Coated Cathode Material, All-Solid-State Battery and Preparation Method Thereof

Abstract

The present invention provides a coated cathode material, an all-solid-state battery and a preparation method thereof, and a supercritical fluid coating device, which includes a high-pressure reaction kettle. A pressure gauge is provided on the high-pressure reaction kettle. One side of the high-pressure reaction kettle is also connected to a high-pressure gas cylinder through a fluid pipeline and a hydraulic pump; an air outlet is provided on the other side of the high-pressure reaction kettle; a mesh drum is arranged inside the high-pressure reaction kettle. The mesh drum is coaxially installed in the high-pressure reaction kettle through a rotating shaft. The mesh drum rotates driven by the rotating shaft, and a material placement cavity is inside the mesh drum. By using the supercritical fluid coating method, the supercritical fluid and the entrainer act synergistically on the surface of the cathode particles to form a coating layer. On the one hand, it can solve the disadvantages that the traditional coating method is difficult to penetrate into the interior of the particles and cannot well coat and protect the internal small particles, etc. On the other hand, it solves the problem that other expensive methods cannot be prepared on a large scale.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state batteries, and particularly relates to a coated cathode material, an all-solid-state battery and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have been widely used in the fields of consumer electronics and power batteries. However, there are still some basic scientific problems in lithium-ion batteries, such as the interface problems between electrodes and electrolytes, and the ion transport problems in multi-scale complex systems, which still need to be explored urgently. At present, commercial lithium-ion batteries mostly use liquid organic electrolytes. However, liquid lithium-ion batteries face various failure problems and manufacturing process challenges, such as the formation and reaction of solid electrolyte interphases, dead lithium and lithium plating, internal short circuit, dissolution of cathode transition metals, oxidation of electrolytes, rapid attenuation of high-temperature performance, corrosion and oxidation of positive and negative current collectors, etc. At the same time, for the current lithium-ion battery material system, liquid organic electrolytes limit the further improvement of energy density, making the development of power batteries close to the limit.

[0003] However, there are incompatible characteristics between solid electrolytes and cathodes, especially high-voltage cathodes such as high-nickel and lithium iron phosphate cathodes. During the cycling process, thick interfacial films are formed on the cathode particles, causing particle cracking, which leads to serious problems such as the peeling off of the entire electrode and battery failure.

[0004] Coating, as a very important and effective method, is widely used in the protection measures of lithium-ion battery cathode materials. On the one hand, it greatly improves the compatibility between lithium-ion battery cathode materials and solid electrolytes. On the other hand, it also prevents the cracking of particles caused by stress-strain and peeling off from the current collector, thus playing a good protective role.

[0005] Therefore, it is very necessary to perform necessary surface coating on the cathode material to protect the particles and form a well-compatible interfacial layer.

[0006] Current coating methods include liquid-phase coating, atomic layer deposition coating and other technologies, but they have disadvantages such as inability to penetrate deep into the particles and difficulty in large-scale production. Summary of the Invention

[0007] In view of the above technical problems, the present invention provides a coated cathode material, an all-solid-state battery and a preparation method thereof. The supercritical fluid coating method is adopted, and the supercritical fluid and the entrainer act synergistically on the surface of the cathode particles to form a coating layer. On the one hand, it can solve the disadvantages of traditional coating methods that are difficult to penetrate deep into the particles and cannot well coat and protect internal small particles. On the other hand, it solves the problem that other expensive methods cannot be prepared on a large scale.

[0008] The specific technical solution is as follows:

[0009] A supercritical fluid coating device includes a high-pressure reaction kettle, on which a pressure gauge is provided. One side of the high-pressure reaction kettle is also connected to a high-pressure gas cylinder through a fluid pipeline and a hydraulic pump; an air outlet is provided on the other side of the high-pressure reaction kettle.

[0010] Inside the high-pressure reaction kettle, there is a mesh drum, which is coaxially installed in the high-pressure reaction kettle through a rotating shaft. The mesh drum rotates driven by the rotating shaft, and the inside of the mesh drum is a material placement cavity.

[0011] The mesh holes of the mesh drum are 600 - 2000 meshes.

