Positive electrode materials and their preparation methods, positive electrode sheets, lithium-ion batteries and electrical devices

Abstract

This application belongs to the field of battery technology, specifically relating to cathode materials and their preparation methods, cathode sheets, lithium-ion batteries, and power devices. The cathode material includes cathode material particles, comprising: Li... a Na b Ni 0.6‑h‑i Mn 0.4+h M i O 2‑j X k The cathode material belongs to the P63mc space group. The cathode material was tested in a half-cell with a lithium metal sheet as the counter electrode. Under conditions of 2.0V~4.6V and 0.1C / 0.1C, the capacity / voltage differential curves showed a first set of redox peaks and a second set of redox peaks between 2.0V and 4.6V; the peak voltage difference of these redox peaks was ≤100mV. This cathode material exhibits excellent electrochemical performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to cathode materials and their preparation methods, cathode sheets, lithium-ion batteries and electrical devices. Background Technology

[0002] Currently, ternary layered oxides (R-3m space group) can significantly improve specific capacity by increasing nickel content and raising cutoff voltage. However, these materials still suffer from poor cycle stability, unsatisfactory fast-charging performance, and low ionic conductivity. Furthermore, they are prone to capacity decay, voltage decay, and structural phase transitions at high voltages. Traditional modification processes are complex and costly, making it difficult to meet the demands of high-performance batteries. Therefore, cathode materials require further improvement. Summary of the Invention

[0003] This application aims to at least partially solve one of the technical problems in the related art. To this end, this application proposes a positive electrode material, positive electrode sheet, battery, and electrical device with high structural stability, specific capacity, energy density, and rate performance.

[0004] A first aspect of this application provides a cathode material comprising cathode material particles, wherein the cathode material particles comprise: Li a Na b Ni 0.6-h-i Mn 0.4+h M i O 2-j X k Wherein, 0.65≤a≤1.0, 0≤b≤0.03, 0<h≤0.4, 0<i≤0.1, 0<j≤0.05, 0≤k≤0.05; M includes at least one of Co, B, Mg, Al, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Zr, Nb, Ba, Mo, Ru, Sn, La, Sr, Y, Ca, W, Eu, and Bi; X includes at least one of N, P, S, F, Cl, and Br; The cathode material is in space group P63mc. The positive electrode material was tested in a half-cell with a lithium metal sheet as the counter electrode. Under the conditions of 2.0 V to 4.6 V and 0.1C / 0.1C, the capacity / voltage differential curve showed a first set of redox peaks and a second set of redox peaks between 2.0 V and 4.6 V. The peak voltage difference of the first group of redox peaks and the peak voltage difference of the second group of redox peaks each independently satisfy: ΔEp≤100 mV; The peak voltage difference ΔEp refers to the absolute value of the difference between the peak potential of the oxidation peak Epa and the peak potential of the reduction peak Epc of the same redox pair, i.e., ΔEp = |Epa - Epc|.

[0005] According to embodiments of this application, the above-mentioned cathode material satisfies at least one of the following conditions: The peak voltage difference of the first group of redox peaks satisfies: ΔEp1≤40 mV; The peak voltage difference of the second set of redox peaks satisfies: ΔEp2≤60 mV.

[0006] According to embodiments of this application, the above-mentioned cathode material satisfies at least one of the following conditions: The equilibrium potential of the first group of redox peaks is 2.80 V ± 0.02 V; The equilibrium potential of the second set of redox peaks is 3.88 V ± 0.02 V.

[0007] According to the embodiments of this application, the sum of the peak intensities of the first group of redox peaks I P1 The sum of the peak intensities of the second group of redox peaks I P2 satisfy: I P1 >2 I P2 Among them, the sum of peak intensities refers to the sum of the peak intensities of the oxidation peak and the reduction peak in the same group of redox peaks.

[0008] According to embodiments of this application, the above-mentioned cathode material satisfies at least one of the following conditions: The 2θ of the X-ray diffraction peak corresponding to the (002) crystal plane of the cathode material is 17.75°~18.50°; The 2θ of the X-ray diffraction peak corresponding to the crystal plane of the cathode material (101) is 37.40°~37.60°; The 2θ of the X-ray diffraction peak corresponding to the crystal plane of the cathode material (103) is 45.55°~46.80°.

[0009] According to an embodiment of this application, the cell parameters of the cathode material satisfy: 2.820≤a=b≤2.890, 9.770≤c≤9.880, α=β=90°, γ=120°.

[0010] According to an embodiment of this application, the positive electrode material particle includes a core and a coating layer covering at least a portion of the surface of the positive electrode material; The kernel includes Li a Na b Ni0.6-h-i Mn 0.4+h M i O 2-j X k ; Wherein, 0.65≤a≤1.0, 0≤b≤0.03, 0<h≤0.4, 0<i≤0.2, 0<j≤0.05, 0≤k≤0.05; M includes at least one of Co, B, Mg, Al, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Zr, Nb, Ba, Mo, Ru, Sn, La, Sr, Y, Ca, W, Eu, and Bi; X includes at least one of N, P, S, F, Cl, and Br; The covering layer includes A' u M' v X' w ; 0 ≤ u ≤ 0.01, 0 ≤ v ≤ 0.01, 0 < w ≤ 0.01 Wherein, A' includes at least one of Group IA elements and Group IIA elements, M' includes at least one of transition metal elements, IIIA elements, IVA elements, and VA elements, and X' includes at least one of Group IVA elements, Group VA elements, Group VIA elements, and Group VIIA elements.

[0011] According to embodiments of this application, the above-mentioned cathode material satisfies at least one of the following conditions: A' includes at least one of Li, Na, K, Mg, Ca, Sr, and Ba; M' includes at least one of Ti, V, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, La, Ce, Hf, Ta, W, Os, Al, Ge, Sn, and Sb; X' includes at least one of C, Si, N, P, O, S, F, Cl, and Br.

[0012] According to an embodiment of this application, the mass ratio of the coating layer to the core is 0.05-1.

[0013] According to embodiments of this application, the above-mentioned cathode material satisfies at least one of the following conditions: The pH of the positive electrode material is 10-11.5, preferably 10.2-11.0, and more preferably 10.3-10.5; The specific surface area of ​​the cathode material is 2.8 m². 2 / g-3.6 m 2 / g, preferably 2.9 m 2 / g-3.4m 2 / g, more preferably 3.0m 2 / g-3.2m 2 / g; The particle size D of the positive electrode material V The thickness of 50 is 3μm-7μm, preferably 4.1μm-6μm, and more preferably 4.5μm-5μm.

[0014] A second aspect of this application provides a method for preparing the cathode material described in the first aspect, comprising: mixing a nickel-manganese source, a sodium source, an M source, an X source and an optional first lithium source to obtain a raw material mixture; The raw material mixture is subjected to a first sintering to obtain a first intermediate; The first intermediate is mixed with the second lithium source, and the resulting mixture is subjected to heat treatment, washing, and drying in sequence to obtain the cathode material; The total molar ratio of sodium in the sodium source to nickel and manganese in the nickel-manganese source is 0.65~1.00:1. The molar ratio of lithium in the second lithium source to sodium in the first intermediate is 1.5~15:1.

[0015] The preparation method of this application is simple to operate, low in cost, and easy to mass-produce.

[0016] According to an embodiment of this application, the total molar ratio of sodium in the sodium source to nickel and manganese in the nickel-manganese source is 0.67~0.90:1, preferably 0.67~0.80:1.

[0017] According to embodiments of this application, the above method satisfies at least one of the following conditions: The first sintering includes sintering at a temperature of 700℃~950℃ for 8h~48h; The heat treatment includes holding at a temperature of 20℃ to 350℃ for 0.5h to 36h.

