Cathode active material and manufacturing method, positive plate, secondary battery, battery module, battery pack and electrical equipment

Abstract

The present application provides a positive electrode active material, a method for manufacturing the same, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electrical device; the positive electrode active material comprises a core containing Li1+xMn1-yAyP1-zRzO4, a first coating layer containing crystalline pyrophosphate LiaMP2O7 and / or Mb(P2O7)c coating the core, a second coating layer containing crystalline oxide M′dOe coating the first coating layer, and a third coating layer containing carbon coating the second coating layer. The positive electrode active material of the present application can reduce the occurrence of Li / Mn antisite defects, reduce manganese leaching, and lower the crystal lattice change rate, improve the capacity of the secondary battery, and improve the cycle performance, high-temperature storage performance, and safety performance of the secondary battery.

Description

Technology Field

[0001] The present application relates to the field of secondary battery technology, and in particular to a positive electrode active material, a method for manufacturing a positive electrode active material, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electrical device. Background Technology

[0002] In recent years, as the scope of applications for secondary batteries has expanded, they are widely applied in various fields, including energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. With the tremendous advancement of secondary batteries, requirements regarding energy density, cycle performance, and safety performance are also increasing. During the charge-discharge process of lithium manganese phosphate, a conventional cathode active material for secondary batteries, Li / Mn antisite defects are prone to occur and manganese leaching is relatively severe, affecting the capacity per gram of the secondary battery and thereby degrading the safety and cycle performance of the secondary battery. The problem to be solved

[0003] This application has been made in consideration of the above-mentioned problem, and its purpose is to provide a cathode active material, a method for manufacturing the cathode active material, a cathode plate, a secondary battery, a battery module, a battery pack, and an electrical device for solving problems such as low capacity, poor safety performance, and cycle performance of secondary batteries by resolving the issues of existing lithium manganese phosphate cathode active materials being prone to Li / Mn antisite defects and relatively serious manganese leaching during the charge-discharge process. means of solving the problem

[0004] To achieve the above objective, the first aspect of the present application provides an anode active material having a core-shell structure, wherein the anode active material comprises a core and a shell covering the core, and

[0005] The core is Li 1+x Mn 1-y A y P 1-zR z Includes O4, where x is any number in the range of -0.100 to 0.100, y is any number in the range of 0.001 to 0.600, z is any number in the range of 0.001 to 0.100, A is one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, optionally one or more elements selected from Fe, V, Ni, Co, and Mg, R is one or more elements selected from B, Si, N, and S, optionally one or more elements selected from Si, N, and S;

[0006] The shell includes a first covering layer covering the core, a second covering layer covering the first covering layer, and a third covering layer covering the second covering layer, wherein,

[0007] The first coating layer is crystalline pyrophosphate Li a MP2O7 and / or M b (P2O7) c Includes, where a is greater than 0 and less than or equal to 2, b is any value within the range of 1 to 4, c is any value within the range of 1 to 3, and crystalline pyrophosphate Li a MP2O7 and M b (P2O7) c M in is each independently one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and optionally one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, and Al;

[0008] The second coating layer is crystalline oxide M′ d O eIncludes, wherein d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is one or more elements selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and Sb, optionally one or more elements selected from Li, Be, B, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, W, La and Ce, and more optionally one or more elements selected from Mg, Al, Si, Ti, V, Ni, Cu, Zr and W;

[0009] The third coating layer contains carbon.

[0010] The inventors of this application discovered in actual practice that lithium manganese phosphate cathode active materials easily develop Li / Mn antisite defects during deep charge-discharge processes, and that manganese leaching is relatively severe. The leached manganese migrates to the anode and is reduced to metallic manganese. This generated metallic manganese acts as a 'catalyst' and can catalyze the decomposition of the SEI film (solid electrolyte interphase) on the anode surface. Since some of the generated byproducts are gaseous, they tend to cause the battery to swell, affecting the safety performance of the secondary battery. Additionally, other parts are deposited on the anode surface, obstructing the pathway for lithium ions to enter and exit the anode, thereby increasing the resistance of the secondary battery and affecting its kinetic and cycle performance. Furthermore, to replenish the lost SEI film, the electrolyte and active lithium within the battery are continuously consumed, having an irreversible effect on the capacity retention rate of the secondary battery.

[0011] Thus, the applicant unexpectedly provided a novel cathode active material having a core-shell structure capable of significantly reducing the occurrence of Li / Mn antisite defects, significantly lowering manganese leaching, lowering the crystal lattice change rate, and increasing compressive density by doping the manganese site of lithium manganese phosphate with element A and doping the phosphorus site with element R to obtain a doped lithium manganese phosphate core and sequentially coating the core surface with three layers. It was discovered that applying this to a secondary battery can improve the capacity of the secondary battery and enhance the cycle performance, high-temperature storage performance, and safety performance of the secondary battery. Here, since the crystalline oxide in the second coating layer has high structural stability and low surface activity, interfacial side reactions can be effectively reduced by coating the second coating layer, thereby improving the performance of the battery, such as high-temperature cycling and high-temperature storage.

[0012] Here, the crystalline state refers to a degree of crystallization of 50% or more, that is, 50%-100%. A degree of crystallization less than 50% is called the glassy state.

[0013] The degree of crystallization of the crystalline pyrophosphate of the present application is 50% to 100%. A pyrophosphate having a constant degree of crystallization is advantageous not only for fully exhibiting the ability to hinder manganese leaching from the pyrophosphate coating layer and the function of reducing interfacial side reactions, but also for enabling better crystal lattice matching between the pyrophosphate coating layer and the oxide coating layer, thereby enabling close bonding between the coating layers.

[0014] Unless otherwise specified, chemical formula Li 1+x Mn 1-y A y P 1-z R zIn O4, when A is two or more elements, the limitation on the numerical range of y is not only a limitation on the stoichiometric number of each element as A, but also a limitation on the sum of the stoichiometric numbers of each element as A. For example, when A is two or more elements A1, A2… … An, the stoichiometric numbers y1, y2… … yn of each of A1, A2… … An must all be within the numerical range limited for y in this application, and the sum of y1, y2… … yn must also be within this numerical range. Similarly, for the case where R is two or more elements, the limitation on the numerical range of the stoichiometric number of R in this application has the above meaning.

[0015] Unless otherwise specified, chemical formula M b (P2O7) c In this case, when M is two or more elements, the limitation on the numerical range of b is not only a limitation on the stoichiometric number of each element as M, but also a limitation on the sum of the stoichiometric numbers of each element as M. For example, when M is two or more elements M1, M2…Mn, the stoichiometric numbers b1, b2…bn of each M1, M2…Mn must all be within the numerical range limited to b in this application, and the sum of b1, b2…bn must also be within this numerical range. Similarly, the chemical formula M′ d O e In the case where M′ is two or more elements, the limitation on the numerical range of the stoichiometric number d of M′ in this application also has the above meaning.

[0016] In any embodiment of the first aspect, the crystal plane spacing range of the crystalline pyrophosphate in the first coating layer is 0.293 to 0.470 nm, and the angle range of the crystal direction (111) is 18.00° to 32.00°;

[0017] Optionally, the crystal plane spacing range of the crystalline pyrophosphate in the first coating layer is 0.297 to 0.462 nm; and / or,

[0018] Optionally, the angle range of the crystal direction (111) of the crystalline pyrophosphate in the first coating layer is 19.211° to 30.846°.

[0019] In the positive active material of the present application, the first coating layer uses a crystalline material, and the crystal plane spacing and angle range are within the above range. In this way, impurity phases within the coating layer can be effectively avoided, thereby improving the capacity per gram of the material and improving the cycle performance and rate performance of the secondary battery.

[0020] In any embodiment of the first aspect, the ratio of y to 1-y in the core is 1:10 to 1:1, and optionally 1:4 to 1:1. In this way, the cycle performance and rate performance of the secondary battery are further improved.

[0021] In any embodiment of the first aspect, the ratio of z to 1-z in the core is 1:9 to 1:999, and optionally 1:499 to 1:249. In this way, the cycle performance and rate performance of the secondary battery are further improved.

[0022] In any embodiment of the first aspect, the carbon in the third coating layer is a mixture of SP2-type carbon and SP3-type carbon; optionally, the molar ratio of SP2-type carbon and SP3-type carbon is any value in the range of 0.07 to 13, more optionally any value in the range of 0.1 to 10, and more optionally any value in the range of 2.0 to 3.0.

[0023] In this application, the overall performance of a secondary battery is improved by limiting the molar ratio of SP2-type carbon and SP3-type carbon to within the above range.

[0024] In any embodiment of the first aspect, the coating amount of the first coating layer is greater than 0 and less than or equal to 6 wt%, optionally greater than 0 and less than or equal to 5.5 wt%, more optionally greater than 0 and less than or equal to 2 wt%, and is calculated based on the weight of the core; and / or

[0025] The coating amount of the second coating layer is greater than 0 and less than or equal to 6 wt%, optionally greater than 0 and less than or equal to 5.5 wt%, more optionally 2 wt% to 4 wt%, calculated based on the weight of the core; and / or

[0026] The coating amount of the third coating layer is greater than 0 and less than or equal to 6 wt%, optionally greater than 0 and less than or equal to 5.5 wt%, more optionally greater than 0 and less than or equal to 2 wt%, and is calculated based on the weight of the core.

[0027] In the positive electrode active material having a core-shell structure of the present application, the coating amount of the three-layer coating layer is preferably within the above range, thereby sufficiently coating the core and, at the same time, further improving the kinetic performance and safety performance of the secondary battery without sacrificing the capacity per gram of the positive electrode active material.

[0028] In any embodiment of the first aspect, the thickness of the first coating layer is 2 to 10 nm. In the present application, if the thickness range of the first coating layer is 2 to 10 nm, the elution and migration of transition metal ions can be further reduced and the kinetic performance of the secondary battery can be improved.

[0029] In any embodiment of the first aspect, the thickness of the second coating layer is 3 to 15 nm. If the thickness of the second coating layer is within the range of 3 to 15 nm, the surface structure of the second coating layer is stable and the side reaction with the electrolyte is small, so the interfacial side reaction can be effectively reduced and the high-temperature performance of the secondary battery can be improved.

[0030] In any embodiment of the first aspect, the thickness of the third coating layer is 5 to 25 nm. If the thickness range of the third coating layer is 5 to 25 nm, the conductivity performance of the material can be improved and the compression density performance of the battery electrode plate manufactured using the positive electrode active material can be improved.

[0031] In any embodiment of the first aspect, calculated based on the weight of the anode active material;

[0032] The manganese elemental content is in the range of 10 wt% to 35 wt%, optionally in the range of 15 wt% to 30 wt%, and more optionally in the range of 17 wt% to 20 wt%;

[0033] The phosphorus elemental content is in the range of 12 wt% to 25 wt%, and optionally in the range of 15 wt% to 20 wt%;

[0034] Optionally, the weight ratio of manganese to phosphorus is in the range of 0.90 to 1.25, and more optionally in the range of 0.95 to 1.20.

[0035] In the positive electrode active material having a core-shell structure according to the present application, since the content of the manganese element is within the above range, the structural stability and density of the positive electrode active material can be effectively improved, thereby improving performance such as cycle, storage, and compression density of the secondary battery; and the energy density of the secondary battery can be improved by maintaining a constant voltage plateau height.

[0036] In the anode active material having a core-shell structure according to the present application, since the content of the phosphorus element is within the above range, the conductivity of the anode active material can be effectively improved and the structural stability of the anode active material can be improved.

[0037] In the positive electrode active material having a core-shell structure according to the present application, if the weight ratio of manganese and phosphorus elements is within the above range, the leaching of transition metals can be reduced to improve the stability of the positive electrode active material and the cycle and storage performance of the secondary battery, and the energy density of the secondary battery can be improved by maintaining a constant discharge voltage plateau height.

[0038] In any embodiment of the first aspect, the crystal lattice change rate before and after complete lithium desorption of the positive active material is 50% or less, optionally 4% or less, more optionally 3.8% or less, and more optionally 2.0% to 3.8%.

[0039] The positive electrode active material having a core-shell structure of the present application can achieve a relatively low crystal lattice change rate before and after lithium extraction. Therefore, using the positive electrode active material can improve the capacity per gram and rate performance of the secondary battery.

