A method for manufacturing a positive electrode active material, a positive electrode active material, a positive electrode sheet, and a battery

Abstract

The application relates to a preparation method of a positive electrode active material, the positive electrode active material, a positive electrode sheet and a battery in the technical field of lithium battery production, and the method comprises the following steps: S1, uniformly mixing a manganese-containing precursor, a lithium source, a W source, a Nb source and a metal source M to obtain a mixture; and S2, roasting the mixture to obtain the positive electrode active material. The combination of doping and coating can be realized through one-step calcination, the process is simple, the cost is low, and the method is suitable for industrial production; the incorporation of metal elements can stabilize the crystal lattice structure of lithium manganate, prevent the crystal lattice distortion of lithium manganate in the charging and discharging process, and prevent the structure from collapsing; in the sintering process, W and Nb elements diffuse, are uniformly enriched on the surface of the material, perform surface layer doping of the material, and uniformly form LiNbO3 and Li2WO4 coating layers on the surface of the material, the formation of the two coating layers effectively eliminates residual Li on the surface of the material, effectively improves the capacity of the battery and improves the cycle performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery production, and particularly relates to a preparation method of a positive electrode active material, the positive electrode active material, a positive electrode sheet and a battery. BACKGROUND

[0002] Compared with other rechargeable battery systems, lithium ion secondary batteries have the advantages of high working voltage, light weight, small size, no memory effect, low self-discharge rate, long cycle life and high energy density, and have been widely used in mobile phones, notebook computers, tablet computers, electric vehicles and energy storage power grids. In recent years, with the rapid development of electric vehicles, people have higher pursuit of battery energy density, safety, cost and environmental protection.

[0003] Lithium manganate has been widely concerned due to its abundant resources and low price, but a large amount of trivalent manganese ions exist in lithium manganate, which is easy to cause side reactions with electrolyte, resulting in the cycle performance degradation of the battery. In the prior art, the preparation method of lithium manganate composite material is generally to dope first and then coat, which is a relatively complex process, and the formed coating layer has a high thickness and poor uniformity, which is not conducive to the capacity performance and rate performance of the battery. SUMMARY

[0004] In order to solve the above technical problems, a preparation method of a positive electrode active material, the positive electrode active material, a positive electrode sheet and a battery are disclosed in the present application, and the technical scheme of the present application is as follows:

[0005] The first aspect of the present application provides a preparation method of a positive electrode active material, which comprises the following steps:

[0006] S1, uniformly mixing a manganese-containing precursor, a lithium source, a W source, a Nb source and a metal M source to obtain a mixture;

[0007] S2, calcining the mixture to obtain a positive electrode active material.

[0008] In some embodiments, in step S1, the W source is tungsten oxide.

[0009] In some embodiments, in step S1, the metal M source comprises at least two metal elements.

[0010] In some embodiments, the metal elements comprise at least two of Mg, Al, Ca, Ti, Cu, Zn, Y, Zr, Ru, Sn and Sb.

[0011] In some preferred embodiments, the metal elements comprise at least two of Al, Mg, Sn and Ti.

[0012] In some embodiments, step S1 comprises mixing the manganese-containing precursor, the lithium source, the W source, the Nb source, the metal M source uniformly, and the molar ratio of Li, Mn, W, Nb, M is (1.001-1.2) : (1.5-1.996) : (0.001-0.1) : (0.001-0.1) : (0.001-0.1).

[0013] In some embodiments, in step S2, the calcination temperature is 400-1000℃.

[0014] In some preferred embodiments, in step S2, the calcination temperature is 600-900℃.

[0015] In some embodiments, the calcination time is 5-24h.

[0016] In some preferred embodiments, the calcination time is 8-20h.

[0017] In some embodiments, the manganese-containing precursor is Mn3O4.

[0018] In some embodiments, the lithium source is one or both of active lithium carbonate and lithium hydroxide.

[0019] The second aspect of the present application provides a positive electrode active material, which is prepared by the method disclosed in the first aspect of the present application, and has the chemical formula Li 1+a Mn 2-a-b-c-d W b Nb c M d O4.

[0020] Wherein, 0.001≤a≤0.30, 0.001≤b≤0.1, 0.001≤c≤0.1, 0.001≤d≤0.1.

[0021] In some embodiments, the positive electrode active material comprises a core material and a coating layer formed on the surface of the core material, and the coating layer comprises LiNbO3 and Li2WO4.

[0022] In some embodiments, the thickness of the coating layer is 0.1-20nm.

[0023] The third aspect of the present application provides a positive electrode sheet, which comprises the positive electrode active material disclosed in the second aspect of the present application.

[0024] The fourth aspect of the present application provides a battery, which comprises the positive electrode sheet disclosed in the third aspect of the present application.

[0025] The advantages of the present application are as follows:

[0026] The present application realizes the combination of doping and coating through one-step calcination, is simple in process, low in cost and suitable for industrial production.

