Positive electrode material and lithium ion secondary battery

Abstract

The invention relates to the technical field of batteries, in particular to a positive electrode material and a lithium ion secondary battery comprising the positive electrode material. The positive electrode material comprises a lithium-rich manganese-based material, the lithium-rich manganese-based material comprises a matrix, the chemical formula of the matrix is Li1 + qNixCoyMnzAkO2, q is greater than 0 and less than or equal to 0.5, x is greater than or equal to 0.2 and less than or equal to 0.45, y is greater than or equal to 0.02 and less than or equal to 0.2, z is greater than or equal to 0.35 and less than or equal to 0.78, k is greater than or equal to 0 and less than or equal to 0.1, and A comprises at least one of Al, Mg, Ti, Zr, Nb, La, W and Y; the matrix comprises a central area, a transition area and a surface area, the mass content of the element Co in the surface area is larger than that of the element Co in the transition area and larger than that of the element Co in the central area, and the element Co in the transition area has an increasing concentration gradient; the lithium ion secondary battery provided by the invention has relatively high first coulombic efficiency and relatively good rate capability and cycling stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a positive electrode material and a lithium ion secondary battery comprising the same. BACKGROUND

[0002] Lithium ion batteries, as a kind of secondary batteries that can be repeatedly charged and discharged, have been widely used in the fields of communication, transportation, military, medical treatment, entertainment and the like. In recent years, high specific energy and high power lithium ion batteries have become the inevitable direction of the development of future lithium ion batteries. The specific capacity of the currently commercialized positive electrode materials (such as LiCoO2, LiFePO4, LiMn2O4 and ternary materials) is lower than 200 mAh / g, which is the main factor limiting the specific energy of the battery. Therefore, it is urgent to find a positive electrode material with higher specific capacity. Among them, lithium-rich materials have the advantages of high capacity, low cost and low toxicity, and are expected to be applied to the next generation of high specific energy lithium ion batteries as positive electrode materials.

[0003] However, the lithium-rich material has problems such as low first coulomb efficiency, low material conductivity and poor cycle performance in the synthesis process, which limits its practical application in high energy density lithium ion batteries. SUMMARY

[0004] The present application aims to overcome the above-mentioned problems existing in the prior art, and provides a positive electrode material and a lithium ion secondary battery comprising the same. The lithium ion secondary battery (hereinafter referred to as battery) of the present application has a high first coulomb efficiency, a good rate performance and a cycle stability, while ensuring that the positive electrode material has a high specific capacity, a high conductivity and a good cycle performance.

[0005] In the prior art, the problems of low first coulomb efficiency and low conductivity of lithium-rich materials are usually solved only by coating materials. However, due to the fact that the interface combination between the conventional coating material and the lithium-rich material is not ideal, the difference in expansion coefficient and the difference in chemical activity between the two during the charging and discharging process can easily lead to stress concentration at the interface, thereby destroying the integrity of the coating layer, allowing the electrolyte to penetrate to the surface of the lithium-rich material, triggering a side reaction, and causing a certain loss of the capacity of the positive electrode material, and at the same time, new problems such as capacity decrease and insignificant cycle performance improvement may occur.

[0006] The inventors of the present application found that the lithium-rich manganese-based material containing element Co can stabilize the crystal structure of the material, significantly improve the electronic and ionic conductivity of the lithium-rich manganese-based material, inhibit the oxygen precipitation of the lithium-rich manganese-based material during the charging and discharging process, alleviate the capacity attenuation of the battery, and improve the initial coulomb efficiency. When element Mn and element Ni coexist in the lithium-rich manganese-based material, the high electronic conductivity of element Co can compensate for the poor conductivity of element Mn, and the low cost and abundant resources of element Mn can reduce the cost of the material. At the same time, element Ni has a high capacity contribution, and the synergistic effect of element Co can further improve the overall performance of the lithium-rich manganese-based material.

[0007] Further, by adjusting the element Co concentration in different regions of the lithium-rich manganese-based material matrix, the electronic conductivity of the lithium-rich manganese-based material can be effectively improved. The reasons are as follows: first, cobalt ions (such as Co 3+ / Co 4+ ) have excellent electronic conductivity, and a higher and stable element Co concentration in the surface region of the lithium-rich manganese-based material can construct a continuous electronic conduction channel, reduce the contact resistance between particles and the particle surface, and accelerate the transmission efficiency of electrons at the electrode interface. Second, the increasing element Co concentration gradient from the inside to the outside of the transition region can alleviate the difference in electronic conduction in different regions, reduce the internal resistance, optimize the continuity of the material lattice structure, relieve the lattice stress, reduce the electronic scattering center (such as lattice defects and cation disorder), and improve the overall electronic migration efficiency.

[0008] Based on this, the inventors of the present application propose the following solutions:

[0009] The first aspect of the present application provides a positive electrode material, which comprises a lithium-rich manganese-based material, wherein the lithium-rich manganese-based material comprises a matrix, and the chemical formula of the matrix is Li 1+q Ni x Co y Mn z A kO2, and 0 < q < 0.5, 0.2 < x < 0.45, 0.02 < y < 0.2, 0.35 < z < 0.78, 0 < k < 0.1, A comprises at least one of Al, Mg, Ti, Zr, Nb, La, W and Y; the substrate comprises a center region, a transition region and a surface layer region; wherein the center region is a region formed by a point at a distance of 0%-30% of the center in the direction from the center to the surface, the surface layer region is a region formed by a point at a distance of 0%-10% of the surface in the direction from the surface to the center, and the transition region is located between the center region and the surface layer region; the mass content of element Co in the surface layer region is 10%-20% based on the total weight of the lithium-rich manganese-based material; the surface layer region contains the Co element at a constant concentration; the content of element Co in the center region is < 3%; in the transition region, the mass content of element Co has an increasing concentration gradient in the direction from the center to the surface; the mass content of element Co in the surface layer region is greater than that in the transition region, and the mass content of element Co in the transition region is greater than that in the center region.

[0010] The second aspect of the present application provides a lithium ion secondary battery comprising the positive electrode material of the first aspect of the present application.

[0011] Compared with the prior art, the present application has at least the following advantages:

[0012] (1) The positive electrode material provided by the present application has high specific capacity, high electrical conductivity and good cycle performance.

[0013] (2) The lithium ion secondary battery comprising the positive electrode material has high initial coulombic efficiency, good rate performance and cycle stability during long-term cycling.

[0014] The endpoints of the ranges and any values disclosed in this document are not limited to the precise values recited as the exact dimensions are not critical to the present application. The ranges and values should be interpreted as being approximate such that modest variation from the recited values of the endpoints is intended. The ranges and values of numerical limits in this disclosure are not to be interpreted as being bound by the recited exact numerical values. Each numerical limit should at least be construed as subject to a 10% variance thereof. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A structure schematic diagram of a substrate in an example of the present application is shown.

[0016] Figure 2 A curve diagram of the mass content of elements Ni, Co and Mn changing with the radius of the lithium-rich manganese-based material in an example of the present application is shown.

[0017] Figure 3X-ray diffraction spectrum of a positive electrode material in an example of the present application is shown.

[0018] Figure 4 A scanning electron microscope (SEM) image of a substrate in an example of the present application is shown. DETAILED DESCRIPTION

[0019] The specific embodiments of the present application are described in detail below. It should be appreciated that the detailed description of the specific embodiments is merely intended for explaining and illustrating the present application, and is not intended to limit the present application.

[0020] The first aspect of the present application provides a positive electrode material, the positive electrode material comprising a lithium-rich manganese-based material, the lithium-rich manganese-based material comprising a substrate, the substrate having a chemical formula of Li 1+q Ni x Co y Mn z A k O2, and 0 < q < 0.5 (e.g. 0.1, 0.2, 0.3, 0.4 or 0.5), 0.2 < x < 0.45 (e.g. 0.2, 0.25, 0.3, 0.35, 0.4 or 0.45), 0.02 < y < 0.2 (e.g. 0.02, 0.05, 0.1, 0.15 or 0.20), 0.35 < z < 0.78 (e.g. 0.35, 0.4, 0.5, 0.6, 0.7 or 0.78), 0 < k < 0.1 (e.g. 0, 0.02, 0.04, 0.06, 0.08 or 0.1), and A comprising at least one of Al, Mg, Ti, Zr, Nb, La, W and Y.

