Positive electrode material and preparation method thereof, and lithium ion battery

Abstract

The present application relates to the technical field of lithium-ion batteries, and in particular to a positive electrode material and a preparation method thereof and a lithium-ion battery. The preparation method comprises the following steps: mixing a nickel-containing metal oxide precursor prepared by spray pyrolysis with a metal hydroxide and water to obtain a first mixture, sintering the first mixture once to obtain a precursor; mixing the precursor with a lithium source, a halogen remover and an alkali metal dopant to obtain a second mixture, sintering the second mixture twice to obtain a matrix; mixing the matrix with a surface coating agent to obtain a third mixture, sintering the third mixture three times to obtain a positive electrode material. The present application gradually removes or transforms impurities in the nickel-containing metal oxide precursor through a stepwise reaction, and finally transforms them into dopants and coatings that improve the performance of the material, thereby improving the structural stability of the material, and also improving the rate performance and cycle performance of the material.

Description

Technical Field

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

[0002] Ternary materials have many advantages such as high specific capacity, good cycle performance and thermal stability, low cost, and good safety. They are an ideal positive electrode material for lithium-ion batteries. The synthesis of ternary materials requires the synthesis of nickel-containing metal oxide precursors. In recent years, spray pyrolysis synthesis technology has been applied to the synthesis of nickel-containing metal oxide precursors because of its advantages such as rapid reaction, large output, and no wastewater generation. However, the nickel-containing metal oxide precursor synthesized by spray pyrolysis synthesis technology contains a large amount of impurities and the precursor has crystal defects, and the crystal structure is unstable, resulting in structural defects in the synthesized ternary materials and poor electrochemical performance. Summary of the invention

[0003] The present application provides a positive electrode material, a preparation method thereof and a lithium-ion battery to solve the problem that the nickel-containing metal oxide precursor synthesized by the existing spray pyrolysis synthesis technology contains a large amount of impurities and the precursor has crystal defects and an unstable crystal structure, resulting in structural defects in the synthesized positive electrode material and poor electrochemical performance.

[0004] According to a first aspect of the present application, the present application provides a positive electrode material, comprising:

[0005] Lithium nickel metal composite oxide; and

[0006] The coating layer, at least part of which is located on the surface of the lithium nickel metal composite oxide; the coating layer includes a first coating layer and a second coating layer located on the surface of the first coating layer, the first coating layer includes a halide solid electrolyte; the second coating layer includes a sulfate fast ion conductor.

[0007] In some embodiments, the general chemical formula of the halide solid electrolyte is LixN´yN´´z, wherein 1≤x≤2, 1≤y≤3, 2≤z≤8, N´ includes at least one of Ti, Mn, Al, Fe, Sm, Sn, In, and Co; and N´´ includes at least one of Cl and Br.

[0008] In some embodiments, the halide solid electrolyte includes at least one of LiSmCl6, LiYBr6, Li2TiCl4, LiYCl6, LiSnCl6, Li2FeCl4, Li2CoCl6, Li1.5Mn1.2Cl4, LiAlCl4 and Li2MnCl4.

[0009] In some embodiments, the general chemical formula of the sulfate fast ion conductor is LiaMbSO4, wherein 0≤a≤4, 0≤b≤3, and M includes at least one of Na, Li, and K.

[0010] In some embodiments, the sulfate fast ion conductor includes at least one of NaSO4, LiNaSO4, Li2SO4, and LiKSO4.

[0011] In some embodiments, the second coating layer further includes a phosphate compound, and the phosphate compound includes at least one of lithium phosphate, calcium phosphate, lithium titanium phosphate, calcium hydrogen phosphate and lithium hydrogen phosphate.

[0012] In some embodiments, the first coating layer further comprises a sulfide, the chemical formula of the sulfide being Li x S, where 0.8≤x≤3.

[0013] In some embodiments, based on the positive electrode material, the content of the halide solid electrolyte is 400ppm-8000ppm.

[0014] In some embodiments, based on the positive electrode material, the content of the sulfate fast ion conductor is 500ppm-6000ppm.

[0015] In some embodiments, in the lithium nickel metal composite oxide bulk phase, the chemical formula of the halide is Li x N´ y N´´ z , wherein 1≤x≤2, 1≤y≤3, 2≤z≤8, N´ includes at least one of Ti, Mn, Al, Fe, Sm, Sn and Co, and N´´ includes at least one of Cl and Br.

[0016] In some embodiments, in the lithium nickel metal composite oxide bulk phase, the general chemical formula of the sulfide is LixS, wherein 0.8≤x≤3.

[0017] In some embodiments, based on the positive electrode material, in the lithium nickel metal composite oxide bulk phase, the halide content is 200ppm-30000ppm, and the sulfide solid electrolyte content is 500ppm-2000ppm.

[0018] In some embodiments, the lithium nickel metal composite oxide has a general chemical formula of Li a Ni b Co c M 1-b-c O 2; Among them, 0.95≤a≤1.2, 0<b≤1, c≤0.1, b+c≤1, and M includes at least one of Mn, Al, Zr, Mg, Ti, Ba, Sr, Mg, Cr, Zn, V, and Cu.

[0019] In some embodiments, the cell parameter Dp of the positive electrode material measured by XRD is 70nm-120nm.

[0020] In some embodiments, the diffraction peak intensity I of the positive electrode material tested by XRD is 003 / I 104 ≥1.0.

[0021] In some embodiments, the specific surface area S1 of the positive electrode material is 0.5 m 2 / g-1.2m 2 / g.

[0022] In some embodiments, the tap density of the positive electrode material is ρ1>1.8 g / cm 3 .

[0023] In some embodiments, the powder compaction density of the positive electrode material is ρ2≥2.8 g / cm 3 .

[0024] In some embodiments, the positive electrode material has Cl - and SO 4 2- The content is less than 100ppm.

[0025] In some embodiments, the powder conductivity of the positive electrode material is > .

[0026] In some embodiments, the positive electrode material satisfies the following conditions: ; BET is the specific surface area of ​​the positive electrode material, FWHM (003) is the half-peak width of the 003 peak in the XRD test, and D (003) is the grain size of the 003 peak.

[0027] In some embodiments, the content of fluorine in the positive electrode material is 50ppm-2000ppm.

[0028] In some embodiments, the coating layer of the positive electrode material has a thickness of 3nm-700nm.

[0029] In some embodiments, the first coating layer has a thickness of 5 nm to 60 nm.

[0030] In some embodiments, the second coating layer has a thickness of 3 nm to 15 nm.

[0031] In some embodiments, the molar ratio of metallic lithium to transition metal in the positive electrode material is between 1.01 and 1.04.

[0032] In some embodiments, the total impedance R of the positive electrode material at a voltage of 3.0V-4.3V, a temperature of 5°C, and 100% SOC satisfies: 20Ω<R<80Ω.

[0033] A method for preparing a positive electrode material comprises the following steps:

[0034] Mixing a nickel-containing metal oxide precursor prepared by spray pyrolysis with a metal hydroxide and water to obtain a first mixture, and sintering the first mixture once to obtain a precursor;

[0035] The precursor is mixed with a lithium source, a halogen removal agent and an alkali metal dopant to obtain a second mixture, and the second mixture is subjected to secondary sintering to obtain a matrix;

[0036] The substrate is mixed with a surface coating agent to obtain a third mixture, and the third mixture is sintered three times to obtain a positive electrode material.

[0037] In some embodiments, the nickel-containing metal oxide precursor comprises a nickel-containing metal composite oxide, and the nickel-containing metal composite oxide has a chemical formula of Ni b Co c M 1-b-c O 2 , wherein 0<b≤1, c≤0.1, b+c≤1, M includes at least one of Mn, Al, Zr, Mg, Ti, Ba, Sr, Mg, Cr, Zn, V, Cu, and does not include Na.

[0038] In some embodiments, the particle size D50 of the nickel-containing metal oxide precursor is 1 μm-3 μm.

[0039] In some embodiments, the metal hydroxide comprises NaOH.

[0040] In some embodiments, the metal hydroxide further comprises Al(OH) 3 、Fe(OH) 3 、Mn(OH) 4 、Ti(OH) 3 At least one of .

[0041] In some embodiments, the particle size D50 of the metal hydroxide is 0.1 μm-12 μm.

[0042] In some embodiments, the mass addition amount of the metal hydroxide is 0.002%-1% of the nickel-containing metal oxide precursor.

[0043] In some embodiments, the weight ratio of the nickel-containing metal oxide precursor to the metal hydroxide to water is 10:1-50:1.

