Positive electrode material, preparation method and use

Abstract

A positive electrode material having excellent cycle performance under a high voltage, a preparation method and a use. A tight oxide and fluoride coating layer is selected to be constructed on the surface of a positive electrode material having a spinel-layered intergrowth structure, wherein the spinel-layered intergrowth structure have high capacity and excellent cycle stability, and oxide coating has good chemical stability, and prevents a coated sample from being corroded by an electrolyte. In addition, a multi-element low-melting-point coating agent can reduce a coating temperature, and is beneficial to forming a compact coating layer on the surface of LixNiyMn1-yO2 of spinel and layered structures.

Description

A positive electrode material, preparation method and application Technical Field

[0001] The present disclosure relates to the technical field of lithium-ion batteries, and in particular to a positive electrode material, a preparation method and applications thereof. Background Art

[0002] Oil and natural gas are primary energy sources. Their refining and secondary energy use processes generate greenhouse gases and harmful gases, depleting Earth's resources and causing environmental pollution. Faced with limited resources and the growing global acceptance of sustainable development, humanity urgently needs to develop green and environmentally friendly energy sources. Lithium batteries, as a new energy storage method, utilize lithium ion insertion and extraction to achieve energy conversion, a process that produces no harmful substances. Therefore, lithium batteries are widely used in modern life, such as smartphones, home appliances, electric vehicles, drones, and energy storage. With technological advancements, the requirements for lithium battery capacity, power, and cycle performance are becoming increasingly stringent. These performance characteristics are closely related to the cathode materials used in lithium-ion batteries. Currently, the main cathode materials on the market are lithium iron phosphate and ternary nickel-cobalt-manganese materials. Lithium iron phosphate is inexpensive and highly safe, but suffers from low conductivity and limited rate capability. Carbon coating solutions can mitigate these shortcomings to some extent, but due to material structure limitations, their rate capability and capacity remain insufficient to meet future market demands. Ternary materials offer high theoretical capacity, but excessive lithium extraction from their layered structure causes structural transformations, impairing cycling performance. Lanthanum nickelate coated ternary materials improve their cycle performance, but are still limited by the excessive release of the layered structure of the ternary material, which leads to structural phase transition. Spinel materials have three-dimensional lithium ion channels, stable spinel structure, and can operate in a very wide voltage range of 2.5V to 5V. However, traditional spinel materials LiMnO4 and LiNi 0.5 Mn 1.5 The theoretical specific capacity of O4 is low, only ~146 mAh / g. In view of the above problems, a LixNi with both specific capacity and stability is proposed. y Mn 1-y O2 positive electrode material.

[0003] Summary of the Invention

[0004] The purpose of this disclosure is to provide a positive electrode material, a preparation method and an application thereof, so that Li x Ni y Mn 1-y O2 positive electrode materials have both specific capacity and stability.

[0005] The present disclosure is achieved as follows:

[0006] In a first aspect, the present disclosure provides a positive electrode material, comprising a core and a coating layer, wherein:

[0007] The general formula of the core is Li x Niy Mn 1-y O 2， 0.9 < x < 1.05, 0.1 < y < 0.8, and the core includes a spinel-structured Li x Ni y Mn 1-y O2 material and a layered-structured Li x Ni y Mn 1-y O2 material;

[0008] The coating layer includes an oxide and a fluoride. Among them, the oxide includes at least one of TeO2, Ga2O3, MgO, ZnO, TiO2, and ZrO2, and the fluoride includes at least one of ZrF4, CeF3, NH4F, LiF, NaF, and KF.

[0009] In some embodiments, the mass ratio of the spinel-structured Li x Ni y Mn 1-y O2 material to the layered-structured Li x Ni y Mn 1-y O2 material is (5 - 45):(55 - 95).

[0010] In some embodiments, the dQ / dV curve of the positive electrode material has two oxidation peaks and two reduction peaks at 2.5 - 4.65V.

[0011] In some embodiments, the dQ / dV curve of the positive electrode material has two oxidation peaks and two reduction peaks. The two oxidation peaks are respectively located at 3.75 - 3.85V and 4.50 - 4.65V, and the two reduction peaks are respectively located at 3.5 - 3.6V and 3.6 - 3.7V.

[0012] In some embodiments, the molar ratio of the oxide to the fluoride in the coating layer is (56 - 77):(23 - 44).