[0040] In any embodiment of the first aspect, the Li / Mn antisite defect concentration of the anode active material is 5.3% or less, optionally 4% or less, more optionally 2.2% or less, and more optionally 1.5% to 2.2%. If the Li / Mn antisite defect concentration is within the above range, Li + It can improve the transport of and, at the same time, improve the capacity per gram of the positive active material and the rate performance of the secondary battery.

[0041] In any embodiment of the first aspect, the compressive density of the anode active material at 3T is 1.95 g / cm³ 3 That is the limit, and optionally 2.2 g / cm³ 3 That is the limit, and more optionally 2.2 g / cm³ 3 Above 2.8 g / cm² 3 Less than, and more optionally 2.2 g / cm³ 3 Above 2.65 g / cm³ 3 The following applies. Thus, by improving the compression density and increasing the weight of the positive active material per unit volume, it is advantageous for improving the energy density per unit volume of the secondary battery.

[0042] In any embodiment of the first aspect, the surface oxygen atom state of the positive active material is -1.89 or lower, and optionally -1.90 to -1.98. Thus, by limiting the surface oxygen atom state of the positive active material to within the above range as described above, side reactions at the interface between the positive material and the electrolyte can be reduced, thereby improving performance such as battery cell cycles and high-temperature storage gas generation.

[0043] In providing a method for manufacturing an anode active material in the second aspect of the present application,

[0044] Step of providing core material - the core material is Li 1+x Mn 1-y A y P 1-z R z Contains O4, where x is any number in the range of -0.100 to 0.100, y is any number in the range of 0.001 to 0.600, z is any number in the range of 0.001 to 0.100, A is one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and optionally one or more elements selected from Fe, V, Ni, Co, and Mg, and R is one or more elements selected from B, Si, N, and S, and optionally one or more elements selected from Si, N, and S - ;

[0045] First coating step - Li pyrophosphate a MP2O7 and / or M b (P2O7) c A first mixture comprising is supplied, and after mixing the core material and the first mixture, a material coated with a first coating layer is obtained through drying and sintering, wherein a is greater than 0 and less than or equal to 2, b is any value within the range of 1 to 4, c is any value within the range of 1 to 3, and pyrophosphate Li a MP2O7 and M b (P2O7)c M in is each independently one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and optionally one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, and Al - ;

[0046] Second coating step - Oxide M′ d O e A second mixture comprising... is provided, and a material coated with a first coating layer is mixed with the second mixture, followed by drying and sintering, to obtain a material coated with a two-layer coating, wherein d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is one or more elements selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements, and Sb, optionally one or more elements selected from Li, Be, B, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, W, La, and Ce, and more optionally one or more elements selected from Mg, Al, Si, Ti, V, Ni, Cu, Zr, and W It is an element - ;

[0047] Third coating step - providing a third mixture containing a carbon source, mixing the material coated with a two-layer coating with the third mixture, and then drying and sintering to obtain an anode active material - ; including,

[0048] Here, the positive active material has a core-shell structure, which includes a core and a shell covering the core, and the core is Li 1+x Mn 1-y A y P 1-z R zIt includes O4, and the shell includes a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer, and the first coating layer is a crystalline pyrophosphate Li a MP2O7 and / or M b (P2O7) c It includes, and the second coating layer is a crystalline oxide M′ d O e It includes, and the third coating layer includes carbon.

[0049] Thus, the present application provides a novel cathode active material having a core-shell structure capable of significantly reducing the occurrence of Li / Mn antisite defects, significantly lowering manganese leaching, lowering the crystal lattice change rate, and increasing the compressive density by doping the manganese site of lithium manganese phosphate with element A and doping the phosphorus site with element R to obtain a doped lithium manganese phosphate core and sequentially coating the core surface with three layers. When applied to a secondary battery, the capacity of the secondary battery can be improved, and the cycle performance, high-temperature storage performance, and safety performance of the secondary battery can be improved.

[0050] In any embodiment of the second aspect of the present application, the step of providing a core material is,

[0051] Step (1) of obtaining a mixture by mixing a manganese source, a source of element A, and an acid;

[0052] The mixture obtained in step (1) is mixed with a lithium source, a phosphorus source, a source of element R, and an optional solvent, and then sintered under the protection of an inert gas to obtain Li 1+x Mn 1-y A y P 1-z R z It includes the step (2) of obtaining a core material containing O4.

[0053] In any embodiment of the second aspect of the present application, step (1) is carried out at 20°C to 120°C, optionally 40°C to 120°C; and / or, in step (1), mixing is performed by stirring at a rotational speed of 400 to 700 rpm for 1 to 9 hours.

[0054] In any embodiment of the second aspect of the present application, in step (2), mixing is performed for 1 to 10 hours at a temperature of 20 to 120°C, optionally 40 to 120°C.

[0055] In any embodiment of the second aspect of the present application,

[0056] In the first coating step, a source of element M, a phosphorus source, an acid, an optionally selected lithium source, and an optionally selected solvent are mixed to obtain a first mixture; and / or,

[0057] In the second coating step, element M′ and a solvent are mixed to obtain a second mixture; and / or,

[0058] In the third coating step, a carbon source and a solvent are mixed to obtain a third mixture.

[0059] In any embodiment of the second aspect of the present application, in the first coating step, a source of element M, a source of phosphorus, an acid, an optionally selected lithium source, and an optionally selected solvent are mixed at room temperature for 1 to 5 hours, then heated again to 50°C to 120°C and mixed at this temperature for 2 to 10 hours, and the mixing is all carried out under conditions where the pH is 3.5 to 6.5.

[0060] In any embodiment of the second aspect of the present application, in the second coating step, a source of element M′ and a solvent are mixed at room temperature for 1 to 10 hours, then heated again to 60°C to 150°C and mixed at this temperature for 2 to 10 hours.

[0061] In any embodiment of the second aspect of the present application, the source of element A is one or more selected from the element A, carbonate, sulfate, halide, nitrate, organic acid, oxide, and hydroxide; and / or,

[0062] The source of element R is one or more selected from inorganic acids, organic acids, sulfates, halides, nitrates, organic acid salts, oxides, and hydroxides of element R.

[0063] In any embodiment of the second aspect of the present application, sintering in the first coating step is carried out at 650 to 800°C for 2 to 8 hours; and / or, sintering in the second coating step is carried out at 400 to 750°C for 6 to 10 hours; and / or, sintering in the third coating step is carried out at 600 to 850°C for 6 to 10 hours.

[0064] In providing an anode plate in a third aspect of the present application, the anode plate comprises an anode current collector and an anode film layer installed on at least one surface of the anode current collector, wherein the anode film layer comprises an anode active material according to the first aspect of the present application or an anode active material manufactured through the manufacturing method of the second aspect of the present application; optionally, the content of the anode active material in the anode film layer is 90 to 99.5 weight%, more optionally 95 to 99.5 weight%, and is calculated based on the total weight of the anode film layer.

[0065] In providing a secondary battery in the fourth aspect of the present application, the secondary battery comprises a positive active material according to the first aspect of the present application, a positive active material manufactured through the manufacturing method of the second aspect of the present application, or a positive plate according to the third aspect of the present application.

[0066] In providing a battery module in the fifth aspect of the present application, it includes a secondary battery according to the fourth aspect of the present application.

[0067] In providing a battery pack in the sixth aspect of the present application, it includes a battery module according to the fifth aspect of the present application.

[0068] In providing an electric device in the seventh aspect of the present application, it comprises at least one selected from a secondary battery according to the fourth aspect of the present application, a battery module according to the fifth aspect of the present application, and a battery pack according to the sixth aspect of the present application. Brief explanation of the drawing

[0069] FIG. 1 is a schematic diagram of an anode active material having a three-layer coating structure according to one embodiment of the present application. FIG. 2 is a schematic diagram of a secondary battery according to one embodiment of the present application. FIG. 3 is an exploded view of a secondary battery according to one embodiment of the present application shown in FIG. 2. FIG. 4 is a schematic diagram of a battery module according to one embodiment of the present application. FIG. 5 is a schematic diagram of a battery pack according to one embodiment of the present application. FIG. 6 is an exploded view of a battery pack according to one embodiment of the present application illustrated in FIG. 5. FIG. 7 is a schematic diagram of an electric device using a secondary battery as a power source according to one embodiment of the present application. Specific details for implementing the invention

[0070] In the following, embodiments specifically disclosing the positive active material, the method for manufacturing the positive active material, the positive plate, the secondary battery, the battery module, the battery pack, and the electrical device of the present application will be described in detail with appropriate reference to the drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of known matters or repetitive descriptions of identical structures may be omitted. This is to avoid making the following description unnecessarily long and to aid the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided to facilitate a sufficient understanding of the present application by those skilled in the art and are not intended to limit the essence described in the claims.

[0071] The 'range' disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by the selection of one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a specific range. A range limited in this way may include or not include boundary values, and may also be arbitrarily combined. That is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, it can be understood that ranges of 60 to 110 and 80 to 120 are also expected. Additionally, if minimum range values ​​1 and 2 and maximum range values ​​3, 4 and 5 are listed, all ranges may be expected to be 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise noted, the numeric range 'a to b' represents an abbreviated expression of any combination of real numbers from a to b, where a and b are real numbers. For example, the numeric range '0 to 5' indicates that all real numbers between '0 to 5' are listed here, and '0 to 5' is an abbreviated expression of such combination of numbers. Additionally, if a specific parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that this parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0072] In this application, the ranges of 'less than or equal to a specific value' and 'greater than or equal to a specific value' indicate a range that limits a specific value to an upper or lower limit.

[0073] Unless otherwise specified, all embodiments and optional embodiments of the present application may be combined with one another to form a new technical solution.

[0074] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with one another to form a new technical solution.

[0075] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, but sequentially is preferred. For example, if a method comprises steps (a) and (b), it indicates that the method may comprise steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if a method further comprises step (c), it indicates that step (c) may be added to the method in any order. For example, a method may comprise steps (a), (b), and (c), steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0076] Unless otherwise specified, the terms 'include' and 'have' as used in this application are open forms and may also be closed forms. For example, 'include' and 'have' may indicate that other unlisted components may be included or have, or that only the listed components may be included or have.

[0077] Unless otherwise specified, the term 'or' in this application is inclusive. For example, the phrase 'A or B' indicates 'A, B, or A and B'. More specifically, any of the following conditions satisfy the condition 'A or B': A being true (or existing) and B being false (or absent); A being false (or absent) and B being true (or existing); or both A and B being true (or existing).

[0078] Unless otherwise specified, the term "coating layer" in this application refers to a layer of material covering the core, and the material layer may completely or partially cover the core; the use of "coating layer" is for convenience of explanation only and is not intended to limit the invention.

[0079] Unless otherwise specified, in this application, the term 'thickness of the coating layer' refers to the thickness of the coating layer in the core radial direction, and the definition of the term 'coating layer' is as above.

[0080] [Rechargeable Battery]

[0081] Secondary batteries, also known as rechargeable batteries or storage batteries, refer to batteries that can be continuously used by reactivating active materials through a charging method after discharge.

[0082] Generally, a secondary battery comprises a positive plate, a negative plate, a separator, and an electrolyte. During the charging and discharging process, active ions (e.g., lithium ions) reciprocate between the positive and negative plates, undergoing insertion and extraction. The separator is installed between the positive and negative plates to prevent short circuits between them while allowing active ions to pass through. The electrolyte serves to conduct active ions between the positive and negative plates.

[0083] [Anode Active Material]

[0084] The present application provides an anode active material having a core-shell structure, comprising a core and a shell covering the core, and

[0085] The core is Li 1+x Mn 1-y A y P 1-z R z Includes O4, where x is any number in the range of -0.100 to 0.100, y is any number in the range of 0.001 to 0.600, z is any number in the range of 0.001 to 0.100, A is one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, optionally one or more elements selected from Fe, V, Ni, Co, and Mg, R is one or more elements selected from B, Si, N, and S, optionally one or more elements selected from Si, N, and S;

[0086] The shell includes a first covering layer covering the core, a second covering layer covering the first covering layer, and a third covering layer covering the second covering layer, wherein,

[0087] The first coating layer is crystalline pyrophosphate Li a MP2O7 and / or M b (P2O7) c Includes, where a is greater than 0 and less than or equal to 2, b is any value within the range of 1 to 4, c is any value within the range of 1 to 3, and crystalline pyrophosphate Li a MP2O7 and M b (P2O7) c M in is each independently one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and optionally one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, and Al;

[0088] The second coating layer is crystalline oxide M′ d O e Includes, wherein d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is one or more elements selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and Sb, optionally one or more elements selected from Li, Be, B, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, W, La and Ce, and more optionally one or more elements selected from Mg, Al, Si, Ti, V, Ni, Cu, Zr and W;

[0089] The third coating layer contains carbon.

