Positive electrode material and battery

Abstract

The present application relates to a cathode material and a battery. At least a part of the surface of the cathode material has a coating layer; the chemical general formula of the cathode material is Li<subgt;a< / subgt;Ni<subgt;x< / subgt>Co<subgt;y< / subgt>M<subgt;z< / subgt>N<subgt;bO<subgt;2< / subgt>, where 0.95 ≤ a ≤ 1.1, 0.6 ≤ x < 1, 0 < y < 0.4, 0 < z < 0.4, x + y + z + b = 1, 0 < b < 0.4, M is Mn and / or Al, and N is a coating element; in the particle size volume distribution map of the cathode material, the volume fraction of particles with a particle size less than 1.2 μm is δ1%, and the volume fraction of particles with a particle size greater than 7 μm is δ2%, and 1 ≤ δ2 / δ1 ≤ 10 is satisfied. The cathode material of the present application can reduce the interfacial impedance between particles of the cathode material, enabling the cathode material to meet the electrochemical performance requirements and also meet the dry electrode preparation process.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials, and particularly to cathode materials and batteries. Background Art

[0002] High energy density, high working voltage, long cycle life and high safety are urgent requirements for the wide and large-scale application of lithium-ion batteries. The cathode material has a direct and dominant influence on the performance of the lithium-ion battery pack, and its performance will directly affect the overall performance of the lithium-ion battery. The high-nickel ternary cathode material LiMO2 (where M is usually Ni, Co, Mn or Al, and the mole fraction of Ni is above 0.6) has become one of the most viable options due to its high specific capacity, high packing density and low cost. However, as the nickel content in the polycrystal increases, its discharge capacity increases proportionally, but there are a series of defects such as rapid capacity decay, unstable structure, deteriorated thermal performance and high residual alkali, which limit its commercial application. The main reason is that a series of harmful processes occur during the electrochemical cycling process, including bulk and surface phase transitions, and intergranular cracking is prone to occur in secondary particles, resulting in the continuous formation of new by-products on the cathode surface, thereby consuming valuable electrolytes, generating gases and causing side reactions of transition metal dissolution.

[0003] Compared with the wet process for preparing electrode sheets, the electrode sheets prepared by the dry process lack the infiltration process between the solvent material and the powder material, resulting in poor contact between the powder material particles, large interfacial impedance, and low adhesion between the material particles in the electrode sheet, which significantly affects the fast charging performance, capacity and stability of lithium-ion batteries.

[0004] Therefore, how to reduce the interfacial impedance between the particles of the cathode material so that the cathode material can meet the electrochemical performance requirements and also meet the dry electrode preparation process, making the prepared electrode sheet have the advantages of high energy density, high working voltage, long cycle life, etc., is still a technical problem to be solved at present. Summary of the Invention

[0005] The purpose of this application is to provide a cathode material and a battery, which can improve the structural stability and cycle stability of the cathode material, and at the same time reduce the interfacial impedance between the particles of the cathode material.

[0006] In the first aspect, this application provides a cathode material, at least part of the surface of which has a coating layer;

[0007] The chemical general formula of the cathode material is Li a Ni x Co y M z N bO2, where 0.95 ≤ a ≤ 1.1, 0.6 ≤ x < 1, 0 < y < 0.4, 0 < z < 0.4, x + y + z + b = 1, 0 < b < 0.4, M is Mn and / or Al, and N is a coating element;

[0008] In the particle size volume distribution map of the positive electrode material, the volume ratio of particles with a particle size less than 1.2 μm is δ1%, and the volume ratio of particles with a particle size greater than 7 μm is δ2%, and 1 ≤ δ2 / δ1 ≤ 10 is satisfied.

[0009] In some embodiments, in the XRD pattern of the positive electrode material, the peak intensity of the positive electrode material on the (006) crystal plane is I 006 , the peak intensity on the (101) crystal plane is I 101 , and the peak intensity on the (102) crystal plane is I 102 , 0.5 ≤ (I 006 + I 102 ) / I 101 ≤ 1.00.

[0010] In some embodiments, in the XRD pattern of the positive electrode material, the peak position of the positive electrode material on the (110) crystal plane is 2θ 110 , and the peak position on the (108) crystal plane is 2θ 108 , and 0.2 ≤ |2θ 110 - 2θ 108 | ≤ 0.6.

[0011] In some embodiments, 0.1 < δ1 < 10 and 0.02 < δ2 < 10.

[0012] In some embodiments, N includes at least one of Y, W, Sr, Zr, La, Ce, Co, Ti, Mg, Al, Sb, Nb, Ta, V, B, S, and Ba.

[0013] In some embodiments, the coating layer includes at least one of an oxide of the N element, a hydroxide of the N element, and a lithium composite oxide of the N element.

[0014] In some embodiments, the coating layer includes a first coating layer and a second coating layer. The thickness of the first coating layer is 2 nm to 100 nm, and the thickness of the second coating layer is 2 nm to 80 nm.

[0015] In some embodiments, the particle size D 50 of the positive electrode material is 2 μm to 6 μm.

[0016] In some embodiments, the specific surface area of the positive electrode material is 0.2 m 2 / g to 1.3 m 2 / g.

[0017] In some embodiments, the mass content of free lithium in the positive electrode material is 500 ppm to 2000 ppm.

[0018] In some embodiments, the tap density of the positive electrode material is 3.0 g / cm 3 to 3.6 g / cm 3 .

[0019] In some embodiments, the bulk density of the positive electrode material is 0.6 g / cm 3 to 2.0 g / cm 3 .

[0020] In some embodiments, the powder conductivity of the positive electrode material under a pressure of 8 kN / cm 2 is 1×10 -3 S / cm to 6×10 -2 S / cm.

[0021] In some embodiments, the positive electrode material contains single grains with the same orientation, wherein the average particle size of the single grains is 1 μm to 5 μm.

[0022] In some embodiments, the lithium ion diffusion coefficient of the positive electrode material is 1×10 -9 cm 2 / s to 1×10 -6 cm 2 / s.

[0023] In some embodiments, the spatula angle of the positive electrode material particles is between 10° and 80°.

[0024] In some embodiments, the positive electrode material, conductive carbon black, and polytetrafluoroethylene are mixed in a mass ratio of 8:1:1 and then hot-pressed to obtain a dry electrode film, and the sheet rebound rate of the dry electrode film is <20%.

[0025] In a second aspect, the present application provides a battery, and the battery includes any one of the positive electrode materials described in the first aspect.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] The positive electrode material proposed in this application has a coating layer on at least part of its surface. The coating layer helps to enhance the structural stability and chemical stability of the positive electrode material, reduce the precipitation of lattice oxygen, improve the phase transition reversibility of the crystal phase structure of the positive electrode material. The coating layer can also inhibit the sliding of the crystal layer structure and the generation of microcracks within the crystal, reduce the cracks generated during the cycling of the positive electrode material, and improve the cycling stability of the positive electrode material; it can also help the rapid deintercalation and intercalation of lithium ions, which is beneficial to improving the rate performance and capacity retention rate of the positive electrode material. In this application, while performing coating modification, the particle size limit is set between 1.2 μm and 7 μm, aiming to precisely control the quantity of fine powder and agglomerates. At the same time, controlling 1 ≤ δ2 / δ1 ≤ 10 within the above range, setting the particle size limit greater than 7 μm or less than 1.2 μm will result in the existence of excessive primary particle agglomerates or excessive generation of fine powder due to the breakage of primary particles, thereby affecting the performance of the positive electrode material and the electrode sheet. By precisely controlling the particle size distribution of the positive electrode material, larger particles can play a skeletal role in the dry-process electrode sheet, and smaller particles can connect larger particles, which can effectively improve the connectivity inside the positive electrode sheet, increase the cohesion between the materials inside the positive electrode sheet, improve the contact between the particles of the powder material, effectively reduce the porosity in the electrode sheet, reduce the interfacial impedance between particles, facilitate the formation of an integrated structure by the positive electrode material particles, effectively enhance the reaction kinetics of the positive electrode sheet, and the dry-process electrode has good film-forming properties; it can also effectively alleviate the rebound rate after the positive electrode sheet is roll-pressed, further improve the peel strength of the positive electrode sheet, so that the prepared positive electrode sheet can have the advantages of high energy density, high working voltage, and long cycle life. Brief Description of the Drawings

[0028] The present invention will be further described below in conjunction with the drawings and embodiments.

[0029] Figure 1 It is an electron micrograph of the positive electrode material particles prepared in Example 1 of this application.

[0030] Figure 2 It is an electron micrograph of the positive electrode material particles prepared in Example 8 of this application.

[0031] Figure 3 It is an electron micrograph of the positive electrode material particles prepared in Comparative Example 1 of this application.

[0032] Figure 4 It is an electrochemical impedance spectroscopy diagram of the positive electrode materials prepared in Example 1, Example 6, Example 8, and Comparative Example 2 of this application at low temperature.

[0033] Figure 5 It is a comparison diagram of the overcharge performance of the positive electrode materials prepared in Example 1 and Comparative Example 3 of this application.