[0013] In some embodiments, the mass fraction of the coating layer is 0.05% - 0.5%.

[0014] In some embodiments, the molar ratio of TeO2, Ga2O3, MgO, ZnO, TiO2, ZrO2, ZrF4, CeF3, NH4F, LiF, NaF, KF in the coating layer is (0 - 10):(0 - 10)(0 - 40):(0 - 25):(0 - 50):(0 - 30):(0 - 50):(0 - 60):(0 - 45):(0 - 15):(T0 - 10):(0 - 10).

[0015] In some embodiments, the molar ratio of TeO2, Ga2O3, MgO, ZnO, TiO2, ZrO2, ZrF4, CeF3, NH4F, LiF, NaF, and KF in the coating layer is (0-5):(0-5):(2-10):(2-10):(25-50):(5-20):(5-15):(0-15):(0-10):(5-10):(2-5):(2-5).

[0016] In a second aspect, the present disclosure provides a method for preparing the positive electrode material according to any one of the aforementioned embodiments, comprising sintering a mixture containing the core and the composite coating agent slurry to obtain the positive electrode material.

[0017] In some embodiments, the composite coating agent slurry includes a coating agent, a binder, and a solvent, and the coating agent includes an oxide and a fluoride.

[0018] In some embodiments, the Dv50 of the oxide in the coating agent is 0.3 um to 0.7 um, and the Dv50 of the fluoride is 0.2 um to 0.5 um.

[0019] In some embodiments, the adhesive is carboxymethyl cellulose, and the mass fraction of the carboxymethyl cellulose in the composite coating agent slurry is 2% to 10%.

[0020] In some embodiments, the solvent consists of ethanol and water, and the mass fraction of ethanol in the solvent is 85% to 95%.

[0021] In some embodiments, the mass fraction of the coating agent in the composite coating agent slurry is 1.5% to 2.0%.

[0022] In some embodiments, the sintering temperature is 360°C to 550°C.

[0023] In some embodiments, the residual lithium content on the surface of the core material is 1000 ppm to 2000 ppm.

[0024] In a third aspect, the present disclosure provides an application of the positive electrode material described in any one of the aforementioned embodiments or the positive electrode material obtained by the method described in any one of the aforementioned embodiments in a lithium-ion battery.

[0025] In a fourth aspect, the present disclosure provides an electrode comprising the positive electrode material described in any one of the aforementioned embodiments or the positive electrode material obtained by the method described in any one of the aforementioned embodiments.

[0026] In a fifth aspect, the present disclosure provides a lithium-ion battery comprising the electrode described in the aforementioned embodiment.

[0027] In a sixth aspect, the present disclosure provides an electrical device comprising the lithium-ion battery described in the aforementioned embodiment.

[0028] The present disclosure has the following beneficial effects:

[0029] In the present disclosure, the space group of the spinel structure is Fd-3m, which is a cubic crystal system. In the highly delithiated state, the Mn and Ni located at the 16d site can support the unit cell structure and stabilize the crystal structure. The material capacity in the layered structure is high, and lithium ions can be intercalated and deintercalated in an orderly manner. Therefore, the spinel and layered symbiotic positive electrode material has the high specific capacity of the layered structure and the stability of the spinel, taking into account both capacity and cycle performance at high voltage.

[0030] In this disclosure, oxides and fluorides are used together as coating agents. The oxides are chemically stable, reducing high-voltage interfacial side reactions and thus improving the stability of the cathode material. Fluorine, with its strong electronegativity, occupies oxygen sites upon entering the crystal lattice, thereby inhibiting oxygen evolution under high voltage. By adjusting the component ratios to form a low-melting-point composite coating agent and lowering the coating temperature, a dense coating layer is formed on the material surface, reducing electrolyte corrosion on the active material under high voltage.