[0012] A method for supercritical fluid coating, which uses the cooperation of supercritical fluid and entrainer to act on the surface of the positive electrode particles to form a coating layer.

[0013] The positive electrode material prepared by the above method specifically includes the following steps:

[0014] Step 1: Place the positive electrode material, entrainer, and coating agent in the material placement cavity, and close the high-pressure reaction kettle.

[0015] Among them, the coating agent is a metal or non-metal organic ester such as organic borate, phosphate, titanate, silicate, etc., and the entrainer is a surfactant such as sodium dodecyl sulfate, perfluoroether, laurate, etc.

[0016] In step 1, the positive electrode material is a ternary layered electrode material Li w Ni x Mn y Co z O2 (x + y + z = 1), LiCoO2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiFePO4, LiMnPO4, LiCoPO4, or a mixture of one or more of them.

[0017] Among them, by mass, the positive electrode material is 97 - 99 parts, the coating agent is 1 - 2.9 parts, and the entrainer is 0.1 - 1 part.

[0018] Step 2: Open the high-pressure gas cylinder and pump the gas into the high-pressure reaction kettle. Control the pressure of the high-pressure reaction kettle to be 20 - 80 MPa, carry out the reaction in the sealed high-pressure reaction kettle for 20 min - 10 h, the volume of the supercritical fluid in the high-pressure reaction kettle is 1 / 3 - 2 / 3 of the volume of the high-pressure reaction kettle, and the rotation speed is 5 - 500 rad / min.

[0019] In step 2, the gas is one or more of CO2, CO, NH3, CF4, methanol.

[0020] Step 3: After the reaction is completed, open the outlet on the other side of the high-pressure reactor to release the fluid for recycling.

[0021] Step 4: Open the high-pressure reactor, take out the positive electrode material, and anneal it in an inert gas at 500 - 1000 °C for 30 min - 10 h to obtain the coated positive electrode material.

[0022] The present invention also provides a all-solid-state battery, which includes a positive electrode layer containing the above-mentioned coated positive electrode material, a negative electrode layer containing a negative electrode material, and a solid electrolyte layer. The solid electrolyte layer is located between the positive electrode layer and the negative electrode layer. The manufacturing method includes the following steps:

[0023] Step 1: Mix and stir evenly the above-mentioned coated positive electrode material, conductive agent, electrolyte, binder, and dispersant to prepare a positive electrode paste.

[0024] Step 2: Uniformly coat the prepared positive electrode paste on an aluminum foil with a coating thickness of 50 - 250 μm, place it in a blast drying oven at 60 - 80 °C for drying for 1 - 2 hours, then transfer it to a vacuum drying oven and dry it at 60 - 80 °C for 6 - 12 hours. Cut it into corresponding sizes according to the requirements of the battery size to obtain a positive electrode sheet.

[0025] Step 3: If the negative electrode is pure metallic lithium or a lithium alloy, directly proceed to Step 5;

[0026] Or mix and stir evenly the negative electrode material, conductive agent, electrolyte, binder, and dispersant to prepare a negative electrode paste.

[0027] Step 4: Uniformly coat the prepared negative electrode paste on a copper foil with a coating thickness of 50 - 250 μm, place it in a blast drying oven at 60 - 80 °C for drying for 1 - 2 hours, then transfer it to a vacuum drying oven and dry it at 60 - 80 °C for 6 - 12 hours. Cut it into the size corresponding to the positive electrode sheet to obtain a negative electrode sheet.

[0028] Step 5: Perform hot roll pressing or flat hot pressing on the positive electrode sheet, solid electrolyte, and negative electrode sheet in sequence, and carry out the encapsulation in the form of a battery.

[0029] Among them, in Step 1:

[0030] By mass, the coated positive electrode material is 50 parts - 95 parts;

[0031] The conductive agent is a dispersion of conductive carbon black Super - P, vapor - grown carbon fiber VGCF, single - wall or multi - wall carbon nanotubes; 3 parts - 20 parts;

[0032] The binder is polyvinylidene fluoride, polyvinylidene chloride, polyimide; 1 part - 10 parts;

[0033] The dispersant is one or more of N-methylpyrrolidone, acetonitrile, and dimethyl carbonate; 1 part to 10 parts.