[0021] In the present application, the mass content of element Co in the lithium-rich manganese-based material is 1% to 20% (e.g. 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18% or 20%).

[0022] In an example, the mass content of element Co in the lithium-rich manganese-based material is 5% to 10%.

[0023] In the present application, the lithium-rich manganese-based material comprises a substrate. As Figure 1The structure of the substrate in an example of the present application is shown in the figure. As can be seen from the figure, the substrate includes a center region, a transition region and a surface layer region in sequence from the center to the surface. The center region refers to a region within 0-30% of the radius from the center to the surface, from the geometric center of the substrate, in the radial direction from the center to the surface, with the radius from the center to the surface as the reference. The surface layer region refers to a region within 0-10% of the radius from the surface to the center, from the surface of the substrate, in the radial direction from the surface to the center, with the radius from the surface to the center as the reference. The transition region is located between the center region and the surface layer region. The mass content of element Co in the surface layer region is 10-20% (for example, 10%, 12%, 14%, 16%, 18% or 20%) based on the total weight of the lithium-rich manganese-based material.

[0024] As Figure 2 The mass content of elements Ni, Co and Mn in the lithium-rich manganese-based material varies with the radius in an example of the present application. The abscissa is the radial position from the center to the surface of the substrate, and the ordinate is the mass content of element Ni, Co or Mn in the substrate. As can be seen from the figure, the surface layer region contains the Co element at a constant concentration. In the transition region, the mass content of element Co has an increasing concentration gradient in the direction from the center to the surface. The mass content of element Co in the surface layer region is greater than that in the transition region, which is greater than that in the center region.

[0025] In the present application, the center of the substrate can be obtained by importing the SEM image of the substrate into image processing software (such as ImageJ), processing the particle outline, and then calling the mass center calculation function of the software to obtain the geometric center coordinates of the particle.

[0026] In the present application, the surface layer region contains the Co element at a constant concentration, which is specifically manifested as follows: 10 random points are selected in the radial direction from the center to the surface in the surface layer region of the substrate, and the mass content of element Co at each point is C1. The average of the maximum and minimum values of the mass content of element Co at the 10 points is C2. When |(C1-C2)|×100% / C2≤10%, it is considered that the surface layer region contains the Co element at a constant concentration.

[0027] In the present application, the "the mass content of element Co has an increasing concentration gradient in the transition zone along the center-to-surface direction" is specifically manifested as follows: the position of the transition zone is determined by scanning electron microscopy (SEM) cross-section analysis, within the transition zone, a number of points are selected at equal distances along the radial direction from the center to the center, and the mass content of element Co at each point is measured by energy dispersive spectrometer (EDS) point scanning. The results show that the mass content of element Co gradually increases along the direction.

[0028] In the present application, the mass content of element Co in the lithium-rich manganese-based material can be obtained by conventional methods in the art, for example, the battery is discharged to 0% SOC (for example, the battery is discharged to 2.7V), the positive electrode sheet is taken out by disassembly, the cross-section of the positive electrode sheet is polished using an argon ion grinder, the cross-section of the lithium-rich manganese-based material is scanned using an energy dispersive spectrometer (EDS), the scanning area is not less than 50% of the cross-section, and the scanning range should be completely within the cross-section, and the mass content of element Co in the lithium-rich manganese-based material is calculated.

[0029] In the present application, the mass content of element Co in the surface layer zone can be obtained by conventional methods in the art, for example, the battery is discharged to 0% SOC, the positive electrode sheet is taken out by disassembly, the positive electrode sheet is laser cut using an argon ion grinder (CP), the surface layer zone can be observed in a SEM or TEM device, the cross-section of the surface layer zone of the substrate is scanned using an energy dispersive spectrometer (EDS), the scanning area is not less than 50% of the cross-section of the surface layer zone, and the scanning range should be completely within the cross-section, and the mass content of element Co in the surface layer zone is calculated.

[0030] In the present application, the mass content of element Co in the center zone is ≤3% (for example, 3%, 2.5%, 2%, 1.5%, 1%, 0.5% or 0) based on the total weight of the lithium-rich manganese-based material; the mass content of element Co in the transition zone is 3%-10% (for example, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%).

[0031] In an example, the mass content of element Co in the center zone is 1%-3% based on the total weight of the lithium-rich manganese-based material.

[0032] In an example, the difference in the mass content of element Co between the innermost point and the outermost point in the center region is less than the difference in the mass content of element Co between the innermost point and the outermost point in the transition region in the direction from the center to the surface. Specifically, the center region and the transition region are determined by SEM cross-section analysis, and in the center region and the transition region, equidistant characteristic sites (such as adjacent points with a distance of 100 nm) are continuously selected from the geometric center of the substrate in the direction from the center to the surface, and the mass content of element Co at each site is measured. The results show that the difference in the mass content of element Co between adjacent sites in the center region is small (for example, stable at 0.2%-0.5%), showing a gentle increasing trend; and after entering the transition region, the difference in the mass content of element Co between adjacent sites at the same distance significantly increases (for example, the difference increases to 1.0%-2.5%), and the difference remains at a high level in the direction away from the center region.

[0033] In the present application, element Co in the substrate has a certain concentration gradient, and the overall concentration gradually increases from the inside to the outside, and the concentration of element Co tends to be stable after a certain thickness. The positive electrode material prepared by the method has higher electrical conductivity. Among them, the content of element Co in the center region is low and the increasing speed is slow, which can inhibit cation mixing, reduce lattice distortion, and reduce local stress concentration caused by ion deintercalation during charging and discharging; the increasing speed of Co content in the transition region is greater than that in the center region, which can improve the electronic conductivity and ion diffusion rate of the material. The rapid increase of Co content in the transition region can form a "gradient conduction channel", which can reduce the resistance of lithium ion migration from the center region to the surface layer, accelerate the transmission of electrons and lithium ions, especially under high-rate charging and discharging conditions, which can more effectively reduce the polarization phenomenon, ensure the rapid intercalation and deintercalation of lithium ions, and thus improve the rate performance of the material.

[0034] In the present application, the test method of the mass content of element Co in the center region and the transition region is the same as the test method of the mass content of element Co in the surface layer, which is not described here.

[0035] In the present application, in the center region and the transition region, the mass content of element Ni has a decreasing concentration gradient in the direction from the center to the surface. Specifically, the position of the center region or the transition region is determined by scanning electron microscope (SEM) cross-section analysis, and in the center region or the transition region, a plurality of sites are selected along the radial direction from the center to the center, and the mass content of element Ni at each site is measured by energy dispersive spectrometer (EDS) point scanning. The results show that the mass content of element Ni gradually decreases in this direction.

[0036] In the present application, the mass content difference of element Ni between the innermost point and the outermost point in the center region is less than the mass content difference of element Ni between the innermost point and the outermost point in the transition region along the center-to-surface direction. Specifically, the center region and the transition region are determined by SEM cross-section analysis, and within the center region and the transition region, starting from the geometric center of the substrate, equidistant characteristic sites (such as adjacent points with a distance of 100 nm) are continuously selected along the center-to-surface direction, and the mass content of element Ni at each site is determined. The results show that the mass content difference of element Ni between adjacent sites in the center region is relatively small (for example, stable at 0.2%-0.5%), showing a gentle decreasing trend; while entering the transition region, the mass content difference of element Ni between adjacent sites at the same interval significantly increases (for example, the difference increases to 1.0%-2.5%), and the difference remains at a high level in the direction away from the center region.

[0037] In the present application, the Ni element is contained in the surface layer region at a constant concentration. For the explanation of "the Ni element is contained in the surface layer region at a constant concentration", reference can be made to the explanation of element Co in the surface layer region, which will not be repeated here.

[0038] In an example, the content of element Ni in the surface layer region is 20%-30% (for example, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%) based on the total weight of the lithium-rich manganese-based material.

