Positive electrode material and secondary battery

Abstract

Positive electrode material, characterized in that it has particles of a positive active material, wherein the particles of the positive active material are provided with a coating layer and the coating layer has a metal oxide; the positive electrode material: 0.2 ≤ K / Rn ≤ 1.2 is fulfilled; where “K %” is the percentage of a free transition metal element from the particles of the positive active material with respect to a transition metal element contained in the particles of the positive active material, after the particles of the positive active material have been immersed for 72 hours at 70 °C in a hydrofluoric acid solution with a concentration of 20 wt% in a solid-liquid ratio of 1 g:5 ml; where “Rn” is the roundness of the particles of the positive active material.

Description

TECHNICAL AREA

[0001] The present application relates to the technical field of a battery and in particular a positive electrode material and a secondary battery. STATE OF THE ART

[0002] In existing secondary batteries, particularly lithium-ion secondary batteries, predominant positive active materials include lithium nickel cobalt manganese oxide materials, lithium iron phosphate, and spinel-structured lithium nickel manganese oxide. Although these materials exhibit desirable electrochemical activity, they invariably suffer from the problem of transition metal ion dissolution (specifically, the dissolution of nickel, cobalt, and manganese in ternary materials, iron in lithium iron phosphate, and nickel and manganese in lithium nickel manganese oxide).This increases the likelihood of side reactions between dissolved transition metal ions and an electrolyte after the secondary battery has been in operation for a period of time, resulting in increased gas production and a deterioration of battery performance, particularly in high-temperature environments where side reactions can intensify and even cause safety problems.

[0003] Attempts have been made to modify positive active materials by coating them, thereby reducing the dissolution of transition metal ions through the inert protection of a coating layer. The materials used in such coating processes are predominantly insulating or semi-insulating materials with low conductivity, which can influence the ion / electron transport efficiency of positive active materials. SUMMARY OF THE INVENTION

[0004] The subject matter of the present application consists of overcoming shortcomings in the prior art by providing a positive electrode material. In this electrode material, a coating layer is provided on the surface of a positive active material, and the ratio between the roundness of the positive electrode material after coating and the percentage of free transition metal ions after acid corrosion of the positive electrode material is controlled, thereby coordinating the balance between stability and conductivity in the positive electrode material. The secondary battery produced with the positive electrode material exhibits desirable electrochemical properties, in particular superior cycle stability and storage capacity retention rate at high temperatures.

[0005] To solve the above problem, a positive electrode material is provided in a first aspect of the present application, comprising particles of a positive active material, wherein the particles of the positive active material are provided with a coating layer and the coating layer comprises a metal oxide; the positive electrode material: 0.2 ≤ K / Rn ≤ 1.2 is fulfilled; where “K %” is the percentage of a free transition metal element from the particles of the positive active material in relation to a transition metal element contained in the particles of the positive active material after the particles of the positive active material have been immersed for 72 hours at 70 °C in a hydrofluoric acid solution with a concentration of 20 wt% in a solid-liquid ratio of 1 g:5 ml; where “Rn” is the roundness of the particles of the positive active material.

[0006] The beneficial effects of the present application are as follows: The present application provides a positive electrode material. In this electrode material, a coating layer is applied to the surface of a positive active material, and the ratio between the roundness of the positive electrode material after coating and the percentage of free transition metal ions after acid corrosion of the positive electrode material is controlled, thereby coordinating the balance between stability and conductivity in the positive electrode material. The secondary battery produced with the positive electrode material exhibits desirable electrochemical properties, in particular superior cycle stability and storage capacity retention rate at high temperatures. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0007] To clarify the objective, technical solutions, and advantages of the embodiments of the present application, the technical solutions in the embodiments of the present application are described clearly and completely below. It is obvious that the described embodiments represent only a subset of the embodiments of the present application and not all embodiments. Based on the embodiments of the present application, all other embodiments that could be obtained by those skilled in the art without inventive work fall within the scope of protection of the present application.

[0008] The present invention includes, with respect to technical features described in an open manner, both closed technical solutions composed of the listed features and open technical solutions containing the listed features.

[0009] In this application, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as any value between these minimum and maximum values. If the range refers to integers, any integer between the minimum and maximum values ​​of the range is also included. If several ranges are provided to describe features or characteristics, these ranges may be combined. In other words, all ranges disclosed herein are to be understood as including any and all subranges contained therein, unless otherwise stated.

[0010] The present application is further elaborated by specific embodiments below: A positive electrode material comprising particles of a positive active material, wherein the particles of the positive active material are provided with a coating layer and the coating layer comprises a metal oxide; the positive electrode material: 0.2 ≤ K / Rn ≤ 1.2 is fulfilled; where “K %” is the percentage of a free transition metal element from the particles of the positive active material in relation to a transition metal element contained in the particles of the positive active material after the particles of the positive active material have been immersed for 72 hours at 70 °C in a hydrofluoric acid solution with a concentration of 20 wt% in a solid-liquid ratio of 1 g:5 ml; where “Rn” is the roundness of the particles of the positive active material.

[0011] Before a positive active material is used for a positive electrode material, an inert metal oxide coating is generally applied to the particle surface to suppress the dissolution of transition metal elements in the particles during charge-discharge cycles and to reduce the likelihood of side reactions occurring after contact with an electrolyte. This coating provides insulation and inhibits the dissolution of transition metal elements within the particles. However, the introduction of such coatings impedes the ion / electron transport kinetics of the positive active material particles and reduces their overall conductivity, ultimately resulting in lower electrochemical performance.To overcome this technical difficulty, the technical solution of the present application provides a metal oxide coating layer on the surface of particles of the positive active material and simultaneously controls the coating effect by adjusting the ratio between the roundness of the applied particles of the positive active material and the percentage of free transition metal ions after acid corrosion. This coordinates the balance between the stability and the ion / electron transport kinetics of the entire electrode material after coating. The roundness of the particles of the positive active material is related to the irregularity of the particle shape and the surface smoothness, which in turn influences the contact effect with an electrolyte and the overall path length of the ion / electron transport.On the other hand, the free level of the transition metal element changes after the coating layer is applied. By controlling the free content of transition metal elements after acid etching of particles of the positive active material, the structural stability and the ion / electron conductivity of the electrode material can be controlled simultaneously. In the present application, if the K / Rn ratio of the two key factors mentioned above is controlled to be in the range of 0.2–1.2, the positive electrode material can achieve a balance of conductivity and structural stability when used in secondary batteries. This reduces the likelihood of side reactions after contact with an electrolyte without weakening the ion / electron transport kinetics of the electrode material itself, allowing the secondary battery to exhibit excellent electrochemical performance.If the K / Rn ratio is set inappropriately, it can result in an excessively high probability of side reactions between particles of the positive active material and an electrolyte, which affects the operating time of the secondary battery or even causes safety problems, or it can result in lower charge-discharge efficiency and reduced energy density of the secondary battery.

