction and good cycle performance. The method is simple in process, high in feasibility, low in raw material cost and easy to realize industrial production through a solution system.

The invention discloses a preparation method and application of a prussian blue material, and belongs to the field of battery materials.The preparation method of the prussian blue material comprises the following steps that S1, a solution containing ferrocyanide is prepared to serve as a raw material A, a solution containing transition metal salt is prepared to serve as a raw material B, a to-be-doped solution C containing alkali metal ions is prepared, the method comprises the following steps: S1, preparing a to-be-doped solution C containing transition metal ions, S2, adding a base solution into a container, continuously adding the raw material A and the raw material B into the base solution, and stirring and mixing to form a precipitate, and S3, in the precipitation process, continuously adding the to-be-doped solution C into the raw material A and continuously adding the to-be-doped solution D into the raw material B until the precipitation is finished to obtain the Prussian blue material. According to the invention, the moisture resistance, the rate capability and the cycle stability of the Prussian blue material are greatly improved.

The invention discloses a silicon carbon material, a preparation method thereof and a lithium ion battery. The preparation method of the silicon-carbon material comprises the following steps: S1, adding an alkaline reagent into a mixed solution containing a porous carbon-loaded silicon substrate, transition metal salt and a solvent, and drying to obtain a first precursor; s2, performing carbon deposition on the first precursor by adopting a chemical vapor deposition method, performing in-situ growth of a carbon nanotube, and then performing acid pickling and drying to obtain a second precursor; s3, performing silicon deposition on the second precursor by adopting a chemical vapor deposition method, and forming silicon nanoparticles and / or silicon nanowires in the carbon nanotubes in situ to obtain a third precursor; and S4, carrying out carbon coating on the third precursor to obtain the silicon carbon material. The silicon-carbon material is excellent in expansion inhibition performance and compressive strength and has excellent conductivity, and the lithium ion battery containing the silicon-carbon material can give consideration to excellent capacity performance, rate performance and cycle performance.

The invention provides a hard carbon material and a preparation method thereof, and the preparation method comprises the following steps: (S1) crushing asphalt, and carrying out heat treatment in an oxidizing atmosphere to obtain a pre-oxidized precursor; (S2) uniformly mixing the pre-oxidized precursor with a cross-linking agent I, and carrying out primary cross-linking under inert atmosphere and heating conditions to obtain a cross-linked precursor I; the cross-linking agent I is a polymer of which the side chain contains carboxyl; (S3) uniformly mixing the cross-linked precursor I and a cross-linking agent II, and carrying out secondary cross-linking in an inert atmosphere under a heating condition to obtain a cross-linked precursor II; the cross-linking agent II is a micromolecular aromatic hydrocarbon compound (S4) cross-linking precursor II containing a plurality of anhydrides and / or carboxyl groups, calcining, cooling and grinding in an inert atmosphere to obtain the amorphous sodium ion battery negative electrode material. The negative electrode material obtained by the preparation method disclosed by the invention has the advantages of high capacity, high magnification, low cost, simple preparation process, adjustable disorder degree and high carbon yield, and is a carbon material suitable for large-scale production.

The invention relates to the technical field of sodium ion batteries, in particular to a sodium ferric sulfate positive electrode material and a preparation method and application thereof. The preparation method of the sodium ferric sulfate positive electrode material comprises the following steps: obtaining a carbon foam substrate; weighing raw materials according to the stoichiometric ratio of the sodium ferric sulfate positive electrode material, and adding the raw materials into a solvent to obtain a mixed solution; depositing the mixed solution on a carbon foam substrate by adopting an electrostatic spray deposition method to obtain a precursor film; and sintering the precursor film to obtain the sodium ferric sulfate positive electrode material. According to the preparation method, the carbon foam is adopted as a substrate material, the sodium ferric sulfate precursor is prepared through electrostatic spray deposition, and then the sodium ferric sulfate material is obtained through sintering treatment, so that the specific discharge capacity, the rate capability and the cycle performance of the sodium ferric sulfate material are all remarkably improved.