[0039] In the present application, the Mn element is contained in the surface layer region at a constant concentration. For the explanation of "the Mn element is contained in the surface layer region at a constant concentration", reference can be made to the explanation of element Co in the surface layer region, which will not be repeated here.

[0040] In an example, the content of element Mn in the surface layer region is 50%-70% (for example, 50%, 55%, 60%, 65% or 70%) based on the total weight of the lithium-rich manganese-based material.

[0041] In the present application, the lithium-rich manganese-based material further comprises a cladding layer located on the outer surface of the substrate; the cladding layer comprises a metal oxide and / or a fast ion conductor; the metal oxide comprises at least one of oxides of Al, Ti, Zr, Nb and W; the fast ion conductor comprises Li 12 (LLZO), Li 1.5 Al 0.5 Ge 1.5 (PO4)3(LAGP), Li 1.5 Al 0.5 Si 1.5(PO4)3 (LASP), LiAlTi(PO4)3 (LATP) and Li 10 GeP2S 12 At least one of (LGPS).

[0042] In one example, the mass content of the coating layer in the lithium-rich manganese-based material is 1000ppm-20000ppm (e.g., 1000ppm, 5000ppm, 10000ppm, 15000ppm or 20000ppm).

[0043] In one example, the mass content of the coating layer in the lithium-rich manganese-based material is 5000ppm-10000ppm.

[0044] In one example, the coating layer includes a first coating layer and a second coating layer, wherein the first coating layer is located between the substrate and the second coating layer; the first coating layer includes the metal oxide, such as at least one selected from Al2O3, TiO2, ZrO2, Nb2O3, and WO3; and the second coating layer includes the fast ion conductor, such as at least one selected from LLZO, LAGP, LASP, LATP, and LGPS.

[0045] In this invention, coating the surface of the matrix particles further improves the cycle performance and first-cycle coulombic efficiency of the cathode material. This is because the composite structure formed by the matrix surface region and the surface coating layer can maintain the electron conduction network on the particle surface through the high electronic conductivity of element Co, and can also alleviate concentration polarization through the ion conduction channels of the coating layer, avoiding severe side reactions caused by electrolyte intrusion. This ensures that the cathode material maintains a stable electrochemical reaction interface after long-term charge and discharge, resulting in a significant improvement in cycle performance. At the same time, the synergistic effect of the coating layer and the elemental Co gradient region of the matrix can also reduce the polarization voltage during the first charge cycle, allowing more lithium ions to participate in reversible insertion and extraction, thus improving the first-cycle coulombic efficiency.

[0046] This invention achieves a balance between high structural stability and high rate performance in batteries through the synergistic effect of two coating layers. The first coating layer (metal oxide) exhibits high chemical stability, effectively isolating the cathode material from direct contact with the electrolyte, suppressing interfacial side reactions, reducing the corrosion of the cathode material by HF in the electrolyte, and inhibiting the dissolution of transition metal ions, thus enhancing the structural stability of the cathode material. The second coating layer (fast ion conductor) possesses high ionic conductivity, serving as a "high-speed channel" for lithium-ion transport, promoting efficient lithium-ion shuttling between the cathode surface and the electrolyte, thereby improving the battery's fast-charging capability and high-rate performance.

[0047] In the present application, the mass content of the coating layer in the lithium-rich manganese-based material can be obtained by testing by a method conventional in the art, for example, discharging the battery to 0% SOC, disassembling to take out the positive electrode sheet, soaking in DMC solvent for 12 h, then rinsing with DMC solvent to remove the lithium salt attached to the positive electrode sheet, calcining the electrode sheet in an air atmosphere at 450 degrees for 3 hours, then scraping the positive electrode material from the positive electrode sheet with a ceramic knife, then etching the positive electrode material with concentrated hydrochloric acid (concentration of 36%-38%) for different times, then combining inductively coupled plasma (ICP) measurement to obtain the mass content of the coating layer in the lithium-rich manganese-based material.

[0048] In the present application, the lithium-rich manganese-based material comprises secondary particles formed by a plurality of primary particles, the average particle size of the primary particles of the lithium-rich manganese-based material is 55 nm-150 nm (for example, 55 nm, 60 nm, 80 nm, 100 nm, 120 nm or 150 nm); the particle size Dv10 of the lithium-rich manganese-based material is 1 μm-5 μm (for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or 5 μm), the Dv50 is 5 μm-20 μm (for example, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm or 20 μm), and the Dv90 is 15 μm-50 μm (for example, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm); 0.3≤(Dv90-Dv10) / Dv50≤4 (for example, 0.3, 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4).

[0049] In an example, 1.5≤(Dv90-Dv10) / Dv50≤2.5.

[0050] In the present application, the substrate comprises secondary particles formed by a plurality of primary particles, the average particle size of the primary particles of the substrate is 20 nm-100 nm (for example, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm); and the average particle size of the substrate is 6 μm-12 μm (for example, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm or 12 μm).

[0051] In the present application, the specific surface area of the substrate is 20 m 2 / g-60 m 2 / g (for example, 20 m 2 / g, 30 m 2 / g, 40 m 2 / g, 50 m 2 / g or 60 m 2 / g).

[0052] In the present application, the specific surface area of the lithium-rich manganese-based material is 2m 2 / g-5m 2 / g (for example, 2m 2 / g, 3m 2 / g, 4m 2 / g or 5m 2 / g).

[0053] In the present application, the average particle size of the primary particles of the lithium-rich manganese-based material can be obtained by a method conventional in the art, for example, discharging the battery to 0% SOC, disassembling to take out the positive electrode sheet, polishing the cross section of the positive electrode sheet with an argon ion grinder, and then in the SEM device mirror image, selecting at least 20 primary particles of the lithium-rich manganese-based material, measuring the particle size of each particle, and taking the average value. If the primary particle is a regular circle in the mirror image, then the particle size of the particle is the diameter of the circle; if the primary particle is not a "regular circle" in the mirror image, connecting any two points on the edge of the particle to form a straight line segment inside the particle, and selecting the longest straight line segment inside the particle as the particle size of the primary particle of the lithium-rich manganese-based material.

[0054] In the present application, the particle size Dv10, Dv50 and Dv90 of the lithium-rich manganese-based material can be obtained by a method conventional in the art, for example, by a laser particle size analyzer.

[0055] In the present application, the test method of the average particle size of the primary particles and the secondary particles of the substrate is the same as the test method of the average particle size of the primary particles of the lithium-rich manganese-based material described above, which will not be described here.

[0056] In the present application, the specific surface area of the substrate and the specific surface area of the lithium-rich manganese-based material can be obtained by a method conventional in the art, for example, a specific surface area analyzer-nitrogen adsorption method.

[0057] As Figure 3 The XRD diffraction pattern of the positive electrode material in an example of the present application is shown in the figure, and it can be seen from the figure that there is a first diffraction peak at 17°-19°, a second diffraction peak at 43°-46°, and a third diffraction peak at 20°-25°.

[0058] In an example, the peak intensity I1 of the first diffraction peak and the peak intensity I2 of the second diffraction peak satisfy: 1.1 < I1 / I2 ≤ 3 (for example, 1.1, 1.3, 1.5, 1.7, 2, 2.2, 2.5 or 3); the peak intensity I3 of the third diffraction peak is 500-1000 (for example, 500, 600, 700, 800, 900 or 1000).

[0059] When the ratio of I1 to I2 is in the above specific range, the cycle stability of the positive electrode material can be effectively improved, because the appropriate ratio of Li / Ni mixed arrangement can effectively prevent the migration of transition metals to the Li layer in the high delithiation state; at the same time, the trace passivated Ni in the lithium layer 2+ The lithium layer spacing can be significantly increased, the shrinkage of the lithium layer in the high delithiation process is avoided, and therefore the rate performance and long cycle stability of the positive electrode material are synergistically improved.

[0060] Compared with conventional lithium transition metal oxides, the lithium-rich manganese-based material has a third diffraction peak, which can better reflect the performance of the lithium-rich material.