[0034] Figure 6 It is an X-ray diffraction diagram of the positive electrode material prepared in Example 6 of this application. Detailed implementation manners

[0035] For a better understanding of the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0036] It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0037] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms of "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0038] It should be understood that the term " / and" used herein is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the front and back associated objects.

[0039] Compared with the wet process for preparing electrodes, for the electrode sheet prepared by the dry process, since there is no infiltration process between the solvent material and the powder material, the contact between the powder material particles is poor, the interfacial impedance is large, and the bonding force between the material particles in the electrode sheet is low, which significantly affects the fast charging performance, capacity and stability performance of the lithium-ion battery.

[0040] In a first aspect, the present application provides a positive electrode material, at least a part of the surface of the positive electrode material has a coating layer, and the chemical general formula of the positive electrode material is Li a Ni x Co y M z N b O2, where 0.95 ≤ a ≤ 1.1, 0.6 ≤ x < 1, 0 < y < 0.4, 0 < z < 0.4, x + y + z + b = 1, 0 < b < 0.4, M is Mn and / or Al, and N is a coating element;

[0041] In the particle size volume distribution map of the positive electrode material, the volume ratio of particles with a particle size less than 1.2 μm is δ1%, and the volume ratio of particles with a particle size greater than 7 μm is δ2%, and 1 ≤ δ2 / δ1 ≤ 10 is satisfied.

[0042] The positive electrode material proposed in this application has a coating layer on at least part of its surface. The coating layer helps to enhance the structural stability and chemical stability of the positive electrode material, reduce the precipitation of lattice oxygen, improve the phase change reversibility of the crystal phase structure of the positive electrode material. The coating layer can also inhibit the sliding of the crystal layer structure and the generation of microcracks within the crystal, reduce the cracks generated in the positive electrode material during cycling, and improve the cycling stability of the positive electrode material; it can also help the rapid deintercalation and intercalation of lithium ions, which is beneficial to improving the rate performance and capacity retention rate of the positive electrode material. In this application, while performing coating modification, the particle size limit is set between 1.2 μm and 7 μm, aiming to precisely control the amount of fine powder and aggregates. At the same time, controlling 1 ≤ δ2 / δ1 ≤ 10 within the above range, if the particle size limit is set greater than 7 μm or less than 1.2 μm, it will lead to the existence of excessive primary particle aggregates or excessive fine powder generated by the rupture of primary particles, thereby affecting the performance of the positive electrode material and the electrode sheet. By precisely controlling the particle size distribution of the positive electrode material, larger particles can play a skeletal role in the dry-process electrode sheet, and smaller particles can connect larger particles, effectively improving the connectivity inside the positive electrode sheet, increasing the cohesion between the materials inside the positive electrode sheet, improving the contact between the powder material particles, effectively reducing the porosity in the electrode sheet, reducing the interfacial impedance between particles, being beneficial to the positive electrode material particles to form an integrated structure, effectively enhancing the reaction kinetics of the positive electrode sheet, and having good film-forming properties for dry-process electrodes; it can also effectively alleviate the rebound rate of the positive electrode sheet after rolling, further improve the peel strength of the positive electrode sheet, so that the prepared positive electrode sheet can have the advantages of high energy density, high working voltage, and long cycle life.

[0043] In this application, the chemical general formula of the positive electrode material is Li a Ni x Co y M z N b O2, where 0.95 ≤ a ≤ 1.1, 0.6 ≤ x < 1, 0 < y < 0.4, 0 < z < 0.4, x + y + z + b = 1, 0 < b < 0.4. The value of a can be 0.95, 0.98, 0.99, 1.0, 1.05, 1.06, 1.08, 1.09, or 1.1, etc. When the molar content of Li in the positive electrode material is within the above range, the battery using this positive electrode material has a relatively high charge-discharge specific capacity; when the molar content of Li in the positive electrode material is relatively low, Ni easily enters the Li layer, resulting in obvious cation mixing and poor stability of the electrochemical cycle. When the molar content of Li in the positive electrode material is relatively high, excess residual alkali will form on the material surface, and it is easy to form a jelly-like state during the preparation of the slurry, affecting the coating effect; secondly, the influence of the residual alkali on the electrochemical performance is mainly reflected in increasing the irreversible capacity loss and deteriorating the cycle performance at the same time.

[0044] The value of x can be, for example, 0.6, 0.7, 0.8, 0.85, 0.86, 0.87, 0.88, 0.9, 0.92, 0.95, 0.97 or 0.99, etc.; the value of y can be, for example, 0.01, 0.05, 0.08, 0.1, 0.15, 0.16, 0.18, 0.2, 0.3, 0.37 or 0.39, etc.; the value of z can be, for example, 0.01, 0.05, 0.08, 0.1, 0.15, 0.16, 0.18, 0.2, 0.3, 0.37 or 0.39, etc., which is not limited herein. When the total molar content of Ni, Co and M in the cathode material is within the above range, the battery has good electrochemical performance. When the total molar content of Ni, Co and M in the cathode material is less, the first irreversible capacity of the battery is high, and the cycle and rate performance are poor; when the total molar content of Ni, Co and M in the cathode material is more, the capacity of the battery is low, which cannot meet the requirement of energy density and affects the practical application. The value of b can be, for example, 0.01, 0.05, 0.1, 0.2, 0.3, 0.35 or 0.39, etc.

[0045] In some embodiments, the coating element N includes at least one of Y, W, Sr, Zr, La, Ce, Co, Ti, Mg, Al, Sb, Nb, Ta, V, B, S and Ba.

[0046] In some embodiments, in the particle size volume distribution map of the cathode material, the volume proportion of particles with a particle size less than 1.2 μm is δ1%, and the volume proportion of particles with a particle size greater than 7 μm is δ2%, and 1≤δ2 / δ1≤10 is satisfied. Specifically, the value of δ2 / δ1 can be 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 5.5, 6.5, 8, 9.5 or 10, etc. Of course, it can also be other values within the above range, which is not limited herein. Setting the particle size limit greater than 7 μm or less than 1.2 μm will result in the existence of too many primary particle aggregates or the generation of too much fine powder due to the breakage of primary particles, thereby affecting the performance of the cathode material and the electrode sheet. When the volume ratio of particles with a particle size less than 1.2 μm to particles with a particle size greater than 7 μm is controlled within the above range in this application, the larger particles can play a role in supporting the skeleton in the electrode sheet under the action of the binder, which can effectively support the electrode sheet. The smaller particles can connect the larger particles in the electrode sheet, improve the connectivity inside the electrode sheet, increase the cohesion between the particles inside the electrode sheet, improve the contact between the particles, reduce the resistance between the particles in the electrode sheet, and effectively enhance the reaction kinetics of the electrode sheet. Moreover, controlling the particle size volume distribution of the cathode material within the above range can further alleviate the rebound rate after the electrode sheet is roll-pressed, improve the peel strength of the electrode sheet, and enhance the cycle stability, high safety and fast charging performance of the battery.

[0047] When δ2 / δ1 is too large, that is, the proportion of larger-sized particles in the positive electrode material is higher, the adsorption capacity between particles decreases, the cohesive force between particles decreases, and the adhesive force between the positive electrode material and the current collector also decreases. This can cause a small portion of the positive electrode material to separate from the current collector and float in the electrolyte to contact the negative electrode material, resulting in local battery short-circuiting. When δ2 / δ1 is too small, that is, the proportion of smaller-sized particles in the positive electrode material is higher, the particles of the positive electrode material are extremely prone to agglomeration, the fluidity between particles decreases, the distribution of the active material in the electrode sheet is uneven, the degree of the electrochemical reaction is uneven, and there are local overcharge and over-discharge phenomena, and the battery performance deteriorates. At the same time, when the particles are too small, it is easy to cause surface defects, induce battery polarization, and the stability of the positive electrode sheet decreases.

[0048] In some embodiments, 0.1 < δ1 < 10, that is, the volume proportion of particles with a particle size less than 1.2 μm can specifically be 9.9%, 8.8%, 7.6%, 6.5%, 4%, 3.5%, 3%, 2.5% or 0.15%, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0049] In some embodiments, 0.02 < δ2 < 10, that is, the volume proportion of particles with a particle size greater than 7 μm can specifically be 9.9%, 8.8%, 7.6%, 6.5%, 5%, 4%, 3.5%, 3.0%, 2.5% or 0.025%, etc.

[0050] It can be understood that when δ1 < 0.1%, δ2 > 10%, the volume proportion of smaller-sized particles is too small, and the cohesive force between particles and between the particles and the current collector is too small. The positive electrode material will separate from the current collector, and the cycle stability of the positive electrode sheet decreases; when δ1 > 10%, δ2 < 0.02%, the volume proportion of smaller-sized particles is too large, reducing the fluidity between particles, resulting in uneven dispersion of the positive electrode material particles, conductive agent, and binder, thereby affecting the film-forming property of the dry electrode.