[0018] According to embodiments of this application, the above method satisfies at least one of the following conditions: When the second lithium source is provided in liquid phase, the temperature of the heat treatment is 20°C to 60°C, and the time of the heat treatment is 3h to 36h. When the second lithium source is provided in solid form, the temperature of the heat treatment is 150°C to 280°C, and the time of the heat treatment is 0.5h to 6h.

[0019] According to embodiments of this application, the above method satisfies at least one of the following conditions: The nickel-manganese source includes at least one of nickel-manganese oxide, nickel-manganese hydroxide, hydroxy nickel-manganese oxide, nickel-manganese carbonate, a mixture of nickel oxalate and manganese oxalate, a mixture of nickel sulfate and cobalt sulfate, and a mixture of nickel nitrate and cobalt nitrate. The sodium source includes at least one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium sulfate, sodium chloride, sodium phosphate, sodium acetate, and sodium oxalate. The M source includes at least one of oxides, sulfides, chlorides, hydroxides, carbonates, silicates, phosphates, and sulfates containing the M element; The X source includes at least one of ionic compounds containing the element X and covalent compounds containing the element X; The first lithium source and the second lithium source each independently include at least one of lithium carbonate, lithium hydroxide, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium borate, lithium nitrate, lithium phosphate, lithium sulfate, lithium dihydrogen phosphate, lithium hydrogen phosphate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonylimide. Preferably, the second lithium source includes at least one of a mixture of lithium hydroxide and lithium chloride, a mixture of lithium nitrate and lithium hydroxide, a mixture of lithium nitrate and lithium chloride, and a mixture of lithium nitrate-lithium hydroxide-lithium chloride.

[0020] According to embodiments of this application, the above method satisfies at least one of the following conditions: The washing process includes washing with deionized water until the solution is neutral; The drying temperature is 80℃~150℃, and the drying time is 3h~15h.

[0021] According to an embodiment of this application, the method further includes: mixing at least one of A' source, M' source, X' source and the first intermediate, and subjecting the resulting mixture to a second sintering to form a second intermediate containing a coating layer; The second intermediate and the second lithium source are mixed, and the resulting mixture is subjected to heat treatment, washing, and drying in sequence to obtain the cathode material.

[0022] According to embodiments of this application, the above method satisfies at least one of the first conditions: The second sintering process includes sintering at a temperature of 300℃ to 700℃ for 2 hours to 12 hours; The atmosphere for the second sintering includes at least one of air and oxygen; The M' source includes at least one of oxides, sulfides, chlorides, hydroxides, carbonates, silicates, phosphates, and sulfates containing the M' element; The X' source includes at least one of an ionic compound containing the X' element and a covalent compound containing the X' element; The A' source includes at least one of oxides, sulfides, chlorides, hydroxides, carbonates, silicates, and phosphates containing the element A'.

[0023] A third aspect of this application provides a positive electrode sheet comprising the positive electrode material of the first aspect or the positive electrode material prepared by the method of the second aspect. This positive electrode sheet includes all the features and advantages of the positive electrode material of the first aspect or the positive electrode material prepared by the method of the second aspect, which will not be elaborated upon here.

[0024] A fourth aspect of this application provides a lithium-ion battery comprising the cathode material of the first aspect, the cathode material prepared by the method described in the second aspect, or the cathode material of the third aspect. This lithium-ion battery exhibits high specific capacity, energy density, cycle performance, and rate performance.

[0025] A fifth aspect of this application provides an electrical device comprising the positive electrode material of the first aspect, the positive electrode material prepared by the method of the second aspect, the positive electrode material of the third aspect, or the lithium-ion battery of the fourth aspect. This electrical device incorporates all the features and advantages of the positive electrode material of the first aspect, the positive electrode material prepared by the method of the second aspect, the positive electrode material of the third aspect, or the lithium-ion battery of the fourth aspect, which will not be elaborated upon here. Attached Figure Description

[0026] Figure 1 This is a comparison diagram of the XRD patterns of the cathode materials of Examples 1, 6 and 12 of this application with the P63mc (PDF-040288925) standard card. Figure 2 This is the charge-discharge specific capacity curve of the positive electrode material of Example 1 of this application at 2.00 V-4.60 V. Figure 3 The charge-discharge specific capacity curves of the positive electrode material in Example 1 of this application at 1.50 V-4.60 V are shown. Figure 4 This is the charge-discharge specific capacity curve of the positive electrode material of Example 12 of this application at 2.00 V-4.60 V. Figure 5 This is the capacity / voltage differential curve of the positive electrode material provided in Embodiment 1 of this application in the voltage range of 2.00 V-4.60 V. Figure 6 This is the capacity / voltage differential curve of the cathode material provided in Embodiment 12 of this application in the voltage range of 2.00 V-4.60 V. Detailed Implementation The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0027] A first aspect of this application provides a cathode material comprising cathode material particles, wherein the cathode material particles comprise: Li a Na b Ni 0.6-h-i Mn 0.4+h M i O 2-j X k Wherein, 0.6≤a≤1.0, 0≤b≤0.03, 0<h≤0.4, 0<i≤0.1, 0<j≤0.05, 0≤k≤0.05; M includes at least one of Co, B, Mg, Al, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Zr, Nb, Ba, Mo, Ru, Sn, La, Sr, Y, Ca, W, Eu, and Bi; X includes at least one of N, P, S, F, Cl, and Br; The cathode material is in space group P63mc. The positive electrode material was tested in a half-cell with a lithium metal sheet as the counter electrode. Under the conditions of 2.0 V to 4.6 V and 0.1C / 0.1C, the capacity / voltage differential curve showed a first set of redox peaks and a second set of redox peaks between 2.0 V and 4.6 V. The peak voltage difference of the first group of redox peaks and the peak voltage difference of the second group of redox peaks each independently satisfy: ΔEp≤100 mV (specifically such as 100 mV, 90 mV, 80 mV, 70 mV, 60 mV, 50 mV, 40 mV, 30 mV, 20 mV, 10 mV, 5 mV, etc.). The cathode material in this application exhibits two sets of redox peaks in its capacity / voltage differential curve between 2.0V and 4.6V under 0.1C / 0.1C conditions. These redox peaks correspond to the phase transition processes initiated by lithium-ion extraction and insertion during charging and discharging. By controlling the peak voltage difference of these redox peaks within a small range, the cathode material possesses high crystal structure symmetry (i.e., high orderliness of atomic arrangement within the crystal) and good kinetic characteristics, thus demonstrating excellent reversibility of lithium extraction and insertion. Furthermore, the cathode material can obtain a stable P63mc pure phase, reduce the presence of the P2 phase, and fully utilize the capacity advantages and structural stability of this phase structure. This allows the cathode material to achieve a high specific capacity while simultaneously improving structural stability, initial efficiency, rate capability, and discharge performance. Furthermore, the multi-element synergistic doping among Ni, Mn, M and other elements in this cathode material can further improve the intrinsic structural stability and electrochemical performance of the cathode material by suppressing lattice oxygen evolution, transition metal dissolution, and broadening lithium-ion diffusion channels.

[0028] In this paper, the peak voltage difference refers to the absolute value of the difference between the peak potential of the oxidation peak and the peak potential of the reduction peak for the same redox pair, i.e., ΔEp = |Epa - Epc|. The capacity / voltage (dQ / dV) differential curve can be tested using the following method: Assemble a coin cell according to the requirements of GB / T 23365-2023. Test the charge-discharge curve of the cathode material at 0.1C rate, and plot the capacity / voltage differential curve with voltage (V) on the x-axis and (dQ / dV) on the y-axis.

