Ternary material and preparation method therefor, lithium-ion battery, and electric device

Abstract

Provided is a ternary material. The chemical formula of the ternary material is LiNi1-x-yCoxMnyMaO2, wherein 0<x≤0.1, 0<y≤0.1, 0<a≤0.05, and M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, W, Al and B; the ternary material comprises polycrystalline particles; and in an X-ray diffraction spectrum of the ternary material, the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° and the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° satisfy the following relational expression: (a)

Description

Ternary material and preparation method thereof, lithium-ion battery and electrical equipment

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on December 29, 2023, with application number 202311871074.8 and invention name “A ternary material, its preparation method, positive electrode sheet, lithium-ion battery and electrical equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present disclosure belongs to the field of energy storage technology, and specifically relates to a ternary material and a preparation method thereof, a lithium-ion battery, and electrical equipment. Background Art

[0003] Lithium-ion battery cathode materials are a crucial component and a key factor influencing their performance. Lithium nickel cobalt manganese oxide (ternary material) combines the advantages of lithium manganese oxide, lithium cobalt oxide, and lithium nickel oxide, offering high specific capacity and excellent discharge rate, making it the primary cathode material for lithium-ion batteries.

[0004] High nickel content is a major development trend in ternary materials, as it can improve their specific capacity. However, the ionic radius of nickel ions is similar to that of lithium ions, which can easily cause lithium-nickel mixing. This mixing becomes more severe with higher nickel content, affecting the orderliness of the ternary material structure and leading to poor cycling performance in ternary lithium batteries. The development of high-nickel ternary materials that combine high specific capacity with long cycle life is of great significance. Summary of the Invention

[0005] The first aspect of the present disclosure provides a ternary material, wherein the chemical formula of the ternary material is LiNi 1-x-y Co x Mn y M a O2, wherein 0<x≤0.1, 0<y≤0.1, 0<a≤0.05, M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W and B; the ternary material comprises polycrystalline particles; in the X-ray diffraction spectrum of the ternary material, there is a (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° and a (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°; the (108) diffraction peak and the (110) diffraction peak satisfy the following relationship: Wherein, FWHM(108) is the half-maximum width of the (108) diffraction peak at a diffraction angle of 2θ = (64±0.5)°; FWHM(110) is the half-maximum width of the (110) diffraction peak at a diffraction angle of 2θ = (65±0.5)°.

[0006] In a second aspect, the present disclosure provides a method for preparing the above-mentioned ternary material, comprising the following steps: 1) mixing a first lithium source with a transition metal precursor to obtain a first mixture, and adding a first dopant to the first mixture to obtain a first doped mixture; wherein the transition metal precursor includes nickel, cobalt, and manganese elements; the molar ratio of the nickel, cobalt, and manganese elements is (1-xy): x:y, 0<x≤0.1, 0<y≤0.1; the molar ratio of the lithium element in the first lithium source to the sum of the nickel, cobalt, and manganese elements in the precursor is (0.3-0.7):1; 2) mixing the first doped mixture with a second lithium source to obtain a second mixture, and sintering the second mixture for the first time in an oxygen-containing atmosphere to obtain a primary sintered product; wherein the lithium element in the second lithium source and the nickel, cobalt, and manganese elements in the precursor The molar ratio of the total is (0.35-0.75):1; the first lithium source and the second lithium source may be the same or different; 3) the primary sintered product is mixed with an optional second dopant, and the second sintering is performed in an oxygen-containing atmosphere to obtain a secondary sintered product; 4) the secondary sintered product is mixed with an optional third dopant, and the third sintering is performed in an oxygen-containing atmosphere to obtain the ternary material; wherein the first dopant, the second dopant, and the third dopant include M element, M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W and B; the ratio of the sum of the molar amounts of the M element in the first dopant, the second dopant and the third dopant to the sum of the molar amounts of nickel, cobalt and manganese elements in the precursor is a:1, 0<a≤0.05.

[0007] In a third aspect, the present disclosure provides a positive electrode sheet comprising the above-mentioned ternary material, or a ternary material prepared by the above-mentioned method for preparing the ternary material.

[0008] In a fourth aspect, the present disclosure provides a positive electrode sheet comprising a ternary material, wherein the chemical formula of the ternary material is LiNi 1-x-y Co x Mn y M a O2, wherein 0<x≤0.1, 0<y≤0.1, 0<a≤0.05, M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W and B; the ternary material comprises polycrystalline particles; in the X-ray diffraction spectrum of the positive electrode sheet, there is a (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° and a (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°; the (108) diffraction peak and the (110) diffraction peak satisfy the following relationship: Wherein, FWHM(108) is the half-maximum width of the (108) diffraction peak at a diffraction angle of 2θ = (64±0.5)°; FWHM(110) is the half-maximum width of the (110) diffraction peak at a diffraction angle of 2θ = (65±0.5)°.

[0009] In a fifth aspect, the present disclosure provides a lithium-ion battery comprising the above-mentioned positive electrode sheet.

[0010] In a sixth aspect, the present disclosure provides an electrical device comprising the above-mentioned lithium-ion battery.

