A positive electrode material for lithium ion batteries, a preparation method thereof, a positive electrode sheet, and a lithium ion battery

Abstract

To overcome the technical problems of how to control the atomic arrangement and layered order of modified ternary materials, the application provides a positive electrode material for a lithium ion battery, the positive electrode material has a chemical formula of LiNi 1‑x‑y Co x M y M' b O2, wherein 0 The X-ray diffraction spectrum of the positive electrode material has 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: 0.5≤(I(108) / I(110))≤1.5. The application provides a positive electrode material for a lithium ion battery, and the satisfaction of the relationship can ensure that the material has good layered structure order and reasonable atomic arrangement, so that the prepared positive electrode material has a high mass specific capacity and a long cycle life.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy storage, and particularly relates to a positive electrode material for a lithium ion battery, a preparation method thereof, a positive electrode sheet and a lithium ion battery. BACKGROUND

[0002] The positive electrode material of a lithium ion battery is a main material of the lithium ion battery, and its performance is one of key factors affecting the energy density of the lithium ion battery. The positive electrode material of the lithium ion battery is generally lithium iron phosphate, lithium manganate, lithium cobaltate, lithium nickelate and lithium nickel cobalt manganate. Among them, lithium nickel cobalt manganate (ternary material) has the advantages of lithium manganate, lithium cobaltate and lithium nickelate, has a high specific capacity, a good discharge rate and excellent cycle performance, is one of main directions of the development of the positive electrode material technology, and is a core material affecting the performance, application scene and market potential of the lithium ion battery.

[0003] In order to meet the market demand of the lithium ion battery and further improve the specific capacity and cycle performance of the ternary material, the existing technology usually adopts the modes of surface coating, element doping and increasing the nickel content to optimize the ternary material. The introduction of new elements or the change of the atomic ratio in the ternary material will affect the internal atomic arrangement and layer order, and the atomic arrangement and layer order in the crystal structure of the ternary material will affect the lithium storage performance. Therefore, it has important research significance and research value to reasonably control the atomic arrangement and layer order of the modified ternary material and prepare high-performance modified ternary material. SUMMARY

[0004] The purpose of the present application is to provide a positive electrode material for a lithium ion battery, a preparation method thereof, a positive electrode sheet and a lithium ion battery. The high-performance lithium ion battery positive electrode material is prepared by reasonably controlling the internal atomic arrangement and layer order of the positive electrode material.

[0005] In order to solve the above problems, the present application provides a positive electrode material for a lithium ion battery, the chemical formula of the positive electrode material is LiNi 1-x-y Co x M y M' b O2, wherein 0 < x < 0.3, 0 < y < 0.4, 0 < b < 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al;

[0006] In the X-ray diffraction spectrum of the positive electrode material, there are 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)°;

[0007] The (108) diffraction peak and the (110) diffraction peak satisfy the following relationship:

[0008]

[0009] FWHM(108) is the half-peak width of the (108) diffraction peak at a diffraction angle 2θ=(64±0.5)°;

[0010] FWHM(110) is the half-peak width of the (110) diffraction peak at a diffraction angle 2θ=(65±0.5)°.

[0011] Preferably, the positive electrode material is a polycrystalline ternary material; the positive electrode material has a chemical formula of LiNi 1-x-y Co x M y M' b O2, wherein 0.1≤x≤0.2, 0.1≤y≤0.35, 0

[0012] Preferably, the (108) diffraction peak and the (110) diffraction peak satisfy the following relationship:

[0013] Preferably, the (108) diffraction peak and the (110) diffraction peak satisfy the following relationship:

[0014] Preferably, in the X-ray diffraction spectrum of the positive electrode material, the half-peak width FWHM(108) of the (108) diffraction peak at a diffraction angle 2θ=(64±0.5)° ranges from 0.1 to 0.3.

[0015] Preferably, in the X-ray diffraction spectrum of the positive electrode material, the half-peak width FWHM(110) of the (110) diffraction peak at a diffraction angle 2θ=(65±0.5)° ranges from 0.1 to 0.3.

[0016] Preferably, the positive electrode material has an α-NaFeO2 layered structure.

[0017] In a second aspect, the present application provides a preparation method of the positive electrode material for lithium ion batteries, comprising the following steps:

[0018] The lithium-containing compound, the soluble metal salt, the cobalt acetate, the nickel acetate and the doped metal salt are dispersed in a solvent to obtain a dispersion solution, a pH regulator is added to the dispersion solution to make the pH of the dispersion solution 7-8, and a precursor material is obtained by drying; the precursor material is sequentially subjected to first sintering, first cooling, second sintering and second cooling to obtain the positive electrode material.

[0019] The first sintering comprises the following steps: the precursor material is subjected to first sintering in an air atmosphere environment, the first sintering temperature is 300-600 ℃, the first sintering time is 3-6 h, and first cooling is performed after the first sintering is completed.

[0020] The second sintering comprises the following steps: after the first cooling is completed, the second sintering is performed in a pure oxygen atmosphere environment, the second sintering temperature is 700-950 ℃, the second sintering time is 8-15 h, and second cooling is performed after the second sintering is completed.

[0021] Preferably, the soluble metal salt and the doped metal salt each comprise one or more of manganese acetate, titanium acetate, zinc acetate, magnesium acetate, molybdenum acetate, vanadium acetate, germanium acetate, aluminum acetate, zirconium acetate, manganese nitrate, titanium nitrate, zinc nitrate, magnesium nitrate, molybdenum nitrate, vanadium nitrate, germanium nitrate, aluminum nitrate, zirconium nitrate, manganese hydroxide, titanium hydroxide, zinc hydroxide, magnesium hydroxide, molybdenum hydroxide, vanadium hydroxide, germanium hydroxide, aluminum hydroxide and zirconium hydroxide.

