Positive electrode material and preparation method therefor, and battery

Abstract

The present invention relates to the field of positive electrode materials, and provides a positive electrode material and a preparation method therefor, and a battery. The positive electrode material comprises a base material and a coating layer located on the surface of the base material. The chemical general formula of the base material is LiaNibCocMdO2, wherein 0.95≤a≤1.08, 0.3≤b≤1, 0≤c≤0.7, 0≤d≤0.2, b+c+d=1, and M is a metal element. The coating layer comprises a fast ion conductor material. In an XRD spectrum of the positive electrode material, the number of crystal planes of the positive electrode material on a crystal plane (003) is P003, the number of crystal planes of the positive electrode material on a crystal plane (104) is P104, 10≤P003≤300, 10≤P104≤400, and 0.55≤P003 / P104. According to the positive electrode material, the impedance of the positive electrode material is reduced, the transmission of lithium ions is accelerated, and the initial discharge capacity and the initial coulombic efficiency are improved.

Description

Positive electrode material and preparation method thereof, and battery Technical Field

[0001] The present application relates to the technical field of positive electrode materials, and in particular to positive electrode materials, preparation methods thereof, and batteries. Background Art

[0002] As the price of cobalt sources rises, the nickel content in cathode materials is gradually being increased to reduce the demand for cobalt. However, relevant research shows that as the Ni content increases, the structural stability of the cathode material also deteriorates. During the charge and discharge process, phase transitions can cause significant changes in crystal size, making the cathode material susceptible to pulverization and cracking, ultimately leading to irreversible loss of the cathode material's capacity. As a result, the initial efficiency and first discharge capacity of the cathode material are often low, and the cycle stability is also poor.

[0003] Summary of the Invention

[0004] The present application proposes a positive electrode material, a preparation method thereof, and a battery. The positive electrode material of the present application can effectively reduce the impedance of the positive electrode material, accelerate the transmission of lithium ions, and improve the first discharge capacity and the first coulombic efficiency.

[0005] In a first aspect, an embodiment of the present application provides a positive electrode material, the positive electrode material comprising a base material and a coating layer located on the surface of the base material, the chemical formula of the base material is Li a Ni b Co c M d O2, where 0.95≤a≤1.08, 0.3≤b≤1, 0≤c≤0.7, 0≤d≤0.2, b+c+d=1, and M is a metal element;

[0006] In the XRD spectrum of the positive electrode material, the number of crystal planes of the positive electrode material in the (003) crystal plane is P 003 , the number of crystal planes in the (104) crystal plane is P 104 , 10≤P 003 ≤300, 10≤P 104 ≤400, 0.55≤P 003 / P 104 .

[0007] In combination with the first aspect, in some embodiments, the coating layer is a fast ion conductor material.

[0008] In combination with the first aspect, in some embodiments, the fast ion conductor material includes at least one of an oxide of the element N and a lithium composite oxide of the element N, and the element N includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B, and P;

[0009] In combination with the first aspect, in some embodiments, the fast ion conductor material includes at least one of an oxide of the element N and a lithium composite oxide of the element N, and the mass content of the element N in the positive electrode material is 0.01 wt% to 2 wt%;

[0010] In combination with the first aspect, in some embodiments, the metal element M includes at least one of Co, Mn, Sb, Zr, Sr, Co, Ba, Y, Ce, Al, Mg, La, Ti, and Ca;

[0011] In combination with the first aspect, in some embodiments, the particle size D50 of the positive electrode material is 2 μm to 20 μm;

[0012] In combination with the first aspect, in some embodiments, the mass content of the metal element M in the positive electrode material is 0.01 wt% to 2 wt%;

[0013] In combination with the first aspect, in some embodiments, the chemical formula of the positive electrode material is x Li a Ni b Co c M d O2·(1-x)Li e N f O g , 0<x<1, e, f, g are all integers and satisfy 2g=e+f×h, where h is the valence of element N, and the N element includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B, F and P.

[0014] In a second aspect, an embodiment of the present application provides a positive electrode material, the positive electrode material comprising a base material and a coating layer located on the surface of the base material, the chemical formula of the base material is Li a Ni b Co c M d O2, where 0.95≤a≤1.08, 0.3≤b≤1, 0≤c≤0.7, 0≤d≤0.2, b+c+d=1, and M is a metal element;

[0015] A button cell made of a positive electrode containing the positive electrode material as a working electrode, a lithium sheet as a negative electrode, and a lithium ion-containing electrolyte is charged and discharged at 3.0V to 4.3V at 0.1C, and a differential value dQ / dV obtained by differentiating the charge and discharge capacity Q with the potential V of the working electrode is obtained; with dQ / dV as the ordinate and the potential V of the working electrode as the abscissa, a relationship curve between dQ / dV and the potential V is obtained, wherein the positive electrode material has discharge peaks at 4.17V±0.1V, 4.0V±0.1V, and 3.65V±0.1V, and the absolute values ​​of the three discharge peak intensities are I 4.17V , I 4.0V , I 3.65V , and 0.2≤I 4.17V / (I 4.0V +I 3.65V )≤2.5.

[0016] In conjunction with the second aspect, in some embodiments, in the positive electrode material, when 0.3≤b≤0.7, I 4.17V ≤15mAh / V.

[0017] In conjunction with the second aspect, in some embodiments, in the positive electrode material, when 0.7<b≤0.8, I 4.17V ≤20mAh / V.

[0018] In conjunction with the second aspect, in some embodiments, in the positive electrode material, when 0.8<b≤0.9, I 4.17V ≤30mAh / V.

[0019] In conjunction with the second aspect, in some embodiments, in the positive electrode material, when 0.9<b≤1.0, I 4.17V ≤50mAh / V.

[0020] In combination with the second aspect, in some embodiments, in the positive electrode material, the coating layer is a fast ion conductor material.

[0021] In combination with the second aspect, in some embodiments, in the positive electrode material, the fast ion conductor material includes at least one of an oxide of the element N and a lithium composite oxide of the element N, and the element N includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B and P.

[0022] In combination with the second aspect, in some embodiments, in the positive electrode material, the fast ion conductor material includes at least one of an oxide of the element N and a lithium composite oxide of the element N, and the mass content of the element N in the positive electrode material is 0.01 wt% to 2 wt%.

[0023] In combination with the second aspect, in some embodiments, in the positive electrode material, the metal element M includes at least one of Co, Mn, Sb, Zr, Sr, Co, Ba, Y, Ce, Al, Mg, La, Ti and Ca.

[0024] In combination with the second aspect, in some embodiments, in the positive electrode material, the particle size D50 of the positive electrode material is 2 μm to 20 μm.

[0025] In combination with the second aspect, in some embodiments, in the positive electrode material, the mass content of the metal element M in the positive electrode material is 0.01 wt % to 2 wt %.

[0026] In conjunction with the second aspect, in some embodiments, in the positive electrode material, the chemical formula of the positive electrode material is xLi a Ni b Co c M d O2·(1-x)Li e N f O g , 0<x<1, e, f, g are all integers and satisfy 2g=e+f×h, where h is the valence of element N, and the N element includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B, F and P.

