Positive electrode material and preparation method thereof, battery and electric device

Abstract

The invention provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a spinel positive electrode material and a carbon-coated phosphate positive electrode material; wherein the turbidity value of the carbon-coated phosphate positive electrode material is 1 NTU to 60 NTU. The positive electrode material provided by the invention has the advantages of low dissolution amount of transition metal ions and excellent cycle performance.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a positive electrode material and a preparation method thereof, a battery, and an electrical device. Background Art

[0002] In recent years, the application of lithium-ion batteries has become increasingly widespread. They are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As lithium-ion batteries have achieved significant development, higher performance requirements have been placed on them. Consequently, the market has also placed more diverse demands on cathode materials. Summary of the Invention

[0003] The present application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode material and a preparation method thereof. The positive electrode material includes a spinel positive electrode material and a carbon-coated phosphate positive electrode material with a turbidity value of 1NTU to 60NTU. For the carbon-coated phosphate positive electrode material with a turbidity value of 1NTU to 60NTU, its carbon coating layer is moderately dense and can effectively adsorb the transition metal ions to be dissolved in the spinel positive electrode material, thereby reducing the dissolution amount of transition metal ions and improving the cycle performance of the battery. In addition, the purpose of the present application is to provide a battery and an electrical device comprising the positive electrode material.

[0004] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode material, which includes a spinel positive electrode material and a carbon-coated phosphate positive electrode material; wherein the turbidity value of the carbon-coated phosphate positive electrode material is 1NTU to 60NTU. The positive electrode material of the present application includes a carbon-coated phosphate positive electrode material. The turbidity value of the carbon-coated phosphate positive electrode material is 1NTU to 60NTU, so that a moderately dense carbon coating layer exists on the surface of the phosphate positive electrode material. The moderately dense carbon coating layer has a strong adsorption effect on the transition metal ions to be dissolved, can better inhibit the transition metal ions from escaping into the electrolyte, reduce the dissolution amount of transition metal ions, and improve the cycle performance of the battery.

[0005] In some embodiments, the turbidity value of the carbon-coated phosphate cathode material is 8 NTU to 54 NTU. By controlling the turbidity value of the carbon-coated phosphate cathode material within the above range, it is beneficial to improve the cycle performance of the battery while suppressing the dissolution of transition metal ions.

[0006] In some embodiments, the turbidity value is measured according to the following method: 1 g of carbon-coated phosphate positive electrode material is uniformly dispersed in 35 ml of deionized water to obtain a dispersion; the dispersion is centrifuged at a speed of 3000 rpm for 30 minutes to obtain an upper liquid; 10 ml of the upper liquid is taken to test the turbidity to obtain the turbidity value.

[0007] In some embodiments, the carbon content of the carbon-coated phosphate cathode material is 0.85 wt % to 1.9 wt %. By controlling the carbon content within the above range, the turbidity value of the carbon-coated phosphate cathode material is maintained within a desired range, while the carbon coating does not adversely affect the phosphate cathode material's function as a cathode material.

[0008] In some embodiments, the carbon-coated phosphate cathode material includes small particles with an average particle size of less than 300 nm, medium particles with an average particle size of 300 nm to 800 nm, and large particles with an average particle size of greater than 800 nm and less than or equal to 3000 nm. The wide range of particle sizes of the carbon-coated phosphate cathode material particles facilitates better adhesion of the phosphate cathode material to the surface of the spinel cathode material, increases the contact area between the phosphate cathode material and the spinel cathode material, and enhances the adsorption capacity of the carbon coating layer of the phosphate cathode material for transition metal ions.

[0009] In some embodiments, the proportion of the small particles, XS, satisfies 60%≤XS≤80%, the proportion of the medium particles, XM, satisfies 10%≤XM≤36%, and the proportion of the large particles, XL, satisfies 4%≤XL≤10%. By controlling the proportion of small particles to a high level, the phosphate cathode material is better adhered to the surface of the spinel cathode material, increasing the contact area between the phosphate cathode material and the spinel cathode material, and further enhancing the adsorption capacity.

[0010] In some embodiments, the Dv50 of the carbon-coated phosphate cathode material is 0.5 μm to 2 μm; and / or the Dv50 of the spinel cathode material is 6 μm to 24 μm.

[0011] By controlling the Dv50 of the carbon-coated phosphate cathode material to 0.5 μm to 2 μm, it is beneficial for the carbon-coated phosphate cathode material particles to be uniformly attached to the surface of the spinel cathode material, which can increase the contact area between the carbon coating layer of the phosphate cathode material and the spinel cathode material, and is beneficial for the carbon coating layer to absorb Mn 2+ In addition, it is beneficial for the phosphate positive electrode material to exert its own gram capacity in the positive electrode material and achieve good cycle performance and processing performance.

[0012] By controlling the Dv50 of the spinel cathode material within the range of 6 μm to 24 μm, the spinel cathode material can exert its own specific capacity in the cathode material and achieve good cycle performance and processing performance.

[0013] In some embodiments, the ratio σ of the Dv50 of the spinel cathode material to the Dv50 of the carbon-coated phosphate cathode material satisfies σ = 7 to 20. By controlling σ within the above range, the carbon-coated phosphate cathode material has better adhesion to the spinel cathode material and good processing performance.

[0014] In some embodiments, the carbon-coated phosphate cathode material is attached to the spinel cathode material, thereby increasing the contact area between the carbon coating layer of the phosphate cathode material and the spinel cathode material, which is beneficial for the adsorption of transition metal ions by the carbon coating layer.

[0015] In some embodiments, the weight ratio ω of the carbon-coated phosphate cathode material to the spinel cathode material satisfies 0.3:9.7≤ω≤8:2. By controlling ω within the above range, the carbon-coated phosphate cathode material is able to exert its ability to adsorb transition metal ions, while the content of the spinel cathode material is maintained within an appropriate range, thereby facilitating the utilization of the advantages of the spinel cathode material.

[0016] In some embodiments, the weight ratio ω of the carbon-coated phosphate cathode material to the spinel cathode material satisfies 0.3:9.7≤ω≤1:1. By controlling ω within the above range, the carbon-coated phosphate cathode material and the spinel cathode material can further exert their respective advantages.

[0017] In some embodiments, the chemical formula of the spinel cathode material includes Li a A 2-b M b O 4-z X z , wherein 1≤a≤1.2, 0≤b≤0.6, 0≤z≤0.1; A includes Mn and optionally Ni; M includes at least one of V, Co, Mg, Fe, Al, Zn, Ca, Zr, Y, Nb, Mo, Cr, Li or W; and X includes at least one of S, F or Cl.

[0018] In some embodiments, the chemical formula of the spinel cathode material includes Li a A 2-b M b O 4-z X z, where 1≤a≤1.2, 0.001≤b≤0.6, and 0.001≤z≤0.1; A includes Mn and optionally Ni; M includes at least one of Co, Mg, Al, Zr, Mo, Li, or W; and X includes at least one of S, F, or Cl. The introduction of M and X can suppress the Jahn-Teller effect of the spinel cathode material during charge and discharge, thereby improving the stability of the spinel cathode material's crystal structure and reducing the possibility of transition metal ion dissolution.

[0019] In some embodiments, the chemical formula of the phosphate cathode material includes Li α Fe 1-β E β PO 4-n-δ D n , wherein E comprises at least one of Mn, Ti, V, Zr, Ni, Mg, Co, Ga, Sn, Sb, Nb, or Ge, D comprises at least one of S, F, Cl, or Br, 0.9≤α≤1.1, 0≤β≤1, 0≤n≤0.1, and -0.1≤δ≤0.1. The above-mentioned phosphate positive electrode material can, on the one hand, serve as a carrier for the carbon coating layer, and on the other hand, the phosphate positive electrode material itself can also be used as a positive electrode material, thereby performing the carrier function without sacrificing the specific capacity of the positive electrode material.

[0020] The second aspect of the present application provides a method for preparing a positive electrode material, the method comprising: providing a spinel positive electrode material; providing a carbon-coated phosphate positive electrode material, wherein the turbidity value of the carbon-coated phosphate positive electrode material is 1NTU to 60NTU; treating the spinel positive electrode material and the carbon-coated phosphate positive electrode material to form the positive electrode material. A positive electrode material comprising a spinel positive electrode material and a carbon-coated phosphate positive electrode material having a turbidity value of 1NTU to 60NTU is prepared by this method. For the carbon-coated phosphate positive electrode material having a turbidity value of 1NTU to 60NTU, its carbon coating layer is moderately dense and can effectively adsorb transition metal ions to be dissolved in the spinel positive electrode material, thereby reducing the dissolution amount of transition metal ions and improving the cycle performance of the battery.

[0021] In some embodiments, providing a carbon-coated phosphate positive electrode material includes: mixing a first lithium source, an iron source, a phosphorus source, an optional E source, an optional D source and a first carbon source to obtain a first mixture, wherein the first carbon source includes a solid carbon source; performing a first sintering on the first mixture under an inert gas atmosphere, and at the same time, applying a second carbon source to the first mixture so that the first mixture undergoes the first sintering in the presence of the second carbon source, thereby obtaining the carbon-coated phosphate positive electrode material, wherein the second carbon source includes a liquid carbon source; wherein the E source includes at least one of an oxide, hydroxide or salt of an E element, and the E element includes at least one of Mn, Ti, V, Zr, Ni, Mg, Co, Ga, Sn, Sb, Nb or Ge, and the D source includes at least one of a simple substance or salt of the D element, and the D element includes at least one of S, F, Cl or Br.

[0022] In some embodiments, the first carbon source comprises at least one of polyethylene glycol, glucose, sucrose, or starch; and / or the second carbon source comprises at least one of acetone, methanol, ethanol, or ethylene glycol.