[0031] In this disclosure, to improve the coating agent's dispersibility and surface adhesion during low-temperature sintering, a widely available, non-toxic carboxymethyl cellulose adhesive is used. Carboxymethyl cellulose's water-soluble, viscous properties allow the composite coating agent to adhere to the material surface, while ethanol acts as a dispersant to evenly disperse the composite coating agent. This ensures adherence to the material surface during ball milling while also addressing the problem of uneven dispersion caused by the composite coating agent's viscous nature. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0033] FIG1 is a flow chart of the preparation of the positive electrode material in Example 2;

[0034] FIG2 is a comparison of the morphologies of the positive electrode materials after coating in Example 2(a) and Comparative Example 4(b);

[0035] FIG3 is an XRD pattern of the positive electrode material prepared in Example 2;

[0036] FIG4 is a TEM image of the positive electrode material prepared in Example 2;

[0037] FIG5 is a dQ / dV curve of the material in Example 2. Detailed implementation manners

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0039] Some embodiments of the present disclosure provide a cathode material, including a core and a coating layer, wherein,

[0040] The general formula of the core is Li x Ni y Mn 1-y O 2， 0.9 < x < 1.05, 0.1 < y < 0.8, and the core includes a spinel-structured Li x Ni y Mn 1-y O2 material and a layered-structured Li x Ni y Mn 1-y O2 material;

[0041] The coating layer includes an oxide and a fluoride. Among them, the oxide includes at least one of TeO2, Ga2O3, MgO, ZnO, TiO2, and ZrO2, and the fluoride includes at least one of ZrF4, CeF3, NH4F, LiF, NaF, and KF.

[0042] In this embodiment, the space group of the spinel structure is Fd-3m, which is a cubic crystal system. In the high delithiated state, Mn and Ni located at the 16d site can support the unit cell structure and stabilize the crystal structure. The material in the layered structure has a high capacity, and lithium ions can be deintercalated and intercalated orderly. Therefore, the spinel and layered coexisting cathode material has the high specific capacity of the layer structure and the stability of the spinel, and takes into account the capacity and cycle performance at high voltages.

[0043] The oxide has stable chemical properties and can inhibit the corrosion of the material by the electrolyte. However, the oxide has a high melting point and it is difficult to form a dense coating layer with the cathode material during the sintering process. Generally, the melting point of the fluoride is lower than that of the oxide. Coupled with the catalytic effect of transition metal ions, it can achieve the coating of the surface of the cathode material at a lower temperature and form a dense coating layer. At the same time, fluorine has a strong electronegativity. During the coating process, it can occupy the oxygen position in the lattice, stabilize the lattice structure, and inhibit the occurrence of Mn disproportionation reaction. However, the chemical stability of the coating with only fluoride is not as good as that of the oxide. Through the synergistic effect of the oxide and the fluoride, the corrosion of the electrolyte to the cathode material is reduced, the dissolution of Mn is inhibited, and the interfacial side reaction is reduced.

[0044] In the disclosed embodiments, oxides and fluorides are used together as coating agents. Oxides are chemically stable, reducing high-voltage interfacial side reactions and thus improving the stability of the cathode material. Fluorine, with its strong electronegativity, occupies oxygen sites upon entering the crystal lattice, thereby inhibiting oxygen evolution under high voltage. By adjusting the component ratios to form a low-melting-point composite coating agent and lowering the coating temperature, a dense coating layer is formed on the material surface, reducing electrolyte corrosion on the active material under high voltage.

[0045] The core of this embodiment is made of Ni y Mn (1-y) The (OH)2 precursor is sintered with lithium carbonate and flux at 350-550°C, wherein the flux is a sulfate of a metal element of the first and second main groups, such as calcium sulfate, etc. The specific core has a spinel structure of Li x Ni y Mn 1-y O2 cathode material and layered Li x Ni y Mn 1-y The ratio of O2 positive electrode materials can be adjusted by changing the temperature. The lower the temperature, the more Li x Ni y Mn 1-y The greater the proportion of O2 positive electrode material.

[0046] In this embodiment, the spinel and layered Li x Ni y Mn 1-y The O2 positive electrode material is co-coated with oxide-fluoride to improve the electrical performance of the positive electrode material.

[0047] In some embodiments, the spinel structured Li x Ni y Mn 1-y O2 materials and layered Li x Ni y Mn 1-y The mass ratio of O2 materials is (5-45): (55-95), specifically 5:95, 10:90, 20:80, 30:70, 40:60, 45:55 or any value between (5-45): (55-95). x Ni y Mn 1-y O2 materials and layered Li x Ni y Mn 1-y The ratio of O2 materials is optimized so that the obtained spinel and layered symbiotic positive electrode material has the high specific capacity of layered and the stability of spinel, taking into account both capacity and cycle performance at high voltage.

