Positive electrode material, electrochemical device, and electric power tool

Abstract

The application relates to the technical field of energy storage, in particular to a positive electrode material, an electrochemical device and an electric equipment. The positive electrode material comprises a first powder, the first powder comprises first secondary particles, the first secondary particles comprise at least two first primary particles, the average particle size D1 of the first primary particles is 500 nm to 3 um, the average particle size D2 of the first secondary particles is 2 um to 8 um, and the ratio K1 of D2 / D1 satisfies: 2<=K1<=10; and the first powder comprises an element Co and optionally further comprises a metal element M, the metal element M comprises at least one of Mn, Al, W, Ti, Zr, Mg, La, Y, Sr or Ce; wherein the molar ratio R1 of Co and M is greater than or equal to 5. The positive electrode material has higher rate performance and safety in the case of having higher energy density.

Description

[0001] This application is a divisional application of the invention patent application (application date January 13, 2021, application number 202180003796.4, invention name "cathode material, electrochemical device and electric equipment").

TECHNICAL FIELD

[0002] The present application relates to the field of energy storage, in particular to a cathode material, an electrochemical device and an electric equipment.

BACKGROUND

[0003] With the development of electric vehicles and energy storage industry, the requirements for secondary batteries are getting higher and higher, and secondary batteries are required to have low cost, high energy density, long cycle life and high power density and other performances. In lithium ion batteries, high-nickel cathode materials are favored by the electric tool market due to their low cost and high energy density, but at the same time, high-nickel cathode materials also have problems such as low compaction, poor rate performance, high temperature rise and serious gas production. In existing batteries containing high-nickel cathode materials, in order to improve the energy density of high-nickel materials, the particle size of high-nickel cathode materials is usually made very small to improve the compaction density of high-nickel cathode materials, or the nickel content in high-nickel cathode materials is increased to more than 95%, which will reduce the rate performance of high-nickel materials, and make the gas production of high-nickel materials more serious, thereby reducing the safety performance of lithium ion batteries.

SUMMARY

[0004] The primary purpose of the present application is to propose a cathode material to solve the problems of low rate performance, serious gas production and low battery safety of existing high-nickel cathode materials with high energy density.

[0005] The second application purpose of the present application is to propose an electrochemical device to improve the capacity, rate performance and safety of the electrochemical device.

[0006] The third application purpose of the present application is to propose an electric equipment to improve the safety of the electric equipment.

[0007] In order to achieve the purpose of the present application, the technical scheme adopted is: the present application relates to a cathode material, which comprises a first powder, the first powder comprises a first secondary particle, the first secondary particle comprises at least two first primary particles, the average particle size D1 of the first primary particle is 500nm to 3um, the average particle size D2 of the first secondary particle is 2um to 8um, and the ratio K1 of D2 / D1 satisfies: 2≤K1≤10.

[0008] Further, the first powder material includes element Co and optionally further includes metal element M, the metal element M including at least one of Mn, Al, W, Ti, Zr, Mg, La, Y, Sr or Ce; wherein a molar ratio R1 of Co and M is greater than or equal to 5.

[0009] The positive electrode material of the embodiment of the present application, by controlling the size of the first secondary particles and the first primary particles and the relative size of the two, and by controlling the molar ratio of Co and other metal element M in the positive electrode material, can improve the rate performance of the positive electrode material while keeping the capacity of the positive electrode material high, and at the same time, make the gas generation of the positive electrode material occur at a lower cycle capacity retention rate, to improve the safety performance of the positive electrode material.

[0010] Further, the molar ratio R1 of element Co and metal element M in the first powder material satisfies: 11≤R1≤500.

[0011] Further, the first powder material includes lithium transition metal composite oxide, the composition of the first powder material further includes element Li and Ni, the molar content of Li element is n Li , the molar content of Ni element is n Ni , the molar content of Co element is n Co , the molar content of M element is n M , and the sum of the molar contents of Ni, Co and M elements is n Ni+Co+M , at least one of the following conditions is satisfied: (1) the ratio of n Li to n Ni+Co+M is 0.85≤n1<1.1; (2) the ratio of n Ni to n Ni+Co+M is 0.5≤x1<1; (3) the ratio of n Co to n Ni+Co+M is 0.01≤y1<0.5; (4) the ratio of n M to n Ni+Co+M is 0≤z1≤0.02.

[0012] Further, the composition of the first powder material includes Lin1Nix1Coy1Mz1O 2±m1 , wherein 0.85≤n1<1.1, 0.5≤x1<1, 0.01≤y1<0.5, 0≤z1≤0.02, x1+y1+z1=1, 0≤m1≤0.1.

[0013] Further, the metal element M contains Al, wherein the molar ratio N1 of Al element to transition metal element in the first powder material satisfies: 0.1%≤N1≤0.5%.

[0014] Further, the metal element M contains Mn, wherein the molar ratio of Mn element to transition metal element in the first powder material is less than 0.5%.

[0015] Further, the surface of the first secondary particle has a coating layer, the coating layer comprising element Z, the element Z comprising at least one of Al, W, Ti, Zr, B, P or F; the molar ratio of the element Z to the transition metal element in the first powder is less than or equal to 0.5%.

[0016] Further, the positive electrode material comprises a second powder, the second powder comprising second secondary particles, the second secondary particles comprising at least two second primary particles, the average particle size D3 of the second primary particles being 300 nm to 800 nm, the average particle size D4 of the second secondary particles being 8 um to 15 um, the ratio K2 of D4 / D3 satisfying: 15≤K2≤30.

[0017] Further, the second powder comprises element Co and metal element M, and the molar ratio R2 of the element Co to the metal element M in the second powder satisfies: 0.1≤R2≤5.

[0018] Further, the second powder comprises lithium transition metal composite oxide, the composition of the second powder further comprising element Li and Ni, the molar content of the element Li being n Li , the molar content of the element Ni being n Ni , the molar content of the element Co being n Co , the molar content of the element M being n M , the sum of the molar contents of the elements Ni, Co and M being n Ni+Co+M , at least one of the following conditions being satisfied: (a) the ratio of n Li to n Ni+Co+M is 0.85≤n2<1.1; (b) the ratio of n Ni to n Ni+Co+M is 0.5≤x2<1; (c) the ratio of n Co to n Ni+Co+M is 0.01≤y2≤0.49; (d) the ratio of n M to n Ni+Co+M is 0.01≤z2≤0.5.