[0022] The lithium-containing compound comprises one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate, lithium chloride, lithium fluoride and lithium iodide.

[0023] The solvent comprises one or more of deionized water, ethanol, methanol, isopropanol, n-butanol, octanol and decanol.

[0024] Preferably, the lithium compound, the soluble metal salt, the nickel acetate, the cobalt acetate and the doped metal salt have a metal element molar ratio of (1-1.2):y:1-x-y:x:b, wherein 0

[0025] Preferably, the concentration of the pH regulator is 1-3 mol / L, and the pH regulator comprises one or more of citric acid, acetic acid, oxalic acid, benzoic acid, acrylic acid, carboxylated graphene and carboxylated graphite.

[0026] Preferably, in the step of drying to obtain the precursor material, the drying method is one or more of spray drying, flash evaporation, stirring drying and dynamic drying.

[0027] Preferably, the first sintering is performed at a heating rate of 1-8℃ / min, the first cooling temperature is 20-30℃, and the cooling mode is quenching, and the material after the first sintering is directly transferred to room temperature;

[0028] The second sintering is performed at a heating rate of 1-8℃ / min, the second cooling temperature is 20-30℃, and the cooling mode is quenching, and the material after the second sintering is directly transferred to room temperature.

[0029] In a third aspect, the present application provides a positive electrode sheet comprising the positive electrode material for lithium ion batteries or the positive electrode material prepared by the preparation method of the positive electrode material for lithium ion batteries.

[0030] Preferably, the compaction density of the positive electrode sheet is 3-3.7g / cm 3 .

[0031] In a fourth aspect, the present application provides a positive electrode sheet comprising a positive electrode material, the positive electrode material having a chemical formula of Li z Ni 1-x-y Co x M y M' b O2, wherein 0

[0032] The positive electrode sheet has 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)° in an X-ray diffraction spectrum of the positive electrode sheet;

[0033] The (108) diffraction peak and the (110) diffraction peak satisfy the following relationship:

[0034]

[0035] FWHM(108) is the half-peak width of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)°; and FWHM(110) is the half-peak width of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°.

[0036] In a fifth aspect, the present application provides a lithium ion battery comprising the positive electrode sheet.

[0037] The lithium ion battery positive electrode material provided in the application has (110) diffraction peak at diffraction angle 2θ of (65±0.5)° and (108) diffraction peak at diffraction angle 2θ of (64±0.5)° in the X-ray diffraction spectrum of the positive electrode material, and satisfies the relationship: The relationship can ensure good layer structure order and reasonable atomic arrangement of the material, so that the prepared positive electrode material has high mass specific capacity and cycle performance.

[0038] The lithium ion battery positive electrode sheet provided in the application has (110) diffraction peak at diffraction angle 2θ of (65±0.5)° and (108) diffraction peak at diffraction angle 2θ of (64±0.5)° in the X-ray diffraction spectrum of the positive electrode material, and satisfies the relationship: The lithium ion battery containing the positive electrode sheet has higher cycle life. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is the XRD spectrum of the positive electrode material prepared in Example 1;

[0040] Figure 2 is the XRD spectrum of the positive electrode material prepared in Example 2;

[0041] Figure 3 is the XRD spectrum of the positive electrode material prepared in Example 3;

[0042] Figure 4 is the XRD spectrum of the positive electrode material prepared in Example 4;

[0043] Figure 5 is the comparison diagram of the XRD spectra of the positive electrode materials in Comparative Example 1 and Examples 1-4; DETAILED DESCRIPTION

[0044] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0045] As shown in Figures 1-4 , the present application provides a positive electrode material for lithium ion battery, the chemical formula of the positive electrode material is LiNi 1-x-y Co x M y M' bO2, wherein 0 < x ≤ 0.3, 0 < y ≤ 0.4, 0 ≤ b ≤ 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al, M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al; 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)° in the X-ray diffraction spectrum of the positive electrode material;

[0046] The (108) diffraction peak and the (110) diffraction peak satisfy the following relationship:

[0047]

[0048] FWHM(108) is the half-peak width of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)°;

[0049] FWHM(110) is the half-peak width of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°.

[0050] The lithium nickel cobalt manganese oxide (ternary material) combines the advantages of lithium manganate, lithium cobaltate and lithium nickelate, and is widely used as a positive electrode material in lithium ion batteries. The ternary nickel cobalt manganese material has a hexagonal layered structure, and transition metal ions and lithium ions alternately occupy the octahedral voids, arranged in layers. This atomic arrangement structure makes the ternary material have superior electrochemical performance. Lithium ions can be freely inserted and extracted between layers to realize energy storage. However, during the insertion and extraction of lithium ions, the crystal structure inside the ternary material will change to varying degrees, for example, the rearrangement of atoms between layers and the change in the order of the layered structure will directly affect the performance of the material.

[0051] Since the ternary material is hexagonal, and the (110) crystal face is related to the a and b axes, the unit cell parameter a is related to the (110) crystal face spacing; the (108) crystal face spacing is more strongly related to the unit cell parameter c value; and the distance relationship between the (110) crystal face and the (108) crystal face will affect the layered order of the ternary material. At the same time, the half-peak width in the XRD spectrum of the (110) crystal face and the (108) crystal face will directly or indirectly reflect the order of the arrangement of atoms in the corresponding layered lattice. The inventors have found through extensive research that when the (108) diffraction peak and the (110) diffraction peak satisfy the relationship: not only can the order of the layered structure of the material be determined, but also the rationality of the arrangement of atoms between layers can be evaluated, and satisfying this relationship can ensure that the positive electrode material has good layered structure order and a reasonable atomic arrangement, so that the positive electrode material has a high specific capacity and improves the cycle life of the battery.

