Composite solid electrolyte as well as preparation method and application thereof

Abstract

The invention provides a composite solid-state electrolyte. The composite solid-state electrolyte has a multi-coating structure. The composite solid-state electrolyte comprises a solid-state electrolyte serving as a core; a lithium salt layer is compounded on the surface of the solid electrolyte; a calcium phosphate layer and a mesoporous silica shell layer are arranged on the surface of the lithium salt layer; the solid-state battery prepared from the composite solid-state electrolyte provided by the invention has high ion mobility and interface compatibility, and can give consideration to both safety performance and cycle performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a composite solid electrolyte and a preparation method and application thereof. Background Art

[0002] With the increasingly serious environmental damage caused by global economic development, people are increasingly aware of the importance of ecological protection. Therefore, clean and renewable solar energy, wind energy, tidal energy, etc. have been vigorously developed. The continuous improvement of the energy structure has also driven the research and development of high-energy and high-power energy storage devices. Due to the advantages of high operating voltage, high specific energy, and long cycle life, lithium-ion batteries (LIBs) have been widely used in portable electronic devices and automobiles. However, due to the serious safety hazards of the liquid electrolyte used, such as flammability, explosion, leakage, and corrosion. In order to solve the safety hazards of liquid electrolytes in lithium-ion batteries, researchers have begun to study solid electrolytes. The application of solid electrolytes can not only solve safety problems, but also apply metal lithium, which has good matching properties, to batteries, which can further improve the energy density of batteries.

[0003] At present, the research on solid electrolytes is mainly focused on two categories: polymers and inorganic solid electrolytes. Among them, inorganic solid electrolytes have high electrical conductivity, are dense inside, and have greatly reduced grain boundary blocking effects. However, inorganic solid electrolytes have low electrical conductivity, low interfacial lithium ion migration numbers, a lithium or sodium depleted space charge layer formed due to the huge chemical potential difference between ceramics and electrode materials, and the common phenomenon of interface deterioration caused by element mutual diffusion and / or reactivity, making it difficult to simultaneously take into account the requirements of safety performance and cycle performance. At present, research on solid-state battery issues has achieved remarkable results, but there are still many key issues to be resolved, including the optimization of the solid-solid interface, and further modification of the interface of the solid-state battery to achieve high ion mobility and interface compatibility based on the interface problem.

[0004] Therefore, providing a solid-state battery with high ion mobility and interface compatibility becomes a problem to be solved. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a composite solid electrolyte and a preparation method and application thereof. The solid-state battery prepared by the composite solid electrolyte provided by the present invention has high ion mobility and interface compatibility, and can take into account both safety performance and cycle performance.

[0006] The present invention provides a composite solid electrolyte, wherein the composite solid electrolyte presents a multi-coating structure, and comprises, from the inside to the outside:

[0007] Solid electrolytes;

[0008] A lithium salt layer coated on the surface of the solid electrolyte;

[0009] A calcium phosphate layer coated on the surface of the lithium salt layer;

[0010] Mesoporous silica layer coated on the surface of the calcium phosphate layer

[0011] Preferably, the size of the solid electrolyte is 100 to 800 nm, and may be 100, 200, 300, 400, 500, 600, 700, 800, or any value between 100 and 800 nm;

[0012] The pore size of the mesopores of the mesoporous silica shell layer is 2 to 50 nm, and can be 2, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or any value between 2 and 50 nm.

[0013] The present invention also provides a method for preparing a composite solid electrolyte, comprising the following steps:

[0014] A) modifying the solid electrolyte with an amino compound to obtain an amino-functionalized solid electrolyte;

[0015] B) mixing the amino-functionalized solid electrolyte with an organic carbon aqueous solution for heating reaction, and calcining the heating reaction product under vacuum conditions to obtain a carbon-coated solid electrolyte;

[0016] C) mixing the carbon-coated solid electrolyte, a silane coupling agent, a silicon source, a mesoporous template agent, aqueous ammonia and ethanol for a first reaction to obtain a solid electrolyte sequentially coated with a carbon layer and a mesoporous silica layer;

[0017] D) calcining a solid electrolyte coated with a carbon layer and a mesoporous silica layer in sequence under air conditions to obtain a solid electrolyte with a cavity formed by removing the carbon layer;

[0018] E) mixing a lithium salt solution containing phosphate radicals with a solid electrolyte having a cavity formed by removing the carbon layer, and drying the mixture to obtain a solid electrolyte containing a lithium salt containing phosphate radicals in the cavity;

[0019] F) mixing a solid electrolyte of a lithium salt containing phosphate radicals in the cavity, a calcium source compound and water to react to obtain a composite solid electrolyte having a first coating layer of a lithium salt layer, a second coating layer of a calcium phosphate layer and a third coating layer of a mesoporous silica layer.

