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

Abstract

The application relates to a positive electrode active material and a preparation method thereof, a positive electrode sheet and a battery in the technical field of lithium battery production, wherein the positive electrode active material comprises a single-crystal-like lithium manganate material and a coating layer formed on the surface of the single-crystal-like lithium manganate material; the coating layer comprises CeO2 and a fast ion conductor; and the core material has a general formula of Li 1+ a Mn 2‑a‑b‑c B b M c O4; wherein 0.001<=a<=0.30, 0.001<=b<=0.2, 0.001<=c<=0.2; and M is a metal element. The application coats the single-crystal-like lithium manganate material with a coating layer comprising CeO2 and a fast ion conductor, effectively isolates the contact between electrolyte and lithium manganate material, effectively alleviates the damage of rolling to the single-crystal-like lithium manganate material, and thus 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 positive electrode active material, a preparation method thereof, 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 number of trivalent manganese ions exist in lithium manganate, which is easy to cause side reactions with electrolyte, resulting in the deterioration of the cycle performance of the battery. The battery prepared by single crystal lithium manganate has good cycle performance, but the capacity is low. The battery prepared by polycrystalline lithium manganate has high capacity, but the cycle performance of the battery is poor. The paracrystalline lithium manganate has a unique microstructure of agglomeration, compactness, small intergranular gap and smooth surface, which can effectively reduce the exposed area of the material and the contact with the electrolyte. In order to further improve the cycle performance of the battery and prevent the paracrystalline lithium manganate structure from being damaged during the preparation of the positive electrode, the paracrystalline lithium manganate is coated. The existing coating layer has poor lithium ion transmission, which cannot show the advantage of fast lithium ion diffusion of the paracrystalline lithium manganate, and the coating increases the internal resistance of the battery. SUMMARY

[0004] In order to solve the above technical problems, the present application discloses a positive electrode active material, a preparation method thereof, a positive electrode sheet and a battery. The coating layer including CeO2 and fast ion conductor is coated on the surface of lithium manganate, which can effectively isolate the contact between the electrolyte and the lithium manganate material, and effectively improve the cycle performance of the battery.

[0005] The technical scheme of the present application is implemented as follows:

[0006] In a first aspect, the present application provides a positive electrode active material, which comprises a paracrystalline lithium manganate material and a coating layer formed on the surface of the paracrystalline lithium manganate material, wherein the coating layer comprises CeO2 and a fast ion conductor.

[0007] The general formula of the paracrystalline lithium manganate material is Li 1+a Mn 2-a-b-c B b M c O4, wherein 0.001≤a≤0.30, 0.001≤b≤0.2, 0.001≤c≤0.2, and M is a metal element.

[0008] In one embodiment, the fast ion conductor is at least one of LiNbO3, Li4Ti5O 12 , Li2TiO3, LiAlO2, LiTaO3, LiMoO3, Li2RuO3, or Li2WO4.

[0009] In one embodiment, M includes at least two of Mg, Al, Ca, Ti, Cu, Zn, Y, Zr, Nb, Mo, Ru, Sn, and Sb.

[0010] In one preferred embodiment, M includes at least two of Al, Mg, Ti, Co, and Nb.

[0011] In one embodiment, the thickness of the coating layer is 10 nm to 50 nm.

[0012] In one embodiment, the mass ratio of the fast ion conductor is 0.1% to 2% based on 100% of the mass of the positive electrode active material.

[0013] In one embodiment, the mass ratio of CeO2 is 0.1% to 2% based on 100% of the mass of the positive electrode active material.

[0014] In one embodiment, the mass ratio of CeO2 to the fast ion conductor is (4:6) to (7:3).

[0015] In one embodiment, the particle size ratio of CeO2 to the fast ion conductor is (1 to 1.5):1.

[0016] A second aspect of the present application is to provide a preparation method of a positive electrode active material, which is used to prepare the positive electrode active material disclosed in the first aspect of the present application. The preparation method includes the following steps:

[0017] S1, uniformly mixing a spherical or spherical-like Mn-containing precursor, a lithium source, a B source, and an M source to form a first mixture;

[0018] S2, obtaining a single-crystal-like lithium manganate material after calcining the first mixture in an air atmosphere;

[0019] S3, weighing the single-crystal-like lithium manganate material obtained in step S2, adding a solvent, and uniformly stirring to form a first solution;

[0020] S4, adding CeO2 material and a fast ion conductor to the first solution prepared in step S3, and continuously stirring to form a suspension;

[0021] S5, drying;

[0022] S6, calcining the dried powder obtained in step S5 in an air atmosphere to obtain a positive electrode active material;

[0023] The particle size of the Mn-containing precursor is 1-5 μm.

[0024] The calcination temperature in step S2 is 600-880 °C.

[0025] In one embodiment, the Mn-containing precursor comprises one or a mixture of two of trimanganese tetraoxide, dimanganese trioxide, or manganese carbonate.

[0026] In one embodiment, the lithium source is one or both of lithium carbonate and lithium hydroxide.

[0027] In one embodiment, the M source is an oxide or sulfate of a metal element M, wherein the metal element M comprises at least two of Mg, Al, Ca, Ti, Cu, Zn, Y, Zr, Nb, Mo, Ru, Sn, and Sb.

[0028] In one embodiment, the metal element M comprises at least two of Al, Mg, Ti, Co, and Nb.

[0029] In one embodiment, the calcination time in step S2 is 5-24 h.

[0030] In one embodiment, the calcination time in step S2 is 8-20 h.

[0031] In specific applications, in addition to the end points of 8 h and 20 h, any value in the above range can be selected, such as 10 h, 12 h, 15 h, 18 h, etc. The present application does not make any limitation in this regard.

[0032] In one embodiment, in step S2, the stirring is continued at 40-60 °C for 2-8 h to obtain a suspension of the mixture of the three.

[0033] In one embodiment, in step S6, the dry powder obtained in step S5 is calcined in an air atmosphere at 400-600 °C for 6-15 h to obtain the positive electrode active material.

[0034] A third aspect of the present application is to provide a positive electrode sheet comprising the positive electrode active material according to the first aspect of the present application, a conductive agent, and a binder.

