Composite cathode material, preparation method thereof and full-solid-state lithium ion battery

Abstract

The application provides a composite positive electrode material, a preparation method thereof, and a full-solid-state lithium ion battery. The composite positive electrode material comprises an in-situ reaction product of a first positive electrode active material and a second positive electrode active material; the first positive electrode active material comprises a zirconium-based fluorine-containing halide Li2ZrA x F y wherein 3<=x<=5, 1<=y<=3, x+y=6, A comprises one or more of Cl, Br and I; the second positive electrode active material comprises a fluorinated lithium-rich manganese-based active Li 1+m Mn m M 1‑m O 2‑m‑n F 2n wherein 0.1<=m<=0.9, 0<n<=0.05, M comprises one or more of Ni, Co, Mn and Al. The first positive electrode active material can construct a high-ion-conductivity fluoride interface for the second positive electrode active material through in-situ reaction, improve the cycle performance of the composite positive electrode material, and the in-situ generated fluoride interface has stable coating effect and continuously provides a high-ion-conductivity channel in the electrochemical process. Meanwhile, the doping of fluorine can significantly inhibit the participation of lattice oxygen in the material in oxidation and reduction, thereby inhibiting the phase transition of the composite positive electrode material from an interlayer phase to a spinel phase in the charging and discharging process.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a composite cathode material and its preparation method, and an all-solid-state lithium-ion battery. Background Technology

[0002] All-solid-state lithium-ion batteries boast exceptional safety and are widely recognized as one of the most promising new energy storage devices. Currently, commercially available high-capacity cathode materials are primarily ternary materials, but their specific capacity is relatively low compared to other all-solid-state batteries. Lithium-rich manganese-based cathodes have attracted significant attention due to their high specific capacity (>250 mAh / g) and low cost, and are expected to become the preferred cathode material for next-generation all-solid-state lithium-ion battery systems.

[0003] Due to the loss of lattice oxygen and the phase transition from layered to spinel phase during cycling, lithium-rich manganese-based cathode materials suffer from low first-cycle coulombic efficiency and poor cycle and rate performance. This is the biggest obstacle to the commercial application of lithium-rich manganese-based cathode materials. Summary of the Invention

[0004] This application provides a composite cathode material and its preparation method, as well as an all-solid-state lithium-ion battery, which can improve the efficiency of battery cycle performance testing.

[0005] In a first aspect, embodiments of this application provide a composite cathode material, comprising in-situ reaction products of a first cathode active material and a second cathode active material; the first cathode active material comprises a zirconium-based fluorinated halide, Li₂ZrA. x F y Where 3≤x≤5, 1≤y≤3, x+y=6, and A includes one or more of Cl, Br, and I; the second positive electrode active material includes lithium-rich manganese-based fluorinated active material Li. 1+m Mn m M 1-m O 2-m-n F 2n Where 0.1≤m≤0.9, 0<n≤0.05, and M includes one or more of Ni, Co, Mn, and Al.

[0006] According to an embodiment of the first aspect of this application, the mass ratio of the first positive electrode active material and the second positive electrode active material is 1:(0.5~1).

[0007] According to an embodiment of the first aspect of this application, it further includes a conductive medium, wherein the ratio of the sum of the masses of the first positive electrode active material and the second positive electrode active material to the mass of the conductive medium is 100:(0.1 to 10).

[0008] According to an embodiment of the first aspect of this application, the conductive medium includes one or more of carbon nanotubes, graphene, acetylene black, conductive carbon black, and carbon fibers.

[0009] Secondly, embodiments of this application provide a method for preparing a composite cathode material, comprising:

[0010] Provide a first positive electrode active material, the first positive electrode active material including zirconium-based fluorine halide Li2ZrA x F y Where 3≤x≤5, 1≤y≤3, x+y=6, and A includes one or more of Cl, Br, and I; a second positive electrode active material is provided, the second positive electrode active material including lithium-rich manganese fluoride active material Li 1+m Mn m M 1-m O 2-m-n F 2n Where 0.1≤m≤0.9, 0<n≤0.05, and M includes one or more of Ni, Co, Mn, and Al; the first positive electrode active material and the second positive electrode active material are reacted in situ to obtain a composite positive electrode material.

[0011] According to an embodiment of the second aspect of this application, the step of obtaining a composite positive electrode material by in-situ reaction of the first positive electrode active material and the second positive electrode active material includes: ball milling the first positive electrode active material and the second positive electrode active material, wherein the ball milling speed is 250-500 rpm and the ball milling time is 10-20 min.

[0012] According to an embodiment of the second aspect of this application, the step of providing a first positive electrode active material includes: mixing LiA, ZrA, and ZrF in a stoichiometric ratio and then grinding them to obtain a first mixture, wherein A includes one or more of Cl, Br, and I; and sintering the first mixture to obtain the first positive electrode active material, wherein the sintering temperature is 400℃~600℃ and the sintering time is 8h~12h.