[0023] In some embodiments, the amount of the first carbon source added is 0.29 wt% to 1.37 wt% relative to the total weight of the first lithium source, iron source, phosphorus source, optional E source, and optional D source; and / or, the amount of the second carbon source added is 0.10% wt% to 0.91 wt% relative to the total weight of the first lithium source, iron source, phosphorus source, optional E source, and optional D source.

[0024] In some embodiments, the mass ratio of the first carbon source to the second carbon source is 1:1 to 4:1, calculated based on the mass of carbon elements.

[0025] In some embodiments, the mixing ratio of the first lithium source, iron source, E source, phosphorus source and D source is α:1-β:β:1:n, based on the molar ratio of lithium element, iron element, E element, phosphorus element and D element, wherein 0.9≤α≤1.1, 0≤β≤1, and 0≤n≤0.1.

[0026] In some embodiments, applying the second carbon source to the first mixture includes spraying the second carbon source onto a surface of the first mixture.

[0027] In some embodiments, the sintering temperature of the first sintering is 500° C. to 800° C.; and / or the sintering time of the first sintering is 5 hours to 16 hours.

[0028] In some embodiments, providing the spinel positive electrode material includes: mixing a second lithium source, an A source, an optional M source, and an optional X source to obtain a second mixture, wherein the mixing ratio of the second lithium source, the A source, the M source, and the X source is a:2-b:b:z, based on the molar ratio of the lithium element, the A element, the M element, and the X element, wherein 1≤a≤1.2, 0≤b≤0.6, and 0≤z≤0.1, and the A source includes at least one of an oxide, hydroxide, or salt of the A element, the A element includes Mn and optionally Ni, the M source includes at least one of an oxide, hydroxide, or salt of the M element, the M element includes at least one of V, Co, Mg, Fe, Al, Zn, Ca, Zr, Y, Nb, Mo, Cr, Li, or W, and the X source includes at least one of a simple substance or oxide of the X element, the X element includes at least one of S, F, or Cl; and performing a second sintering on the second mixture to obtain the spinel positive electrode material.

[0029] In some embodiments, the sintering temperature of the second sintering is 500° C. to 950° C.; and / or the sintering time of the second sintering is 5 hours to 30 hours.

[0030] The third aspect of the present application provides a positive electrode plate, which includes a positive electrode collector and a positive electrode film layer located on at least one surface of the positive electrode collector, and the positive electrode film layer includes the positive electrode material of the first aspect or the positive electrode material prepared according to the method of the second aspect.

[0031] The fourth aspect of the present application provides a battery, comprising the positive electrode sheet of the third aspect of the present application.

[0032] The fifth aspect of the present application provides an electrical device comprising the battery of the fourth aspect of the present application.

[0033] The present application provides a positive electrode material. The positive electrode material comprises a spinel positive electrode material and a carbon-coated phosphate positive electrode material; wherein the carbon-coated phosphate positive electrode material has a turbidity value of 1 to 60 NTU. Thus, a moderately dense carbon coating layer exists on the surface of the phosphate positive electrode material. The moderately dense carbon coating layer can effectively adsorb transition metal ions that are about to be dissolved from the spinel positive electrode material, thereby reducing the amount of transition metal ions dissolved and improving the cycle performance of the battery.

[0034] The present application also provides a method for preparing a positive electrode material. The positive electrode material prepared by this method includes a spinel positive electrode material and a carbon-coated phosphate positive electrode material; wherein the turbidity value of the carbon-coated phosphate positive electrode material is 1 NTU to 60 NTU. As a result, a moderately dense carbon coating layer is present on the surface of the phosphate positive electrode material. The moderately dense carbon coating layer can effectively adsorb transition metal ions that are about to be dissolved from the spinel positive electrode material, thereby reducing the amount of transition metal ions dissolved and improving the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of a battery cell according to one embodiment of the present application.

[0036] Figure 2 yes Figure 1 FIG. 1 is an exploded view of a battery cell according to an embodiment of the present application.

[0037] Figure 3 Schematic diagram of a battery module according to one embodiment of the present application.

[0038] Figure 4 Schematic diagram of a battery pack according to one embodiment of the present application.

[0039] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0040] Figure 6 Schematic diagram of an electrical device using a battery as a power source according to one embodiment of the present application.

[0041] Figure 7 This is a scanning electron microscope image of the positive electrode material of Example 1 of the present application.

[0042] Figure 8 This is the first cycle charge and discharge curve of a button battery prepared using the positive electrode material of Example 1 of the present application.

[0043] Figure 9 This is a cycle capacity retention curve of a battery prepared using the positive electrode material of Example 1 of the present application.

[0044] Description of reference numerals:

[0045] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0046] Below, the cathode material and its preparation method, battery and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0047] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0049] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0050] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0051] Unless otherwise specified, the terms used in this application have the common meanings generally understood by those skilled in the art.

[0052] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in this application.

[0053] Unless otherwise specified, the term "Dv50" in this application has a well-known meaning in the art, representing the particle size corresponding to the 50% cumulative volume distribution percentage of a material. Dv50 can be measured using instruments and methods known in the art. For example, it can be measured using a laser particle size analyzer in accordance with GB / T 19077-2016. An example of such a measuring instrument may be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0054] Unless otherwise specified, in this application, the term "active ions" refers to ions that can be intercalated and extracted back and forth between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.

[0055] Spinel cathode materials have attracted much attention due to their abundant resources, low cost, good safety, and environmental friendliness, and are considered to be a promising cathode material. However, during charging and discharging, the transition metal ions (e.g., manganese ions) inside the spinel cathode material have serious dissolution problems, which leads to the Jahn-Teller effect and loss of active substances. The dissolved transition metal ions will escape into the electrolyte, migrate and deposit on the surface of the negative electrode, destroying the solid electrolyte interface (SEI) film of the negative electrode, accelerating the battery capacity decay, and reducing the battery's cycle performance. Extensive research has been conducted in the industry to address the problem of transition metal ion dissolution, but current research results still cannot effectively inhibit the dissolution and deposition of transition metal ions (e.g., manganese ions) on the negative electrode.

[0056] Therefore, the problem of how to reduce the dissolution of transition metal ions in spinel positive electrode materials and improve the cycle performance of batteries still needs to be further solved.

[0057] Based on this, the present application proposes a positive electrode material and a preparation method thereof, as well as a battery and an electrical device using the positive electrode material as a positive electrode active material. The present invention and optional embodiments are described in more detail below.

[0058] cathode materials

[0059] In a first aspect, the present application provides a positive electrode material comprising a spinel positive electrode material and a carbon-coated phosphate positive electrode material, wherein the turbidity value of the carbon-coated phosphate positive electrode material is 1 NTU to 60 NTU.

[0060] The cathode material of the present application includes a carbon-coated phosphate cathode material. The turbidity value of the carbon-coated phosphate cathode material is controlled to be between 1 and 60 NTU, thereby forming a moderately dense carbon coating layer on the surface of the phosphate cathode material. The moderately dense carbon coating layer has a strong adsorption effect on the transition metal ions that are about to be dissolved from the spinel cathode material, effectively suppressing the escape of the transition metal ions into the electrolyte and reducing the amount of transition metal ions dissolved.

[0061] On the one hand, the phosphate positive electrode material can act as a carrier for supporting the carbon coating layer. On the other hand, the phosphate positive electrode material itself can also be used as a positive electrode material, thereby playing the role of a carrier without losing the gram capacity of the positive electrode material.

[0062] In related technologies, transition metal ions that escape from spinel cathode materials into the electrolyte can deposit on the anode, damaging the SEI membrane and increasing the consumption of active lithium, thereby accelerating battery capacity decay. The carbon-coated phosphate cathode material in this application has a moderate turbidity value and can effectively adsorb transition metal ions that would otherwise dissolve into the electrolyte, reducing the amount of transition metal ions dissolved, thereby improving cycle performance.

[0063] In the present application, the turbidity value is an indicator for characterizing the density of the carbon coating layer of the carbon-coated phosphate positive electrode material. A small turbidity value indicates that the carbon-coated phosphate positive electrode material has poor dispersibility in water and is prone to agglomeration and sedimentation. In this case, the carbon coating layer has few polar functional groups, a high degree of graphitization, and a dense coating. The polar functional groups of the carbon coating layer originate from the carbon source that generates the carbon coating layer. During the process of graphitization of the carbon source to generate the carbon coating layer, a portion of the polar functional groups remain on the carbon coating layer due to differences in the degree of decomposition. The higher the degree of decomposition of the carbon source, the higher the degree of graphitization, and the fewer polar functional groups remain on the carbon coating layer. The fewer polar functional groups remain on the carbon coating layer, the smaller the interaction force between the carbon-coated phosphate positive electrode material and water in the aqueous dispersion, and the easier it is to agglomerate and settle, resulting in a smaller turbidity value of the carbon-coated phosphate positive electrode material in the aqueous dispersion. On the contrary, the more polar functional groups remain on the carbon coating layer, the greater the interaction between the carbon-coated phosphate cathode material and water in the aqueous dispersion, and it is less likely to agglomerate and settle, resulting in a greater turbidity value of the carbon-coated phosphate cathode material in the aqueous dispersion.

[0064] In the present application, the turbidity value is measured according to the following method: 1 g of carbon-coated phosphate positive electrode material is uniformly dispersed in 35 ml of deionized water to obtain a dispersion; the dispersion is centrifuged at a speed of 3000 rpm for 30 minutes to obtain an upper layer liquid; 10 ml of the upper layer liquid is taken to test the turbidity to obtain the turbidity value.