[0027] The incorporation of metal elements can stabilize the crystal lattice structure of lithium manganate, prevent lithium manganate from lattice distortion and structure collapse during charging and discharging.

[0028] The elements W and Nb diffuse during sintering, are uniformly enriched on the surface of the material, and form LiNbO3 and Li2WO4 coating layers on the surface of the material, the formation of the two coating layers effectively eliminates residual Li on the surface of the material, effectively improves the capacity of the battery and improves the cycle performance of the battery, and meanwhile, LiNbO3 and Li2WO4 have good lithium ion transmission capacity, which is beneficial to improving the rate performance of the battery. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application, obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] Unless otherwise defined, all technical and scientific terms used in the present application have the same meanings as those commonly understood by those skilled in the art to which the present application belongs; the terms used in the detailed description are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application are intended to cover non-exclusive inclusion.

[0031] In the description of the specific embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0032] In the present application, the phrase "embodiment" means that the specific features, structures or properties described in combination with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase at various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the described embodiments of the present application can be combined with other embodiments.

[0033] In the description of the embodiments of the present application, the term "and / or" is merely an association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A existing alone, A and B existing simultaneously, and B existing alone. In addition, the character " / " in the present application generally represents an "or" relationship between the front and rear associated objects.

[0034] Throughout the present application, numerical values represent approximate measures or limits of ranges to encompass minor deviations from given values as well as embodiments having about the mentioned values and embodiments having the mentioned exact values. Except for the working examples provided at the end of the specific embodiments, all numerical values of parameters (e.g., amounts or conditions) in the present specification (including the appended claims) should be understood in all cases as being modified by the term "about", whether or not the term "about" actually appears before the numerical value. "About" indicates that the stated numerical value allows for some minor inaccuracy (is close to the exact value of the stated value to some extent; is approximately or reasonably close to the stated value; is almost). If the inaccuracy provided by "about" is not otherwise understood in the art in such ordinary meaning, "about" as used in the present application at least indicates the variation that can be produced by ordinary methods of measuring and using such parameters. For example, "about" can include a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some aspects, optionally less than or equal to 0.1%.

[0035] In addition, the disclosure of a range includes all values and further partitioned range disclosures within the entire range, including the endpoints and subranges given for these ranges.

[0036] The preparation method of the lithium manganate composite material in the prior art is generally doping first and then coating, which is a relatively complex process, and the formed coating layer has a high thickness and poor uniformity, which is not conducive to the capacity performance and rate performance of the battery.

[0037] To solve the above problems, the present application proposes a technical solution to solve the above problems.

[0038] The first aspect of the present application is to provide a preparation method of a positive electrode active material, which comprises the following steps:

[0039] S1, uniformly mixing a manganese-containing precursor, a lithium source, a W source, a Nb source, and a metal M source to obtain a mixture;

[0040] S2, calcining the mixture to obtain a positive electrode active material.

[0041] The present application realizes the combination of doping and coating through one-step calcination, which is simple in process, low in cost, and suitable for industrial production.

[0042] The incorporation of metal elements can stabilize the crystal lattice structure of lithium manganate, preventing the crystal lattice distortion and structure collapse of lithium manganate under the action of trivalent manganese ions.

[0043] During the sintering process, the W and Nb elements diffuse and are uniformly enriched on the surface of the material to perform surface doping of the material, and LiNbO3 and Li2WO4 coating layers are uniformly formed on the surface of the material, which effectively eliminates the residual Li on the surface of the material and effectively improves the capacity and cycle performance of the battery.

[0044] In some embodiments, in step S1, the W source is tungsten oxide.

[0045] Tungsten oxide can induce the formation of oxygen vacancies on the surface of the material, and the formation of surface oxygen vacancies helps the adsorption and storage of active oxygen, improves the interface stability, and thus improves the cycle stability. In addition, oxygen vacancies help to reduce the energy barrier for lithium ion migration, resulting in improved diffusion dynamics.

[0046] In some embodiments, in step S1, the metal M source includes at least two metal elements.

[0047] The metal elements include at least two of Mg, Al, Ca, Ti, Cu, Zn, Y, Zr, Ru, Sn, and Sb.

[0048] The "at least two" referred to in the present application means that two are selected from the above-mentioned materials for mixing, but is not limited to two. A person skilled in the art can select a larger number. Within the understanding of a person skilled in the art, it can be freely implemented. The present application does not make any limitation on this.

[0049] In some embodiments, the metal elements include Al, Mg, Sn, and Ti.

[0050] The addition of metal elements fixes the lattice sites of lithium manganate, and the doped metal elements do not change in valence state with charging and discharging, thus playing the role of a pillar inside lithium manganate, slowing down the volume change during charging and discharging, enhancing the structural stability of the material, and forming a bond between the doped metal elements and oxygen, enhancing the metal-oxygen framework, effectively fixing the lattice oxygen of lithium manganate, inhibiting the dissolution of Mn during the cycle process, and prolonging the cycle performance of lithium manganate.

