109results about How to "High voltage platform" patented technology

The present invention relates to a nitrogen-doped porous carbon material for a lithium-air battery positive electrode, wherein the nitrogen-doped porous carbon material has an interconnected graded pore structure, N is uniformly doped in the C skeleton, N accounts for 0.2-15% of the carbon material atomic ratio, the graded pores comprise mass transfer pores and deposition holes, the deposition holes account for 40-95% of the total pore volume, and the mass transfer pores account for 4-55% of the total pore volume. According to the present invention, with application of the carbon material as the lithium-air battery electrode material, the space utilization rate of the carbon material during the charge-discharge process can be increased at a maximum, and the energy density and the power density of the lithium-air battery can be effectively increased; and the preparation process is simple, the material source is wide, the pore structure of the graded pore carbon material can be regulated, the regulation manner is diverse, and the nitrogen doping manner is easily achieved.

The invention relates to an application of a porous carbon material with a grading pore structure in a lithium-air cell anode, and is characterized in that the carbon material has mutually communicated grading pore structure distribution which has a mesoporous structure for depositing the discharge products and a macroporous structure suitable for transmission of oxygen and an electrolyte. When the carbon material is taken as a material of the lithium-air cell anode, the space utilization rate of carbon material can be increased at maximum limitation during a charge and discharge process, specific discharge capacity, voltage platform and multiplying power discharge capability of the cell can be effectively increased, so that the energy density and power density of the lithium-air cell can be increased. The porous carbon material has the advantages that the preparation technology is simple, the material source is wide, the grading pore carbon material pore structure enables regulation and control, the regulation and control modes are various, and the doping of metal / metal oxide can be easily and simultaneously realized.

The invention discloses a high-voltage high-capacity anode material for a lithium ion battery. The anode material contains a cobalt source substance, a lithium source substance, a dopant M and a coating material, wherein the molar ratio of Li to Co is 0.95-1.2, the doping amount of the dopant M is 0.01-10wt%, and the total doping amount of the coating material is 0.01-20wt%. The structural stability of lithium cobalt oxide is enhanced by means of doping, the advantages of the lithium cobalt oxide in a base layer and the active material in a coating layer are complemented mutually by means of coating with an active substance, so that the electrochemical performance of the anode material is enhanced; stable cycling can be achieved under the condition of high voltage of 3.0-4.5V and the anode material has excellent electrochemical performance. In a word, the anode material has the advantages of high voltage platform, high reversible specific capacity, excellent thermal cycling performance, stable structure, good safety and the like; the problem that the calcination temperature of the base layer and the coating layer cannot be unified is solved and the anode material has excellent uniformity.

The invention provides an off-grid and grid-connected operation light and storage joint power supply system which comprises a DC / AC converter for connecting a direct current bus and an alternating current bus. The alternating current bus is connected with a power grid. The alternating current bus and the direct current bus are connected with an alternating current load and a direct current load respectively. The direct current bus is connected with a photovoltaic array and a battery system through a photovoltaic DC / DC converter and an energy storage DC / DC converter respectively. According to the off-grid and grid-connected operation light and storage joint power supply system, control strategies of the off-grid and grid-connected operation light and storage joint power supply system are provided and include the off-grid state operation control strategy and the grid-connected state operation control strategy. By means of the system and a method, the defects that an existing photovoltaic power supply system is instable in power supply quality, poor in schedulability, single in operation mode, low in energy conversion efficiency and the like are overcome.

The invention discloses a fluorinated graphene electrode material and a preparation method thereof. The preparation method comprises the steps: carrying out thermal intercalation of graphite fluoride by using an organic solvent with low boiling point; carrying out ultrasonic stripping of graphite fluoride; centrifuging to remove graphite fluoride which is not stripped, carrying out suction filtration of the centrifuged upper solution to obtain fluorinated graphene, and adding a conductive agent and an adhesive into fluorinated graphene to obtain the fluorinated graphene electrode material. According to the technical scheme of the invention, the prepared composite material has the advantages of high specific capacitance and voltage platform and the like, and is suitable for use in electrode materials of lithium batteries.

