Positive electrode active material, method for producing same, positive electrode sheet, battery, battery device, and power using device

Abstract

This application provides a positive electrode active material and its preparation method, a positive electrode sheet, a battery, a battery device, and an electrical device. The positive electrode active material includes a positive electrode active material matrix and a coating layer disposed on at least a portion of the surface of the positive electrode active material matrix. The coating layer includes a first coating layer and a second coating layer. The first coating layer is disposed on at least a portion of the surface of the positive electrode active material matrix and includes A. x (PO4) y Wherein, 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance; A includes at least one of Y, Al, Zr, Ca, and Mg; a second coating layer is disposed on at least a portion of the surface of the first coating layer; the second coating layer includes G. p F q Wherein, 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and G includes at least one of Y, Al, Zr, Ca, and Mg. The positive electrode active material of this application exhibits high structural stability and excellent cycle performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a positive electrode active material and its preparation method, a positive electrode sheet, a battery, a battery device, and an electrical device. Background Technology

[0002] Batteries are widely used as a core power supply component in end products such as smartphones, digital cameras, laptops, and electric vehicles.

[0003] During battery operation, the positive electrode active material of traditional batteries shrinks or expands significantly, resulting in poor structural durability and easy material cracking, which directly affects the structural stability and cycle life of the battery. Summary of the Invention

[0004] In view of this, this application provides a positive electrode active material and its preparation method, a positive electrode sheet, a battery, a battery device, and an electrical device, which can make the structure of the positive electrode active material more stable and improve the cycle life of the battery.

[0005] The first aspect of this application provides a positive electrode active material, the positive electrode active material comprising a positive electrode active material matrix and a coating layer disposed on at least a portion of the surface of the positive electrode active material matrix, the coating layer comprising a first coating layer and a second coating layer;

[0006] The first coating layer is disposed on at least a portion of the surface of the positive electrode active material substrate, and the first coating layer includes A x (PO4) y Where 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance, and A includes at least one of Y, Al, Zr, Ca, and Mg;

[0007] The second coating layer is disposed on at least a portion of the surface of the first coating layer; the second coating layer includes G p F q Where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and G includes at least one of Y, Al, Zr, Ca, and Mg.

[0008] This application provides a coating layer on at least a portion of the outer surface of the positive electrode active material, wherein the coating layer includes a first coating layer and a second coating layer, and A in the first coating layer x (PO4) y Suitable for bonding with the positive electrode active material matrix, with high structural stability, and G in the second coating layer p F q It possesses a certain degree of insulation, which can effectively inhibit the migration of electrons to the electrolyte, thereby effectively reducing oxidative decomposition, inhibiting interfacial side reactions, and improving cycle performance.

[0009] Optionally, the thickness of the first coating layer is 5nm-10nm, and / or the thickness of the second coating layer is 3nm-7nm.

[0010] Optionally, the coating layer further includes a first transition layer, which is disposed between the first coating layer and the second coating layer, and the first transition layer includes A. x (PO4) y and G p F q Where 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance, 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and A and G each independently include at least one of Y, Al, Zr, Ca, and Mg.

[0011] Optionally, the coating layer includes a third coating layer, wherein at least a portion of the outer surface of the second coating layer is provided with the third coating layer, and the third coating layer includes Li. m E n F O Wherein, 1≤m≤5, 0.9≤n≤1.1, 4≤o≤16, and m, n and o satisfy charge balance, wherein E includes at least one of Y, Al, Zr, Ca and Mg.

[0012] Optionally, the thickness of the third coating layer is 4nm-10nm.

[0013] Optionally, the coating layer further includes a second transition layer disposed between the second coating layer and the third coating layer, the second transition layer including G. p F q and Li m E n F O , where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, 1≤m≤5, 0.9≤n≤1.1, 4≤o≤16, and m, n and o satisfy charge balance, where G and E each independently include at least one of Y, Al, Zr, Ca, and Mg.

[0014] Optionally, the thickness of the coating layer is h, where 8nm ≤ h ≤ 20nm.

[0015] Optionally, the positive electrode active material matrix includes LiNi. a Co b Mn c T dO2, where 0.3≤a≤0.9, 0.05≤b≤0.35, 0.05≤c≤0.3, 0.001≤d≤0.05, a+b+c+d=1, and T includes one or more elements from Y, Al, Zr, Ca, and Mg.

[0016] Optionally, the first coating layer has chemical bonds with the positive electrode active material matrix, the chemical bonds being formed by A, O and N, wherein A includes at least one of Y, Al, Zr, Ca and Mg, and N includes at least one of Ni, Co and Mn.

[0017] Optionally, the positive electrode active material matrix has a granular structure, and the median particle size of the positive electrode active material matrix particles is Dv50, where 2μm≤Dv50≤15μm.

[0018] Optionally, the positive electrode active material matrix has a granular structure, the median particle size of the positive electrode active material matrix particles is Dv50, and the thickness of the coating layer is h, where h:Dv50 = 1:100-1:1875.

[0019] Secondly, this application provides a method for preparing a positive electrode active material, comprising:

[0020] A positive electrode active material precursor and an active source are mixed to form a positive electrode active material matrix;

[0021] Provide A x (PO4) y The source is used to form a first coating layer, the first coating layer being disposed on at least a portion of the surface of the positive electrode active material substrate, the first coating layer comprising A x (PO4) y Where 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance, and A includes at least one of Y, Al, Zr, Ca, and Mg;

[0022] Provide G p F q The source is used to form a second coating layer, the second coating layer being disposed on at least a portion of the surface of the first coating layer, the second coating layer including G p F q Where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and G includes at least one of Y, Al, Zr, Ca, and Mg.

[0023] Optionally, the A x (PO4) y The source includes source A and source P, which react to generate the first coating layer.

[0024] Optionally, the G pF q The sources include G source and F source, which are provided in A x (PO4) y Before forming the first coating layer, the method further includes mixing the F source with the positive electrode active material matrix to form an intermediate product, the intermediate product including a first intermediate product; after forming the first coating layer, the method further includes reacting the first intermediate product through the first coating layer with a G source to generate a second coating layer.

[0025] Optionally, the first intermediate product reacts with the G source to form the second coating layer at a first temperature, wherein the first temperature is 60°C-120°C.