[0011] The alternating arrangement of transition metals and lithium in the ternary material disclosed in the present invention is more regular, with less lithium-nickel mixing and higher specific capacity; and the layer structure formed by the alternation of transition metals and lithium is more stable, which can ensure that the ternary material has a higher energy density and cycle life. Compared with the prior art, the preparation method of the ternary material provided by the present invention has the following effects: First, the step-by-step lithium mixing process makes the lithium source and the ternary material precursor mix more evenly, so that the lithium ions are orderly embedded in the high-nickel ternary precursor lattice, alleviating lithium-nickel mixing; second, the step-by-step sintering process can adjust the sintering conditions multiple times, improve the negative impact of continuous high temperature on the lithium-nickel mixing of the ternary material, ensure the consistency of crystallinity inside and outside the ternary material, and be more conducive to forming a ternary material with a stable and uniform structure; third, the doping process stabilizes the crystal structure of the ternary material and improves the cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings are used to provide further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure, but do not constitute a limitation of the present disclosure.

[0013] FIG1 is a SEM image of the transition metal precursor in Example 1 of the present disclosure at a magnification of 10,000 times;

[0014] FIG2 is a SEM image of the transition metal precursor in Example 1 of the present disclosure magnified 50,000 times;

[0015] FIG3 is a SEM image of the ternary material prepared in Example 1 of the present disclosure at a magnification of 10,000 times. DETAILED DESCRIPTION

[0016] In order to make the technical problems, technical solutions and beneficial effects solved by the present disclosure more clearly understood, the present disclosure is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not intended to limit the present disclosure.

[0017] Lithium nickel cobalt manganese oxide (ternary material) combines the advantages of lithium manganese oxide, lithium cobalt oxide, and lithium nickel oxide, and is widely used as a ternary material in lithium-ion batteries. In the crystal structure of the ternary material, transition metal ions and lithium ions alternately occupy the octahedral voids and are arranged in layers. This atomic arrangement gives the ternary material excellent electrochemical properties. High nickel content is one of the main directions of development of ternary materials. High nickel content can increase the specific capacity of ternary materials and increase the battery's range. However, since the ionic radius of nickel ions is close to that of lithium ions, it is easy to cause lithium and nickel mixing. The higher the nickel content, the more serious the mixing phenomenon, which in turn affects the orderliness of the ternary material structure and leads to poor cycle performance of ternary lithium batteries. It is of great significance to prepare high nickel ternary materials that have both high specific capacity and long cycle life.

[0018] The first embodiment of the present disclosure provides a ternary material, wherein the chemical formula of the ternary material is LiNi 1-x-y Co x Mn y M a O2, wherein 0<x≤0.1, 0<y≤0.1, 0<a≤0.05, M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W and B; the ternary material comprises polycrystalline particles; in the X-ray diffraction spectrum of the ternary material, there is a (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° and a (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°; the (108) diffraction peak and the (110) diffraction peak satisfy the following relationship: Wherein, FWHM(108) is the half-maximum width of the (108) diffraction peak at a diffraction angle of 2θ = (64±0.5)°; FWHM(110) is the half-maximum width of the (110) diffraction peak at a diffraction angle of 2θ = (65±0.5)°.

[0019] Ternary materials belong to the hexagonal crystal system, in which the (110) crystal plane is related to the a and b axes, while the (108) crystal plane is more strongly related to the c axis; furthermore, the combination of the (110) crystal plane and the (108) crystal plane can reflect the characteristics of the three directions of the a, b and c axes in the unit cell of the ternary material, and can be used to evaluate the crystal structure of the ternary material. It can roughly determine the orderliness of the layered structure of the ternary material, and can also evaluate the rationality of the atomic arrangement between each layer. In the XRD spectrum of the ternary material, the two diffraction peaks of the (108) and (110) crystal planes show obvious split peaks, which is a sign that the crystal structure of the ternary material has reached a suitable range. At this time, a regular lamellar structure composed of alternating transition metals and lithium is formed in the ternary material. After a lot of research, the inventors of the present disclosure found that when the (108) diffraction peak and the (110) diffraction peak satisfy the relationship: The alternating arrangement of transition metals and lithium in ternary materials is more regular, with less lithium-nickel mixing and higher specific capacity; and the layer structure formed by the alternation of transition metals and lithium is more stable, which can ensure that the ternary material has a higher energy density and cycle life.

[0020] In the present disclosure, polycrystalline particles refer to secondary spherical particles formed by the aggregation of multiple primary particles.

[0021] Specifically, in the relationship, 2θ(110) refers to the specific position of the (110) diffraction peak in the X-ray diffraction spectrum actually obtained when performing XRD testing on the ternary material. Similarly, 2θ(108) refers to the specific position of the (108) diffraction peak in the X-ray diffraction spectrum actually obtained when performing XRD testing on the powder of the ternary material.

[0022] In some preferred embodiments of the present disclosure, the chemical formula of the ternary material is LiNi 1-x-y Co x Mn y M a O2, wherein 0<x≤0.1, 0<y≤0.05, 0<a≤0.05, and M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W and B.

[0023] As the Ni content in the ternary material increases, the specific capacity of the ternary material will increase significantly; however, as the Ni content increases, the risk of lithium-nickel mixing also increases, resulting in a decrease in its cycle life. Therefore, when the above relationship is met, the stability of the high-nickel ternary material layer structure and the orderly arrangement of the transition metal elements and lithium between the layers can be guaranteed, allowing the ternary material to have a higher specific capacity while also taking into account a long cycle life.

[0024] In some preferred embodiments of the present disclosure, the (108) diffraction peak and the (110) diffraction peak satisfy the following relationship: When the relationship is within the above preferred range, the layered structure of the ternary material is more ordered and the atomic arrangement between the transition metal layers is more stable, so that the ternary material has a higher specific capacity while also taking into account a long cycle life.