[0035] A fourth aspect of the present application is to provide a battery comprising the positive electrode sheet according to the third aspect of the present application, a negative electrode sheet, a separator, and an electrolyte.

[0036] The advantages of the present application are as follows:

[0037] By coating the surface of the quasi-single-crystal lithium manganate material with a coating layer comprising CeO2 and a fast ion conductor, the contact between the electrolyte and the lithium manganate material can be effectively isolated, the cycle performance of the battery can be improved, and the damage of the quasi-single-crystal lithium manganate material caused by rolling can be effectively prevented. In addition, the synergistic effect of CeO2 and the fast ion conductor can effectively improve the lithium ion transmission rate of the coating layer, which is conducive to the preparation of a thin and good isolation effect coating layer, so as to effectively exert the advantages of the quasi-single-crystal lithium manganate material, improve the rate performance of the battery prepared therefrom, and reduce the internal resistance of the battery.

[0038] Furthermore, the lithium manganate material is co-doped with B and at least two metal elements, and the B element doping can effectively reduce the melting temperature of the raw material during sintering, which is conducive to the formation of a quasi-single-crystal structure and the improvement of the lattice stability of the quasi-single-crystal lithium manganate material, thereby further improving the cycle performance of the battery prepared therefrom. DETAILED DESCRIPTION

[0039] The technical solutions of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a 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.

[0040] Unless otherwise defined, all technical and scientific terms used in the present application have the same meanings as commonly understood by those skilled in the art to which the present application belongs; the terms used in the specific embodiments are only for the purpose of describing the 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.

[0041] 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.

[0042] In the present application, the phrase "embodiment" means that the specific features, structures or properties described in conjunction 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.

[0043] 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.

[0044] Throughout this application, numerical values represent approximate measures or limits of a range to encompass slight deviations from a given value and embodiments having about the value mentioned and embodiments having the exact value mentioned. Except in the operating examples provided at the end of the detailed description, all numerical values of parameters (e.g., amounts or conditions) in this specification, including the attached claims, are to be reinterpreted as modified by the term "about" in all instances, even though the term "about" is not expressly recited in the value itself. "About" indicates that the stated numerical value is permitted to vary from the exact value by some minor amount (is close to the exact value to some degree; is approximately or reasonably close to the value; is nearly). If the imprecision provided by "about" is not otherwise understood in the art with respect to a given value, then "about" at least indicates variations that can be produced by ordinary methods of measuring and using such parameters. For example, "about" can include variations 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 certain aspects, optionally less than or equal to 0.1%.

[0045] In addition, the disclosure of ranges includes all values and further subdivisions between the recited ranges and the endpoints of those ranges and subranges.

[0046] On the one hand, the lithium manganate material contains trivalent manganese ions, and in the charging and discharging process, the lithium manganate material will have a side reaction with the electrolyte, causing the trivalent manganese ions in the lithium manganate to undergo disproportionation reaction to generate divalent manganese ions, which migrate to the negative side and are reduced, damaging the SEI film on the negative side, causing the SEI film on the negative side to be continuously damaged and regenerated, consuming lithium ions, thereby causing the cycle performance of the battery to deteriorate. On the other hand, affected by the Jiang-Taylor effect, the lithium manganate material is prone to crystal structure changes during the charging and discharging process, affecting its cycle stability.

[0047] The single-crystal-like lithium manganate has a unique microstructure of agglomeration density, small inter-particle gap, and smooth surface, which can effectively reduce the exposed area of the material and the contact with the electrolyte, thereby slowing down the dissolution of Mn 3+ and improving the cycle stability of the material. However, during the preparation of the battery positive electrode, the positive electrode sheet needs to be rolled to adjust the thickness and compaction density of the positive electrode sheet, and the large pressure will damage the structure of the single-crystal-like lithium manganate.

[0048] In order to further improve the cycle performance of the battery and prevent the single-crystal structure of lithium manganate from being damaged due to rolling during preparation of the positive electrode, the lithium manganate is coated, and the coating layer in the prior art has poor lithium ion transmission, so that the advantage of fast lithium ion diffusion of the single-crystal lithium manganate cannot be exhibited, and the coating increases the internal resistance of the battery.

[0049] In order to solve the above technical problems, a positive electrode active material and a preparation method thereof, a positive electrode sheet and a battery are disclosed in the present application.

[0050] The technical scheme of the present application is implemented as follows:

[0051] In a first aspect, the present application provides a positive electrode active material, which comprises a single-crystal lithium manganate material and a coating layer formed on the surface of the single-crystal lithium manganate material, wherein the coating layer comprises CeO2 and a fast ion conductor.

[0052] The general formula of the single-crystal lithium manganate material is Li 1+a Mn 2-a-b-c B b M c O4, wherein 0.001≤a≤0.30, 0.001≤b≤0.2, and 0.001≤c≤0.2.

[0053] M is a metal element.

[0054] On the one hand, CeO2 has good electron conductivity, and the fast ion conductor has good ion conductivity but poor electronic conductivity, and the synergistic effect of the two is conducive to improving the lithium ion transmission capacity of the coating layer, thereby improving the rate performance of the battery prepared therefrom and reducing the internal resistance of the battery.

[0055] In addition, when CeO2 is used as a coating layer material, the lithium ions vertically diffuse, and the transmission path is short, which is conducive to the rapid transmission of lithium ions, and in combination with the lithium ion transmission of the fast ion conductor, the ion conduction capacity of the combination of CeO2 and the fast ion conductor is further improved.

[0056] Furthermore, the lithium manganate material is co-doped with B and metal elements, the B element doping can effectively reduce the melting temperature of raw materials during sintering, which is beneficial to form a single crystal structure, and is beneficial to improve the lattice stability of the single crystal lithium manganate material, thereby further improving the cycle performance of the battery prepared therefrom.

[0057] In an embodiment, the fast ion conductor is at least one of LiNbO3, Li4Ti5O 12 , Li2TiO3, LiAlO2, LiTaO3, LiMoO3, Li2RuO3 or Li2WO4.

[0058] The "at least one" in the present application refers to selecting one from the listed materials, or selecting two or more materials for mixing. Within the scope of understanding of those skilled in the art, those skilled in the art can freely select. The present application does not make any limitation.