[0012] In some embodiments, “K / Rn” is a value of or a value in a range of any two of 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15 and 1.2.

[0013] In some embodiments, 0.4 ≤ Rn ≤ 0.8.

[0014] More preferred is “Rn” a value of or a value in a range of any two of 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 and 0.8.

[0015] A more preferred value is 0.6 ≤ Rn ≤ 0.7.

[0016] If the roundness of the positive active material particles is low after the coating layer has been applied, this indicates insufficient surface smoothness and high particle irregularity. High roundness indicates good coating coverage and greater particle regularity. Positive active material particles with varying roundness exhibit different contact areas with the electrolyte.

[0017] Furthermore, the regularity of the particles also influences the degree of compaction and structural stability when used for electrode fabrication. If the roundness is preferably within the range mentioned above, the particles of the positive active material can achieve a moderate contact area with the electrolyte and control the balance between the probability of transition metal ion dissolution and the difficulty of ion / electron transport by adjusting the coating density. Moreover, ideal electrode stability and density can be achieved during fabrication, resulting in improved overall electrochemical performance of the electrode material.

[0018] It should be noted that the roundness “Rn” of the positive active material particles in the present application is tested as follows: The positive electrode material is dispersed in ethanol, and then an OCCHIO FC200s+HR particle morphology analyzer is used as the test instrument (10 million pixel camera resolution, telecentric zoom lens, Callisto analysis processing software, version 2012). The ethanol dispersion of the positive electrode material is pumped into the sample pool of the instrument via a 5 mm sampling tube. After image acquisition and analysis, the mean values ​​of “Ai” and “A” of the positive electrode material are confirmed, where “Ai” is the maximum inscribed circular area of ​​the positive active material particles and “A” is the projection area of ​​the positive active material particles.Finally, the roundness of the particles of the positive active material in the positive electrode material is automatically calculated using the software via “Rn = Ai / A”.

[0019] In some embodiments, the roundness of the positive active material particles can be adjusted via the calcination temperature and duration during production. However, the present application is not limited to this. Those skilled in the art can also adjust the roundness using conventional methods for producing or processing positive active material particles, such as ball milling and spray treatment, according to the actual requirements.

[0020] In some embodiments, 0.1% ≤ K ≤ 0.5%.

[0021] More preferred is “K” a value of or a value in a range of any two of 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% and 0.5%.

[0022] A stronger preference is 0.2% ≤ K ≤ 0.3%.

[0023] Following acid etching, the percentage of free transition metal elements in the particles of the positive active material is related to both the type of positive active material and the coating effect of the coating layer. Therefore, the value of "K" also influences the ion / electron transport capacity and the structural stability of the positive active material particles. If the value of "K" of the positive active material particles is preferably within the range described above, the resulting positive electrode material exhibits improved structural stability and conductivity.

[0024] It should be noted that the value of ‘K’ of the particles of the positive active material in the present application is tested as follows: The positive electrode material is placed in a solution containing 40 wt% sodium hydroxide for a digestion treatment, followed by ICP tests.Conditions of the ICP tests: A spectral wavelength for the detection of an element is selected, and suitable operating conditions of the ICP instrument are set according to the sample characteristics and the elements to be detected, including a gas flow rate of 0.5 l / min and a power of 1150 W; the content of transition elements is tested by ICP to confirm the total content “M1” of transition metal elements in the particles of the positive active material (where lithium nickel manganese oxide is used as an example, the total content of transition metal elements is the total content of the two elements nickel and manganese; when lithium iron phosphate is used as an example, it is the total content of the element iron; when lithium nickel cobalt manganese oxide is used as an example, it is the total content of the three elements nickel, cobalt, and manganese).A parallel sample is then taken and immersed at 70 °C in a 20 wt% hydrofluoric acid solution at a solid-liquid ratio of 1 g:5 ml and allowed to soak for 72 h. The supernatant of the hydrofluoric acid solution is used for ICP testing. ICP test conditions: A spectral wavelength for the detection of an element is selected, and suitable operating conditions of the ICP instrument are set according to the sample characteristics and the elements to be detected, including a gas flow rate of 0.5 l / min and a power of 1150 W. The content of transition metals is tested by ICP, confirming the total content “M2” of free transition metal elements after acid etching, and the final result is calculated according to “K = M2 / M1 * 100%”.

[0025] In some embodiments, “K” can be controlled by the number of deposition cycles during the ALD deposition of atomic layers of the coating layer. However, the present application is not limited to this. Those skilled in the art can also adjust it according to actual requirements by adjusting other conditions during deposition, as well as other process conditions, such as the temperature and time during the production and sintering of the positive active material particles.

[0026] In some embodiments, the metal oxide comprises one selected from aluminum oxide, tungsten oxide and / or zirconium oxide.

[0027] The metal oxides described above, used as coating layers for particles of the positive active material, can protect them from corrosion by acidic substances, such as hydrofluoric acid in an electrolyte, upon contact with the electrolyte. This corrosion prevents the formation of byproducts that affect the electrochemical activity and service life. However, the metal oxides are not limited to the three types mentioned above; other metal oxides with similar inert protective properties can be used as substitutes.

[0028] In some embodiments, the mean particle size “Dv50” of the particles of the positive active material is 4 - 8 µm;

[0029] In the present application, the mean particle size of the particles of the positive active material is directly tested using a laser particle size analyzer.

[0030] In some embodiments, the concentration of the metal oxide in the positive electrode material is 100 - 4000 ppm.

[0031] In some embodiments, the particles of the positive active material include one selected from lithium nickel cobalt manganese oxide particles, lithium iron phosphate particles and / or lithium nickel manganese oxide particles.

[0032] The particles of the positive active material in the positive electrode material of the present application can be particles of the positive high-voltage material lithium nickel manganese oxide or layered lithium nickel cobalt manganese oxide particles with the chemical formula LiNi x Co y Mn (1-x-y )O2, where 0 < x < 1, 0 < y < 1, or lithium iron phosphate particles with an olivine structure with the chemical formula LiFe x Mn 1-xPO4, where 0 < x < 1, is used. As long as the ratio between the value of "K" and the roundness after the formation of a surface coating layer is effectively controlled so that it lies within the specific range of "0.2 ≤ K / Rn ≤ 1.2", improved structural stability can be achieved compared to conventional positive electrode materials of the same system. Furthermore, high conductivity can be maintained, enabling the electrode material to exhibit ideal cycle life and capacity performance when used in secondary batteries, especially in high-temperature environments.