[0051] In some embodiments, in step S1, the manganese-containing precursor, the lithium source, the W source, the Nb source, and the metal M source are mixed uniformly in a molar ratio of Li:Mn:W:Nb:M of (1.001-1.2):(1.5-1.996):(0.001-0.1):(0.001-0.1):(0.001-0.1).

[0052] In some embodiments, in step S2, the calcination temperature is 400-1000℃.

[0053] In some embodiments, in step S2, the calcination time is 5-24h.

[0054] In specific applications, in addition to the end points of the temperature range of 400℃ and 1000℃, any value in the above temperature range can be selected. For example, 450℃, 500℃, 650℃, 680℃, 700℃, 750℃, 780℃, 800℃, 820℃, 850℃, 900℃, 950℃, etc. In addition to the time end points of 5h and 24h, any value in the above time range can be selected, for example, 6h, 8h, 10h, 15h, 20h, etc. The present application does not make any limitation in this regard.

[0055] In some preferred embodiments, in step S2, the calcination temperature is 600-900℃; in some preferred embodiments, in step S2, the calcination time is 8-20h.

[0056] In specific applications, in addition to the end points of the temperature range of 600℃ and 900℃, any value in the above temperature range can be selected. For example, 650℃, 680℃, 700℃, 750℃, 780℃, 800℃, 820℃, 850℃, 880℃, etc. In addition to the time end points of 8h and 20h, any value in the above time range can be selected, for example, 10h, 15h, 18h, etc. The present application does not make any limitation in this regard.

[0057] In some embodiments, the manganese-containing precursor is Mn3O4.

[0058] In some embodiments, the lithium source is one or both of active lithium carbonate and lithium hydroxide.

[0059] In specific applications, the lithium source can be active lithium carbonate, can be lithium hydroxide, or can be a mixture of the two, and can be freely implemented without exceeding the understanding of those skilled in the art. The present application does not make any limitation in this regard.

[0060] The second aspect of the present application proposes a positive electrode active material, which is prepared by the method disclosed in the first aspect of the present application, and has a chemical formula of Li 1+a Mn 2-a-b-c-d W b Nb c M d O4.

[0061] In the formula, 0.001≤a≤0.30, 0.001≤b≤0.1, 0.001≤c≤0.1, 0.001≤d≤0.1.

[0062] In some embodiments, the positive electrode active material comprises a core material and a coating layer formed on the surface of the core material, the coating layer comprising LiNbO3 and Li2WO4.

[0063] In some embodiments, the thickness of the coating layer is 0.1 nm to 20 nm. The coating layer formed by the migration of elements Nb and W has the advantages of being thin and uniform.

[0064] In specific applications, the thickness of the coating layer can be selected from 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, or any value within the range, without any limitation.

[0065] A third aspect of the present application provides a positive electrode sheet, which comprises the positive electrode active material disclosed in the second aspect of the present application.

[0066] In some embodiments, the positive electrode sheet comprises a positive electrode material layer, and the positive electrode material layer comprises the positive electrode active material disclosed in the second aspect of the present application.

[0067] In some embodiments, the positive electrode material layer further comprises a binder. The binder improves the binding between the positive electrode active material particles and also improves the binding between the positive electrode material layer and the positive electrode current collector.

[0068] In some embodiments, non-limiting examples of the binder include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, nylon, and the like.

[0069] In some embodiments, the positive electrode material layer comprises a conductive agent, thereby imparting electrical conductivity to the electrode. The conductive agent can comprise any electrically conductive material, provided that it does not cause chemical changes. Non-limiting examples of the conductive material include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, and the like), metal-based materials (e.g., metal powder, metal fibers, and the like, including, for example, copper, nickel, aluminum, silver, and the like), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0070] In some embodiments, the positive electrode sheet comprises a positive electrode current collector, which can be, for example, aluminum (Al), but is not limited thereto.

[0071] In some embodiments, the mass percentage of the positive electrode active material particles in the positive electrode material layer is 80% to 99%, based on the total mass of the positive electrode material layer.

[0072] In some embodiments, the mass of the conductive agent is 1-20% of the mass of the positive electrode material layer.

[0073] In some embodiments, the mass of the binder is 1-20% of the mass of the positive electrode material layer.

[0074] In some embodiments, the positive electrode tab provided by the present application further comprises a solid-state electrolyte powder for improving the ionic conductivity of the composite positive electrode. The present application does not limit the type of solid-state electrolyte powder, which can be an oxide solid-state electrolyte powder, a sulfide solid-state electrolyte powder, or a halide solid-state electrolyte powder. Optionally, the mass of the solid-state electrolyte powder is 1-20% of the mass of the positive electrode tab; preferably 5-20%.