[0019] Further, the composition of the second powder comprises Lin2Nix2Coy2Mz2O 2±m2 , wherein 0.85≤n2<1.1, 0.5≤x2<1, 0.01≤y2≤0.49, 0.01≤z2≤0.5, x2+y2+z2=1, 0≤m2≤0.1.

[0020] Further, the second powder comprises at least one of B and Al, wherein the ratio of the total molar amount of B and Al to the molar amount of transition metal element in the second powder is 0.1% to 0.5%.

[0021] Further, the weight of the first powder accounts for 15-60% of the total weight of the first powder and the second powder.

[0022] The application also relates to an electrochemical device comprising the positive electrode material.

[0023] The electrochemical device provided by the application has high rate performance and good safety performance while maintaining high energy density.

[0024] The application also relates to a power utilization device comprising the battery.

[0025] The power utilization device provided by the application has better power supply, higher safety and reliability.

[0026] The application is further described below in combination with specific examples. It should be understood that the examples are only used to illustrate the application and not used to limit the scope of the application. The formula, ratio and the like in the examples can be selected according to local conditions and have no substantial influence on the results.

Specific Embodiment

[0027] The positive electrode material, secondary battery and power utilization device according to the application are described in detail below.

[0028] In the first aspect, the embodiments of the application provide a positive electrode material, which comprises a first powder, the first powder comprises first secondary particles, the first secondary particles comprise at least two first primary particles, the average particle size D1 of the first primary particles is 500 nm to 3 um, the average particle size D2 of the first secondary particles is 2 um to 8 um, the ratio K1 of D2 / D1 satisfies: 2≤K1≤10; and the first powder comprises element Co and optionally further comprises metal element M, the metal element M comprises at least one of Mn, Al, W, Ti, Zr, Mg, La, Y, Sr or Ce; wherein the molar ratio R1 of Co and M is ≥5.

[0029] The metal element M can be selectively added, and the added metal element M is used to improve the cycle performance of the positive electrode material. However, the content of the added metal element M should not be too high. For example, when R1<5, the capacity retention rate of the electrochemical device containing the positive electrode material is still maintained at a high level when the gas production reaches a critical level, so that the consumer still repeatedly uses the electrochemical device, and with the continuous occurrence of gas production, a safety hazard is caused. By controlling the molar ratio R1 of Co to M to be greater than or equal to 5, the capacity retention rate of the electrochemical device when the gas production reaches a critical level can be ensured to be relatively low, for example, less than 90% in some embodiments, and less than 80% in other embodiments, so that the management system of the electrochemical device can remind the consumer to replace the electrochemical device in time according to the capacity retention rate, thereby avoiding the repeated use of the electrochemical device for many times under the condition that the gas production reaches a critical level, and improving the safety performance.

[0030] The positive electrode material of the embodiment of the present application can improve the rate performance of the positive electrode material while maintaining a high capacity of the positive electrode material, and make the gas production of the positive electrode material occur at a lower cycle retention rate, so as to improve the safety performance of the positive electrode material, by controlling the size of the first secondary particles and the first primary particles and the relative size of the two, and by controlling the molar ratio of Co to other metal elements M in the positive electrode material.

[0031] It should be noted that the first secondary particles of the embodiment of the present application are composed of the first primary particles, and the first primary particles have a small particle size. Meanwhile, the first primary particles form the first secondary particles after agglomeration.

[0032] The lower limit value of the average particle size D1 of the first primary particles is typically but not limited to 500 nm, 520 nm, 550 nm, 570 nm, 580 nm, 600 nm, 610 nm, 630 nm, 650 nm, 680 nm or a higher value, and the upper limit value of the average particle size D1 of the first primary particles is typically but not limited to 3 um, 2.8 um, 2.5 um, 2.3 um, 2.1 um, 2 um, 1.8 um, 1.7 um, 1.5 um, 1.3 um, 1.1 um, 1 um or a lower value.

[0033] The lower limit value of the average particle size D2 of the first secondary particles is typically but not limited to 2 um, 2.2 um, 2.5 um, 2.7 um, 2.8 um, 3 um, 3.2 um or a higher value, and the upper limit value of the average particle size D2 of the first secondary particles is typically but not limited to 8 um, 7.8 um, 7.5 um, 7.3 um, 7.1 um, 6 um, 6.8 um, 6.7 um, 6.5 um, 6.3 um, 6.1 um, 6 um or a lower value.

[0034] The ratio K1 of the average particle size D2 of the first secondary particles to the average particle size D1 of the first primary particles is typically, but not limited to, for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0035] The molar ratio R1 of the cobalt Co and the metal element M is typically, but not limited to, for example, 5, 6, 8, 10, 15, 18, 20, 22, 24, 26, 28, 30, or higher.

[0036] In some embodiments of the present application, the molar ratio R1 of the element Co and the metal element M in the first powder satisfies: 11≤R1≤500. The upper limit of the molar ratio R1 of the cobalt element Co and the metal element M is typically, but not limited to, for example, 500, 480, 460, 440, 420, 400, 380, 350, or a lower value, which is not listed one by one here.

[0037] In some embodiments of the present application, the first powder comprises a lithium transition metal composite oxide, and the composition of the first powder further comprises elements Li and Ni, the molar content of the Li element is n Li , the molar content of the Ni element is n Ni , the molar content of the Co element is n Co , the molar content of the M element is n M , and the sum of the molar contents of the Ni, Co, and M elements is n Ni+Co+M , at least one of the following conditions is satisfied: (1) the ratio of the n Li to the n Ni+Co+M is 0.85≤n1<1.1; (2) the ratio of the n Ni to the n Ni+Co+M is 0.5≤x1<1; (3) the ratio of the n Co to the n Ni+Co+M is 0.01≤y1<0.5; (4) the ratio of the n M to the n Ni+Co+M is 0≤z1≤0.02.