[0090] The cathode active material of the present application can improve the capacity per gram, cycle performance, and safety performance of a secondary battery. Although the mechanism is not clear, measurements indicate that the cathode active material of the present application has a core-shell structure, and if element A and element R are doped into the manganese sites and phosphorus sites of the lithium manganese phosphate core, respectively, manganese leaching can be effectively reduced, furthermore, the migration of manganese ions to the anode can be reduced, the electrolyte consumed due to SEI film decomposition can be reduced, and the cycle performance and safety performance of the secondary battery can be improved, as well as promote Mn-O bond adjustment, lower the lithium ion migration barrier, promote lithium ion migration, and improve the rate performance of the secondary battery; by coating the core with a first coating layer containing crystalline pyrophosphate, the migration resistance of manganese is increased to reduce its leaching, the surface lithium doping content is reduced, the contact between the core and the electrolyte is reduced to reduce interfacial side reactions, gas generation is reduced, and the high-temperature storage performance, cycle performance, and safety performance of the secondary battery can be improved; Additionally, by coating with a crystalline oxide coating layer having high stability, interfacial side reactions on the surface of the cathode active material can be effectively reduced, and furthermore, the high-temperature cycle and storage performance of the secondary battery can be improved; furthermore, by coating with a carbon layer as a third coating layer, the safety performance and kinetic performance of the secondary battery can be further improved. In addition, element A doped in the manganese sites of lithium manganese phosphate in the core helps reduce the crystal lattice change rate of lithium manganese phosphate during the lithium delithiation process of this material, improves the structural stability of the cathode material, significantly reduces manganese leaching, and lowers oxygen activity on the particle surface; and element R doped in the phosphorus sites helps change the difficulty of Mn-O bond length change, thereby improving electronic conductivity, lowering the lithium ion transport barrier, promoting lithium ion transport, and improving the rate performance of the secondary battery.

[0091] Unless otherwise specified, chemical formula Li 1+x Mn 1-y A y P 1-z R z In O4, when A is two or more elements, the limitation on the numerical range of y is not only a limitation on the stoichiometric number of each element as A, but also a limitation on the sum of the stoichiometric numbers of each element as A. For example, when A is two or more elements A1, A2… … An, the stoichiometric numbers y1, y2… … yn of each of A1, A2… … An must all be within the numerical range limited for y in this application, and the sum of y1, y2… … yn must also be within this numerical range. Similarly, for the case where R is two or more elements, the limitation on the numerical range of the stoichiometric number of R in this application has the above meaning.

[0092] In some embodiments, when A is one, two, three, or four elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, A y is Q n1 D n2 E n3 K n4And, where n1+n2+n3+n4=y, and also n1, n2, n3, and n4 are all integers and are not simultaneously zero, and Q, D, E, and K are each independently selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and optionally, at least one of Q, D, E, and K is Fe. Optionally, one of n1, n2, n3, and n4 is zero and the others are not zero; more optionally, two of n1, n2, n3, and n4 are zero and the others are not zero; more optionally, three of n1, n2, n3, and n4 are zero and the others are not zero. Core Li 1+x Mn 1-y A y P 1-z R z It is advantageous to dope one, two, three, or four of the above-mentioned A elements at the manganese sites in O4, optionally dope one, two, or three of the above-mentioned A elements; additionally, it is advantageous to dope one or two of the above-mentioned R elements at the phosphorus sites, which is advantageous for a uniform distribution of the doping elements.

[0093] In some embodiments, the values ​​of x, y, and z satisfy the conditions for maintaining electrical neutrality of the entire core.

[0094] Core Li 1+x Mn 1-y A y P 1-z R zIn O4, to ensure that the entire system exhibits electrical neutrality, the size of x is influenced by the valence state sizes of A and R, and the sizes of y and z. If the value of x is too small, the lithium content of the entire core system decreases, affecting the capacity per gram of the material. The value of y limits the total amount of all doping elements; if y is too small, i.e., if the doping amount is too low, the doping elements do not function, and if y exceeds 0.5, the Mn content in the system becomes relatively low, affecting the voltage plateau of the material. Since the R element is doped at the P position and the PO tetrahedron is relatively stable, and if the value of z is too large, it affects the stability of the material, the value of z is limited to 0.001 to 0.100.

[0095] In addition, the entire core system maintains electrical neutrality, ensuring that defects and impurity phases in the cathode active material are minimized. If an excess of transition metals (e.g., manganese) is present in the cathode active material, the remaining transition metals are likely to precipitate in the form of elements or form impurity phases within the crystal lattice because the structure of the material system itself is relatively stable; therefore, maintaining electrical neutrality can minimize these impurity phases. Furthermore, ensuring the electrical neutrality of the system allows for the creation of lithium vacancies in the material under certain conditions, thereby improving the material's kinetic performance.

[0096] Through process control (e.g., sufficiently mixing and grinding materials from various sources), it is possible to ensure that each element is uniformly distributed within the crystal lattice and that there is no aggregation. The position of the major characteristic peak in the XRD graph of lithium manganese phosphate after doping with elements A and R coincides with that of undoped LiMnPO4; since this indicates that no impurity phase was introduced during the doping process, the improvement in core performance is attributed primarily to elemental doping rather than the impurity phase. The inventors of this application discovered that after manufacturing the cathode active material, they cut an intermediate region of the completed cathode active material particles using a focused ion beam (FIB) and measured the results using a transmission electron microscope (TEM) and an X-ray energy dispersive spectrometer (EDS), finding that each element is uniformly distributed and does not aggregate.

[0097] In some embodiments, the values ​​of a, b, and c are crystalline pyrophosphate Li a MP2O7 or M b (P2O7) c It satisfies the conditions for maintaining electrical neutrality.

[0098] In some embodiments, the values ​​of d and e are crystalline state M′ d O e It satisfies the conditions for maintaining electrical neutrality.

[0099] In some embodiments, the crystalline state means that the degree of crystallization is 50% or more, i.e., 50% to 100%. A degree of crystallization less than 50% is called a glassy state.

[0100] In some embodiments, the degree of crystallization of the crystalline pyrophosphate of the present application is 50% to 100%. A pyrophosphate having a constant degree of crystallization is advantageous not only for fully exhibiting the ability to hinder manganese leaching from the pyrophosphate coating layer and the function of reducing interfacial side reactions, but also for enabling better crystal lattice matching between the pyrophosphate coating layer and the oxide coating layer, thereby enabling a tighter bonding of the coating layers.

[0101] In some embodiments, the degree of crystallinity of the crystalline pyrophosphate, which is the first coating layer material of the anode active material, may be measured using general technical means in the art, such as density methods, infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance, or may be measured using X-ray diffraction.

[0102] Specifically, a method for measuring the degree of crystallization of the crystalline pyrophosphate of the first coating layer of the anode active material using X-ray diffraction may include the following steps.

[0103] A certain amount of anode active material powder is collected, and the total scattering intensity is measured using X-rays, which is the sum of the scattering intensities of the entire spatial material and is related only to the primary line intensity, the chemical structure of the anode active material powder, and the total number of electrons participating in diffraction, i.e., the mass size, and is not related to the order of the samples; then, crystalline scattering and amorphous scattering are separated from the diffraction pattern, and the degree of crystallinity is the ratio of the crystalline partial scattering to the total scattering intensity.

[0104] It should be noted that in some embodiments, the degree of crystallinity of the pyrophosphate in the coating layer can be controlled by adjusting process conditions of the sintering process, such as sintering temperature and sintering time.

[0105] In some embodiments, since metal ions have difficulty migrating from pyrophosphate, using pyrophosphate as the first coating layer can effectively isolate doped metal ions from the electrolyte. Since the structure of crystalline pyrophosphate is stable, coating with crystalline pyrophosphate can effectively suppress the leaching of transition metals and improve cycle performance.

[0106] In some embodiments, the bond between the first coating layer and the core is similar to a heterojunction, and the strength of the bond is limited by the degree of crystal lattice mismatch. When the crystal lattice mismatch is 5% or less, the crystal lattice mismatch is relatively good, and the two are easily bonded tightly. A tight bond ensures that the coating layer does not detach during subsequent cycling processes and is advantageous for ensuring the long-term stability of the material. The degree of bonding between the first coating layer and the core is determined primarily by calculating the degree of mismatch between the core and each crystal lattice constant of the coating. In the present application, after the core is doped with elements A and R, the degree of match between the core and the first coating layer is improved compared to when the elements are not doped, and a tighter bond can be formed between the core and the pyrophosphate coating layer.

[0107] The reason for using a crystalline oxide as the second coating layer is, first, that the degree of crystal lattice matching with the crystalline pyrophosphate, which is the first coating material, is relatively high (the degree of mismatch is 3%); and second, that since the stability of the crystalline oxide itself as the second coating layer is better than that of pyrophosphate, using it to coat the pyrophosphate is advantageous for the stability of the material. Since the structure of the crystalline oxide as the second coating layer is very stable, using the crystalline oxide for coating can effectively reduce interfacial side reactions on the surface of the positive electrode active material, thereby improving the high-temperature cycle and storage performance of the secondary battery. The crystal lattice matching method between the second coating layer and the first coating layer is similar to the bonding situation between the first coating layer and the core, and when the crystal lattice mismatch is 5% or less, the crystal lattice matching is relatively good, and the two are easily and closely bonded.

[0108] The primary reason for using carbon as the third-layer coating is the relatively good electronic conductivity of the carbon layer. Since electrochemical reactions occur when applied to secondary batteries, electron participation is required; therefore, a coating using carbon with excellent conductivity can be applied to increase electron transport between particles and electron transport to different positions within the particles. Carbon coating can effectively improve the conductivity and desolvation capabilities of the cathode active material.

[0109] FIG. 1 is a schematic diagram of an anode active material having an ideal three-layer coating structure. As shown in the figure, the innermost circle represents the core, and sequentially from inside out are the first coating layer, the second coating layer, and the third coating layer. This figure represents an ideal state where each layer is completely covered, but in reality, each coating layer may be completely covered or partially covered.

[0110] In some embodiments, the crystal plane spacing range of the crystalline pyrophosphate in the first coating layer is 0.293 to 0.470 nm, and the angle range of the crystal direction (111) is 18.00° to 32.00°;

[0111] Optionally, the crystal plane spacing range of the crystalline pyrophosphate in the first coating layer is 0.297 to 0.462 nm; and / or,

[0112] Optionally, the angle range of the crystal direction (111) of the crystalline pyrophosphate in the first coating layer is 19.211° to 30.846°.

[0113] The crystalline pyrophosphate of the first coating layer can be characterized by general technical means in the field or by transmission electron microscopy (TEM). In TEM, the core and the coating layer can be distinguished by measuring the crystal plane spacing.

[0114] A specific method for measuring the inter-plane spacing and angle of the crystal planes of the crystalline pyrophosphate of the first coating layer may include the following steps.

[0115] A certain amount of coated anode active material sample powder is placed in a test tube, a solvent such as alcohol is injected into the test tube, and then sufficiently stirred to disperse it. Then, an appropriate amount of the solution is taken using a clean disposable plastic suction tube and dropped onto a 300-mesh copper mesh, at which point some powder remains on the copper mesh. The copper mesh is then transferred to a TEM sample room along with the sample and measured to obtain an original TEM image, and the original image is saved.

[0116] The original photograph obtained from the above TEM measurement is opened in diffractometer software, a diffraction pattern is obtained through Fourier transform, the crystal surface spacing is obtained by measuring the distance from the diffraction spot of the diffraction pattern to the center position, and the narrow angle is obtained by calculating according to Bragg's law.

