Positive electrode material composition, method for manufacturing the same, positive electrode sheet containing the same, secondary battery, and power consumption device

Abstract

The present invention relates to a positive electrode material composition, a method for producing the same, and a positive electrode sheet, a secondary battery, and a power consuming device each including the same. The positive electrode material composition includes a positive electrode active material having a core-shell structure and an organopolysiloxane compound, the positive electrode active material including a kernel and a shell that covers the kernel, and the chemical formula of the kernel is Li 1+x Mn 1-y A y P 1-z R z O4, and the shell includes a first coating layer that coats the kernel, a second coating layer that coats the first coating layer, and a third coating layer that coats the second coating layer. The positive electrode material composition can provide a secondary battery with high energy density and simultaneously achieve improved cycle performance, safety performance, and / or rate performance. Figure 1

Description

[Technical Field]

[0001] This application relates to the field of battery technology, and more specifically to a positive electrode material composition, a method for manufacturing the same, a positive electrode sheet containing the same, a secondary battery, and a power consumption device. [Background technology]

[0002] In recent years, secondary batteries have been widely used in many fields, including energy storage and 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 application and widespread use of secondary batteries, their safety performance is attracting increasing attention. Lithium manganese phosphate is currently one of the most noteworthy cathode active materials due to its advantages such as high capacity, good safety, and abundant raw material sources. However, manganese ions tend to dissolve during charging, causing a rapid decrease in capacity. [Overview of the Initiative]

[0003] The object of this application is to provide a positive electrode material composition, a method for manufacturing the same, a positive electrode sheet containing the same, a secondary battery, and a power consumption device. A secondary battery using the positive electrode material composition has a high energy density and can achieve improved cycle performance, safety performance, and / or rate performance simultaneously.

[0004] A first aspect of this application is a cathode material composition comprising a cathode active material having a core-shell structure and an organopolysiloxane compound, wherein the cathode active material comprises a kernel and a shell covering the kernel, and the chemical formula of the kernel is Li 1+x Mn 1-y A y P 1-z R zIt is O4, x is any numerical value within the range of -0.100 to 0.100, optionally any numerical value within the range of -0.005 to 0.002, y is any numerical value within the range of 0.001 to 0.500, z is any numerical value within the range of 0.001 to 0.100, the said 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, Ti, V, Ni, Co and Mg, the said R is one or more elements selected from B, Si, N and S, optionally, the said R is one element selected from B, Si, N and S, the values of the said x, y and z satisfy the condition that the whole kernel maintains electrical neutrality, the said shell includes a first coating layer covering the kernel, a second coating layer covering the first coating layer and a third coating layer covering the second coating layer, the first coating layer is crystalline pyrophosphate Li a MP2O7 and / or M b (P2O7) c containing, 0≦a≦2, 1≦b≦4, 1≦c≦6, the crystalline pyrophosphate Li a MP2O7 and M b (P2O7) c wherein M in is each independently one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al, the values of the said a, b and c satisfy the condition that the crystalline pyrophosphate Li a MP2O7 or M b (P2O7) c maintains electrical neutrality, the second coating layer contains crystalline phosphate XPO4, the said X is one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al, the third coating layer is carbon, providing a cathode material composition.

[0005] The inventors, through extensive research, have found that by modifying lithium manganese phosphate and coating it with multiple layers, the elution of manganese ions can be significantly reduced, and the lattice change rate can be lowered. This allows for the creation of a novel positive electrode active material with a core-shell structure that can be used in secondary batteries, improving the battery's cycle performance, rate performance, and safety performance, and enhancing its capacity. When the positive electrode active material of this application is used in combination with an organopolysiloxane compound, surface erosion of the positive electrode active material by the electrolyte can be mitigated and manganese ion elution can be reduced, which is advantageous for improving the electrochemical performance of the positive electrode active material. Therefore, positive electrode sheets and power consumption devices such as secondary batteries employing the positive electrode material composition of this application can have high energy density and achieve improved cycle performance, safety performance, and / or rate performance simultaneously.

[0006] In any embodiment of this application, the organopolysiloxane compound comprises at least one structural unit represented by formula 1. [ka] R1 and R2 each independently represent at least one selected from the group consisting of -COOH, -OH, -SH, -CN, -SCN, amino group, phosphate ester group, carboxylic acid ester group, amide group, aldehyde group, sulfonyl group, polyether segment, C1-C20 aliphatic hydrocarbon group, C1-C20 halogenated aliphatic hydrocarbon group, C1-C20 heteroaliphatic hydrocarbon group, C1-C20 halogenated heteroaliphatic hydrocarbon group, C6-C20 aromatic hydrocarbon group, C6-C20 halogenated aromatic hydrocarbon group, C2-C20 heteroaromatic hydrocarbon group, or H. Selectively, R1 and R2 each independently represent at least one selected from the group consisting of -COOH, -OH, -SH, amino group, phosphate ester group, polyether segment, C1-C8 alkyl group, C1-C8 halogenated alkyl group, C1-C8 heteroalkyl group, C1-C8 halogenated heteroalkyl group, C2-C8 alkenyl group, C2-C8 halogenated alkenyl group, or phenyl group, or H. More selectively, R1 and R2 each independently represent at least one selected from the group consisting of -OH, -SH, amino group, phosphate ester group, polyether segment, C1-C8 alkyl group, C1-C8 halogenated alkyl group, C1-C8 heteroalkyl group, C1-C8 halogenated heteroalkyl group, C2-C8 alkenyl group, or C2-C8 halogenated alkenyl group, or H. This further reduces the elution of manganese ions, thereby significantly improving the cycle performance and storage performance of the secondary battery.

[0007] In any embodiment of this application, the organopolysiloxane compound comprises one or more selected from linear polysiloxanes and cyclic polysiloxanes. Selectively, the organopolysiloxane compound is selected from linear polysiloxanes.

[0008] This further mitigates erosion of the positive electrode active material surface by acidic substances in the electrolyte, reduces manganese ion elution, and significantly improves the cycle performance and storage performance of secondary batteries. Because cyclic polysiloxanes have a certain degree of delocalization of electrons in the ring, their Si-O framework has less affinity for electron-rich F-containing ions compared to linear polysiloxanes. Furthermore, their removal rate from F-containing ions in the electrolyte is somewhat lower, resulting in a slightly weaker effect in reducing manganese ion elution and a slightly lower improvement in the cycle performance of secondary batteries.

[0009] In any embodiment of this application, the linear polysiloxane further comprises a choke group. Selectively, the choke group comprises at least one selected from the group consisting of polyether, C1-C8 alkyl group, C1-C8 halogenated alkyl group, C1-C8 heteroalkyl group, C1-C8 halogenated heteroalkyl group, C2-C8 alkenyl group, C2-C8 halogenated alkenyl group, C6-C20 aromatic hydrocarbon group, C1-C8 alkoxy group, C2-C8 epoxy group, hydroxyl group, C1-C8 hydroxyalkyl group, amino group, C1-C8 aminoalkyl group, carboxyl group, and C1-C8 carboxyalkyl group.

[0010] In any embodiment of this application, the linear polysiloxane is polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polymethylvinylsiloxane, polyphenylmethylsiloxane, polymethylhydrogensiloxane, carboxyl-functionalized polysiloxane, polymethylchloropropylsiloxane, polymethyltrifluoropropylsiloxane, perfluorooctylmethylpolysiloxane, mercaptopropylpolysiloxane, aminoethylaminopropylpolydimethylsiloxane The polysiloxane comprises one or more of the following: methoxy-terminated polydimethylsiloxane, hydroxypropyl-terminated polydimethylsiloxane, aminopropyl-terminated polydimethylsiloxane, terminal epoxypolysiloxane, terminal hydroxypolydimethylsiloxane, terminal polyether polydimethylsiloxane, side-chain aminopropylpolysiloxane, side-chain hydroxylmethylpolysiloxane, side-chain hydroxylpropylpolysiloxane, side-chain polyether-grafted polydimethylsiloxane, and side-chain phosphate-grafted polydimethylsiloxane. Selectively, the linear polysiloxane comprises one or more of the following: polydimethylsiloxane, polymethylchloropropylsiloxane, polymethyltrifluoropropylsiloxane, mercaptopropylpolysiloxane, aminoethylaminopropylpolydimethylsiloxane, terminal hydroxypolydimethylsiloxane, terminal polyether polydimethylsiloxane, and side-chain phosphate-grafted polydimethylsiloxane.

[0011] In any embodiment of this application, the cyclic polysiloxane comprises one or more of cyclic polydimethylsiloxane, cyclic polymethylvinylsiloxane, cyclic polymethylhydrogensiloxane, and cyclic polymethyltrifluoropropylsiloxane. Selectively, the cyclic polysiloxane comprises one or more of 1,3,5,7-octamethylcyclotetrasiloxane, 1,3,5,7-tetrahydro-1,3,5,7-tetramethylcyclotetrasiloxane, cyclopentapolydimethylsiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, hexadecamethyloctasiloxane, and tetradecamethylcycloheptasiloxane.

[0012] In any embodiment of this application, the number-average molecular weight of the organopolysiloxane compound is 300,000 or less, and selectively between 400 and 80,000. This enables the secondary battery to achieve both good dynamic performance and high-temperature storage performance.

[0013] In any embodiment of this application, the mass percentage of polar functional groups in the organopolysiloxane compound is α, where 0 ≤ α < 50%, and selectively 5% ≤ α ≤ 30%. This can further improve the cycle performance and storage performance of the secondary battery.

[0014] In any embodiment of this application, the content of the organopolysiloxane compound is 0.01% to 2% by weight, and selectively 0.1% to 2% by weight, relative to the total weight of the cathode material composition. This can further improve the cycle performance and storage performance of the secondary battery.

[0015] In any embodiment of this application, the amount of the first coating layer is greater than 0 and 6% by weight or less, selectively greater than 0 and 5.5% by weight or less, and more selectively greater than 0 and 2% by weight or less, relative to the weight of the kernel.

[0016] In any embodiment of this application, the amount of the second coating layer is greater than 0 and 6% by weight or less, selectively greater than 0 and 5.5% by weight or less, and more selectively 2% to 4% by weight, relative to the weight of the kernel.

[0017] In any embodiment of this application, the amount of the third coating layer is greater than 0 and 6% by weight or less, selectively greater than 0 and 5.5% by weight or less, and more selectively greater than 0 and 2% by weight or less, relative to the weight of the kernel.

[0018] In the positive electrode active material having a core-shell structure according to this application, it is preferable that the amount of coverage of the three coating layers is within the above range. This allows the kernel to be sufficiently covered, and further improves the cycle performance, safety performance, and / or rate performance of the secondary battery without sacrificing the gram capacity (capacity per gram) of the positive electrode active material.

[0019] In any embodiment of this application, the thickness of the first coating layer is 1 nm to 10 nm. In this case, it is possible to avoid adverse effects on the dynamic performance of the positive electrode active material that may occur if the first coating layer is too thick, and to avoid the problem that the migration of transition metal ions cannot be effectively inhibited if the first coating layer is too thin.

[0020] In any embodiment of this application, the thickness of the second coating layer is 2 nm to 15 nm. In this case, the surface structure of the second coating layer is stable and side reactions with the electrolyte are small, effectively reducing side reactions at the interface, thereby improving the high-temperature cycling performance and high-temperature storage performance of the secondary battery.

[0021] In any embodiment of this application, the thickness of the third coating layer is 2 nm to 25 nm. In this case, the conductivity of the positive electrode active material can be improved, and the compressive density of the positive electrode sheet made using the positive electrode active material can be improved.

[0022] In any embodiment of this application, the lattice plane spacing of the crystalline pyrophosphate in the first coating layer is in the range of 0.293 nm to 0.470 nm, and the range of the included angle for the crystal orientation (111) is in the range of 18.00° to 32.00°.

[0023] In any embodiment of this application, the lattice plane spacing of the crystalline phosphate in the second coating layer is in the range of 0.244 nm to 0.425 nm, and the range of the included angle for the crystal orientation (111) is in the range of 20.00° to 37.00°.

[0024] Crystalline pyrophosphates and crystalline phosphates within the above-mentioned lattice plane spacing and angle range can more effectively suppress the lattice change rate of lithium manganese phosphate and the elution of manganese ions during the lithium insertion and deinsertion process, thereby improving the high-temperature cycle performance and high-temperature storage performance of secondary batteries.

[0025] In any embodiment of this application, the ratio of y to 1-y in the kernel is 1:10 to 1:1, and selectively 1:4 to 1:1. This further improves the cycle performance and rate performance of the secondary battery.

[0026] In any embodiment of this application, the ratio of z to 1-z in the kernel is 1:9 to 1:999, and selectively 1:499 to 1:249. This further improves the cycle performance and rate performance of the secondary battery.

[0027] In any embodiment of this application, the carbon in the third coating layer is a mixture of SP2 form carbon and SP3 form carbon, and selectively, the molar ratio of SP2 form carbon to SP3 form carbon is any value within the range of 0.1 to 10, and selectively, any value within the range of 2.0 to 3.0. This application improves the overall performance of a secondary battery by limiting the molar ratio of SP2 form carbon to SP3 form carbon within the above range.

[0028] In any embodiment of this application, the manganese content is in the range of 10% to 35% by weight, selectively in the range of 15% to 30% by weight, and more selectively in the range of 17% to 20% by weight, relative to the weight of the positive electrode active material. In this case, if the manganese content is too high, problems such as poor structural stability of the positive electrode active material and decreased density can be effectively avoided, thereby improving the performance of the secondary battery, such as cycle, storage, and compression density. Conversely, if the manganese content is too low, problems such as a low voltage platform can be avoided, thereby improving the energy density of the secondary battery.

[0029] In any embodiment of this application, the phosphorus content is in the range of 12% to 25% by weight, and selectively in the range of 15% to 20% by weight, relative to the weight of the positive electrode active material. In this case, the following situations can be effectively avoided: If the phosphorus content is too high, the covalent bonding of PO is too strong, which may affect the conductivity of the small polarons and thus affect the conductivity of the positive electrode active material; if the phosphorus content is too low, the stability of the lattice structure of the kernel, the pyrophosphate in the first coating layer and / or the phosphate in the second coating layer is reduced, which may affect the overall stability of the positive electrode active material.

[0030] In any embodiment of this application, the weight ratio of manganese to phosphorus relative to the weight of the positive electrode active material is in the range of 0.90 to 1.25, and selectively 0.95 to 1.20. In this case, the following situations can be effectively avoided: If the weight ratio is too high, the elution of manganese ions will increase, which may affect the stability of the positive electrode active material and the cycle performance and storage performance of the secondary battery; if the weight ratio is too low, the discharge voltage platform of the positive electrode active material will decrease, which may reduce the energy density of the secondary battery.

[0031] In any embodiment of this application, the positive electrode active material has a lattice change rate of 4% or less before and after complete insertion and deinsertion of lithium, selectively 3.8% or less, and more selectively 2.0% to 3.8%. In this case, the positive electrode active material can improve the capacity and rate performance of the secondary battery.

[0032] In any embodiment of this application, the Li / Mn antistructure defect concentration of the positive electrode active material is 4% or less, selectively 2.2% or less, and more selectively 1.5% to 2.2%. By having the Li / Mn antistructure defect concentration within the above range, Mn 2+ Li + This method can improve the capacity and rate performance of the positive electrode active material while avoiding interference with its transport.

[0033] In any embodiment of this application, the compressed density of the positive electrode active material at 3T is 2.2 g / cm³. 3 The above is the result, and selectively 2.2 g / cm³ 3 The above and 2.8 g / cm³ 3 The following is the result. This is advantageous for improving the volumetric energy density of secondary batteries.

[0034] In any embodiment of this application, the oxygen valence on the surface of the positive electrode active material is -1.90 or less, and selectively between -1.90 and -1.98. By setting the oxygen valence on the surface of the positive electrode active material within this range, side reactions at the interface between the positive electrode active material and the electrolyte can be reduced, thereby improving the cycle performance and storage performance of the secondary battery.

[0035] In any embodiment of this application, the positive electrode material composition further comprises a conductive agent and a binder. Selectively, the content of the binder is 1.79% to 10% by weight relative to the total weight of the positive electrode material composition, and selectively, the content of the conductive agent is 0.2% to 10% by weight relative to the total weight of the positive electrode material composition.

[0036] In any embodiment of this application, the powder resistivity of the positive electrode material composition at 12 MPa is 4 Ω / cm to 55 Ω / cm, and selectively 4 Ω / cm to 40 Ω / cm. This allows the secondary battery to have superior dynamic performance.

[0037] In any embodiment of this application, the specific surface area of ​​the cathode material composition is 8 m². 2 / g~20m 2 / g, selectively 8m 2 / g~15m 2 This allows secondary batteries to have better electrochemical performance.

[0038] A second aspect of this application provides a method for producing a cathode material composition, comprising the steps of providing a kernel material, coating, and mixing.

[0039] As a step of providing the kernel material, the chemical formula of the kernel is Li 1+x Mn 1-y A y P 1-z R z The molecule is O4, where x is any number in the range of -0.100 to 0.100, selectively any number in the range of -0.005 to 0.002, y is any number in the range of 0.001 to 0.500, 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, selectively one or more elements selected from Fe, Ti, V, Ni, Co, and Mg, R is one or more elements selected from B, Si, N, and S, selectively R is one element selected from B, Si, N, and S, and the values ​​of x, y, and z satisfy the condition that the entire kernel maintains electrical neutrality.