[0038] When the ratio D2 / D1 of the average particle size of the first secondary particles to the average particle size of the first primary particles satisfies 2≤K1≤10, and the molar ratio R1 of Co and M is R1≥5, by controlling the proportions of Li, Ni, Co, and the metal element M in the first powder, the energy density and cycle stability of the battery can be further improved. Wherein by controlling the content of Ni to satisfy 0.5≤x1<1, the battery using the positive electrode material can have high capacity and rate performance at the same time.

[0039] In some embodiments of the present application, the composition of the first powder comprises Lin1Nix1Coy1Mz1O2±m1 wherein 0.85≤n1<1.1, 0.5≤x1<1, 0.01≤y1<0.5, 0≤z1≤0.02, x1+y1+z1=1, 0≤m1≤0.1.

[0040] In some embodiments of the present application, the metal element M comprises Al, wherein the mole ratio N1 of the Al element to the transition metal element in the first powder satisfies: 0.1%≤N1≤0.5%.

[0041] In some embodiments of the present application, the metal element M comprises Mn, wherein the mole ratio of the Mn element to the transition metal element in the first powder is less than 0.5%.

[0042] The addition of Al and Mn elements can better inhibit gas production, improve the cycle performance and thermal stability of lithium ion batteries.

[0043] In some embodiments of the present application, the surface of the first secondary particle has a coating layer, and the coating layer comprises an element Z, the element Z comprising at least one of Al, W, Ti, Zr, B, P or F; wherein the mole ratio of the element Z to the transition metal element in the first powder is less than or equal to 0.5%.

[0044] By setting a coating layer on the surface of the first secondary particle and controlling the content of the element Z, the capacity retention rate of the battery using the positive electrode material can be maintained at a low level when gas is produced, while improving the cycle performance, thereby ensuring the safety performance.

[0045] In some embodiments of the present application, the positive electrode material comprises a second powder, the second powder comprising second secondary particles, the second secondary particles comprising at least two second primary particles, the average particle size D3 of the second primary particles being 300nm to 800nm, the average particle size D4 of the second secondary particles being 8um to 15um, and the ratio K2 of D4 / D3 satisfying: 15≤K2≤30.

[0046] By adding the second powder and limiting the particle size of the second secondary particles and the second primary particles in the second powder, the capacity and rate performance of the positive electrode material can be further improved.

[0047] In some embodiments of the present application, the second powder comprises an element cobalt Co and the metal element M, and the mole ratio R2 of Co and the metal element M in the second powder is 0.1-5. The second powder with R2≤5 has better cycle performance, but R2 should not be too small, and when R2<0.1, the capacity and rate performance of the material will be reduced.

[0048] By limiting the molar ratio of Co and metal element M in the second powder, the capacity and cycle performance of the positive electrode material can be further improved. In the second powder, the lower limit value of the molar ratio R2 of Co and metal element M can be, for example, typically but not limited to 0.1, 0.2, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3, 1.5, 1.8 or higher; the upper limit value of R2 can be, for example, typically but not limited to 5, 4.8, 4.6, 4.4, 4.2, 4.0, 3.8, 3.6, 3.4, 3.2 or lower.

[0049] In some embodiments of the present application, the composition of the second powder further includes elements Li and Ni, the molar content of the Li element is n Li , the molar content of the Ni element is n Ni , the molar content of the Co element is n Co , the molar content of the M element is n M , the sum of the molar contents of the Ni, Co and M elements is n Ni+Co+M , at least one of the following conditions is met: (a) the ratio of n Li to n Ni+Co+M is 0.85≤n2<1.1; (b) the ratio of n Ni to n Ni+Co+M is 0.5≤x2<1; (c) the ratio of n Co to n Ni+Co+M is 0.01≤y2≤0.49; (d) the ratio of n M to n Ni+Co+M is 0.01≤z2≤0.5.

[0050] As an exemplary illustration, in some embodiments of the present application, the composition of the second powder includes Lin2Nix2Coy2Mz2Om2 2±m2 , wherein 0.85≤n2<1.1, 0.5≤x2<1, 0.01≤y2≤0.49, 0.01≤z2≤0.5, x2+y2+z2=1, 0≤m2≤0.1.

[0051] In some embodiments of the present application, the second powder includes at least one of B and Al, and the ratio of the total molar amount of B and Al to the molar amount of transition metal elements in the second powder is 0.1% to 0.5%. Among them, the B element can improve the cycle performance while improving the capacity of the material; the Al element can improve the cycle performance and rate performance.

[0052] In some embodiments of the present application, the weight of the first powder accounts for 15%-60% of the total weight of the first powder and the second powder.

[0053] By optimizing the proportion of the first powder, the energy density, rate performance and gas generation performance of the positive electrode material can be balanced, so that the comprehensive performance of the obtained positive electrode material is more excellent.

[0054] As an exemplary illustration, the first secondary particles and the second secondary particles in the electrochemical device can be obtained by the following ways:

[0055] Step S1) After the electrochemical device is fully discharged, the lithium ion battery is disassembled to obtain a positive electrode sheet;

[0056] Step S2) After the positive electrode sheet is soaked in an N-methyl pyrrolidone (NMP) solution for 24 hours, the positive electrode sheet is calcined in an air atmosphere at 500°C for 5 hours;

[0057] Step S3) The positive electrode active material layer on the calcined positive electrode sheet is scraped off, and the positive electrode current collector is not scraped;

[0058] Step S4) The obtained positive electrode material powder is uniformly ground and passed through a 400-mesh sieve;

[0059] Step S5) The powder passing through the 400-mesh sieve is collected to obtain a positive electrode material powder;

[0060] Step S6) The positive electrode material powder is uniformly dispersed in an NMP solution, ultrasonically dispersed for 12 hours, and uniformly stirred to obtain a suspension containing the positive electrode material powder;

[0061] Step S7) The suspension is slowly poured onto a 1500-mesh sieve, and a part of small particles pass through the sieve into the filtrate. The powder obtained by drying the filtrate is the first powder of the present application; the other part of large particles remains on the sieve, and the powder obtained by drying is the second powder of the present application.

