Positive electrode material and preparation method and application thereof

Abstract

The invention provides a positive electrode material and a preparation method and application thereof. The positive electrode material at least comprises a positive electrode active material; the coating layer is coated on the positive electrode active material, and the coating layer comprises halide solid electrolyte; wherein the positive electrode active material comprises nLi2MnO3. (1-n) LiMnaCobNicO2, n is greater than or equal to 0.2 and less than or equal to 0.5, and a + b + c is equal to 1; the chemical formula of the halide solid electrolyte is Li < 2 + > mZr < 1-m > FemCl < 6-x-y > Br < x > I < y >, wherein m is more than 0 and less than or equal to 0.5; x = 0-6, y = 0-6, and x + y < = 6. According to the positive electrode material and the preparation method and application thereof, the interface stability of a positive electrode plate and a solid electrolyte can be improved, and the stability and the cycle performance of a lithium ion battery are improved.

Description

Technical Field

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

[0002] With the development of secondary batteries, mainly lithium-ion batteries, lithium-ion batteries have been widely used in portable electronic products and electric vehicles. However, the frequent safety accidents of new energy vehicles recently are due to the use of flammable organic solvents as electrolytes in traditional lithium-ion batteries, which poses serious safety hazards. This problem cannot be completely solved by conventional improvement methods. In contrast, all-solid-state lithium-ion batteries using inorganic solid electrolytes have higher safety. Among the existing inorganic solid electrolytes, sulfide solid electrolytes have good application prospects due to their advantages such as high lithium ion conductivity, low interface resistance and Young's modulus. However, the interface instability between high-voltage positive electrode materials and sulfide solid electrolytes leads to poor cycle performance of the positive electrode. This problem can be improved by modifying the surface of high-voltage lithium-manganese-rich positive electrode materials with a stable oxide coating, but it requires specialized equipment and high costs. Summary of the invention

[0003] The present invention proposes a positive electrode material and a preparation method and application thereof. Through the positive electrode material and the preparation method and application thereof provided by the present invention, the cost can be significantly reduced, the side reaction of the positive electrode material and the sulfide electrolyte under high voltage can be effectively inhibited, and the interface stability between the electrode and the solid electrolyte can be improved, thereby improving the stability and cycle performance of the battery.

[0004] To solve the above technical problems, the present invention is implemented through the following technical solutions.

[0005] The present invention provides a positive electrode material, comprising at least:

[0006] positive electrode active material; and

[0007] A coating layer coated on the positive electrode active material, wherein the coating layer comprises a halide solid electrolyte;

[0008] Wherein: the positive electrode active material includes nLi 2 MnO 3 ·(1-n)LiMn a Co b Ni c O 2 , and 0.2≤n≤0.5, a+b+c=1; the chemical formula of the halide solid electrolyte is Li 2+m Zr 1-m Fe m Cl 6-x-y Br x Iy , and 0<m≤0.5; x=0~6, y=0~6, x+y≤6.

[0009] In one embodiment of the present invention, the molar ratio of iron atoms on the surface of the positive electrode material measured by an energy dispersive X-ray spectrometer is 0.4%-7%.

[0010] In one embodiment of the present invention, the chemical formula of the halide solid electrolyte is Li 2.3 Zr 0.7 Fe 0.3 Cl 6 .

[0011] In one embodiment of the present invention, the positive electrode active material is in a spherical form.

[0012] In one embodiment of the present invention, the median particle size D50 of the spherical positive electrode active material is 8 μm-20 μm.

[0013] The present invention also provides a method for preparing a positive electrode material, which comprises at least the following steps:

[0014] According to the chemical formula of the halide solid electrolyte, corresponding amounts of compounds containing Li, Zr and Fe elements are mixed, and the mixture is ground and sintered for the first time to obtain the halide solid electrolyte; and

[0015] The halide solid electrolyte and the positive electrode active material are blended according to a mass ratio and sintered for a second time to obtain a positive electrode material.