[0117] Crystalline pyrophosphate within the above crystal plane spacing and narrow angle range can more effectively suppress the crystal lattice change rate and Mn elution of lithium manganese phosphate during the lithium desorption process, thereby improving the high-temperature cycle performance, rate performance, cycle stability, and high-temperature storage performance of the secondary battery.

[0118] In some embodiments, the ratio of y to 1-y in the core is 1:10 to 1:1, and optionally 1:4 to 1:1. Here, y represents the sum of the stoichiometric numbers of Mn-site doping element A. When the above conditions are satisfied, the energy density, rate performance, and cycle performance of a secondary battery using the positive electrode active material can be further improved.

[0119] In some embodiments, the ratio of z to 1-z in the core is 1:9 to 1:999, and optionally 1:499 to 1:249. Here, z represents the sum of the stoichiometric numbers of the p-site doping element R. When the above conditions are satisfied, the energy density, rate performance, and cycle performance of a secondary battery using the positive electrode active material can be further improved.

[0120] In some embodiments, the carbon in the third coating layer is a mixture of SP2-type carbon and SP3-type carbon; optionally, the molar ratio of SP2-type carbon and SP3-type carbon is any value in the range of 0.07 to 13, more optionally any value in the range of 0.1 to 10, and more optionally any value in the range of 2.0 to 3.0.

[0121] In some embodiments, the molar ratio of SP2 form carbon to SP3 form carbon may be about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, or about 10, or may be within any range of any of the above values.

[0122] In this application, the specific numerical value 'approx.' represents a range, and represents a range of ±10% of this value.

[0123] The overall electrical performance of a secondary battery is improved by selecting the form of carbon within the carbon coating layer. Specifically, by using a mixture of SP2 and SP3 carbon forms and limiting the ratio of SP2 to SP3 carbon to a certain range, good conductivity can be achieved and the pathway for lithium ions can be ensured, which is advantageous for the implementation of secondary battery functions and cycle performance.

[0124] The mixing ratio of SP2 and SP3 forms of carbon in the third coating layer can be controlled through sintering conditions such as sintering temperature and sintering time. For example, when manufacturing the third coating layer using sucrose as a carbon source, the sucrose decomposes at high temperature and is deposited on the second coating layer, simultaneously producing a carbon coating layer that possesses both SP3 and SP2 forms under high temperature action. The ratio of SP2 form carbon to SP3 form carbon can be adjusted by selecting high-temperature decomposition conditions and sintering conditions.

[0125] The structure and characteristics of the third coating layer carbon can be measured through Raman spectra, and the specific measurement method is to determine the molar ratio of the two by obtaining Id / Ig (where Id is the peak intensity of the SP3 form carbon and Ig is the peak intensity of the SP2 form carbon) through peak separation of the energy spectrum of the Raman measurement.

[0126] In some embodiments, the coating amount of the first coating layer is greater than 0 and less than or equal to 6 wt%, optionally greater than 0 and less than or equal to 5.5 wt%, more optionally greater than 0 and less than or equal to 2 wt%, and is calculated based on the weight of the core; and / or

[0127] The coating amount of the second coating layer is greater than 0 and less than or equal to 6 wt%, optionally greater than 0 and less than or equal to 5.5 wt%, more optionally 2 wt% to 4 wt%, calculated based on the weight of the core; and / or

[0128] The coating amount of the third coating layer is greater than 0 and less than or equal to 6 wt%, optionally greater than 0 and less than or equal to 5.5 wt%, more optionally greater than 0 and less than or equal to 2 wt%, and is calculated based on the weight of the core.

[0129] In the present application, the coverage amount of each layer is not all zero.

[0130] In the positive electrode active material having a core-shell structure of the present application, the coating amount of the three-layer coating layer is preferably within the above range, thereby sufficiently coating the core and, at the same time, further improving the kinetic performance and safety performance of the secondary battery without sacrificing the capacity per gram of the positive electrode active material.

[0131] In the case of the first coating layer, if the coating amount is within the above range, the leaching of transition metals can be reduced and the smooth movement of lithium ions can be ensured, thereby improving the rate performance of the positive electrode active material.

[0132] In the case of the second coating layer, if the coating amount is within the above range, a constant flat voltage of the anode active material can be maintained and the coating effect can be guaranteed.

[0133] In the case of the third coating layer, the carbon coating primarily acts to increase electron transport between particles, and since a large amount of amorphous carbon is contained within the structure, the carbon density is relatively low, and if the coating amount is within the above range, the compressive density of the electrode plate can be ensured.

[0134] In some embodiments, the thickness of the first coating layer is 2 to 10 nm; and / or

[0135] The thickness of the second coating layer is 3 to 15 nm; and / or

[0136] The thickness of the third coating layer is 5 to 25 nm.

[0137] In some embodiments, the thickness of the first coating layer may be about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, or about 10 nm, or may be within any range of any of the above values.

[0138] In some embodiments, the thickness of the second coating layer may be about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 11 nm, about 12 nm, about 13 nm, about 14 nm, about 15 nm, or may be within any range of any of the above values.

[0139] In some embodiments, the thickness of the third layer coating layer may be about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 11 nm, about 12 nm, about 13 nm, about 14 nm, about 15 nm, about 16 nm, about 17 nm, about 18 nm, about 19 nm, about 20 nm, about 21 nm, about 22 nm, about 23 nm, about 24 nm, or about 25 nm, or may be within any range of any of the above values.

[0140] If the thickness range of the first coating layer is 2 to 10 nm, the leaching of transition metals can be effectively reduced and the kinetic performance of the secondary battery can be ensured.

[0141] If the thickness of the second coating layer is within the range of 3 to 15 nm, the surface structure of the second coating layer is stable and the side reaction with the electrolyte is small, so the interfacial side reaction can be effectively reduced and the high-temperature performance of the secondary battery can be improved.

[0142] If the thickness range of the third coating layer is 5 to 25 nm, the conductivity performance of the material can be improved and the compression density performance of the battery electrode plate manufactured using the positive active material can be improved.

[0143] The thickness of the coating layer is mainly measured using FIB, and the specific method involves randomly selecting a single particle from the target anode active material powder, cutting a thin section with a thickness of approximately 100 nm at or near the middle of the selected particle, performing TEM measurements on the thin section to measure the thickness of the coating layer, and taking the average value by measuring at 3 to 5 locations.

[0144] In some embodiments, based on the weight of the cathode active material, the manganese element content is in the range of 10 wt% to 35 wt%, optionally in the range of 15 wt% to 30 wt%, more optionally in the range of 17 wt% to 20 wt%, the phosphorus element content is in the range of 12 wt% to 25 wt%, optionally in the range of 15 wt% to 20 wt%, and the weight ratio range of manganese element to phosphorus element is 0.90 to 1.25, optionally 0.95 to 1.20.

[0145] In the present application, the manganese content can correspond to the content of the core only when the core of the anode active material contains manganese.

[0146] In the present application, limiting the content of the manganese element to within the above range ensures that the stability and density of the positive electrode active material are relatively stable, thereby improving performance such as cycle, storage, and compression density of the secondary battery, and also improves the energy density of the secondary battery by maintaining a constant voltage plateau height.

[0147] In the present application, limiting the content of the phosphorus element to within the above range can effectively improve the conductivity of the material and improve the overall stability of the material.

[0148] In the present application, if the weight ratio of manganese to phosphorus content is within the above range, the leaching of transition metal manganese can be effectively reduced, the stability and capacity per gram of the positive electrode active material can be improved, and furthermore, the cycle performance and storage performance of the secondary battery can be improved, and at the same time, the impurity phase in the material can be reduced and the height of the discharge voltage flat region of the material can be maintained, thereby improving the energy density of the secondary battery.

[0149] Manganese and phosphorus elements can be measured using general technical means in this field. In particular, the content of manganese and phosphorus elements can be measured using the following method. The material is dissolved in dilute hydrochloric acid (concentration 10–30%), the content of each element in the solution is measured using ICP, and then the content of manganese element is measured and converted to obtain its weight share.

[0150] In some embodiments, the crystal lattice change rate of the positive electrode active material having a core-shell structure before and after complete lithium extraction is 50% or less, optionally 4% or less, more optionally 3.8% or less, and more optionally 2.0% to 3.8%.

[0151] The lithium delithiasis process of lithium manganese phosphate (LiMnPO4) is a two-phase reaction. The interfacial stress of the two phases is determined by the magnitude of the crystal lattice change rate before and after lithium delithiasis; the smaller the crystal lattice change rate, the lower the interfacial stress, and Li+ Transport is easier. Therefore, if the rate of change in the crystal lattice of the core is reduced, Li + It is advantageous for improving the transport capacity of the secondary battery, thereby improving the rate performance of the secondary battery. Since the positive electrode active material having a core-shell structure of the present application can achieve a relatively low crystal lattice change rate before and after lithium extraction, using the positive electrode active material can improve the rate performance of the secondary battery. The crystal lattice change rate can be measured by methods known in the art, such as X-ray diffraction (XRD).

[0152] In some embodiments, the concentration of Li / Mn antisite defects in the anode active material having a core-shell structure is 5.3% or less, optionally 4% or less, more optionally 2.2% or less, and more optionally 1.5% to 2.2%.

[0153] The Li / Mn antisite defect of the present application is Li in the LiMnPO4 crystal lattice. + and Mn 2+ This means that the positions are compatible. Correspondingly, the Li / Mn antisite defect concentration is Mn 2+ Li that is compatible with + This Li + It means the percentage of the total amount. In this application, the Li / Mn antisite defect concentration can be measured, for example, based on JIS K 0131-1996.

[0154] The anode active material having a core-shell structure of the present application can achieve the above-mentioned relatively low Li / Mn antisite defect concentration. Although the mechanism is not clear, according to measurements by the inventor of the present application, Li in the LiMnPO4 crystal lattice + and Mn 2+ Positional compatibility occurs at, and Li + Since the transport channel is a one-dimensional channel, Mn 2+ This Li + It is difficult to move in the passage, and furthermore, Li +It hinders the transport of. Thus, since the anode active material having a core-shell structure of the present application has a relatively low Li / Mn antisite defect concentration and is within the above range, Li + Mn for transport 2+ It can reduce interference and, at the same time, improve the capacity per gram and rate performance of the anode active material.

[0155] In some embodiments, the compressive density of the anode active material at 3T is 1.95 g / cm³ 3 That is the limit, and optionally 2.2 g / cm³ 3 That is the limit, and more optionally 2.2 g / cm³ 3 Above 2.8g / cm² 3 Less than, and more optionally 2.2 g / cm³ 3 Above 2.65 g / cm² 3 The following applies. Since a higher compression density results in a larger weight of active material per unit volume, increasing compression density is advantageous for improving the energy density per unit volume of a battery cell. Compression density can be measured based on GB / T 24533-2009.

[0156] In some embodiments, the surface oxygen atom state of the anode active material is -1.89 or lower, and optionally -1.90 to ~1.98.

[0157] The stable valence state of oxygen is -2, and as the valence state approaches -2, its electron-gaining ability becomes stronger, i.e., its oxidizing potential becomes stronger; under general conditions, its surface valence state is -1.7 or lower. Since the surface oxygen valence state of the cathode active material of the present application is within the above range, side reactions at the interface between the cathode material and the electrolyte can be mitigated, thereby improving performance such as battery cell cycling and the generation of high-temperature storage gas.

[0158] The surface oxygen atom state can be measured using methods known in the field, such as electron energy loss spectroscopy (EELS).

[0159] Selecting doping elements within the above range is advantageous for enhancing the doping effect, while on the one hand, it further reduces the crystal lattice change rate to suppress manganese leaching and reduce the consumption of electrolyte and active lithium, and on the other hand, it further lowers surface oxygen activity and reduces interfacial side reactions between the cathode active material and the electrolyte, thereby being advantageous for improving the cycle performance and high-temperature storage performance of the secondary battery.

[0160] In some embodiments, x in the core of the positive active material is any number within the range of -0.005 to 0.002, e.g. -0.004, -0.003, -0.002, -0.001, 0, 0.001, 0.002.

[0161] In some embodiments, y in the core of the positive active material may be, for example, 0.001, 0.002, 0.3, 0.35, 0.4, or 0.5.