[0075] In some embodiments, the thickness of the positive electrode material layer in the positive electrode tab provided by the present application is 30-400 μm, for example, 30 μm, 40 μm, 50 μm, 80 μm, 110 μm, 200 μm, 300 μm, 400 μm, preferably 50-110 μm.

[0076] Negative electrode tab:

[0077] In some embodiments, the negative electrode tab comprises a current collector and a negative electrode active material layer disposed on the current collector.

[0078] In the present application, the specific type of negative electrode active material is not specifically limited and can be selected as needed. Specifically, the negative electrode active material is selected from one or more of natural graphite, artificial graphite, mesophase carbon microbeads (MCMB for short), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithiated TiO2-Li4Ti5O12, and Li-Al alloy. Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon, and mixtures thereof. The crystalline carbon can be amorphous or flaky, small flaky, spherical, or fibrous natural graphite or artificial graphite. The amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, etc. 12

[0079] In some embodiments, elemental metals and metal-based compounds can also be selected as negative electrode active materials, such as compounds containing Li, Ag, Al, Bi, Cu, Ga, Ge, In, Ni, Pb, Sb, Si, Sn, Sr, Zn, etc.

[0080] In some embodiments, the mass fraction of the negative electrode active material contained in the negative electrode active material layer can be 80-99%, for example, 80%, 85%, 90%, 95%, 97%, 99%, etc., preferably 95-97%. ​

[0081] In some embodiments, the negative electrode material layer can include a binder; the binder improves the binding of the negative active material particles to each other and the binding of the negative active material to the current collector.

[0082] In some embodiments, non-limiting examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, butadiene-styrene rubber, acrylated butadiene-styrene rubber, epoxy resin, nylon, and the like.

[0083] In some embodiments, the negative electrode active material layer can be obtained by coating a negative electrode slurry on a negative electrode current collector, followed by drying and the like, the negative electrode slurry including at least a negative electrode active material and a negative electrode binder. When an aqueous solvent is used as the liquid medium for forming the negative electrode slurry, it is preferable to use a viscosity enhancer for slurry formation, which is generally used to adjust the viscosity of the slurry.

[0084] In some embodiments, the aforementioned viscosity enhancer can be one or more of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphated starch, casein and its salts, and the like.

[0085] In some embodiments, the mass percentage of the viscosity enhancer in the negative electrode slurry can be 0.1% to 5%, for example, 0.1%, 0.2%, 0.5%, 0.6%, 1%, 2%, 3%, 4%, 5%, and the like, preferably 0.5% to 3%, and further preferably 0.6% to 2%.

[0086] In some embodiments, the negative electrode active material layer includes a conductive material, thereby imparting electrical conductivity to the electrode. The conductive material can include any conductive material that does not cause chemical changes. Non-limiting examples of the conductive material include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, and the like), metal-based materials (e.g., metal powder, metal fibers, and the like, such as copper, nickel, aluminum, silver, and the like), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0087] In some embodiments, the negative electrode current collector can be selected from copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, a polymer substrate coated with a conductive metal, and combinations thereof.

[0088] Separator:

[0089] In some embodiments, the lithium battery and the electrochemical device of the present application are provided with a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separator used in the electrochemical device of the present application are not particularly limited and can be any of the techniques disclosed in the prior art.

[0090] In some embodiments, the separator includes a polymer or inorganic material formed of a material stable to the electrolyte of the present application, etc.

[0091] In some embodiments, the separator can include a base material layer and a surface treatment layer. The base material layer is a non-woven fabric, a film or a composite film having a porous structure, and the material of the base material layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.

[0092] Electrolyte:

[0093] The lithium battery and the electrochemical device to which the present application relates further include an electrolyte.

[0094] In some embodiments, the electrolyte includes a lithium salt and a solvent.

[0095] In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis-trifluoromethanesulfonimide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalato)borate LiB(C2O4)2 (LiBOB) or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB).

[0096] In some embodiments, the solvent can be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0097] In some embodiments, the electrolyte can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature performance of the battery, and the like.

[0098] In some embodiments, the aforementioned additive includes at least one of 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sulfonic acid lactone, ethylene sulfate, 4-methyl ethylene sulfate, propylene sulfate, saturated phosphoric acid ester compounds and unsaturated phosphoric acid ester compounds, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) borate, tris(triethylsilyl) borate, butanedinitrile, pentanedinitrile, ethylene glycol bis(propionitrile) ether, hexanetetracarbonitrile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile, decanedinitrile, and a compound including the following formula:

[0099]

[0100] wherein R 41 , R 42 , R 43 are each independently selected from a C1-C5 saturated hydrocarbon group, an unsaturated hydrocarbon group, a halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 41 , R 42 , R 43 is at least one unsaturated hydrocarbon group.