[0026] Optionally, the active source is a lithium source, the intermediate product includes a second intermediate product, the second intermediate product includes LiF, and after forming the second coating layer, the method further includes: providing an E source, passing the second intermediate product through the first coating layer and the second coating layer and reacting it with the E source to generate a third coating layer, the third coating layer including LiF. m E n F O Wherein, 1≤m≤5, 0.9≤n≤1.1, 4≤o≤16, and m, n and o satisfy charge balance, wherein E includes at least one of Y, Al, Zr, Ca and Mg.

[0027] Optionally, the second intermediate product and the E source are reacted to form the third coating layer at a second temperature, which is 500°C-700°C.

[0028] Optionally, the method further includes: mixing a Ni source, a Co source, a Mn source, and a T source to form the positive electrode active material precursor, wherein the active source is a lithium source; and sintering the positive electrode active material precursor with the lithium source to obtain the positive electrode active material matrix, wherein the positive electrode active material matrix includes LiNi. a Co b Mn c T d O2, where 0.3≤a≤0.9, 0.05≤b≤0.35, 0.05≤c≤0.3, 0.001≤d≤0.05, a+b+c+d=1, and T includes one or more elements from Y, Al, Zr, Ca, and Mg.

[0029] Thirdly, this application provides a positive electrode sheet, which includes the positive active material as described in the first aspect of this application or the positive active material prepared by the preparation method described in the second aspect of this application.

[0030] Fourthly, this application provides a battery comprising a positive electrode active material as described in the first aspect of this application, a positive electrode active material prepared by the preparation method described in the second aspect of this application, or a positive electrode sheet as described in the third aspect of this application.

[0031] Fifthly, this application provides a battery device comprising a positive electrode active material as described in the first aspect of this application, a positive electrode active material prepared by the preparation method described in the second aspect of this application, a positive electrode sheet as described in the third aspect of this application, or a battery as described in the fourth aspect of this application.

[0032] Sixthly, this application provides an electrical device comprising a positive electrode active material as described in the first aspect of this application, a positive electrode active material prepared by the preparation method described in the second aspect of this application, a positive electrode sheet as described in the third aspect of this application, a battery as described in the fourth aspect of this application, or a battery device as described in the fifth aspect of this application. Detailed Implementation

[0033] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0034] The positive electrode active material provided in the first aspect of this application includes a positive electrode active material matrix and a coating layer disposed on at least a portion of the surface of the positive electrode active material matrix. The coating layer includes a first coating layer and a second coating layer. The first coating layer is disposed on at least a portion of the surface of the positive electrode active material matrix and includes A. x (PO4) y Wherein, 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance; A includes at least one of Y, Al, Zr, Ca, and Mg; a second coating layer is disposed on at least a portion of the surface of the first coating layer; the second coating layer includes G. p F q Where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and G includes at least one of Y, Al, Zr, Ca, and Mg.

[0035] The physicochemical properties of the positive electrode active material are closely related to the battery's cycle performance. During long-term charge and discharge, the positive electrode active material inevitably undergoes volume shrinkage and expansion. This volume change is significantly negatively correlated with the material's structural durability; that is, the greater the volume change, the more easily the integrity of its internal crystal structure is damaged, and the material's structural durability decreases sharply, leading to a deterioration in battery cycle stability. More importantly, the positive electrode active material generates internal stress during volume change, and this internal stress accumulates with increasing charge and discharge cycles, making the positive electrode active material highly susceptible to cracking. Once cracked, the fresh surfaces created by the cracks are exposed to the electrolyte system, which includes both liquid and solid electrolytes. When these fresh surfaces come into contact with the electrolyte, they trigger numerous side reactions, not only consuming the effective active material inside the battery but also significantly reducing the overall structural stability of the battery and shortening its cycle life.

[0036] This application provides a coating layer on at least a portion of the outer surface of the positive electrode active material, wherein the coating layer includes a first coating layer and a second coating layer, and A in the first coating layer x (PO4) y Suitable for bonding with the positive electrode active material matrix, with high structural stability, and G in the second coating layer p F q It possesses a certain degree of insulation, which can effectively suppress the migration of electrons into the electrolyte, thereby suppressing interfacial side reactions.

[0037] Further research revealed that A x (PO4) y It has strong acid resistance, while G p F q It can passivate the electrolyte, and the two work together to prevent the electrolyte from eroding the positive electrode active material matrix, thereby further improving the structural stability of the battery.

[0038] The cathode active material matrix of this application embodiment may include at least one of lithium-ion cathode active material matrix, sodium-ion cathode active material matrix, and sulfur-containing cathode active material matrix.

[0039] Lithium-ion cathode active materials may include at least one of lithium transition metal oxides, lithium-containing phosphates with olivine structures, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Examples of lithium-containing phosphates with olivine structures may include, but are not limited to, at least one of lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate.

[0040] In some embodiments of this application, lithium nickel cobalt manganese oxide has advantages such as high energy density, good cycle performance, safety and environmental friendliness, and the positive electrode active material matrix may include lithium nickel cobalt manganese oxide (LiNi). a Co b Mn c T d O2, where 0.3≤a≤0.9, 0.05≤b≤0.35, 0.05≤c≤0.3, 0.001≤d≤0.05, a+b+c+d=1, and T includes one or more elements from Y, Al, Zr, Ca, and Mg.

[0041] In nickel-cobalt-manganese ternary materials, nickel is the main active element, cobalt stabilizes the layered structure of the material and inhibits lithium-nickel mixing, while manganese reduces material cost and improves material safety and structural stability. The value of 'a' can be 0.3, 0.33, 0.5, 0.6, 0.65, 0.7, 0.74, 0.75, 0.77, 0.8, 0.85, 0.87, 0.88, 0.89, etc. The value of 'b' can be 0.05, 0.06, 0.07, 0.1, 0.12, 0.15, 0.2, 0.25, 0.3, 0.33, 0.35, etc. The value of 'c' can be 0.05, 0.06, 0.07, 0.1, 0.12, 0.15, 0.2, 0.25, 0.3, etc.

[0042] T d The doping element includes one or more of Y, Al, Zr, Ca, and Mg. Doping with T results in better structural order, smaller changes in interlayer spacing during charging and discharging, and smaller changes in cell volume, making the cathode active material matrix more stable. The value of d can be 0.001, 0.003, 0.005, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, etc.

