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 positive electrode active material comprises LiNi < 0.5 > Mn < 1.5 > O < 4 >; the positive electrode active material is coated with the coating layer, the coating layer comprises a halide solid electrolyte, the chemical formula of the halide solid electrolyte is Li < 2 + a > Zr < 1-a > Fe Cl < 6-x-y > Br < x > I < y >, and a is more than 0 and less than or equal to 0.5; x = 0-6, y = 0-6, and x + y < = 6. The invention provides a positive electrode material as well as a preparation method and application thereof. The rate capability and the cycle performance of a lithium ion battery can be 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 recent frequent safety accidents of new energy vehicles 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 high lithium ion conductivity, low interface resistance and Young's modulus, but the interface instability between high-voltage positive electrode materials and sulfide solid electrolytes leads to poor cycle performance of the positive electrode, especially for high-voltage lithium nickel manganese oxide materials. This problem can be avoided by modifying a stable oxide coating on the surface of high-voltage lithium nickel manganese oxide materials, but generally requires specialized equipment and high costs, which limits its application scenarios. 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 rate performance 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, the positive electrode active material comprising LiNi 0.5 Mn 1.5 O4; and

[0007] A coating layer is coated on the positive electrode active material, wherein the coating layer comprises a halide solid electrolyte, and the chemical formula of the halide solid electrolyte is Li 2+a Zr 1-a Fe a Cl 6-x-y Br x I y , where 0<a≤0.5; x=0~6, y=0~6, x+y≤6.

[0008] 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 0.2%-5%.

[0009] 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 Cl6.

[0010] In one embodiment of the present invention, the positive electrode active material is in a secondary spherical form or a single crystal form.

[0011] In one embodiment of the present invention, the median particle size D50 of the positive electrode active material in the secondary spherical form is 10 μm-40 μm.

[0012] In one embodiment of the present invention, the median particle size D50 of the single-crystal positive electrode active material is 1 μm-16 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 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 (0.1-1.2): (99.9-98.8).

[0017] In one embodiment of the present invention, the blending conditions include: a mixing speed of 100 rpm-10000 rpm, and a mixing time of 1 h-48 h.

[0018] In one embodiment of the present invention, the temperature of the first sintering is 250° C.-350° C., and the sintering time is 3 h-5 h.

[0019] In one embodiment of the present invention, the temperature of the second sintering is 200° C.-500° C., and the sintering time is 6 h-18 h.

[0020] 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.

[0021] The present invention also provides an electronic device, comprising the lithium-ion battery described above.

[0022] In summary, the present invention proposes a positive electrode material and a preparation method and application thereof, 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 nickel manganese oxide positive electrode active materials and sulfide solid electrolytes. It can improve the lithium ion conductivity of the positive electrode material, and at the same time effectively suppress the side reaction of the positive electrode material and the sulfide electrolyte under high voltage. The halide solid electrolyte has good compatibility with the high-voltage lithium nickel manganese oxide positive electrode active material, and can effectively improve the ion transfer kinetics, thereby improving the rate performance of the battery. It can effectively suppress 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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.

[0024] Figure 1 The present invention is a flow chart of a method for preparing a positive electrode material.

[0025] Figure 2 This is a scanning electron microscope image of the positive electrode material in Example 2 of the present invention.

[0026] Figure 3 This is the EDS energy spectrum of the positive electrode material in Example 2 of the present invention.

[0027] Figure 4 This is a scanning electron microscope image of the positive electrode material in Comparative Example 2 of the present invention.

[0028] Figure 5 This is the EDS energy spectrum of the positive electrode material in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0029] 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.

[0030] It should be understood that the present invention can be implemented in different forms and should not be interpreted as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0031] 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.

[0032] The present invention provides a positive electrode material, which includes 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 nickel manganese oxide positive electrode active material, and further includes LiNi 0.5 Mn 1.5 O4, etc. The coating layer includes a halide solid electrolyte, and the chemical formula of the halide solid electrolyte is, for example, Li 2+a Zr 1-a Fe a Cl 6-x-y Br x I y , wherein 0<a≤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 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 replacement of can improve the ionic conductivity of the halide solid electrolyte. At the same time, the halide solid electrolyte coated on the high-voltage lithium nickel manganese oxide positive electrode active material can effectively inhibit the side reaction between the positive electrode active 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.

[0033] In one embodiment of the present invention, the positive electrode active material is, for example, in the form of a secondary sphere or a single crystal, wherein the median particle size D50 of the positive electrode active material in the form of a secondary sphere is 10 μm-40 μm, and the median particle size D50 of the positive electrode active material in the form of a single crystal is 1 μm-16 μm. By controlling the median particle size of the positive electrode active material, the processing performance is prevented from being deteriorated due to the particle size being too small, and the electrochemical performance is prevented from being deteriorated due to the particle size being too large, and the processing performance and electrochemical performance of the positive electrode active material are improved.