[0033] In some embodiments, the particles of the positive active material further include one selected from doped lithium nickel cobalt manganese oxide particles, doped lithium iron phosphate particles and / or doped lithium nickel manganese oxide particles.

[0034] With the above three active materials with a doping modification, an ideal improvement in electrochemical performance can also be achieved using the modification method and the resulting positive electrode material in the technical scheme of the present application. Therefore, the particles of the positive active material in the technical scheme of the present application are not limited to the three undoped systems of positive electrode materials.

[0035] In some embodiments, the particles of the positive active material include lithium nickel manganese oxide particles, and 0.3 ≤ K / Rn ≤ 0.5.

[0036] In some embodiments, the particles of the positive active material are LiNi. x Mn y O4, where 0 < x ≤ 0.5, y = 2-x.

[0037] Compared to ternary materials or lithium iron phosphate materials, lithium nickel manganese oxide particles exhibit a higher working stress, resulting in relatively poorer stability, inherently more structural angles, and lower surface smoothness. Therefore, the coating effect of the coating layer must be carefully controlled to prevent angle breakage during electrode rolling, which can lead to partial failure of the surface coating layer and an increased likelihood of side reactions with the electrolyte. When the K / Rn ratio is controlled to the range of 0.3–0.5, the particles of the positive active material exhibit good coating effect, complete angle coverage, high surface smoothness, and a lower dissolution rate of transition metal elements. Furthermore, the conductivity is higher, resulting in improved overall performance.

[0038] In one embodiment, the technical solution of the present application also provides a positive electrode which has the positive electrode material of the present application.

[0039] In some embodiments, the positive electrode comprises a current collector and a layer of a positive electrode material. The layer of positive electrode material contains the positive electrode material of the present application.

[0040] In some embodiments, the layer of positive electrode material further comprises a conductive agent and a binder.

[0041] More preferably, the conductive agent comprises one selected from acetylene carbon black and / or carbon nanotubes, and the binder comprises polyvinylidene fluoride.

[0042] In one embodiment, the technical solution of the present application further provides a secondary battery which has the positive electrode of the present application.

[0043] In some embodiments, the secondary battery also includes a negative electrode and an electrolyte.

[0044] In some embodiments, the negative electrode comprises a negative active material.

[0045] In some embodiments, the negative active material comprises one selected from carbon-based materials, silicon-based materials and / or silicon-carbon composite materials.

[0046] More preferably, the layer of negative material comprises a negative material, a binder, a thickening agent and a conductive agent.

[0047] In some embodiments, the electrolyte comprises a solvent and a lithium salt.

[0048] In some embodiments, the solvent comprises carbonate solvents, carboxylate solvents, ether solvents, sulfone solvents, nitrile solvents and / or phosphate solvents.

[0049] For example, the carbonate solvents include, but are not limited to, one selected from propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and / or ethyl methyl carbonate (EMC); the carboxylate solvents include, but are not limited to, one selected from ethyl acetate, methyl formate and / or 1,4-butyrolactone; the ether solvents include, but are not limited to, one selected from dimethyltetrahydrofuran, tetrahydrofuran and / or 1,2-dimethoxyethane; the sulfone solvents include, but are not limited to, one selected from methyl sulfone and / or dimethyl sulfoxide; the nitrile solvents include, but are not limited to, one selected from propionitrile, butyronitrile, 1-(2-cyanoethyl)pyrrole and / or 1,3,6-hexantrinitrile; The phosphate solvents include one selected from trimethyl phosphate and / or triethyl phosphate.

[0050] More preferably, the solvent comprises one selected from, but not limited to, fluorinated derivatives of carbonate solvents, fluorinated derivatives of carboxylate solvents, fluorinated derivatives of ether solvents, fluorinated derivatives of sulfone solvents, fluorinated derivatives of nitrile solvents and / or fluorinated derivatives of phosphate solvents.

[0051] In some embodiments, the lithium salt comprises one selected from lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonate, lithium bis(fluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorobis(oxalato)phosphate and / or lithium tetrafluoro(oxalato)phosphate.

[0052] The concentration of the lithium salt in the electrolyte is preferably 0.8 - 2.5 mol / l.

[0053] A more preferred concentration is that of the lithium salt in the electrolyte equal to a value of or a value in a range of any two of 0.8 mol / l, 1 mol / l, 1.2 mol / l, 1.5 mol / l, 1.8 mol / l, 2 mol / l, 2.2 mol / l and 2.5 mol / l.

[0054] In some embodiments, the secondary battery is manufactured by the following method: Production of the positive active material: A lithium source, a nickel source, and a manganese source are mixed according to a target molar ratio and combined with zirconium oxide beads with a diameter of 0.6–1.0 mm in a bead-to-material ratio of 5:1–8:1. The mixture is then pellet-milled for 5–12 hours at a speed of 1700–2300 rpm. The pellet-milled mixture is then calcined for 6–20 hours at a temperature of 600–1200 °C and cooled to room temperature, yielding spinel-type lithium nickel manganese oxide.

[0055] In the present embodiment, the lithium source is selected from: lithium carbonate, lithium hydroxide;

[0056] The nickel source is selected from: nickel hydroxide, nickel carbonate, nickel oxide;

[0057] The manganese source is selected from: manganese hydroxide, manganese carbonate, manganese oxide. Alternatively:

[0058] A lithium source, a nickel source, a cobalt source, and a manganese source are mixed according to a target molar ratio and combined with zirconium oxide beads with a diameter of 0.6–1.0 mm in a bead-to-material ratio of 5:1–8:1. The mixture is then sphere-milled for 5–12 hours at a speed of 1700–2300 rpm. The sphere-milled mixture is then calcined for 6–20 hours at a temperature of 600–1200 °C and cooled to room temperature, yielding lithium nickel cobalt manganese oxide.

