Positive electrode material, method for preparing the same, and application

Abstract

To provide a positive electrode material, a preparing method for the same, and an application, capable of enhancing the rate characteristic and cycle characteristic of a lithium ion battery.SOLUTION: A positive electrode material includes at least a positive electrode active material containing LiNi0.5Mn1.5O4 and a coating layer applied on the positive electrode active material. The coating layer includes a halide solid electrolyte. The chemical formula of the halide solid electrolyte is Li2+aZr1-aFeaCl6-x-yBrxIy, in which 0<a≤0.5, x=0 to 6, y=0 to 6, and x+y≤6 are satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a cathode material, a method for preparing the same, and an application thereof.

Background Art

[0002] With the development of secondary batteries, mainly lithium-ion batteries, lithium-ion batteries are widely used in portable electronic products and electric vehicles. However, the frequent accidents in new energy vehicles recently are due to the use of flammable organic solvents as electrolytes in conventional lithium-ion batteries, which pose a significant safety risk. This problem cannot be completely solved by conventional improvement methods. In contrast, all-solid-state lithium-ion batteries using inorganic solid electrolytes are safer. Among existing inorganic solid electrolytes, sulfide solid electrolytes have high lithium-ion conductivity, low interfacial resistance, and low Young's modulus, so the application prospect is good. However, the instability of the interface between the high-voltage cathode material and the sulfide solid electrolyte, especially in the case of high-voltage lithium nickel manganate materials, reduces the cycle performance of the cathode. By modifying the surface of the high-voltage lithium nickel manganate material with a stable oxide coating layer, this problem can be avoided. However, generally, dedicated equipment and high costs are required, so the application scenarios are limited.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The present invention proposes a cathode material, a method for preparing the same, and an application thereof. By the cathode material, the method for preparing the same, and the application according to the present invention, the cost can be significantly reduced, the side reaction between the high-voltage cathode material and the sulfide electrolyte can be effectively suppressed, thereby improving the instability of the interface between the electrode and the solid electrolyte, and improving the rate performance and cycle performance of the battery.

Means for Solving the Problems

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

[0005] The present invention proposes a positive electrode material comprising at least the following: LiNi 0.5 Mn 1.5 a cathode active material containing O4, and a coating layer coated on the cathode active material, the coating layer containing a halide solid electrolyte, and the chemical formula of the halide solid electrolyte being Li 2+ aZr 1-a Fe a Cl 6-x-y Br x I y where 0 < a ≤ 0.5, x = 0 to 6, y = 0 to 6, and x + y ≤ 6.

[0006] 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 analyzer is 0.2% to 5%.

[0007] 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.

[0008] In one embodiment of the present invention, the cathode active material is in a secondary spherical form or a single crystal form.

[0009] In one embodiment of the present invention, the median particle size D50 of the cathode active material in the secondary spherical form is 10 μm to 40 μm.

[0010] In one embodiment of the present invention, the median particle size D50 of the cathode active material in the single crystal form is 1 μm to 16 μm.

[0011] The present invention also provides a method for preparing a positive electrode material comprising at least the following steps: Mix compounds containing corresponding amounts of Li, Zr, and Fe based on the chemical formula of the halide solid electrolyte, perform grinding, and carry out the first sintering to obtain the halide solid electrolyte. Perform blending of the halide solid electrolyte and the cathode active material based on the mass ratio, and carry out the second sintering to obtain a cathode material.

[0012] In one embodiment of the present invention, the mass ratio of the halide solid electrolyte to the cathode active material is (0.1 to 1.2):(99.9 to 98.8).

[0013] In one embodiment of the present invention, the blending conditions include a mixing speed of 100 rpm to 10,000 rpm and a mixing time of 1 hour to 48 hours.

[0014] In one embodiment of the present invention, for the first sintering, the temperature is 250°C to 350°C and the sintering time is 3 hours to 5 hours.

[0015] In one embodiment of the present invention, for the second sintering, the temperature is 200°C to 500°C and the sintering time is 6 hours to 18 hours.

[0016] The present invention also provides a lithium-ion battery including the above cathode material or a cathode material obtained by the above preparation method.

[0017] The present invention also provides an electronic device including the above lithium-ion battery.