[0020] Preferably, the solid electrolyte is selected from NASICON type solid electrolyte Li 1+x Al x Ti 2-x(PO4)3, 0≤x<1, Garnet-type solid electrolyte Li 3x La 2 / 3-x TiO3, Li 7-x LqCy 2-x M x O 12 , M is one or more of Nb, Al or Ta, 0≤x<1, and the particle size D50 of the solid electrolyte is 200nm~500nm.

[0021] Preferably, the amino compound is selected from N-(2-hydroxyethyl)caprolactam (MEHA), diethanolamine (DEA), methyldiethanolamine (MDEA), tetraethylenepentamine (TEPA), 3-aminopropyltrimethoxysilane (APS);

[0022] The ratio of the solid electrolyte to the amino compound is 5 g: 1 to 4 mol;

[0023] The modification time is 12 to 24 hours.

[0024] Preferably, in step B), the organic carbon is selected from one or more of glucose, fructose and citric acid;

[0025] The heating reaction temperature is 100-250°C and the time is 5-10h;

[0026] The calcination temperature is 500-1000°C and the calcination time is 1-4h;

[0027] The mass percentage of the organic carbon in the solid electrolyte is 5% to 15%.

[0028] Preferably, in step C), the silane coupling agent is one or more of aminoethylaminopropyl polydimethylsiloxane, KH550 and KH560, and the amount of the coupling agent is 1 to 5 wt% of the solid electrolyte;

[0029] The silicon source is one or more of ethyl orthosilicate, methyl orthosilicate and tetraethoxysilane, and the amount of the silicon source is 3-8 wt % of the solid electrolyte.

[0030] The mesoporous template agent is one or more of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and polyvinylpyrrolidone, and the amount of the mesoporous template agent is 0.2-1wt% of the solid electrolyte;

[0031] The reaction time is 1 to 2 hours.

[0032] Preferably, in step D), the calcination temperature is 500-800° C. and the calcination time is 3-8 hours.

[0033] Preferably, in step E), the lithium salt containing phosphate is one or more of lithium phosphate, lithium dihydrogen phosphate, lithium phosphite and lithium hypophosphite, and the mass of the lithium salt containing phosphate is 0.5-2wt% of the solid electrolyte.

[0034] Preferably, in step F), the calcium source compound is selected from one or more of calcium chloride, calcium nitrate and calcium iodide.

[0035] The present invention also provides a positive electrode material, comprising: a positive electrode material matrix and a first atomic deposition layer and a second atomic deposition layer sequentially compounded on the surface of the positive electrode material matrix, wherein the first atomic deposition layer is obtained by atomic layer deposition of the above-mentioned composite solid electrolyte, and the second atomic deposition layer is obtained by atomic layer deposition of a water source.

[0036] Preferably, the cathode material matrix is ​​LiMn2O4, LiCoO2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiFePO4, Li3V2(PO4)3, LiMn x Fe 1-x PO4, where 0≤x≤1, LiVOPO4, LiNiPO4, LiNi 0.5 Mn 1.5 O4、Li x V2O4, wherein 0<x<2, one or more of LiCoPO4, LiNiO2, LiNiO.

[0037] The present invention also provides a method for preparing the above-mentioned positive electrode material, comprising the following steps:

[0038] The composite solid electrolyte is introduced into the vacuum reaction chamber to perform a first atomic layer deposition on the cathode material substrate, and then nitrogen is purged to obtain a cathode material composited with the first atomic deposition layer;

[0039] After introducing a water source to perform a second atomic layer deposition on the positive electrode material composited with the first atomic deposition layer, nitrogen is purged to obtain the positive electrode material.

