Positive electrode material, positive plate and battery

Abstract

The invention provides a positive electrode material, a positive plate and a battery. The positive electrode material comprises a substrate and a coating layer, the coating layer coats at least part of the surface of the substrate, and the coating layer contains a zirconium element; the positive electrode material is etched through argon ions, the etching rate is 0.25 nm / s, the etched positive electrode material is characterized through X-ray photoelectron spectroscopy, the positive electrode material has 3d peaks of Zr element at the positions where the etching time is 120 seconds, 240 seconds and 360 seconds, and the 3d peaks of Zr element have 3d peaks of Zr element at the positions where the etching time is 120 seconds, 240 seconds and 360 seconds, and the 3d peaks of Zr element have 3d peaks of Zr element at the positions where the etching time is 120 seconds, 240 seconds and 360 seconds. The absolute value of the difference value of the Zr element 3d peak binding energy of the positive electrode material at any two etching times is less than or equal to 0.5 eV. The area, close to the base material, of the coating layer is the transition layer area, and the transition layer area is stable, so that sufficient chemical bonding is generated between the transition layer area and the base material, the possibility of harmful phase change is reduced, the positive electrode material has better stability, and the cycling stability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of positive electrode materials for batteries, and in particular to a positive electrode material, a positive electrode sheet and a battery. Background Art

[0002] Lithium-ion batteries (LIBs) have the characteristics of high energy density, high power density, long cycle life and low self-discharge, and have been widely used in energy storage and transportation fields such as 3C electronic products and electric vehicles. As related technologies gradually improve and the application market matures, consumers have put forward more stringent requirements on the energy density, cycle life, safety and other aspects of lithium-ion batteries; as one of the core components, the positive electrode material plays a vital role in the various performance indicators of lithium-ion batteries. Layered LiNi 1-x-y Co x M y O2 multi-element positive electrode materials (where M is usually Mn or Al) have many advantages such as high energy density, long cycle life, and low cost, and are widely favored by the market and consumers.

[0003] Although ternary cathode materials have been widely used industrially, many issues remain to be addressed. First, safety. As the nickel content in the cathode material increases, its thermal stability deteriorates, making it susceptible to thermal runaway and potentially causing lithium dendrite growth and short circuits. Second, cycle life is affected by capacity decay, and residual alkali on the surface can affect the material's gas production and other properties. Furthermore, the material's rate performance also needs improvement. Summary of the Invention

[0004] The main purpose of the present invention is to provide a positive electrode material, a positive electrode sheet and a battery to solve the problems of high internal resistance and insufficient stability of positive electrode materials in the prior art.

[0005] To achieve the above-mentioned object, according to one aspect of the present invention, a positive electrode material is provided, which includes a substrate and a coating layer, wherein the coating layer is coated on at least a portion of the surface of the substrate; the positive electrode material is etched by argon ions at an etching rate of 0.25 nm / s, and the etched positive electrode material is characterized by X-ray photoelectron spectroscopy. The positive electrode material has a 3d peak of the Zr element at etching times of 120 seconds, 240 seconds, and 360 seconds. When the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in binding energy of the 3d peak of the Zr element of the positive electrode material at any two etching times is less than or equal to 0.5 eV.

[0006] Furthermore, the 3d peak of the Zr element of the positive electrode material is subjected to peak separation processing to obtain a 3d peak. 5 / 2 Peak and 3D 3 / 2 Peak, at any one of the etching times of 120 seconds, 240 seconds and 360 seconds, 3d5 / 2 Peak and 3D 3 / 2 The peak separation is ≤1.

[0007] Furthermore, the positive electrode material has a Zr element 3d peak at an etching time of 0 seconds, and the Zr 3d peak of the positive electrode material at an etching time of 0 seconds 5 / 2 The binding energy of the peak is related to the Zr 3d at any one of the etching times of 120 seconds, 240 seconds and 360 seconds. 5 / 2 The difference in binding energy of the peaks is greater than or equal to 0.5 eV.

[0008] Furthermore, the positive electrode material satisfies at least one of the following conditions:

[0009] (1) The binding energy of the Zr element 3d peak of the positive electrode material at the etching time of 0 seconds is greater than the binding energy of the Zr element 3d peak at the etching time of 120 seconds, 240 seconds and 360 seconds by more than 0.5 eV;

[0010] (2) The 3d peak of the Zr element of the positive electrode material is subjected to peak separation processing to obtain a 3d 5 / 2 Peak and 3D 3 / 2 Peak, 3d at etching time of 0 seconds 5 / 2 Peak and 3D 3 / 2 The peak separation degree is 1 to 2.

[0011] Furthermore, the positive electrode material satisfies at least one of the following conditions:

[0012] (1) The binding energy of the 3d peak of the Zr element in the positive electrode material is 175-190 eV;

[0013] (2) When the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the 3d peak binding energy of the Zr element of the positive electrode material at any two etching times may be 0.1 eV, 0.2 eV, 0.3 eV, 0.4 eV, 0.5 eV, or within the range of any two of the above values;

[0014] (3) When the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the 3d peak binding energy of the Zr element of the positive electrode material at any two etching times can be 0.1 eV to 0.3 eV;

[0015] (4) When the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the 3d peak binding energy of the Zr element of the positive electrode material at any two etching times can be 0.2 eV to 0.4 eV;

[0016] (5) When the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the 3d peak binding energy of the Zr element of the positive electrode material at any two etching times can be 0.3 eV to 0.5 eV.

[0017] Furthermore, the positive electrode material satisfies at least one of the following conditions:

[0018] (1) The general chemical formula of the positive electrode material is LiNi 1-e-f-g Co e M1 f M2 g Zr h O2, M includes at least one of Zr, Al, W, Sr, Y, and Ti, 0≤e≤0.2, 0≤f≤0.5, 0≤g≤0.1, and 0<h≤0.1; M1 is Mn and / or Al; M2 is one or more of Al, Ti, Y, Zr, Mg, Sr, W, Nb, Ce, La, Mo, Ba, and B;

[0019] (2) The general chemical formula of the positive electrode material can be LiNi a Co b M c M' 1-a-b-c O2·αLiNi a’ Co b’ M c’ Zr d M' 1-a’-b’-c’-d O2, where LiNi a Co b M c M' 1-a-b-c O2 is the general chemical formula of the matrix of the positive electrode material, 0.3≤a<1.0, 0.01≤b≤0.3, 0≤c≤0.5, 0≤1-abc≤0.01; αLiNi a’ Co b’ M c’ Zr d M' 1-a’-b’-c’-d O2 is the general chemical formula of the coating layer of the positive electrode material, 0.001≤α≤0.1, 0.3≤a'<1.0, and a'≤a, 0.01≤b'≤0.3, 0≤c'≤0.5, 0≤d≤0.1, 0≤1-a'-b'-c'-d≤0.1; M is Mn and / or Al; M' is one or more of Al, Ti, Y, Zr, Mg, Sr, W, Nb, Ce, La, Mo, Ba, and B.

[0020] Furthermore, the positive electrode material satisfies at least one of the following conditions:

[0021] (1) The span value of the positive electrode material is 0.3 to 1.0;

[0022] (2) The volume distribution median particle size D50 of the positive electrode material is 5 μm to 10 μm;

[0023] (3) The free lithium content of the positive electrode material is 0.10 wt% to 0.3 wt%.

[0024] Furthermore, the positive electrode material satisfies at least one of the following conditions:

[0025] (1) The BET specific surface area of the positive electrode material is 0.15 m 2 / g~0.8m 2 / g;

[0026] (2) The grain size of the D104 crystal plane of the positive electrode material is 60nm to 100nm;

[0027] (3) Based on the total mass of the positive electrode material, the mass content of the Zr element is 500 to 5000 ppm.

