Halide solid electrolyte-coated modified positive electrode material and preparation method

Abstract

The present application relates to the field of cobaltate positive electrode materials, and particularly relates to a halide solid electrolyte coated modified positive electrode material, a preparation method thereof and a lithium ion battery. The halide solid electrolyte coated modified positive electrode material comprises a base and a coating layer, the base comprises a lithium cobaltate base, and the coating layer comprises a halide solid electrolyte. The halide solid electrolyte coated modified positive electrode material can protect the lithium cobaltate base, improve the conduction efficiency of electrons and ions in the outer coating layer, and thus improve the specific capacity of the lithium ion battery, while effectively slowing down the harmful phase change in the high-voltage charging and discharging process, slowing down the dissolution of cobalt, and improving the cycle stability of the battery at high voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cobaltate cathode materials, in particular to a halide solid electrolyte coated modified cathode material and a preparation method thereof. BACKGROUND

[0002] With the progress of society and the development of economy, electronic products have gradually become indispensable consumer goods in everyone's hands. However, with the further integration and high energy consumption of consumer electronics, the requirements for batteries, especially cobalt lithium batteries, are becoming higher and higher. The actual available specific capacity of cobalt lithium cathode material is much lower than its theoretical specific capacity. Therefore, improving the actual available specific capacity of cobalt lithium material is of great significance to promote the development and further research of consumer electronics.

[0003] Nowadays, the reasons for the accelerated degradation of high-voltage cobalt lithium materials can be roughly divided into two categories: one is that more lithium extraction-embedding amount causes more serious crystal structure changes of cobalt lithium; the other is that high application cutoff voltage can aggravate the interface side reaction between the electrode material and the electrolyte. Therefore, improving the structural stability of high-voltage cobalt lithium and reducing the interface side reaction are technical problems that need to be focused on for cobalt lithium batteries. SUMMARY

[0004] In order to solve the above problems, the present application provides a halide solid electrolyte coated modified cathode material, which comprises a substrate and a coating layer, the substrate comprises a lithium cobaltate substrate; the coating layer comprises a halide solid electrolyte.

[0005] The cathode material provided in the present application uses halide solid electrolyte as coating layer material, which not only effectively blocks the direct contact between lithium cobaltate cathode material and electrolyte under high lithium extraction state, reduces the occurrence of side reactions, and improves the surface structure stability of lithium cobaltate material; but also improves the conductivity of electrons and ions, and improves the electrochemical performance of lithium ion battery.

[0006] As a preferred scheme, the molecular formula of the lithium cobaltate substrate is Li 1-x Co 1-y M (x+y) / n O2, wherein 0≤x+y≤0.05, M is a metal element, the valence state of M is 1-5, and n is the valence of M element; wherein the metal element M in the lithium cobaltate substrate is selected from at least one of Al, Mg, Ti, Sn, V, Zr, Cr, Mn, Ni, Fe, Ga, Mo, Sb, W, Y, La and Nb.

[0007] As a preferred scheme, the metal element M is at least one of Mg, Al, Ti and Ni.

[0008] As a preferred embodiment, the metal element M is Mg or Al.

[0009] As a preferred embodiment, the molecular formula of the halide solid electrolyte is Li. z AE 4+z Wherein, A is a tetravalent metal, preferably, A is Zr and / or Ti; E is at least one of F, Cl, and Br; and 1.5 ≤ z ≤ 2.5.

[0010] As a preferred embodiment, A is Zr and Ti, with a molar ratio of 0.5-1:0-0.5.

[0011] As a preferred embodiment, A is Zr and Ti, with a molar ratio of 0.5:0.5.

[0012] As a preferred embodiment, the weight ratio of the lithium cobalt oxide matrix to the halide solid electrolyte is 1:(0.0005~0.05).

[0013] As a preferred embodiment, the coating layer further includes a second coating material, which is selected from at least one oxide, hydroxide, or inorganic salt containing elements Al, Mg, Ti, Sn, V, Cu, Zn, Zr, Cr, Li, Mn, Ni, Fe, Ga, Co, Mo, Sb, W, Y, La, and Nb.