[0013] According to an embodiment of the second aspect of this application, in the step of mixing LiA, ZrA, and ZrF in stoichiometric ratio and then grinding them to obtain a first mixture, the molar ratio of LiA to the sum of the amounts of ZrA and ZrF is 2:1.

[0014] According to an embodiment of the second aspect of this application, the molar ratio of ZrA to ZrF is 1:3 to 3:1.

[0015] According to an embodiment of the second aspect of this application, the mass ratio of the first positive electrode active material to the second positive electrode active material is 1:(0.5~1).

[0016] According to an embodiment of the second aspect of this application, the step of reacting the first positive electrode active material and the second positive electrode active material in situ to obtain a composite positive electrode material further includes adding a conductive medium, ball milling the first positive electrode active material and the second positive electrode active material to obtain the composite positive electrode material, wherein the ratio of the sum of the mass of the first positive electrode active material and the second positive electrode active material to the mass of the conductive medium is 100:(0.1~10).

[0017] According to an embodiment of the second aspect of this application, the step of providing a second positive electrode active material includes: providing an aqueous solution containing a metal salt M and an aqueous solution containing a precipitant, mixing the aqueous solution containing the metal salt M and the aqueous solution containing the precipitant, and preparing a precursor by precipitation reaction, wherein M includes one or more of Ni, Co, Mn, and Al;

[0018] The precursor, lithium source and lithium fluoride are mixed and sintered to obtain the second positive electrode active material;

[0019] The molar ratio of the precursor to the lithium source (in terms of the number of lithium atoms) is 1:1 to 1:1.3, and the molar ratio of lithium fluoride to the lithium source (in terms of the number of lithium atoms) is 0.1 to 5:100.

[0020] According to an embodiment of the second aspect of this application, the step of providing an aqueous solution containing an M metal salt and an aqueous solution containing a carbonate precipitant includes,

[0021] Thirdly, this application provides an all-solid-state lithium-ion battery, including a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes the aforementioned composite positive electrode material.

[0022] Compared with the prior art, this application has at least the following beneficial effects:

[0023] The composite cathode material of this application includes the in-situ reaction products of a first cathode active material and a second cathode active material. Through in-situ reaction, the first cathode active material can construct a high ionic conductivity fluoride interface for the second cathode active material in situ, which improves the cycle performance of the composite cathode material. The in-situ generated fluoride interface has a stable coating effect and continuously provides a high ionic conductivity pathway during the electrochemical process. At the same time, fluorine doping can significantly inhibit the participation of lattice oxygen in the material in redox reactions, thereby inhibiting the phase transformation of the composite cathode material from the interlayer phase to the spinel phase during the charge and discharge process. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0025] Figure 1 The first active material Li was prepared in Example 1 of this application. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.95 F 0.1 Scanning electron microscope (SEM) image of fluorinated lithium-rich manganese-based cathode material;

[0026] Figure 2 This is a cross-sectional scanning electron microscope (SEM) image of the composite cathode material prepared in Example 2 of this application;

[0027] Figure 3 These are energy distribution surface scanning (EDS-Mapping) images of the first and second positive electrode active materials prepared in Example 2 of this application after ball milling.

[0028] Figure 4 The image shows a side scanning electron microscope (SEM) image of the composite cathode prepared in Example 3 of this application.

[0029] Figure 5 This is a graph showing the relationship between the discharge specific capacity and the number of cycles of the composite cathode prepared in Example 1 of this application in an all-solid-state battery. Detailed Implementation

[0030] To make the purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0031] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0032] In the description of this application, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.

[0033] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0034] Due to the loss of lattice oxygen and the phase transition from layered to spinel phase during cycling, lithium-rich manganese-based cathode materials suffer from low first-cycle coulombic efficiency and poor cycle and rate performance. Furthermore, while existing technologies can improve the electrochemical performance of lithium-rich manganese-based cathode materials through ion doping or interfacial coating, the inventors of this application have noted that traditional doping and coating processes are complex, costly, and difficult to simultaneously achieve the effects of doping and coating, thus limiting their large-scale application.

[0035] In view of this, the inventors of this application provide a composite cathode material and its preparation method, as well as an all-solid-state lithium-ion battery, to improve the efficiency of battery cycle performance testing.

[0036] In a first aspect, this application provides a composite cathode material, comprising the in-situ reaction products of a first cathode active material and a second cathode active material;

[0037] The first positive electrode active material includes zirconium-based fluorinated halide Li₂ZrA. x F y Where 3≤x≤5, 1≤y≤3, x+y=6, and A includes one or more of Cl, Br, and I;

[0038] The second positive electrode active material includes lithium-rich manganese fluoride-based active material Li. 1+m Mn m M 1-m O 2-m-n F 2n Where 0.1≤m≤0.9, 0<n≤0.05, and M includes one or more of Ni, Co, Mn, and Al.

