Positive electrode material, positive electrode plate, secondary battery and electronic device

Abstract

The invention provides a positive electrode material, a positive electrode plate, a secondary battery and an electronic device, the positive electrode material comprises lithium manganese iron phosphate, the positive electrode material comprises a first element and a second element, the first element comprises at least one of a magnesium element, a nickel element, a cobalt element or a zinc element, and the second element comprises at least one of a titanium element or a zirconium element; the mass ratio of the first element to the second element is 1 to 20. The positive electrode material meets the characteristics, the dynamic performance and the cycle performance of the positive electrode material can be improved, and meanwhile, the positive electrode material has relatively high capacity.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a positive electrode material, a positive electrode sheet, a secondary battery and an electronic device. Background Art

[0002] In order to solve the severe problems of global energy crisis, environmental pollution, climate change, low-carbon economy, etc., the research and development and application of power sources in electric vehicles, large-scale power sources and energy storage fields have become inevitable. As an important component of them, lithium iron phosphate batteries have the advantages of long life, safety and low cost, but lithium iron phosphate has the problem of low energy density.

[0003] Lithium iron manganese phosphate (LiFeMnPO4) adds a certain proportion of Mn to lithium iron phosphate to increase its average voltage and energy density. However, lithium iron manganese phosphate has the Jan-Taylor effect, and its kinetic and cycle performances are poor. Summary of the invention

[0004] The purpose of this application is to provide a positive electrode material, a positive electrode sheet, a secondary battery and an electronic device to improve the kinetic performance and cycle performance of the positive electrode material, while also making the positive electrode material have a higher capacity. The specific technical solution is as follows: The first aspect of the present application provides a positive electrode material, the positive electrode material includes lithium manganese iron phosphate, the positive electrode material includes a first element and a second element, the first element includes at least one of magnesium, nickel, cobalt or zinc, the second element includes at least one of titanium or zirconium, and the mass ratio of the first element to the second element is 1 to 20. When the positive electrode material includes lithium manganese iron phosphate, the positive electrode material includes the first element and the second element, and the types and mass ratios of the first element and the second element are within the scope of the present application, the kinetic performance and cycle performance of the positive electrode material can be improved, and the positive electrode material can also have a higher capacity.

[0005] In one or more embodiments of the present application, at least a portion of the surface of the lithium manganese iron phosphate is provided with a carbon material. At least a portion of the surface of the lithium manganese iron phosphate is provided with a carbon material, which can improve the electronic conductivity of the lithium manganese iron phosphate and improve the kinetic performance and cycle performance of the positive electrode material.

[0006] In one or more embodiments of the present application, the first element includes magnesium, the second element includes titanium, and the mass ratio of magnesium to titanium is 1 to 8. By regulating the types of the first element and the second element and their mass ratio within the scope of the present application, the first element includes magnesium, and doping with magnesium can improve the lattice volume change between the de-lithiated MnFeMgPO4 and the lithium-embedded LiMnFeMgPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, titanium is a high-valent metal element that can reduce the particle size, and the small particle size can further improve the kinetics of the positive electrode material. The improvement in kinetics will bring about an improvement in cycle performance, and the magnesium and titanium elements have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0007] In one or more embodiments of the present application, the first element includes nickel, the second element includes titanium, and the mass ratio of nickel to titanium is 1 to 15. By regulating the types of the first element and the second element and their mass ratio within the scope of the present application, the first element includes nickel, and doping with nickel can improve the lattice volume change between the de-lithiated MnFeNiPO4 and the lithium-embedded LiMnFeNiPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, titanium is a high-valent metal element that can reduce the particle size, and the small particle size can further improve the kinetics of the positive electrode material. The improvement in kinetics will bring about an improvement in cycle performance, and the nickel element and titanium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0008] In one or more embodiments of the present application, the first element includes cobalt, the second element includes titanium, and the mass ratio of cobalt to titanium is 1 to 15. By regulating the types of the first element and the second element and their mass ratio within the scope of the present application, the first element includes cobalt, and doping with cobalt can improve the lattice volume change between the de-lithiated MnFeCoPO4 and the lithium-embedded LiMnFeCoPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, titanium is a high-valent metal element that can reduce the particle size, and the small particle size can further improve the kinetics of the positive electrode material. The improvement in kinetics will bring about an improvement in cycle performance, and the cobalt element and titanium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0009] In one or more embodiments of the present application, the first element includes zinc, the second element includes titanium, and the mass ratio of zinc to titanium is 1 to 20. By regulating the types of the first element and the second element and their mass ratio within the scope of the present application, the first element includes zinc, and doping with zinc can improve the lattice volume change between the de-lithiated MnFeZnPO4 and the lithium-embedded LiMnFeZnPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, titanium is a high-valent metal element that can reduce the particle size, and the small particle size can further improve the kinetics of the positive electrode material. The improvement in kinetics will bring about an improvement in cycle performance, and the zinc and titanium elements have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0010] In one or more embodiments of the present application, the first element includes magnesium, the second element includes zirconium, and the mass ratio of magnesium to zirconium is 1 to 4. By regulating the types of the first element and the second element and their mass ratio within the scope of the present application, the first element includes magnesium, and doping with magnesium can improve the lattice volume change between the de-lithiated MnFeMgPO4 and the lithium-embedded LiMnFeMgPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, the second element includes zirconium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetics of the positive electrode material, and the improvement of the kinetics will bring about the improvement of the cycle performance. In addition, the magnesium element and the zirconium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0011] In one or more embodiments of the present application, the first element includes nickel, the second element includes zirconium, and the mass ratio of nickel to zirconium is 1 to 6. By regulating the types of the first element and the second element and their mass ratio within the scope of the present application, the first element includes nickel, and doping with nickel can improve the lattice volume change between the de-lithiated MnFeNiPO4 and the lithium-embedded LiMnFeNiPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, the second element includes zirconium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetics of the positive electrode material, and the improvement of the kinetics will bring about the improvement of the cycle performance. In addition, the nickel element and the zirconium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0012] In one or more embodiments of the present application, the first element includes cobalt, the second element includes zirconium, and the mass ratio of cobalt to zirconium is 1 to 6. By regulating the types of the first element and the second element and their mass ratio within the scope of the present application, the first element includes cobalt, and doping with cobalt can improve the lattice volume change between the de-lithiated MnFeCoPO4 and the lithium-embedded LiMnFeCoPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, the second element includes zirconium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetics of the positive electrode material, and the improvement of the kinetics will bring about the improvement of the cycle performance. In addition, the cobalt element and the zirconium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0013] In one or more embodiments of the present application, the first element includes zinc, the second element includes zirconium, and the mass ratio of zinc to zirconium is 1 to 10. By regulating the types of the first element and the second element and their mass ratio within the scope of the present application, the first element includes zinc, and doping with zinc can improve the lattice volume change between the de-lithiated MnFeZnPO4 and the lithium-embedded LiMnFeZnPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, the second element includes zirconium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetics of the positive electrode material, and the improvement of the kinetics will bring about the improvement of the cycle performance. In addition, the zinc element and the zirconium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0014] In one or more embodiments of the present application, the positive electrode material further includes a third element, and the third element includes at least one of niobium, vanadium or tungsten. The positive electrode material further includes a third element and the type of the third element is within the scope of the present application. The third element is a high-valent metal element, which can reduce the particle size. The small particle size can further improve the kinetic performance of the positive electrode material, and the improvement of the kinetic performance will bring about the improvement of the cycle performance; and the third element can improve the electronic conductivity and ionic conductivity, and improve the gram capacity and kinetic performance of the positive electrode material.