[0162] In some embodiments, z in the core of the positive active material may be, for example, 0.001, 0.002, 0.003, 0.005, or 0.1.

[0163] In some embodiments, d in the second coating layer of the positive active material may be any value within the range of 1 to 2.

[0164] In some embodiments, in the second coating layer of the positive active material, e may be any number within the range of 1 to 5.

[0165] [Method for manufacturing positive active material]

[0166] The present application provides a method for manufacturing an anode active material, wherein,

[0167] Step of providing core material - the core material is Li 1+x Mn 1-y A y P 1-z R zContains O4, where x is any number in the range of -0.100 to 0.100, y is any number in the range of 0.001 to 0.600, z is any number in the range of 0.001 to 0.100, A is one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and optionally one or more elements selected from Fe, V, Ni, Co, and Mg, and R is one or more elements selected from B, Si, N, and S, and optionally one or more elements selected from Si, N, and S - ;

[0168] First coating step - Li pyrophosphate a MP2O7 and / or M b (P2O7) c A first mixture comprising is supplied, and after mixing the core material and the first mixture, a material coated with a first coating layer is obtained through drying and sintering, wherein a is greater than 0 and less than or equal to 2, b is any value within the range of 1 to 4, c is any value within the range of 1 to 3, and pyrophosphate Li a MP2O7 and M b (P2O7) c M in is each independently one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and optionally one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, and Al - ;

[0169] Second coating step - Oxide M′ d O eA second mixture comprising... is provided, and a material coated with a first coating layer is mixed with the second mixture, followed by drying and sintering, to obtain a material coated with a two-layer coating, wherein d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is one or more elements selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements, and Sb, optionally one or more elements selected from Li, Be, B, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, W, La, and Ce, and more optionally one or more elements selected from Mg, Al, Si, Ti, V, Ni, Cu, Zr, and W It is an element - ;

[0170] Third coating step - providing a third mixture containing a carbon source, mixing the material coated with a two-layer coating with the third mixture, and then drying and sintering to obtain an anode active material - ; including,

[0171] Here, the positive active material has a core-shell structure, which includes a core and a shell covering the core, and the core is Li 1+x Mn 1-y A y P 1-z R z It includes O4, and the shell includes a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer, and the first coating layer is a crystalline pyrophosphate Li a MP2O7 and / or M b (P2O7) c It includes, and the second coating layer is a crystalline oxide M′ d O eIt includes, and the third coating layer includes carbon. The definitions of A, R, M, M′, x, y, z, a, b, c, d, and e are as described above.

[0172] Thus, the present application provides a novel cathode active material having a core-shell structure capable of significantly reducing the occurrence of Li / Mn antisite defects, significantly lowering manganese leaching, lowering the crystal lattice change rate, and increasing the compressive density by doping the manganese site of lithium manganese phosphate with element A and doping the phosphorus site with element R to obtain a doped lithium manganese phosphate core and sequentially coating the core surface with three layers. When applied to a secondary battery, the capacity of the secondary battery can be improved, and the cycle performance, high-temperature storage performance, and safety performance of the secondary battery can be improved.

[0173] In some embodiments, the step of providing a core material is,

[0174] Step (1) of obtaining a mixture by mixing a manganese source, a source of element A, and an acid;

[0175] The mixture obtained in step (1) is mixed with a lithium source, a phosphorus source, a source of element R, and an optional solvent, and then sintered under the protection of an inert gas to obtain Li 1+x Mn 1-y A y P 1-z R z The method includes the step (2) of obtaining a core material containing O4. The definitions of A and R are as described above.

[0176] In some embodiments, step (1) is performed at 20°C to 120°C, optionally 40°C to 120°C (e.g., about 30°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about 110°C or about 120°C); and / or, in step (1), the mixture is mixed by stirring at a rotational speed of 400 to 700 rpm for 1 to 9 h (optional 3 to 7 h, e.g., about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours or about 9 hours).

[0177] In some embodiments, in step (2), mixing is performed for 1 to 10 hours (e.g., about 2 hours, about 3 hours, about 4 hours, about 50 degrees, about 60 degrees, about 70 degrees, about 80 degrees, about 90 degrees, about 100 degrees, about 110 degrees or about 120 degrees) at a temperature of 20 to 120 degrees, optionally 40 to 120 degrees (e.g., about 30 degrees, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, about 10 hours, about 11 hours or about 12 hours).

[0178] If the temperature and time during the core particle manufacturing process are within the above range, the crystal lattice defects of the manufactured core and the cathode active material manufactured using it are relatively low, which is advantageous for suppressing manganese leaching and reducing interfacial side reactions between the cathode active material and the electrolyte, thereby improving the cycle performance and safety performance of the secondary battery.

[0179] In some embodiments, in step (2), mixing is performed under conditions where the pH is 3.5 to 6, optionally the pH is 4 to 6, and more optionally the pH is 4 to 5. It should be noted in the present application that the pH can be adjusted through methods commonly used in the art, such as adding an acid or an alkali.

[0180] In some optional embodiments, the mixture obtained in step (1) is filtered and dried and then sanded to obtain manganese salt particles doped with element A having a particle size of 50 to 200 nm, and the manganese salt particles doped with element A are mixed in step (2) with a lithium source, a phosphorus source, a source of element R, and an optional solvent.

[0181] In some embodiments, optionally, in step (2), the molar ratio of the mixture or manganese salt particles doped with element A to the lithium source and the phosphorus source is 1:0.5 to 2.1:0.5 to 2.1, and optionally about 1:1:1.

[0182] In some embodiments, in step (2), sintering is performed at 600 to 950°C for 4 to 10 hours in an inert gas or an inert gas and hydrogen mixed gas atmosphere; optionally, the protective gas atmosphere is a mixed gas of 70 to 90 volume% nitrogen and 10 to 30 volume% hydrogen; optionally, sintering is performed at about 650°C, about 700°C, about 750°C, about 800°C, about 850°C, or about 900°C for about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, or about 10 hours; Optionally, the sintering temperature and sintering time may be within any range of the above arbitrary values, which can improve the crystallinity of the core, reduce the formation of impurity phases, and ensure that the core maintains a constant particle size, thereby improving the capacity per gram and compression density of the positive active material and improving the overall performance of the secondary battery, including rate performance.

[0183] In some optional embodiments, the mixed material in step (2) is dried to obtain a powder material, and then the powder material is sintered to obtain Li 1+x Mn 1-y A y P 1-z R z Obtain the core material of O4.

[0184] In some embodiments, in the first coating step, a source of element M, a source of phosphorus, an acid, an optionally selected lithium source, and an optionally selected solvent are mixed to obtain a first mixture; and / or,

[0185] In the second coating step, element M′ and a solvent are mixed to obtain a second mixture; and / or,

[0186] In the third coating step, a carbon source and a solvent are mixed to obtain a third mixture.

[0187] In some embodiments, the first mixture, the second mixture, and the third mixture may be provided in the form of a suspension.

[0188] In some embodiments, in the first coating step, a source of element M, a source of phosphorus, an acid, an optionally selected lithium source, and an optionally selected solvent are mixed at room temperature for 1 to 5 hours (e.g., about 1.5 hours, about 2 hours, about 3 hours, about 4 hours, about 4.5 hours, or about 5 hours), then heated to 50°C to 120°C (e.g., 55°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about 110°C, or about 120°C) and mixed while maintaining this temperature for 2 to 10 hours (e.g., about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, or about 10 hours), and all said mixing is performed under conditions where the pH is 3.5 to 6.5 (e.g., 4 to 6).

[0189] In some embodiments, in the second coating step, a source of element M′ and a solvent are mixed at room temperature for 1 to 10 hours (e.g., 1.5 hours, about 2 hours, about 3 hours, about 4 hours, about 4.5 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, or about 10 hours), then heated again to 60°C to 150°C (e.g., about 65°C, about 70°C, about 80°C, about 90°C, about 100°C, about 110°C, about 120°C, about 130°C, about 140°C, or about 150°C) and mixed while maintaining this temperature for 2 to 10 hours (e.g., about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, or about 10 hours).

[0190] The manufacturing method of the present application does not specifically limit the source of the material, and the source of a specific element may include one or more of the element's elemental body, sulfate, halide, nitrate, organic acid salt, oxide, and hydroxide, and is based on the premise that such source can achieve the purpose of the manufacturing method of the present application.

[0191] In some embodiments, the source of element A is one or more selected from the element A, carbonate, sulfate, halide, nitrate, organic acid, oxide, and hydroxide; and / or,

[0192] The source of element R is one or more selected from inorganic acids, organic acids, sulfates, halides, nitrates, organic acid salts, oxides, and hydroxides of element R.

[0193] In some embodiments, the source of element M is one or more selected from the element M element, carbonate, sulfate, halide, nitrate, organic acid, oxide, and hydroxide.

[0194] In some embodiments, the source of element M' is one or more selected from the element M' element, carbonate, sulfate, halide, nitrate, organic acid, oxide, and hydroxide.

[0195] The addition amounts of each source for elements A, R, M, and M' are determined according to the target doping amount, and the usage ratios of the lithium, manganese, and phosphorus sources correspond to the stoichiometric ratio.

[0196] In this application, the manganese source may be a manganese-containing material that can be used in the manufacture of lithium manganese phosphate known in the art. As an example, the manganese source may be one or more selected from elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, and manganese carbonate.

[0197] In the present application, the acid may be one or more selected from inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, silicic acid, metasilicic acid, and organic acids such as oxalic acid. In some embodiments, the acid is a dilute organic acid with a concentration of 60% by weight or less.

[0198] In this application, the lithium source may be a lithium-containing material that can be used to manufacture lithium manganese phosphate, which is already known in the art. As an example, the lithium source is one or more selected from lithium carbonate, lithium hydroxide, lithium phosphate, and lithium dihydrogen phosphate.

[0199] In this application, the phosphorus source may be a phosphorus-containing material that can be used in the production of lithium manganese phosphate known in the art. As an example, the phosphorus source is one or more selected from ammonium dihydrogen phosphate, ammonium phosphate, ammonium phosphate, and phosphoric acid.

[0200] In the present application, as an example, the carbon source is one or more selected from starch, sucrose, glucose, polyvinyl alcohol, polyethylene glycol, and citric acid.

[0201] In some embodiments, in the first coating step, sintering is carried out at 650 to 800°C (e.g., about 650°C, about 700°C, about 750°C, or about 800°C) for 2 to 8 hours (about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 8 hours); and / or,

[0202] In the second coating step, sintering is carried out at 400–750°C (e.g., approx. 400°C, approx. 450°C, approx. 500°C, approx. 550°C, approx. 600°C, approx. 700°C, approx. 750°C) for 6–10 hours (e.g., approx. 6 hours, approx. 7 hours, approx. 8 hours, approx. 9 hours, or approx. 10 hours); and / or,

[0203] In the third coating step, sintering is carried out at 600 to 850°C (e.g., about 600°C, about 650°C, about 700°C, about 750°C, about 800°C, about 850°C) for 6 to 10 hours (e.g., about 6 hours, about 7 hours, about 8 hours, about 9 hours, or about 10 hours).

[0204] In the first, second, and third coating steps, drying is carried out at a temperature of 80°C to 200°C, optionally at 80°C to 190°C, more optionally at 120°C to 180°C, even more optionally at 120°C to 170°C, and most optionally at 120°C to 160°C, and the drying time is 3 to 9h, optionally 4 to 8h, more optionally 5 to 7h, and most optionally about 6h.

[0205] [Polar Plate]

[0206] The present application provides an anode plate, which comprises an anode current collector and an anode film layer installed on at least one surface of the anode current collector, wherein the anode film layer comprises an anode active material or an anode active material manufactured through the aforementioned manufacturing method, and furthermore, the content of the anode active material in the anode film layer is 10% by weight or more and is calculated based on the total weight of the anode film layer.

[0207] In some embodiments, the content of the positive active material in the positive film layer is 90 to 99.5 weight% and is calculated based on the total weight of the positive film layer. This ensures that the secondary battery has a relatively high capacity and relatively good cycle performance, high-temperature storage performance and safety performance.

