Positive electrode material, positive electrode sheet and battery

Abstract

A positive electrode material, a positive electrode sheet and a battery. The general chemical formula of the positive electrode material is LiaNixCoyMzNbO2, wherein 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 metallic element. In the volume-based particle size distribution plot of the positive electrode material, the volume proportion of particles with a particle size of less than 1.2 μm is δ1%, and the volume proportion of particles with a particle size of more than 7 μm is δ2%, both satisfying 1≤δ2 / δ1≤10. The positive electrode material can reduce the inter-particle interfacial impedance of the positive electrode material, thereby enabling the positive electrode material to meet both the electrochemical performance requirements and the requirements of a preparation process for a dry electrode.

Description

Positive electrode material, positive electrode sheet and battery Cross-references to related applications

[0001] This application claims priority to Chinese patent application filed on May 9, 2024, with application number 202410584784.0 and entitled "Cathode Material and Battery". Technical Field

[0002] This invention relates to the field of cathode material technology, and more particularly to cathode materials, cathode plates, and batteries. Background Technology

[0003] With the rapid development of the new energy industry, lithium-ion batteries urgently need to balance high energy density, high operating voltage, long cycle life, and high safety. The cathode material is a major component of lithium-ion batteries and has a direct and dominant impact on the performance of the lithium-ion battery pack; its performance directly affects the overall performance of the lithium-ion battery.

[0004] Among cathode materials, high-nickel ternary cathode material LiMO2 (where M is typically Ni, Co, Mn, or Al, with Ni having a molar fraction of 0.6 or higher) is widely used in lithium-ion batteries due to its high specific capacity, high packing density, and low cost. However, as the nickel content in the cathode material increases, it leads to problems such as faster capacity decay, structural instability, deterioration of thermal performance, and higher residual alkali content, thus limiting its application.

[0005] Meanwhile, compared to the wet electrode preparation process, the dry electrode preparation process lacks the wetting process between solvent materials and powder materials, resulting in poor contact between powder material particles, high interfacial impedance, and low adhesion between material particles in the electrode sheet, which significantly affects the fast charging performance, capacity, and stability of lithium-ion batteries.

[0006] Therefore, how to reduce the interparticle impedance of cathode materials so that the cathode materials can meet the electrochemical performance requirements and also match the dry electrode preparation process, so that the prepared electrode can have the advantages of high energy density, high operating voltage and long cycle life, remains a technical problem that needs to be solved. Summary of the Invention

[0007] The purpose of this application is to provide a positive electrode material, a positive electrode sheet, and a battery that can improve the structural stability and cycle stability of the positive electrode material, while reducing the interparticle interface impedance of the positive electrode material.

[0008] In a first aspect, this application provides a cathode material, wherein at least a portion of the surface of the cathode material has a coating layer; the general chemical formula of the cathode material is Li. a Ni x Co y Mz 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 the coating element; in the particle size volume distribution spectrum of the cathode material, the volume ratio of particles with a particle size less than 1.2μm is δ1%, the volume ratio of particles with a particle size greater than 7μm is δ2%, and 1≤δ2 / δ1≤10 is satisfied.

[0009] Secondly, this application provides a cathode material with the general chemical formula LiaNixCoyMzNbO2, wherein 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 element includes at least one of Y, W, Sr, Zr, La, Ce, Co, Ti, Mg, Al, Sb, Nb, Ta, V, B, S and Ba; in the particle size distribution spectrum of the cathode material, the volume percentage of particles with a diameter less than 1.2 μm is δ1%, the volume percentage of particles with a diameter greater than 7 μm is δ2%, and satisfies 1≤δ2 / δ1≤10.

[0010] Thirdly, this application provides a positive electrode sheet, including any of the positive electrode materials described in the first aspect.

[0011] Fourthly, this application provides a battery, the battery comprising any of the positive electrode materials described in the first aspect and the second aspect or the positive electrode sheet described in the third aspect.

[0012] Compared with the prior art, the present invention has at least the following beneficial effects:

[0013] The cathode material proposed in this application has a particle size distribution spectrum in which particles smaller than 1.2 μm account for δ1% of the volume, and particles larger than 7 μm account for δ2% of the volume, where 1 ≤ δ2 / δ1 ≤ 10. This particle size distribution allows larger particles to act as a framework in the dry electrode sheet, while smaller particles connect to larger particles. This effectively improves the internal connectivity of the cathode sheet, increases the cohesive force between materials within the cathode sheet, and enhances the contact between powder particles. Simultaneously, it effectively reduces the porosity of the electrode sheet, lowers the interfacial impedance between particles, and facilitates the formation of an integrated structure of cathode material particles. This effectively enhances the reaction kinetics of the cathode sheet, resulting in good film formation properties in the dry electrode. Furthermore, it effectively alleviates the rebound rate after rolling of the cathode sheet, further improving the peel strength of the cathode sheet. This allows the resulting cathode sheet to possess advantages such as high energy density, high operating voltage, and long cycle life. However, when the particle size distribution of the cathode material is set to δ2 / δ1>10 or δ2 / δ1<1, it will lead to the presence of excessive primary particle agglomerates or excessive microparticle breakage, thereby affecting the performance of the cathode material and the electrode sheet. This application can precisely control the particle size distribution of the cathode material through the above-mentioned particle size limits and ranges. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Figure 1 is an electron microscope image of the cathode material particles prepared in Example 1 of this application.

[0016] Figure 2 is an electron microscope image of the cathode material particles prepared in Example 8 of this application.

[0017] Figure 3 is an electron microscope image of the cathode material particles prepared in Comparative Example 1 of this application.

[0018] Figure 4 shows the electrochemical impedance spectroscopy of the cathode materials prepared in Examples 1, 6, 8 and Comparative Example 2 of this application at low temperatures.

[0019] Figure 5 is a comparison of the overcharge performance of the cathode materials prepared in Example 1 and Comparative Example 3 of this application.

[0020] Figure 6 is an X-ray diffraction pattern of the cathode material prepared in Example 6 of this application. Detailed Implementation

[0021] To better understand 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.

[0022] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0024] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0025] Compared to wet electrode fabrication processes, dry electrode fabrication lacks the wetting process between solvent and powder materials, resulting in poor contact between powder particles, high interfacial impedance, and low adhesion between material particles in the electrode sheet. This significantly affects the fast-charging performance, capacity, and stability of lithium-ion batteries.

[0026] In a first aspect, this application provides a cathode material, wherein at least a portion of the surface of the cathode material has a coating layer, and the general chemical formula of the cathode 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 the covering element;

[0027] In the particle size distribution spectrum of the cathode material, the volume percentage of particles with a diameter less than 1.2 μm is δ1%, and the volume percentage of particles with a diameter greater than 7 μm is δ2%, and the condition 1≤δ2 / δ1≤10 is satisfied.

[0028] The cathode material proposed in this application has a particle size distribution spectrum in which particles smaller than 1.2 μm account for δ1% of the volume, and particles larger than 7 μm account for δ2% of the volume, where 1 ≤ δ2 / δ1 ≤ 10. This particle size distribution allows larger particles to act as a framework in the dry electrode sheet, while smaller particles connect to larger particles. This effectively improves the internal connectivity of the cathode sheet, increases the cohesive force between materials within the cathode sheet, and enhances the contact between powder particles. Simultaneously, it effectively reduces the porosity of the electrode sheet, lowers the interfacial impedance between particles, and facilitates the formation of an integrated structure of cathode material particles. This effectively enhances the reaction kinetics of the cathode sheet, resulting in good film formation properties in the dry electrode. Furthermore, it effectively alleviates the rebound rate after rolling of the cathode sheet, further improving the peel strength of the cathode sheet. This allows the resulting cathode sheet to possess advantages such as high energy density, high operating voltage, and long cycle life. When the particle size distribution of the cathode material is set to δ2 / δ1>10, it will lead to the existence of excessive primary particle agglomerates. When δ2 / δ1<1, it will cause primary particles to break down and generate excessive microparticles, thereby affecting the performance of the cathode material and the electrode sheet. This application can precisely control the particle size distribution of the cathode material through the above-mentioned particle size limits and ranges.

[0029] In this application, the general chemical formula of the cathode 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, and 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 cathode material is within the above range, the battery using this cathode material has a high charge-discharge specific capacity. When the molar content of Li in the cathode material is low, Ni easily enters the Li layer, and cation mixing is obvious, leading to poor stability of electrochemical cycling. When the molar content of Li in the cathode material is high, excess residual alkali will form on the material surface, which can easily form a jelly-like state during slurry preparation, affecting the coating effect; secondly, the impact of residual alkali on the electrochemical performance of the cathode material is mainly reflected in increasing irreversible capacity loss and deteriorating cycle performance.

[0030] 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.; and 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., without limitation. When the total molar content of Ni, Co, and M in the cathode material is within the above range, the battery exhibits good electrochemical performance. When the total molar content of Ni, Co, and M in the cathode material is relatively high, the battery has a high initial irreversible capacity, but poor cycle and rate performance. When the total molar content of Ni, Co, and M in the cathode material is low, the battery capacity is low and cannot meet the energy density requirements, affecting practical applications. The value of b can be, for example, 0.01, 0.05, 0.1, 0.2, 0.3, 0.35, or 0.39, etc.