[0015] In one or more embodiments of the present application, the third element includes niobium, and the mass ratio of magnesium to niobium is 5 to 9. By regulating the type of the third element and the mass ratio of magnesium to the third element within the scope of the present application, the third element includes niobium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetic properties of the positive electrode material, and the improvement of the kinetic properties will bring about the improvement of the cycle performance; and the niobium element can improve the electronic conductivity and ionic conductivity, and improve the gram capacity and kinetic properties of the positive electrode material; doping with magnesium can reduce volume expansion, and further improve the kinetic properties and cycle performance of the positive electrode material; and the magnesium element and the niobium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0016] In one or more embodiments of the present application, the third element includes vanadium, and the mass ratio of magnesium to vanadium is 2 to 5. By regulating the type of the third element and the mass ratio of magnesium to the third element within the scope of the present application, the third element includes vanadium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetic properties of the positive electrode material, and the improvement of the kinetic properties will bring about the improvement of the cycle performance; and the vanadium element can improve the electronic conductivity and ionic conductivity, and improve the gram capacity and kinetic properties of the positive electrode material; doping with magnesium can reduce volume expansion, further improve the kinetic properties and cycle performance of the positive electrode material; and the magnesium element and the vanadium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0017] In one or more embodiments of the present application, the third element includes tungsten, and the mass ratio of magnesium to tungsten is 10 to 20. By regulating the type of the third element and the mass ratio of magnesium to the third element within the scope of the present application, the third element includes tungsten, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetic properties of the positive electrode material, and the improvement in kinetic properties will bring about an improvement in cycle performance; and tungsten can improve electronic conductivity and ionic conductivity, and improve the gram capacity and kinetic properties of the positive electrode material; doping with magnesium can reduce volume expansion, further improving the kinetic properties and cycle performance of the positive electrode material; and magnesium and tungsten have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0018] In one or more embodiments of the present application, the positive electrode material further includes a fourth element, and the fourth element includes at least one of sodium or potassium. The positive electrode material further includes a fourth element and the type of the fourth element is within the scope of the present application, and doping the fourth element in the lithium position can further improve the conductivity of the positive electrode material and further improve the kinetic performance of the positive electrode material.

[0019] In one or more embodiments of the present application, the fourth element includes sodium, and the mass ratio of magnesium to sodium is 10 to 14. By regulating the type of the fourth element and the mass ratio of magnesium to the fourth element within the scope of the present application, the fourth element includes sodium, and doping sodium at the lithium position can further improve the conductivity of the positive electrode material and the kinetic properties of the positive electrode material; doping magnesium can reduce volume expansion and further improve the kinetic properties and cycle performance of the positive electrode material; and magnesium and sodium have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0020] In one or more embodiments of the present application, the fourth element includes potassium, and the mass ratio of magnesium to potassium is 10 to 20. By regulating the type of the fourth element and the mass ratio of magnesium to the fourth element within the scope of the present application, the fourth element includes potassium, and doping potassium at the lithium position can further improve the conductivity of the positive electrode material and the kinetic properties of the positive electrode material; doping magnesium can reduce volume expansion and further improve the kinetic properties and cycle performance of the positive electrode material; and magnesium and potassium have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0021] In one or more embodiments of the present application, the mass ratio of magnesium to manganese is 0.01 to 0.02. Doping with magnesium can improve the lattice volume change between the de-lithiation state MnFeMgPO4 and the lithium insertion state LiMnFeMgPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material. The manganese element in the positive electrode material can improve the energy density of the positive electrode material. By adjusting the mass ratio of magnesium to manganese within the scope of the present application, the positive electrode material has a higher energy density while having higher kinetics and cycle performance.

[0022] The second aspect of the present application provides a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, the positive electrode material layer includes the positive electrode material in any of the above embodiments. Therefore, the positive electrode plate is applied to a secondary battery, and the secondary battery has good dynamic performance and cycle performance, and also has a higher capacity.

[0023] The third aspect of the present application provides a secondary battery, the secondary battery comprising the positive electrode sheet in any of the above embodiments. Therefore, the secondary battery provided by the present application has good dynamic performance and cycle performance, and also has a high capacity.

[0024] The fourth aspect of the present application provides an electronic device, which includes the secondary battery in any of the above embodiments. Therefore, the electronic device provided by the present application has good dynamic performance and cycle performance, and also has a high capacity.

[0025] Beneficial effects of this application: The present application provides a positive electrode material, a positive electrode plate, a secondary battery and an electronic device, wherein the positive electrode material comprises lithium manganese iron phosphate, the positive electrode material comprises a first element and a second element, the first element comprises at least one of magnesium, nickel, cobalt or zinc, the second element comprises at least one of titanium or zirconium, and the mass ratio of the first element to the second element is 1 to 20. The positive electrode material satisfies the above characteristics, can improve the kinetic performance and cycle performance of the positive electrode material, and also enables the positive electrode material to have a higher capacity.

[0026] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0028] Figure 1 This is a scanning electron microscope image of the positive electrode material of Example 1-1 of the present application. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0030] It should be noted that in the following content, the present application is explained by taking a lithium-ion battery as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0031] The first aspect of the present application provides a positive electrode material, the positive electrode material includes lithium manganese iron phosphate, the positive electrode material includes a first element and a second element, the first element includes at least one of magnesium element Mg, nickel element Ni, cobalt element Co or zinc element Zn, the second element includes at least one of titanium element Ti or zirconium element Zr, and the mass ratio of the first element to the second element is 1 to 20. Exemplarily, the mass ratio of the first element to the second element can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or a range consisting of any two of the above values. It is understood that the first element and the second element can be used as doping elements.

[0032] The inventors have found that the positive electrode material includes lithium manganese iron phosphate, and the positive electrode material includes a first element and a second element, wherein the first element is an inactive element and its radius is between Mn 2+ / Fe 2+ and Mn 3+ / Fe 3+ Doping with the first element can improve the lattice volume change between the de-lithiated lithium manganese iron phosphate and the embedded lithium manganese iron phosphate, reduce volume expansion, and improve the kinetic performance and cycle performance of the positive electrode material; at the same time, the second element is a high-valent metal element, which can reduce the particle size. The small particle size can improve the kinetic performance of the positive electrode material, and the improvement of the kinetic performance will bring about the improvement of the cycle performance. When the doping amount of the first element and / or the second element is too high, it will cause the capacity loss of the positive electrode material; when the doping amount of the first element and / or the second element is too low, the improvement of the kinetic performance and cycle performance of the positive electrode material is small. Therefore, when the positive electrode material includes lithium manganese iron phosphate, the positive electrode material includes the first element and the second element, and the types and mass ratios of the first element and the second element are within the scope of this application, the kinetic performance and cycle performance of the positive electrode material can be improved, and the positive electrode material can also have a higher capacity.