[0014] The combined effect of halide solid electrolyte and second coating material can not only further reduce the occurrence of side reactions between cathode material and electrolyte and enhance the stability of matrix structure, but also endow cathode material with good electronic and ionic conductivity, reduce the occurrence of lithium-poor phenomenon at the cathode material and electrolyte interface, and thus improve the specific capacity and cycle performance of lithium-ion battery under high voltage.

[0015] As a preferred embodiment, the second coating material is at least one oxide containing elements of Al, Mg, Ti, Sn, V, Cu, Zn, Zr, Cr, Li, Mn, Ni, Fe, Ga, Co, Mo, Sb, W, Y, La and Nb.

[0016] As a preferred embodiment, the second coating material contains at least one of Al, Ti, Y, and Zr oxides.

[0017] As a preferred embodiment, the weight ratio of the halide solid electrolyte to the second coating material in the coating layer is (0.05-5):1.

[0018] As a preferred embodiment, the mass ratio of the lithium cobalt oxide matrix, the halide solid electrolyte, and the second coating material is (95-98.5):(0.5-4):1.

[0019] As a preferred embodiment, the mass ratio of the lithium cobalt oxide matrix, the halide solid electrolyte, and the second coating material is (97-98.5):(0.5-2):1.

[0020] In this application, when the mass ratio of lithium cobalt oxide matrix, halide solid electrolyte, and second coating material is (97-98.5):(0.5-2):1, while satisfying the coating properties, the combined effect of the three can effectively reduce interfacial side reactions between the matrix material and the electrolyte, improve the overall structural stability, and improve the coulombic efficiency and cycle performance of the lithium-ion battery.

[0021] As a preferred embodiment, the cathode material satisfies at least one of the following conditions:

[0022] (1) The particle size of the matrix is ​​1 to 55 μm;

[0023] (2) The thickness of the coating layer of the positive electrode material is 5 to 500 nm;

[0024] (3) The tap density of the positive electrode material is 2.5–3.5 g / cm³. 3 ;

[0025] (4) The compaction density of the positive electrode material is 3-5 g / cm³. 3 ;

[0026] (5) The specific surface area of ​​the positive electrode material is 0.15–0.25 m². 2 / g.

[0027] In this application, the tap density and compaction density of the cathode material are relatively high, not less than 2.5 and 3 g / cm³, respectively. 3 This lays a solid foundation for improving the energy density of cathode materials and is also of great significance for the lightweight design of batteries.

[0028] A second aspect of the present invention provides a method for preparing the above-mentioned halide solid electrolyte coated and modified cathode material, comprising the following steps:

[0029] (1) Under an inert atmosphere, LiE and AE4 were mixed and ball-milled to obtain a halide solid electrolyte;

[0030] (2) After mixing the substrate and the coating material, solid-state sintering is performed to obtain the cathode material.

[0031] As a preferred embodiment, the preparation method of the halide solid electrolyte coated and modified cathode material includes the following steps:

[0032] (1) Under an inert atmosphere, LiE and AE4 are mixed evenly and manually ground for 20-30 min. Then, the mixture is intermittently ball-milled at 400-600 r / min for 36-72 hours to obtain halide solid electrolyte powder.

[0033] (2) Mix the lithium cobalt oxide matrix, solid electrolyte powder, and second coating material in proportion and mix them in a high-speed mixing device at 600-1000 r / min for 20-60 min until uniform. After uniform mixing, place the mixture in a small sagger and sinter it using solid-state sintering method. Raise the temperature to 400-650℃ at a rate of 1-10℃ / min and hold it at that temperature for 1-5 hours. Then raise the temperature to 700-1000℃ and hold it at that temperature for 4-12 hours. After naturally cooling to room temperature, take it out and grind it manually for 5-10 min. Then pass it through a 300-500 mesh sieve to obtain the final product.