[0040] As a coating step, Li a MP2O7 and / or M b (P2O7) cand an XPO4 suspension are provided, the kernel material is added to the suspension and mixed, and sintered to obtain a positive electrode active material, wherein the positive electrode active material has a core-shell structure, which includes the kernel and a shell covering the kernel, the shell includes a first coating layer covering the kernel, 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 crystalline pyrophosphate Li a MP2O7 and / or M b (P2O7) c It includes, 0≦a≦2, 1≦b≦4, 1≦c≦6, and the crystalline pyrophosphate Li a MP2O7 and M b (P2O7) c In this formula, M is one or more elements independently selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and the values ​​of a, b, and c are crystalline pyrophosphate Li a MP2O7 or M b (P2O7) c The conditions for maintaining electrical neutrality are met, the second coating layer contains crystalline phosphate XPO4, where X is one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and the third coating layer is carbon.

[0041] As a mixing step, the obtained positive electrode active material is uniformly mixed with an organopolysiloxane compound, a selectable binder, and a selectable conductive agent to obtain a positive electrode material composition.

[0042] In any embodiment of this application, the step of providing the kernel material includes the following steps (1) and (2).

[0043] In step (1), the manganese source, element A dopant, and acid are mixed and stirred in a container to obtain manganese salt particles doped with element A.

[0044] In step (2), the manganese salt particles doped with element A, a lithium source, a phosphorus source, and a dopant of element R are mixed in a solvent to obtain a slurry, which is then sintered under the protection of an inert gas atmosphere to obtain a kernel doped with elements A and R, where the kernel doped with elements A and R is Li 1+x Mn 1-y A y P 1-z R z The element is O4, x is any number within the range of -0.100 to 0.100, selectively any number within the range of -0.005 to 0.002, y is any number within the range of 0.001 to 0.500, z is any number within 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, selectively one or more elements selected from Fe, Ti, V, Ni, Co, and Mg, R is one or more elements selected from B, Si, N, and S, selectively R is one element selected from B, Si, N, and S.

[0045] In any embodiment of this application, step (1) is performed by mixing at a temperature of 20°C to 120°C, selectively 40°C to 120°C.

[0046] In any embodiment of this application, the stirring in step (1) is performed at 400 rpm to 700 rpm for 1 to 9 hours, or selectively for 3 to 7 hours.

[0047] When the heating temperature and stirring time in the kernel particle manufacturing process are within the above range, the manufactured kernel and the cathode active material produced therefrom have fewer lattice defects, which is advantageous in suppressing the elution of manganese ions, and reduces interfacial side reactions between the cathode active material and the electrolyte, thereby improving the cycle performance and safety performance of the secondary battery.

[0048] In any embodiment of this application, step (2) is to mix at a temperature of 20°C to 120°C, selectively 40°C to 120°C, for 1 to 10 hours.

[0049] In any embodiment of this application, the dopant of element A is one or more elements selected from the elements, carbonates, sulfates, chlorides, nitrates, organic acid salts, oxides, and hydroxides of 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.

[0050] In any embodiment of this application, the dopant of element R is one or more selected from inorganic acids, organic acids, sulfates, chlorides, nitrates, organic acid salts, oxides, and hydroxides of one or more elements selected from B, Si, N, and S.

[0051] In any embodiment of this application, the coating step includes a first coating step, a second coating step, and a third coating step.

[0052] As a first coating step, a source of element M, a phosphorus source, an acid, and a selectable lithium source are dissolved in a solvent to obtain a first coating layer suspension. The kernel obtained in the step of providing the kernel material and the first coating layer suspension obtained in the first coating step are thoroughly mixed, dried, and then sintered to obtain a material coated with the first coating layer.

[0053] As a second coating step, a source of element X, a phosphorus source, and an acid are dissolved in a solvent to obtain a second coating layer suspension. The material coated with the first coating layer obtained in the first coating step and the second coating layer suspension obtained in the second coating step are thoroughly mixed, dried, and then sintered to obtain a material coated with two layers.

[0054] In the third coating step, a carbon source is dissolved in a solvent and thoroughly dissolved to obtain a third coating layer solution. Then, the material coated with two coating layers obtained in the second coating step is added to the third coating layer solution, mixed uniformly, dried, and sintered to obtain a material coated with three coating layers, i.e., a positive electrode active material.

[0055] In any embodiment of this application, the first coating step involves controlling the pH of the solution of the source containing element M, the phosphorus source, and the acid, as well as a selectable lithium source, to 3.5 to 6.5, then stirring to allow the reaction to proceed for 1 to 5 hours, and then raising the temperature of the solution to 50°C to 120°C and maintaining that temperature for 2 to 10 hours.

[0056] In any embodiment of this application, the first coating step is performed at 650°C to 800°C for 2 to 6 hours.

[0057] By setting the conditions of the first coating step within the above range, it is possible not only to maintain but also to further improve the capacity, cycle performance, high-temperature storage performance, and rate performance of the secondary battery manufactured using the positive electrode active material.

[0058] In any embodiment of this application, in the second coating step, the source of element X, the phosphorus source, and the acid are dissolved in a solvent, then stirred and reacted for 1 to 10 hours, and then the solution is heated to 60°C to 150°C and maintained at that temperature for 2 to 10 hours.

[0059] In any embodiment of this application, in the second coating step, sintering is carried out at 500°C to 700°C for 6 to 10 hours.

[0060] In the steps of providing the kernel material, the first coating step, and the second coating step, before sintering, that is, in the production of the kernel material (steps (1) and (2)) and the production of the first and second coating layer suspensions, the reaction temperature and reaction time selected as described above can be used to avoid situations where, if the reaction temperature is too low, the reaction cannot occur or the reaction rate is too slow; if the temperature is too high, the product decomposes or forms impurities; if the reaction time is too long, the particle size of the product may be large, increasing the time and difficulty of subsequent processes; and if the reaction time is too short, the reaction is incomplete and the amount of product obtained is small.

[0061] In any embodiment of this application, the sintering in the third coating step is carried out at 700°C to 800°C for 6 to 10 hours.

[0062] By setting the conditions of the third coating step within the above range, the capacity expression and compressibility of the positive electrode active material can be improved.

[0063] The method for producing a positive electrode active material according to this application is advantageous for industrialization because it has a wide range of raw material sources, low costs, and a simple process.

[0064] A third aspect of this application provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode material composition according to the first aspect of this application or a positive electrode material composition manufactured by the method according to the second aspect of this application, and the content of the positive electrode material composition in the positive electrode film layer is 50% by weight or more with respect to the total weight of the positive electrode film layer.

[0065] In any embodiment of this application, the content of the positive electrode material composition in the positive electrode film layer is 90% to 100% by weight relative to the total weight of the positive electrode film layer.

[0066] In any embodiment of this application, the solid-liquid contact angle between the positive electrode film layer and the non-aqueous organic solvent is 3° to 90°, selectively 3° to 60°, and more preferably 10° to 30°. When the contact angle is within an appropriate range, the secondary battery can achieve both high energy density and improved cycle performance, safety performance, and / or rate performance.

[0067] In any embodiment of this application, the porosity of the positive electrode film layer is 15% to 50%, and selectively 15% to 30%. When the porosity is within an appropriate range, the secondary battery can achieve both high energy density and improved cycle performance, safety performance, and / or rate performance.

[0068] In any embodiment of this application, the resistance of the positive electrode film layer is greater than 0 and 6Ω or less. This allows the secondary battery to have better dynamic performance.

[0069] In any embodiment of this application, the adhesive force between the positive electrode film layer and the positive electrode current collector is 0.5 MPa or higher. This is advantageous for achieving secondary battery performance.

[0070] In any embodiment of this application, the surface density of the positive electrode film layer is 0.006 g / cm³. 2 ~0.065 g / cm³ 2 This is advantageous for improving the volumetric energy density of secondary batteries.

[0071] In any embodiment of this application, the absorption rate of the electrolyte into the positive electrode film layer is 0.0125 μg / s to 100 μg / s, and selectively 0.5 μg / s to 40 μg / s. This is advantageous for improving the electrochemical performance of the secondary battery.

[0072] The positive electrode sheet of this application can be used in secondary batteries and can improve the energy density, cycle performance, safety performance, and / or rate performance of the secondary battery.

[0073] A fourth aspect of this application provides a secondary battery comprising a positive electrode active material according to the first aspect of this application, a positive electrode active material manufactured by the method of the second aspect of this application, or a positive electrode sheet according to the third aspect of this application.

[0074] A fifth aspect of this application provides a power consumption device including a secondary battery according to the fourth aspect of this application.

[0075] The positive electrode sheet, secondary battery, and power consumption device of this application include the positive electrode material composition of this application and therefore have at least the same advantages as the said positive electrode material composition. [Brief explanation of the drawing]

[0076] To more clearly illustrate the technical concept of the embodiments of this application, the drawings that need to be used in the embodiments of this application are briefly described below. Obviously, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any creative effort. [Figure 1] This is a schematic diagram of one embodiment of the secondary battery disclosed herein. [Figure 2] Figure 1 is a schematic diagram of an exploded view of an embodiment of a secondary battery. [Figure 3] This is a schematic diagram of one embodiment of the battery module of this application. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of this application. [Figure 5] Figure 4 is an exploded schematic diagram of an embodiment of the battery pack shown. [Figure 6] This is a schematic diagram of one embodiment of a power consumption device that includes a secondary battery as a power source according to this application. The drawing is not necessarily drawn to actual scale. [Explanation of Symbols]

[0077] 1 Battery pack 2 Upper cabinet 3 Lower cabinet 4 Battery Modules 5 Secondary battery 51 cases 52 Electrode Assembly 53 Cover Plate [Modes for carrying out the invention]

[0078] The following describes in detail, with reference to the drawings as appropriate, embodiments of the positive electrode material composition, the method for manufacturing the same, and the positive electrode sheet, secondary battery, and power consumption device containing the same, as specifically disclosed in this application. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of already well-known matters and redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding by those skilled in the art. The accompanying drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter described in the claims.

[0079] The “range” disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting one lower limit and one upper limit, the selected lower limit and upper limit limit the boundary of a special range. The range thus limited may be an endpoint or a range that does not include endpoints, or may be any combination thereof, that is, any lower limit may be combined with any upper limit. For example, if the ranges 60-120 and 80-110 are given for a particular parameter, the ranges 60-110 and 80-120 can also be expected. Also, if the minimum range values ​​1 and 2 and the maximum range values ​​3, 4 and 5 are given, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 can all be expected. In this application, unless otherwise stated, the numerical range “a-b” is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" in this specification indicates that all real numbers between "0 to 5" are listed, and "0 to 5" is an abbreviation for combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0080] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined to form new technical concepts. Such technical concepts should be considered to be included in the disclosures of this application.

[0081] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical concepts. Such technical concepts should be considered to be included in the disclosures of this application.

[0082] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if it is mentioned that the method may further include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0083] Unless otherwise specified, the terms "contains," "possesses," and "equip" as used in this application mean open-ended, or they may also mean closed-ended. For example, the terms "contains," "possesses," and "equip" can mean further "contains," "possesses," or "equips" other components not listed, or "contains," "possesses," or "equips" only the listed components.

[0084] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0085] In this specification, the terms "plural" and "plural species" mean two or more.

[0086] In this specification, "approximately" means that a given number represents a range, and that range is ±10% of that number.

[0087] In this specification, the term “coating layer” refers to a material layer that coats a lithium manganese phosphate kernel, and the material layer may completely or partially coat the lithium manganese phosphate kernel. The use of “coating layer” is for illustrative purposes only and is not intended to limit this application. Furthermore, each coating layer may be a complete coating or a partial coating. Similarly, the term “thickness of the coating layer” refers to the thickness of the material layer coating the lithium manganese phosphate kernel in the radial direction of the lithium manganese phosphate kernel.

[0088] In this specification, median diameter Dv50 refers to the particle size corresponding to the point at which the cumulative volume distribution percentage of the material reaches 50%. In this application, the median diameter Dv50 of the material can be measured by laser diffraction particle size analysis. For example, it is measured using a laser particle size analyzer (e.g., Malvern Master Size 3000) with reference to standard GB / T 19077-2016.

[0089] In this specification, substituents of compounds are disclosed in groups or ranges. Such descriptions are clearly expected to include each member of these groups and ranges as well as individual subcombinations. For example, the term "C1-C8 alkyl group" is clearly expected to disclose C1, C2, C3, C4, C5, C6, C7, C8, C1-C8, C1-C7, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C8, C2-C7, C2-C6, C2-C5, C2-C4, C2-C3, C3-C8, C3-C7, C3-C6, C3-C5, C3-C4, C4-C8, C4-C7, C4-C6, C4-C5, C5-C8, C5-C7, C5-C6, C6-C8, C6-C7 and C7-C8 alkyl groups individually.

[0090] In this specification, the term "aliphatic hydrocarbon group" includes alkyl groups, alkenyl groups, and alkynyl groups, and the term "heteroaliphatic hydrocarbon group" means that an aliphatic hydrocarbon group contains a heteroatom (e.g., N, O, S, etc.). The term "heteroalkyl group" refers to an alkyl group containing a heteroatom (e.g., N, O, S, etc.), which may be an alkoxy group, an alkylthio group, etc.

[0091] The inventors of this application have discovered, in practical work, that conventional lithium manganese phosphate (LiMnPO4) cathode active materials suffer from severe manganese ion leaching during deep charge-discharge processes. While prior art attempts to reduce interfacial side reactions by coating lithium iron phosphate with lithium manganese phosphate, such coatings fail to prevent the leached manganese ions from continuing to migrate to the electrolyte. The leached manganese ions then migrate to the negative electrode and are reduced to metallic manganese. This metallic manganese acts as a catalyst, catalyzing the decomposition of the SEI film (solid electrolyte interphase) on the negative electrode surface and generating byproducts. Some of these byproducts are gases, causing expansion of the secondary battery and affecting its safety performance. Other byproducts accumulate on the negative electrode surface, obstructing the channels through which lithium ions enter and exit the negative electrode, increasing the battery's resistance and affecting its dynamic performance. Furthermore, in order to compensate for the lost SEI film, the electrolyte and active lithium inside the battery are continuously consumed, which irreversibly affects the capacity retention rate of the secondary battery.

[0092] As a result of diligent research by the inventors, it is possible to modify lithium manganese phosphate and coat it with multiple layers, thereby significantly reducing the elution of manganese ions and lowering the lattice change rate. This allows for the creation of a novel positive electrode active material with a core-shell structure that can be used in secondary batteries, improving the battery's cycle performance, rate performance, and safety performance, and enhancing its capacity. Simultaneously, as a discovery by the inventors of this application, it is possible to use the positive electrode active material in combination with an organopolysiloxane compound, which can mitigate surface erosion of the positive electrode active material by the electrolyte and is advantageous in fully exhibiting the electrochemical properties of the positive electrode active material. Cathode material composition

[0093] Specifically, a first aspect of this application proposes a cathode material composition comprising a cathode active material having a core-shell structure and an organopolysiloxane compound.

[0094] The positive electrode active material includes a kernel and a shell covering the kernel. The chemical formula of the kernel is Li 1+x Mn 1-y A y P 1-z R z The O4 is such that x is any number within the range of -0.100 to 0.100, y is any number within the range of 0.001 to 0.500, z is any number within 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 selectively one or more elements selected from Fe, Ti, V, Ni, Co, and Mg, R is one or more elements selected from B, Si, N, and S, and selectively R is one element selected from B, Si, N, and S, and the values ​​of x, y, and z satisfy the conditions for maintaining the entire kernel in an electrically neutral state. The shell includes a first coating layer covering the kernel, 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 made of crystalline pyrophosphate Li a MP2O7 and / or M b (P2O7) c It includes, 0≦a≦2, 1≦b≦4, 1≦c≦6, and the crystalline pyrophosphate Li a MP2O7 and M b (P2O7) c In this formula, M is one or more elements independently selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and the values ​​of a, b, and c are crystalline pyrophosphate Li a MP2O7 or M b (P2O7) c The conditions for maintaining electrical neutrality are met, the second coating layer contains crystalline phosphate XPO4, where X is one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and the third coating layer is carbon.

[0095] Unless otherwise specified, in the chemical formula of the kernel described above, if A is two or more elements, the limitation on the numerical range of y refers not only to the limitation on each individual stoichiometric number of A as an element, but also to the limitation on the sum of the stoichiometric numbers of A as an element. For example, if A is two or more elements A1, A2...An, then the stoichiometric numbers y1, y2...yn of A1, A2...An must each fall within the numerical range limited for y in this application, and the sum of y1, y2...yn must also fall within that numerical range. Similarly, if R is two or more elements, the limitation on the numerical range of the stoichiometric number of R in this application has the same meaning as described above.

[0096] In one selectable embodiment, 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, y Q n1 D n2 E n3 K n4 The following conditions apply: n1+n2+n3+n4=y, and n1, n2, n3, and n4 are all positive numbers and simultaneously non-zero. 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 selectively at least one of Q, D, E, and K is Fe. Selectively, one of n1, n2, n3, and n4 is zero and the rest are non-zero; more selectively, two of n1, n2, n3, and n4 are zero and the rest are non-zero; and even more selectively, three of n1, n2, n3, and n4 are zero and the rest are non-zero. The kernel Li 1+x Mn 1-y A y P 1-z R z In O4, it is advantageous to dope manganese sites with one, two, three, or four of the above-mentioned A elements, and it is also advantageous to selectively dope with one, two, or three of the above-mentioned A elements, and to dope phosphorus sites with one or two of the above-mentioned R elements, and thus it is advantageous to uniformly distribute the doping elements.

[0097] The kernel Li 1+x Mn 1-y A y P 1-z R z In O4, the magnitude of x is influenced by the magnitudes of the valence states of A and R, and the magnitudes of y and z, ensuring that the entire system exhibits electrical neutrality. If the value of x is too small, the lithium content of the entire kernel system decreases, affecting the capacity of the positive electrode active 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 will not function, and if y exceeds 0.5, the Mn content in the system decreases, affecting the voltage platform of the material. The R element is doped at the P position, the PO tetrahedron is stable, and if the z value is too large, it affects the stability of the material, so the z value is limited to 0.001 to 0.100.