[0044] In some embodiments, the primary sintering temperature is 400°C-700°C.

[0045] In some implementations, the primary sintering time is 6h-8h.

[0046] In some embodiments, the primary sintering is performed in an air atmosphere.

[0047] In some embodiments, the lithium salt includes at least one of lithium hydroxide and lithium carbonate.

[0048] In some embodiments, the ratio of the sum of the molar amounts of the nickel-containing metal oxide precursor and the impurities in the nickel-containing metal oxide precursor to the molar amount of the lithium salt is 0.98-1.01.

[0049] In some embodiments, the halogen removal agent includes at least one of a transition metal oxide and a transition metal halide.

[0050] In some embodiments, the halogen removal agent includes InBr 3 , YBr 3 , Y 2 O 3 ,In 2 O 3 , CaBr 2 , CeO 2 and SmO 2 At least one of .

[0051] In some embodiments, the alkali metal dopant includes a fluoride salt.

[0052] In some embodiments, the fluoride salt includes at least one of NaF, LiF, and KF.

[0053] In some embodiments, the secondary sintering temperature is 500°C-900°C.

[0054] In some embodiments, the secondary sintering time is 8h-10h.

[0055] In some embodiments, the secondary sintering is performed in an oxygen atmosphere.

[0056] In some embodiments, the secondary sintering temperature is greater than the primary sintering temperature.

[0057] In some embodiments, the surface coating agent includes a phosphate.

[0058] In some embodiments, the surface coating agent comprises a phosphate, wherein the phosphate comprises H 3 PO 4 , Li 3 PO 4 , LiH 2 PO 4 , K 3 PO 4 、Na 3 PO 4 NH 4 PO 4 At least one of .

[0059] In some embodiments, the surface coating agent further comprises CaO, CaCO 3 , SnO, TiO2.

[0060] In some embodiments, the tertiary sintering temperature is 400°C-800°C.

[0061] In some embodiments, the three sintering times are 5 hours to 8 hours.

[0062] In some embodiments, the third sintering is performed in an oxygen atmosphere.

[0063] According to the third aspect of the present application, the present application also provides a lithium-ion battery, comprising the above-mentioned positive electrode material or the positive electrode material obtained by the above-mentioned preparation method.

[0064] The technical solution of this application has at least the following beneficial effects:

[0065] The above-mentioned positive electrode material includes a first coating layer and a second coating layer, the first coating layer includes a halide solid electrolyte, and the second coating layer includes a sulfate fast ion conductor. The halide solid electrolyte also has good mechanical properties, high ion conductivity, and excellent electrochemical activity. The sulfate fast ion conductor has superionic conductivity. The halide solid electrolyte and the sulfate fast ion conductor are sequentially coated on the surface of the lithium nickel metal composite oxide as coating layers, which is beneficial to improving the corrosion of the electrolyte to the material body. Since the halide solid electrolyte and the sulfate fast ion conductor have lithium ion diffusion coefficients of different orders of magnitude, the combination of the inner and outer layers is beneficial to reducing the interface impedance of lithium ions diffusing from the electrolyte to the inside of the material, reducing the diffusion barrier, improving the interface reaction, accelerating the conduction of lithium ions, and improving the rate performance of the material.

[0066] The preparation method of the positive electrode material of the present application gradually eliminates or transforms the impurities incidental to the nickel-containing metal oxide precursor prepared by spray pyrolysis through step-by-step reaction, and selects specific halogen removal agents and surface coating agents, and finally transforms them into dopants and coatings that improve the performance of the material, thereby improving the structural stability of the final product, improving the rate performance and cycle performance of the material, and transforming the residual alkali and impurities on the surface of the material, reducing the process cost and the risk of gas production of the material. In this way, not only the technical drawbacks of the nickel-containing metal oxide precursor are solved, but also the favorable transformation of impurities is more effectively utilized.

[0067] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 A flow chart of a method for preparing a positive electrode material provided in this application.

[0069] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. DETAILED DESCRIPTION

[0070] The following is a preferred implementation of the embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the embodiment of the present invention. These improvements and modifications are also considered to be within the scope of protection of the embodiment of the present invention.

[0071] In a first aspect, the present application provides a positive electrode material, the positive electrode material comprising: a lithium nickel metal composite oxide; and

[0072] The coating layer, at least part of which is located on the surface of the lithium nickel metal composite oxide; the coating layer includes a first coating layer and a second coating layer located on the surface of the first coating layer, the first coating layer includes a halide solid electrolyte; the second coating layer includes a sulfate fast ion conductor.

[0073] The above-mentioned positive electrode material includes a first coating layer and a second coating layer, the first coating layer includes a halide solid electrolyte, and the second coating layer includes a sulfate fast ion conductor. The halide solid electrolyte also has good mechanical properties, high ion conductivity, and excellent electrochemical activity. The sulfate fast ion conductor has superionic conductivity. The halide solid electrolyte and the sulfate fast ion conductor are sequentially coated on the surface of the lithium nickel metal composite oxide as coating layers, which is beneficial to improving the corrosion of the electrolyte to the material body. Since the halide solid electrolyte and the sulfate fast ion conductor have lithium ion diffusion coefficients of different orders of magnitude, the combination of the inner and outer layers is beneficial to reducing the interface impedance of lithium ions diffusing from the electrolyte to the inside of the material, reducing the diffusion barrier, improving the interface reaction, accelerating the conduction of lithium ions, and improving the rate performance of the material.

[0074] The following is a detailed description of this program:

[0075] In some embodiments, in the first coating layer, the general chemical formula of the halide solid electrolyte is LixN´yN´´z, wherein 1≤x≤2, 1≤y≤3, 2≤z≤8, N´ includes at least one of Ti, Mn, Al, Fe, Sm, Sn, In, and Co; and N´´ includes at least one of Cl and Br.

[0076] In some embodiments, in the first coating layer, the halide solid electrolyte includes LiSmCl 6 ,LiYBr 6 , Li 2 TiCl 4 、LiYCl 6 、LiSnCl 6 , Li 2 FeCl 4 , Li 2 CoCl 6 , Li 1.5 Mn 1.2 Cl 4 、LiAlCl 4 Li 2 MnCl 4 At least one of .

[0077] In some embodiments, the chemical formula of the sulfate fast ion conductor is Li a M b SO 4 , wherein 0≤a≤4, 0≤b≤3, and M includes at least one of Na, Li, and K.

[0078] In some embodiments, the sulfate fast ion conductor comprises NaSO 4 、LiNaSO 4 , Li 2 SO4 ,LiKSO 4 At least one of .

[0079] In some embodiments, the second coating layer further includes a phosphate compound, and the phosphate compound includes at least one of lithium phosphate, calcium phosphate, lithium titanium phosphate, calcium hydrogen phosphate and lithium hydrogen phosphate;

[0080] In some embodiments, the first coating layer further comprises a sulfide, and the chemical formula of the sulfide is LixS, wherein 0.8≤x≤3;

[0081] In some embodiments, based on the positive electrode material, the content of the halide in the first coating layer is 400 ppm-8000 ppm.

[0082] Optionally, the halide content may be 400 ppm, 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, 7000 ppm or 8000 ppm, etc., and may also be other values ​​within the above range, which are not limited here.

[0083] It can be understood that by limiting the content of the halide in the first coating layer, the first coating layer can exhibit better electrical conductivity, which is beneficial to improving the electronic conductivity of the positive electrode material.

[0084] In some embodiments, based on the positive electrode material, the content of the sulfate fast ion conductor is 500 ppm-6000 ppm.

[0085] Optionally, the content of the sulfate fast ion conductor may be 500 ppm, 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm or 6000 ppm, etc., and may also be other values ​​within the above range, which are not limited here.

[0086] It can be understood that by limiting the content of the sulfate fast ion conductor in the second coating layer, the second coating layer can exhibit better electrical conductivity, which is beneficial to improving the electronic conductivity of the positive electrode material.

[0087] In some embodiments, the bulk phase of the lithium nickel metal composite oxide contains at least one of a halide and a sulfide solid electrolyte. It should be noted that the bulk phase refers to the interior of the material lattice or the non-surface layer of the material.

[0088] In some embodiments, in the lithium nickel metal composite oxide bulk phase, the general chemical formula of the halide is LixN´yN´´z, wherein 1≤x≤2, 1≤y≤3, 2≤z≤8, N´ includes at least one of Ti, Mn, Al, Fe, Sm, Sn, In, and Co; and N´´ includes at least one of Cl and Br.

[0089] In some embodiments, in the lithium nickel metal composite oxide bulk phase, the chemical formula of the sulfide is Li x S, where 0.8≤x≤3.