[0028] In order to achieve the above object, according to one aspect of the present invention, a positive electrode sheet is provided, which contains the above positive electrode material.

[0029] According to another aspect of the present invention, a battery is provided, comprising the above-mentioned positive electrode sheet.

[0030] According to the technical solution of the present invention, the positive electrode material includes a base material and a coating layer located on at least a portion of the surface of the base material. The area of the coating layer close to the base material is the transition layer area, that is, the area with an etching time between 120 seconds and 360 seconds. During the deep delithiation process, the positive electrode material is more likely to undergo harmful phase changes (such as layered → spinel phase) in the transition layer area. Therefore, by having the absolute value of the difference in the binding energy of the Zr element 3d peak of the positive electrode material at any two etching times of 120 seconds, 240 seconds and 360 seconds being less than or equal to 0.5 eV, it is indicated that there is no large structural difference in the transition layer area of the positive electrode material, so that the positive electrode material of the present application has a stable transition layer area, so that the transition layer area and the base material produce sufficient chemical bonding, reducing the possibility of harmful phase changes, thereby making the positive electrode material have better stability and improving the cycle stability of the positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 A schematic structural diagram of a battery according to an embodiment of the present invention is shown;

[0033] Figure 2 The 3d peak of the Zr element of the positive electrode material at different etching times according to Example 1 of the present invention is shown.

[0034] Among them, the above drawings include the following figure marks: 1. positive electrode sheet; 2. diaphragm; 3. negative electrode sheet. DETAILED DESCRIPTION

[0035] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0036] As analyzed in the background of this application, the prior art has problems with high internal resistance and insufficient stability of positive electrode materials. To address this problem, this application provides a positive electrode material, a positive electrode sheet, and a battery.

[0037] According to a typical embodiment of the present application, the present application provides a positive electrode material, which includes a substrate and a coating layer, wherein the coating layer is coated on at least a portion of the surface of the substrate; the positive electrode material is etched by argon ions at an etching rate of 0.25 nm / s, and the etched positive electrode material is characterized by X-ray photoelectron spectroscopy. The positive electrode material has a Zr element 3d peak at etching times of 120 seconds, 240 seconds and 360 seconds. When the etching time is 120 seconds, 240 seconds and 360 seconds, the absolute value of the difference in binding energy of the Zr element 3d peak of the positive electrode material at any two etching times is less than or equal to 0.5 eV.

[0038] The positive electrode material includes a substrate and a coating located on at least a portion of the substrate's surface. The area of the coating close to the substrate is the transition layer region, i.e., the region where the etching time is between 120 seconds and 360 seconds. During deep delithiation, the positive electrode material is more susceptible to harmful phase transitions (e.g., from layered to spinel phase) in the transition layer region. The area of the coating away from the substrate is the surface region, and the surface region is the region where the etching time is between 0 seconds and 120 seconds.

[0039] Therefore, by the absolute value of the difference in the binding energy of the Zr element 3d peak of the positive electrode material at any two etching times of 120 seconds, 240 seconds and 360 seconds being less than or equal to 0.5 eV, it is indicated that there is no large structural difference in the transition layer region of the positive electrode material, so that the positive electrode material of the present application has a stable transition layer region, so that the transition layer region and the matrix material produce sufficient chemical bonding, reducing the possibility of harmful phase change, thereby making the positive electrode material have better stability and improving the cycle stability of the positive electrode material.

[0040] Specifically, when the etching time of the positive electrode material is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the binding energy of the 3d peak of the Zr element of the positive electrode material at any two etching times may be 0.1 eV, 0.2 eV, 0.3 eV, 0.4 eV, 0.5 eV, or other values within the above range. Wherein, the binding energy of the 3d peak of Zr refers to the binding energy corresponding to the maximum peak intensity of the 3d peak.

[0041] In some embodiments, when the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the binding energy of the 3d peak of the Zr element of the positive electrode material at any two etching times can be 0.1 eV to 0.3 eV. This indicates that there are no significant structural differences in the transition layer region of the positive electrode material, so that the positive electrode material of the present application has a stable transition layer region, so that the transition layer region and the base material form sufficient chemical bonds, reducing the possibility of harmful phase changes, thereby giving the positive electrode material better stability and improving the cycle stability of the positive electrode material.

[0042] In some embodiments, when the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the 3d peak binding energy of the Zr element of the positive electrode material at any two etching times can be 0.2 eV to 0.4 eV. This indicates that there are no significant structural differences in the transition layer region of the positive electrode material, so that the positive electrode material of the present application has a stable transition layer region, so that the transition layer region and the base material form sufficient chemical bonds, reducing the possibility of harmful phase changes, thereby giving the positive electrode material better stability and improving the cycle stability of the positive electrode material.

[0043] In some embodiments, when the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the binding energy of the 3d peak of the Zr element of the positive electrode material at any two etching times can be 0.3 eV to 0.5 eV. This indicates that there are no significant structural differences in the transition layer region of the positive electrode material, so that the positive electrode material of the present application has a stable transition layer region, so that the transition layer region and the base material are sufficiently chemically bonded, reducing the possibility of harmful phase changes, thereby giving the positive electrode material better stability and improving the cycle stability of the positive electrode material.

[0044] In some embodiments of the present application, the 3d peak of the Zr element of the positive electrode material is subjected to peak separation processing to obtain a 3d peak. 5 / 2 Peak and 3D 3 / 2 Peak, at any one of the etching times of 120 seconds, 240 seconds and 360 seconds, 3d 5 / 2 Peak and 3D 3 / 2The peak separation is ≤1, and can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or any value less than or equal to 1. The Zr element of the positive electrode material is in 3d 5 / 2 Peak and 3D 3 / 2 The smaller separation indicates that after the electrons are excited by X-rays, the coupling between high-spin and low-spin electrons and electron orbits is weakened, that is, the electron energy is increased and the stability is reduced. This means that there are more structural micro-defects in the transition layer region, which can tolerate wider valence fluctuations of transition metals, giving the transition layer region a certain fault tolerance effect, which is beneficial to the multiple insertion and extraction of lithium ions, reducing the possibility of harmful phase changes, and thus significantly improving the cycle stability of the positive electrode material.

[0045] Among them, the 3d peak of the Zr element is separated as follows: Use avantage software, select the data file in vgp. format that needs to be processed, and open the corresponding XPS spectrum. First, use the mouse pointer to select the C1s spectrum, read the C1s binding energy position of the C-C bond on the current C1s spectrum, and record the current charge shift with C1s = 284.8eV as the reference value. Select all XPS spectra (including Survey spectra and narrow scan spectra of elements) and perform charge shift on the XPS spectra. Use the mouse pointer to select the narrow scan spectrum of the 3d peak of the Zr element that needs to be separated, and then use the double vertical line pointer to select the peak separation range in the spectrum. For the peaks with correlation, the "Peak / BE", "FWHM / eV" and "L / G%" in the peak separation parameters are set for correlation. In the "Peak Fitting" window, select "Fit Peaks" and click "Fit This Level" several times until a satisfactory fitting result is obtained, that is, the normalized chi-square after fitting the peaks is between 1 and 3, and the standard deviation is less than 1.