[0098] The positive electrode active material of this application can improve the capacity, cycle performance, and safety performance of secondary batteries. Although the mechanism is not clear, a possible reason is that the lithium manganese phosphate positive electrode active material of this application has a core-shell structure, and by doping the manganese sites and phosphorus sites of the lithium manganese phosphate kernel with elements A and R, respectively, the elution of manganese ions is effectively reduced, further reducing the amount of manganese ions that have moved to the negative electrode, reducing the electrolyte consumed by the decomposition of the SEI film, thereby improving the cycle performance and safety performance of the secondary battery. In addition, it can promote the adjustment of Mn-O bonds, lower the lithium ion migration barrier, promote lithium ion migration, and improve the rate performance of the secondary battery. By coating the kernel with a first coating layer containing crystalline pyrophosphate, the resistance to manganese ion migration is further increased, reducing its elution, reducing the content of lithium impurities on the surface, and reducing contact between the kernel and the electrolyte, thereby reducing interfacial side reactions, reducing gas generation, and improving the high-temperature storage performance, cycle performance, and safety performance of the secondary battery. By further coating with a crystalline phosphate coating layer that has excellent lithium ion conductivity, side reactions at the interface between the positive electrode active material and the electrolyte can be effectively reduced, and the high-temperature cycling and storage performance of the secondary battery can be further improved. By further coating with a carbon layer to form a third coating layer, the safety and dynamic performance of the secondary battery can be improved.

[0099] Furthermore, in the kernel, element A doped into the manganese sites of lithium manganese phosphate reduces the lattice change rate of lithium manganese phosphate during the lithium insertion and deinsertion process of the material, improving the structural stability of the lithium manganese phosphate cathode active material, significantly reducing the elution of manganese ions, and lowering the oxygen activity on the particle surface. Element R doped into the phosphorus sites also helps to change the difficulty of changing the length of the Mn-O bond, thereby improving electron conductivity, lowering the lithium ion transport barrier, promoting lithium ion transport, and improving the rate performance of the secondary battery.

[0100] Furthermore, maintaining electrical neutrality throughout the kernel system minimizes defects and impurities in the positive electrode active material. If excess transition metals (e.g., manganese) are present in the positive electrode active material, the stable structure of the material system itself may lead to the extra transition metals precipitating as elemental particles or forming impurities within the crystal lattice. Maintaining electrical neutrality minimizes such impurities. Additionally, while ensuring the electrical neutrality of the system, lithium vacancies can be introduced into the positive electrode active material in some cases, resulting in improved dynamic performance of the positive electrode active material.

[0101] The positive electrode material composition of this application comprises a positive electrode active material and an organopolysiloxane compound. The inventors of this application have discovered that using the above positive electrode active material and organopolysiloxane compound in combination can mitigate erosion of the surface of the positive electrode active material by the electrolyte and reduce the elution of manganese ions, which is advantageous for improving the electrochemical performance of the positive electrode active material. Possible reasons for this include the fact that the Si-O skeleton of the organopolysiloxane compound can remove F-containing ions in the electrolyte, thereby reducing the acidity of the electrolyte and mitigating erosion of the surface of the positive electrode active material by acidic substances in the electrolyte. Furthermore, the organopolysiloxane compound also possesses a certain degree of water repellency, and after manufacturing a positive electrode sheet together with the positive electrode active material, the contact angle between the obtained positive electrode sheet and the electrolyte increases, thereby mitigating erosion of the surface of the positive electrode active material by the electrolyte.

[0102] Therefore, a positive electrode sheet and a power consumption device such as a secondary battery employing the positive electrode material composition of this application have high energy density and can achieve improved cycle performance, safety performance, and / or rate performance simultaneously.

[0103] The average particle size range of the kernels manufactured in this application is 50 nm to 500 nm, and for Dv50 it is 200 nm to 300 nm. The size of the primary particles of the kernels is 50 nm to 500 nm in all cases, and for Dv50 it is 200 nm to 300 nm. If the average particle size of the kernels is too large (exceeding 500 nm), it will affect the capacity of the secondary battery using this material, and if the average particle size of the kernels is too small, its specific surface area will be large, making it prone to aggregation and making it difficult to achieve a uniform coating.

[0104] Process control (e.g., thoroughly mixing and polishing materials from various sources) can ensure that each element is uniformly distributed in the crystal lattice and does not aggregate. The fact that the main characteristic peak positions in the X-ray diffraction (XRD) pattern of lithium manganese phosphate doped with elements A and R coincide with those of undoped LiMnPO4 indicates that no impurity phase was introduced in the doping process. Therefore, the improvement in kernel performance is mainly due to elemental doping and not due to impurity phases. After manufacturing the positive electrode active material according to this application, the inventors of this application cut out the intermediate region (kernel region) of the positive electrode active material particles manufactured by focused ion beam (FIB) and measured it by transmission electron microscopy (TEM) and X-ray spectroscopy (EDS). They found that each element was uniformly distributed and no aggregation occurred.

[0105] In this application, crystallinity (crystalline state) means a degree of crystallinity of 50% or more, i.e., 50% to 100%. A degree of crystallinity of less than 50% is called a glassy state (or amorphous). The degree of crystallinity of the crystalline pyrophosphate and crystalline phosphate described in this application is 50% to 100%. Pyrophosphates and phosphates having a certain degree of crystallinity are advantageous not only in allowing the pyrophosphate coating layer to fully exhibit its functions of inhibiting manganese ion elution, its excellent lithium ion conductivity, and its reduction of interfacial side reactions, but also in enabling better lattice matching between the pyrophosphate coating layer and the phosphate coating layer, thereby achieving a tighter bond in the coating layer.

[0106] In this application, the degree of crystallinity of the crystalline pyrophosphate of the first coating layer material and the crystalline phosphate of the second coating layer material of the positive electrode active material may be measured by conventional technical means in the art, such as density methods, infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance absorption spectroscopy, or by X-ray diffraction, for example.

[0107] A specific X-ray diffraction method for measuring the crystallinity of the crystalline pyrophosphate in the first coating layer and the crystalline phosphate in the second coating layer of a positive electrode active material may include the following steps: taking a certain amount of positive electrode active material powder, measuring the total scattering intensity, which is the sum of the scattering intensities of the material in the entire space, using X-rays; and determining that this total scattering intensity is related only to the intensity of the primary radiation, the chemical structure of the positive electrode active material powder, and the total number of electrons participating in the diffraction, i.e., the mass, and not the ordered state of the sample. Subsequently, the crystalline scattering and amorphous scattering are separated from the diffraction pattern, and the crystallinity is the ratio of the scattering of the crystalline portion to the total scattering intensity.

[0108] In this application, the degree of crystallinity of pyrophosphate and phosphate in the coating layer can be adjusted, for example, by adjusting the process conditions of the sintering process, such as the sintering temperature and sintering time.

[0109] In this application, since metal ions do not easily migrate to pyrophosphate, the pyrophosphate can be used as the first coating layer to effectively isolate doped metal ions from the electrolyte. Because crystalline pyrophosphate has a stable structure, the crystalline pyrophosphate coating can effectively suppress the elution of transition metals and improve cycle performance.

[0110] 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 lattice matching. When the lattice mismatch is 5% or less, the lattice matching is good, and the two tend to bond tightly. Tight bonding is advantageous in ensuring the long-term stability of the cathode active material because it can guarantee that the coating layer will not detach during subsequent cycle processes. The degree of bonding between the first coating layer and the core is evaluated mainly by calculating the degree of mismatch of the lattice constants of the core and the coating. In this application, after doping the kernel with elements A and R, the degree of matching between the kernel and the first coating layer is improved compared to when the doped elements are not present, and the kernel and the pyrophosphate coating layer can bond more tightly.

[0111] Crystalline phosphate was selected as the second coating layer because, firstly, it has a high degree of lattice matching with the crystalline pyrophosphate of the first coating layer (the degree of mismatch is only 3%), and secondly, the stability of the phosphate itself is better than that of pyrophosphate, which is advantageous for improving the stability of the positive electrode active material. Because crystalline phosphate has a stable structure and excellent lithium ion conductivity, coating with crystalline phosphate effectively reduces side reactions at the interface between the positive electrode active material and the electrolyte, thereby improving the high-temperature cycle performance and high-temperature storage performance of the secondary battery. The way in which the second coating layer and the first coating layer are lattice-matched is similar to the case of bonding between the first coating layer and the core as described above, and if the lattice mismatch is 5% or less, the lattice matching is good and the two layers are likely to bond tightly.

[0112] The main reason for selecting carbon as the third coating layer is its good electronic conductivity. Since electrochemical reactions occur during secondary battery applications, requiring the involvement of electrons, the positive electrode active material can be coated with carbon, which possesses excellent conductivity, in order to increase electron transport between particles and between different positions on the particles. Carbon coating can effectively improve the conductivity and desolvation ability of the positive electrode active material.

[0113] In some embodiments, the average particle size of the primary particles of the positive electrode active material is 50 nm to 500 nm, and the volume median diameter Dv50 is in the range of 200 nm to 300 nm. Due to particle aggregation, the actual measured size of the aggregated secondary particles may be 500 nm to 40000 nm. The size of the positive electrode active material particles affects the processing of the material and the compressive density performance of the electrode sheet. By selecting the average particle size of the primary particles to be within the above range, it is possible to effectively avoid the following problems: if the average particle size of the primary particles of the positive electrode active material is too small, particle aggregation may occur, making dispersion difficult and requiring a lot of binder, thus worsening the brittleness of the electrode sheet; and if the average particle size of the primary particles of the positive electrode active material is too large, the voids between particles may become large, potentially reducing the compressive density.

[0114] The above proposed technology effectively suppresses the lattice change rate of lithium manganese phosphate and the elution of manganese ions during the lithium insertion and deinsertion process, thereby improving the high-temperature cycle performance and high-temperature storage performance of secondary batteries.

[0115] In some embodiments, the lattice plane spacing of the crystalline pyrophosphate in the first coating layer is in the range of 0.293 nm to 0.470 nm, and the included angle range for the crystal orientation (111) is in the range of 18.00° to 32.00°, while the lattice plane spacing of the crystalline phosphate in the second coating layer is in the range of 0.244 nm to 0.425 nm, and the included angle range for the crystal orientation (111) is in the range of 20.00° to 37.00°.

[0116] The first and second coating layers in the positive electrode active material of this application both utilize crystalline materials. The crystalline pyrophosphate and crystalline phosphate in the coating layers can be characterized by conventional technical means in the art. For example, they can be characterized by transmission electron microscopy (TEM). In TEM, the kernel and coating layers can be distinguished by measuring the lattice plane spacing.

[0117] A specific method for measuring the lattice plane spacing and binding angle between crystalline pyrophosphate and crystalline phosphate in a coating layer may include the steps of: placing a certain amount of coated cathode active material sample powder into a test tube; pouring a solvent, such as alcohol, into the test tube; thoroughly stirring and dispersing the powder; then taking an appropriate amount of the solution with a clean disposable plastic pipette and dropping it onto a 300-mesh copper mesh, at which point some of the powder will remain on the copper mesh; transferring the copper mesh together with the sample to the TEM sample chamber for testing and obtaining a raw image of the TEM test. The raw image obtained from the TEM test can be run on diffractometer software to obtain a diffraction pattern by performing a Fourier transform; measuring the distance from the diffraction spot to the center position in the diffraction pattern allows the lattice plane spacing to be obtained; and the binding angle can be calculated based on the Bragg equation.

[0118] Crystalline pyrophosphates are distinguished from crystalline phosphates by the range of their lattice plane spacing, and can be directly identified by the numerical value of the lattice plane spacing.

[0119] Crystalline pyrophosphates and crystalline phosphates within the above-mentioned lattice plane spacing and angle range can more effectively suppress the lattice change rate of lithium manganese phosphate and the elution of manganese ions during lithium insertion and deinsertion processes, thereby improving the high-temperature cycle performance and high-temperature storage performance of secondary batteries.

[0120] In the kernel described above, x is any number within the range of -0.100 to 0.100, for example, x may be 0.001, 0, -0.001, -0.002, -0.003, -0.004, or -0.005. Selectively, x is any number within the range of -0.005 to 0.002.

[0121] In the kernel described above, y is any number within the range of 0.001 to 0.500. For example, y may be 0.001, 0.100, 0.200, 0.300, 0.350, 0.400, 0.450, or 0.500.

[0122] In the kernel described above, z is any number within the range of 0.001 to 0.100, for example, z may be 0.001, 0.002, 0.003, 0.004, 0.005, or 0.100.

[0123] In some embodiments, the ratio of y to 1-y in the kernel is 1:10 to 1:1, and selectively 1:4 to 1:1. Here, y represents the sum of the stoichiometric numbers of doped element A at the Mn site. By satisfying the above conditions, the energy density and cycle performance of the secondary battery using the positive electrode active material can be further improved.

[0124] In some embodiments, the ratio of z to 1-z in the kernel is 1:9 to 1:999, and selectively 1:499 to 1:249, where z represents the sum of the stoichiometric numbers of the doped element R at the P site. By satisfying the above conditions, the energy density and cycle performance of the secondary battery using the positive electrode active material can be further improved.

[0125] In some embodiments, the carbon in the third coating layer is a mixture of SP2 form carbon and SP3 form carbon, and selectively, the molar ratio of SP2 form carbon to SP3 form carbon is any value in the range of 0.1 to 10, and selectively, any value in the range of 2.0 to 3.0.

[0126] 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 within any range of any of the above values.

[0127] By selecting the form of carbon in the carbon coating layer, the overall electrochemical performance of the secondary battery can be improved. Specifically, by using a mixed form of SP2 and SP3 carbon and limiting the ratio of SP2 to SP3 carbon within a certain range, it is possible to effectively avoid situations where, if all the carbon in the coating layer is amorphous SP3, conductivity is poor, and if all is graphitized SP2, conductivity is good but there are few lithium ion channels, which do not contribute to lithium ion insertion and removal. Furthermore, by limiting the molar ratio of SP2 to SP3 carbon within the above range, it is possible to secure lithium ion channels while achieving good conductivity, which is advantageous for improving the dynamic performance and cycle performance of the secondary battery.

[0128] The mixing ratio of SP2 and SP3 forms of the third coating carbon can be controlled by sintering conditions such as sintering temperature and sintering time. For example, when producing the third coating layer using sucrose as a carbon source, the sucrose is decomposed at high temperature and deposited on the second coating layer, and a carbon coating layer containing both SP3 and SP2 forms is produced at high temperature. The ratio of SP2 form carbon to SP3 form carbon can be controlled by selecting high-temperature decomposition conditions and sintering conditions.

[0129] The structure and characteristics of the carbon in the third coating layer can be measured by Raman spectroscopy, and the specific test method involves performing peak splitting on the energy spectrum of the Raman test, d / I g (I d This is the peak intensity of carbon in the SP3 form, and I g The peak intensity of carbon in the SP2 form is obtained, and the molar ratio of the two is confirmed.

[0130] In some embodiments, the amount of the first coating layer is greater than 0 and 6% by weight or less relative to the weight of the kernel, selectively greater than 0 and 5.5% by weight or less, and more selectively greater than 0 and 2% by weight or less.

[0131] In some embodiments, the amount of the second coating layer is greater than 0 and 6% by weight or less relative to the weight of the kernel, selectively greater than 0 and 5.5% by weight or less, and more selectively 2% to 4% by weight.

[0132] In some embodiments, the amount of the third coating layer is greater than 0 and 6% by weight or less relative to the weight of the kernel, selectively greater than 0 and 5.5% by weight or less, and more selectively greater than 0 and 2% by weight or less.

[0133] In this application, the coverage amount of each layer is not zero.

[0134] In the positive electrode active material having a core-shell structure according to this application, it is preferable that the amount of coverage of the three coating layers is within the above range. This allows the kernel to be sufficiently covered, and further improves the cycle performance, safety performance, and / or rate performance of the secondary battery without sacrificing the gram capacity of the positive electrode active material.

[0135] Regarding the first coating layer, if the coating amount is within the above range, then if the coating amount is too small, it means the thickness of the coating layer is too thin, which may not effectively inhibit the movement of the transition metal, and if the coating amount is too large, it means the coating layer is too thick, Li + This effectively avoids affecting the movement of the material and, consequently, the rate performance of the positive electrode active material.

[0136] Regarding the second coating layer, by keeping the coating amount within the above range, it is possible to effectively avoid the possibility that too much coating may affect the plateau voltage of the entire positive electrode active material, or that too little coating may not provide sufficient coating effect.

[0137] For the third coating layer, the carbon coating primarily plays a role in enhancing electron transport between particles, but because it contains a large amount of amorphous carbon in its structure, the carbon density is low. Therefore, if the coating amount is too large, it will affect the compressive density of the electrode sheet.

[0138] In some embodiments, the thickness of the first coating layer is 1 nm to 10 nm.

[0139] In some embodiments, the thickness of the second coating layer is 2 nm to 15 nm.

[0140] In some embodiments, the thickness of the third coating layer is 2 nm to 25 nm.

[0141] 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 any range of any of the above values.

[0142] In some embodiments, the thickness of the second 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, about 10 nm, about 11 nm, about 12 nm, about 13 nm, about 14 nm, or about 15 nm, or any range of any of the above values.

[0143] In some embodiments, the thickness of the third coating layer may be approximately 2 nm, approximately 3 nm, approximately 4 nm, approximately 5 nm, approximately 6 nm, approximately 7 nm, approximately 8 nm, approximately 9 nm, approximately 10 nm, approximately 11 nm, approximately 12 nm, approximately 13 nm, approximately 14 nm, approximately 15 nm, approximately 16 nm, approximately 17 nm, approximately 18 nm, approximately 19 nm, approximately 20 nm, approximately 21 nm, approximately 22 nm, approximately 23 nm, approximately 24 nm, or approximately 25 nm, or it may be within any range of any of the above values.