The invention relates to the technical field of battery materials, in particular to a graphite negative electrode material and a preparation method and application thereof. The graphite negative electrode material comprises graphite particles, the average length La of the graphite particles in the alpha-axis direction of microcrystals is larger than or equal to 40 nm, the average thickness Lc of the graphite particles in the c-axis direction of the microcrystals is larger than or equal to 25 nm, and the interlayer spacing d002 ranges from 0.336 nm to 0.338 nm, and the number parameter of the microcrystals contained in each single graphite particle is defined as N = D503 / (La2 * Lc); d50 is the median particle size of the graphite particles, the unit is [mu] m, and the numerical value of N is more than 0 and less than or equal to 0.04. The graphite negative electrode material disclosed by the embodiment of the invention comprises the graphite particles with stable microcrystalline structure, large microcrystalline size and large interlayer spacing, so that the expansion and stress distribution uniformity of the negative electrode material in the circulation process is improved, the diffusion of ions in the graphite particles is facilitated, the consumption of active lithium is reduced, and the service life of the negative electrode material is prolonged. And the dynamic and super-long cycle stability of the graphite negative electrode material is improved.

The invention provides a silicon-carbon composite material as well as a preparation method and application thereof. The silicon-carbon composite material comprises a porous carbon material; the silicon particles are distributed on the surface layer of the porous carbon material and in pore channels in the porous carbon material, the distribution concentration of the silicon particles in the surface layer of the porous carbon material is smaller than that of the silicon particles in the porous carbon material, and the particle size of the silicon particles in the surface layer of the porous carbon material is smaller than that of the silicon particles in the porous carbon material; the silicon dioxide layer is formed on the surface of the silicon particles; and the carbon coating layer is formed on the surface of the silicon dioxide layer. The lithium ion battery prepared by taking the silicon-carbon composite material as a positive electrode active material shows good electrochemical performance, and has relatively high specific capacity, good cycling stability and rate capability.

The invention discloses a preparation method of a hard-soft carbon coated silicon-carbon negative electrode material, which comprises the following steps: S1, mixing nano silicon and graphite to obtain silicon-carbon mixed powder; s2, dissolving asphalt in absolute ethyl alcohol, then mixing with the silicon-carbon mixed powder, and carrying out carbonization treatment; s3, dissolving sucrose in water, then mixing with the composite material obtained in S2, and performing carbonization treatment to obtain a hard-soft carbon coated silicon carbon negative electrode material; wherein the carbonization temperature in the step 2 and the carbonization temperature in the step 3 are both 1200-1300 DEG C. According to the hard-soft carbon coated silicon-carbon negative electrode material and the preparation method thereof, the mixture of silicon and graphite is subjected to soft carbon coating and hard carbon coating through asphalt and cane sugar in sequence, so that the obtained hard-soft carbon coated silicon-carbon negative electrode material not only can inhibit volume expansion of silicon, but also shows excellent rate capability and cycle performance.

The invention relates to the field of lithium ion batteries, in particular to a fluorine-containing soluble polyimide adhesive special for a lithium battery and a preparation method and application of the fluorine-containing soluble polyimide adhesive. The fluorine-containing polyimide is prepared by reacting dianhydride and diamine, the dianhydride comprises 4, 4 '-hexafluoroisopropyl phthalic anhydride (6FDA), the diamine comprises 4, 4'-diaminodiphenylamine (NDA), and the structural formula of the fluorine-containing polyimide (6FDA-NDA) is # imgabs0 #. The electrode material prepared from the adhesive material obtained by the invention has the characteristics of low impedance and high adhesion, the assembled lithium battery shows higher magnification, and the adhesive material shows excellent magnification performance and adhesion performance when being applied to the lithium ion battery, especially a silicon-containing negative electrode lithium ion battery, and has a good industrial prospect.

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 invention discloses a method for preparing a composite iron-based polyanion positive electrode material. The structural formula of the positive electrode material is represented as Na4Fe3 (PO4) 2 (P2O7) (at) Camp, mXenes are sodium ferric pyrophosphate compositely coated by an MXenes material and a carbonaceous precursor, and the preparation method comprises the following steps: weighing a sodium source, a ferrous source, a phosphorus source and a carbon source according to a stoichiometric ratio, uniformly mixing, grinding, spray-drying and sintering at high temperature to obtain the composite iron-based polyanion positive electrode material, and the carbon source comprises iron-nickel doped polyethylene glycol. The composite iron-based polyanion positive electrode material provided by the invention is remarkably improved in the aspects of energy density, rate capability and cycle life, and the preparation process is simple to operate, reliable in flow, quick in preparation process and easy for industrial production, so that an ideal scheme is provided for commercialized sodium ion battery positive electrode materials.