[0101] The fourth aspect of the present application proposes a battery, which includes the positive electrode sheet disclosed in the third aspect of the present application.

[0102] In some embodiments, the secondary battery according to the present application includes the aforementioned positive electrode sheet, negative electrode sheet, separator, electrolyte, and the like, but is not limited thereto.

[0103] In some embodiments, the secondary battery according to the present application is manufactured by stacking the aforementioned positive and negative electrode sheets.

[0104] In some embodiments, the secondary battery according to the present application can include an outer package, which can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, and the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.

[0105] In some embodiments, the present application also provides a battery module. The battery module comprises the secondary battery described above. The number of secondary batteries contained in the battery module of the present application can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0106] In some embodiments, the present application also provides a battery pack comprising the battery module described above. The number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0107] The embodiments of the present application will be described in more detail by examples and comparative examples. Among them, all examples and comparative examples are a group of lithium ion battery samples prepared by the same process.

[0108] In order to intuitively and comprehensively reflect the advantages of the present application, all examples and comparative examples are recorded or tested as follows: coating layer thickness recording, 200 cycle battery capacity retention rate, rate performance test.

[0109] It should be noted that the embodiments of the present application are not limited to only these examples.

[0110] Example 1

[0111] I. Preparation of positive electrode active material:

[0112] S1, mix the manganese-containing precursor Mn3O4, lithium source Li2CO3, W source WO 2.72 , Nb source Nb2O5, and metal oxide Al2O3, MgO according to the molar ratio of Mn, Li, W, Nb, Al, Mg 1.9:1:0.005:0.005:0.06:0.03, and mix uniformly to obtain a mixture;

[0113] S2, calcine the mixture to obtain positive electrode active material LiMn 1.9 W 0.005 Nb 0.005 Al 0.06 Mg 0.03 O4. The calcination temperature is 680℃, and the calcination time is 16h. Record the coating layer thickness of the positive electrode active material.

[0114] II. Preparation of positive electrode sheet:

[0115] Take and mix the positive electrode active material prepared in step I, conductive agent Super-P, and binder PVDF according to the mass ratio of 95:3:2, mix with solvent NMR to obtain positive electrode slurry, uniformly coat on aluminum foil to form positive electrode sheet.

[0116] III. Preparation of negative electrode sheet:

[0117] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are weighed according to the mass ratio of 95:3:1:1, uniformly mixed, mixed with the solvent deionized water, to obtain a negative electrode slurry, which is uniformly coated on a copper foil to form a negative electrode sheet.

[0118] Four, preparation of the battery:

[0119] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator are assembled, and the electrolyte is injected to form a battery.

[0120] Example 2:

[0121] One, preparation of the positive active material:

[0122] S1, the manganese-containing precursor Mn3O4, the lithium source Li2CO3, the W source WO 2.72 , the Nb source Nb2O5, and the metal oxide Al2O3, MgO are uniformly mixed according to the molar ratio of Mn, Li, W, Nb, Al, and Mg of 1.908:1:0.001:0.001:0.06:0.03 to obtain a mixture;

[0123] S2, the mixture is calcined to obtain a positive active material LiMn 1.908 W 0.001 Nb 0.001 Al 0.06 Mg 0.03 O4. The calcination temperature is 680 DEG C, and the calcination time is 16 h. The coating layer thickness of the positive active material is recorded.

[0124] Two, preparation of the positive electrode sheet:

[0125] The positive active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed according to the mass ratio of 95:3:2, uniformly mixed, mixed with the solvent NMR to obtain a positive electrode slurry, which is uniformly coated on an aluminum foil to form a positive electrode sheet.

[0126] Three, preparation of the negative electrode sheet:

[0127] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are weighed according to the mass ratio of 95:3:1:1, uniformly mixed, mixed with the solvent deionized water, to obtain a negative electrode slurry, which is uniformly coated on a copper foil to form a negative electrode sheet.

[0128] Five, preparation of the battery:

[0129] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator are assembled, and the electrolyte is injected to form a battery.

[0130] Example 3:

[0131] I. Preparation of the positive electrode active material:

[0132] S1, the manganese-containing precursor Mn3O4, lithium source Li2CO3, W source WO 2.72 , Nb source Nb2O5 and metal oxide Al2O3, MgO were mixed uniformly according to the molar ratio of Mn, Li, W, Nb, Al, Mg 1.71:1:0.1:0.1:0.06:0.03, to obtain a mixture;

[0133] S2, the mixture was calcined to obtain a positive electrode active material LiMn 1.71 W 0.1 Nb 0.1 Al 0.06 Mg 0.03 O4. The calcination temperature was 680℃, and the calcination time was 16h. The coating thickness of the positive electrode active material was recorded.

[0134] II. Preparation of the positive electrode sheet:

[0135] The positive electrode active material prepared in step one, the conductive agent Super-P, and the binder PVDF were weighed according to the mass ratio 95:3:2 and mixed uniformly, mixed with the solvent NMR to obtain a positive electrode slurry, uniformly coated on an aluminum foil to form a positive electrode sheet.