[0065] In the present application, there is no particular limitation on the method for testing the turbidity of the upper liquid, and a turbidity testing method commonly used in the art, such as a scattering method, can be used.

[0066] In some embodiments, the turbidity value of the carbon-coated phosphate cathode material is 1 NTU to 60 NTU, optionally 8 NTU to 54 NTU. For example, the turbidity value of the carbon-coated phosphate cathode material can be 1 NTU, 2 NTU, 5 NTU, 8 NTU, 10 NTU, 20 NTU, 30 NTU, 40 NTU, 50 NTU, 60 NTU, or a range between any two values, but is not limited thereto. By controlling the turbidity value of the carbon-coated phosphate cathode material within the above range, the dissolution amount of transition metal ions can be reduced, thereby improving the cycle performance of the battery.

[0067] In some embodiments, the carbon-coated phosphate positive electrode material is attached to the spinel positive electrode material. As a result, the contact area between the carbon coating layer of the phosphate positive electrode material and the spinel positive electrode material can be increased, which is beneficial to the adsorption of transition metal ions by the carbon coating layer. Optionally, the particles of the carbon-coated phosphate positive electrode material are also distributed between the particles of the spinel positive electrode material. The particles of the carbon-coated phosphate positive electrode material distributed between the particles of the spinel positive electrode material are beneficial to increasing the processing performance of the positive electrode material, such as increasing the compaction density.

[0068] In the present application, the spinel cathode material includes a lithium transition metal oxide. The lithium transition metal oxide may be undoped or doped. When the lithium transition metal oxide is doped, the doped element can suppress the Jahn-Teller effect of the spinel cathode material during the charge and discharge process, thereby improving the stability of the crystal structure of the spinel cathode material and reducing the possibility of transition metal ions undergoing disproportionation reactions to generate soluble transition metal ions. As a result, the amount of transition metal ions dissolved can be further reduced.

[0069] In some embodiments, the chemical formula of the spinel cathode material includes Li a A 2-b M b O 4-z X z, wherein 1≤a≤1.2, 0≤b≤0.6, and 0≤z≤0.1; A comprises a transition metal element, optionally, A comprises Mn and optionally Ni; M comprises a transition metal site doping element, optionally, M comprises at least one of V, Co, Mg, Fe, Al, Zn, Ca, Zr, Y, Nb, Mo, Cr, Li, or W; and X comprises an oxygen site doping element, optionally, X comprises at least one of S, F, or Cl.

[0070] In some embodiments, 1≤a≤1.2. For example, a can be 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, or a value between any two values, but is not limited thereto.

[0071] In some embodiments, 0≤b≤0.6. For example, b can be 0, 0.001, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58, 0.6, or a range between any two values, but is not limited thereto.

[0072] In some embodiments, 0≤z≤0.1. For example, z can be 0, 0.001, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.1, or a range between any two values, but is not limited thereto.

[0073] In some embodiments, the chemical formula of the spinel cathode material includes Li a A 2-b M b O 4-z X z , wherein 1≤a≤1.2, 0.001≤b≤0.6, 0.001≤z≤0.1; A comprises a transition metal element, optionally, A comprises Mn and optionally Ni; M comprises a transition metal site doping element, optionally, M comprises at least one of Co, Mg, Al, Zr, Mo, Li or W; X comprises an oxygen site doping element, optionally, X comprises at least one of S, F or Cl.

[0074] Optionally, in the above-mentioned spinel positive electrode material, the transition metal sites and / or oxygen sites in the spinel positive electrode material are at least partially doped with a transition metal site doping element M and / or an oxygen site doping element X. The transition metal site doping element M and / or the oxygen site doping element X can suppress the Jahn-Teller effect of the spinel positive electrode material during charge and discharge, thereby improving the stability of the crystal structure of the spinel positive electrode material and reducing the possibility of transition metal ion dissolution.

[0075] In some embodiments, the Dv50 of the spinel positive electrode material is 6 μm to 24 μm. For example, the Dv50 of the spinel positive electrode material can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, or a range between any two values, but is not limited thereto. By controlling the Dv50 of the spinel positive electrode material within the above range, it is beneficial for the spinel positive electrode material to exert its own gram capacity in the positive electrode material and achieve good cycle performance and processing performance.

[0076] In some embodiments, the chemical formula of the phosphate cathode material includes Li α Fe 1-β E β PO 4-n-δ D n , wherein E includes at least one of Mn, Ti, V, Zr, Ni, Mg, Co, Ga, Sn, Sb, Nb or Ge, D includes at least one of S, F, Cl or Br, 0.9≤α≤1.1, 0≤β≤1, 0≤n≤0.1, and -0.1≤δ≤0.1.

[0077] In some embodiments, the chemical formula of the phosphate cathode material includes Li α Fe 1-β Mn β PO4, optionally including LiFe 1-β Mn βPO4, wherein 0.9≤α≤1.1, 0≤β≤1. For example, α can be 0.9, 1 or 1.1, but is not limited thereto. Alternatively, α can be 1. For example, β can be 0, 0.1, 0.15, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1 or a value between the ranges consisting of any two values, but is not limited thereto. Alternatively, β can be 0 or 1. Alternatively, β can be 0. On the one hand, the above-mentioned phosphate positive electrode material can act as a carrier for supporting the carbon coating layer, and on the other hand, the phosphate positive electrode material itself can also be used as a positive electrode material, thereby playing the role of a carrier without losing the gram capacity of the positive electrode material.

[0078] In some embodiments, the carbon-coated phosphate cathode material has a Dv50 of 0.5 μm to 2 μm. For example, the Dv50 of the carbon-coated phosphate positive electrode material can be 0.5μm, 0.55μm, 0.6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm, 0.95μm, 1μm, 1.05μm, 1.1μm, 1.15μm, 1.2μm, 1.25μm, 1.3μm, 1.35μm, 1.4μm, 1.45μm, 1.5μm, 1.55μm, 1.6μm, 1.65μm, 1.7μm, 1.75μm, 1.8μm, 1.85μm, 1.9μm, 1.95μm, 2μm or a value between the range consisting of any two values, but is not limited to this. By controlling the Dv50 of the carbon-coated phosphate cathode material within the above range, it is beneficial for the carbon-coated phosphate cathode material particles to be uniformly attached to the surface of the spinel cathode material, which can increase the contact area between the carbon coating layer of the phosphate cathode material and the spinel cathode material, and is beneficial for the carbon coating layer to absorb Mn 2+ In addition, it is beneficial for the phosphate positive electrode material to exert its own gram capacity in the positive electrode material and achieve good cycle performance and processing performance.

[0079] In some embodiments, the ratio σ of the Dv50 of the spinel positive electrode material to the Dv50 of the carbon-coated phosphate positive electrode material satisfies σ=7-20. For example, σ can be 7, 7.3, 8, 9, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, or a range between any two values, but is not limited thereto. By controlling σ within the above range, the carbon-coated phosphate positive electrode material has a better adhesion effect on the spinel positive electrode material, and is also conducive to having good processing performance.

[0080] In some embodiments, the carbon-coated phosphate cathode material includes small particles with an average particle size of less than 300 nm, medium particles with an average particle size of 300 nm to 800 nm, and large particles with an average particle size of greater than 800 nm and less than or equal to 3000 nm. The wide range of particle sizes of the carbon-coated phosphate cathode material particles facilitates better adhesion of the phosphate cathode material to the surface of the spinel cathode material, increases the contact area between the phosphate cathode material and the spinel cathode material, and enhances the adsorption capacity of the carbon coating layer of the phosphate cathode material for transition metal ions.

[0081] The carbon-coated phosphate cathode material mentioned in this application includes small particles, medium particles, and large particles, which can be directly observed and distinguished in a microscopic image of a cross-section of the carbon-coated phosphate cathode material (e.g., a scanning electron microscope image). Small particles, medium particles, and large particles can be distinguished through microscopic images, and parameters such as the average particle size and number percentage of small particles, medium particles, and large particles can be obtained through measurement and statistics.

[0082] In some embodiments, in the carbon-coated phosphate positive electrode material, the proportion XS of small particles with an average particle size of less than 300 nm satisfies 60%≤XS≤80%, the proportion XM of medium particles with an average particle size of 300 nm to 800 nm satisfies 10%≤XM≤36%, and the proportion XL of large particles with an average particle size greater than 800 nm and less than or equal to 3000 nm satisfies 4%≤XL≤10%. For example, XS can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or a value between any two values, but is not limited thereto. For example, XM can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, or a value between any two values, but is not limited to this. For example, XL can be 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 5.2%, 5.4%, 5.6%, 5.8%, 6%, 6.2%, 6.4%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.6%, 7.8%, 8%, 8.2%, 8.4%, 8.6%, 8.8%, 9%, 9.2%, 9.4%, 9.6%, 9.8%, 10% or a value between the ranges consisting of any two values, but is not limited thereto. In these embodiments, the number of small particles with an average particle size of less than 300 nm accounts for a high proportion, which is conducive to better adhesion of the phosphate positive electrode material to the surface of the spinel positive electrode material, increasing the contact area between the phosphate positive electrode material and the spinel positive electrode material, and further enhancing the adsorption capacity.