[0061] As Figure 4 The scanning electron microscope image of the substrate in an example of the present application is shown, and it can be seen from the figure that the surface of the substrate is not completely dense, and there are a small amount of fine cracks in the local area.

[0062] In the present application, the method for preparing the positive electrode material at least comprises the following steps:

[0063] (1) The nickel source and the manganese source are configured into solution A, and the cobalt source is configured into solution B; the sodium carbonate and the complexing agent are configured into alkali liquor;

[0064] (2) Deionized water is added into a reaction container, the solution A and the alkali liquor obtained in step (1) are added into the reaction container at a first flow rate, stirring is performed, and the solution B is added into the reaction container at a second flow rate, and reaction is performed;

[0065] (3) The material obtained in step (2) is washed, first dried, and filtered;

[0066] (4) The material obtained in step (3) is mixed with a lithium source, and first sintering is performed.

[0067] In the present application, the specific amount of the material used is as described above, and will not be repeated here.

[0068] In an example, the nickel source comprises nickel sulfate hexahydrate.

[0069] In an example, the cobalt source comprises cobalt sulfate heptahydrate.

[0070] In an example, the manganese source comprises manganese sulfate monohydrate.

[0071] In an example, the complexing agent comprises at least one of ammonia, ammonium oxalate and ammonium citrate.

[0072] In an example, the lithium source comprises lithium carbonate and / or lithium hydroxide.

[0073] In an example, the reaction container comprises a reaction kettle.

[0074] In an example, the molar ratio of elements Li, Ni, Mn and Co in the lithium source, the nickel source, the manganese source and the cobalt source is (1.05-1.5):(0.2-0.45):(0.35-0.78):(0.02-0.2).

[0075] In the present application, by configuring two different solutions (solution A and solution B), the element Co in the substrate has a certain concentration gradient.

[0076] In the present application, 10g-20g of the complexing agent is contained in 1L of the alkali liquid.

[0077] In the present application, the concentration of the solution A and the alkali liquid is independently 1mol / L-2.5mol / L, and the concentration of the solution B is 1mol / L-2mol / L. Among them, the solvent in the solution A and the solution B is deionized water; the molar ratio of the nickel source and the manganese source in the solution A is (0.4-0.54):1; and the molar ratio of sodium carbonate and the complexing agent in the alkali liquid is 1:(0.1-0.2).

[0078] In an example, the temperature of the reaction container in the step (2) is 30℃-60℃; the pH of the reaction is 7.0-8.5; the mass ratio of the solution A, the alkali liquid and the solution B is 1:(0.8-1.2):(0.15-0.2); the content of the deionized water is 10%-20% based on the total volume of the reaction container; the feeding start and end time of the solution A is 0h-40h, and the first flow rate is 350mL / h-450mL / h; the feeding start and end time of the solution B is 0h-40h, and the second flow rate is 50mL / h-200mL / h.

[0079] In an example, the mass ratio of the material obtained in the step (3) and the lithium source is 1:(0.4-0.5).

[0080] In an example, the temperature of the first drying in the step (3) is 80℃-150℃; and the time of the first drying is 12h-36h.

[0081] In an example, the first sintering in the step (4) at least includes a first stage and a second stage; the temperature of the first stage is 450℃-600℃, and the time of the first stage is 4h-6h; the temperature of the second stage is 750℃-900℃, and the time of the second stage is 12h-20h.

[0082] In the present application, the first sintering is carried out in an air atmosphere, and compressed air is supplemented at a speed of 30L / min-40L / min.

[0083] In the present application, the step (4) further comprises performing a second sintering and a third sintering after the first sintering.

[0084] In an example, the second sintering is performed at a temperature of 600-800℃, with 0.05%-1% mass fraction of metal oxide added during sintering, and for a sintering time of 8-12h.

[0085] In an example, the third sintering is performed at a temperature of 600-800℃, with 0.05%-1.5% mass fraction of fast ion conductor added during sintering, and for a sintering time of 8-12h.

[0086] In an example, the third sintering further comprises a second drying after the third sintering.

[0087] The second aspect of the present application provides a battery, which comprises the positive electrode material of the first aspect of the present application.

[0088] In the present application, the battery can further comprise a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.

[0089] In the present application, the positive electrode sheet comprises a positive electrode current collector and a positive electrode coating layer coated on at least one side surface of the positive electrode current collector, and the positive electrode coating layer can comprise the positive electrode material.

[0090] The positive electrode coating layer can further comprise a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent can comprise a conductive agent commonly used in the art, for example comprising at least one of conductive carbon black, Ketjen black and acetylene black. The positive electrode binder can comprise a binder commonly used in the art, for example comprising at least one of polyvinylidene fluoride, butadiene rubber and sodium carboxymethyl cellulose.

[0091] The content of the positive electrode material can be 80-99% by weight, the content of the positive electrode binder can be 0.5-10% by weight, and the content of the positive electrode conductive agent can be 0.5-10% by weight, based on the total weight of the positive electrode coating layer.

[0092] In the present application, the negative electrode sheet comprises a negative electrode current collector and a negative electrode coating layer coated on at least one side surface of the negative electrode current collector, and the negative electrode coating layer can comprise a negative electrode material.

[0093] The negative electrode material can comprise a negative electrode material commonly used in the art, for example comprising at least one of graphite, soft carbon, hard carbon and silicon material.

[0094] The negative electrode coating can further include a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent can include a conductive agent conventionally used in the art, for example, including at least one of conductive carbon black, Ketjen black, and acetylene black. The negative electrode binder can include a binder conventionally used in the art, for example, including at least one of polyvinylidene fluoride, styrene butadiene rubber, and sodium carboxymethyl cellulose.

[0095] In the present application, the content of the negative electrode material can be 80-99% by weight, the content of the negative electrode binder can be 0.5-10% by weight, and the content of the negative electrode conductive agent can be 0.5-10% by weight, based on the total weight of the negative electrode coating.

[0096] In the present application, the separator includes a base material layer, a ceramic layer located on at least one side surface of the base material layer, and a glue layer located on both outer surfaces of the separator, the ceramic layer at least facing the positive electrode sheet.

[0097] In an embodiment, the ceramic layer is located only on one side surface of the base material and faces the positive electrode sheet.

[0098] In an example, the ceramic layer includes at least one of CeO2, MgAl2O4, ZrO, and TiO2.

[0099] In an example, the base material layer includes a base film, which can include at least one of polyethylene, polyvinyl chloride, polyethylene oxide, polypropylene, nylon, glass fiber, polyethylene terephthalate (PET), polyimide (PI), aramid fiber, cellulose, and non-woven fabric.

[0100] In an example, the glue layer includes at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), sodium carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), lithium carboxymethyl cellulose (CMC-Li), and polyvinylpyrrolidone (PVP).

[0101] In the present application, the electrolyte can include an electrolyte conventionally used in the art, for example, the electrolyte includes an organic solvent, an electrically conductive lithium salt, and an additive. The organic solvent includes a carbonate-based solvent and / or a carboxylate-based solvent. The carbonate-based solvent can include a cyclic carbonate-based solvent and a chain carbonate-based solvent. The cyclic carbonate-based solvent can include a cyclic carbonate conventionally used in the art, for example, including at least one of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). The chain carbonate-based solvent can include a chain carbonate conventionally used in the art, for example, including at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC). The carboxylate-based solvent can include a carboxylate conventionally used in the art, for example, including at least one of methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB). The electrolyte salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methide, or lithium bis(trifluoromethylsulfonyl)imide. The additive includes at least one of vinylene carbonate, 1,3-propane sultone, vinyl ethylene carbonate, vinylene sulfate, butanedinitrile, pentanedinitrile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile, 1,3,6-hexanetristitnitrile (HTCN), glycerol trinitrate, and 1,2-bis(2-cyanoethoxy)ethane.

[0102] The assembly of the battery can be performed in a manner conventionally used in the art.

[0103] It should be noted that the "first", "second", and the like in the present application are merely used to distinguish different substances or usage manners, and do not represent the difference in order.