[0144] If the thickness of the first coating layer is in the range of 1 nm to 10 nm, it is possible to avoid the problem that if it is too thick, it will negatively affect the dynamic performance of the positive electrode active material, and if it is too thin, it will not be able to effectively inhibit the movement of transition metal ions.

[0145] When the thickness of the second coating layer is within the range of 2 nm to 15 nm, the surface structure of the second coating layer is stable and side reactions with the electrolyte are small, thereby effectively reducing interfacial side reactions and improving the high-temperature cycle performance and high-temperature storage performance of the secondary battery.

[0146] When the thickness range of the third coating layer is 2 nm to 25 nm, the conductivity of the positive electrode active material can be improved, and the compressive density of the positive electrode sheet manufactured using the positive electrode active material can be improved.

[0147] The thickness of the coating layer is primarily tested using FIB (Fibrillation-Induced Beam). A specific method may involve randomly selecting a single particle from the positive electrode active material powder under test, cutting a thin slice approximately 100 nm thick from the midpoint or near the midpoint of the selected particle, performing TEM (Temperature-Emissions Measurement) on the slice to measure the thickness of the coating layer, measuring at 3 to 5 locations, and taking the average value.

[0148] In some embodiments, the manganese content is in the range of 10% to 35% by weight, selectively in the range of 15% to 30% by weight, and more selectively in the range of 17% to 20% by weight, relative to the weight of the positive electrode active material.

[0149] In some embodiments, the phosphorus content is in the range of 12% to 25% by weight, and selectively in the range of 15% to 20% by weight, relative to the weight of the positive electrode active material.

[0150] In some embodiments, the weight ratio of manganese to phosphorus is in the range of 0.90 to 1.25, and selectively between 0.95 and 1.20.

[0151] In this application, if manganese is contained only in the kernel of the positive electrode active material, the manganese content may correspond to the content of the kernel.

[0152] In this application, by limiting the manganese content to the above range, problems such as poor structural stability and reduced density of the positive electrode active material when the manganese content is too high can be effectively avoided, thereby improving the performance of the secondary battery, including cycle, storage, and compression density. Conversely, problems such as a low voltage platform when the manganese content is too low can be avoided, thereby improving the energy density of the secondary battery.

[0153] In this application, by limiting the phosphorus content to the above range, it is possible to effectively avoid the following: if the phosphorus content is too high, the covalent bonding of PO is too strong, which may affect the conductivity of the small polarons and thus the conductivity of the positive electrode active material; and if the phosphorus content is too low, the stability of the lattice structure of the kernel, the pyrophosphate in the first coating layer and / or the phosphate in the second coating layer may decrease, which may affect the overall stability of the positive electrode active material.

[0154] The weight ratio of manganese to phosphorus has the following effects on the performance of a secondary battery: If the weight ratio is too high, it means there is too much manganese, which increases the elution of manganese ions, affecting the stability and capacity of the positive electrode active material, and further affecting the cycle performance and storage performance of the secondary battery. If the weight ratio is too low, it means there is too much phosphorus, which makes it easier to form impurity phases, lowers the discharge voltage platform of the positive electrode active material, and reduces the energy density of the secondary battery.

[0155] The manganese and phosphorus elements can be measured using conventional technical means in this art. Specifically, the material is dissolved in dilute hydrochloric acid (concentration 10-30%), the content of each element in the solution is measured by ICP, the manganese content is measured and converted, and the weight ratio is obtained to determine the manganese and phosphorus content.

[0156] In some embodiments, the cathode active material having the core-shell structure has a lattice change rate of 4% or less, selectively 3.8% or less, and more selectively 2.0% to 3.8% before and after complete insertion and extraction of lithium.

[0157] The lithium insertion and extraction process of lithium manganese phosphate (LiMnPO4) is a two-phase reaction. The interfacial stress between the two phases is determined by the magnitude of the lattice change rate before and after lithium insertion and extraction. The smaller the lattice change rate, the smaller the interfacial stress, and the easier the transport of Li + is. Therefore, reducing the lattice change rate of the kernel is beneficial to enhancing the transport ability of Li + and improving the rate performance of the secondary battery. The cathode active material with the core-shell structure according to the present application can have a lattice change rate of 4% or less before and after lithium insertion and extraction, so the rate performance of the secondary battery can be improved. The lattice change rate can be measured by a method known in the art, such as an X-ray diffraction (XRD) pattern.

[0158] In some embodiments, the Li / Mn anti-structure defect concentration of the cathode active material having the core-shell structure is 4% or less, selectively 2.2% or less, and more selectively 1.5% to 2.2%. The Li / Mn anti-structure defect described in the present application refers to the exchange of the positions of Li + and Mn 2+ in the LiMnPO4 crystal lattice. Correspondingly, the Li / Mn anti-structure defect concentration refers to the percentage of Li 2+ exchanged with Mn + in the total amount of Li + In the present application, the Li / Mn anti-structure defect concentration can be measured, for example, according to JISK0131-1996.

[0159] The cathode active material having the core-shell structure according to the present application can achieve the above low Li / Mn anti-structure defect concentration. Although the mechanism has not been fully elucidated, according to the reasoning of the inventors of the present application, in the LiMnPO4 crystal lattice, the positions of Li + and Mn 2+ are exchanged, and Li +Since the transport channel of 2+ is Mn + and it is difficult for Mn to move in the Li + channel, which inhibits the transport of Li. Thus, since the cathode active material having the core-shell structure according to the present application has a low Li / Mn inverse structure defect concentration within the above range, Mn 2+ avoids inhibiting the transport of Li + while improving the capacity performance and rate performance of the cathode active material.

[0160] In some embodiments, the compression density of the cathode active material having the core-shell structure at 3T is 2.2 g / cm 3 [[ID= sixteenth]]or more, and optionally 2.2 g / cm 3 or more and 2.8 g / cm 3 or less. The higher the compression density, the greater the weight per volume of the cathode active material. Therefore, increasing the compression density contributes to increasing the volume energy density of the secondary battery. The compression density can be measured according to GB / T24533-2009.

[0161] In some embodiments, the valence of oxygen atoms on the surface of the cathode active material having the core-shell structure is -1.90 or less, and optionally -1.90 to -1.98. The stable valence of oxygen is -2. The closer the valence is to -2, the stronger its electron acquisition ability, that is, the stronger its oxidizing property. Usually, the valence on its surface is -1.7 or less. By limiting the surface oxygen valence of the cathode active material within the above range as described above, the present application can reduce the interfacial side reaction between the cathode active material and the electrolyte, and improve the cycle performance and storage performance of the secondary battery, etc. The surface oxygen valence can be measured by a method known in the art, such as electron energy loss spectrum (EELS).

[0162] In some embodiments, the organopolysiloxane compound contains at least one structural unit represented by Formula 1.

Chemical formula

[0163] These functional groups can complex manganese ions and / or react with acidic substances in the electrolyte, thereby reducing the elution of manganese ions and further improving the cycle performance and storage performance of secondary batteries.

[0164] If these functional groups also possess electron-withdrawing properties, the Si in the Si-O framework of the organopolysiloxane compound can be made more electron-deficient, thereby further increasing its affinity with F ions in the electrolyte, further mitigating erosion of the surface of the positive electrode active material by acidic substances in the electrolyte, and reducing the elution of manganese ions, thereby significantly improving the cycle performance and storage performance of the secondary battery.

[0165] In some embodiments, the organopolysiloxane compound comprises one or more selected from linear polysiloxanes and cyclic polysiloxanes. Selectively, the organopolysiloxane compound is selected from linear polysiloxanes.

[0166] This further mitigates erosion of the positive electrode active material surface by acidic substances in the electrolyte, reduces manganese ion elution, and significantly improves the cycle performance and storage performance of secondary batteries. However, cyclic polysiloxanes have a certain degree of delocalization of electrons within the ring, resulting in a lower affinity of the Si-O framework for electron-rich F-containing ions compared to linear polysiloxanes. Furthermore, their removal rate from F-containing ions in the electrolyte is somewhat lower, resulting in a weaker effect in reducing manganese ion elution and a somewhat lower improvement in the cycle performance of secondary batteries.

[0167] In some embodiments, the linear polysiloxane may further contain a choke group. Selectively, the choke group includes at least one selected from the group consisting of polyether, C1-C8 alkyl group, C1-C8 halogenated alkyl group, C1-C8 heteroalkyl group, C1-C8 halogenated heteroalkyl group, C2-C8 alkenyl group, C2-C8 halogenated alkenyl group, C6-C20 aromatic hydrocarbon group, C1-C8 alkoxy group, C2-C8 epoxy group, hydroxyl group, C1-C8 hydroxyalkyl group, amino group, C1-C8 aminoalkyl group, carboxyl group, and C1-C8 carboxyalkyl group.

[0168] In some embodiments, the molecular formula of the cyclic polysiloxane is represented by formula 2, where n represents the degree of polymerization of the structural unit represented by formula 1. Selectively, n ≤ 12, n ≤ 11, n ≤ 10, n ≤ 9, or n ≤ 8. [ka]

[0169] For example, the linear polysiloxanes include polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polymethylvinylsiloxane, polyphenylmethylsiloxane, polymethylhydrogensiloxane, carboxyl-functionalized polysiloxane, polymethylchloropropylsiloxane, polymethyltrifluoropropylsiloxane, perfluorooctylmethylpolysiloxane, mercaptopropylpolysiloxane, aminoethylaminopropylpolydimethylsiloxane, and methoxy-terminated polydimethylsiloxane. The polysiloxanes include, but are not limited to, one or more of the following: hydroxypropyl-terminated polydimethylsiloxane, aminopropyl-terminated polydimethylsiloxane, terminal epoxypolysiloxane, terminal hydroxypolydimethylsiloxane, terminal polyether polydimethylsiloxane, side-chain aminopropylpolysiloxane, side-chain hydroxylmethylpolysiloxane, side-chain hydroxylpropylpolysiloxane, side-chain polyether-grafted polydimethylsiloxane, and side-chain phosphate-grafted polydimethylsiloxane. Selectively, the linear polysiloxanes include one or more of the following: polydimethylsiloxane, polymethylchloropropylsiloxane, polymethyltrifluoropropylsiloxane, mercaptopropylpolysiloxane, aminoethylaminopropylpolydimethylsiloxane, terminal hydroxypolydimethylsiloxane, terminal polyether polydimethylsiloxane, and side-chain phosphate-grafted polydimethylsiloxane.

[0170] For example, the cyclic polysiloxane includes, but is not limited to, one or more of cyclic polydimethylsiloxane, cyclic polymethylvinylsiloxane, cyclic polymethylhydrogensiloxane, and cyclic polymethyltrifluoropropylsiloxane. Selectively, the cyclic polysiloxane includes one or more of 1,3,5,7-octamethylcyclotetrasiloxane, 1,3,5,7-tetrahydro-1,3,5,7-tetramethylcyclotetrasiloxane, cyclopentapolydimethylsiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, hexadecamethyloctasiloxane, and tetradecamethylcycloheptasiloxane.

[0171] In some embodiments, the number-average molecular weight of the organopolysiloxane compound is 300,000 or less, and may be, for example, 400-300,000, 400-200,000, 400-100,000, 400-80,000, 400-50,000, 400-20,000, 400-10,000, 1,000-100,000, 1,000-50,000, 1,000-20,000, or 1,000-10,000. The number-average molecular weight of the organopolysiloxane compound can be measured by methods known in the art, for example, by gel permeation chromatography (GPC). A PL-GPC220 high-temperature gel permeation chromatograph can be used as the measuring instrument. In this application, the "organopolysiloxane compound" may be an oligomer or a high polymer.

[0172] When the number-average molecular weight of the organopolysiloxane compound is within an appropriate range, secondary batteries can achieve both good dynamic performance and high-temperature storage performance. The following situations can be effectively avoided: If the number-average molecular weight of the organopolysiloxane compound is too small, its hydrophobicity may be poor, making it difficult to effectively increase the contact angle between the positive electrode film layer and the electrolyte. This prevents effective mitigation of electrolyte erosion on the surface of the positive electrode active material, potentially resulting in a lack of significant improvement in the cycle performance and storage performance of the secondary battery. Conversely, if the number-average molecular weight of the organopolysiloxane compound is too large, its hydrophobicity may be too strong, which is also unfavorable for slurry dispersion and affects the improvement in the performance of the secondary battery.

[0173] In some embodiments, the mass percentage of polar functional groups in the organopolysiloxane compound is α, where 0 ≤ α < 50%, and selectively 5% ≤ α ≤ 30%.

[0174] In this application, "mass percentage of polar functional groups in an organopolysiloxane compound" means the mass ratio of polar functional groups in R1, R2 and the sealing group in the organopolysiloxane compound. In this application, polar functional groups include one or more of the following: -COOH, -OH, -SH, -CN, -SCN, amino groups (including -NH2 and -NH-), phosphate ester groups, carboxylate groups (-COO-), amide groups (-CONH-), aldehyde groups (-CHO), sulfonyl groups (-S(=O)2-), polyether segments, halogen atoms, alkoxy groups, and epoxy groups. When the polar functional group is directly bonded to a silicon atom, α represents the mass fraction of these polar functional groups in the organopolysiloxane compound. When the polar functional group and the silicon atom are not directly bonded, α represents the sum of the mass fractions of the polar functional group and the divalent to tetravalent methyl groups (e.g., -CH2, -CH-, -C-, etc.) directly bonded to it in the organopolysiloxane compound, where "divalent to tetravalent methyl groups" represent carbon atoms directly bonded to the polar functional group and located between the polar functional group and the silicon atom, as well as other nonpolar functional groups bonded to carbon atoms. Taking polymethyltrifluoropropylsiloxane as an example, α represents the mass percentage of -CF3 and does not include the ethylene group. Taking polymethylchloropropylsiloxane as an example, α represents the mass percentage of -CH2Cl and does not include the ethylene group. Taking hydroxypropyl-terminated polydimethylsiloxane as an example, α represents the mass percentage of -CH2OH. The mass percentage of polar functional groups in organopolysiloxane compounds can be measured by methods known in the art, for example, by titration (e.g., acid-alkali titration, redox titration, precipitation titration), infrared spectroscopy, and nuclear magnetic resonance spectroscopy.

[0175] When the content of polar functional groups in the organopolysiloxane compound is within an appropriate range, the effect of reducing the acidity of the electrolyte and removing F ions from the electrolyte is better. This better mitigates the erosion of the surface of the positive electrode active material by acidic substances in the electrolyte, thereby improving the cycle performance and storage performance of the secondary battery. Furthermore, the following situation can be effectively avoided: If the content of polar functional groups in the organopolysiloxane compound is too high, the effect of reducing the acidity of the electrolyte and removing F ions from the electrolyte is not further improved, but the contact angle between the positive electrode film layer and the electrolyte becomes small, and as a result, the improvement in the cycle performance of the secondary battery is not significant.

[0176] In some embodiments, the content of the organopolysiloxane compound is 0.01% to 2% by weight, and selectively 0.1% to 2% by weight, based on the total weight of the cathode material composition.

[0177] When the organopolysiloxane compound content is within an appropriate range, it reduces the acidity of the electrolyte and effectively removes F ions from the electrolyte. This better mitigates the erosion of acidic substances in the electrolyte from the surface of the positive electrode active material, thereby improving the cycle performance and storage performance of the secondary battery. Furthermore, the following situations can be effectively avoided: If the organopolysiloxane compound content is too high, it may affect the wettability of the positive electrode film layer to the electrolyte, potentially impacting the dynamic performance of the secondary battery. Also, because the organopolysiloxane compound does not provide capacity, excessively high content can reduce the energy density of the secondary battery. If the organopolysiloxane compound content is too low, the effect of reducing the acidity of the electrolyte and removing F ions from the electrolyte is not clear, and the erosion of acidic substances in the electrolyte from the surface of the positive electrode active material cannot be effectively mitigated, resulting in no clear improvement in the cycle performance and high-temperature storage performance of the secondary battery.

[0178] In some embodiments, the cathode material composition may further contain a binder. The binder may be a substance that exhibits a known binding effect in the art. Selectively, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a ternary copolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a ternary copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, or a fluorine-containing acrylate resin.

[0179] Selectively, the binder content is 1.79% to 10% by weight, and selectively 2% to 5% by weight, based on the total weight of the cathode material composition.

[0180] In some embodiments, the cathode material composition may further contain a conductive agent. The conductive agent may be a substance that exhibits electron transport effects known in the art. Selectively, the cathode conductive agent comprises at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, kecheng black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Selectively, the content of the conductive agent is 0.2% to 10% by weight, and selectively 0.5% to 5% by weight, based on the total weight of the cathode material composition.

[0181] In some embodiments, the powder resistivity of the positive electrode material composition at 12 MPa is 4 Ω / cm to 55 Ω / cm, and selectively between 4 Ω / cm and 40 Ω / cm or less. By adjusting the powder resistivity of the positive electrode material composition to an appropriate range, the dynamic performance of the secondary battery can be improved. The powder resistivity of the positive electrode material composition can be measured by methods known in the art. For example, it can be tested using a powder resistivity meter, referring to GB / T 30835-2014. One exemplary test method involves weighing a specified amount of powder of the sample to be measured, placing it in a dedicated mold, and setting a test pressure to obtain powder resistivity under different pressures. In this application, the test pressure can be set to 12 MPa. The measuring instrument may be a Suzhou Crystal ST2722-SZ type four-probe powder resistivity meter.