Advantages of the Invention

[0018] In summary, the present invention can obtain a halide solid electrolyte with low cost, high ionic conductivity, and high voltage resistance, and proposes a positive electrode material, a preparation method thereof, and an application that can solve the problem of instability at the interface between a high-voltage lithium nickel manganate positive electrode active material and a sulfide solid electrolyte. It is possible to improve the lithium ion conductivity of the positive electrode material while effectively suppressing side reactions between the positive electrode material and the sulfide electrolyte at high voltage. The halide solid electrolyte has good compatibility with the high-voltage lithium nickel manganate positive electrode active material, which can effectively improve ion transport dynamics, thereby improving the rate performance of the battery. Side reactions between the positive electrode material and the sulfide electrolyte at high voltage are effectively suppressed, the instability at the interface between the electrode and the electrolyte is improved, and thereby the stability and cycle performance of the battery are improved.

Brief Description of the Drawings

[0019] To clearly explain the technical solutions of the embodiments of the present invention, the drawings necessary for explaining the embodiments are briefly described below. In particular, the drawings in the following description are merely some embodiments of the present invention. Those skilled in the art can obtain other drawings based on these drawings without creative efforts.

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0021] Embodiments of the present invention will be described below with reference to specific examples. Those skilled in the art can easily understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied by other different specific implementation methods. The details of this specification can also be modified or changed based on different perspectives and applications without departing from the spirit of the present invention.

[0022] It should be understood that the present invention can be implemented in different forms and should not be limited to the embodiments described in this specification. Rather, the embodiments are provided so that the present invention is thorough and complete, and the scope of the present invention is fully conveyed to those skilled in the art. Unless otherwise specified, "%" and "parts" in the following examples respectively mean "mass %" and "parts by mass".

[0023] The technical solution of the present invention will be further described in more detail below with reference to several embodiments and drawings. In particular, the described embodiments are only a part, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts are included within the protection scope of the present invention.

[0024] The present invention proposes a positive electrode material. The positive electrode material includes a positive electrode active material and a coating layer coated on the positive electrode active material, and the positive electrode active material is a high-voltage positive electrode active material. The high-voltage active material is, for example, a lithium nickel manganese oxide positive electrode active material, such as LiNi 0.5 Mn 1.5 O4 and the like are also included. The coating layer contains 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 where 0 < a ≤ 0.5, x = 0 to 6, y = 0 to 6, and x + y ≤ 6. In one embodiment of the present invention, the halide solid electrolyte is, for example, Li 2.3 Zr 0.7 Fe 0.3It is Cl6. In an embodiment, the halide solid electrolyte does not contain rare earth metals, which significantly reduces the cost. The halide solid electrolyte uses iron as a doping element, and the substitution of Fe 3+ in the crystal lattice can improve the ionic conductivity of the halide solid electrolyte while further reducing the cost. At the same time, the halide solid electrolyte is coated on the high-voltage lithium nickel manganate cathode active material, which can effectively suppress the side reaction between the cathode active material and the sulfide electrolyte at high voltage, improve the interfacial stability between the cathode and the solid electrolyte, thereby improving the stability and cycle characteristics of the battery.

[0025] In one embodiment of the present invention, the cathode active material is, for example, in a secondary spherical form or a single crystal form. The median particle size D50 of the cathode active material in the secondary spherical form is 10 μm to 40 μm, and the median particle size D50 of the cathode active material in the single crystal form is 1 μm to 16 μm. The median particle size of the cathode active material is controlled to prevent poor processing performance due to a small particle size or poor electrochemical performance due to a large particle size, thereby simultaneously improving the processing performance and electrochemical performance of the cathode active material.

[0026] In one embodiment of the present invention, in the cathode material, the halide solid electrolyte is uniformly coated on the surface of the cathode active material. To determine the coating amount and coating uniformity of the halide solid electrolyte, the distribution of iron atoms on the surface of the cathode material is measured by an energy-dispersive X-ray analyzer (EDS). In this embodiment, the molar ratio of iron atoms on the surface of the cathode material is, for example, 0.2% to 5%. That is, the halide solid electrolyte has good compatibility with high-voltage lithium nickel 0.5 manganese 1.5 oxide LiNiO4. At the same time, by coating the surface of the cathode active material with a halide solid electrolyte having a high ionic conductivity, the ion transport dynamics can be effectively improved, thereby improving the rate characteristics of the battery.