[0016] In one embodiment of the present invention, the mass ratio of the halide solid electrolyte to the positive electrode active material is (0.2-6): (99.9-94).

[0017] In one embodiment of the present invention, the blending conditions include: a mixing speed of 100 rpm-800 rpm, and a mixing time of 1 h-6 h.

[0018] In one embodiment of the present invention, the temperature of the second sintering is 950° C.-1050° C., and the sintering time is 6 h-18 h.

[0019] The present invention also provides a lithium ion battery, comprising the positive electrode material described above or the positive electrode material obtained by the preparation method described above.

[0020] The present invention also provides an electronic device, comprising the lithium-ion battery described above.

[0021] In summary, the present invention proposes a positive electrode material and its preparation method and application, which can obtain a low-cost, high ionic conductivity and high-voltage resistant halide solid electrolyte, and solve the problem of interface instability between high-voltage lithium-rich manganese-based positive electrode materials and sulfide solid electrolytes. The halide solid electrolyte has good compatibility with the high-voltage lithium-rich manganese-based positive electrode material, can improve the lithium ion conductivity of the positive electrode material, and effectively improve the ion transfer kinetics, thereby improving the rate performance of the battery. It can effectively inhibit the side reactions of the positive electrode material and the sulfide electrolyte under high voltage, and improve the interface stability between the electrode and the solid electrolyte, thereby improving the stability and cycle performance of the battery. It can improve the reversible redox ability of the oxygen element during the cycle, thereby inhibiting the dissolution of transition metals and the release of oxygen from the positive electrode, thereby improving the first-week coulomb efficiency and cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0023] Figure 1 The present invention is a flow chart of a method for preparing a positive electrode material.

[0024] Figure 2 This is a scanning electron microscope image of the positive electrode material in Example 1 of the present invention.

[0025] Figure 3 This is the EDS energy spectrum of the positive electrode material in Example 1 of the present invention.

[0026] Figure 4 This is a scanning electron microscope image of the positive electrode material in Comparative Example 1 of the present invention.

[0027] Figure 5 This is the EDS energy spectrum of the positive electrode material in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] It should be understood that the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, providing these embodiments will make disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. If not otherwise specified, the "%" and "parts" shown in the following examples refer to "mass %" and "mass parts" respectively.

[0030] The technical solution of the present invention is further described in detail below in conjunction with several embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] The present invention provides a positive electrode material, comprising: a positive electrode active material and a coating layer coated on the positive electrode active material, wherein the positive electrode active material is a high voltage positive electrode active material, and the high voltage positive electrode active material is, for example, a lithium-rich manganese-based positive electrode material, and further comprises nLi 2 MnO 3 ·(1-n)LiMn a Co b Ni c O 2 etc., and 0.2≤n≤0.5, a+b+c=1. The coating layer includes a halide solid electrolyte, and the chemical formula of the halide solid electrolyte is, for example, Li 2+m Zr 1-m Fe m Cl 6-x-y Br x I y , and 0<m≤0.5; x=0~6, y=0~6, x+y≤6. In one embodiment of the present invention, the halide solid electrolyte is, for example, Li 2.3 Zr 0.7 Fe 0.3 Cl 6 In the present application, the halide solid electrolyte does not contain rare earth metals, which can significantly reduce the cost, and the halide solid electrolyte uses iron as a doping element, which further reduces the cost while increasing the Fe content in the lattice. 3+ The substitution of can improve the ionic conductivity of the halide solid electrolyte, and the Fe element has a stronger ability to bind to the O element in the lithium-rich manganese-based positive electrode material, which is beneficial to improve the reversible redox ability of the O element during the cycle, thereby inhibiting the dissolution of transition metals and the release of oxygen from the positive electrode, thereby improving the first-week coulomb efficiency and cycle life. The halide solid electrolyte coated on the high-voltage lithium-rich manganese-based positive electrode material can effectively inhibit the side reaction of the positive electrode active material and the sulfide electrolyte at high voltage, improve the interface stability between the electrode and the solid electrolyte, and thus improve the stability and cycle performance of the battery.