[0029] As an example, the specific manufacturing method of a button cell can be carried out as follows: A positive electrode slurry was prepared by adding the aforementioned positive electrode material, polyvinylidene fluoride (PVDF), and conductive agent in a weight ratio of (100-ts):t:s (where 1≤t≤10, 1≤s≤10, 80≤100-ts≤99) to N-methylpyrrolidone (NMP). The viscosity of the positive electrode slurry was adjusted to 1000 mPa·s-20000 mPa·s, and the mixed positive electrode slurry was uniformly coated on one side of an aluminum foil, with a single-sided coating thickness of 10 μm-200 μm. After drying and rolling, an electrode was formed, wherein the electrode surface density was 5 mg / cm³. 2 -50 mg / cm 2 The cathode material is then dried and cut into circular positive electrode sheets with a diameter of 5 mm to 20 mm.

[0030] The separator is punched into circular pieces with a diameter of 10mm-30mm; the negative electrode uses a lithium metal sheet with a diameter of 18mm; LiPF6 is added to a solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a weight ratio of 1:1:1 and mixed evenly to obtain an electrolyte, wherein the mass concentration of LiPF6 is 12.5%; the positive electrode, separator, negative electrode (lithium metal sheet), electrolyte, battery casing, and other accessories are moved into a glove box; the battery is assembled in a stacking order from bottom to top and the electrolyte is injected, and then sealed on a packaging machine to obtain a button cell battery.

[0031] It should be noted that the positive electrode material used to prepare coin cells can be obtained directly from positive electrode material powder, or by scraping powder off the positive electrode sheet after disassembling the battery.

[0032] As an example, the capacity / voltage differential (dQ / dV) curve can be obtained by performing the following test on the aforementioned coin cell: At 25℃, the button cell was charged and discharged at a current of 0.1C within the voltage range of 2.0V to 4.6V to obtain the capacity / voltage differential (dQ / dV) curve. Specifically, 1C = 200 mA / g, the equipment was a Xinwei test cabinet, model: CT4008Tn-5V20mA-HWX, and the test steps were: (1) 0.1C constant current charging; (2) constant voltage charging at 4.6V, I≤0.01C, and standing for 5min; (3) 0.1C constant current discharging to 2.0V; (4) stopping.

[0033] According to an embodiment of this application, the peak voltage difference of the first group of redox peaks satisfies: ΔEp1 ≤ 40 mV. Specifically, ΔEp1 can be 40 mV, 35 mV, 30 mV, 25 mV, 20 mV, 15 mV, 10 mV, 5 mV, 1 mV, 0.5 mV, etc. Within the above range, the cathode material has high structural symmetry, which further improves the kinetic characteristics, lithium extraction and insertion reversibility, and rate performance.

[0034] According to embodiments of this application, the peak voltage difference of the second set of redox peaks satisfies: ΔEp2 ≤ 60 mV. Specifically, ΔEp1 can be 60 mV, 55 mV, 50 mV, 45 mV, 40 mV, 35 mV, 30 mV, 25 mV, 20 mV, 15 mV, 10 mV, 5 mV, 1 mV, 0.5 mV, etc. Within the above range, the cathode material has high structural symmetry, which further improves the kinetic characteristics, lithium extraction and insertion reversibility, and rate capability.

[0035] According to an embodiment of this application, the equilibrium potential of the first set of redox peaks is 2.80 V ± 0.02 V, specifically 2.80 V ± 0.015 V, and more specifically 2.80 V ± 0.01 V. As a specific example, the equilibrium potential of the first set of redox peaks can be 2.78 V, 2.785 V, 2.79 V, 2.795 V, 2.80 V, 2.805 V, 2.81 V, 2.815 V, 2.82 V, or any range between these values. Within the above equilibrium potential range, the structural stability and lithium insertion / extraction reversibility of the cathode material are relatively good. When the first set of redox peaks deviates from the above equilibrium potential, the lithium insertion / extraction reversibility and structural stability of the cathode material may relatively deteriorate: when the equilibrium potential of the first set of redox peaks is high, it indicates that the polarization of the cathode material increases, and the rate performance may decrease; when the equilibrium potential of the first set of redox peaks is low, it indicates that the lithium extraction initiation potential of the cathode material is low, and the energy density of the cathode material may decrease.

[0036] According to an embodiment of this application, the equilibrium potential of the second set of redox peaks is 3.88 V ± 0.02 V, specifically 3.88 V ± 0.015 V, and more specifically 3.88 V ± 0.01 V. As a specific example, the equilibrium potential of the first set of redox peaks can be 3.86 V, 3.865 V, 3.87 V, 3.875 V, 3.88 V, 3.885 V, 3.89 V, 3.895 V, 3.90 V, or any range between these values. Within the above equilibrium potential range, the structural stability and lithium insertion / extraction reversibility of the cathode material are better. When the second set of redox peaks deviates from the above equilibrium potential, the lithium insertion / extraction reversibility and structural stability of the cathode material may also relatively deteriorate, for the same reason as the aforementioned first set of redox peaks.

[0037] In this article, the equilibrium potential of the redox peak refers to the peak voltage V of the oxidation peak. O With the peak-to-peak voltage V of the reduction R The median, where oxidation potential represents the change in valence of elements (such as transition metals) in the material from a reduced state (such as TM). 2+ / 3+ ) transforms into an oxidized state (such as TM) 3+ / 4+ The reduction potential is the potential corresponding to the oxidation state of an element in a material (e.g., TM). 3+ / 4+ ) transforms into a reduced state (such as TM) 2+ / 3+The equilibrium potential corresponds to the lithium insertion / extraction mechanism in layered oxide LiMO2 cathodes. Since LiMO2 cathodes typically utilize a solid solution lithium insertion / extraction mechanism, the oxidation and reduction processes occur within a continuous voltage range, varying with the lithium content, and involve phase transitions. Therefore, the charge / discharge curves exhibit one or more plateaus of varying lengths. After capacity / voltage differentiation, one or more redox peaks emerge, corresponding to different spatial configurations, compositions, or phases of the material. Because the peak shape and position are closely related to both the cathode material's structural characteristics and the current density, the equilibrium potentials mentioned in this paper refer to values ​​measured under low current density (e.g., 0.1C) conditions to more accurately reflect the material's microscopic lithium insertion / extraction mechanism, structural characteristics, and phase changes.

[0038] According to an embodiment of this application, the sum of the absolute values ​​of the peak intensities of the first group of redox peaks I P1 The sum of the peak intensities of the second group of redox peaks I P2 satisfy: I P1 >2 I P2 The sum of peak intensities refers to the sum of the peak intensities of the oxidation peak (maximum positive value of dQ / dV) and the reduction peak (absolute value of the minimum negative value of dQ / dV) within the same set of redox peaks. When the above conditions are met, the cathode material exhibits good lithium intercalation reversibility and kinetic characteristics, thus possessing high capacity and high rate performance.

[0039] The maximum or minimum value (dQ / dV) near the equilibrium potential, where the peak value of the oxidation peak is exactly the maximum value of dQ / dV, located to the right of the equilibrium potential, and the voltage corresponding to this maximum value is the peak voltage of the oxidation peak; the peak value of the reduction peak is negative, which is the minimum value of dQ / dV located to the left of the equilibrium potential, and the voltage corresponding to this minimum value is the peak voltage of the reduction peak.