[0104] The present application will be described in detail below through examples. The examples described in the present application are only a part of the examples of the present application, rather than all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0105] In the following examples, the materials used are commercially available analytical pure unless otherwise specified.

[0106] The following preparation examples are used to prepare the lithium-rich manganese-based material of the present application.

[0107] Preparation Example 1

[0108] The lithium-rich manganese-based material is prepared according to the following method

[0109] (1) Deionized water is used as a solvent, and nickel sulfate hexahydrate and manganese sulfate monohydrate are weighed and added to the solvent according to the molar ratio of element Ni to element Mn of 0.73:1.49 to obtain solution A (16 L, with a concentration of 2.22 mol / L); cobalt sulfate heptahydrate is weighed and configured into solution B (4 L, with a concentration of 1.23 mol / L); sodium carbonate and a complexing agent (ammonia) are added to the solvent according to the molar ratio of 1:0.15 to obtain an alkali solution (20 L, with a concentration of 2 mol / L).

[0110] (2) Based on the total volume of the reaction kettle, 15% of deionized water is added; solution A obtained in step (1) and the alkali solution are added to the reaction kettle through a peristaltic pump according to a first flow rate of 400 mL / h, and the liquid inlet starts and stops at 0 h-40 h, while solution B is added to the reaction container according to a second flow rate of 80 mL / h, and the liquid inlet starts and stops at 0 h-40 h, and the reaction is carried out. The mass ratio of solution A, the alkali solution and solution B is 1:1:0.18, the temperature of the reaction container is 45°C, and the pH of the reaction is 8.0.

[0111] (3) The material obtained in step (2) is washed with deionized water, first dried, and finally filtered through a 400-mesh screen. The first drying temperature is 130°C, and the first drying time is 24 h.

[0112] (4) The material obtained in step (3) is mixed with lithium carbonate according to a mass ratio of 1:0.45, and first sintering is carried out, the first stage temperature is 550°C, the first stage time is 5 h; the second stage temperature is 800°C, the second stage time is 16 h; after the first sintering, second sintering and third sintering are carried out, the second sintering temperature is 700°C, WO3 with a mass fraction of 0.5% is added during sintering, and the sintering time is 10 h; the third sintering temperature is 700°C, LATP with a mass fraction of 1% is added during sintering, and the sintering time is 10 h; after the third sintering, second drying is carried out, the second drying temperature is 130°C, and the second drying time is 24 h.

[0113] The chemical formula of the lithium-rich manganese-based material is Li 1.4 Ni 0.318 Co 0.082 Mn 0.6O2, the mass content of element Co in the lithium-rich manganese-based material is 8.5%; the matrix of the lithium-rich manganese-based material comprises a central region, a transition region and a surface layer region; in the transition region, the mass content of element Co has an increasing concentration gradient along the direction from the center to the surface; the difference between the mass content of element Co at the innermost point and the outermost point in the central region is less than the difference between the mass content of element Co at the innermost point and the outermost point in the transition region; in the central region and the transition region, the mass content of element Ni has a decreasing concentration gradient, and the difference between the mass content of element Ni at the innermost point and the outermost point in the central region is less than the difference between the mass content of element Ni at the innermost point and the outermost point in the transition region; the mass content of element Co in the central region is 2%, the mass content of element Co in the transition region is 6.8%, and the mass content of element Co in the surface layer region is 15.2%; the mass content of the coating layer in the lithium-rich manganese-based material is 8156 ppm, the first coating layer is 0.5% WO3, and the second coating layer is 1% LATP; the average particle size of the primary particles of the lithium-rich manganese-based material is 105 nm, the particle size Dv10 of the lithium-rich manganese-based material is 3 μm, the particle size Dv50 is 11 μm, the particle size Dv90 is 38 μm, and (Dv90-Dv10) / Dv50 is 3.2; the specific surface area of the lithium-rich manganese-based material is 3.5 m 2 / g; the average particle size of the primary particles of the matrix is 64 nm, the average particle size of the matrix is 9.5 μm, and the specific surface area of the matrix is 43 m 2 / g; I1 / I2 is 2.15, and I3 is 765.

[0114] Preparation Example 2

[0115] The lithium-rich manganese-based material is prepared according to the following method

[0116] (1) Deionized water is used as a solvent, and nickel sulfate hexahydrate and manganese sulfate monohydrate are weighed and added to the solvent according to a molar ratio of element Ni to element Mn of 0.8:1.49 to obtain solution A (16 L, a concentration of 2.29 mol / L); cobalt sulfate heptahydrate is weighed and configured into solution B (4 L, a concentration of 0.78 mol / L); sodium carbonate and a complexing agent (ammonium oxalate) are added to the solvent according to a molar ratio of 1:0.1 to obtain a lye (20 L, a concentration of 2 mol / L).

[0117] (2) Based on the total volume of the reaction kettle, 10% deionized water is added; solution A and the lye obtained in step (1) are added to the reaction kettle through a peristaltic pump according to a first flow rate of 400 ml / h, and the liquid inlet starts and stops at 0 h-40 h, while solution B is added to the reaction container according to a second flow rate of 80 ml / h, and the liquid inlet starts and stops at 0 h-40 h, and the reaction is carried out. Among them, the mass ratio of solution A, lye and solution B is 1:0.8:0.2, the temperature of the reaction container is 30°C, and the pH of the reaction is 7.0.

[0118] (3) The material obtained in step (2) is washed with deionized water, first dried, and finally filtered through a 400-mesh screen. The temperature of the first drying is 150℃, and the duration of the first drying is 12h.

[0119] (4) The material obtained in step (3) is mixed with lithium carbonate at a mass ratio of 1:0.4, first sintered, the first stage temperature is 450℃, the first stage time is 6h; the second stage temperature is 750℃, the second stage time is 20h; after the first sintering, second sintering and third sintering are carried out, the second sintering temperature is 600℃, WO3 with a mass fraction of 0.2% is added during sintering, and the sintering time is 12h; the third sintering temperature is 600℃, LATP with a mass fraction of 0.5% is added during sintering, and the sintering time is 12h; after the third sintering, second drying is carried out, the second drying temperature is 150℃, and the second drying duration is 12h.

[0120] The chemical formula of the lithium-rich manganese-based material is Li 1.4 Ni 0.348 Co 0.052 Mn 0.6 O2, the mass content of element Co in the lithium-rich manganese-based material is 5.2%; the substrate of the lithium-rich manganese-based material includes a central region, a transition region, and a surface layer region; in the transition region, along the direction from the center to the surface, the mass content of element Co has an increasing concentration gradient; the mass content difference of element Co between the innermost point and the outermost point in the central region is less than the mass content difference of element Co between the innermost point and the outermost point in the transition region; in the central region and the transition region, the mass content of element Ni has a decreasing concentration gradient, and the mass content difference of element Ni between the innermost point and the outermost point in the central region is less than the mass content difference of element Ni between the innermost point and the outermost point in the transition region; the mass content of element Co in the central region is 1%, the mass content of element Co in the transition region is 3.1%, and the mass content of element Co in the surface layer region is 10.5%; the mass content of the coating layer in the lithium-rich manganese-based material is 5058ppm, the first coating layer is 0.2% WO3, and the second coating layer is 0.5% LATP; the average particle size of the primary particles of the lithium-rich manganese-based material is 55nm, the particle size Dv10 of the lithium-rich manganese-based material is 1μm, the particle size Dv50 is 5μm, the particle size Dv90 is 15μm, and (Dv90-Dv10) / Dv50 is 2.8; the specific surface area of the lithium-rich manganese-based material is 2.2m 2 / g; the average particle size of the primary particles of the substrate is 25nm, the average particle size of the substrate is 6.1μm, and the specific surface area of the substrate is 24m 2 / g; I1 / I2 is 1.26, and I3 is 556.

[0121] Preparation Example 3

[0122] A lithium-rich manganese-based material is prepared according to the following method

[0123] (1) Deionized water is used as a solvent, and nickel sulfate hexahydrate and manganese sulfate monohydrate are weighed and added to the solvent according to a molar ratio of element Ni to element Mn of 0.64:1.49 to obtain solution A (16 L, a concentration of 2.13 mol / L); cobalt sulfate heptahydrate is weighed and configured into solution B (4 L, a concentration of 1.5 mol / L); sodium carbonate and a complexing agent (ammonium citrate) are added to the solvent according to a molar ratio of 1:0.2 to obtain a lye (20 L, a concentration of 2 mol / L).