[0062] The above steps are carried out in a dry room with a relative humidity of <2%.

[0063] In a second aspect, the embodiments of the present application provide an electrochemical device, which comprises the positive electrode material of the first aspect of the present application.

[0064] The electrochemical device of the embodiments of the present application can be any device that can undergo an electrochemical reaction, and specific examples thereof include but are not limited to all kinds of primary batteries, secondary batteries or capacitors. In particular, the electrochemical device can be a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery. The electrochemical device comprises a positive electrode, a negative electrode and a separator film arranged between the positive electrode and the negative electrode.

[0065] The electrochemical device can be a lithium ion battery. The lithium ion battery includes a positive electrode containing a positive electrode material, a negative electrode containing a negative electrode material, an electrolyte, and a separator between the positive electrode and the negative electrode. Among them, the positive electrode material is the positive electrode material of the first aspect of the present application. The positive electrode material can be coated on the positive electrode current collector to form the positive electrode, and the negative electrode material can be coated on the surface of the negative electrode current collector to form the negative electrode. Among them, the positive electrode current collector can be an aluminum foil or a nickel foil, and the negative electrode current collector can be a copper foil or a nickel foil.

[0066] The negative electrode material can absorb and release lithium (hereinafter, sometimes referred to as "negative electrode material capable of absorbing / releasing lithium"). Examples of the negative electrode material capable of absorbing / releasing lithium can include carbon materials, metal compounds, oxides, sulfides, nitrides of lithium such as LiN3, lithium metal, metals that form alloys with lithium, and polymer materials.

[0067] Examples of the carbon material can include low graphitizable carbon, easily graphitizable carbon, artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, pyrolytic carbon, coke, glassy carbon, sintered body of organic polymer compound, carbon fiber, and activated carbon. Among them, the coke can include pitch coke, needle coke, and petroleum coke. The sintered body of organic polymer compound refers to a material obtained by calcining a polymer material such as phenol plastic or furan resin at an appropriate temperature to carbonize it, and some of these materials are classified into low graphitizable carbon or easily graphitizable carbon. Examples of the polymer material can include polyacetylene and polypyrrole.

[0068] Among these negative electrode materials capable of absorbing / releasing lithium, a material having a charge and discharge voltage close to that of lithium metal is selected. This is because the lower the charge and discharge voltage of the negative electrode material, the more easily the lithium ion battery has a higher energy density. Among them, the carbon material can be selected as the negative electrode material because their crystal structure has only a small change at the time of charge and discharge, and thus, good cycle characteristics and large charge and discharge capacity can be obtained. For example, graphite is selected because it can give a large electrochemical equivalent and a high energy density.

[0069] In addition, the negative electrode material capable of absorbing / releasing lithium can include elemental lithium metal, metal elements and semimetal elements capable of forming alloys with lithium, alloys and compounds containing such elements, and the like. For example, they are used together with the carbon material, and in this case, good cycle characteristics and high energy density can be obtained. In addition to the alloy containing two or more metal elements, the alloy used here also includes an alloy containing one or more metal elements and one or more semimetal elements. The alloy can be in the following states: solid solution, eutectic crystal, intermetallic compound, and a mixture thereof.

[0070] Examples of the metal element and the semi-metal element can include tin (Sn), lead (Pb), aluminum (Al), indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y), or hafnium (Hf). Examples of the alloy and the compound described above can include materials having a chemical formula of MasMbtLiu and materials having a chemical formula of MapMcqMdr. In these chemical formulas, Ma represents at least one element among the metal element and the semi-metal element capable of forming an alloy with lithium; Mb represents at least one element among the metal element and the semi-metal element other than lithium and Ma; Mc represents at least one element among the non-metal element; Md represents at least one element among the metal element and the semi-metal element other than Ma; and s, t, u, p, q, and r satisfy s > 0, t ≥ 0, u ≥ 0, p > 0, q > 0, and r ≥ 0.

[0071] The separator of the lithium ion battery includes, but is not limited to, at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid. For example, the polyethylene includes at least one component selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene have a good effect on preventing short circuiting and can improve the stability of the battery through a shutdown effect.

[0072] The surface of the separator can further include a porous layer disposed on at least one surface of the separator, the porous layer including one or both of inorganic particles and a binder, the inorganic particles being selected from a combination of one or more of aluminum oxide (Al2O3), silicon oxide (SiO2), magnesium oxide (MgO), titanium oxide (TiO2), hafnium dioxide (HfO2), tin oxide (SnO2), cerium dioxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (y2O3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from a combination of one or more of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0073] The porous layer can improve the heat resistance, oxidation resistance, and electrolyte impregnation of the separator, and enhance the adhesion between the separator and the positive electrode tab or the negative electrode tab.

[0074] The above lithium ion battery further includes an electrolyte, the electrolyte including a compound having not less than 2 cyano groups; the electrolyte can be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution, the electrolytic solution including a lithium salt and a nonaqueous solvent.

[0075] The lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, or lithium difluoroborate. For example, the lithium salt is selected as LiPF6because it can give a high ionic conductivity and improve cycle characteristics.

[0076] The nonaqueous solvent can be a carbonate compound, a carboxylic acid ester compound, an ether compound, other organic solvents, or a combination thereof.

[0077] The carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorinated carbonate compound, or a combination thereof.

[0078] Examples of the chain carbonate compound are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and a combination thereof. Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), or a combination thereof. Examples of the fluorinated carbonate compound are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methyl ethylene carbonate, 1-fluoro-1-methyl ethylene carbonate, 1,2-difluoro-1-methyl ethylene carbonate, 1,1,2-trifluoro-2-methyl ethylene carbonate, trifluoromethyl ethylene carbonate, or a combination thereof.

[0079] Examples of the carboxylic acid ester compound are methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decalactone, valerolactone, methylvaleronolactone, caprolactone, methyl formate, or a combination thereof.

[0080] Examples of the ether compound are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, or a combination thereof.