[0034] As a preferred embodiment, the heating rate in the solid-state sintering is 2-5℃ / min, the temperature is raised to 500-600℃ and held for 1-3 hours, and then raised to 700-900℃ and held for 6-10 hours.

[0035] A third aspect of the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator and an electrolyte located between the positive electrode and the negative electrode, characterized in that the positive electrode comprises a positive electrode material modified by the above-mentioned halide solid electrolyte coating.

[0036] Beneficial effects:

[0037] 1. This application provides a halide solid electrolyte-coated modified cathode material. By adding a halide solid electrolyte as a coating layer material, it not only effectively reduces interfacial side reactions between the matrix material and the electrolyte, improving the surface structural stability of the LCO material, but also improves electron and ion conduction, thereby enhancing the electrochemical performance of the lithium-ion battery. Furthermore, when the coating layer simultaneously contains a halide solid electrolyte and a second coating material, the specific capacity and cycle performance of the lithium-ion battery can be further improved.

[0038] 2. The method for preparing the cathode material provided in this application is simple and easy to implement, and has the potential for large-scale application. Furthermore, as shown in the examples, the lithium-ion battery provided in this application achieves an initial coulombic efficiency of 92.64%, and retains more than 88% of its efficiency after 50 cycles at 45°C. Attached Figure Description

[0039] Figure 1 This is an SEM image of the product sample from Example 1 of this application.

[0040] Figure 2 This is an SEM image of the product sample from Example 2 of this application.

[0041] Figure 3 This is an SEM image of the product sample from Example 3 of this application.

[0042] Figure 4 This is an SEM image of the product sample from Example 4 of this application.

[0043] Figure 5 This is a SEM image of the product sample of Comparative Example 1 of this application.

[0044] Figure 6 This is a SEM image of the product sample of Comparative Example 2 of this application.

[0045] Figure 7 This is a SEM image of the product sample of Comparative Example 3 of this application.

[0046] Figure 8 The high-temperature cycling performance curves for the embodiments and comparative examples of this application are shown; the test temperature is 45°C, the test voltage is 3.0 to 4.6V, and the charge / discharge rate is 1.0C. Detailed Implementation

[0047] Example 1

[0048] Example 1 provides a cathode material modified with halide solid electrolyte coating. The cathode material includes a matrix and a coating layer. The matrix is ​​a lithium cobalt oxide matrix, and the coating layer includes a halide solid electrolyte and a second coating material.

[0049] The lithium cobalt oxide matrix is ​​a Mg-doped lithium cobalt oxide matrix with the structural formula Li. 0.98 CoMg 0.01 O2.

[0050] The halide solid electrolyte is Li₂Zr 0.5 Ti 0.5 Cl6 solid powder.

[0051] The second coating material is Al2O3.

[0052] The above-mentioned cathode material preparation steps include: (1) under argon atmosphere protection, anhydrous LiCl, anhydrous ZrCl4, and anhydrous TiCl4 are mixed in a molar ratio of 2:0.5:0.5 and manually ground for 20 min, and then ball-milled intermittently at 500 r / min for 48 h to obtain halide solid electrolyte; (2) the obtained halide solid electrolyte powder is added to the second coating material and the lithium cobalt oxide matrix in a mass ratio of 0.5:1:98.5 and placed in a high-speed mixing device. Mix at 800r / min for 30min until uniform, then place in a small 80*80*60mm sagger, and further place the small sagger in the center of a large 330*330*100mm sagger and fix it. Sinter using solid-state sintering method, raise the temperature to 500℃ at a rate of 3℃ / min and hold for 2h, then raise it to 800℃ and hold for 8h to carry out the reaction; (3) After the reaction is completed, cool naturally to room temperature and then take it out and grind manually for 7min, and pass it through a 300 mesh sieve to obtain the product.

[0053] During the intermittent ball milling process, the intermittent ball milling pattern is as follows: 5 minutes of forward rotation, 5 minutes of intermittent rotation, 5 minutes of reverse rotation, and 5 minutes of intermittent rotation.