[0059] In an embodiment, M includes at least two of Mg, Al, Ca, Ti, Cu, Zn, Y, Zr, Nb, Mo, Ru, Sn, and Sb.

[0060] The "at least two" in the present application refers to selecting any two or more materials from the above listed materials for mixing. Within the scope of understanding of those skilled in the art, those skilled in the art can freely select. The present application does not make any limitation.

[0061] In an embodiment, M includes Al, and at least two of Mg, Ti, Co, and Nb.

[0062] The metal element can form a chemical bond with O, which is beneficial to improve the crystal structure stability of the lithium manganate material.

[0063] In an embodiment, the thickness of the coating layer is 10 nm to 50 nm.

[0064] The thickness range of the coating layer disclosed in the present application refers to that those skilled in the art can implement any numerical value in the range in addition to the end points 10 nm and 50 nm of the thickness of the coating layer, such as 12 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, etc. The present application does not make any limitation.

[0065] In an embodiment, the mass fraction of the fast ion conductor is 0.1% to 2% based on 100% of the mass of the positive electrode active material.

[0066] The mass ratio of the fast ion conductor to the positive active material disclosed in the present application can be any value in the range, except that the endpoints 0.1% and 2% can be implemented. For example, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, etc. The present application does not make any limitation on this.

[0067] In an embodiment, the mass ratio of CeO2 to the positive active material is 0.1% to 2%, based on 100% of the mass of the positive active material.

[0068] The mass ratio of CeO2 to the positive active material disclosed in the present application can be any value in the range, except that the endpoints 0.1% and 2% can be implemented. For example, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, etc. The present application does not make any limitation on this.

[0069] In an embodiment, the mass ratio of CeO2 to the fast ion conductor is (4:6) to (7:3). Too large or too small mass ratio is not conducive to the synergistic cooperation of CeO2 and the fast ion conductor, and is not conducive to further improving the lithium ion transmission rate in the coating layer. Therefore, the present application limits the mass ratio of CeO2 to the fast ion conductor to the above range, which is more conducive to the rapid transmission of lithium ions in the coating layer.

[0070] The mass ratio of CeO2 to the fast ion conductor disclosed in the present application can be any value in the range, except that the endpoints 4:6 and 7:3 can be implemented. For example, 4:5, 4:3, 5:6, 5:5, 5:4, 6:6, 6:4, 7:6, 7:4, etc. The present application does not make any limitation on this.

[0071] In an embodiment, the particle size ratio of CeO2 to the fast ion conductor is (1-1.5):1. By controlling the particle size ratio of CeO2 to the fast ion conductor, the present application can further enhance the isolation effect on the electrolyte.

[0072] The particle size ratio of CeO2 to the fast ion conductor disclosed in the present application can be any value in the range, except that the endpoints 1:1 and 1.5:1 can be implemented. For example, 1.1:1, 1.2:1, 1.3:1, 1.4:1, etc. The present application does not make any limitation on this.

[0073] The second aspect of the present application is to propose a preparation method of a positive active material, which is used to prepare the positive active material disclosed in the first aspect of the present application. The preparation method comprises the following steps:

[0074] S1, uniformly mixing a spherical or spherical-like Mn-containing precursor, a lithium source, a B source, and an M source to form a first mixture;

[0075] S2, the first mixture is calcined in an air atmosphere to obtain a single-crystal-like lithium manganate material;

[0076] S3, the single-crystal-like lithium manganate material obtained in step S2 is weighed, a solvent is added, and stirring is performed until a first solution is formed;

[0077] S4, the CeO2 material and the fast ion conductor are added to the first solution prepared in step S3, and stirring is continued until a suspension is formed;

[0078] S5, drying;

[0079] S6, the dried powder obtained in step S5 is calcined in an air atmosphere to obtain a positive electrode active material;

[0080] The particle size of the Mn-containing precursor is 1-5 μm; the particle size range of the Mn-containing precursor disclosed in the present application refers to any value within the range, except for the endpoints 1 μm and 5 μm. For example, 2 μm, 3 μm, 4 μm, etc. The present application does not make any limitation on this. The small particle size and narrow distribution of the Mn-containing precursor are beneficial to the preparation of the single-crystal-like lithium manganate material.

[0081] In step S2, the calcination temperature is 600-880 °C;

[0082] A calcination temperature that is too high is not conducive to the formation of a single-crystal-like structure. In the present application, the calcination temperature is set within the above range, which can promote the formation of a single-crystal-like structure. In specific applications, any value within the above range can be selected, except for the endpoints 600 °C and 880 °C. For example, 650 °C, 680 °C, 700 °C, 750 °C, 780 °C, 800 °C, 820 °C, 850 °C, etc. The present application does not make any limitation on this.

[0083] In one embodiment, the Mn-containing precursor includes one or a mixture of two of trimanganese tetraoxide, dimanganese trioxide, or manganese carbonate.

[0084] In one embodiment, the lithium source is one or both of lithium carbonate and lithium hydroxide.

[0085] In one embodiment, the amount of the lithium source needs to be 1-5% more than the theoretical value.

[0086] The present application increases the amount of the lithium source based on the theoretical value, which can compensate for the volatilization of lithium elements during high-temperature calcination.

[0087] In one embodiment, the M source refers to an oxide or sulfate containing a metal element M; the metal element M includes at least two of Mg, Al, Ca, Ti, Cu, Zn, Y, Zr, Nb, Mo, Ru, Sn, and Sb.

[0088] In one embodiment, the metal element M includes at least two of Al, Mg, Ti, Co, and Nb.

[0089] In one embodiment, the calcination time in step S2 is 5 h to 24 h.

[0090] In one embodiment, the calcination time in step S2 is 8 h to 20 h.

[0091] In specific applications, in addition to the end points of 8 h and 20 h, any value in the above range can be selected, such as 10 h, 12 h, 15 h, 18 h, etc. The present application does not make any limitation in this regard.

[0092] In one embodiment, in step S2, the stirring is continued at 40 °C to 60 °C for 2 h to 8 h to obtain a suspension of the three.

[0093] In one embodiment, in step S6, the dry powder obtained in step S5 is calcined in an air atmosphere at 400 °C to 600 °C for 6 h to 15 h to obtain the positive electrode active material.