[0083] In some embodiments, the carbon content of the carbon-coated phosphate positive electrode material is 0.8 wt % to 2 wt %, optionally 0.85 wt % to 1.9 wt %. For example, the carbon content of the carbon-coated phosphate positive electrode material can be 0.8 wt %, 0.85 wt %, 0.9 wt %, 0.95 wt %, 1 wt %, 1.05 wt %, 1.1 wt %, 1.15 wt %, 1.2 wt %, 1.25 wt %, 1.3 wt %, 1.35 wt %, 1.4 wt %, 1.45 wt %, 1.5 wt %, 1.55 wt %, 1.6 wt %, 1.65 wt %, 1.7 wt %, 1.75 wt %, 1.8 wt %, 1.85 wt %, 1.9 wt %, 1.95 wt %, 2 wt %, or a value between any two values, but is not limited thereto. By controlling the carbon content within the above range, on the one hand, it is beneficial to maintain the turbidity value of the carbon-coated phosphate positive electrode material within the required range, and on the other hand, the carbon coating will not adversely affect the phosphate positive electrode material's function as a positive electrode material.

[0084] In some embodiments, in the positive electrode material, the weight ratio ω of the carbon-coated phosphate positive electrode material to the spinel positive electrode material satisfies 0.3:9.7≤ω≤8:2, optionally 0.3:9.7≤ω≤7:3, optionally 0.3:9.7≤ω≤1:1. For example, ω can be 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9, 0.5:9.5, 0.3:9.7 or a value between the ranges consisting of any two values, but is not limited thereto. By controlling ω within the above range, it is beneficial for the carbon-coated phosphate positive electrode material to exert its ability to adsorb transition metal ions (for example, Mn 2+ ) and at the same time keeping the content of spinel positive electrode material within an appropriate range is conducive to giving full play to the advantages of the spinel positive electrode material itself.

[0085] It should be noted that in the embodiments of the present application, the chemical formulas of the spinel positive electrode material and the phosphate positive electrode material are the chemical formulas of the materials used in the battery preparation process. In the positive electrode sheets, battery cells, and electrical devices, due to the formation and circulation processes, those skilled in the art will understand that the elements in the above chemical formulas may be lost. For example, in the positive electrode sheets, battery cells, and electrical devices, due to the circulation processes, the oxygen element in the positive electrode material is lost, so the measured oxygen content in the positive electrode material will be reduced.

[0086] It should be noted that lithium ions are consumed in the positive electrode sheets, battery cells, and electrical devices during the formation and circulation processes, resulting in a decrease in the measured lithium content in the positive electrode material. Furthermore, if lithium is replenished in the positive and negative electrode sheets, the measured lithium content in the positive electrode material may increase after the formation and circulation processes.

[0087] Method for preparing positive electrode material

[0088] In a second aspect, the present application provides a method for preparing a positive electrode material. The method comprises:

[0089] Provide spinel cathode materials;

[0090] Providing a carbon-coated phosphate cathode material, wherein the turbidity value of the carbon-coated phosphate cathode material is 1 NTU to 60 NTU;

[0091] The spinel cathode material and the carbon-coated phosphate cathode material are processed to form the cathode material.

[0092] In the above method, a positive electrode material is obtained using a spinel positive electrode material and a carbon-coated phosphate positive electrode material having a turbidity value of 1 to 60 NTU. A moderately dense carbon coating layer is present on the surface of the carbon-coated phosphate positive electrode material having a turbidity value of 1 to 60 NTU. This moderately dense carbon coating layer has a strong adsorption effect on transition metal ions that are intended to be dissolved from the spinel positive electrode material, effectively suppressing the escape of transition metal ions into the electrolyte, reducing the amount of transition metal ions dissolved, and improving the cycle performance of the battery.

[0093] In some embodiments, treating the spinel positive electrode material and the carbon-coated phosphate positive electrode material may include mixing the spinel positive electrode material and the carbon-coated phosphate positive electrode material. In some embodiments, treating the spinel positive electrode material and the carbon-coated phosphate positive electrode material may include mixing the spinel positive electrode material and the carbon-coated phosphate positive electrode material and ball milling. By treating the spinel positive electrode material and the carbon-coated phosphate positive electrode material, the carbon-coated phosphate positive electrode material is attached to the spinel positive electrode material. Thereby, the contact area between the carbon coating layer of the phosphate positive electrode material and the spinel positive electrode material can be increased, which is beneficial to the adsorption of transition metal ions by the carbon coating layer.

[0094] In some embodiments, providing a carbon-coated phosphate cathode material comprises: mixing a first lithium source, an iron source, a phosphorus source, an optional E source, an optional D source, and a first carbon source to obtain a first mixture, wherein the first carbon source comprises a solid carbon source;

[0095] Performing a first sintering on the first mixture under an inert gas atmosphere, and at the same time, adding a second carbon source to the first mixture, so that the first mixture is first sintered in the presence of the second carbon source, thereby obtaining the carbon-coated phosphate positive electrode material, wherein the second carbon source comprises a liquid carbon source;

[0096] Wherein, the E source includes at least one of an oxide, hydroxide or salt of an E element, and the E element includes at least one of Mn, Ti, V, Zr, Ni, Mg, Co, Ga, Sn, Sb, Nb or Ge,

[0097] The D source includes at least one of a simple substance or a salt of a D element, and the D element includes at least one of S, F, Cl or Br.

[0098] In the above method, on the one hand, the solid carbon source can be evenly dispersed in the raw material for forming the phosphate positive electrode material, and on the other hand, while performing the first sintering, a liquid carbon source is applied to achieve synchronous reduction of the solid carbon source and the liquid carbon source. Thus, by adopting a specific first carbon source and applying a specific second carbon source at the same time during the sintering process, it is beneficial to form a carbon coating layer with moderate density on the surface of the phosphate positive electrode material. The carbon coating layer with moderate density has a strong adsorption effect on the transition metal ions in the spinel positive electrode material, can better inhibit the escape of transition metal ions into the electrolyte, reduce the dissolution amount of transition metal ions, and improve the cycle performance of the battery.

[0099] The first lithium source includes a substance that can provide lithium elements, for example, can include one or more of lithium carbonate (Li2CO3), lithium dihydrogen phosphate (LiH2PO4), and lithium phosphate (Li3PO4).

[0100] The iron source includes substances that can provide iron elements, for example, one or more of ferrous sulfate heptahydrate (FeSO4·7H2O), ferric sulfate (Fe2(SO4)3), ferric phosphate (FePO4), ferrous chloride (FeCl2), ferrous oxalate (FeC2O4), ferrous oxide (Fe2O3), and ferrous sulfate (FeSO4), but is not limited thereto.

[0101] The phosphorus source includes a substance that can provide phosphorus element, for example, it can include one or more of ammonium dihydrogen phosphate (NH4H2PO4) and phosphoric acid (H3PO4).

[0102] The D source includes a substance that can provide the D element. The D element includes at least one of S, F, Cl, or Br. The D source may include, for example, at least one of the elements or salts thereof. For example, the D source may include one or more of elemental sulfur (S), lithium fluoride, sodium fluoride, potassium fluoride, ammonium fluoride, lithium chloride, sodium chloride, potassium chloride, aluminum chloride, magnesium chloride, lithium bromide, sodium bromide, potassium bromide, aluminum bromide, and magnesium bromide, but is not limited thereto.

[0103] The E source includes a substance that can provide the E element. The E element includes at least one of Mn, Ti, V, Zr, Ni, Mg, Co, Ga, Sn, Sb, Nb, or Ge. The E source may, for example, include at least one of the oxides, hydroxides, or salts of these elements. For example, the E source may include one or more of manganese dioxide (MnO2), titanium dioxide (TiO2), vanadium pentoxide (V2O5), zirconium dioxide (ZrO2), nickel carbonate (NiCO3), magnesium oxide (MgO), cobalt trioxide (Co3O4), gallium trioxide (Ga2O3), tin dioxide (SnO2), antimony trioxide (Sb2O3), niobium pentoxide (Nb2O5), and germanium dioxide (GeO2).

[0104] In some embodiments, the E element may include manganese. Accordingly, the E source may include a manganese source. The manganese source includes substances that can provide the manganese element, for example, one or more of manganese sulfate (MnSO4), manganese phosphate (Mn3(PO4)2), manganese chloride (MnCl2), manganese oxalate (MnC2O4), manganese trioxide (Mn2O3), electrolytic manganese dioxide, and manganese tetraoxide.

[0105] Phosphate-based iron sources or E sources, in addition to providing iron or E elements, can also be used as phosphorus sources to provide phosphorus elements.

[0106] In the above method, the first carbon source comprises a solid carbon source. Alternatively, the first carbon source may comprise at least one of polyethylene glycol, glucose, sucrose, or starch. Further alternatively, the first carbon source may comprise at least one of polyethylene glycol or glucose. While the first mixture is being sintered, a second carbon source is applied to the first mixture. The second carbon source comprises a liquid carbon source. Alternatively, the second carbon source may comprise at least one of acetone, methanol, ethanol, or ethylene glycol. Further alternatively, the second carbon source may comprise acetone.

[0107] In some embodiments, the first carbon source may be added in an amount of 0.29 wt % to 1.37 wt % relative to the total weight of the first lithium source, the iron source, the phosphorus source, the optional E source, and the optional D source.

[0108] In some embodiments, the amount of the second carbon source added may be 0.10% wt% to 0.91 wt% relative to the total weight of the first lithium source, the iron source, the phosphorus source, the optional E source, and the optional D source.

[0109] In some embodiments, the mass ratio of the first carbon source to the second carbon source, calculated on the mass of the carbon element, may be 1:1 to 4:1. For example, the mass ratio of the first carbon source to the second carbon source, calculated on the mass of the carbon element, may be 1:1, 2:1, 7:3, 3:1, or 4:1, but is not limited thereto.

[0110] In some embodiments, by adjusting the amount of the first carbon source and / or the second carbon source added, the carbon content in the carbon-coated phosphate positive electrode material is 0.8 wt % to 2 wt %, optionally 0.85 wt % to 1.9 wt %.