[0090] In some embodiments, based on the positive electrode material, the content of halide in the lithium nickel metal composite oxide bulk phase is 200 ppm-30000 ppm, and the content of sulfide solid electrolyte is 500 ppm-2000 ppm.

[0091] In some embodiments, the general chemical formula of the lithium nickel metal composite oxide is ; wherein 0.95≤a≤1.2, 0<b≤1, c≤0.1, b+c≤1, M includes at least one of Mn, Al, Zr, Mg, Ti, Ba, Sr, Mg, Cr, Zn, V, Cu, and does not include Na.

[0092] Optionally, the value of a can be 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, 1.1 or 1.2, etc., and of course it can be other values ​​within the above range, which is not limited here; the value of b can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc., and of course it can be other values ​​within the above range, which is not limited here; c can be 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02 or 0.01, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0093] In some implementations, the positive electrode material is tested by XRD, and the unit cell parameter Dp of the positive electrode material is obtained to be 70nm-120nm.

[0094] Optionally, the unit cell parameter Dp of the positive electrode material can be 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm, 115nm or 120nm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0095] It can be understood that the positive electrode material within such a unit cell parameter range can maintain the interlayer spacing of the positive electrode material within an appropriate range, which is beneficial to the embedding and extraction of ions, and reduces the impedance of the positive electrode material during the charging and discharging process, thereby improving the rate performance and cycle performance of the positive electrode material, especially the rate performance and cycle performance at higher voltages.

[0096] In some embodiments, the diffraction peak intensity I of the XRD test is 003 / I 104 ≥1.0.

[0097] Optionally, the diffraction peak intensity I003 / I104 of the XRD test can be 1.0, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4 or 1.45, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0098] In some embodiments, the specific surface area S1 of the positive electrode material is 0.5 m 2 / g-1.2 m 2 / g.

[0099] Optionally, the specific surface area S1 of the positive electrode material can be 0.5 m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g or 1.2 m 2 / g, etc., and can certainly be other values ​​within the above range, which are not limited here.

[0100] It can be understood that by limiting the specific surface area S1 of the positive electrode material, it is possible to ensure that the lithium-ion battery has excellent rate performance, cycle performance and storage performance. 2 / g, the rate performance, cycle performance and storage performance of the battery are not ideal. When the specific surface area S1 of the positive electrode material is greater than 1.2m 2 / g, the battery has good rate performance, but it is easy to react with the electrolyte, resulting in poor cycle performance and storage performance.

[0101] In some embodiments, the tap density of the positive electrode material is 1 >1.8g / cm 3 .

[0102] Optionally, the tap density of the positive electrode material is 1 Can be 1.82g / cm 3 , 1.83g / cm3 、1.84g / cm 3 , 1.85g / cm 3 , 1.86g / cm 3 , 1.87g / cm 3 、1.88g / cm 3 、1.89g / cm 3 or 1.90g / cm 3 wait.

[0103] It can be understood that the tap density of the positive electrode material is limited to 1 >1.8g / cm 3 It can ensure that the positive electrode material has enough active substances per unit volume, thereby ensuring the performance of the battery.

[0104] In some embodiments, the powder compaction density ρ 2 ≥2.8 g / cm 3 .

[0105] Optionally, the powder compaction density ρ 2 Can be 2.8g / cm 3 , 2.82g / cm 3 , 2.85g / cm 3 , 2.88g / cm 3 , 2.9g / cm 3 , 2.92g / cm 3 or 2.95g / cm 3 wait.

[0106] It can be understood that the powder compaction density ρ is limited 2 ≥2.8 g / cm 3 It can increase the discharge capacity of the battery, reduce internal resistance, reduce polarization loss, extend the cycle life of the battery, and improve the utilization rate of lithium-ion batteries.

[0107] In some embodiments, the Cl in the positive electrode material - and SO 4 2- Content <100ppm.

[0108] In some embodiments, the powder conductivity of the positive electrode material is > .

[0109] In some embodiments, the content of fluorine in the positive electrode material is 50ppm-2000ppm. It should be noted that fluorine usually exists in the positive electrode material in the form of ions.

[0110] In some embodiments, the thickness of the coating layer of the positive electrode material is 3nm-700nm. It should be noted that the thickness of the coating layer of the positive electrode material can be measured by XPS, TEM and other testing methods.

[0111] Optionally, the thickness of the coating layer of the positive electrode material can be 3nm, 5nm, 8nm, 10nm, 20nm, 50nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm or 700nm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0112] It can be understood that by limiting the thickness of the coating layer of the positive electrode material to a reasonable range, the conductivity of the positive electrode material can be effectively improved. When the thickness of the coating layer of the positive electrode material is less than 3nm, the amount of electrolyte and fast conductor in the coating layer cannot be guaranteed, so that the conductivity of the positive electrode material is limited. When the thickness of the coating layer of the positive electrode material is greater than 700nm, it is not conducive to the conduction of lithium ions and will also lead to a decrease in conductivity.

[0113] In some embodiments, the ratio of metallic lithium to transition metal in the positive electrode material is between 1.01 and 1.04.

[0114] Optionally, the ratio of metallic lithium to transition metal in the positive electrode material may be 1.01, 1.02, 1.03 or 1.04, etc., and may also be other values ​​within the above range, which is not limited here.

[0115] In some embodiments, the total impedance R of the positive electrode material at a voltage of 3.0V-4.3V, a temperature of 5°C, and 100% SOC satisfies: 20Ω<R<80Ω. It should be noted that the total impedance R=Rct+Rf+Rs, wherein Rct refers to the charge transfer impedance, Rf refers to the SEI film impedance, and Rs refers to the contact impedance.

[0116] The positive electrode material meets the following conditions: ≤D50 / D(003)≤ ; BET is the specific surface area of ​​the positive electrode material, FWHM (003) is the half-peak width of the 003 peak in the XRD test, and D003 is the grain size of the 003 peak.

[0117] It can be understood that the specific surface area and particle size D50 of the positive electrode material are inversely correlated, that is, the larger the particle size D50, the smaller the specific surface area. At the same time, the particle size D50 is related to the crystal structure, where the half-peak width of the 003 crystal plane and the grain size of the 003 crystal plane are representative parameters of the crystal structure of the ternary positive electrode material. In summary, the particle size, specific surface area, and unit cell parameters of the ternary single crystal positive electrode material are related to each other. The larger the half-peak width of the 003 peak, the smaller the particle size D50, the smaller the D003, and the larger the specific surface area; according to the data summary, the product value of the specific surface area and the half-peak width of the 003 peak falls between 1 / 4 and 1 / 2 of the ratio of D50 to D003. The positive electrode material that meets the above conditions has a better material energy density due to its better particle size and grain size, which is more conducive to the improvement of the electrical performance of the positive electrode material.

[0118] In a first aspect, the present application provides a method for preparing a positive electrode material, such as Figure 1 As shown, the preparation method includes the following steps S1 to S3:

[0119] Step S1: mixing a nickel-containing metal oxide precursor prepared by spray pyrolysis with a metal hydroxide and water to obtain a first mixture, and sintering the first mixture once to obtain a precursor;

[0120] Step S2: mixing the precursor with a lithium source, a halogen removal agent and an alkali metal dopant to obtain a second mixture, and performing secondary sintering on the second mixture to obtain a matrix;

[0121] Step S3: mixing the substrate and the surface coating agent to obtain a third mixture, and sintering the third mixture three times to obtain a positive electrode material.

[0122] It should be noted that spray pyrolysis refers to a method in which a metal salt solution precursor is atomized and then decomposed at high temperature to form a metal oxide powder. It simplifies multiple steps such as atomization-precipitation-thermal decomposition into a continuous, rapid and easy-to-control process. It does not require the subsequent filtration-washing-drying-crushing-calcination steps required in the conventional liquid phase method, nor does it require the ultra-high vacuum conditions required by the gas phase method.

[0123] In the above scheme, the preparation method of the present application is to mix the prepared nickel-containing metal oxide precursor with metal hydroxide and water in step S1 and then perform a first calcination. In this step, appropriate water is used to remove some impurities (such as Cl - or SO 4 2- ) is dissolved, and the dissolved Cl - or SO 4 2-It can react with metal hydroxide to generate halides, which can be fixed on the surface or surface layer of the material. - or SO 4 2- The complexing agent volatilizes and decomposes during high-temperature calcination and is removed from the material. The unreacted raw material is oxidized during high-temperature calcination to form a qualified oxide precursor. This step can eliminate and transform most impurities in the nickel-containing metal oxide precursor.