[0052] Specifically, in the formula, 2θ(110) refers to the specific position of the (110) diffraction peak at a diffraction angle of (65±0.5)° in the X-ray diffraction spectrum actually obtained when performing XRD testing based on the cathode material. Generally, the value range of 2θ(110) is (65±0.5)°. Similarly, 2θ(108) refers to the specific position of the (108) diffraction peak at a diffraction angle of (64±0.5)° in the X-ray diffraction spectrum actually obtained when performing XRD testing based on the cathode material powder.

[0053] In some preferred embodiments, the cathode material is a polycrystalline ternary material; the chemical formula of the cathode material is LiNi. 1-x-y Co x M y M' b O2, where 0.1≤x≤0.2, 0.1≤y≤0.35, 0<b≤0.05, and M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga, and Al; M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga, and Al.

[0054] In some preferred embodiments, the positive electrode material has the chemical formula LiNi. 1-x-y Co x M y M' b O2, where 0.1≤x≤0.2, 0.1≤y≤0.3, 0<b≤0.05, and M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga, and Al; M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga, and Al.

[0055] With a high Ni content in the cathode material, the specific capacity of the ternary material increases significantly. However, a high Ni content also alters the atomic composition of the ternary material, increasing the risk of lithium-nickel mixing and reducing its cycle life. Therefore, satisfying the above relationship ensures that the layered structure of the high-nickel cathode material has high order, guaranteeing high specific capacity and cycle life.

[0056] In some preferred embodiments, the positive electrode material has the chemical formula LiNi. 1-x-y Co x M y M' b O2, where 0.1≤x≤0.3, 0.1≤y≤0.3, 0<b≤0.05, and M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga, and Al; M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga, and Al.

[0057] In some preferred embodiments, the (108) diffraction peak and the (110) diffraction peak satisfy the following relationship:

[0058] In some preferred embodiments, the (108) diffraction peak and the (110) diffraction peak satisfy the following relationship:

[0059] The relationship is within the above preferred range, the layered structure of the positive electrode material layer has high order, the atomic arrangement between the layers has high stability, the specific capacity of the prepared positive electrode material is high, and the cycle performance of the prepared lithium ion battery is better.

[0060] In some embodiments, in the X-ray diffraction spectrum of the positive electrode material, the half-peak width FWHM(108) of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° ranges from 0.1 to 0.3.

[0061] Specifically, the half-peak width FWHM(108) of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° refers to the value of the half-peak width of the (108) diffraction peak at the position of the half-peak height of the (108) diffraction peak in the X-ray diffraction spectrum, which is parallel to the horizontal axis of the diffraction angle 2θ. The FWHM(108) ranges from 0.1 to 0.3 and satisfies the relationship: The prepared positive electrode material has good layered structure order and high specific capacity.

[0062] In some embodiments, in the X-ray diffraction spectrum of the positive electrode material, the half-peak width FWHM(110) of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° ranges from 0.1 to 0.3.

[0063] Specifically, the half-peak width FWHM(110) of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° refers to the value of the half-peak width of the (110) diffraction peak at the position of the half-peak height of the (110) diffraction peak in the X-ray diffraction spectrum, which is parallel to the horizontal axis of the diffraction angle 2θ. The FWHM(110) ranges from 0.1 to 0.3 and satisfies the relationship: The prepared positive electrode material has good layered structure order and high specific capacity.

[0064] In some embodiments, the positive electrode material has an α-NaFeO2 layered structure.

[0065] It can be understood that the X-ray diffraction spectrum of the positive electrode material in the present application can be obtained by scanning with a copper target X-ray generator at a scanning rate of 6° / min from 10° to 80°.

[0066] In a second aspect, the application provides a preparation method of a positive electrode material for a lithium ion battery, comprising the following steps: dispersing a lithium-containing compound, a soluble metal salt, a cobalt acetate, a nickel acetate and a doped metal salt in a solvent to obtain a dispersion solution, adding a pH regulator to the dispersion solution to make the pH of the dispersion solution 7-8, and drying to obtain a precursor material; the spherical precursor material is sequentially subjected to first sintering, first cooling, second sintering and second cooling to obtain the positive electrode material.

[0067] The first sintering comprises the following steps: first sintering the precursor material in an air atmosphere environment, the first sintering temperature is 300-600°C, the first sintering time is 3-6h, and first cooling is performed after the first sintering is completed.

[0068] The second sintering comprises the following steps: after the first cooling is completed, second sintering is performed in a pure oxygen atmosphere environment, the second sintering temperature is 700-950°C, the second sintering time is 8-15h, and second cooling is performed after the second sintering is completed.

[0069] The preparation method of the positive electrode material for a lithium ion battery provided by the application has the following effects compared with the prior art: (1) the spherical precursor material is prepared by one-step method, the mixing is uniform during the preparation process, no waste liquid is generated, it is green and clean, the preparation process is simple and controllable, the spherical precursor material obtained after drying is uniformly dispersed and has regular surface morphology, compared with other synthesis methods, the precursor material prepared by the application can improve the compaction density of the positive electrode sheet. (2) The pH regulator added during the preparation of the precursor makes the obtained precursor have an organic coating, and no secondary coating is needed, the residual carbon content of the finished positive electrode material obtained after sintering is 0.1wt%-3wt%. (3) Two sintering processes are adopted to make the finished product crystallize and the coating carbonize, two cooling processes are adopted to control the grain size of the intermediate product, make the material grain size quickly and stably fixed at a fixed size, which is beneficial to improve the compaction density of the positive electrode material, and can also avoid the generation of other impurities and improve the order degree of the layered structure of the positive electrode material; the two sintering and cooling processes save the cooling time of the sintering equipment, shorten the process time, and are also beneficial to obtain a positive electrode material with a highly ordered layered structure, so that the positive electrode material has a high specific capacity.