[0043] The matrix of sodium-ion cathode active materials can include at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. Sodium transition metal oxides refer to compounds composed of sodium and oxides containing transition metal elements, where the transition metal element can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Polyanionic compounds can have sodium ions or tetrahedral anionic units, specifically phosphate systems, pyrophosphate systems, fluoropyrophosphate systems, sulfate systems, mixed anionic systems, etc. Prussian blue compounds are a class of compounds containing sodium ions, transition metal ions, and cyano groups, where the transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce.

[0044] The sulfur-containing cathode active material matrix can include at least one of elemental sulfur, sulfur-based composite materials, and polysulfide compounds. Elemental sulfur can be at least one of S2, S4, S6, and S8, offering advantages such as low cost and environmental friendliness, effectively reducing battery production costs and minimizing negative environmental impacts. Sulfur-based composite materials are composed of sulfur and functional materials, including but not limited to conductive carbon materials, metal oxides, and polymers, thereby giving the material excellent conductivity, mechanical properties, or chemical stability. Polysulfide compounds can be Li2S. n Where 4≤n≤8, it helps to fully utilize the high theoretical specific capacity of sulfur, thereby improving the energy density of the battery.

[0045] In some embodiments of this application, the positive electrode active material matrix has a granular structure, and the median particle size of the positive electrode active material matrix particles is Dv50, which satisfies 2μm≤Dv50≤15μm. Controlling the particle size of the positive electrode active material matrix can ensure the diffusion rate of active ions inside the positive electrode active material matrix, which is beneficial to the specific capacity of the positive electrode active material matrix and the cycle performance of the battery. At the same time, a suitable particle size range can also reduce the side reactions of the electrolyte on the surface of the positive electrode active material matrix, reduce gas generation and heat generation, thereby further improving the cycle performance of the positive electrode active material matrix. Specifically, the particle size Dv50 can be 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, or 15μm.

[0046] The particle size of the above-mentioned positive electrode active material matrix can be tested using instruments and methods known in the art, such as transmission electron microscopy (TEM) analysis or laser particle size analyzer.

[0047] The median particle size Dv50 of the positive electrode active material matrix can be specifically defined as the particle size Dv50 corresponding to the cumulative volume percentage of the positive electrode active material matrix particles reaching 50%. Dv50 can be tested using instruments and methods known in the art. For example, random sampling of the positive electrode sheet can be performed, and the particle size of the positive electrode active material matrix in the positive electrode active material can be observed under a transmission electron microscope (TEM) (the number of positive electrode active material particles in the sample is generally 50). The particle size corresponding to the cumulative volume percentage or the cumulative number percentage of the positive electrode active material matrix particles reaching 50% can be determined.

[0048] The positive electrode active material substrate has a coating layer on at least part of its surface. The coating layer can protect the positive electrode active material substrate, reduce its direct contact with the electrolyte, and further improve the cycle performance of the battery. The coating layer can completely cover the positive electrode active material substrate or partially cover it, depending on the amount of each substance used in the coating layer.

[0049] In some embodiments of this application, the thickness of the coating layer is h, where 8nm ≤ h ≤ 20nm. This effectively protects the positive electrode active material matrix while ensuring the capacity of the positive electrode active material matrix. Specifically, the thickness of the coating layer can be 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, or 20nm, further improving the structural stability and cycle life of the battery.

[0050] The thickness of the coating layer can be specifically understood as the average thickness of the coating layer. The average thickness of the coating layer can be tested using instruments and methods known in the art. For example, the positive electrode active material can be cut to obtain a cross-section using methods such as FIB (Focused Ion Beam) or CP (Ion Beam Cross-Section Polishing). The cross-sectional morphology can then be observed under a transmission electron microscope (TEM). A clear boundary can be observed at the coating interface. Based on the TEM image, the average thickness of the coating layer at least 5 locations in the cross-section of a single positive electrode active material particle can be analyzed. This average thickness of the coating layer of the particle can be used as the average thickness of the coating layer of that particle. At least 10 positive electrode active material particles are selected for cross-sectional morphology observation. The average thickness of the coating layer of the multiple positive electrode active material particles is then averaged again to calculate the average thickness of the coating layer.

[0051] In some embodiments of this application, the positive electrode active material matrix has a granular structure, the median particle size of the positive electrode active material matrix particles is Dv50, and the thickness of the coating layer is h, where h:Dv50 = 1:100-1:1875. The combination of the two can effectively reduce the direct contact between the positive electrode active material matrix and the electrolyte, while enhancing the buffering effect of the coating layer on the volume change of the positive electrode active material matrix. In addition, the positive electrode active material matrix and the coating layer can also cooperate to form a suitable ion diffusion path, thereby achieving synergistic optimization of the structural stability and capacity of the positive electrode active material. Specifically, h:Dv50 = 1:100, 1:200, 1:300, 1:400, 1:500, 1:600, 1:700, 1:800, 1:900, 1:1000, 1:1100, 1:1200, 1:1300, 1:1400, 1:1500, 1:1600, 1:1700, 1:1800, 1:1875.

[0052] The coating layer includes a first coating layer, which is disposed on at least a portion of the surface of the positive electrode active material substrate. The first coating layer includes A. x (PO4) y Where 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance, A includes at least one of Y, Al, Zr, Ca, and Mg, and A in the first coating layer x (PO4) y It exhibits strong adhesion to lithium transition metal oxide substrates, which can further improve the surface stability of the positive electrode active material and enhance the cycle life of the battery. Specifically, A x (PO4) y It can be AlPO4, Zr3(PO4)4, YPO4, Ca3(PO4)2, or Mg3(PO4)2.

[0053] In some embodiments of this application, the first coating layer and the positive electrode active material matrix are chemically bonded, with the chemical bonds formed by A, O, and N, wherein A includes at least one of Y, Al, Zr, Ca, and Mg, and N includes at least one of Ni, Co, and Mn. The chemical bonds enable bonding between the first coating layer and the positive electrode active material matrix, improving interfacial adhesion and enhancing the bonding force of the first coating layer on the positive electrode active material matrix. Simultaneously, they reduce interfacial impedance, improve ion transport channels, and further enhance the structural stability and cycle performance of the battery.