The invention discloses a zinc negative electrode protective layer material of an aqueous zinc ion battery as well as a preparation method and application of the zinc negative electrode protective layer material. The method comprises the following steps: dispersing a carbon material in an acidic liquid, stirring at room temperature, and fully mixing to obtain a uniform suspension; adding manganese salt into the mixed solution, stirring at room temperature, and then performing constant-temperature water bath; washing, centrifuging, drying and calcining a product obtained by the reaction to obtain expanded graphite; uniformly dispersing expanded graphite in a solvent, and stirring to obtain a dispersion liquid; adding a titanium-containing organic compound into the dispersion liquid and stirring; adding deionized water into the dispersion liquid and refluxing; and centrifuging, washing, drying and calcining to obtain the protective layer. According to the composite material, expanded graphite is prepared firstly, and then titanium dioxide quantum dots are anchored on the expanded graphite. Due to excellent zinc ion rate, compared with the prior art, the material has lower interface resistance and good cycling stability and rate capability, and the problems of interface dendritic crystal growth and the like are solved.

The invention relates to the technical field of lithium ion battery materials, and provides a lithium iron phosphate positive electrode material, a preparation method thereof and a lithium battery. The preparation method of the lithium iron phosphate positive electrode material comprises the following steps: performing a first coprecipitation reaction on a first iron source solution and a first phosphorus source solution in the presence of a polymer monomer to obtain an iron phosphate seed crystal; performing a second coprecipitation reaction on the second iron source solution and the second phosphorus source solution in the presence of a polymer monomer and an iron phosphate seed crystal to obtain iron phosphate dihydrate; iron phosphate dihydrate, a lithium source and a carbon source are mixed and then subjected to spray drying, the mixture is placed in a rotary kiln to be sintered, carbon-coated lithium iron phosphate with the large particle size and carbon-coated lithium iron phosphate with the small particle size are prepared at different sintering temperatures respectively, and the carbon-coated lithium iron phosphate with the different particle sizes are mixed according to the mass ratio to obtain the lithium iron phosphate positive electrode material. The lithium iron phosphate positive electrode material has relatively good spherical morphology, so that the lithium iron phosphate positive electrode material has relatively high compaction density and electrical properties after grading.

The invention belongs to the technical field of lithium batteries, and discloses a lithium nickel manganese oxide positive electrode material, a preparation method thereof and a lithium ion battery. Wherein the lithium nickel manganese oxide positive electrode material has a regular truncated octahedron single crystal structure, and the ratio K of a (111) crystal face orientation parameter to a (100) crystal face orientation parameter in an XRD (X-Ray Diffraction) spectrogram of the lithium nickel manganese oxide positive electrode material is 1-1.6. The lithium nickel manganese oxide positive electrode material provided by the invention has excellent rate capability and cycling stability, and can be well applied to production and manufacturing of lithium ion batteries.

The invention provides a lithium manganese iron phosphate material as well as a preparation method and application thereof. The lithium manganese iron phosphate material sequentially comprises a lithium manganese iron phosphate matrix inner core, a first coating layer and a second coating layer from inside to outside, the first coating layer comprises a carbon material, the second coating layer comprises a composite material, and the composite material comprises carbon nitride and a conductive polymer. Through doping and coating of the carbon material in the first coating layer and synergistic cooperation of the conductive polymer and the carbon nitride in the second coating layer, the conductivity of the lithium manganese iron phosphate material is improved, and the cycling stability, the capacity and the rate capability of the lithium manganese iron phosphate material are improved.

The invention relates to a lithium manganese iron phosphate positive electrode material and a preparation method thereof, and an electrochemical device, the preparation method of the lithium manganese iron phosphate positive electrode material comprises the following steps: mixing a manganese source, an iron source, a first phosphorus source, a lithium source, a first carbon source and a magnesium source, and carrying out primary grinding to obtain a first slurry; carrying out primary sintering on the first slurry to obtain a lithium manganese iron phosphate precursor; mixing the lithium manganese iron phosphate precursor, a second phosphorus source, a second carbon source and a niobium source, and performing secondary grinding to obtain second slurry; the second slurry is subjected to secondary sintering, the lithium manganese iron phosphate positive electrode material is obtained, the magnesium element exists in a bulk phase of the lithium manganese iron phosphate positive electrode material in a doping mode, and the niobium element exists in a coating layer of the lithium manganese iron phosphate positive electrode material in a coating mode. According to the preparation method, magnesium and niobium are co-doped and coated, and through the synergistic effect of magnesium and niobium, the electron and ion conductivity, the specific capacity and the cycle performance of the lithium manganese iron phosphate positive electrode material are jointly improved.