[0124] (2) Based on the total volume of the reaction kettle, 20% deionized water is added; solution A obtained in step (1) and the lye are added to the reaction kettle by a peristaltic pump according to a first flow rate of 400 ml / h, and the liquid inlet starts and stops at 0 h-40 h, while solution B is added to the reaction container according to a second flow rate of 80 ml / h, and the liquid inlet starts and stops at 0 h-40 h, and the reaction is carried out. The mass ratio of solution A, the lye and solution B is 1:1.2:0.15, the temperature of the reaction container is 60°C, and the pH of the reaction is 8.5.

[0125] (3) The material obtained in step (2) is washed with deionized water, first dried, and finally filtered through a 400-mesh screen. The first drying temperature is 80°C, and the first drying time is 36 h.

[0126] (4) The material obtained in step (3) is mixed with lithium carbonate according to a mass ratio of 1:0.5, and first sintering is carried out, the first stage temperature is 600°C, the first stage time is 4 h; the second stage temperature is 900°C, the second stage time is 12 h; after the first sintering, second sintering and third sintering are carried out, the second sintering temperature is 800°C, WO3 with a mass fraction of 1% is added during sintering, and the sintering time is 8 h; the third sintering temperature is 800°C, LATP with a mass fraction of 1.5% is added during sintering, and the sintering time is 8 h; after the third sintering, second drying is carried out, the second drying temperature is 80°C, and the second drying time is 36 h.

[0127] The chemical formula of the lithium-rich manganese-based material is Li 1.4 Ni 0.302 Co 0.098 Mn 0.6O2, the mass content of element Co in the lithium-rich manganese-based material is 9.8%; the matrix of the lithium-rich manganese-based material comprises a central zone, a transition zone and a surface layer zone; in the transition zone, the mass content of element Co has an increasing concentration gradient along the direction from the center to the surface; the difference between the mass content of element Co at the innermost point and the outermost point in the central zone is less than the difference between the mass content of element Co at the innermost point and the outermost point in the transition zone; in the central zone and the transition zone, the mass content of element Ni has a decreasing concentration gradient, and the difference between the mass content of element Ni at the innermost point and the outermost point in the central zone is less than the difference between the mass content of element Ni at the innermost point and the outermost point in the transition zone; the mass content of element Co in the central zone is 3%, the mass content of element Co in the transition zone is 9.6%, and the mass content of element Co in the surface layer zone is 19.8%; the mass content of the coating layer in the lithium-rich manganese-based material is 9986ppm, the first coating layer is 1% of WO3, and the second coating layer is 1.5% of LATP; the average particle size of the primary particles of the lithium-rich manganese-based material is 152nm, the particle size Dv10 of the lithium-rich manganese-based material is 5μm, the particle size Dv50 is 20μm, the particle size Dv90 is 50μm, and (Dv90-Dv10) / Dv50 is 2.3; the specific surface area of the lithium-rich manganese-based material is 4.8m 2 / g; the average particle size of the primary particles of the matrix is 96nm, the average particle size of the matrix is 11.5μm, and the specific surface area of the matrix is 60m 2 / g; I1 / I2 is 2.43, and I3 is 995.

[0128] Preparation Example 4 group

[0129] The preparation examples in this group are prepared by referring to Preparation Example 1, except that the mass content of element Co in the lithium-rich manganese-based material is regulated by changing the mass of cobalt sulfate heptahydrate added in step (1), which is as follows:

[0130] Preparation Example 4a, the mass content of element Co in the lithium-rich manganese-based material is 1.5%; the chemical formula of the lithium-rich manganese-based material is Li 1.4 Ni 0.385 Co 0.015 Mn 0.6 O2;

[0131] Preparation Example 4b, the mass content of element Co in the lithium-rich manganese-based material is 19.6%; the chemical formula of the lithium-rich manganese-based material is Li 1.4 Ni 0.204 Co 0.196 Mn 0.6 O2.

[0132] Preparation Example 5

[0133] The present preparation example is performed with reference to Preparation Example 1, except that the increasing gradient or decreasing gradient of the mass content of element Co or element Ni in the central zone and the transition zone is regulated by changing the second flow rate of solution B added in step (2) and the liquid feeding time, specifically as follows:

[0134] The second flow rate of solution B added in step (2) is 160 ml / h within 0h-10h, and the second flow rate is 80 ml / h within 10h-30h thereafter; the mass content difference of element Co between the innermost point and the outermost point in the central zone is greater than the mass content difference of element Co between the innermost point and the outermost point in the transition zone; the mass content difference of element Ni between the innermost point and the outermost point in the central zone is greater than the mass content difference of element Ni between the innermost point and the outermost point in the transition zone.

[0135] Preparation Example 6 group

[0136] The present preparation example is performed with reference to Preparation Example 1, except that the type of the coating layer is regulated by changing the metal oxide and fast ion conductor added during the second sintering and the third sintering in step (4), specifically as follows:

[0137] Preparation Example 6a, the temperature of the second sintering is 700℃, and 0.5% of Al2O3 by mass fraction is added during sintering, and the sintering time is 10h; the temperature of the third sintering is 700℃, and 1% of LGPS by mass fraction is added during sintering, and the sintering time is 10h;

[0138] Preparation Example 6b, the temperature of the second sintering is 700℃, and 0.5% of LATP by mass fraction is added during sintering, and the sintering time is 10h; the temperature of the third sintering is 700℃, and 1% of WO3 by mass fraction is added during sintering, and the sintering time is 10h;

[0139] Preparation Example 6c, the temperature of the second sintering is 700℃, and 0.5% of WO3 and 1% of LATP by mass fraction are directly added during sintering, and the sintering time is 10h; no third sintering is included;

[0140] Preparation Example 6d, no third sintering is included, and no second coating layer LATP is present;

[0141] Preparation Example 6e, no second sintering is included, and no first coating layer WO3 is present;

[0142] Preparation Example 7 group

[0143] The present preparation example is performed with reference to Preparation Example 1, except that the mass content of the coating layer in the lithium-rich manganese-based material is regulated by changing the mass fraction of the metal oxide and the fast ion conductor added during the second sintering and the third sintering in step (4), specifically as follows:

[0144] Preparation Example 7a, 0.05% by mass of WO3 is added in the second sintering, 0.05% by mass of LATP is added in the third sintering, and the mass content of the coating layer in the lithium-rich manganese-based material is 1000 ppm;

[0145] Preparation Example 7b, 1% by mass of WO3 is added in the second sintering, 0.9986% by mass of LATP is added in the third sintering, and the mass content of the coating layer in the lithium-rich manganese-based material is 19986 ppm.

[0146] Comparative Preparation Example 1

[0147] Preparation Example 1 is referred to, except that the mass of the cobalt sulfate heptahydrate added in step (1) is changed, and the details are as follows:

[0148] Comparative Preparation Example 1a, the mass content of element Co in the lithium-rich manganese-based material is 0.2%; the chemical formula of the lithium-rich manganese-based material is Li 1.4 Ni 0.398 Co 0.0028 Mn 0.6 O2.

[0149] Comparative Preparation Example 1b, the mass content of element Co in the lithium-rich manganese-based material is 25%; the chemical formula of the lithium-rich manganese-based material is Li 1.4 Ni 0.152 Co 0.25 Mn 0.6 O2.

[0150] Comparative Preparation Example 2

[0151] Preparation Example 1 is referred to, except that in step (1), the cobalt sulfate heptahydrate and the manganese sulfate monohydrate are weighed according to a molar ratio of element Co to element Mn of 0.73:1.49 and added to the solvent to obtain solution A (16 L, a concentration of 2.22 mol / L); the nickel sulfate hexahydrate is weighed and configured into solution B (4 L, a concentration of 1.23 mol / L). Among them, the mass content of element Co in the central zone and the transition zone has a decreasing concentration gradient.