[0059] In the present embodiment, the lithium source is selected from: lithium carbonate, lithium hydroxide;

[0060] The nickel source is selected from: nickel hydroxide, nickel carbonate, nickel oxide;

[0061] The cobalt source is selected from: cobalt hydroxide, cobalt carbonate, cobalt oxide;

[0062] The manganese source is selected from: manganese hydroxide, manganese carbonate, manganese oxide. Alternatively:

[0063] A lithium source, an iron source, and a phosphorus source are mixed according to a target molar ratio and combined with zirconium oxide beads with a diameter of 0.6–1.0 mm in a bead-to-material ratio of 5:1–8:1. The mixture is then pellet-milled for 5–12 hours at a speed of 1700–2300 rpm. The pellet-milled mixture is then calcined for 6–20 hours at a temperature of 500–800 °C and cooled to room temperature, yielding lithium iron phosphate.

[0064] In the present embodiment, the lithium source is selected from: lithium carbonate, lithium hydroxide;

[0065] The iron source is selected from: iron(II) oxalate, iron(II) acetate;

[0066] The phosphorus source is selected from: ammonium phosphate, ammonium dihydrogen phosphate.

[0067] A positive active material, a conductive agent, and a binder are mixed in 1-methyl-2-pyrrolidinone (NMP) in a mass ratio of (94.0 - 99.85):(0.05 - 1.0):(0.1 - 5.0), yielding a positive electrode slurry. The positive electrode slurry is applied to aluminum foil, resulting in a positive electrode coated aluminum foil. After drying, the aluminum foil is rolled and cut to size, yielding a positive electrode.

[0068] The binder is selected from polytetrafluoroethylene or polyvinylidene fluoride.

[0069] The conductive medium is selected from conductive carbon black, acetylene carbon black and / or carbon nanotubes.

[0070] One method for manufacturing a negative electrode for a secondary battery is as follows: A negative material, a binder, and a conductive agent are dispersed in deionized water in a mass ratio of (93.0 - 99.8): (0.1 - 2.0):(0.1 - 5.0), resulting in a slurry of the negative electrode, and the slurry of the negative electrode is applied to copper foil; after drying, cold pressing, and cutting, the negative electrode is obtained.

[0071] The negative main material is selected from natural graphite, artificial graphite, soft carbon and / or hard carbon;

[0072] The binder is selected from polyacrylic acid (PAA), styrene-butadiene rubber (SBR) and / or carboxymethylcellulose (CMC);

[0073] The conductive medium is selected from conductive carbon black and / or carbon nanotubes.

[0074] One method for producing an electrolyte for a secondary battery is as follows: A solvent and a lithium salt are mixed in a mass ratio of (98 - 99.99):(0.01:2), resulting in an electrolyte.

[0075] The solvent is selected from carbonate solvents, carboxylate solvents, ether solvents, sulfone solvents, nitrile solvents and / or phosphate solvents.

[0076] The carbonate solvents are selected from propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and / or ethyl methyl carbonate (EMC); the carboxylate solvents are selected from ethyl acetate, methyl formate and / or 1,4-dibutyl butyrate; the ether solvents are selected from dimethyltetrahydrofuran, tetrahydrofuran and / or 1,2-dimethoxyethane; the sulfone solvents are selected from methyl sulfone and / or dimethyl sulfoxide; the nitrile solvents are selected from propionitrile, butyronitrile, 1-(2-cyanoethyl)pyrrole and / or 1,3,6-hexantrinitrile; the phosphate solvents are selected from trimethyl phosphate and / or triethyl phosphate.

[0077] The lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalato)phosphate (LiDFOP) and / or lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0078] After receiving all components, the positive electrode, a separator, and the negative electrode are stacked and wound together to assemble a cell. The cell is then packed, electrolyte is injected, and the cell is sealed, undergoes formation and capacity sorting, and thus obtains the secondary battery.

[0079] In the present embodiment, the electrolyte of the secondary battery in the present application can be produced by combining suitable types of solvents and lithium salts and adjusting the lithium salt concentration according to the actual requirements, as long as a normal benefit can be achieved, and it is not limited by the described scheme.

[0080] The present invention is further elaborated by specific embodiments below, which, however, are not to be understood as limiting the scope of protection claimed by the present invention: Example 1

[0081] Positive electrode material and secondary battery, wherein a method for manufacturing thereto comprises the following steps: (1) Preparation of a positive electrode material: Li2CO3, NiCO3 and MnO2 are pellet-milled in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for H hours at T °C in an air atmosphere. The temperature is then increased to 850 °C, and calcination is carried out for 12 hours, producing particles of the positive active material LiNi 0,5 Mn 1,5 O4 is obtained. Then, an ALD atomic deposition instrument is used with aluminum oxide powder as the starting material, the deposition pressure is set to "h", and the number of deposition cycles is set to "C" cycles, whereby aluminum oxide is deposited on the surface of the particles of the positive active material, thus obtaining the positive electrode material; The preparation and characteristic features of the positive electrode material are shown in Table 1; (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode; The resistance value of the obtained positive electrode is measured directly with a resistance meter; (3) Preparation of a negative electrode: A negative active material, a conductive material (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode. The negative material is graphite. (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected; (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l; (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve, and an electrolyte is injected after drying. The cell is then vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, resulting in the secondary battery. Examples 2 - 14

[0082] Positive electrode material and secondary battery, which differ from Example 1 only in that the parameters of the manufacturing process and characteristic parameters of the positive electrode material are different, as shown in Table 1. Examples 15-18

[0083] Positive electrode material and secondary battery, which differ from Example 1 only in that the parameters of the manufacturing process and characteristic parameters of the positive electrode material are different and that the starting material for ALD deposition is replaced by zirconium oxide powder, as shown in Table 1. Examples 19 - 22

[0084] Positive electrode material and secondary battery, which differ from Example 1 only in that the parameters of the manufacturing process and characteristic parameters of the positive electrode material are different and that the starting material for ALD deposition is replaced by tungsten oxide powder, as shown in Table 1. Examples 23 - 28

[0085] Positive electrode material and secondary battery, which differ from Example 1 only in that the parameters of the manufacturing process and characteristic parameters of the positive electrode material are different, as shown in Table 1. Example 29

[0086] Positive electrode material and secondary battery, wherein a method for manufacturing thereto comprises the following steps: (1) Preparation of a positive electrode material: Li2CO3, NiCO3 and MnO2 are pellet-milled in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for “H” hours at T °C in an air atmosphere. The temperature is then increased to 850 °C, and calcination is carried out for 12 hours, producing particles of the positive active material LiNi 0,5 Mn 1,5 O4 is obtained. Then, an ALD atomic deposition instrument is used with aluminum oxide powder as the starting material, the deposition pressure is set to "h", and the number of deposition cycles is set to "C" cycles, whereby aluminum oxide is deposited on the surface of the particles of the positive active material, thus depositing the positive electrode material LiNi. 0,2 Mn 1,8 O4 is obtained; The production and characteristic features of the positive electrode material are shown in Table 1; (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode; The resistance value of the obtained positive electrode is measured directly with a resistance meter; (3) Preparation of a negative electrode: A negative active material, a conductive agent (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode, the negative material being graphite. (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected; (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l; (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve. After drying, an electrolyte is injected. The cell is then vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, resulting in the secondary battery. Example 30