[0031] In some embodiments, element N is a metallic element. More specifically, in some embodiments, at least a portion of the surface of the cathode material has a coating layer, and element N is a coating element, including at least one selected from Y, W, Sr, Zr, La, Ce, Co, Ti, Mg, Al, Sb, Nb, Ta, V, B, S, and Ba. The coating element can be obtained by characterizing the surface of the cathode material, for example, using energy-dispersive X-ray spectroscopy (EDS).

[0032] In some embodiments, in the particle size distribution map of the cathode material, the volume percentage of particles smaller than 1.2 μm is δ1%, and the volume percentage of particles larger than 7 μm is δ2%, with the values ​​of δ1 and δ2 satisfying 1 ≤ δ2 / δ1 ≤ 10. 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, or other values ​​within the above range, which are not limited here. Setting the particle size distribution to δ2 / δ1 > 10 will lead to the presence of excessive primary particle agglomerates, while δ2 / δ1 < 1 will lead to the breakage of primary particles, generating excessive fine powder, thereby affecting the performance of the cathode material and the electrode sheet. When the volume ratio of particles smaller than 1.2 μm to particles larger than 7 μm is controlled within the aforementioned range, the larger particles, under the action of the binder, can act as a supporting skeleton in the electrode, effectively supporting the electrode. The smaller particles can connect with the larger particles within the electrode, improving internal connectivity, increasing cohesion between particles, enhancing particle contact, reducing inter-particle resistance, and effectively enhancing the reaction kinetics of the electrode. Furthermore, controlling the particle size and volume distribution of the positive electrode material within the aforementioned range can further mitigate the rebound rate after electrode rolling, improve the electrode peel strength, and enhance the battery's cycle stability, safety, and fast-charging performance.

[0033] However, when δ2 / δ1 is too large, meaning there is a higher proportion of larger particles in the positive electrode material, the adsorption capacity and adhesion between particles decrease, and the adhesion between the positive electrode material and the current collector also decreases. This can cause a small portion of the positive electrode material to detach from the current collector and come into contact with the negative electrode material in the electrolyte, resulting in a localized short circuit. When δ2 / δ1 is too small, meaning there is a higher proportion of smaller particles in the positive electrode material, the positive electrode material particles are prone to agglomeration, reducing the fluidity between particles. This leads to uneven distribution of active materials in the electrode sheet, uneven electrochemical reaction, and localized overcharging and over-discharging, resulting in decreased battery performance. At the same time, excessively small particles are prone to surface defects, inducing battery polarization and reducing the stability of the positive electrode sheet.

[0034] In some implementations, 0.1 < δ1 < 10, that is, the volume percentage of particles with a diameter less than 1.2 μm can be 9.9%, 8.8%, 7.6%, 6.5%, 4%, 3.5%, 3%, 2.5%, or 0.15%, etc., or other values ​​within the above range, which are not limited here.

[0035] In some implementations, 0.02 < δ2 < 10, meaning that the volume percentage of particles with a diameter greater than 7 μm can be 9.9%, 8.8%, 7.6%, 6.5%, 5%, 4%, 3.5%, 3.0%, 2.5%, or 0.025%, etc.

[0036] Understandably, when δ1 < 0.1% and δ2 > 10%, the volume ratio of small particles is too small, while the volume ratio of large particles is too large. This reduces the contact area between particles and between particles and the current collector, resulting in insufficient adhesion. Consequently, the positive electrode material will detach from the current collector, and the cycle stability of the positive electrode sheet will decrease. When δ1 > 10% and δ2 < 0.02%, the volume ratio of small particles is too large, while the volume ratio of large particles is too small. This reduces the fluidity between particles, resulting in uneven dispersion of the positive electrode material particles, conductive agent, and binder, which in turn affects the film formation properties of the dry electrode.

[0037] In some embodiments, in the XRD pattern of the cathode material, the peak intensity of the cathode material on the (006) crystal plane is I. 006 The peak intensity on the (101) crystal plane is I. 101 The peak intensity on the (102) crystal plane is I. 102 , 0.5≤(I 006 +I 102 ) / I 101 ≤1.00. (I 006 +I 102 ) / I 101 The ratio can be 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 1.0, or other values ​​within the above range, which are not limited here.

[0038] In this application, the cathode material (I) 006 +I 102 ) / I 101 It can reflect the ordered nature of the crystal structure of the cathode material, among which Li + Occupying position 3b, transition metals such as Ni, Co, and Mn randomly occupy position 3a, but due to Li + and Ni 2+ Ions with similar radii often occupy each other's positions, forming cation mixing. When Ni atoms occupy sites in the lithium layer, the intensity of the 101 peak in the cathode material rapidly decreases, leading to a reduction in the structural order of the cathode material. There is a close relationship between the orderliness of the crystal structure of the cathode material and its performance. The XRD spectrum of the cathode material satisfies 0.5 ≤ (I 006 +I 102 ) / I 101 ≤1.00 is beneficial for reducing the degree of cation mixing in the cathode material; improving the orderliness of the cathode material structure and reducing the interfacial impedance between particles; increasing the lithium-ion diffusion rate of the cathode material, which in turn is beneficial for the cathode material particles to form an integrated structure and enhance the reaction kinetics of the cathode electrode.

[0039] Furthermore, through numerous experiments, it was found that (I 006 +I 102 ) / I 101 The value and the particle volume ratio δ1 have a synergistic relationship, (I 006 +I 102 ) / I 101 The value increases with the increase of δ1, which can also indirectly reflect the volume ratio of fine particles. This application controls (I 006 +I 102 ) / I 101 Maintaining a value within the range of 0.5 to 1.0 while simultaneously controlling 1≤δ2 / δ1≤10 effectively regulates the close contact between powder material particles, improves the internal connectivity of the positive electrode, reduces interfacial resistance between particles, enhances the lithium-ion diffusion rate of the positive electrode material, and improves its rate performance. It also improves the film-forming properties of the dry electrode. This is because the high structural order and low cation mixing degree of the positive electrode material are conducive to Li+ diffusion, increasing the rate. Furthermore, controlling the volume ratio of small particles promotes inter-particle contact, reduces contact resistance, and further facilitates Li+ diffusion, thus increasing the rate.

[0040] From a crystal structure analysis perspective, when (I) 006 +I 102 ) / I 101 When the ratio is greater than 1.00, the degree of cation mixing in the cathode material increases, the structural order of the material decreases, and lithium-ion insertion / extraction is hindered. It should be noted that the structural order of the cathode material includes the structural order of the matrix material and the structural order of the coating layer. The formation of residual alkali on the cathode material surface exacerbates the ion rearrangement phenomenon on the cathode material surface, thereby reducing the structural order of the coating layer and hindering Li+ diffusion. Therefore, controlling the ratio to 0.5 ≤ (I0.00) is crucial. 006 +I 102 ) / I 101 When the value is ≤1.00, the structural order of the cathode material is improved, which helps to reduce the interfacial impedance between particles, increase the lithium-ion diffusion rate of the cathode material, and enhance the reaction kinetics of the cathode electrode.

[0041] In some embodiments, in the XRD pattern of the cathode material, the peak position of the cathode material on the (110) crystal plane is 2θ. 110 The peak position on the (108) crystal plane is 2θ. 108 It satisfies 0.2≤|2θ 110 -2θ 108 |≤0.6.2θ 110 -2θ 108The absolute value can be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, or 0.6, etc., and is not limited here. In this application, 0.2 ≤ |2θ is controlled. 110 -2θ 108 |≤0.6, the (108) and (110) diffraction peaks are clearly split, indicating that the cathode material forms a good layered structure, which can promote the formation of Li + Rapid insertion and extraction in the crystal structure and surface layer endows the cathode material with high rate performance and better kinetic stability, and reduces the impedance of the cathode material.

[0042] In some embodiments, at least a portion of the surface of the cathode material has a coating layer. The coating layer helps enhance the structural and chemical stability of the cathode material, reduces the precipitation of lattice oxygen, improves the phase transition reversibility of the cathode material's crystal structure, and can also suppress the slippage of the crystal layer structure and the generation of intracrystalline microcracks, reducing cracks generated in the cathode material during cycling and improving the cycling stability of the cathode material; it can also facilitate the rapid insertion and extraction of lithium ions, which is beneficial to improving the rate performance and capacity retention of the cathode material.

[0043] In some embodiments, the coating layer includes at least one of nitrogen oxides, nitrogen hydroxides, and nitrogen-containing lithium composite oxides. Understandably, the coating layer on the primary particle surface can improve the smoothness of the cathode material particle surface, while simultaneously isolating the cathode material from direct contact with the electrolyte and enhancing the particle flowability of the cathode material. This results in more uniform dispersion of the cathode material, conductive agent, and binder, further improving the film uniformity of the dry electrode.