[0040] It is understandable that X-ray diffraction peaks are of great reference value for characterizing the crystal features of cathode materials. The full width at half maximum (FWHM) 2θ of an X-ray diffraction peak reflects the crystallinity and grain size of the crystal. The narrower the FWHM, the higher the crystallinity and the more uniform the grain size. The peak intensity of an X-ray diffraction peak reflects the diffraction ability of the corresponding crystal plane. The higher the peak intensity, the higher the orientation degree of the crystal plane and the better the crystal integrity.

[0041] The X-ray diffraction (XRD) patterns of this application were tested using the following methods: The XRD pattern was obtained using a Rietveld powder X-ray diffractometer (Smartlab 9KW) from Japan. The target wavelength was 1.5418462 Å, tube voltage was 40 kV, tube current was 200 mA, scanning speed was 5 Hz / min, and the scanning range was 10–80 Å. A one-dimensional detector (1D) was used for measurement. Specific test conditions were: operating temperature: 21 ± 5 °C, humidity: <65%; cooling water circulator: temperature: 23 ± 1 °C, water pressure: 0.36 MPa; high-pressure refrigerant: 0.8 MPa–1.8 MPa, low-pressure refrigerant: 0.4 MPa–0.7 MPa; step size: 0.0200 °C. The unit cell parameters were obtained by Rietveld refinement calculations on the full XRD pattern.

[0042] According to embodiments of this application, the 2θ of the X-ray diffraction peak corresponding to the crystal plane of the cathode material (002) is 17.75°~18.50°, specifically 17.75°, 17.85°, 17.95°, 18.05°, 18.15°, 18.25°, 18.35°, 18.45°, 18.50° or any two of these ranges. Within the above range, the surface cathode material (002) crystal plane has high crystallinity and a suitable grain size.

[0043] According to an embodiment of this application, the 2θ of the X-ray diffraction peak corresponding to the crystal plane of the cathode material (101) is 37.40°~37.60°, specifically 37.40°, 37.45°, 37.50°, 37.55°, 37.60° or any two of these ranges. Within the above range, the surface cathode material (101) crystal plane has high crystallinity and a suitable grain size.

[0044] According to an embodiment of this application, the 2θ of the X-ray diffraction peak corresponding to the crystal plane of the cathode material (103) is 45.55°~46.80°, specifically 45.55°, 45.60°, 45.65°, 45.70°, 45.75°, 46.80° or any two of these ranges. Within the above range, the surface cathode material (103) crystal plane has high crystallinity and a suitable grain size.

[0045] According to embodiments of this application, the cell parameters of the cathode material satisfy: 2.820≤a=b≤2.890, 9.770≤c≤9.880, α=β=90°, γ=120°. Suitable cell parameters can effectively alleviate the structural stress caused by lattice contraction and expansion during lithium-ion insertion / extraction, suppress crystal structure distortion and collapse, improve material structural stability, and thus improve the cycle stability and service life of the cathode material.

[0046] According to an embodiment of this application, the positive electrode material particle includes a core and a coating layer covering at least a portion of the surface of the core, the coating layer including A' u M' v X' w The aforementioned cathode material serves as the core; Wherein, 0≤u≤0.01, 0≤v≤0.01, 0<w≤0.01; A' includes at least one of Group IA elements and Group IIA elements; M' includes at least one of transition metal elements, Group IIIA elements, Group IVA elements, and Group VA elements; and X' includes at least one of Group IVA elements, Group VA elements, Group VIA elements, and Group VIIA elements.

[0047] This coating layer further physically isolates the electrolyte from the cathode material, suppresses interfacial side reactions, and improves the cycle stability of the battery. It should also be noted that A' and M' cannot both be 0.

[0048] According to embodiments of this application, A' includes at least one of Li, Na, K, Mg, Ca, Sr, and Ba. These elements can broaden the lithium-ion transport channels, thereby improving the structural stability of the cathode material during electrochemical cycling.

[0049] According to embodiments of this application, M' includes at least one of Ti, V, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, La, Ce, Hf, Ta, W, Os, Al, Ge, Sn, and Sb. These elements can introduce stronger MO bonds, larger ionic radii, etc., suppressing lattice oxygen and transition metal migration, thereby improving the structural stability of the cathode material.

[0050] According to embodiments of this application, X' includes at least one of C, Si, N, P, O, S, F, Cl, and Br. The above elements can be introduced to suppress the evolution of lattice oxygen by introducing different anions with higher electronegativity, thereby improving the structural stability of the cathode material.

[0051] According to embodiments of this application, the mass ratio of the coating layer to the core is 0.5-1. A suitable mass ratio indicates that the coating layer has a suitable thickness, enabling the single-crystal cathode material to effectively suppress interfacial side reactions while maintaining structural stability.

[0052] According to embodiments of this application, the pH of the positive electrode material is 10-11.5, further 10.2-11.0, and even further 10.2-10.5. As a specific example, the pH of the positive electrode material can be 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.8, 11, 11.2, 11.3, 11.5, etc. When the pH is greater than 11.5, the residual alkali content on the surface of the positive electrode material is too high, and the viscosity of the positive electrode material tends to increase rapidly during slurry preparation, resulting in a jelly-like consistency, which affects the coating uniformity of the electrode sheet and the electrochemical performance of the battery. Therefore, when the pH of the positive electrode material is less than 11.5, it is beneficial to improve the uniformity of the electrode sheet, thereby enhancing the electrochemical performance of the lithium-ion battery.

[0053] In this article, the pH value of the positive electrode material can be detected by the method specified in GB / T 1717 "Determination of pH value of pigment aqueous suspension".

[0054] According to an embodiment of this application, the specific surface area of ​​the positive electrode material is 2.8 m². 2 / g-3.6 m 2 / g, further showing a specific surface area of ​​2.9 m² for the cathode material. 2 / g-3.4 m 2 / g, and the specific surface area of ​​the further improved cathode material is 3.0 m². 2 / g-3.2m 2 / g. As a specific example, the specific surface area of ​​the cathode material can be 2.8 m². 2 / g、2.9 m 2 / g, 3.0 m 2 / g、3.2 m 2 / g、3.4 m 2 / g, 3.6 m 2 / g, etc. When the specific surface area is greater than 3.6 m² 2 When the specific surface area of ​​the cathode material is within a certain range, side reactions between the cathode material particles and the electrolyte are easily aggravated, leading to increased impedance, gas generation, and decreased cycle retention. Controlling the specific surface area of ​​the cathode material within this range is beneficial for improving the battery's cycle performance.

[0055] In this article, the specific surface area of ​​the cathode material refers to the surface area per unit mass of cathode material, and the test method can be carried out in accordance with the method specified in GB / T 13390 "Determination of Specific Surface Area of ​​Metal Powders - Nitrogen Adsorption Method".

[0056] According to an embodiment of this application, the particle size D of the positive electrode material is... V 50 is 3 μm-7 μm; further, the particle size D of the cathode material V50 has a particle size of 4.1 μm-6 μm; furthermore, the particle size D of the cathode material... V 50 represents a particle size of 4.5 μm-5 μm. As a specific example, the particle size D of the cathode material... V 50 can be 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, etc. When the particle size D... V When the particle size D of the cathode material is greater than 7 μm, the lithium-ion diffusion path is prolonged, which may lead to a deterioration in rate performance. V When the thickness is less than 7 μm, it is beneficial to improve the rate performance of the battery.

[0057] In particle size distribution, D V 50, also known as the median particle size, means that 50% of the volume of particles are smaller than or equal to this value. It can be measured using a Malvern particle size analyzer: disperse the cathode material in a dispersant (ethanol or acetone, or other surfactants), sonicate for 30 minutes, add the sample to the Malvern particle size analyzer, and start the test.