[0048] In some embodiments, the dQ / dV curve of the cathode material has two oxidation peaks and two reduction peaks at 2.5-4.65V, and the specific peak positions are consistent with the spinel structure of LixNi in the core. y Mn 1-y O2 materials and layered Li x Ni y Mn 1-y The mass ratio of the O2 material is related to the positive electrode material. When the dQ / dV curve of the positive electrode material has two oxidation peaks and two reduction peaks, with the two oxidation peaks located at 3.75-3.85V and 4.50-4.65V, and the two reduction peaks located at 3.5-3.6V and 3.6-3.7V, respectively, the positive electrode material can achieve both capacity and cycle performance.

[0049] In some embodiments of the present disclosure, the molar ratio of oxide to fluoride in the coating layer is (56-77):(23-44), specifically 56:44, 65:35, 77:23 or any value between (56-77):(23-44).

[0050] If the amount of oxide is too small, the stability of the positive electrode material will be limited. If the amount of fluoride is too small, the coating temperature cannot be effectively reduced, and it is difficult to form a dense coating layer on the surface of the lithiated spinel, thereby affecting the bonding strength between the lithiated spinel and the coating layer.

[0051] In some embodiments of the present disclosure, the mass fraction of the coating layer in the positive electrode material is 0.05% to 0.5%, specifically 0.05%, 0.15%, 0.25%, 0.35%, 0.45%, 0.5% or any value between 0.05% and 0.5%.

[0052] Since most coating elements are electrochemically inactive, excessive addition can reduce lithium ion diffusion and capacity. Too little coating agent can leave some surfaces uncoated, failing to achieve the desired coating effect. The thickness of the coating layer is determined by the amount of coating applied, so the proper amount of coating agent is crucial for positive electrode materials.

[0053] In some embodiments of the present disclosure, the molar ratio of TeO2, Ga2O3, MgO, ZnO, TiO2, ZrO2, ZrF4, CeF3, NH4F, LiF, NaF, and KF in the coating layer is (0-10):(0-10)(0-40):(0-25):(0-50):(0-30):(0-50):(0-60):(0-45):(0-15):(0-10):(0-10).

[0054] TeO2, Ga2O3, MgO, ZnO, TiO2 and ZrO2 are all oxides with relatively low melting points, and ZrF4, CeF3, NH4F, LiF, NaF and KF are all fluorides with relatively low melting points. The selection of oxides and fluorides with relatively low melting points is beneficial for low-temperature coating and is also beneficial for improving the density of the coating layer.

[0055] In some embodiments of the present disclosure, the molar ratio of TeO2, Ga2O3, MgO, ZnO, TiO2, ZrO2, ZrF4, CeF3, NH4F, LiF, NaF, and KF in the coating layer is (0-5):(0-5):(2-10):(2-10):(25-50):(5-20):(5-15):(0-15):(0-10):(5-10):(2-5):(2-5). Oxides with good chemical stability and acid corrosion resistance, as well as fluorides with strong ionic bonds between anions and cations, are selected to make it easier for fluoride ions to ionize and enter the surface lattice. Optimizing the composition of the coating layer is more conducive to reducing the corrosion of the electrolyte on the positive electrode material, inhibiting the dissolution of Mn, and reducing interfacial side reactions.

[0056] Other embodiments of the present disclosure provide a method for preparing the positive electrode material described in any one of the aforementioned embodiments, wherein a mixture containing the core and the composite coating agent slurry is sintered to obtain the positive electrode material.

[0057] In some embodiments of the present disclosure, the composite coating agent slurry includes a coating agent, a binder, and a solvent, wherein the coating agent includes an oxide and a fluoride. The solvent facilitates dispersion of the coating agent, and the binder helps improve adhesion between the coating agent and the core in the mixture, thereby facilitating uniform coating of the coating layer.

[0058] In some embodiments of the present disclosure, the Dv50 of the oxide in the coating agent is 0.3um to 0.7um, and the Dv50 of the fluoride is 0.2um to 0.5um. Reducing the particle size of the coating agent is beneficial to the dispersion of the coating agent, but if the particle size of the coating agent is too small, it may also be easy to agglomerate.