The invention discloses a ferrous lithium salt composite anode material and thepreparation method thereof. The technical problems which are needed to be solved are to enhance the high-rate electricity discharging of the anode material, and the manufacturing and the processing performances of battery electrodes are improved. The ferrous lithium salt composite anode material has lithium iron phosphate, and forms the composite material by adulterated with or covered by nickel-cobalt-manganese-lithium or nickel-cobalt-aluminum-lithium material. The weight ratio of the lithium iron phosphate and the nickel-cobalt-manganese-lithium or the nickel-cobalt-aluminum-lithium material is 9 to 7 : 1 to 3, and the micro-morphology is in a sphericity , or is like a sphericity, with a ration between a horizontal length and a vertical length of 1.2 to 2.5. The crystal is in the structure of an olivine type, a space group is Pbnm, and a particle diameter is 1 to 20microns. The preparation method comprises mixture, fusion processing and screen separation. Compared with the prior art, the ferrous lithium salt composite anode material has the advantages of capable of lowering specific surface area, capable of enhancing the voltage platform of the anode material, favorable processing performance, high tap density, favorable conductivity, favorable rate discharge performance and safe performance, capable of improving high and low temperature cycling performance, and favorable compatibility with various cathodes and electrolytes.

The invention provides positive electrode material Fe<x>Co<1-x>S<2> powder of a thermal battery and preparation method for the powder. In the Fe<x>Co<1-x>S<2> powder, x is greater than 0 and less than 1. The positive electrode material Fe<x>Co<1-x>S<2> powder of the thermal battery is prepared by combination of advantages of two kinds of positive electrode materials of CoS<2> and FeS<2> by a method in combination of chemical deposition and high-temperature solid-phase reaction. The positive electrode material Fe<x>Co<1-x>S<2> powder of the thermal battery has the advantages of high capacity and high voltage platform of the FeS<2>, as well as the advantages of low electrical resistivity and thermal stability of CoS<2>, and is a novel positive electrode material of the thermal battery.

The invention specifically discloses a phosphate-pyrophosphate composite polyanionic iron-based positive electrode material with a chemical formula of Na4Fe2M(PO4)2(P2O7), belonging to the field of positive electrode materials for sodium-ion batteries. In the chemical formula, M is at least one selected from a group consisting of Mn, Co and Ni. In addition, the invention also discloses a preparation method and application of the positive electrode material. The positive electrode material provided by the invention has good electrical properties. Study results show that the positive electrode material has a high voltage platform of 3.5 v or more and excellent thermal stability, rate performance and cycle performance. The preparation method of the invention is simple in process, high in repeatability and low in cost and has great commercial application prospects.

The invention discloses a preparing technology of high-energy Li-marcasite battery material, which comprises the following steps: covering conductivity and stable metal oxide on the surface of marcasite with composite conductive; setting the percentage of marcasite at 82-94 percent, conductive percentage at 4-10 percent and metal oxide percentage at 2-8 percent. The method reduces grain size of natural marcasite material through wetting ball grinding technology, which prepares the needed anode material.

The invention discloses a method for preparing lithium manganese iron phosphate by a solid phase method. The preparation method comprises the following steps: weighing a certain amount of a manganese source and an iron source according to a molar ratio of 7:3, weighing a lithium source, a phosphorus source, a carbon source and a dopant according to a certain stoichiometric ratio, adding pure water, carrying out ball milling and sanding, controlling the sanding particle size D50 to be less than or equal to 300 nm, and carrying out spray drying to obtain brown precursor powder; and sintering the precursor under the protection of a nitrogen atmosphere, controlling the sintering temperature to be 600-700 DEG C, then performing crushing and screening, and removing iron to obtain the lithium manganese iron phosphate positive electrode material. The lithium manganese iron phosphate prepared by the method is simple in process and easy to control in process, compared with existing lithium iron phosphate and ternary materials, the lithium manganese iron phosphate is lower in cost and higher in voltage platform, and meanwhile, the obtained lithium manganese iron phosphate has good electrical performance and cycle performance.