[0033] In the present application, based on the mass of the positive electrode material, the mass percentage content W1 of the first element is 0.1% to 1.5%, and the mass percentage content W2 of the second element is 0.02% to 0.1%. When the first element includes two or more elements, the present application has no particular restrictions on the mass percentage content of each element, as long as the mass percentage content of the first element meets the scope of the present application. When the second element includes two or more elements, the present application has no particular restrictions on the mass percentage content of each element, as long as the mass percentage content of the second element meets the scope of the present application.

[0034] In one or more embodiments of the present application, at least a portion of the surface of the lithium iron manganese phosphate is provided with a carbon material. The lithium iron manganese phosphate may be provided with a carbon material on a portion of the surface, or may be provided with a carbon material on the entire surface. The above-mentioned carbon material can be obtained by carbonizing an organic matter, and the organic matter may include but is not limited to glucose. At least a portion of the surface of the lithium iron manganese phosphate is provided with a carbon material, which can improve the electronic conductivity of the lithium iron manganese phosphate and can improve the kinetic performance and cycle performance of the positive electrode material.

[0035] In one or more embodiments of the present application, the first element includes magnesium, the second element includes titanium, and the mass ratio of magnesium to titanium is 1 to 8. Exemplarily, the mass ratio of magnesium to titanium can be 1, 2, 3, 4, 5, 6, 7, 8 or a range consisting of any two of the above values. By regulating the types and mass ratios of the first element and the second element within the scope of the present application, the first element includes magnesium, and doping with magnesium can improve the lattice volume change between the de-lithiated MnFeMgPO4 and the lithium-embedded LiMnFeMgPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, titanium is a high-valent metal element that can reduce the particle size, and the small particle size can further improve the kinetics of the positive electrode material. The improvement in kinetics will bring about an improvement in cycle performance, and the magnesium element and the titanium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0036] In one or more embodiments of the present application, the first element includes nickel, the second element includes titanium, and the mass ratio of nickel to titanium is 1 to 15. Exemplarily, the mass ratio of nickel to titanium can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a range consisting of any two of the above values. By regulating the type and mass ratio of the first element and the second element within the scope of the present application, the first element includes nickel, and doping with nickel can improve the lattice volume change between the de-lithiation state MnFeNiPO4 and the lithium insertion state LiMnFeNiPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, titanium is a high-valent metal element that can reduce the particle size, and the small particle size can further improve the kinetics of the positive electrode material. The improvement of the kinetics will bring about the improvement of the cycle performance, and the nickel element and the titanium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0037] In one or more embodiments of the present application, the first element includes cobalt, the second element includes titanium, and the mass ratio of cobalt to titanium is 1 to 15. Exemplarily, the mass ratio of cobalt to titanium can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a range consisting of any two of the above values. By regulating the types and mass ratios of the first element and the second element within the scope of the present application, the first element includes cobalt, and doping with cobalt can improve the lattice volume change between the de-lithiation state MnFeCoPO4 and the lithium insertion state LiMnFeCoPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, titanium is a high-valent metal element that can reduce the particle size, and the small particle size can further improve the kinetics of the positive electrode material. The improvement of the kinetics will bring about an improvement in the cycle performance, and the cobalt element and the titanium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0038] In one or more embodiments of the present application, the first element includes zinc, the second element includes titanium, and the mass ratio of zinc to titanium is 1 to 20. Exemplarily, the mass ratio of zinc to titanium can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or a range consisting of any two of the above values. By regulating the type and mass ratio of the first element and the second element within the scope of the present application, the first element includes zinc, and doping with zinc can improve the lattice volume change between the de-lithiation state MnFeZnPO4 and the lithium insertion state LiMnFeZnPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, titanium is a high-valent metal element, which can reduce the particle size, and the small particle size can further improve the kinetics of the positive electrode material. The improvement of the kinetics will bring about the improvement of the cycle performance, and the zinc element and the titanium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0039] In one or more embodiments of the present application, the first element includes magnesium, the second element includes zirconium, and the mass ratio of magnesium to zirconium is 1 to 4. Exemplarily, the mass ratio of magnesium to zirconium can be 1, 2, 3, 4 or a range consisting of any two of the above values. By regulating the types and mass ratios of the first element and the second element within the scope of the present application, the first element includes magnesium, and doping with magnesium can improve the lattice volume change between the de-lithiated MnFeMgPO4 and the lithium-embedded LiMnFeMgPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, the second element includes zirconium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetics of the positive electrode material. The improvement in kinetics will bring about an improvement in cycle performance, and the magnesium element and the zirconium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0040] In one or more embodiments of the present application, the first element includes nickel, the second element includes zirconium, and the mass ratio of nickel to zirconium is 1 to 6. Exemplarily, the mass ratio of nickel to zirconium can be 1, 2, 3, 4, 5, 6 or a range consisting of any two of the above values. By regulating the types and mass ratios of the first element and the second element within the scope of the present application, the first element includes nickel, and doping with nickel can improve the lattice volume change between the de-lithiated MnFeNiPO4 and the lithium-embedded LiMnFeNiPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, the second element includes zirconium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetics of the positive electrode material. The improvement in kinetics will bring about an improvement in cycle performance, and the nickel element and the zirconium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0041] In one or more embodiments of the present application, the first element includes cobalt, the second element includes zirconium, and the mass ratio of cobalt to zirconium is 1 to 6. Exemplarily, the mass ratio of cobalt to zirconium can be 1, 2, 3, 4, 5, 6 or a range consisting of any two of the above values. By regulating the types and mass ratios of the first element and the second element within the scope of the present application, the first element includes cobalt, and doping with cobalt can improve the lattice volume change between the de-lithiated MnFeCoPO4 and the lithium-embedded LiMnFeCoPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, the second element includes zirconium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetics of the positive electrode material. The improvement in kinetics will bring about an improvement in cycle performance, and the cobalt element and the zirconium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0042] In one or more embodiments of the present application, the first element includes zinc, the second element includes zirconium, and the mass ratio of zinc to zirconium is 1 to 10. Exemplarily, the mass ratio of zinc to zirconium can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a range consisting of any two of the above values. By regulating the type and mass ratio of the first element and the second element within the scope of the present application, the first element includes zinc, and doping with zinc can improve the lattice volume change between the de-lithiated MnFeZnPO4 and the lithium-embedded LiMnFeZnPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material; at the same time, the second element includes zirconium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetics of the positive electrode material. The improvement of the kinetics will bring about an improvement in the cycle performance, and the zinc and zirconium elements have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0043] In one or more embodiments of the present application, the positive electrode material further includes a third element, and the third element includes at least one of niobium element Nb, vanadium element V, or tungsten element W. The positive electrode material further includes a third element and the type of the third element is within the scope of the present application. The third element is a high-valent metal element, which can reduce the particle size. The small particle size can further improve the kinetic performance of the positive electrode material, and the improvement of the kinetic performance will bring about the improvement of the cycle performance; and the third element can improve the electronic conductivity and ionic conductivity, and improve the gram capacity and kinetic performance of the positive electrode material.

[0044] In the present application, based on the mass of the positive electrode material, the mass percentage content W3 of the third element is 0.03% to 0.75%.