[0034] Among them, in step 3:

[0035] The thickness of the pure lithium metal or lithium alloy is 10 to 200 microns.

[0036] The negative electrode material is graphite, hard carbon, silicon / carbon negative electrode material, or silicon oxide / carbon negative electrode material, or tin-based negative electrode material, in terms of mass parts, 50 parts to 95 parts;

[0037] The conductive agent is a dispersion liquid of conductive carbon black Super-P, vapor-grown carbon fiber VGCF, single-walled or multi-walled carbon nanotubes; 3 parts to 20 parts;

[0038] The binder is one or more of polyvinylidene fluoride, polyvinylidene chloride, polyimide, sodium carboxymethyl cellulose, and styrene-butadiene rubber; 1 part to 10 parts;

[0039] The dispersant is one or more of N-methylpyrrolidone, acetonitrile, dimethyl carbonate, and deionized water; 1 part to 10 parts.

[0040] Among them, in step 5, the pressure of hot rolling or flat hot pressing is 1-100 MPa, and the temperature is 40-200 °C.

[0041] The technical effects of the present invention are:

[0042] A method of forming a coating layer by the synergistic action of supercritical fluid and entrainer on the surface of positive electrode particles. On the one hand, it can solve the shortcomings that traditional coating methods are difficult to penetrate into the interior of particles and cannot well coat and protect internal small particles, and on the other hand, it solves the problems that other expensive methods cannot be prepared on a large scale.

[0043] The provided all-solid-state battery has good interface stability between the solid electrolyte and the positive electrode and has a high energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic structural diagram of the device of the present invention;

[0045] Figure 2 is a schematic structural diagram of the battery in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0046] The specific technical solutions of the present invention are described in combination with embodiments.

[0047] Such as Figure 1As described above, a supercritical fluid coating device includes a high-pressure reaction kettle 1, on which a pressure gauge 2 is provided. One side of the high-pressure reaction kettle 1 is also connected to a high-pressure gas cylinder 8 through a fluid pipeline 6 and a hydraulic pump 7; on the other side of the high-pressure reaction kettle 1, there is an air outlet 9.

[0048] Inside the high-pressure reaction kettle 1, there is a mesh drum 3, which is coaxially installed in the high-pressure reaction kettle 1 through a rotating shaft 5. The mesh drum 3 rotates driven by the rotating shaft 5, and inside the mesh drum 3 is a material placement cavity 4.

[0049] The mesh holes of the mesh drum 3 are 600 - 2000 mesh.

[0050] Example 1

[0051] Step 1: Place the positive electrode material LiFePO4, the entrainer sodium dodecyl sulfonate, and the coating agent triethyl borate in the material placement cavity 4, and close the high-pressure reaction kettle 1.

[0052] Among them, by mass fraction, the positive electrode material is 97 parts, the coating agent is 2 parts, and the entrainer is 1 part.

[0053] Step 2: Open the high-pressure gas cylinder 8 and pump the gas CO2 into the high-pressure reaction kettle 1. Control the pressure of the high-pressure reaction kettle 1 to be 60 MPa, carry out the reaction in the sealed high-pressure reaction kettle 1 for 20 minutes. The volume of the supercritical fluid in the high-pressure reaction kettle 1 is 1 / 2 of the volume of the high-pressure reaction kettle 1, and the rotation speed of the mesh drum 3 is 100 rad / min.

[0054] Step 3: After the reaction is completed, open the air outlet 9 on the other side of the high-pressure reaction kettle 1 to release the fluid for recycling.

[0055] Step 4: Open the high-pressure reaction kettle 1, take out the positive electrode material, anneal it at 600 degrees for 1 hour in an inert gas N2, and then take out the coated positive electrode material for use.

[0056] Such as Figure 2 , a all-solid-state battery includes a positive electrode layer containing the above-coated positive electrode material, a negative electrode layer containing a negative electrode material, and a solid electrolyte layer, and the solid electrolyte layer is located between the positive electrode layer and the negative electrode layer.