[0054] In some embodiments of this application, the thickness of the first coating layer is 5nm-10nm, thereby enabling the positive electrode active material to balance structural stability and high capacity. Specifically, the thickness of the first coating layer can be 5nm, 6nm, 7nm, 8nm, 9nm, or 10nm. The thickness of the first coating layer can be understood as the average thickness of the first coating layer, which can be measured using instruments and methods known in the art, such as the method described above for measuring coating layer thickness.

[0055] The coating layer includes a second coating layer disposed on at least a portion of the surface of the first coating layer; the second coating layer includes G p F q Where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and G includes at least one of Y, Al, Zr, Ca, and Mg. G in the second coating layer p F q It possesses a certain degree of insulation, which can effectively suppress the migration of electrons into the electrolyte, thereby suppressing interfacial side reactions. Specifically, G p F q It can be YF3, AlF3, ZrF4, MgF2, or CaF2.

[0056] The G element in the second coating layer can be the same as the A element in the first coating layer, thereby simplifying the raw material preparation and manufacturing process, improving production efficiency, reducing interfacial impedance, and improving ion transport efficiency. Alternatively, the G element in the second coating layer can be a different element from the A element in the first coating layer, thereby utilizing the complementary properties between elements to improve the overall performance of the battery.

[0057] In some embodiments of this application, the thickness of the second coating layer is 3nm-7nm, thereby enabling the second coating layer to form a sufficiently electronic insulating layer while ensuring a suitable ion diffusion path, further enhancing the isolation effect between the positive electrode active material matrix and the electrolyte, and further improving the structural stability and cycle performance of the battery. Specifically, the thickness of the second coating layer can be 3nm, 4nm, 5nm, 6nm, or 7nm. The thickness of the second coating layer can be specifically understood as the average thickness of the second coating layer, which can be tested using instruments and methods known in the art, such as the method described above for testing the coating layer thickness.

[0058] In some embodiments of this application, the covering layer further includes a first transition layer, which is disposed between the first covering layer and the second covering layer. The first transition layer includes A. x (PO4) y and G p F q Wherein, 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance; 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance; A and G each independently include at least one of Y, Al, Zr, Ca, and Mg. That is, the first transition layer simultaneously includes compounds from both the first and second coating layers, forming a buffer region between the bilayer structure to mitigate compositional and performance gradient changes. During battery charging and discharging, this transition layer effectively alleviates interfacial stress caused by differences in thermal expansion coefficients and ion diffusion rates between the first and second coating layers, enhancing the operational stability of the coating layer.

[0059] The coating layer includes a third coating layer, and at least a portion of the outer surface of the second coating layer is provided with the third coating layer. The third coating layer includes Li. m E n F O Where 1≤m≤5, 0.9≤n≤1.1, 4≤o≤16, and m, n, and o satisfy charge balance, and E includes at least one of Y, Al, Zr, Ca, and Mg. The Li in the third coating layer... m E n F O Formation of continuous Li + Migration channels can effectively promote Li +Improving ion transport efficiency and enhancing battery cycle performance. Specifically, Li m E n F O It can be LiYF4, Li3AlF6, Li2ZrF6, LiCaF3, or LiMgF3.

[0060] Li in the third coating layer m E n F O With A in the first coating layer x (PO4) y G in the second coating layer p F q The crystal form is well-matched, the compatibility is good, and the interfacial stability is high, thus reducing interlayer pressure. Meanwhile, Li... m E n F O As a fast ion conductor, it can promote Li+ transport, while A x (PO4) y and G p F q Possessing a certain degree of insulation and suppressing electron conduction, this synergistic effect of "ion conduction-electron blocking" helps improve the electrochemical performance of the positive electrode active material. Meanwhile, A x (PO4) y It has strong acid resistance, while G p F q and Li m E n F O They can work together to passivate the material, and the three components work synergistically to prevent the electrolyte from eroding the positive electrode active material matrix, thereby further improving the structural stability of the battery.

[0061] The element E in the third coating layer can be the same as the element G in the second coating layer and the element A in the first coating layer. This "same" can mean that E and G are the same element, E and A are the same element, or all three elements (E, G, and A) are the same. This simplifies raw material preparation and the manufacturing process, improves production efficiency, reduces interfacial impedance, and enhances ion transport efficiency. Alternatively, the element E in the third coating layer can be different from the element G in the second coating layer and the element A in the first coating layer, thus leveraging the complementary properties of the elements to improve the overall performance of the battery.

[0062] In some embodiments of this application, the thickness of the third coating layer is 4nm-10nm, which can form a suitable ion transport path, effectively reduce ion migration impedance, and simultaneously achieve an optimal thickness combination with the first and second coating layers, enabling the positive electrode active material to balance structural stability and high capacity. Specifically, the thickness of the third coating layer can be 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, or 10nm. The thickness of the third coating layer can be understood as the average thickness of the third coating layer, which can be measured using instruments and methods known in the art, such as the method described above for measuring coating layer thickness.

[0063] In some embodiments of this application, the covering layer further includes a second transition layer, which is disposed between the second covering layer and the third covering layer. The second transition layer includes G. p F q and Li m E n F O Where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance; 1≤m≤5, 0.9≤n≤1.1, 4≤o≤16, and m, n, and o satisfy charge balance; and G and E each independently include at least one of Y, Al, Zr, Ca, and Mg. That is, the second transition layer simultaneously includes compounds from both the second and third coating layers, forming a buffer region between the bilayer structure to mitigate compositional and performance gradient changes. During battery charging and discharging, this transition layer effectively alleviates interfacial stress caused by differences in thermal expansion coefficients and ion diffusion rates between the second and third coating layers, enhancing the operational stability of the coating layer.

[0064] This application also provides a method for preparing the above-mentioned positive electrode active material, including the following steps:

[0065] A positive electrode active material precursor and an active source are mixed to form a positive electrode active material matrix;

[0066] Provide A x (PO4) y The source is used to form a first coating layer, the first coating layer being disposed on at least a portion of the surface of the positive electrode active material substrate, the first coating layer comprising A x (PO4) y Where 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance, and A includes at least one of Y, Al, Zr, Ca, and Mg;

[0067] Provide G p F q The source is used to form a second coating layer, the second coating layer being disposed on at least a portion of the surface of the first coating layer, the second coating layer including G p Fq Where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and G includes at least one of Y, Al, Zr, Ca, and Mg.