[0040] Preferably, the temperature of the composite solid electrolyte is 80-90° C., and the time for the first atomic layer deposition is 2-3 s;

[0041] The temperature of the water source was 25°C, and the time for the second atomic layer deposition was 1 to 2 s;

[0042] The temperature in the vacuum reaction chamber is 220-250°C;

[0043] The nozzle temperature of the vacuum reaction chamber is 170-180°C.

[0044] The present invention also provides a lithium ion battery comprising the above-mentioned positive electrode material.

[0045] Compared with the prior art, the present invention provides a composite solid electrolyte, which has a multi-layer coating structure, and includes, from the inside to the outside, a solid electrolyte; a lithium salt layer coated on the surface of the solid electrolyte; a calcium phosphate layer coated on the surface of the lithium salt layer; and a mesoporous silica layer coated on the surface of the calcium phosphate layer. The composite solid electrolyte provided by the present invention has a multiple coating structure, which enhances the large surface area / pore volume of the mesoporous shell, can increase more space to promote the conduction of lithium ions, and can also provide a certain buffer space. The solid electrolyte shell provided by the present invention is mesoporous silica, which helps the solid electrolyte to be better compatible with other materials, optimizes the interface performance, and at the same time inhibits the expansion and contraction of the solid electrolyte to a certain extent, maintaining its stable performance. At the same time, the mesopores of silica are used to increase the specific area of ​​its surface, increase more lithium ion adsorption sites, and improve the energy density of the battery. The solid electrolyte surface has lithium salt, which can be processed simply to achieve the effect of pre-lithiation, and also provide a stable carrier for lithium ions, reduce the side reaction at the interface and reduce the interface impedance, and also make up for the lithium ions consumed by the construction of the CEI film during the cycle, effectively improving the energy storage per unit volume or mass, and meeting the demand for high energy density of modern electronic devices. The composite solid electrolyte provided by the present invention, wherein the calcium phosphate deposited on the surface of the lithium salt layer can be used as a blocking layer inside the mesoporous silica shell layer, can effectively prevent the internal lithium ion leakage, thereby achieving loading and blocking, and increasing the ionic conductivity and lithium transfer number. At the same time, under open circuit conditions, the interface resistance value is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram of the structure of the composite solid electrolyte provided by the present invention;

[0047] Figure 2 This is a transmission electron microscopy image of the composite solid electrolyte prepared in Example 1. DETAILED DESCRIPTION

[0048] The present invention provides a composite solid electrolyte, wherein the composite solid electrolyte has a multi-coating structure, comprising:

[0049] Solid electrolytes;

[0050] A lithium salt layer coated on the surface of the solid electrolyte;

[0051] A calcium phosphate layer coated on the surface of the lithium salt layer;

[0052] Mesoporous silica layer coated on the surface of the calcium phosphate layer

[0053] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of the composite solid electrolyte provided by the present invention.

[0054] The composite solid electrolyte provided by the present invention has a multi-coating structure, including a core, wherein the core is a solid electrolyte. The solid electrolyte is selected from a NASICON type solid electrolyte Li 1+x Al x Ti 2-x (PO4)3, 0≤x<1, Garnet-type solid electrolyte Li 3x La 2 / 3-x TiO3, Li 7-x Ln3Z 2-x M x O 12 , M is one or more of Nb, Al or Ta, 0≤x<1, and the particle size D50 of the solid electrolyte is 200nm~500nm, which can be 200, 250, 300, 350, 400, 450, 500, or any value between 200nm and 500nm.

[0055] A lithium salt layer is composited on the surface of the solid electrolyte, and the thickness of the lithium salt layer is 10 to 500 nm, which can be 10, 50, 70, 100, 120, 150, 170, 200, 220, 250, 270, 300, 320, 350, 370, 400, 420, 450, 470, 500, or any value between 10 and 500 nm, and the lithium salt is selected from one or more of lithium chloride, lithium nitrate and lithium iodide.

[0056] The composite solid electrolyte provided by the present invention also includes a mesoporous silica shell layer, the thickness of the mesoporous silica shell layer is 5 to 100 nm, and can be 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or any value between 5 and 100 nm. The pore size of the mesopore is 2 to 50 nm, and can be 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or any value between 2 and 50 nm.