[0027] In a second aspect, an embodiment of the present application provides a battery comprising the positive electrode material as described above.

[0028] The technical solution of this application has at least the following beneficial effects:

[0029] The positive electrode active material provided by the present application adjusts the number and ratio of the (003) crystal plane and the (104) crystal plane of the positive electrode material so that P 003 / P 104 ≥0.4, during the charge and discharge process, lithium ions mainly migrate within the (003) crystal plane of the positive electrode material, and fewer lithium ions migrate within the (104) crystal plane, which can effectively shorten the migration path of lithium ions; control P 003 / P 104 ≥0.55, which is beneficial to reducing the impedance of the positive electrode material, accelerating the transmission of lithium ions, and improving the first discharge capacity and the first coulombic efficiency.

[0030] The positive electrode active material provided by the present application is controlled by 0.2≤I 4.17V / (I 4.0V +I 3.65V)≤2.5, which can increase the peak intensity of the positive electrode material's H1 phase transformation to the M phase during the first charge and discharge process, as well as the peak intensity of the positive electrode material's M phase transformation to the H2 phase, reduce the peak intensity of the H2 phase transformation to the H3 phase, and reduce the lattice distortion of the positive electrode material. The positive electrode material can not only have a stable layered structure during the cycle process, but also reduce the risk of cracks and gas production in the positive electrode material during the cycle process, thereby improving the structural stability and safety of the positive electrode material and reducing gas production; in addition, it can also improve the reversibility of the phase change of the positive electrode material, so that the positive electrode material has both high cycle performance and high capacity, and reduces the pulverization of the positive electrode material particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG1 is a schematic flow chart of a method for preparing a positive electrode material provided in an embodiment of the present application.

[0032] FIG2 is a graph showing the relationship between the dQ / dV of the positive electrode material and the potential V of the working electrode provided in Example 1 of the present application.

[0033] FIG3 is a graph showing the relationship between the dQ / dV of the positive electrode material and the potential V of the working electrode provided in Example 2 of the present application.

[0034] FIG4 is a graph showing the relationship between the dQ / dV of the positive electrode material and the potential V of the working electrode provided in Example 3 of the present application.

[0035] FIG5 is a graph showing the relationship between the dQ / dV of the positive electrode material and the potential V of the working electrode provided in Example 4 of the present application.

[0036] FIG6 is a graph showing the relationship between the dQ / dV of the positive electrode material and the potential V of the working electrode provided in Comparative Example 1 of the present application.

[0037] FIG7 is a graph showing the relationship between the dQ / dV of the positive electrode material and the potential V of the working electrode provided in Comparative Example 2 of the present application.

[0038] FIG8 is a graph showing the relationship between the dQ / dV of the positive electrode material and the potential V of the working electrode provided in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0039] The following are preferred implementations of the embodiments of the present invention. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the embodiments of the present invention. These improvements and modifications are also considered to be within the scope of protection of the embodiments of the present invention.

[0040] The inventors discovered that increasing the nickel content in the positive electrode material can increase the capacity of the positive electrode material. However, the H2-H3 phase transition occurs at 4.2V to 4.3V. At this time, the lattice size of the positive electrode material undergoes significant changes, which in turn causes irreversible transformation of part of the lattice. This increases the stress generated by the lattice phase transition within the positive electrode material, which in turn leads to a decrease in the structural stability and cycle stability of the material. To this end, the inventors improved the product process and increased the structural stability and cycle stability of the positive electrode material by controlling the temperature and heating rate at different stages. After research, the inventors found that the performance changes of the positive electrode material can be reflected in two aspects: the number of (003) crystal planes and the change in unit cell volume during the H2 phase to H3 phase transition. Specifically, during the transformation from the H2 phase to the H3 phase, lithium ions transfer from tetrahedral positions to octahedral positions. This process will cause the unit cell volume to expand first and then shrink. The change in the unit cell volume is likely to affect the structural stability of the positive electrode material. The inventors speculate that by increasing the number of 003 crystal faces, the layer space of the unit cell in the c-axis direction is increased. On the one hand, more movement space is provided for the migration of lithium ions, thereby making the migration process of lithium ions from tetrahedral positions to octahedral positions smoother. On the other hand, more interlayer space makes the lithium ions more evenly distributed between layers, reducing local stress, thereby reducing the mutation of the unit cell volume during the transformation from the H2 phase to the H3 phase, and increasing the structural stability and cycle stability of the positive electrode material.

[0041] Furthermore, the embodiment of the present application provides a positive electrode material, which includes a base material and a coating layer located on the surface of the base material. The chemical formula of the base material is Li a Ni b Co c M d O2, wherein 0.95≤a≤1.08, 0.3≤b≤1, 0≤c≤0.7, 0≤d≤0.2, b+c+d=1, and M is a metal element.

[0042] In the XRD spectrum of the positive electrode material, the number of crystal planes in the (003) crystal plane of the positive electrode material is P 003 , the number of crystal planes in the (104) crystal plane is P 104 , 10≤P 003 ≤300, 10≤P 104 ≤400, 0.55≤P 003 / P 104 .

[0043] The positive electrode active material provided in the present application has a coating layer on its surface. By adjusting the number and ratio of the (003) crystal plane and the (104) crystal plane of the positive electrode material, P 003 / P 104≥0.4, during the charge and discharge process, lithium ions mainly migrate within the (003) crystal plane of the positive electrode material, and fewer lithium ions migrate within the (104) crystal plane. The migration path of lithium ions within the (003) crystal plane is shorter than that within the (104) crystal plane, which can effectively shorten the migration path of lithium ions during the charge and discharge process; thus, by controlling P 003 / P 104 ≥0.55, which is beneficial to reducing the impedance of the positive electrode material, accelerating the transmission of lithium ions, and improving the first discharge capacity and first coulombic efficiency.

[0044] In some embodiments, the positive electrode material has the general chemical formula x Li a Ni b Co c M d O2·(1-x)Li e N f O g , 0<x<1, e, f, g are all integers and meet 2g=e+f×h, where h is the valence of element N. It can be understood that xLiaNibCocMdO2·(1-x)Li e N f O g Indicates that the matrix material and the coating form a composite, where Li a Ni b Co c M d O2 represents the matrix material, Li e N f O g represents the fast ion conductor material, and x represents the molar ratio of the matrix material in the positive electrode material. Specifically, x can be 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, etc., and can also be other values ​​within the above range, which is not limited here. It should be noted that Li e N f O g represents a fast ion conductor material, wherein the number of oxygen atoms can be adaptively adjusted according to the valence of the N element, which is not limited here.