[0068] The positive electrode active material prepared in this application has a coating layer on at least a portion of its outer surface, wherein the coating layer includes a first coating layer and a second coating layer, and A in the first coating layer x (PO4) y Suitable for bonding with the positive electrode active material matrix, with high structural stability, and G in the second coating layer p F q It possesses a certain degree of insulation, which can effectively suppress the migration of electrons into the electrolyte, thereby suppressing interfacial side reactions.

[0069] Further research revealed that A x (PO4) y It has strong acid resistance, while G p F q It can passivate the electrolyte, and the two work together to prevent the electrolyte from eroding the positive electrode active material matrix, thereby further improving the structural stability of the battery.

[0070] To ensure that the battery possesses advantages such as high energy density, good cycle performance, safety, and environmental friendliness, the positive electrode active material matrix includes LiNi. a Co b Mn c T d O2, where 0.3≤a≤0.9, 0.05≤b≤0.35, 0.05≤c≤0.3, 0.001≤d≤0.05, a+b+c+d=1, and T includes one or more elements from Y, Al, Zr, Ca, and Mg.

[0071] The precursor for the positive electrode active material can be a precursor formed by mixing Ni, Co, Mn, and T sources. The Ni source can be one or more of Ni-containing oxides, hydroxides, carbonates, and sulfates, such as nickel sulfate hexahydrate (NiSO4·6H2O). The Co source can be one or more of Co-containing oxides, hydroxides, carbonates, and sulfates, such as cobalt sulfate heptahydrate (CoSO4·7H2O). The Mn source can be one or more of Mn-containing oxides, hydroxides, carbonates, and sulfates, such as cobalt sulfate monohydrate (MnSO4·H2O). The T source can be one or more of T-containing hydroxides, oxides, phosphates, carbonates, and nitrates, and can be selected according to actual needs. For example, it can be a nitrate of M. The precursor for the positive electrode active material can be obtained by methods known in the art, such as co-precipitation, gelation, or solid-phase methods.

[0072] The active source is a lithium source, which can be one or more of lithium hydroxide (LiOH), lithium oxide (Li2O), lithium phosphate (Li3PO4), lithium carbonate (Li2CO3), and lithium nitrate (LiNO3), for example, lithium hydroxide.

[0073] In some embodiments of this application, A x (PO4) y Sources A and P react to form the first coating layer. Source A can be one or more of the following: hydroxide, oxide, phosphate, carbonate, and nitrate of element A. The choice can be made based on specific needs; for example, it could be a nitrate of element A. Source P can be one or more of the following: phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate. The choice can be made based on specific needs; for example, it could be diammonium hydrogen phosphate. Sources A and P can react to form A… x (PO4) y Thus, the first coating layer is obtained.

[0074] In some embodiments of this application, G p F q The source includes a G source and an F source. The G source can be one or more of the following: hydroxides, oxides, phosphates, carbonates, and nitrates of element G. It can be selected according to actual needs, for example, it can be a nitrate of G. The F source can be one or more of polytetrafluoroethylene, ammonium fluoride, and lithium fluoride, for example, it can be ammonium fluoride.

[0075] In providing A x (PO4) y Before forming the first coating layer, the method further includes mixing the F source with the positive electrode active material matrix to form an intermediate product, the intermediate product including a first intermediate product; after forming the first coating layer, the method further includes reacting the first intermediate product through the first coating layer with a G source to generate the second coating layer. That is, the second coating layer is formed through an in-situ fluorination reaction, thereby resulting in better coating uniformity of the second coating layer, effectively enhancing the interfacial stability with the first coating layer, while simplifying the preparation process and improving production efficiency.

[0076] The above-mentioned mixing method between the F source and the positive electrode active material matrix can be as follows: the positive electrode active material matrix is ​​dispersed in an organic solvent to form a dispersion, and the F source is added to the dispersion to carry out a mixing reaction. The organic solvent can be ethanol. The above-mentioned first intermediate product may include LiF.

[0077] In some embodiments of this application, the first intermediate product and the G source form a second coating layer at a first temperature, which is 60°C-120°C. By controlling the first temperature, the first intermediate product and the G source can react fully, and the second coating layer can be uniformly coated on the surface of the first coating layer, thereby more effectively isolating the positive electrode active material matrix from the electrolyte and improving the structural stability and cycle performance of the battery. Specifically, the second temperature can be 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C.

[0078] In some embodiments of this application, the active source is a lithium source, and the intermediate product includes a second intermediate product, which includes LiF. After forming the second coating layer, the method further includes: providing an E source, passing the second intermediate product through the first and second coating layers, and reacting it with the E source to generate a third coating layer, the third coating layer including LiF. m E n F O Wherein, 1≤m≤5, 0.9≤n≤1.1, 4≤o≤16, and m, n, and o satisfy charge balance, and E includes at least one of Y, Al, Zr, Ca, and Mg. That is, the third coating layer is formed through an in-situ fluorination reaction, resulting in better coating uniformity and effectively enhancing the interfacial stability with the second coating layer. Simultaneously, the preparation process is simple and improves production efficiency.

[0079] In some embodiments of this application, the second intermediate product reacts with the E source to form a third coating layer at a second temperature, which is 500°C-700°C. By controlling the second temperature, the second intermediate product and the E source can react fully, and the third coating layer can be uniformly coated on the surface of the second coating layer, thereby more effectively isolating the positive electrode active material matrix from the electrolyte and improving the structural stability and cycle performance of the battery. Specifically, the second temperature can be 500°C, 550°C, 600°C, 650°C, or 700°C.

[0080] This application also provides a positive electrode sheet, which includes the positive active material of the first aspect of this application or the positive active material prepared by the preparation method of the second aspect of this application.

[0081] In some embodiments of this application, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on the positive current collector. The positive current collector can be made of materials such as metal foil, carbon-coated metal foil, or porous metal plate, for example, aluminum foil. The positive active material layer can include the aforementioned positive active material. In some embodiments of this application, the positive active material layer further includes a positive conductive agent and a positive binder, wherein the positive conductive agent can be one or more of acetylene black, carbon black, carbon nanotubes, carbon nanofibers, activated carbon, and graphene, and the positive binder can be one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polyamide, polyacrylonitrile, and polyacrylate.

[0082] This application also provides a battery comprising the positive electrode active material of the first aspect of this application, the positive electrode active material prepared by the preparation method of the second aspect of this application, or the positive electrode sheet of the third aspect of this application.