[0208] In some embodiments, a metal foil or a composite current collector may be used as the positive current collector. For example, an aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material substrate (e.g., a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0209] In some embodiments, the anode film layer may further comprise other anode active materials for batteries known in the art. As an example, the anode active material may comprise at least one of a lithium-containing phosphate having an olivine-type structure and a modified compound thereof. The present application is not limited to these materials and may use other conventional materials that can be used as anode active materials for batteries. Such anode active materials may be used alone or in combination of two or more. Here, examples of lithium-containing phosphates having an olivine-type structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), and a composite material of lithium manganese phosphate and carbon.

[0210] In some embodiments, the anode film layer also optionally comprises a binder. As an example, the binder may comprise at least one of polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethene terpolymer, tetrafluoroethene-hexafluoropropylene copolymer, and fluoroacrylate resin.

[0211] In some embodiments, the anode film layer may also optionally include a conductor. As an example, the conductor may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene, and carbon nanofibers.

[0212] [Cathode]

[0213] The cathode plate comprises a cathode current collector and a cathode film layer disposed on at least one surface of the cathode current collector, and the cathode film layer comprises a cathode active material.

[0214] As an example, the cathode current collector has two opposing surfaces in its thickness direction, and the cathode film layer is installed on one or both of the two opposing surfaces of the cathode current collector.

[0215] In some embodiments, a metal foil or a composite current collector may be used as a negative current collector. For example, a copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material substrate (e.g., a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0216] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of synthetic graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be at least one selected from silicon element, silicon-oxygen compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material may be at least one selected from tin element, tin-oxygen compound, and tin alloy. The present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may be used. Such negative electrode active materials may be used individually or in combination of two or more.

[0217] In some embodiments, the cathode film layer further optionally comprises a binder. As an example, the binder may be at least one selected from styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0218] In some embodiments, the cathode film layer may also optionally include a conductor. As an example, the conductor may be at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene, and carbon nanofibers.

[0219] In some embodiments, the cathode film layer further optionally includes other auxiliary agents such as a thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0220] In some embodiments, the cathode plate may be manufactured in the following manner. Components for manufacturing the cathode plate, such as a cathode active material, a conductor, and a binder, and any other components may be dispersed in a solvent (e.g., deionized water) to form a cathode slurry, the cathode slurry may be coated onto a cathode current collector, and the cathode plate may be obtained through processes such as drying and cold pressing.

[0221] [Electrolyte]

[0222] The electrolyte acts to conduct ions between the positive plate and the negative plate. In this application, the type of electrolyte is not specifically limited and can be selected according to demand. For example, the electrolyte may be a liquid, a gel, or a solid.

[0223] In some embodiments, the electrolyte is a liquid and includes an electrolyte salt and a solvent.

[0224] In some embodiments, the electrolyte salt may be at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroacenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalate)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0225] In some embodiments, the solvent may be at least one selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, 1,2-butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, methyl butyrate, ethyl butyrate, gamma-butyrolactone, tetramethylene sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0226] In some embodiments, the electrolyte further optionally includes additives. As an example, the additives may include a cathode film-forming additive and an anode film-forming additive, and may further include additives that can improve some performance of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high or low temperature performance of the battery, etc.

[0227] [Separator]

[0228] In some embodiments, the secondary battery further comprises a separator. The present application does not particularly limit the type of separator, and any known porous separator with excellent chemical stability and mechanical stability may be selected.

[0229] In some embodiments, the material of the separator may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene difluoride. The separator may be a single-layer thin film or a multilayer composite thin film, and is not particularly limited thereto. When the separator is a multilayer composite thin film, the material of each layer may be the same or different, and is not particularly limited thereto.

[0230] In some embodiments, the positive plate, the negative plate, and the separator can be manufactured into an electrode assembly through a winding process or a lamination process.

[0231] In some embodiments, the secondary battery may include an external package. This external package may be used to package the electrode assembly and the electrolyte.

[0232] In some embodiments, the external package of the secondary battery may be a rigid shell, such as a rigid plastic shell, an aluminum shell, a steel shell, etc. The external package of the secondary battery may be a flexible package, such as a pouch-type flexible package. The material of the flexible package may be plastic, and the plastic may be, for example, polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0233] In this application, the shape of the secondary battery is not specifically limited and may be cylindrical, prismatic, or any other shape. For example, FIG. 2 illustrates a secondary battery (5) with a prismatic structure as an example.

[0234] In some embodiments, referring to FIG. 3, the external package may include a housing (51) and a cover plate (53). Here, the housing (51) may include a bottom plate and a side plate connected to the bottom plate, and may form a receiving cavity by being enclosed by the bottom plate and the side plate. The housing (51) has an opening communicating with the receiving cavity, and the cover plate (53) may cover the opening to close the receiving cavity. The positive plate, the negative plate, and the separator may form an electrode assembly (52) through a winding process or a lamination process. The electrode assembly (52) is packaged within the receiving cavity. The electrolyte is impregnated into the electrode assembly (52). The number of electrode assemblies (52) included in the secondary battery (5) may be one or many, and a person skilled in the art may select according to specific actual needs.

[0235] In some embodiments, the secondary battery may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or many, and a person skilled in the art may select a specific number depending on the application and capacity of the battery module.

[0236] FIG. 4 shows a battery module (4) as an example. Referring to FIG. 4, in the battery module (4), a plurality of secondary batteries (5) may be arranged sequentially along the length direction of the battery module (4). Of course, they may also be arranged in any other arbitrary manner. Additionally, a plurality of secondary batteries (5) may be fixed by a fixing member.

[0237] Optionally, the battery module (4) may further include an outer casing having a receiving space, and a plurality of secondary batteries (5) are received in this receiving space.

[0238] In some embodiments, the aforementioned battery module may also be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or many, and a person skilled in the art may select a specific number depending on the application and capacity of the battery pack.

[0239] FIGS. 5 and 6 illustrate a battery pack (1) as an example. Referring to FIGS. 5 and 6, the battery pack (1) may include a battery case and a plurality of battery modules (4) installed within the battery case. The battery case includes an upper case (2) and a lower case (3), and the upper case (2) may cover the lower case (3) to form a sealed space for accommodating the battery modules (4). Multiple battery modules (4) may be arranged within the battery case in any manner.

[0240] Additionally, the present application also provides an electric device, the electric device comprising at least one of a secondary battery, a battery module, or a battery pack according to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electric device or as an energy storage device for the electric device. The electric device may include mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0241] As an electrical device, a secondary battery, battery module, or battery pack can be selected depending on the usage requirements.

[0242] FIG. 7 is an example of an electric device. This electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A battery pack or battery module may be used to meet the requirements of the electric device for high power and high energy density of a secondary battery.

[0243] [Example]

[0244] The embodiments of this application are described below. The embodiments described below are illustrative and are intended for interpretation purposes only and should not be construed as a limitation to this application. Specific techniques or conditions not specified in the embodiments shall follow the techniques or conditions described in literature in the field or product descriptions. Testers or equipment used without manufacturer's indication are commercially available conventional products.

[0245] The sources of the raw materials mentioned in the embodiments of the present application are as follows.

[0246]

[0247] Preparation of cathode active materials and the slurry thereof

[0248] Example 1

[0249] Step S1: Prepare manganese oxalate co-doped with Fe, Co, V and S.

[0250] 689.6 g of manganese carbonate, 455.27 g of ferrous carbonate, 4.65 g of cobalt sulfate, and 4.87 g of vanadium dichloride are placed in a mixer and mixed thoroughly for 6 hours. The resulting mixture is transferred to a reaction kettle, 5 L of deionized water and 1260.6 g of oxalic acid dihydrate are added, heated to 80°C, stirred thoroughly for 6 hours at a rotational speed of 500 rpm, and mixed uniformly until the reaction is complete and no bubbles are formed to obtain a manganese oxalate suspension co-doped with Fe, Co, and V. The suspension is then filtered, dried at 120°C, and sanded to obtain manganese oxalate particles with a particle size of 100 nm.

[0251] Step S2: Core Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O 4 manufactures

[0252] 1793.1 g of manganese oxalate prepared in (1), 368.3 g of lithium carbonate, 1146.6 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid were added to 20 L of deionized water and stirred thoroughly. The mixture was then uniformly mixed and reacted at 80°C for 10 hours to obtain a slurry. The slurry was placed in a spray dryer and spray-dried to obtain a powder material by drying at a temperature of 250°C. Under a protective gas atmosphere (90% nitrogen and 10% hydrogen), the powder material was placed in a continuous calcination furnace at 700°C and sintered for 4 hours to obtain a core material. The elemental content of the core material was detected using an inductively coupled plasma emission spectrum (ICP), and the obtained core chemical formula is as above.

[0253] Step S3: Preparation of the first coating layer suspension

[0254] Preparation of Li2FeP2O7 solution: 7.4g of lithium carbonate, 11.6g of ferrous carbonate, 23.0g of ammonium dihydrogen phosphate, and 12.6g of oxalic acid dihydrate are dissolved in 500mL of deionized water, the pH is adjusted to 5, then stirred and reacted at room temperature for 2h to obtain a solution, then the solution is heated to 80℃ and maintained at this temperature for 4h to obtain a first coating layer suspension.

[0255] Step S4: Coating of the first coating layer

[0256] 1571.9 g of the doped lithium manganese phosphate core material obtained in step S2 is added to the first coating layer suspension (coating material content is 15.7 g) obtained in step S3, and then mixed by stirring sufficiently for 6 hours. After being uniformly mixed, it is placed in an oven at 120°C and dried for 6 hours, and then sintered at 650°C for 6 hours to obtain a material coated with pyrophosphate.

[0257] Step S5: Preparation of the second coating layer suspension

[0258] 47.1 g of nanometer-sized Al2O3 (particle size of about 20 nm) is dissolved in 1500 mL of deionized water and stirred for 2 hours to obtain a second coating layer suspension.

[0259] Step S6: Coating of the second coating layer

[0260] 1586.8g of the material after pyrophosphate coating obtained in step S4 is added to the second coating layer suspension (containing 47.1g of coating material) obtained in step S5, and then mixed by stirring sufficiently for 6 hours. After being uniformly mixed, it is placed in an oven at 120°C and dried for 6 hours, and then sintered at 700°C for 8 hours to obtain the material after two layers of coating.

[0261] Step S7: Preparation of the third coating layer aqueous solution

[0262] 37.3g of sucrose is dissolved in 500g of deionized water, then stirred and sufficiently dissolved to obtain an aqueous sucrose solution.

[0263] Step S8: Coating of the third coating layer

[0264] 1633.9g of the material after the 2-layer coating obtained in step S6 is added to the sucrose solution obtained in step S7 and mixed by stirring together for 6 hours. After being uniformly mixed, it is placed in an oven at 150°C and dried for 6 hours, and then sintered at 700°C for 10 hours to obtain the material after the 3-layer coating.

[0265] Examples 2 to 56 and Comparative Examples 1 to 17

[0266] The positive active materials of Examples 2 to 56 and Comparative Examples 1 to 17 are prepared in a manner similar to Example 1, and differences in the preparation of the positive active materials can be seen in Tables 1 to 6.

[0267] Here, Comparative Examples 1-2, 4-10 and 12 do not have steps S3-S4 because the first layer is not covered, and Comparative Examples 1-11 do not have steps S5-S6 because the second layer is not covered.

[0268] Table 1: Preparation of manganese oxalate co-doped with Fe, Co, V, and S and preparation of core (steps S1–S2)

[0269]

[0270]

[0271]

[0272]

[0273] For detailed measurement methods, refer to the 'Performance Measurement of Anode Active Materials' section described later.

[0274] Table 2: Preparation of the first coating layer suspension (Step S3)

[0275]

[0276] For detailed measurement methods, refer to the 'Performance Measurement of Anode Active Materials' section described later.

[0277] Table 3: Covering of the first covering layer (Step S4)

[0278]

[0279]

[0280]

[0281] For detailed measurement methods, refer to the 'Performance Measurement of Anode Active Materials' section described later.

[0282] Table 4: Preparation of the second coating layer suspension (Step S5)

[0283]

[0284]

[0285]

[0286] For detailed measurement methods, refer to the 'Performance Measurement of Anode Active Materials' section described later.

[0287] Table 5: Covering of the second covering layer (Step S6)

[0288]

[0289]

[0290]

[0291] For detailed measurement methods, refer to the 'Performance Measurement of Anode Active Materials' section described later.