[0070] In some embodiments, the soluble metal salt and the doping metal salt each comprises one or more of manganese acetate, titanium acetate, zinc acetate, magnesium acetate, molybdenum acetate, vanadium acetate, germanium acetate, aluminum acetate, zirconium acetate, manganese nitrate, titanium nitrate, zinc nitrate, magnesium nitrate, molybdenum nitrate, vanadium nitrate, germanium nitrate, aluminum nitrate, zirconium nitrate, manganese hydroxide, titanium hydroxide, zinc hydroxide, magnesium hydroxide, molybdenum hydroxide, vanadium hydroxide, germanium hydroxide, zirconium hydroxide, aluminum hydroxide;

[0071] The lithium-containing compound comprises one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate, lithium chloride, lithium fluoride, lithium iodide;

[0072] The solvent comprises one or more of deionized water, ethanol, methanol, isopropanol, n-butanol, octanol, decanol.

[0073] In the preparation of the quasi-spherical precursor material, the addition of the soluble metal salt facilitates dissolution in the solvent, accelerates the dispersion speed, and improves the mixing uniformity of the mixture.

[0074] For example, when the solvent is water, soluble metal salts such as manganese acetate, aluminum acetate, and aluminum nitrate can be dissolved in water.

[0075] In some preferred embodiments, the lithium-containing compound is lithium hydroxide.

[0076] In some embodiments, the lithium-containing compound, the soluble metal salt, the nickel acetate, the cobalt acetate, and the doping metal salt are in a metal element molar ratio of (1-1.2):y:1-x-y:x:b, where 0

[0077] Specifically, controlling the lithium-containing compound, the soluble metal salt, the nickel acetate, and the cobalt acetate to be in a metal element molar ratio of (1-1.2):y:1-x-y:x, can prepare a positive electrode material of the formula LiNi 1-x-y Co x M y O2, where 0 1-x-y Co x M y M' bO2, wherein 0 < x < 0.3, 0 < y < 0.4, 0 < b < 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al.

[0078] In some embodiments, the pH adjusting agent has a concentration of 1 mol / L to 3 mol / L, and the pH adjusting agent includes, but is not limited to, one or more of citric acid, acetic acid, oxalic acid, benzoic acid, acrylic acid, carboxylated graphene, and carboxylated graphite.

[0079] Specifically, the pH adjusting agent is added in the preparation of the quasi-spherical precursor material, the obtained quasi-spherical precursor material is an organic coating, and a second coating is not needed, thereby saving cost and shortening process time, and meanwhile, the residual carbon content of the finished positive electrode material after sintering of the quasi-spherical precursor material ranges from 0.1%wt to 3%wt.

[0080] In some preferred embodiments, the adjusting agent is citric acid. The citric acid is a carbon-containing compound, the pH of the solution is adjusted by using the citric acid, the obtained quasi-spherical precursor material is also an organic coating, a second coating is not needed, cost is saved, process time is shortened, and meanwhile, the residual carbon content of the finished positive electrode material after sintering of the quasi-spherical precursor material ranges from 0.1%wt to 3%wt.

[0081] If the residual carbon content of the positive electrode material is too low, the conductivity of the positive electrode material is reduced, and the battery impedance is increased; if the residual carbon content of the positive electrode material is higher than 3%wt, the carbon content in the positive electrode material per unit mass is too high, the active lithium ion content is relatively reduced, and the energy density of the battery is reduced.

[0082] In some embodiments, the lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate have a metal element molar ratio of 1.02:y:1-x-y:x, wherein 0 < x < 0.3 and 0 < y < 0.4.

[0083] In some preferred embodiments, the lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate have a metal element molar ratio of 1.02:y:1-x-y:x, wherein 0 < x < 0.2 and 0 < y < 0.2.

[0084] In some embodiments, the lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate have a metal element molar ratio of 1.02:y:1-x-y:x:b, wherein 0 < x < 0.3, 0 < y < 0.4, and 0 < b < 0.05.

[0085] In some embodiments, the lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate have a metal element molar ratio of 1.02:0.2:0.6:0.2.

[0086] In some embodiments, the lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate are in a molar ratio of 1.02:0.2:0.5:0.2 in terms of metal elements.

[0087] In some embodiments, the lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate are in a molar ratio of 1.02:0.2:0.7:0.2 in terms of metal elements.

[0088] In some embodiments, the lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate are in a molar ratio of 1.02:0.2:0.8:0.2 in terms of metal elements. In some embodiments, in the step of drying to obtain the spherical-like material precursor, the drying method is one or more of spray drying, flash drying, stirring drying, and dynamic drying. Further preferably, the drying method is spray drying.

[0089] Specifically, the dynamic drying includes reduced pressure drying method and freeze drying method. The precursor material prepared by using the drying methods such as spray drying method and dynamic drying method has a spherical or disc-shaped structure, i.e., a spherical-like precursor material, and can obtain a precursor material with uniform dispersion and regular surface morphology.