[0083] A battery may include a positive electrode, a negative electrode, an insulating film, and an electrolyte. During charging, active ions are released from the positive electrode, pass through the electrolyte, and then deposited on the negative electrode. During discharging, active ions are released from the negative electrode, pass through the electrolyte, and then embedded in the positive electrode. The battery provided in this application has high cycle stability because it uses the positive active material of the first aspect of this application, the positive active material prepared by the preparation method of the second aspect of this application, or the positive electrode of the third aspect of this application.

[0084] In some embodiments of this application, the negative electrode sheet of the battery includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode current collector includes copper foil, and the negative electrode active material layer may include a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. The negative electrode active material includes one or more of lithium metal, natural graphite, artificial graphite, hard carbon, soft carbon, elemental silicon, silicon dioxide, silicon-oxygen composite materials, and silicon-carbon composite materials. The negative electrode binder includes one or more of polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), and styrene-butadiene latex (SBR). The negative electrode conductive agent includes one or more of acetylene black, Ketjen carbon black, Super-P, carbon nanotubes, carbon nanofibers, activated carbon, and graphene. In this application, the negative electrode can be prepared using any method known in the art.

[0085] In this application, the insulating film of the battery can be any insulating film known to those skilled in the art, such as one or more of polyolefin microporous membranes, polyethylene terephthalate, polyethylene felt, glass fiber felt, or ultrafine glass fiber paper.

[0086] In this application, the electrolyte of the battery may include at least one of liquid electrolyte and solid electrolyte.

[0087] The liquid electrolyte comprises a solution of an electrolyte lithium salt in a non-aqueous solvent. The electrolyte lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluorosilicate (Li2SiF6), lithium tetraphenylborate (LiB(C6H5)4), lithium chloride (LiCl), lithium bromide (LiBr), lithium chloroaluminate (LiAlCl4), lithium fluorocarbon sulfonate (LiC(SO2CF3)3), LiCH3SO3, LiN(SO2CF3)2, and LiN(SO2C2F5)2. In some embodiments of this application, the non-aqueous solvent includes one or more of chain esters and cyclic esters. In some embodiments of this application, the chain ester includes one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), and dipropyl carbonate (DPC). In some embodiments of this application, the chain esters include fluorinated, sulfur-containing, or unsaturated chain organic esters. In some embodiments of this application, the cyclic esters include one or more of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), γ-butyrolactone (γ-BL), and sulpholactone. In some embodiments of this application, the cyclic esters include fluorinated, sulfur-containing, or unsaturated cyclic organic esters. In some embodiments of this application, the non-aqueous solvent includes one or more of chain ethers and cyclic ether solutions. In some embodiments of this application, the cyclic ethers include one or more of tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1,3-dioxolane (DOL), and 4-methyl-1,3-dioxolane (4-MeDOL). In some embodiments of this application, the cyclic ethers include fluorinated, sulfur-containing, or unsaturated cyclic organic ethers. In some embodiments of this application, the chain ether includes one or more of dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), 1,2-dimethoxypropane (DMP), and diethylene glycol dimethyl ether (DG). In some embodiments of this application, the chain ether includes fluorine-containing, sulfur-containing, or unsaturated chain organic ethers. In some embodiments of this application, the concentration of the electrolyte lithium salt in the electrolyte is 0.1 mol / L to 15 mol / L. In some embodiments of this application, the concentration of the electrolyte lithium salt is 1 mol / L to 10 mol / L.

[0088] Solid electrolytes can include at least one of inorganic solid electrolytes and polymer solid electrolytes. Inorganic solid electrolytes can include one or more of sulfide electrolytes, fast ion conductors, and oxide electrolytes. Polymer solid electrolytes can include at least one of polyvinylpyrrolidone, polyvinyl alcohol, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyacrylonitrile, and polymethyl methacrylate. When the electrolyte is a solid electrolyte, it can serve as an insulating membrane, disposed between the positive and negative electrode plates.

[0089] This application also provides a battery device, which includes the positive electrode active material of the first aspect of this application, the positive electrode active material prepared by the preparation method of the second aspect of this application, the positive electrode sheet of the third aspect of this application, or the battery of the fourth aspect of this application. The battery device may include one or more batteries. The connection method between multiple batteries can be conventional in the art, such as series connection, parallel connection, or a hybrid connection including these connection methods, wherein a hybrid connection refers to multiple batteries being connected in both series and parallel configurations, and there is no particular limitation thereto.

[0090] This application also provides an electrical device, which includes the positive electrode active material of the first aspect of this application, the positive electrode active material prepared by the preparation method of the second aspect of this application, the positive electrode sheet of the third aspect of this application, the battery of the fourth aspect of this application, or the battery device of the fifth aspect of this application. The electrical device can be, but is not limited to, power equipment (such as electric vehicles, electric cars, spacecraft), electronic equipment (such as mobile phones, tablets, laptops, digital cameras, electric toys, etc.), wearable devices (such as watches, bracelets, VR glasses, etc.), energy storage power stations, etc.

[0091] The technical solution of this application will be further described below with reference to several embodiments.

[0092] Example 1

[0093] Preparation of the positive electrode sheet:

[0094] (1) Preparation of the positive electrode active material matrix: Ni source NiSO4·6H2O, Co source CoSO4·7H2O, Mn source MnSO4·H2O and doped T source Y(NO3)3 were prepared into a 2 mol% salt solution according to the stoichiometric ratio. The salt solution was added to the reactor and stirred at 600 rpm under a nitrogen protective atmosphere. The mixture was heated to 50°C and ammonia was added to adjust the pH of the reaction system to 11.2 to carry out a co-precipitation reaction, generating the positive electrode active material precursor Ni. 0.77 Co 0.1 Mn 0.1 Y 0.03(OH)2 was then used to mix the positive electrode active material precursor and the active source LiOH in a ball mill with an oxygen flow rate of 8 L / min. The mixture was then sintered in an oxygen furnace at 900 °C for 12 h. After crushing, batch mixing, and iron removal, the positive electrode active material matrix LiNi was prepared. 0.77 Co 0.1 Mn 0.1 Y 0.03 The median particle size Dv50 of the positive electrode active material matrix particles is 10 μm.