[0025] In some preferred embodiments of the present disclosure, in the X-ray diffraction spectrum of the ternary material, the half-maximum width FWHM (108) of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° ranges from 0.1 to 0.2.

[0026] Specifically, the half-maximum width (FWHM) (108) of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° refers to the half-maximum width of the (108) diffraction peak at the half-maximum height of the (108) diffraction peak, which is parallel to the horizontal axis of the diffraction angle 2θ in the X-ray diffraction spectrum. When the FWHM (108) ranges from 0.1 to 0.2, the resulting ternary material has a stable crystal structure, unobstructed lithium ion insertion and extraction channels, and good rate performance.

[0027] In some preferred embodiments of the present disclosure, in the X-ray diffraction spectrum of the ternary material, the half maximum width FWHM (110) of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° ranges from 0.1 to 0.2.

[0028] Specifically, the half-maximum width (FWHM) (110) of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° refers to the half-maximum width of the (110) diffraction peak in the X-ray diffraction spectrum, which is parallel to the horizontal axis of the diffraction angle 2θ and is at the half-maximum height of the (110) diffraction peak. When the FWHM (110) ranges from 0.1 to 0.2, the resulting ternary material has a stable crystal structure, unobstructed lithium ion insertion and extraction channels, and good rate performance.

[0029] In some preferred embodiments of the present disclosure, the ternary material has an α-NaFeO2 layered structure.

[0030] It is understood that the X-ray diffraction spectrum of the ternary material in the present disclosure can be obtained by scanning with a copper target X-ray generator at 3° to 90° at a scanning rate of 2 to 5° / min.

[0031] In some preferred embodiments of the present disclosure, the particle size (D50) of the ternary material is 5 μm-20 μm, preferably 8 μm-15 μm. Within this particle size range, the ternary material can be guaranteed to have a better compaction density.

[0032] According to a second aspect of the present disclosure, a method for preparing a ternary material is provided, comprising the following steps: 1) mixing a first lithium source with a transition metal precursor to obtain a first mixture, and adding a first dopant to the first mixture to obtain a first doped mixture; wherein the transition metal precursor includes nickel, cobalt, and manganese elements; the molar ratio of the nickel, cobalt, and manganese elements is (1-xy): x:y, 0<x≤0.1, 0<y≤0.1; the molar ratio of the lithium element in the first lithium source to the total of the nickel, cobalt, and manganese elements in the precursor is (0.3-0.7):1; 2) mixing the first doped mixture with a second lithium source to obtain a second mixture, and sintering the second mixture for the first time in an oxygen-containing atmosphere to obtain a primary sintered product; wherein the lithium element in the second lithium source and the total of the nickel, cobalt, and manganese elements in the precursor are and is in a molar ratio of (0.35-0.75):1; the first lithium source and the second lithium source may be the same or different; 3) mixing the primary sintered product with an optional second dopant, and performing a second sintering in an oxygen-containing atmosphere to obtain a secondary sintered product; 4) mixing the secondary sintered product with an optional third dopant, and performing a third sintering in an oxygen-containing atmosphere to obtain the ternary material; wherein the first dopant, the second dopant, and the third dopant include an M element, and M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W, and B; the ratio of the sum of the molar amounts of the M element in the first dopant, the second dopant, and the third dopant to the sum of the molar amounts of nickel, cobalt, and manganese in the precursor is a:1, 0<a≤0.05.

[0033] Compared with the prior art, the preparation method of the ternary material provided by the present invention has the following effects: first, the step-by-step lithium mixing process makes the mixing of the lithium source and the ternary material precursor more uniform, so that the lithium ions are orderly embedded in the high-nickel ternary precursor lattice, alleviating the lithium-nickel mixing; second, the step-by-step sintering process can adjust the sintering conditions multiple times, improve the negative impact of continuous high temperature on the lithium-nickel mixing of the ternary material, ensure the consistency of the crystallinity inside and outside the ternary material, and be more conducive to the formation of a ternary material with a stable and uniform structure; third, the doping process stabilizes the crystal structure of the ternary material and improves the cycle performance.

[0034] Specifically, the transition metal precursor is suitable for preparing ternary polycrystalline particles.

[0035] In some preferred embodiments of the present disclosure, the D50 of the transition metal precursor is approximately between 8 μm and 15 μm, showing a large secondary ball agglomeration, and its primary particles are relatively small. The appearance of the secondary balls can be inherited by the ternary polycrystalline particles after sintering.

[0036] In some preferred embodiments of the present disclosure, the nickel-cobalt-manganese precursor includes at least one of a hydroxide precursor or a carbonate precursor.

[0037] In some preferred embodiments of the present disclosure, the first lithium source and the second lithium source are each independently a lithium-containing compound. Preferably, the lithium-containing compound includes one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate, lithium chloride, lithium fluoride, and lithium iodide.

[0038] In the present disclosure, in some preferred embodiments, the first dopant, the second dopant, and the third doping element may be the same or different. The above dopants are compounds containing doping elements. The doping elements include M elements, and M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W, and B. Optionally, the compound containing doping elements includes at least one of zinc hydroxide, magnesium hydroxide, molybdenum hydroxide, vanadium hydroxide, germanium hydroxide, aluminum hydroxide, titanium dioxide powder, zirconium oxide powder, tantalum pentoxide, yttrium oxide, boric acid, and tungstic acid. The above doping elements are similar to the radius of transition metal ions and have a strong binding energy with oxygen, which makes the crystal structure of the obtained ternary material more stable and the lattice order higher, which is beneficial to reduce the lithium-nickel mixed arrangement of high-nickel ternary materials.