[0124] In the preparation method of the present application, in step S2, the precursor calcined in the first step is mixed with a lithium salt, a halogen remover, and an alkali metal dopant, and then sintered at a higher temperature for a second time. In this step, the halogen remover undergoes a solid phase exchange reaction with an impurity with a higher melting point, and the impurity is volatilized by the exchange reaction to generate a reactant with a lower melting point, or converted into an electrochemically active substance as an additive and enters the material. In addition, the halide formed by the reaction in step S1 will further react with the lithium salt to form a solid electrolyte coated on the surface of the material, while the unreacted Cl in the bulk phase - or SO 4 2- At higher temperatures, it either evaporates or reacts with alkali metal dopants and lithium salts to form solid electrolytes (such as sulfide and sulfate solid electrolytes) that are fixed in the bulk of the material, thereby stabilizing the structure of the material, thereby reducing the impedance of the material and greatly improving the rate performance of the material.

[0125] In the preparation method of the present application, in step S3, the substrate obtained by calcining in the second step is mixed with the surface coating agent and then sintered three times. In this step, the difficult-to-react SO in the nickel-containing metal oxide precursor is 4 2- Ions can react with the surface coating agent and residual lithium to form a fast ion conductor material similar to a solid electrolyte, which is coated on the surface of the material to improve the electronic conductivity of the material. In addition, the additional surface coating agent can be reduced with the cooperation of some transition metals and chlorides on the surface of the material, generating point-shaped metal objects (such as Mn, Fe, Al, etc.) on the surface of the material, and attached to the surface of the material in a discrete form, which can improve the electronic conductivity of the material and increase the powder conductivity of the material.

[0126] The preparation method of the present application uses a step-by-step reaction, a halogen removal agent and a surface coating agent to gradually eliminate or transform the impurities in the nickel-containing metal oxide precursor, and finally transform them into dopants and coatings that improve the performance of the material, thereby improving the structural stability of the final product, improving the rate performance and cycle performance of the material, and transforming the residual alkali and impurities on the surface of the material, reducing the process cost and the risk of gas production of the material. In this way, not only the technical drawbacks of the nickel-containing metal oxide precursor are solved, but also the favorable transformation of impurities is more effectively utilized.

[0127] The following is a detailed description of this program:

[0128] In some embodiments, the nickel-containing metal oxide precursor comprises a nickel-containing metal composite oxide, and the nickel-containing metal composite oxide has a chemical formula of , wherein 0<b≤1, c≤0.1, b+c≤1, M includes at least one of Mn, Al, Zr, Mg, Ti, Ba, Sr, Mg, Cr, Zn, V, Cu, and does not include Na.

[0129] It should be noted that the chemical formula is The nickel-containing metal oxide precursor is synthesized by spray pyrolysis, which is generally obtained by dissolving a mixed solution containing ternary metals by hydrochloric acid and sulfuric acid, and other complexing agents are used. Due to the fast reaction speed of spray pyrolysis, there are a large number of mixtures such as chlorides, sulfates and complexes that have not reacted in time, and these impurities will be brought into the nickel-containing metal oxide precursor along with normal materials. In addition, due to the fast reaction speed, some unreacted products (raw materials) that have not been oxidized are also brought into the nickel-containing metal oxide precursor at the same time. These mixture impurities and unreacted products that have not been oxidized will form many impurities and impurities after general sintering with lithium salts and are introduced into the finished material, resulting in deterioration of the electrochemical properties of the material, especially poor cycle performance of the final product and severe gas production.

[0130] In some embodiments, the particle size D50 of the nickel-containing metal oxide precursor is 1 μm-3 μm.

[0131] It should be noted that the particle size D50 represents the particle size of the material when the volume percentage content on the cumulative curve reaches 50%. Optionally, the particle size D50 of the nickel-containing metal oxide precursor can be 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.5 μm, 2.8 μm or 3 μm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0132] In some embodiments, the metal hydroxide comprises NaOH.

[0133] It can be understood that by adding a metal hydroxide containing NaOH in step S1, NaOH can enter the crystal structure of the nickel-containing metal oxide precursor to eliminate the structural defects of the material, and can also react with some impurities (such as chloride) in the nickel-containing metal oxide precursor to achieve the purpose of removing some impurities.

[0134] In some embodiments, the metal hydroxide further comprises Al(OH) 3 、Fe(OH) 3 、Mn(OH) 4 、Ti(OH)3 One or more of .

[0135] It is understood that metal hydroxides also include Al(OH) 3 、Fe(OH) 3 、Mn(OH) 4 、Ti(OH) 3 One or more of these metal hydroxides work synergistically with NaOH to better eliminate material structural defects and remove impurities.

[0136] In some embodiments, the particle size D50 of the metal hydroxide is 0.1 μm to 12 μm.

[0137] Optionally, in the first mixture, the particle size D50 of the metal hydroxide can be 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm or 12μm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0138] It can be understood that by specifically limiting the particle size of the metal hydroxide, it can match the particle size of the nickel-containing metal oxide precursor, and can ensure that the metal hydroxide can successfully penetrate into the material at the lower sintering temperature in step S2, enter the crystal structure of the material, and eliminate the structural defects of the material. When the particle size D50 of the metal hydroxide is less than 100nm, the particle size is too small to cause the metal hydroxide to fail to play a supporting role after entering the material, and the effect of eliminating the structural defects of the material cannot be achieved. When the particle size D50 is greater than 12μm, the particle size is too large to cause the metal hydroxide to fail to enter the material, and the effect of removing impurities in the nickel-containing metal oxide precursor cannot be achieved.

[0139] In some embodiments, the mass addition amount of the metal hydroxide is 0.002%-1% of the nickel-containing metal oxide precursor.

[0140] Optionally, the amount of metal hydroxide added to the nickel-containing metal oxide precursor can be 0.002%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0141] It can be understood that by specifically limiting the amount of metal hydroxide added, the purpose of better eliminating material structural defects and removing impurities can be achieved. When the amount of metal hydroxide added is less than 0.002% of the nickel-containing metal oxide precursor, it cannot eliminate material structural defects and remove impurities. When the amount of metal hydroxide added is greater than 1% of the nickel-containing metal oxide precursor, too much metal hydroxide is used, which will increase the cost of preparing raw materials and may also introduce new impurities.

[0142] In some embodiments, the ratio of the weight of water to the sum of the weight of the nickel-containing metal oxide precursor and the metal hydroxide is 1:10-1:50.

[0143] Optionally, the ratio of the weight of water to the sum of the weights of the nickel-containing metal oxide precursor and the metal hydroxide can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 or 1:50, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0144] It can be understood that by limiting the water-to-material ratio in the first mixture, impurities in the nickel-containing metal oxide precursor can be effectively dissolved. When the water-to-material ratio in the first mixture is less than 1:10, the amount of water is too small to effectively dissolve the impurities in the nickel-containing metal oxide precursor. When the water-to-material ratio in the first mixture is greater than 1:50, the concentration of the first mixture is too dilute, which will affect the contact and reaction efficiency between the raw materials.

[0145] In some embodiments, during the primary sintering process, the sintering temperature is 400°C-700°C.

[0146] Optionally, during a sintering process, the sintering temperature may be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C or 700°C, etc. Of course, it may also be other values ​​within the above range, which is not limited here.

[0147] In some embodiments, during a sintering process, the calcination time is 6 hours to 8 hours.

[0148] Optionally, during a sintering process, the calcination time may be 6 h, 6.5 h, 7.0 h, 7.5 h or 8 h, etc., and may also be other values ​​within the above range, which are not limited here.

[0149] In some embodiments, during the primary sintering process, calcination is performed in an air atmosphere.

[0150] It can be understood that by limiting the sintering temperature, calcination time and calcination atmosphere during the first calcination process, it is possible to ensure that the partially dissolved Cl - or SO 42- The complexing agent volatilizes and decomposes during high-temperature calcination and is removed from the material. The unreacted raw material is oxidized during high-temperature calcination to form a qualified oxide precursor, thereby improving calcination efficiency.

[0151] In some embodiments, the lithium salt is selected from at least one of lithium hydroxide and lithium carbonate.

[0152] It can be understood that by selecting lithium hydroxide or lithium carbonate as the lithium salt, these lithium salts react with the halide in the precursor to produce not only fast ion conductor materials, but also water and carbonates. Water and carbonates are easily removed during the calcination process, avoiding the introduction of new impurities in the nickel-containing metal oxide precursor due to improper selection of lithium salts.