[0034] 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, 0.2%-5%. That is, the halide solid electrolyte and the high voltage lithium nickel manganese oxide LiNi 0.5 Mn 1.5 O4 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 0.3Cl6, the selected raw materials are, for example, lithium chloride (LiCl), zirconium chloride (ZrCl4) and ferric chloride (FeCl3). 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.

[0039] 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 isovalent substitution of can improve the ionic conductivity of the halide solid electrolyte. In one embodiment of the present invention, the ionic conductivity of the halide solid electrolyte is greater than or equal to 1 mS / cm.

[0040] 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 a mass ratio. In this embodiment, the mass ratio of the halide solid electrolyte to the positive electrode active material is (0.1-1.2): (99.9-98.8), and for example, 0.4:99.6, 0.6:99.4, 0.7:99.3, 0.8:99.8 or 1:99, etc. During the blending process, the speed of the mixer is, for example, 100rpm-10000rpm, and the mixing time is, for example, 1h-48h. 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, 1°C / min-4°C / min, the second sintering temperature is, for example, 200°C-500°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, LiNi 0.5 Mn 1.5 O4, and the positive electrode active material is in the form of secondary spheres or single crystals, and the secondary sphere-shaped LiNi 0.5 Mn 1.5 The D50 of O4 is, for example, 5 μm-40 μm, and the single crystal form of LiNi 0.5 Mn 1.5 The D50 of O4 is, for example, 1 μm-16 μm, and the molar ratio of Fe atoms on the surface of the obtained positive electrode material is 0.2%-5% as measured by energy dispersive X-ray spectroscopy. The second sintering helps the halide solid electrolyte and the nickel manganese oxide lithium positive electrode active material to form a good ion transmission interface, while controlling the sintering temperature to prevent the halide solid electrolyte from being insufficiently compact due to the low sintering temperature, resulting in a poor interface and low ion conductivity, and to prevent the sintering temperature from being too high, resulting in the decomposition of part of the halide solid electrolyte, thereby obtaining a high-quality positive electrode material.

[0041] The present invention also proposes a lithium ion battery, comprising a positive electrode, a solid electrolyte and a negative electrode, wherein the solid electrolyte is arranged between the positive electrode and the negative electrode. Wherein, the solid electrolyte is obtained by, for example, pressing a fast ion conductor, and for example, maintaining the pressure for 3min-8min at a pressure of 0.8-1.5 tons. In other embodiments, other preparation methods can 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, Li6PS5Cl. The positive electrode includes a positive electrode material, a fast ion conductor, and a conductive agent, etc., wherein the positive electrode material is a positive electrode material coated with the above-mentioned halide solid electrolyte, and the fast ion conductor is, for example, the same as the fast ion conductor in the solid electrolyte, or it may be different. In this embodiment, the fast ion conductor in the positive electrode is, for example, Li6PS5Cl, 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). The positive electrode material, the fast ion conductor and the conductive agent are ground in a mortar for 15 min-30 min, and then mixed evenly to obtain a composite positive electrode powder. The composite positive electrode powder is pressed on a solid electrolyte, and the pressure is maintained for 3 min-8 min at a pressure of 0.8-1.5 tons, for example, to obtain a positive electrode. The negative electrode is, for example, a metal lithium sheet, and the metal lithium sheet is pressed on the side of the solid electrolyte away from the positive electrode, 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. The assembly process of the all-solid-state lithium-ion battery is completed in a glove box with an argon atmosphere.

[0042] 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.

[0043] Example 1

[0044] Li was added at a mass ratio of 0.6:99.4 2.3 Zr 0.7 Fe 0.3 Cl6 and single crystal LiNi 0.5 Mn 1.5O4 is placed in a mixer for blending, wherein the mixing speed is 5000rpm and the mixing time is 24h. The mixed powder is then placed in a muffle furnace for sintering treatment, the heating rate is 2℃ / min, the sintering temperature is 350℃, the sintering time is 12h, and the atmosphere introduced is argon. After sintering, the positive electrode material of high-voltage lithium nickel manganese oxide coated with a halide solid electrolyte is obtained by grinding and sieving. The energy dispersive X-ray spectrum test shows that the molar ratio of Fe atoms on the surface of the positive electrode material is 2.4%.