[0136] III. Preparation of the negative electrode sheet:

[0137] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and SBR were weighed according to the mass ratio 95:3:1:1 and mixed uniformly, mixed with the solvent deionized water to obtain a negative electrode slurry, uniformly coated on a copper foil to form a negative electrode sheet.

[0138] IV. Preparation of the battery:

[0139] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator were assembled, and the electrolyte was injected to form a battery.

[0140] Example 4:

[0141] I. Preparation of the positive electrode active material:

[0142] S1, the manganese-containing precursor Mn3O4, lithium source Li2CO3, W source WO 2.72 , Nb source Nb2O5 and metal oxide Al2O3, MgO were mixed uniformly according to the molar ratio of Mn, Li, W, Nb, Al, Ti 1.81:1:0.05:0.05:0.06:0.015, to obtain a mixture;

[0143] S2, the mixture was calcined to obtain a positive electrode active material LiMn 1.81 W0.05 Nb 0.05 Al 0.06 Ti 0.015 O4。Baking temperature is 680℃, and baking time is 16h. The coating thickness of the positive electrode active material is recorded.

[0144] II. Preparation of the positive electrode sheet:

[0145] The positive electrode active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed according to the mass ratio of 95:3:2, uniformly mixed, mixed with the solvent NMR to obtain a positive electrode slurry, uniformly coated on an aluminum foil to form a positive electrode sheet.

[0146] III. Preparation of the negative electrode sheet:

[0147] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and SBR are weighed according to the mass ratio of 95:3:1:1, uniformly mixed, mixed with the solvent deionized water to obtain a negative electrode slurry, uniformly coated on a copper foil to form a negative electrode sheet.

[0148] IV. Preparation of the battery:

[0149] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator are assembled, and the electrolyte is injected to form a battery.

[0150] Example 5

[0151] I. Preparation of the positive electrode active material:

[0152] S1, the manganese-containing precursor Mn3O4, the lithium source Li2CO3, the W source sodium tungstate, the Nb source Nb2O5, and the metal oxide Al2O3 and MgO are uniformly mixed according to the molar ratio of Mn, Li, W, Nb, Al, and Mg of 1.9:1:0.005:0.005:0.06:0.03 to obtain a mixture;

[0153] S2, the mixture is calcined to obtain the positive electrode active material LiMn 1.9 W 0.005 Nb 0.005 Al 0.06 Mg 0.03 O4. Baking temperature is 680℃, and baking time is 16h. The coating thickness of the positive electrode active material is recorded.

[0154] II. Preparation of the positive electrode sheet:

[0155] The positive electrode active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed according to the mass ratio of 95:3:2, uniformly mixed, mixed with the solvent NMR to obtain a positive electrode slurry, uniformly coated on an aluminum foil to form a positive electrode sheet.

[0156] III. Preparation of the negative electrode sheet:

[0157] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and SBR were weighed according to the mass ratio of 95:3:1:1, mixed uniformly, mixed with the solvent deionized water to obtain a negative electrode slurry, uniformly coated on a copper foil to form a negative electrode sheet.

[0158] VI. Preparation of the battery:

[0159] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator were assembled, and the electrolyte was injected to form a battery.

[0160] The difference between this example and example 1 is that the W source is sodium tungstate.

[0161] Example 6

[0162] I. Preparation of the positive electrode active material:

[0163] S1, the manganese-containing precursor Mn3O4, the lithium source Li2CO3, the W source WO 2.72 , the Nb source Nb2O5, and the metal oxide Al2O3 were mixed uniformly according to the molar ratio of Mn, Li, W, Nb, and Al of 1.93:1:0.005:0.005:0.06 to obtain a mixture;

[0164] S2, the mixture was calcined to obtain the positive electrode active material LiMn 1.93 W 0.005 Nb 0.005 Al 0.06 O4. The calcination temperature was 680°C, and the calcination time was 16 h. The coating layer thickness of the positive electrode active material was recorded.

[0165] II. Preparation of the positive electrode sheet:

[0166] The positive electrode active material prepared in step one, the conductive agent Super-P, and the binder PVDF were weighed according to the mass ratio of 95:3:2, mixed uniformly, mixed with the solvent NMR to obtain a positive electrode slurry, uniformly coated on an aluminum foil to form a positive electrode sheet.

[0167] III. Preparation of the negative electrode sheet:

[0168] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and SBR were weighed according to the mass ratio of 95:3:1:1, mixed uniformly, mixed with the solvent deionized water to obtain a negative electrode slurry, uniformly coated on a copper foil to form a negative electrode sheet.

[0169] IV. Preparation of the battery:

[0170] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three and the separator are assembled, electrolyte is injected, and a battery is formed.