[0039] According to embodiments of this application, the first positive electrode active material includes zirconium-based fluorinated halide Li₂ZrA. x F y Where 3≤x≤5, 1≤y≤3, x+y=6, and A includes one or more of Cl, Br, and I. Since fluoride ions are difficult to oxidize, fluorine doping in the first positive electrode active material can improve its stability and high-voltage resistance. The second positive electrode active material includes fluorinated lithium-rich manganese-based active material Li. 1+m Mn m M 1-m O 2-m-n F 2nWhere 0.1≤m≤0.9, 0<n≤0.05, and M includes one or more of Ni, Co, Mn, and Al. By doping fluorine into the second positive electrode active material, it is possible to increase the interlayer spacing, improve the migration of metal ions, and stabilize the lattice oxygen, thereby enhancing its electrochemical performance.

[0040] Both the first and second positive electrode active materials contain fluorine, which can make the ion pathway of the composite positive electrode material smoother when it is in operation.

[0041] In-situ reaction refers to the reaction of reactants without any further treatment, thereby efficiently introducing the desired components into the matrix material to form composite materials with new structures and properties, in order to improve the properties of a single substance.

[0042] For example, the in-situ reaction can be achieved by ball milling, mechanical stirring or fluidized bed mixing, which can cause the first positive electrode active material and the second positive electrode active material to be vigorously mixed, thereby causing the in-situ reaction.

[0043] The first positive electrode active material can improve the ionic conductivity of the composite positive electrode material. Due to the compatibility of the fluorine-doped interface between the first and second positive electrode active materials, they can undergo in-situ reactions to form a grain boundary gradient phase. This phase can tolerate a certain degree of volume deformation during charging and discharging, thus the generated fluoride interface has a stable effect. Through in-situ reaction, the first positive electrode active material can construct a high ionic conductivity fluoride interface for the second positive electrode active material, improving the cycle performance of the composite positive electrode material. The in-situ generated fluoride interface has a stable coating effect and continuously provides a high ionic conductivity pathway during the electrochemical process. At the same time, fluorine doping can significantly inhibit the participation of lattice oxygen in the material in redox reactions, thereby inhibiting the phase transformation of the composite positive electrode material from the interlayer phase to the spinel phase during charging and discharging.

[0044] In some embodiments, the mass ratio of the first positive electrode active material to the second positive electrode active material is 1:(0.5 to 1).

[0045] According to the embodiments of this application, when the mass ratio of the first positive electrode active material and the second positive electrode active material is within the above-mentioned range, it helps to coat the surface of the second positive electrode active material as a fluoride interface coating layer. The fluoride interface coating layer has a wide electrochemical window, with an oxidation upper limit of up to 6.5V (vs. Li / Li). + It can well match the high voltage requirements of lithium-rich manganese-based materials.

[0046] For example, the mass ratio of the first positive electrode active material to the second positive electrode active material can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1.

[0047] In some embodiments, the composite cathode material further includes a conductive medium, and the ratio of the sum of the masses of the first cathode active material and the second cathode active material to the mass of the conductive medium is 100:(0.1 to 10).

[0048] The conductive medium is used to improve the conductivity of the composite cathode material. When the ratio of the sum of the masses of the first cathode active material and the second cathode active material to the mass of the conductive medium is within the above range, a composite cathode material with high ionic conductivity and good cycle performance can be obtained.

[0049] The ratio of the sum of the masses of the first positive electrode active material and the second positive electrode active material to the mass of the conductive medium can be 100:0.5, 100:1, 100:2, 100:3, 100:4, 100:5, 100:6 or 100:7.

[0050] In some embodiments, the conductive medium includes one or more of carbon nanotubes, graphene, acetylene black, conductive carbon black, and carbon fibers, with carbon materials having good electrical conductivity.

[0051] In some embodiments, an adhesive may be used to bond the components of the composite electrode material together. The adhesive may include one or more of polytetrafluoroethylene, polyvinylidene fluoride, hydrogenated nitrile rubber, polyacrylonitrile, polyacrylic acid, and polymethyl methacrylate.

[0052] Secondly, this application provides a method for preparing a composite cathode material, comprising:

[0053] Provide a first positive electrode active material, the first positive electrode active material including zirconium-based fluorine halide Li2ZrA x F y Where 3≤x≤5, 1≤y≤3, x+y=6, and A includes one or more of Cl, Br, and I; a second positive electrode active material is provided, the second positive electrode active material including lithium-rich manganese fluoride active material Li 1+m Mn m M 1-m O 2-m-n F 2n Where 0.1≤m≤0.9, 0<n≤0.05, and M includes one or more of Ni, Co, Mn, and Al; the first positive electrode active material and the second positive electrode active material are reacted in situ to obtain a composite positive electrode material.