[0044] In some embodiments, the coating layer is a double coating layer, including a first coating layer located on the inner side and covering the substrate surface, and a second coating layer located on the outer side and covering the first coating layer. The total thickness of the coating layer is 2 nm to 180 nm. The inner side refers to the side closer to the coated object, and the outer side refers to the side farther away from the coated object. Understandably, if the coating layer is too thin, the contact inhibition effect between the cathode material and the electrolyte will decrease; if the coating layer is too thick, the coating material on the surface of the cathode material will form small metal oxide particles, which will increase the roughness of the cathode material particles, reduce particle flowability, and lead to a decrease in the uniformity of dispersion of the cathode material with the conductive agent and binder, resulting in poor film formation of the dry electrode.

[0045] In this application, the double-layer coating structure on the surface of the matrix material effectively improves the contact between powder particles, forming an integrated structure and enhancing the structural stability of the cathode material. Here, the matrix material refers to cathode material particles without any coating.

[0046] In some embodiments, the thickness of the first coating layer is 2nm to 100nm, specifically 2nm, 5nm, 6nm, 8nm, 10nm, 12nm, 15nm, 20nm, 30nm, 40nm, 50nm, 80nm, 90nm or 100nm, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0047] In some embodiments, the first coating layer includes a first coating element, which includes at least one selected from Y, W, Sr, Zr, La, Co, Ti, Mg, Al, Sb, Nb, and Ta. The first coating element is a crystal modifying element, and the distribution of the modifying element within the crystal optimizes the Li content inside the cathode particles. + Migration channels reduce the impedance increase caused by the large particle diameter. The coating elements can be characterized, for example, by energy-dispersive X-ray spectroscopy (EDS) of the cathode material surface.

[0048] In some embodiments, the thickness of the second coating layer is 2nm to 80nm, specifically 2nm, 5nm, 6nm, 8nm, 10nm, 12nm, 15nm, 20nm, 30nm, 40nm, 50nm or 80nm, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0049] In some embodiments, the second coating layer includes a second coating element, which includes at least one selected from Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb. The second coating element is a coating modification element, and the presence of the second coating layer allows lithium ions to pass through rapidly, assisting in the rapid insertion and extraction of lithium ions, thereby effectively improving the rate performance of the cathode material.

[0050] In this application, the coating material in the double-layer coating structure reacts with residual lithium on the particle surface, thus reducing the residual active lithium on the cathode material surface. This effectively improves the capacity retention of the cathode material and avoids direct contact between the cathode material and the electrolyte, enhancing the coating / main interface stability and consequently improving the cycle stability of the ternary cathode material. The synergistic effect of coating modification and crystal structure doping modification of the cathode material endows the cathode material with excellent structural stability and a high ion diffusion coefficient.

[0051] In some embodiments, the free lithium content in the cathode material is 500 ppm to 2000 ppm by mass. Specifically, it can be 500 ppm, 550 ppm, 600 ppm, 650 ppm, 700 ppm, 800 ppm, 1000 ppm, 1500 ppm, or 2000 ppm, etc., and is not limited here. It is understood that controlling the surface free lithium content of the cathode material within the above range indicates 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.

[0052] In some embodiments, the cathode material is a single-crystal cathode material. In this application, controlling the cathode material to have a single-crystal structure helps to further avoid the loss of residual unstable lattice oxygen, and has a dual effect of inhibiting the in-plane migration of transition metal ions, thereby inhibiting slip and the generation of intracrystalline microcracks, and thus improving the cycle stability of the material.

[0053] In some embodiments, the cathode material contains single grains with the same orientation, wherein the average grain size of the single grain is 1 μm to 5 μm. The cathode material particles of this application contain single grains with the same orientation, ranging from 1 to 5 μm in size. This can control the crystal structure of the cathode material and reduce the generation of oxygen vacancies in the bulk phase of the cathode material. At the same time, it works synergistically with the coating layer on the surface of the cathode material to help avoid the loss of residual unstable lattice oxygen. This dual effect inhibits the in-plane migration of transition metal ions, thereby suppressing slip and the generation of intragranular microcracks, and thus improving the cycle stability of the material.

[0054] It should be noted that the grain orientation of the cathode material can be tested by electron backscatter diffraction (EBSD) at least. Ten individual grains with the same orientation are randomly selected to measure the grain size of each grain, and the arithmetic mean is taken as the average grain size of the individual grains.

[0055] It is important to note that the difference between single-crystal cathode materials and polycrystalline cathode materials (i.e., polycrystalline secondary particles) lies in the fact that the smallest particles in polycrystalline secondary particles are formed by the agglomeration of nanoscale primary particles. In contrast, the smallest particles in single-crystal cathode materials are typically micrometer-sized single primary particles. Generally, in addition to EBSD testing, scanning electron microscopy (SEM) and other characterization methods can be used to determine whether the obtained cathode product is a single-crystal material. For example, for single-crystal cathode materials, SEM can characterize the morphology of single-crystal particles, showing that they are generally regular or irregular spherical in shape, with no significant particle agglomeration. EBSD can also characterize the orientation of single-crystal cathode materials. EBSD observation shows that at least one grain has the same color, indicating that at least one grain has the same orientation; grains with the same orientation are single crystals. It is important to specifically clarify that the "single-crystal cathode material" known to those skilled in the art is not a "single crystal" in the strict crystallographic sense. In crystallography, an ideal single crystal refers to a crystal with completely identical arrangement and orientation. However, due to limitations such as impurities, strain, and crystal defects, ideal single crystals are very rare and difficult to produce in the laboratory. Therefore, the single-crystal cathode materials known in the art are actually more "single-crystal-like" cathode materials, which only differ from polycrystalline materials composed of numerous small primary particles in size, exhibiting a large particle size similar to single crystals.

[0056] In some embodiments, the volume distribution particle size D of the cathode material 50 The particle size is 2μm to 6μm, specifically 2μm, 3μm, 4μm, 5μm, 5.5μm, or 6μm, or other values ​​within the above range; no limitation is made here. The particle size D of the cathode material... 50 When the particle size is too large, the increased particle size lengthens the lithium-ion transport path, limiting the lithium-ion diffusion kinetics within the particles and reducing the rate performance of the cathode material. The particle size D of the cathode material... 50 If the particle size is too small, the specific surface area of ​​the cathode material increases, requiring more binder during dry electrode fabrication and leading to a decrease in the specific capacity of the cathode. Controlling the particle size of the cathode material within the aforementioned range can improve both the specific capacity and the reaction kinetics of the cathode material, thereby enhancing its rate performance, especially during fast charging.

[0057] In some implementations, the specific surface area of ​​the cathode material is 0.2 m². 2 / g~1.3m 2 / g, specifically 0.2m 2 / g, 0.3m 2 / g, 0.5m 2 / g, 0.8m 2 / g, 1.0m 2 / g, 1.1m2 / g, 1.2m 2 / g or 1.3m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. 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.

[0058] In some embodiments, the tap density of the cathode material is 0.6 g / cm³. 3 ~2.0g / cm 3 Specifically, it can be 0.6 g / cm³ 3 0.8g / cm 3 1.0g / cm 3 1.2g / cm 3 1.5g / cm 3 1.8g / cm 3 1.9g / cm 3 Or 2.0g / cm 3 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0059] In some embodiments, the compaction density of the cathode material is 3.0 g / cm³. 3 ~3.6g / cm 3 Specifically, it can be 3.0 g / cm³. 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 3 3.4g / cm 3 3.5g / cm 3 Or 3.6g / cm 3 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0060] In some embodiments, the positive electrode material is at 8 kN / cm 2 Powder conductivity under pressure 1*10 -3 S / cm~6*10 -2 S / cm, specifically 1*10 -3 S / cm, 2*10 -3 S / cm, 4*10 -3 S / cm, 510 -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 -2S / cm, etc., can also be other values ​​within the above range, and are not limited here.

[0061] In some embodiments, the lithium-ion diffusion coefficient of the cathode material is 1*10⁻⁶. -9 cm 2 / s~1*10 -6 cm 2 / s. The lithium-ion diffusion coefficient was measured at 100% SOC (Stage of Charge) after the cathode material was assembled into a coin cell.

[0062] In some embodiments, the scraping 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°, or other values ​​within the above range, which are not limited here. Controlling the scraping angle of the positive electrode material particles within the above range increases the fluidity of the particles, improves the uniformity of dispersion of the particles with the conductive agent and binder, and enhances the film-forming properties of the dry electrode. If the scraping angle α > 80°, the fluidity of the positive electrode material particles decreases, and the uniformity of dispersion of the particles with the conductive agent and binder decreases; if the scraping angle α < 10°, the good fluidity of the positive electrode material particles corresponds to a higher proportion of larger particles, resulting in relatively poor particle adsorption, weak adhesion between particles and between particles and the current collector, and poor film-forming properties of the dry electrode.