[0046] Zr 3d 5 / 2 and Zr 3d 3 / 2 The calculation method of the separation degree of the diffraction peak is as follows: After the 3d peak of the Zr element is separated, the Zr 3d 5 / 2 and Zr 3d 3 / 2 The diffraction peaks are P1, P2, Zr 3d 5 / 2 and Zr 3d 3 / 2 The half-maximum widths of the diffraction peaks are FWHM1 and FWHM2, respectively. The separation degree of the two diffraction peaks is calculated to be α=2*(P2-P1) / (FWHM1+FWHM2), and α≤1.

[0047] In some embodiments, the binding energy of the Zr element 3d peak at an etching time of 0 seconds of the positive electrode material is greater than the binding energy of the Zr element 3d peak at etching times of 120 seconds, 240 seconds, and 360 seconds by more than 0.5 eV. This indicates that the binding energy of the Zr element on the surface of the positive electrode material is greater than the binding energy of the Zr element in the transition layer region. The greater the binding energy, the more stable the formation of Zr-O bonds, so that a relatively stable Zr oxide passivation layer is formed on the surface of the positive electrode material of the present application. The surface passivation layer can effectively protect the material and reduce side reactions caused by contact with the electrolyte. At the same time, the surface passivation layer is located in the surface region, making the surface passivation layer thinner, so it will not significantly hinder the diffusion of lithium ions, so that the DCIR will not be significantly deteriorated under long cycles.

[0048] In some embodiments of the present application, the Zr 3d 5 / 2 The binding energy of the peak is higher than that of the Zr 3d at any one of the etching times of 120 seconds, 240 seconds and 360 seconds. 5 / 2 The binding energy of the peak is greater than 0.5eV. 5 / 2 The peak binding energy is relatively high, which can reflect the formation of a large number of more stable Zr-O bonds. The etching time of the positive electrode material of this application is Zr 3d at 0 seconds. 5 / 2 The peak relative to the Zr 3d at any one of the etching times of 120 seconds, 240 seconds and 360 seconds 5 / 2 The binding energy of the peak is higher by more than 0.5eV, which makes the surface of the positive electrode material of the present application form a relatively stable Zr oxide passivation layer. The surface passivation layer can effectively protect the material and reduce the side reactions caused by contact with the electrolyte. At the same time, the surface passivation layer is located in the surface area, making the surface passivation layer thinner, so it will not significantly hinder the diffusion of lithium ions, so that the DCIR will not deteriorate significantly under long cycles. Specifically, the Zr 3d 5 / 2 The binding energy of the peak is related to the Zr 3d at any one of the etching times of 120 seconds, 240 seconds and 360 seconds. 5 / 2 The difference in binding energy of the peaks can be 0.5eV, 1eV, 2eV, 3eV, 4eV, 5eV, etc., which is not limited in this application. Preferably, the Zr 3d 5 / 2 The binding energy of the peak is related to the Zr3d at any one of the etching times of 120 seconds, 240 seconds and 360 seconds. 5 / 2 The difference in binding energy of the peaks is 0.5 eV to 3 eV.

[0049] In some embodiments of the present application, the Zr 3d 5 / 2 peak and Zr 3d 3 / 2The peak separation degree is 1 to 2. Therefore, the Zr 3d 5 / 2 peak and Zr 3d 3 / 2 The high peak separation indicates the formation of stable Zr-O bonds on the cathode material's surface, resulting in a relatively stable Zr oxide passivation layer on the surface of the cathode material. This surface passivation layer effectively protects the material from side reactions with the electrolyte while not significantly hindering lithium ion diffusion, thus preventing significant degradation of the DCIR over long cycles.

[0050] It is important to emphasize that the 3D 5 / 2 Peak and 3D 3 / 2 Peak separation requirements, and Zr 3d at etching time of 0 seconds 5 / 2 The peak and the Zr 3d at etching time of 120 seconds, 240 seconds or 360 seconds 5 / 2 The positive electrode material that meets the requirements for the difference in binding energy of the peaks and the offset distance of the Zr element 3d peak when the etching time is 120 seconds, 240 seconds and 360 seconds not only has a stable surface ultra-thin passivation layer and a stable transition layer, but also has a wide bond energy of the transition layer. This allows the positive electrode material to effectively ensure the stability of the material coating layer on the one hand, avoiding the deterioration and failure of the material surface due to the coating layer being too thin or too thick. On the other hand, it can better tolerate the wider valence fluctuations of the transition metal, so that the transition layer has a certain fault tolerance effect, thereby significantly improving the stability of the material during multiple charge and discharge. In addition, the thinner inactive layer on the surface can also effectively protect the material from contact with the electrolyte, avoid a large number of side reactions on the surface of the material, and reduce the gas production of the lithium-ion battery; ultimately achieving the effects of improving the cycle life, impedance amplification, and safety of the lithium-ion battery.

[0051] In some embodiments of the present application, the binding energy of the 3d peak of the Zr element of the positive electrode material is in the range of 175 to 190 eV, specifically 175 eV, 180 eV, 185 eV, 190 eV or other values within the above range.

[0052] In some embodiments of the present application, the general chemical formula of the positive electrode material is LiNi a Co b M1 c M2 1-a-b-c-d Zr d O2, M includes at least one of Zr, Al, W, Sr, Y, and Ti, 0.3≤a<1.0, 0.01≤b≤0.3, 0≤c≤0.5, 0≤1-abc≤0.01; M1 is Mn and / or Al; M2 is one or more of Al, Ti, Y, Zr, Mg, Sr, W, Nb, Ce, La, Mo, Ba, and B.

[0053] In some embodiments of the present application, the general chemical formula of the positive electrode material can be LiNi a Co b M c M' 1-a-b-c O2·αLiNi a’ Co b’ M c’ Zr d M' 1-a’-b’-c’-d O2, where LiNi a Co b M c M' 1-a-b-c O2 is the general chemical formula of the matrix of the positive electrode material, 0.3≤a<1.0, 0.01≤b≤0.3, 0≤c≤0.5, 0≤1-abc≤0.01; αLiNi a’ Co b’ M c’ Zr d M' 1-a’-b’-c’- d O2 is the general chemical formula of the coating layer of the positive electrode material, 0.001≤α≤0.1, 0.3≤a'<1.0, and a'≤a, 0.01≤b'≤0.3, 0≤c'≤0.5, 0≤d≤0.1, 0≤1-a'-b'-c'-d≤0.1; M is Mn and / or Al; M' is one or more of Al, Ti, Y, Zr, Mg, Sr, W, Nb, Ce, La, Mo, Ba, and B. Thus, by having the composition of the coating layer close to that of the base material, the coating layer can effectively react with the residual lithium on the surface, and avoid mismatching caused by the large difference in lattice parameters between the coating layer material and the base material, thereby making the coating layer material have better stability and coating effect. At the same time, the Ni content of the coating layer is lower than that of the base material to ensure better thermal stability of the surface material.

[0054] In the chemical formula of the above positive electrode material, α represents the chemical formula LiNi a’ Co b’ M c’ Zr d M' 1-a’-b’-c’-d The coating layer of O2 is LiNi a Co b M c M' 1-a-b-c The molar ratio of the matrix of O2, the value of α can be 0.001, 0.005, 0.01, 0.02, 0.04, 0.05, 0.07, 0.09 or 0.1, etc., or other values within the above range, which are not limited here.

[0055] Wherein, a in the chemical formula of the substrate and a' in the chemical formula of the coating layer can be independently 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 0.95, or other values within the above range, and a'≤a.

[0056] b in the chemical formula of the substrate and b' in the chemical formula of the coating layer can independently be 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, etc., or other values within the above ranges.

[0057] c in the matrix chemical formula and c' in the coating chemical formula can independently be 0, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc., or other values within the above ranges.