[0292] Table 6: Covering of the third layer (step S8)

[0293]

[0294]

[0295]

[0296] For detailed measurement methods, refer to the 'Performance Measurement of Anode Active Materials' section described later.

[0297] Manufacturing of anode plates

[0298] The anode active material prepared above after the 3-layer coating, acetylene black as a conductive agent, and polyvinylidene difluoride (PVDF) as a binder are added to N-methylpyrrolidone (NMP) in a weight ratio of 97.0:1.2:1.8, stirred, and uniformly mixed to obtain an anode slurry. The anode slurry is 0.280 g / 1540.25 mm 2 According to the above, the aluminum foil is uniformly coated, and an anode plate is obtained through drying, cold pressing, and slitting.

[0299] Manufacturing of cathode plates

[0300] Synthetic graphite as the cathode active material, superconducting carbon black (Super-P) as the conductor, styrene butadiene rubber (SBR) as the binder, and sodium carboxymethylcellulose (CMC-Na) as the thickener were dissolved in deionized water in a mass ratio of 95%:1.5%:1.8%:1.7%, thoroughly stirred, and uniformly mixed to obtain a cathode slurry having a viscosity of 3000 mPa·s and a solid content of 52%; the cathode slurry was coated onto a 6 μm copper foil cathode current collector, dried at 100°C for 4 hours, and rolled to obtain a compressive density of 1.75 g / cm³ 3 Obtain a negative electrode plate.

[0301] Separator

[0302] Polypropylene film is used.

[0303] Preparation of electrolyte

[0304] Ethylene carbonate, dimethyl carbonate, and 1,2-propylene carbonate are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the solution to obtain an electrolyte. In this electrolyte, the concentration of LiPF6 is 1 mol / L.

[0305] Manufacturing of complete batteries

[0306] The above-mentioned positive plate, separator, and negative plate are sequentially stacked, and the separator is interposed between the positive and negative electrodes to provide isolation, and a bare cell is obtained through winding. The bare cell is placed in an external package, the above-mentioned electrolyte is injected, and the package is sealed to obtain a complete battery (hereinafter also referred to as a 'complete battery').

[0307] manufacturing of button batteries

[0308] A button battery (hereinafter also referred to as a 'button battery') is assembled in a button battery box using the above positive plate, negative electrode, and electrolytic core.

[0309] I. Performance Measurement of Anode Active Materials

[0310] 1. Method for measuring the rate of change in crystal lattice:

[0311] In a constant temperature environment of 25°C, a sample of the anode active material is placed in an XRD (model name Bruker D8 Discover), the sample is measured at 1° / min, and the measurement data is organized and analyzed. Then, the crystal lattice constants a0, b0, c0, and v0 are calculated by referring to a standard PDF card (a0, b0, and c0 represent the length dimensions of each direction of the unit cell, and v0 represents the volume of the unit cell, which can be obtained directly from the refined XRD results).

[0312] Using the above method for manufacturing a button battery, a sample of positive active material is manufactured into a button battery, and the button battery is charged at a low rate of 0.05C until the current decreases to 0.01C. Then, the positive plate of the button battery is removed and immersed in dimethyl carbonate (DMC) for 8 hours. Then, it is dried, the powder is scraped off, and particles smaller than 500nm in diameter are filtered out. A sample is taken, and its unit cell volume v1 is calculated in the same manner as the new sample measurement, and (v0-v1) / v0×100% is used as the crystal lattice change rate (unit cell volume change rate) before and after complete lithium desorption.

[0313] 2. Measurement of Li / Mn antisite defect concentration:

[0314] The Li / Mn antisite defect concentration is obtained by comparing the XRD results measured in the 'Crystal Lattice Change Rate Measurement Method' with the Powder Diffraction File (PDF) card of a standard crystal. Specifically, the XRD results measured in the 'Crystal Lattice Change Rate Measurement Method' are input into General Structural Analysis System (GSAS) software to automatically obtain refined results, which include the positional occupancy status of different atoms, and the Li / Mn antisite defect concentration is obtained by interpreting the refined results.

[0315] 3. Measurement of Compressed Density:

[0316] 5g of the above-mentioned manufactured cathode active material powder is placed in a compression mold (USA CARVER mold, 13mm model), and then the mold is placed on a compression density meter. A pressure of 3T is applied, and the powder thickness under pressure (thickness after pressure removal) is read by the equipment. The compression density is calculated using the formula ρ=m / v, where the area value used is a standard small photographic area of ​​1540.25mm². 2 am.

[0317] 4. Measurement of 3C charging constant current ratio:

[0318] In a constant temperature environment of 25°C, the new complete batteries prepared in each of the above examples and comparative examples are left standing for 5 minutes and discharged to 2.5V at 1 / 3C. After leaving standing for 5 minutes, they are charged to 4.3V at 1 / 3C, and then charged at a constant voltage from 4.3V until the current is less than or equal to 0.05mA. After leaving standing for 5 minutes, the charge capacity at this time is recorded as C0. Discharge to 2.5V at 1 / 3C, leave standing for 5 minutes, charge again to 4.3V at 3C, leave standing for 5 minutes, and record the charge capacity at this time as C1. The 3C charging constant current ratio is C1 / C0 × 100%.

[0319] The higher the 3C charging constant current ratio, the better the rate performance of the secondary battery.

[0320] 5. Measurement of transition metal Mn (and Fe doped in Mn sites):

[0321] A complete battery prepared with the positive active material of each of the above examples and comparative examples, whose capacity has been reduced to 80% by cycling at 45°C, is discharged at a rate of 0.1C to a cutoff voltage of 2.0V. Then, the battery is disassembled to remove the negative plate, and from the negative plate, a unit area (1540.25mm²) 2 Thirty wafers are randomly selected, and the inductively coupled plasma emission spectrum (ICP) is measured using an Agilent ICP-OES730. Based on the ICP results, the amounts of Fe (when Fe is doped into the Mn sites of the anode active material) and Mn are calculated, and the amount of Mn (and Fe doped into the Mn sites) leached out after cycling is calculated. The measurement standard is based on EPA-6010D-2014.

[0322] 6. Measurement of surface oxygen valence state:

[0323] 5g of the above-prepared positive active material sample is manufactured into a button battery according to the button battery manufacturing method. The button battery is charged at a low rate of 0.05C until the current decreases to 0.01C. Then, the positive plate of the button battery is removed and immersed in DMC for 8 hours. Then, it is dried, the powder is scraped off, and particles smaller than 500nm in diameter are filtered out. The obtained particles are measured by electron energy loss spectroscopy (EELS, the instrument model used is Talos F200S) to obtain the near-energy loss edge structure (ELNES), which reflects the density of states and energy level distribution of the elements. Based on the density of states and energy level distribution, the number of occupied electrons is calculated by integrating with the valence band density of states data, and the valence state of surface oxygen after charging is estimated.

[0324] 7. Measurement of Manganese and Phosphorus Elements in Anode Active Material:

[0325] 5g of the above-prepared anode active material is dissolved in 100ml of reverse aqua regia (concentrated hydrochloric acid:concentrated nitric acid = 1:3) (concentrated hydrochloric acid concentration ~37%, concentrated nitric acid concentration ~65%), and the content of each element in the solution is measured using ICP. Then, the content of manganese or phosphorus is measured and converted (amount of manganese or phosphorus / amount of anode active material * 100%) to obtain the weight share ratio.

[0326] 8. Method for Measuring Initial Capacity Per Gram of Button Battery:

[0327] At 2.5~4.3V, the button battery prepared in each of the above examples and comparative examples is charged to 4.3V at 0.1C, then charged at 4.3V at a constant voltage until the current is less than or equal to 0.05mA, left to stand for 5 min, then discharged to 2.0V at 0.1C, and the discharge capacity at this time is the initial capacity per gram and is recorded as D0.

[0328] 9. Measurement of battery cell expansion after storing a complete battery at 60°C for 30 days:

[0329] The complete batteries prepared in each of the above examples and comparative examples are stored at 60°C with a 100% State of Charge (SOC). Before, during, and after the magnetic field process, the Open Circuit Voltage (OCV) and Internal Resistance (IMP) of the battery cells are measured to monitor the SOC, and the volume of the battery cells is measured. Here, every 48 hours, the complete batteries are removed, left to stand for 1 hour, and then the Open Circuit Voltage (OCV) and Internal Resistance (IMP) are measured. After cooling to room temperature, the volume of the battery cells is measured using the drainage method. The drainage method involves first individually measuring the gravitational force F1 of the battery cells using a scale that automatically converts the units of the dial data, and then immersing the entire battery cell in deionized water (density is 1 g / cm³). 3 After completely immersing it in (known as), measure the gravitational force F2 of the battery cell at this time, and the buoyancy F acting on the battery cell 부 is F1-F2, and Archimedes' principle F 부 배 Depending on, the volume of the battery cell V=(F1-F2) / Calculate.

[0330] According to the OCV and IMP measurement results, the batteries of all embodiments always maintain an SOC of 99% or higher until storage ends during the experiment.

[0331] After storing for 30 days, measure the battery cell volume and calculate the percentage increase in battery cell volume after storage relative to the battery cell volume before storage.

[0332] 10. Measurement of cycle performance of a full battery at 45℃:

[0333] In a constant temperature environment of 45℃, charge from 2.5~4.3V to 4.3V at 1C, then charge from 4.3V at a constant voltage up to a current ≤ 0.05mA, stand for 5 min, then discharge to 2.5V at 1C, and the capacitance is D n It is recorded as (n=0,1,2,……). The above process is repeated until the capacity is faded to 80%, and the number of repetitions is recorded, which is the number of cycles corresponding to an 80% capacity retention rate at 45°C.

[0334] 11. Measurement of crystal plane spacing and angles:

[0335] 1g of each of the above-prepared cathode active material powders is taken and placed in a 50mL test tube, 10mL of alcohol with a mass fraction of 75% is injected into the test tube, and then stirred sufficiently to disperse for 30 minutes, and then an appropriate amount of the above solution is dropped onto a 300-mesh copper mesh using a clean disposable plastic straw, at which time some powder remains on the copper mesh, and the copper mesh is transferred together with the sample to a TEM (Talos F200s G2) sample chamber for measurement to obtain an original TEM measurement image, and the original image format (xx.dm3) is saved.

[0336] The original image obtained from the above TEM measurement is opened in DigitalMicrograph software, and a Fourier transform (automatically completed by the software after clicking) is performed to obtain a diffraction pattern. The distance from the diffraction spot of the diffraction pattern to the center position is measured, i.e., the crystal plane spacing is obtained, and the angle is obtained by calculating according to Bragg's law.

[0337] By comparing the obtained crystal plane spacing and corresponding angle data with the standard values, identification of the material and crystal state of different coating layers can be performed.

[0338] 12. Measurement of coating layer thickness:

[0339] The thickness of the coating layer is mainly measured by cutting a thin section with a thickness of approximately 100 nm from the middle of a single particle of the anode active material prepared above via FIB, then performing TEM measurements on the thin section to obtain an original TEM measurement image, and saving the original image format (xx.dm3).

[0340] The original image obtained from the above TEM measurement is opened in DigitalMicrograph software, and the coating layer is identified through crystal lattice spacing and angle information, and the thickness of the coating layer is measured.

[0341] For the selected particle, measure the thickness at 3 locations and take the average value.

[0342] 13. Measurement of the molar ratio of SP2 and SP3 forms of carbon in the third cladding layer:

[0343] This measurement is performed using Raman spectra. Id / Ig is obtained through peak separation of the energy spectrum of the Raman measurement, where Id is the peak intensity of the SP3 form carbon and Ig is the peak intensity of the SP2 form carbon, thereby confirming the molar ratio of the two.

[0344] 14. Measurement of core chemical formula and different coating layer components:

[0345] High spatial resolution characterization of the internal microstructure and surface structure of the anode active material is performed using an aberration-corrected scanning transmission electron microscope (ACSTEM), and the core chemical formula of the anode active material and the components of different coating layers are obtained in combination with 3D reconstruction technology.

[0346] Refer to the table below for the performance measurement results of the positive active materials of the examples and comparative examples.