[0032] In one embodiment of the present invention, the positive electrode active material is in a spherical form, wherein the median particle size D50 of the spherical positive electrode active material is 8 μm-20 μm. By controlling the median particle size of the positive electrode active material, the processing performance is prevented from being deteriorated due to too small a particle size, and the electrochemical performance is prevented from being deteriorated due to too large a particle size, and the processing performance and electrochemical performance of the positive electrode active material are improved.

[0033] In one embodiment of the present invention, in the positive electrode material, the halide solid electrolyte is uniformly coated on the surface of the positive electrode active material, and the distribution of iron atoms on the surface of the positive electrode material is measured by an energy dispersive X-ray spectrometer (EDS) to determine the coating amount and uniformity of the halide solid electrolyte. In this embodiment, the molar ratio of iron atoms on the surface of the positive electrode material is, for example, 0.4%-7%. That is, the halide solid electrolyte and the high-voltage lithium-rich manganese-based positive electrode material nLi 2 MnO 3 ·(1-n)LiMn a Co b Ni c O 2 It has good compatibility. At the same time, by coating the surface of the positive electrode active material with a halide solid electrolyte with high ionic conductivity, the ion transfer kinetics can be effectively improved, thereby improving the battery's rate performance.

[0034] See also Figure 1 As shown, the present invention further provides a method for preparing a positive electrode active material, and the preparation method includes but is not limited to steps S100 to S200.

[0035] Step S100: According to the chemical formula of the halide solid electrolyte, corresponding amounts of compounds containing Li, Zr and Fe are mixed, and ground and sintered for the first time to obtain the halide solid electrolyte.

[0036] Step S200: blending the halide solid electrolyte and the positive electrode active material according to a mass ratio and sintering for a second time to obtain a positive electrode material.

[0037] See also Figure 1 As shown, in one embodiment of the present invention, in step S100, according to the chemical formula of the halide solid electrolyte Li 2+a Zr 1-a Fe a Cl (6-x-y) Br x I y, compounds containing Li, Zr and Fe ions in corresponding molar amounts are mixed to form a mixture, and then ground and sintered for the first time to obtain a halide solid electrolyte. In one embodiment of the present invention, the chemical formula of the halide solid electrolyte is, for example, Li 2.3 Zr 0.7 Fe 0.3 Cl 6 The raw materials selected are, for example, lithium chloride (LiCl), zirconium chloride (ZrCl 4 ) and ferric chloride (FeCl 3 ) etc. In this embodiment, the multiple raw materials are mixed, for example, by ball milling, so that the raw materials are mixed and contacted more evenly, and the rotation speed of the ball milling is, for example, 400rpm-700rpm, and for example, 500rpm, the ball milling mixing time is, for example, 1.5h-3h, and for example, 2h, the diameter of the ball milling zirconium beads is, for example, 8mm-15mm, and for example, 10mm, and the ball-to-material ratio is, for example, (20-30):1, and for example, 30:1.

[0038] See also Figure 1 As shown, in one embodiment of the present invention, in step S100, after obtaining the mixture, the mixture is processed by, for example, ball milling, solid phase sintering or heating eutectic method, and the mixture is prepared by grinding and sintering method. The grinding speed is, for example, 900rpm-1200rpm, and for example, 1000rpm, and the grinding time is, for example, 8h-15h, and for example, 10h. The ground mixture is subjected to a first sintering treatment to obtain a halide solid electrolyte. The sintering heating rate is, for example, 4°C / min-5°C / min, the first sintering temperature is, for example, 250°C-350°C, the sintering time is 3-5 hours, the sintering atmosphere is, for example, an inert gas, and the sintering time is the time after the temperature is raised to the first sintering temperature. The first sintering process can enhance the crystallinity of the halide solid electrolyte. After the sintering is completed, the halide solid electrolyte is cooled by furnace cooling. In the halide solid electrolyte, the present invention uses Fe element as the doping element, and Fe in the lattice 3+ The same-valent substitution can improve the ionic conductivity of the electrolyte. In one embodiment of the present invention, the ionic conductivity of the halide solid electrolyte is ≥ 1 mS / cm.