[0059] In some embodiments of the present disclosure, the adhesive is carboxymethyl cellulose, and the mass fraction of carboxymethyl cellulose in the composite coating agent slurry is 2% to 10%, specifically 2%, 4%, 6%, 8%, 10% or any value between 2% and 10%.

[0060] The property of carboxymethyl cellulose being easily soluble in water but insoluble in ethanol makes the slurry have a certain viscosity while maintaining good dispersibility. By configuring a low-viscosity slurry containing a coating agent and mixing it with the raw materials, the coating agent and the material have a certain adhesion effect, and the slurry has a certain dispersibility. After mixing, the coating agent can be evenly attached to the surface of the core material, which is conducive to uniform coating. The mixing method can be stirring or ball milling.

[0061] In some embodiments of the present disclosure, the solvent is composed of ethanol and water, and the mass fraction of ethanol in the solvent is 85% to 95%, specifically 85%, 90%, 95% or any value between 85% and 95%. The water in the ethanol-water solution can dissolve carboxymethyl cellulose, so that the solution has a certain viscosity, while carboxymethyl cellulose is insoluble in ethanol. The components of the solvent are reasonably selected so that the viscosity of the solution is not too large, which is beneficial to the dispersion of the slurry and improves the coating uniformity.

[0062] In some embodiments of the present disclosure, the mass fraction of the coating agent in the composite coating agent slurry is 1.5% to 2.0%, specifically 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0% or any value between 1.5% and 2.0%.

[0063] To prepare the composite coating agent slurry, first prepare an ethanol-water solution, add a binder to a binder mass fraction of 2% to 10%, and stir at room temperature to prepare pre-slurry B. The coating agent and pre-slurry B are then mixed to a coating agent mass fraction of 1.5% to 2%. The coating agent concentration should be moderate. Excessive concentrations make uniform dispersion difficult, while low concentrations result in a low coating agent content in the resulting cathode material, resulting in insignificant performance improvements.

[0064] In some embodiments of the present disclosure, the sintering temperature is 360°C to 550°C, specifically 360°C, 400°C, 450°C, 550°C, or any value between 360°C and 550°C. The present disclosure uses a simple and effective coating scheme to obtain a positive electrode material with high capacity, high pressure resistance, and good cycle stability through only one low-temperature sintering. If the sintering temperature is too high, it may affect the structure of the core material. If the sintering temperature is too low, the bonding between the coating layer and the core is weak, resulting in poor cycle performance.

[0065] In some embodiments of the present disclosure, the residual lithium content on the surface of the core material is 1000 ppm to 2000 ppm. Too much residual lithium or too little residual lithium due to excessive water washing will affect the stability of the material.

[0066] Another embodiment of the present disclosure provides an electrode, comprising the positive electrode material described in any one of the aforementioned embodiments or the positive electrode material obtained by the method described in any one of the aforementioned embodiments.

[0067] Another embodiment of the present disclosure provides a lithium ion battery including the electrode described in the above embodiment.

[0068] Another embodiment of the present disclosure provides an electric device including the lithium-ion battery described in the above embodiment.

[0069] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0070] Example 1:

[0071] This embodiment provides a method for preparing a positive electrode material, comprising the following steps:

[0072] (1) With the spinel structure of Li x Ni y Mn 1-y O2 materials and layered Li x Ni y Mn 1-y The core material is a material with an O2 mass ratio of 20:80, the spinel structure space group is Fd-3m, and the layered structure space group is R-3m. On the dQ / dV curve, the core material exhibits oxidation peaks at 3.78V and 4.60V, and splitting reduction peaks at 3.55V and 3.63V, respectively.

[0073] (2) Select an oxide with a Dv50 of 0.3 μm and a fluoride with a Dv50 of 0.2 μm. Mix them in a molar ratio of TeO2:Ga2O3:MgO:ZnO:TiO2:ZrO2:ZrF4:CeF3:NH4F:LiF:NaF:KF=5:5:2:2:25:5:5:10:5:5:5:5 to form a composite coating agent A.

[0074] (3) Prepare a 90% ethanol aqueous solution and add carboxymethyl cellulose to prepare a pre-slurry B, wherein the mass fraction of carboxymethyl cellulose is 10%. Mix the composite coating agent A with the pre-slurry B to prepare a slurry C, wherein the mass fraction of the composite coating agent in the slurry C is 1.5%.