[0045] In one or more embodiments of the present application, the third element includes niobium, and the mass ratio of magnesium to niobium is 5 to 9. Exemplarily, the mass ratio of magnesium to niobium can be 5, 6, 7, 8, 9 or a range consisting of any two of the above values. By regulating the type of the third element and the mass ratio of magnesium to the third element within the scope of the present application, the third element includes niobium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetic properties of the positive electrode material, and the improvement of the kinetic properties will bring about the improvement of the cycle performance; and the niobium element can improve the electronic conductivity and ionic conductivity, and improve the gram capacity and kinetic properties of the positive electrode material; doping with magnesium can reduce volume expansion, further improve the kinetic properties and cycle performance of the positive electrode material; and the magnesium element and the niobium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0046] In one or more embodiments of the present application, the third element includes vanadium, and the mass ratio of magnesium to vanadium is 2 to 5. Exemplarily, the mass ratio of magnesium to vanadium can be 2, 3, 4, 5 or a range consisting of any two of the above values. By regulating the type of the third element and the mass ratio of magnesium to the third element within the scope of the present application, the third element includes vanadium, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetic properties of the positive electrode material, and the improvement of the kinetic properties will bring about the improvement of the cycle performance; and the vanadium element can improve the electronic conductivity and ionic conductivity, and improve the gram capacity and kinetic properties of the positive electrode material; doping with magnesium can reduce volume expansion, further improve the kinetic properties and cycle performance of the positive electrode material; and the magnesium element and the vanadium element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0047] In one or more embodiments of the present application, the third element includes tungsten, and the mass ratio of magnesium to tungsten is 10 to 20. Exemplarily, the mass ratio of magnesium to tungsten can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or a range consisting of any two of the above values. By regulating the type of the third element and the mass ratio of magnesium to the third element within the scope of the present application, the third element includes tungsten, which is a high-valent metal element that can reduce the particle size. The small particle size can further improve the kinetic properties of the positive electrode material, and the improvement of the kinetic properties will bring about the improvement of the cycle performance; and the tungsten element can improve the electronic conductivity and ionic conductivity, and improve the gram capacity and kinetic properties of the positive electrode material; doping with magnesium can reduce volume expansion, further improve the kinetic properties and cycle performance of the positive electrode material; and the magnesium element and the tungsten element have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0048] In one or more embodiments of the present application, the positive electrode material further includes a fourth element, and the fourth element includes at least one of a sodium element Na or a potassium element K. The positive electrode material further includes a fourth element and the type of the fourth element is within the scope of the present application, and doping the fourth element at the lithium site can further improve the conductivity of the positive electrode material and further improve the kinetic performance of the positive electrode material.

[0049] In the present application, based on the mass of the positive electrode material, the mass percentage content W4 of the fourth element is 0.005% to 0.05%.

[0050] In one or more embodiments of the present application, the fourth element includes sodium, and the mass ratio of magnesium to sodium is 10 to 14. Exemplarily, the mass ratio of magnesium to sodium can be 10, 11, 12, 13, 14, or a range consisting of any two of the above values. By regulating the type of the fourth element and the mass ratio of magnesium to the fourth element within the scope of the present application, the fourth element includes sodium, and doping sodium at the lithium position can further improve the conductivity of the positive electrode material and further improve the kinetic properties of the positive electrode material; doping magnesium can reduce volume expansion and further improve the kinetic properties and cycle performance of the positive electrode material; and magnesium and sodium have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0051] In one or more embodiments of the present application, the fourth element includes potassium, and the mass ratio of magnesium to potassium is 10 to 20. Exemplarily, the mass ratio of magnesium to potassium can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or a range consisting of any two of the above values. By regulating the type of the fourth element and the mass ratio of magnesium to the fourth element within the scope of the present application, the fourth element includes potassium, and doping potassium at the lithium position can further improve the conductivity of the positive electrode material and further improve the kinetic properties of the positive electrode material; doping magnesium can reduce volume expansion and further improve the kinetic properties and cycle performance of the positive electrode material; and magnesium and potassium have a suitable mass ratio, and the positive electrode material has a higher capacity and compaction density.

[0052] In one or more embodiments of the present application, the mass ratio of magnesium to manganese Mn is 0.01 to 0.02. Exemplarily, the mass ratio of magnesium to manganese can be 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02 or a range consisting of any two of the above values. Doping with magnesium can improve the lattice volume change between the de-lithiated MnFeMgPO4 and the lithium-embedded LiMnFeMgPO4, reduce volume expansion, and further improve the kinetics and cycle performance of the positive electrode material. The manganese element in the positive electrode material can improve the energy density of the positive electrode material. By regulating the mass ratio of magnesium to manganese within the scope of the present application, the positive electrode material has a higher energy density while having higher kinetics and cycle performance.

[0053] The present application has no particular restrictions on the preparation method of the positive electrode material. Exemplarily, the preparation method of the positive electrode material may include but is not limited to the following steps: adding a manganese source, an iron source, a lithium source, a phosphorus source, and a doping element precursor to water in a certain molar ratio, adding glucose to obtain an intermediate solution, mixing and grinding the intermediate solution, and then spray granulating, sintering, cooling, and obtaining the positive electrode material by air flow grinding.

[0054] When glucose is added, glucose reacts with the precursor during heating, causing Mn 3+ / Fe 3+ Reduction to Mn 2+ / Fe 2+, forming LiFeMnPO4; and the addition of glucose can also form a carbon coating layer to improve the electronic conductivity of the positive electrode material. The positive electrode material includes lithium iron manganese phosphate. The above-mentioned precursors refer to manganese sources, iron sources, lithium sources and phosphorus sources. The present application has no special restrictions on the manganese source, as long as the purpose of the present application can be achieved. For example, the manganese source may include but is not limited to Mn3O4. The present application has no special restrictions on the iron source, as long as the purpose of the present application can be achieved. For example, the iron source may include but is not limited to FePO4. The present application has no special restrictions on the lithium source, as long as the purpose of the present application can be achieved. For example, the lithium source may include but is not limited to Li2CO3. The present application has no special restrictions on the phosphorus source, as long as the purpose of the present application can be achieved. For example, the phosphorus source may include but is not limited to LiH2PO4. The present application has no special restrictions on the doping element precursor, as long as the purpose of the present application can be achieved. For example, the doping element precursor may include but is not limited to the oxide, carbonate, hydroxide, sulfate or phosphate of the doping element. Exemplarily, the oxide of the doping element may include but is not limited to MgO, TiO2, NiO, CoO, ZnO, ZrO2, Nb2O5, V2O5 or WO3; the carbonate of the doping element may include but is not limited to Na2CO3 or K2CO3; the hydroxide of the doping element may include but is not limited to Mg(OH)2 or NaOH; the sulfate of the doping element may include but is not limited to MgSO4 or CoSO4; the phosphate of the doping element may include but is not limited to Na2HPO4 or NaH2PO4. The present application has no particular restrictions on the mass ratio of glucose to lithium manganese iron phosphate, as long as the purpose of the present application can be achieved. For example, the mass ratio of glucose to lithium manganese iron phosphate can be (0.04:1) to (0.2:1). The present application has no particular restrictions on the solid content of the intermediate solution, as long as the purpose of the present application can be achieved. For example, the solid content of the intermediate solution can be 20wt% to 35wt%. The present application has no particular limitation on the sintering temperature and sintering time, as long as the purpose of the present application can be achieved. For example, the sintering temperature can be 600° C. to 800° C.; the sintering time can be 6 h to 20 h.