[0057] Perform electrochemical tests on the coated positive electrode material obtained in the above Step 4, and the steps are as follows:

[0058] 1) Prepare the slurry: Mix LiFePO4, conductive agent acetylene black, binder PVDF and N-methylpyrrolidone according to a mass ratio of 8:1:1, stir evenly to make an electrode slurry.

[0059] 2) Coating: The prepared electrode slurry was evenly coated on the aluminum foil with a coating thickness of 100 μm, dried in a forced-air drying oven at 80 °C for 2 h, and then transferred to a vacuum oven and dried at 80 °C for 12 h to obtain the LiFePO4 electrode sheet;

[0060] 3) Battery assembly: The LiFePO4 electrode sheet was used as the positive electrode of the coin cell, a 100-μm-thick lithium sheet was used as the negative electrode, and the solid electrolyte membrane LiTFSI / PEO was used as the electrolyte for coin cell assembly;

[0061] 4) Electrochemical performance test: The prepared coin cell was subjected to electrochemical performance test using a LANHE charge-discharge device and a thermostat.

[0062] Example 2

[0063] Step 1: The positive electrode material LiFePO4, the entrainer laurate, and the coating agent tetraethyl titanate were placed in the material placement chamber 4, and the high-pressure reactor 1 was closed.

[0064] Among them, by mass fraction, the proportion of the positive electrode material was 98 parts, the proportion of the coating agent was 1 part, and the proportion of the entrainer was 1 part.

[0065] Step 2: Open the high-pressure gas cylinder 8 to pump the gas CO2 into the high-pressure reactor 1, control the pressure of the high-pressure reactor 1 to be 60 MPa, carry out the reaction in the sealed high-pressure reactor 1 for 30 min, the volume of the supercritical fluid in the high-pressure reactor 1 was 1 / 2 of the volume of the high-pressure reactor 1, and the rotation speed of the mesh drum 3 was 100 rad / min.

[0066] Step 3: After the reaction, open the other gas outlet 9 of the high-pressure reactor 1 to release the fluid for recycling.

[0067] Step 4: Open the high-pressure reactor 1, take out the positive electrode material, anneal it at 600 °C for 1 h in an inert gas N2, and then take out the coated positive electrode material for use.

[0068] A all-solid-state battery includes a positive electrode layer containing the above-coated positive electrode material, a negative electrode layer containing a negative electrode material, and a solid electrolyte layer, and the solid electrolyte layer is located between the positive electrode layer and the negative electrode layer.

[0069] The coated positive electrode material obtained in the above step 4 was subjected to electrochemical testing, and the steps were as follows:

[0070] 1) Slurry preparation: The coated LiFePO4, the conductive agent acetylene black, the binder PVDF were mixed with N-methylpyrrolidone according to a mass ratio of 8:1:1, and stirred evenly to prepare an electrode slurry;

[0071] 2) Coating: The prepared electrode slurry was evenly coated on the aluminum foil with a coating thickness of 100 μm, dried in a forced-air drying oven at 80 °C for 2 h, and then transferred to a vacuum oven and dried at 80 °C for 12 h to obtain the LiFePO4 electrode sheet;

[0072] 3) Battery assembly: The LiFePO4 electrode sheet was used as the positive electrode of the button battery, a 100-μm-thick metallic lithium negative electrode sheet was used as the negative electrode, and the solid electrolyte membrane LiTFSI / PEO was used as the electrolyte for button battery assembly;

[0073] 4) Electrochemical performance test: The prepared button battery was subjected to an electrochemical performance test using a LANHE charge-discharge device and a thermostat.

[0074] Example 3

[0075] Step 1: The positive electrode material LiNi 0.8 Mn 0.1 Co 0.1 O2, the entrainer laurate, and the coating agent tetraethyl titanate were placed in the material placement chamber 4, and the high-pressure reactor 1 was closed.

[0076] Among them, by mass fraction, the proportion of the positive electrode material is 97 parts, the proportion of the coating agent is 2 parts, and the proportion of the entrainer is 1 part.