[0039] In some preferred embodiments of the present disclosure, the molar ratio of lithium in the lithium compound to the M element in the dopant is 1:(0.001-0.05); wherein the dopant comprises a first dopant, a second dopant, and a third dopant. By controlling the molar ratio of lithium to the doping element within the above range, the effectiveness of elemental doping can be improved. Appropriate elemental doping can reduce the degree of nickel ion mixing in the material, improve the stability of the crystal surface structure, effectively suppress the lattice distortion generated by the ternary material during the charge and discharge process, and enable faster lithium ion intercalation and deintercalation during cycling, thereby improving the structural stability and rate performance of the material.

[0040] In the present disclosure, some preferred embodiments, the first sintering includes: performing the first sintering in an oxygen-containing atmosphere, the first sintering temperature is 600℃~800℃, the first sintering time is 12h~24h, and performing the first cooling after the first sintering is completed. The first cooling temperature is 20-30℃, and the cooling method adopts sudden cooling, and the first sintering product after sintering is directly transferred to room temperature. Performing the first sintering operation on the transition metal precursor helps to form a ternary material with good crystallinity, and at the same time carbonizes the polymer coating layer of the transition metal precursor, improves the true density of the material, and adjusts the specific surface area of ​​the material. The first cooling operation is performed after the first sintering is completed, and its purpose is to control the grain size of the intermediate product, so that the material grains are quickly stabilized at a fixed size, which can ensure the rapid crystallization of the ternary material, avoid the generation of other miscellaneous products, and improve the orderliness of the layered structure of the ternary material.

[0041] In the present disclosure, some preferred embodiments, the second sintering includes: after the first cooling is completed, a second sintering is carried out in a pure oxygen atmosphere, the second sintering temperature is 300℃~600℃, the second sintering time is 10h~20h, and a second cooling is carried out after the second sintering is completed. The second cooling temperature is 20-30℃, and the cooling method adopts sudden cooling, and the second sintering product after sintering is directly transferred to room temperature. Specifically, the pure oxygen atmosphere environment refers to a space filled with pure oxygen, and the second sintering is carried out in a space filled with pure oxygen. The first sintering and the second sintering have the same effect, which is to help form a ternary material with better crystallinity and improve the density of the ternary material. The first cooling and the second cooling also have the same effect, which is to control the grain size of the intermediate product, so that the grains of the ternary material are quickly stabilized at a fixed size, and increase the compaction density of the ternary material when preparing the pole piece. At the same time, it can also ensure the rapid crystallization of the ternary material, avoid the generation of other miscellaneous products, and improve the orderliness of the layered structure of the ternary material.

[0042] In some preferred embodiments of the present disclosure, the third sintering includes: performing a third sintering in a pure oxygen atmosphere after the second cooling is completed, the third sintering temperature is 200°C to 400°C, the third sintering time is 5 hours to 10 hours, and a third cooling is performed after the third sintering is completed. The third cooling temperature is 20-30°C, and the cooling method is quenching, and the third sintered product after sintering is directly transferred to room temperature.

[0043] It is understandable that the equipment used for the first sintering, the second sintering and the third sintering includes one of a tube furnace, a box furnace, a fluidized bed, a rotary kiln, a microwave oven and a tunnel furnace.

[0044] The triple sintering method achieves high crystallinity in the ternary material, while the triple cooling method controls the grain size of the intermediate product, stabilizing the ternary material grains within an appropriate size range. This helps to increase the compaction density of the ternary material while also preventing the formation of other impurities and improving the orderliness of the ternary material's layered structure. The triple sintering and cooling method saves sintering equipment cooling time, shortens process time, and is also conducive to obtaining a highly ordered layered structure of the ternary material, giving the ternary material a higher specific capacity.

[0045] During the three sintering processes, the sintering temperature and sintering time are successively reduced, showing a gradient sintering trend, which can ensure that the sites of lithium ion embedding in the transition metal precursor are more uniform. During the first sintering, the lithium content in the transition metal precursor is relatively low, and high temperature is conducive to the rapid penetration of lithium ions. During the second and third sintering, as the amount of lithium ion embedding increases, the repulsive force between atoms strengthens, making lithium ion embedding more difficult. At this time, if high-temperature sintering is continued, it is easy to cause lithium-nickel mixing. Therefore, the sintering temperature and sintering time are subsequently reduced to alleviate lithium-nickel mixing.

[0046] In some preferred embodiments of the present disclosure, the heating rate of the first sintering is ≤ the heating rate of the second sintering ≤ the heating rate of the third sintering.

[0047] During the three sintering processes, the heating rate increases successively, showing a gradient upward trend, which can ensure that the sites of lithium ion embedding in the ternary material precursor are more uniform; during the first sintering, the temperature is slowly increased to ensure that the transformation of the transition metal precursor to the ternary material crystal phase is more stable and avoid lattice distortion. This process is also the process of lithium ion embedding in the crystal phase. Slow heating is beneficial to reduce the mixing of lattices; during the second and third sintering, the heating rate increases successively, which is beneficial to increase the stability of the ternary material crystal phase and save sintering time.

[0048] In some preferred embodiments of the present disclosure, the heating rate of the first sintering is 2° C. / min to 5° C. / min.

[0049] In some preferred embodiments of the present disclosure, the heating rate of the second sintering is 5°C / min to 10°C / min.

[0050] In some preferred embodiments of the present disclosure, the heating rate of the third sintering is 10°C / min to 20°C / min. When the above heating rate is met, the obtained ternary material has better performance.