[0039] See also Figure 1As shown, in one embodiment of the present invention, in step S200, after obtaining the halide solid electrolyte, the halide solid electrolyte and the positive electrode active material are blended according to the mass ratio. In this embodiment, the mass ratio of the halide solid electrolyte to the positive electrode active material is (0.2-6): (99.99-94), and for example, 0.8:99.8, 1:99, 2:98, 3:97, 4:96 or 5:95. During the blending process, the speed of the mixer is, for example, 100rpm-800rpm, the mixing time is, for example, 1h-6h, and the ball-to-material ratio is, for example, 20:1;. Then, the mixed halide solid electrolyte and positive electrode active material are subjected to a second sintering, wherein the sintering heating rate is, for example, 8°C / min-10°C / min, the second sintering temperature is, for example, 950°C-1050°C, the sintering time is, for example, 6h-18h, the sintering atmosphere is, for example, an inert gas, and the sintering time is the time after the temperature is raised to the second sintering temperature. In this embodiment, the positive electrode active material is, for example, nLi 2 MnO 3 ·(1-n)LiMn a Co b Ni c O 2 etc., and 0.2≤n≤0.5, a+b+c=1, and the positive electrode active material is in spherical form. The obtained positive electrode material is tested by energy dispersive X-ray spectroscopy to obtain a molar ratio of surface Fe atoms of 0.4%-7%. The second sintering helps the halide solid electrolyte and the lithium-rich manganese-based positive electrode material to form a good ion transport interface, while improving the compactness of the halide solid electrolyte, thereby obtaining a high-quality positive electrode material.

[0040] The present invention also provides a lithium-ion battery, comprising a positive electrode plate, a solid electrolyte and a negative electrode plate, wherein the solid electrolyte is disposed between the positive electrode plate and the negative electrode plate. The solid electrolyte is obtained by, for example, pressing a fast ion conductor, and for example, maintaining the pressure at a pressure of 0.8-1.5 tons for 3 minutes to 8 minutes. In other embodiments, other preparation methods may also be used to obtain the solid electrolyte. In this embodiment, the fast ion conductor includes, for example, a sulfide fast ion conductor, and the sulfide fast ion conductor is, for example, Li 6 PS 5 The positive electrode plate includes a positive electrode material, a fast ion conductor, and a conductive agent, wherein the positive electrode material is a positive electrode material coated with the above-mentioned halide solid electrolyte, and the fast ion conductor is the same as or different from the fast ion conductor in the solid electrolyte. In this embodiment, the fast ion conductor in the positive electrode plate is, for example, Li 6 PS 5Cl, etc., and the conductive agent is, for example, conductive carbon black (Super P, SP), carbon nanotubes (CNT), vapor-grown carbon fiber (VGCF), graphene, silver powder or aluminum powder, etc. In one embodiment of the present invention, the mass ratio of the positive electrode material, the fast ion conductor and the conductive agent is, for example, (65-89): (10-30): (1-5), and the positive electrode material, the fast ion conductor and the conductive agent are ground in a mortar for 15min-30min, and then mixed evenly to obtain a composite positive electrode powder. The composite positive electrode powder is pressed on the solid electrolyte, and the pressure is maintained for 3min-8min at a pressure of 0.8-1.5 tons, for example, to obtain a positive electrode plate. The negative electrode plate is, for example, a metal lithium plate, and the metal lithium plate is pressed on the side of the solid electrolyte away from the positive electrode plate, and the pressure is maintained at a pressure of 0.1-0.2 tons, for example, to obtain an all-solid-state lithium ion battery. Among them, the assembly process of the all-solid-state lithium ion battery is completed in a glove box with an argon atmosphere.