[0182] In some embodiments, the specific surface area of ​​the positive electrode material composition is 8 m². 2 / g~20m 2 / g, selectively 8m 2 / g~15m 2 The value is / g. By adjusting the specific surface area of ​​the positive electrode material composition to an appropriate range, interfacial side reactions between the positive electrode sheet and the electrolyte can be reduced, thereby reducing the volume expansion of the secondary battery. This can improve the electrochemical performance of the secondary battery. The specific surface area of ​​the positive electrode material composition can be measured by methods known in the art. For example, it can be tested by the nitrogen gas adsorption specific surface area analysis test method, referring to GB / T19587-2017, and calculated by the BET (Brunauer-Emmett-Teller) method. The nitrogen gas adsorption specific surface area analysis test can be performed using the Tri-Star 3020 specific surface area pore size analyzer from Micromeritics, Inc., USA. Manufacturing method

[0183] A second aspect of this application provides a method for manufacturing a cathode material composition that can produce the cathode material composition of the first aspect of this application.

[0184] Specifically, the manufacturing method includes the steps of providing the kernel material, coating, and mixing.

[0185] As a step of providing the kernel material, the chemical formula of the kernel is Li 1+x Mn 1-y A y P 1-z R z The molecule is O4, where x is any number in the range of -0.100 to 0.100, selectively any number in the range of -0.005 to 0.002, y is any number in the range of 0.001 to 0.500, 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, selectively one or more elements selected from Fe, Ti, V, Ni, Co, and Mg, R is one or more elements selected from B, Si, N, and S, selectively R is one element selected from B, Si, N, and S, and the values ​​of x, y, and z satisfy the condition that the entire kernel maintains electrical neutrality.

[0186] As a coating step, Li a MP2O7 and / or M b (P2O7) c and an XPO4 suspension are provided, the kernel material is added to the suspension and mixed, and sintered to obtain a positive electrode active material, wherein the positive electrode active material has a core-shell structure, which includes the kernel and a shell covering the kernel, the shell includes a first coating layer covering the kernel, 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 crystalline pyrophosphate Li a MP2O7 and / or M b (P2O7) c It includes, 0≦a≦2, 1≦b≦4, 1≦c≦6, and the crystalline pyrophosphate Li a MP2O7 and M b (P2O7) cIn this formula, M is one or more elements independently selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and the values ​​of a, b, and c are crystalline pyrophosphate Li a MP2O7 or M b (P2O7) c The conditions for maintaining electrical neutrality are met, the second coating layer contains crystalline phosphate XPO4, where X is one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and the third coating layer is carbon.

[0187] As a mixing step, the obtained positive electrode active material is uniformly mixed with an organopolysiloxane compound, a selectable binder, and a selectable conductive agent to obtain a positive electrode material composition.

[0188] In some embodiments, the step of providing the kernel material includes the following steps (1) and (2).

[0189] In step (1), the manganese source, element A dopant, and acid are mixed and stirred in a container to obtain manganese salt particles doped with element A.

[0190] In step (2), the manganese salt particles doped with element A, a lithium source, a phosphorus source, and a dopant of element R are mixed in a solvent to obtain a slurry, which is then sintered under the protection of an inert gas atmosphere to obtain a kernel doped with elements A and R, where the kernel doped with elements A and R is Li 1+x Mn 1-y A y P 1-z R zThe element is O4, x is any number within the range of -0.100 to 0.100, selectively any number within the range of -0.005 to 0.002, y is any number within the range of 0.001 to 0.500, z is any number within 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, selectively one or more elements selected from Fe, Ti, V, Ni, Co, and Mg, R is one or more elements selected from B, Si, N, and S, selectively R is one element selected from B, Si, N, and S.

[0191] The manufacturing method of this application is not particularly limited in terms of the source of materials, and the source of an element may include one or more of the element in its elemental form, sulfate, halide, nitrate, organic acid salt, oxide, or hydroxide form. The premise is that the source can achieve the objectives of the manufacturing method of this application.

[0192] In some embodiments, the dopant of element A is one or more elements selected from the elements, carbonates, sulfates, chlorides, nitrates, organic acid salts, oxides, and hydroxides of 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.

[0193] In some embodiments, the dopant of element R is one or more inorganic acids, acidous acids, organic acids, sulfates, chlorides, nitrates, organic acid salts, oxides, and hydroxides of one or more elements selected from B, Si, N, and S.

[0194] In this application, the manganese source may be a manganese-containing substance known in the art that can be used to produce lithium manganese phosphate. For example, the manganese source may be one or more selected from elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, and manganese carbonate.

[0195] In this application, the acid may be one or more selected from organic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, silicic acid, silicous acid, and oxalic acid. In some embodiments, the acid is a dilute organic acid with a concentration of 60% by weight or less.

[0196] In this application, the lithium source may be a lithium-containing substance known in the art that can be used to produce lithium manganese phosphate. For example, the lithium source may be one or more selected from lithium carbonate, lithium hydroxide, lithium phosphate, and lithium dihydrogen phosphate.

[0197] In this application, the phosphorus source may be a phosphorus-containing substance known in the art that can be used in the production of lithium manganese phosphate. For example, the phosphorus source may be one or more selected from diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, and phosphoric acid.

[0198] In some embodiments, the manganese source, the element A dopant, and the acid are reacted in a solvent to obtain a manganese salt suspension doped with element A. The suspension is then filtered, dried, and sand-milled to obtain manganese salt particles doped with element A with a particle size of 50 to 200 nm.

[0199] In some embodiments, the slurry in step (2) is dried to obtain a powder material, and then the powder material is sintered to obtain a kernel doped with elements A and R.

[0200] In some embodiments, step (1) involves mixing at a temperature of 20°C to 120°C, selectively between 40°C and 120°C.

[0201] In some embodiments, in step (1), the stirring is performed at 400 rpm to 700 rpm for 1 to 9 hours, or selectively for 3 to 7 hours.

[0202] Selectively, the reaction temperature in step (1) may be approximately 30°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C. The stirring in step (1) may be carried out for approximately 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or 9 hours. Selectively, the reaction temperature and stirring time in step (1) may be within any range of the above values.

[0203] In some embodiments, step (2) involves mixing at a temperature of 20°C to 120°C, selectively 40°C to 120°C, for 1 to 12 hours. Selectively, the reaction temperature in step (2) can be 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. The mixing in step (2) can be about 2 hours, about 3 hours, 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. Selectively, the reaction temperature and mixing time in step (2) can be within any range of the above values.

[0204] When the temperature and time during the kernel particle manufacturing process are within the above range, the manufactured kernel and the cathode active material produced therefrom have fewer lattice defects, which is advantageous in suppressing the elution of manganese ions, and reduces interfacial side reactions between the cathode active material and the electrolyte, thereby improving the cycle performance and safety performance of the secondary battery.

[0205] In some embodiments, the pH of the solution is selectively controlled to 3.5-6, selectively controlled to 4-6, and more selectively controlled to 4-5, during the process of producing lithium manganese phosphate particles doped with elements A and R. In this application, the pH of the resulting mixture can be adjusted by methods commonly used in the art, such as adding an acid or a base.

[0206] In some embodiments, selectively, in step (2), the molar ratio of the element A-doped manganese salt particles to the lithium source and phosphorus source is 1:(0.5~2.1):(0.5~2.1), and more selectively, the molar ratio of the element A-doped manganese salt particles to the lithium source and phosphorus source is approximately 1:1:1.

[0207] In some embodiments, the sintering conditions in the process of producing lithium manganese phosphate doped with elements A and R are sintering at 600°C to 950°C for 4 to 10 hours in an atmosphere of inert gas or a mixture of inert gas and hydrogen gas. Selectively, the sintering can be performed at approximately 650°C, approximately 700°C, approximately 750°C, approximately 800°C, approximately 850°C, or approximately 900°C for approximately 2 hours, approximately 3 hours, approximately 4 hours, approximately 5 hours, approximately 6 hours, approximately 7 hours, approximately 8 hours, approximately 9 hours, or approximately 10 hours. Selectively, the sintering temperature and sintering time may be within any range of the above arbitrary values. In the process of producing lithium manganese phosphate doped with elements A and R, if the sintering temperature is too low and the sintering time is too short, the crystallinity of the kernel of the positive electrode active material will be low, affecting the overall performance; if the sintering temperature is too high, impurities are likely to form in the kernel of the positive electrode active material, affecting the overall performance; and if the sintering time is too long, the particles of the kernel of the positive electrode active material will be elongated, affecting capacity, compressibility, and rate performance.

[0208] In some embodiments, the protective atmosphere is selectively a mixed gas of 70–90 volume% nitrogen gas and 10–30 volume% hydrogen gas.

[0209] In some embodiments, the coating step includes a first coating step, a second coating step, and a third coating step.

[0210] As a first coating step, a source of element M, a phosphorus source, an acid, and a selectable lithium source are dissolved in a solvent to obtain a first coating layer suspension. The kernel obtained in the step of providing the kernel material and the first coating layer suspension obtained in the first coating step are thoroughly mixed, dried, and then sintered to obtain a material coated with the first coating layer.

[0211] As a second coating step, a source of element X, a phosphorus source, and an acid are dissolved in a solvent to obtain a second coating layer suspension. The material coated with the first coating layer obtained in the first coating step and the second coating layer suspension obtained in the second coating step are thoroughly mixed, dried, and then sintered to obtain a material coated with two layers.

[0212] In the third coating step, a carbon source is dissolved in a solvent and thoroughly dissolved to obtain a third coating layer solution. Then, the material coated with two coating layers obtained in the second coating step is added to the third coating layer solution, mixed uniformly, dried, and sintered to obtain a material coated with three coating layers, i.e., a positive electrode active material.

[0213] In some embodiments, the source of element M is one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, as well as one or more carbonates, sulfates, chlorides, nitrates, organic acid salts, oxides, and hydroxides.

[0214] In some embodiments, the source of element X is one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, as well as one or more carbonates, sulfates, chlorides, nitrates, organic acid salts, oxides, and hydroxides.

[0215] The amount of each of the aforementioned elements A, R, M, and X added depends on the target doping amount, and the ratio of the amounts used from the lithium, manganese, and phosphorus sources satisfies the stoichiometric ratio.

[0216] For example, the carbon source is one or more selected from starch, sucrose, glucose, polyvinyl alcohol, polyethylene glycol, and citric acid.

[0217] In some embodiments, in the first coating step, the pH of the solution containing the source of element M, the phosphorus source, the acid, and a selectable lithium source is controlled to 3.5 to 6.5, the mixture is then stirred and reacted for 1 to 5 hours, and the solution is then heated to 50°C to 120°C and maintained at that temperature for 2 to 10 hours. In some embodiments, in the first coating step, sintering is carried out at 650°C to 800°C for 2 to 6 hours.

[0218] Selectively, the reaction proceeds sufficiently in the first coating step. Selectively, in the first coating step, the reaction takes place for about 1.5 hours, about 2 hours, about 3 hours, about 4 hours, about 4.5 hours, or about 5 hours. Selectively, in the first coating step, the reaction time of the reaction may be within any range of the above arbitrary values.

[0219] Selectively, in the first coating step, the pH of the solution is controlled to 4-6. Selectively, in the first coating step, the solution is heated to approximately 55°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C, and held at that temperature for approximately 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours. Selectively, in the first coating step, the heating temperature and holding time may be within any range of the above arbitrary values.

[0220] Selectively, in the first coating step, the sintering may be carried out at approximately 650°C, approximately 700°C, approximately 750°C, or approximately 800°C for approximately 2 hours, approximately 3 hours, approximately 4 hours, approximately 5 hours, or approximately 6 hours. Selectively, the sintering temperature and sintering time may be within any range of the above values.

[0221] In the first coating step, by controlling the sintering temperature and time within the above range, if the sintering temperature is too low and the sintering time is too short in the first coating step, the crystallinity of the first coating layer is low and there is a large amount of amorphous material, so the effect of suppressing metal dissolution is reduced and affects the cycle performance and storage performance of the secondary battery; if the sintering temperature is too high, an impurity phase appears in the first coating layer, which also affects the effect of suppressing metal dissolution and affects the cycle performance and storage performance of the secondary battery, etc.; if the sintering time is too long, the thickness of the first coating layer increases, Li + This effectively avoids situations where the movement of the cathode active material is affected, impacting its capacity and rate performance.

[0222] In some embodiments, in the second coating step, the source of element X, the phosphorus source, and the acid are dissolved in the solvent, stirred and reacted for 1 to 10 hours, and then the solution is heated to 60°C to 150°C and held at that temperature for 2 to 10 hours. In some embodiments, in the second coating step, sintering is carried out at 500°C to 700°C for 6 to 10 hours.

[0223] Selectively, in the second coating step, the reaction proceeds sufficiently. Selectively, in the second coating step, the reaction is carried out for about 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. Selectively, in the second coating step, the reaction time of the reaction may be within any range of the above arbitrary values.

[0224] Selectively, in the second coating step, the solution is heated to approximately 65°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C, and held at that temperature for approximately 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours. Selectively, in the second coating step, the heating temperature and holding time may be within any range of the above values.

[0225] In the steps of providing the kernel material, the first coating step, and the second coating step, before sintering, i.e., in the production of the kernel material in which a chemical reaction occurs (steps (1) and (2)), and in the production of the first coating layer suspension and the second coating layer suspension, by selecting an appropriate reaction temperature and reaction time as described above, it is possible to effectively avoid situations where, if the reaction temperature is too low, the reaction cannot occur or the reaction rate is too slow; if the temperature is too high, the product decomposes or forms an impure phase; if the reaction time is too long, the particle size of the product may be large, potentially increasing the time and difficulty of subsequent processes; and if the reaction time is too short, the reaction is incomplete and the resulting product is small.

[0226] Selectively, in the second coating step, the sintering may be carried out at approximately 550°C, approximately 600°C, or approximately 700°C for approximately 6 hours, approximately 7 hours, approximately 8 hours, approximately 9 hours, or approximately 10 hours. Selectively, the sintering temperature and sintering time may be within any range of the above values.

[0227] In the second coating step, by controlling the sintering temperature and time within the above range, if the sintering temperature is too low and the sintering time is too short in the second coating step, the crystallinity of the second coating layer will be low and the amount of amorphous material will be high, reducing its ability to reduce the reaction activity of the surface of the positive electrode active material, which will affect the cycle performance and storage performance of the secondary battery; if the sintering temperature is too high, an impurity phase will appear in the second coating layer, which will also affect the effect of reducing the reaction activity of the surface of the positive electrode active material, which will affect the cycle performance and storage performance of the secondary battery; and if the sintering time is too long, the thickness of the second coating layer will increase, which will affect the voltage platform of the positive electrode active material, which will reduce the energy density of the secondary battery. These situations can be effectively avoided.

[0228] In some embodiments, the sintering in the third coating step is carried out at 700°C to 800°C for 6 to 10 hours. Selectively, in the third coating step, the sintering may be carried out at approximately 700°C, approximately 750°C, or approximately 800°C for approximately 6, approximately 7, approximately 8, approximately 9, or approximately 10 hours. Selectively, the sintering temperature and sintering time may be within any range of the above arbitrary values.

[0229] In the third coating step, by controlling the sintering temperature and time within the above range, if the sintering temperature in the third coating step is too low, the degree of graphitization of the third coating layer decreases, affecting its conductivity and thus affecting the capacity of the positive electrode active material; if the sintering temperature is too high, the degree of graphitization of the third coating layer becomes too high, Li + This effectively avoids situations such as: if the sintering time is too short, the coating layer is too thin, affecting its conductivity and thus the capacity of the positive electrode active material; and if the sintering time is too long, the coating layer is too thick, affecting the compressive density of the positive electrode active material.

[0230] In the first coating step, second coating step, and third coating step described above, the drying can be carried out at a drying temperature of 100°C to 200°C, selectively 110°C to 190°C, more selectively 120°C to 180°C, even more selectively 120°C to 170°C, and most selectively 120°C to 160°C. The drying time may be 3 to 9 hours, selectively 4 to 8 hours, more selectively 5 to 7 hours, and most selectively about 6 hours.

[0231] The positive electrode active material produced by the method for producing positive electrode active material according to this application exhibits reduced leaching of Mn and doped elements at Mn sites after cycling of the manufactured secondary battery, and improved high-temperature storage performance, cycling performance, and rate performance. Furthermore, it has a wide range of raw material sources, low costs, a simple process, and is advantageous for industrialization. Positive electrode sheet

[0232] A third aspect of the present application is a positive electrode sheet including a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, where the positive electrode film layer contains the positive electrode material composition of the first aspect of the present application or the positive electrode material composition manufactured by the method of the second aspect of the present application, and the content of the positive electrode material composition in the positive electrode film layer is 50% by weight or more based on the total weight of the positive electrode film layer. The positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode film layer is provided on the two facing surfaces of the positive electrode current collector.

[0233] In some embodiments, optionally, the content of the positive electrode material composition in the positive electrode film layer is 90% to 100% by weight based on the total weight of the positive electrode film layer.

[0234] The positive electrode film layer does not exclude other components other than the positive electrode material composition of the first aspect of the present application or the positive electrode material composition manufactured by the method of the second aspect of the present application. For example, the positive electrode film layer may further contain other positive electrode active materials other than the positive electrode active material coated with the above three layers of the present application. Optionally, the other positive electrode active material may contain at least one of lithium transition metal oxides and their modified compounds. As an example, the other positive electrode active material may contain at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their respective modified compounds.

[0235] In some embodiments, the positive electrode current collector can use a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may be at least one selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0236] In some embodiments, the solid-liquid contact angle between the positive electrode film layer and the non-aqueous organic solvent is 3° to 90°, optionally 3° to 60°, and further 10° to 30°. When the contact angle is within an appropriate range, the secondary battery can achieve both high energy density and improved cycle performance, safety performance, and / or rate performance. Also, the following situations can be effectively avoided. If the contact angle is too small, the erosion of acidic substances in the electrolyte on the surface of the positive electrode active material cannot be effectively alleviated, and the effect of improving the cycle performance may not be obvious. If the contact angle is too large, the wettability of the positive electrode film layer to the electrolyte deteriorates, which may affect the rate performance and cycle performance of the secondary battery. The solid-liquid contact angle between the positive electrode film layer and the non-aqueous organic solvent has the meaning known in the art and can be tested using methods known in the art. For example, it can be measured by referring to GBT 30693-2014. As an exemplary test method, at room temperature, a droplet of non-aqueous organic solvent is dropped onto the surface of the positive electrode sheet, and the contact angle for 60 seconds is measured by a contact angle measuring device. The test equipment can use the LSA 200 type optical contact angle measuring instrument of LAUDA Scientific, Germany. As the non-aqueous organic solvent, a non-aqueous organic solvent used in the non-aqueous electrolyte of a secondary battery known in the art can be used. Optionally, the non-aqueous organic solvent uses ethylene carbonate (EC).