[0051] In some preferred embodiments of the present disclosure, in step 1), a gelling agent may be added to the first mixture. The order of adding the gelling agent and the dopant is not limited; the gelling agent may be added first and mixed with the first mixed product before the dopant is added; the dopant may be added first and mixed with the first mixed product before the gelling agent is added; and the gelling agent and the dopant may be added simultaneously and mixed with the first product.

[0052] In some preferred embodiments of the present disclosure, the gelling agent comprises a solvent, a complexing agent, and a polymer monomer; wherein the mass percentage of the solvent in the gelling agent is 10wt%-50wt%, and the solvent comprises at least one of anhydrous ethanol or deionized water. When the mass percentage of the solvent in the gelling agent is within the above range, it can effectively disperse the lithium source, uniformly dispersing the lithium ions on the surface of the transition metal precursor, facilitating lithiation.

[0053] In some preferred embodiments of the present disclosure, the mass percentage of the complexing agent in the gelling agent is 0.2 wt% to 2 wt%; the complexing agent includes sodium dodecyl sulfate (SDS). The complexing agent facilitates the bonding of the gelling agent and the lithium source, and the mass percentage of the complexing agent within the above range facilitates the dispersion of the lithium source in the gelling agent, thereby facilitating the formation of a more stable ternary material.

[0054] In the present disclosure, in some preferred embodiments, the volume ratio of the polymer monomer to the solvent is (0.1-0.4):1; the polymer monomer includes at least one of methyl methacrylate, styrene or acrylonitrile; preferably methyl methacrylate. The polymer monomer is a precursor for forming a gel. By controlling the volume ratio of the polymer monomer to the solvent within the above range, it is beneficial to form a gel with better coating performance, which is convenient for improving the crystallinity after lithiation. Among them, the methyl methacrylate will polymerize into polymethyl methacrylate during the mixing process, which has higher dispersibility for lithium sources and better bonding with the surface of the metal precursor. The residual carbon content of the finished product of polymethyl methacrylate after sintering is in the range of 0.1%wt to 3%wt. The residual carbon rate in this range is conducive to further improving the rate performance.

[0055] In some preferred embodiments of the present disclosure, in the process of adding the gelling agent and the optional dopant to the first mixture to obtain gel particles, appropriate heating treatment can be performed at a heating temperature of 40°C to 80°C, which is conducive to the polymerization reaction.

[0056] In a third aspect of the present disclosure, a positive electrode sheet is provided, comprising the above-mentioned ternary material, or a ternary material prepared by the above-mentioned method for preparing the ternary material.

[0057] The positive electrode sheet prepared using the above-mentioned ternary material is used in a battery, and the battery has a higher energy density and cycle life.

[0058] In some preferred embodiments of the present disclosure, the compaction density of the positive electrode sheet is 3g / cm 3 ~3.7g / cm 3 .

[0059] The positive electrode sheet prepared using the ternary material prepared in the present disclosure has a relatively complete layered structure and a high compaction density. When used in batteries, it can improve the energy density and cycle life of the battery.

[0060] In a fourth aspect of the present disclosure, a positive electrode sheet is provided, comprising a ternary material, wherein the chemical formula of the ternary material is LiNi 1-x-y Co x Mn y M a O2, wherein 0<x≤0.1, 0<y≤0.1, 0<a≤0.05, M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W and B; the ternary material is a polycrystalline particle; in the X-ray diffraction spectrum of the positive electrode sheet, there is a (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° and a (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°; the (108) diffraction peak and the (110) diffraction peak satisfy the following relationship: Wherein, FWHM(108) is the half-maximum width of the (108) diffraction peak at a diffraction angle of 2θ = (64±0.5)°; FWHM(110) is the half-maximum width of the (110) diffraction peak at a diffraction angle of 2θ = (65±0.5)°.

[0061] In a fifth aspect, the present disclosure provides a lithium-ion battery comprising the above-mentioned positive electrode sheet. The lithium-ion battery using the present disclosure has a high energy density and a high cycle life.

[0062] The lithium-ion battery further comprises a negative electrode sheet, a diaphragm and an electrolyte. The negative electrode sheet comprises a current collector and a negative electrode active material layer coated on at least one side of the current collector; the negative electrode active material layer comprises a negative electrode active material, a conductive agent and a binder.

[0063] The negative electrode active material includes a carbon-based material; the carbon-based material includes one or more of artificial graphite, natural graphite, hard carbon material or soft carbon material.

[0064] The negative electrode active material also includes one or more of silicon-based materials, tin-based materials, and lithium titanate materials. The silicon-based material can be elemental silicon, silicon oxide (SiO x , 0<x<2), silicon alloy or a combination of one or more. The tin-based material can be elemental tin, tin oxide (SnO x , 0<x≤2), a combination of one or more of tin alloys. The lithium titanate material can be Li4Ti5O 12 wait.

[0065] The binder can be a combination of one or more of styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyethylene acrylic acid (PEAA), sodium alginate, carboxymethyl chitosan, polyacrylonitrile (PAN) and polyvinyl alcohol (PVA).

[0066] The current collector can be any one of copper foil, carbon-coated copper foil, polymer-coated copper foil, carbon cloth, carbon nanotube film or carbon paper.

[0067] The diaphragm can be one of polyethylene, polypropylene, polyvinylidene fluoride, or a composite membrane of multiple materials.

[0068] The electrolyte is an organic solvent in which carrier ions are dissolved. The present disclosure does not limit the electrolyte and the electrolyte can be prepared according to the actual situation.