The invention is applicable to the technical field of lithium batteries, and provides a high-energy density type lithium cobaltate cathode material and a preparation method thereof. According to the high-energy density type lithium cobaltate cathode material and the preparation method thereof, doped type primary lithium cobaltate particles are generated by performing solid phase reaction on a cobalt source which is pre-doped with Ni element, an additive and a lithium source, and then the surfaces of the doped type primary lithium cobaltate particles are coated with a doped N element-containingLiVPO4F material which is stable under high voltage, wherein the cobalt source is pre-doped with Ni, so that the Ni element can be distributed more uniformly in a substrate, and a material structureis more stable in a charging-discharging cyclic process; meanwhile, the substrate is added with an M element, so that the effect of stabilizing the material structure is further achieved. The LiVPO4Fmaterial has the advantages of stable structure, high voltage platform and the like; the lithium ion conductivity of the LiVPO4F material can be further improved through doping. The lithium cobaltatecathode material provided by the invention can be normally used under the max charge voltage of 4.50 V, and has excellent cycle performance and safety performance.

A cathode material is disclosed. The cathode material comprises lithium vanadium phosphate and a lithium ion battery cathode active compound. According to the cathode material, through blending the lithium vanadium phosphate and the lithium ion battery cathode active compound, present secondary lithium ion battery cathode materials are greatly improved, and characteristics of a high energy density, low-temperature discharging, high-current discharging and high-temperature safety of secondary lithium ion batteries are taken into account. In addition, a lithium ion battery including the cathode material is also disclosed. The lithium ion battery has a high energy density, a high voltage platform, long cyclic service lifetime, excellent low-temperature performance and good rate charge-discharge performance, and can meet energy density requirements of digital products and high-current charge-discharge requirements of electric tools. In addition, a preparing method of the lithium ion battery is also provided.

A method for preparing positive electrode multielement active material containing lithium / manganese composite oxide includes directly using lithium hydroxide coprecipitation to prepare M ( OH )2 , mixing it with lithium salt in grinding , forming plate by pressing , prebaking , cooled ball grinding , forming plate by pressing and backing . In the method , applied nickel salt is nickel acetate or nickel nitrate , applied cobalt salt is cobalt acetate or cobalt nitrate, applied manganese salt is manganese nitrate or manganese acetate and applied lithium salt is lithium carbonate or lithium acetate .

The invention relates to a nitrogen-doped porous carbon material used for anode of a lithium-air cell, which has a mutually communicated graded pore structure, N is uniformly doped in a C frame, wherein N accounts for 0.2-15% of carbon material, the graded pore comprises a mass transfer pore and a deposition pore, the pore volume of the deposition pore accounts for 40-95% of total pore volume, and the pore volume of the mass transfer pore accounts for 4-55% of total pore volume. The carbon material as the lithium-air cell material can greatly increase the space utilization rate of the carbon material during a charge and discharge process at maximum limit, so that lithium-air cell energy density and power density can be effectively increased. The nitrogen-doped porous carbon material used for anode of lithium-air cell has the advantages that the preparation technology is simple, the material source is wide, the pore structure of the graded aperture carbon material enables regulation and control, and the regulation and control modes are various, and the nitrogen doping mode is easy to realize.

The present invention relates to a nitrogen-doped porous carbon material for a lithium-air battery positive electrode. The nitrogen-doped porous carbon material is characterized in that the nitrogen-doped porous carbon material has an interconnected graded pore structure, N is uniformly doped in the C skeleton, N accounts for 0.2-15% of the carbon material atomic ratio, the graded pores comprise mass transfer pores and deposition holes, the deposition holes account for 40-95% of the total pore volume, and the mass transfer pores account for 4-55% of the total pore volume. According to the present invention, with application of the carbon material as the lithium-air battery electrode material, the space utilization rate of the carbon material during the charge-discharge process can be increased at a maximum, and the energy density and the power density of the lithium-air battery can be effectively increased; and the preparation process is simple, the material source is wide, the pore structure of the graded pore carbon material can be regulated, the regulation manner is diverse, and the nitrogen doping manner is easily achieved.

The invention discloses an application method of MnxCe(l-x)O2 nanoparticles. The MnxCe(l-x)O2 nanoparticles are used as a catalyst for manufacturing a catalytic film of an air electrode of an aluminum air battery, wherein x is greater than 0 but less than 1. The particles are superfine nanoparticles about 5nm, and have the advantages of large specific surface area, high electric catalytic activity, good chemical stability and the like. The air electrode is compressed by the catalytic film, a waterproof ventilating film and a current collector. The polarization current of the air electrode prepared by using the catalyst at -0.55V (the reference electrode is Hg / HgO) is 469Ma / cm<2>. The voltage platform of the air electrode forming the aluminum air battery under full current constant-current discharge of 200Ma / cm<2> is 1.24V.