[0058] A second aspect of this application provides a method for preparing the cathode material described in the first aspect, comprising: S10: Mix the nickel-manganese source, sodium source, M source, X source and optionally the first lithium source to obtain a raw material mixture.

[0059] In this step, there are no restrictions on the mixing process parameters and specific operating methods; they can be flexibly selected according to the actual situation. As an example, the nickel-manganese source, sodium source, M source, X source, and optionally the first lithium source can be weighed according to the Na / (Ni+Mn) stoichiometry and mixed evenly in a high-speed mixer to obtain a raw material mixture.

[0060] It should be noted that the first lithium source can be added or not added in this step as needed. That is, when the first lithium source needs to be introduced for pre-doping lithium to improve the material performance, the nickel-manganese source, sodium source, M source, X source and the first lithium source are mixed in this step to obtain a raw material mixture.

[0061] According to embodiments of this application, the total molar ratio of sodium in the sodium source to nickel and manganese in the nickel-manganese source is 0.65~1.00:1, further 0.67~0.90:1, and even further 0.67~0.80:1. As a specific example, the total molar ratio of sodium in the sodium source to nickel and manganese in the nickel-manganese source can be 0.65:1, 0.66:1, 0.67:1, 0.68:1, 0.69:1, 0.70:1, 0.75:1, 0.80:1, 0.85:1, 0.90:1, or any two of these ranges. Within these ranges, the reaction is more complete, raw material waste is reduced, and the resulting cathode material has a smaller peak-to-peak voltage difference between the redox peaks, thereby contributing to improved structural stability and electrochemical performance of the cathode material.

[0062] According to embodiments of this application, the molar ratio of lithium in the second lithium source to sodium in the first intermediate is 1.5 to 15:1, specifically 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, or any two of these ranges. Within this range, the reaction is more complete, raw material waste is reduced, and the resulting cathode material has a smaller peak-to-peak voltage difference between redox peaks, thereby contributing to improved structural stability and electrochemical performance of the cathode material.

[0063] According to embodiments of this application, the nickel-manganese source includes at least one of nickel-manganese oxide, nickel-manganese hydroxide, hydroxy nickel-manganese oxide, nickel-manganese carbonate, a mixture of nickel oxalate and manganese oxalate, a mixture of nickel sulfate and cobalt sulfate, and a mixture of nickel nitrate and cobalt nitrate. Therefore, the material is widely available and has a low cost.

[0064] According to embodiments of this application, the sodium source includes at least one selected from sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium sulfate, sodium chloride, sodium phosphate, sodium acetate, and sodium oxalate. These sodium sources are widely available and relatively inexpensive.

[0065] According to embodiments of this application, when the nickel-manganese source contains a dopant element M, it is understood that, in this case, a separate source M is no longer necessary.

[0066] According to embodiments of this application, the M source includes at least one selected from oxides, sulfides, chlorides, hydroxides, carbonates, silicates, phosphates, and sulfates containing the element M. As examples, the M source includes, but is not limited to, La₂O₃, ZrO₂, TiO₂, and MgO. The aforementioned M sources are widely available and have low cost.

[0067] According to embodiments of this application, the X source includes at least one of ionic compounds containing element X and covalent compounds containing element X. X sources include, but are not limited to, LiCl, LiF, NH4F, etc. These X sources are widely available and have low cost.

[0068] According to embodiments of this application, the first lithium source includes at least one selected from lithium carbonate, lithium hydroxide, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium borate, lithium nitrate, lithium phosphate, lithium sulfate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonylimide. These lithium sources are widely available and have low costs.

[0069] S20: The raw material mixture is subjected to a first sintering to obtain a first intermediate.

[0070] In this step, the raw material mixture can be placed in a high-temperature sintering furnace for the first sintering, and after sintering, a sodium-based precursor, i.e., the first intermediate, is obtained.

[0071] According to an embodiment of this application, the first sintering can be performed by heating to the target temperature in one go. The temperature of the first sintering is 700℃~950℃, for example, it can be 700℃, 750℃, 800℃, 850℃, 900℃, or 950℃. Within the above range, it helps the first sintering to proceed fully and reduces raw material waste.

[0072] According to an embodiment of this application, the heating rate of the first sintering is 0.5 ℃ / min-6 ℃ / min, specifically 0.5 ℃ / min, 1 ℃ / min, 2 ℃ / min, 3 ℃ / min, 4 ℃ / min, 5 ℃ / min, 6 ℃ / min, or any range between two of these. Within the above range, the system temperature can be steadily increased, ensuring uniform grain growth.

[0073] According to embodiments of this application, the first sintering time is 8 h to 48 h, for example, it can be 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, 48 h, or any range between two of these. Within the above range, it helps the first sintering to proceed sufficiently, reducing raw material waste and also reducing wasted time.

[0074] According to an embodiment of this application, the first sintering process may also be segmented sintering, in which one or more low-temperature platforms exist. As a specific example, the low-temperature platform temperature range is 400℃~700℃, for example, 400℃, 450℃, 550℃, 600℃, or 700℃, etc., and the low-temperature platform holding time is 2h~8h, for example, 2h, 3h, 4h, 6h, or 8h, etc.; the high-temperature platform temperature is 700℃~950℃, for example, 700℃, 750℃, 800℃, 850℃, 900℃, or 950℃, etc., and the high-temperature platform holding time is 8h~48h, for example, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, 38h, 40h, 42h, 44h, 46h, or 48h, etc. This allows the raw materials to react fully and rapidly, yielding a high-quality first intermediate.

[0075] According to an embodiment of this application, after the first sintering is completed, a pulverization process can be performed to obtain a first intermediate with a suitable particle size (exemplarily 4μm-5μm). The pulverization process includes, but is not limited to, jaw crushing, roller crushing, etc.

[0076] S30: The first intermediate is mixed with the second lithium source, and the resulting mixture is subjected to heat treatment, washing and drying in sequence to obtain the cathode material.

[0077] In this step, lithium ions from the second lithium source diffuse into the layered structure of the sodium-based precursor, eventually replacing some or all of the sodium ions to obtain the cathode material.

[0078] According to embodiments of this application, the second lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium borate, lithium nitrate, lithium phosphate, lithium sulfate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonylimide. Specifically, the second lithium source includes at least one of a mixture of lithium hydroxide and lithium chloride, a mixture of lithium nitrate and lithium hydroxide, and a mixture of lithium nitrate-lithium hydroxide-lithium chloride. The aforementioned second lithium source is widely available and has low cost.

[0079] According to embodiments of this application, the heat treatment temperature is 20°C to 350°C, specifically within the ranges of 20°C, 30°C, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, or any two of these ranges. Within these ranges, the exchange reaction between lithium ions and sodium ions is more efficient, leading to the acquisition of a cathode material with better performance.

[0080] According to embodiments of this application, the heat treatment time is 0.5 h to 36 h, specifically within the range of 0.5 h, 1 h, 2 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 36 h, or any two of these ranges. Within this range, the exchange reaction between lithium ions and sodium ions is more complete, which helps to obtain a cathode material with better performance.

[0081] It should be noted that the mixing method between the first intermediate and the second lithium source can be either solid-phase mixing or liquid-phase mixing. That is, the second lithium source can be provided in liquid phase or solid phase, and the specific choice can be made flexibly according to the specific needs.

[0082] In some embodiments, the second lithium source is provided in a liquid phase, and the molar ratio of lithium in the second lithium source to sodium in the first intermediate is 5-10:1; the temperature of the first heat treatment is 20°C-60°C, and the time of the first heat treatment is 3 h-36 h. When the second lithium source is provided in a liquid phase, it is first prepared into a solution (the solvent used includes, but is not limited to, water), so that the solution contains a large number of solvated lithium ions, which serve as the diffusion driving force to replace sodium ions. This reaction can be carried out at a lower temperature, the reaction conditions are milder, and it helps to suppress the occurrence of side reactions.