[0054] The overall structural formula of the obtained cathode material is Li 0.98 CoM g0.01 O2·Al2O3·Li2Zr 0.5 Ti 0.5 Cl6.

[0055] Example 2

[0056] Example 2 provides a cathode material modified with a halide solid electrolyte coating. The cathode material includes a matrix and a coating layer. The matrix is ​​a lithium cobalt oxide matrix, and the coating layer includes a halide solid electrolyte and a second coating material.

[0057] The lithium cobalt oxide matrix is ​​an Al-doped lithium cobalt oxide matrix with the structural formula Li. 0.95 CoAl 0.05 / 3 O2.

[0058] The halide solid electrolyte is Li₂Zr 0.8 Ti 0.2 F6 solid powder.

[0059] The second coating material is TiO2.

[0060] The above-mentioned cathode material preparation steps include: (1) under argon atmosphere protection, anhydrous LiF, anhydrous ZrF4, and anhydrous TiF4 are mixed in a molar ratio of 2:0.8:0.2 and manually ground for 25 min, and then ball-milled intermittently at 450 r / min for 60 h to obtain halide solid electrolyte; (2) the obtained halide solid electrolyte powder is added to the second coating material and the lithium cobalt oxide matrix in a mass ratio of 2:1:97 and placed in a high-speed mixing device. Mix at 900r / min for 25min until uniform, then place in a small 80*80*60mm sagger, and further place the small sagger in the center of the large sagger and fix it. Sinter using solid-state sintering method, raise the temperature to 600℃ at a rate of 5℃ / min and hold for 1.5h, then raise to 700℃ and hold for 9.5h to carry out the reaction; (3) After the reaction is completed, cool naturally to room temperature and then take it out and grind manually for 5min, and pass through a 300 mesh sieve to obtain the product.

[0061] During the intermittent ball milling process, the intermittent ball milling pattern is as follows: 5 minutes of forward rotation, 5 minutes of intermittent rotation, 5 minutes of reverse rotation, and 5 minutes of intermittent rotation.

[0062] The overall structural formula of the obtained cathode material is Li 0.95 CoAl 0.05 / 3 O2·TiO2·Li2Zr 0.8 Ti 0.2 F6.

[0063] Example 3

[0064] Example 3 provides a cathode material modified with halide solid electrolyte coating. The cathode material includes a matrix and a coating layer. The matrix is ​​a lithium cobalt oxide matrix, and the coating layer includes a halide solid electrolyte and a second coating material.

[0065] The lithium cobalt oxide matrix is ​​a lithium cobalt oxide matrix doped with Ti, and its structural formula is Li. 0.98 CoTi 0.005 O2.

[0066] The halide solid electrolyte is Li 2.5 ZrBr 6.5 Solid powder.

[0067] The second coating material is Y2O3.

[0068] The above-mentioned cathode material preparation steps include: (1) under argon atmosphere protection, anhydrous LiBr and anhydrous ZrBr4 are mixed at a molar ratio of 2.5:1 and manually ground for 30 min, then ball milled intermittently at 550 r / min for 40 h to obtain halide solid electrolyte; (2) the obtained halide solid electrolyte powder is added to the second coating material and lithium cobalt oxide matrix at a mass ratio of 4:1:95, and placed in a high-speed mixing device at 700 r / min. Mix for 50 minutes until homogeneous, then place in a small 80*80*60mm sagger, and further place the small sagger in the center of a large 330*330*100mm sagger and fix it. Sinter using solid-state sintering method, raise the temperature to 400℃ at a rate of 7℃ / min and hold for 3 hours, then raise it to 800℃ and hold for 8 hours to carry out the reaction; (3) After the reaction is completed, cool naturally to room temperature and then take it out and grind manually for 5 minutes, and pass it through a 300-mesh sieve to obtain the product.

[0069] During the intermittent ball milling process, the intermittent ball milling pattern is as follows: 5 minutes of forward rotation, 5 minutes of intermittent rotation, 5 minutes of reverse rotation, and 5 minutes of intermittent rotation.