[0051] In some embodiments, in the XRD pattern of the positive electrode material, the peak intensity of the positive electrode material at the (006) crystal plane is I 006 , the peak intensity at the (101) crystal plane is I 101 , the peak intensity at the (102) crystal plane is I 102 , 0.5 ≤ (I 006 + I 102 ) / I 101 ≤ 1.00. The ratio of (I 006 + I 102 ) / I 101 can specifically be 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 1.0, etc. Of course, it can also be other values within the above range, which are not limited herein. In this application, for the positive electrode material, (I006 +I 102 ) / I 101 can reflect the orderliness of the crystal structure of the cathode material, where Li + occupies the 3b site, and transition metals such as Ni, Co, and Mn randomly occupy the 3a site. However, due to the similar ionic radii of Li + and Ni 2+ , they often occupy each other's positions, forming so-called cation mixing. When Ni atoms occupy the sites in the lithium layer, the intensity of the 101 peak of the cathode material rapidly decays, resulting in a decrease in the structural orderliness of the cathode material. There is a close relationship between the orderliness of the crystal structure of the cathode material and the performance of the cathode material. By controlling 0.5 ≤ (I 006 +I 102 ) / I 101 ≤ 1.00, it indicates that the cathode material has good orderliness of the hexagonal crystal structure. The cathode material is of a layered structure, which is conducive to reducing the degree of cation mixing in the cathode material, improving the orderliness of the cathode material structure, conducive to reducing the interfacial impedance between particles, enhancing the lithium-ion diffusion rate of the cathode material, and conducive to the formation of an integrated structure of the cathode material particles, effectively enhancing the reaction kinetics of the cathode electrode.

[0052] In addition, through a large number of experiments, it is found that there is a synergistic relationship between the value of (I 006 +I 102 ) / I 101 and the particle volume fraction δ1. The value of (I 006 +I 102 ) / I 101 increases with the increase of the value of δ1, and can indirectly reflect the volume fraction of fine particles. In this application, by controlling the value of (I 006 +I 102 ) / I 101 within the range of 0.5 to 1.0 and simultaneously controlling 1 ≤ δ2 / δ1 ≤ 10, the contact tightness relationship between the powder material particles can be effectively adjusted, the connectivity inside the cathode electrode can be opened up, the interfacial impedance between particles can be reduced, the lithium-ion diffusion rate of the cathode material can be enhanced, the rate performance of the cathode material can be improved, and at the same time, the film-forming property of the dry electrode can also be improved.

[0053] From the crystal structure analysis, when the ratio of (I 006 +I 102 ) / I 101 is greater than 1.00, the degree of cation mixing in the cathode material increases, the structural orderliness of the material decreases, and the insertion and extraction of lithium ions in the material are hindered. It should be noted that the structural orderliness of the cathode material includes the structural orderliness of the matrix material and the structural orderliness of the coating layer. The formation of residual alkali on the surface of the cathode material will exacerbate the ion rearrangement phenomenon on the surface of the cathode material, thereby reducing the structural orderliness of the cathode material. However, appropriate residual alkali on the surface of the cathode material is helpful for Li+ Diffusion promotes the improvement of electrochemical performance. Therefore, when controlling 0.5 ≤ (I 006 +I 102 ) / I 101 ≤ 1.00, the structural orderliness of the positive electrode material is improved, which is beneficial to reducing the interfacial impedance between particles, enhancing the lithium ion diffusion rate of the positive electrode material, and at the same time, the appropriate amount of residual alkali on the surface of the positive electrode material can be used to further promote the diffusion of lithium ions and enhance the reaction kinetics of the positive electrode sheet.

[0054] In some embodiments, in the XRD pattern of the positive electrode material, the peak position of the positive electrode material at the (110) crystal plane is 2θ 110 , and the peak position at the (108) crystal plane is 2θ 108 , which satisfies 0.2 ≤ ∣2θ 110 -2θ 108 ∣ ≤ 0.6. The absolute value of 2θ 110 -2θ 108 can specifically be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55 or 0.6, etc., which is not limited herein. In the present application, by controlling 0.2 ≤ ∣2θ 110 -2θ 108 ∣ ≤ 0.6, the diffraction peaks of (108) and (110) are significantly split, indicating that the positive electrode material forms a good layered structure, which can promote the rapid deintercalation and intercalation of Li + in the crystal phase structure and the surface layer, endowing the positive electrode material with high rate performance and better kinetic stability, and reducing the impedance of the positive electrode material.

[0055] In some embodiments, the positive electrode material includes secondary particles formed by agglomeration of a plurality of primary particles, and the secondary particles are spherical structures.

[0056] In some embodiments, the coating layer includes at least one of an oxide of N element, a hydroxide of N element, and a lithium composite oxide of N element. It can be understood that the coating layer on the surface of the primary particles and / or secondary particles can improve the smoothness of the surface of the positive electrode material particles. While isolating the direct contact between the positive electrode material and the electrolyte, it can also improve the particle fluidity of the positive electrode material, making the dispersion between the positive electrode material, the conductive agent, and the binder more uniform, and can further improve the film forming uniformity of the dry electrode.

[0057] In some embodiments, the coating layer includes a first coating layer located on the inner side and a second coating layer located on the outer side, and the total thickness of the coating layer is 2 nm to 180 nm. It is understood that if the coating layer is too thin, the contact inhibition effect between the positive electrode material and the electrolyte is reduced; if the coating layer is too thick, the coating layer material on the surface of the positive electrode material will form small metal oxide particles, which will increase the roughness of the positive electrode material particles, reduce the particle flowability, and lead to a decrease in the uniformity of the dispersion of the positive electrode material, the conductive agent, and the binder, resulting in poor film formation of the dry electrode.

[0058] In the present application, the double-layer coating structure on the surface of the base material can effectively improve the contact between the particles of the powder material, together forming an integrated structure, and effectively enhancing the reaction kinetics.

[0059] In some embodiments, the thickness of the first coating layer is 2 nm to 100 nm, specifically 2 nm, 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 80 nm, 90 nm or 100 nm, etc. Of course, it can also be other values within the above range, which is not limited here.

[0060] In some embodiments, the first coating layer includes a first coating element, and the first coating element includes at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, Sb, Nb, and Ta. The first coating element is a crystal modifying element, and the Li inside the positive electrode particles is optimized by the distribution of the modifying element inside the crystal. + Migration channel, reducing the impedance increase caused by the large diameter of large particles.

[0061] In some embodiments, the thickness of the second coating layer is 2 nm to 80 nm, specifically 2 nm, 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm or 80 nm, etc. Of course, it can also be other values within the above range, which is not limited here.

[0062] In some embodiments, the second coating layer includes a second coating element, which includes at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb. The second coating element is a coating-modifying element. The presence of the second coating layer allows lithium ions to pass through quickly, facilitating rapid lithium ion insertion and extraction, thereby effectively improving the rate performance of the positive electrode material.

[0063] In the present application, the double-layer coating structure can reduce the residual active lithium on the surface, thereby effectively improving the capacity retention rate of the cathode material, effectively avoiding the direct contact between the cathode material and the electrolyte, improving the coating / main interface stability, and thus enhancing the cycling stability of the ternary cathode material. Under the dual synergistic effects of the improvement of the coating layer and the doping modification of the crystal structure of the cathode material, the cathode material is endowed with good structural stability and a high ion diffusion coefficient.

[0064] In some embodiments, the mass content of free lithium in the cathode material is 500 ppm to 2000 ppm. Specifically, it can be 500 ppm, 550 ppm, 600 ppm, 650 ppm, 700 ppm, 800 ppm, 1000 ppm, 1500 ppm, 2000 ppm, etc., which are not limited herein. It can be understood that when the surface free lithium content of the cathode material is controlled within the above range, it can be seen that the residual alkali on the surface of the cathode material particles is effectively controlled, which is beneficial to improving the rate performance of the cathode material, especially the rate performance under fast charging conditions.

[0065] In some embodiments, the cathode material is a single-crystalline cathode material. In the present application, controlling the cathode material to be a single-crystalline structure helps to further avoid the loss of residual unstable lattice oxygen, and inhibits the in-plane migration of transition metal ions through dual effects, thereby inhibiting the generation of sliding and intragranular microcracks, and further enhancing the cycling stability of the material.

[0066] In some embodiments, the cathode material contains a single grain with the same orientation, wherein the average particle size of the single grain is 1 μm to 5 μm. The cathode material particles of the present application containing particles with a size of 1 to 5 μm are single grains with the same orientation, which can control the crystal structure of the cathode material and reduce the generation of bulk oxygen vacancies in the cathode material; at the same time, it synergistically acts with the coating layer on the surface of the cathode material, helps to avoid the loss of residual unstable lattice oxygen, and inhibits the in-plane migration of transition metal ions through dual effects, thereby inhibiting the generation of sliding and intragranular microcracks, and further enhancing the cycling stability of the material.

[0067] It should be noted that the grain orientation of the cathode material can be measured by electron backscatter diffraction (EBSD) at least. Randomly select ten single grains with the same orientation and measure the particle size of each grain, and the arithmetic mean is the average particle size of the above single grains.