[0054] According to the embodiments of this application, by carrying out an in-situ reaction between a fluorinated first positive electrode active material and a fluorinated second positive electrode active material, a fluoride interface with high ionic conductivity can be formed, which has good cycle performance. At the same time, a grain boundary gradient phase can be formed, which can tolerate a certain degree of volume deformation during charging and discharging. Therefore, the generated fluoride interface has a stable effect.

[0055] Both the first and second positive electrode active materials contain fluorine, which can make the ion pathway of the composite positive electrode material smoother when it is in operation.

[0056] For example, the in-situ reaction can be achieved by ball milling, mechanical stirring or fluidized bed mixing, which can cause the first positive electrode active material and the second positive electrode active material to be vigorously mixed, thereby causing the in-situ reaction.

[0057] In some embodiments, the step of reacting the first positive electrode active material and the second positive electrode active material in situ to obtain the composite positive electrode material includes:

[0058] The first positive electrode active material and the second positive electrode active material were ball-milled at a speed of 250 rpm to 500 rpm for 10 min to 20 min.

[0059] This application employs ball milling to vigorously mix the first and second positive electrode active materials for in-situ reaction, thereby constructing a high-voltage resistant and high-ionic-conductivity fluoride interface on the surface of the first positive electrode active material. This improves the cycle stability and capacity of the lithium-rich manganese-based positive electrode and is simpler than traditional coating methods.

[0060] In some embodiments, the step of providing the first positive electrode active material includes: mixing LiA, ZrA, and ZrF in stoichiometric ratio and then grinding them to obtain a first mixture, wherein A includes one or more of Cl, Br, and I; and sintering the first mixture to obtain the first positive electrode active material, wherein the sintering temperature is 400℃~600℃ and the sintering time is 8h~12h.

[0061] For example, in the step of mixing LiA, ZrA, and ZrF in stoichiometric ratio and then grinding to obtain a first mixture, the ball milling speed is 250 rpm-500 rpm and the ball milling time is 5 h-50 h. In the step of sintering the first mixture to obtain a first positive electrode active material, the heating rate is 1-10 °C / min. Sintering under these conditions is beneficial for obtaining a second positive electrode active material with uniform grain size.

[0062] This application obtains the first positive electrode active material by sintering, and fluorine can improve the stability and high voltage resistance of the first positive electrode active material.

[0063] In some embodiments, in the step of mixing LiA, ZrA, and ZrF in stoichiometric ratio and then grinding them to obtain a first mixture, the molar ratio of LiA to the sum of the amounts of ZrA and ZrF is 2:1.

[0064] This application achieves a first positive electrode active material with high ionic conductivity by setting the molar ratio of LiA to the sum of ZrA and ZrF to 2:1, thus making the ratio of Li to Zr in the first positive electrode active material 2:1.

[0065] In some implementations, the molar ratio of ZrA to ZrF is 1:3 to 3:1.

[0066] This application allows for the adjustment of fluorine doping by changing the molar ratio of ZrA and ZrF, resulting in a first positive electrode active material that is resistant to high voltage and exhibits good stability.

[0067] In some embodiments, the mass ratio of the first positive electrode active material to the second positive electrode active material is 1:(0.5 to 1).

[0068] According to the embodiments of this application, when the mass ratio of the first positive electrode active material and the second positive electrode active material is within the above-mentioned range, it helps to coat the surface of the second positive electrode active material as a fluoride interface coating layer. The fluoride interface coating layer has a wide electrochemical window, with an oxidation upper limit of up to 6.5V (vs. Li / Li). + It can well match the high voltage requirements of lithium-rich manganese-based materials.

[0069] For example, the mass ratio of the first positive electrode active material to the second positive electrode active material can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1.

[0070] In some embodiments, the step of reacting the first positive electrode active material and the second positive electrode active material in situ to obtain the composite positive electrode material further includes adding a conductive medium, ball milling the first positive electrode active material and the second positive electrode active material to obtain the composite positive electrode material, wherein the ratio of the sum of the mass of the first positive electrode active material and the second positive electrode active material to the mass of the conductive medium is 100:(0.1~10).

[0071] The conductive medium is used to improve the conductivity of the composite cathode material. When the ratio of the sum of the masses of the first cathode active material and the second cathode active material to the mass of the conductive medium is within the above range, a composite cathode material with high ionic conductivity and good cycle performance can be obtained.

[0072] In some embodiments, the step of providing the second positive electrode active material includes: providing an aqueous solution containing an M metal salt and an aqueous solution containing a precipitant; mixing the aqueous solution containing the M metal salt and the aqueous solution containing the precipitant; and preparing a precursor by precipitation reaction, wherein M includes one or more of Ni, Co, Mn, and Al; and mixing the precursor, a lithium source, and lithium fluoride, followed by sintering to obtain the second positive electrode active material.