[0094] A third aspect of the present application is to provide a positive electrode sheet including the positive electrode active material according to the first aspect of the present application, a conductive agent, and a binder.

[0095] 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.

[0096] In one embodiment, 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, etc.

[0097] In one embodiment, the mass of the binder is 1% to 20% of the mass of the positive electrode material layer.

[0098] The conductive agent imparts electrical conductivity to the electrode.

[0099] In one embodiment, the conductive agent can include any electrically conductive material, provided that it does not cause chemical changes. Non-limiting examples of the electrically conductive material include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, etc.), metal-based materials (e.g., metal powder, metal fibers, etc., including, for example, copper, nickel, aluminum, silver, etc.), electrically conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0100] In an embodiment, the conductive agent has a mass percentage of 1% to 20% of the mass of the positive electrode material layer.

[0101] In an embodiment, the positive electrode tab includes a positive electrode current collector. The positive electrode current collector can be, for example, aluminum (Al), but is not limited thereto.

[0102] A fourth aspect of the present application is to provide a battery including the positive electrode tab, the negative electrode tab, the separator, and the electrolyte solution.

[0103] The negative electrode tab includes a current collector and a negative electrode active material layer disposed on the current collector.

[0104] In an embodiment, the negative electrode tab includes a current collector and a negative electrode active material layer disposed on the current collector.

[0105] In the present application, the specific type of the negative electrode active material is not particularly limited and can be selected as needed. Specifically, the negative electrode active material is selected from one or more of natural graphite, artificial graphite, meso-carbon microbe (MCMB), 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, or the like. 12

[0106] In an embodiment, elemental metals and metal-based compounds can also be selected as the negative electrode active material, such as compounds containing Li, Ag, Al, Bi, Cu, Ga, Ge, In, Ni, Pb, Sb, Si, Sn, Sr, Zn, and the like.

[0107] In an embodiment, the mass percentage of the negative electrode active material included in the negative electrode active material layer can be 80% to 99%, such as 80%, 85%, 90%, 95%, 97%, 99%, and the like, and is preferably 95% to 97%.

[0108] In an embodiment, the negative electrode material layer can include a binder. The binder improves the binding between the negative electrode active material particles and the binding between the negative electrode active material and the current collector.

[0109] ​In one embodiment, 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 polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, nylon, and the like.

[0110] In one embodiment, the negative active material layer can be obtained by coating a negative electrode slurry on a negative current collector, followed by drying and the like. The negative electrode slurry includes at least a negative active material and a negative binder. When an aqueous solvent is used as a liquid medium for forming the negative electrode slurry, it is preferable to use a viscosity increasing agent for slurry formation, which is generally used to adjust the viscosity of the slurry.

[0111] In one embodiment, the aforementioned viscosity increasing agent can be one or more of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphated starch, casein, and salts thereof, and the like.

[0112] In one embodiment, the mass ratio of the viscosity increasing agent 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%.

[0113] In one embodiment, the negative 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 fiber, and the like), metal-based materials (e.g., metal powder, metal fiber, and the like, such as copper, nickel, aluminum, silver, and the like), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0114] In one embodiment, the negative 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.

[0115] Separator:

[0116] In one embodiment, the lithium battery and the electrochemical device of the present application include a separator between the positive electrode and the negative electrode to prevent short circuiting. 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.

[0117] In one embodiment, the separator includes a polymer or inorganic material formed of a material stable to the electrolyte of the present application, and the like.

[0118] In one embodiment, the separator can include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, a film or a composite film having a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.

[0119] The electrolyte solution:

[0120] The lithium battery and the electrochemical device according to the present application further include an electrolyte solution.

[0121] In one embodiment, the electrolyte solution includes a lithium salt and a solvent.

[0122] In one embodiment, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0123] In one embodiment, 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).

[0124] In one embodiment, 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).

[0125] In one embodiment, the electrolyte solution can further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature performance of the battery, an additive for improving low-temperature performance of the battery, etc.

[0126] In some embodiments of the present application, 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 phosphorus ester compounds and unsaturated phosphorus 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:

[0127]

[0128] wherein R 41 , R 42 , R 43 are each independently selected from a saturated C1-C5 hydrocarbon group, an unsaturated C1-C5 hydrocarbon group, a halogenated C1-C5 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 at least one of which is an unsaturated C1-C5 hydrocarbon group.

[0129] Secondary battery:

[0130] In an embodiment, the secondary battery according to the present application includes the aforementioned positive electrode sheet, negative electrode sheet, separator, electrolyte, etc., but is not limited thereto.

[0131] In an embodiment, the secondary battery according to the present application is manufactured by stacking the aforementioned positive and negative electrode sheets.

[0132] In an embodiment, 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, etc. 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), etc.

[0133] In an embodiment, the present application also provides a battery module. The battery module includes the aforementioned secondary battery. The number of secondary batteries included in the battery module according to the present application can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0134] In an embodiment, the present application also provides a battery pack including the aforementioned battery module. The number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0135] The embodiments of the present application will be described in more detail by examples and comparative examples. Among them, all the examples and comparative examples are a group of lithium ion battery samples prepared by the same process.

[0136] In order to intuitively and comprehensively embody the advantages of the present application, all the examples and comparative examples are recorded or tested as follows: coating thickness recording, discharge capacity test, capacity retention rate under 3C working condition, battery internal resistance test, 200 cycle battery capacity retention rate, Mn dissolution content test.

[0137] It should be noted that the embodiments of the present application are not limited to these examples only.

[0138] Example 1

[0139] I. Preparation of positive electrode active material:

[0140] 1. Mix the lithium source Li2CO3, spherical manganese-containing precursor Mn3O4, H3BO3, and metal oxides Al2O3 and Nb2O5 according to the stoichiometric ratio n(Li):n(Mn):n(B):n(Al):n(Nb) = 1:1.85:0.05:0.05:0.05 to form a first mixture, and the particle size D50 of the precursor Mn3O4 is 3.5 μm;

[0141] 2. The first mixture is calcined at 750°C in air for 16 hours to obtain a single-crystal-like lithium manganate material;

[0142] 3. The single-crystal-like lithium manganate material obtained in step 2 is weighed, and a solvent, anhydrous ethanol, is added and stirred uniformly. CeO2 material and fast ion conductor LiNbO3 are added to the above solution, and the mixture is continuously stirred at 460°C for 6h to obtain a suspension of the three materials, and the suspension is dried for 12h. The dried powder is calcined at 550°C in air for 10h to obtain a single-crystal-like lithium manganate positive electrode active material coated with CeO2 and LiNbO3. The coating thickness is recorded.