[0069] In a sixth aspect of the present disclosure, an electrical device is provided, comprising the above-mentioned lithium-ion battery.

[0070] The electric device prepared using the lithium-ion battery disclosed herein can have higher market competitiveness.

[0071] In some embodiments of the present disclosure, the above-mentioned electrical devices include but are not limited to mobile phones, laptops, tablet computers, smart watches and other wearable electronic devices, electronic cigarettes, new energy vehicles, electric assisted bicycles, etc.

[0072] The present disclosure is further described in detail below through examples.

[0073] Example 1

[0074] This embodiment is used to illustrate the ternary material disclosed in the present disclosure and its preparation method, which includes the following steps:

[0075] 1) Use Ni 0.90 Co 0.05 Mn 0.05 A hydroxide precursor is prepared, using LiOH as a lithium source, and first adding lithium hydroxide in a ratio of lithium:transition metal element = 0.4 and mixing to obtain a first mixed product; titanium dioxide powder (calculated based on the molar content of titanium element to obtain 1500ppm), zirconium oxide powder (calculated based on the molar content of zirconium element to obtain 2500ppm), tantalum pentoxide (calculated based on the molar content of tantalum element to obtain 1000ppm) and yttrium oxide powder (calculated based on the molar content of yttrium element to obtain a supplementary content of 1000ppm) are further added to the first mixed product, and high-speed mixing is performed for 8 hours; the mixture is then poured into a ball mill and ball-milled with anhydrous ethanol for 8 hours, and then 0.4wt% sodium lauryl sulfate, 30wt% H2O, and methyl methacrylate with a volume ratio of 0.25 to water are added to the mixture, and stirred for 1 hour to obtain a mixture of a gel-encapsulated precursor, a lithium salt, and an additive, and the above mixture is heated to 80°C, kept warm for 1 hour, and gel particles are collected;

[0076] 2) The gel particles were then mixed again with LiOH at a ratio of lithium to transition metal element = 0.63 at high speed, and then sintered for the first time in an oxygen atmosphere at a heating rate of 3°C / min and a sintering temperature of 700°C for 15 hours, followed by sieving to obtain a first sintered product;

[0077] 3) The first sintered product was mixed with alumina powder (calculated based on the molar content of aluminum element to obtain 1500 ppm) and subjected to a second sintering process at a heating rate of 8°C / min, a sintering temperature of 500°C, a sintering time of 12 hours, and an oxygen atmosphere to obtain a second sintered product;

[0078] 4) The second sintered product was mixed with boric acid (calculated based on the molar content of boron to obtain 1000 ppm) and tungstic acid powder (calculated based on the molar content of tungsten to obtain 1000 ppm) and sintered for a third time at a heating rate of 15°C / min and sintered at 350°C in an oxygen atmosphere for 8 hours to obtain the final ternary material.

[0079] Among them, Ni 0.90 Co 0.05 Mn 0.05 The D50 of the hydroxide precursor is 11 μm, and its SEM images at different magnifications are shown in Figures 1 and 2. In the low-magnification SEM (Figure 1), Ni 0.90 Co 0.05 Mn 0.05 The hydroxide precursor is composed of secondary spherical particles accumulated from primary particles; in high-magnification SEM (Figure 2), the primary particles are relatively slender. The obtained ternary material (LiNi 0.90 Co 0.05 Mn 0.05 O2) has a D50 of 11 μm, and its SEM is shown in Figure 3. 0.90 Co 0.05 Mn 0.05 MO2 is a secondary spherical particle formed by the accumulation of primary particles.

[0080] The finished ternary material was subjected to XRD testing using a copper target X-ray generator and scanned at a scanning rate of 3° / min in the range of 10-80°. The XRD spectrum was analyzed based on the peak positions and half-peak widths of the (108) diffraction peak and the (110) diffraction peak. The data are listed in Table 1.

[0081] Example 2

[0082] The difference between Example 2 and Example 1 is that titanium dioxide and tantalum pentoxide are not added during the sintering in step 1).

[0083] Example 3

[0084] The difference between Example 3 and Example 1 is that no aluminum oxide is added in step 2).

[0085] Example 4

[0086] The difference between Example 4 and Example 1 is that no tungstic acid is added in step 4).

[0087] Example 5

[0088] The difference between Example 5 and Example 1 is that tantalum pentoxide and yttrium oxide powder are not added in the sintering in step 1); aluminum oxide is not added in step 2); and tungstic acid is not added in step 4).

[0089] Example 6

[0090] The difference between Example 6 and Example 5 is that, unlike Example 1, Ni 0.88 Co 0.06 Mn 0.06 The precursor of the ratio was sintered at 750℃ for the first time for 10h and 600℃ for the second time for 8h.

[0091] Example 7

[0092] The difference between Example 7 and Example 5 is that Ni 0.83 Co 0.12 Mn 0.05 The cobalt-free precursor has a first sintering temperature of 820°C for 14h; the second sintering temperature is 660°C for 8h.

[0093] Example 8

[0094] Example 8 differs from Example 5 in that, in step 1), lithium hydroxide is added at a ratio of lithium:transition metal element=0.6; and in step 2), lithium hydroxide is added at a ratio of lithium:transition metal element=0.46.

[0095] Example 9

[0096] Example 9 differs from Example 5 in that, in step 1), lithium hydroxide is added at a ratio of lithium:transition metal element=0.9; and in step 2), lithium hydroxide is added at a ratio of lithium:transition metal element=0.15.

[0097] Example 10

[0098] The difference between Example 10 and Example 5 is that the three sinterings adopt the same heating rate of 10°C / min.