[0111] In some embodiments, the mixing ratio of the first lithium source, the iron source, the E source, the phosphorus source and the D source is α:1-β:β:1:n, based on the molar ratio of lithium element, iron element, E element, phosphorus element and D element, wherein 0.9≤α≤1.1, 0≤β≤1, and 0≤n≤0.1. α Fe 1-β E β PO 4-n-δ D n The phosphate positive electrode material, wherein -0.1≤δ≤0.1. The selection of the E element and the D element is as described above and will not be repeated here.

[0112] In some embodiments, the iron source, manganese source, first lithium source, phosphorus source and first carbon source can be mixed. The mixing ratio of the first lithium source, iron source, manganese source and phosphorus source is α:1-β:β:1 based on the molar ratio of lithium element, iron element, manganese element and phosphorus element, wherein 0.9≤α≤1.1, 0≤β≤1. Thus, the chemical formula including Li α Fe 1-β Mn β PO4 phosphate positive electrode material. Optionally, α=1.

[0113] In the above method, the mixing method of the raw materials is not particularly limited. For example, the raw materials can be mixed using a plowshare mixer, a high-speed mixer, or an inclined mixer.

[0114] In some embodiments, applying the second carbon source to the first mixture comprises spraying the second carbon source onto a surface of the first mixture.

[0115] In some embodiments, the first sintering is performed under an inert gas atmosphere. Inert gases include, but are not limited to, nitrogen, helium, neon, and argon. Using an inert gas as a protective gas facilitates the conversion of the first and second carbon sources, which serve as reducing agents, into carbon during the sintering process and is deposited on the phosphate cathode material.

[0116] In the above method, the sintering temperature and sintering time of the first sintering are not particularly limited. For example, the sintering temperature of the first sintering can be 500°C to 800°C. The sintering time of the first sintering can be 5 hours to 16 hours. For example, the sintering temperature of the first sintering can be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, but is not limited thereto. The sintering time of the first sintering can be 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or 16 hours, but is not limited thereto.

[0117] In some embodiments, the preparation method further includes a pulverization step of pulverizing the carbon-coated phosphate cathode material, thereby facilitating the carbon-coated phosphate cathode material to include: small particles with an average particle size less than 300 nm, medium particles with an average particle size of 300 nm to 800 nm, and large particles with an average particle size greater than 800 nm and less than or equal to 3000 nm. The pulverization of the carbon-coated phosphate cathode material facilitates obtaining a carbon-coated phosphate cathode material with a wide particle size range, thereby achieving better adhesion of the carbon-coated phosphate cathode material to the spinel cathode material.

[0118] In some embodiments, in the carbon-coated phosphate positive electrode material, the proportion XS of small particles having an average particle size of less than 300 nm satisfies 60%≤XS≤80%, the proportion XM of medium particles having an average particle size of 300 nm to 800 nm satisfies 10%≤XM≤36%, and the proportion XL of large particles having an average particle size greater than 800 nm and less than or equal to 3000 nm satisfies 4%≤XL≤10%. Specific examples of XS, XM, and XL can be found above.

[0119] In some embodiments, the preparation method further comprises testing the turbidity value of the obtained carbon-coated phosphate positive electrode material.

[0120] The test method for the turbidity value of the carbon-coated phosphate positive electrode material is as described above and will not be repeated here.

[0121] In some embodiments, providing a spinel cathode material includes:

[0122] mixing a second lithium source, an A source, an optional M source, and an optional X source to obtain a second mixture, wherein the mixing ratio of the second lithium source, the A source, the M source, and the X source is a:2-b:b:z, based on the molar ratio of the lithium element, the A element, the M element, and the X element, wherein 1≤a≤1.2, 0≤b≤0.6, and 0≤z≤0.1, the A source comprises at least one of an oxide, a hydroxide, or a salt of the A element, the A element comprises Mn and optionally Ni, the M source comprises at least one of an oxide, a hydroxide, or a salt of the M element, the M element comprises at least one of V, Co, Mg, Fe, Al, Zn, Ca, Zr, Y, Nb, Mo, Cr, Li, or W, the X source comprises at least one of a simple substance or an oxide of the X element, and the X element comprises at least one of S, F, or Cl;

[0123] The second mixture is subjected to a second sintering process to obtain the spinel positive electrode material.

[0124] In some embodiments, providing a spinel cathode material includes:

[0125] mixing a second lithium source, an A source, an optional M source, and an optional X source to obtain a second mixture, wherein the mixing ratio of the second lithium source, the A source, the M source, and the X source is a:2-b:b:z, based on the molar ratio of the lithium element, the A element, the M element, and the X element, wherein 1≤a≤1.2, 0.001≤b≤0.6, and 0.001≤z≤0.1, the A source includes at least one of an oxide, a hydroxide, or a salt of the A element, the A element includes Mn and optionally Ni, the M source includes at least one of an oxide, a hydroxide, or a salt of the M element, the M element includes at least one of Co, Mg, Al, Zr, Mo, Li, or W, the X source includes at least one of a simple substance or an oxide of the X element, and the X element includes at least one of S, F, or Cl;

[0126] The second mixture is subjected to a second sintering process to obtain the spinel positive electrode material.

[0127] The definition of the second lithium source is the same as that of the first lithium source described above. Specific examples of the second lithium source can be found above. The specific selection of the second lithium source and the first lithium source can be the same or different.

[0128] The A source includes a substance that can provide the A element. The A element includes manganese and optionally nickel. The A source includes at least one of an oxide, hydroxide, or salt of the A element. The manganese source that provides the manganese element may, for example, include electrolytic manganese dioxide, manganese sulfate (MnSO4), manganese phosphate (Mn3(PO4)2), manganese chloride (MnCl2), manganese oxalate (MnC2O4), manganese trioxide (Mn2O3), or manganese tetraoxide. The nickel source that provides the nickel element may, for example, include one or more of nickel oxide, nickel hydroxide, nickel carbonate, nickel sulfate, nickel nitrate, or nickel oxalate.

[0129] The M source includes at least one of an oxide, hydroxide, or salt of the M element. The M element includes at least one of V, Co, Mg, Fe, Al, Zn, Ca, Zr, Y, Nb, Mo, Cr, Li, or W. The M source may include one or more of the oxide, hydroxide, nitrate, sulfate, hydrochloride, carbonate, phosphate, acetate, and oxalate of the M element, but is not limited thereto. For example, the M source may include an oxide of the M element, such as one or more of vanadium pentoxide, cobalt trioxide, cobaltous oxide, magnesium oxide, ferrous oxide, aluminum oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, niobium pentoxide, molybdenum oxide, chromium oxide, titanium oxide, and tungsten oxide, but is not limited thereto. Alternatively, the M source includes one or more of aluminum oxide (Al2O3), niobium pentoxide (Nb2O5), titanium oxide (TiO2), and zirconium oxide (ZrO2).

[0130] The X source may include at least one of a simple substance or an oxide of element X, wherein the X element includes at least one of S, F, or Cl. For example, the X source may include one or more of elemental sulfur (S), lithium fluoride, sodium fluoride, potassium fluoride, ammonium fluoride, lithium chloride, sodium chloride, potassium chloride, aluminum chloride, and magnesium chloride, but is not limited thereto.

[0131] There is no particular limitation on the sintering temperature and sintering time of the second sintering of the second mixture. In some embodiments, the sintering temperature of the second sintering may be 500°C to 950°C. In some embodiments, the sintering time of the second sintering may be 5h to 30h. For example, the sintering temperature of the second sintering may be 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 950°C or a value between any two values, but is not limited thereto. For example, the sintering time of the second sintering can be 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h or a value between the ranges consisting of any two values, but is not limited thereto.

[0132] In some embodiments, in the step of processing the spinel positive electrode material and the carbon-coated phosphate positive electrode material to form a positive electrode material, the weight ratio (ω) of the carbon-coated phosphate positive electrode material to the spinel positive electrode material satisfies 0.3:9.7≤ω≤8:2, optionally, 0.3:9.7≤ω≤7:3, optionally 0.3:9.7≤ω≤1:1. Specific examples of ω can be found above.

[0133] The positive electrode material obtained by the above method has the same technical advantages as the positive electrode material of the first aspect of the present application. Please refer to the detailed description of the positive electrode material of the first aspect of the present application above, which will not be repeated here.

[0134] In some embodiments of the present application, a positive electrode material prepared by the method of the present application is proposed, wherein the positive electrode material includes a spinel positive electrode material and a carbon-coated phosphate positive electrode material; wherein the turbidity value of the carbon-coated phosphate positive electrode material is 1NTU to 60NTU, optionally 8NTU to 54NTU.

[0135] In some embodiments of the present application, a composite cathode material is provided. The composite cathode material includes a spinel cathode material and a carbon-coated phosphate cathode material; wherein the carbon-coated phosphate cathode material has a turbidity value of 1 NTU to 60 NTU, and optionally 8 NTU to 54 NTU.

[0136] In some embodiments of the present application, the use of a carbon-coated phosphate positive electrode material in reducing manganese dissolution and / or improving cycle performance in positive electrode materials including spinel positive electrode materials and carbon-coated phosphate positive electrode materials is proposed, wherein the turbidity value of the carbon-coated phosphate positive electrode material is 1NTU to 60NTU, optionally 8NTU to 54NTU.

[0137] Battery

[0138] In some embodiments of the present application, a battery is provided.

[0139] The term "battery" mentioned herein refers to a battery cell, battery module, or battery pack. Each of these is described below.

[0140] Typically, a battery cell consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0141] Positive electrode

[0142] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode material of the first aspect of the present application or the positive electrode material prepared according to the method of the second aspect of the present application as the positive electrode active material.