[0083] In other embodiments, the second lithium source is provided in a solid phase, and the molar ratio of lithium in the second lithium source to sodium in the first intermediate is 1.5 to 5:1; the temperature of the first heat treatment is 150 ℃ to 280 ℃, and the time of the first heat treatment is 0.5 h to 6 h. When the second lithium source is provided in a solid phase, the second lithium source is directly added to the reaction system in solid form. During the reaction, the second lithium source will first melt into a molten state, and the higher heat treatment provides kinetic drive for lithium ions, resulting in higher exchange efficiency between lithium ions and sodium ions.

[0084] According to an embodiment of this application, the washing includes washing with deionized water until neutral.

[0085] According to embodiments of this application, the drying temperature is 80°C to 150°C, and the drying time is 3 h to 15 h. Within the above-mentioned drying time and temperature range, it helps to fully remove moisture from the cathode material, resulting in a cathode material with better performance.

[0086] According to an embodiment of this application, in preparing the coating layer, at least one of A' source and M' source, X' source and the first intermediate are mixed, and the resulting mixture is subjected to a second sintering to form a second intermediate containing the coating layer; the second intermediate and the second lithium source are mixed, and the resulting mixture is subjected to heat treatment, washing and drying in sequence to obtain the cathode material.

[0087] Thus, the A', M', and X' sources form a continuous and uniform sodium-based coating layer on the surface of the first intermediate (i.e., the core), which is then ion-exchanged to obtain the coating layer. This coating layer can physically isolate the electrolyte from the cathode material, suppress interfacial side reactions, and thereby improve the electrochemical performance of the battery.

[0088] According to embodiments of this application, the A' source includes at least one of the following: oxides, sulfides, chlorides, hydroxides, carbonates, silicates, and phosphates of element A. The aforementioned X source is widely available and inexpensive.

[0089] According to embodiments of this application, the M' source includes at least one of oxides, sulfides, chlorides, hydroxides, carbonates, silicates, phosphates, and sulfates containing the element M'. The aforementioned X sources are widely available and inexpensive.

[0090] According to embodiments of this application, the X' source includes at least one of an ionic compound containing the X' element and a covalent compound containing the X' element. The aforementioned X sources are widely available and have low cost.

[0091] According to embodiments of this application, the second sintering includes sintering at a temperature of 300 °C to 700 °C for 2 h to 12 h. Under these conditions, ion exchange can be fully carried out, resulting in a cathode material with better performance.

[0092] According to an embodiment of this application, the atmosphere for the second sintering includes at least one of air and oxygen.

[0093] According to the embodiments of this application, the heat treatment, washing, drying and other steps in this process can be consistent with the aforementioned preparation method for preparing a coating layer-free material, and will not be described in detail here.

[0094] A third aspect of this application provides a positive electrode sheet comprising the positive electrode material described in the first aspect or the positive electrode material prepared by the method described in the second aspect. This positive electrode sheet encompasses all the features and advantages of the positive electrode material described in the first aspect or the positive electrode material prepared by the method described in the second aspect, which will not be elaborated upon here.

[0095] According to an embodiment of this application, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side surface of the positive current collector, wherein the positive active material layer includes the single-crystal positive electrode material, positive conductive agent and positive binder described in the first aspect.

[0096] According to embodiments of this application, the positive current collector can be a metal current collector or a composite current collector. Metal current collectors include at least one of aluminum foil current collectors and carbon-coated aluminum foil current collectors; composite current collectors may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. Composite current collectors can be formed by forming a metal material (copper, copper 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.).

[0097] According to embodiments of this application, the positive electrode binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0098] According to embodiments of this application, the positive electrode conductive agent in the positive electrode active material layer may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0099] A fourth aspect of this application provides a lithium-ion battery comprising the positive electrode material described in the first aspect, the positive electrode material prepared by the method described in the second aspect, or the positive electrode sheet described in the third aspect. This lithium-ion battery exhibits high capacity, energy density, excellent rate performance, and cycle performance.

[0100] According to an embodiment of this application, the lithium-ion battery further includes a negative electrode, an electrolyte, and a separator. The positive electrode, negative electrode, and separator are all immersed in the electrolyte. During the charging and discharging process of the battery, lithium ions are inserted and extracted back and forth between the positive and negative electrodes. The electrolyte plays the role of conducting ions between the positive and negative electrodes. The separator is disposed between the positive and negative electrodes, mainly to prevent short circuits between the positive and negative electrodes, while allowing lithium ions to pass through.

[0101] According to an embodiment of this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located at least on one side of the negative electrode sheet, the negative electrode active material layer including a negative electrode active material.

[0102] According to embodiments of this application, the negative current collector includes copper foil or aluminum foil.

[0103] According to embodiments of this application, the negative electrode active material layer may include a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

[0104] According to embodiments of this application, the negative electrode active material may include carbon-based materials (such as hard carbon, soft carbon, etc.), metals and their compounds, organic compound materials, etc.

[0105] According to embodiments of this application, the negative electrode binder in the negative electrode active material layer includes 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).

[0106] According to embodiments of this application, the negative electrode conductive agent in the negative electrode active material layer includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] According to embodiments of this application, the diaphragm includes polyethylene diaphragm, polypropylene diaphragm, polyethylene / polypropylene composite diaphragm, etc.

[0108] A fifth aspect of this application provides an electrical device comprising the positive electrode material described in the first aspect, the positive electrode sheet described in the third aspect, or the lithium-ion battery described in the fourth aspect. This electrical device incorporates all the features and advantages of the positive electrode material described in the first aspect, the positive electrode sheet described in the third aspect, or the lithium-ion battery described in the fourth aspect, which will not be elaborated upon here.

[0109] It is understood that there are no particular restrictions on the specific type of electrical device, and it can be any device that uses the aforementioned lithium-ion battery as a power source or energy storage unit. As examples, electrical devices include, but are not limited to, 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.), mobile terminals (such as mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, etc.

[0110] It is understandable that, in addition to the lithium-ion battery mentioned above, the electrical device also includes necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be described in detail here.

[0111] The embodiments of this application are described in detail below.

[0112] Example 1 Preparation of cathode material: The chemical formula was designed based on Na / (Ni+Mn) = 0.7, ensuring Na is not excessive; nickel-manganese hydroxide Ni... 0.25 Mn 0.75 (OH)2, sodium carbonate, lanthanum oxide (La2O3), and lithium fluoride were weighed and mixed according to the designed stoichiometric ratio as nickel-manganese source, sodium source, M source, and X source, respectively. The mixture was then placed in a sintering furnace and heated to 450°C at a rate of 2°C / min under dry air conditions, held at that temperature for 4 hours, and then heated to 850°C at a rate of 2°C / min for 10 hours. After natural cooling, the sintered material was removed and subjected to jaw crusher, roller crusher, airflow powder or mechanical powdering, and passed through a 400-mesh sieve to obtain the first intermediate. Lanthanum oxide (La2O3) and the first intermediate were mixed according to the stoichiometric ratio. The mixture was then heated to 600°C in a sintering furnace under dry air conditions at a heating rate of 2°C / min, held at that temperature for 6 hours, and then allowed to cool naturally. The sintered material was then removed and subjected to jaw crushing, roller crushing, air-flow pulverizing, or mechanical pulverizing, and passed through a 400-mesh sieve to obtain the second intermediate.