[0099] Example 11

[0100] The difference between Example 11 and Example 5 is that the second sintering temperature is higher than the first sintering temperature, which is 750°C.

[0101] Comparative Example 1

[0102] The difference between Comparative Example 1 and Example 1 is that no dopant is added.

[0103] Comparative Example 2

[0104] The difference between Comparative Example 2 and Example 1 is that the lithium source is not added in batches as in Example 1, and in the first mixing process, lithium hydroxide is added at a ratio of lithium to transition metal element = 1.05.

[0105] Comparative Example 3

[0106] The difference between Comparative Example 3 and Example 6 is that the stepwise sintering of Example 6 is not performed, and a single sintering is adopted. The sintering temperature is 800°C and the sintering time is 33h.

[0107] Comparative Example 4

[0108] The difference between Comparative Example 4 and Example 6 is that,

[0109] Using Ni 0.78 Mn 0.22 The precursor of the embodiment 1 was sintered at a temperature of 750°C for 14 hours for the first time, 600°C for 8 hours for the second time, and 300°C for 4 hours for the third time. The gel coating treatment, the addition of lithium in stages, and the doping treatment in Example 1 were not performed. Lithium hydroxide was added at a ratio of lithium to transition metal element = 1.05.

[0110] The carbon residue data of the ternary materials prepared in the above Examples 1-11 and Comparative Examples 1-4 were tested using a CS analyzer.

[0111] The specific data of FWHM(108), FWHM(110), 2θ(108), and 2θ(110) in the XRD spectra obtained after XRD testing of the ternary materials prepared in the above Examples 1-11 and Comparative Examples 1-4 are recorded in Table 1. The XRD half-peak width and peak position data are derived from the analysis of the XRD original test file by the processing software MDIJade 6. The specific data are shown in Table 1.

[0112] Table 1 Partial data of ternary materials of Examples 1-11 and Comparative Examples 1-4

[0113] The positive electrode sheet S containing the ternary materials of Examples 1 and 6 and Comparative Examples 1 and 3 was selected, and the specific data of FWHM(108), FWHM(110), 2θ(108), and 2θ(110) in the XRD spectrum obtained after XRD testing of the above positive electrode sheet were recorded in Table 2. The XRD half-peak width and peak position data were derived from the analysis of the XRD original test file by the processing software MDIJade 6. The specific data are shown in Table 2.

[0114] Table 2 Positive electrode part data table

[0115] Performance testing:

[0116] The ternary materials prepared in the above Examples 1-11 and Comparative Examples 1-4 were used to prepare positive electrode sheets and batteries, and the following tests were performed.

[0117] Specific capacity test: The above ternary materials were mixed with PVDF and SP in a ratio of 96:3:1 using NMP as solvent for 2 hours to form a stable and uniform positive electrode slurry. The positive electrode slurry was coated on aluminum foil using a coating machine, dried, and cold pressed to obtain a compaction density of 3.6g / cm 3 The positive electrode sheet was dried at 120°C for 24 hours. A lithium sheet was used as the negative electrode, a Cellgard 2300 porous membrane was used as the separator, and a 1 mol / L LiPF6 + DMC (volume ratio 1:1) mixed electrolyte was used as the electrolyte. A button cell 2032 was assembled and tested. Charge and discharge tests were performed at a 0.2C rate. The specific capacity of the third discharge test was taken as the specific capacity of the ternary material.

[0118] Using deionized water as solvent, 95wt% of negative electrode active material graphite, 2wt% of binder SBR, 2wt% of conductive agent graphite and 1wt% of thickener CMC were added to deionized water to prepare negative electrode slurry. The negative electrode slurry was coated on copper foil, dried and cold pressed to obtain a compacted density of 1.7g / cm 3 .

[0119] Battery preparation: The positive electrode sheet, negative electrode sheet and separator prepared above are made into bare cells according to conventional preparation processes, and the bare cells are dried, injected with electrolyte, and packaged to finally make batteries.

[0120] Among them, the negative electrode active material artificial graphite, conductive carbon black, thickener (CMC), and binder (SBR) are mixed in a ratio of 96:1:1:2, and the powder and deionized water are stirred into a negative electrode slurry using a homogenizer and evenly coated on a copper foil to obtain a negative electrode sheet.

[0121] Room temperature cycle performance test: The formed cells were subjected to a room temperature 25°C cycle test, with charge and discharge tests performed at 0.5C / 0.5C, and the discharge capacity retention of the battery after 500 cycles was recorded.

[0122] Direct current internal resistance (DCIR) test: The formed cells were subjected to a high temperature 45°C cycle test, with charge and discharge tests performed at 1C / 1C, and the DCIR retention of the battery was recorded after 500 cycles.

[0123] Table 2 Performance data of Examples 1-11 and Comparative Examples 1-4

[0124] It can be seen from the data in Table 3 that the ternary material provided in the embodiment of the present disclosure meets the crystal structure characteristics required by the present disclosure, and the discharge capacity, cycle performance and DCIR of the obtained battery are improved compared with the control example.

[0125] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A ternary material, wherein, The chemical formula of the ternary material is LiNi 1-x-y Co x Mn y M a O2, where 0 < x ≤ 0.1, 0 < y ≤ 0.1, 0 < a ≤ 0.05, and M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W, and B; The ternary material includes polycrystalline grains; In the X-ray diffraction spectrum of the ternary material, there are (108) diffraction peaks with a diffraction angle 2θ at (64 ± 0.5)° and (110) diffraction peaks with a diffraction angle 2θ at (65 ± 0.5)°; The (108) diffraction peak and the (110) diffraction peak satisfy the following relationship: Wherein, FWHM(108) is the full width at half maximum of the (108) diffraction peak at the diffraction angle 2θ = (64 ± 0.5)°; FWHM(110) is the full width at half maximum of the (110) diffraction peak at the diffraction angle 2θ = (65 ± 0.5)°.