[0070] The overall structural formula of the obtained cathode material is Li 0.98 CoTi 0.005 O2·Y2O3·Li 2.5 ZrBr 6.5 .

[0071] Example 4

[0072] Example 4 provides a cathode material modified with halide solid electrolyte coating. The cathode material includes a matrix and a coating layer. The matrix is ​​a lithium cobalt oxide matrix, and the coating layer includes a halide solid electrolyte and a second coating material.

[0073] The lithium cobalt oxide matrix is ​​a Ni-doped lithium cobalt oxide matrix with the structural formula Li. 0.98 CoNi 0.01 O2.

[0074] The halide solid electrolyte is Li 1.5 Zr 0.5 Ti 0.5 Cl 5.5 Solid powder.

[0075] The second coating material is ZrO2.

[0076] The above-mentioned cathode material preparation steps include: (1) under argon atmosphere protection, LiCl, anhydrous ZrCl4, and anhydrous TiCl4 are mixed in a molar ratio of 1.5:0.5:0.5 and manually ground for 25 min, then ball milled intermittently at 500 r / min for 48 h to obtain halide solid electrolyte; (2) the obtained halide solid electrolyte powder is added to the second coating material and the lithium cobalt oxide matrix in a mass ratio of 1:1:98, and placed in a high-speed mixing device at 8 Mix at 00r / min for 30min until uniform, then place in a small 80*80*60mm sagger, and further place the small sagger in the center of a large 330*330*100mm sagger and fix it. Sinter using solid-state sintering method, raise the temperature to 500℃ at a rate of 3℃ / min and hold for 2h, then raise it to 900℃ and hold for 6h to carry out the reaction; (3) After the reaction is completed, cool naturally to room temperature and then take it out and grind manually for 5min, and pass it through a 300 mesh sieve to obtain the product.

[0077] During the intermittent ball milling process, the intermittent ball milling pattern is as follows: 5 minutes of forward rotation, 5 minutes of intermittent rotation, 5 minutes of reverse rotation, and 5 minutes of intermittent rotation.

[0078] The overall structural formula of the obtained cathode material is Li 0.98 CoNi 0.01 O2·ZrO2·Li 1.5 Zr 0.5 Ti 0.5 Cl 5.5 .

[0079] Comparative Example 1

[0080] Comparative Example 1 provides a non-halogenated solid electrolyte coated modified cathode material. The cathode material includes a matrix and a coating layer. The matrix is ​​a lithium cobalt oxide matrix, and the coating layer is a second coating material.

[0081] The lithium cobalt oxide matrix is ​​a Mg-doped lithium cobalt oxide matrix with the structural formula Li. 0.98 CoMg 0.01 O2.

[0082] The second coating material is Al2O3.

[0083] The above-mentioned cathode material preparation steps include: adding the second coating material and the lithium cobalt oxide matrix in a mass ratio of 1:99, and placing them in a high-speed mixing device to mix at 800r / min for 30min until uniform. Then, placing them in a small 80*80*60mm sagger and further placing the small sagger in the center of a large 330*330*100mm sagger and fixing it. Sintering is carried out by solid-state sintering, raising the temperature to 500℃ at a rate of 3℃ / min and holding it at that temperature for 2h, and then raising it to 800℃ and holding it at that temperature for 8h to carry out the reaction; (3) After the reaction is completed, after naturally cooling to room temperature, take it out and manually grind it for 5min, and pass it through a 300-mesh sieve to obtain the product.

[0084] During the intermittent ball milling process, the intermittent ball milling pattern is as follows: 5 minutes of forward rotation, 5 minutes of intermittent rotation, 5 minutes of reverse rotation, and 5 minutes of intermittent rotation.

[0085] The overall structural formula of the obtained cathode material is Li 0.98 CoMg 0.01 O2·Al2O3.

[0086] Comparative Example 2

[0087] Comparative Example 2 provides a non-halide solid electrolyte coated modified cathode material. The cathode material includes a matrix and a coating layer. The matrix is ​​a lithium cobalt oxide matrix, and the coating layer includes a second coating material and an oxide solid electrolyte.