[0063] Secondly, this application provides a method for preparing a positive electrode material, which includes the following steps:

[0064] Step S10: The mixture containing the cathode material precursor, lithium-containing compound and dopant is subjected to a first sintering treatment, and the first sintering product is crushed to obtain a matrix material. In the particle size distribution spectrum of the matrix material, the volume ratio of particles with a particle size less than 1 μm is δ3%, the volume ratio of particles with a particle size greater than 7 μm is δ4%, and the condition 0.01≤δ3 / δ4≤3.5 is met.

[0065] In some implementations, the general chemical 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.

[0066] In some embodiments, the lithium-containing compound includes at least one selected from lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate. Preferably, the lithium-containing compound includes lithium hydroxide, and specifically, lithium hydroxide includes at least one selected from anhydrous lithium hydroxide and lithium hydroxide monohydrate.

[0067] In some embodiments, the molar ratio of metallic Me to Li in the lithium-containing compound in the cathode material precursor 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., where Me represents the molar content of all metals in the cathode material precursor. Controlling the molar ratio of metallic Me 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 cathode material. Preferably, 1.0 < Li / Me < 1.02.

[0068] In some embodiments, the mass ratio of the cathode material precursor to the dopant is (50-500):1, specifically 50:1, 80:1, 100:1, 150:1, 200:1, 250:1, 300:1, 400:1, 450:1 or 500:1, etc., which are not limited here.

[0069] 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.

[0070] In some embodiments, a single sintering process includes a first sintering stage and a second sintering stage. The temperature of the first sintering stage is 400℃ to 700℃, specifically 400℃, 420℃, 450℃, 500℃, 520℃, 550℃, 600℃, 650℃, or 700℃, etc., or other values ​​within the aforementioned range, which are not limited here. The duration of the first sintering stage is 1 hour to 6 hours, specifically 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 5.5 hours, and 6 hours, etc., or other values ​​within the aforementioned range, which are not limited here.

[0071] In some embodiments, the temperature of the second sintering stage is 700℃ to 950℃. Specifically, the temperature of the second sintering stage is 700℃, 720℃, 750℃, 800℃, 820℃, 850℃, 900℃, or 950℃, etc., or other values ​​within the above range, which are not limited here. 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., or other values ​​within the above range, which are not limited here.

[0072] In some embodiments, the primary sintering process is carried out in an oxygen-containing atmosphere, wherein 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., and of course, other values ​​within the above range are also possible, which are not limited here. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0073] In some implementations, the equipment for primary sintering includes stationary box furnaces, roller kiln continuous furnaces, etc.

[0074] In some embodiments, the primary sintering product is crushed using an air crusher, and the volumetric particle size D of the crushed matrix material is... 50 The value is 2μm to 6μm. Specifically, it can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm or 6μm, etc., or other values ​​within the above range. No limitation is made here.

[0075] In some embodiments, the particle size D of the matrix material 50 The value of D is inversely proportional to the grading parameters of the gas crusher. The larger the grading parameters of the gas crusher, the greater the value of D. 50 The smaller.

[0076] In some embodiments, the single feed rate of the gas crusher is 2 kg, the air pressure is 1 MPa, and the grading parameters of the gas crusher are 80 Hz to 200 Hz, specifically 80 Hz, 90 Hz, 100 Hz, 120 Hz, 150 Hz, 180 Hz or 200 Hz, etc., which are not limited here.

[0077] In some embodiments, in the particle size distribution spectrum of the matrix material, the volume percentage of particles smaller than 1 μm is δ3%, and the volume percentage of particles larger than 7 μm is δ4%, satisfying 0.01 ≤ δ3 / δ4 ≤ 3.5. 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., or other values ​​within the above range, which are not limited here.

[0078] In some embodiments, δ3 < 5, meaning the volume percentage of particles with a diameter less than 1 μm can be 4.9%, 4.8%, 4.6%, 4.5%, 4%, 3.5%, 3%, 2.5%, or 0.5%, etc., or other values ​​within the above range, which are not limited here. δ4 < 5, meaning the volume percentage of particles with a diameter greater than 7 μm can be 4.9%, 4.8%, 4.6%, 4.5%, 4%, 3.5%, 3%, 2.5%, or 0.5%, etc.

[0079] Understandably, by controlling the particle size and volume distribution of the matrix material, the volume distribution of the coated cathode material particles can be further regulated to a suitable range. This allows larger particles to act as a supporting framework in the electrode under the action of the binder, effectively supporting the electrode. Smaller particles can connect with larger particles in the electrode, improving the internal connectivity of the electrode, increasing the cohesive force between particles, improving the contact between particles, reducing the resistance between particles in the electrode, and effectively enhancing the reaction kinetics of the electrode.

[0080] Step S20: The matrix material is mixed with the first coating agent and then subjected to a second sintering treatment to obtain the coating product obtained in the first stage.

[0081] Understandably, during the secondary sintering process, the first coating agent can slowly penetrate into the crystal surface of the matrix material, increasing the structural and chemical stability of the cathode material, reducing the escape of lattice oxygen from the cathode material, and reducing lattice phase transitions.

[0082] In some embodiments, the first coating agent may include a compound containing nitrogen, wherein nitrogen includes at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, Sb, and Ce.

[0083] In some embodiments, the mass ratio of the matrix material to the first coating agent is 1:(0.001 to 1), specifically 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, other values ​​within the above range are also possible and are not limited here.

[0084] In some embodiments, the temperature of the secondary sintering treatment is 300℃ to 850℃. Specifically, the temperature of the secondary sintering treatment is 300℃, 350℃, 450℃, 500℃, 550℃, 650℃, 700℃, 750℃, and 850℃, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the temperature of the secondary sintering treatment is 600℃ to 700℃.

[0085] In some embodiments, the secondary sintering treatment time is 1h to 20h. Specifically, the secondary sintering treatment time 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, other values ​​within the above range are also possible and are not limited here.

[0086] In some embodiments, the secondary sintering process is carried out in an oxygen-containing atmosphere, wherein 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., and of course, other values ​​within the above range are also possible, which are not limited here. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0087] In some implementations, the equipment for secondary sintering includes stationary box furnaces, roller kiln continuous furnaces, etc.

[0088] Step S30: The material obtained from the first coating is mixed with the second coating agent and then subjected to three sintering processes to obtain the cathode material.

[0089] In some embodiments, the mass ratio of the primary coating agent to the second coating agent is 1:(0.001 to 0.1), specifically 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, other values ​​within the above range are also possible and are not limited here.

[0090] In some embodiments, the temperature for the three sintering processes is 300°C to 850°C. Specifically, the temperatures for the three sintering processes are 300°C, 350°C, 380°C, 400°C, 450°C, 500°C, 550°C, 650°C, 700°C, and 850°C, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the temperature for the three sintering processes is 500°C to 550°C.

[0091] In some embodiments, the duration of the three sintering processes is 1 hour to 20 hours. Specifically, the duration of the three sintering processes is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, and 20 hours, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the duration of the three sintering processes is 5 hours to 10 hours.

[0092] In some embodiments, the three sintering processes are carried out in an oxygen-containing atmosphere, wherein 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., and of course, other values ​​within the above range are also possible, which are not limited here. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0093] In some embodiments, the tertiary sintering process also includes sieving and demagnetizing steps.

[0094] This application also provides a positive electrode sheet, which includes a dry electrode film, wherein the dry electrode film includes the aforementioned positive electrode material. Specifically, the positive electrode material is mixed uniformly with a conductive agent and a binder in a certain proportion, for example, the positive electrode material is mixed uniformly with conductive carbon black and polytetrafluoroethylene in a mass ratio of 8:1:1, and then the dry electrode film is prepared by high-speed stirring and rolling.

[0095] In some embodiments, the electrode rebound rate of the dry electrode film is <20%. Specifically, the electrode rebound rate of the dry electrode film can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or 19%.

[0096] In some embodiments, the peel strength of the dry electrode film is >309 mN / mm. Specifically, the peel strength of the dry electrode film can be 310 mN / mm, 330 mN / mm, 380 mN / mm, 410 mN / mm, 430 mN / mm, 460 mN / mm, 480 mN / mm, 510 mN / mm, 550 mN / mm, 580 mN / mm, or 590 mN / mm.

[0097] The cathode material provided in this application can meet both the product performance requirements and the requirements of the dry electrode preparation process, and a lithium-ion battery with high energy density, high operating voltage, long cycle life, high safety and fast charging performance can be obtained through the dry electrode preparation process.

[0098] This application also provides a battery, including: a negative electrode, a positive electrode, a separator, and an electrolyte, wherein the positive electrode includes a dry electrode film.

[0099] This application also provides an electrical device that includes a battery. Improved battery performance leads to enhanced performance of the electrical device using the battery.

[0100] The embodiments of the present invention will be further described below with reference to several examples. However, the embodiments of the present invention are not limited to the specific embodiments described below. Appropriate modifications can be made within the scope of the original claims.