The invention provides a lithium-air battery based on an oxidized graphene-carbon paper gas catalytic electrode. The positive electrode of the battery is an oxidized graphene catalytic electrode which is prepared by the following method and is supported by carbon paper. A preparation method comprises the steps of performing ultrasonic dispersion on oxidized graphene in a phosphate buffering solution to form a suspension state so as to prepare electrolyte; then the carbon paper is used as positive electrode, and a platinum electrode is used as a negative electrode; the voltage of an electrolytic battery is controlled to be 5-20V; under a proper stirring speed and proper temperature, electrophoresis-electrolysis is performed for 5-30 minutes; after electrolytic deposition is ended, oxidized graphene is loaded on the carbon paper; the carbon paper is washed by secondary distilled water and is dried under vacuum; finally a load of the oxidized graphene on the carbon paper is weighed and metered by an analysis balance. The preparation steps are simple; operation parameters are easy to control; the performance of the electrodes is stable, and reproduction is realized; under the current density of 0.1mA / cm<2>, the first discharge capacity is 11,553mAh / g; after the circulating battery runs for 520 hours, the performance is stable.

The invention discloses a lithium-rich vanadium lithium iron phosphate anode material, aiming to overcome the respective defects of lithium iron phosphate and lithium vanadium phosphate. The material comprises LixFe1-3yV2yPO4 / C, wherein the x is great than or equal to 1.0 and less than or equal to 1.15 and the y is equal to 0.01-0.2. The material simultaneously has the composite crystal structures of olivine lithium iron phosphate and monoclinic lithium vanadium phosphate. The preparation method comprises the following steps of: weighing the initial raw materials, namely a lithium source, an iron source, a vanadium source and a phosphorus source in the molar ratio of x:(1-3y):2y:1, adding a carbon source and a dispersing agent, ball-milling and mixing in a liquid medium, subjecting to low-temperature pre-sintering and high-temperature sintering under the protection of an inert gas or a reducing gas, and cooling to the room temperature, thereby obtaining the vanadium lithium iron phosphate anode material.

The invention discloses the application of organic sulfur in second magnesium battery anode material, employing organic sulfur as anode, magnesium as cathode, and Mg[AlCl2(C4H9)(C2H5)]2 / tetrahydrofuran as electrolytic solution to form second magnesium battery. The application of organic sulfur as anode material for second magnesium battery, is characterized by large capacity, high voltage plat, and first discharge capacity reaching 110 mAh / g, stable discharge voltage plat reaching about 1.6 V; and by simple process, low cost, and designable structure compared with Mo3S4 for current second magnesium battery.

The invention provides a servo power supply which is applied to an electromechanical servo system and belongs to the electromechanical field. The servo power supply source comprises a lithium battery pack (1) and a power supply management unit (2). The power supply management unit (2) is composed of a main control unit (2.1), a monomer voltage detection unit (2.2), a battery equalization management unit (2.3), a battery thermal management unit (2.4) and a peak compensation unit (2.5). The lithium battery pack (1) provides a power supply required by the electromechanical servo system. The power supply management unit (2) carries out peak current compensation and regeneration energy absorption, and carries out system management and equalization on the lithium battery pack (1). The servo power supply provided by the invention can work for a long time, can be reused, has the advantages of large capacity, high reliability, low cost and small volume, can absorb regeneration energy, can carry out large pulse discharge, and is especially suitable for an aerospace servo power supply system.

The invention discloses a preparation method of an all-solid-state battery employing a lithium metal as a negative electrode. The method is characterized by comprising the following steps: (101) pressing the lithium metal on a current collector in the preparation process of an all-solid-state battery core; (102) coating the surface of the lithium metal with a negative material thin layer; and (103) finishing pressing and molding of a solid electrolyte and a composite positive material and preparation of the all-solid-state battery core. Negative material thin layer coating is carried out on the surface of the negative electrode of the lithium metal; and the lithium metal and the solid electrolyte material are physically isolated, so that the solid electrolyte material is prevented from directly contacting the lithium metal for reaction. With the painted negative material thin layer as a transitional material, the all-solid-state battery has electronic conductivity, and meanwhile, shuttling of lithium ions in the charge-discharge cycle process of the all-solid-state battery is not hindered.