[0045] In some embodiments, the value of a can be 0.95, 0.96, 0.98, 1.0, 1.02, 1.05, 1.06 or 1.08, etc., the value of b can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0, etc., the value of c can be 0, 0.01, 0.02, 0.05, 0.08, 0.1, 0.3, 0.5, 0.6 or 0.7, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0046] In some embodiments, in the XRD spectrum of the positive electrode material, the number of crystal planes of the positive electrode material in the (003) crystal plane is P 003 , the number of crystal planes in the (104) crystal plane is P 104 , 0.55≤P 003 / P 104 Specifically, P 003 / P 104 It can be 0.55, 0.58, 0.59, 0.6, 0.62, 0.64, 0.67, 0.69, 0.7 or 0.8, etc., and of course it can be other values ​​within the above range, which is not limited here. During the charge and discharge process, lithium ions mainly migrate within the (003) crystal plane of the positive electrode material. The migration path of lithium ions in the (003) crystal plane is shorter than that in the (104) crystal plane, so controlling P 003 / P 104 The ratio of is within the above range, which is beneficial to reducing the impedance of the positive electrode material and improving the rate performance of the positive electrode material.

[0047] In some embodiments, 10≤P 003 ≤300, P 003 Specifically, it can be 10, 50, 80, 100, 120, 130, 150, 160, 180, 200, 220, 250, 280 or 300, etc. Of course, it can also be other values ​​within the above range, which is not limited here. 104 ≤400, P 104 Specifically, it can be 10, 50, 80, 100, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380 or 400, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0048] In this application, XRD testing of the positive electrode material was performed to characterize the 003 and 104 crystal planes. When performing XRD testing on the material, Cu-Kα radiation was used as the X-ray source. The test conditions were 10-90° (2θ) with a scanning step of 0.05°. The full width at half maximum of the (003) and (104) crystal plane diffraction peaks, and the interplanar spacing of the (003) and (104) crystal planes were measured.

[0049] In this application, the number of crystal planes P = D / d, where D is the average thickness of the grain perpendicular to the crystal plane. d is the interplanar spacing.

[0050] K is the Scherrer constant. When B is the half-maximum width of the diffraction peak, K = 0.89; when B is the integrated height-width of the diffraction peak, K = 1.

[0051] B is the half-height width of the diffraction peak of the positive electrode material, which needs to be converted into radians (rad);

[0052] θ is the Bragg diffraction angle, in degrees;

[0053] γ is the wavelength of X-rays, using Cu kα, which is generally

[0054] In some embodiments, a button cell comprising a positive electrode containing a positive electrode material as a working electrode, a lithium sheet as a negative electrode, and a lithium ion-containing electrolyte is subjected to 0.1C charge and discharge at 3.0V to 4.3V to obtain a differential value dQ / dV obtained by differentiating the charge and discharge capacity Q with respect to the potential V of the working electrode; a graph of the relationship between dQ / dV and the potential V is obtained with dQ / dV as the ordinate and the potential V of the working electrode as the abscissa, and there are at least three obvious discharge platforms in the graph of the relationship between dQ / dV and the potential V.

[0055] Specifically, in the relationship curve of dQ / dV and potential V, the positive electrode material has discharge peaks at 4.17V±0.1V, 4.0V±0.1V and 3.65V±0.1V, and the absolute values ​​of the three discharge peak intensities are I 4.17V , I 4.0V , I 3.65V , and 0.2≤I 4.17V / (I 4.0V +I 3.65V )≤2.5. The positive electrode material mainly undergoes H1 phase to M phase transformation at 3.65V±0.1V, mainly M phase to H2 phase transformation at 4.0V±0.1V, and mainly H2 phase to H3 phase transformation at 4.17V±0.1V. Among them, the unit cell volume of the positive electrode material changes slightly when the M phase transforms to the H2 phase, while the unit cell volume changes significantly when the H2 phase transforms to the H3 phase. This application controls 0.2≤I 4.17V / (I 4.0V +I 3.65V )≤2.5, which can increase the peak intensity of the positive electrode material's H1 phase transformation to the M phase during the first charge and discharge process, as well as the peak intensity of the positive electrode material's M phase transformation to the H2 phase, reduce the peak intensity of the H2 phase transformation to the H3 phase, and reduce the lattice distortion of the positive electrode material. The positive electrode material can not only have a stable layered structure during the cycle process, but also reduce the risk of cracks and gas production in the positive electrode material during the cycle process, thereby improving the structural stability and safety of the positive electrode material and reducing gas production; in addition, it can also improve the reversibility of the phase change of the positive electrode material, so that the positive electrode material has both high cycle performance and high capacity, and reduces the pulverization of the positive electrode material particles.

[0056] In some embodiments, I4.17V / (I 4.0V +I 3.65V ) can be specifically 0.2, 0.3, 0.5, 0.8, 0.9, 1.0, 1.2, 1.5, 1.8, 2.0, 2.2, 2.3 or 2.5, etc., and of course it can be other values ​​within the above range, which is not limited here. It can be understood that the lower the peak intensity ratio, the higher the positive electrode material is in the transition from H1 phase to M phase and from M phase to H2 phase, which can reduce the transition from H2 phase to H3 phase, and the layered structure of the positive electrode material is more stable. Preferably, 0.2≤I 4.17V / (I 4.0V +I 3.65V )≤1.5.

[0057] In some embodiments, in the positive electrode material, when 0.3≤b≤0.7, I 4.17V ≤15mAh / V, specifically can be 15mAh / V, 14mAh / V, 13mAh / V, 12mAh / V, 11mAh / V, 10mAh / V, 9mAh / V or 8mAh / V, etc., which is not limited here.

[0058] In some embodiments, in the positive electrode material, when 0.7<b≤0.8, I 4.17V ≤20mAh / V, specifically can be 20mAh / V, 19mAh / V, 18mAh / V, 17mAh / V, 15mAh / V, 14mAh / V, 13mAh / V, 12mAh / V, 11mAh / V, 10mAh / V, 9mAh / V or 8mAh / V, etc., without limitation here.

[0059] In some embodiments, in the positive electrode material, when 0.8<b≤0.9, I 4.17V ≤30mAh / V, specifically can be 30mAh / V, 25mAh / V, 22mAh / V, 20mAh / V, 19mAh / V, 18mAh / V, 17mAh / V, 15mAh / V or 10mAh / V, etc., which is not limited here.

[0060] In some embodiments, in the positive electrode material, when 0.9<b≤1.0, I 4.17V ≤50mAh / V, specifically can be 50mAh / V, 40mAh / V, 30mAh / V, 25mAh / V, 20mAh / V or 10mAh / V, etc., which is not limited here.

[0061] It can be understood that within different nickel content ranges, the positive electrode material has different discharge peak intensities at 4.17V±0.1V. The higher the nickel content, the higher the peak value at 4.17V±0.1V, and the larger the range of allowable peak intensity fluctuations, the more effectively the structural stability, rate and cycle performance of the positive electrode material can be modified.

[0062] In some embodiments, the metal element M includes at least one of Co, Mn, Sb, Zr, Sr, Ba, Y, Ce, Al, Mg, Nb, W, La, Ti, and Ca.

[0063] In some embodiments, the positive electrode material includes secondary particles formed by agglomeration of a plurality of primary particles, and the secondary particles are spherical in structure.