[0087] Positive electrode material and secondary battery, wherein a method for manufacturing thereto comprises the following steps: (1) Preparation of a positive electrode material: Li2CO3, NiCO3, Co(OH)2 and MnO2 are pelletized in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for “H” hours at T °C in an air atmosphere. The temperature is then increased to 900 °C, and calcination is carried out for 12 hours, producing particles of the positive active material LiNi 0,4 Co 0,2 Mn 0,4 O2 is obtained. Then, an ALD atomic deposition instrument is used with aluminum oxide powder as the starting material, the deposition pressure is set to "h", and the number of deposition cycles is set to "C" cycles, whereby aluminum oxide is deposited on the surface of the particles of the positive active material, thus depositing the positive electrode material LiNi. 0,4 Co 0,2 Mn 0,4 O2 will be received; The manufacturing process and characteristic features of the positive electrode material are shown in Table 1; (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode; The resistance value of the obtained positive electrode is measured directly with a resistance meter; (3) Preparation of a negative electrode: A negative active material, a conductive agent (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode, the negative material being graphite. (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected; (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l; (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve. After drying, an electrolyte is injected, and then the cell is vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, thus obtaining the secondary battery. Example 31

[0088] Positive electrode material and secondary battery, wherein a method for manufacturing thereto comprises the following steps: (1) Preparation of a positive electrode material: Li2CO3, FeC2O4·2H2O and NH4H2PO4 are pelletized in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for “H” hours at T °C in an argon atmosphere. The temperature is then increased to 750 °C, and calcination is carried out for 12 hours, yielding particles of the positive active material LiFePO4. An ALD atomic deposition instrument using aluminum oxide powder as the starting material is then used, the deposition pressure is set to “h”, and the number of deposition cycles is set to “C” cycles, depositing aluminum oxide on the surface of the positive active material particles, thus obtaining the positive electrode material LiFePO4; The manufacturing process and characteristic features of the positive electrode material are shown in Table 1; (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode; The resistance value of the obtained positive electrode is measured directly with a resistance meter; (3) Preparation of a negative electrode: A negative active material, a conductive agent (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode, the negative material being graphite. (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected; (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l; (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve. After drying, an electrolyte is injected. The cell is then vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, resulting in the secondary battery. Comparison examples 1-4

[0089] Positive electrode material and secondary battery, which differ from Example 1 only in that the parameters of the manufacturing process and characteristic parameters of the positive electrode material are different, as shown in Table 1. Comparative examples 5-6

[0090] Positive electrode material and secondary battery, which differ from Example 1 only in that the parameters of the manufacturing process and characteristic parameters of the positive electrode material are different and that the starting material for ALD deposition is replaced by zirconium oxide powder, as shown in Table 1. Comparative example 7

[0091] Positive electrode material and secondary battery, (1) Preparation of a positive electrode material: Li2CO3, NiCO3 and MnO2 are pelletized in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for “H” hours at T °C in an air atmosphere. Then the temperature is increased to 850 °C, and calcination is carried out for 12 hours, producing particles of the positive active material LiNi 0,5 Mn 1,5 O4 is obtained. Then, an ALD atomic deposition instrument is used with aluminum oxide powder as the starting material, the deposition pressure is set to "h", and the number of deposition cycles is set to "C" cycles, whereby aluminum oxide is deposited on the surface of the particles of the positive active material, thus depositing the positive electrode material LiNi. 0,2 Mn 1,8 O4 will be received;

[0092] The manufacturing process and characteristic features of the positive electrode material are shown in Table 1;

[0093] (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode. The resistance of the resulting positive electrode is measured directly using a resistance meter.

[0094] (3) Preparation of a negative electrode: A negative active material, a conductive agent (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode, the negative material being graphite.

[0095] (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected;

[0096] (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l;

[0097] (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve. After drying, an electrolyte is injected, and then the cell is vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, thus obtaining the secondary battery. Comparative example 8

[0098] Positive electrode material and secondary battery, (1) Preparation of a positive electrode material: Li2CO3, NiCO3 and MnO2 are pelletized in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for “H” hours at T °C in an air atmosphere. Then the temperature is increased to 850 °C, and calcination is carried out for 12 hours, producing particles of the positive active material LiNi 0,5 Mn 1,5 O4 is obtained. Then, an ALD atomic deposition instrument is used with aluminum oxide powder as the starting material, the deposition pressure is set to "h", and the number of deposition cycles is set to "C" cycles, whereby aluminum oxide is deposited on the surface of the particles of the positive active material, thus depositing the positive electrode material LiNi. 0,2 Mn 1,8 O4 will be received;

[0099] The manufacturing process and characteristic features of the positive electrode material are shown in Table 1;

[0100] (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode; The resistance value of the obtained positive electrode is measured directly with a resistance meter;

[0101] (3) Preparation of a negative electrode: A negative active material, a conductive agent (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode, the negative material being graphite.

[0102] (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected;

[0103] (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l;

[0104] (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve. After drying, an electrolyte is injected, and then the cell is vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, thus obtaining the secondary battery. Comparative example 9

[0105] Positive electrode material and secondary battery, wherein a method for manufacturing thereto comprises the following steps: (1) Preparation of a positive electrode material: Li2CO3, NiCO3, Co(OH)2 and MnO2 are pelletized in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for “H” hours at T °C in an air atmosphere. The temperature is then increased to 900 °C, and calcination is carried out for 12 hours, producing particles of the positive active material LiNi 0,4 Co 0,2 Mn 0,4 O2 is obtained. Then, an ALD atomic deposition instrument is used with aluminum oxide powder as the starting material, the deposition pressure is set to "h", and the number of deposition cycles is set to "C" cycles, whereby aluminum oxide is deposited on the surface of the particles of the positive active material, thus depositing the positive electrode material LiNi. 0,4 Co 0,2 Mn 0,4O2 will be received; The manufacturing process and characteristic features of the positive electrode material are shown in Table 1; (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode; The resistance value of the obtained positive electrode is measured directly with a resistance meter; (3) Preparation of a negative electrode: A negative active material, a conductive agent (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode, the negative material being graphite. (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected; (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l; (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve. After drying, an electrolyte is injected. The cell is then vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, resulting in the secondary battery. Comparative example 10