[0073] The metal salt M can be one or more of the sulfate, acetate, and nitrate salts of M. For example, the metal salt M can be nickel sulfate, aluminum nitrate, or a mixture of nickel sulfate and aluminum nitrate.

[0074] The precipitant is one or more of sodium carbonate, potassium carbonate, sodium hydroxide, or potassium hydroxide. For example, the precipitant can be sodium carbonate, sodium hydroxide, or a mixture of sodium carbonate and sodium hydroxide.

[0075] When the precipitant is sodium carbonate, potassium carbonate, or a mixture of both in any proportion, adjusting the pH of the reaction system to 7-9, the system temperature to 40℃-70℃, and the reaction time to 10h-30h is beneficial for obtaining a precursor with uniform crystal grains.

[0076] The lithium source can provide lithium element, which can be one or both of lithium carbonate and lithium oxide.

[0077] The precursor, lithium source, and lithium fluoride can be mixed by ball milling at a speed of 250-500 rpm for 5-20 hours.

[0078] In the step of sintering the precursor, lithium source and lithium fluoride to obtain the second positive electrode active material, the high-temperature sintering temperature is 400℃-600℃, the time is 8h-12h, and the heating rate is 1~10℃ / min.

[0079] Sintering under these conditions is beneficial for obtaining a second positive electrode active material with uniform grain size.

[0080] In some embodiments, the molar ratio of the precursor to the lithium source, expressed in molar numbers of lithium atoms, is 1:1 to 1:1.3.

[0081] According to an embodiment of the second aspect of this application, the molar ratio of lithium fluoride to lithium source in terms of the number of lithium atoms is 0.1 to 5:100.

[0082] In some embodiments, the concentration of the aqueous solution containing the metal salt M is 0.5 mol / L to 1.5 mol / L; the concentration of the precipitant solution is 0.5 to 3 mol / L.

[0083] Thirdly, this application provides an all-solid-state lithium-ion battery, including a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes the aforementioned composite positive electrode material.

[0084] The composite cathode material can be mixed with a binder and then coated onto the current collector to form a cathode, or a binder can be added during the process of in-situ reaction of the first cathode active material and the second cathode active material to obtain the composite cathode material, and the final product can be coated onto the current collector to form a cathode.

[0085] For example, the ratio of the sum of the masses of the first positive electrode active material and the second positive electrode active material to the mass of the conductive medium and the binder is 100:(0.1 to 10):(0.1 to 10).

[0086] Example

[0087] The following embodiments describe the disclosure of this application in more detail. These embodiments are for illustrative purposes only, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0088] Example 1:

[0089] The first positive electrode active material, Li2ZrCl3F3, is prepared by the following method:

[0090] Lithium chloride, zirconium chloride, and zirconium fluoride in a stoichiometric ratio of 8:1:3 were ball-milled at 400 rpm for 15 hours to mix evenly. The mixture was then fed into a muffle furnace and heated to 500°C at a heating rate of 10°C / min. The mixture was kept at 500°C for 10 hours to obtain the zirconium-based fluorinated halide electrolyte Li2ZrCl3F3.

[0091] Second positive electrode active material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F 0.04 The preparation method is as follows:

[0092] Manganese sulfate, nickel sulfate, and cobalt sulfate in a stoichiometric ratio of 5.4:1.3:1.3 were dissolved in deionized water to obtain a transition metal salt solution with a Mn, Ni, and Co metal ion concentration of 1.5 mol / L. Sodium carbonate in a metal ion stoichiometric ratio of 1.2 was dissolved in deionized water to obtain a carbonate precipitant solution. The transition metal salt solution and carbonate precipitant solution were slowly added dropwise to deionized water, and a precipitation reaction occurred. The reaction was carried out hydrothermally at 60℃ for 10 h. After aging, filtration, washing, and drying, a lithium-rich manganese-based precursor was obtained. The lithium-rich manganese-based precursor, lithium carbonate, lithium oxide, and lithium fluoride in a stoichiometric ratio of 100:65:65:4 were ball-milled at 400 rpm for 15 h to mix evenly. The mixture was then fed into a muffle furnace and heated to 500℃ at a heating rate of 10℃ / min. The mixture was held at 500℃ for 10 h to obtain the fluorine-containing second cathode active material Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F 0.04 Product morphology as follows Figure 1 As shown.

[0093] The composite cathode material is prepared by the following method:

[0094] Take 50g of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F 0.04 50g of Li2ZrCl3F3, 5g of carbon nanotubes, 1g of graphene and 4g of polyacrylonitrile were ball-milled in a ball mill at 400rpm for 20min to mix evenly, and then pressed onto aluminum foil to obtain a lithium-rich manganese-based positive electrode sheet with an in-situ constructed high ionic conductivity fluoride interface.