[0143] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0144] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0145] In some embodiments, the positive electrode active material may further include positive electrode active materials for lithium ion batteries known in the art. As an example, these positive electrode active materials may include at least one of the following materials: lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), LiMnO2, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.1 Al 0.05 O2) and at least one of its modified compounds, etc.

[0146] The battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states. In the chemical formulas for the positive electrode active materials in this application, the molar Li content refers to the material's initial state, i.e., the state before addition of the materials. When the positive electrode active material is used in a battery system, the molar Li content will change over the course of charge and discharge cycles.

[0147] In the chemical formula of the positive electrode active material in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0148] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0149] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0150] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0151] Negative electrode

[0152] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0153] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0154] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0155] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0156] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0157] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0158] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0159] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0160] electrolytes

[0161] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0162] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0163] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0164] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0165] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0166] Isolation film

[0167] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0168] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0169] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0170] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0171] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0172] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 1 The battery cell 5 is a square structure as an example.

[0173] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a top cover assembly 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0174] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0175] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of battery cells 5 may further be fixed by fasteners.

[0176] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0177] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0178] Figure 4 and Figure 5 The battery pack 1 is used as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0179] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0180] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0181] Figure 6 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0182] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0183] Example

[0184] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0185] Example 1

[0186] Preparation of positive electrode materials

[0187] (1) Preparation of carbon-coated phosphate cathode materials

[0188] Step (a1): 1762 g of ferrous sulfate heptahydrate, 235 g of lithium carbonate, 730 g of ammonium dihydrogen phosphate, and 15.54 g of polyethylene glycol (PEG4000, average molecular weight: 3600-4400, available from Xingtai Xinlanxing Technology Co., Ltd.) were uniformly mixed to obtain a first mixture S. The ferrous sulfate heptahydrate, lithium carbonate, and ammonium dihydrogen phosphate were mixed in a molar ratio of 1:1:1 between the iron element, the lithium element, and the phosphorus element. The polyethylene glycol was added in an amount of 0.57 wt % relative to the total weight of the ferrous sulfate heptahydrate, the lithium carbonate, and the ammonium dihydrogen phosphate.

[0189] Step (a2): The first mixture (S) is placed in a sintering furnace and sintered at 750°C for 10 hours in a nitrogen atmosphere. Acetone is sprayed onto the mixture during sintering. The amount of acetone sprayed is 5.8 g. The amount of acetone sprayed is 0.21 wt % relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate, and ammonium dihydrogen phosphate. The mass ratio of the first carbon source, polyethylene glycol, to the second carbon source, acetone, is 7:3, based on the mass of the carbon element. The carbon source is pyrolyzed at high temperature and deposited on the surface of the resulting phosphate material to form a carbon coating.

[0190] Step (a3): After the temperature of the product obtained in step (a2) is reduced to below 185°C, it is crushed using a jet mill and crushed under a crushing pressure of 0.3 MPa to obtain a carbon-coated phosphate positive electrode material with a Dv50 of 1.1 μm. In the above-mentioned carbon-coated phosphate positive electrode material, the number of small particles accounts for 70%, the number of medium particles accounts for 23%, and the number of large particles accounts for 7%. Among them, the average particle size of the small particles is less than 300nm, the average particle size of the medium particles is 300nm to 800nm, and the average particle size of the large particles is greater than 800nm ​​and less than or equal to 3000nm. A picture containing 100±50 particles is selected by scanning electron microscopy, the longest and shortest diameters of a single particle are measured, and the average value of the longest diameter and the shortest diameter is taken as the average particle size of the particle. The average particle size is used to determine whether each particle is a small particle, a medium particle or a large particle, and the number proportion of each type of particle is thus counted.

[0191] (2) Preparation of spinel positive electrode materials

[0192] Step (b1): lithium carbonate, manganese dioxide, aluminum oxide, and lithium fluoride are uniformly mixed according to a molar ratio of Li, Mn, Al, and F of 1.03:1.8:0.2:0.05 to obtain a second mixture T.

[0193] Step (b2): placing the second mixture T in a sintering furnace and performing high-temperature sintering at 850° C. for 12 hours to obtain a sintered product.

[0194] Step (b3): ​​The sintered product obtained in step (b2) is crushed using a jet mill at a crushing pressure of 0.3 MPa to obtain a spinel positive electrode material with a Dv50 of 14.0 μm.

[0195] (3) Preparation of positive electrode materials

[0196] Step (c): The carbon-coated phosphate positive electrode material prepared in the above step (a3) ​​and the spinel positive electrode material prepared in the step (b3) are mixed in a weight ratio (ω) of 3:7, and ball milled at a speed of 40 rpm using a horizontal dry ball mill to obtain the positive electrode material.

[0197] The scanning electron microscope image of the positive electrode material prepared in Example 1 can be found in Figure 7 .from Figure 7 It can be seen that the carbon-coated phosphate cathode material is evenly attached to the spinel cathode material.

[0198] Carbon content testing

[0199] The carbon content in the carbon-coated phosphate cathode material was tested using an HX-HW8B high-frequency infrared carbon-sulfur analyzer.

[0200] Determination of turbidity value of carbon-coated phosphate cathode materials

[0201] 1 g of carbon-coated phosphate cathode material was uniformly dispersed in 35 ml of deionized water to obtain a dispersion; the dispersion was centrifuged at 3000 rpm for 30 minutes; 10 mL of the upper layer liquid was taken and the turbidity of the upper layer liquid was tested using a Leizhi WZS-186 turbidimeter to obtain the turbidity value of the carbon-coated phosphate cathode material.

[0202] Preparation of secondary batteries

[0203] (1) Preparation of positive electrode sheet

[0204] The positive electrode material, conductive agent (super-P), carbon nanotubes (CNTs), and polyvinylidene fluoride (PVDF) were thoroughly mixed in N-methylpyrrolidone (NMP) at a mass ratio of 95:1.5:0.5:3 to prepare a positive electrode slurry. This slurry was then coated onto a 13μm aluminum foil. After vacuum drying at 120°C, cold pressing, and slitting, the positive electrode sheets were obtained.

[0205] (2) Preparation of negative electrode sheet

[0206] The active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) were thoroughly stirred and mixed in a deionized water solvent system in a mass ratio of 95:2:2:1, and then coated on a Cu foil, dried, and cold pressed to obtain a negative electrode sheet.

[0207] (3) Preparation of electrolyte

[0208] Lithium salt LiPF6 was added to a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 35:65, and the mixture was mixed to obtain an electrolyte solution. The molar concentration of LiPF6 in the electrolyte solution was 1 mol / L.

[0209] (4) Assembly of secondary batteries

[0210] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes. Winding is performed to obtain a bare cell. The bare cell is placed in an outer packaging, injected with the prepared electrolyte, and packaged. After formation and exhaust processes, a lithium-ion secondary battery is obtained.

[0211] Preparation of button cells

[0212] A button cell was assembled using the prepared positive electrode sheet as the positive electrode and the lithium sheet as the negative electrode.

[0213] Electrochemical performance test

[0214] (1) Test of button battery capacity in grams

[0215] After the assembled button battery was left to stand for 120 minutes, it was charged at a constant current of 0.1C to 4.3V in a constant temperature environment of 25°C. It was then charged at a constant voltage of 4.3V until the current dropped to 0.05C. It was then discharged at a constant current of 0.33C to 3V. The first cycle discharge capacity in grams was obtained.

[0216] Figure 8 This is the first cycle charge and discharge curve of the button cell prepared using the positive electrode material of Example 1. Figure 8 It can be seen from the figure that among the positive electrode materials, the gram capacity of both spinel positive electrode materials and phosphate positive electrode materials can function normally, and the gram capacity of the button battery in the first cycle of discharge can reach 120.5mAh / g.

[0217] (2) Cycle performance test of secondary batteries

[0218] The lithium-ion battery is charged at a constant current of 0.33C to 4.3V at a constant temperature of 25°C, then charged at a constant voltage of 4.3V until the current drops to 0.05C, and then discharged at a constant current of 0.33C to 2.8V, and the first cycle discharge capacity (C0) is obtained. This charge and discharge is repeated until the 500th cycle, and the discharge capacity after 500 cycles is obtained, which is recorded as C n .

[0219] Capacity retention rate = discharge capacity after 500 cycles (C n ) / first cycle discharge capacity (C0).

[0220] Figure 9 is a cycle capacity retention curve of a battery prepared using the positive electrode material of Example 1 of the present application. Figure 9 It can be seen that the capacity retention rate can reach 97.50% after the battery is cycled 500 times.

[0221] (3)Mn 2+ Dissolution test

[0222] After 500 cycles, the lithium-ion battery was disassembled, the negative electrode sheet was removed, the negative electrode material of the negative electrode sheet was scraped off with a scraper, and dissolved with a mixed solvent (for example, 0.4 g of negative electrode material was dissolved in 10 mL of aqua regia (nitric acid and hydrochloric acid mixed in a volume ratio of 1:1)), the volume was fixed to 100 mL, and then the manganese content (g / mL) in the solution was tested using an ICP analyzer.

[0223] Manganese content in the negative electrode (ppm) = manganese content in the solution × 100mL ÷ mass of negative electrode material used.

[0224] Among them, the manganese content in the negative electrode is used to characterize the Mn content of the positive electrode material.2+ Dissolution amount. The greater the manganese content of the negative electrode sheet, the higher the Mn content of the positive electrode material. 2+ The more dissolution.