[0152] Comparative Preparation Example 3

[0153] Preparation Example 1 is referred to, except that in step (2), solution A and solution B are mixed in advance, and element Co does not have a concentration gradient.

[0154] Comparative Preparation Example 4

[0155] Preparation Example 1 is referred to, except that only solution A is added to synthesize the lithium-rich manganese-based material; the chemical formula of the lithium-rich manganese-based material is Li 1.4 Ni 0.45 Mn 0.6O2.

[0156] Comparative Preparation Example 5

[0157] Preparation Example 1 was referred to, except that the start and end time of solution B and the second flow rate were changed, and the details were as follows:

[0158] In Comparative Preparation Example 5a, solution B was fed from 0 h to 20 h, and the second flow rate was 160 ml / h; the mass content of element Co in the surface layer zone was 1%;

[0159] In Comparative Preparation Example 5b, solution B was fed from 20 h to 40 h, and the second flow rate was 160 ml / h; the mass content of element Co in the surface layer zone was 50%.

[0160] The following examples are used to illustrate the battery of the present application.

[0161] Example 1

[0162] The battery was prepared according to the following method:

[0163] (1) Preparation of positive electrode sheet

[0164] The lithium-rich manganese-based material prepared in Preparation Example 1, acetylene black and polyvinylidene fluoride were mixed in a mass ratio of 90:5:5, N-methyl pyrrolidone was added, and stirring was carried out under the action of a vacuum stirrer until uniform mixing to obtain a positive electrode slurry with a solid content of 75%; the positive electrode slurry was uniformly coated on both sides of the surface of an aluminum foil, and after baking, rolling, slitting, a positive electrode sheet was obtained.

[0165] (2) Preparation of negative electrode sheet

[0166] Artificial graphite, superconducting carbon black, butadiene rubber and sodium carboxymethyl cellulose were mixed in a mass ratio of 96:1.5:1.5:1, deionized water was added, and a negative electrode slurry with a solid content of 45% was obtained; the negative electrode slurry was uniformly coated on both sides of the surface of a copper foil, and after drying, rolling, die cutting and sheeting, a negative electrode sheet was obtained.

[0167] (3) Preparation of battery

[0168] The positive electrode sheet prepared in step (1), the separator (a polyethylene film with a thickness of 8 μm) and the negative electrode sheet prepared in step (2) were sequentially stacked in place, with the separator between the positive and negative electrode sheets to play a separating role, and then a bare cell was obtained by winding; the bare cell was placed in an aluminum plastic film shell, and an electrolyte (a mixed solution of lithium hexafluorophosphate dissolved in ethylene carbonate / dimethyl carbonate (volume ratio 1:1) and 5 vol.% fluoroethylene carbonate, wherein the concentration of lithium hexafluorophosphate was 1 mol / L) was injected into the dried bare cell, and after vacuum packaging, standing, formation, shaping, sorting and other processes, a lithium ion battery was obtained.

[0169] Example 2

[0170] The battery was prepared according to the following method:

[0171] (1) Preparation of the positive electrode sheet

[0172] The lithium-rich manganese-based material prepared in Preparation Example 2, acetylene black and polyvinylidene fluoride were mixed in a mass ratio of 90:5:5, N-methylpyrrolidone was added, and stirring was performed under the action of a vacuum stirrer until the mixture was uniform to obtain a positive electrode slurry with a solid content of 75%; the positive electrode slurry was uniformly coated on both sides of an aluminum foil, and baking, rolling, slitting were performed to obtain a positive electrode sheet.

[0173] (2) Preparation of the negative electrode sheet

[0174] Artificial graphite, superconducting carbon black, butadiene rubber and sodium carboxymethyl cellulose were mixed in a mass ratio of 96:1.5:1.5:1, deionized water was added, and a negative electrode slurry with a solid content of 45% was obtained; the negative electrode slurry was uniformly coated on both sides of a copper foil, and baking, rolling, die cutting and sheeting were performed to obtain a negative electrode sheet.

[0175] (3) Preparation of the battery

[0176] The positive electrode sheet prepared in step (1), a separator (a polyethylene film with a thickness of 8 μm) and the negative electrode sheet prepared in step (2) were sequentially stacked in place, with the separator between the positive and negative electrode sheets to play a role of isolation, and then a bare cell was obtained by winding; the bare cell was placed in an aluminum-plastic film shell, and an electrolyte (a mixed solution in which lithium hexafluorophosphate was dissolved in ethylene carbonate / dimethyl carbonate (volume ratio 1:1) and 5 vol.% fluoroethylene carbonate, wherein the concentration of lithium hexafluorophosphate was 1 mol / L) was injected into the dried bare cell, and the lithium ion battery was obtained after vacuum packaging, standing, formation, shaping, sorting and other processes.

[0177] Example 3

[0178] The battery was prepared according to the following method:

[0179] (1) Preparation of the positive electrode sheet

[0180] The lithium-rich manganese-based material prepared in Preparation Example 3, acetylene black and polyvinylidene fluoride were mixed in a mass ratio of 90:5:5, N-methylpyrrolidone was added, and stirring was performed under the action of a vacuum stirrer until the mixture was uniform to obtain a positive electrode slurry with a solid content of 75%; the positive electrode slurry was uniformly coated on both sides of an aluminum foil, and baking, rolling, slitting were performed to obtain a positive electrode sheet.

[0181] (2) Preparation of the negative electrode sheet

[0182] The artificial graphite, superconducting carbon black, butadiene styrene rubber and sodium carboxymethyl cellulose are mixed according to a mass ratio of 96:1.5:1.5:1, deionized water is added, and a negative electrode slurry with a solid content of 45% is obtained; the negative electrode slurry is uniformly coated on the surfaces of both sides of a copper foil, dried, rolled, die-cut and sheeted to obtain a negative electrode sheet.

[0183] (3) Preparation of a battery

[0184] The positive electrode sheet prepared in step (1), a separator (a polyethylene film with a thickness of 8 μm) and the negative electrode sheet prepared in step (2) are sequentially stacked, with the separator between the positive and negative electrode sheets to play a role of isolation, and then a bare cell is obtained by winding; the bare cell is placed in an aluminum plastic film shell, and an electrolyte (a mixed solution of lithium hexafluorophosphate dissolved in ethylene carbonate / dimethyl carbonate (volume ratio 1:1) and 5 vol.% fluoroethylene carbonate, wherein the concentration of lithium hexafluorophosphate is 1 mol / L) is injected into the dried bare cell, and a lithium ion battery is obtained after processes such as vacuum packaging, standing, formation, shaping, sorting, etc.

[0185] Examples 4-7 and Comparative Examples 1-5 are prepared according to Example 1, except that the lithium-rich manganese-based material prepared in Preparation Example 1 is replaced by an equal amount of another material, as shown in Tables 1 and 2.

[0186] Test Example

[0187] (1) First efficiency test

[0188] The batteries prepared in the examples and comparative examples are subjected to a first efficiency test, and the specific test method is as follows:

[0189] At 25°C, constant current charging is carried out at a charge-discharge rate of 0.1 C to an upper limit voltage of 4.5 V, and then constant voltage charging is carried out at a charge rate of 0.05 C to an upper limit voltage of 4.5 V; then discharging is carried out at a discharge rate of 0.1 C to 2.0 V, the first charge and discharge capacities are counted, the first efficiency = (first discharge capacity) / (first charge capacity) x 100%, and the test results are recorded in Table 1.

[0190] (2) Gram capacity test

[0191] The batteries prepared in the examples and comparative examples are subjected to a gram capacity test, and the specific test method is as follows:

[0192] At 25°C, constant current charging is carried out at a charge-discharge rate of 0.1 C to an upper limit voltage of 4.8 V, and then constant voltage charging is carried out at a charge rate of 0.05 C to an upper limit voltage of 4.8 V; then discharging is carried out at a discharge rate of 0.1 C to 2.0 V, the discharge capacity is counted, and the gram capacity = (discharge capacity) / (positive electrode material weight), and the results are recorded in Table 1.