[0237] In some embodiments, the porosity of the positive electrode film layer is 15% to 50%, and selectively 15% to 30%. When the porosity is within an appropriate range, the secondary battery can achieve both high energy density and improved cycle performance, safety performance, and / or rate performance. Furthermore, the following situations can be effectively avoided: If the porosity is too small, the wettability of the positive electrode film layer to the electrolyte will be poor, which may affect the rate performance and cycle performance of the secondary battery; if the porosity is too large, it may affect the overall energy density of the secondary battery. The porosity of the positive electrode film layer has a meaning known in the art and can be measured by methods known in the art. For example, it can be measured by referring to GB / T 24586-2009 after peeling off the positive electrode film layer with adhesive tape. The porosity P = [(V2-V1) / V2] × 100%. V1(cm 3 V2(cm²) represents the true volume and can be measured by combining Archimedes' principle and Bohr's law using a substitution method with an inert gas having a small molecular diameter (e.g., helium gas). 3 ) represents the apparent volume, V² = S × H × A, S (cm 2 ) represents area, H(cm) represents thickness, and A represents the number of samples.

[0238] In some embodiments, the resistance of the positive electrode film layer is greater than 0 and less than or equal to 6Ω. This allows the positive electrode sheet to have good conductivity, thus enabling the secondary battery to have better dynamic performance. The resistance of the positive electrode film layer can be tested using methods known in the art, for example, by using a polarity resistor. As one exemplary measurement method, a positive electrode sheet coated on one side and cold-pressed (or, in the case of a positive electrode sheet coated on both sides, a positive electrode film layer from which one side can be wiped first) is placed parallel to the two conductive terminals of a polarity sheet resistor and fixed with a constant pressure, i.e., the resistance of the positive electrode film layer is obtained. Selectively, the diameter of the conductive terminals may be 14 mm, the applied pressure may be 15 to 27 MPa, and the time range of the test point may be 10 to 20 s. The test equipment can be an IEST BER1000 type polarity resistor from Yuanneng Science and Technology Co., Ltd.

[0239] In some embodiments, the adhesive strength between the positive electrode film layer and the positive electrode current collector is 0.5 MPa or higher. Within this range, the occurrence of powder shedding from the positive electrode sheet can be prevented, which is advantageous for achieving secondary battery performance. The adhesive strength between the positive electrode film layer and the positive electrode current collector is well known in the art and can be tested using methods known in the art. As one exemplary test method, a positive electrode sheet is cut into a test specimen measuring 100 mm in length and 10 mm in width. A 25 mm wide stainless steel plate is taken, double-sided tape (e.g., 11 mm wide) is attached to it, and the test specimen is attached to the double-sided tape on the stainless steel plate. The surface is then passed back and forth three times with a 2000 g press roll (e.g., roll press speed 300 mm / min), the test specimen is folded 180°, and the positive electrode film layer and positive electrode current collector of the test specimen are manually peeled off by 25 mm. The test specimen is then fixed to a testing machine (e.g., INSTRON336), the peeled surface is aligned with the force lines of the testing machine, and the test machine is continuously peeled at 30 mm / min. The peeling force curve obtained is defined as the average value of the milder segments, and the adhesive force between the positive electrode film layer and the positive electrode current collector is F0 / width of the test specimen.

[0240] In some embodiments, the surface density of the positive electrode film layer is 0.006 g / cm³. 2 ~0.065 g / cm³ 2 This is advantageous for improving the volumetric energy density of secondary batteries. The surface density of the positive electrode film layer is a well-known concept in the art and can be tested using methods known in the art. As one exemplary test method, a positive electrode sheet coated on one side and cold-pressed (if the positive electrode sheet is coated on both sides, the positive electrode film layer on one side can be wiped off first) is punched out onto a wafer with a small area S1, its weight is recorded as M1, then the positive electrode film layer of the weighed positive electrode sheet is wiped off, the weight of the positive electrode current collector is weighed and recorded as M0, and the surface density of the positive electrode film layer = (M1-M0) / S1.

[0241] In some embodiments, the absorption rate of the positive electrode film layer into the electrolyte is 0.0125 μg / s to 100 μg / s, and selectively 0.5 μg / s to 40 μg / s. This ensures that the electrolyte has good wettability in the electrode assembly, allows it to quickly enter the interior of the electrode assembly, and enables the timely formation of the SEI film on the surface of the positive electrode sheet, thereby improving the electrochemical performance of the secondary battery.

[0242] The positive electrode film layer is typically formed by applying a positive electrode slurry to a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing a positive electrode active material, a selectable conductive agent, a selectable binder, and any other components in a solvent and stirring them uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP).

[0243] The parameters of each positive electrode film layer provided in this application (e.g., contact angle, porosity, resistance, adhesion, surface density, electrolyte absorption rate, etc.) all refer to the parameters of the positive electrode film layer on one side of the positive electrode current collector. If positive electrode film layers are provided on both sides of the positive electrode current collector, it is considered that the protection scope of this application is met if the parameters of either one of the positive electrode film layers meet the requirements of this application.

[0244] Furthermore, the testing of each parameter for the positive electrode film layer may be performed by sampling during the manufacturing process of the positive electrode sheet or battery, or by sampling from the manufactured battery.

[0245] When the above test sample is sampled from a manufactured battery, for example, the battery may be discharged (generally to a fully discharged state for safety); after disassembling the battery, the positive electrode sheet may be removed, the positive electrode sheet may be immersed in dimethyl carbonate (DMC) for a certain period of time (e.g., 2 to 10 hours), the positive electrode sheet may be removed and dried at a certain temperature and time (e.g., 60°C for 4 hours), and after drying, the positive electrode sheet may be removed. At this time, the parameters relating to the positive electrode film layer described in this application may be sampled and tested on the dried positive electrode sheet. secondary battery

[0246] A fourth aspect of this application provides a secondary battery including the positive electrode sheet of the third aspect of this application.

[0247] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be used continuously after discharge by recharging to activate the active material. Typically, secondary batteries consist of an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is placed between the positive and negative electrode sheets and primarily serves to prevent short circuits between the positive and negative electrodes, while simultaneously allowing active ions to pass through. The electrolyte plays a role in transporting active ions between the positive and negative electrode sheets. [Positive electrode sheet]

[0248] The positive electrode sheet used in the secondary battery of this application is the positive electrode sheet described in any embodiment of the third aspect of this application. [Negative electrode sheet]

[0249] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in the thickness direction, and the negative electrode film layer is provided on the two opposing surfaces of the negative electrode current collector.

[0250] As the negative electrode active material, negative electrode active materials for secondary batteries known in the art can be used. For example, the negative electrode active material includes, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material. This application is not limited to these materials, and other conventionally known materials used as negative electrode active materials for secondary batteries may be used. These negative electrode active materials may be used individually or in combination of two or more.

[0251] In some embodiments, the negative electrode film layer may optionally further contain a negative electrode conductive agent. The type of the negative electrode conductive agent is not particularly limited in this application. For example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0252] In some embodiments, the negative electrode film layer may optionally further contain a negative electrode binder. The type of the negative electrode binder is not particularly limited in this application. For example, the negative electrode binder may contain at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0253] In some embodiments, the negative electrode film layer may selectively further contain other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC) or PTC thermistor material.

[0254] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. Copper foil can be used as an example of a metal foil. A composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may be at least one selected from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0255] The negative electrode film layer is typically formed by applying a negative electrode slurry to a negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing a negative electrode active material, a selectable conductive agent, a selectable binder, and other selectable auxiliary agents in a solvent and stirring them uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0256] The negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet according to the present application is sandwiched between the negative electrode current collector and the negative electrode film layer, and further includes a conductive primer layer (for example, composed of a conductive agent and a binder) provided on the surface of the negative electrode current collector. In some other embodiments, the negative electrode sheet described in the present application further includes a protective layer covering the surface of the negative electrode film layer. [Electrolyte]

[0257] In the present application, the type of the electrolyte is not particularly limited and can be selected according to requirements. For example, the electrolyte may be at least one selected from a solid electrolyte and a liquid electrolyte (electrolyte solution).

[0258] In some embodiments, the electrolyte uses an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0259] The type of the electrolyte salt is not particularly limited and can be selected according to actual requirements. In some embodiments, for example, the electrolyte salt may include at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoroborate (LiDFOB), lithium diborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodiphosphate (LiDFOP), and lithium tetrafluoroborate (LiTFOP).

[0260] The type of solvent is not particularly limited and can be selected according to the actual requirements. In some embodiments, the solvent may, for example, include at least one of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0261] In some embodiments, the electrolyte may further selectively contain additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve some aspects of the battery's performance, such as additives that improve the battery's overcharge performance, additives that improve the battery's high-temperature performance, and additives that improve the battery's low-temperature power performance. [Separator]

[0262] In secondary batteries using an electrolyte or a solid electrolyte, a separator is also included. The separator is provided between the positive electrode sheet and the negative electrode sheet and mainly serves to prevent short circuits between the positive and negative electrodes, while simultaneously allowing active ions to pass through. In this application, the type of separator is not particularly limited, and any known porous structure separation membrane having good chemical and mechanical stability can be selected.

[0263] In some embodiments, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. If the separator is a multilayer composite film, the materials of each layer may be the same or different.

[0264] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be assembled into an electrode assembly by a winding process or a lamination process.

[0265] In some embodiments, the secondary battery may include an enclosure, which is used to seal the electrode assembly and electrolyte described above.

[0266] In some embodiments, the casing of the secondary battery may be a hard case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a soft bag, such as a bag soft bag. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0267] In this application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular, or any other shape. Figure 1 shows a rectangular secondary battery 5 as an example.

[0268] In some embodiments, as shown in Figure 2, the exterior may include a case 51 and a cover plate 53. The case 51 includes a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates enclose each other to form a housing chamber. The case 51 has an opening that communicates with the housing chamber, and the cover plate 53 covers the opening to seal the housing chamber. The positive electrode sheet, negative electrode sheet and separator can be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged into the housing chamber. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and may be adjusted as required.

[0269] The method for manufacturing a secondary battery described in this application is known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, an electrode assembly can be formed by winding or laminating a positive electrode sheet, a separator, and a negative electrode sheet, the electrode assembly can be placed in an outer casing, dried, and then the electrolyte can be injected. A secondary battery can then be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0270] In some embodiments of this application, the secondary battery according to this application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0271] Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple secondary batteries 5 may be fixed together with fasteners.

[0272] Selectively, the battery module 4 further includes a housing having a housing space, and a plurality of secondary batteries 5 are housed in the housing space.

[0273] In some embodiments, the battery modules may be assembled into a battery pack. The number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0274] Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery housing and a plurality of battery modules 4 provided in the battery housing. The battery housing includes an upper housing 2 and a lower housing 3, with the upper housing 2 covering the lower housing 3 to form a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery housing in any manner. power consumption equipment

[0275] A fifth aspect of this application provides a power consumption device comprising at least one of the secondary battery, battery module, or battery pack of this application. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage means for the power consumption device. The power consumption device may be, but is not limited to, 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.), trains, ships, and satellites, energy storage systems, etc.

[0276] The aforementioned power consumption device can select a secondary battery, battery module, or battery pack depending on the demand.

[0277] Figure 6 is a schematic diagram of an example of a power consumption device. This power consumption device includes pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, etc. To meet the high power and high energy density requirements of this power consumption device, battery packs or battery modules can be used.

[0278] Other examples of power-consuming devices may include mobile phones, tablet computers, and laptop computers. These power-consuming devices are typically required to be thin, and rechargeable batteries can be used as their power source. Examples

[0279] The following examples illustrate the contents of this application in more detail; however, these examples are merely illustrative, and it will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the disclosure of this application. All parts, percentages, and ratios described in the following examples are based on mass unless otherwise specified. Furthermore, all reagents used in the examples may be commercially available or synthesized according to conventional methods, and may be used as is without requiring further processing. Furthermore, all apparatus used in the examples are commercially available.

[0280] The raw materials for the embodiments of this application are as follows:

[0281] [Table 1] I. Battery Construction Example 1 Step 1: Manufacturing of the positive electrode active material Step S1: Preparation of Fe, Co, V, and S co-doped manganese oxalate

[0282] 689.6g of manganese carbonate, 455.27g of ferrous carbonate, 4.65g of cobalt sulfate, and 4.87g of vanadium dichloride were placed in a mixer and thoroughly mixed for 6 hours. Then, the resulting mixture was transferred to a reaction vessel, 5L of deionized water and 1260.6g of oxalic acid dihydrate were added, and the mixture was heated to 80°C and stirred thoroughly at a rotation speed of 500 rpm for 6 hours, mixing uniformly until the reaction was complete, to obtain a manganese oxalate suspension co-doped with Fe, Co, and V. Next, the suspension was filtered, dried at 120°C, and then sand-milled to obtain manganese oxalate particles with a particle size of 100 nm. Step S2: Kernel Li 0.997 Mn 0.60Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4 manufacturing

[0283] 1793.1 g of manganese oxalate, 368.3 g of lithium carbonate, 1146.6 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid prepared in (1) were taken and added to 20 L of deionized water, stirred thoroughly, and mixed uniformly at 80°C for 10 hours to obtain a slurry. The slurry was transferred to a spray dryer and spray-dried and granulated, and dried at a temperature of 250°C to obtain a powder. The powder was sintered in a roller hearth kiln at 700°C for 4 hours in a protective atmosphere (90% nitrogen gas and 10% hydrogen gas) to obtain the kernel material. Step S3: Preparation of the first coating layer suspension

[0284] A Li2FeP2O7 solution was prepared by dissolving 7.4 g of lithium carbonate, 11.6 g of ferrous carbonate, 23.0 g of ammonium dihydrogen phosphate, and 12.6 g of oxalic acid dihydrate in 500 mL of deionized water. After controlling the pH to 5, the mixture was reacted at room temperature for 2 hours with stirring to obtain the solution. Subsequently, the solution was heated to 80°C and maintained at this temperature for 4 hours to obtain the first coating layer suspension. Step S4: Application of the first coating layer

[0285] 1571.9g of the doped lithium manganese phosphate kernel material obtained in step S2 was added to the first coating layer suspension (containing 15.7g of coating material) obtained in step S3, and the mixture was thoroughly stirred and mixed for 6 hours until uniformly mixed. After that, it was transferred to 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. Step S5: Preparation of the second coating layer suspension

[0286] 3.7 g of lithium carbonate, 11.6 g of ferrous carbonate, 11.5 g of ammonium dihydrogen phosphate, and 12.6 g of oxalic acid dihydrate were dissolved in 1500 mL of deionized water and reacted with stirring for 6 hours to obtain a solution. After that, the temperature of this solution was raised to 120°C and maintained at this temperature for 6 hours to obtain a suspension of the second coating layer. Step S6: Application of the second coating layer

[0287] 1586.8g of the pyrophosphate-coated material obtained in step S4 was added to the second coating layer suspension (containing 47.1g of coating material) obtained in step S5, and the mixture was thoroughly stirred and mixed for 6 hours until uniformly mixed. After that, it was transferred to an oven at 120°C and dried for 6 hours, and then sintered at 700°C for 8 hours to obtain a two-layer coated material. Step S7: Preparation of the third coating layer aqueous solution

[0288] 37.3 g of sucrose was dissolved in 500 g of deionized water, then stirred to ensure complete dissolution, and a sucrose aqueous solution was obtained. Step S8: Application of the third coating layer

[0289] 1633.9g of the two-layer coated material obtained in step S6 was added to the sucrose solution obtained in step S7, and both were stirred and mixed for 6 hours until uniformly mixed. After that, the mixture was transferred to an oven at 150°C and dried for 6 hours, and then sintered at 700°C for 10 hours to obtain a three-layer coated material, i.e., a positive electrode active material. Step 2: Manufacturing of the positive electrode sheet

[0290] A positive electrode material composition was obtained by stirring the positive electrode active material, the conductive agent acetylene black, the binder polyvinylidene fluoride (PVDF), and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) in a weight ratio of 93.4:1.5:4.5:0.6 with a stirrer until the materials were uniformly mixed. Next, the positive electrode material composition was added to N-methylpyrrolidone (NMP) and mixed uniformly to obtain a positive electrode slurry. Next, the positive electrode slurry was coated to a surface density of 0.018 g / cm³. 2The material was then uniformly applied to aluminum foil, dried, cold-pressed, and slit to obtain a positive electrode sheet. Step 3: Manufacturing of the negative electrode sheet

[0291] A negative electrode slurry was prepared by dissolving the negative electrode active material (artificial graphite), hard carbon, conductive agent (acetylene black), binder (styrene-butadiene rubber (SBR)), and thickener (carboxymethylcellulose sodium (CMC)) in deionized water as a solvent in a weight ratio of 90:5:2:2:1 and uniformly stirring and mixing the mixture. The negative electrode slurry was then coated to a surface density of 0.0075 g / cm³. 2 The material was then uniformly applied to the copper foil of the negative electrode current collector, dried, cold-pressed, and slit to obtain a negative electrode sheet. Step 4: Manufacturing the electrolyte

[0292] In a glove box under an argon gas atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC), which are organic solvents, were uniformly mixed in a volume ratio of 3 / 7. 12.5% ​​by weight (based on the weight of the ethylene carbonate / ethyl methyl carbonate solvent) of LiPF6 was added and dissolved in the organic solvent, and the mixture was uniformly stirred to obtain an electrolyte. Step 5: Separator Manufacturing

[0293] A commercially available microporous film of PP-PE copolymer with a thickness of 20 μm and an average pore size of 80 nm was used (manufactured by Zhuo Gao Electronic Science and Technology Co., Ltd., model number 20). Step 6: Manufacturing all batteries

[0294] The positive electrode sheet, separator, and negative electrode sheet obtained above are stacked in order, with the separator positioned between the positive and negative electrodes to act as a separator, and the assembly is wound up to obtain an electrode assembly. The electrode assembly is placed in an outer casing, the electrolyte is injected and sealed to obtain a full cell (hereinafter also referred to as "full cell"). [Manufacturing of coin cells]

[0295] A cathode material composition was obtained by stirring a positive electrode active material, a conductive agent (acetylene black), a binder (polyvinylidene fluoride (PVDF)), and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number-average molecular weight of 3700) in a weight ratio of 89.4:5:5:0.6 until the materials were uniformly mixed. Then, the cathode material composition was added to N-methylpyrrolidone (NMP) and stirred in a drying chamber to prepare a slurry. The slurry was applied to aluminum foil, dried, and cold-pressed to produce a cathode sheet. The coating surface density was 0.015 g / cm³. 2 The compressed density is 2.0 g / cm³. 3 That was the case.