[0143] Among them, the mass percentage of CeO2 in the positive electrode active material is 1%, and the mass percentage of the fast ion conductor is 1%.

[0144] II. Preparation of positive electrode sheet:

[0145] The positive electrode active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed and mixed uniformly according to the mass ratio of 95:3:2, and 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.

[0146] III. Preparation of negative electrode sheet:

[0147] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are 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.

[0148] Four, 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 an electrolyte is injected to form a battery.

[0150] Example 2

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

[0152] 1. The lithium source Li2CO3, the spherical manganese-containing precursor Mn3O4, H3BO3, and the metal oxide Al2O3 and Nb2O5 are uniformly mixed according to a stoichiometric ratio of n(Li):n(Mn):n(B):n(Al):n(Nb) = 1:1.85:0.05:0.05:0.05 to form a first mixture, and the particle size D50 of the precursor Mn3O4 is 3.5 μm;

[0153] 2. The first mixture is calcined in an air atmosphere at 750°C for 16 hours to obtain a lithium manganate material with a single crystal structure;

[0154] 3. The lithium manganate material with a single crystal structure obtained in step 2 is weighed, and a solvent anhydrous ethanol is added and stirred uniformly. CeO2 material and fast ion conductor LiNbO3 are added to the above solution, and the mixture is continuously stirred at 460°C for 6h to obtain a suspension of the three, which is dried for 12h. The dried powder is calcined at 550°C in an air atmosphere for 10h to obtain a lithium manganate material with a single crystal structure coated with CeO2 and LiNbO3. The thickness of the coating layer is recorded.

[0155] In the positive active material, the mass ratio of CeO2 is 1%, and the mass ratio of the fast ion conductor is 0.1%.

[0156] II. Preparation of the positive electrode sheet:

[0157] The positive active material prepared in step one, the conductive agent Super-P, and the binder PVDF are 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.

[0158] III. Preparation of the negative electrode sheet:

[0159] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are 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.

[0160] Four, preparation of the battery:

[0161] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator are assembled, and an electrolyte is injected to form a battery.

[0162] Example 3

[0163] I. Preparation of the positive active material:

[0164] 1. The lithium source Li2CO3, the spherical manganese-containing precursor Mn3O4, H3BO3, and the metal oxide Al2O3 and Nb2O5 are uniformly mixed according to a stoichiometric ratio of n(Li):n(Mn):n(B):n(Al):n(Nb) = 1:1.85:0.05:0.05:0.05 to form a first mixture, and the particle size D50 of the precursor Mn3O4 is 3.5 μm;

[0165] 2. The first mixture is calcined in an air atmosphere at 750°C for 16 hours to obtain a lithium manganate material with a single crystal structure;

[0166] 3. The lithium manganate material with a single crystal structure obtained in step 2 is weighed, and a solvent anhydrous ethanol is added and uniformly stirred. CeO2 material and fast ion conductor LiNbO3 are added to the above solution, and the mixture is continuously stirred at 460°C for 6h to obtain a suspension of the three materials, and the mixture is dried for 12h. The dried powder is calcined at 550°C in an air atmosphere for 10h to obtain a lithium manganate material with a single crystal structure coated with CeO2 and LiNbO3. The thickness of the coating layer is recorded.

[0167] In the positive active material, the mass percentage of CeO2 is 1%, and the mass percentage of the fast ion conductor is 2%.

[0168] II. Preparation of the positive electrode sheet:

[0169] The positive active material prepared in step one, the conductive agent Super-P, and the binder PVDF are 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.

[0170] III. Preparation of the negative electrode sheet:

[0171] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are 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.

[0172] Four, preparation of the battery:

[0173] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator are assembled, and an electrolyte is injected to form a battery.

[0174] Example 4

[0175] I. Preparation of the positive active material:

[0176] 1. The lithium source Li2CO3, the spherical manganese-containing precursor Mn3O4, H3BO3, and the metal oxide Al2O3 and Nb2O5 are uniformly mixed according to a stoichiometric ratio of n(Li):n(Mn):n(B):n(Al):n(Nb) = 1:1.85:0.05:0.05:0.05 to form a first mixture, and the particle size D50 of the precursor Mn3O4 is 3.5 μm;

[0177] 2. The first mixture is calcined in an air atmosphere at 750°C for 16 hours to obtain a lithium manganate material with a single crystal structure;

[0178] 3. The lithium manganate material with a single crystal structure obtained in step 2 is weighed, and a solvent anhydrous ethanol is added and uniformly stirred. CeO2 material and fast ion conductor LiNbO3 are added to the above solution, and the mixture is continuously stirred at 460°C for 6h to obtain a suspension of the three materials, and the mixture is dried for 12h. The dried powder is calcined at 550°C in an air atmosphere for 10h to obtain a lithium manganate material with a single crystal structure coated with CeO2 and LiNbO3. The thickness of the coating layer is recorded.

[0179] In the positive active material, the mass percentage of CeO2 is 0.1%, and the mass percentage of the fast ion conductor is 1%.

[0180] II. Preparation of the positive electrode sheet:

[0181] The positive active material prepared in step one, the conductive agent Super-P, and the binder PVDF are 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.

[0182] III. Preparation of the negative electrode sheet:

[0183] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are 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.

[0184] Four, preparation of the battery:

[0185] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator are assembled, and an electrolyte is injected to form a battery.