[0153] In some embodiments, the ratio of the sum of the molar amount of the nickel-containing metal oxide precursor and the molar amount of the impurities in the nickel-containing metal oxide precursor to the molar amount of the lithium salt is 0.98-1.01.

[0154] It should be noted that after the nickel-containing metal oxide precursor is prepared, the impurities therein are measured by ICP test to determine the content of impurities in the nickel-containing metal oxide precursor. It can be understood that by limiting the ratio of the sum of the molar amount of the nickel-containing metal oxide precursor and the molar amount of the impurities in the nickel-containing metal oxide precursor to the molar amount of the lithium salt in the second mixture, the impurities in the nickel-containing metal oxide precursor can be more effectively converted into electrochemically active substances, thereby improving the electrochemical performance of the material.

[0155] In some embodiments, the halogen scavenger includes a transition metal oxide or a transition metal halide.

[0156] In some embodiments, the halogen removal agent includes InBr 3 , YBr 3 , Y 2 O 3 ,In 2 O 3 , CaBr 2 , CeO 2 , SmO 2 At least one of .

[0157] It can be understood that by specifically limiting the type of halogen remover, impurities with higher melting points in the nickel-containing metal oxide precursor can undergo a more effective solid-phase exchange reaction with the halogen remover, thereby more effectively volatilizing the impurities through the exchange reaction to generate reactants with lower melting points, or converting them into electrochemically active substances as additives and entering the material, thereby achieving the purpose of removing impurities and improving the electrochemical properties of the material.

[0158] In some embodiments, the alkali metal dopant includes a fluoride salt, and specifically can be selected from at least one of NaF, LiF, and KF.

[0159] It can be understood that the main function of the alkali metal dopant is to dope the alkali metal ions into the nickel-containing metal oxide precursor, which can increase the thickness of the lithium oxygen layer of the material, reduce the cation anti-site defects, and reduce the cation mixing, so as to further eliminate the structural defects of the material and improve the performance of the material. - or SO 4 2- The reaction forms a solid electrolyte to further remove impurities in the material. Alkali metal dopants are selected from fluoride salts, which can be more easily doped into the material. After the alkali metal ions of the fluoride salts are removed, the fluoride ions are stable anions and can be stably present in the material, enhancing the structural stability of the material. It is also easier to react with anions to achieve the effect of removing impurities in the material.

[0160] In some embodiments, during the secondary sintering process, the sintering temperature is 500°C-900°C.

[0161] Optionally, during the secondary sintering process, the sintering temperature can be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0162] In some embodiments, during the secondary sintering process, the calcination time is 8h-10h.

[0163] Optionally, during the secondary sintering process, the calcination time may be 8 h, 8.5 h, 9.0 h, 9.5 h or 10 h, etc., and of course may be other values ​​within the above range, which are not limited here.

[0164] In some embodiments, during the secondary sintering process, calcination is performed in an oxygen atmosphere.

[0165] It can be understood that by limiting the sintering temperature, sintering time and sintering atmosphere during the second sintering process, the sintering efficiency of the secondary sintering can be guaranteed, so that the impurities can be more fully volatilized after the exchange reaction to generate reactants with lower melting points, or can be more effectively converted into electrochemically active substances as additives and enter the material. The halide formed by the reaction in step S1 will further react with the lithium salt to form a solid electrolyte coated on the surface of the material, while the unreacted Cl in the bulk phase - or SO 4 2-At higher temperatures, it either evaporates or reacts with alkali metal dopants and lithium salts to form solid electrolytes (such as sulfide and sulfate solid electrolytes) that are fixed in the bulk of the material, thereby stabilizing the structure of the material, thereby reducing the impedance of the material and greatly improving the rate performance of the material.

[0166] In some embodiments, during the secondary sintering process, the sintering temperature of the secondary sintering is greater than the sintering temperature of the primary sintering.

[0167] It can be understood that the purpose of step S2 includes removing impurities with higher melting points than the impurities in step S1. In order to achieve a more effective impurity removal effect, the sintering temperature of the secondary sintering is designed to be greater than the sintering temperature of the first calcination.

[0168] In some embodiments, the surface coating agent comprises a phosphate, wherein the phosphate comprises H 3 PO 4 , Li 3 PO 4 , LiH 2 PO 4 , K 3 PO 4 、Na 3 PO 4 NH 4 PO 4 At least one of .

[0169] It is understandable that phosphate can react with SO which is difficult to react in step S3. 4 2- , the residual lithium reacts to generate the chemical formula Li a M b SO 4 The fast ion conductor compounds and phosphate coatings are coated on the surface of the material, which is beneficial to the conduction of lithium ions to improve the electrochemical properties of the material.

[0170] In some embodiments, the surface coating agent further comprises CaO, CaCO 3 、SnO、TiO 2 At least one of .

[0171] It can be understood that the surface coating agent also includes CaO, CaCO 3 、SnO、TiO 2 At least one of the above substances is added, and the addition of such substances is conducive to the formation of a solid electrolyte, and substances that do not react with the electrolyte can be coated on the surface.

[0172] In some embodiments, during the three sintering processes, the sintering temperature is 400°C-800°C.

[0173] Optionally, during the three sintering processes, the sintering temperature can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0174] In some embodiments, during the three sintering processes, the calcination time is 5 h to 8 h.

[0175] Optionally, during the three sintering processes, the calcination time can be 5 h, 5.5 h, 6 h, 6.5 h, 7.0 h, 7.5 h or 8 h, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0176] In some embodiments, during the tertiary sintering process, calcination is performed in an oxygen atmosphere.

[0177] It can be understood that by limiting the sintering temperature, calcination time and calcination atmosphere during the three sintering processes, the calcination efficiency of the three sintering processes can be guaranteed, so that the SO 4 2- The ions can better react with the surface coating agent and residual lithium to generate a fast ion conductor material similar to a solid electrolyte, which is coated on the surface of the material and improves the electronic conductivity of the material.

[0178] In a third aspect, the present application also provides a positive electrode material for a lithium-ion battery, wherein the positive electrode material for a lithium-ion battery comprises the positive electrode material described above or the positive electrode material obtained by the preparation method described above.

[0179] The following is a further description of the embodiments of the present application in multiple embodiments. The embodiments of the present application are not limited to the following specific embodiments. Within the scope of protection, appropriate changes can be made to the implementation.

[0180] Example 1

[0181] A method for preparing a positive electrode material comprises the following steps:

[0182] Step S1: Prepare a mixed solution of metal salts according to the molar ratio of Ni:Co:Mn=0.65:0.1:0.25, and prepare a nickel-containing metal oxide precursor Ni by spray pyrolysis granulation. 0.65 Co 0.1 Mn 0.25 O 2 .

[0183] 300 g of the prepared nickel-containing metal oxide precursor, 0.09 g of Mn(OH) with a particle size of D50 = 700 nm, 4and 0.7 g of NaOH with a particle size of D50 = 800 nm are added to a mixing container, and then deionized water is added to ensure that the water-to-material ratio is 1:15, and mixed evenly to obtain a first mixture; the obtained first mixture is placed in a box furnace and sintered at 500° C. for 6 hours in an air atmosphere to obtain a precursor.

[0184] Step S2: The obtained precursor was crushed, and 100 g of the crushed precursor was mixed with 52 g of LiOH and 0.6 g of YBr 3 , and 1.5 g NaF are mixed evenly to obtain a second mixture; the obtained second mixture is placed in a box furnace and secondary sintered at 900° C. for 10 h in an oxygen atmosphere to obtain a matrix material.

[0185] Step S3: crush the obtained matrix, take 50g of the crushed matrix and mix it with 1g Li 3 PO 4 , 0.7 g CaO and mixed evenly to obtain a third mixture; the obtained third mixture was placed in a box furnace and sintered three times at 550° C. for 5 h in an oxygen atmosphere, and then crushed and sieved to obtain a positive electrode material.

[0186] The positive electrode material includes LiNi 0.65 Co 0.1 Mn 0.25 O 2 and a coating layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer comprising Li 2 MnCl 6、 Yj Y 6、 Li 2 S, the second coating layer includes Li 3 PO 4 , Ca 3 (PO 4 ) 2 And Na 2 SO 4 .

[0187] Example 2

[0188] A method for preparing a positive electrode material comprises the following steps:

[0189] Step S1: Prepare a mixed solution of metal salts according to the molar ratio of Ni:Co:Al=0.9:0.1:0.1, and prepare a nickel-containing metal oxide precursor Ni by spray pyrolysis granulation. 0.9 Co 0.1 Al 0.1 O 2 .