[0064] In some embodiments, the cathode material has a core-shell structure, wherein the primary particles in the shell have a coating layer on their surface, and the coating layer comprises a fast ion conductor material. It is understood that the coating layer on the surface of the primary particles can reduce direct contact between the electrolyte and the matrix material, reduce the occurrence of side reactions, and thereby improve the cycling stability of the cathode material.

[0065] In some embodiments, the coating layer comprises a fast ion conductor material. It should be noted that a fast ion conductor refers to a material with an ionic conductivity of less than 1x10 -6 Ionic conductor materials with an ionic conductivity activation energy of 0.40 eV or less.

[0066] In some embodiments, the fast ion conductor material includes at least one of an oxide of the element N and a lithium composite oxide of the element N, and the element N includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B, F and P.

[0067] In some embodiments, the fast ion conductor material has the general chemical formula Li e N f O g , where e, f, and g are all integers and satisfy 2g=e+f×h, where h is the valence of element N. Exemplary fast ion conductor materials include Li2WO4, LiYO2, LiNbO3, LiAlO2, LiCoO2, Li8ZrO6, Li4TiO4, etc., which are not limited here.

[0068] In some embodiments, based on the mass of the positive electrode material being 100 wt%, the mass content of the N element in the positive electrode material is 0.01 wt% to 2 wt%, specifically 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt% or 2.0 wt%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0069] In some embodiments, the particle size D50 of the positive electrode material is 2 μm to 20 μm, specifically 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 13 μm, 15 μm, 18 μm, 19 μm, or 20 μm, etc., and of course other values ​​within the above range are also possible, and are not limited here. Controlling the particle size of the positive electrode material within the above range is beneficial to improving the rate performance and cycle stability of the positive electrode material.

[0070] In a second aspect, the present application provides a method for preparing a positive electrode material, as shown in FIG1 , the method for preparing a positive electrode material comprises the following steps:

[0071] S10: preparing a mixture comprising a cathode material precursor, a lithium source, and a dopant; wherein the ratio n of the molar amount of Li in the lithium source to the total molar amount of transition metal in the cathode material precursor is controlled. Li / n Me ≥1;

[0072] S20: sintering the mixture once to obtain a matrix material; the primary sintering process includes a temperature rising section and a temperature falling section performed in sequence, the temperature rising section includes a first constant temperature stage, a second constant temperature stage and a third constant temperature stage, the temperature of the first constant temperature stage is 470° C. to 600° C., the temperature of the second constant temperature stage is 650° C. to 700° C., the temperature of the third constant temperature stage is 700° C. to 1000° C., and the temperature of the temperature falling section is 500° C. to 700° C.;

[0073] S30: After mixing the base material and the coating agent, a secondary sintering process is performed to obtain a positive electrode material.

[0074] The preparation method of the positive electrode material provided by the present application first controls the lithium ratio of the positive electrode material precursor and the lithium source so that the sintered base material is slightly lithium-rich, and in the first sintering process, first passes through the temperature rising stage, the growth crystal plane of the base material tends to grow toward the (003) crystal plane, and the migration path of lithium ions in the (003) crystal plane is shorter, which is beneficial to improving the rate performance of the positive electrode material. In the first constant temperature stage, the lithium source can fully melt and react with the positive electrode material precursor to form the base material. In the second constant temperature stage, the crystal of the positive electrode material fully grows, and the growth crystal plane tends to grow toward the 003 crystal plane. Then, it enters the third constant temperature stage to make the crystal structure fully crystallized; and then passes through the temperature falling stage to improve the stability of the crystal structure of the positive electrode material. Finally, the base material and the coating agent are subjected to secondary sintering, so that the coating layer containing the fast ion conductor material is in situ synthesized on the surface of the positive electrode material, inhibiting the penetration of the electrolyte, improving the ion transmission efficiency and rate performance of the positive electrode material, especially the low-temperature rate performance of the positive electrode material. The preparation method provided in this application is simple and can realize mass production, thereby improving the rate performance and cycle stability of the positive electrode material.

[0075] The preparation method of the present application is described in detail below with reference to the examples:

[0076] S10, performing a sintering process on the mixture of the positive electrode material precursor, the lithium source and the dopant to obtain a matrix material.

[0077] In some embodiments, the chemical formula of the cathode material precursor is Ni a1 Co b1 M c1 (OH)2, wherein a1+b1+c1=1, 0.3≤a1≤1, 0≤b1≤0.7, 0≤c1≤0.2, and the element M includes at least one of Co, Mn, Sb, Zr, Sr, Co, Ba, Y, Ce, Al, Mg, La, Ti and Ca.

[0078] Typical examples of combinations include: Ni 0.88 Co 0.09 Mn 0.03 (OH)2,Ni 0.92 Co 0.05 Mn 0.02 (OH)2,Ni 0.94 Co 0.06 (OH)2,Ni 0.96 Co 0.03 Mn 0.01 (OH)2, etc.

[0079] In some embodiments, the particle size D50 of the positive electrode material precursor is 2 μm to 18 μm, specifically 2 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 13 μm, 15 μm, or 18 μm. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the particle size D50 of the positive electrode material precursor is 7 μm to 13 μm.

[0080] In some embodiments, the dopant includes at least one of an oxide of element M, a hydroxide of element M, a boride of element M, and a phosphate of element M.

[0081] In some embodiments, the particle size D50 of the dopant is 10 nm to 500 nm, specifically 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm or 500 nm, etc., and of course other values ​​within the above range are also possible, which are not limited here. The particle size of the dopant is nanometer-scale, and dopants of appropriate size can better be doped into the interior of the positive electrode material precursor to achieve uniform doping modification. Preferably, the particle size D50 of the dopant is 20 nm to 300 nm, and more preferably, the particle size D50 of the dopant is 30 nm to 200 nm.

[0082] In some embodiments, the amount of dopant added is controlled to meet the following requirements: the mass content of the metal element M in the positive electrode material is 0.01wt% to 2wt%, specifically 0.01wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.5wt%, 0.8wt%, 1.0wt%, 1.2wt%, 1.5wt%, 1.8wt% or 2.0wt%, etc., and of course other values ​​within the above range are also possible, and are not limited here. Preferably, the mass content of the metal element M in the positive electrode material is 0.02wt% to 1wt%, more preferably 0.03wt% to 0.3wt%.

[0083] In some embodiments, the lithium source comprises at least one of lithium hydroxide, lithium oxide, lithium sulfate, lithium carbonate, lithium nitrate, lithium acetate, lithium phosphate, and lithium oxalate. Preferably, the lithium source comprises lithium hydroxide.

[0084] In some embodiments, the ratio of the molar amount of Li in the lithium source to the total molar amount of transition metal in the positive electrode material precursor is controlled to satisfy 1.0≤n Li / n Me≤1.08. For example, the ratio of the total molar amount of Ni and M to the molar amount of Li in the positive electrode material precursor is 1:(1.0-1.08); specifically, it can be 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07 or 1:1.08, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Preferably, 1.02≤n Li / n Me ≤1.07, more preferably, 1.03≤n Li / n Me ≤1.06, so that the mixture is slightly lithium-rich after one sintering.