[0077] Step 2: Open the high-pressure gas cylinder 8 to pump the gas CO2 into the high-pressure reactor 1, control the pressure of the high-pressure reactor 1 to be 60 MPa, carry out the reaction in the sealed high-pressure reactor 1 for 30 min, the volume of the supercritical fluid in the high-pressure reactor 1 is 1 / 2 of the volume of the high-pressure reactor 1, and the rotation speed of the mesh drum 3 is 100 rad / min.

[0078] Step 3: After the reaction is completed, open the other gas outlet 9 of the high-pressure reactor 1 to release the fluid for recycling.

[0079] Step 4: Open the high-pressure reactor 1, take out the positive electrode material, anneal it in an inert gas N2 at 600 °C for 1 h, and then take out the coated positive electrode material for use.

[0080] A all-solid-state battery includes a positive electrode layer containing the above-coated positive electrode material, a negative electrode layer containing a negative electrode material, and a solid electrolyte layer, and the solid electrolyte layer is located between the positive electrode layer and the negative electrode layer.

[0081] The coated positive electrode material obtained in Step 4 above was subjected to an electrochemical test, and the steps are as follows:

[0082] 1) Slurry preparation: The coated positive electrode material LiNi 0.8 Mn 0.1 Co 0.1Mix O2, conductive agent vapor-deposited carbon fiber, binder PVDF and N-methylpyrrolidone, stir evenly to make electrode paste;

[0083] 2) Coating: Uniformly coat the prepared electrode paste on aluminum foil, with a coating thickness of 100 μm, place it in a blast drying oven at 80 °C for 2 h, then transfer it to a vacuum oven and dry it at 80 °C for 12 h to obtain a LiNi 0.8 Mn 0.1 Co 0.1 O2 electrode sheet;

[0084] 3) Battery assembly: Use the LiNi 0.8 Mn 0.1 Co 0.1 O2 electrode sheet as the positive electrode of the button cell, a 100-μm-thick metallic lithium negative electrode sheet as the negative electrode, and a solid electrolyte membrane LiTFSI / PEO as the electrolyte to assemble the button cell;

[0085] 4) Electrochemical performance test: Use a LANHE charge and discharge device and a thermostat to conduct electrochemical performance tests on the prepared button cell.

[0086] Example 4

[0087] Step 1: Place the positive electrode material LiNi 0.8 Mn 0.1 Co 0.1 O2, entrainer sodium dodecyl sulfate, and coating agent triethyl borate in the material placement chamber 4, and close the autoclave 1.

[0088] Among them, by mass, the proportion of the positive electrode material is 97 parts, the proportion of the coating agent is 2 parts, and the proportion of the entrainer is 1 part.

[0089] Step 2: Open the high-pressure gas cylinder 8 and pump the gas CO2 into the autoclave 1, control the pressure of the autoclave 1 to be 60 MPa, carry out the reaction in the sealed autoclave 1 for 20 min, the volume of the supercritical fluid in the autoclave 1 is 1 / 2 of the volume of the autoclave 1, and the rotation speed of the mesh drum 3 is 100 rad / min.

[0090] Step 3: After the reaction is completed, open the other gas outlet 9 of the autoclave 1 to release the fluid for recycling.

[0091] Step 4: Open the autoclave 1, take out the positive electrode material, anneal it at 600 °C for 1 h in an inert gas N2, and then take out the coated positive electrode material for use.

[0092] A all-solid-state battery, comprising a positive electrode layer containing the above-coated positive electrode material, a negative electrode layer containing a negative electrode material, and a solid electrolyte layer, the solid electrolyte layer being located between the positive electrode layer and the negative electrode layer.