[0068] In some embodiments, the particle size D of the cathode material 50The particle size is from 2 μm to 6 μm, specifically, it can be 2 μm, 3 μm, 4 μm, 5 μm, 5.5 μm, 6 μm, etc. Of course, it can also be other values within the above range, which are not limited herein. When the D50 of the cathode material particle size is too large, the increase in particle size will extend the lithium-ion transmission path, resulting in limited lithium-ion diffusion kinetics rate inside the particles and a decline in the rate performance of the cathode material. When the D50 of the cathode material particle size is too small, the specific surface area of the cathode material increases, and more binder is consumed during the preparation of the dry electrode sheet, resulting in a decrease in the specific capacity of the cathode sheet. Controlling the particle size of the cathode material within the above range can improve the specific capacity of the cathode material, enhance the reaction kinetics of the cathode material, and improve the rate performance of the cathode material, especially the rate performance during fast charging.

[0069] In some embodiments, the specific surface area of the cathode material is 0.2 m 2 / g to 1.3 m 2 / g, specifically, it can be 0.2 m 2 / g, 0.3 m 2 / g, 0.5 m 2 / g, 0.8 m 2 / g, 1.0 m 2 / g, 1.1 m 2 / g, 1.2 m 2 / g, or 1.3 m 2 / g, etc. Of course, it can also be other values within the above range, which are not limited herein. Controlling the specific surface area of the cathode material within the above range is beneficial to improving the rate performance and cycle stability of the cathode material.

[0070] In some embodiments, the tap density of the cathode material is 0.6 g / cm 3 to 2.0 g / cm 3 , specifically, it can be 0.6 g / cm 3 , 0.8 g / cm 3 , 1.0 g / cm 3 , 1.2 g / cm 3 , 1.5 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 or 2.0 m 2 / g, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0071] In some embodiments, the compression density of the cathode material is 3.0 g / cm 3 to 3.6 g / cm 3 , specifically, it can be 3.0 g / cm 3 , 3.1 g / cm 3 , 3.2 g / cm3 、 3.3 g / cm 3 、 3.4 g / cm 3 、 3.5 g / cm 3 or 3.6 m 2 / g, etc. Of course, it can also be other values within the above range, which are not limited here.

[0072] In some embodiments, the powder conductivity of the positive electrode material under a pressure of 8 kN / cm 2 is 1×10 -3 S / cm to 6×10 -2 S / cm. Specifically, it can be 1×10 -3 S / cm, 2×10 -3 S / cm, 4×10 -3 S / cm, 5×10 -3 S / cm, 1×10 -2 S / cm, 3×10 -2 S / cm, 4×10 -2 S / cm, 5×10 -2 S / cm, 5.5×10 -2 S / cm or 6×10 -2 S / cm, etc. Of course, it can also be other values within the above range, which are not limited here.

[0073] In some embodiments, the lithium ion diffusion coefficient of the positive electrode material is 1×10 -9 cm 2 / s to 1×10 -6 cm 2 / s. After the positive electrode material is assembled into a button cell, the lithium ion diffusion coefficient is measured at 100% SOC.

[0074] In some embodiments, the spatula angle of the positive electrode material particles is between 10° and 80°. Specifically, it can be 10°, 20°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75° or 80°, etc. Of course, it can also be other values within the above range, which are not limited here. When the spatula angle of the positive electrode material particles is controlled within the above range, the fluidity of the positive electrode material particles increases, and the dispersion uniformity of the positive electrode material particles with the conductive agent and the binder increases, and the film-forming property of the dry electrode is better. If the spatula angle α > 80°, the fluidity of the positive electrode material particles decreases, and the dispersion uniformity of the positive electrode material particles with the conductive agent and the binder decreases; if the spatula angle α < 10°, the fluidity of the positive electrode material particles is good, corresponding to a relatively large proportion of larger particles, resulting in relatively poor adsorption of the particles, and the adhesion force between the particles and between the particles and the current collector is too small, and the film-forming property of the dry electrode is poor.

[0075] Second aspect, the present application provides a method for preparing a cathode material, and the method for preparing the cathode material includes the following steps:

[0076] Step S10: subject a mixture including a cathode material precursor, a lithium-containing compound, and a dopant to a first sintering treatment, and crush the first sintered product to obtain a matrix material. Among them, in the particle size volume distribution map of the matrix material, the volume percentage of particles with a particle size less than 1 μm is δ3%, and the volume percentage of particles with a particle size greater than 7 μm is δ4%, and 0.01 ≤ δ3 / δ4 ≤ 3.5 is satisfied.

[0077] In some embodiments, the chemical general formula of the cathode material precursor is Ni a1 Co b1 M c1 (OH)2 or Ni a1 Co b1 Mn c1 O2, where 0.6 ≤ a1 < 1, 0 < b1 < 0.4, 0 ≤ c1 < 0.4, a1 + b1 + c1 = 1, and M is Mn or Al.

[0078] In some embodiments, the lithium-containing compound includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate. Preferably, the lithium-containing compound includes lithium hydroxide. Specifically, the lithium hydroxide includes at least one of anhydrous lithium hydroxide and monohydrate lithium hydroxide.

[0079] In some embodiments, the molar ratio of metal Me in the cathode material precursor to Li in the lithium-containing compound is 0.95 ≤ Li / Me ≤ 1.1. Specifically, Li / Me can be 0.95, 0.96, 0.98, 0.99, 1.01, 1.025, 1.028, 1.03, 1.035, 1.04, 1.05, 1.06, 1.065, 1.07, 1.085, 1.09, 1.1, etc. Me represents the molar content of all metals in the cathode material precursor. Controlling the molar ratio of metal Me in the cathode material precursor to Li in the lithium-containing compound within the above range is beneficial to the formation of matrix material grains and the improvement of the electrochemical performance of the material. Preferably, 1.0 < Li / Me < 1.02.

[0080] In some embodiments, the mass ratio of the cathode material precursor to the dopant is (50 - 500):1. Specifically, it can be 50:1, 80:1, 100:1, 150:1, 200:1, 250:1, 300:1, 400:1, 450:1, or 500:1, etc., which is not limited herein.

[0081] In some embodiments, the N element in the dopant includes at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, Sb, Nb, Ta, and Ce.

[0082] In some embodiments, the primary sintering process includes a first sintering stage and a second sintering stage. Among them, the temperature of the first sintering stage is 400°C to 700°C. Specifically, the temperature of the first sintering stage is 400°C, 420°C, 450°C, 500°C, 520°C, 550°C, 600°C, 650°C, or 700°C, etc. Of course, it can also be other values within the above range, which are not limited herein. The time of the first sintering stage is 1h to 6h. Specifically, the time of the first sintering stage is 1h, 2h, 3h, 4h, 5h, 5.5h, and 6h, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0083] In some embodiments, the temperature of the second sintering stage is 700°C to 950°C. Specifically, the temperature of the second sintering stage is 700°C, 720°C, 750°C, 800°C, 820°C, 850°C, 900°C, or 950°C, etc. Of course, it can also be other values within the above range, which are not limited herein. The time of the second sintering stage is 8h to 16h. Specifically, the time of the first sintering stage is 8h, 9h, 10h, 12h, 13h, 15h, and 16h, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0084] In some embodiments, the primary sintering process is carried out in an oxygen-containing atmosphere, and the oxygen content of the oxygen-containing gas is greater than or equal to 90%. Specifically, the oxygen content of the oxygen-containing gas can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 100%, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0085] In some embodiments, the equipment for the primary sintering process includes a stationary box furnace, a roller hearth kiln continuous furnace, etc.

[0086] In some embodiments, a gas crusher is used to crush the primary sintering product, and the particle size D of the matrix material after the crushing process 50 is 2μm to 6μm. Specifically, it can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or 6μm, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0087] In some embodiments, the particle size D of the matrix material 50 is inversely proportional to the classification parameters of the gas crusher.

[0088] In some embodiments, the single feeding amount of the air crusher is 2 Kg, the air pressure is 1 Mpa, and the classification parameter of the air crusher is 80 Hz to 200 Hz. Specifically, it can be 80 Hz, 90 Hz, 100 Hz, 120 Hz, 150 Hz, 180 Hz or 200 Hz, etc., which is not limited herein.

[0089] In some embodiments, in the particle size volume distribution map of the matrix material, the particle volume ratio with a particle size less than 1 μm is δ3%, and the particle volume ratio with a particle size greater than 7 μm is δ4%, and 0.01 ≤ δ3 / δ4 ≤ 3.5 is satisfied. Specifically, it can be 0.01, 0.05, 0.1, 0.5, 0.8, 1, 1.5, 2.0, 2.5, 2.8, 3.0 or 3.5, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0090] In some embodiments, δ3 < 5, that is, the particle volume ratio with a particle size less than 1 μm can specifically be 4.9%, 4.8%, 4.6%, 4.5%, 4%, 3.5%, 3%, 2.5% or 0.5%, etc. Of course, it can also be other values within the above range, which is not limited herein. δ4 < 5, that is, the particle volume ratio with a particle size greater than 7 μm can specifically be 4.9%, 4.8%, 4.6%, 4.5%, 4%, 3.5%, 3%, 2.5% or 0.5%, etc.