[0055] The present application has no particular restrictions on the method for regulating the mass ratio of the first element to the second element, as long as the purpose of the present application can be achieved. For example, the positive electrode material can have the corresponding element by adding the corresponding doping element precursor, and then the mass ratio of the first element to the second element can be regulated by regulating the mass of the added corresponding doping element precursor.

[0056] The present application has no particular restrictions on the method for regulating the mass ratio of magnesium to the third element, as long as the purpose of the present application can be achieved. For example, the positive electrode material can have the corresponding element by adding the corresponding doping element precursor, and then the mass ratio of magnesium to the third element can be regulated by regulating the mass of the added corresponding doping element precursor.

[0057] The present application has no particular restrictions on the method for regulating the mass ratio of magnesium to the fourth element, as long as the purpose of the present application can be achieved. For example, the corresponding doping element precursor can be added to make the positive electrode material have the corresponding element, and then the mass ratio of magnesium to the fourth element can be regulated by regulating the mass of the added corresponding doping element precursor.

[0058] The present application has no particular restrictions on the method for regulating the mass ratio of magnesium to manganese, as long as the purpose of the present application can be achieved. For example, the corresponding doping element precursor can be added to make the positive electrode material have the corresponding element, and then the mass ratio of magnesium to manganese can be regulated by regulating the mass of the added corresponding doping element precursor and the mass of the manganese source.

[0059] The second aspect of the present application provides a positive electrode plate, which includes a positive electrode collector and a positive electrode material layer disposed on at least one surface of the positive electrode collector, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material includes the positive electrode material in any of the aforementioned embodiments. Therefore, the positive electrode plate is applied to a secondary battery, and the secondary battery has good dynamic performance and cycle performance, and also has a high capacity. The above-mentioned "positive electrode material layer disposed on at least one surface of the positive electrode collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode collector along the thickness direction of itself, or it can be disposed on two surfaces of the positive electrode collector along the thickness direction of itself. It should be noted that the "surface" here can be the entire area of ​​the positive electrode collector, or it can be a partial area of ​​the positive electrode collector. There is no special limitation in this application, as long as the purpose of this application can be achieved.

[0060] The present application has no particular limitation on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector).

[0061] The positive electrode material layer of the present application also includes a positive electrode conductor and a positive electrode binder. The present application has no special restrictions on the positive electrode conductor and the positive electrode binder in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the positive electrode conductor may include but is not limited to at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials or conductive polymers. The above-mentioned conductive carbon black may include but is not limited to at least one of Super P, acetylene black or Ketjen black. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powders and / or metal fibers. Specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymer may include but is not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. The positive electrode binder may include at least one of polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, polystyrene butadiene copolymer (styrene butadiene rubber, SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, lithium carboxymethyl cellulose, lithium polyacrylate, sodium hydroxymethyl cellulose or potassium hydroxymethyl cellulose. The present application has no particular restrictions on the mass ratio of the positive electrode active material, the positive electrode conductor, and the positive electrode binder in the positive electrode material layer, and those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved.

[0062] The present application has no particular limitation on the thickness of the positive electrode current collector, as long as the purpose of the present application can be achieved, for example, the thickness of the positive electrode current collector is 6 μm to 25 μm. The present application has no particular limitation on the thickness of the positive electrode material layer, as long as the purpose of the present application can be achieved, for example, the thickness of the single-sided positive electrode material layer is 25 μm to 250 μm.

[0063] Optionally, the positive electrode plate may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. The present application has no particular restrictions on the composition of the conductive layer, which may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, which may be at least one of the above-mentioned positive electrode conductive agent and the above-mentioned positive electrode binder. The present application has no particular restrictions on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved.

[0064] The third aspect of the present application provides a secondary battery, the secondary battery comprising the positive electrode sheet in any of the above embodiments. Therefore, the secondary battery provided by the present application has good dynamic performance and cycle performance, and also has a high capacity.

[0065] In the present application, the secondary battery also includes a negative electrode plate, which includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or a partial area of ​​the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0066] The present application has no particular limitation on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper or a composite current collector.

[0067] The negative electrode material layer of the present application includes a negative electrode active material. The present application has no particular limitation on the negative electrode active material, as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0.5<x<1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithium titanate Li4Ti5O 12 , Li-Al alloy or metallic lithium, etc. The negative electrode material layer of the present application also includes a negative electrode binder and a negative electrode conductive agent. The present application has no special restrictions on the negative electrode binder and the negative electrode conductive agent in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the negative electrode binder can be at least one of the above-mentioned positive electrode binders, and the negative electrode conductive agent can be at least one of the above-mentioned positive electrode conductive agents. The present application has no special restrictions on the mass ratio of the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent in the negative electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. The present application has no special restrictions on the Dv50 of the negative electrode active material, as long as the purpose of the present application can be achieved. In the present application, Dv50 refers to the particle size measured from the small particle size in the volume-based particle size distribution of the material to reach 50% of the volume accumulation.

[0068] The present application has no particular limitation on the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode current collector is 4 μm to 20 μm. The present application has no particular limitation on the thickness of the negative electrode material layer, as long as the purpose of the present application can be achieved, for example, the thickness of the single-sided negative electrode material layer is 30 μm to 250 μm.

[0069] Optionally, the negative electrode plate may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular restrictions on the composition of the conductive layer, which may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, which may be at least one of the above-mentioned negative electrode conductive agent and the above-mentioned negative electrode binder. The present application has no particular restrictions on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art may select according to actual needs, as long as the purpose of the present application can be achieved.

[0070] In the present application, the secondary battery also includes an electrolyte. The electrolyte includes a lithium salt. The present application has no particular restrictions on the type of lithium salt, and lithium salts known in the art can be used. For example, the lithium salt may include but is not limited to lithium hexafluorophosphate (LiPF6), lithium bistrifluoromethanesulfonyl imide (LiN(CF3SO2)2, LiTFSI), lithium bis(fluorosulfonyl) imide (Li(N(SO2F)2), LiFSI), lithium difluorophosphate (LiPO2F2), lithium bis(oxalate borate) (LiB(C2O4)2, LiBOB) or lithium difluorooxalate borate (LiBF2(C2O4), LiDFOB). The present application has no particular restrictions on the mass percentage of lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. The electrolyte also includes a non-aqueous organic solvent. The present application has no particular restrictions on the non-aqueous organic solvent, as long as the purpose of the present application can be achieved. For example, the non-aqueous organic solvent may include at least one of a carbonate compound, a carboxylate compound, an ether compound or other organic solvents. The carbonate compound may include but is not limited to at least one of a chain carbonate compound, a cyclic carbonate compound or a fluorinated carbonate compound. The chain carbonate compound may include but is not limited to at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC) or ethyl methyl carbonate (EMC). The cyclic carbonate compound may include but is not limited to at least one of ethylene carbonate (EC), vinylene carbonate, propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The fluorinated carbonate compound may include, but is not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The carboxylate compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate. The ether compound may include, but is not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The above-mentioned other organic solvents may include, but are not limited to, at least one of 1,3-propanesultone, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphate ester.The present application has no particular limitation on the mass percentage of the non-aqueous organic solvent in the electrolyte, as long as the purpose of the present application can be achieved.