[0058] The value of 1-abc in the matrix chemical formula may be 0, 0.002, 0.004, 0.005, 0.006, 0.007, 0.008, 0.01, etc., or other values within the above range.

[0059] In the general chemical formula of the coating layer, the value of d can be 0, 0.002, 0.004, 0.006, 0.008, 0.01, 0.03, 0.0, 0.05, 0.07, 0.09, 0.1, etc., or other values within the above range; the value of 1-a'-b'-c'-d can be 0, 0.02, 0.04, 0.05, 0.06, 0.07, 0.08, 0.1, etc., or other values within the above range.

[0060] In some embodiments of the present application, the span value of the positive electrode material is 0.3 to 1.0, specifically 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0, or other values within the above range. The span value is a parameter to measure the uniformity of the particle size distribution. The smaller the span value, the more uniform the particle size distribution of the positive electrode material. When the span value of the positive electrode material is within the above range, the particle size distribution is uniform, which helps to improve the compaction density of the electrode material and the consistency between particles, thereby improving the overall performance of the lithium-ion battery, such as improving the energy density and cycle stability.

[0061] In some embodiments of the present application, the volume distribution median particle size D50 of the positive electrode material is 5μm to 10μm, specifically 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc., or other values within the above range. The volume distribution median particle size D50 refers to the particle size of the particles at the volume median position in the particle size distribution of the positive electrode material. The volume distribution median particle size D50 of the positive electrode material is within the above range, which is conducive to further improving the electronic and ionic conductivity of the positive electrode material, while avoiding the problems of too long lithium ion transmission path caused by too large particles and too many surface active sites and increased side reactions caused by too small particles. Such a particle size range helps to improve the rate performance and cycle stability of the material.

[0062] BET specific surface area refers to the total surface area of a material measured by the BET (Brunauer-Emmett-Teller) method. In some embodiments of the present application, the BET specific surface area of the positive electrode material is 0.15 m 2 / g~0.8m 2 / g, which can make the contact area between the positive electrode material surface and the electrolyte moderate, neither aggravating the side reaction due to too large a surface area nor affecting the surface transmission of lithium ions due to too small a surface area. This helps to control the surface reactivity of the material, reduce gas generation, and improve the electrochemical stability and safety of the material. Specifically, the BET specific surface area of the positive electrode material can be 0.15m 2 / g, 0.2m 2 / g, 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, etc., and may also be other values within the above range, which is not limited here.

[0063] The grain size of the D104 crystal plane is related to the crystallinity and stability of the material. In some embodiments of the present application, the grain size of the D104 crystal plane of the positive electrode material is 60nm to 100nm. This grain size range is beneficial to improving the structural stability of the material, reducing the lattice strain of lithium ions during the charge and discharge process, thereby reducing the volume change and structural damage of the material, and improving the cycle performance and thermal stability of the material. At the same time, a suitable grain size is also conducive to the diffusion of lithium ions and improves the rate performance of the battery. Specifically, the grain size of the D104 crystal plane of the positive electrode material can be 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, etc., or other values within the above range, which are not limited here.

[0064] In some embodiments of the present application, the free lithium content of the positive electrode material is 0.10wt% to 0.3wt%, specifically 0.10wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, etc., or other values within the above range. The free lithium of the positive electrode material easily reacts with the electrolyte to produce gas, affecting the capacity retention and safety of the battery. The free lithium content within the above range can effectively control the side reactions on the surface of the material, reduce gas generation, and improve the cycle stability and safety of the material. In addition, a lower free lithium content also helps to improve the compaction density and electrochemical properties of the material, reduce the internal resistance of the battery, and reduce the increase in DCIR (direct current internal resistance), thereby improving the overall performance of the battery.

[0065] In some embodiments of the present application, based on the total mass of the positive electrode material, the mass content of the Zr element in the positive electrode material is 500-5000ppm. Specifically, the mass content of the Zr element can be 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1200ppm, 1400ppm, 1600ppm, 1800ppm, 2000ppm, 2200ppm, 2500ppm, 2800ppm, 3200ppm, 3600ppm, 3800ppm, 4000ppm, 4500ppm, 5000ppm or any value within the above range. Preferably, the mass content of the Zr element in the positive electrode material is 500-1500ppm. More preferably, the mass content of the Zr element in the positive electrode material is 800-1200ppm. Therefore, by keeping the Zr content within the above range, the stability of the positive electrode material can be effectively improved, surface side reactions can be suppressed, and lithium ion migration can be optimized, thereby further improving the cycle performance, safety, and energy density of the lithium-ion battery.

[0066] According to another typical embodiment of the present application, a method for preparing a positive electrode material is provided, the preparation method comprising: first mixing a first positive electrode material precursor, a lithium source and a first additive to obtain a first mixture; first calcining the first mixture, and crushing, screening and demagnetizing the first calcined product to obtain a base material; the first additive is any one or more of an aluminum source and a manganese source; second mixing a second positive electrode material precursor, a second additive and a zirconium source in a solvent to obtain a coating additive slurry, wet spraying the coating additive slurry onto the base material for mixing and drying to obtain a second mixture; second sintering the second mixture, and crushing, screening and demagnetizing the second sintered product to obtain a positive electrode material; D of the second positive electrode material precursor 50The second additive contains an M' element, which is one or more of Al, Ti, Y, Mg, Sr, W, Nb, Ce, La, Mo, Ba, and B. The first positive electrode material precursor and the second positive electrode material precursor are multi-element positive electrode material precursors.

[0067] Since the use of a zirconium source alone or an additive containing an M' element for surface mixed coating can easily lead to poor adhesion of the coating layer, the resulting positive electrode material is prone to harmful phase changes in the transition layer region, and after a long period of charge and discharge, it is affected by the structural deformation stress caused by lithium deintercalation on the surface of the material, resulting in shedding. The preparation method of the positive electrode material in the present application uses a second positive electrode material precursor as a coating buffer material for coating to form a stable transition layer region. On the other hand, since the first positive electrode material precursor and the second positive electrode material precursor are both multi-element positive electrode material precursors, the components of the first positive electrode material precursor and the second positive electrode material precursor are similar, and the lattice parameter difference between the second positive electrode material precursor and the second positive electrode material precursor can be made smaller, thereby avoiding the mismatch caused by the large difference in lattice parameters between the second positive electrode material precursor and the second positive electrode material precursor, so that the second positive electrode material precursor can be used as an adhesive between the first positive electrode material precursor and the coating layer, increasing the stability of the Zr element in the transition layer region. On the other hand, the second cathode material precursor can serve as a "solvent" for the additive element, ensuring the uniform distribution of the Zr element in the precursor nano-scale coating layer, thereby ensuring the structural stability of the Zr element in the transition layer region of the cathode material. 50 Less than or equal to 2μm, which can ensure that the material is evenly coated on the surface of the material during the wet coating process.

[0068] Furthermore, the present application coats the base material through wet spray mixing, which can effectively ensure the effective mixing of the coating additive slurry and the positive electrode base material, and ensure that a more uniform coating layer can be formed after the materials are mixed. The coating layer particles coated on the surface are smaller and there is less agglomeration. At the same time, the early dissolution and mixing of various coating additives can also allow Zr and other coating elements to be mixed with the precursor coating layer in advance, thereby improving the distribution uniformity of the Zr element in the intermediate layer area.

[0069] In summary, the positive electrode material prepared by the preparation method of the present application meets the following requirements when XPS characterization is performed: the positive electrode material has a Zr element 3d peak at etching times of 120 seconds, 240 seconds, and 360 seconds, and the Zr element 3d peak offset distance of the positive electrode material at any two etching times of 120 seconds, 240 seconds, and 360 seconds is less than or equal to 0.5 eV. Therefore, the positive electrode material prepared by this method has excellent safety, cycle performance, and low DCIR growth rate.