[0081] Examples of other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, phosphates or combinations thereof.

[0082] The positive electrode material of the present application will be further explained in combination with examples and comparative examples, and the performance of the positive electrode material of the present application will be explained in combination with lithium ion batteries.

[0083] Preparation of positive electrode sheet: the positive electrode material obtained in the following examples, conductive agent conductive carbon black, and binder polyvinylidene fluoride were mixed in a weight ratio of 97:1.5:1.5 in an N-methyl pyrrolidone (NMP) solvent system, and then stirred sufficiently to form a positive electrode slurry. The positive electrode slurry was coated on an aluminum foil, and then dried, cold-pressed, and cut to obtain a positive electrode sheet.

[0084] Preparation of negative electrode sheet: artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose were mixed in a weight ratio of 96:2:2, and then dispersed in deionized water and stirred sufficiently to form a negative electrode slurry. The negative electrode slurry was coated on a copper foil, and then dried, cold-pressed, and cut to obtain a negative electrode sheet.

[0085] Preparation of separator: a polyethylene porous polymer film was used.

[0086] Preparation of electrolyte: lithium hexafluorophosphate (1.15 mol / L) was mixed with a non-aqueous organic solvent (ethylene carbonate (EC): propylene carbonate (PC): diethyl carbonate (DEC) = 1:1:1, weight ratio) in an environment with a water content of less than 10 ppm to obtain an electrolyte.

[0087] Preparation of lithium ion battery: the positive electrode sheet, the separator, and the negative electrode sheet were sequentially stacked in order, with the separator between the positive electrode and the negative electrode to play a separating role, and then wound to obtain an electrode assembly. The electrode assembly was placed in an outer packaging aluminum plastic film, and then dehydrated at 80°C. The electrolyte described above was injected and packaged after the dehydration. The lithium ion battery was obtained after processes such as formation, degassing, and shaping.

[0088] The test items and test methods of the positive electrode material and the lithium ion battery are as follows.

[0089] 1. Measurement method of particle size of primary particles (including first primary particles and second primary particles) and secondary particles (including first secondary particles and second secondary particles):

[0090] For example, the average particle size of the primary particles is imaged by a scanning electron microscope (ZEISS Sigma-02-33, Germany). The sample is spread on a test sample table, and a photo of different areas of the sample is taken by the scanning electron microscope. Then, 20 primary particles with complete shape and no occlusion are randomly selected from the SEM photos using image analysis software, the area of each primary particle is calculated, and then the particle size R (diameter) of each primary particle is calculated by the following formula: R = 2 x (S / π) 1 / 2 ; wherein S is the area of the primary particle; the above-mentioned primary particle size R is calculated for 5 SEM images, and the particle sizes of the obtained 100 (20 x 5) primary particles are arithmetically averaged to obtain the average particle size of the primary particles.

[0091] The secondary particle size is measured in the same way as the primary particle.

[0092] 2. Cycle capacity retention rate and cycle gas production test:

[0093] The lithium ion battery is placed in a constant temperature oven at 45°C ± 2°C for 2 hours, charged at 1.5C constant current to 4.25V, then charged at 4.25V constant voltage to 0.02C and kept for 15 minutes; then discharged at 4.0C constant current to 2.8V, which is a one-time charge-discharge cycle process, and the discharge capacity of the first cycle is recorded; then the above-mentioned method is repeated for 500 times of charge-discharge cycle process, and the discharge capacity of the 500th cycle is recorded.

[0094] 4 lithium ion batteries are taken from each group, and the average value of the capacity retention rate of the lithium ion battery is calculated. The cycle capacity retention rate of the lithium ion battery = the discharge capacity of the nth cycle (mAh) / the discharge capacity of the first cycle (mAh) x 100%.

[0095] Determination of capacity retention rate C when obvious gas production starts: the beginning of obvious gas production during the cycle process refers to the maximum thickness of the lithium ion battery at the end of charging as Hc, and the thickness at the end of discharging as Hd, when (Hc-Hd) / Hd≥2%, the capacity retention rate is determined as the capacity retention rate C when obvious gas production starts.

[0096] 3. Rate test:

[0097] The lithium ion battery is placed in a constant temperature oven at 25°C ± 2°C for 2 hours, charged at 0.2C constant current to 4.25V, then charged at 4.25V constant voltage to 0.02C and kept for 15 minutes; discharged at 0.2C and 8C constant current to 2.8V respectively, and the 8C rate retention rate = 8C discharge capacity / 0.2C discharge capacity x 100%.

[0098] Example 1 : Ni 0.88 Co 0.12 (OH)2precursor and LiOH were mixed in a molar ratio of Li / (Ni+Co) = 1.03. After one-time calcination at 840°C for 20 h, the obtained product was crushed, sieved and washed with water to obtain a first powder. By controlling the parameters of crushing, sieving and water washing, the particle size D1 of the first primary particles in the first powder was 1.7 μm and the particle size D2 of the first secondary particles was 3.7 μm.

[0099] Example 2: The difference from Example 1 is that Ni 0.88 Co 0.12 (OH)2precursor, LiOH and ZrO2were mixed in a molar ratio of Li / (Ni+Co+Zr) = 1.03 and Zr / (Ni+Co+Zr) = 0.001. D1 of the first powder was 1.8 μm and D2 was 3.7 μm.

[0100] Example 3: The difference from Example 1 is that Ni 0.88 Co 0.12 (OH)2precursor, LiOH and ZrO2were mixed in a molar ratio of Li / (Ni+Co+Zr) = 1.03 and Zr / (Ni+Co+Zr) = 0.003. D1 of the first powder was 1.7 μm and D2 was 3.8 μm.

[0101] Example 4: The difference from Example 1 is that Ni 0.88 Co 0.115 Mn 0.005 (OH)2precursor, LiOH and ZrO2were mixed in a molar ratio of Li / (Ni+Co+Mn+Zr) = 1.03 and Zr / (Ni+Co+Mn+Zr) = 0.003. D1 of the first powder was 1.8 μm and D2 was 3.7 μm.