[0101] Example 1

[0102] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 is added at a mass ratio of 300:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850℃ for 6 hours. The first sintering product is crushed by an air crusher with a single batch input of 2 kg, an air pressure of 1 MPa, and a grading parameter of 150 Hz to obtain the matrix material with a median particle size of 3 μm. The matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0103] (2) After the matrix material and Al2O3 are mixed evenly at a mass ratio of 1:0.007, they are placed in an oxygen-filled atmosphere (oxygen content 95%) for a second sintering treatment for 10 hours. The temperature of the second sintering treatment is controlled at 600℃ to obtain the first coating product.

[0104] (3) The first coating product and H3BO3 were mixed evenly at a mass ratio of 1:0.01 and then placed in an oxygen-filled atmosphere for three sintering treatments for 8 hours. The temperature of the three sintering treatments was controlled at 500℃ to obtain the modified cathode material.

[0105] Figure 1 is an electron microscope image of the cathode material particles prepared in Example 1 of this application. As shown in Figure 1, the primary particles of the cathode material prepared in Example 1 are rounded with wrinkles on the surface and a continuous coating layer, while the particles are well dispersed. The first and second coating layers can be detected by TEM and EDS together. In contrast, Figure 3 is an SEM image of the uncoated matrix material, which has sharp edges on its surface.

[0106] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr-Al-B) 0.0193 O2.

[0107] Other parameters are detailed in Table 1.

[0108] Example 2

[0109] The only difference between this embodiment and Embodiment 1 is that...

[0110] (2) After the matrix material and TiO2 are mixed evenly at a mass ratio of 1:0.007, they are placed in an oxygen-filled atmosphere (oxygen content 95%) for a second sintering treatment for 10 hours. The temperature of the second sintering treatment is controlled at 600℃ to obtain the first coating product.

[0111] All other conditions are exactly the same as in Example 1.

[0112] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8910 Co 0.0502 Mn 0.0488 (Zr-Ti-B) 0.01 O2.

[0113] Other parameters are detailed in Table 1.

[0114] Example 3

[0115] The only difference between this embodiment and Embodiment 1 is that...

[0116] (2) After the matrix material and Co(OH)2 are mixed evenly at a mass ratio of 1:0.007, the mixture is placed in an oxygen-filled atmosphere (oxygen content 95%) for a second sintering treatment for 10 hours. The temperature of the second sintering treatment is controlled at 600℃ to obtain the first coating product.

[0117] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8872 Co 0.0572 Mn 0.0485 (Zr-Co-B) 0.0071 O2.

[0118] Other parameters are detailed in Table 1.

[0119] Example 4

[0120] The only difference between this embodiment and Embodiment 1 is that...

[0121] (2) After the matrix material and WO3 are mixed evenly at a mass ratio of 1:0.007, the mixture is placed in an oxygen-filled atmosphere (oxygen content 95%) for a second sintering treatment for 10 hours. The temperature of the second sintering treatment is controlled at 500℃ to obtain the first coating product.

[0122] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1.01 Ni 0.8934 Co 0.0503 Mn 0.0489 (Zr-WB) 0.0074 O2.

[0123] Other parameters are detailed in Table 1.

[0124] Example 5

[0125] The only difference between this embodiment and Embodiment 1 is that...

[0126] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Mn 0.05 Y2O3 was added at a mass ratio of (OH)2:Y2O3 of 300:1, and the mixture was crushed and ground to obtain a mixture. The mixture was sintered in a box furnace at 550°C for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850°C for 6 hours. The first sintering product was crushed to obtain the matrix material with a median particle size of 3 μm. The matrix material was stored in a polyethylene bag and sealed with aluminum-plastic film.

[0127] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8825 Co 0.0497 Mn 0.0483 (Y-Al-B) 0.0195 O2.

[0128] Other parameters are detailed in Table 1.

[0129] Example 6

[0130] The only difference between this embodiment and Embodiment 1 is that...

[0131] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Mn 0.05Y₂O₃ and Sr(OH)₂ (Y₂O₃ to Sr(OH)₂ mass ratio of 1:2.5) were added at a mass ratio of 300:1. The mixture was then pulverized and ground to obtain a mixture. The mixture was sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850℃ for 6 hours. The first sintering product was crushed by an air crusher with a single batch input of 2 kg, an air pressure of 1 MPa, and a grading 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 aluminum-plastic film.

[0132] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8835 Co 0.0498 Mn 0.0483 (Y-Sr-Al-B) 0.0184 O2.

[0133] Other parameters are detailed in Table 1.

[0134] Example 7

[0135] The only difference between this embodiment and Embodiment 1 is that...

[0136] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 is added at a mass ratio of 300:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850℃ for 6 hours. The first sintering product is crushed by an air crusher. The single batch input is 2 kg, the air pressure is 1 MPa, the grading parameter is 200 Hz, the matrix material has a median particle size of 1.5 μm, and the matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0137] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr-Al-B) 0.0193O2.

[0138] Other parameters are detailed in Table 1.

[0139] Example 8

[0140] The only difference between this embodiment and Embodiment 1 is that...

[0141] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 is added at a mass ratio of 300:1, and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850℃ for 6 hours. The first sintering product is crushed by an air crusher. The single batch input is 2 kg, the air pressure is 1 MPa, the grading 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 aluminum-plastic film.

[0142] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr-Al-B) 0.0193 O2.

[0143] Figure 2 is an electron microscope image of the cathode material particles prepared in Example 8 of this application. As shown in Figure 2, the cathode material particles exhibit a small amount of agglomeration. Other parameters are detailed in Table 1.

[0144] Example 9

[0145] The only difference between this embodiment and Embodiment 1 is that...

[0146] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Mn 0.05(OH)2:ZrO2 is added at a mass ratio of 300:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850℃ for 6 hours. The first sintering product is crushed by an air crusher. The single batch input is 2 kg, the air pressure is 1 MPa, the grading parameter is 100 Hz, the matrix material has a median particle size of 6 μm, and the matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0147] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr-Al-B) 0.0193 O2.

[0148] Other parameters are detailed in Table 1.

[0149] Example 10

[0150] The only difference between this embodiment and Embodiment 1 is that...

[0151] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 is added at a mass ratio of 300:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850℃ for 6 hours. The first sintering product is crushed by an air crusher. The single batch input is 2 kg, the air pressure is 1 MPa, the grading parameter is 160 Hz, the matrix material has a median particle size of 2.5 μm, and the matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0152] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8827 Co 0.0497 Mn 0.0483 (Zr-Al-B) 0.0193 O2.

[0153] Other parameters are detailed in Table 1.

[0154] Example 11

[0155] The only difference between this embodiment and Embodiment 1 is that...

[0156] (2) After the matrix material and Al2O3 are mixed evenly at a mass ratio of 1:0.007, they are placed in an oxygen-filled atmosphere for a second sintering treatment. The temperature of the second sintering treatment is controlled at 600℃ to obtain the first coated product. That is, step (3) is not performed in Example 11, and the other conditions are exactly the same as in Example 1.

[0157] The cathode material prepared in this embodiment includes a matrix material and a single coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8866 Co 0.0499 Mn 0.0485 (Zr-Al) 0.015 O2.

[0158] Other parameters are detailed in Table 1.

[0159] Example 12

[0160] The only difference between this embodiment and Embodiment 1 is that...

[0161] (3) After the matrix material and H3BO3 are mixed evenly at a mass ratio of 1:0.01, they are placed in an oxygen-filled atmosphere for a second sintering treatment. The temperature of the second sintering treatment is controlled at 500℃ to obtain a first-coated product. That is, step (2) is not performed in Example 12, and the other conditions are exactly the same as in Example 1.

[0162] The cathode material prepared in this embodiment includes a matrix material and a single coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8937 Co 0.0503 Mn 0.0489 (Zr-B) 0.0071 O2.

[0163] Example 13

[0164] The only difference between this embodiment and Embodiment 1 is that...

[0165] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Mn0.05 (OH)2:ZrO2 is added at a mass ratio of 900:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850℃ for 6 hours. The first sintering product is crushed to obtain the matrix material with a median particle size of 3μm. The matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0166] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8915 Co 0.0497 Mn 0.0483 (Zr-Al-B) 0.0105 O2.

[0167] Other parameters are detailed in Table 1.

[0168] Example 14

[0169] The only difference between this embodiment and Embodiment 1 is that...

[0170] (1) Ni cobalt manganese precursor Ni 0.7 Co 0.1 Mn 0.2 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.7 Co 0.1 Mn 0.2 (OH)2:ZrO2 is added at a mass ratio of 300:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 900℃ for 6 hours. The first sintering product is crushed to obtain the matrix material with a median particle size of 3μm. The matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0171] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.6905 Co 0.097 Mn 0.193 (Zr-Al-B) 0.0195 O2.

[0172] Other parameters are detailed in Table 1.

[0173] Example 15

[0174] The only difference between this embodiment and Embodiment 1 is that...