[0090] In some preferred embodiments, the specific steps of obtaining the spherical-like material precursor by using the spray drying method are as follows: the dispersion liquid is spray dried to obtain the spherical-like precursor material, and the specific parameters of the spray drying are as follows: feed rate 35 mL / min, air inlet temperature 150°C, and nozzle rotation speed 240 rpm.

[0091] In some embodiments, the first sintering includes the following steps: the spherical-like material precursor is sintered in an air atmosphere environment, the first sintering has a temperature rising rate of 1-8°C / min, the first sintering is performed at a first sintering temperature of 300-600°C for a first sintering time (or first holding time) of 3-6h, and after the first sintering is completed, first cooling is performed, the first cooling temperature is 20-30°C, the cooling method is quenching, and the sintered material is directly transferred to room temperature.

[0092] Specifically, the air atmosphere environment refers to the atmospheric environment. The first sintering operation of the spherical precursor material helps to form a positive electrode material with good crystallinity, carbonize the organic coating layer of the spherical precursor material, improve the true density of the material, and adjust the specific surface area of the material. After the first sintering is completed, the first cooling operation is performed, which aims to control the grain size of the intermediate product, stabilize the material grain at a fixed size quickly, ensure the rapid crystallization of the material, avoid the generation of other impurities, and improve the order degree of the layered structure of the material. Specifically, the first sintering temperature can be 300°C, 350°C, 380°C, 400°C, 430°C, 460°C, 500°C, 530°C, 550°C, 580°C, 600°C, etc., as long as the first sintering temperature is between 300°C and 600°C.

[0093] In some preferred embodiments, the spherical precursor material is sintered in an air atmosphere environment at a first sintering temperature of 300°C for 3h, and then a first cooling step is performed.

[0094] In some embodiments, the second sintering includes the following steps: after the first sintering is completed, the second sintering is performed in a pure oxygen atmosphere environment, the second sintering has a heating rate of 1-8°C / min, a second sintering temperature of 700°C-950°C, a second sintering time (or second holding time) of 8h-15h, and a second cooling temperature of 20-30°C after the second sintering is completed. The cooling method is quenching, and the sintered material is directly transferred to room temperature.

[0095] Specifically, the pure oxygen atmosphere environment refers to a space filled with pure oxygen, and the second sintering is performed in a space filled with pure oxygen. The first sintering and the second sintering have the same effect, which helps to form a positive electrode material with good crystallinity, carbonize the organic coating layer of the spherical precursor material, improve the density of the material, and improve the specific surface area of the material. The first cooling and the second cooling also have the same effect, which aims to control the grain size of the intermediate product, stabilize the material grain at a fixed size quickly, increase the compaction density of the positive electrode material when the electrode sheet is prepared, and also ensure the rapid crystallization of the material, avoid the generation of other impurities, and improve the order degree of the layered structure of the material. Specifically, the second sintering temperature can be 700°C, 730°C, 750°C, 790°C, 800°C, 820°C, 850°C, 870°C, 900°C, 930°C, 950°C, etc., as long as the second sintering temperature is between 700°C and 950°C.

[0096] In some preferred embodiments, the spherical precursor material is sintered in a pure oxygen atmosphere environment at a second sintering temperature of 950°C for 10h, and then a second cooling step is performed.

[0097] If the first sintering temperature is lower than 300℃, or the second sintering temperature is lower than 700℃, the crystallinity of the positive electrode material is low, and the crystallization is not perfect enough, which affects the cycle performance of the battery, and the sintering temperature that is too low is easy to cause incomplete reaction of the material and easy to produce impurity phase; if the first sintering temperature is higher than 600℃, or the second sintering temperature is higher than 950℃, the particle size of the finished material obtained is large, the lithium ion conduction path is too long, which affects the discharge specific capacity of the battery and the internal resistance of the battery, and is easy to cause the carbon content to be too low.

[0098] It can be understood that the equipment selected for the first sintering and the second sintering includes one of a tube furnace, a box furnace, a fluidized bed, a rotary kiln, a microwave oven, and a tunnel furnace.

[0099] In some embodiments, the step of dispersing the lithium-containing compound, the soluble metal salt, the cobalt acetate, and the nickel acetate in the solvent includes at least one of ultrasonic, mechanical stirring, magnetic stirring, high-energy ball milling, jar milling, high-shear dispersion, and high-pressure dispersion.

[0100] In a third aspect, the present application provides a positive electrode sheet, which comprises the positive electrode material described above or the positive electrode material prepared by the preparation method of the positive electrode material for lithium ion batteries described above.

[0101] The positive electrode sheet provided by the present application contains the positive electrode material described above, has a higher specific capacity, and the battery prepared therefrom has a better cycle life.

[0102] In some embodiments, the positive electrode sheet comprises a positive electrode material, and the positive electrode material has a chemical formula of LiNi 1-x-y Co x M y O2, wherein 0

[0103] or the positive electrode material has a chemical formula of LiNi 1-x-y Co x M y M' b O2, wherein 0

[0104] The positive electrode sheet prepared by using the positive electrode material described above is applied to a battery, and the battery has a higher energy density, capacity, and improved cycle life.

[0105] In some embodiments, the positive electrode sheet has a compaction density of 3 g / cm 3~3.7g / cm 3 .

[0106] Compared with the prior art, the positive electrode material prepared by the application has a relatively complete layered structure and a high compaction density, and when applied to a battery, can improve the cycle life of the battery.

[0107] In a fourth aspect, the application provides a positive electrode sheet, comprising a positive electrode material, the chemical formula of the positive electrode material is Li z Ni 1-x-y Co x M y M' b O2, wherein 0

[0108] The positive electrode sheet has 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)° in an X-ray diffraction spectrum of the positive electrode sheet.