[0102] Example 5: The difference from Example 1 is that Ni 0.88 Co 0.11 Mn 0.01 (OH)2precursor, LiOH and ZrO2were mixed in a molar ratio of Li / (Ni+Co+Mn+Zr) = 1.03 and Zr / (Ni+Co+Mn+Zr) = 0.003. D1 of the first powder was 1.7 μm and D2 was 3.7 μm.

[0103] Example 6: The difference from Example 1 is that Ni 0.88 Co 0.105 Mn 0.015The (OH)2precursor, LiOH and Zr02are mixed in molar ratios of Li / (Ni+Co+Mn+Zr) = 1.03, Zr / (Ni+Co+Mn+Zr) = 0.003. D1 of the first powder sample is 1.7 pm, D2 is 3.8 pm.

[0104] Example 7: differs from example 1 in that Ni 0.88 Co 0.10 Mn 0.02 The (OH)2precursor, LiOH and Zr02are mixed in molar ratios of Li / (Ni+Co+Mn+Zr) = 1.03, Zr / (Ni+Co+Mn+Zr) = 0.003. D1 of the first powder sample is 1.7 pm, D2 is 3.8 pm.

[0105] Example 8: differs from example 1 in that Ni 0.88 Co 0.12 The (OH)2precursor, LiOH and Zr02are mixed in molar ratios of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. D1 of the first powder sample is 2.0 pm, D2 is 4.2 pm.

[0106] Example 9: differs from example 1 in that Ni 0.88 Co 0.12 The (OH)2precursor, LiOH and Zr02are mixed in molar ratios of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. D1 of the first powder sample is 0.8 pm, D2 is 2.6 pm.

[0107] Example 10: differs from example 1 in that Ni 0.88 Co 0.12 The (OH)2precursor, LiOH and Zr02are mixed in molar ratios of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. D1 of the first powder sample is 1.2 pm, D2 is 4.7 pm.

[0108] Example 11: differs from example 1 in that Ni 0.88 Co 0.12 The (OH)2precursor, LiOH and Zr02are mixed in molar ratios of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. D1 of the first powder sample is 1.4 pm, D2 is 7.5 pm.

[0109] Example 12: differs from example 1 in that Ni 0.88 Co0.12 The (OH)2precursor, LiOH and ZrO2are mixed in a molar ratio of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. The D1 of the first powder is 0.6 μm and the D2 is 5.7 μm.

[0110] Comparative Example 1: Preparation of Precursor Ni 0.88 Co 0.06 Mn 0.06 The (OH)2precursor is mixed with LiOH in a molar ratio of Li / (Ni+Co) = 1.03, and after one-time calcination at 840°C for 20 h, the obtained product is sequentially crushed, sieved and washed with water. By controlling the parameters of crushing, sieving and washing, the D1 of the obtained first powder sample is 1.7 μm and the D2 is 3.8 μm.

[0111] Comparative Example 2: Preparation of Precursor Ni 0.88 Co 0.12 The (OH)2precursor is mixed with LiOH in a molar ratio of Li / (Ni+Co) = 1.03, and after one-time calcination at 800°C for 20 h, the obtained product is sequentially crushed, sieved and washed with water. By controlling the parameters of crushing, sieving and washing, the D1 of the obtained first powder sample is 0.4 μm and the D2 is 5.6 μm.

[0112] Lithium ion batteries are prepared using the positive electrode materials provided in Examples 1-12 and Comparative Examples 1-2, respectively, and the performance test results are shown in Table 1.

[0113] Table 1

[0114]

[0115]

[0116] Referring to Table 1, from the comparative data of Examples 1 to 7, it can be seen that under the same Ni content and substantially the same D2, D1 and D2 / D1, the greater the R1 value, the more likely the gas generation occurs at a lower cycle retention rate, and thus the safety performance of the lithium ion battery is better. Meanwhile, the greater the R1 value, the better the capacity and rate performance of the material. When R1 and D2 / D1 are not within the ranges defined in the present application, the cycle capacity retention rate when gas generation is obvious is too high, and the safety performance of the lithium ion battery is poor.

[0117] From Examples 8 to 12, it can be seen that when the value of R1 is the same, the smaller the D2 / D1, the more likely the cycle capacity retention rate when gas generation is obvious is lower, and the safety performance is higher. However, D2 / D1 should not be too small, otherwise the capacity and rate performance of the material will decrease.

[0118] Examples 13 to 17 give materials with different Ni, Co contents

[0119] Example 13: differs from Example 1 in that Ni 0.96 Co 0.04 The (OH)2precursor, LiOH and ZrO2are mixed in molar ratios of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. The sample has a D1 of 1.7 μm and a D2 of 3.8 μm.

[0120] Example 14: differs from Example 1 in that Ni 0.83 Co 0.17 The (OH)2precursor, LiOH and ZrO2are mixed in molar ratios of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. The sample has a D1 of 1.7 μm and a D2 of 3.8 μm.

[0121] Example 15: differs from Example 1 in that Ni 0.70 Co 0.30 The (OH)2precursor, LiOH and ZrO2are mixed in molar ratios of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. The sample has a D1 of 1.8 μm and a D2 of 3.7 μm.

[0122] Example 16: differs from Example 1 in that Ni 0.60 Co 0.40 The (OH)2precursor, LiOH and ZrO2are mixed in molar ratios of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. The sample has a D1 of 1.7 μm and a D2 of 3.6 μm.

[0123] Example 17: differs from Example 1 in that Ni 0.50 Co 0.50 The (OH)2precursor, LiOH and ZrO2are mixed in molar ratios of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. The sample has a D1 of 1.7 μm and a D2 of 3.8 μm.

[0124] Lithium ion batteries are prepared using the positive electrode materials provided in Examples 13 to 17, respectively, and the performance test structure is shown in Table 2.

[0125] Table 2

[0126]

[0127] As can be seen from the data of Example 3 and Examples 13 to 17 in Table 2, when Co / M and D2 / D1 satisfy the ranges defined in the present application, the higher the Ni content, the relatively lower the retention rate during gas production, but the Ni content is too high, the rate performance will decrease rapidly and the temperature rise will increase significantly.