[0070] The following is a detailed description of the preparation method of the positive electrode material of the present application with reference to the examples:

[0071] First, a first cathode material precursor, a lithium source and a first additive are mixed to obtain a first mixture; the first mixture is calcined, and the first calcined product is crushed, sieved and demagnetized to obtain a matrix material.

[0072] The first cathode material precursor and the second cathode material precursor are multi-component cathode material precursors, for example, they may be any one or more of an NCM multi-component precursor and an NCA multi-component precursor.

[0073] In some embodiments of the present application, the chemical formula of the first cathode precursor is: Ni a Co b M c OH2, wherein 0.3≤a<1.0, 0.01≤b≤0.3, 0≤c≤0.5, and M is Mn and / or Al.

[0074] In some embodiments of the present application, the chemical formula of the second positive electrode precursor is: Ni a’ Co b’ M c’ OH2, wherein 0.3≤a'<1.0, 0.01≤b'≤0.3, 0≤c'≤0.5, M is Mn and / or Al, and a'≤a, so that the Ni content of the coating layer is lower than the Ni content of the base material to ensure better thermal stability of the surface material.

[0075] In some embodiments of the present application, D of the first cathode material precursor 50 The particle size is 3 to 15 μm, and the D of the first cathode material precursor is 50 The particle size can be 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um or any value in the above range.

[0076] In some embodiments of the present application, the lithium source includes, but is not limited to, any one or more of lithium hydroxide and lithium carbonate.

[0077] In some embodiments of the present application, the aluminum source includes any one or more of aluminum oxide, aluminum hydroxide, and aluminum oxyhydroxide.

[0078] In some embodiments of the present application, the manganese source is any one or more of manganese sulfate, manganese oxide, and manganese hydroxide.

[0079] In some embodiments of the present application, the molar ratio of the first cathode material precursor to the lithium source is 1:(1.00-1.20).

[0080] In some embodiments of the present application, the molar amount of the first additive is 0.01% to 2% of the molar amount of the first mixture.

[0081] In some embodiments of the present application, the mixing ratio of the first positive electrode material precursor, the lithium source and the first additive is based on the chemical formula of the positive electrode material matrix LiNi a Co b M c M' 1-a-b-c O2 is used to determine the ratio of precursor to lithium source, and the range is 1:0.98~1.1:0.0001~0.01.

[0082] In some embodiments of the present application, the first mixing is stirring mixing, and the speed of the first mixing is ≥300rpm / min, such as 300rpm / min, 400rpm / min, 500rpm / min, 600rpm / min, etc., and can also be other values within the above range; the time of the first mixing is ≥20min, such as 20min, 25min, 30min, 35min, 40min, 50min, etc., and can also be other values within the above range.

[0083] In some embodiments of the present application, the first calcination temperature is 700°C to 1000°C, the time is 4 hours to 10 hours, and the calcination atmosphere is air and / or oxygen. Specifically, the first calcination temperature can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, etc., and the first calcination time can be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc., or other values within the above range.

[0084] The second positive electrode material precursor, the second additive and the zirconium source are mixed for a second time in a solvent to obtain a coating additive slurry, and the coating additive slurry is wet-sprayed onto the base material for mixing and drying to obtain a second mixture; the second mixture is sintered for a second time, and the second sintered product is crushed, screened and demagnetized to obtain the positive electrode material.

[0085] The D of the second cathode material precursor 50 The particle size is less than or equal to 2 μm, specifically 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, etc., or other values within the above range. Preferably, the D of the second cathode material precursor is 50 The particle size is 0.1μm~1μm.

[0086] The second cathode material precursor is also a multi-component cathode material precursor, such as an NCM multi-component precursor and / or an NCA multi-component precursor. The chemical composition of the second cathode material precursor may be the same as or different from that of the first cathode material precursor.

[0087] In some embodiments of the present application, the specific surface area of the second cathode material precursor is greater than or equal to 20 m 2 / g.

[0088] In some embodiments of the present application, the zirconium source is zirconium oxide.

[0089] In some embodiments of the present application, the solvent used in the second mixture includes water, such as pure water, deionized water, etc., which has good dispersion properties for the second positive electrode material precursor, the second additive and the zirconium source and is relatively environmentally friendly.

[0090] In some embodiments of the present application, the water-to-material ratio of the coating additive slurry is 0.5-10. The water-to-material ratio represents the mass ratio of the water in the coating additive slurry to the sum of the mass of the solutes and insolubles therein, that is, the mass ratio of water to the sum of the mass of the second cathode material precursor, the second additive, and the zirconium source. Specifically, the water-to-material ratio of the coating additive slurry can be 0.5, 0.8, 1, 2, 3, 5, 7, 9, 10, etc., and of course other values within the above range are also possible.

[0091] In some embodiments of the present application, the molar amount of the second cathode material precursor is 0.01% to 2% of the molar amount of the first cathode material precursor.

[0092] In some embodiments of the present application, the mass of the coated additive slurry after drying accounts for 0.1% to 10wt% of the mass of the second mixture, that is, the sum of the masses of the second positive electrode material precursor, the second additive and the zirconium source accounts for 0.1wt% to 10wt% of the mass of the second mixture, which can be specifically 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, etc., or other values within the above range.

[0093] In some embodiments of the present application, the coating additive slurry is wet-sprayed onto the base material and then mixed and dried under stirring conditions. Preferably, the stirring speed is ≥300 rpm / min.

[0094] In some embodiments of the present application, the spraying time is 10 min to 120 min, specifically 10 min, 30 min, 50 min, 70 min, 90 min, 100 min, 120 min, etc., or other values within the above range.

[0095] In some embodiments of the present application, the drying temperature is 100-200°C, and the drying time is 7-30 hours. Specifically, the drying temperature can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, etc., or other values within the above range; the drying time can be 7 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 25 hours, 30 hours, or other values within the above range, and is not limited here.

[0096] Furthermore, it is preferred that the second sintering is performed in an oxygen atmosphere.

[0097] In some embodiments of the present application, the furnace pressure for the second sintering is 8 Pa to 15 Pa, specifically 8 Pa, 9 Pa, 10 Pa, 11 Pa, 12 Pa, 13 Pa, 14 Pa, 15 Pa, etc., or other values within the above range. The furnace pressure represents the pressure difference between the gas inside the kiln and the external atmospheric pressure. Maintaining this furnace pressure range ensures a sufficient reaction between the coating layer and the substrate material, and further ensures that the coating layer does not fall off, which would cause failure of the surface layer of the material.

[0098] In some embodiments of the present application, the second sintering temperature is 600°C-900°C. Performing the second sintering at this temperature facilitates better adhesion of the coating material to the substrate surface. If the sintering temperature is too low, the Zr coating layer will not adhere firmly to the material. When the coating layer is relatively thick, the surface passivation layer will easily hinder the diffusion of lithium ions, resulting in a decrease in the material's capacity and DCIR. Specifically, the second sintering temperature can be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, etc., or other values within the above range.

[0099] Preferably, the second sintering time is 4 hours to 10 hours, specifically 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc., or other values within the above range.

[0100] According to another typical embodiment of the present application, a positive electrode sheet is provided, which contains any one of the above-mentioned positive electrode materials or a positive electrode material prepared by any one of the above-mentioned preparation methods.

[0101] Due to the use of the above-mentioned positive electrode material, the positive electrode sheet of the present application has a lower resistance when used in a battery, and has good cycle performance and stability.