[0085] In some embodiments, the mixture of the positive electrode material precursor, the lithium source, and the dopant can be mixed by dry grinding, ball milling, etc., which is not limited here, as long as the components are mixed evenly.

[0086] In some embodiments, the mixing device may be at least one of a ball mill, a three-dimensional mixer, a high-speed mixer, and a VC mixer.

[0087] In some embodiments, the primary sintering process is performed in an oxygen-containing atmosphere, which may be air or a mixture of air and oxygen.

[0088] In some embodiments, the volume content of oxygen in the oxygen-containing atmosphere is greater than 95%.

[0089] In step S20, the mixture is subjected to a sintering treatment to obtain a matrix material; the sintering treatment includes a heating section and a cooling section performed in sequence, the heating section includes a first constant temperature stage, a second constant temperature stage and a third constant temperature stage, the temperature of the first constant temperature stage is 470°C to 600°C, the temperature of the second constant temperature stage is 650°C to 700°C, the temperature of the third constant temperature stage is 700°C to 1000°C, and the temperature of the cooling section is 500°C to 700°C.

[0090] In some embodiments, the temperature of the first constant temperature stage can be specifically 470°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 570°C, 580°C or 600°C, etc. The time of the first constant temperature stage is ≥10h, and the time of the first constant temperature stage can be specifically 10h, 12h, 13h, 14h, 15h, 18h, 20h or 24h, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. Preferably, the time of the first constant temperature stage is 10h to 24h. The temperature of the first constant temperature stage is relatively low, at which time the lithium source can be fully melted and react with the positive electrode material precursor to form a core part with a relatively dense structure in the matrix material.

[0091] In some embodiments, the temperature of the second constant temperature stage can be specifically 650°C, 660°C, 670°C, 680°C, 690°C or 700°C, etc., but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable.

[0092] In some embodiments, the second constant temperature stage lasts for 5 to 24 hours. Specifically, the second constant temperature stage lasts for 5 hours, 8 hours, 10 hours, 12 hours, 13 hours, 14 hours, or 15 hours, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable. During the second constant temperature stage, the crystals of the positive electrode material are fully grown, and the growth crystal plane tends to grow toward the 003 crystal plane, thereby increasing the number of (003) crystal planes in the positive electrode material.

[0093] In some embodiments, the temperature of the third constant temperature stage can be specifically 700°C, 750°C, 780°C, 800°C, 850°C, 880°C, 900°C, 940°C, 950°C, 970°C or 1000°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0094] In some embodiments, the third constant temperature stage lasts for 5 to 24 hours. Specifically, the third constant temperature stage may last for 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, or 24 hours, but is not limited to the listed values. Other values ​​not listed within this range are also applicable. The third constant temperature stage can fully crystallize the crystal structure of the positive electrode material.

[0095] In some embodiments, the temperature of the cooling section is between 500°C and 700°C, specifically 470°C, 480°C, 490°C, 500°C, 520°C, 550°C, 570°C, 600°C, 650°C, 680°C or 700°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0096] In some embodiments, the cooling period is 5 hours to 24 hours, such as 5 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours or 24 hours, but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0097] The method further comprises cooling, shaping and screening the product after the primary sintering. The shaping comprises at least one of crushing, grinding, ball milling or gas crushing.

[0098] Step S30 : After mixing the base material and the coating agent, perform a secondary sintering process to obtain a positive electrode material.

[0099] The mixing method is the same as that in step S10 and will not be described again here.

[0100] In some embodiments, the coating agent includes a compound containing element N, and the element N includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B, F, and P.

[0101] It can be understood that the compound containing N element includes N element oxide or N element hydroxide, which can form Li with high lithium ion conductivity at the grain boundary between primary particles. e N f O g , which reduces the grain boundary transmission impedance and is beneficial to improving the rate performance of the positive electrode material.

[0102] In some embodiments, the capping agent further comprises a solid electrolyte LATP.

[0103] In some embodiments, the amount of coating agent added is controlled to satisfy the following: the mass content of elemental N in the positive electrode material is 0.01wt% to 2wt%. Specifically, it can be 0.01wt%, 0.02wt%, 0.03wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.8wt%, 1.0wt%, 1.5wt% or 2.0wt%, etc., without limitation herein. Preferably, the mass content of metallic element N in the positive electrode material is 0.02wt% to 1wt%, more preferably 0.03wt% to 0.5wt%.

[0104] In some embodiments, the particle size of the coating agent ranges from 10 nm to 500 nm; specifically, it can be 10 nm, 20 nm, 50 nm, 60 nm, 100 nm, 200 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. It can be understood that the particle size of the coating agent is nanometer-scale. Controlling the particle size of the coating agent can allow part of the coating agent to enter the interior of the matrix material, so that the primary particles close to the surface of the matrix material can be effectively coated, or a dense coating layer is formed between the primary particles on the surface, thereby reducing the direct contact between the primary particles and the electrolyte. The composite metal oxide in the coating layer can act as a fast ion conductor to accelerate the transmission efficiency of lithium ions, so that the positive electrode material has both high capacity and high cycle stability. Preferably, the particle size of the coating agent is in the range of 20 nm to 300 nm, and more preferably, the particle size of the coating agent is in the range of 30 nm to 200 nm.

[0105] In some embodiments, the secondary sintering process is performed in an oxygen-containing atmosphere; the oxygen-containing atmosphere may be air or a mixed gas of oxygen.

[0106] In some embodiments, the temperature of the secondary sintering process is 200°C to 800°C; specifically, it can be 200°C, 300°C, 400°C, 450°C, 500°C, 520°C, 550°C, 600°C, 650°C, 680°C, 700°C, or 800°C, but is not limited to the listed values. Other values ​​not listed in this numerical range are also applicable. Preferably, the temperature of the secondary sintering process is 550°C to 700°C. Preferably, the temperature of the secondary sintering process is 300°C to 750°C.

[0107] In some embodiments, the secondary sintering treatment time is 5 hours to 24 hours; specifically, it can be 5 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 15 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. Preferably,

[0108] By controlling the temperature, time, type and amount of the coating agent during the secondary sintering process, it is possible to ensure that the coating agent can form a dense coating layer on the surface of the secondary particles of the positive electrode material. Part of the coating agent can also enter the interior of the positive electrode material and coat the primary particles inside, thereby achieving double protection for the secondary particles and the primary particles in the shell layer, improving the structural stability of the positive electrode material, and thereby improving the cycle stability.

[0109] In some embodiments, the preparation method further comprises cooling, shaping, and screening the product after secondary sintering. The shaping comprises at least one of pulverizing, grinding, ball milling, or gas crushing.

[0110] In a third aspect, the present application provides a battery comprising the above-mentioned positive electrode material or the positive electrode material prepared by the above-mentioned preparation method. Specifically, the battery can be a lithium-ion battery, a sodium-ion battery, etc., which is not limited here.