[0091] It can be understood that by controlling the particle size volume distribution of the matrix material, the volume distribution of the coated cathode material particles can be further regulated within a suitable range, so that the larger particles can play a role in supporting the skeleton in the electrode under the action of the binder, effectively supporting the electrode, and the smaller particles can connect the larger particles in the electrode, improving the connectivity inside the electrode, increasing the cohesion between the particles inside the electrode, improving the contact between the particles, reducing the resistance between the particles in the electrode, and effectively enhancing the reaction kinetics of the electrode sheet.

[0092] Step S20: Mix the matrix material with the first coating agent and then perform secondary sintering treatment to obtain the product of primary coating.

[0093] It can be understood that during the secondary sintering treatment, the first coating agent can slowly penetrate into the crystal surface of the matrix material, increasing the structural stability and chemical stability of the cathode material, reducing the escape of lattice oxygen in the cathode material, and reducing lattice phase transformation.

[0094] In some embodiments, the first coating agent may include a compound containing N element, and the N element includes at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, Sb and Ce.

[0095] In some embodiments, the mass ratio of the matrix material to the first coating agent is 1:(0.001 - 1), specifically, it can be 1:0.001, 1:0.002, 1:0.004, 1:0.006, 1:0.008, 1:0.009, 1:0.01, 1:0.03, 1:0.05, 1:0.09, 1:0.1, 1:0.5 or 1:1, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0096] In some embodiments, the temperature of the secondary sintering treatment is 300°C - 850°C. Specifically, the temperature of the secondary sintering treatment is 300°C, 350°C, 450°C, 500°C, 550°C, 650°C, 700°C, 750°C and 850°C, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the temperature of the secondary sintering treatment is 600°C - 700°C.

[0097] In some embodiments, the time of the secondary sintering treatment is 1h - 20h. Specifically, the time of the secondary sintering treatment is 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h and 20h, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0098] In some embodiments, the secondary sintering treatment is carried out in an oxygen-containing atmosphere, and the oxygen content of the oxygen-containing gas is greater than or equal to 90%. Specifically, the oxygen content of the oxygen-containing gas can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 100%, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0099] In some embodiments, the equipment for the secondary sintering treatment includes a stationary box furnace, a roller hearth kiln continuous furnace, etc.

[0100] Step S30: Mix the product obtained from the first coating with the second coating agent and then carry out a third sintering treatment to obtain the cathode material.

[0101] In some embodiments, the mass ratio of the product obtained from the first coating to the second coating agent is 1:(0.001 - 0.1), specifically, it can be 1:0.001, 1:0.002, 1:0.004, 1:0.006, 1:0.008, 1:0.01, 1:0.02, 1:0.05, 1:0.08, 1:0.09 or 1:0.1, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0102] In some embodiments, the temperature of the three - stage sintering treatment is 300°C to 850°C. Specifically, the temperature of the three - stage sintering treatment is 300°C, 350°C, 380°C, 400°C, 450°C, 500°C, 550°C, 650°C, 700°C, 850°C, etc. Of course, it can also be other values within the above range, which is not limited herein. Preferably, the temperature of the three - stage sintering treatment is 500°C to 550°C.

[0103] In some embodiments, the time of the three - stage sintering treatment is 1h to 20h; the time of the three - stage sintering treatment is 5h to 20h. Specifically, the time of the three - stage sintering treatment is 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, etc. Of course, it can also be other values within the above range, which is not limited herein. Preferably, the time of the three - stage sintering treatment is 5h to 10h.

[0104] In some embodiments, the three - stage sintering treatment is carried out in an oxygen - containing atmosphere, and the oxygen content of the oxygen - containing gas is greater than or equal to 90%. Specifically, the oxygen content of the oxygen - containing gas can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 100%, etc. Of course, it can also be other values within the above range, which is not limited herein. Preferably, the oxygen content of the oxygen - containing gas is greater than or equal to 95%.

[0105] In some embodiments, the three - stage sintering treatment further includes the steps of screening and demagnetization.

[0106] The present application also provides a dry - process electrode film, and the dry - process electrode film includes the above - mentioned positive electrode material. Specifically, the positive electrode material is mixed evenly with a conductive agent and a binder in a certain proportion, and then a dry - process electrode film is prepared through high - speed stirring and rolling.

[0107] The positive electrode material provided by the present application can not only meet the product performance requirements but also meet the requirements of the dry - process electrode preparation process. A lithium - ion battery with high energy density, high working voltage, long cycle life, high safety and fast - charging performance is obtained through the dry - process electrode preparation process.

[0108] The present application also provides a battery, including: a negative electrode sheet, a positive electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet includes a dry - process electrode film.

[0109] The present application also provides an electrical device, and the electrical device includes the battery. The performance of the battery is improved, and the performance of the electrical device using the battery will also be improved.

[0110] The embodiments of the present invention will be further described below with multiple examples. Among them, the embodiments of the present invention are not limited to the following specific examples. Within the scope of the main rights unchanged, appropriate changes can be made for implementation.

[0111] Example 1

[0112] (1) Nickel-cobalt-manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added in a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and ZrO2 is added in a mass ratio of Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 of 300:1, and then pulverized, ground and mixed to obtain a mixture; the mixture is heated to 550 °C in a box furnace under an oxygen atmosphere for 4 h of sintering treatment, and then heated continuously to 850 °C for 6 h of sintering treatment. The primary sintered product is crushed by an air crusher, the single-batch input amount is 2 kg, the air pressure is 1 Mpa, and the classification parameter is 150 Hz to obtain a matrix material with a median particle size of 3 μm, and the matrix material is stored in a polyethylene bag and sealed with an aluminum-plastic film.

[0113] (2) The matrix material and Al2O3 are mixed evenly at a mass ratio of 1:0.007, and then put into an oxygen-containing atmosphere for secondary sintering treatment. The temperature of the secondary sintering treatment is controlled at 600 °C to obtain a primary coated product.

[0114] (3) The primary coated product and H3BO3 are mixed evenly at a mass ratio of 1:0.01 and then put into an oxygen-containing atmosphere for three times of sintering treatment for 8 h. The temperature of the three times of sintering treatment is controlled at 500 °C to obtain a modified cathode material.

[0115] Figure 1 This is the electron microscope image of the cathode material particles prepared in Example 1 of this application. As Figure 1 shown, the primary particles of the cathode material prepared in Example 1 are round, there is a continuous coating layer, and at the same time, the particles are well dispersed.

[0116] The cathode material prepared in this example, the cathode material includes a matrix material and a coating layer, and the chemical general formula of the cathode material is Li 1.01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr-Al-B) 0.0193 O2. [[ID=AF45]]

[0117] For other parameters, see Table 1.

[0118] Example 2

[0119] This embodiment is only different from Embodiment 1 in that,

[0120] (3) After uniformly mixing the matrix material and TiO2 at a mass ratio of 1:0.007, it is put into an oxygen-containing atmosphere for secondary sintering treatment, and the temperature of the secondary sintering treatment is controlled at 600 °C to obtain a primary coating product.

[0121] Other conditions are exactly the same as those in Embodiment 1.

[0122] The positive electrode material prepared in this embodiment, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8910 Co 0.0502 Mn 0.0488 (Zr-Ti-B) 0.01 O2.

[0123] For other parameters, please refer to Table 1.

[0124] Embodiment 3

[0125] This embodiment is only different from Embodiment 1 in that,

[0126] (3) After uniformly mixing the matrix material and Co(OH)2 at a mass ratio of 1:0.007, it is put into an oxygen-containing atmosphere for secondary sintering treatment, and the temperature of the secondary sintering treatment is controlled at 600 °C to obtain a primary coating product.

[0127] The positive electrode material prepared in this embodiment, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8872 Co 0.0572 Mn 0.0485 (Zr-B) 0.0071 O2.

[0128] For other parameters, please refer to Table 1.

[0129] Embodiment 4

[0130] This embodiment is only different from Embodiment 1 in that,

[0131] (3) After uniformly mixing the matrix material and WO3 at a mass ratio of 1:0.007, it is put into an oxygen-containing atmosphere for secondary sintering treatment, and the temperature of the secondary sintering treatment is controlled at 500 °C to obtain a primary coating product.

[0132] The positive electrode material prepared in this embodiment, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8934 Co 0.0503 Mn 0.0489 (Zr-W-B)0.0074 O2。

[0133] For other parameters, see Table 1.

[0134] Example 5

[0135] The difference between this example and Example 1 is only that

[0136] (1) The nickel-cobalt-manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are in a molar ratio of [n(Ni) + n(Co) + n(Mn)]:n(Li) = 1.04:1, and Y2O3 is added in a mass ratio of Ni 0.9 Co 0.05 Mn 0.05 (OH)2:Y2O3 = 300:1, and they are crushed, ground and mixed to obtain a mixture; the mixture is heated to 550 °C in an oxygen atmosphere in a box furnace for 4 h of sintering treatment, and then heated continuously to 850 °C for 6 h of sintering treatment. The primary sintered product is broken to obtain a matrix material with a median particle size of 3 μm, and the matrix material is stored in a polyethylene bag and sealed with an aluminum-plastic film.