[0109] The (108) diffraction peak and the (110) diffraction peak satisfy the following relationship:

[0110]

[0111] FWHM(108) is the half-peak width of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)°; and FWHM(110) is the half-peak width of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°.

[0112] The positive electrode sheet provided by the application has the (108) diffraction peak and the (110) diffraction peak satisfying the following relationship in the X-ray diffraction spectrum of the positive electrode sheet: Not only can the crystal structure integrity of the positive electrode material in the positive electrode sheet be ensured, and damage to the positive electrode material during sheet preparation be prevented, but also the lithium ion battery prepared from the positive electrode sheet satisfying the relationship has better specific capacity and cycle life.

[0113] In a fifth aspect, the application provides a lithium ion battery, comprising the positive electrode sheet described above.

[0114] The lithium ion battery prepared using the positive electrode material of the application has a relatively complete layered structure of the positive electrode material, has a high specific capacity, and has a long cycle life.

[0115] The application will be further described in detail through the following examples.

[0116] Example 1

[0117] This example is used to illustrate the positive electrode material for lithium ion battery and the preparation method thereof disclosed by the present application, which comprises the following steps:

[0118] Lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate and zirconium nitrate (dopant) are weighed according to the molar ratio of metal elements 1.03:0.35:0.50:0.15:0.003, and then dispersed and dissolved by mechanical stirring to obtain a dispersion solution. Then, a citric acid solution with a concentration of 1 mol / L as a pH regulator is added dropwise into the dispersion solution until the pH of the dispersion solution is 8. After that, the solution is introduced into a spray dryer, and the solution feeding rate is adjusted to 35 mL / min, the inlet air temperature is 150℃, and the nozzle rotation speed is 240 rpm. The dry powder is collected to obtain a spherical precursor material. Then, the spherical precursor material is subjected to a first sintering in an air atmosphere using a tube furnace, with a heating rate of 3℃ / min, and heated to 300℃, and then sintered at 300℃ for 3 hours. After that, the first cooling is performed, which is a quenching, i.e. the sintered material is directly placed in a room temperature state for cooling through air exchange, or the material is cooled by a rapid cooling program (the cooling rate is 50℃ / min, and the temperature is lowered to 25℃). Then, the second sintering is performed in a pure oxygen atmosphere, with a heating rate of 5℃ / min, and heated to 950℃, and then sintered at the second sintering temperature 950℃ for 10 hours. After that, the second cooling is performed, i.e. the sintered material is directly placed in a room temperature state for cooling through air exchange, or the material is cooled by a rapid cooling program (the cooling rate is 50℃ / min, and the temperature is lowered to 25℃), to obtain the finished positive electrode material. The finished positive electrode material is subjected to XRD testing, using a copper target X-ray generator, and scanned at 10-80° with a scanning rate of 6° / min, to finally obtain the XRD spectrum as shown in FIG. 1. Figure 1

[0119] Example 2

[0120] The difference between Example 2 and Example 1 is that the second sintering temperature is different, and the specific difference is as follows: the second sintering temperature is 850℃, and the rest is the same as the preparation method of Example 1.

[0121] Example 3

[0122] The difference between Example 3 and Example 1 is that the second sintering temperature and time are different in Example 3, and the specific difference is that the second sintering is performed at a temperature of 950℃ for 15 hours, and the rest is the same as the preparation method of Example 1.

[0123] Example 4

[0124] ​Example 4 differs from Example 1 in that the second sintering temperature and time are different in Example 4, specifically, the second sintering temperature is 950℃ and the sintering time is 6 hours, and the rest is the same as the preparation method of Example 1.

[0125] Example 5

[0126] Example 5 differs from Example 1 in that the first sintering temperature is different, the first sintering temperature is 600℃ and the sintering time is 3 hours, and the rest is the same as Example 1.

[0127] Example 6

[0128] Example 6 differs from Example 1 in that the first sintering time is different, the first sintering temperature is 300℃ and the sintering time is 6 hours, and the rest is the same as Example 1.

[0129] Example 7

[0130] Example 7 differs from Example 1 in that the second sintering temperature is different, the second sintering temperature is 700℃ and the sintering time is 10 hours, and the rest is the same as Example 1.

[0131] Example 8

[0132] Example 8 differs from Example 1 in that no doping metal salt (zirconium acetate) is added to the reactants, and the molar ratio of lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate metal elements is 1.03:0.35:0.50:0.15, and the rest is the same.

[0133] Example 9

[0134] Example 9 differs from Example 1 in that the molar ratio of the reactants is different, specifically, the molar ratio of lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate is 1.03:0.35:0.50:0.15:0.045 in terms of metal elements, and the rest is the same.

[0135] Example 10

[0136] Example 10 differs from Example 1 in that the molar ratio of the reactants is different, specifically, the molar ratio of lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate is 1.03:0.35:0.50:0.15:0.02 in terms of metal elements, and the rest is the same.

[0137] Example 11

[0138] Example 11 differs from Example 1 in that the molar ratio of the reactants is different, specifically, the molar ratio of lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate is 1.03:0.35:0.50:0.15:0.001 in terms of metal elements, and the rest is the same.

[0139] Example 12

[0140] Example 12 is different from Example 1 in that the molar ratio of the reactants is different, specifically the molar ratio of lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate is 1.02:0.28:0.60:0.22:0.01 in terms of metal elements, and the rest is the same.

[0141] Comparative Example 1

[0142] Comparative Example 1 is different from Example 1 in that the second sintering conditions are different, specifically as follows: the second sintering is carried out under a pure air atmosphere, and the second sintering is carried out at a second sintering temperature of 650°C for 10 hours, and the rest is the same as the preparation method of Example 1.