[0171] Comparative Example 1

[0172] I. Preparation of a positive electrode active material:

[0173] S1, a manganese-containing precursor Mn304, a lithium source Li2CO3, a Nb source Nb2O5, and metal oxides Al2O3 and MgO were uniformly mixed according to a molar ratio of Mn:Li:Nb:Al:Mg of 1.905:1:0.005:0.06:0.03 to obtain a mixture;

[0174] S2, the mixture was calcined to obtain a positive electrode active material. The calcination temperature was 680°C, and the calcination time was 16h. The thickness of the coating layer of the positive electrode active material was recorded.

[0175] II. Preparation of a positive electrode sheet:

[0176] The positive electrode active material prepared in step I, a conductive agent Super-P, and a binder PVDF were weighed according to a mass ratio of 95:3:2 and uniformly mixed, mixed with a solvent NMR to obtain a positive electrode slurry, uniformly coated on an aluminum foil to form a positive electrode sheet.

[0177] III. Preparation of a negative electrode sheet:

[0178] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and SBR were weighed according to a mass ratio of 95:3:1:1 and uniformly mixed, mixed with a solvent deionized water to obtain a negative electrode slurry, uniformly coated on a copper foil to form a negative electrode sheet.

[0179] IV. Preparation of a battery:

[0180] The positive electrode sheet prepared in step II, the negative electrode sheet prepared in step III, and the separator were assembled, electrolyte was injected, and a battery was formed.

[0181] Comparative Example 2

[0182] I. Preparation of a positive electrode active material:

[0183] S1, a manganese-containing precursor Mn304, a lithium source Li2CO3, a W source WO 2.72 and metal oxides Al2O3 and MgO were uniformly mixed according to a molar ratio of Mn:Li:W:Al:Mg of 1.905:1:0.005:0.06:0.03 to obtain a mixture;

[0184] S2, the mixture was calcined to obtain a positive electrode active material. The calcination temperature was 680°C, and the calcination time was 16h. The thickness of the coating layer of the positive electrode active material was recorded.

[0185] II. Preparation of the positive electrode sheet:

[0186] The positive electrode active material prepared in step one, the conductive agent Super-P, and the binder PVDF were weighed in a mass ratio of 95:3:2 and mixed uniformly, mixed with the solvent NMR to obtain a positive electrode slurry, uniformly coated on an aluminum foil to form a positive electrode sheet.

[0187] III. Preparation of the negative electrode sheet:

[0188] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and SBR were weighed in a mass ratio of 95:3:1:1 and mixed uniformly, mixed with the solvent deionized water to obtain a negative electrode slurry, uniformly coated on a copper foil to form a negative electrode sheet.

[0189] IV. Preparation of the battery:

[0190] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator were assembled, and an electrolyte was injected to form a battery.

[0191] Comparative Example 3

[0192] I. Preparation of the positive electrode active material:

[0193] S1, the manganese-containing precursor Mn3O4, the lithium source Li2CO 3、 The metal oxides Al2O3 and MgO were mixed uniformly in a molar ratio of Mn:Li:Al:Mg of 1.91:1:0.06:0.03 to obtain a mixture;

[0194] S2, the mixture was calcined to obtain a positive electrode active material. The calcination temperature was 680°C, and the calcination time was 16h. The coating layer thickness of the positive electrode active material was recorded.

[0195] II. Preparation of the positive electrode sheet:

[0196] The positive electrode active material prepared in step one, the conductive agent Super-P, and the binder PVDF were weighed in a mass ratio of 95:3:2 and mixed uniformly, mixed with the solvent NMR to obtain a positive electrode slurry, uniformly coated on an aluminum foil to form a positive electrode sheet.

[0197] III. Preparation of the negative electrode sheet:

[0198] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and SBR were weighed in a mass ratio of 95:3:1:1 and mixed uniformly, mixed with the solvent deionized water to obtain a negative electrode slurry, uniformly coated on a copper foil to form a negative electrode sheet.

[0199] IV. Preparation of the battery:

[0200] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three and the separator are assembled, electrolyte is injected, and a battery is formed.

[0201] Comparative Example 4

[0202] I. Preparation of a positive electrode active material:

[0203] S1, a manganese-containing precursor Mn3O4, a lithium source Li2CO3, a W source WO 2.72 , and a Nb source Nb2O5 are mixed uniformly in a molar ratio of Mn:Li:W:Nb of 1.99:1:0.005:0.005 to obtain a mixture;

[0204] S2, the mixture is calcined to obtain a positive electrode active material. The calcination temperature is 680°C, and the calcination time is 16h. The coating layer thickness of the positive electrode active material is recorded.

[0205] II. Preparation of a positive electrode sheet:

[0206] The positive electrode active material prepared in step I, a conductive agent Super-P, and a binder PVDF are weighed in a mass ratio of 95:3:2 and mixed uniformly, mixed with a solvent NMR to obtain a positive electrode slurry, uniformly coated on an aluminum foil to form a positive electrode sheet.