[0045] Take 50 mg of Li6PS5Cl and put it into the mold. Press it into a solid electrolyte under a pressure of 1 ton for 5 minutes. Weigh the positive electrode material, Li6PS5Cl and conductive agent conductive carbon black in turn according to the mass ratio of 70:29:1, add them to the mortar and grind them by hand for 20 minutes to obtain a composite positive electrode powder. Then place 10 mg of the composite positive electrode powder on the solid electrolyte and hold the pressure at 1 ton for 5 minutes to form a positive electrode. After taking it out, turn the solid electrolyte over, place a metal lithium sheet on the side of the solid electrolyte relative to the positive electrode, the diameter of the metal lithium sheet is 10 mm, pressurize it to 0.1 tons and hold the pressure 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.

[0046] Example 2

[0047] Li was added at a mass ratio of 0.6:99.4 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn 1.5 O4 is placed in a mixer for blending, wherein the mixing speed is 5000rpm and the mixing time is 24h. The mixed powder is then placed in a muffle furnace for sintering treatment, the heating rate is 2℃ / min, the sintering temperature is 350℃, the sintering time is 12h, and the atmosphere introduced is argon. After sintering, the positive electrode material of high-voltage lithium nickel manganese oxide coated with a halide solid electrolyte is obtained by grinding and sieving. The energy dispersive X-ray spectrum test shows that the molar ratio of Fe atoms on the surface of the positive electrode material is 2.2%.

[0048] Take 50 mg of Li6PS5Cl and put it into the mold. Press it into a solid electrolyte under a pressure of 1 ton for 5 minutes. Weigh the positive electrode material, Li6PS5Cl and conductive agent conductive carbon black in turn according to the mass ratio of 70:29:1, add them to the mortar and grind them by hand for 20 minutes to obtain a composite positive electrode powder. Then place 10 mg of the composite positive electrode powder on the solid electrolyte and hold the pressure at 1 ton for 5 minutes to form a positive electrode. After taking it out, turn the solid electrolyte over, place a metal lithium sheet on the side of the solid electrolyte relative to the positive electrode, the diameter of the metal lithium sheet is 10 mm, pressurize it to 0.1 tons and hold the pressure 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.

[0049] Example 3

[0050] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and single crystal LiNi 0.5 Mn 1.5 The mass ratio of O4 is 0.1:99.9, and other operations are consistent with Example 1.

[0051] Example 4

[0052] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn 1.5 The mass ratio of O4 is 0.1:99.9, and other operations are consistent with Example 2.

[0053] Example 5

[0054] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and single crystal LiNi 0.5 Mn 1.5 The mass ratio of O4 is 1.2:98.8, and other operations are consistent with Example 1.

[0055] Example 6

[0056] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn 1.5 The mass ratio of O4 is 1.2:98.8, and other operations are consistent with Example 2.

[0057] Comparative Example 1

[0058] Uncoated single crystal LiNi 0.5 Mn1.5 Energy dispersive X-ray spectroscopy test showed that the molar ratio of Fe atoms on the surface of O4 was 0%. 50 mg of Li6PS5Cl was placed in a mold and pressed into a solid electrolyte at a pressure of 1 ton for 5 minutes. LiNi 0.5 Mn 1.5 O4, Li6PS5Cl 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. After taking it out, the solid electrolyte is turned over, and a metal lithium sheet with a diameter of 10 mm is placed on the side of the solid electrolyte opposite to the positive electrode. 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.

[0059] Comparative Example 2

[0060] Uncoated polycrystalline LiNi 0.5 Mn 1.5 Energy dispersive X-ray spectroscopy test showed that the molar ratio of Fe atoms on the surface of O4 was 0%. 50 mg of Li6PS5Cl was placed in a mold and pressed into a solid electrolyte at a pressure of 1 ton for 5 minutes. LiNi 0.5 Mn 1.5 O4, Li6PS5Cl 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. After taking it out, the solid electrolyte is turned over, and a metal lithium sheet with a diameter of 10 mm is placed on the side of the solid electrolyte opposite to the positive electrode. 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.

[0061] Comparative Example 3

[0062] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and single crystal LiNi 0.5 Mn 1.5 The mass ratio of O4 is 0.05:99.95, and other operations are consistent with Example 1.

[0063] Comparative Example 4

[0064] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn1.5 The mass ratio of O4 is 0.05:99.95, and other operations are consistent with Example 2.

[0065] Comparative Example 5

[0066] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and single crystal LiNi 0.5 Mn 1.5 The mass ratio of O4 is 10:90, and other operations are consistent with Example 1.

[0067] Comparative Example 6

[0068] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn 1.5 The mass ratio of O4 is 10:90, and other operations are consistent with Example 2.