[0143] Comparative Example 2

[0144] Comparative Example 2 is different from Example 1 in that the first sintering temperature and time are different, specifically as follows: the first sintering is carried out at a first sintering temperature of 250°C for 3 hours, and the rest is the same as the preparation method of Example 1.

[0145] Comparative Example 3

[0146] Comparative Example 3 is different from Example 1 in that the first sintering conditions are different, specifically as follows: the first sintering is carried out under a pure air atmosphere, and the first sintering is carried out at a first sintering temperature of 650°C for 3 hours, and the rest is the same as the preparation method of Example 1.

[0147] Comparative Example 4

[0148] Comparative Example 4 is different from Example 1 in that the second sintering conditions are different, specifically as follows: the second sintering is carried out under a pure oxygen atmosphere, and the second sintering is carried out at a second sintering temperature of 1100°C for 10 hours, and the rest is the same as the preparation method of Example 1.

[0149] Comparative Example 5

[0150] Comparative Example 5 is different from Example 1 in that the first cooling is not carried out, and the second sintering is directly carried out under a pure oxygen atmosphere, and the rest is the same as the preparation method of Example 1.

[0151] Comparative Example 6

[0152] Comparative Example 6 is different from Example 12 in that the second sintering conditions are different, specifically as follows: the second sintering is carried out under a pure oxygen atmosphere, and the second sintering is carried out at a second sintering temperature of 650°C for 10 hours, and the rest is the same as the preparation method of Example 12.

[0153] The carbon residual amount of the positive electrode material prepared in the above Examples 1-12 and Comparative Examples 1-6 is tested by a CS analyzer.

[0154] The FWHM (108), FWHM (110), 2θ (108), 2θ (110) of the XRD spectrum of the positive electrode materials prepared in Examples 1-12 and Comparative Examples 1-6 after XRD test are recorded in Table 1. The XRD half-peak width and peak position data are derived from the analysis of the XRD raw test file by the processing software MDI Jade 6. The specific data are shown in Table 1. The XRD spectrum of the positive electrode materials prepared in Examples 1-4 is shown in FIG. 1, and the comparative diagram of the XRD spectrum of the positive electrode materials prepared in Example 1 and Comparative Example 1 is shown in FIG. 2. Figures 1-4 Figure 5 .

[0155] Table 1 Partial data table of positive electrode materials of Examples 1-16 and Comparative Examples 1-8

[0156]

[0157] The positive electrode sheets S containing the positive electrode materials of Examples 1, 4, 7, 10 and Comparative Examples 1, 3 were selected. The FWHM (108), FWHM (110), 2θ (108), 2θ (110) of the XRD spectrum of the above positive electrode sheets after XRD test are recorded in Table 2. The XRD half-peak width and peak position data are derived from the analysis of the XRD raw test file by the processing software MDI Jade 6. The specific data are shown in Table 2.

[0158] Table 2 Partial data table of positive electrode sheets

[0159]

[0160] Performance test:

[0161] The positive electrode materials prepared in Examples 1-12 and Comparative Examples 1-6 were prepared into positive electrode sheets and batteries, and the following tests were performed.

[0162] Specific capacity test: The above positive electrode materials, PVDF and SP were blended in a ratio of 96:3:1 with NMP as the solvent for 2 h to form a stable and uniform positive electrode slurry. The positive electrode slurry was coated on an aluminum foil using a coating machine, dried, and cold-pressed to obtain a positive electrode sheet with a compaction density of 3.0-3.70 g / cm 3 The specific capacity of the positive electrode material was determined by taking the specific capacity of the third discharge test as the specific capacity of the positive electrode material.

[0163] The compaction density of the positive electrode sheet was tested by a commonly used test method in the art.​

[0164] Cycling performance test: 95wt% of negative active material graphite, 2wt% of binder SBR, 2wt% of conductive agent graphite and 1wt% of thickening agent CMC were added into deionized water to prepare negative electrode slurry, the negative electrode slurry was coated on copper foil, dried, cold-pressed to obtain a compacted density of 1.6-1.7g / cm 3 .

[0165] Preparation of the battery: the positive electrode sheet and the negative electrode sheet prepared above and the separator film were prepared into a bare cell according to the conventional preparation process, the bare cell was dried, injected with electrolyte, packaged, and finally a battery was prepared.

[0166] Normal temperature cycling performance test: the cycled cell was subjected to normal temperature 25℃ cycling test, 0.5C / 0.5C charging and discharging test was carried out, and the cycle number of the battery charging and discharging was recorded when the discharge capacity was maintained at 80%.

[0167] Table 2 Performance data table of examples 1-12 and comparative examples 1-6

[0168]

[0169]

[0170] By table 1, 2, Figures 1-5 It can be seen from the comparison that, in comparison of examples 1-12 and comparative examples 1-6, in the X-ray diffraction spectrum of the positive electrode material in the comparative examples 1-6, The specific capacity of the prepared positive electrode material is low, and the cycle life of the battery is short, which shows that the positive electrode material of the application has 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° in its X-ray diffraction spectrum, and the (108) diffraction peak and the (110) diffraction peak satisfy the relationship formula The rationality of the synthesis route and the performance of the material can be predicted, the layer structure of the positive electrode material layer has high order, the specific capacity of the prepared positive electrode material is high, and the cycle life of the prepared battery at normal temperature is long.