[0296] A lithium sheet was used as the negative electrode, and a solution of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1 mol / L LiPF6 in a 1:1:1 ratio was used as the electrolyte. Together with the positive electrode sheet manufactured above, a coin cell (hereinafter also referred to as "coin cell") was assembled in an electrical buckle box. Examples 2-29

[0297] The positive electrode active materials of Examples 2 to 29 were manufactured in a manner similar to Example 1, but the differences in the manufacturing of the positive electrode active materials are shown in Tables 2 to 7, and the rest of the process was the same as that of Example 1. Examples 30-42

[0298] The positive electrode active materials of Examples 30 to 42 were manufactured in a manner similar to Example 1, with differences in the manufacturing of the positive electrode active materials referred to in Tables 8 and 9, and the rest of the process being the same as that of Example 1. Examples 43-47

[0299] In the production of full cells and coin cells, the process was the same as in Example 1, except that the weight percentage of aminoethylaminopropyl polydimethylsiloxane in the cathode material composition was adjusted. See Table 10 for the differences. Example 43

[0300] Manufacturing of the full cell: The cathode active material, acetylene black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) were mixed in a weight ratio of 93.99:1.5:4.5:0.01 using a stirrer until the materials were uniformly mixed to obtain the cathode material composition.

[0301] Coin cell manufacturing: The positive electrode active material, acetylene black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) were mixed in a weight ratio of 89.99:5:5:0.01 using a stirrer until the materials were uniformly mixed to obtain the positive electrode material composition. Example 44

[0302] Manufacturing of the full cell: The cathode active material, acetylene black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and alkylaminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) were mixed in a weight ratio of 93.9:1.5:4.5:0.1 using a stirrer until the materials were uniformly mixed to obtain the cathode material composition.

[0303] Coin cell manufacturing: The positive electrode active material, acetylene black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) were mixed in a weight ratio of 89.9:5:5:0.1 using a stirrer until the materials were uniformly mixed to obtain the positive electrode material composition. Example 45

[0304] Manufacturing of the full cell: The cathode active material, acetylene black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) were mixed in a weight ratio of 93:1.5:4.5:1 using a stirrer until the materials were uniformly mixed to obtain the cathode material composition.

[0305] Coin cell manufacturing: The positive electrode material composition was obtained by stirring the positive electrode active material, the conductive agent acetylene black, the binder polyvinylidene fluoride (PVDF), and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) in a weight ratio of 89:5:5:1 with a stirrer until the materials were uniformly mixed. Example 46

[0306] Manufacturing of the full cell: The cathode active material, acetylene black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) were mixed in a weight ratio of 92:1.5:4.5:2 using a stirrer until the materials were uniformly mixed to obtain the cathode material composition.

[0307] Coin cell manufacturing: The positive electrode material composition was obtained by stirring the positive electrode active material, the conductive agent acetylene black, the binder polyvinylidene fluoride (PVDF), and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) in a weight ratio of 88:5:5:2 with a stirrer until the materials were uniformly mixed. Example 47

[0308] Manufacturing of the full cell: The cathode active material, acetylene black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) were mixed in a weight ratio of 89:1.5:4.5:5 using a stirrer until the materials were uniformly mixed to obtain the cathode material composition.

[0309] Coin cell manufacturing: The positive electrode material composition was obtained by stirring the positive electrode active material, acetylene black (a conductive agent), polyvinylidene fluoride (PVDF) (a binder), and aminoethylaminopropyl polydimethylsiloxane (with polar functional groups -CH2NH2 and -CH2NH-, a mass percentage α of approximately 12%, and a number average molecular weight of 3700) in a weight ratio of 85:5:5:5 until the materials were uniformly mixed using a stirrer. Examples 48 to 65

[0310] In the production of full cells and coin cells, the process was the same as in Example 1, except that aminoethylaminopropyl polydimethylsiloxane in the cathode material composition was replaced with the following organopolysiloxane compounds, respectively. See Table 10 for the differences.

[0311] Example 48: Polydimethylsiloxane (polar functional group content α is approximately 0%, number average molecular weight is 1200).

[0312] Example 49: Polymethylchloropropylsiloxane (polar functional group -CH2Cl, mass percentage α is approximately 30.2%, number average molecular weight is 2500).

[0313] Example 50: Polymethyltrifluoropropylsiloxane (polar functional group -CF3, mass percentage α is approximately 44.0%, number average molecular weight is 1400).

[0314] Example 51: Mercaptopropyl polysiloxane (polar functional group -CH2SH, mass percentage α is approximately 15.0%, number average molecular weight is 2000).

[0315] Example 52: Terminal hydroxypolydimethylsiloxane (polar functional group is -OH, mass percentage α is approximately 3.4%, number average molecular weight is 1000).

[0316] Example 53: Methoxy-terminated polydimethylsiloxane (polar functional group is a methoxy group, mass percentage α is approximately 3.1%, number average molecular weight is 2800).

[0317] Example 54: Terminal polyether polydimethylsiloxane (polar functional group is polyether segment, mass percentage α is approximately 10.0%, number average molecular weight is 2110).

[0318] Example 55: Side-chain phosphate ester grafted polydimethylsiloxane (polar functional group is a phosphate ester group, mass percentage α is approximately 1.4%, number average molecular weight is 15600),

[0319] Example 56: 1,3,5,7-Octamethylcyclotetrasiloxane (Polar functional group content α is approximately 0%, molecular weight 280).

[0320] Example 57: Cyclopentadimethylsiloxane (mass percentage α of polar functional groups is approximately 0%, molecular weight is 370).

[0321] Example 58: Terminal polyether polydimethylsiloxane (polar functional group is polyether segment, mass percentage α is approximately 55.0%, number average molecular weight is 25132).

[0322] Example 59: Polydimethylsiloxane (Polar functional group content α is approximately 0%, number average molecular weight is 400).

[0323] Example 60: Polydimethylsiloxane (polar functional group content α is approximately 0%, number average molecular weight is 10,000).

[0324] Example 61: Polydimethylsiloxane (Polar functional group content α is approximately 0%, number average molecular weight is 50,000).

[0325] Example 62: Polydimethylsiloxane (Polar functional group content α is approximately 0%, number average molecular weight is 80,000).

[0326] Example 63: Polydimethylsiloxane (polar functional group content α is approximately 0%, number average molecular weight is 100,000).

[0327] Example 64: Polydimethylsiloxane (polar functional group content α is approximately 0%, number average molecular weight is 300,000).

[0328] Example 65: Polydimethylsiloxane (Polar functional group content α is approximately 0%, number average molecular weight is 400,000). Comparative Examples 1 to 18

[0329] The positive electrode active materials for Comparative Examples 1 to 18 were manufactured in a manner similar to Example 1, with differences in the manufacturing of the positive electrode active materials being referred to in Tables 2 to 7. Comparative Examples 1 to 2, Comparative Examples 4 to 10, and Comparative Example 12 do not have a first coating layer, so steps S3 and S4 are omitted. Comparative Examples 1 to 11 do not have a second coating layer, so steps S5 and S6 are omitted.

[0330] Full cells and coin cells of Comparative Examples 1 to 18 were manufactured in a manner similar to Example 1, with the only difference being that aminoethylaminopropyl polydimethylsiloxane was not added to the cathode material composition. All other conditions were the same as in Example 1.

[0331] Furthermore, in all examples and comparative examples of this application, unless otherwise specified, it is assumed that both the first coating material and / or the second coating material used are crystalline.

[0332] Raw materials for kernel production [Table 2A] [Table 2B] [Table 2C]

[0333] Preparation of the first coating layer suspension (Step S3) [Table 3]

[0334] Coating of the first coating layer (Step S4) [Table 4]

[0335] Preparation of the second coating layer suspension (Step S5) [Table 5]

[0336] Coating of the second coating layer (Step S6) [Table 6A] [Table 6B]

[0337] Coating of the third coating layer (Step S8) [Table 7A] [Table 7B]

[0338] Consideration of the first coating layer material [Table 8]

[0339] Consideration of the second coating layer material [Table 9]

[0340] Consideration of organopolysiloxane compounds [Table 10] II. Performance Evaluation 1. Method for measuring the rate of change in the grid

[0341] Under constant temperature conditions of 25°C, the cathode active material sample is placed in an X-ray powder diffractometer (model: Bruker D8 Discover), the sample is measured at 1° / min, the measurement data is compiled and analyzed, and the lattice constants a0, b0, c0, and v0 are calculated by referring to a standard PDF card (a0, b0, and c0 represent the magnitude of the length of the unit cell in each direction, and v0 represents the volume of the unit cell, which can be directly obtained from the XRD precision correction results).

[0342] Using the coin battery manufacturing method described in the above embodiment, the positive electrode active material sample was manufactured into a coin battery, and the coin battery was charged at a low rate of 0.05C until the current decreased to 0.01C. Then, the positive electrode sheet was removed from the coin battery and immersed in dimethyl carbonate (DMC) for 8 hours. Afterward, it was dried, the powder was scraped off, and particles smaller than 500 nm were selected. A sample was taken, and its unit cell volume v1 was calculated in the same manner as the fresh sample in the above test. (v0-v1) / v0 × 100% is shown in the table as the lattice change rate (lattice volume change rate) before and after complete insertion and removal of lithium. 2. Li / Mn antistructure defect concentration

[0343] The XRD results measured using the "Method for Measuring Lattice Change Rate" are compared with a PDF (Powder Diffraction File) card of a standard crystal to obtain the Li / Mn antistructure defect concentration. Specifically, the XRD results measured using the "Method for Measuring Lattice Change Rate" are imported into the General Structure Analysis System (GSAS) software, and the software automatically acquires a precise correction result that includes the site occupation status of different atoms. The Li / Mn antistructure defect concentration is then obtained by reading this precise correction result. 3. Oxygen valence on the surface

[0344] Five g of the positive electrode active material sample produced above was used to manufacture a coin battery according to the coin battery manufacturing method described in the above example. The coin battery was charged at a low rate of 0.05 C until the current decreased to 0.01 C. After that, the positive electrode sheet was removed from the coin battery and immersed in DMC for 8 hours. After drying, the powder was scraped off and particles with a particle size smaller than 500 nm were selected. The obtained particles were measured using electron energy loss spectroscopy (EELS, instrument model Talos F200S) to obtain energy loss spectral fine structure (ELNES) that reflects the density of states and energy level distribution of the elements. From the density of states and energy level distribution, the number of electrons occupied was calculated by integrating the density of states data of the valence band, and the valence number of oxygen atoms on the surface after charging was estimated. 4. Compression density

[0345] 5g of the positive electrode active material powder produced as described above was placed in a compression mold (CARVER mold, model 13mm, USA), and then the mold was placed on a compression density meter. A pressure of 3 tons was applied, and the thickness of the powder under pressure (thickness after pressure release; the area of ​​the container used for the test was 1540.25 mm²) was measured. 2 The readings were taken from the equipment, and the compressive density was calculated using ρ=m / v. 5. Testing of powder resistivity

[0346] By placing a sample powder of the cathode material composition for producing an appropriate amount of full cells into a dedicated mold of the powder resistivity meter and setting the test pressure, powder resistivity can be obtained at different pressures. In this application, the test pressure is 12 MPa. The measuring instrument is a Suzhou Crystal ST2722-SZ type four-probe powder resistivity meter. 6. Test of specific surface area

[0347] A 5g sample of the cathode material composition for fabricating a full cell was taken, and its specific surface area was tested using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, Inc., USA. The specific surface area was calculated using the BET (Brunauer Emmett Teller) method. 7. Contact angle test

[0348] At room temperature, droplets of ethylene carbonate (EC) were dropped onto the surface of the positive electrode film layer, and the solid-liquid contact angle was measured within 60 seconds using an LSA 200 optical contact angle meter from LAUDA Scientific GmbH, Germany. 8. Method for measuring the initial gram capacity of a coin cell

[0349] The coin cells manufactured in each of the above examples and comparative examples were charged to 4.3V at 0.1C, then charged at a constant voltage of 4.3V until the current was 0.05mA or less, left to stand for 5 minutes, and then discharged to 2.0V at 0.1C. The discharge capacity at this time was the initial gram capacity and is denoted as D0. 9.3C charging constant current ratio

[0350] Under a constant temperature environment of 25°C, the new full cells manufactured in each of the above examples and comparative examples were left standing for 5 minutes and discharged to 2.5V at 1 / 3C. After standing for 5 minutes, they were charged to 4.3V at 1 / 3C, and then charged at a constant voltage of 4.3V until the current was 0.05mA or less. The charge capacity after standing for 5 minutes was recorded as C0. The charge capacity after discharging to 2.5V at 1 / 3C, standing for 5 minutes, and then charging to 4.3V at 3C, and standing for 5 minutes, was recorded as C1. The constant current ratio for 3C charging is C1 / C0 × 100%. A higher constant current ratio for 3C charging indicates better rate performance of the secondary battery. 10. Testing of battery swelling after storing all batteries at 60°C for 30 days.

[0351] Full cells manufactured in each of the above examples and comparative examples, in a 100% charged state of charge (SOC), were stored at 60°C. Before, during, and after storage, the open-circuit voltage (OCV) and AC internal resistance (IMP) of the battery were measured to monitor the SOC, and the battery volume was measured. Every 48 hours, a full cell was removed, left to stand for 1 hour, and then the open-circuit voltage (OCV) and internal resistance (IMP) were measured. After cooling to room temperature, the battery volume was measured by the drainage method. In the drainage method, the gravitational force F1 of the battery was measured alone using a balance that automatically performs unit conversion using dial data, and then the battery was completely deionized with water (density 1 g / cm³). 3The battery was placed in a known position, and its gravitational force F2 was measured. The buoyancy F acting on the battery was then determined to be F1-F2. Next, the battery levitated based on Archimedes' principle F, and the battery volume V=(F1-F2) / was calculated.

[0352] Based on the OCV and IMP test results, all batteries in this test consistently maintained a State of Charge (SOC) of 99% or higher until storage was completed.

[0353] After 30 days of storage, the battery volume was measured, and the volume after storage was compared to the volume before storage. 11. Full cell cycle performance test at 45°C

[0354] Under constant temperature conditions of 45°C, a full cell is charged to 4.3V at 1C, then charged to a constant voltage of 4.3V with a current of ≤0.05mA, left to stand for 5 minutes, and then discharged to 2.5V at 1C, with the capacity set to D0. The above process is repeated until the capacity decays to 80% of D0, and the number of repetitions is recorded, which corresponds to the number of cycles that maintain 80% capacity at 45°C. 12. Testing of the elution of transition metal Mn (and Fe doped at Mn sites)

[0355] The full cells produced in each of the above examples and comparative examples were cycled at 45°C until their capacity was reduced to 80%, and then discharged at a rate of 0.1C to a cutoff voltage of 2.0V. Afterward, the batteries were disassembled, the negative electrode sheet was removed, and 30 units of a unit area (1540.25 mm²) were extracted from the negative electrode sheet. 2 Wafers were randomly selected, and inductively coupled plasma atomic emission spectrometry (ICP) was measured using an Agilent ICP-OES730. From the ICP results, the amounts of Fe and Mn were calculated when Fe was doped into the Mn sites of the cathode active material, and the amount of Mn (and Fe doped into the Mn sites) leached out after cycling was calculated. The test standard was in accordance with EPA-6010D-2014. 13. Measurement of manganese and phosphorus elements in the positive electrode active material

[0356] 5 g of the positive electrode active material obtained above was dissolved in 100 mL of reverse aqua regia (concentrated hydrochloric acid:concentrated nitric acid = 1:3), and the content of each element in the solution was measured by ICP. Then, the content of manganese or phosphorus was measured and converted (amount of manganese or phosphorus / amount of positive electrode active material × 100%) to obtain the weight ratio. 14. Testing the thickness of the coating layer

[0357] The thickness of the coating layer was mainly determined by cutting a thin section approximately 100 nm thick from the middle of a single particle of the cathode active material manufactured as described above using FIB, performing a TEM test on the section, and obtaining the original image of the TEM test.

[0358] The raw images obtained from the TEM test described above were processed using digital micrographing software to identify the coating layer based on the grid spacing and angle information, and the thickness of the coating layer was measured.