[0106] Positive electrode material and secondary battery, wherein a method for manufacturing thereto comprises the following steps: (1) Preparation of a positive electrode material: Li2CO3, NiCO3, Co(OH)2 and MnO2 are pelletized in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for “H” hours at T °C in an air atmosphere. The temperature is then increased to 900 °C, and calcination is carried out for 12 hours, producing particles of the positive active material LiNi 0,4 Co 0,2 Mn 0,4 O2 is obtained. Then, an ALD atomic deposition instrument is used with aluminum oxide powder as the starting material, the deposition pressure is set to "h", and the number of deposition cycles is set to "C" cycles, whereby aluminum oxide is deposited on the surface of the particles of the positive active material, thus depositing the positive electrode material LiNi. 0,4 Co 0,2 Mn 0,4 O2 will be received; The manufacturing process and characteristic features of the positive electrode material are shown in Table 1; (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode; The resistance value of the obtained positive electrode is measured directly with a resistance meter; (3) Preparation of a negative electrode: A negative active material, a conductive agent (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode, the negative material being graphite. (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected; (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l; (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve. After drying, an electrolyte is injected. The cell is then vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, resulting in the secondary battery. Comparative example 11

[0107] Positive electrode material and secondary battery, wherein a method for manufacturing thereto comprises the following steps: (1) Preparation of a positive electrode material: Li2CO3, FeC2O4·2H2O and NH4H2PO4 are pelletized in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for “H” hours at T °C in an argon atmosphere. The temperature is then increased to 750 °C, and calcination is carried out for 12 hours, yielding particles of the positive active material LiFePO4. An ALD atomic deposition instrument using aluminum oxide powder as the starting material is then used, the deposition pressure is set to “h”, and the number of deposition cycles is set to “C” cycles, depositing aluminum oxide on the surface of the positive active material particles, thus obtaining the positive electrode material LiFePO4; The manufacturing process and characteristic features of the positive electrode material are shown in Table 1; (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode; The resistance value of the obtained positive electrode is measured directly with a resistance meter; (3) Preparation of a negative electrode: A negative active material, a conductive agent (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode, the negative material being graphite. (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected; (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l; (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve. After drying, an electrolyte is injected, and then the cell is vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, thus obtaining the secondary battery. Comparative example 12

[0108] Positive electrode material and secondary battery, wherein a method for manufacturing thereto comprises the following steps: (1) Preparation of a positive electrode material: Li2CO3, FeC2O4·2H2O and NH4H2PO4 are pelletized in a stoichiometric ratio “B” for hours at a rate “A”, then calcined for “H” hours at T °C in an argon atmosphere. The temperature is then increased to 750 °C, and calcination is carried out for 12 hours, yielding particles of the positive active material LiFePO4. An ALD atomic deposition instrument using aluminum oxide powder as the starting material is then used, the deposition pressure is set to “h”, and the number of deposition cycles is set to “C” cycles, depositing aluminum oxide on the surface of the positive active material particles, thus obtaining the positive electrode material LiFePO4; The manufacturing process and characteristic features of the positive electrode material are shown in Table 1; (2) Preparation of a positive electrode: A positive active material, a conductive medium consisting of carbon nanotubes, and a binder consisting of polyvinylidene fluoride are dispersed in 1-methyl-2-pyrrolidinone in a mass ratio of 97:1:2. A slurry is prepared by stirring under vacuum, then applied to both sides of an aluminum foil current collector and dried, cold-pressed, and cut open to obtain the positive electrode; The resistance value of the obtained positive electrode is measured directly with a resistance meter; (3) Preparation of a negative electrode: A negative active material, a conductive agent (acetylene carbon black), a thickening agent (sodium carboxymethylcellulose), and a binder (styrene-butadiene rubber) are dispersed in water in a mass ratio of 96.4:1:1.2:1.4. A slurry is prepared by stirring under vacuum, then applied to both sides of a copper foil current collector and dried, cold-pressed, and cut open to obtain the negative electrode, the negative material being graphite. (4) Selection of a separator: A commercially available polyethylene separator with a thickness of 15 µm is selected; (5) Preparation of an electrolyte: Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1, giving an organic solvent, and then the lithium salt LiPF6 is added to dissolve in the organic solvent mixture, giving an electrolyte with a concentration of 1 mol / l; (6) The positive electrode, separator, and negative electrode are stacked and wound together to assemble a cell. The cell is placed in an outer packaging sleeve. After drying, an electrolyte is injected, and then the cell is vacuum-sealed, left to stand for 24 hours, and subjected to formation and capacity sorting, thus obtaining the secondary battery. Table 1 parameter A U. / min, B h T °C H h C cycles h Pa Rn K % K / Rn Example 1 1800, 10 600 6 60 10 0,4 0,48 1,2 Example 2 1800, 10 1000 18 450 10 0,75 0,15 0,2 Example 3 1800, 10 800 8 210 10 0,6 0,3 0,5 Example 4 1800, 10 860 8 310 10 0,7 0,21 0,3 Example 5 1800, 10 880 7 260 10 0,65 0,26 0,4 Example 6 1800, 10 600 7 80 10 0,42 0,42 1 Example 7 1800, 10 800 8 60 10 0,6 0,48 0,8 Example 8 1800, 10 700 9 240 10 0,5 0,28 0,56 Example 9 1800, 10 1200 18 305 10 0,8 0,2 0,25 Example 10 1800, 10 650 8 390 10 0,45 0,18 0,4 Example 11 1800, 10 760 9 270 10 0,55 0,25 0,45 Example 12 1800, 10 1100 12 180 10 0,7 0,35 0,5 Example 13 1800, 10 900 8 270 10 0,68 0,25 0,37 Example 14 1800, 10 900 7 240 10 0,66 0,28 0,42 Example 15 1800, 10 900 8 280 10 0,68 0,24 0,35 Example 16 1800, 10 900 8 210 10 0,68 0,3 0,44 Example 17 1800, 10 1100 14 395 10 0,74 0,17 0,23 Example 18 1800, 10 800 8 180 10 0,6 0,35 0,58 Example 19 1800, 10 900 8 245 10 0,68 0,27 0,4 Example 20 1800, 10 890 8 210 10 0,67 0,3 0,45 Example 21 1800, 10 600 7 460 10 0,41 0,12 0,29 Example 22 1800, 10 1200 11 100 10 0,77 0,4 0,52 Example 23 2000, 10 700 8 180 11 0,6 0,3 0,5 Example 24 2200, 11 700 8 180 12 0,75 0,25 0,33 Example 25 1700, 7 700 8 180 13 0,4 0,18 0,45 Example 26 1750, 9 700 8 180 12 0,55 0,25 0,45 Example 27 2100, 10 700 8 180 14 0,68 0,15 0,22 Example 28 1700, 9 700 8 180 8 0,5 0,45 0,9 Example 29 1800, 10 880 7 240 10 0,65 0,28 0,43 Example 30 1800, 10 880 7 260 10 0,66 0,27 0,41 Example 31 1800, 10 880 7 260 10 0,64 0,28 0,44 Comparative example 1 1800, 10 1200 18 460 10 0,8 0,12 0,15 Comparative example 2 1800, 10 600 6 50 10 0,4 0,5 1,25 Comparative example 3 1800, 10 1000 18 500 10 0,75 0,1 0,13 Comparative example 4 1800, 10 500 6 30 10 0,3 0,6 2 Comparative example 5 1800, 10 600 7 40 10 0,42 0,56 1,33 Comparative example 6 1800, 10 1100 12 500 10 0,7 0,1 0,14 Comparative example 7 1800, 10 1000 17 450 10 0,73 0,13 0,18 Comparative example 8 1800, 10 600 6 50 10 0,4 0,52 1,3 Comparative example 9 1800, 10 1000 17 450 10 0,76 0,11 0,14 Comparative example 10 1800, 10 600 6 50 10 0,41 0,54 1,32 Comparative example 11 1800, 10 1000 17 450 10 0,76 0,12 0,16 Comparative example 12 1800, 10 600 6 50 10 0,4 0,55 1,38 Examples of the effect