The invention discloses a preparation method of an ultrathin lithium metal negative electrode, and belongs to the technical field of lithium primary batteries. The thickness of ultrathin lithium metalis less than 100[mu]m; and the preparation method of the ultrathin lithium metal negative electrode is characterized by comprising the following steps: step 1, cutting an ultrathin lithium strip intoultrathin lithium sheets according to requirements; step 2, cutting a copper foil into tabs according to requirements; step 3, lithium sheet treatment: brushing a lithium sheet and tab bonding area with at least one of natural bristles, horse hairs, sisal hemp, soft plastic fibers, nylon, polypropylene, polyethylene and PBT to remove a lithium sheet passivation layer in the tab area; and step 4,negative electrode piece pressing: adhering a current collecting tab to the treated lithium sheet area, adopting plane pressing equipment and setting equipment pressure; wrapping the upper part and the lower part of the prepared negative electrode piece with polypropylene films respectively; and placing the negative electrode piece between an upper plate and a lower plate of a flat plate pressingmachine, and pressing to obtain the tightly combined negative electrode piece.

The present invention relates to an application of a graded pore structure porous carbon material in a lithium-air battery. The porous carbon material is characterized in that the porous carbon material has interconnected graded pore structure distribution, wherein the interconnected graded pore structure distribution comprises a mesopore structure for discharge product deposition and a macropore structure for oxygen and electrolyte transmission. According to the present invention, with application of the carbon material as the lithium-air battery electrode material, the space utilization rate of the carbon material during the charge-discharge process can be increased at a maximum, and the discharge specific capacity, the voltage platform and the rate discharge capability of the battery can be effectively increased so as to increase the energy density and the power density of the lithium-air battery; and the preparation process is simple, the material source is wide, the pore structure of the graded pore carbon material can be regulated, the regulation manner is diverse, and the metal / metal oxide doping can be concurrently and easily achieved.

The invention provides a method for preparing lithium iron manganese phosphate from waste lithium iron phosphate and a lithium manganate material. The method comprises the following steps: (1) recycling waste lithium manganate to obtain a filtrate A; (2) recycling the waste lithium iron phosphate to obtain filtrate B; (3) carrying out ICP (Inductively Coupled Plasma) test on the filtrate A and thefiltrate B to obtain the content of each main element in the two groups of filtrate; (4) the ratio of the filtrate A to the filtrate B is determined according to the mole number x + y = 1 of Fe and Mn elements in the two groups of filtrate, x is equal to (0.9-0.1), and y is equal to (0.1-0.9); supplementing a phosphorus source and a lithium source according to the required molar ratio of P, Li, Mn and Fe, and reacting to obtain a lithium ferric manganese phosphate precursor; and then carrying out high-temperature roasting thermal reaction to obtain the lithium iron manganese phosphate positive electrode material. The method provided by the invention is relatively simple in process and convenient to operate, the two waste raw materials are wide in source and low in price, the loss of resources and the addition of auxiliary materials can be reduced, the material recovery rate can be increased, and the cost of equipment, production, raw materials and the like can be reduced.

The invention discloses a novel lithium / carbon fluoride battery in the technical field of a battery. The novel lithium / carbon fluoride battery comprises an anode, a cathode, a diaphragm and electrolyte; the active component of the anode is fluoridate black, and the anode further comprises binding agent, conductive agent and anode carrier; the cathode comprises metal lithium and a cathode carrier;the diaphragm is PP / PE composite film or PI film; the electrolyte is lithium hexafluorophosphate. The novel carbon fluoride battery uses fluoridate black as anode material, so its excellent conductivity and corrected potential of the fluoridate black are used; when the battery discharges, the inner resistance is small, the polarization phenomenon is reduced, and the battery discharge ability is obviously improved. Therefore, the novel lithium / carbon fluoride battery can provide primary battery with high voltage platform and big energy density; the novel lithium / carbon fluoride battery is significant to extend the service life of mini type medical treatment devices and electronic products in a human body, and has very good commercial value.