[0186] Example 5

[0187] I. Preparation of the positive active material:

[0188] 1. The lithium source Li2CO3, the spherical manganese-containing precursor Mn3O4, H3BO3, and the metal oxide Al2O3 and Nb2O5 are uniformly mixed according to a stoichiometric ratio of n(Li):n(Mn):n(B):n(Al):n(Nb) = 1:1.85:0.05:0.05:0.05 to form a first mixture, and the particle size D50 of the precursor Mn3O4 is 3.5 μm;

[0189] 2. The first mixture is calcined in an air atmosphere at 750°C for 16 hours to obtain a single-crystal-like lithium manganate material;

[0190] 3. The single-crystal-like lithium manganate material obtained in step 2 is weighed, and a solvent anhydrous ethanol is added and uniformly stirred. CeO2 material and fast ion conductor LiNbO3 are added to the above solution, and the mixture is continuously stirred at 460°C for 6h to obtain a suspension of the three, which is dried for 12h. The dried powder is calcined at 550°C in an air atmosphere for 10h to obtain a single-crystal-like lithium manganate positive active material coated with CeO2 and LiNbO3. The thickness of the coating layer is recorded.

[0191] In the positive active material, the mass percentage of CeO2 is 2%, and the mass percentage of the fast ion conductor is 1%.

[0192] II. Preparation of the positive electrode sheet:

[0193] The positive active material prepared in step one, the conductive agent Super-P, and the binder PVDF are 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.

[0194] III. Preparation of the negative electrode sheet:

[0195] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are weighed according to a mass ratio of 95:3:1:1, mixed uniformly, mixed with the solvent deionized water, a negative electrode slurry is obtained, and the negative electrode slurry is uniformly coated on a copper foil to form a negative electrode sheet.

[0196] Four, preparation of the battery:

[0197] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator are assembled, and an electrolyte is injected to form a battery.

[0198] Example 6

[0199] One, preparation of the positive active material:

[0200] 1. The lithium source Li2CO3, the spherical manganese-containing precursor Mn3O4, H3BO3, and the metal oxide Al2O3 and Nb2O5 are mixed uniformly according to a stoichiometric ratio of n(Li):n(Mn):n(B):n(Al):n(Nb) = 1:1.85:0.05:0.05:0.05 to form a first mixture, and the particle size D50 of the precursor Mn3O4 is 3.5 μm.

[0201] 2. The first mixture is calcined in an air atmosphere at 750°C for 16 hours to obtain a lithium manganate material with a single crystal structure.

[0202] 3. The lithium manganate material with a single crystal structure obtained in step 2 is weighed, and the solvent anhydrous ethanol is added and stirred uniformly. The CeO2 material and the fast ion conductor LiNbO3 are added to the above solution, and the stirring is continued at 460°C for 6h to obtain a suspension of the three mixed materials, and the suspension is dried for 12h. The dried powder is calcined in an air atmosphere at 550°C for 10h to obtain a lithium manganate material with a single crystal structure coated with CeO2 and LiNbO3. The thickness of the coating layer is recorded.

[0203] In the positive active material, the mass ratio of CeO2 is 0.5%, and the mass ratio of the fast ion conductor is 2.5%.

[0204] Two, preparation of the positive electrode sheet:

[0205] The positive active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed according to a mass ratio of 95:3:2, mixed uniformly, mixed with the solvent NMR to obtain a positive electrode slurry, and the positive electrode slurry is uniformly coated on an aluminum foil to form a positive electrode sheet.

[0206] Three, preparation of the negative electrode sheet:

[0207] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are weighed according to a mass ratio of 95:3:1:1, mixed uniformly, mixed with the solvent deionized water, a negative electrode slurry is obtained, and the negative electrode slurry is uniformly coated on a copper foil to form a negative electrode sheet.

[0208] Four, preparation of the battery:

[0209] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator are assembled, and an electrolyte is injected to form a battery.

[0210] Example 7

[0211] I. Preparation of the positive active material:

[0212] 1. The lithium source Li2CO3, the spherical manganese-containing precursor Mn3O4, H3BO3, and the metal oxide Al2O3 and Nb2O5 are mixed uniformly according to a stoichiometric ratio of n(Li):n(Mn):n(B):n(Al):n(Nb) = 1:1.85:0.05:0.05:0.05 to form a first mixture, and the particle size D50 of the precursor Mn3O4 is 3.5 μm.

[0213] 2. The first mixture is calcined in an air atmosphere at 750°C for 16 hours to obtain a lithium manganate material with a single crystal structure.

[0214] 3. The lithium manganate material with a single crystal structure obtained in step 2 is weighed, and the solvent anhydrous ethanol is added and stirred uniformly. The CeO2 material and the fast ion conductor Li2TiO3 are added to the above solution, and the stirring is continued at 460°C for 6h to obtain a suspension of the three mixed materials, and the suspension is dried for 12h. The dried powder is calcined in an air atmosphere at 550°C for 10h to obtain a lithium manganate material with a single crystal structure coated with CeO2 and Li2TiO3. The thickness of the coating layer is recorded.

[0215] In the positive active material, the mass ratio of CeO2 is 1%, and the mass ratio of the fast ion conductor Li2TiO3 is 1%.

[0216] II. Preparation of the positive electrode sheet:

[0217] The positive active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed according to a mass ratio of 95:3:2, mixed uniformly, mixed with the solvent NMR to obtain a positive electrode slurry, and the positive electrode slurry is uniformly coated on an aluminum foil to form a positive electrode sheet.

[0218] III. Preparation of the negative electrode sheet:

[0219] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are weighed according to a mass ratio of 95:3:1:1, mixed uniformly, mixed with the solvent deionized water, a negative electrode slurry is obtained, and the negative electrode slurry is uniformly coated on a copper foil to form a negative electrode sheet.

[0220] Four, preparation of the battery:

[0221] The positive electrode sheet prepared in step two, the negative electrode sheet prepared in step three, and the separator are assembled, and an electrolyte is injected to form a battery.

[0222] Example 8

[0223] One, preparation of the positive active material:

[0224] 1. The lithium source Li2CO3, the spherical manganese-containing precursor Mn3O4, H3BO3, and the metal oxides Al2O3, Nb2O5, and CoO are mixed uniformly according to a stoichiometric ratio of n(Li):n(Mn):n(B):n(Al):n(Nb):n(Co) = 1:1.85:0.05:0.05:0.02:0.03 to form a first mixture, and the particle size D50 of the precursor Mn3O4 is 3.5 μm.