[0095] Example 2:

[0096] The first positive electrode active material, Li2ZrCl5F, is prepared by the following method:

[0097] Lithium chloride, zirconium chloride, and zirconium fluoride in a stoichiometric ratio of 8:3:1 were ball-milled at 400 rpm for 15 hours to mix evenly. The mixture was then fed into a muffle furnace and heated to 500°C at a heating rate of 10°C / min. The mixture was kept at 500°C for 10 hours to obtain the zirconium-based fluorinated halide electrolyte Li2ZrCl5F.

[0098] Second positive electrode active material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F0.04 The preparation method is the same as in Example 1.

[0099] The composite cathode material is prepared by the following method:

[0100] Take 50g of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F 0.04 50g of Li₂ZrCl₅F, 5g of carbon nanotubes, 1g of graphene, and 4g of polyacrylonitrile were ground and mixed, then pressed onto aluminum foil to obtain a lithium-rich manganese-based positive electrode with an in-situ constructed high ionic conductivity fluoride interface. The cross-sectional morphology and corresponding elemental distribution of this lithium-rich manganese-based positive electrode are shown in the figure. Figure 2 , Figure 3 As shown.

[0101] Example 3:

[0102] The first positive electrode active material, Li2ZrCl5F, was prepared using the same method as in Example 2.

[0103] Second positive electrode active material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.95 F 0.1 The preparation method is as follows:

[0104] Manganese sulfate, nickel sulfate, and cobalt sulfate in a stoichiometric ratio of 5.4:1.3:1.3 were dissolved in deionized water to obtain a transition metal salt solution with a Mn, Ni, and Co metal ion concentration of 1.5 mol / L. Sodium carbonate in a metal ion stoichiometric ratio of 1.2 was dissolved in deionized water to obtain a carbonate precipitant solution. The transition metal salt solution and carbonate precipitant solution were slowly added dropwise to deionized water, and a precipitation reaction occurred. The reaction was carried out hydrothermally at 60℃ for 10 h. After aging, filtration, washing, and drying, a lithium-rich manganese-based precursor was obtained. The lithium-rich manganese-based precursor, lithium carbonate, lithium oxide, and lithium fluoride in a stoichiometric ratio of 100:65:65:10 were ball-milled at 400 rpm for 15 h to mix evenly. The mixture was then fed into a muffle furnace and heated to 500℃ at a heating rate of 10℃ / min. The mixture was held at 500℃ for 10 h to obtain the fluorinated lithium-rich manganese-based cathode material Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.9 5F 0.1 .

[0105] The composite cathode material is prepared by the following method:

[0106] Take 50g of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F 0.04 50g of Li₂ZrCl₅F, 5g of carbon nanotubes, 1g of graphene, and 4g of polyacrylonitrile were ball-milled at 400 rpm for 20 minutes to obtain a homogeneous mixture. The mixture was then pressed onto aluminum foil to obtain a lithium-rich manganese-based positive electrode with an in-situ constructed high ionic conductivity fluoride interface. The side morphology of this lithium-rich manganese-based positive electrode is shown in the figure. Figure 4 As shown.

[0107] Example 4:

[0108] The first positive electrode active material, Li2ZrCl5F, was prepared using the same method as in Example 2.

[0109] Second positive electrode active material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F 0.04 The preparation method is the same as in Example 1.

[0110] The composite cathode material is prepared by the following method:

[0111] Take 80g of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F 0.04 20g of Li2ZrCl5F, 5g of carbon nanotubes, 1g of graphene and 4g of polyacrylonitrile were ball-milled at 400rpm for 20min to mix evenly, and then pressed onto aluminum foil to obtain a lithium-rich manganese-based positive electrode with an in-situ constructed high ionic conductivity fluoride interface.

[0112] Example 5:

[0113] The first positive electrode active material, Li2ZrCl5F, was prepared using the same method as in Example 2.

[0114] Second positive electrode active material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F 0.04 The preparation method is the same as in Example 1.

[0115] The composite cathode material is prepared by the following method:

[0116] Take 50g of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 1.98 F 0.04 50g of Li2ZrCl5F, 5g of carbon nanotubes, 1g of graphene and 4g of polytetrafluoroethylene were ball-milled at 500rpm for 10min to mix them evenly. The mixture was then pressed onto aluminum foil to obtain a lithium-rich manganese-based positive electrode with an in-situ constructed high ionic conductivity fluoride interface.

[0117] Test section:

[0118] The lithium-rich manganese-based cathode sheets with in-situ constructed high ionic conductivity fluoride interfaces prepared in Examples 1 to 5 were used as electrolytes, and lithium metal sheets were assembled into all-solid-state batteries in an argon-filled glove box. Electrochemical performance was tested at 25°C, 0.2C rate, and charge / discharge cutoff voltage of 3.3-4.8V. The performance of the lithium-rich manganese-based cathode sheet with in-situ constructed high ionic conductivity fluoride interfaces prepared in Example 1 was as follows: Figure 5 As shown, the lithium-rich manganese-based cathode with an in-situ constructed high-ionic-conductivity fluoride interface has a maximum specific capacity of 240 mAh / g and a capacity retention of 85% after 100 cycles, demonstrating the excellent cycling stability of this material.