[0137] The positive electrode material prepared in this example includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8825 Co 0.0497 Mn 0.0483 (Y-Al-B) 0.0195 O2.

[0138] For other parameters, see Table 1.

[0139] Example 6

[0140] The difference between this example and Example 1 is only that

[0141] (1) The nickel-cobalt-manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are in a molar ratio of [n(Ni) + n(Co) + n(Mn)]:n(Li) = 1.04:1, and in accordance with Ni 0.9 Co 0.05 Mn 0.05(OH)2:Y2O3 was added to Y2O3 at a mass ratio of 300:1 to Sr(OH)2 (the mass ratio of Y2O3 to Sr(OH)2 was 1:2.5), and the mixture was obtained by pulverizing and grinding. The mixture was sintered at 550 °C for 4 h in an oxygen atmosphere in a box furnace, and then heated to 850 °C and sintered for 6 h. The primary sintered product was crushed by a gas crusher, with a single batch input of 2 kg, a pressure of 1 Mpa, and a classification parameter of 130 Hz to obtain the matrix material with a median particle size of 4 μm. The matrix material was stored in a polyethylene bag and sealed with an aluminum-plastic film.

[0142] The positive electrode material prepared in this example, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8835 Co 0.0498 Mn 0.0483 (Y - Sr - Al - B) 0.0184 O2.

[0143] For other parameters, see Table 1.

[0144] Example 7

[0145] The difference between this example and Example 1 is only that

[0146] (1) The nickel - cobalt - manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH were in a molar ratio of [n(Ni) + n(Co) + n(Mn)]:n(Li) of 1.04:1, and ZrO2 was added at a mass ratio of Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 of 300:1, and the mixture was obtained by pulverizing and grinding. The mixture was sintered at 550 °C for 4 h in an oxygen atmosphere in a box furnace, and then heated to 850 °C and sintered for 6 h. The primary sintered product was crushed by a gas crusher, with a single batch input of 2 kg, a pressure of 1 Mpa, and a classification parameter of 200 Hz for the matrix material with a median particle size of 1.5 μm. The matrix material was stored in a polyethylene bag and sealed with an aluminum - plastic film.

[0147] The positive electrode material prepared in this example, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr - Al - B) 0.0193 O2.

[0148] For other parameters, see Table 1.

[0149] Example 8

[0150] The difference between this example and Example 1 is only that

[0151] (1) The nickel-cobalt-manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are in a molar ratio of [n(Ni) + n(Co) + n(Mn)]:n(Li) of 1.04:1, and ZrO2 is added in a mass ratio of Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 of 300:1, and pulverized, ground and mixed to obtain a mixture; the mixture is heated to 550 °C in an oxygen atmosphere in a box furnace and sintered for 4 h, then heated to 850 °C and sintered for 6 h. The primary sintered product is crushed by a gas crusher, the single-batch input amount is 2 kg, the air pressure is 1 Mpa, the classification parameter is 50 Hz, the matrix material has a median particle size of 8 μm, and the matrix material is stored in a polyethylene bag and sealed with an aluminum-plastic film.

[0152] The positive electrode material prepared in this example, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr-Al-B) 0.0193 O2.

[0153] Figure 2 is the electron microscope image of the positive electrode material particles prepared in Example 8 of this application. As Figure 2 shown, there is a small amount of agglomeration of the positive electrode material particles. See Table 1 for other parameters.

[0154] Example 9

[0155] The difference between this example and Example 1 is only that

[0156] (1) The nickel-cobalt-manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are in a molar ratio of [n(Ni) + n(Co) + n(Mn)]:n(Li) of 1.04:1, and in accordance with Ni 0.9 Co 0.05 Mn 0.05ZrO2 was added in a mass ratio of (OH)2:ZrO2 of 300:1, and pulverized, ground and mixed to obtain a mixture; the mixture was sintered at 550 °C for 4 h in an oxygen atmosphere in a box furnace, then further heated to 850 °C and sintered for 6 h. The primary sintered product was crushed by a jet mill, with a single batch input of 2 kg, a gas pressure of 1 Mpa, a classification parameter of 100 Hz, a matrix material with a median particle size of 6 μm, and the matrix material was stored in a polyethylene bag and sealed with an aluminum-plastic film.

[0157] The positive electrode material prepared in this example, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr - Al - B) 0.0193 O2

[0158] For other parameters, see Table 1.

[0159] Example 10

[0160] The difference between this example and Example 1 is only that,

[0161] (1) The nickel - cobalt - manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2, LiOH were in a molar ratio of [n(Ni) + n(Co) + n(Mn)]:n(Li) of 1.04:1, and ZrO2 was added in a mass ratio of Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 of 300:1, and pulverized, ground and mixed to obtain a mixture; the mixture was sintered at 550 °C for 4 h in an oxygen atmosphere in a box furnace, then further heated to 850 °C and sintered for 6 h. The primary sintered product was crushed by a jet mill, with a single batch input of 2 kg, a gas pressure of 1 Mpa, a classification parameter of 160 Hz, a matrix material with a median particle size of 2.5 μm, and the matrix material was stored in a polyethylene bag and sealed with an aluminum - plastic film.

[0162] The positive electrode material prepared in this example, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr - Al - B) 0.0193 O2

[0163] For other parameters, see Table 1.

[0164] Example 11

[0165] This embodiment is only different from Embodiment 1 in that

[0166] (3) After uniformly mixing the matrix material and Al2O3 at a mass ratio of 1:0.007, it is put into an oxygen-containing atmosphere for secondary sintering treatment, and the temperature of the secondary sintering treatment is controlled at 600 °C to obtain a primary coated product.

[0167] The positive electrode material prepared in this embodiment, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8866 Co 0.0499 Mn 0.0485 (Zr - Al) 0.015 O2.

[0168] Other parameters are shown in Table 1.

[0169] Embodiment 12

[0170] This embodiment is only different from Embodiment 1 in that

[0171] (3) After uniformly mixing the matrix material and H3BO3 at a mass ratio of 1:0.01, it is put into an oxygen-containing atmosphere for secondary sintering treatment, and the temperature of the secondary sintering treatment is controlled at 500 °C to obtain a primary coated product.

[0172] The positive electrode material prepared in this embodiment, the positive electrode material includes a matrix material and a coating layer, and the chemical general formula of the positive electrode material is Li 1.01 Ni 0.8937 Co 0.0503 Mn 0.0489 (Zr - B) 0.0071 O2.

[0173] Other parameters are shown in Table 1.

[0174] Comparative Example 1

[0175] This embodiment is only different from Embodiment 1 in that

[0176] (1) The nickel-cobalt-manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are crushed, ground and mixed according to the molar ratio [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1 to obtain a mixture; the mixture is heated to 550 °C in an oxygen atmosphere in a box furnace for 4 h of sintering treatment, and then heated to 850 °C for 6 h of sintering treatment. The primary sintered product is crushed by an air crusher, the single-batch input amount is 2 kg, the air pressure is 1 Mpa, the classification parameter is 150 Hz, the median particle size of the positive electrode material is 3 μm, and the positive electrode material is stored in a polyethylene bag and sealed with an aluminum-plastic film.

[0177] The cathode material prepared in this example has a chemical general formula of Li 1.01 Ni 0.9 Co 0.05 Mn 0.05 O2, and other parameters are shown in Table 1.

[0178] Comparative Example 2

[0179] (1) Mix the nickel-cobalt-manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH in a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and add ZrO2 in a mass ratio of Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 of 300:1, and carry out pulverization, grinding and mixing to obtain a mixture; heat the mixture to 550 °C in an oxygen atmosphere in a box furnace for sintering treatment for 4 h, then continue to heat to 850 °C for sintering treatment for 6 h. The primary sintered product is crushed by an air crusher, the single-batch input amount is 2 kg, the air pressure is 1 Mpa, the classification parameter is 150 Hz, the matrix material, the median particle size is 3 μm, and the matrix material is stored in a polyethylene bag and sealed with an aluminum-plastic film.

[0180] Figure 3 is the electron microscope image of the cathode material prepared in Comparative Example 1 of this application, as Figure 3 shown, the surface of the cathode material is not coated, and the primary particles have distinct edges and corners.

[0181] Comparative Example 3

[0182] (1) Mix the nickel-cobalt-manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH in a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and carry out pulverization, grinding and mixing to obtain a mixture; heat the mixture to 550 °C in an oxygen atmosphere in a box furnace for sintering treatment for 4 h, then continue to heat to 850 °C for sintering treatment for 6 h. The primary sintered product is crushed by an air crusher, the single-batch input amount is 2 kg, the air pressure is 1 Mpa, the classification parameter is 150 Hz, the matrix material, the median particle size is 3 μm, and the matrix material is stored in a polyethylene bag and sealed with an aluminum-plastic film.