[0102] According to another typical embodiment of the present application, a battery is provided, which includes the above-mentioned positive electrode sheet. Due to the use of the above-mentioned positive electrode sheet, the battery of the present application has a lower resistance value and has good cycle performance and stability.

[0103] The embodiment of the present invention further provides a battery, the battery comprising a housing and an electrode assembly, such as Figure 1 As shown, the electrode assembly includes a positive electrode sheet 1, a negative electrode sheet 3, and a separator 2, with the separator being disposed between the positive and negative electrode sheets. The positive electrode sheet 1 contains the aforementioned positive electrode material. The electrode assembly can be a laminated structure, formed by alternatingly stacking the positive electrode sheet 1, the separator 2, and the negative electrode sheet 3. In other embodiments, the electrode assembly can also be a wound structure, formed by stacking the positive electrode sheet 1, the separator 2, and the negative electrode sheet 3 in sequence and then winding them.

[0104] In some embodiments, the positive electrode sheet 1 includes a positive electrode current collector and a positive electrode active layer disposed on at least one surface of the positive electrode current collector.

[0105] In some embodiments, the positive electrode current collector may be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil (aluminum foil or nickel foil, etc.) and a polymer substrate. The positive electrode active layer includes the positive electrode active material described above.

[0106] In some embodiments, the negative electrode sheet 3 includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.

[0107] In some embodiments, the negative electrode current collector may be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or a carbon-based current collector. It may also be any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and a polymer substrate. The negative electrode active material layer includes a negative electrode material, which may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials; other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination. The batteries provided in the embodiments of this application have the advantages of high capacity, high initial efficiency, long cycle life, excellent rate capability, and low expansion. The battery may be a lithium-ion battery, a sodium-ion battery, a solid-state electrolyte battery, or the like, without limitation.

[0108] The following examples and comparative examples will further illustrate the beneficial effects that can be achieved by the present application.

[0109] Example 1

[0110] 1) The first cathode material precursor Ni 0.85 Co0.03 Mn 0.12 (OH)2(D 50 The nanostructured particles (particle size: 9 μm) were uniformly mixed with a lithium source LiOH (the molar amount of the lithium salt was calculated as Li element) and a nanoscale additive Al2O3 in a molar ratio of 1:1.05:0.001 using a high-speed mixer at a mixing speed of 1000 rpm for 30 min to obtain a mixture A.

[0111] 2) calcining the mixture A obtained in step 1) at 720° C. for 8 hours in a pure oxygen atmosphere, followed by cooling, roller + air flow milling, 400 mesh screening, and demagnetization to obtain a matrix material B;

[0112] 3) The second cathode material precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2(D 50 The particle size is 0.6 μm and the specific surface area is 30 m 2 / g) was mixed with ZrO2, WO3 and water in a mass ratio of 1:0.1:0.1:1, the mixing speed was 30 rpm, and the mixing time was 20 min to obtain a coating additive C;

[0113] 4) spraying the coating additive C obtained in step 3) onto the surface of the base material B obtained in step 2) in the form of a spray, wherein the molar ratio of the second positive electrode material precursor to the base material B is 0.01:1, and the spraying time is 30 minutes. At this time, the base material is continuously stirred in a mixing dryer at a stirring speed of 60 rpm for 7 hours and a drying temperature of 130° C. to obtain a coating mixture D;

[0114] 5) The coating mixture D obtained in step 4) was sintered at a temperature of 700° C. for 8 h in a pure oxygen atmosphere with a furnace pressure of 10 Pa. The mixture was then cooled, roller crushed, 400 mesh screened, and demagnetized to obtain a uniformly coated multi-element positive electrode material.

[0115] The positive electrode material was subjected to XPS etching test, and the Zr binding energy test results at different etching times (0 seconds, 120 seconds, 240 seconds and 360 seconds) were as follows: Figure 2 shown.

[0116] Example 2

[0117] The only difference from Example 1 is that in step 4), the molar ratio of the added amount of the second positive electrode material precursor to the matrix material B is 0.005.

[0118] Example 3

[0119] The only difference from Example 1 is that in step 4), the molar ratio of the added amount of the second positive electrode material precursor to the matrix material B is 0.02.

[0120] Example 4

[0121] The only difference from Example 1 is that in step 4), the molar ratio of the added amount of the second positive electrode material precursor to the matrix material B is 0.05.

[0122] Example 5

[0123] The only difference from Example 1 is that in step 1), the cathode material precursor Ni 0.85 Co 0.03 Mn 0.12 The addition ratio of (OH)2, lithium source LiOH (the molar amount of lithium salt is calculated as Li element), and nano-scale additive Al2O3 is 1:1.03:0.001.

[0124] Example 6

[0125] The only difference from Example 1 is that in step 1), the cathode material precursor Ni 0.85 Co 0.03 Mn 0.12 The addition ratio of (OH)2, lithium source LiOH (the molar amount of lithium salt is calculated as Li element), and nano-scale additive Al2O3 is 1:1.06:0.001.

[0126] Example 7

[0127] The only difference from Example 1 is that the sintering temperature in step 5) is 500°C.

[0128] Example 8

[0129] The only difference from Example 1 is that the sintering temperature in step 5) is 600°C.

[0130] Example 9

[0131] The only difference from Example 1 is that in step 4), the spraying time is 10 minutes.

[0132] Example 10

[0133] The only difference from Example 1 is that in step 1), the cathode material precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2(D 50 Particle size 9μm) replaced by Ni 0.7 Co 0.1 Mn 0.2(OH)2; and in step 3), the precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2 is replaced by Ni 0.7 Co 0.1 Mn 0.2 (OH)2(D 50 The particle size is 0.6 μm and the specific surface area is 30 m 2 / g);

[0134] Example 11

[0135] The only difference from Example 1 is that in step 1), the cathode material precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2(D 50 Particle size 9μm) replaced by Ni 0.55 Co 0.2 Mn 0.25 (OH)2; and in step 3), the precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2 is replaced by Ni 0.55 Co 0.2 Mn 0.25 (OH)2(D 50 The particle size is 0.6 μm and the specific surface area is 30 m 2 / g);

[0136] Example 12

[0137] The only difference from Example 1 is that in step 1), the cathode material precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2(D 50 Particle size 9μm) replaced by Ni 0.9 Co 0.05 Mn 0.05 (OH)2; and in step 3), the precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2 is replaced by Ni 0.9 Co 0.05 Mn 0.05 (OH)2(D 50 The particle size is 0.6 μm and the specific surface area is 30 m 2 / g);

[0138] Example 13

[0139] The only difference from Example 1 is that in step 1), the cathode material precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2(D 50 The addition ratio of the nanoparticles (particle size is 9 μm) to the lithium source LiOH (the molar amount of the lithium salt is calculated as Li element) and the nanoscale additive Al2O3 is 1:1.01:0.001.

[0140] Example 14

[0141] The only difference from Example 1 is that in step 3), the same proportion of precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 replaces the precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2.

[0142] Comparative Example 1

[0143] The difference from Example 1 is that in step 1), the cathode material precursor Ni 0.85 Co 0.03 Mn 0.12 The addition ratio of (OH)2, lithium source LiOH (the molar amount of lithium salt is calculated as Li element) and nano-scale additive Al2O3 is 1:1.05:0.001; in step 3), the second positive electrode material precursor Ni is not added. 0.85 Co 0.03 Mn 0.12 (OH)2, mix ZrO2, WO3 and water in a ratio of 0.1:0.1:1.