[0041] Hereinafter, the present invention will be explained in more detail by citing examples, which should not be construed as limiting. Appropriate modifications may be made within the scope consistent with the gist of the present invention, all of which fall within the technical scope of the present invention.

[0042] Example 1

[0043] Li was added at a mass ratio of 3:97 2.3 Zr 0.7 Fe 0.3 Cl 6 and 0.5Li 2 MnO 3 0.5LiMn 1 / 3 Co 1 / 3 Ni 1 / 3 O 2 The mixture was placed in a ball mill for blending, wherein the mixing speed was 600 rpm, the mixing time was 3 hours, and the ball milling ratio was 20:1. The mixed powder was then placed in a muffle furnace for sintering, the heating rate was 10°C / min, the sintering temperature was 1000°C, the sintering time was 12 hours, and the atmosphere introduced was argon. After sintering, a high-voltage lithium-rich manganese-based positive electrode material coated with a halide solid electrolyte was obtained by grinding and sieving, and the molar ratio of Fe atoms on the surface of the positive electrode material was 2.8% as determined by the energy dispersive X-ray spectrum test.

[0044] Take 50 mg of Li 6 PS 5 Cl was put into the mold and pressed into a solid electrolyte at a pressure of 1 ton for 5 minutes. The coated positive electrode material and Li 6 PS 5Cl and conductive carbon black are added to a mortar and hand-ground for 20 minutes to obtain a composite positive electrode powder. Then 10 mg of the composite positive electrode powder is placed on the solid electrolyte and maintained at a pressure of 1 ton for 5 minutes to form a positive electrode plate. After taking it out, the solid electrolyte is turned over, and a metal lithium sheet is placed on the side of the solid electrolyte relative to the positive electrode plate. The diameter of the metal lithium sheet is 10 mm, and the pressure is increased to 0.1 tons and maintained to obtain an all-solid-state lithium-ion battery. Among them, the assembly process of the all-solid-state lithium-ion battery is completed in a glove box with an argon atmosphere.

[0045] Example 2

[0046] Li 2.3 Zr 0.7 Fe 0.3 Cl 6 and 0.5Li 2 MnO 3 0.5LiMn 1 / 3 Co 1 / 3 Ni 1 / 3 O 2 The mass ratio of is 6:94, and the molar ratio of Fe atoms on the surface of the positive electrode material is 6.8%. His operation is consistent with that in Example 1.

[0047] Example 3

[0048] Li 2.3 Zr 0.7 Fe 0.3 Cl 6 and 0.5Li 2 MnO 3 0.5LiMn 1 / 3 Co 1 / 3 Ni 1 / 3 O 2 The mass ratio of is 0.2:99.8, the molar ratio of Fe atoms on the surface of the positive electrode material is 0.5%, and other operations are consistent with Example 1.

[0049] Comparative Example 1

[0050] Take 50 mg of Li 6 PS 5 Cl was placed in a mold and pressed into a solid electrolyte at a pressure of 1 ton for 5 minutes. Uncoated 0.5Li 2 MnO 3 0.5LiMn 1 / 3 Co 1 / 3 Ni 1 / 3 O 2 , Li 6 PS 5Cl and conductive carbon black are added to a mortar and hand-ground for 20 minutes to obtain a composite positive electrode powder. Then 10 mg of the composite positive electrode powder is placed on the solid electrolyte and maintained at a pressure of 1 ton for 5 minutes to form a positive electrode plate. After taking it out, the solid electrolyte is turned over, and a metal lithium sheet is placed on the side of the solid electrolyte relative to the positive electrode plate. The diameter of the metal lithium sheet is 10 mm, and the pressure is increased to 0.1 tons and maintained to obtain an all-solid-state lithium-ion battery. Among them, the assembly process of the all-solid-state lithium-ion battery is completed in a glove box with an argon atmosphere.