[0225] 2. The first mixture is calcined in an air atmosphere at 750°C for 16 hours to obtain a lithium manganate material with a single crystal structure.

[0226] 3. The lithium manganate material with a single crystal structure obtained in step 2 is weighed, and the solvent anhydrous ethanol is added and stirred uniformly. The CeO2 material and the fast ion conductor LiNbO3 are added to the above solution, and the stirring is continued at 460°C for 6h to obtain a suspension of the three mixed materials, and the suspension is dried for 12h. The dried powder is calcined in an air atmosphere at 550°C for 10h to obtain a lithium manganate material with a single crystal structure coated with CeO2 and LiNbO3. The thickness of the coating layer is recorded.

[0227] In the positive active material, the mass ratio of CeO2 is 0.5%, and the mass ratio of the fast ion conductor is 2.5%.

[0228] Two, preparation of the positive electrode sheet:

[0229] The positive active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed according to a mass ratio of 95:3:2, mixed uniformly, mixed with the solvent NMR to obtain a positive electrode slurry, and the positive electrode slurry is uniformly coated on an aluminum foil to form a positive electrode sheet.

[0230] Three, preparation of the negative electrode sheet:

[0231] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are weighed according to a 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.

[0232] Four, preparation of the battery:

[0233] 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.

[0234] Comparative Example 1

[0235] One, preparation of the positive active material:

[0236] 1. The lithium source Li2CO3, the spherical manganese-containing precursor Mn3O4, H3BO3, and the metal oxide Al2O3 and Nb2O5 are uniformly mixed according to a stoichiometric ratio of n(Li):n(Mn):n(B):n(Al):n(Nb) = 1:1.85:0.05:0.05:0.05 to form a first mixture, and the particle size D50 of the precursor Mn3O4 is 3.5 μm.

[0237] 2. The first mixture is calcined in an air atmosphere at 750°C for 16 hours to obtain a single-crystal-like lithium manganate positive active material.

[0238] Two, preparation of the positive electrode sheet:

[0239] The positive active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed according to a 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.

[0240] Three, preparation of the negative electrode sheet:

[0241] The negative active material graphite, the conductive agent Super-P, the binder CMC, and SBR are weighed according to a 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.

[0242] Four, preparation of the battery:

[0243] 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.

[0244] Comparative Example 2

[0245] One, preparation of the positive active material:

[0246] 1, a lithium source Li2CO3, spherical manganese-containing precursor Mn3O4, H3BO3 and metal oxide Al2O3, Nb2O5 are mixed uniformly according to the stoichiometric ratio n(Li):n(Mn):n(B):n(Al):n(Nb)=1:1.85:0.05:0.05:0.05, forming a first mixture, the particle size D50 of the precursor Mn3O4 is 3.5 μm;

[0247] 2, the first mixture is calcined at 750℃ in air for 16 hours to obtain a single-crystal-like lithium manganate material;

[0248] 3, the single-crystal-like lithium manganate material obtained in step 2 is weighed, a solvent anhydrous ethanol is added, and stirring is uniform, a fast ion conductor LiNbO3 is added to the above solution, and stirring is continued at 460℃ for 6h to obtain a suspension of the three mixed, and the powder is dried for 12h. The dried powder is calcined at 550℃ in air for 10h to obtain a single-crystal-like lithium manganate anode active material coated with LiNbO3. The thickness of the coating layer is recorded.

[0249] Among them, the mass ratio of the fast ion conductor in the positive electrode active material is 1%.

[0250] II. Preparation of the positive electrode sheet:

[0251] The positive electrode active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed and mixed uniformly according to the mass ratio of 95:3:2, mixed with the solvent NMR to obtain a positive electrode slurry, uniformly coated on an aluminum foil to form a positive electrode sheet.

[0252] III. Preparation of the negative electrode sheet:

[0253] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and the binder SBR are weighed and mixed uniformly according to the mass ratio of 95:3:1:1, mixed with the solvent deionized water to obtain a negative electrode slurry, uniformly coated on a copper foil to form a negative electrode sheet.

[0254] IV. Preparation of the battery:

[0255] 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.

[0256] Comparative Example 3

[0257] I. Preparation of the positive electrode active material:

[0258] 1, a lithium source Li2CO3, spherical manganese-containing precursor Mn3O4, H3BO3 and metal oxide Al2O3, Nb2O5 are mixed uniformly according to the stoichiometric ratio n(Li):n(Mn):n(B):n(Al):n(Nb)=1:1.85:0.05:0.05:0.05 to form a first mixture, the particle size D50 of the precursor Mn3O4 is 3.5 μm;

[0259] 2, the first mixture is calcined at 750℃ in air for 16 hours to obtain a lithium manganese oxide material;

[0260] 3, the lithium manganese oxide material obtained in step 2 is weighed, a solvent anhydrous ethanol is added, and the mixture is stirred uniformly. CeO2 material is added to the above solution, and a suspension is obtained after stirring at 460℃ for 6h, and the suspension is dried for 12h. The dried powder is calcined at 550℃ in air for 10h to obtain a CeO2-coated lithium manganese oxide positive electrode active material. The thickness of the coating layer is recorded.

[0261] Among them, the mass ratio of CeO2 in the positive electrode active material is 1%.

[0262] II. Preparation of the positive electrode sheet:

[0263] The positive electrode active material prepared in step one, the conductive agent Super-P, and the binder PVDF are weighed and mixed uniformly according to the mass ratio of 95:3:2, and 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.

[0264] III. Preparation of the negative electrode sheet:

[0265] The negative electrode active material graphite, the conductive agent Super-P, the binder CMC, and the binder SBR are weighed and mixed uniformly according to the mass ratio of 95:3:1:1, and 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.

[0266] IV. Preparation of the battery:

[0267] 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.

[0268] Comparative Example 4

[0269] I. Preparation of the positive electrode active material:

[0270] 1, a lithium source Li2CO3, spherical manganese-containing precursor Mn3O4, H3BO3 are mixed uniformly according to the stoichiometric ratio 1:1.85:0.05 to form a first mixture, the particle size D50 of the precursor Mn3O4 is 3.5 μm;

[0271] 2. The first mixture was calcined at 750℃ in air for 16 hours to obtain a single-crystal-like lithium manganate positive electrode active material.