[0119] In summary, the composite cathode material provided in this application effectively achieves ion doping and interface coating, and constructs a high ionic conductivity fluoride interface in situ, thereby extending the cycle life of lithium-rich manganese-based cathode materials.

[0120] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A composite cathode material, characterized in that, The in-situ reaction products of the first positive electrode active material and the second positive electrode active material are included, and the in-situ reaction is achieved by mechanical stirring and mixing. The first positive electrode active material includes zirconium-based fluorinated halides Li₂ZrA x F y Where 3≤x≤5, 1≤y≤3, x+y=6, and A includes one or more of Cl, Br, and I; The second positive electrode active material includes lithium-rich manganese-based fluorinated active material Li. 1+m Mn m M 1-m O 2-m-n F 2n Where 0.1≤m≤0.9, 0<n≤0.05, and M includes one or more of Ni, Co, Mn, and Al.

2. The composite cathode material according to claim 1, characterized in that, The mass ratio of the first positive electrode active material to the second positive electrode active material is 1:(0.5~1).

3. The composite cathode material according to claim 1 or 2, characterized in that, It also includes a conductive medium, wherein the ratio of the sum of the masses of the first positive electrode active material and the second positive electrode active material to the mass of the conductive medium is 100:(0.1~10).

4. The composite cathode material according to claim 3, characterized in that, The conductive medium includes one or more of carbon nanotubes, graphene, conductive carbon black, and carbon fibers.

5. The composite cathode material according to claim 3, characterized in that, The conductive medium includes acetylene black.

6. A method for preparing a composite cathode material, characterized in that, include: A first positive electrode active material is provided, the first positive electrode active material comprising zirconium-based fluorinated halide Li₂ZrA x F y Where 3≤x≤5, 1≤y≤3, x+y=6, and A includes one or more of Cl, Br, and I; A second positive electrode active material is provided, the second positive electrode active material comprising a fluorinated lithium-rich manganese-based active material Li. 1+m Mn m M 1- m O 2-m-n F 2n Where 0.1≤m≤0.9, 0<n≤0.05, and M includes one or more of Ni, Co, Mn, and Al; The first positive electrode active material and the second positive electrode active material are reacted in situ to obtain a composite positive electrode material. The in situ reaction is achieved by mechanical stirring and mixing.

7. The method for preparing the cathode material according to claim 6, characterized in that, The steps for obtaining a composite cathode material by in-situ reaction of the first and second positive electrode active materials include: The first positive electrode active material and the second positive electrode active material were ball-milled at a speed of 250 rpm to 500 rpm for 10 min to 20 min.

8. The method for preparing the cathode material according to claim 6, characterized in that, The step of providing the first positive electrode active material includes: LiA, ZrA, and ZrF are mixed in stoichiometric ratio and then ground to obtain a first mixture, wherein A includes one or more of Cl, Br, and I. The first mixture is sintered to obtain the first positive electrode active material, wherein the sintering temperature is 400°C to 600°C and the sintering time is 8 h to 12 h.

9. The method for preparing the cathode material according to claim 8, characterized in that, In the step of mixing LiA, ZrA, and ZrF in stoichiometric ratio and then grinding them to obtain the first mixture, The molar ratio of LiA to the sum of the amounts of ZrA and ZrF is 2:

1.

10. The method for preparing the cathode material according to claim 8, characterized in that, The molar ratio of ZrA to ZrF is 1:3 to 3:

1.

11. The method for preparing the cathode material according to claim 6, characterized in that, The mass ratio of the first positive electrode active material to the second positive electrode active material is 1:(0.5~1).

12. The method for preparing the cathode material according to claim 6, characterized in that, The step of reacting the first positive electrode active material and the second positive electrode active material in situ to obtain the composite positive electrode material also includes... A conductive medium is added, and the first positive electrode active material and the second positive electrode active material are ball-milled to obtain the composite positive electrode material. The ratio of the sum of the masses of the first positive electrode active material and the second positive electrode active material to the mass of the conductive medium is 100:(0.1~10).

13. The method for preparing the cathode material according to claim 6, characterized in that, The step of providing the second positive electrode active material includes: An aqueous solution containing a metal salt M and an aqueous solution containing a precipitant are provided. The aqueous solution containing the metal salt M and the aqueous solution containing the precipitant are mixed, and a precursor is prepared by precipitation reaction. The M includes one or more of Ni, Co, Mn, and Al. The precursor, lithium source and lithium fluoride are mixed and sintered to obtain the second positive electrode active material; The molar ratio of the precursor to the lithium source (in terms of the number of lithium atoms) is 1:1 to 1:1.3, and the molar ratio of the lithium fluoride to the lithium source (in terms of the number of lithium atoms) is 0.1 to 5:

100.