[0071] In the present application, the secondary battery also includes a diaphragm. The diaphragm is used to separate the positive electrode plate and the negative electrode plate, prevent the internal short circuit of the secondary battery, allow the electrolyte ions to pass freely, and do not affect the electrochemical charge and discharge process. The present application has no special restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm may include but is not limited to polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of diaphragm may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane.

[0072] In the present application, the diaphragm may include a substrate and a surface treatment layer. The substrate may be a non-woven fabric or a composite film having a porous structure, and the material of the substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a diaphragm binder, and the present application has no particular restrictions on the above-mentioned inorganic particles, for example, it may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The present application has no particular restrictions on the above-mentioned diaphragm binder, for example, it may be at least one of the aforementioned negative electrode binders. The polymer layer contains a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene fluoride or vinylidene fluoride-hexafluoropropylene copolymer.

[0073] The secondary battery of the present application also includes a packaging bag for containing a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, as well as other components known in the art in the secondary battery, and the present application does not limit the above other components. The present application does not specifically limit the packaging bag, and it can be a packaging bag known in the art, as long as it can achieve the purpose of the present application.

[0074] The present application does not particularly limit the type of secondary battery, which may include any device that generates an electrochemical reaction. In the present application, the secondary battery may include, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery or a lithium ion polymer secondary battery (lithium ion polymer battery), etc.

[0075] The preparation process of the secondary battery of the present application is well known to those skilled in the art, and the present application has no special restrictions. For example, it may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the pre-lithiated negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly of a winding structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the positive electrode sheet, the separator and the pre-lithiated negative electrode sheet in order, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly of a stacked structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, overcurrent protection components, guide plates, etc. may also be placed in the packaging bag as needed to prevent the pressure inside the secondary battery from rising and overcharging and discharging.

[0076] The fourth aspect of the present application provides an electronic device, which includes the secondary battery in any of the above embodiments. Therefore, the electronic device provided by the present application has good dynamic performance and cycle performance, and also has a high capacity.

[0077] The present application does not particularly limit the type of electronic device, which can be any electronic device known in the prior art. In some embodiments, the electronic device can include but is not limited to a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0078] Example Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are by mass.

[0079] Test methods and equipment: Element mass ratio test: Disassemble the lithium-ion battery, take out the positive electrode sheet, clean the positive electrode sheet with DMC, and dry the positive electrode sheet. Then scrape the positive electrode material layer powder with a ceramic knife, and use an inductively coupled plasma emission spectrometer (ICP) to detect the types of elements in the positive electrode material layer powder and the mass ratio of different elements. Weigh 0.2g of the above positive electrode material layer powder, dissolve it in a nitric acid solution with a concentration of 42%, and then detect the nitric acid solution that dissolves the positive electrode material layer powder to obtain the types of elements in the positive electrode material layer powder and the mass ratio of different elements.

[0080] DC resistance (DCR) test: At 25°C, the lithium-ion battery is charged to 4.3V at a constant current of 0.1C, and then charged to 0.025C at a constant voltage of 4.3V, and left to stand for 10 minutes; then discharged at a constant current of 0.1C for 5 hours (at this time the lithium-ion battery is at a 50% state of charge); then discharged at a constant current of 1C for 1 second; the voltage before the above 1C constant current discharge is V0, the voltage after the above 1C constant current discharge is V1, and the current of the above 1C constant current discharge is A. The DC impedance R corresponding to the 50% state of charge (SOC) of the lithium-ion battery is calculated to be (V0-V1) / A.

[0081] The smaller the DC impedance corresponding to 50% state of charge (SOC) of a lithium-ion battery, the better the dynamic performance of the lithium-ion battery.

[0082] Cycle performance test: At 45°C, the lithium-ion battery is charged and discharged for the first time. The specific steps are: charge the lithium-ion battery to 4.3V at a constant current of 0.5C, charge to 0.025C at a constant voltage of 4.3V, let it stand for 10 minutes, and then discharge to 2.5V at a constant current of 0.5C. The ratio of the discharge energy to the discharge capacity in the above discharge process is the initial equalizing voltage, which is a charge and discharge cycle. According to the above steps, 100 cycles of charging and discharging are performed. The ratio of the discharge energy to the discharge capacity in the 100th cycle of discharge process is the equalizing voltage of the 100th cycle, and the difference between the equalizing voltage of the 100th cycle (cls) and the initial equalizing voltage is the equalizing voltage drop. Among them, the unit of discharge energy is mWh, and the unit of discharge capacity is Ah.

[0083] The smaller the average voltage drop, the better the stability of the positive electrode material and the better the cycle performance of the lithium-ion battery.

[0084] Gram Capacity Test: Take the positive electrode sheet in Example 1-1, punch it into small discs required for 2025 button batteries, and obtain positive electrode discs. Stack the lithium sheet, separator, and positive electrode disc in order to assemble into a button battery, and inject 50 microliters of electrolyte. The electrolyte includes a basic solvent and lithium salt LiPF6. The basic solvent is obtained by mixing EC:EMC:DEC in a mass ratio of 30:50:20, and the mass percentage of LiPF6 in the electrolyte is 12.5%.

[0085] At 25°C, the assembled button cell was charged to 4.3V at a constant current of 0.5C, then charged to 0.025C at a constant voltage of 4.3V, left to stand for 10 minutes, and then discharged to 2.5V at a constant current of 0.5C. The discharge capacity of the discharge process was recorded. Gram capacity = discharge capacity / mass of positive electrode material.

[0086] Example 1-1 <Preparation of positive electrode material> The manganese source Mn3O4, the iron source FePO4, the lithium source Li2CO3, the phosphorus source LiH2PO4, MgO, and TiO2 are designed according to the corresponding molar ratio of this embodiment. 0.6 Fe 0.3763 Mg 0.0203 Ti 0.0034 The molar ratio of PO4 is added to water, glucose is added, glucose and LiMn 0.6 Fe 0.3763 Mg 0.0203 Ti 0.0034 The mass ratio of PO4 is 0.15:1, and an intermediate solution is obtained. The solid content of the intermediate solution is 30wt%. The intermediate solution is mixed and ground, then spray granulated, and sintered in a nitrogen atmosphere. The sintering temperature is 700°C and the sintering time is 8h. Then it is cooled and pulverized by air flow to obtain the positive electrode material.

[0087] <Preparation of positive electrode sheet> After mixing the above-mentioned positive electrode material, positive electrode conductive agent Super P, and positive electrode binder polyvinylidene fluoride (PVDF) in a weight ratio of 96.7:0.8:2.5, N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred and mixed evenly to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry was 60wt%; the positive electrode slurry was evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 12μm, and dried at 90°C to obtain a positive electrode sheet coated with a positive electrode material layer on one side. Repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode material layer on both sides. Dry under vacuum conditions at 90°C for 1h, and then obtain a positive electrode sheet with a specification of 74mm×867mm after cold pressing, cutting, and slitting. Among them, the coating weight of the positive electrode material layer is 180g / m², and the compaction density of the cold pressing process is 2.3g / cm 3 .