[0183] (2) Mix the matrix material and Al2O3 evenly at a mass ratio of 1:0.05, and then put it into an oxygen-containing atmosphere for secondary sintering treatment. The temperature of the secondary sintering treatment is controlled at 600 °C to obtain a primary coated product.

[0184] (3) The primary coating product was mixed evenly with H3BO3 in a mass ratio of 1:0.01 and then placed in an oxygen-permeable atmosphere for a third sintering treatment for 8 hours. The temperature of the third sintering treatment was controlled at 500°C to obtain a modified positive electrode material.

[0185] Test method:

[0186] (1) Test method for particle size of matrix material and positive electrode material:

[0187] The particle size test method refers to GB / T 19077-2016. Specifically, the particle size volume distribution of cathode particles dispersed in a specific aqueous solution can be measured using a Malvern Mastersizer 3000 laser particle size analyzer. In the particle size volume distribution of the cathode material, the volume fraction of particles with a diameter less than 1.2 μm is denoted as δ1%, and the volume fraction of particles with a diameter greater than 7 μm is denoted as δ2%.

[0188] (2) Testing method of specific surface area of positive electrode material:

[0189] The specific surface area of the positive electrode material was measured by the gas adsorption method. Specifically, Micromeritics Tristar II was used to perform N2 adsorption tests and calculate the adsorption values at different equilibrium pressures. The isothermal adsorption line was obtained and the specific surface area of the positive electrode material was calculated.

[0190] (3) Test method for the thickness of the coating layer of the positive electrode material:

[0191] Using a focused ion beam (FIB), the cathode material sample is thinned to obtain a flat and transparent cross-section. At the same time, a transmission electron microscope (TEM) is used to measure the thickness of each coating layer using the TEM's built-in ruler at a magnification of 50k-100k.

[0192] (4) Test method for bulk elastic modulus of positive electrode materials:

[0193] A Kistler pressure sensor was used to measure pressure. The sensor signal was processed by an amplifier for pressure data acquisition. A high-pressure pump from SITEC, Switzerland, was used to gradually apply pressure to the material. The positive electrode material decreases in volume under pressure, demonstrating its compressive properties, namely its bulk elastic modulus, defined as E = -V dp / dV, where p is the pressure applied to the positive electrode material and V is its volume.

[0194] (5) Test method for tap density of positive electrode material:

[0195] Use the American Quantacon tap density tester (model: DAT-4-220) and the steps are as follows:

[0196] Clean the graduated cylinder, and then weigh the mass of the graduated cylinder as m1; Add about 50 g of the sample into the graduated cylinder, try to make the surface of the sample horizontal, and wipe the surroundings with a tissue; Weigh the total mass of the sample and the graduated cylinder as m2; Place the graduated cylinder on the vibration platform and fix it with three symmetric fixed feet; Turn on the instrument and set the number of vibrations to 5000 times; Turn on the vibration switch, and the instrument will stop automatically after vibrating to the specified number of times; Take out the graduated cylinder and read the volume of the sample. If the surface of the sample is horizontal after tapping, directly read the volume; If it is in an inclined state, take the average value V of the readings at the highest point and the lowest point; Tapped density = (m2 - m1) / V.

[0197] (6) Test method for the tapped density of the positive electrode material:

[0198] The tapped density of the positive electrode material is tested using a Carver 4350 from the United States. The steps are as follows: Weigh 1 g of the sample and put it into a mold, press it with a pressure of 3 T for 30 s, and then measure the height after pressing to calculate the tapped density, which is the ratio of the mass to the volume after pressing.

[0199] (7) Test method for the powder conductivity in the positive electrode material:

[0200] Use a Mettler FE38 to test the powder conductivity of the positive electrode material.

[0201] (8) XRD test of the positive electrode material:

[0202] Use an XRD diffractometer (RIGAKU UITIMAIV) to characterize the positive electrode material, and obtain that the peak intensity of the (006) crystal plane of the positive electrode material is I 006 , the peak intensity on the (101) crystal plane is I 101 , and the peak intensity on the (102) crystal plane is I 102 . In the XRD pattern of the positive electrode material, the peak position of the positive electrode material on the (110) crystal plane is 2θ 110 , and the peak position on the (108) crystal plane is 2θ 108 .

[0203] (9) Test of the particle scraping angle of the positive electrode material:

[0204] Determine the particle scraping angle through a Hosokawa Micron Powder Systems PT-X.

[0205] (10) Test for the mass content of free lithium in the positive electrode material:

[0206] Immerse 5.0 g of the cathode material powder in 100 mL of deionized water and stir for 10 minutes in a sealed glass flask. After thorough stirring, filter the suspension to obtain a clear solution. Then, while stirring, titrate 90 mL of the clear solution by recording the pH curve during the addition of 0.1 mol / L HCl solution at a rate of 0.5 mL / min until the pH reaches 3. Determine the low concentrations of LiOH and Li2CO3 dissolved in deionized water by titration to obtain a reference voltage curve. The first plateau with an end point y1 (in mL) between pH 8 - 9 is for determining the mass content of OH - / H2O, and the second plateau with an end point y2 (in mL) between pH 4 - 6 is for determining the mass content of HCO3 - / H2CO3. The inflection point y1 between the first and second plateaus and the inflection point y2 after the second plateau are obtained from the corresponding minimum values of the derivative dpH / dVol of the pH curve. Then the results are expressed as weight percentages of LiOH and Li2CO3 as shown in the following formulas (1) and (2):

[0207]

[0208]

[0209] Free Li wt%=LiOH wt%*6.94 / 23.95+Li2CO3 wt%*6.94*2 / 73.89(3).

[0210] (11) Test of the lithium ion diffusion coefficient of the cathode material

[0211] Weigh 0.8 g of the cathode material and 0.1 g of conductive carbon black, put them into a ball milling jar and mix evenly. Then add 0.1 g of polytetrafluoroethylene into a blender, rotate at 5000 rpm for 10 min, and prepare a dry electrode film by hot pressing treatment with a roll press. Stick the dry electrode film on an aluminum foil and hot press to obtain a positive electrode plate.

[0212] Use a lithium sheet as the negative electrode, the separator is Celgard 2400, and the electrolyte is a 1 mol / L LiPF6 solution (the solvent is a mixture of ethyl methyl carbonate and dimethyl carbonate with a volume ratio of 1:1). Assemble it into a 2016 button cell in a glove box.

[0213] Activate for two weeks at 0.1C current, apply a pulsed potential to the system under conditions close to the equilibrium state using the potentiostatic intermittent titration technique, and then measure the current change.

[0214] The test was carried out using the CT2001A battery testing system of Wuhan Blue Electronic Co., Ltd. Charge-discharge tests were performed at a rate of 0.1C / 0.1C and 0.5C / 1C in the discharge range of 3.0V - 4.3V at 25°C to obtain the initial discharge specific capacity, and 100 cycle tests were carried out at a rate of 0.5C / 1C. The test results are shown in Table 1 and Table 2.

[0215] Table 1. Physical and chemical properties of the cathode materials prepared in the comparative examples and examples

[0216]

[0217] Table 2. Electrochemical performance test of the cathode materials

[0218]

[0219]

[0220] It can be seen from the examples and Table 1 and Table 2 that for the cathode material of the present application, the cathode material includes a matrix material and a coating layer on its surface. The presence of the coating layer can improve the conductivity of the cathode material particles and enhance the lithium ion migration rate, thereby improving the electronic and lithium ion conductivity of the cathode material, reducing the overpotential of the cathode electrode, effectively reducing the residual alkali on the surface of the cathode material, reducing the direct contact between the cathode material and the electrolyte, improving the interfacial stability of the contact between the cathode material particles and the electrolyte, improving the specific capacity of the cathode material while improving the cycle performance and rate performance of the cathode material. Controlling δ2 / δ1 within the above range during coating modification can effectively improve the connectivity inside the cathode electrode, increase the cohesion between the materials inside the cathode electrode, improve the contact between the powder material particles, reduce the interfacial impedance between the particles, increase the lithium ion diffusion rate of the cathode material, facilitate the formation of an integrated structure of the cathode material particles, improve the conductivity of the cathode material, effectively enhance the reaction kinetics of the cathode electrode, and have good dry electrode film-forming properties; it can also effectively alleviate the rebound rate of the cathode electrode after rolling, further improve the peel strength of the cathode electrode, so that the prepared cathode electrode can have the advantages of high energy density, high working voltage, and long cycle life.

[0221] Figure 4 is the electrochemical impedance spectrogram of the cathode materials prepared in Example 1, Example 6, Example 8 and Comparative Example 2 of the present application at low temperature, as Figure 4 shown. Since the sample of Example 1 has doping and coating and a suitable particle size, its impedance is significantly lower than that of the uncoated cathode material of Example 8 and also lower than that of the cathode material sample of Comparative Example 2 with a particle size volume distribution outside the appropriate range. According to the test data of Example 6, the double coating layer of Example 6 can further improve the crystal structure stability, which is beneficial to Li +Diffusion in the lattice bulk phase of the cathode material, the impedance within the particles of the cathode material decreases, and the impedance is the smallest compared to Example 1 and Example 8. The cathode material has a relatively high conductivity and Li + diffusion coefficient.