14. A composite cathode material, characterized in that, The in-situ reaction products of the first positive electrode active material and the second positive electrode active material are included, and the in-situ reaction is achieved by ball milling or fluidized bed mixing. The first positive electrode active material includes zirconium-based fluorinated halides Li₂ZrA x F y Where 3≤x≤5, 1≤y≤3, x+y=6, and A includes one or more of Cl, Br, and I; The second positive electrode active material includes lithium-rich manganese-based fluorinated active material Li. 1+m Mn m M 1-m O 2-m-n F 2n Where 0.1≤m≤0.9, 0<n≤0.05, and M includes one or more of Ni, Co, Mn, and Al.

15. The composite cathode material according to claim 14, characterized in that, The mass ratio of the first positive electrode active material to the second positive electrode active material is 1:(0.5~1).

16. The composite cathode material according to claim 13 or 14, characterized in that, It also includes a conductive medium, wherein the ratio of the sum of the masses of the first positive electrode active material and the second positive electrode active material to the mass of the conductive medium is 100:(0.1~10).

17. The composite cathode material according to claim 16, characterized in that, The conductive medium includes one or more of carbon nanotubes, graphene, conductive carbon black, and carbon fibers.

18. The composite cathode material according to claim 16, characterized in that, The conductive medium includes acetylene black.

19. A method for preparing a composite cathode material, characterized in that, include: A first positive electrode active material is provided, the first positive electrode active material comprising zirconium-based fluorinated halide Li₂ZrA x F y Where 3≤x≤5, 1≤y≤3, x+y=6, and A includes one or more of Cl, Br, and I; A second positive electrode active material is provided, the second positive electrode active material comprising a fluorinated lithium-rich manganese-based active material Li. 1+m Mn m M 1- m O 2-m-n F 2n Where 0.1≤m≤0.9, 0<n≤0.05, and M includes one or more of Ni, Co, Mn, and Al; The first positive electrode active material and the second positive electrode active material are subjected to an in-situ reaction to obtain a composite positive electrode material. The in-situ reaction is achieved by ball milling or fluidized bed mixing.

20. The method for preparing the cathode material according to claim 19, characterized in that, The steps for obtaining a composite cathode material by in-situ reaction of the first and second positive electrode active materials include: The first positive electrode active material and the second positive electrode active material were ball-milled at a speed of 250 rpm to 500 rpm for 10 min to 20 min.

21. The method for preparing the cathode material according to claim 19, characterized in that, The step of providing the first positive electrode active material includes: LiA, ZrA, and ZrF are mixed in stoichiometric ratio and then ground to obtain a first mixture, wherein A includes one or more of Cl, Br, and I. The first mixture is sintered to obtain the first positive electrode active material, wherein the sintering temperature is 400°C to 600°C and the sintering time is 8 h to 12 h.

22. The method for preparing the cathode material according to claim 21, characterized in that, In the step of mixing LiA, ZrA, and ZrF in stoichiometric ratio and then grinding them to obtain the first mixture, The molar ratio of LiA to the sum of the amounts of ZrA and ZrF is 2:

1.

23. The method for preparing the cathode material according to claim 21, characterized in that, The molar ratio of ZrA to ZrF is 1:3 to 3:

1.

24. The method for preparing the cathode material according to claim 19, characterized in that, The mass ratio of the first positive electrode active material to the second positive electrode active material is 1:(0.5~1).

25. The method for preparing the cathode material according to claim 19, characterized in that, The step of reacting the first positive electrode active material and the second positive electrode active material in situ to obtain the composite positive electrode material also includes... A conductive medium is added, and the first positive electrode active material and the second positive electrode active material are ball-milled to obtain the composite positive electrode material. The ratio of the sum of the masses of the first positive electrode active material and the second positive electrode active material to the mass of the conductive medium is 100:(0.1~10).

26. The method for preparing the cathode material according to claim 19, characterized in that, The step of providing the second positive electrode active material includes: An aqueous solution containing a metal salt M and an aqueous solution containing a precipitant are provided. The aqueous solution containing the metal salt M and the aqueous solution containing the precipitant are mixed, and a precursor is prepared by precipitation reaction. The M includes one or more of Ni, Co, Mn, and Al. The precursor, lithium source and lithium fluoride are mixed and sintered to obtain the second positive electrode active material; The molar ratio of the precursor to the lithium source (in terms of the number of lithium atoms) is 1:1 to 1:1.3, and the molar ratio of the lithium fluoride to the lithium source (in terms of the number of lithium atoms) is 0.1 to 5:

100.

27. An all-solid-state lithium-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises a composite positive electrode material as described in any one of claims 1-5 or a composite positive electrode material as described in any one of claims 14-18.

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