[0088] <Preparation of negative electrode sheet> After mixing the negative electrode active material artificial graphite, the negative electrode conductive agent Super P, and the negative electrode binder lithium polyacrylate (PAA-Li) in a weight ratio of 97.3:1.5:1.2, deionized water is added as a solvent, and the mixture is stirred and mixed to obtain a negative electrode slurry, wherein the solid content of the negative electrode slurry is 50wt%; the negative electrode slurry is evenly coated on one surface of the negative electrode current collector copper foil with a thickness of 6μm, and dried at 110°C to obtain a negative electrode sheet coated with a negative electrode material layer on one side. Repeat the above steps on the other surface of the copper foil to obtain a negative electrode sheet coated with a negative electrode material layer on both sides. Dry under vacuum conditions at 110°C for 1h, and then cold press, cut and slit to obtain a negative electrode sheet with a specification of 78mm×875mm. Among them, the particle size Dv50 of the negative electrode active material artificial graphite is 14μm; the coating weight of the negative electrode material layer is 84g / m², and the compaction density of the cold pressing process is 1.6g / cm 3 .

[0089] <Preparation of Electrolyte> In an argon atmosphere glove box with a water content of less than 10ppm, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a mass ratio of EC:EMC:DEC=30:50:20 to obtain a base solvent, and then lithium salt lithium hexafluorophosphate (LiPF6) was added and mixed evenly to obtain an electrolyte. Based on the mass of the electrolyte, the mass percentage of lithium salt LiPF6 was 12.5%, and the remainder was the base solvent.

[0090] <Preparation of Separator> The membrane binder PVDF and inorganic particle alumina were mixed in a mass ratio of 1:2, NMP was added as a solvent, and an inorganic layer slurry with a solid content of 12wt% was prepared. The inorganic layer slurry was evenly coated on one surface of a polyethylene substrate with a thickness of 15μm, and dried at 85℃ for 4h to obtain a single-sided inorganic layer-coated membrane with a coating thickness of 3μm. Then PVDF was added to the NMP solvent and stirred evenly to prepare a polymer layer slurry with a solid content of 25wt%, and then the polymer layer slurry was evenly coated on the surface of the inorganic layer. The coating weight of the coated polymer layer slurry was 1.5mg / 1540.25mm 2 , and then dried at 85°C for 4 hours, and finally the polymer layer slurry was evenly coated on the other surface of the polyethylene substrate, and the coating weight of the polymer layer slurry was 1.5 mg / 1540.25 mm 2 , and then dried at 85°C for 4 hours to obtain a diaphragm coated with an inorganic layer and a polymer layer on one side and only a polymer layer on the other side.

[0091] <Preparation of lithium-ion batteries> The prepared positive electrode sheet, separator, negative electrode sheet and separator are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the electrode assembly is wound. After welding the pole ear, the electrode assembly is placed in an aluminum plastic film packaging bag, placed in an 85°C vacuum oven for 12 hours to remove moisture, and the electrolyte is injected. After vacuum packaging, standing, formation (charging to 3.3V at a constant current of 0.02C, and then charging to 4.3V at a constant current of 0.3C), degassing, trimming, and capacity processing steps, a lithium-ion battery is obtained.

[0092] Example 1-2 to Example 1-30 Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0093] Example 2-1 Except for preparing the positive electrode material according to the following method, the rest is the same as Example 1-1.

[0094] <Preparation of positive electrode material> The manganese source Mn3O4, the iron source FePO4, the lithium source Li2CO3, the phosphorus source LiH2PO4, MgO, TiO2, and Nb2O5 are designed according to the corresponding molar ratio of this embodiment. 0.6 Fe 0.3752 Mg 0.0203 Ti 0.0034 Nb 0.0011 The molar ratio of PO4 is added to water, glucose is added, glucose and LiMn 0.6 Fe 0.3752 Mg 0.0203 Ti 0.0034 Nb 0.0011 The mass ratio of PO4 is 0.15:1, and an intermediate solution is obtained. The solid content of the intermediate solution is 30wt%. The intermediate solution is mixed and ground, then spray granulated, and sintered in a nitrogen atmosphere. The sintering temperature is 700°C and the sintering time is 8h. Then it is cooled and pulverized by air flow to obtain the positive electrode material.

[0095] Example 2-2 to Example 2-12 Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as Example 2-1.

[0096] Example 2-13 Except for preparing the positive electrode material according to the following method, the rest is the same as Example 1-1.

[0097] <Preparation of positive electrode material> Manganese source Mn3O4, iron source FePO4, lithium source Li2CO3, phosphorus source LiH2PO4, MgO, TiO2, Na2CO3 are designed according to the corresponding molar ratio of this embodiment. 0.9979 Na 0.0021 Mn 0.6 Fe 0.3763 Mg 0.0203 Ti 0.0034 The molar ratio of PO4 is added to water, glucose is added, glucose and Li 0.9979 Na 0.0021 Mn 0.6 Fe 0.3763 Mg 0.0203 Ti 0.0034 The mass ratio of PO4 is 0.15:1, and an intermediate solution is obtained. The solid content of the intermediate solution is 30wt%. The intermediate solution is mixed and ground, then spray granulated, and sintered in a nitrogen atmosphere. The sintering temperature is 700°C and the sintering time is 8h. Then it is cooled and pulverized by air flow to obtain the positive electrode material.

[0098] Example 2-14 to Example 2-19 Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as Example 2-13.

[0099] Example 2-20 to Example 2-24 Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as Example 2-1.

[0100] Comparative Example 1 Except for preparing the positive electrode material according to the following method, the rest is the same as Example 1-1.

[0101] <Preparation of positive electrode material> The manganese source Mn3O4, the iron source FePO4, the lithium source Li2CO3, and the phosphorus source LiH2PO4 are designed according to the corresponding molar ratio of the comparative ratio. 0.6 Fe 0.4 The molar ratio of PO4 is added to water, glucose is added, glucose and LiMn 0.6 Fe 0.4 The mass ratio of PO4 is 0.15:1, and an intermediate solution is obtained. The solid content of the intermediate solution is 30wt%. The intermediate solution is mixed and ground, then spray granulated, and sintered in a nitrogen atmosphere. The sintering temperature is 700°C and the sintering time is 8h. Then it is cooled and pulverized by air flow to obtain the positive electrode material.

[0102] Comparative Examples 2 to 5 Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0103] The preparation parameters and electrical performance parameters of each embodiment and comparative example are shown in Tables 1 and 2.

[0104] Table 1

[0105] Note: (1) In Table 1, “ / ” indicates that there are no relevant preparation parameters; (2) Taking Example 1-1 as an example, “doping element precursor” is “MgO+TiO2”, “first element” is “Mg”, and “second element” is “Ti”, indicating that “MgO” is the doping element precursor corresponding to the first element Mg, and “TiO2” is the doping element precursor corresponding to the second element Ti, and the same applies to other examples; (3) Taking Example 1-25 as an example, “doping element precursor” is “MgO+NiO+TiO2”, “first element” is “Mg+Ni (mass ratio is 1:1)”, and “second element” is “Ti”, indicating that the first element includes Mg and Ni, “MgO” is the doping element precursor corresponding to Mg, “NiO” is the doping element precursor corresponding to Ni, and the mass ratio of Mg to Ni is 1:1, and “TiO2” is the doping element precursor corresponding to the second element Ti, and the same applies to other examples.