[0190] 200 g of the prepared nickel-containing metal oxide precursor, 0.05 g of Al(OH) 3 and 0.2 g of NaOH with a particle size of D50 = 200 nm are added to a mixing container, and then deionized water is added to ensure that the water-to-material ratio is 1:20, and mixed evenly to obtain a first mixture; the obtained first mixture is placed in a box furnace and sintered at 450° C. for 6 hours in an air atmosphere to obtain a precursor.

[0191] Step S2: The obtained precursor was crushed, and 100 g of the crushed precursor was mixed with 53 g of Li 2 CO 3 、0.3gInBr 3 , and 1.2 g KF were mixed evenly to obtain a second mixture; the obtained second mixture was placed in a box furnace and secondary sintered at 700° C. for 8 h in an oxygen atmosphere to obtain a matrix material.

[0192] Step S3: crush the obtained matrix, take 50g of the crushed matrix and mix it with 2.2g NH 4 PO 4 , 0.4 g SnO were mixed evenly to obtain a third mixture; the third mixture was placed in a box furnace and sintered three times at 600° C. for 5 h in an oxygen atmosphere, and then crushed and sieved to obtain a positive electrode material.

[0193] The positive electrode material includes LiNi 0.9 Co 0.1 Al 0.1 O 2 and a coating layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer comprising LiAlCl 4 、LiInBr 6 , Li 2 S and LiSnCl 6 The second coating layer includes LiHPO 4 ,LiKSO 4 and LiNaSO 4 .

[0194] Example 3

[0195] A method for preparing a positive electrode material comprises the following steps:

[0196] Step S1: Prepare a mixed solution of metal salts according to the molar ratio of Ni:Co:Mn=0.83:0.1:0.07, and prepare a nickel-containing metal oxide precursor Ni by spray pyrolysis granulation. 0.83 Co 0.1 Mn 0.07 O 2 .

[0197] 500 g of the prepared nickel-containing metal oxide precursor and 2.4 g of Al(OH) 3 , 2.5 g of NaOH with a particle size of D50 = 500 nm is added to a mixing container, and then deionized water is added to ensure that the water-to-material ratio is 1:25, and mixed evenly to obtain a first mixture; the obtained first mixture is placed in a box furnace and sintered at 600° C. for 6 hours in an air atmosphere to obtain a precursor.

[0198] Step S2: The obtained precursor was crushed, and 300 g of the crushed precursor was mixed with 157 g of Li 2 CO 3 、1.4gIn 2 O 3 , and 1.2 g LiF were mixed evenly to obtain a second mixture; the obtained second mixture was placed in a box furnace and secondary sintered at 800° C. for 10 h in an oxygen atmosphere to obtain a matrix material.

[0199] Step S3: The obtained matrix was crushed, and 100 g of the crushed matrix was mixed with 4.2 g NH 4 PO 4 , 0.7 g CaCO 3 The mixture was mixed evenly to obtain a third mixture; the third mixture was placed in a box furnace and sintered three times at 650° C. for 5 hours in an oxygen atmosphere, and then crushed and sieved to obtain a positive electrode material.

[0200] The positive electrode material includes LiNi 0.83 Co 0.1 Mn 0.07 O 2 and a coating layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer comprising LiAlCl 4 、LiInCl 6 Li 2 S, the second coating layer includes Ca 3 (PO 4 ) 2 , Li 2 SO 4 .

[0201] Example 4

[0202] Step S1: Prepare a mixed solution of metal salts according to the molar ratio of Ni:Mn=0.8:0.2, and prepare a nickel-containing metal oxide precursor Ni by spray pyrolysis granulation. 0.8 Mn 0.2 O 2 .

[0203] 200 g of the prepared nickel-containing metal oxide precursor and 0.4 g of Al(OH)3 and 1.3 g of NaOH with a particle size of D50 = 600 nm are added to a mixing container, and then deionized water is added to ensure that the water-to-material ratio is 1:30, and mixed evenly to obtain a first mixture; the obtained first mixture is placed in a box furnace and sintered at 500° C. for 6 hours in an air atmosphere to obtain a precursor.

[0204] Step S2: The obtained precursor was crushed, 100 g of the crushed precursor was taken and added with 59 g LiOH, 3.7 g SmO 2 , and 1.7 g LiF were mixed evenly to obtain a second mixture; the obtained second mixture was placed in a box furnace and secondary sintered at 810° C. for 10 h in an oxygen atmosphere to obtain a matrix material.

[0205] Step S3: crush the obtained matrix, take 50g of the crushed matrix and mix it with 0.8g Na 3 PO 4 , 0.2 g CaO and evenly mixed to obtain a third mixture; the obtained third mixture was placed in a box furnace and sintered three times at 700° C. for 5 h in an oxygen atmosphere, and then crushed and sieved to obtain a positive electrode material.

[0206] The positive electrode material includes LiNi 0.8 Mn 0.2 O 2 and a coating layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer comprising LiAlCl 4 ;Li 2 SmCl 6 Li 2 S, the second coating layer includes Ca 3 (PO 4 ) 2 , Li 2 SO 4 、LiNaSO 4 Li 3 PO 4 .

[0207] Example 5

[0208] Step S1: Prepare a mixed solution of metal salts according to the molar ratio of Ni:Co:Mn=0.88:0.1:0:02, and prepare a nickel-containing metal oxide precursor Ni by spray pyrolysis granulation. 0.88 Co 0.1 Mn 0.05 O 2 .

[0209] 200 g of the prepared nickel-containing metal oxide precursor, 0.2 g of Fe(OH) 3, 1.3 g of NaOH with a particle size of D50 = 2 μm is added to a mixing container, and then deionized water is added to ensure that the water-to-material ratio is 1:17, and mixed evenly to obtain a first mixture; the obtained first mixture is placed in a box furnace and sintered once at 550° C. for 8 hours in an air atmosphere to obtain a precursor.

[0210] Step S2: The obtained precursor was crushed, and 100 g of the crushed precursor was mixed with 54 g of LiOH and 0.7 g of Y 2 O 3 , and 1.0 g NaF were mixed evenly to obtain a second mixture; the obtained second mixture was placed in a box furnace and secondary sintered at 800° C. for 10 h in an oxygen atmosphere to obtain a matrix material.

[0211] Step S3: crush the obtained matrix, take 50g of the crushed matrix, 0.4g K 3 PO 4 , 0.2 g Ca(OH) 2 The mixture was mixed evenly to obtain a third mixture; the third mixture was placed in a box furnace and sintered three times at 750° C. for 8 hours in an oxygen atmosphere, and then crushed and sieved to obtain a positive electrode material.

[0212] The positive electrode material includes LiNi 0.88 Co 0.1 Mn 0.05 O 2 and a coating layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer comprising Li 2 FeCl 4 ;LiYCl 6 Li 2 S, the second coating layer includes Ca 3 (PO 4 ) 2 , Li 2 SO 4 ,LiKSO 4 Li 3 PO 4 .

[0213] Example 6

[0214] Step S1: Prepare a mixed solution of metal salts according to the molar ratio of Ni:Co:Al=0.94:0.05:0:01, and prepare a nickel-containing metal oxide precursor Ni by spray pyrolysis granulation. 0.94 Co 0.05 Al 0.01 O 2 .

[0215] 300 g of the prepared nickel-containing metal oxide precursor, 0.7 g of Co(OH) 2 and 1.5 g of NaOH with a particle size of D50 = 5 μm are added to a mixing container, and then deionized water is added to ensure that the water-to-material ratio is 1:22, and mixed evenly to obtain a first mixture; the obtained first mixture is placed in a box furnace and sintered once at 650° C. for 8 hours in an air atmosphere to obtain a precursor.

[0216] Step S2: The obtained precursor was crushed, and 200 g of the crushed precursor was mixed with 98 g of LiOH and 0.8 g of Y 2 O 3 , and 1.0 g of LiF were mixed evenly to obtain a second mixture; the obtained second mixture was placed in a box furnace and secondary sintered at 740° C. for 10 h in an oxygen atmosphere to obtain a matrix material.

[0217] Step S3: crush the obtained matrix, take 100g of the crushed matrix and mix it with 0.8g H 3 PO 4 , 0.6 g TiO 2 The mixture was mixed evenly to obtain a third mixture; the third mixture was placed in a box furnace and sintered three times at 750° C. for 8 hours in an oxygen atmosphere, and then crushed and sieved to obtain a positive electrode material.

[0218] The positive electrode material includes LiNi 0.94 Co 0.05 Al 0.01 O 2 and a coating layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer comprising Li 2 CoCl 6 、LiYCl 6 ;Li 2 TiCl 6 Li 2 S, the second coating layer includes Li 3 PO 4 , Li 2 SO 4 Li 2 Ti(PO 4 ) 2 .