[0144] Comparative Example 2

[0145] 1) The first cathode material precursor Ni 0.85 Co 0.03 Mn 0.12 (OH)2, lithium source LiOH (the molar amount of lithium salt is calculated as Li element), and nano-scale additive Al2O3 are uniformly mixed in a high-speed mixer at a molar ratio of 1:1.05:0.001 at a mixing speed of 1000 rpm for 30 min to obtain mixture A;

[0146] 2) calcining the mixture A obtained in step 1) at 720° C. for 8 hours in a pure oxygen atmosphere, followed by cooling, roller + air flow milling, 400 mesh screening, and demagnetization to obtain a matrix material B;

[0147] 3) ZrO2 and WO3 are mixed in a mass ratio of 1:1 to obtain a coating additive C;

[0148] 4) dry-mixing the base material B from step 2) and the coating additive C from step 3) in a high-speed mixer at a molar ratio of the second cathode material precursor to the base material of 0.01:1, stirring at a speed of 300 rpm / min for 30 min to obtain a coating mixture D;

[0149] 5) The coating mixture D obtained in step 4) was sintered at a temperature of 500° C. for 8 h in a pure oxygen atmosphere with a furnace pressure of 10 Pa. The mixture was then cooled, roller crushed, 400 mesh screened, and demagnetized to obtain a uniformly coated multi-element positive electrode material.

[0150] The positive electrode materials prepared in the above examples and comparative examples were subjected to performance tests according to the following methods. The test results are listed in Tables 1 and 2.

[0151] XPS test: Take some finished example materials and comparative example materials, use argon ions (Ar+) to etch from the surface of the secondary particles of the positive electrode material toward the center of the particles, and the etching rate is 0.25nm / s. Use X-ray photoelectron spectroscopy to characterize the surface of the etched positive electrode material at etching times of 0 seconds, 120 seconds, 240 seconds, and 360 seconds, respectively, to obtain the XPS full spectrum and Ni element fine spectrum, and record the atomic content percentage of Zr at different etching times. For the Zr 3d peak, first perform peak separation (see below for the peak separation method). 5 / 2 The peak position difference of the Zr 3d peak is used to define the offset distance and peak position difference of the Zr 3d peak. 5 / 2 The peak shift refers to the Zr 3d peak of the cathode material at the etching time of 0 seconds. 5 / 2 The binding energy of the peak is related to the Zr3d at any one of the etching times of 120 seconds, 240 seconds and 360 seconds. 5 / 2 The maximum difference in the binding energy of the peaks. Among them, the binding energy of the 3d peak of Zr refers to the 3d 5 / 2 The binding energy corresponding to the maximum peak intensity. 5 / 2 The binding energy of the peak refers to the Zr 3d 5 / 2 The binding energy corresponding to the maximum peak intensity at the peak. 3 / 2 The binding energy of the peak refers to the Zr 3d 3 / 2 The binding energy corresponding to the maximum peak intensity at the peak. 5 / 2 and Zr 3d 3 / 2 The diffraction peaks are P1, P2, Zr 3d 5 / 2 and Zr 3d 3 / 2The half-maximum widths of the diffraction peaks are FWHM1 and FWHM2, respectively. The separation degree of the two diffraction peaks is calculated to be α=2*(P2-P1) / (FWHM1+FWHM2), and 0.5≤α≤1.

[0152] Peak fitting method: Using Avantage software, select the vgp. format data file to be processed and open the corresponding XPS spectrum. First, use the mouse cursor to select the C1s spectrum. Read the C1s binding energy position of the C-C bond in the current C1s spectrum. Using C1s = 284.8 eV as the reference value, record the current charge shift. Select all XPS spectra (including survey spectra and element-specific narrow-scan spectra) and perform charge shift on the XPS spectra. Use the mouse cursor to select the narrow-scan spectrum of the Zr 3d peak to be processed, and then use the double vertical line pointer to select the peak range in this spectrum. For correlated peaks, set the correlation between the peaks in the peak fitting parameters "Peak / BE", "FWHM / eV", and "L / G%". Select "Fit Peaks" in the "Peak Fitting" window and click "Fit This Level" repeatedly until a satisfactory fit is obtained, i.e., the normalized chi-square value after fitting and peak separation is between 1 and 3, and the standard deviation is less than 1.

[0153] Particle size test method of positive electrode material: The particle size distribution range of the material is tested by Malvern laser particle size analyzer to obtain the D50 particle size and span value.

[0154] Specific surface area test method of positive electrode material: gas adsorption method is used to test the specific surface area, which utilizes the adsorption characteristics of gas on the solid surface - the adsorbent (particle) surface has reversible physical adsorption of adsorbate (gas molecules), and the corresponding equilibrium adsorption amount under a certain pressure is used to calculate the specific surface area from the adsorption amount through a theoretical model.

[0155] Test of free lithium content of positive electrode material: Weigh 5.0±0.1g sample in a 100ml beaker. Accurately take 100mL of ultrapure water (23-24℃) from a 100mL volumetric flask and pour it into the beaker containing the sample. Quickly seal the mouth of the beaker with a sealing film. Place it on a magnetic stirrer for 10 minutes and stir at a speed of 450r / min. After the magnetic stirring is completed, immediately pour the sample into the suction filtration device for filtration. After suction and filtration, transfer the sample to a 100ml volumetric flask without constant volume. Take 50mL of filtrate into the titration cup, place it on the titration stand, and click "OK" to start the test.

[0156] Table 1

[0157]

[0158]

[0159] Table 2

[0160]

[0161]

[0162] The electrochemical performance of the positive electrode materials prepared in the above examples and comparative examples was tested according to the following method. The test results are listed in Table 3.

[0163] The positive electrode material and SP:PVDF glue were mixed in a mass ratio of 93:5:2 and then evenly slurried. The slurry was then evenly coated on a 16μm-thick aluminum foil and dried in a 100°C oven for 12 hours. A 16mm-diameter, 1mm-thick lithium metal sheet was used as the negative electrode. A 20μm-thick polyethylene porous membrane was used as the separator. The electrolyte was a mixture of equal parts ethylene carbonate (EC) and diethyl carbonate (DEC) with 1 mol / L LiPF6. The positive electrode sheet, separator, negative electrode sheet, and electrolyte were assembled into 2016-type button cells in an Ar glove box with water and oxygen contents below 5ppm. Performance testing was performed as follows.

[0164] Capacity test method: The electrical performance test was performed using a blue electric test system (charge and discharge voltage was 3.0-4.3V, temperature condition was 25°C), 0.1C charge, 0.1C discharge, constant voltage cutoff current was 0.005C, and the discharge capacity (CmAh / g) was calculated based on the discharge capacity.

[0165] Cycle performance test method: Under 25℃ conditions, charge at 0.1C and discharge at 0.1C for two weeks, the constant voltage cut-off current is 0.005C, charge at 0.33C and discharge at 0.33C for one week, the constant voltage cut-off current is 0.033C, charge at 0.5C and discharge at 0.5C for one week, the constant voltage cut-off current is 0.05C, charge at 0.5C and discharge at 1C for one week, the constant voltage cut-off current is 0.05C, charge at 0.5C and discharge at 1C for one week, the constant voltage cut-off current is 0.05C, charge at 0.5C and discharge at 2C for one week, the constant voltage cut-off current is 0.05C, charge at 0.5C and discharge at 1C for 50 cycles, the constant voltage cut-off current is 0.05C, among which the ratio of 1C discharge capacity to 0.1C discharge capacity is the rate, and the final capacity retention rate after 50 cycles is the cycle performance.