[0027] Referring to FIG. 1, the present invention also proposes a method for preparing a positive electrode active material. The preparation method includes, but is not limited to, steps S100 to S200.

[0028] Step S100: Based on the chemical formula of the halide solid electrolyte, compounds containing corresponding amounts of Li, Zr, and Fe are mixed, ground, and subjected to a first sintering to obtain the halide solid electrolyte.

[0029] Step S200: Based on the mass ratio, the halide solid electrolyte and the positive electrode active material are blended, and a second sintering is performed to obtain a positive electrode material.

[0030] Referring to FIG. 1, in one embodiment of the present invention, in step S100, based on the chemical formula Li 2+ aZr 1-a Fe a Cl 6-x-y Br x I y of the halide solid electrolyte, compounds containing corresponding molar amounts of Li, Zr, and Fe ions are mixed to obtain a mixture. Then, to obtain the halide solid electrolyte, the mixture is pulverized and subjected to a first sintering. 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 Cl6, and the selected raw materials are, for example, LiCl, ZrCl4, and FeCl3. In this embodiment, various raw materials are mixed, for example, by a ball mill, and the raw materials are uniformly mixed and contacted. Also, the rotation speed of the ball mill is, for example, 400 rpm to 700 rpm, or for example, 500 rpm. The mixing time of the ball mill is, for example, 1.5 hours to 3 hours, or for example, 2 hours. The diameter of the zirconium beads of the ball mill is, for example, 8 mm to 15 mm, or for example, 10 mm. The ball-to-material ratio is, for example, (20 to 30):1, or for example, 30:1.

[0031] Referring to FIG. 1, in one embodiment of the present invention, in step S100, after obtaining the mixture, the mixture is processed by, for example, the ball milling method, the solid-phase sintering method, or the heat eutectic method, and the mixture is prepared by, for example, the pulverization and sintering method. The rotation speed of the pulverization is, for example, 900 rpm to 1200 rpm, or for example, 1000 rpm, and the pulverization time is, for example, 8 hours to 15 hours, or for example, 10 hours. The first sintering is performed on the pulverized mixture to obtain a halide solid electrolyte. The temperature rise rate of the sintering is, for example, 4 ° C / min to 5 ° C / min, the temperature of the first sintering is, for example, 250 ° C to 350 ° C, the sintering time is 3 hours to 5 hours, the sintering atmosphere is, for example, an inert gas, and the sintering time is the time after the temperature rises to the temperature of the first sintering. Through the first sintering process, the crystallinity of the halide solid electrolyte can be improved. After the sintering is completed, the halide solid electrolyte is cooled by furnace cooling. In the halide solid electrolyte, the Fe element is used as a doping element in the present invention, and the isovalent substitution of Fe 3+ in the crystal lattice 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 1 mS / cm or more.

[0032] Referring to FIG. 1, 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 based on the mass ratio. In this embodiment, the mass ratio of the halide solid electrolyte to the positive electrode active material is (0.1 to 1.2):(99.9 to 98.8), or for example 0.4:99.6, 0.6:99.4, 0.7:99.3, 0.8:99.2, or 1:99. During the blending process, the rotation speed of the mixer is, for example, 100 rpm to 10,000 rpm, and the blending time is, for example, 1 hour to 48 hours. Then, a second sintering is performed on the blended halide solid electrolyte and the positive electrode active material. The temperature increase rate of the sintering is, for example, 1 °C / min to 4 °C / min, the temperature of the second sintering is, for example, 200 °C to 500 °C, the sintering time is, for example, 6 hours to 18 hours, the sintering atmosphere is, for example, an inert gas, and the sintering time is the time after the temperature has risen to the temperature of the second sintering. In this embodiment, the positive electrode active material is, for example, LiNi 0.5 Mn 1.5 O4, the positive electrode active material is in a secondary spherical form or a single crystal form, the D50 of the secondary spherical LiNi 0.5 Mn 1.5 O4 is, for example, 5 μm to 40 μm, and the D50 of the single crystal LiNi 0.5 Mn 1.5 O4 is, for example, 1 μm to 16 μm. The obtained positive electrode material was tested by an energy dispersive X-ray analyzer, and it was found that the molar ratio of Fe atoms on the surface was 0.2% to 5%. The second sintering helps the halide solid electrolyte and the lithium nickel manganese oxide positive electrode active material to form a good ion conduction interface. At the same time, in order to avoid the problems of poor interface and low ion conductivity due to insufficient densification of the halide solid electrolyte caused by a low sintering temperature, and to avoid the problem of partial decomposition of the halide solid electrolyte caused by a high sintering temperature, the sintering temperature is controlled, whereby a high-quality positive electrode material can be obtained.