[0222] According to the test data of Examples 1 to 12 (Tables 1 and 2), due to the differences in coating elements, coatings, and particle sizes, there are also differences in the modified cathode materials. By synchronously optimizing the particle size volume distribution and coating modification of the cathode material, it is beneficial to exert the maximum synergistic effect and achieve the effect of 1 + 1 > 2.

[0223] According to the test data of Examples 1 to 12, the (I 006 +I 102 ) / I 101 value of the cathode material can reflect the orderliness of the hexagonal crystal structure of the cathode material, and there is a close relationship between the orderliness of its crystal structure and the performance of the cathode material. The peak intensity I 006 of the (006) crystal plane, the peak intensity I 101 of the (101) crystal plane, and the peak intensity I 102 of the (102) crystal plane of the cathode material measured by X-ray diffraction pattern satisfy the relationship: 0.5 ≤ (I 006 +I 102 ) / I 101 ≤ 1.00, indicating that the cathode material has good orderliness of the hexagonal crystal structure, and the cathode material is a layered structure. In an ideal situation, Li + occupies the 3b position in the crystal, and transition metals such as Ni, Co, and Mn randomly occupy the 3a position. However, due to the similar ionic radii of Li + and Ni 2+ , they often occupy each other's positions, resulting in cation mixing. When Ni atoms occupy the sites in the lithium layer, the intensity of the 101 peak rapidly decays, and the orderliness of the hexagonal crystal structure decreases, leading to a reduction in the structural orderliness of the cathode material.

[0224] Figure 5 This is a comparison chart of the overcharge performance of the cathode materials prepared in Example 1 and Comparative Example 3 of this application. As Figure 5 shown, the cathode material of Example 1 satisfies 0.5 ≤ (I 006 +I 102 ) / I 101 ≤ 1.00, and the cathode has good structural orderliness and better overcharge resistance performance.

[0225] According to the data of the examples, as the volume fraction δ1% of the particles with a particle size less than 1.2 μm in the cathode material increases, the (I 006 +I 102 ) / I101 The ratio also increases accordingly. When (I 006 + I 102 ) / I 101 > 1.00, the proportion of the volume of particles with a particle size less than 1.2 μm is too large, the positive electrode material particles are extremely easy to agglomerate, the fluidity between the particles decreases, the distribution of the active material on the electrode sheet is uneven, and the film-forming property of the dry electrode is poor. When (I 006 + I 102 ) / I 101 < 0.5, the proportion of the volume of particles with a particle size less than 1.2 μm is too small, the adsorption capacity between the particles decreases, the cohesive force between the particles decreases, and the cohesive force between the positive electrode material and the current collector also decreases. This will cause a small part of the positive electrode material to detach from the current collector and float in the electrolyte to contact the negative electrode material, resulting in a local battery short-circuit phenomenon; at the same time, the film-forming property of the dry electrode is poor.

[0226] In some embodiments, the relationship between the peak position 2θ of the (110) crystal plane and the peak position 2θ of the (108) crystal plane of the positive electrode material measured by using an X-ray diffraction pattern satisfies: |2θ 110 - 2θ 108 | = 0.2 - 0.6. When the value of |2θ 110 - 2θ 108 | is within the above range, as 110 - 2θ 108 | is shown, the diffraction peaks of (108) and (110) are significantly split, indicating that the positive electrode material forms a good layered structure, which can promote the rapid deintercalation and intercalation of Li Figure 6 in the crystal phase structure of the matrix material and the crystal structure of the coating layer, endowing the positive electrode material with high rate performance and better kinetic stability, and showing low impedance. + For the positive electrode material prepared in Comparative Example 1, without doping and coating treatment, the cation mixing in the positive electrode material is aggravated, Ni atoms occupy the lithium-ion sites in the lithium layer, and in the XRD of the positive electrode material, the intensity of the 101 peak rapidly decays, that is, the order of the hexagonal crystal structure of the positive electrode material decreases, resulting in an increase in the interfacial impedance between the particles of the positive electrode material, a significant decrease in the lithium-ion diffusion rate of the positive electrode material compared with Example 1, and a significant decrease in the conductivity of the positive electrode material.

[0227]

[0228] The positive electrode material prepared in Comparative Example 2 was only doped and not coated. The residual alkali content on the surface of the positive electrode material increased, and the residual alkali on the surface of the positive electrode material aggravated the cation rearrangement phenomenon on the surface of the positive electrode material, thereby reducing the structural order of the positive electrode material. In the XRD of the positive electrode material, the intensity of the 101 peak rapidly decayed, that is, the order of the hexagonal crystal structure of the positive electrode material decreased, resulting in an increase in the interfacial impedance between the particles of the positive electrode material. The lithium ion diffusion rate of the positive electrode material decreased significantly compared with that of Example 1, and the conductivity of the positive electrode material also decreased significantly.

[0229] The positive electrode material prepared in Comparative Example 3 was only coated and not doped. The cation mixing in the positive electrode material was aggravated, and Ni atoms occupied the lithium ion sites in the lithium layer. In the XRD of the positive electrode material, the intensity of the 101 peak rapidly decayed, that is, the order of the hexagonal crystal structure of the positive electrode material decreased, resulting in an increase in the interfacial impedance between the particles of the positive electrode material. The lithium ion diffusion rate of the positive electrode material decreased significantly compared with that of Example 1, and the conductivity of the positive electrode material also decreased significantly.

[0230] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical scope of the present invention, various simple deformations can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature in any way. These simple deformations and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A cathode material, characterized in that, At least a part of the surface of the positive electrode material has a coating layer; The chemical general formula of the positive electrode material is Li a Ni x Co y M z N b O2, where 0.95 ≤ a ≤ 1.1, 0.6 ≤ x < 1, 0 < y < 0.4, 0 < z < 0.4, x + y + z + b = 1, 0 < b < 0.4, M is Mn and / or Al, and N is a coating element; In the particle size volume distribution map of the positive electrode material, the volume ratio of particles with a particle size less than 1.2 μm is δ1%, and the volume ratio of particles with a particle size greater than 7 μm is δ2%, and 1 ≤ δ2 / δ1 ≤ 10 is satisfied, where 0.46 < δ1 < 4.6 and 3 < δ2 < 10; The positive electrode material, conductive carbon black, and polytetrafluoroethylene are mixed in a mass ratio of 8:1:1 and then hot-pressed to obtain a dry electrode film, and the pole piece rebound rate of the dry electrode film < 20%; 2. The cathode material according to claim 1, characterized in that, In the XRD pattern of the positive electrode material, the peak intensity of the positive electrode material at the (006) crystal plane is I 006 , the peak intensity at the (101) crystal plane is I 101 , the peak intensity at the (102) crystal plane is I 102 , 0.5 ≤ (I 006 + I 102 ) / I 101 ≤ 1.

00.

3. The cathode material according to claim 2, wherein, In the XRD pattern of the positive electrode material, the peak position of the positive electrode material on the (110) crystal plane is 2θ 110 , and the peak position on the (108) crystal plane is 2θ 108 , which satisfies 0.2 ≤ ∣2θ 110 - 2θ 108 ∣ ≤ 0.

6.

4. The cathode material according to claim 1, characterized in that, The positive electrode material satisfies at least one of the following characteristics: (1) N includes at least one of Y, W, Sr, Zr, La, Ce, Co, Ti, Mg, Al, Sb, Nb, Ta, V, B, S, and Ba; (2) The coating layer includes at least one of an oxide of N element, a hydroxide of N element, and a lithium composite oxide of N element; (3) The coating layer includes a first coating layer and a second coating layer, the thickness of the first coating layer is 2 nm to 100 nm, and the thickness of the second coating layer is 2 nm to 80 nm.

5. The cathode material according to any one of claims 1 to 4, characterized in that, The positive electrode material satisfies at least one of the following characteristics: (1) The particle size D of the positive electrode material 50 is 2 μm to 6 μm; (2) The specific surface area of the positive electrode material is 0.2 m 2 / g to 1.3 m 2 / g; (3) The mass content of free lithium in the positive electrode material is 500 ppm to 2000 ppm; (4) The tap density of the positive electrode material is 3.0 g / cm 3 to 3.6 g / cm 3 ; (5) The tap density of the positive electrode material is 0.6 g / cm 3 ~2.0 g / cm 3 ; (6) The powder conductivity of the positive electrode material is 1×10 2 S / cm to 6×10 -3 S / cm under a pressure of 8 kN / cm -2 ; (7) The positive electrode material contains single crystal grains with the same orientation, where the average particle size of the single crystal grains is 1 μm to 5 μm.

6. The cathode material according to any one of claims 1 to 4, characterized in that, The lithium ion diffusion coefficient of the positive electrode material is 1×10 -9 cm 2 / s to 1×10 -6 cm 2 / s.

7. The cathode material according to any one of claims 1 to 4, characterized in that, The spatula angle of the positive electrode material particles is between 10° and 80°.

8. A battery, characterized in that, The battery includes the positive electrode material according to any one of claims 1 to 7.

Images