[0359] For the selected particles, the thickness was measured at three points and averaged. 15. Measurement of grid plane spacing and included angle

[0360] Place 1 g of each cathode active material powder prepared as described above into a 50 mL test tube. Pour 10 mL of 75% alcohol into the test tube and stir for 30 minutes to disperse. Then, using a clean, disposable plastic pipette, take an appropriate amount of the above solution and drop it onto a 300-mesh copper mesh. At this time, some of the powder will remain on the copper mesh. Transfer the copper mesh along with the sample to the TEM (Talos F200s G2) sample chamber and perform the test to obtain the original image of the TEM test.

[0361] The original images obtained from the TEM test described above are processed using digital micrographing software, and a Fourier transform (automatically completed by the software after a click) is performed to obtain a diffraction pattern. By measuring the distance from the diffraction spot to the center position in the diffraction pattern, the grid plane spacing can be obtained, and the included angle is calculated based on the Bragg equation.

[0362] By comparing the obtained lattice plane spacing with the corresponding angle data, it is possible to identify different materials in the coating layer. 16. Measurement of the molar ratio of SP2 and SP3 forms in the carbon of the third coating layer.

[0363] This study was performed using Raman spectroscopy. By splitting the Raman spectrum, I d / I g Obtaining I d The peak intensity for SP3 form carbon is shown, and Ig is shown, representing the peak intensity for SP2 form carbon. The molar ratio of the two was then confirmed. 17. Measurement of different kernel chemical formulas and coating layers

[0364] Using spherical aberration electron microscopy (ACSTEM), we perform high-spatial-resolution characterization of the internal microstructure and surface structure of the cathode active material, and combine this with three-dimensional reconstruction techniques to obtain the kernel chemical formula of the cathode active material and the composition of different coating layers.

[0365] Table 11 shows the performance data obtained for the positive electrode active material, positive electrode material composition, positive electrode sheet, coin electrode, or full electrode in Examples 1 to 29 and Comparative Examples 1 to 18, measured according to the performance test method described above.

[0366] Table 12 shows the thickness of the coating layer for each layer and the weight ratio of manganese to phosphorus in the positive electrode active materials produced in Examples 1-14 and Comparative Examples 3-4 and 12.

[0367] Table 13 shows the lattice plane spacing and clamping angle of the first and second coating layer materials in the positive electrode active materials produced in Examples 1, 30-42.

[0368] Table 14 shows the performance data obtained for the positive electrode active material, positive electrode material composition, positive electrode sheet, coin electrode, or full electrode in Examples 30 to 42, measured according to the performance test method described above.

[0369] Table 15 shows the performance data measured according to the performance test method described above for the positive electrode material compositions, positive electrode sheets, coin electrodes, or full electrodes in Examples 43 to 65.

[0370] [Table 11A] [Table 11B]

[0371] [Table 12]

[0372] [Table 13]

[0373] [Table 14]

[0374] [Table 15]

[0375] As can be seen from Table 11, compared to the comparative example, the example achieved a smaller lattice change rate, a smaller Li / Mn antistructure defect concentration, a higher compressive density, a surface oxygen valence closer to -2, less Mn and Fe leaching after cycling, and better battery performance, such as better high-temperature storage performance and high-temperature cycling performance. By using the positive electrode active material and organopolysiloxane compound of the example of this application in combination, erosion of the positive electrode active material surface by the electrolyte can be further mitigated, the amount of Mn and Fe leaching after cycling can be reduced, and the battery's cycling performance can be further improved.

[0376] As can be seen from Table 12, doping and coating the manganese and phosphorus sites of lithium iron manganese phosphate (manganese content 35%, phosphorus content approximately 20%) clearly reduced the manganese content and the weight ratio of manganese to phosphorus in the positive electrode active material. Furthermore, comparing Examples 1-14 with Comparative Examples 3, 4, and 12, as can be seen from Table 11, the reduction in manganese and phosphorus content in the positive electrode active material reduced the amount of manganese and iron ions eluted, and improved the performance of the manufactured batteries.

[0377] As can be seen from Table 13, the lattice plane spacing and binding angle of the first and second coating layers in the positive electrode active material of this application are both within the range specified in this application. As can be seen from Table 14, even when the first and second coating layers contain other elements within the range specified in this application, a positive electrode active material with good performance can be obtained, resulting in good battery performance.

[0378] As can be seen from Table 15, when the positive electrode active material is the same, the battery's cycle performance can be further improved without affecting energy density and dynamic performance by selecting an organopolysiloxane compound that satisfies one or more of the following conditions: appropriate polar functional group content, number-average molecular weight, and addition amount, and using it in combination with the positive electrode active material.

[0379] As can be seen from Examples 1, 43-47, the powder resistance of the positive electrode active material composition initially decreased and then increased as the amount of organopolysiloxane compound added increased. This is thought to be because, when the amount of organopolysiloxane compound added is within a certain range, its hydrophobic properties reduce the interaction between conductive agents, alleviate aggregation of conductive agents, and form a better conductive network.

[0380] This application is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea and produces similar effects within the technical scope of this application is included. Furthermore, any modifications to the embodiments that a person skilled in the art could conceive, or other forms constructed by combining some of the components of the embodiments, are also included within the scope of this application, as long as they do not depart from the spirit of this application.

Claims

1. A cathode material composition comprising a cathode active material having a core-shell structure and an organopolysiloxane compound, The positive electrode active material includes a kernel and a shell covering the kernel. The chemical formula of the kernel is Li １＋ｘ Mn １－ｙ A ｙ P １－ｚ R ｚ O ４ The values ​​of x, y, and z are such that x is any number within the range of -0.100 to 0.100, y is any number within the range of 0.001 to 0.500, z is any number within the range of 0.001 to 0.100, A includes one or more elements from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, R includes one or more elements from B, Si, N, and S, and the values ​​of x, y, and z satisfy the condition that the entire kernel maintains electrical neutrality. The shell includes a first coating layer covering the kernel, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer. The first coating layer contains crystalline pyrophosphate Li ａ MP ２ O ７ and / or M ｂ (P ２ O ７ ) ｃ where 0 ≤ a ≤ 2, 1 ≤ b ≤ 4, 1 ≤ c ≤ 6. In the crystalline pyrophosphate Li ａ MP ２ O ７ and M ｂ (P<OO00018>O ７ ) ｃ M independently includes one or more elements of Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al. The values of a, b, and c satisfy the condition that the crystalline pyrophosphate Li ａ MP ２ O ７ or M ｂ (P ２ O ７ ) ｃ maintains electrical neutrality. The second coating layer contains crystalline phosphate XPO ４ where X includes one or more elements of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al. The third coating layer is carbon. Cathode material composition.

2. The cathode material composition according to claim 1, wherein the organopolysiloxane compound comprises at least one structural unit represented by formula 1. 【Chemistry 1】 R １ , R ２ Each of these independently represents at least one selected from the group consisting of -COOH, -OH, -SH, -CN, -SCN, amino group, phosphate ester group, carboxylic acid ester group, amide group, aldehyde group, sulfonyl group, polyether segment, C1-C20 aliphatic hydrocarbon group, C1-C20 halogenated aliphatic hydrocarbon group, C1-C20 heteroaliphatic hydrocarbon group, C1-C20 halogenated heteroaliphatic hydrocarbon group, C6-C20 aromatic hydrocarbon group, C6-C20 halogenated aromatic hydrocarbon group, C2-C20 heteroaromatic hydrocarbon group, or H.

3. The cathode material composition according to claim 1, wherein the organopolysiloxane compound comprises one or more polysiloxanes with a linear structure and polysiloxanes with a cyclic structure.

4. The positive electrode material composition according to claim 3, wherein the linear polysiloxane further comprises a chelating group.

5. The aforementioned linear polysiloxanes include polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polymethylvinylsiloxane, polyphenylmethylsiloxane, polymethylhydrogensiloxane, carboxyl-functionalized polysiloxane, polymethylchloropropylsiloxane, polymethyltrifluoropropylsiloxane, perfluorooctylmethylpolysiloxane, mercaptopropylpolysiloxane, aminoethylaminopropylpolydimethylsiloxane, and methoxy-terminated polydimethylsiloxane. It contains one or more of the following: hydroxysiloxane, hydroxypropyl-terminated polydimethylsiloxane, aminopropyl-terminated polydimethylsiloxane, terminal epoxypolysiloxane, terminal hydroxypolydimethylsiloxane, terminal polyetherpolydimethylsiloxane, side-chain aminopropylpolysiloxane, side-chain hydroxylmethylpolysiloxane, side-chain hydroxylpropylpolysiloxane, side-chain polyether-grafted polydimethylsiloxane, and / or The positive electrode material composition according to claim 3, wherein the cyclic polysiloxane comprises one or more of cyclic polydimethylsiloxane, cyclic polymethylvinylsiloxane, cyclic polymethylhydrogensiloxane, and cyclic polymethyltrifluoropropylsiloxane.

6. The cathode material composition according to claim 1, wherein the number average molecular weight of the organopolysiloxane compound is 300,000 or less.

7. The positive electrode material composition according to claim 1, wherein the mass percentage of polar functional groups in the organopolysiloxane compound is α, and 0 ≤ α < 50%.

8. The cathode material composition according to claim 1, wherein the content of the organopolysiloxane compound is 0.01% by weight to 2% by weight with respect to the total weight of the cathode material composition.

9. The amount of coverage of the first coating layer is greater than 0 and 6% or less by weight relative to the weight of the kernel. The amount of coverage of the second coating layer is greater than 0 and 6% or less by weight relative to the weight of the kernel. The cathode material composition according to claim 1, wherein the amount of the third coating layer is greater than 0 and 6% by weight or less relative to the weight of the kernel.

10. The thickness of the first coating layer is 1 nm to 10 nm, and / or The thickness of the second coating layer is 2 nm to 15 nm, and / or The cathode material composition according to claim 1, wherein the thickness of the third coating layer is 2 nm to 25 nm.

11. The lattice plane spacing of the crystalline pyrophosphate in the first coating layer is in the range of 0.293 nm to 0.470 nm, the included angle range for the crystal orientation (111) is in the range of 18.00° to 32.00°, and / or The cathode material composition according to claim 1, wherein the lattice plane spacing of the crystalline phosphate in the second coating layer is in the range of 0.244 nm to 0.425 nm, and the range of the included angle for the crystal orientation (111) is in the range of 20.00° to 37.00°.

12. In the kernel described above, the ratio of y to 1-y is 1:10 to 1:1, and / or The positive electrode material composition according to claim 1, wherein in the kernel, the ratio of z to 1-z is 1:9 to 1:

999.

13. The positive electrode material composition according to claim 1, wherein the carbon in the third coating layer is a mixture of SP2 form carbon and SP3 form carbon.

14. The manganese content is in the range of 10% to 35% by weight relative to the weight of the positive electrode active material, and / or The phosphorus content is within the range of 12% to 25% by weight relative to the weight of the positive electrode active material, and / or The positive electrode material composition according to claim 1, wherein the weight ratio of manganese element to phosphorus element with respect to the weight of the positive electrode active material is in the range of 0.90 to 1.

25.

15. The positive electrode material composition according to claim 1, wherein the positive electrode active material satisfies at least one of the following conditions (1) to (4). (1) The positive electrode active material has a lattice change rate of 4% or less before and after complete insertion and removal of lithium. (2) The Li / Mn antistructure defect concentration of the positive electrode active material is 4% or less. (3) The compressible density of the positive electrode active material at 3T is 2.2 g / cm³. ３ That's all. (4) The oxygen valence on the surface of the positive electrode active material is -1.90 or less.

16. The positive electrode material composition according to claim 1, further comprising a conductive agent and a binder.

17. The powder resistivity of the aforementioned positive electrode material composition at 12 MPa is 4 Ω / cm to 55 Ω / cm, and / or, The specific surface area of ​​the aforementioned cathode material composition is 8 m². ２ / g to 20m ２ The positive electrode material composition according to claim 1, wherein the value is / g.

18. A method for producing a positive electrode material composition, The process includes the steps of providing kernel material, coating, and mixing, The step of providing the kernel material includes the step of providing the kernel whose chemical formula is Li １＋ｘ Mn １－ｙ A ｙ P １－ｚ R ｚ O ４ Here, x is any number in the range of -0.100 to 0.100, y is any number in the range of 0.001 to 0.500, z is any number in the range of 0.001 to 0.100, A includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, R includes one or more elements of B, Si, N, and S, and the values ​​of x, y, and z satisfy the condition that the entire kernel is maintained in an electrically neutral state. The coating step includes Li ａ MP ２ O ７ and / or M ｂ (P ２ O ７ ) ｃ and XPO ４ Each suspension is provided, the kernel material is added to the suspension and mixed, and sintered to obtain a positive electrode active material, wherein the positive electrode active material has a core-shell structure and includes the kernel and a shell covering the kernel, the shell includes a first coating layer covering the kernel, 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 made of crystalline pyrophosphate Li ａ MP ２ O ７ and / or M ｂ (P ２ O ７ ) ｃ The crystalline pyrophosphate Li contains 0 ≤ a ≤ 2, 1 ≤ b ≤ 4, 1 ≤ c ≤ 6. ａ MP ２ O ７ and M ｂ (P ２ O ７ ) ｃ In this formula, M independently comprises one or more elements from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and the values ​​of a, b, and c are crystalline pyrophosphate Li ａ MP ２ O ７ or M ｂ (P ２ O ７ ) ｃ The conditions for maintaining electrical neutrality are met, and the second coating layer is made of crystalline phosphate XPO ４ The third coating layer is carbon, wherein X includes one or more elements of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al. In the mixing step, the obtained positive electrode active material is uniformly mixed with an organopolysiloxane compound, a binder, and a conductive agent to obtain a positive electrode material composition.

19. The step of providing the kernel material includes the following steps (1) and (2): In step (1) above, a manganese source, a dopant of element A, and an acid are mixed and stirred in a container to obtain manganese salt particles doped with element A. In step (2), the manganese salt particles doped with element A are mixed in a solvent with a lithium source, a phosphorus source and a dopant of element R to obtain a slurry, which is then sintered under the protection of an inert gas atmosphere to obtain a kernel doped with elements A and R, where the kernel doped with elements A and R is Li １＋ｘ Mn １－ｙ A ｙ P １－ｚ R ｚ O ４ The method according to claim 18, wherein x is any number in the range of -0.100 to 0.100, y is any number in the range of 0.001 to 0.500, z is any number in the range of 0.001 to 0.100, A comprises one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and R comprises one or more elements of B, Si, N, and S.

20. Step (1) is to perform mixing at a temperature of 20°C to 120°C and / or, In step (1) above, the stirring is performed at 400 rpm to 700 rpm for 1 to 9 hours, and / or The method according to claim 19, wherein step (2) is to mix at a temperature of 20°C to 120°C for 1 to 10 hours.

21. The dopant of element A includes one or more elements, carbonates, sulfates, chlorides, nitrates, organic acid salts, oxides, and / or, one or more of the elements Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and / or The method according to claim 19 or 20, wherein the dopant of element R comprises one or more inorganic acids, organic acids, sulfates, chlorides, nitrates, organic acid salts, oxides, and hydroxides of one or more elements B, Si, N, and S.

22. The coating step includes a first coating step, a second coating step, and a third coating step, The first coating step involves dissolving a source of element M, a phosphorus source, an acid, and a lithium source in a solvent to obtain a first coating layer suspension, thoroughly mixing the kernel obtained in the step of providing the kernel material with the first coating layer suspension obtained in the first coating step, drying, and then sintering to obtain a material coated with the first coating layer. In the second coating step, a source of element X, a phosphorus source, and an acid are dissolved in a solvent to obtain a second coating layer suspension. The material coated with the first coating layer obtained in the first coating step and the second coating layer suspension obtained in the second coating step are thoroughly mixed, dried, and then sintered to obtain a material coated with two layers. The method according to claim 18, wherein the third coating step involves dissolving a carbon source in a solvent and thoroughly dissolving it to obtain a third coating layer solution, then adding the material coated with two coating layers obtained in the second coating step to the third coating layer solution, mixing uniformly, drying, and then sintering to obtain a material coated with three coating layers, i.e., a positive electrode active material.

23. In the first coating step, the pH of the solution containing the dissolved element M, the phosphorus source, the acid, and the lithium source is controlled to 3.5 to 6.5, then the mixture is reacted for 1 to 5 hours while stirring, then the solution is heated to 50°C to 120°C and maintained at that temperature for 2 to 10 hours, and / or The sintering in the first coating step is carried out at 650°C to 800°C for 2 to 6 hours, and / or In the second coating step, after dissolving the source of element X, the phosphorus source and the acid in the solvent, the reaction is carried out by stirring for 1 to 10 hours, and then the temperature of the solution is raised to 60°C to 150°C and maintained at that temperature for 2 to 10 hours, and / or The sintering in the second coating step is carried out at 500°C to 700°C for 6 to 10 hours, and / or The method according to claim 22, wherein the sintering in the third coating step is carried out at 700°C to 800°C for 6 to 10 hours.

24. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode material composition described in any one of claims 1 to 17, and the content of the positive electrode material composition in the positive electrode film layer is 50% by weight or more relative to the total weight of the positive electrode film layer.

25. The positive electrode sheet according to claim 24, wherein the positive electrode sheet satisfies at least one of the following conditions (1) to (6). (1) The solid-liquid contact angle between the positive electrode film layer and the non-aqueous organic solvent is 3° to 90°. (2) The porosity of the positive electrode film layer is 15% to 50%. (3) The resistance of the positive electrode film layer is greater than 0 and 6Ω or less. (4) The adhesive force between the positive electrode film layer and the positive electrode current collector is 0.5 MPa or more. (5) The surface density of the positive electrode film layer is 0.006 g / cm³. ２ ~0.065g / cm ２ That is the case. (6) The absorption rate of the electrolyte by the positive electrode film layer is 0.0125 μg / s to 100 μg / s.

26. A secondary battery comprising the positive electrode material composition according to any one of claims 1 to 17.

27. A power consumption device comprising the secondary battery described in claim 26.

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