[0088] The lithium cobalt oxide matrix is ​​a Y-doped lithium cobalt oxide matrix with the structural formula Li. 0.97 CoY 0.01 O2.

[0089] The oxide solid electrolyte is Li 3.3 La 0.56 TiO3.

[0090] The second coating material is TiO2.

[0091] The above-mentioned positive electrode material preparation steps include: adding the second coating material, oxide solid electrolyte and lithium cobalt oxide matrix in a mass ratio of 0.5:1:98.5, and placing them in a high-speed mixing device to mix at 800r / min for 30min until uniform. Then, placing them in a small 80*80*60mm sagger and further placing the small sagger in the center of a large 330*330*100mm sagger and fixing it. Sintering is carried out by solid-state sintering, raising the temperature to 500℃ at a rate of 3℃ / min and holding it at that temperature for 2h, and then raising it to 800℃ and holding it at that temperature for 8h to carry out the reaction; (3) After the reaction is completed, after naturally cooling to room temperature, take it out and manually grind it for 5min, and pass it through a 300-mesh sieve to obtain the product.

[0092] During the intermittent ball milling process, the intermittent ball milling pattern is as follows: 5 minutes of forward rotation, 5 minutes of intermittent rotation, 5 minutes of reverse rotation, and 5 minutes of intermittent rotation.

[0093] The overall structural formula of the obtained cathode material is Li 0.97 CoY 0.01 O2·TiO2·Li 3.3 La 0.56 TiO3.

[0094] Comparative Example 3

[0095] Comparative Example 3 provides a non-halide solid electrolyte coated modified cathode material. The cathode material includes a matrix and a coating layer. The matrix is ​​a lithium cobalt oxide matrix, and the coating layer includes a second coating material and a sulfide solid electrolyte.

[0096] The lithium cobalt oxide matrix is ​​an Al-doped lithium cobalt oxide matrix with the structural formula Li. 0.97 CoAl 0.01 O2.

[0097] The sulfide solid electrolyte is Li2S-P2S5.

[0098] The second coating material is La2O3.

[0099] The above-mentioned positive electrode material preparation steps include: adding the second coating material, sulfide solid electrolyte and lithium cobalt oxide matrix in a mass ratio of 0.5:1:98.5, and placing them in a high-speed mixing device to mix at 800r / min for 30min until uniform. Then, placing them in a small 80*80*60mm sagger and further placing the small sagger in the center of a large 330*330*100mm sagger and fixing it. Sintering is carried out by solid-state sintering, raising the temperature to 500℃ at a rate of 3℃ / min and holding it at that temperature for 2h, and then raising it to 800℃ and holding it at that temperature for 8h to carry out the reaction; (3) After the reaction is completed, after naturally cooling to room temperature, take it out and manually grind it for 5min, and pass it through a 300-mesh sieve to obtain the product.

[0100] During the intermittent ball milling process, the intermittent ball milling pattern is as follows: 5 minutes of forward rotation, 5 minutes of intermittent rotation, 5 minutes of reverse rotation, and 5 minutes of intermittent rotation.

[0101] The overall structural formula of the obtained cathode material is Li 0.97 CoAl 0.01 O2·La2O3·Li2S-P2S5.

[0102] Performance Evaluation

[0103] Preparation of lithium-ion half-cells: The lithium cobalt oxide positive electrode material obtained in the examples and comparative examples was uniformly mixed with conductive agent acetylene black (Super P) and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1. The mixture was then prepared into a slurry using N-methylpyrrolidone (NMP), uniformly coated onto aluminum foil, vacuum dried, pressed into sheets, and cut into positive electrode sheets of the required size. The lithium-ion battery is assembled from the above-mentioned positive electrode sheet, lithium negative electrode, separator between the positive and negative electrodes, and electrolyte. The assembled battery was used for capacity testing and cycle testing.