[0033] The present invention also proposes a lithium-ion battery including a positive electrode, a solid electrolyte, and a negative electrode. The solid electrolyte is disposed between the positive electrode and the negative electrode. The solid electrolyte is obtained, for example, by pressing a fast ion conductor into a flat plate and maintaining the pressure for 3 to 8 minutes under a pressure of 0.8 to 1.5 tons. In other embodiments, other preparation methods may be used to obtain the solid electrolyte. In this embodiment, the fast ion conductor is, 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, a conductive agent, etc. The positive electrode material is a positive electrode material coated with a 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 is Li6PS5Cl, and the conductive agent is, for example, conductive carbon black (Super P, SP), carbon nanotube (CNT), carbon fiber (VGCF), graphene, silver powder, or aluminum powder. 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 to 89):(10 to 30):(1 to 5). The positive electrode material, the fast ion conductor, and the conductive agent are ground in a mortar for, for example, 15 to 30 minutes, and then uniformly mixed to obtain a composite positive electrode powder. The composite positive electrode powder is pressed onto the solid electrolyte, and the pressure is maintained for 3 to 8 minutes under a pressure of 0.8 to 1.5 tons, for example, to obtain a positive electrode. The negative electrode is, for example, a metal lithium sheet. The metal lithium sheet is pressed onto the side opposite to the positive electrode of the solid electrolyte, and a all-solid-state lithium-ion battery is obtained by maintaining the pressure under a pressure of 0.1 to 0.2 tons, for example. The assembly process of the all-solid-state lithium-ion battery is completed in a glove box under an argon atmosphere.

[0034] Hereinafter, the present invention will be described with reference to specific examples. The examples are not intended to limit the present invention. Appropriate modifications can be made within the technical scope of the present invention without departing from the gist of the present invention.

[0035] Example 1

[0036] Li 2.3 Zr 0.7Fe 0.3 Cl6 and single crystal LiNi 0.5 Mn 1.5 O4 were placed in a mixer at a mass ratio of 0.6:99.4 for blending. The rotation speed of the mixer was 5000 rpm and the mixing time was 24 hours. Then, the mixed powder was placed in a muffle furnace for sintering. The heating rate was 2 °C / min, the sintering temperature was 350 °C, the sintering time was 12 hours, and the atmosphere was argon. After sintering, a positive electrode material of lithium nickel manganate coated with a halide solid electrolyte was obtained by grinding and sieving. Energy dispersive X-ray analysis test showed that the molar ratio of Fe atoms on the surface of the positive electrode material was 2.4%.

[0037] 50 mg of Li6PS5Cl was obtained, put into a mold, and pressed under a pressure of 1 ton for 5 minutes to form a solid electrolyte. The positive electrode material, Li6PS5Cl, and a conductive carbon black conductive agent were obtained in a mass ratio of 70:29:1 in sequence and added to a mortar, and ground by hand for 20 minutes to obtain a composite positive electrode powder. Then, 10 mg of the composite positive electrode powder was placed on the solid electrolyte, and the pressure was maintained under a pressure of 1 ton for 5 minutes to form a positive electrode. After taking it out, the solid electrolyte was inverted, and a metallic lithium sheet was placed on the side opposite to the positive electrode of the solid electrolyte. The diameter of the metallic lithium sheet was 10 mm, and the pressure was applied up to 0.1 ton and the pressure was maintained to obtain an all-solid-state lithium-ion battery. The assembly process of the all-solid-state lithium-ion battery was completed in a glove box under an argon atmosphere.