2. The ternary material according to claim 1, wherein The chemical formula of the ternary material is LiNi 1-x-y Co x Mn y M a O2, where 0 < x ≤ 0.1, 0 < y ≤ 0.05, 0 < a ≤ 0.05, and M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W, and B.

3. The ternary material according to claim 1 or 2, wherein The (108) diffraction peak and the (110) diffraction peak satisfy the following relational expression:

4. The ternary material according to any one of claims 1-3, wherein, In the X-ray diffraction spectrum of the ternary material, the full width at half maximum FWHM(108) of the (108) diffraction peak ranges from 0.1 to 0.2; and / or The full width at half maximum FWHM(110) of the (110) diffraction peak ranges from 0.1 to 0.

2.

5. A method for preparing the ternary material according to any one of claims 1-4, wherein, It includes the following steps: 1) Mix the first lithium source with the transition metal precursor to obtain a first mixture, and add a first dopant to the first mixture to obtain a first doped mixture; wherein, the transition metal precursor includes nickel, cobalt, and manganese elements; the molar ratio of the nickel, cobalt, and manganese elements is (1 - x - y):x:y, 0 < x ≤ 0.1, 0 < y ≤ 0.1; the molar ratio of the lithium element in the first lithium source to the total of the nickel, cobalt, and manganese elements in the precursor is (0.3 - 0.7):1; 2) Mix the first doped mixture with the second lithium source to obtain a second mixture, and perform a first sintering on the second mixture in an oxygen-containing atmosphere to obtain a first sintered product; wherein, the molar ratio of the lithium element in the second lithium source to the total of the nickel, cobalt, and manganese elements in the precursor is (0.35 - 0.75):1; the first lithium source and the second lithium source can be the same or different; 3) Mix the first sintered product with an optional second dopant, and perform a second sintering in an oxygen-containing atmosphere to obtain a second sintered product; 4) Mix the second sintered product with an optional third dopant, and perform a third sintering in an oxygen-containing atmosphere to obtain the ternary material; wherein, the first dopant, the second dopant, and the third dopant include element M, and M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W, and B; the ratio of the sum of the molar amounts of element M in the first dopant, the second dopant, and the third dopant to the sum of the molar amounts of the nickel, cobalt, and manganese elements in the precursor is a:1, 0 < a ≤ 0.

05.

6. The method according to claim 5, wherein The first sintering includes: performing a first sintering in an oxygen-containing atmosphere, the first sintering temperature is 600°C to 800°C, the first sintering time is 12h to 24h, and after the first sintering is completed, a first cooling is performed; and / or The second sintering includes: after the first cooling is completed, performing a second sintering in a pure oxygen atmosphere, the second sintering temperature is 300°C to 600°C, the second sintering time is 10h to 20h, and after the second sintering is completed, a second cooling is performed; and / or The third sintering includes: after the second cooling ends, performing the third sintering in a pure oxygen atmosphere, with the third sintering temperature being 200°C to 400°C and the third sintering time being 5h to 10h, and performing the third cooling after the third sintering ends; Among them, the heating rate of the first sintering ≤ the heating rate of the second sintering ≤ the heating rate of the third sintering.

7. The method according to claim 5 or 6, wherein The heating rate of the first sintering is 2°C / min to 5°C / min; and / or the heating rate of the second sintering is 5°C / min to 10°C / min; and / or the heating rate of the third sintering is 10°C / min to 20°C / min.

8. The method according to any one of claims 5-7, wherein A gelling agent can also be added to the first mixture; the gelling agent includes a solvent, a complexing agent, and a polymer monomer; among them, based on the total mass of the gelling agent, the mass percentage of the solvent is 10wt% - 50wt%; the mass percentage of the complexing agent is 0.2wt% - 2wt%; the volume ratio of the polymer monomer to the solvent is (0.1 - 0.4):

1.

9. A lithium-ion battery, including a positive electrode sheet, where the positive electrode sheet includes the ternary material according to any one of claims 1 - 4, or the ternary material prepared by the method according to any one of claims 6 - 8.

10. The lithium-ion battery according to claim 9, wherein, The chemical formula of the ternary material is LiNi 1-x-y Co x Mn y M a O2, where 0 < x ≤ 0.1, 0 < y ≤ 0.1, 0 < a ≤ 0.05, and M is selected from one or more of Zr, Ti, Zn, Mg, Ta, V, Al, Y, W, and B; The ternary material includes polycrystalline grains; In the X-ray diffraction spectrum of the positive electrode sheet, there are a (108) diffraction peak with a diffraction angle 2θ at (64 ± 0.5)° and a (110) diffraction peak with a diffraction angle 2θ at (65 ± 0.5)°. The (108) diffraction peak and the (110) diffraction peak satisfy the following relationship: Among them, FWHM(108) is the full width at half maximum of the (108) diffraction peak at the diffraction angle 2θ = (64 ± 0.5)°. FWHM(110) is the full width at half maximum of the (110) diffraction peak at the diffraction angle 2θ = (65 ± 0.5)°.

11. An electrical device, characterized in that, Including the lithium-ion battery according to claim 9 or 10.

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