[0104] Table 1

[0105]

[0106] By comparing the SEM images of samples from Examples 1-4 and Comparative Examples 1-3, it can be seen that the surface coating of lithium cobalt oxide modified with halide solid electrolyte coating is more dense and uniform, and less prone to peeling off. In contrast, the coating on the surface of the materials in the comparative examples is more porous and easily peels off, which is detrimental to the improvement of the performance of lithium cobalt oxide materials.

[0107] Examples 1-4, Comparative Examples 1-3, and Table 1 show that after coating the lithium cobalt oxide cathode material with a halide solid electrolyte and a second coating material, the formation of the coating layer effectively blocks the direct contact between lithium cobalt oxide and the electrolyte in the high delithiation state, reduces the occurrence of side reactions, and improves the surface structure stability of the lithium cobalt oxide material. Moreover, compared with coating with sulfide and oxide solid electrolytes, the interaction between the halide solid electrolyte and lithium ions is weaker, and it has a faster lithium ion conduction capacity, which improves the electron and ion conduction on the surface of the lithium cobalt oxide cathode material, increases the specific capacity of the lithium cobalt oxide battery, and can effectively slow down the harmful phase transition during high-voltage charging and discharging, slow down cobalt dissolution, and improve the cycle stability of lithium cobalt oxide under high voltage.

Claims

1. A cathode material modified with halide solid electrolyte coating, characterized in that, The positive electrode material includes a matrix and a coating layer, wherein the matrix includes a lithium cobalt oxide matrix; and the coating layer includes a halide solid electrolyte. The molecular formula of the lithium cobalt oxide matrix is ​​Li 1-x Co 1-y M (x+y) / n O2, where 0≤x+y≤0.05, M is a metallic element with a valence state of 1~5, and n is the valence of element M; wherein, the metallic element M in the lithium cobalt oxide matrix is ​​selected from at least one of Al, Mg, Ti, Sn, V, Zr, Cr, Mn, Ni, Fe, Ga, Mo, Sb, W, Y, La and Nb; The molecular formula of the halide solid electrolyte is Li z AE 4+z Wherein, A is a tetravalent metal, A is Zr and / or Ti; E is at least one of F, Cl, and Br; and 1.5 ≤ z ≤ 2.

5. The weight ratio of the lithium cobalt oxide matrix to the halide solid electrolyte is 1:(0.0005~0.05). The coating layer further includes a second coating material, which is selected from at least one of oxides, hydroxides or inorganic salts containing elements Al, Mg, Ti, Sn, V, Cu, Zn, Zr, Cr, Li, Mn, Ni, Fe, Ga, Co, Mo, Sb, W, Y, La and Nb. The weight ratio of the halide solid electrolyte to the second coating material in the coating layer is (0.05~5):1; The cathode material satisfies at least one of the following conditions: (1) The particle size of the matrix is ​​1~55μm; (2) The thickness of the coating layer of the positive electrode material is 5~500nm; (3) The tap density of the positive electrode material is 2.5~3.5 g / cm³. 3 ; (4) The compaction density of the positive electrode material is 3~5 g / cm³. 3 ; (5) The specific surface area of ​​the positive electrode material is 0.15~0.25m². 2 / g.

2. A method for preparing a halide solid electrolyte coated and modified cathode material according to claim 1, characterized in that, Includes the following steps: (1) Under an inert atmosphere, LiE and AE4 were mixed and ball-milled to obtain a halide solid electrolyte; (2) After mixing the substrate and the coating material, solid-state sintering is performed to obtain the cathode material.

3. The method for preparing the halide solid electrolyte coated and modified cathode material according to claim 2, characterized in that: The heating rate during solid-state sintering is 1~10℃ / min, the temperature is raised to 400~650℃ and held for 1~5 hours, and then raised to 700~1000℃ and held for 4~12 hours.

4. A lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator and an electrolyte located between the positive electrode and the negative electrode, characterized in that, The positive electrode comprises the halide solid electrolyte coated and modified positive electrode material as described in claim 1.

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