[0038] Example 2

[0039] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn 1.5O4 was placed in a mixer at a mass ratio of 0.6:99.4 for blending. The rotation speed of the mixer was 5000 rpm and the blending time was 24 hours. Then, the blended powder was placed in a muffle furnace for sintering. The heating rate was 2 °C / min, the sintering temperature was 350 °C, the sintering time was 12 hours, and the atmosphere was argon. After sintering, a cathode material of lithium nickel manganate coated with a halide solid electrolyte was obtained by grinding and sieving. Energy-dispersive X-ray analysis test showed that the molar ratio of Fe atoms on the surface of the cathode material was 2.2%.

[0040] 50 mg of Li6PS5Cl was obtained, put into a mold, and pressed under a pressure of 1 ton for 5 minutes to form a solid electrolyte. The cathode material, Li6PS5Cl, and a conductive carbon black conductive agent were obtained in sequence based on a mass ratio of 70:29:1 and added to a mortar, and ground by hand for 20 minutes to obtain a composite cathode powder. Then, 10 mg of the composite cathode powder was placed on the solid electrolyte and the pressure was maintained under a pressure of 1 ton for 5 minutes to form a cathode. After taking it out, the solid electrolyte was inverted and a lithium metal sheet was placed on the side opposite to the cathode of the solid electrolyte. The diameter of the lithium metal sheet was 10 mm, and the pressure was increased to 0.1 ton and the pressure was maintained to obtain an all-solid-state lithium-ion battery. The assembly process of the all-solid-state lithium-ion battery was completed in a glove box under an argon atmosphere.

[0041] Example 3

[0042] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and single crystal LiNi 0.5 Mn 1.5 The mass ratio of O4 was set to 0.1:99.9, and the other procedures were the same as in Example 1.

[0043] Example 4

[0044] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn 1.5The mass ratio of O4 was set to 0.1:99.9, and the other procedures were the same as in Example 2.

[0045] Example 5

[0046] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and single crystal LiNi 0.5 Mn 1.5 The mass ratio of O4 was set to 1.2:98.8, and the other procedures were the same as in Example 1.

[0047] Example 6

[0048] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn 1.5 The mass ratio of O4 was set to 1.2:98.8, and the other procedures were the same as in Example 2.

[0049] Comparative Example 1

[0050] Uncoated single crystal LiNi 0.5 Mn 1.5 The energy-dispersive X-ray analysis test of O4 showed that the molar ratio of Fe atoms on the surface was 0%. 50 mg of Li6PS5Cl was obtained, put into a mold, and pressed under a pressure of 1 ton for 5 minutes to form a solid electrolyte. LiNi 0.5 Mn 1.5 O4, Li6PS5Cl, and conductive carbon black were obtained in sequence based on a mass ratio of 70:29:1 and added to a mortar, and ground by hand for 20 minutes to obtain composite cathode powder. Then, 10 mg of the composite cathode powder was placed on the solid electrolyte, and the pressure was maintained under a pressure of 1 ton for 5 minutes to form a cathode. After taking it out, the solid electrolyte was inverted, and a metallic lithium sheet was placed on the side opposite to the cathode of the solid electrolyte. The diameter of the metallic lithium sheet was 10 mm, and pressure was applied up to �.1 ton and the pressure was maintained to obtain an all-solid-state lithium-ion battery. The assembly process of the all-solid-state lithium-ion battery was completed in a glove box under an argon atmosphere.

[0051] Comparative Example 2

[0052] Uncoated polycrystalline LiNi 0.5 Mn 1.5 The energy-dispersive X-ray analysis test of O4 showed that the molar ratio of Fe atoms on the surface was 0%. 50 mg of Li6PS5Cl was obtained, placed in a mold, and pressed under a pressure of 1 ton for 5 minutes to form a solid electrolyte. LiNi 0.5 Mn 1.5 O4, Li6PS5Cl, and conductive carbon black were obtained in sequence based on a mass ratio of 70:29:1 and added to a mortar, and ground by hand for 20 minutes to obtain composite cathode powder. Next, 10 mg of the composite cathode powder was placed on the solid electrolyte, and the pressure was maintained under a pressure of 1 ton for 5 minutes to form a cathode. After taking it out, the solid electrolyte was inverted, and a metallic lithium sheet was placed on the side opposite to the cathode of the solid electrolyte. The diameter of the metallic lithium sheet was 10 mm, and the pressure was applied up to 0.1 ton and the pressure was maintained to obtain an all-solid-state lithium-ion battery. The assembly process of the all-solid-state lithium-ion battery was completed in a glove box under an argon atmosphere.