[0113] The second intermediate was mixed with the second lithium source, pure lithium nitrate (LiNO3, solid form), and designed according to the molar ratio of lithium in the second lithium source to sodium in the first intermediate, n(Li) / n(Na) = 4:1. Then, it was heat-treated at 265°C for 2 hours, crushed, washed with deionized water until the solution was neutral, and dried under vacuum at 120°C for 6 hours to obtain the cathode material.

[0114] Preparation of the positive electrode sheet: The above-mentioned positive electrode material, polyvinylidene fluoride (Arkema, France), and acetylene black (Shanghai Huazhongrong Co., Ltd.) were mixed in the solvent N-methylpyrrolidone (Henan Maiqi Technology Co., Ltd.) at a mass ratio of 95:2.5:2.5 to obtain a positive electrode slurry with a solid content of 60%. The above slurry was coated on aluminum foil (16 μm thick, produced in Tianjin, battery grade), dried at 135 °C for 0.5 h, and rolled under 10 MPa pressure to form a positive electrode sheet with a thickness of about 35 μm (diameter 11 mm, positive electrode material content of about 10 mg).

[0115] Preparation of negative electrode: lithium metal sheet (Tianjin Zhongneng Lithium Industry).

[0116] Membrane preparation: Celgard membrane 2325 / 25μm (Celgard Corporation, USA).

[0117] Electrolyte preparation: The electrolyte (LiPF6 (concentration of 12.5%), propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (weight ratio 1:1:1) is used. The positive electrode, separator, negative electrode (lithium metal sheet), electrolyte, battery casing and other accessories are moved into the glove box and assembled into a CR2025 button battery in an argon atmosphere glove box.

[0118] The specific parameters for Examples 2 to 5 and Comparative Examples 1 to 3 are shown in Tables 1 and 2. Examples 6-19 differ from Example 1 in that the coating step is omitted; the remaining parameters are shown in Tables 1 and 2.

[0119] Performance testing XRD testing: X-ray diffractometer (Smartlab 9KW) from Rigaku, Japan, was used with a finely tuned setup. The Cu target wavelength was 1.5418462 Å, tube voltage was 40 kV, tube current was 200 mA, scanning speed was 5 Hz / min, and the scanning range was 10–80 Å. A one-dimensional detector (1D) was used. Specific testing conditions were: operating temperature: 21 ± 5 °C, humidity: <65%; cooling water circulator: temperature: 23 ± 1 °C, water pressure: 0.36 MPa; high-pressure refrigerant: 0.8–1.8 MPa, low-pressure refrigerant: 0.4–0.7 MPa; step size: 0.0200 °C.

[0120] P63mc Space Group: Compare with standard card PDF-040288925.

[0121] Specific surface area: The specific surface area of ​​the cathode material can be measured using a surface analyzer based on the static adsorption principle of N2, such as the Tristar 3020 surface analyzer from Micromeritics. The specific procedure may include: gradually adding N2 to the test material (after pre-removing physically adsorbed components) under vacuum conditions in the testing apparatus; calculating the pressure change caused by N2 adsorption using the constant volume method; and determining the amount of N2 adsorbed according to the gas equation. This yields the amount of N2 adsorbed from 0 atm to 0.3 atm at liquid nitrogen temperature, which can then be converted into specific surface area per unit weight.

[0122] D V 50: Bulk median particle size D of the cathode material 50 Test: Particle size distribution was measured using a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with standard GB / T 19077-2016 "Laser Diffraction Method".

[0123] Electrochemical performance testing Charge and discharge tests were performed on the above-mentioned button cells: (1) At 25°C, the button cell was charged and discharged at a current of 0.1C in the voltage range of 2.0V to 4.6V to obtain the capacity / voltage curve and dQ / dV curve.

[0124] (2) At 25°C, the above-mentioned button cell was charged and discharged at 2.0V-4.6V and 0.1C to evaluate the first charge and discharge capacity and first efficiency (the ratio of the first discharge specific capacity to the first charge specific capacity) of the cathode material.

[0125] 2.0-4.6V discharge specific capacity: obtained by dividing the initial discharge capacity by the mass of the cathode material through the first charge-discharge test at a current density of 0.1C.

[0126] Second charge-discharge efficiency: The ratio of discharge specific capacity to charge specific capacity obtained by charge-discharge test (i.e., second cycle) after electrochemical lithium replenishment (first charge-discharge).

[0127] Average voltage from 2.0 to 4.6 V: the effective area of ​​the voltage-capacity curve (i.e., battery charge / discharge energy) divided by the capacity; Figure 2 For example, the effective area of ​​the voltage-capacity curve refers to the area enclosed by the two curves and the horizontal and vertical axes in the figure, and the capacity refers to the value of the horizontal axis (210 mAh / g).

[0128] 0.1C / 1C: Constant current charge-discharge performance was tested using a CT-3008-5V battery tester (Shenzhen Xinwei Company). The test temperature was constant at 25 °C, the voltage range was 2.0-4.6 V, and the nominal specific capacity was 1C=200mAh / g. The rate performance of the samples was tested at different rates of 0.1C, 0.2C, 0.33C, 0.5C, and 1C. The ratio of the 1C discharge specific capacity to the 0.1C discharge specific capacity was obtained.

[0129] Capacity retention rate at room temperature (25℃) and 1C & 150 cycles: The sample was subjected to 150 charge-discharge cycles at 2.0-4.6 V and 1C. The capacity retention rate was obtained by comparing the discharge specific capacity after 150 cycles with the discharge specific capacity after the first cycle.

[0130] Table 1

[0131] Table 2

[0132] Table 3

[0133] Table 4

[0134] Conclusion: The cathode material of this application exhibits two sets of redox peaks in the range of 2.0V to 4.6V. By controlling the peak voltage difference, high crystal structure symmetry and good kinetic characteristics can be obtained, achieving a stable P63mc pure phase and reducing the P2 phase. Simultaneously, multi-element synergistic doping can suppress lattice oxygen evolution and transition metal dissolution, broaden lithium-ion diffusion channels, and further improve structural stability and electrochemical performance.

[0135] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0136] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0137] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A positive electrode material, characterized in that, Includes positive electrode material particles, said positive electrode material particles comprising: Li a So b Ni 0.6-h-i Mr 0.4+h M i O 2-j X k Wherein, 0.6≤a≤1.0, 0≤b≤0.03, 0<h≤0.4, 0<i≤0.1, 0<j≤0.05, 0≤k≤0.05; M includes at least one of Co, B, Mg, Al, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Zr, Nb, Ba, Mo, Ru, Sn, La, Sr, Y, Ca, W, Eu, and Bi; X includes at least one of N, P, S, F, Cl, and Br; The cathode material is in space group P63mc. The positive electrode material was tested in a half-cell with a lithium metal sheet as the counter electrode. Under the conditions of 2.0V~4.6V and 0.1C / 0.1C, the capacity / voltage differential curve showed a first set of redox peaks and a second set of redox peaks between 2.0V and 4.6V. The peak voltage difference of the first group of redox peaks and the peak voltage difference of the second group of redox peaks each independently satisfy: ΔEp≤100 mV; The peak voltage difference ΔEp refers to the absolute value of the difference between the peak potential of the oxidation peak Epa and the peak potential of the reduction peak Epc of the same redox pair, i.e., ΔEp = |Epa - Epc|.

2. The cathode material according to claim 1, characterized in that, At least one of the following conditions must be met: The peak voltage difference of the first group of redox peaks satisfies: ΔEp1≤40 mV; The peak voltage difference of the second set of redox peaks satisfies: ΔEp2≤60 mV.

3. The cathode material according to claim 2, characterized in that, At least one of the following conditions must be met: The equilibrium potential of the first group of redox peaks is 2.80 V ± 0.02 V; The equilibrium potential of the second set of redox peaks is 3.88 V ± 0.02 V.