[0225] Example 2

[0226] The positive electrode material was prepared according to the method of Example 1, with the only difference being that glucose was used as the first carbon source in step (a1), and the amount of glucose added was 21 grams (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate and ammonium dihydrogen phosphate, the amount of glucose added was 0.76 wt %); in step (a2), the amount of acetone sprayed was 5.8 grams (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate and ammonium dihydrogen phosphate, the amount of acetone sprayed was 0.21 wt %). In terms of the mass of carbon element, the mass ratio of the first carbon source, glucose, to the second carbon source, acetone, was 7:3. Button batteries and secondary batteries were made using the prepared positive electrode material. Performance testing was carried out in the same manner as in Example 1.

[0227] Example 3

[0228] The positive electrode material was prepared according to the method of Example 1, except that the amount of polyethylene glycol added in step (a1) was 10.91 g (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate and ammonium dihydrogen phosphate, the amount of polyethylene glycol added was 0.40 wt%); and the amount of acetone sprayed in step (a2) was 9.54 g (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate and ammonium dihydrogen phosphate, the amount of acetone sprayed was 0.35 wt%). The mass ratio of the first carbon source polyethylene glycol to the second carbon source acetone was 1:1, based on the mass of carbon element. Button batteries and secondary batteries were made using the prepared positive electrode material. Performance tests were performed in the same manner as in Example 1.

[0229] Example 4

[0230] The positive electrode material was prepared according to the method of Example 1, except that the amount of polyethylene glycol added in step (a1) was 17.72 g (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate, and ammonium dihydrogen phosphate, the amount of polyethylene glycol added was 0.65 wt %); and the amount of acetone sprayed in step (a2) was 3.82 g (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate, and ammonium dihydrogen phosphate, the amount of acetone sprayed was 0.14 wt %). The mass ratio of the first carbon source polyethylene glycol to the second carbon source acetone, calculated on a carbon elemental basis, was 4:1. Button cells and secondary batteries were made using the prepared positive electrode material. Performance testing was performed in the same manner as in Example 1.

[0231] Example 5

[0232] The positive electrode material was prepared according to the method of Example 1, except that the amount of polyethylene glycol added in step (a1) was 24.61 g (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate and ammonium dihydrogen phosphate, the amount of polyethylene glycol added was 0.89 wt %); and the amount of acetone sprayed in step (a2) was 9.19 g (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate and ammonium dihydrogen phosphate, the amount of acetone sprayed was 0.33 wt %). The mass ratio of the first carbon source polyethylene glycol to the second carbon source acetone was 7:3, based on the mass of carbon element. Button cells and secondary batteries were made using the prepared positive electrode material. Performance tests were performed in the same manner as in Example 1.

[0233] Example 6

[0234] The positive electrode material was prepared according to the method of Example 1, except that the amount of polyethylene glycol added in step (a1) was 11.01 g (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate and ammonium dihydrogen phosphate, the amount of polyethylene glycol added was 0.40 wt%); and the amount of acetone sprayed in step (a2) was 4.11 g (relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate and ammonium dihydrogen phosphate, the amount of acetone sprayed was 0.15 wt%). The mass ratio of the first carbon source polyethylene glycol to the second carbon source acetone was 7:3, based on the mass of carbon element. Button cells and secondary batteries were made using the prepared positive electrode material. Performance tests were performed in the same manner as in Example 1.

[0235] Example 7 to Example 8

[0236] A positive electrode material was prepared according to the method of Example 1, except that in step (c), the carbon-coated phosphate positive electrode material and the spinel positive electrode material were mixed in a weight ratio (ω) of 5:5 and 6:4, respectively. Coin-type batteries and secondary batteries were manufactured using the prepared positive electrode materials. Performance testing was performed in the same manner as in Example 1.

[0237] Example 9 to Example 10

[0238] Positive electrode materials were prepared according to the method of Example 1, except that in step (b2), the second sintering temperatures were set at 700°C and 870°C, respectively. The resulting spinel positive electrode materials had Dv50 values ​​of 8.0 μm and 21.3 μm, respectively. Coin-type batteries and secondary batteries were fabricated using the prepared positive electrode materials. Performance testing was conducted in the same manner as in Example 1.

[0239] Example 11 to Example 14

[0240] A positive electrode material was prepared according to the method of Example 1, except that in step (b1), the molar ratios of Li, Mn, Al, and F were 1.03:1.6:0.4:0.05, 1.03:1.9:0.1:0.05, 1.03:1.8:0.2:0.09, and 1.03:1.8:0.2:0.02, respectively. Coin-type batteries and secondary batteries were fabricated using the prepared positive electrode materials. Performance tests were conducted in the same manner as in Example 1.

[0241] Comparative Example 1

[0242] A positive electrode material was prepared according to the method of Example 1, with the only difference being that, in step (a1), glucose was used instead of polyethylene glycol. The amount of glucose added was 30 g (1.09 wt% relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate, and ammonium dihydrogen phosphate). Acetone was not sprayed during the sintering step (a2). Coin-type batteries and secondary batteries were fabricated using the prepared positive electrode material. Performance testing was conducted in the same manner as in Example 1.

[0243] Comparative Example 2

[0244] The positive electrode material was prepared according to the method of Example 1, with the only difference being step (a1) and step (a2).

[0245] In step (a1) of Comparative Example 2, no solid carbon source was added as the first carbon source. In step (a2) of Comparative Example 2, the first mixture S, which did not contain a solid carbon source, was sintered while being sprayed with acetone. The amount of acetone sprayed was 19.34 g (0.70 wt % relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate, and ammonium dihydrogen phosphate).

[0246] The prepared positive electrode material was used to make button batteries and secondary batteries, and performance tests were performed in the same manner as in Example 1.

[0247] Comparative Example 3

[0248] A positive electrode material was prepared according to the method of Example 1, except that the first carbon source was not added in step (a1), the second carbon source was not added in step (a2), and sintering was performed under a reducing atmosphere (hydrogen). Coin-type batteries and secondary batteries were fabricated using the prepared positive electrode material. Performance tests were conducted in the same manner as in Example 1.

[0249] Comparative Example 4

[0250] A positive electrode material was prepared according to the method of Example 1, except that the amount of polyethylene glycol added in step (a1) was 45.33 g (1.63 wt % relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate, and ammonium dihydrogen phosphate); and the amount of acetone sprayed in step (a2) was 16.93 g (0.61 wt % relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate, and ammonium dihydrogen phosphate). Coin-type batteries and secondary batteries were fabricated using the prepared positive electrode material. Performance testing was performed in the same manner as in Example 1.

[0251] Table 1 shows the preparation parameters of the positive electrode materials in each embodiment and comparative example. Table 2 shows the physical and chemical performance parameters of the positive electrode materials in each embodiment and comparative example. Table 3 shows the electrochemical performance test results of the positive electrode materials in each embodiment and comparative example.

[0252] Table 1

[0253]

[0254]

[0255] In Table 1, “ / ” indicates that there is no relevant item; the mass ratio of the first carbon source to the second carbon source refers to: the mass ratio of the first carbon source to the second carbon source based on the mass of the carbon element; the added amount of the first carbon source and the added amount of the second carbon source are each relative to the total weight of ferrous sulfate heptahydrate, lithium carbonate, and ammonium dihydrogen phosphate; the mixing ratio of phosphate and spinel refers to: the weight ratio ω of the carbon-coated phosphate positive electrode material and the spinel positive electrode material.

[0256] Table 2

[0257]

[0258]

[0259] Table 3

[0260]

[0261]

[0262] As can be seen from the results in Table 1, compared with Comparative Examples 1 to 3, in Examples 1 to 14, by using a solid carbon source as the first carbon source in step (a1) and simultaneously applying a liquid carbon source as the second carbon source during the sintering process in step (a2), a carbon-coated phosphate positive electrode material with a turbidity value in the range of 1 NTU to 60 NTU was obtained. The positive electrode material thus prepared has a low manganese dissolution amount and excellent cycle performance. This shows that the carbon-coated phosphate positive electrode material in Examples 1 to 14 can effectively adsorb manganese ions to be dissolved in the spinel positive electrode material, reduce the dissolution amount of manganese ions, and improve the cycle performance of the battery.

[0263] In Comparative Example 1, a carbon-coated phosphate cathode material with a turbidity value of 71 NTU was obtained using only solid-state carbon source glucose as the carbon source. The resulting cathode material exhibited increased manganese dissolution and reduced cycling performance. This suggests that the carbon-coated phosphate cathode material in Comparative Example 1 weakened its adsorption of manganese ions intended to dissolve from the spinel cathode material, resulting in increased manganese ion dissolution and reduced cycling performance.

[0264] In Comparative Example 2, only liquid carbon source acetone was used as the carbon source for sintering, and the turbidity value of the obtained carbon-coated phosphate positive electrode material was 0.7. Although the manganese dissolution amount of the positive electrode material thus obtained was reduced, the cycle performance dropped sharply. This shows that the carbon coating layer of the phosphate positive electrode material of Comparative Example 2 is too dense and has a very high degree of graphitization. In this case, under the high operating voltage of the spinel positive electrode material, the carbon reaction activity in the carbon coating layer is strong, which promotes the decomposition of the electrolyte on the surface of the phosphate positive electrode material, accelerates the consumption of the electrolyte, and a large amount of side reaction products accumulate on the surface of the phosphate positive electrode material, thereby accelerating the battery capacity decay.

[0265] In Comparative Example 3, the obtained phosphate cathode material had no carbon coating layer and a turbidity value of 65. The manganese dissolution amount of the cathode material thus prepared increased, and the cycle performance also decreased.

[0266] Compared with Comparative Example 4, the carbon content of the carbon-coated phosphate positive electrode materials in Examples 1, 5 and 6 is lower, and the manganese dissolution amount of the positive electrode materials obtained thereby is low, and the cycle performance is excellent.