[0095] Preparation of positive electrode active material: The positive electrode active material matrix was dispersed in anhydrous ethanol at a rate of 60 mg / s under the action of an ultrasonic field, and the ultrasonic temperature was controlled at 20℃. Subsequently, the solution was placed on a stirring and heating platform and stirred at 400 rpm for 0.5 h at 30℃ to form a dispersion. Ammonium fluoride (NH4F) source F is added to the dispersion to obtain a reaction solution. An intermediate product is generated through the reaction. Yttrium nitrate (Y(NO3)3) source A and ammonium dihydrogen phosphate (NH4H2PO4) source P are added to the reaction solution and mixed to generate a first coating layer containing YPO4. Y(NO3)3 is added to the system. A portion of Y(NO3)3 acts as a source G and reacts with the first intermediate product LiF in the intermediate product at 100°C to generate a second coating layer containing YF3 and a first transition layer containing YF3 and YPO4. The reaction system is then annealed at 600°C for 8 hours in an oxygen atmosphere, so that another portion of Y(NO3)3 acts as a source E and reacts with the second intermediate product LiF in the intermediate product to generate a third coating layer containing LiYF4 and a second transition layer containing LiYF4 and YF3, thus obtaining a positive electrode active material. In the positive electrode active material, the thickness of the first coating layer is 7 nm, the thickness of the second coating layer is 5 nm, and the thickness of the third coating layer is 7 nm.

[0096] Example 2-18

[0097] Unlike Example 1, the relevant parameters in the preparation steps of the positive electrode active material were changed to obtain a positive electrode active material with predetermined parameter characteristics, as detailed in Table 1.

[0098] Table 1. Relevant parameters of the positive electrode active materials in Examples 1-18

[0099]

[0100] To highlight the beneficial effects of this application, the following comparative examples are provided.

[0101] Comparative Example 1

[0102] Unlike Example 1, the positive electrode active material in Comparative Example 1 is a positive electrode active material matrix and does not contain a coating layer.

[0103] Comparative Example 2

[0104] Unlike Example 1, the positive electrode active material in Comparative Example 2 does not include a first coating layer.

[0105] Comparative Example 3

[0106] Unlike Example 1, the positive electrode active material in Comparative Example 3 does not include a second coating layer.

[0107] Comparative Example 4

[0108] Unlike Example 1, no F-source ammonium fluoride (NH4F) and P-source ammonium dihydrogen phosphate (NH4H2PO4) were added during the coating stage. Instead, Y(NO3)3 was added to the dispersion to form a Y2O3 coating layer on the surface of the positive electrode active material matrix.

[0109] Effect Example

[0110] To strongly support the beneficial effects of the technical solutions in the embodiments of this application, the following tests are provided:

[0111] Ionic conductivity testing: The lithium-ion migration ability of the bulk phase and interface of the material was determined by electrochemical impedance spectroscopy (EIS), and the ionic conductivity (σ) was calculated. The positive electrode active materials prepared in Examples 1-18 and Comparative Examples 1-4 were mixed with LiPSC solid electrolyte at a mass ratio of 9:1 and pressed into discs with a diameter of 10 mm and a thickness of 1 mm (pressure 10 MPa, holding pressure for 5 min). A gold electrode (blocking electrode) was sprayed onto the surface to eliminate electronic conduction interference. Frequency range: 0.1 Hz-1 MHz, amplitude 10 mV; temperature: 25℃ constant temperature environment (temperature control accuracy ±0.5℃). The bulk resistance (Rb) and interface resistance (Rint) were calculated by fitting the equivalent circuit (e.g., R / / CPE model) using a Nyquist plot. Ionic conductivity formula: Conductivity is calculated using the formula σ = L / (Rb*A) (unit: S / cm), where L is the sample thickness (cm) and A is the electrode contact area (cm²).

[0112] Thermal decomposition temperature test: The thermal stability and decomposition temperature of the material were determined by a combination of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). 5 mg of dried positive electrode active material powder was placed in an alumina crucible. Heating rate: 10 °C / min; temperature range: 25-600 °C; atmosphere: nitrogen protection (flow rate 50 mL / min). DSC curve: The endothermic / exothermic peaks correspond to the phase transition or decomposition temperatures. TGA curve: The temperature (Td) corresponding to a 5% mass loss is defined as the thermal decomposition temperature.

[0113] Cyclic capacity retention test: The capacity decay rate of the material during long-term cycling is evaluated through constant current charge-discharge testing. Positive electrode active material: Conductive agent (Super P): Binder (PVDF) = 8:1:1, slurry coated on aluminum foil (area density 15 mg / cm²). Vacuum drying: 120℃ for 12 hours, pressing (pressure 10 MPa). Battery assembly: 2032 coin cell (positive electrode / separator (Celgard 2325) / lithium sheet), electrolyte is 1M LiPF6 and EC / DEC (volume ratio 1:1). Voltage range: 2.8-4.3V (vs. Li+ / Li); Current density: 0.5C (1C = 200 mA / g); Cycle count: 100 cycles; Temperature: 25℃ or 60℃ (high-temperature cycling tests require a temperature-controlled chamber). Data Analysis: Capacity Retention Rate (Cr) Calculation: Cr = C100 / C1 * 100% where C1 is the initial discharge capacity and C100 is the capacity after the 100th discharge.

[0114] Table 2 Performance test results of the positive electrode active materials of Examples 1-18 and Comparative Examples 1-4

[0115]

[0116] As can be seen from Table 2, the positive electrode active material provided by this application has significantly improved structural stability, ionic conductivity and cycle retention.

[0117] The above description represents the preferred embodiments of this application, but should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material includes a positive electrode active material matrix and a coating layer disposed on at least a portion of the surface of the positive electrode active material matrix, wherein the coating layer includes a first coating layer and a second coating layer; The first coating layer is disposed on at least a portion of the surface of the positive electrode active material matrix, and the first coating layer includes A x (PO4) y Where 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance, and A includes at least one of Y, Al, Zr, Ca, and Mg; The second coating layer is disposed on at least a portion of the surface of the first coating layer; the second coating layer includes G p F q Where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and G includes at least one of Y, Al, Zr, Ca, and Mg.

2. The positive electrode active material as described in claim 1, characterized in that, The thickness of the first coating layer is 5nm-10nm, and / or the thickness of the second coating layer is 3nm-7nm.