[0166] DCIR amplification test method: Based on the cycle test, the battery after stage cycling is left at rest for 1 hour, charged with a current of 1C to the target SOC, and left at rest for 30 minutes, with the voltage V0 recorded as OCV. Then, the battery is charged with a charging current I2 for ts and the voltage V1 at ts is recorded. The DC internal resistance is calculated as DCIR = (V1-V0) / I2.

[0167] Table 3

[0168]

[0169]

[0170] The data in Tables 1, 2, and 3 indicate that the positive electrode materials prepared in Examples 1-14, when characterized by XPS etching, exhibit minimal shift in the zirconium 3d peak in the transition layer region, indicating that there are no significant structural differences in the transition layer region. Consequently, the positive electrode materials of the present application possess a stable transition layer region, allowing for sufficient chemical bonding between the transition layer region and the matrix material, reducing the likelihood of harmful phase transitions. Compared to Comparative Examples 1 and 2, the positive electrode materials exhibit higher capacity and cycle stability, while also exhibiting a relatively small increase in DCIR during charge and discharge.

[0171] Compared with Example 1, the positive electrode materials prepared in Example 7 and Example 14 have a minimum value of the deviation of the 3d peak of the zirconium element at the etching time of 0 second and the 3d peak of the zirconium element at the etching time of 120 seconds, 240 seconds and 360 seconds that is less than 0.5 eV. The cycle performance of the prepared positive electrode materials is reduced, and the DCIR increase during the charge and discharge process is also relatively high.

[0172] Compared with Example 1, the positive electrode materials prepared in Example 13 and Example 12 have maximum separation values greater than 1 when the etching time is 120 seconds, 240 seconds and 360 seconds. The cycle performance of the prepared positive electrode materials is reduced, and the DCIR increase during the charge and discharge process is also relatively high.

[0173] For the positive electrode material prepared in Comparative Example 1-2, the Zr 3d peak offset at any two etching times of 120 seconds, 240 seconds, and 360 seconds is greater than 1, indicating that the positive electrode material cannot form a stable transition layer region, resulting in low capacity of the positive electrode material, decreased cycle life, and significant impedance growth.

[0174] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A positive electrode material, characterized in that The invention comprises a substrate and a coating layer, wherein the coating layer is coated on at least a portion of the surface of the substrate; the positive electrode material is etched by argon ions at an etching rate of 0.25 nm / s, and the etched positive electrode material is characterized by X-ray photoelectron spectroscopy. The positive electrode material has a 3d peak of the Zr element at etching times of 120 seconds, 240 seconds, and 360 seconds. Among the etching times of 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in binding energy of the 3d peak of the Zr element of the positive electrode material at any two etching times is less than or equal to 0.5 eV.

2. The positive electrode material according to claim 1, characterized in that The 3d peak of the Zr element of the positive electrode material is subjected to peak separation processing to obtain a 3d 5 / 2 Peak and 3D 3 / 2 Peak, at any one of the etching times of 120 seconds, 240 seconds and 360 seconds, 3d 5 / 2 Peak and 3D 3 / 2 The peak separation is ≤1.

3. The positive electrode material according to claim 2, characterized in that The positive electrode material has a Zr element 3d peak at an etching time of 0 seconds, and the Zr 3d peak of the positive electrode material at an etching time of 0 seconds 5 / 2 The binding energy of the peak is related to the Zr 3d at any one of the etching times of 120 seconds, 240 seconds and 360 seconds. 5 / 2 The difference in binding energy of the peaks is greater than or equal to 0.5 eV.

4. The positive electrode material according to claim 1, characterized in that The positive electrode material satisfies at least one of the following conditions: (1) The binding energy of the Zr element 3d peak of the positive electrode material at an etching time of 0 seconds is greater than the binding energy of the Zr element 3d peak at etching times of 120 seconds, 240 seconds, and 360 seconds by more than 0.5 eV; (2) After the 3d peak of the Zr element of the positive electrode material is subjected to peak separation processing, it has a 3d5 / 2 peak and a 3d3 / 2 peak, and the separation degree of the 3d5 / 2 peak and the 3d3 / 2 peak at the etching time of 0 seconds is 1 to 2.

5. The positive electrode material according to claim 1, characterized in that The positive electrode material satisfies at least one of the following conditions: (1) The binding energy of the 3d peak of the Zr element of the positive electrode material is 175 to 190 eV; (2) When the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the 3d peak binding energy of the Zr element of the positive electrode material at any two etching times may be 0.1 eV, 0.2 eV, 0.3 eV, 0.4 eV, 0.5 eV, or within the range of any two of the above values; (3) When the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the 3d peak binding energy of the Zr element of the positive electrode material at any two etching times can be 0.1 eV to 0.3 eV; (4) When the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the 3d peak binding energy of the Zr element of the positive electrode material at any two etching times can be 0.2 eV to 0.4 eV; (5) When the etching time is 120 seconds, 240 seconds, and 360 seconds, the absolute value of the difference in the 3d peak binding energy of the Zr element of the positive electrode material at any two etching times can be 0.3 eV to 0.5 eV.

6. The positive electrode material according to claim 1, characterized in that The positive electrode material satisfies at least one of the following conditions: (1) The chemical formula of the positive electrode material is LiNi 1-e-f-g Co e M1 f M2 g Zr h O2, M includes at least one of Zr, Al, W, Sr, Y, and Ti, 0≤e≤0.2, 0≤f≤0.5, 0≤g≤0.1, and 0<h≤0.1; M1 is Mn and / or Al; M2 is one or more of Al, Ti, Y, Zr, Mg, Sr, W, Nb, Ce, La, Mo, Ba, and B; (2) The general chemical formula of the positive electrode material can be LiNi a Co b M c M' 1-a-b-c O2·αLiNi a’ Co b’ M c’ Zr d M' 1-a’-b’-c’-d O2, where LiNi a Co b M c M' 1-a-b-c O2 is the general chemical formula of the matrix of the positive electrode material, 0.3≤a<1.0, 0.01≤b≤0. 3, 0≤c≤0.5, 0≤1-abc≤0.01; αLiNi a’ Co b’ M c’ Zr d M' 1-a’-b’-c’-d O2 is the general chemical formula of the coating layer of the positive electrode material, 0.001≤α≤0.1, 0.3≤a'<1.0, and a'≤a, 0.01≤b'≤0.3, 0≤c'≤0.5, 0≤d≤0.1, 0≤1-a'-b'-c'-d≤0.1; M is Mn and / or Al; M' is one or more of Al, Ti, Y, Zr, Mg, Sr, W, Nb, Ce, La, Mo, Ba, and B.

7. The positive electrode material according to any one of claims 1 to 5, characterized in that The positive electrode material satisfies at least one of the following conditions: (1) The span value of the positive electrode material is 0.3 to 1.0; (2) The volume distribution median particle size D50 of the positive electrode material is 5 μm to 10 μm; (3) The free lithium content of the positive electrode material is 0.10 wt% to 0.3 wt%.

8. The positive electrode material according to any one of claims 1 to 6, characterized in that The positive electrode material satisfies at least one of the following conditions: (1) The BET specific surface area of the positive electrode material is 0.15 m 2 / g~0.8m 2 / g; (2) The grain size of the D104 crystal plane of the positive electrode material is 60 nm to 100 nm; (3) Based on the total mass of the positive electrode material, the mass content of the Zr element is 500 to 5000 ppm.

9. A positive electrode sheet, characterized in that: Contains the positive electrode material according to any one of claims 1 to 8.

10. A battery, characterized in that: A positive electrode sheet comprising the positive electrode sheet according to claim 9.

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