[0111] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0112] Example 1

[0113] A method for preparing a positive electrode material comprises the following steps:

[0114] (1) Provide n Ni :n Co :n Mn The nickel-cobalt-manganese precursor (Ni 0.88 Co 0.09 Mn 0.03(OH)2), nickel cobalt manganese precursor (D50 = 10um) and lithium hydroxide, dopant WO3 (D 50 =50nm) to obtain a mixture; wherein n Me :n Li =1:1.03, Me=Ni+Co+Mn+W.

[0115] (2) In an oxygen atmosphere, the mixture was heated to 600°C and sintered for 10 h, then heated to 670°C at a rate of 10°C / min and sintered for 15 h, and then heated to 750°C at a rate of 2°C / min and sintered for 8 h. During the cooling process, the mixture was kept at 650°C for 8 h, and the sintered product was crushed to obtain the matrix material.

[0116] (3) Combine the matrix material with Nb2O5(D 50 =50nm) were mixed, sintered at high temperature in an oxygen atmosphere at a temperature of 600°C for 12h, and sieved to obtain a positive electrode material.

[0117] The positive electrode material prepared in this embodiment is 0.999Li 1.03 Ni 0.8795 Co 0.09 Mn 0.03 W 0.0005 O2·(0.001)LiNbO3; the mass content of W element in the positive electrode material is 0.1wt%, and the mass content of Nb element in the positive electrode material is 0.1wt%.

[0118] Example 2

[0119] (1) Provide n Ni :n Co :n Mn The nickel-cobalt-manganese precursor (Ni 0.92 Co 0.06 Mn 0.02 (OH)2), nickel cobalt manganese precursor (D50 = 10um) and lithium hydroxide, dopant MgO (D 50 =20nm) to obtain a mixture; wherein, n Me :n Li =1:1.01, Me=Ni+Co+Mn+Mg.

[0120] (2) In an oxygen atmosphere, the mixture was heated to 500°C and sintered for 10 h, then heated to 700°C at a rate of 15°C / min and sintered for 15 h, and then heated to 740°C at a rate of 2°C / min and sintered for 5 h. During the cooling process, the mixture was kept at 650°C for 10 h, and the sintered product was crushed to obtain the matrix material.

[0121] (3) The matrix material and La2O3(D 50=50nm) were mixed, sintered at high temperature in an oxygen atmosphere at a temperature of 600°C for 12h, and sieved to obtain a positive electrode material.

[0122] The positive electrode material prepared in this embodiment is 0.9993Li 1.01 Ni 0.912 Co 0.06 Mn 0.02 Mg 0.008 O2·0.0007LiLaO2; the mass content of Mg element in the positive electrode material is 0.2wt%, and the mass content of La element in the positive electrode material is 0.1wt%.

[0123] Example 3

[0124] (1) Provide n Ni :n Co :n Mn The nickel-cobalt-manganese precursor (Ni 0.96 Co 0.03 Mn 0.01 (OH)2), nickel cobalt manganese precursor (D50 = 10um) and lithium hydroxide, dopant B2O3 (D 50 =500nm) to obtain a mixture; wherein, n Me :n Li =1:1.05, Me=Ni+Co+Mn+B.

[0125] (2) In an oxygen atmosphere, the mixture was heated to 500°C and sintered for 24 h, then heated to 650°C at a rate of 10°C / min and sintered for 8 h, and then heated to 700°C at a rate of 2°C / min and sintered for 8 h. During the cooling process, the mixture was kept at 520°C for 8 h. The sintered product was crushed to obtain the matrix material.

[0126] (3) The matrix material and MoO3(D 50 =100nm) were mixed, sintered at high temperature in an oxygen atmosphere at a temperature of 600°C for 12h, and sieved to obtain a positive electrode material.

[0127] The positive electrode material prepared in this embodiment is 0.9948Li 1.05 Ni 0.9554 Co 0.03 Mn 0.01 B 0.0046 O2·0.0052LiMoO2; the mass content of the B element in the positive electrode material is 0.08wt%, and the mass content of the Mo element in the positive electrode material is 0.5wt%.

[0128] Example 4

[0129] (1) Provide n Ni:n Co :n Mn The nickel-cobalt-manganese precursor (Ni 0.96 Co 0.03 Mn 0.01 (OH)2), nickel cobalt manganese precursor (D50 = 10um) and lithium hydroxide, dopant Ba (OH)2 (D 50 =150nm) to obtain a mixture; wherein, n Me :n Li =1:1.08, Me=Ni+Co+Mn+Ba.

[0130] (2) Under an oxygen atmosphere, the mixture was sintered at 470°C for 10 h, then heated to 650°C at a rate of 10°C / min and sintered for 15 h, and then heated to 770°C at a rate of 2°C / min and sintered for 8 h. During the cooling process, the mixture was kept at 650°C for 15 h. The sintered product was crushed to obtain the matrix material.

[0131] (3) Combine the matrix material with TiO2(D 50 =500nm) were mixed, sintered at high temperature in an oxygen atmosphere at a temperature of 700°C for 5 h, and sieved to obtain a positive electrode material.

[0132] The positive electrode material prepared in this embodiment is 0.99Li 1.08 Ni 0.8996 Co 0.05 Mn 0.05 Ba 0.0004 O2·0.01LiTiO2; the mass content of Ba element in the matrix material is 0.05wt%, and the mass content of Ti element in the positive electrode material is 0.5wt%.

[0133] Example 5

[0134] Different from Example 1,

[0135] (2) Under an oxygen atmosphere, the mixture was heated to 470°C and sintered for 10 h, then heated to 650°C at a rate of 10°C / min and sintered for 15 h, and then heated to 750°C at a rate of 2°C / min and sintered for 8 h. During the cooling process, the mixture was kept at 650°C for 8 h. The sintered product was crushed to obtain the matrix material.

[0136] Example 6

[0137] Different from Example 1,

[0138] (2) In an oxygen atmosphere, the mixture was heated to 600°C and sintered for 10 h, then heated to 700°C at a rate of 10°C / min and sintered for 15 h, and then heated to 750°C at a rate of 2°C / min and sintered for 8 h. During the cooling process, the mixture was kept at 650°C for 8 h. The sintered product was crushed to obtain the matrix material.

[0139] Example 7

[0140] The difference from Example 1 is that the WO3 particle size is 2 μm, and all other operations and raw material ratios are the same as those in Example 1.