[0053] Comparative Example 3

[0054] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and single-crystalline LiNi 0.5 Mn 1.5 The mass ratio of O4 was 0.05:99.95, and other procedures were the same as those in Example 1.

[0055] Comparative Example 4

[0056] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn 1.5 The mass ratio of O4 was 0.05:99.95, and other procedures were the same as those in Example 2.

[0057] Comparative Example 5

[0058] Li 2.3 Zr 0.7 Fe0.3 Cl6 and single crystal LiNi 0.5 Mn 1.5 The mass ratio of O4 was set to 10:90, and other procedures were the same as in Example 1.

[0059] Comparative Example 6

[0060] Li 2.3 Zr 0.7 Fe 0.3 Cl6 and polycrystalline LiNi 0.5 Mn 1.5 The mass ratio of O4 was set to 10:90, and other procedures were the same as in Example 2.

[0061] In Examples 1 to 6 and Comparative Examples 1 to 6 of the present invention, different cathode materials were used to fabricate lithium ion batteries. In an environment of 25°C, the above all-solid-state lithium ion batteries were tested using a LAND electrochemical workstation based on the standard method for testing gram capacity and initial Coulomb efficiency. The voltage range was 3.2 to 4.95 V, and the test rate was 0.1C.

[0062] Table 1: Performance test results of lithium ion batteries in Examples 1 to 6 and Comparative Examples 1 to 6

[0063]

Table 1

[0064] Referring to FIGS. 2 to 5, the scanning electron microscope (SEM) images and EDS energy spectrum diagrams of the coated cathode material prepared in Example 2 are shown in FIGS. 2 and 3. As can be seen from FIGS. 2 and 3, after being coated with the halide solid electrolyte, a layer of the coated material containing Fe element appears on the surface, and the layer of the material is not damaged. The scanning electron microscope images and EDS energy spectrum diagrams of the untreated cathode active material in Comparative Example 2 are shown in FIGS. 4 and 5. As can be seen from FIGS. 4 and 5, the surface of the uncoated lithium nickel manganate particles is smooth and does not contain Fe element. Therefore, in the present invention, the halide solid electrolyte can be uniformly coated on the lithium nickel manganate particles without affecting the morphology of the lithium nickel manganate particles.

[0065] As shown in FIG. 1, by comparing Examples 1 to 6 with Comparative Examples 1 to 2, the gram capacity of the lithium-ion battery can be improved by coating with the halide solid electrolyte, and the Coulomb efficiency is improved. That is, the halide solid electrolyte has good compatibility with the high-voltage lithium nickel manganate particles, which can effectively improve the ion transport dynamics, thereby improving the rate performance of the battery. Coating the high-voltage lithium nickel manganate cathode material with the halide solid electrolyte can effectively suppress the side reaction between the cathode material and the sulfide electrolyte at high voltage, improve the interfacial stability between the cathode and the solid electrolyte, and improve the stability and cycle performance of the lithium-ion battery.

[0066] As shown in Table 1, when comparing Examples 1 to 6 with Comparative Examples 3 to 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 improve. Also, when the coating amount is low, side reactions increase, oxygen release from the positive electrode increases, leading to a decrease in the initial Coulomb efficiency. When the coating amount is high, side reactions decrease, oxygen release from the positive electrode decreases, and the initial Coulomb efficiency increases, but the electron conductivity is poor, polarization increases, and thereby the capacity decreases. This indicates that the halide solid electrolyte has high ionic conductivity and high voltage resistance, which can improve the lithium-ion conductivity of the composite positive electrode. Also, controlling the coating amount of the halide solid electrolyte on the surface of the positive electrode active material can simultaneously enhance the capacity and cycle characteristics of the lithium-ion battery.