[0219] Example 7

[0220] The difference from Example 1 is that in step S1, the metal hydroxide is Mn(OH) with a particle size D50=100 nm. 4 and NaOH with particle size D50=100nm.

[0221] Example 8

[0222] The difference from Example 1 is that in step S1, the metal hydroxide is Mn(OH) with a particle size D50=12 μm. 4 and NaOH with particle size D50 = 12 μm.

[0223] Example 9

[0224] The difference from Example 1 is that in step S1, the metal hydroxide is Mn(OH) with a particle size D50=50 nm. 4 and NaOH with particle size D50=80nm.

[0225] Example 10

[0226] The difference from Example 1 is that in step S1, the metal hydroxide is Mn(OH) with a particle size D50=50 μm. 4 and NaOH with particle size D50 = 60 μm.

[0227] Embodiment 11

[0228] The difference from Example 1 is that in step S1, the metal hydroxide is Al(OH) with a particle size D50=10 μm. 3 and Mn(OH) with particle size D50=7μm 2 .

[0229] Example 12

[0230] Different from Example 1, in step S1, the water-to-material ratio is 1:10.

[0231] Embodiment 13

[0232] The difference from Example 1 is that in step S1, the water-to-material ratio is 1:50.

[0233] Embodiment 14

[0234] Different from Example 1, in step S1, the water-to-material ratio is 1:4.

[0235] Embodiment 15

[0236] Different from Example 1, in step S1, the water-to-material ratio is 1:80.

[0237] Example 16

[0238] Different from Example 1, in step S1, the amount of the metal hydroxide added is 1.8% of the nickel-containing metal oxide precursor.

[0239] Embodiment 17

[0240] Different from Example 1, in step S1, the primary sintering temperature is 400°C, in step S2, the secondary sintering temperature is 500°C, and in step S3, the third sintering temperature is 400°C.

[0241] Embodiment 18

[0242] The difference from Example 1 is that in step S2, the halogen removal agent is MgO.

[0243] Embodiment 19

[0244] The difference from Example 1 is that in step S3, the surface coating agent is Al 2 O 3 .

[0245] Comparative Example 1

[0246] A method for preparing a positive electrode material in this comparative example comprises the following steps:

[0247] Step S1: Prepare a mixed solution of metal salts according to the molar ratio of Ni:Co:Mn=0.65:0.1:0.25, and prepare a nickel-containing metal oxide precursor Ni by spray pyrolysis granulation. 0.65 Co 0.1 Mn 0.25 O 2 .

[0248] Step S2: 200 g of the prepared nickel-containing metal oxide precursor and 90 g of Li 2 CO 3 , 0.4g Al 2 O 3 The mixture was mixed evenly to obtain a mixture; the mixture was placed in a box furnace and calcined at 780° C. for 10 h in an oxygen atmosphere, and then crushed and sieved to obtain a positive electrode material.

[0249] Comparative Example 2

[0250] A method for preparing a positive electrode material in this comparative example comprises the following steps:

[0251] Step S1: Prepare a mixed solution of metal salts according to the molar ratio of Ni:Co:Mn=0.83:0.1:0.07, and prepare a nickel-containing metal oxide precursor Ni by spray pyrolysis granulation. 0.83 Co 0.1 Mn 0.07 O 2 .

[0252] Step S2: 200 g of the prepared nickel-containing metal oxide precursor was mixed with 98 g of LiOH and 0.5 g of TiO 2The mixture was mixed evenly to obtain a mixture; the mixture was placed in a box furnace and calcined at 800° C. for 10 h in an oxygen atmosphere, and then crushed and sieved to obtain a positive electrode material.

[0253] Test Method

[0254] The performance of the positive electrode materials obtained in the above examples and comparative examples was tested using the following method.

[0255] The test method of the unit cell parameter Dp is as follows:

[0256] XRD diffractometer was used to test the unit cell parameter Dp and diffraction peak intensity I003 / I104. The peak intensity of 003 and 104 diffraction peaks was measured by XRD and I 003 / I 104 The half-peak widths of 003 and 104 were measured by XRD, and Dp was calculated by the Bragg formula.

[0257] Diffraction peak intensity I 003 / I 104 The test method is as follows:

[0258] XRD diffractometer was used to test the unit cell parameter Dp and diffraction peak intensity I 003 / I 104 , the peak intensities of the 003 and 104 diffraction peaks were measured by XRD, and I 003 / I 104 .

[0259] The test method for the specific surface area S1 of the positive electrode material is as follows:

[0260] The specific surface area was tested using an American Micrometer tester: the test was performed after degassing at 300°C in vacuum for 1 hour.

[0261] The test method for the tap density ρ1 of the positive electrode material is as follows:

[0262] Dandong Better BT-303 was used to test the compacted density: vibration rate 3000 times / min, vibration time 1min, vibration amplitude 3mm±0.1mm.

[0263] The test method of the powder compaction density ρ2 of the positive electrode material is as follows:

[0264] The compaction density of the powder was tested using a compaction density meter: 6t pressure for 30s.

[0265] This application uses an ICP tester to test the content of each element in the positive electrode material.

[0266] Ion chromatography was used to test the Cl content in the positive electrode material. - 、SO 4 2-The content of ppm refers to Cl - 、SO 4 2- The mass accounts for parts per million of the positive electrode material mass.

[0267] The following method was used to test the electrochemical cycle performance: the positive electrode material was mixed with conductive carbon black and binder PVDF (polyvinylidene fluoride) in a mass ratio of 80:10:10, and NMP (N-methylpyrrolidone) was added to make a uniform slurry and applied on copper foil, dried in an oven, and rolled at a pressure of 10 MPa, and then cut into a circular electrode with a diameter of 14 mm. The lithium-ion battery was assembled according to the industrial CR2025 button battery, the diaphragm was Cellgard diaphragm, and the electrolyte was 1 mol / L LiPF with EC / PC / DEC as the solvent. 6 The solution is a lithium sheet. The entire assembly process is carried out in a glove box filled with argon gas, and the oxygen content and moisture content in the glove box are controlled below 0.5 ppm. The lithium-ion battery test conditions are: temperature is 25℃±1℃, the voltage range of the charge and discharge cycle is 3.0V-4.3V, the current size is 0.1C (20mAh / g), and the cycle test is carried out for 100 weeks at 0.5C charge and 1C discharge.

[0268] The electrochemical impedance of the positive electrode material was tested by the following method. The button cell assembled above was subjected to a 2.5-week charge and discharge test. The fully charged button cell was then placed in a -20°C constant temperature box and the low-temperature electrochemical impedance of the positive electrode material was tested using an Arbin electrochemical workstation. The total impedance value R of Rf+Rs+Rct was calculated by impedance fitting.

[0269] Table 1 Comparison of the performance of the positive electrode materials obtained in the examples and comparative examples after being assembled into batteries

[0270]

[0271] Table 2 Comparison of particle sizes of positive electrode materials obtained in Examples and Comparative Examples

[0272]

[0273] As shown in Table 1, according to the experimental results of Example 1 and Comparative Example 1, and Example 3 and Comparative Example 3, it can be seen that compared with the one-time calcination process, the present application adopts three step-by-step reactions, and different impurity removers are selected in each step of the reaction, which can effectively eliminate Cl in the nickel-containing metal oxide precursor. - 、SO 4 2-It can also convert some impurities in the nickel-containing metal oxide precursor into electrochemically active substances as additives and enter the material or coat the surface of the material, thereby effectively reducing the impedance of the positive electrode material. It can be seen from the experimental results of Examples 1-19 that the impedance of the positive electrode material prepared by the preparation method of the present application at -20°C can reach a minimum of 27Ω, which can improve the rate performance of the positive electrode material.

[0274] The selection of process parameters in each step of the reaction of this application is also very important. It can be seen from the experimental results of Examples 1-19 that the selection of metal hydroxides with different particle sizes has a great influence on the removal of impurities in the nickel-containing metal oxide precursor and the impedance of the final positive electrode material. The selection of metal hydroxides with a particle size D50 of 100nm-12μm for reaction has a better impurity removal effect and can further reduce the impedance of the positive electrode material. Compared with other impurity removers, the halogen remover selected InBr 3 , YBr 3 , Y 2 O 3 ,In 2 O 3 , CaBr 2 , CeO 2 , SmO 2 At least one of the following, the surface coating agent is CaO, CaCO 3 , SnO, TiO 2 At least one of them can be combined with phosphate to achieve better impurity removal effect and reduce the impedance of the positive electrode material.