[0051] Comparative Example 2

[0052] Li 2.3 Zr 0.7 Fe 0.3 Cl 6 and 0.5Li 2 MnO 3 0.5LiMn 1 / 3 Co 1 / 3 Ni 1 / 3 O 2 The mass ratio of is 0.05:99.95, the molar ratio of Fe atoms on the surface of the positive electrode material is 0.1%, and other operations are consistent with Example 1.

[0053] Comparative Example 3

[0054] Li 2.3 Zr 0.7 Fe 0.3 Cl 6 and 0.5Li 2 MnO 3 0.5LiMn 1 / 3 Co 1 / 3 Ni 1 / 3 O 2 The mass ratio of is 15:85, the molar ratio of Fe atoms on the surface of the positive electrode material is 10%, and other operations are consistent with Example 1.

[0055] In Examples 1-3 and Comparative Examples 1-3 of the present invention, different positive electrode materials are used to prepare lithium-ion batteries. At 25°C, a BlueDyne electrochemical workstation is used to test the above-prepared all-solid-state lithium-ion batteries according to the standard method of testing gram capacity and first-week coulombic efficiency, and the voltage range is 2.0-4.8V and the test rate is 0.1C.

[0056] Table 1. Performance test results of lithium ion batteries in Examples 1-3 and Comparative Examples 1-3

[0057]

[0058] See also Figures 2 to 5As shown, the scanning electron microscope (SEM) image and EDS spectrum of the coated positive electrode material prepared in Example 1 are as follows Figure 2 and Figure 3 As shown. Figure 2 and Figure 3 It can be seen that after being coated with the halide solid electrolyte, a layer of coating material containing Fe element appears on the surface, and the surface of the material is not damaged. The scanning electron microscope image and EDS spectrum of the untreated positive electrode active material in Comparative Example 1 are shown in FIG. Figure 4 and Figure 5 As shown. Figure 4 and Figure 5 It can be seen that the surface of the uncoated lithium-rich manganese-based positive electrode material particles is smooth and does not contain Fe. Therefore, in the present application, the halide solid electrolyte can be evenly coated on the particles of the lithium-rich manganese-based positive electrode material without affecting the morphology of the particles of the lithium-rich manganese-based positive electrode material.

[0059] Please refer to Table 1. By comparing Examples 1-3 and Comparative Example 1, coating with a halide solid electrolyte can increase the gram capacity of the lithium-ion battery and improve the coulombic efficiency. That is, the halide solid electrolyte has good compatibility with the particles of the high-voltage lithium-rich manganese-based positive electrode material, which can effectively improve the ion transfer kinetics, thereby improving the rate performance of the battery. The halide solid electrolyte coating of the high-voltage lithium-rich manganese-based positive electrode material can effectively inhibit the side reaction of the positive electrode material and the sulfide electrolyte under high voltage, improve the interface stability between the positive electrode and the solid electrolyte, and thus improve the stability and cycle performance of the lithium-ion battery.

[0060] Please refer to Table 1, comparing Examples 1-3 and Comparative Examples 2-3, as the molar ratio of Fe atoms on the surface of the positive electrode material increases or decreases, the coating amount of the halide solid electrolyte changes synchronously. When the coating is too little, a small amount of coating layer cannot suppress the side reaction of the high-voltage positive electrode active material with the sulfide electrolyte, so the first week coulomb efficiency and positive electrode gram capacity are low. When the coating is too much, the halide solid electrolyte coating layer with low electronic conductivity affects the electronic contact of the positive electrode active material, so the gram capacity is affected. Therefore, by controlling the coating amount of the halide solid electrolyte on the surface of the positive electrode active material, the capacity and cycle performance of the lithium-ion battery can be improved at the same time.