[0109] The following tests were performed on the positive electrode materials and secondary batteries obtained from all examples and comparison examples: (1) Testing the resistance value of the positive electrode: Tests are carried out as described above, and therefore details are not repeated here; (2) High-temperature cycle performance test: The secondary batteries obtained from each example and comparison example are charged at room temperature using a LAND charge-discharge system with a constant current at a rate of 0.33 C up to an upper voltage limit; then they are discharged for 2 cycles at a constant current at a rate of 0.33 C up to a lower voltage limit, then they are placed in an environment of 45 °C and charged and discharged at a rate of 1 C / 1 C in 100 cycles using the same system at the same operating voltage, recording the discharge capacity at each cycle number, and finally the high-temperature cycle capacity retention rate (%) is calculated as: secondary battery discharge capacity after 100 cycles at a rate of 1 C / 1 C / secondary battery discharge capacity at the first cycle at a rate of 1 C / 1 C; For the batteries obtained from examples 1-29 and comparison examples 1-8, the lower voltage limit is 2.5 V and the upper voltage limit is 4.25 V; For the batteries obtained from Example 30 and the comparative examples 9-10, the lower voltage limit is 3.7 V and the upper voltage limit is 4.2 V; For the batteries obtained from Example 31 and the comparative examples 11-12, the lower voltage limit is 2.2 V and the upper voltage limit is 3.7 V; (3) High-temperature storage performance test: The secondary batteries obtained from each example and comparison example are charged at room temperature using a LAND charge-discharge system with a constant current at a rate of 0.33 C up to an upper voltage limit; then they are discharged with a constant current at a rate of 0.33 C for 2 cycles down to a lower voltage limit, then stored for 15 days in an environment of 45 °C, and after completion of storage, the secondary batteries are removed and charged and discharged once at room temperature using the same system at the same operating voltage and rate, and finally the high-temperature storage capacity retention rate (%) is calculated as: secondary battery discharge capacity after storage at room temperature at a rate of 0.33 C / secondary battery discharge capacity before storage at room temperature at a rate of 0.33 C; For the batteries obtained from examples 1-29 and comparison examples 1-8, the lower voltage limit is 2.5 V and the upper voltage limit is 4.25 V; For the batteries obtained from Example 30 and the comparative examples 9-10, the lower voltage limit is 3.7 V and the upper voltage limit is 4.2 V; For the batteries obtained from Example 31 and the comparative examples 11-12, the lower voltage limit is 2.2 V and the upper voltage limit is 3.7 V;

[0110] The test results are listed in Table 2. Table 2 Performance Resistance value of the positive electrode (mΩ) High-temperature cycle capacity retention rate (%) High-temperature storage capacity retention rate (%) Example 1 300 81 82 Example 2 290 82 80 Example 3 225 93 91 Example 4 217 92 90 Example 5 224 95 93 Example 6 293 82 81 Example 7 282 81 83 Example 8 288 82 80 Example 9 279 80 79 Example 10 262 87 88 Example 11 257 89 86 Example 12 245 88 87 Example 13 223 93 94 Example 14 225 95 92 Example 15 223 93 92 Example 16 221 94 93 Example 17 291 81 82 Example 18 299 80 81 Example 19 221 92 91 Example 20 220 93 92 Example 21 299 82 82 Example 22 289 81 83 Example 23 211 91 90 Example 24 204 90 91 Example 25 258 87 85 Example 26 250 86 86 Example 27 285 81 80 Example 28 291 80 79 Example 29 215 92 91 Example 30 265 90 90 Example 31 175 91 89 Comparison example 1 224 74 76 Comparison example 2 289 75 72 Comparison example 3 243 72 73 Comparison example 4 321 74 75 Comparison example 5 289 71 72 Comparison example 6 267 72 70 Comparison example 7 262 68 70 Comparison example 8 305 72 70 Comparison example 9 345 69 74 Comparison example 10 366 71 73 Comparison example 11 246 72 75 Comparison example 12 289 71 72