The invention discloses an intelligent commercial vehicle diesel engine start / stop system, which can realize an idle speed start / stop function, an intelligent power generation function and finished vehicle energy management and optimization on the basis of a reinforcement starter scheme. In order to meet the frequent start and stop requirements of a city bus, a reinforcement starter with long service life is developed; in order to carry out scientific finished vehicle energy management and ensure the safe and reliable start of a finished vehicle, an intelligent LIN generator is matched, and a 24V lead-acid cell controller LBMS is developed, so that the charge state, the function state and the health state of a cell are monitored; START / STOP system control and diagnosis logic are developed to be perfectly integrated with a fuel oil control system of a diesel engine ECU. The intelligent generator carries out communication with the cell controller LBMS by LIN, and the cell controller LBMS carries out communication with a generator ECU by a CAN. According to the intelligent start / stop system, signals of a finished vehicle, an engine, the cell, the generator and the like are obtained by the CAN and a LIN network, and the diesel engine START / STOP control, generator control and cell monitoring are scientifically and reliably realized.

The invention provides a lithium nickel manganese oxide positive electrode material, a preparation method thereof and a lithium ion battery. The preparation method of the lithium nickel manganese oxide positive electrode material comprises the steps that a lithium source, a nickel source, a manganese source, water, beta-cyclodextrin, a complexing agent and an alkaline regulator are subjected to a gel reaction, a precursor gel is obtained, wherein the molar ratio of lithium elements in the lithium source to nickel elements in the nickel source to manganese elements in the manganese source is (1.00-1.06): (0.45-0.55): (1.45-1.85); and dehydrating and calcining of the precursor gel are carried out to obtain the lithium nickel manganese oxide positive electrode material. According to the preparation method, anchoring of nickel and manganese can be realized, so that the probability of mixed arrangement of lithium ions and nickel ions in the lithium nickel manganese oxide positive electrode material is reduced, the structural stability of the lithium nickel manganese oxide positive electrode material is improved, a spinel type structure is formed, and the prepared lithium nickel manganese oxide positive electrode material has good first discharge efficiency, rate capability, capacity recovery and cycling stability.

The invention relates to an ultrahigh voltage lithium cobaltate material and a preparation method thereof. The material is mainly used on a lithium ion secondary battery, so that the charging cut-off voltage of the battery can be up to 4.50V, and material has excellent cycle performance and safety performance. The general formula of the structure of the material is LiNixCo1-x-y-MyO2, wherein x is not smaller than 0.01 and is not greater than 0.08, and y is not smaller than 0.005 and is not greater than 0.1.The preparation method of the material comprises the following steps: separately mixing, ball milling and sintering a cobalt resource and a lithium source containing a doped element Ni with a compound containing an element M to obtain primary lithium cobaltate granules B and B1; mixing the primary lithium cobaltate granules B and B1 to obtain an intermediate product C; and mixing, ball milling and sintering the mixed intermediate product C with the compound containing the element M and the element Co to obtain the ultrahigh voltage lithium cobaltate material.

The invention discloses an aluminum-doped nickel-manganese binary precursor with a chemical formula: Ni<x>Mn<3x>Al<y>(OH)<8x+3y>, wherein y / x is larger than 0.068 and is smaller than 0.28, x is largerthan 0, and y is larger than 0; and the aluminum-doped nickel-manganese binary precursor is shaped like a spherical particle with the particle size distribution that D50 is equal to 6-8 [mu]m, D10 isequal to 1-6 [mu]m, and D90 is equal to 10-30 [mu]m. The nickel-manganese binary precursor is narrower in particle size distribution and has the tap density of 1.60g / cm<3>; and a lithium ion batteryobtained after the aluminum-doped nickel-manganese binary precursor is sintered with lithium carbonate is higher in energy density, high in voltage platform, good in circulation performance and safetyand excellent in rate capability. The invention further discloses a preparation method. The spherical particle with narrower particle size distribution is obtained by controlling a co-precipitation process of a reactor; and meanwhile, the reaction pH value and temperature are strictly controlled, so that the problem that the performance of a product becomes poor due to large fluctuation of the particle size is avoided.

Provided are a positive electrode active material and an electrochemical device. The positive electrode active material is of a P63mc crystal structure and is a lithium transition metal composite oxide containing Co and an R element, wherein the M element includes at least one of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, Y, or Zr, the R element includes at least one of F, Cl, and the R element is amolar content of nR; wherein the sum of the molar content of Co and the molar content of M is nCo+M, and the ratio delta of nR to nCo+M is larger than 0 and smaller than or equal to 0.01. The positiveelectrode active material disclosed by the invention is high in crystal structure stability, so that the cycle performance and the thermal stability of an electrochemical device are improved.