[0207] III. Preparation of a negative electrode sheet:

[0208] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and SBR are weighed in a mass ratio of 95:3:1:1 and mixed uniformly, mixed with a solvent deionized water to obtain a negative electrode slurry, uniformly coated on a copper foil to form a negative electrode sheet.

[0209] IV. Preparation of a battery:

[0210] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three and the separator are assembled, electrolyte is injected, and a battery is formed.

[0211] Comparative experiment:

[0212] The batteries of Examples 1-6 and Comparative Examples 1-4 are tested as follows.

[0213] 1. 200 cycle battery capacity retention rate test:

[0214] At a temperature of 45°C, charge to a charge cut-off voltage of 4.2V at a current of 0.2C, convert to constant voltage charging to a cut-off current of 0.05C, stand for 0.5h, discharge to a cut-off voltage of 3.0V at a current of 0.2C, stand for 0.5h, enter the next charge-discharge cycle, and so on, a total of 200 charge-discharge cycles, 200 cycle retention rate = discharge capacity of the battery at the 200th cycle / first discharge capacity.

[0215] 2. Rate capability test:

[0216] At a temperature of 45℃, the full charged battery is discharged to a cut-off voltage of 3.0V at a current of 0.1C, and the capacity obtained is C0;

[0217] At a temperature of 45℃, the full charged battery is discharged to a cut-off voltage of 3.0V at a current of 3C, and the capacity obtained is C1, and C1 / C0 is the 3C discharge capacity retention rate in the following.

[0218] 3. Coating layer thickness test:

[0219] TEM electron microscope is used to measure the thickness at ten different positions, and the average value is taken.

[0220] The test results are shown in the following table.

[0221]

[0222]

[0223] According to the above table:

[0224] Comparative Example 1 and Comparative Examples 3 and 4: Example 1 effectively improves the cycle performance and rate capability of the battery by doping multiple elements in lithium manganate and coating with W and Nb. The possible reason is that the crystal lattice structure of lithium manganate is effectively stabilized by multiple element doping, and the contact between the electrolyte and lithium manganate is effectively isolated by coating, effectively eliminating the excess lithium on the surface of lithium manganate.

[0225] Comparative Example 1 and Comparative Examples 1 and 2: Example 1 effectively improves the cycle performance and rate capability of the battery by using W and Nb for collaborative coating, compared with each single coating.

[0226] Comparative Example 1 and Example 5: The positive active material prepared by using tungsten oxide as a tungsten source in Example 1 has better cycle stability and lithium ion transmission capacity. The possible reason is that tungsten oxide can induce the formation of oxygen vacancies on the material surface, which helps to adsorb and store active oxygen and improve the interface stability, thereby improving the cycle stability. Oxygen vacancies help to reduce the energy barrier for lithium ion migration, resulting in improved diffusion dynamics.

[0227] Comparative Example 1 and Example 6: The use of multiple metal element doping in Example 1 is also beneficial to improve the stability of the positive active material compared to single metal element doping.

[0228] The above is only a possible speculation of the mechanism of the technical solutions of the present application, and does not constitute a limitation on the protection scope of the present application.

[0229] It should be pointed out that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a positive electrode active material, characterized in that, Includes the following steps: S1. Mix the manganese-containing precursor, lithium source, W source, Nb source and metal M source evenly to obtain a mixture; S2. The mixture is calcined to obtain a positive electrode active material; The W source is tungsten oxide; The metal M source includes at least two metallic elements M; The metallic element M includes at least two of the following: Mg, Al, Ca, Ti, Cu, Zn, Y, Zr, Ru, Sn, and Sb. The chemical formula of the positive electrode active material is Li 1+a Mn 2-a-b-c-d W b Nb c M d O4; Where, 0.001≤a≤0.30, 0.001≤b≤0.1, 0.001≤c≤0.1, 0.001≤d≤0.1; The positive electrode active material includes a core material and a coating layer formed on the surface of the core material, wherein the coating layer includes LiNbO3 and Li2WO4.

2. The method according to claim 1, characterized in that, The metallic element M includes at least two of Al, Mg, Sn, and Ti.

3. The method according to claim 1, characterized in that, Step S1 includes mixing the manganese-containing precursor, lithium source, W source, Nb source, and metal M source uniformly according to the molar ratio of Li, Mn, W, Nb, and M as (1.001~1.2):(1.5~1.996):(0.001~0.1):(0.001~0.1):(0.001~0.1).

4. The method according to claim 1, characterized in that, In step S2, the calcination temperature is 400℃~1000℃; and / or, The roasting time is 5h to 24h.

5. A positive electrode sheet comprising a positive electrode active material prepared by the method described in any one of claims 1-4.

6. A battery comprising the positive electrode as described in claim 5.

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