[0175] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Al 0.05 (OH)2 and LiOH are prepared according to a molar ratio of [n(Ni)+n(Co)+n(Al)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Al 0.05 (OH)2:ZrO2 is added at a mass ratio of 300:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550°C for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850°C for 6 hours. The first sintering product is crushed to obtain the matrix material with a median particle size of 3μm. The matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0176] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 1. 01 Ni 0.8825 Co 0.0497 Al 0.0483 (Zr-Al-B) 0.0195 O2.

[0177] Other parameters are detailed in Table 1.

[0178] Example 16

[0179] The only difference between this embodiment and Embodiment 1 is that...

[0180] (1) Ni 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 1.00:1, and according to Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 is added at a mass ratio of 300:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550°C for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850°C for 6 hours. The first sintering product is crushed to obtain the matrix material with a median particle size of 3μm. The matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0181] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 0.96 Ni 0.8829 Co 0.0496 Mn 0.0483 (Zr-Al-B) 0.0192 O2.

[0182] Other parameters are detailed in Table 1.

[0183] Example 17

[0184] The only difference between this embodiment and Embodiment 1 is that...

[0185] (1) Ni cobalt manganese precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.8 Co 0.1 Mn 0.1 (OH)2:ZrO2 is added at a mass ratio of 300:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (oxygen content 95%), and then sintered at 850℃ for 6 hours. The first sintering product is crushed by an air crusher with a single batch input of 2 kg, an air pressure of 1 MPa, and a grading parameter of 150 Hz to obtain the matrix material with a median particle size of 3 μm. The matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0186] The cathode material prepared in this embodiment includes a matrix material and a double coating layer. The general chemical formula of the cathode material is Li. 0. 96 Ni 0.7929 Co 0.0996 Mn 0.0983 (Zr-Al-B) 0.0192 O2.

[0187] Other parameters are detailed in Table 1.

[0188]

[0189] Comparative Example 1

[0190] The only difference between this comparative example and Example 1 is that...

[0191] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05(OH)₂ and LiOH were pulverized and ground to obtain a mixture at a molar ratio of [n(Ni) + n(Co) + n(Mn)]:n(Li) of 1.04:1. The mixture was sintered in a box furnace at 550℃ for 4 hours under an oxygen atmosphere (95% oxygen content), followed by sintering at 850℃ for another 6 hours. The first sintering product was then crushed using an air crusher. The batch size was 2 kg, the gas pressure was 1 MPa, the grading parameter was 150 Hz, and the positive electrode material had a median particle size of 3 μm. The positive electrode material was stored in a polyethylene bag and sealed with aluminum-plastic film. Comparative Example 1 did not undergo any coating treatment.

[0192] The cathode material prepared in this comparative example has the general chemical formula Li. 1.01 Ni 0.9 Co 0.05 Mn 0.05 O2, other parameters are detailed in Table 1.

[0193] Comparative Example 2

[0194] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH are added according to a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1, and according to Ni 0.9 Co 0.05 Mn 0.05 (OH)2:ZrO2 is added at a mass ratio of 300:1 and ZrO2 is crushed and ground to obtain a mixture. The mixture is heated to 550℃ in an oxygen atmosphere in a box furnace and sintered for 4 hours, and then heated to 850℃ and sintered for 6 hours. The first sintering product is crushed by an air crusher. The single batch input is 2kg, the air pressure is 1Mpa, the grading parameter is 150Hz, the matrix material has a median particle size of 3μm, and the matrix material is stored in a polyethylene bag and sealed with aluminum-plastic film.

[0195] The difference between this comparative example and Example 1 is that steps (2) and (3) are not performed.

[0196] All other conditions are exactly the same as in Example 1.

[0197] The cathode material prepared in this comparative example has the general chemical formula Li. 1.01 Ni 0.9 Co 0.049 Mn 0.049 Zr 0.002 O2, other parameters are detailed in Table 1.

[0198] Figure 3 is an electron microscope image of the cathode material prepared in Comparative Example 1 of this application. As shown in Figure 3, the surface of the cathode material is not coated, and the primary particles have distinct edges.

[0199] Comparative Example 3

[0200] (1) Ni cobalt manganese precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH were pulverized and ground to obtain a mixture at a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li) of 1.04:1. The mixture was then sintered in a box furnace at 550°C for 4 hours under an oxygen atmosphere (95% oxygen content) and then sintered at 850°C for 6 hours. The first sintering product was crushed by an air crusher. The single batch input was 2 kg, the air pressure was 1 MPa, the grading parameter was 150 Hz, the matrix material had a median particle size of 3 μm, and the matrix material was stored in a polyethylene bag and sealed with aluminum-plastic film.

[0201] (2) After the matrix material and Al2O3 are mixed evenly at a mass ratio of 1:0.05, they are placed in an oxygen-filled atmosphere (oxygen content 95%) for a second sintering treatment for 10 hours. The temperature of the second sintering treatment is controlled at 600℃ to obtain the first coating product.

[0202] (3) The first coating product and H3BO3 were mixed evenly at a mass ratio of 1:0.01 and then placed in an oxygen-filled atmosphere (oxygen content 95%) for three sintering treatments for 8 hours. The temperature of the three sintering treatments was controlled at 500℃ to obtain the modified cathode material.

[0203] The cathode material prepared in this comparative example has the general chemical formula Li. 1.01 Ni 0.843 Co 0.048 Mn 0.048 (Al-B) 0.061 O2, other parameters are detailed in Table 1.

[0204] Test method:

[0205] (1) Test methods for particle size of matrix materials and cathode materials:

[0206] The particle size distribution test method is in accordance with GB / T 19077-2016. Specifically, the particle size distribution of the cathode particles dispersed in a certain aqueous solution can be tested using a Malvern Mastersizer 3000 laser particle size analyzer. In the particle size distribution map of the cathode material, the volume percentage of particles with a diameter less than 1.2 μm is denoted as δ1%, and the volume percentage of particles with a diameter greater than 7 μm is denoted as δ2%.

[0207] (2) Test method for specific surface area of ​​cathode material:

[0208] The specific surface area of ​​the cathode material was measured by adsorbing gas. Specifically, Micromeritics Tristar II was used to perform N2 adsorption tests and calculate the adsorption amount under different equilibrium pressures. Isothermal adsorption curves were obtained, and then the specific surface area of ​​the cathode material was calculated.

[0209] (3) Test method for the thickness of the coating layer of the positive electrode material:

[0210] Focused ion beam (FIB) was used to thin the cross-section of the cathode material sample to obtain a flat and transparent cross-section. Simultaneously, transmission electron microscopy (TEM) was used to measure the thickness of each coating layer at a magnification of 50k-100k using the TEM's built-in scale.

[0211] (4) Test method for the bulk elastic modulus of cathode materials:

[0212] A Kistler pressure sensor was used to measure the pressure. The signal from the sensor was processed by an amplifier before pressure data acquisition. A high-pressure pump from SITEC, Switzerland, was used to gradually pressurize the material. The cathode material decreased in volume under pressure, exhibiting its compressibility characteristics, i.e., the bulk modulus of elasticity of the cathode material, which is defined as E = -V dp / dV, where p is the pressure on the cathode material and V is the volume of the cathode material.

[0213] (5) Test method for tap density of cathode material:

[0214] The following steps were taken using a Canta vibratory density meter (model: DAT-4-220):

[0215] Clean the graduated cylinder and weigh it to obtain m1. Add approximately 50g of sample to the graduated cylinder, ensuring the sample surface is as horizontal as possible, and wipe the surrounding area with a paper towel. Weigh the total mass of the sample and graduated cylinder to obtain m2. Place the graduated cylinder on the vibration stage and secure it with the three symmetrical feet. Turn on the instrument and set the vibration frequency to 5000 times. Turn on the vibration switch; the instrument will automatically stop after vibrating for the specified number of times. Remove the graduated cylinder and read the sample volume. If the sample surface is horizontal after compaction, read the volume directly; if it is oblique, take the average of the readings at the highest and lowest points, V. The compacted density = (m2 - m1) / V.

[0216] (6) Test method for compaction density of cathode materials:

[0217] The compaction density of the cathode material was tested using a Carver 4350 from the United States. The procedure was as follows: 1g of sample was placed in a mold and pressed with a pressure of 3T for 30s. After pressing, the height was measured and the compaction density was calculated, which is the ratio of mass to volume after compaction.

[0218] (7) Test method for powder conductivity in cathode materials:

[0219] The powder conductivity of the cathode material was tested using a Mettler FE38.

[0220] (8) XRD testing of cathode materials:

[0221] The cathode material was characterized using an XRD diffractometer (RIGAICU UITIMAIV). The peak intensity of the (006) crystal plane was I006, the peak intensity of the (101) crystal plane was I101, and the peak intensity of the (102) crystal plane was I102. In the XRD spectrum of the cathode material, the peak position of the cathode material on the (110) crystal plane was 2θ110, and the peak position of the (108) crystal plane was 2θ108.

[0222] (9) Testing of particle scraping angle of positive electrode material:

[0223] The scraping angle of the particles was determined using the Hosokawa PT-X particle analyzer.