[0106] From Example 1-1 to Example 1-30, Comparative Example 1 to Comparative Example 5, it can be seen that when the positive electrode material includes lithium iron manganese phosphate, the positive electrode material includes the first element and the second element, and the type and mass ratio of the first element and the second element are within the scope of this application, the prepared lithium ion battery has a lower DC impedance, a lower average voltage drop and a higher gram capacity, indicating that the kinetic performance and cycle performance of the positive electrode material can be improved, and the positive electrode material also has a higher capacity. In Comparative Example 1, the positive electrode material does not include the first element and the second element, and the prepared lithium ion battery has a higher DC impedance, a higher average voltage drop and a lower gram capacity, indicating that the kinetic performance and cycle performance of the positive electrode material are relatively poor, and the capacity is low. In Comparative Example 2, the positive electrode material does not include the second element, and the prepared lithium ion battery has a higher DC impedance, a higher average voltage drop and a lower gram capacity, indicating that the kinetic performance and cycle performance of the positive electrode material are relatively poor, and the capacity is low. In Comparative Example 3, the positive electrode material does not include the first element, and the prepared lithium ion battery has a higher DC impedance, a higher average voltage drop and a lower gram capacity, indicating that the kinetic performance and cycle performance of the positive electrode material are relatively poor, and the capacity is low. In Comparative Examples 4 and 5, the mass ratio of the first element to the second element is not within the scope of the present application, and the prepared lithium-ion batteries have a higher DC impedance, a higher average voltage drop, and a lower gram capacity, indicating that the kinetic performance and cycle performance of the positive electrode material are relatively poor, and the capacity is low.

[0107] Depend on Figure 1It can be seen that the morphology of the positive electrode material of Example 1-1 is granular.

[0108] Table 2

[0109] Note: (1) In Table 2, “ / ” indicates no relevant preparation parameters; (2) Taking Example 2-1 as an example, “doping element precursor” is “MgO+TiO2+Nb2O5” and “the third element” is “Nb”, which means that the doping element precursor includes MgO and TiO2, and also includes Nb2O5. “Nb2O5” is the doping element precursor corresponding to the third element Nb, and the same applies to other examples; (3) In Example 2-1, the molar number of Mn element is the same as that in Example 1-1, and the mass ratio of Mg element to Ti element is the same as that in Example 1-1. The same applies to other examples.

[0110] The doping elements in the positive electrode material usually affect the kinetic performance, cycle performance and capacity of the positive electrode material. It can be seen from Examples 1-1, 2-1 to 2-12 that the positive electrode material also includes a third element, and the type of the third element and the mass ratio of the magnesium element to the third element are within the scope of this application. The prepared lithium-ion battery has a lower DC impedance, a lower average voltage drop and a higher gram capacity, indicating that the kinetic performance and cycle performance of the positive electrode material can be improved, while also making the positive electrode material have a higher capacity.

[0111] It can be seen from Example 1-1 and Example 2-13 to Example 2-19 that the positive electrode material also includes a fourth element, and the type of the fourth element and the mass ratio of the magnesium element to the fourth element are within the scope of the present application. The prepared lithium-ion battery has a lower DC impedance, a lower average voltage drop and a higher gram capacity, indicating that the kinetic performance and cycle performance of the positive electrode material can be improved, while also making the positive electrode material have a higher capacity.

[0112] It can be seen from Example 1-1 and Example 2-20 to Example 2-24 that the positive electrode material also includes a third element and a fourth element, and the types of the third element and the fourth element, the mass ratio of the magnesium element to the third element, and the mass ratio of the magnesium element to the fourth element are within the scope of the present application. The prepared lithium-ion battery has a lower DC impedance, a lower average voltage drop, and a higher gram capacity, indicating that the kinetic performance and cycle performance of the positive electrode material can be improved, while also making the positive electrode material have a higher capacity.

[0113] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method or article.

[0114] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0115] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A positive electrode material, comprising lithium iron manganese phosphate, the positive electrode material comprising a first element and a second element, the first element comprising at least one of magnesium, nickel, cobalt or zinc, the second element comprising at least one of titanium or zirconium, and the mass ratio of the first element to the second element is 1 to 20.

2. The positive electrode material according to claim 1, wherein At least a portion of the surface of the lithium manganese iron phosphate is provided with a carbon material.

3. The positive electrode material according to claim 1 or 2, wherein The first element includes magnesium, the second element includes titanium, and the mass ratio of the magnesium element to the titanium element is 1 to 8.

4. The positive electrode material according to claim 1 or 2, wherein The positive electrode material satisfies at least one of the following characteristics: (1) The first element includes nickel, the second element includes titanium, and the mass ratio of the nickel element to the titanium element is 1 to 15; (2) The first element includes cobalt, the second element includes titanium, and the mass ratio of the cobalt element to the titanium element is 1 to 15; (3) The first element includes zinc, the second element includes titanium, and the mass ratio of the zinc element to the titanium element is 1 to 20; (4) The first element includes magnesium, the second element includes zirconium, and the mass ratio of the magnesium element to the zirconium element is 1 to 4; (5) The first element includes nickel, the second element includes zirconium, and the mass ratio of the nickel element to the zirconium element is 1 to 6; (6) The first element includes cobalt, the second element includes zirconium, and the mass ratio of the cobalt element to the zirconium element is 1 to 6; (7) The first element includes zinc, and the second element includes zirconium, and a mass ratio of the zinc element to the zirconium element is 1 to 10.

5. The positive electrode material according to claim 3, wherein The positive electrode material further includes a third element, and the third element includes at least one of niobium, vanadium or tungsten.

6. The positive electrode material according to claim 5, wherein The third element includes niobium, and the mass ratio of the magnesium element to the niobium element is 5 to 9.

7. The positive electrode material according to claim 5, wherein The positive electrode material satisfies at least one of the following characteristics: (1) The third element includes vanadium, and the mass ratio of the magnesium element to the vanadium element is 2 to 5; (2) The third element includes tungsten, and the mass ratio of the magnesium element to the tungsten element is 10 to 20.

8. The positive electrode material according to claim 3, wherein The positive electrode material further includes a fourth element, and the fourth element includes at least one of a sodium element and a potassium element.

9. The positive electrode material according to claim 8, wherein The fourth element includes sodium element, and the mass ratio of the magnesium element to the sodium element is 10 to 14.

10. The positive electrode material according to claim 8, wherein The fourth element includes potassium, and the mass ratio of the magnesium element to the potassium element is 10 to 20.

11. The positive electrode material according to claim 3, wherein The mass ratio of the magnesium element to the manganese element is 0.01 to 0.

02. 12 . A positive electrode plate, comprising a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode material according to claim 1 . 13 . A secondary battery, comprising the positive electrode sheet according to claim 12 . 14 . An electronic device comprising the secondary battery according to claim 13 .

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