[0069] In Examples 1-6 and Comparative Examples 1-6 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 3.2-4.95V and the test rate is 0.1C.

[0070] Table 1. Performance test results of lithium ion batteries in Examples 1-6 and Comparative Examples 1-6

[0071]

[0072] See also Figures 2 to 5 As shown, the scanning electron microscope (SEM) image and EDS spectrum of the coated positive electrode material prepared in Example 2 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 2 are shown in FIG. Figure 4 and Figure 5 As shown. Figure 4 and Figure 5It can be seen that the surface of the uncoated lithium nickel manganese oxide particles is smooth and does not contain Fe. Therefore, in the present application, the halide solid electrolyte can be evenly coated on the lithium nickel manganese oxide particles without affecting the morphology of the lithium nickel manganese oxide particles.

[0073] Please refer to Table 1. By comparing Examples 1-6 and Comparative Examples 1-2, 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 high-voltage lithium nickel manganese oxide particles, and 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 nickel manganese oxide positive electrode material can effectively inhibit the side reaction of the positive electrode material and the sulfide electrolyte under high voltage, and improve the interface stability between the positive electrode and the solid electrolyte, thereby improving the stability and cycle performance of the lithium-ion battery.

[0074] Please refer to Table 1, comparing Examples 1-6 and Comparative Examples 3-6, as the molar ratio of Fe atoms on the surface of the positive electrode material increases, the coating of the halide solid electrolyte increases, and the gram capacity and coulomb efficiency of the lithium-ion battery increase. When the coating amount is too low, the side reactions increase, the positive electrode oxygen release increases, and the first week coulomb efficiency decreases. When the coating amount is too high, the side reactions decrease, the positive electrode oxygen release decreases, and the first week coulomb efficiency increases, but the electronic conductivity deteriorates and the polarization increases, resulting in a decrease in capacity. This shows that the halide solid electrolyte can have high ionic conductivity and high voltage resistance, and can improve the lithium ion conduction capacity of the composite positive electrode. And controlling the coating amount of the halide solid electrolyte on the surface of the positive active material can simultaneously improve the capacity and cycle performance of the lithium-ion battery.

[0075] 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.

[0076] 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 to obtain a low-cost, high ion conductivity and high voltage resistant halide solid electrolyte, and solve the interface instability problem between the high voltage lithium nickel manganese oxide positive electrode active material and the sulfide solid electrolyte. It can improve the lithium ion conductivity of the positive electrode material, and at the same time effectively suppress the side reaction of the positive electrode material and the sulfide electrolyte under high voltage. The halide solid electrolyte has good compatibility with the high voltage lithium nickel manganese oxide positive electrode active material, and can effectively improve the ion transfer kinetics, thereby improving the rate performance of the battery. It can effectively suppress the side reaction of the positive electrode material and the sulfide electrolyte under high voltage to improve the interface stability between the electrode and the solid electrolyte, thereby improving the stability and cycle performance of the battery.

[0077] 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.

[0078] 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, the positive electrode active material comprising LiNi 0.5 Mn 1.5 O4; and A coating layer is coated on the positive electrode active material, wherein the coating layer comprises a halide solid electrolyte, and the chemical formula of the halide solid electrolyte is Li 2+a Zr 1-a Fe a Cl 6-x-y Br x I y , where 0<a≤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 0.2%-5%.

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 secondary spherical form or a single crystal 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 secondary sphere form is 10 μm to 40 μm.

6. The positive electrode material according to claim 4, characterized in that The median particle size D50 of the positive electrode active material in a single crystal form is 1 μm to 16 μm.

7. 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 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.

8. The method for preparing the positive electrode material according to claim 7, characterized in that: The mass ratio of the halide solid electrolyte to the positive electrode active material is (0.1-1.2): (99.9-98.8).

9. The method for preparing the positive electrode material according to claim 7, characterized in that: The blending conditions include: a mixing speed of 100 rpm to 10000 rpm, and a mixing time of 1 h to 48 h.

10. The method for preparing the positive electrode material according to claim 7, characterized in that: The temperature of the first sintering is 250° C.-350° C., and the sintering time is 3 h-5 h.

11. The method for preparing the positive electrode material according to claim 7, characterized in that: The temperature of the second sintering is 200° C.-500° C., and the sintering time is 6 h-18 h.

12. A lithium ion battery, characterized in that: The invention comprises the positive electrode material according to any one of claims 1 to 6 or the positive electrode material obtained by the preparation method according to any one of claims 7 to 11.

13. An electronic device, characterized in that: Includes the lithium ion battery as claimed in claim 12.

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