[0224] (10) Test of the mass content of free lithium in cathode materials:

[0225] 5.0 g of positive electrode material powder was immersed in 100 mL of deionized water and stirred for 10 minutes in a sealed glass flask. After thorough stirring, the suspension was filtered to obtain a clear solution. Then, 90 mL of the clear solution was titrated with 0.1 mol / L HCl solution at a rate of 0.5 mL / min while stirring, and the pH curve was recorded until the pH reached 3. The reference voltage curve was obtained by titrating to determine the low concentrations of LiOH and Li2CO3 dissolved in deionized water. The first plateau with an endpoint y1 (in mL) between pH 8 and 9 is the determined OH- / H2O mass content, and the second plateau with an endpoint y2 (in mL) between pH 4 and 6 is the determined HCO3- / H2CO3 mass content. The inflection point y1 between the first and second plateaus and the inflection point y2 after the second plateau were obtained by the corresponding minimum values ​​of the derivative dpH / dVol of the pH curve. The results were then expressed as weight percentages of LiOH and Li2CO3 as shown in equations (1) and (2) below:

[0226]

[0227]

[0228] Free Liwt%=LiOHwt%*6.94 / 23.95+Li2CO3wt%*6.94*2 / 73.89 (3).

[0229] (11) Testing of lithium-ion diffusion coefficient of cathode material

[0230] Weigh 0.8g of positive electrode material and 0.1g of conductive carbon black and put them into a ball mill jar and mix them evenly. Then add 0.1g of polytetrafluoroethylene into a mixer, and mix at 5000rpm for 10min. Use a roller press to hot press to prepare a dry electrode film. Paste the dry electrode film onto aluminum foil and hot press to obtain the positive electrode sheet.

[0231] Using lithium foil as the negative electrode, Celgard2400 as the separator, and a 1 mol / L LiPF6 solution as the electrolyte (the solvent is a mixture of ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 1:1), a 2016 coin cell was assembled in a glove box.

[0232] After activation at 0.1C for two weeks, a pulse potential was applied to the system under near-equilibrium conditions using a constant potential gap titration technique, and the current change was measured according to formula D. Li + =-dlnI / dt*(4L) 2 / π 2 The lithium-ion diffusion coefficient was calculated, where I is the current value, t is the time, and L is the thickness of the active material.

[0233] The battery testing was conducted using a CT2001A battery testing system from Wuhan Landian Electronics Co., Ltd. Charge-discharge tests were performed at 0.1C / 0.1C and 0.5C / 1C rates within a 3.0V-4.3V discharge range at 25℃ to obtain the initial discharge specific capacity, followed by 100 cycle tests at 0.5C / 1C. Additionally, an electrochemical impedance spectroscopy (EIS) test was performed using a Bio-logic VSP-3e EIS workstation. The assembled battery was placed in the appropriate position on the EIS workstation, ensuring correct wiring. The workstation was started, the impedance measurement mode was selected, and an appropriate frequency range was set. After the system stabilized, the electrode impedance data was recorded. The test results are detailed in Tables 1 and 2.

[0234] (12) Peel strength of positive electrode sheet

[0235] Weigh 0.8g of high-nickel cathode material, 0.1g of conductive carbon black, and 0.1g of polyvinylidene fluoride and place them in a ball mill jar. Add 15mL of N-methylpyrrolidone and ball mill to form a uniform slurry. Then, uniformly coat the slurry onto aluminum foil and vacuum dry at 80℃ for 12h to obtain the cathode sheet.

[0236] The peel strength of the prepared positive electrode sheet was measured by a tensile testing instrument. Specifically, the single-sided electrode sheet was cut into strips of 25mm*200mm. The test side was bonded to a steel plate with double-sided tape (30mm wide). The electrode sheet was parallel to the steel plate and rolled back and forth 3 times with an automatic roller press. The steel plate with the electrode sheet attached was inserted into the lower clamp of the SHIMADZU peel testing machine and fixed vertically. The electrode sheet current collector was inserted into the upper clamp and fixed, so that the electrode sheet attached to the adhesive tape was at 180° with the electrode sheet fixed in the upper clamp. After the test sample was fixed, the test was started at a peel rate of 100mm / min. 3-5 samples were recorded for each material and the average value was taken.

[0237] (13) Electrode rebound performance test

[0238] After pressing the electrode to the specified compaction point, the electrode thickness d1 is measured. The electrode is then placed in an oven at room temperature. After a certain period of time, the electrode thickness dt is measured. The electrode rebound amount is calculated as (dt-d1) / (d1-d0)*100%, where dt and d1 are read directly during measurement, and d0 is the foil thickness. Table 1. Physicochemical properties of the cathode materials prepared in the comparative examples and embodiments. Table 2. Electrochemical performance testing of cathode materials

[0239] As can be seen from the embodiments and Tables 1 and 2, in the particle size distribution spectrum of the cathode material of this application, the volume percentage of particles with a diameter less than 1.2 μm is δ1%, and the volume percentage of particles with a diameter greater than 7 μm is δ2%, where 1 ≤ δ2 / δ1 ≤ 10. The particle percentage of the cathode material is within the above range, which allows larger particles to act as a framework in the dry electrode sheet, and smaller particles to connect with larger particles. This effectively improves the internal connectivity of the cathode sheet, increases the cohesive force between materials within the cathode sheet, enhances the contact between powder particles, reduces interfacial impedance between particles, and increases the lithium-ion diffusion rate of the cathode material. This is beneficial for the cathode material particles to form an integrated structure, improves the conductivity of the cathode material, effectively enhances the reaction kinetics of the cathode sheet, and results in good film formation of the dry electrode. Furthermore, it effectively alleviates the rebound rate after rolling of the cathode sheet, further improves the peel strength of the cathode sheet, and enables the obtained cathode sheet to possess advantages such as high energy density, high operating voltage, and long cycle life.

[0240] Figure 4 shows the electrochemical impedance spectroscopy (EIS) spectra of the cathode materials prepared in Examples 1, 6, 8, and Comparative Example 2 at low temperatures. As shown in Figure 4, because the sample in Example 1 has doped coating and a suitable particle size, its impedance is significantly lower than that of the uncoated cathode material in Example 8, and also lower than that of the cathode material sample prepared in Comparative Example 2, whose particle size and volume distribution deviated from the suitable range. According to the test data from Example 6, the Y and Sr doping and the double-layer coating in Example 6 can further improve the crystal structure stability, which is beneficial to Li… + Diffusion in the lattice phase of the cathode material reduces the impedance within the cathode material particles.

[0241] According to the test data from Examples 1 to 12, the positive electrode material (I) 006 +I 102 ) / I 101 The value reflects the orderliness of the hexagonal crystal structure of the cathode material, and the orderliness of its crystal structure is closely related to the performance of the cathode material. The peak intensity I of the (006) crystal plane of the cathode material, determined by X-ray diffraction pattern, is... 006 Peak intensity I of (101) crystal plane 101 and the peak intensity I of the (102) crystal plane 102 The relationship between them satisfies: 0.5 ≤ (I 006 +I 102 ) / I 101 ≤1.00 indicates that the cathode material has good hexagonal crystal structure order, and the cathode material has a layered structure. Under ideal conditions, Li + The 3b site occupies the crystal, while transition metals such as Ni, Co, and Mn randomly occupy the 3a site. However, due to the presence of Li... + and Ni 2+ Ions with similar radii often occupy each other's positions, leading to cation mixing. When Ni atoms occupy sites in the lithium layer, the intensity of the 101 peak decreases rapidly, the orderliness of the hexagonal crystal structure decreases, and the structural orderliness of the cathode material is reduced.

[0242] Figure 5 is a comparison of the overcharge performance of the cathode materials prepared in Example 1 and Comparative Example 3 of this application. As shown in Figure 5, the cathode material of Example 1 satisfies 0.5≤(I 006 +I 102 ) / I 101 ≤1.00, the cathode material exhibits good structural order and better overcharge resistance. Further, referring to Example 13, the cathode material satisfies 1≤δ2 / δ1≤10, but (I 006 +I 102 ) / I 101 >1.00, and its electrochemical performance is between that of Example 1 and the comparative example.

[0243] According to the data from the embodiments, as the volume percentage δ1% of particles with a diameter less than 1.2 μm in the cathode material increases, the (I) of the cathode material... 006 +I 102 ) / I 101 The ratio also increases accordingly. When (I 006 +I 102 ) / I 101 When the value is greater than 1.00, the volume ratio of particles smaller than 1.2 μm is too high, making the cathode material particles prone to agglomeration, reducing particle flowability, resulting in uneven distribution of active material on the electrode sheet, and poor film formation of the dry electrode. When (I 006 +I 102 ) / I 101 When the value is less than 0.5, the volume ratio of particles with a diameter less than 1.2 μm is too small, the adsorption capacity between particles decreases, the adhesion between particles decreases, and the adhesion 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 detach in the electrolyte, contacting the negative electrode material and causing a local short circuit in the battery; at the same time, the dry electrode has poor film formation properties.