[0141] Example 8

[0142] Different from Example 1,

[0143] (1) Provide n Ni :n Co :n Mn The nickel-cobalt-manganese precursor (Ni 0.70 Co 0.10 Mn 0.20 (OH)2), nickel cobalt manganese precursor (D50 = 9um) and lithium hydroxide, dopant WO3 (D 50 =50nm) to obtain a mixture; wherein n Me :n Li =1:1.03, Me=Ni+Co+Mn+W;

[0144] Example 9

[0145] Different from Example 1,

[0146] (1) Provide n Ni :n Co :n Mn The nickel-cobalt-manganese precursor (Ni 0.50 Co 0.20 Mn 0.30 (OH)2), nickel cobalt manganese precursor (D50 = 6um) and lithium carbonate, dopant WO3 (D 50 =50nm) to obtain a mixture; wherein n Me :n Li =1:1.03, Me=Ni+Co+Mn+W;

[0147] Example 10

[0148] Different from Example 1,

[0149] (1) Provide n Ni :n Co :n MnThe nickel-cobalt-manganese precursor (Ni 0.88 Co 0.09 Mn 0.03 (OH)2), nickel cobalt manganese precursor (D50 = 18um) and lithium oxide, dopant WO3 (D 50 =50nm) to obtain a mixture; wherein n Me :n Li =1:1.03, Me=Ni+Co+Mn+W;

[0150] Comparative Example 1

[0151] Different from Example 1,

[0152] (2) In an oxygen atmosphere, the mixture was heated to 600°C at a rate of 10°C / min and sintered for 10 h, then heated to 750°C at a rate of 2°C / min and sintered for 8 h. During the cooling process, the mixture was kept at 650°C for 8 h. The sintered product was crushed to obtain the matrix material.

[0153] Comparative Example 2

[0154] Different from Example 1,

[0155] (2) In an oxygen atmosphere, the mixture was heated to 600°C and sintered for 10 h, then heated to 670°C at a rate of 10°C / min and sintered for 15 h, and then heated to 750°C at a rate of 2°C / min and sintered for 8 h. The sintered product was crushed to obtain a matrix material.

[0156] Comparative Example 3

[0157] Different from Example 1,

[0158] (1) According to n Ni :n Co :n Mn The nickel-cobalt-manganese precursor (Ni 0.88 Co 0.09 Mn 0.03 (OH)2)(D50=10um) and lithium hydroxide, dopant WO3(D 50 =50nm) to obtain a mixture; wherein n(Ni+Co+Mn+W): n Li =1:0.92.

[0159] Test Method

[0160] 1) Volume distribution particle size test of positive electrode materials:

[0161] The test method for particle volume distribution particle size is based on GB / T 19077-2016. It can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0162] 2) Method for determining the content of elements M / N in the positive electrode material:

[0163] The content of elements M and N in the final product was tested by ICP using Agilent 5110. After the sample was weighed, it was completely digested with aqua regia and an appropriate amount of ultrapure water. After cooling, it was diluted to volume in a 100ml volumetric flask and shaken before testing.

[0164] 3) XRD test of positive electrode material:

[0165] When performing XRD testing on the material, Cu-Kα rays were used as the X-ray source. The test conditions were 10-90° (2θ) with a scanning step of 0.05°. Referring to Table 1, (003) FWHM is the full width at half maximum of the (003) crystal plane diffraction peak; (104) FWHM is the full width at half maximum of the (104) crystal plane diffraction peak; d 003 is the interplanar spacing of the (003) crystal plane; d 104 is the interplanar spacing of the (104) crystal plane; D 003 is the average thickness of the grain perpendicular to the (003) crystal plane; D 104 is the average thickness of the grain perpendicular to the crystal plane (104); 003 is the number of (003) crystal planes; P 104 is the number of (104) crystal planes; P 003 / P 104 is the ratio of the number of (003) crystal planes to the number of (104) crystal planes.

[0166] 4) Power-off test

[0167] The electrochemical performance of the prepared cathode material was evaluated using a coin-type half-cell. The following method was used: the cathode material, conductive carbon powder, and polyvinylidene fluoride (PVDF) were weighed in a 93:5:2 mass ratio. N-methylpyrrolidone (NMP) was added to a 50% solids content. The mixture was mixed into a viscous slurry using a high-speed disperser. The slurry was evenly coated onto aluminum foil using a spatula. After drying in an 80°C oven, the slurry was rolled and cut into 14mm diameter cathode sheets. A 16mm diameter lithium sheet was used as the anode sheet, a polyethylene film was used as the separator, and the electrolyte was a 1 mol / L lithium hexafluorophosphate solution with a 1:1 volume ratio of diethyl carbonate to ethylene carbonate. The cells were assembled in an argon-filled glove box. Capacity, initial efficiency, and rate performance were tested using a LAND battery test system at 25°C and 3.0V to 4.3V. The reference capacity was set at 200mA / g, and 1C corresponds to a current density of 200mA / g.

[0168] The results of the performance test under the above 25°C environment are shown in Table 1 below:

[0169] Table 1. Summary of test data of positive electrode materials

[0170] Table 2. Summary of battery test data made from positive electrode materials

[0171] It should be noted that the 0.1C first discharge capacity in Table 2 represents the first discharge capacity of the battery, columns 8-10 in Table 2 represent the 0.5C, 1C, and 2C rate performances of the battery, respectively, and the 1C 50-week retention rate in Table 2 represents the cycle stability of the battery.

[0172] As shown in Examples 1 to 10 and Comparative Examples 1 to 3, the present application mixes a precursor, a lithium salt, and a dopant and performs a staged heating treatment, adds a cooling stage, adopts a slightly lithium-rich sintering process in the primary sintering stage, adjusts the number and ratio of (003) crystal planes and (104) crystal planes during the sintering process of the material, and obtains a positive electrode material with high capacity, long cycle, and high rate; by adding a cooling stage, the positive electrode material is more structurally stable during the cooling process, the crystal growth is more complete, and it is more conducive to the deintercalation of lithium ions, with better power performance and better rate performance; by adjusting the doping elements through three-stage heating sintering, the crystal plane of the ternary material is directed to grow toward the (003) crystal plane, the crystal structure is optimized from the inside, and by adjusting the lithium metal ratio, a slightly lithium-rich positive electrode material is obtained, which can further inhibit the mixing of lithium and nickel, so that the crystal growth of the positive electrode material has a tendency, and a positive electrode material with a better ratio of the number of (003) crystal planes and (104) crystal planes is obtained. The positive electrode material prepared in this application is beneficial to improving the rate performance and cycle stability of the material, reducing the risk of microcracks appearing during the material cycle, and then pulverizing and producing a large amount of gas, which can greatly improve the structural stability and safety of the material and reduce the gas production of the material.

[0173] Moreover, the cathode material prepared in the present application has at least three obvious discharge platforms during the 0.1C discharge process. From the dQ / dV curve of the first 0.1C discharge, it can be seen that the three discharge peaks are located at 4.17V±0.1V, 4.0V±0.1V, and 3.65V±0.1V (hereinafter referred to as peak intensity). 4.17V , I 4.0V , I 3.65V ), and the ratio of the absolute values ​​of the peak intensities satisfies the relationship: 0.2≤I 4.17V / (I 4.0V +I 3.65V)≤2.5. The lower the ratio, the faster the cathode material transitions from H1 to M phase and from M phase to H2 phase, and the slower the transition from H2 to H3 phase. This reduces the lattice expansion effect of the cathode material, leading to more stable cathode material performance. The in-situ composite coating structure formed on the cathode material surface effectively inhibits electrolyte penetration, improves the material's low-temperature performance, reduces impedance, reduces gas production, and enhances safety.