[0093] Perform electrochemical tests on the coated positive electrode material obtained in step 4 above, and the steps are as follows:

[0094] 1) Slurry preparation: Mix LiNi 0.8 Mn 0.1 Co 0.1 O2, conductive agent acetylene black, binder PVDF and N-methylpyrrolidone in a mass ratio of 8:1:1, stir evenly to make an electrode slurry;

[0095] 2) Coating: Uniformly coat the prepared electrode slurry on aluminum foil, with a coating thickness of 100 μm, place it in a forced-air drying oven at 80 °C for 2 h, then transfer it to a vacuum oven and dry it at 80 °C for 12 h to obtain a LiNi 0.8 Mn 0.1 Co 0.1 O2 electrode sheet;

[0096] 3) Battery assembly: Use the LiNi 0.8 Mn 0.1 Co 0.1 O2 electrode sheet as the positive electrode of a coin cell, a 100-μm-thick lithium sheet as the negative electrode, and a solid electrolyte membrane LiTFSI / PEO as the electrolyte to assemble a coin cell;

[0097] 4) Electrochemical performance test: Use a LANHE charge-discharge device and a thermostat to perform electrochemical performance tests on the prepared coin cell.

[0098] Comparative Example 1

[0099] Use uncoated LiFePO4 for electrochemical tests, and the steps are as follows:

[0100] 1) Slurry preparation: Mix LiFePO4, conductive agent acetylene black, binder PVDF and N-methylpyrrolidone in a mass ratio of 8:1:1, stir evenly to make an electrode slurry;

[0101] 2) Coating: Uniformly coat the prepared electrode slurry on aluminum foil, with a coating thickness of 100 μm, place it in a forced-air drying oven at 80 °C for 2 h, then transfer it to a vacuum oven and dry it at 80 °C for 12 h to obtain a LiFePO4 electrode sheet;

[0102] 3) Battery assembly: Use the LiFePO4 electrode sheet as the positive electrode of a coin cell, a 100-μm-thick lithium sheet as the negative electrode, and a solid electrolyte membrane LiTFSI / PEO as the electrolyte to assemble a coin cell;

[0103] 4) Electrochemical performance test: Use the LANHE charge-discharge equipment and the constant temperature box to conduct the electrochemical performance test on the prepared button cell.

[0104] Comparative Example 2

[0105] Use uncoated LiNi 0.8 Mn 0.1 Co 0.1 O2 for electrochemical testing, the steps are as follows:

[0106] 1) Slurry preparation: Mix LiNi 0.8 Mn 0.1 Co 0.1 O2, conductive agent acetylene black, binder PVDF and N-methylpyrrolidone, stir evenly to make the electrode slurry;

[0107] 2) Coating: Uniformly coat the prepared electrode slurry on the aluminum foil, with a coating thickness of 100 μm, place it in a blast drying oven at 80 °C for 2 h, and then transfer it to a vacuum oven and dry it at 80 °C for 12 h to obtain the LiNi 0.8 Mn 0.1 Co 0.1 O2 electrode sheet;

[0108] 3) Battery assembly: Use the LiNi 0.8 Mn 0.1 Co 0.1 O2 electrode sheet as the positive electrode of the button cell, a 100-μm-thick lithium sheet as the negative electrode, and the solid electrolyte membrane LiTFSI / PEO as the electrolyte to assemble the button cell;

[0109] 4) Electrochemical performance test: Use the LANHE charge-discharge equipment and the constant temperature box to conduct the electrochemical performance test on the prepared button cell.

[0110] Comparative Example 3 has no entraining agent

[0111] Step 1: Place the positive electrode material LiNi 0.8 Mn 0.1 Co 0.1 O2 and the coating agent triethyl borate in the material placement chamber 4, and close the high-pressure reactor 1.

[0112] Among them, according to the mass parts, the proportion of the positive electrode material is 98 parts, and the proportion of the coating agent is 2 parts.

[0113] Step 2: Open the high-pressure gas cylinder 8 and pump CO2 gas into the high-pressure reactor 1. Control the pressure of the high-pressure reactor 1 to be 60 MPa, and carry out the reaction in the sealed high-pressure reactor 1 for 20 minutes. The volume of the supercritical fluid in the high-pressure reactor 1 is 1 / 2 of the volume of the high-pressure reactor 1, and the rotation speed of the mesh drum 3 is 100 rad / min.

[0114] Step 3: After the reaction is completed, open the other gas outlet 9 of the high-pressure reactor 1 to release the fluid for recycling.