[0111] Table 2 shows the following: (1) The positive active material of the present application is produced by providing a coating layer on the surface of a positive active material and simultaneously controlling the ratio between the roundness of the applied positive electrode material and the percentage of free transition metal ions after acid corrosion in order to coordinate the balance between stability and conductivity in the positive electrode material. This allows the secondary battery produced with the positive electrode material to exhibit desirable electrochemical properties. It is evident that the resistance values ​​of the positive electrodes obtained from all the examples are low, with the highest being only 300 mΩ.With secondary batteries manufactured using these positive electrodes, a capacity retention rate of at least 80% can be achieved during high-temperature cyclic operation, and even after storage at high temperature for 15 days, the capacity retention rate can reach at least 79%, demonstrating excellent overall performance. Although the positive electrode materials obtained from comparative examples 1-12 also featured engineered coating layers, the relationship between the balance of roundness and stability of the transition metal elements was not properly controlled in these materials.Not only can it not be guaranteed that these positive electrode materials will have a low resistance value when positive electrodes are manufactured from them, but they also exhibit poor performance at high temperatures, meaning they do not achieve ideal high-temperature stability when secondary batteries are manufactured with them. (2) It is evident from Examples 1-15 and Examples 16-29 that the types of positive active material and the coating layer in the positive electrode material of the present application are not restricted. In particular, when the positive active material is lithium nickel manganese oxide and the K / Rn ratio is controlled to be in the range of 0.3-0.5, the particles of the positive active material exhibit good coating effect, with the angles being completely coated, the surface smoothness being high, and the dissolution rate of the transition metal elements being lower. In addition, the conductivity is higher, resulting in better overall performance.The resistance value of the positive electrodes produced with this positive electrode material can be kept within 270 mΩ, and both the high-temperature cycle operation and the high-temperature storage capacity retention rate can reach more than 85%. (3) When the positive electrode material is controlled, the roundness of the particles of the positive active material after the formation of a surface coating layer affects the completeness of the coating and the overall regularity of the particles, resulting in different contact areas with an electrolyte, different densities, and different structural stability during electrode fabrication. If the roundness of the material is preferably in the range of 0.6–0.7, a moderate contact area with the electrolyte and control of the balance between the probability of transition metal ion dissolution and the difficulty of ion / electron transport can be achieved by controlling the coating density of the particles of the positive active material, thereby achieving ideal electrode stability and density during fabrication.On the other hand, the percentage of free transition metal in the particles of the positive active material after acid etching is related to both the type of positive active material and the coating effect of the coating layer. Therefore, the value of K also influences the ion / electron transport capacity and the structural stability of the particles of the positive active material. If the value of "K" of the particles of the positive active material is preferably in the range of 0.2–0.3%, the resulting positive electrode material exhibits better structural stability and conductivity.If the positive electrode material simultaneously fulfills both preferred ranges and the constructed relationship of the ratio is also within the preferred range, the positive electrodes produced with the resulting positive electrode material can not only maintain their resistance values ​​within 230 mΩ, but the capacity retention rate can reach 90% in an application in the manufacture of secondary batteries after high-temperature cycle operation and storage at high temperature, with the high-temperature cycle capacity retention rate reaching up to 95% and the capacity retention rate after storage at high temperature reaching 94%. QUOTES INCLUDED IN THE DESCRIPTION

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[0018]

Claims

[1] Positive electrode material, characterized by , that it has particles of a positive active material, wherein the particles of the positive active material are provided with a coating layer and the coating layer has a metal oxide; the positive electrode material: 0.2 ≤ K / Rn ≤ 1.2 is fulfilled; where “K %” is the percentage of a free transition metal element from the particles of the positive active material with respect to a transition metal element contained in the particles of the positive active material, after the particles of the positive active material have been immersed for 72 hours at 70 °C in a hydrofluoric acid solution with a concentration of 20 wt% in a solid-liquid ratio of 1 g:5 ml; where “Rn” is the roundness of the particles of the positive active material. [2] Positive electrode material according to claim 1, characterized by , that 0.4 ≤ Rn ≤ 0.

8. [3] Positive electrode material according to claim 2, characterized by , that 0.6 ≤ Rn ≤ 0.

7. [4] Positive electrode material according to any one of the preceding claims, characterized by , that 0.1% ≤ K ≤ 0.5%. [5] Positive electrode material according to claim 4, characterized by , that 0.2% ≤ K ≤ 0.3%. [6] Positive electrode material according to any one of the preceding claims, characterized by , that the particles of the positive active material comprise one selected from lithium nickel cobalt manganese oxide particles, lithium iron phosphate particles and / or lithium nickel manganese oxide particles. [7] Positive electrode material according to claim 6, characterized by , that the particles of the positive active material comprise lithium nickel manganese oxide particles and where 0.3 ≤ K / Rn ≤ 0.

5. [8] Positive electrode material according to claim 6 or 7, characterized by , that the particles of positive LiNi x Mn y O4 are, where 0 < x ≤ 0.5, y = 2-x. [9] Positive electrode material according to any one of the preceding claims, characterized by that the metal oxide in the coating layer is one selected from aluminium oxide, tungsten oxide and / or zirconium oxide. [10] Positive electrode material according to any one of the preceding claims, characterized by , that the mean particle size “Dv50” of the particles of the positive active material is 4 - 8 µm. [11] Positive electrode material according to any one of the preceding claims, characterized by , that the concentration of the metal oxide in the positive electrode material is 100 - 4000 ppm. [12] Positive electrode material according to claim 6, characterized by , that the particles of the positive active material comprise lithium nickel manganese oxide particles and where 0.3 ≤ K / Rn ≤ 0.

5. [13] Positive electrode material according to any one of the preceding claims, characterized bythat the layer of positive electrode material continues to contain a conductive agent and a binder. [14] Positive electrode, characterized by that it has the positive electrode material according to one of the preceding claims. [15] Positive electrode according to claim 14, characterized by that it has a current collector and a layer of a positive electrode material according to one of the preceding claims. [16] Secondary battery, characterized by that it has a positive electrode and the positive electrode has the positive electrode material according to one of claims 1-13. [17] Secondary battery according to claim 16, characterized by that it still has a negative electrode and an electrolyte. [18] Secondary battery according to claim 17, characterized by that the negative electrode has a negative active material. [19] Secondary battery according to claim 18, characterized by, that the negative active material has one that is selected from carbon-based materials, silicon-based materials and silicon-carbon composite materials. [20] Secondary battery according to any one of claims 16 to 19, characterized by that the electrolyte contains a solvent and a lithium salt. [21] Secondary battery according to claim 20, characterized by that the solvent contains carbonate solvent, carboxylate solvent, ether solvent, sulfone solvent, nitrile solvent and / or phosphate solvent. [22] Secondary battery according to claim 20 or 21, characterized by, that the lithium salt comprises one selected from lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonate, lithium bis(fluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorobis(oxalato)phosphate and / or lithium tetrafluoro(oxalato)phosphate. [23] Secondary battery according to any one of claims 20 to 22, characterized by , that the concentration of the lithium salt in the electrolyte is 0.8 - 2.5 mol / l. [24] Electrical device, characterized by that it has the secondary battery according to one of claims 16 to 23 and the secondary battery is configured to serve as the power source of the electrical device.