[0244] In some embodiments, the peak position 2θ of the (110) crystal plane of the cathode material is determined using X-ray diffraction patterns. 110 Peak position 2θ of (108) crystal plane 108 The relationship between them satisfies: |2θ 110 -2θ 108 |=0.2~0.6. When |2θ 110 -2θ 108 When the value of | is within the above range, as shown in Figure 6, the (108) and (110) diffraction peaks are clearly split, indicating that the cathode material forms a good layered structure, which can promote the formation of Li + Rapid insertion / extraction in the crystal structure of the matrix material and the coating layer imparts high rate performance and better kinetic stability to the cathode material, exhibiting low impedance. Furthermore, referring to Example 13, the cathode material satisfies 1≤δ2 / δ1≤10 but |2θ 110 -2θ 108 | = 0.167, and its electrochemical performance is between that of Example 1 and the comparative example.

[0245] The cathode material prepared in Comparative Example 1 was not doped or coated. The mixing of cations in the cathode material was intensified, and Ni atoms occupied the lithium ion sites in the lithium layer. In the XRD of the cathode material, the intensity of the 101 peak rapidly decreased, that is, the order of the hexagonal crystal structure of the cathode material decreased, which led to an increase in the interfacial impedance between the particles of the cathode material. The lithium ion diffusion rate of the cathode material decreased significantly compared with Example 1, and the conductivity of the cathode material also decreased significantly.

[0246] The cathode material prepared in Comparative Example 2 was only doped without coating. The residual alkali content on the surface of the cathode material was increased, which exacerbated the cation rearrangement phenomenon on the surface of the cathode material, thereby reducing the structural order of the cathode material. In the XRD of the cathode material, the intensity of the 101 peak rapidly decayed, that is, the order of the hexagonal crystal structure of the cathode material decreased, which led to an increase in the interfacial impedance between the particles of the cathode material. The lithium ion diffusion rate of the cathode material decreased significantly compared with Example 1, and the conductivity of the cathode material also decreased significantly.

[0247] The cathode material prepared in Comparative Example 3 was only coated and not doped. The mixing of cations in the cathode material was intensified, and Ni atoms occupied the lithium ion sites in the lithium layer. In the XRD of the cathode material, the intensity of the 101 peak decreased rapidly, that is, the order of the hexagonal crystal structure of the cathode material decreased, which led to an increase in the interfacial impedance between the particles of the cathode material. The lithium ion diffusion rate of the cathode material decreased significantly compared with Example 1, and the conductivity of the cathode material also decreased significantly.

[0248] 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 modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A positive electrode material, characterized in that, At least a portion of the surface of the cathode material has a coating layer; The general chemical formula of the cathode 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 the covering element; In the particle size distribution spectrum of the cathode material, the volume percentage of particles with a diameter less than 1.2 μm is δ1%, and the volume percentage of particles with a diameter greater than 7 μm is δ2%, and the condition 1≤δ2 / δ1≤10 is satisfied.

2. The cathode material according to claim 1, characterized in that, In the XRD spectrum of the cathode material, the peak intensity of the cathode material on the (006) crystal plane is I. 006 The peak intensity on the (101) crystal plane is I. 101 The peak intensity on the (102) crystal plane is I. 102 , 0.5≤(I 006 +I 102 ) / I 101 ≤1.

00.

3. The cathode material according to claim 1, characterized in that, In the XRD spectrum of the cathode material, the peak position of the cathode material on the (110) crystal plane is 2θ. 110 The peak position on the (108) crystal plane is 2θ. 108 It satisfies 0.2≤|2θ 110 -2θ 108 |≤0.

6.

4. The cathode material according to claim 1, characterized in that, 0.1<δ1<10, 0.02<δ2<10.

5. The positive electrode material according to claim 1, characterized in that, Furthermore, the positive electrode material satisfies at least one of the following characteristics: (1) 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; (2) The coating layer includes a first coating layer and a second coating layer, wherein the thickness of the first coating layer is 2nm to 100nm and the thickness of the second coating layer is 2nm to 80nm; (3) The positive electrode material includes a matrix material and a coating layer, wherein the coating layer is located on the surface of the matrix material.

6. The cathode material according to claim 1, characterized in that, The nitrogen element includes at least one of the following: Y, W, Sr, Zr, La, Ce, Co, Ti, Mg, Al, Sb, Nb, Ta, V, B, S, and Ba.

7. The cathode material according to any one of claims 1 to 6, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The volume distribution particle size D of the positive electrode material 50 The size ranges from 2μm to 6μm. (2) The specific surface area of ​​the positive electrode material is 0.2 m². 2 / g~1.3m 2 / g; (3) The mass content of free lithium in the cathode material is 500ppm to 2000ppm.

8. The cathode material according to any one of claims 1-7, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The compaction density of the positive electrode material is 3.0 g / cm³. 3 ~3.6g / cm 3 ; (2) The tap density of the positive electrode material is 0.6 g / cm³. 3 ~2.0g / cm 3 .

9. The cathode material according to any one of claims 1-8, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The positive electrode material has a strength of 8 kN / cm 2 The electrical conductivity of the powder under pressure is 1*10 -3 S / cm~6*10 -2 S / cm; (2) The cathode material contains individual grains with the same orientation, wherein the average grain size of the individual grains is 1 μm to 5 μm; (3) The cathode material is a single crystal material.

10. The cathode material according to any one of claims 1 to 9, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The lithium-ion diffusion coefficient of the cathode material is 1*10 -9 cm 2 / s~1*10 -6 cm 2 / s; (2) The scraping angle of the positive electrode material particles is between 10° and 80°.

11. The cathode material according to any one of claims 1 to 10, characterized in that, The positive electrode material is mixed with conductive carbon black and polytetrafluoroethylene in a mass ratio of 8:1:1 and then hot-pressed to obtain a dry electrode film. The electrode rebound rate of the dry electrode film is <20%.

12. A positive electrode material, characterized in that, The general chemical formula of the cathode material is Li. a Ni x Co y M z N b O2, wherein 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 element includes at least one of Y, W, Sr, Zr, La, Ce, Co, Ti, Mg, Al, Sb, Nb, Ta, V, B, S and Ba; In the particle size distribution spectrum of the cathode material, the volume percentage of particles with a diameter less than 1.2 μm is δ1%, and the volume percentage of particles with a diameter greater than 7 μm is δ2%, and the condition 1≤δ2 / δ1≤10 is satisfied.

13. The cathode material according to claim 12, characterized in that, In the XRD spectrum of the cathode material, the peak intensity of the cathode material on the (006) crystal plane is I. 006 The peak intensity on the (101) crystal plane is I. 101 The peak intensity on the (102) crystal plane is I. 102 , 0.5≤(I 006 +I 102 ) / I 101 ≤1.

00.

14. The cathode material according to claim 12, characterized in that, In the XRD spectrum of the cathode material, the peak position of the cathode material on the (110) crystal plane is 2θ. 110 The peak position on the (108) crystal plane is 2θ. 108 It satisfies 0.2≤|2θ 110 -2θ1 08 |≤0.

6.

15. The cathode material according to claim 12, characterized in that, 0.1<δ1<10, 0.02<δ2<10.

16. The cathode material according to any one of claims 12-15, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The positive electrode material has a strength of 8 kN / cm 2 The electrical conductivity of the powder under pressure is 1*10 -3 S / cm~6*10 -2 S / cm; (2) The cathode material contains individual grains with the same orientation, wherein the average grain size of the individual grains is 1 μm to 5 μm; (3) The cathode material is a single crystal material.

17. The cathode material according to any one of claims 12 to 15, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The lithium-ion diffusion coefficient of the cathode material is 1*10 -9 cm 2 / s~1*10 -6 cm 2 / s; (2) The scraping angle of the positive electrode material particles is between 10° and 80°; (3) The positive electrode material includes a matrix material and a coating layer, wherein the coating layer is located on the surface of the matrix material, and element N is a coating element; (4) At least a portion of the surface of the positive electrode material has a coating layer.

18. The cathode material according to any one of claims 12 to 17, characterized in that, The positive electrode material is mixed with conductive carbon black and polytetrafluoroethylene in a mass ratio of 8:1:1 and then hot-pressed to obtain a dry electrode film. The electrode rebound rate of the dry electrode film is <20%.

19. A positive electrode plate, characterized in that, The positive electrode sheet comprises the positive electrode material according to any one of claims 12-18.

20. The positive electrode sheet according to claim 19, characterized in that, The positive electrode sheet includes a dry electrode film, which is obtained by hot pressing a mixture of the positive electrode material with conductive carbon black and polytetrafluoroethylene in a mass ratio of 8:1:

1.

21. The positive electrode sheet according to claim 19, characterized in that, The positive electrode sheet satisfies at least one of the following characteristics: (1) The electrode rebound rate of the positive electrode is <20%; (2) The peel strength of the positive electrode sheet is >309mN / mm.

22. A battery, characterized in that, The battery comprises the positive electrode material according to any one of claims 1 to 18 or the positive electrode sheet according to any one of claims 19 to 21.

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