[0115] Step 4: Open the high-pressure reactor 1, take out the positive electrode material, anneal it in an inert gas N2 at 600 degrees for 1 hour, and then take out the coated positive electrode material for use.

[0116] A all-solid-state battery includes a positive electrode layer containing the above-mentioned coated positive electrode material, a negative electrode layer containing a negative electrode material, and a solid electrolyte layer, and the solid electrolyte layer is located between the positive electrode layer and the negative electrode layer.

[0117] Perform electrochemical tests on the coated positive electrode material obtained in Step 4 above, and the steps are as follows:

[0118] 1) Slurry preparation: Mix LiNi 0.8 Mn 0.1 Co 0.1 O2, conductive agent acetylene black, binder PVDF and N-methylpyrrolidone, and stir evenly to make an electrode slurry;

[0119] 2) Coating: Uniformly coat the prepared electrode slurry on the aluminum foil, with a coating thickness of 100 μm, place it in a blast drying oven at 80 °C for 2 hours, and then transfer it to a vacuum oven and dry it at 80 °C for 12 hours to obtain a LiNi 0.8 Mn 0.1 Co 0.1 O2 electrode sheet;

[0120] 3) Battery assembly: Assemble a coin cell with the LiNi 0.8 Mn 0.1 Co 0.1 O2 electrode sheet as the positive electrode of the coin cell, a 100-μm-thick lithium sheet as the negative electrode, and a solid electrolyte membrane LiTFSI / PEO as the electrolyte;

[0121] 4) Electrochemical performance test: Use a LANHE charge-discharge device and a thermostat to perform electrochemical performance tests on the prepared coin cell.

[0122] The test results are shown in Table 1:

[0123] Table 1

[0124]

[0125] Judging from the experimental results, after coating, both the discharge capacity and the cycle capacity retention rate have been greatly improved. Comparative Example 3 is without a carrying agent. Although the performance has been improved compared with that without coating, there is still a significant gap compared with the examples, indicating the importance of the synergistic effect of the carrying agent and the coating process.

Claims

1. A method for preparing a coated cathode material, characterized in that, An ultra-critical fluid coating device is adopted, and the ultra-critical fluid and the entrainer cooperate to enable the coating agent to act on the surface of the cathode particles to form a coating layer. Among them, the coating agent is one or a mixture of organic borate, phosphate, titanate, and silicate; by mass, the cathode material is 97-99 parts, the coating agent is 1-2.9 parts, and the entrainer is 0.1-1 part. The ultra-critical fluid coating device includes a high-pressure reaction kettle (1). A pressure gauge (2) is provided on the high-pressure reaction kettle (1). One side of the high-pressure reaction kettle (1) is also connected to a high-pressure gas cylinder (8) through a fluid pipeline (6) and a hydraulic pump (7); an air outlet (9) is provided on the other side of the high-pressure reaction kettle (1); a mesh drum (3) is arranged inside the high-pressure reaction kettle (1). The mesh drum (3) is coaxially installed in the high-pressure reaction kettle (1) through a rotating shaft (5). The mesh drum (3) rotates driven by the rotating shaft (5). Inside the mesh drum (3) is a material placement cavity (4), and the cathode material, entrainer, and coating agent are placed in the material placement cavity (4).

2. The method for preparing a coated cathode material according to claim 1, characterized in that, The mesh holes of the mesh drum (3) are 600-2000 meshes.

3. The method for preparing a coated cathode material according to any one of claims 1 or 2, characterized in that, The preparation steps are as follows: Step 1: Place the cathode material, entrainer, and coating agent in the material placement cavity (4), and close the high-pressure reaction kettle (1). Step 2: Open the high-pressure gas cylinder (8) to pump gas into the high-pressure reaction kettle (1). Control the pressure of the high-pressure reaction kettle (1) to be 20-80 MPa. React in the sealed high-pressure reaction kettle (1) for 20 min - 10 h. The volume of the ultra-critical fluid in the high-pressure reaction kettle (1) is 1 / 3 - 2 / 3 of the volume of the high-pressure reaction kettle (1), and the rotation speed of the mesh drum (3) is 5 - 500 rad / min. Step 3: After the reaction is completed, open the air outlet (9) on the other side of the high-pressure reaction kettle (1) to release the fluid for recycling. Step 4: Open the high-pressure reaction kettle (1), take out the cathode material, and anneal it in an inert gas at 500 - 1000 °C for 30 min - 10 h to obtain the coated cathode material.