4. The cathode material according to claim 2, characterized in that, The sum of the peak intensities of the first group of redox peaks I P1 The sum of the peak intensities of the second group of redox peaks I P2 satisfy: I P1 >2 I P2 The sum of peak intensities refers to the sum of the absolute values ​​of the peak intensities of the oxidation peak and the reduction peak in the same group of redox peaks.

5. The positive electrode material according to claim 1, characterized in that, At least one of the following conditions must be met: The 2θ of the X-ray diffraction peak corresponding to the (002) crystal plane of the cathode material is 17.75°~18.50°; The 2θ of the X-ray diffraction peak corresponding to the crystal plane of the cathode material (101) is 37.40°~37.60°; The 2θ of the X-ray diffraction peak corresponding to the crystal plane of the cathode material (103) is 45.55°~46.80°.

6. The cathode material according to claim 5, characterized in that, The cell parameters of the cathode material satisfy: 2.820≤a=b≤2.890, 9.770≤c≤9.880, α=β=90°, γ=120°.

7. The cathode material according to claim 1, characterized in that, The positive electrode material particles include a core and a coating layer covering at least a portion of the surface of the core; The kernel includes Li a Na b Ni 0.6-h-i Mn 0.4+h M i O 2-j X k ; Wherein, 0.65≤a≤1.0, 0≤b≤0.03, 0<h≤0.4, 0<i≤0.2, 0<j≤0.05, 0≤k≤0.05; M includes at least one of Co, B, Mg, Al, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Zr, Nb, Ba, Mo, Ru, Sn, La, Sr, Y, Ca, W, Eu, and Bi; X includes at least one of N, P, S, F, Cl, and Br; The covering layer includes A' u M' v X' w ; Wherein, 0≤u≤0.01, 0≤v≤0.01, 0<w≤0.01; A' includes at least one of Group IA elements and Group IIA elements; M' includes at least one of transition metal elements, Group IIIA elements, Group IVA elements, and Group VA elements; and X' includes at least one of Group IVA elements, Group VA elements, Group VIA elements, and Group VIIA elements.

8. The cathode material according to claim 7, characterized in that, At least one of the following conditions must be met: A' includes at least one of Li, Na, K, Mg, Ca, Sr, and Ba; M' includes at least one of Ti, V, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, La, Ce, Hf, Ta, W, Os, Al, Ge, Sn, and Sb; X' includes at least one of C, Si, N, P, O, S, F, Cl, and Br.

9. The cathode material according to claim 8, characterized in that, The mass ratio of the coating layer to the core is 0.05-1.

10. The cathode material according to any one of claims 1 to 9, characterized in that, At least one of the following conditions must be met: The pH of the positive electrode material is 10-11.5, preferably 10.2-11.0, and more preferably 10.3-10.5; The specific surface area of ​​the cathode material is 2.8 m². 2 / g-3.6 m 2 / g, preferably 2.9 m 2 / g-3.4m 2 / g, more preferably 3.0m 2 / g-3.2m 2 / g; The particle size D of the positive electrode material V The thickness of 50 is 3μm-7μm, preferably 4.1μm-6μm, and more preferably 4.5μm-5μm.

11. A method for preparing the cathode material according to any one of claims 1 to 10, characterized in that, include: The nickel-manganese source, sodium source, M source, X source and optional first lithium source are mixed to obtain a raw material mixture; The raw material mixture is subjected to a first sintering to obtain a first intermediate; The first intermediate is mixed with the second lithium source, and the resulting mixture is subjected to heat treatment, washing, and drying in sequence to obtain the cathode material; The total molar ratio of sodium in the sodium source to nickel and manganese in the nickel-manganese source is 0.65~1.00:

1. The molar ratio of lithium in the second lithium source to sodium in the first intermediate is 1.5~15:

1.

12. The method according to claim 11, characterized in that, At least one of the following conditions must be met: The total molar ratio of sodium in the sodium source to nickel and manganese in the nickel-manganese source is 0.67~0.90:1, preferably 0.67~0.80:1; The first sintering includes sintering at a temperature of 700℃~950℃ for 8h~48h; The heat treatment includes holding at a temperature of 20℃ to 350℃ for 0.5h to 36h.

13. The method according to claim 11, characterized in that, At least one of the following conditions must be met: When the second lithium source is provided in liquid phase, the temperature of the heat treatment is 20°C to 60°C, and the time of the heat treatment is 3h to 36h. When the second lithium source is provided in solid form, the temperature of the heat treatment is 150°C to 280°C, and the time of the heat treatment is 0.5h to 6h.

14. The method according to claim 11, characterized in that, At least one of the following conditions must be met: The nickel-manganese source includes at least one of nickel-manganese oxide, nickel-manganese hydroxide, hydroxy nickel-manganese oxide, nickel-manganese carbonate, a mixture of nickel oxalate and manganese oxalate, a mixture of nickel sulfate and cobalt sulfate, and a mixture of nickel nitrate and cobalt nitrate. The sodium source includes at least one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium sulfate, sodium chloride, sodium phosphate, sodium acetate, and sodium oxalate. The M source includes at least one of oxides, sulfides, chlorides, hydroxides, carbonates, silicates, phosphates, and sulfates containing the M element; The X source includes at least one of ionic compounds containing the element X and covalent compounds containing the element X; The first lithium source and the second lithium source each independently include at least one of lithium carbonate, lithium hydroxide, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium borate, lithium nitrate, lithium phosphate, lithium sulfate, lithium dihydrogen phosphate, lithium hydrogen phosphate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonylimide. Preferably, the second lithium source includes at least one of a mixture of lithium hydroxide and lithium chloride, a mixture of lithium nitrate and lithium hydroxide, a mixture of lithium nitrate and lithium chloride, and a mixture of lithium nitrate-lithium hydroxide-lithium chloride.

15. The method according to claim 11, characterized in that, At least one of the following conditions must be met: The washing process includes washing with deionized water until the solution is neutral; The drying temperature is 80℃~150℃, and the drying time is 3h~15h.

16. The method according to claim 11, characterized in that: At least one of source A' and source M', source X' and the first intermediate are mixed, and the resulting mixture is subjected to a second sintering to form a second intermediate containing a coating layer; The second intermediate and the second lithium source are mixed, and the resulting mixture is subjected to heat treatment, washing and drying in sequence to obtain the cathode material.

17. The method according to claim 16, characterized in that, At least one of the following conditions must be met: The second sintering process includes sintering at a temperature of 300℃ to 700℃ for 2 hours to 12 hours; The atmosphere for the second sintering includes at least one of air and oxygen; The M' source includes at least one of oxides, sulfides, chlorides, hydroxides, carbonates, silicates, phosphates, and sulfates containing the M' element; The X' source includes at least one of an ionic compound containing the X' element and a covalent compound containing the X' element; The A' source includes at least one of oxides, sulfides, chlorides, hydroxides, carbonates, silicates, and phosphates containing the element A'.

18. A positive electrode plate, characterized in that, The cathode material includes the cathode material according to any one of claims 1 to 10 or the cathode material prepared by the method according to any one of claims 11 to 17.

19. A lithium-ion battery, characterized in that, This includes the cathode material according to any one of claims 1 to 10, the cathode material prepared by the method according to any one of claims 11 to 17, or the cathode material according to claim 18.

20. An electrical device, characterized in that, The cathode material includes any one of claims 1 to 10, the cathode material prepared by the method described in any one of claims 11 to 17, the cathode material described in claim 18, or the lithium-ion battery described in claim 19.

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