[0267] In Comparative Example 4, the increased carbon content of the phosphate cathode material reduced the turbidity value to less than 1, and the manganese dissolution of the cathode material also decreased. However, due to the increased carbon content, the high and overly dense carbon coating increased the resistance to lithium insertion and extraction from the phosphate cathode material, which in turn accelerated the decay of the capacity retention rate and reduced cycle performance.

[0268] In Examples 1, 7, and 8, the weight ratios ω of the carbon-coated phosphate cathode material to the spinel cathode material are 3:7, 5:5, and 6:4, respectively. In these examples, the cathode material exhibits low manganese dissolution after 500 cycles, indicating excellent cycling performance.

[0269] In Examples 1, 9 and 10, by changing the Dv50 of the spinel positive electrode material, the ratio σ of the Dv50 of the spinel positive electrode material to the Dv50 of the carbon-coated phosphate positive electrode material is made to be 12.7, 7.3 and 19.3, respectively. It can be seen from these examples that the ratio σ of the Dv50 of the spinel positive electrode material to the Dv50 of the carbon-coated phosphate positive electrode material has a certain influence on the gram capacity, manganese dissolution amount and cycle performance of the positive electrode material. When the ratio σ is large, the carbon-coated phosphate positive electrode material can better adhere to the spinel positive electrode material, which is beneficial to reducing the amount of manganese ion dissolution and improving the cycle performance. When the Dv50 of the carbon-coated phosphate positive electrode material remains unchanged, the reduction of the Dv50 of the spinel positive electrode material is beneficial to the deintercalation of lithium ions and improves the gram capacity of the positive electrode material.

[0270] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode material, characterized in that The positive electrode material includes a spinel positive electrode material and a carbon-coated phosphate positive electrode material; wherein the turbidity value of the carbon-coated phosphate positive electrode material is 1 NTU to 60 NTU.

2. The positive electrode material according to claim 1, characterized in that The turbidity value of the carbon-coated phosphate positive electrode material is 8 NTU to 54 NTU.

3. The positive electrode material according to claim 1 or 2, characterized in that The turbidity value was measured according to the following method: 1 g of carbon-coated phosphate cathode material was uniformly dispersed in 35 ml of deionized water to obtain a dispersion; the dispersion was centrifuged at a speed of 3000 rpm for 30 min to obtain an upper layer liquid; 10 ml of the upper layer liquid was taken to test the turbidity to obtain the turbidity value.

4. The positive electrode material according to any one of claims 1 to 3, characterized in that The carbon content of the carbon-coated phosphate positive electrode material is 0.85 wt % to 1.9 wt %.

5. The positive electrode material according to any one of claims 1 to 4, characterized in that The carbon-coated phosphate positive electrode material includes: small particles with an average particle size of less than 300nm, medium particles with an average particle size of 300nm to 800nm, and large particles with an average particle size of more than 800nm ​​and less than or equal to 3000nm.

6. The positive electrode material according to claim 5, characterized in that The proportion XS of the number of small particles satisfies 60%≤XS≤80%, the proportion XM of the number of medium particles satisfies 10%≤XM≤36%, and the proportion XL of the number of large particles satisfies 4%≤XL≤10%.

7. The positive electrode material according to any one of claims 1 to 6, characterized in that The Dv50 of the carbon-coated phosphate positive electrode material is 0.5 μm to 2 μm; and / or the Dv50 of the spinel positive electrode material is 6 μm to 24 μm.

8. The positive electrode material according to claim 7, characterized in that The ratio σ of the Dv50 of the spinel positive electrode material to the Dv50 of the carbon-coated phosphate positive electrode material satisfies σ=7~20.

9. The positive electrode material according to any one of claims 1 to 8, characterized in that The carbon-coated phosphate positive electrode material is attached to the spinel positive electrode material.

10. The positive electrode material according to any one of claims 1 to 9, characterized in that The weight ratio ω of the carbon-coated phosphate positive electrode material to the spinel positive electrode material satisfies 0.3:9.7≤ω≤8:

2.

11. The positive electrode material according to claim 10, characterized in that The weight ratio ω of the carbon-coated phosphate positive electrode material to the spinel positive electrode material satisfies 0.3:9.7≤ω≤1:

1.

12. The positive electrode material according to any one of claims 1 to 11, characterized in that The chemical formula of the spinel positive electrode material includes Li a A 2-b M b O 4-z X z , wherein 1≤a≤1.2, 0≤b≤0.6, 0≤z≤0.1; A includes Mn and optionally Ni; M includes at least one of V, Co, Mg, Fe, Al, Zn, Ca, Zr, Y, Nb, Mo, Cr, Li or W; and X includes at least one of S, F or Cl.

13. The positive electrode material according to any one of claims 1 to 12, characterized in that The chemical formula of the spinel positive electrode material includes Li a A 2-b M b O 4-z X z , wherein 1≤a≤1.2, 0.001≤b≤0.6, 0.001≤z≤0.1; A includes Mn and optionally Ni; M includes at least one of Co, Mg, Al, Zr, Mo, Li or W; and X includes at least one of S, F or Cl.

14. The positive electrode material according to any one of claims 1 to 13, characterized in that The chemical formula of the phosphate positive electrode material includes Li α Fe 1-β E β PO 4-n-δ D n , wherein E includes at least one of Mn, Ti, V, Zr, Ni, Mg, Co, Ga, Sn, Sb, Nb or Ge, D includes at least one of S, F, Cl or Br, 0.9≤α≤1.1, 0≤β≤1, 0≤n≤0.1, and -0.1≤δ≤0.

1.

15. A method for preparing a positive electrode material, characterized in that: The method comprises: Provide spinel cathode materials; Providing a carbon-coated phosphate cathode material, wherein the turbidity value of the carbon-coated phosphate cathode material is 1 NTU to 60 NTU; The spinel cathode material and the carbon-coated phosphate cathode material are processed to form the cathode material.

16. The method according to claim 15, characterized in that The providing of the carbon-coated phosphate cathode material comprises: mixing a first lithium source, an iron source, a phosphorus source, an optional E source, an optional D source, and a first carbon source to obtain a first mixture, wherein the first carbon source comprises a solid carbon source; Performing a first sintering on the first mixture under an inert gas atmosphere, and at the same time, adding a second carbon source to the first mixture, so that the first mixture undergoes the first sintering in the presence of the second carbon source, thereby obtaining the carbon-coated phosphate positive electrode material, wherein the second carbon source comprises a liquid carbon source; Wherein, the E source includes at least one of an oxide, hydroxide or salt of an E element, and the E element includes at least one of Mn, Ti, V, Zr, Ni, Mg, Co, Ga, Sn, Sb, Nb or Ge, The D source includes at least one of a simple substance or a salt of a D element, and the D element includes at least one of S, F, Cl or Br.

17. The method according to claim 16, characterized in that The first carbon source includes at least one of polyethylene glycol, glucose, sucrose or starch; and / or the second carbon source includes at least one of acetone, methanol, ethanol or ethylene glycol.

18. The method according to claim 16 or 17, characterized in that Relative to the total weight of the first lithium source, iron source, phosphorus source, optional E source, and optional D source, the amount of the first carbon source added is 0.29wt% to 1.37wt%; and / or, relative to the total weight of the first lithium source, iron source, phosphorus source, optional E source, and optional D source, the amount of the second carbon source added is 0.10%wt% to 0.91wt%.

19. The method according to any one of claims 16 to 18, characterized in that Calculated by the mass of carbon elements, the mass ratio of the first carbon source to the second carbon source is 1:1 to 4:

1.

20. The method according to any one of claims 16 to 19, characterized in that Calculated by the molar ratio of lithium, iron, E, phosphorus and D, the mixing ratio of the first lithium source, iron source, E source, phosphorus source and D source is α:1-β:β:1:n, wherein 0.9≤α≤1.1, 0≤β≤1, and 0≤n≤0.

1.

21. The method according to any one of claims 16 to 20, characterized in that Applying the second carbon source to the first mixture includes spraying the second carbon source onto a surface of the first mixture.

22. The method according to any one of claims 16 to 21, characterized in that The sintering temperature of the first sintering is 500° C. to 800° C.; and / or the sintering time of the first sintering is 5 hours to 16 hours.

23. The method according to any one of claims 15 to 22, characterized in that The provision of spinel positive electrode material comprises: mixing a second lithium source, an A source, an optional M source, and an optional X source to obtain a second mixture, wherein the mixing ratio of the second lithium source, the A source, the M source, and the X source is a:2-b:b:z, based on the molar ratio of the lithium element, the A element, the M element, and the X element, wherein 1≤a≤1.2, 0≤b≤0.6, and 0≤z≤0.1, the A source comprises at least one of an oxide, a hydroxide, or a salt of the A element, the A element comprises Mn and optionally Ni, the M source comprises at least one of an oxide, a hydroxide, or a salt of the M element, the M element comprises at least one of V, Co, Mg, Fe, Al, Zn, Ca, Zr, Y, Nb, Mo, Cr, Li, or W, the X source comprises at least one of a simple substance or an oxide of the X element, and the X element comprises at least one of S, F, or Cl; The second mixture is subjected to a second sintering process to obtain the spinel positive electrode material.

24. The method according to claim 23, wherein The sintering temperature of the second sintering is 500° C. to 950° C.; and / or the sintering time of the second sintering is 5 hours to 30 hours.

25. A positive electrode plate, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode material according to any one of claims 1 to 14 or the positive electrode material prepared by the method according to any one of claims 15 to 24.

26. A battery, characterized in that: The battery comprises the positive electrode sheet according to claim 25.

27. An electrical device, characterized in that: The electrical device comprises the battery according to claim 26.

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