[0075] (4) Mixing the slurry C with the core material to obtain a mixed positive electrode slurry D.

[0076] (5) The mixed positive electrode slurry D is poured into a sagger for sintering, and the temperature is raised to 360° C. to obtain a coated spinel material, wherein the mass fraction of the composite coating agent A is 0.5%.

[0077] Example 2:

[0078] This embodiment provides a method for preparing a positive electrode material, as shown in FIG1 , comprising the following steps:

[0079] (1) With the spinel structure of Li x Ni y Mn 1-y O2 materials and layered Li x Ni y Mn 1-y The core material is a material with a mass ratio of 30:70 of O2 materials. The spinel structure space group is Fd-3m, and the layered structure space group is R-3m. The core material has dQ / dV oxidation peaks at 3.72V and 4.55V, and splitting reduction peaks at 3.51V and 3.62V, respectively.

[0080] (2) Select Dv50 as 0.5um oxide and Dv50 as 0.4um fluoride, mix them in the molar ratio of TeO2:Ga2O3:MgO:ZnO:TiO2:ZrO2:ZrF4:CeF3:NH4F:LiF:NaF:KF=3:3:5:5:50:10:15:10:5:2:5:5, and then form a composite coating agent A.

[0081] (3) Prepare a 90% ethanol aqueous solution and add carboxymethyl cellulose to prepare a pre-slurry B, wherein the mass fraction of carboxymethyl cellulose is 10%. Mix all the composite coating agent A with the pre-slurry B to prepare a slurry C, wherein the mass fraction of the composite coating agent is 2%.

[0082] (4) Slurry C is mixed with the positive electrode material to obtain mixed positive electrode slurry D.

[0083] (5) Pour the mixed positive electrode slurry D into a sagger for sintering, and heat it to 400℃ for sintering. Prepare the coated positive electrode material, and the XRD pattern is shown in Figure 3. The XRD pattern of the positive electrode material shows that the material has a spinel structure of LixNi y Mn 1-y O2 materials and layered Li x Ni y Mn 1-y O2 material, through TEM, it can be observed that the spinel phase and the layered phase are dispersed to form a core, and the coating layer is tightly coated on the core. The mass fraction of the composite coating agent A in the positive electrode material is 0.3%

[0084] Example 3:

[0085] This embodiment provides a method for preparing a positive electrode material, comprising the following steps:

[0086] (1) With the spinel structure of Li x Ni y Mn 1-y O2 materials and layered Li x Ni y Mn 1-y The mass ratio of O2 material is 40:60 as the core material, the spinel structure space group is Fd-3m, and the layered structure space group is R-3m. x Ni y Mn 1-y The electrochemical characteristics of the O2-type active material are that the oxidation peaks of the dQ / dV curve are at 3.72V and 4.63V, and the splitting reduction peaks are at 3.52V and 3.68V, respectively.

[0087] (2) Select an oxide with a Dv50 of 0.7 μm and a fluoride with a Dv50 of 0.5 μm. Mix them in a molar ratio of TeO2:Ga2O3:MgO:ZnO:TiO2:ZrO2:ZrF4:CeF3:NH4F:LiF:NaF:KF=2:2:10:10:45:25:5:5:5:3:5:5 to form a composite coating A.

[0088] (3) Prepare a 90% ethanol aqueous solution and add carboxymethyl cellulose to prepare a pre-slurry B, wherein the mass fraction of carboxymethyl cellulose is 5%. Mix the composite coating agent A with the pre-slurry B to prepare a slurry C, wherein the mass fraction of the composite coating agent in the slurry C is 2%.

[0089] (4) Mill the slurry C and the core material in a ball mill to obtain a mixed positive electrode slurry D.

[0090] (5) The mixed positive electrode slurry D is poured into a sagger for sintering at 500° C. After sintering, a coated positive electrode material is obtained, and the mass fraction of the composite coating agent A in the positive electrode material is 0.2%.

[0091] Example 4

[0092] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the composition of the composite coating agent is different, and the molar ratio of MgO:ZnO:TiO2:ZrF4:CeF3 in the composite coating agent is 10:12:50:16:15.

[0093] Example 5

[0094] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the molar ratio of ZnO:CeF3 in the composite coating agent is 61:33.