[0275] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A positive electrode material, It is characterized in that include: Lithium nickel metal composite oxide; and A coating layer, at least part of which is located on the surface of the lithium nickel metal composite oxide; the coating layer includes a first coating layer and a second coating layer located on the surface of the first coating layer, the first coating layer includes a halide solid electrolyte; the second coating layer includes a sulfate fast ion conductor; The chemical formula of the halide solid electrolyte is Li x N´ y N´´ z , wherein 1≤x≤2, 1≤y≤3, 2≤z≤8, N´ includes at least one of Ti, Mn, Al, Fe, Sm, Sn, In, and Co; N´´ includes at least one of Cl and Br; The chemical formula of the sulfate fast ion conductor is Li a M b SO 4 , wherein 0≤a≤4, 0≤b≤3, and M includes at least one of Na, Li, and K.

2. The positive electrode material according to claim 1, It is characterized in that The invention comprises at least one of the following features (1) to (6): (1) The halide solid electrolyte includes LiSmCl 6 ,LiYBr 6 , Li 2 TiCl 4 、LiYCl 6 、LiSnCl 6 , Li 2 FeCl 4 , Li 2 CoCl 6 , Li 1.5 Mn 1.2 Cl 4 、LiAlCl 4 Li 2 MnCl 4 At least one of; (2) The sulfate fast ion conductor includes NaSO 4 、LiNaSO 4 , Li 2 SO 4 ,LiKSO 4 At least one of; (3) The second coating layer further includes a phosphate compound, wherein the phosphate compound includes at least one of lithium phosphate, calcium phosphate, lithium titanium phosphate, calcium hydrogen phosphate and lithium hydrogen phosphate; (4) The first coating layer further comprises a sulfide, the chemical formula of which is Li x S, where 0.8≤x≤3; (5) Based on the positive electrode material, the content of the halide solid electrolyte is 400ppm-8000ppm; (6) Based on the positive electrode material, the content of the sulfate fast ion conductor is 500ppm-6000ppm.

3. The positive electrode material according to claim 1 or 2, It is characterized in that The invention comprises at least one of the following features (1) to (4): (1) The lithium nickel metal composite oxide contains at least one of a halide and a sulfide solid electrolyte in the bulk phase; (2) In the lithium nickel metal composite oxide bulk phase, the chemical formula of the halide is Li x N´ y N´´ z , wherein 1≤x≤2, 1≤y≤3, 2≤z≤8, N´ includes at least one of Ti, Mn, Al, Fe, Sm, Sn and Co, and N´´ includes at least one of Cl and Br; (3) In the lithium nickel metal composite oxide bulk phase, the chemical formula of the sulfide is Li x S, where 0.8≤x≤3; (4) Based on the positive electrode material, the content of halide in the lithium nickel metal composite oxide bulk phase is 200ppm-30000ppm, and the content of sulfide solid electrolyte is 500ppm-2000ppm.

4. The positive electrode material according to claim 1 or 2, It is characterized in that The invention comprises at least one of the following features (1) to (13): (1) The general chemical formula of the lithium nickel metal composite oxide is Li a Ni b Co c M 1-b-c O 2 , wherein 0.95≤a≤1.2, 0<b≤1, c≤0.1, b+c≤1, and M includes at least one of Mn, Al, Zr, Mg, Ti, Ba, Sr, Mg, Cr, Zn, V, and Cu; (2) The unit cell parameter Dp of the positive electrode material measured by XRD is 70nm-120nm; (3) The diffraction peak intensity I of the positive electrode material tested by XRD 003 / I 104 ≥1.0; (4) The specific surface area S1 of the positive electrode material is 0.5 m 2 / g-1.2 m 2 / g; (5) The tap density of the positive electrode material is ρ1>1.8 g / cm 3 ; (6) The powder compaction density of the positive electrode material is ρ2 ≥ 2.8 g / cm 3 ; (7) Cl in the positive electrode material - and SO 4 2- The content is less than 100ppm; (8) The powder conductivity of the positive electrode material is > ; (9) The positive electrode material meets the following conditions: ≤D50 / D(003)≤ ; BET is the specific surface area of ​​the positive electrode material, FWHM (003) is the half-peak width of the 003 peak in the XRD test, and D (003) is the grain size of the 003 peak; (10) The content of fluorine in the positive electrode material is 50ppm-2000ppm; (11) The thickness of the coating layer of the positive electrode material is 3nm-700nm; (12) The thickness of the first coating layer is 5nm-60nm; (13) The thickness of the second coating layer is 3nm-15nm.

5. The positive electrode material according to claim 1, It is characterized in that The invention comprises at least one of the following features (1)-(2): (1) The molar ratio of metallic lithium to transition metal in the positive electrode material is between 1.01 and 1.04; (2) The total impedance R of the positive electrode material at a voltage of 3.0 V to 4.3 V, a temperature of 5° C., and a SOC of 100% satisfies: 20Ω<R<80Ω.

6. A method for preparing the positive electrode material according to any one of claims 1 to 5, It is characterized in that The steps include: Mixing a nickel-containing metal oxide precursor prepared by spray pyrolysis with a metal hydroxide and water to obtain a first mixture, and sintering the first mixture once to obtain a precursor; The precursor is mixed with a lithium source, a halogen removal agent and an alkali metal dopant to obtain a second mixture, and the second mixture is subjected to secondary sintering to obtain a matrix; The substrate is mixed with a surface coating agent to obtain a third mixture, and the third mixture is sintered three times to obtain a positive electrode material.

7. The preparation method according to claim 6, It is characterized in that Satisfy one of the following characteristics (1)-(10): (1) The nickel-containing metal oxide precursor comprises a nickel-containing metal composite oxide, and the nickel-containing metal composite oxide has a general chemical formula of , wherein 0<b≤1, c≤0.1, b+c≤1, M includes at least one of Mn, Al, Zr, Mg, Ti, Ba, Sr, Mg, Cr, Zn, V, Cu, and does not include Na; (2) The particle size D50 of the nickel-containing metal oxide precursor is 1 μm-3 μm; (3) The metal hydroxide includes NaOH; (4) The metal hydroxide also includes Al(OH) 3 、Fe(OH) 3 、Mn(OH) 4 、Ti(OH) 3 At least one of; (5) The particle size D50 of the metal hydroxide is 0.1 μm-12 μm; (6) The mass addition amount of the metal hydroxide is 0.002%-1% of the nickel-containing metal oxide precursor; (7) The weight ratio of the nickel-containing metal oxide precursor to the metal hydroxide to water is 10:1-50:1; (8) The primary sintering temperature is 400°C-700°C; (9) The primary sintering time is 6h-8h; (10) The primary sintering is carried out in an air atmosphere.

8. The preparation method according to claim 6, It is characterized in that Satisfy one of the following characteristics (1)-(10): (1) The lithium source includes at least one of lithium hydroxide and lithium carbonate; (2) The ratio of the sum of the molar amounts of the nickel-containing metal oxide precursor and the impurities in the nickel-containing metal oxide precursor to the molar amount of the lithium source is 0.98-1.01; (3) The halogen removal agent includes at least one of a transition metal oxide and a transition metal halide; (4) The halogen removal agent includes InBr 3 , YBr 3 , Y 2 O 3 ,In 2 O 3 , CaBr 2 , CeO 2 and SmO 2 At least one of; (5) The alkali metal dopant includes a fluoride salt; (6) The fluoride salt includes at least one of NaF, LiF, and KF; (7) The secondary sintering temperature is 500°C-900°C; (8) The secondary sintering time is 8h-10h; (9) The secondary sintering is carried out in an oxygen atmosphere; (10) The secondary sintering temperature is greater than the primary sintering temperature.

9. The preparation method according to claim 6, It is characterized in that Satisfy one of the following characteristics (1)-(5): (1) The surface coating agent includes phosphate; (2) The surface coating agent includes phosphate, and the phosphate includes H 3 PO 4 , Li 3 PO 4 , LiH 2 PO 4 , K 3 PO 4 、Na 3 PO 4 NH 4 PO 4 At least one of; (2) The surface coating agent also includes CaO, CaCO 3 、SnO、TiO 2 At least one of; (3) The three sintering temperatures are 400°C-800°C; (4) The three sintering times are 5h-8h; (5) The three sintering steps are performed in an oxygen atmosphere.

10. A lithium ion battery, It is characterized in that The invention comprises the positive electrode material according to any one of claims 1 to 5 or the positive electrode material obtained by the preparation method according to any one of claims 6 to 9.

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