[0174] According to the data in Table 1 and Table 2, in the preparation process of Example 7, the particle size of the dopant is too large, and some dopants are difficult to be doped into the interior of the particles, resulting in a decrease in the lattice optimization degree of the positive electrode material, a decrease in the half-peak width of the (003) crystal plane and the (104) crystal plane of the positive electrode material, an increase in the size of the primary particles in the positive electrode material, and a decrease in the half-peak width of the (003) crystal plane and the (104) crystal plane of the positive electrode material. 003 / P 104 The ratio of (003) crystal planes decreases, the ratio of (003) crystal planes decreases, and the rate and cycle performance of the positive electrode material are slightly lower than those of other embodiments, but the cycle performance and rate performance are still better than those of comparative examples 1, 2 and 3.

[0175] According to the data in Table 1 and Table 2, in Comparative Example 1, there is no second constant temperature stage in the heating section, the half-peak width of the (104) crystal plane of the positive electrode material decreases, and the number ratio of the (104) crystal plane decreases significantly. 4.17V / (I 4.0V +I 3.65V ) increases, the rate performance of the positive electrode material decreases, and the cycle performance decreases significantly.

[0176] According to the data in Table 1 and Table 2, in Comparative Example 2, there is no cooling stage in the primary sintering stage, the half-peak width of the (104) crystal plane of the positive electrode material is reduced, and the number ratio of the (104) crystal plane is significantly reduced. 4.17V / (I 4.0V +I 3.65V ) increases to 2.58, the rate performance of the positive electrode material decreases, and the cycle performance decreases significantly.

[0177] According to the data in Table 1 and Table 2, in Comparative Example 3, the Li / Me ratio is 0.92, the cathode material is in a lithium-deficient state, the half-peak width of the (003) crystal plane increases, the primary particles decrease, and the crystallinity of the cathode material deteriorates. 003 / P 104 Significantly decreased, I 4.17V / (I 4.0V +I 3.65V ) increases, the specific capacity and cycle performance of the positive electrode material decrease significantly.

[0178] Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the claims. Any person skilled in the art may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims

1. A positive electrode material, characterized in that: The positive electrode material comprises a base material and a coating layer located on the surface of the base material. The general chemical formula of the base material is Li a Ni b Co c M d O2, wherein 0.95≤a≤1.08, 0.3≤b≤1, 0≤c≤0.7, 0≤d≤0.2, b+c+d=1, and M is a metal element; In the XRD spectrum of the positive electrode material, the number of crystal planes of the positive electrode material in the (003) crystal plane is P 003 , the number of crystal planes on the (104) crystal plane is P 104 , 10≤P 003 ≤300, 10≤P 104 ≤400, 0.55≤P 003 / P 104 .

2. The positive electrode material according to claim 1, characterized in that The coating layer is made of fast ion conductor material.

3. The positive electrode material according to claim 2, characterized in that It satisfies at least one of the following characteristics: (1) The fast ion conductor material includes at least one of an oxide of the N element and a lithium composite oxide of the N element, and the N element includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B and P; (2) The fast ion conductor material includes at least one of an oxide of the element N and a lithium composite oxide of the element N, and the mass content of the element N in the positive electrode material is 0.01 wt % to 2 wt %.

4. The positive electrode material according to claim 1, characterized in that It satisfies at least one of the following characteristics: (1) The metal element M includes at least one of Co, Mn, Sb, Zr, Sr, Co, Ba, Y, Ce, Al, Mg, La, Ti and Ca; (2) The particle size D50 of the positive electrode material is 2 μm to 20 μm; (3) The mass content of the metal element M in the positive electrode material is 0.01 wt% to 2 wt%.

5. The positive electrode material according to claim 1, characterized in that The chemical formula of the positive electrode material is xLi a Ni b Co c M d O2·(1-x)Li e N f O g , 0<x<1, e, f, g are all integers and satisfy 2g=e+f×h, wherein h is the valence of element N, and the N element includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B, F and P.

6. A positive electrode material, characterized in that The positive electrode material comprises a base material and a coating layer located on the surface of the base material. The general chemical formula of the base material is Li a Ni b Co c M d O2, wherein 0.95≤a≤1.08, 0.3≤b≤1, 0≤c≤0.7, 0≤d≤0.2, b+c+d=1, and M is a metal element; A button cell made of a positive electrode containing the positive electrode material as a working electrode, a lithium sheet as a negative electrode and an electrolyte containing lithium ions is charged and discharged at 0.1C at 3.0V to 4.3V to obtain a differential value dQ / dV obtained by differentiating the potential V of the working electrode with respect to the charge and discharge capacity Q; a curve diagram of the relationship between the dQ / dV and the potential V is obtained with dQ / dV as the ordinate and the potential V of the working electrode as the abscissa, wherein the positive electrode material has discharge peaks at 4.17V±0.1V, 4.0V±0.1V and 3.65V±0.1V, and the absolute values ​​of the three discharge peak intensities are I 4.17V ,I 4.0V ,I 3.65V , and 0.2≤I 4.17V / (I 4.0V +I 3.65V )≤2.

5.

7. The positive electrode material according to claim 6, characterized in that It satisfies at least one of the following characteristics: (1) In the positive electrode material, when 0.3≤b≤0.7, I 4.17V ≤15mAh / V; (2) In the positive electrode material, when 0.7<b≤0.8, I 4.17V ≤20mAh / V; (3) In the positive electrode material, when 0.8<b≤0.9, I 4.17V ≤30mAh / V; (4) In the positive electrode material, when 0.9<b≤1.0, I 4.17V ≤50mAh / V.

8. The positive electrode material according to claim 6, characterized in that The coating layer is made of fast ion conductor material.

9. The positive electrode material according to claim 8, characterized in that It satisfies at least one of the following characteristics: (1) The fast ion conductor material includes at least one of an oxide of the N element and a lithium composite oxide of the N element, and the N element includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B and P; (2) The fast ion conductor material includes at least one of an oxide of the element N and a lithium composite oxide of the element N, and the mass content of the element N in the positive electrode material is 0.01 wt % to 2 wt %.

10. The positive electrode material according to claim 6, characterized in that It satisfies at least one of the following characteristics: (1) The metal element M includes at least one of Co, Mn, Sb, Zr, Sr, Co, Ba, Y, Ce, Al, Mg, La, Ti and Ca; (2) The particle size D50 of the positive electrode material is 2 μm to 20 μm; (3) The mass content of the metal element M in the positive electrode material is 0.01 wt% to 2 wt%.

11. The positive electrode material according to claim 6, characterized in that The chemical formula of the positive electrode material is xLi a Ni b Co c M d O2·(1-x)Li e N f O g , 0<x<1, e, f, g are all integers and satisfy 2g=e+f×h, wherein h is the valence of element N, and the N element includes at least one of Mn, Ti, W, Mo, Sb, Nb, Zr, Co, Y, Ce, Al, La, B, F and P.

12. A battery, characterized in that: The battery comprises the positive electrode material according to any one of claims 1 to 11.

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