3. The positive electrode active material as described in claim 1 or 2, characterized in that, The covering layer further includes a first transition layer, which is disposed between the first covering layer and the second covering layer. The first transition layer includes A. x (PO4) y and G p F q Where 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance, 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and A and G each independently include at least one of Y, Al, Zr, Ca, and Mg.

4. The positive electrode active material according to any one of claims 1-3, characterized in that, The coating layer includes a third coating layer, wherein at least a portion of the outer surface of the second coating layer is provided with the third coating layer, and the third coating layer includes Li. m E n F O Wherein, 1≤m≤5, 0.9≤n≤1.1, 4≤o≤16, and m, n and o satisfy charge balance, wherein E includes at least one of Y, Al, Zr, Ca and Mg.

5. The positive electrode active material as described in claim 4, characterized in that, The thickness of the third coating layer is 4nm-10nm.

6. The positive electrode active material as described in claim 4 or 5, characterized in that, The covering layer further includes a second transition layer, which is disposed between the second covering layer and the third covering layer. The second transition layer includes G. p F q and Li m E n F O , where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, 1≤m≤5, 0.9≤n≤1.1, 4≤o≤16, and m, n and o satisfy charge balance, where G and E each independently include at least one of Y, Al, Zr, Ca, and Mg.

7. The positive electrode active material according to any one of claims 1-6, characterized in that, The thickness of the coating layer is h, where 8nm ≤ h ≤ 20nm.

8. The positive electrode active material according to any one of claims 1-7, characterized in that, The positive electrode active material matrix includes LiNi. a Co b Mn c T d O2, where 0.3≤a≤0.9, 0.05≤b≤0.35, 0.05≤c≤0.3, 0.001≤d≤0.05, a+b+c+d=1, and T includes one or more elements from Y, Al, Zr, Ca, and Mg.

9. The positive electrode active material as described in claim 8, characterized in that, The first coating layer has chemical bonds with the positive electrode active material matrix, and the chemical bonds are formed by A, O and N, wherein A includes at least one of Y, Al, Zr, Ca and Mg, and N includes at least one of Ni, Co and Mn.

10. The positive electrode active material according to any one of claims 1-9, characterized in that, The positive electrode active material matrix has a granular structure, and the median particle size of the positive electrode active material matrix particles is Dv50, where 2μm≤Dv50≤15μm.

11. The positive electrode active material according to any one of claims 1-10, characterized in that, The positive electrode active material matrix has a granular structure, the median particle size of the positive electrode active material matrix particles is Dv50, and the thickness of the coating layer is h, where h:Dv50 = 1:100-1:1875.

12. A method for preparing a positive electrode active material, characterized in that, include: A positive electrode active material precursor and an active source are mixed to form a positive electrode active material matrix; Provide A x (PO4) y The source is used to form a first coating layer, the first coating layer being disposed on at least a portion of the surface of the positive electrode active material substrate, the first coating layer comprising A x (PO4) y Where 1≤x≤3, 1≤y≤4, and x and y satisfy charge balance, and A includes at least one of Y, Al, Zr, Ca, and Mg; Provide G p F q The source is used to form a second coating layer, the second coating layer being disposed on at least a portion of the surface of the first coating layer, the second coating layer including G p F q Where 0.9≤p≤1.1, 2≤q≤4, and p and q satisfy charge balance, and G includes at least one of Y, Al, Zr, Ca, and Mg.

13. The preparation method according to claim 12, characterized in that, The A x (PO4) y The source includes source A and source P, which react to generate the first coating layer.

14. The preparation method according to claim 12 or 13, characterized in that, The G p F q The sources include G source and F source, which are provided in A x (PO4) y Before the source is used to form the first coating layer, the method further includes mixing the F source with the positive electrode active material matrix to form an intermediate product, the intermediate product including the first intermediate product; After forming the first coating layer, the method further includes: passing the first intermediate product through the first coating layer and reacting it with a G source to generate the second coating layer.

15. The preparation method according to claim 14, characterized in that, The first intermediate product reacts with the G source to form the second coating layer at a first temperature, which is 60°C-120°C.

16. The preparation method according to claim 14 or 15, characterized in that, The active source is a lithium source, and the intermediate product includes a second intermediate product, which includes LiF. After forming the second coating layer, the method further includes: providing an E source, passing the second intermediate product through the first coating layer and the second coating layer, and reacting it with the E source to generate a third coating layer, the third coating layer including LiF. m E n F O Wherein, 1≤m≤5, 0.9≤n≤1.1, 4≤o≤16, and m, n and o satisfy charge balance, wherein E includes at least one of Y, Al, Zr, Ca and Mg.

17. The preparation method according to claim 16, characterized in that, The second intermediate product and the E source generate the third coating layer at a second temperature of 500°C-700°C.

18. The preparation method according to any one of claims 12-17, characterized in that, The method further includes: mixing a Ni source, a Co source, a Mn source, and a T source to form the positive electrode active material precursor, wherein the active source is a lithium source; and sintering the positive electrode active material precursor with the lithium source to obtain the positive electrode active material matrix, wherein the positive electrode active material matrix includes LiNi. a Co b Mn c T d O2, where 0.3≤a≤0.9, 0.05≤b≤0.35, 0.05≤c≤0.3, 0.001≤d≤0.05, a+b+c+d=1, and T includes one or more elements from Y, Al, Zr, Ca, and Mg.

19. A positive electrode plate, characterized in that, The positive electrode sheet includes the positive active material as described in any one of claims 1-11 or the positive active material prepared by the preparation method described in any one of claims 12-18.

20. A battery, characterized in that, The battery includes the positive electrode active material as described in any one of claims 1-11, the positive electrode active material prepared by the preparation method described in any one of claims 12-18, or the positive electrode sheet as described in claim 19.

21. A battery device, characterized in that, The battery includes the positive electrode active material as described in any one of claims 1-11, or the positive electrode active material prepared by the preparation method described in any one of claims 12-18, or the positive electrode sheet as described in claim 19, or the battery as described in claim 20.

22. An electrical appliance, characterized in that, The electrical device includes the positive electrode active material as described in any one of claims 1-11, the positive electrode active material prepared by the preparation method as described in any one of claims 12-18, the positive electrode sheet as described in claim 19, the battery as described in claim 20, or the battery device as described in claim 21.

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