[0193] (3) Conductivity test

[0194] The positive electrode materials prepared in the examples and comparative examples were subjected to conductivity test, and the specific test method was as follows:

[0195] At 25°C, 1 g of material was weighed and added to a mold (Φ12 mm), the surface of the sample was leveled with a glass rod, the mold was placed on the sample platform of the powder compaction conductivity instrument, the pressure program of the conductivity instrument was started, and the initial pressure was increased from 0 MPa to 30 MPa at a rate of 5 MPa / s by the step method, and the target pressure was maintained for 30 s, then the same rate was sequentially increased to 60 MPa, 90 MPa, 120 MPa, 150 MPa, and 180 MPa, and each pressure node was maintained for 30 s, and when the instrument showed that the resistance value was stable (fluctuation

[0196] ≤0.5% / 10s) The stable resistance value at the final pressure node was recorded; at the same time, the actual thickness of the sample under the corresponding pressure was recorded (read by the displacement sensor of the instrument, unit: cm); the conductivity was calculated according to the formula: σ = L / (R×S), wherein σ is the conductivity (unit: S / m), L is the sample thickness (unit: m), R is the resistance value (unit: Ω), and S is the sample cross-sectional area (S = π×(0.06 m) 2 , unit: m 2 ). Each sample was tested 3 times, and the average value of the conductivity of 3 tests was taken as the final result.

[0197] (4) Rate performance test

[0198] The batteries prepared in the examples and comparative examples were subjected to rate test, and the specific test method was as follows:

[0199] At 25°C, the battery was charged at a current density of 1.2C to 4.6V, then charged at 4.6V, the cutoff current was 0.05C, then rested for 10 min, then discharged at a current density of 0.5C to 2.0V, then rested for 10 min, and the above charging and discharging process was repeated 3 times, and the discharge capacity of the battery in the above 3 times was recorded as the discharge capacity at 0.5C; similarly, after the same charging process, the battery reached 4.6V, and then discharged at a current density of 1C, 2C and 3C to 2.0V, and the average value of 3 discharges at each different rate was taken as the discharge capacity at that rate;

[0200] The rate retention rate = specific rate discharge capacity / 0.5C rate discharge capacity x 100%, and the results are shown in Table 2.

[0201] (5) Cycle test

[0202] The batteries prepared in the examples and comparative examples were subjected to cycle test, and the specific test method was as follows:

[0203] The battery was charged at a current density of 1.2C to 4.6V at 25℃, then charged at 4.6V, the cutoff current was 0.05C, then rested for 10min, then discharged at a current density of 0.5C to 2.0V, then rested for 10min, and the discharge capacity of the battery at this time was recorded as the initial capacity; the above charging and discharging process was repeated until the end of the 500th cycle constant voltage charging process and resting for 10min, then discharged at a current density of 0.5C to 2.0V, and rested for 10min, and the discharge capacity of the battery at this time was recorded as the capacity after cycling. The cycle capacity retention rate = (capacity after cycling / initial capacity) x 100%, and the cycle capacity retention rate was recorded in Table 2.

[0204] Table 1

[0205]

[0206]

[0207] Table 2

[0208]

[0209]

[0210] As can be seen from Table 1 and Table 2, compared with the comparative examples, the positive electrode material of the application has higher gram capacity and electrical conductivity, the battery comprising the positive electrode material of the application has higher initial coulombic efficiency, better rate performance and cycle stability, and the comprehensive performance of the battery is significantly improved.

[0211] The above describes the preferred embodiments of the application, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the application and fall within the protection scope of the application.

Claims

1. A positive electrode material, characterized in that, The cathode material includes a lithium-rich manganese-based material, which comprises a matrix having the chemical formula Li. 1+q Ni x Co y Mn z A k O2, and 0 < q ≤ 0.5, 0.2 ≤ x ≤ 0.45, 0.02 ≤ y ≤ 0.2, 0.35 ≤ z ≤ 0.8, 0 ≤ k ≤ 0.1, A includes at least one of Al, Mg, Ti, Zr, Nb, La, W and Y; the matrix includes a central region, a transition region and a surface region; wherein, the central region is the area formed by points 0%-30% away from the center along the direction from the center to the surface, the surface region is the area formed by points 0%-10% away from the surface along the direction from the surface to the center, and the transition region is located between the central region and the surface region; Based on the total weight of the lithium-rich manganese-based material, the surface region contains 10%-20% Co by mass, and the Co element is contained at a constant concentration in the surface region; the central region contains ≤3% Co by mass; and in the transition region, the Co element has an increasing concentration gradient along the direction from the center to the surface. The mass content of element Co in the surface region is greater than that in the transition region, which in turn is greater than that in the central region.

2. The cathode material according to claim 1, wherein, Based on the total weight of the lithium-rich manganese-based material, the content of element Co in the transition region is 3%-10%; Preferably, along the direction from the center to the surface, the difference in the mass content of element Co between the innermost point and the outermost point in the central region is less than the difference in the mass content of element Co between the innermost point and the outermost point in the transition region.

3. The cathode material according to claim 1, wherein, Ten sites are randomly selected along the radial direction from the center of the surface region of the substrate to the surface. The mass content of element Co at each site is C1. The average of the maximum and minimum mass contents of element Co at the ten sites is taken as C2. C1 and C2 satisfy the relationship: |(C1-C2)|×100% / C2≤10%.

4. The cathode material according to claim 1 or 2, wherein, In the central region, the mass content of element Ni exhibits a decreasing concentration gradient along the direction from the center to the surface; And / or, in the transition region, the mass content of element Ni has a decreasing concentration gradient along the direction from the center to the surface; And / or, the surface region contains the Ni element at a constant concentration; preferably, the Ni content in the surface region is 20%-30% based on the total weight of the lithium-rich manganese-based material.

5. The cathode material according to claim 4, wherein, Along the direction from the center to the surface, the difference in the mass content of element Ni between the innermost and outermost points in the central region is less than the difference in the mass content of element Ni between the innermost and outermost points in the transition region.

6. The cathode material according to claim 1 or 2, wherein, The surface region contains the Mn element at a constant concentration; Preferably, based on the total weight of the lithium-rich manganese-based material, the content of element Mn in the surface region is 50%-70%.

7. The cathode material according to claim 1 or 2, wherein, The lithium-rich manganese-based material further includes a coating layer located on the outer surface of the substrate; the coating layer comprises a metal oxide and / or a fast ion conductor; the metal oxide comprises at least one oxide of Al, Ti, Zr, Nb, and W; the fast ion conductor comprises Li7La3Zr2O 12 Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 1.5 Al 0.5 Si 1.5 (PO4)3, LiAlTi(PO4)3 and Li 10 GeP2S 12 At least one of them; Preferably, the mass content of the coating layer in the lithium-rich manganese-based material is 1000ppm-20000ppm; Preferably, the coating layer includes a first coating layer and a second coating layer, wherein the first coating layer is located between the substrate and the second coating layer; Preferably, the first coating layer comprises the metal oxide, and the second coating layer comprises the fast ion conductor.

8. The cathode material according to claim 1 or 2, wherein, The lithium-rich manganese-based material comprises secondary particles formed from a plurality of primary particles, wherein the average particle size of the primary particles is 55nm-150nm; the particle size of the lithium-rich manganese-based material is Dv10 of 1μm-5μm, Dv50 of 5μm-20μm, and Dv90 of 15μm-50μm; 0.3≤(Dv90-Dv10) / Dv50≤4; And / or, the specific surface area of ​​the lithium-rich manganese-based material is 2m². 2 / g-5m 2 / g.

9. The cathode material according to claim 1 or 2, wherein, The XRD diffraction pattern of the cathode material shows a first diffraction peak at 17°-19°, a second diffraction peak at 43°-46°, and a third diffraction peak at 20°-25°. Preferably, the peak intensity I1 of the first diffraction peak and the peak intensity I2 of the second diffraction peak satisfy: 1 ​​< I1 / I2 ≤ 3.

10. A battery, characterized in that, The battery comprises the positive electrode material according to any one of claims 1-9.

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