[0061] The present invention also provides an electronic device, the electronic device includes at least one of the above-mentioned lithium-ion batteries, and the lithium-ion battery is used to provide electrical energy. Among them, the electronic device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. In one embodiment of the present invention, the vehicle is, for example, a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. Spacecraft include airplanes, rockets, space shuttles and spacecrafts, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers, etc. The electronic device includes the above-mentioned lithium-ion battery, so the advantages of the above-mentioned lithium-ion battery are included, which will not be elaborated here.

[0062] In summary, the present invention proposes a positive electrode material and a preparation method and application thereof, by coating a halide solid electrolyte on the positive electrode active material, the halide solid electrolyte includes iron doping, and a low-cost, high ion conductivity and high voltage resistant halide solid electrolyte is obtained, which solves the interface instability problem between the high voltage lithium-rich manganese-based positive electrode material and the sulfide solid electrolyte. The halide solid electrolyte has good compatibility with the high voltage lithium-rich manganese-based positive electrode material, can improve the lithium ion conductivity of the positive electrode material, effectively improve the ion transfer kinetics, and thus improve the rate performance of the battery. It can effectively inhibit the side reaction of the positive electrode material and the sulfide electrolyte under high voltage, improve the interface stability between the electrode and the solid electrolyte, and thus improve the stability and cycle performance of the battery. The iron element in the halide solid electrolyte has a stronger binding ability with the oxygen element in the lithium-rich manganese-based positive electrode material, which is conducive to improving the reversible redox ability of the oxygen element during the cycle, thereby inhibiting the dissolution of transition metals and the release of oxygen from the positive electrode, thereby improving the first week coulomb efficiency and cycle life.

[0063] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept, such as a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0064] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A positive electrode material, characterized in that: At least: Positive electrode active material; as well as A coating layer coated on the positive electrode active material, wherein the coating layer comprises a halide solid electrolyte; Wherein: the positive electrode active material includes nLi2MnO3·(1-n)LiMn a Co b Ni c O2, and 0.2≤n≤0.5, a+b+c=1; the chemical formula of the halide solid electrolyte is Li 2+m Zr 1-m Fe m Cl 6-x-y Br x I y , and 0<m≤0.5; x=0~6, y=0~6, x+y≤6.

2. The positive electrode material according to claim 1, characterized in that The molar ratio of iron atoms on the surface of the positive electrode material measured by an energy dispersive X-ray spectrometer is 0.4%-7%.

3. The positive electrode material according to claim 1, characterized in that The chemical formula of the halide solid electrolyte is Li 2.3 Zr 0.7 Fe 0.3 Cl6.

4. The positive electrode material according to claim 1, characterized in that The positive electrode active material is in a spherical form.

5. The positive electrode material according to claim 4, characterized in that The median particle size D50 of the positive electrode active material in the spherical form is 8 μm to 20 μm.

6. A method for preparing a positive electrode material, characterized in that: At least the following steps are included: According to the chemical formula of the halide solid electrolyte, corresponding amounts of compounds containing Li, Zr and Fe elements are mixed, and ground and sintered for the first time to obtain the halide solid electrolyte; as well as The halide solid electrolyte and the positive electrode active material are blended according to a mass ratio and sintered for a second time to obtain a positive electrode material.

7. The method for preparing the positive electrode material according to claim 6, characterized in that: The mass ratio of the halide solid electrolyte to the positive electrode active material is (0.2-6):(99.9-94).

8. The method for preparing the positive electrode material according to claim 6, characterized in that: The blending conditions include: a mixing speed of 100 rpm to 800 rpm, and a mixing time of 1 h to 6 h.

9. The method for preparing the positive electrode material according to claim 6, characterized in that: The temperature of the second sintering is 950° C.-1050° C., and the sintering time is 6 h-18 h.

10. A lithium ion battery, characterized in that: The invention comprises the positive electrode material described in any one of claims 1 to 5 or the positive electrode material obtained by the preparation method described in any one of claims 6 to 9.

11. An electronic device, characterized in that: Includes the lithium ion battery as claimed in claim 10.

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