[0347] Table 7: Powder material performance and battery performance of positive electrode active materials in Examples 1–56 and Comparative Examples 1–17

[0348]

[0349]

[0350]

[0351] Table 8: Crystal plane spacing and crystal direction (111) of crystalline pyrophosphate in the first coating layer in Examples 1, 30–36

[0352]

[0353] As can be seen from Tables 7 and 8, compared to the comparative example, the embodiments of the present application achieved a smaller crystal lattice change rate, a smaller Li / Mn antisite defect concentration, a larger compressive density, a surface oxygen valence state closer to -2, less Mn and Fe leaching after cycling, and better battery performance (e.g., higher button battery capacity), better high-temperature storage performance, higher safety, and better cycle performance.

[0354] Table 9: Thickness of each layer of the anode active material and weight ratio of manganese and phosphorus elements prepared in Examples 1–11, 13–14 and Comparative Examples 3–4, 12

[0355]

[0356] As can be seen in Table 9, the manganese element content and the weight ratio of manganese and phosphorus elements in the cathode active material are significantly reduced through doping of the manganese and phosphorus sites of lithium iron manganese phosphate (manganese content 35%, phosphorus content about 20%) and three-layer coating; furthermore, when Examples 1 to 14 are compared with Comparative Examples 3, 4, and 12, as can be seen in conjunction with Table 7, when the manganese and phosphorus elements in the cathode active material are reduced, the leaching amount of manganese and iron is lowered, and the battery performance of the secondary battery manufactured therefrom is improved.

[0357] II. Influence of Coating Layer Sintering Method on Anode Active Material Performance

[0358] The battery manufacturing of the examples and comparative examples in the table below is similar to Example 1, with the difference being the use of the method parameters in the table below. Refer to Table 10 below for the results.

[0359] Table 10: Effects of Sintering Temperature and Sintering Time on Anode Active Material Performance in Steps S4, S6, and S8

[0360]

[0361]

[0362] As can be seen from the above, if the sintering temperature range in step S4 is 650~800℃ and the sintering time is 2~6 hours, the sintering temperature in step S6 is 400~600℃ and the sintering time is 6~10 hours, and the sintering temperature in step S8 is 700~800℃ and the sintering time is 6~10 hours, then a smaller crystal lattice change rate, a smaller Li / Mn antisite defect concentration, less leaching of manganese and iron elements, a better 3C charging constant current ratio, a larger battery capacity, better battery cycle performance, and better high-temperature storage stability can be achieved.

[0363] In addition, compared to Example II-16 (the sintering temperature of step S4 is 750°C and the sintering time is 4.5 hours), Example II-1 (the sintering temperature of step S4 is 750°C and the sintering time is 4h) achieved better positive active material performance and battery performance, which indicates that when the sintering temperature of step S4 is 750°C or higher than 750°C, the sintering time must be controlled to be less than 4.5 hours.

[0364] III. Effects of Reaction Temperature and Reaction Time on the Performance of Anode Active Materials in Core Manufacturing

[0365] The manufacturing of the positive electrode active material and battery in the examples in the table below is similar to Example 1, and differences in the manufacturing of the positive electrode active material can be found by referring to the method parameters in the table below. Likewise, the results can be found by referring to the table below.

[0366] Table 11: Effects of Reaction Temperature and Reaction Time on Anode Active Material Performance in Core Fabrication

[0367]

[0368] As can be seen in Table 11, when the reaction temperature range in step S1 is 60–120°C and the reaction time is 2–9 hours, and the reaction temperature range in step S2 is 40–120°C and the reaction time is 1–10 hours, the performance of the positive electrode active material powder (crystal lattice change rate, Li / Mn antisite defect concentration, surface oxygen valence state, compressive density) and the performance of the manufactured battery (electrical capacity, high-temperature cycle performance, high-temperature storage performance) are all excellent.

[0369] It should be noted that the present application is not limited to the embodiments described above. The embodiments described above are merely examples, and any embodiments having substantially the same configuration as the technical concept and producing the same effect within the scope of the technical solution of the present application are also included within the technical scope of the present application. Furthermore, other methods of configuration that apply various modifications conceived by a person skilled in the art to the embodiments without departing from the gist of the present application, and by combining some of the components of the embodiments, are also included within the scope of the present application. Explanation of the symbols

[0370] 1: Battery pack 2: Upper case 3: Lower case 4: Battery Module 5: Secondary battery 51: Housing 52: Electrode assembly 53: Cover plate

Claims

Claim 1 A positively active material having a core-shell structure comprises a core and a shell covering the core, wherein the core is Li 1+x Mn 1-y A y P 1-z R z It includes O4, wherein x is any numeric value within the range of -0.100 to 0.100, y is any numeric value within the range of 0.001 to 0.600, z is any numeric value within the range of 0.001 to 0.100, A is one or more elements selected from V, Ni, Co, and Mg, and R is one or more elements selected from B, N, and S, and the shell includes a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer, wherein the first coating layer is a crystalline pyrophosphate Li a MP2O7 and M b (P2O7) c Includes, wherein a is greater than 0 and less than or equal to 2, b is any numeric value within the range of 1 to 4, c is any numeric value within the range of 1 to 3, and the crystalline pyrophosphate Li a MP2O7 and M b (P2O7) c In this case, M is independently one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; and the second coating layer is a crystalline oxide M′ d O e A positively active material comprising, wherein d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is one or more elements selected from Mg, Al, Si, Ti, V, Ni, Cu, Zr, and W; and wherein the third coating layer comprises carbon. Claim 2 A positively active material according to claim 1, characterized in that the ratio of y to 1-y in the core is 1:10 to 1:

1. Claim 3 An anode active material according to claim 1, characterized in that the ratio of z to 1-z in the core is 1:9 to 1:

999. Claim 4 An anode active material according to claim 1, wherein the carbon in the third coating layer is a mixture of SP2-type carbon and SP3-type carbon; and the molar ratio of the SP2-type carbon and the SP3-type carbon is any value within the range of 0.07 to 13. Claim 5 An anode active material according to claim 1, characterized in that the coating amount of the first coating layer is greater than 0 and less than or equal to 6 weight% and is calculated based on the weight of the core; or the coating amount of the second coating layer is greater than 0 and less than or equal to 6 weight% and is calculated based on the weight of the core; or the coating amount of the third coating layer is greater than 0 and less than or equal to 6 weight% and is calculated based on the weight of the core. Claim 6 An anode active material according to claim 1, characterized in that the thickness of the first coating layer is 2 to 10 nm; or the thickness of the second coating layer is 3 to 15 nm; or the thickness of the third coating layer is 5 to 25 nm. Claim 7 A positively active material according to claim 1, characterized in that the crystal plane spacing range of the crystalline pyrophosphate in the first coating layer is 0.293 to 0.470 nm, and the narrow angle range of the crystal direction (111) is 18.00° to 32.00°. Claim 8 An anode active material according to claim 1, characterized in that it is calculated based on the weight of the anode active material, the manganese element content is within the range of 10% to 35% by weight, the phosphorus element content is within the range of 12% to 25% by weight, and the weight ratio of manganese to phosphorus is within the range of 0.90 to 1.

25. Claim 9 A positive electrode active material according to claim 1, characterized in that the crystal lattice change rate before and after complete lithium extraction of the positive electrode active material is 50% or less. Claim 10 A positive electrode active material according to claim 1, characterized in that the Li / Mn antisite defect concentration of the positive electrode active material is 5.3% or less. Claim 11 In claim 1, the compressive density of the anode active material at 3T is 1.95 g / cm³ 3 A positively active material characterized by the above. Claim 12 A positively active material according to claim 1, characterized in that the surface oxygen atom state of the positively active material is -1.89 or lower. Claim 13 A method for manufacturing a positive electrode active material, comprising the step of providing a core material—the core material being Li 1+x Mn 1-y A y P 1-z R z Containing O4, wherein x is any numeric value within the range of -0.100 to 0.100, y is any numeric value within the range of 0.001 to 0.600, z is any numeric value within the range of 0.001 to 0.100, A is one or more elements selected from V, Ni, Co, and Mg, and R is one or more elements selected from B, N, and S - ; First coating step - Pyrophosphate Li a MP2O7 and M b (P2O7) c A first mixture comprising a core material and the first mixture is mixed, and then subjected to drying and sintering to obtain a material coated with a first coating layer, wherein a is greater than 0 and less than or equal to 2, b is any value within the range of 1 to 4, c is any value within the range of 1 to 3, and the pyrophosphate Li a MP2O7 and M b (P2O7) c M in is one or more elements independently selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al - ; Second coating step - Oxide M′ d O e A second mixture comprising a carbon source is provided, and a material coated with a first coating layer is mixed with the second mixture, followed by drying and sintering to obtain a material coated with a two-layer coating, wherein d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is one or more elements selected from Mg, Al, Si, Ti, V, Ni, Cu, Zr, and W - ; Third coating step - A third mixture comprising a carbon source is provided, and a cathode active material is obtained by mixing the material coated with the two-layer coating with the third mixture, followed by drying and sintering - ; comprising a core-shell structure, wherein the cathode active material comprises a core and a shell coating the core, and the core is Li 1+x Mn 1-y A y P 1-z R z The shell comprises O4, and the shell comprises a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer, wherein the first coating layer is a crystalline pyrophosphate Li a MP2O7 and M b (P2O7) c It includes, and the second coating layer is a crystalline oxide M′ d O e A method for manufacturing an anode active material, characterized in that the third coating layer comprises carbon. Claim 14 In claim 13, the step of providing the core material comprises: a step (1) of obtaining a mixture by mixing a manganese source, a source of element A, and an acid; and a step (1) of mixing the mixture obtained in step (1) with a lithium source, a phosphorus source, a source of element R, and a solvent, and then sintering the mixture under the protection of an inert gas to obtain Li 1+x Mn 1-y A y P 1-z R z A method for manufacturing an anode active material, comprising the step (2) of obtaining a core material containing O4, wherein the step (1) is performed at 20°C to 120°C; mixing at a rotational speed of 400 to 700 rpm for 1 to 9 hours in the step (1); and mixing at a temperature of 20 to 120°C for 1 to 10 hours in the step (2). Claim 15 A method for manufacturing an anode active material according to claim 13, wherein in the first coating step, a source of element M, a source of phosphorus, an acid, a source of lithium, and a solvent are mixed to obtain the first mixture; in the second coating step, a source of element M′ and a solvent are mixed to obtain the second mixture; in the third coating step, a source of carbon and a solvent are mixed to obtain the third mixture; in the first coating step, the source of element M, the source of phosphorus, the acid, the source of lithium, and the solvent are mixed at room temperature for 1 to 5 hours, then heated again to 50°C to 120°C and mixed at this temperature for 2 to 10 hours, wherein all mixing is performed under conditions where the pH is 3.5 to 6.5; and in the second coating step, the source of element M′ and the solvent are mixed at room temperature for 1 to 10 hours, then heated again to 60°C to 150°C and mixed at this temperature for 2 to 10 hours. Claim 16 A method for manufacturing an anode active material according to claim 14, wherein the source of element A is one or more selected from the element A, carbonate, sulfate, halide, nitrate, organic acid salt, oxide, and hydroxide; and the source of element R is one or more selected from the inorganic acid, organic acid, sulfate, halide, nitrate, organic acid salt, oxide, and hydroxide of element R. Claim 17 A method for manufacturing an anode active material according to claim 13, wherein in the first coating step, the sintering is carried out at 650 to 800°C for 2 to 8 hours; in the second coating step, the sintering is carried out at 400 to 750°C for 6 to 10 hours; and in the third coating step, the sintering is carried out at 600 to 850°C for 6 to 10 hours. Claim 18 An anode plate comprising an anode current collector and an anode film layer installed on at least one surface of the anode current collector, wherein the anode film layer comprises an anode active material according to any one of claims 1 to 12; and wherein the content of the anode active material in the anode film layer is 90 to 99.5 weight% and is calculated based on the total weight of the anode film layer. Claim 19 A secondary battery characterized by including a positive plate according to claim 18. Claim 20 A battery module characterized by including a secondary battery according to claim 19. Claim 21 A battery pack characterized by including a battery module according to claim 20. Claim 22 An electric device characterized by including a battery pack according to claim 21.

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