[0067] The present invention further provides an electronic device. The electronic device includes at least one lithium-ion battery, and the lithium-ion battery is used to provide electrical energy. The electronic device may be a vehicle, a mobile phone, a portable device, a laptop, a ship, a spacecraft, an electric toy, an electric tool, etc. In one embodiment of the present invention, the vehicle may be a new energy vehicle, and the new energy vehicle may be an electric vehicle, a hybrid vehicle, or a range-extended vehicle, etc. The spacecraft may be an aircraft, a rocket, a space shuttle, a spaceship, etc. The electric toy may be a fixed or portable electric toy such as a game console, an electric vehicle toy, an electric ship toy, an electric airplane toy. The electric tool includes metal cutting electric tools, polishing electric tools, assembly electric tools, and railway electric tools such as an electric drill, an electric grinder, an electric wrench, an electric driver, an electric hammer, an impact drill, a concrete vibrator, and a planer. The electronic device includes a lithium-ion battery, and thus includes the advantages of the lithium-ion battery, which will not be repeated here.

[0068] In summary, the present invention proposes a positive electrode material, a method for preparing the same, and an application thereof. Coating a positive electrode active material with a halide solid electrolyte, wherein the halide solid electrolyte contains iron element doping, and a halide solid electrolyte with low cost, high ionic conductivity, and high voltage resistance can be obtained, thereby solving the problem of instability at the interface between a high voltage lithium nickel manganate positive electrode active material and a sulfide solid electrolyte. The lithium ion conductivity of the positive electrode material can be improved, and at the same time, side reactions between the positive electrode material and the sulfide electrolyte at high voltage can be effectively suppressed. The halide solid electrolyte has good compatibility with the high voltage lithium nickel manganate positive electrode active material, which can effectively improve ion transport dynamics, thereby improving the rate performance of the battery. Side reactions between the positive electrode material and the sulfide electrolyte at high voltage can be effectively suppressed, and the interface stability between the electrode and the solid electrolyte is improved, thereby enhancing the stability and cycle performance of the battery.

[0069] The above embodiments are merely examples of preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the scope of the present invention related to this application is not limited to the technical solutions formed by specific combinations of the above technical features, but also includes other technical solutions formed by any combination of the above technical features and their equivalent features without departing from the concept of the present invention, such as technical solutions formed by replacing the above features with features having similar functions disclosed in the present invention.

[0070] The remaining technical features other than those described in this specification are known to those skilled in the art. In order to emphasize the innovative features of the present invention, these remaining technical features are not described in detail here.

Industrial Applicability

[0071] The positive electrode material provided by the present invention is applicable to lithium ion batteries.

Explanation of Reference Signs

[0072] S100, S200: Steps

Claims

1. LiNi ０．５ Mn １．５ O ４ and a positive electrode active material containing A cathode material comprising at least a coating layer coated on the cathode active material and and The coating layer contains 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 to 6, y = 0 to 6, and x + y ≤ 6 a cathode active material.

2. The molar ratio of iron atoms on the surface of the cathode material measured by an energy dispersive X-ray analyzer is 0.2% to 5%, The cathode material according to claim 1.

3. The chemical formula of the halide solid electrolyte is Li ２．３ Zr ０．７ Fe ０．３ Cl ６ as follows. The cathode material according to claim 1.

4. The cathode active material is in a secondary spherical form or a single crystal form, The cathode material according to claim 1.

5. The median particle size D50 of the cathode active material in the secondary spherical form is 10 μm to 40 μm, The cathode material according to claim 4.

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

7. Mixing compounds containing corresponding amounts of Li, Zr, and Fe based on the chemical formula of the halide solid electrolyte, performing polishing, and performing a first sintering to obtain the halide solid electrolyte; Blending the halide solid electrolyte and the cathode active material based on the mass ratio and performing a second sintering to obtain a cathode material which is a lithium nickel manganate material and at least including A method for preparing a cathode material.

8. The mass ratio of the halide solid electrolyte to the cathode active material is (0.1 to 1.2):(99.9 to 98.8), The method for preparing a cathode material according to claim 7.

9. The conditions of the blending include a mixing speed of 100 rpm to 10,000 rpm and a mixing time of 1 hour to 48 hours, The method for preparing a cathode material according to claim 7.

10. For the first sintering, the temperature is 250°C to 350°C and the sintering time is 3 hours to 5 hours, The method for preparing a cathode material according to claim 7.

11. For the second sintering, the temperature is 200°C to 500°C and the sintering time is 6 hours to 18 hours, The method for preparing a cathode material according to claim 7.

12. A lithium ion battery comprising the cathode material according to any one of claims 1 to 6.

13. An electronic device comprising the lithium ion battery according to claim 12 and including an electronic device.

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