[0272] II. Preparation of the positive electrode sheet:

[0273] 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, which was uniformly coated on an aluminum foil to form a positive electrode sheet.

[0274] III. Preparation of the negative electrode sheet:

[0275] 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, which was uniformly coated on a copper foil to form a negative electrode sheet.

[0276] IV. Preparation of the battery:

[0277] 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.

[0278] The batteries prepared in Examples 1-8 and Comparative Examples 1-4 were tested as follows.

[0279] First discharge capacity test:

[0280] The battery was discharged at a constant current of 0.1C to a cutoff voltage of 3.0V.

[0281] Rate performance test:

[0282] At room temperature (25℃), a fully charged battery was discharged at a current of 0.1C to a cutoff voltage of 3.0V, and the capacity obtained was C0.

[0283] At room temperature (25℃), a fully charged battery was discharged at a current of 3C to a cutoff voltage of 3.0V, and the capacity obtained was C1, and C1 / C0 was the 3C discharge capacity retention rate in the following.

[0284] Battery internal resistance test:

[0285] Obtained by DCR test, 25℃, 3C discharge for 10 seconds.

[0286] Cycle battery capacity retention rate:

[0287] Charged to 4.2V at 0.2C at 45℃, then charged to 0.05C, rested for 0.5h, discharged to 3.0V at 0.2C, rested for 0.5h, and entered the next charge-discharge cycle, and so on, for a total of 200 charge-discharge cycles.

[0288] Mn dissolution content test:

[0289] About 0.1g of the negative electrode powder of each example was weighed (accurate to ±0.0003g), placed in a 100ml beaker, a small amount of distilled water was added to wet the bottom of the cup, then 5ml of 12mol / L HCl (produced in Shandong, GR) was added for dissolution, heated on an electric heating plate for 20min, cooled, diluted and measured. The prepared series of standard solutions were introduced into an iCAP7000 inductively coupled plasma spectrometer (ICP) (produced in the United States) at the wavelength of the measured element manganese, and the intensity of the manganese element in the standard solution was measured. When the linear correlation coefficient r of the working curve is ≥0.9995, the measurement can be performed.

[0290] The results are shown in the following table.

[0291]

[0292]

[0293] According to the above table: compared with Comparative Example 1 and Comparative Examples 1-3, by coating the surface of the lithium manganese oxide material with CeO2 and fast ion conductor, the CeO2 and fast ion conductor synergistically act, on the one hand, the contact between the electrolyte and the lithium manganese oxide material can be effectively isolated, the dissolution of divalent manganese ions can be reduced, the damage of the rolling to the lithium manganese oxide material can be effectively prevented, the cycle performance of the battery can be improved, on the other hand, the positive active material has good lithium ion transmission performance, the rate performance of the battery is optimized, using CeO2 and fast ion conductor as the coating layer material is conducive to the preparation of a thin coating layer, and the internal resistance of the battery is improved.

[0294] Compared with Comparative Example 1 and Comparative Example 4, the cycle performance and rate performance of the battery in Example 1 are improved by doping and coating the lithium manganese oxide material, which shows that doping and coating the lithium manganese oxide material at the same time is conducive to the improvement of the electrochemical performance of the battery.

[0295] It should be noted 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 principles of the present application shall be included in the protection scope of the present application.

Claims

1. A positive electrode active material characterized by, The coating layer is formed on the surface of the single-crystal-like lithium manganate material. The coating layer comprises CeO2 and a fast ion conductor. The general formula of the single-crystal-like lithium manganate material is Li 1+a Mn 2-a-b-c B b M c O4; 0.001≤a≤0.30, 0.001≤b≤0.2, and 0.001≤c≤0.

2. M is a metal element. The M comprises at least two of Mg, Al, Ca, Ti, Cu, Zn, Y, Zr, Nb, Mo, Ru, Sn, and Sb.

2. The positive electrode active material according to claim 1, characterized by The fast ion conductor comprises at least one of LiNbO3, Li4Ti5O 12 , Li2TiO3, LiAlO2, LiTaO3, LiMoO3, Li2RuO3, or Li2WO4.

3. The positive electrode active material according to claim 1, characterized by The M comprises at least two of Al, Mg, Ti, Co, and Nb.

4. The positive electrode active material according to claim 1, characterized by The thickness of the coating layer is 10-50 nm.

5. The positive electrode active material of claim 1, wherein, the mass fraction of the fast ion conductor is 0.1%-2% based on 100% of the mass of the positive electrode active material; and / or, the mass fraction of the CeO2 is 0.1%-2% based on 100% of the mass of the positive electrode active material.

5. The positive electrode active material of claim 1, wherein, the mass fraction of the fast ion conductor is 0.1%-2% based on 100% of the mass of the positive electrode active material; and / or, the mass fraction of the CeO2 is 0.1%-2% based on 100% of the mass of the positive electrode active material. The method comprises the following steps:

6. A method for producing the positive electrode active material as claimed in claim 1, characterized by, S1. uniformly mixing a spherical or spherical-like Mn-containing precursor, a lithium source, a B source, and an M source to form a first mixture; S2. obtaining a single-crystal-like lithium manganate material after calcining the first mixture in an air atmosphere; S3. weighing the single-crystal-like lithium manganate material obtained in step S2, adding a solvent, and stirring uniformly to form a first solution; S4. adding a CeO2 material and a fast ion conductor to the first solution prepared in step S3, and continuing to stir until a suspension is formed; S5. drying; S6. calcining the dried powder obtained in step S5 in an air atmosphere to obtain a positive electrode active material; The particle size of the Mn-containing precursor is 1-5 μm. In step S2, the calcination temperature is 600-880 °C. The Mn-containing precursor comprises one or two of trimanganese tetraoxide, dimanganese trioxide, and manganese carbonate; and / or, 7. The method of claim 6, wherein, The lithium source is one or both of lithium carbonate and lithium hydroxide; and / or, The M source is an oxide or a sulfate of the metal element M.

8. A positive electrode sheet comprising the positive electrode active material of any one of claims 1-4, a conductive agent, and a binder.

9. A battery comprising the positive electrode sheet of claim 8, a negative electrode sheet, a separator, and an electrolyte. ​

Images