[0128] Examples 18 to 21 give several materials containing coating elements

[0129] Example 18: Ni 0.88 Co 0.12 The Ni(OH)2, Co(OH)2precursor, LiOH and ZrO2are mixed in a molar ratio of Li / (Ni+Co+Zr) = 1.03, Zr / (Ni+Co+Zr) = 0.003. After primary calcination at 840°C for 20h, the obtained product is crushed, sieved and washed with water in sequence to obtain an intermediate powder.

[0130] The obtained intermediate powder and Al2O3are mixed in a molar ratio of Al / (Ni+Co+Zr) = 0.001, and secondary calcination is carried out at 600°C for 10h to obtain a first powder with D1 of 1.8μm and D2 of 3.7μm.

[0131] Example 19: The difference from Example 18 is that the obtained intermediate powder and Al2O3are mixed in a molar ratio of Al / (Ni+Co+Zr) = 0.003. The first powder has D1 of 1.7μm and D2 of 3.8μm.

[0132] Example 20: The difference from Example 18 is that the Ni 0.88 Co 0.12 (OH)2precursor, LiOH, ZrO2and Al2O3are mixed in a molar ratio of Li / (Ni+Co) = 1.03, Zr / (Ni+Co+Zr+Al) = 0.001, Al / (Ni+Co+Zr+Al) = 0.002.

[0133] The obtained intermediate powder and Al2O3are mixed in a molar ratio of Al / (Ni+Co+Zr+Al) = 0.003. The first powder has D1 of 1.8μm and D2 of 3.8μm.

[0134] Example 21: The difference from Example 18 is that the obtained intermediate powder and H3BO3are mixed in a molar ratio of B / (Ni+Co+Zr) = 0.003, and secondary calcination is carried out at 300°C for 10h. The first powder has D1 of 1.7μm and D2 of 3.8μm.

[0135] Lithium ion batteries are prepared using the positive electrode materials provided in Examples 18-21 respectively, and the performance test structure is listed in Table 3.

[0136] Table 3

[0137]

[0138] From the comparative data of Examples 18 to 21 in Table 3, it can be seen that the first secondary particles of the first powder are coated with specific elements, and by adjusting the coating amount of the coating elements, the retention rate during gas production can be further reduced, and the retention rate during gas production can also be reduced, thereby improving the safety performance of the lithium ion battery.

[0139] Examples 22 to 33 are all prepared by mixing the material in Example 3 as the first powder with a second powder to obtain a positive electrode material. The preparation method and mixing ratio of the second powder are described as follows.

[0140] Example 22

[0141] Step 1: Prepare the sample prepared in Example 3 as the first powder;

[0142] Step 2: Prepare a Ni 0.88 Co 0.07 Mn 0.05 (OH)2 precursor with a Dv50 of 8 to 9 μm, mix it with LiOH and ZrO2 according to the molar ratio of Li / (Ni+Co+Mn+Zr)=1.03 and Zr / (Ni+Co+Mn+Zr)=0.003, and after one-time calcination at 780°C for 20 h, the obtained product is sequentially crushed, sieved and washed with water. By controlling the parameters of crushing, sieving and water washing, the D3 of the obtained second powder sample is 0.6 μm and the D4 is 11.1 μm;

[0143] Step 3: Mix the first powder and the second powder according to a mass ratio of 5:5.

[0144] Example 23: The difference from Example 22 is that the Ni 0.88 Co 0.07 Mn 0.05 (OH)2 precursor with a Dv50 of 12 to 13 μm, LiOH and ZrO2 are mixed according to the molar ratio of Li / (Ni+Co+Mn+Zr)=1.03 and Zr / (Ni+Co+Mn+Zr)=0.003. The D3 of the obtained second powder sample is 0.8 μm and the D4 is 15.6 μm.

[0145] Example 24: The difference from Example 22 is that the Ni 0.88 Co 0.07 Mn 0.05The (OH)2precursor, LiOH and Zr02are mixed in molar ratios Li / (Ni+Co+Mn+Zr) = 1.03, Zr / (Ni+Co+Mn+Zr) = 0.003. The D3of the resulting second powder sample is 0.3 pm and the D4is 9.7 pm.

[0146] Example 25: differs from example 22 in that the Ni 0.88 Co 0.10 Mn 0.02 The (OH)2precursor, LiOH and Zr02are mixed in molar ratios Li / (Ni+Co+Mn+Zr) = 1.03, Zr / (Ni+Co+Mn+Zr) = 0.003. The D3of the resulting second powder sample is 0.6 pm and the D4is 11.2 pm.

[0147] Example 26: differs from example 22 in that the Ni 0.80 Co 0.12 Mn 0.08 The (OH)2precursor, LiOH and Zr02are mixed in molar ratios Li / (Ni+Co+Mn+Zr) = 1.03, Zr / (Ni+Co+Mn+Zr) = 0.003, and are once calcined at 800 °C for 20 h. The D3of the resulting second powder sample is 0.6 pm and the D4is 11.1 pm.

[0148] Example 27: differs from example 22 in that the Ni 0.60 Co 0.10 Mn 30 The (OH)2precursor, LiOH and Zr02are mixed in molar ratios Li / (Ni+Co+Mn+Zr) = 1.03, Zr / (Ni+Co+Mn+Zr) = 0.003, and are once calcined at 850 °C for 20 h. The D3of the resulting second powder sample is 0.6 pm and the D4is 10.9 pm.

[0149] Example 28: differs from example 22 in that the Ni 0.50 Co 0.20 Mn 0.30 The (OH)2precursor, LiOH and Zr02are mixed in molar ratios Li / (Ni+Co+Mn+Zr) = 1.03, Zr / (Ni+Co+Mn+Zr) = 0.003, and are once calcined at 860 °C for 20 h. The D3of the resulting second powder sample is 0.6 pm and the D4is 11.2 pm.