The invention relates to the technical field of batteries, in particular to a silicon-carbon negative electrode material and a preparation method and application thereof. The silicon-carbon negative electrode material comprises a carbon substrate, nanometer silicon particles and doping elements, the nanometer silicon particles are uniformly embedded in the carbon substrate, the doping elements are doped in the carbon substrate, and the doping elements comprise fluorine elements and phosphorus elements. The silicon-carbon negative electrode material disclosed by the invention has good uniformity, the nano silicon particles are uniformly embedded in the spherical carbon matrix, and the carbon matrix can effectively relieve volume expansion of the silicon particles in a lithium intercalation / deintercalation process, so that the cycle performance of a battery is improved; and fluorine and phosphorus elements are doped in the carbon matrix, so that the electron / ion conductivity of the silicon-carbon negative electrode material can be improved, and the rate capability of the battery is improved.

The invention relates to the technical field of batteries, in particular to a negative plate and a lithium ion secondary battery. The negative plate comprises a negative current collector and a negative active material layer positioned on at least one side surface of the negative current collector; the negative electrode active material layer comprises a first coating close to the negative electrode current collector and a second coating deviating from the negative electrode current collector; the thickness of the negative plate is 30-1000 [mu] m; the first coating comprises a first negative electrode active substance, the second coating comprises a second negative electrode active substance, and the second negative electrode active substance comprises a second graphite material and hard carbon; the ratio of the average particle size of the second negative electrode active material to the average particle size of the first negative electrode active material is L, 1lt; l < = 2.5; the outer surface of the negative electrode active material layer has a recess. The negative plate disclosed by the invention has excellent lithium ion conduction capability and capacity exertion, and the lithium ion secondary battery comprising the negative plate disclosed by the invention has relatively high energy density and rapid charging capability.

The embodiment of the utility model discloses a secondary battery and a battery pack, the secondary battery comprises an electrode roll formed by winding a first pole piece, a diaphragm and a second pole piece, and the diaphragm is arranged between the first pole piece and the second pole piece; one of the first pole piece and the second pole piece is a positive pole piece, the other one is a negative pole piece, the first pole piece comprises a first active layer, and the second pole piece comprises a second active layer; the electrode roll is provided with a flat part and bent parts located at the two opposite ends of the flat part, at least one of the first active layer and the second active layer is provided with a first groove located in the flat part, at least one of the first active layer and the second active layer is provided with a second groove located in the bent part, and notches of the first groove and the second groove located in the same active layer face the active layer of the adjacent pole piece; in the second direction, the size of the first groove is larger than that of the second groove. By adopting the structural design, the electrolyte infiltration time of the thick-coated pole piece can be shortened, the stress of the pole piece at the bending part can be reduced, and the low-temperature performance, the rate performance and the fast-charge cycle performance of the battery can be improved.

The invention provides carbon-coated lithium iron phosphate and a preparation method thereof, a positive plate and a lithium ion battery. The preparation method comprises the following steps: S1, mixing raw materials including a lithium source, a phosphorus source, an iron source and a first solvent to obtain slurry; s2, sequentially carrying out spray drying and crushing treatment on the slurry to obtain a lithium iron phosphate precursor; s3, carrying out polymerization reaction on raw materials of the lithium iron phosphate precursor, styrene, an initiator and a second solvent in an inert atmosphere, and adding a cationic monomer in the polymerization reaction process to obtain a cationic polystyrene coated lithium iron phosphate precursor; and S4, calcining the cationic polystyrene coated lithium iron phosphate precursor in an inert atmosphere to obtain the carbon coated lithium iron phosphate. According to the preparation method disclosed by the invention, lithium iron phosphate is coated with a layer of porous carbon while being controlled to be nano-sized, so that the electrochemical impedance of the lithium iron phosphate material is reduced, and the rate capability of the lithium iron phosphate material is improved.