[0171] The above only describes the preferred embodiments of the application and is not intended to limit the application, any modification, equivalent replacement and improvement made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A positive electrode material for lithium-ion batteries, characterized in that, The positive electrode material has a chemical formula of LiNi 1-x-y Co x M y M' b O2, wherein 0 < x ≤ 0.3, 0 < y ≤ 0.4, 0 ≤ b ≤ 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga, and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga, and Al. The cathode material has 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)° in an X-ray diffraction spectrum of the cathode material. The (108) diffraction peak and the (110) diffraction peak satisfy the following relationship: 0.67＜ ≤0.75 FWHM(108) is a half-peak width of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)°; FWHM(110) is a half-peak width of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°.

2. The positive electrode material for a lithium-ion battery according to claim 1, characterized by The positive electrode material is a polycrystalline ternary material; the positive electrode material has a chemical formula of LiNi 1-x-y Co x M y M' b O2, wherein 0.1≤x≤0.2, 0.1≤y≤0.35, 0 M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga, and Al; M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga, and Al.

3. The positive electrode material for a lithium-ion battery according to claim 1, characterized by The half-peak width FWHM(108) of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° in the X-ray diffraction spectrum of the cathode material ranges from 0.1 to 0.

3.

4. The positive electrode material for lithium-ion batteries according to claim 1, characterized in that, The half-peak width FWHM(110) of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° in the X-ray diffraction spectrum of the cathode material ranges from 0.1 to 0.

3.

5. The cathode material for lithium ion batteries according to claim 1, characterized in that, The cathode material has an α-NaFeO2 layered structure.

6. A method for producing the positive electrode material for lithium ion batteries as described in any one of claims 1 to 5, characterized by, The method comprises the following steps: dispersing a lithium-containing compound, a soluble metal salt, cobalt acetate, nickel acetate and a doped metal salt in a solvent to obtain a dispersion solution, adding a pH regulator to the dispersion solution to make the pH of the dispersion solution 7-8, and drying to obtain a precursor material; the precursor material is sequentially subjected to first sintering, first cooling, second sintering and second cooling to obtain the cathode material; The first sintering comprises the following steps: sintering the precursor material in an air atmosphere environment, the first sintering temperature is 300-600°C, the first sintering time is 3-6h, and the first sintering is followed by first cooling; The second sintering comprises the following steps: after the first cooling is completed, the second sintering is carried out in a pure oxygen atmosphere environment, the second sintering temperature is 700-950°C, the second sintering time is 8-15h, and the second sintering is followed by second cooling.

7. The method for preparing the positive electrode material for lithium-ion batteries according to claim 6, characterized in that, The soluble metal salt and the doped metal salt each comprise one or more of manganese acetate, titanium acetate, zinc acetate, magnesium acetate, molybdenum acetate, vanadium acetate, germanium acetate, aluminum acetate, zirconium acetate, manganese nitrate, titanium nitrate, zinc nitrate, magnesium nitrate, molybdenum nitrate, vanadium nitrate, germanium nitrate, aluminum nitrate, zirconium nitrate, manganese hydroxide, titanium hydroxide, zinc hydroxide, magnesium hydroxide, molybdenum hydroxide, vanadium hydroxide, germanium hydroxide, aluminum hydroxide and zirconium hydroxide. The lithium-containing compound comprises one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate, lithium chloride, lithium fluoride and lithium iodide. The solvent comprises one or more of deionized water, ethanol, methanol, isopropanol, n-butanol, octanol and decanol.

8. The method for preparing the positive electrode material for lithium-ion batteries according to claim 6, characterized in that, The lithium-containing compound, the soluble metal salt, nickel acetate, cobalt acetate and the doped metal salt have a metal element molar ratio of (1-1.2):y:1-x-y:x:b, wherein 0 9. The method for preparing the positive electrode material for lithium-ion batteries according to claim 6, characterized in that, The concentration of the pH regulator is 1-3 mol / L, and the pH regulator comprises one or more of citric acid, acetic acid, oxalic acid, benzoic acid, acrylic acid, carboxylated graphene, and carboxylated graphite.

10. The method for preparing the positive electrode material for lithium-ion batteries according to claim 6, characterized in that, In the step of drying the precursor material, the drying method is one or more of spray drying, flash evaporation, stirring drying, and dynamic drying.

11. The method for preparing the positive electrode material for lithium-ion batteries according to claim 6, characterized in that, In the first sintering, the heating rate is 1-8 ℃ / min, the first cooling temperature is 20-30 ℃, and the cooling method is quenching; the material after the first sintering is directly transferred to room temperature; In the second sintering, the heating rate is 1-8 ℃ / min, the second cooling temperature is 20-30 ℃, and the cooling method is quenching; the material after the second sintering is directly transferred to room temperature.

12. A positive electrode sheet characterized by comprising: The positive electrode material comprises the positive electrode material according to any one of claims 1-5 or the positive electrode material prepared by the preparation method according to any one of claims 6-11.

13. The positive electrode sheet according to claim 12, characterized by The compacted density of the positive electrode sheet is 3 g / cm 3 3.7 g / cm 3 .

14. A positive electrode sheet characterized by comprising: comprising a cathode material having a chemical formula of Li z Ni 1-x- y Co x M y M' b O2, wherein 0 < x < 0.3, 0 < y < 0.4, 0 < b < 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga, and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga. The X-ray diffraction spectrum of the positive electrode sheet has 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: 0.67＜ ≤0.8 wherein FWHM(108) is the half-peak width of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)°, and FWHM(110) is the half-peak width of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°.

15. A lithium-ion battery, characterized by The positive electrode sheet comprises the positive electrode sheet according to any one of claims 12-13 or the positive electrode sheet according to claim 14.

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