[0095] Comparative Example 1

[0096] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the spinel content is too low, the spinel is 2wt%, the layered phase is 98wt%, the oxidation peak is at 3.88V, and there is only a single reduction peak at 3.71V.

[0097] Comparative Example 2

[0098] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the spinel phase ratio is too high at 80wt%, the layered phase ratio is 20wt%, the oxidation peak is at 3.69V, and the reduction peak is at 3.48V.

[0099] Comparative Example 3

[0100] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that: there is only a layered phase, the oxidation peak is 3.89V, and the reduction peak is at 3.75V.

[0101] Comparative Example 4

[0102] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the composite coating agent A does not contain oxides.

[0103] Comparative Example 5

[0104] This comparative example provides a method for preparing a positive electrode material. Compared to Example 2, the only difference lies in the irrational selection of oxides and fluorides: LiF, NaF, and KF in composite coating agent A are replaced with high-melting-point fluorides such as AlF3, MgF2, and CaF2, with a specific molar ratio of TeO2:Ga2O3:MgO:ZnO:TiO2:ZrO2:ZrF4:CeF3:NH4F:AlF3:MgF2:CaF2 = 3:3:5:5:50:10:15:10:5:2:5:5. The selection of high-melting-point fluorides resulted in the appearance of larger particles, as these cannot form a dense coating film at low temperatures, resulting in an uneven coating layer and the appearance of large particles.

[0105] Comparative Example 6

[0106] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the amount of oxide and fluoride used is unreasonable, and the proportion of oxide is too high: the molar ratio of composite coating agent A includes TeO2:Ga2O3:MgO:ZnO:TiO2:ZrO2:ZrF4:CeF3:NH4F:LiF:NaF:KF=12:12:20:20:50:25:25:10:5:2:1:1.

[0107] Comparative Example 7

[0108] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the amount of oxide and fluoride used is unreasonable, and the proportion of fluoride is too high: the molar ratio of the composite coating agent A includes TeO2:Ga2O3:MgO:ZnO:TiO2:ZrO2:ZrF4:CeF3:NH4F:LiF:NaF:KF=2:2:5:5:50:10:50:20:25:11:2:11.

[0109] Comparative Example 8

[0110] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that carboxymethyl cellulose is replaced by polyvinylidene fluoride.

[0111] Comparative Example 9

[0112] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the solvent in the slurry containing the coating agent is replaced with anhydrous ethanol (ethanol concentration 99.5 wt %).

[0113] Comparative Example 10

[0114] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that 15% by mass of carboxymethyl cellulose is added.

[0115] Comparative Example 11

[0116] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the mass fraction of the coating agent in the slurry containing the coating agent is 5%.

[0117] Comparative Example 12

[0118] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the mass fraction of the coating agent in the positive electrode material is 1%.

[0119] Comparative Example 13

[0120] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the sintering temperature is too high, that is, 700°C.

[0121] Comparative Example 14

[0122] This comparative example provides a method for preparing a positive electrode material. Compared with Example 2, the only difference is that the sintering temperature is too low, that is, the sintering temperature is 200°C.

[0123] Finished product quality:

[0124] Table 1 shows the data of charge-discharge and full-charge capacity retention of the spinels prepared in the examples and comparative examples. The charge-discharge capacity and full-charge cycle tests were tested in accordance with the GB / T37201-2018 standard. As can be seen from Table 1, in terms of discharge capacity, the charge-discharge capacity and capacity retention of the examples are significantly higher than those of the comparative examples, especially Example 2. According to Figure 2, it can be seen that the surface of Example 2 is smoother than that of Comparative Example 4, and there is no large particle surface coating.

[0125] Table 1 Product data Industrial Applicability

[0126] The present disclosure discloses Li with spinel and layered structures. x Ni y Mn 1-y The surface of the O2 cathode material is coated with oxides and fluorides. First, a spinel and layered symbiotic structure balances the capacity of the layered material with the stability of the spinel structure, resulting in excellent cycling performance at high voltages. Second, the use of oxides and fluorides to form a low-melting-point coating system allows the coating agent to tightly bond to the material surface. Third, the use of a carboxymethyl cellulose ethanol solution can evenly disperse the composite coating agent onto the material surface and adhere the composite coating agent to the material surface, improving both coating uniformity and bonding, resulting in a cathode material with high capacity, high-voltage resistance, and excellent cycling stability.