4. The method for preparing a coated cathode material according to claim 3, characterized in that, The entrainer is a surfactant; the positive electrode material is a ternary layered electrode material Li w Ni x Mn y Co z O2, LiCoO2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiFePO4, LiMnPO4, LiCoPO4, or a mixture of one or more of them, where x + y + z = 1.

5. The method for preparing a coated cathode material according to claim 3, characterized in that, In Step 2, the gas is one or several of CO2, CO, NH3, CF4, and methanol.

6. A all-solid-state battery, characterized in that, It includes a cathode layer containing the coated cathode material, a negative electrode layer containing the negative electrode material, and a solid electrolyte layer. The solid electrolyte layer is located between the cathode layer and the negative electrode layer; the coated cathode material is obtained by the preparation method described in any one of Claims 1 to 5.

7. A method for preparing an all-solid-state battery, characterized in that, It includes the following steps: Step 1: Mix the coated cathode material obtained by the preparation method described in any one of Claims 1 to 5 with a conductive agent, an electrolyte, a binder, and a dispersant and stir evenly to prepare a cathode electrode slurry; Step 2: Uniformly coat the prepared cathode electrode slurry on an aluminum foil with a coating thickness of 50 to 250 microns, place it in a forced-air drying oven at 60 to 80 °C and dry for 1 to 2 hours, then transfer it to a vacuum drying oven and dry at 60 to 80 °C for 6 to 12 hours, and cut it into corresponding sizes according to the battery size requirements to obtain a cathode electrode sheet; Step 3: The anode is pure metallic lithium or a lithium alloy with a thickness of 10 to 200 microns, and directly proceed to Step 5; or mix the anode material, a conductive agent, an electrolyte, a binder, and a dispersant and stir evenly to prepare an anode electrode slurry; Step 4: Uniformly coat the prepared anode electrode slurry on a copper foil with a coating thickness of 50 to 250 microns, place it in a forced-air drying oven at 60 to 80 °C and dry for 1 to 2 hours, then transfer it to a vacuum drying oven and dry at 60 to 80 °C for 6 to 12 hours, and cut it into the corresponding size of the cathode sheet to obtain an anode electrode sheet; Step 5: Hot roll or flat hot press the cathode electrode sheet, the solid electrolyte, and the anode electrode sheet in sequence, with a pressure of 1 - 100 MPa and a temperature of 40 - 200 °C; to form a battery-type package.

8. The method for preparing an all-solid-state battery according to claim 7, characterized in that, In Step 1, by mass fraction, the coated cathode material is 50 parts to 95 parts; the conductive agent is a dispersion of conductive carbon black Super-P, vapor-grown carbon fiber VGCF, single-walled or multi-walled carbon nanotubes; 3 parts to 20 parts; the binder is polyvinylidene fluoride, polyvinylidene chloride, polyimide; 1 part to 10 parts; the dispersant is one or more of N-methylpyrrolidone, acetonitrile, dimethyl carbonate; 1 part to 10 parts.

9. The method for preparing an all-solid-state battery according to claim 7, characterized in that, In Step 3, the anode material is graphite, hard carbon, silicon / carbon anode material, or silicon oxide / carbon anode material, or tin-based anode material, by mass fraction, 50 parts to 95 parts; the conductive agent is a dispersion of conductive carbon black Super-P, vapor-grown carbon fiber VGCF, single-walled or multi-walled carbon nanotubes; 3 parts to 20 parts; the binder is one or more of polyvinylidene fluoride, polyvinylidene chloride, polyimide, sodium carboxymethyl cellulose, styrene-butadiene rubber; 1 part to 10 parts; the dispersant is one or more of N-methylpyrrolidone, acetonitrile, dimethyl carbonate, deionized water; 1 part to 10 parts.

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