[0150] Example 29: The difference from Example 22 is that the Ni 0.88 Co 0.07 Mn 0.05 The intermediate powder is obtained by mixing LiOH and Zr02in a molar ratio of Li / (Ni+Co+Mn+Zr) = 1.03 and Zr / (Ni+Co+Mn+Zr) = 0.003, crushing, sieving and washing the obtained product after one-time calcination at 860°C for 20 h. The second powder with a coating layer is obtained by mixing the obtained intermediate powder and H3BO3in a molar ratio of B / (Ni+Co+Mn) = 0.003 and secondary calcination at 300°C for 10 h. The D3of the obtained second powder is 0.6 μm and the D4is 11.2 μm.

[0151] Example 30: The difference from Example 22 is that the intermediate powder is mixed with H3BO3and Al203in a molar ratio of B / (Ni+Co+Mn+Zr) = 0.0015 and Al / (Ni+Co+Mn+Zr) = 0.0015, and secondary calcination at 500°C for 10 h to obtain the second powder with a coating layer. The D3of the obtained second powder is 0.6 μm and the D4is 11.1 μm.

[0152] Example 31: The difference from Example 22 is that the first powder and the second powder are mixed in a ratio of 3:7.

[0153] Example 32: The difference from Example 22 is that the first powder and the second powder are mixed in a ratio of 2:8.

[0154] Example 33: The difference from Example 22 is that the first powder and the second powder are mixed in a ratio of 1:9.

[0155] The specific parameters of the second powder in Examples 22 to 33 are shown in Table 4. The lithium ion batteries are prepared using the positive electrode materials provided in Examples 22-33, respectively, and the performance test results are shown in Table 5.

[0156] Table 4

[0157]

[0158] Table 5

[0159]

[0160]

[0161] From the data in Table 5, it can be seen that, compared with Example 3, the gas generation time retention of Examples 22-33 is improved, the safety slightly decreases, but the capacity and rate performance are obviously improved.

[0162] From the relevant data of the examples of the present application, it can be seen that the positive electrode material obtained by using the conditions defined in the present application can improve the safety and rate performance of the lithium ion battery while having a higher capacity when used in a lithium ion battery.

[0163] Although the present application is disclosed with the preferred embodiments as above, it is not intended to limit the claims, and any person skilled in the art can make several possible changes and modifications without departing from the concept of the present application, so the protection scope of the present application should be defined by the scope of the claims.

Claims

1. A positive electrode material, characterized by, The positive electrode material comprises a second powder, the second powder comprises second secondary particles, the second secondary particles comprise at least two second primary particles, the average particle size D3 of the second primary particles is 300nm to 800nm, the average particle size D4 of the second secondary particles is 8um to 15um, and the ratio K2 of D4 / D3 satisfies: 15≤K2≤30. The second powder comprises the element Co and a metal element M, and a molar ratio R2 of the element Co and the metal element M in the second powder satisfies: 0.1≤R2≤5; a composition of the second powder comprises Lin2Nix2Coy2Mz2O 2±m2 wherein 0.85≤n2<1.1, 0.88≤x2<1, 0.01≤y2≤0.49, 0.01≤z2≤0.5, x2+y2+z2=1, 0≤m2≤0.

1. The second powder comprises B and Al, and the ratio of the total molar amount of B and Al to the molar amount of transition metal elements in the second powder is 0.1% to 0.5%.

2. The positive electrode material of claim 1, wherein, The positive electrode material comprises a first powder, the first powder comprises first secondary particles, the first secondary particles comprise at least two first primary particles, the average particle size D1 of the first primary particles is 500nm to 3um, the average particle size D2 of the first secondary particles is 2um to 8um, and the ratio K1 of D2 / D1 satisfies: 2≤K1≤10.

3. The positive electrode material according to claim 2, characterized in that, At least one of the following is satisfied: (1) the first powder comprises element Co; (2) the first powder comprises element Co and further comprises metal element M, the metal element M comprises at least one of Mn, Al, W, Ti, Zr, Mg, La, Y, Sr or Ce; wherein the molar ratio R1 of Co and M is R1≥5.

4. The positive electrode material according to claim 3, characterized in that, The molar ratio R1 of element Co and metal element M in the first powder satisfies: 11≤R1≤500.

5. The positive electrode material of claim 3, wherein, The first powder further comprises elements Li and Ni, the molar content of the Li element is n Li , the molar content of the Ni element is n Ni , the molar content of the Co element is n Co , the molar content of the M element is n M , the sum of the molar contents of the Ni, Co and M elements is n Ni+Co+M , at least one of the following conditions is met: (1) the ratio of the n Li to the n Ni+Co+M is 0.85≤n1<1.1; (2) the ratio of the n Ni to the n Ni+Co+M is 0.5≤x1<1; (3) the ratio of the n Co to the n Ni+Co+M is 0.01≤y1<0.5; (4) the ratio of the n M to the n Ni+Co+M is 0≤z1≤0.

02.

6. The positive electrode material according to claim 5, characterized in that, The first powder has a composition comprising Lin1Nix1Coy1Mz1O 2±m1 wherein 0.85n1<1.1, 0.5x1<1, 0.01y1<0.5, 0z1<0.02, x1+y1+z1=1, 0m1<0.

1.

7. The cathode material of claim 3, wherein, The metal element M comprises Al, and the molar ratio N1 of Al element to transition metal elements in the first powder satisfies: 0.1%≤N1≤0.5%.

8. The cathode material of claim 3, wherein, The metal element M comprises Mn, and the molar ratio of Mn element to transition metal elements in the first powder is less than 0.5%.

9. The cathode material of claim 2, wherein, The surface of the first secondary particles has a coating layer, the coating layer comprises element Z, the element Z comprises at least one of Al, W, Ti, Zr, B, P or F; The molar ratio of the element Z to the transition metal elements in the first powder is less than or equal to 0.5%.

10. The cathode material of claim 2, wherein, The weight of the first powder accounts for 15% to 60% of the total weight of the first powder and the second powder.

11. An electrochemical device, characterized by, The positive electrode material comprises the positive electrode material according to any one of claims 1-10.

12. An electrical device, characterized by The electrochemical device comprises the positive electrode material according to claim 11.

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