Claims

1. A positive electrode material, characterized in that: It includes a core and a cladding layer, wherein: The general formula of the core is Li x Ni y Mn 1-y O2, where 0.9 < x < 1.05 and 0.1 < y < 0.

8. The core includes a spinel-structured Li x Ni y Mn 1-y O2 material and a layered-structured Li x Ni y Mn 1-y O2 material; The coating layer includes oxide and fluoride, wherein the oxide includes at least one of TeO2, Ga2O3, MgO, ZnO, TiO2 and ZrO2, and the fluoride includes at least one of ZrF4, CeF3, NH4F, LiF, NaF and KF.

2. The positive electrode material according to claim 1, characterized in that The spinel structure of Li x Ni y Mn 1-y O2 materials and layered Li x Ni y Mn 1-y The mass ratio of O2 material is (5~45):(55~95).

3. The positive electrode material according to claim 1 or 2, characterized in that The dQ / dV curve of the positive electrode material has two oxidation peaks and two reduction peaks at 2.5-4.65V.

4. The positive electrode material according to any one of claims 1 to 3, characterized in that The dQ / dV curve of the positive electrode material has two oxidation peaks and two reduction peaks, the two oxidation peaks are respectively located at 3.75-3.85V and 4.50-4.65V, and the two reduction peaks are respectively located at 3.5-3.6V and 3.6-3.7V.

5. The positive electrode material according to any one of claims 1 to 4, characterized in that The molar ratio of oxide to fluoride in the coating layer is (56-77):(23-44).

6. The positive electrode material according to any one of claims 1 to 5, characterized in that The mass fraction of the coating layer is 0.05% to 0.5%.

7. The positive electrode material according to any one of claims 1 to 6, characterized in that: The molar ratios of TeO2, Ga2O3, MgO, ZnO, TiO2, ZrO2, ZrF4, CeF3, NH4F, LiF, NaF and KF in the coating layer are (0~10):(0~10)(0~40):(0~25):(0~50):(0~30):(0~50):(0~60):(0~45):(0~15):(0~10):(0~10).

8. The positive electrode material according to any one of claims 1 to 7, characterized in that: The molar ratios of TeO2, Ga2O3, MgO, ZnO, TiO2, ZrO2, ZrF4, CeF3, NH4F, LiF, NaF and KF in the coating layer are (0-5):(0-5):(2-10):(2-10):(25-50):(5-20):(5-15):(0-15):(0-10):(5-10):(2-5):(2-5).

9. A method for preparing the positive electrode material according to any one of claims 1 to 8, characterized in that: The mixture containing the core material and the composite coating agent slurry is sintered to obtain the positive electrode material.

10. The method for preparing the positive electrode material according to claim 9, characterized in that: The composite coating agent slurry comprises a coating agent, a binder and a solvent, and the coating agent comprises an oxide and a fluoride.

11. The method for preparing the positive electrode material according to claim 10, characterized in that: The Dv50 of the oxide in the coating agent is 0.3um-0.7um, and the Dv50 of the fluoride is 0.2um-0.5um.

12. The method for preparing the positive electrode material according to claim 10 or 11, characterized in that: The adhesive is carboxymethyl cellulose, and the mass fraction of the carboxymethyl cellulose in the composite coating agent slurry is 2% to 10%.

13. The method for preparing a positive electrode material according to any one of claims 10 to 12, characterized in that: The solvent consists of ethanol and water, and the mass fraction of ethanol in the solvent is 85% to 95%.

14. The method for preparing a positive electrode material according to any one of claims 10 to 13, characterized in that: The mass fraction of the coating agent in the composite coating agent slurry is 1.5% to 2.0%.

15. The method for preparing a positive electrode material according to any one of claims 9 to 14, characterized in that: The sintering temperature is 360℃~550℃.

16. The method for preparing a positive electrode material according to any one of claims 9 to 15, characterized in that: The residual lithium content on the surface of the core material is 1000ppm to 2000ppm.

17. An electrode, characterized in that: The invention comprises the positive electrode material according to any one of claims 1 to 8 or the positive electrode material obtained by the method according to any one of claims 9 to 16.

18. A lithium ion battery, characterized in that: Comprising the electrode according to claim 17.

19. An electrical equipment, characterized in that: Comprising the lithium ion battery as claimed in claim 18.

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