[0057] The composite solid electrolyte provided by the present invention deposits a calcium phosphate layer on the surface of the lithium salt layer. The thickness of the calcium phosphate layer is 5 to 100 nm, and can be 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or any value between 5 and 100 nm.

[0058] The present invention also provides a method for preparing the composite solid electrolyte, comprising the following steps:

[0059] A) modifying the solid electrolyte with an amino compound to obtain an amino-functionalized solid electrolyte;

[0060] B) mixing the amino-functionalized solid electrolyte with an organic carbon aqueous solution for heating reaction, and calcining the heating reaction product under vacuum conditions to obtain a carbon-coated solid electrolyte;

[0061] C) mixing the carbon-coated solid electrolyte, a silane coupling agent, a silicon source, a mesoporous template agent, aqueous ammonia and ethanol for a first reaction to obtain a solid electrolyte sequentially coated with a carbon layer and a mesoporous silica layer;

[0062] D) calcining a solid electrolyte coated with a carbon layer and a mesoporous silica layer in sequence in air to obtain a solid electrolyte with a cavity formed by removing the carbon layer;

[0063] E) mixing a lithium salt solution containing phosphate radicals with a solid electrolyte having a cavity formed by removing the carbon layer, and drying the mixture to obtain a solid electrolyte containing a lithium salt containing phosphate radicals in the cavity;

[0064] F) mixing a solid electrolyte containing a lithium salt containing phosphate in the cavity, a calcium source compound and water for a second reaction to obtain a composite solid electrolyte having a first coating layer of a lithium salt layer, a second coating layer of a calcium phosphate layer and a third coating layer of a mesoporous silica layer.

[0065] The present invention first prepares an amino-functionalized solid electrolyte. The present invention selects solid electrolyte powder, and by selectively modifying the powder surface with an amino shell, the compatibility between the solid electrolyte surface and the organic carbon source can be improved, while the adsorption capacity of the organic carbon source is enhanced, so that they can interact more effectively. Specifically, the solid electrolyte, the amino compound and the methanol solution are mixed and stirred, and then the solvent is removed to obtain the amino-functionalized solid electrolyte.

[0066] The solid electrolyte selected in the present invention is an inorganic solid electrolyte powder that is resistant to high temperatures and has high ionic conductivity at room temperature. The solid electrolyte is selected from NASICON solid electrolyte Li 1+x Al x Ti 2-x (PO4)3, 0≤x<1, Garnet-type solid electrolyte Li 3x La 2 / 3-x TiO3, Li 7-x Ln3Z 2-x M x O 12 , M is one or more of Nb, Al or Ta, 0≤x<1, and the particle size D50 of the solid electrolyte is 200nm~500nm.

[0067] The amino compound is selected from one of N-(2-hydroxyethyl)caprolactam (MEHA), diethanolamine (DEA), methyldiethanolamine (MDEA), tetraethylenepentamine (TEPA), and 3-aminopropyltrimethoxysilane (APS);

[0068] The ratio of the solid electrolyte to the amino compound is 5g:(1-4)mol, which can be 5g:1mol, 5g:1.5mol, 5g:2mol, 5g:2.5mol, 5g:3mol, 5g:3.5mol, 5g:4mol, or any value between 5g:(1-4)mol.

[0069] The ratio of the solid electrolyte to the methanol solution is 5g:(10-80)ml, which can be 5g:10ml, 5g:20ml, 5g:30ml, 5g:40ml, 5g:50ml, 5g:60ml, 5g:70ml, 5g:80ml, or any value between 5g:(10-80)ml.

[0070] The modification time, i.e. the mixing and stirring time, is 12 to 24 hours, and can be 12, 15, 18, 21, 24, or any value between 12 and 24 hours.

[0071] After the surface of the solid electrolyte is amino treated, the functional groups and the carboxyl or hydroxyl groups of the organic carbon material form chemical bonds, which enhances the adsorption capacity of the organic carbon material and is beneficial to the uniformity of the dispersion of the carbon source on the powder surface.

[0072] Next, the amino-functionalized solid electrolyte is mixed with an organic carbon aqueous solution and heated in a sealed high-pressure sterilizer for reaction, and then the heated reaction product is calcined under vacuum conditions to obtain a carbon-coated amino-functionalized solid electrolyte (SE@C).

[0073] The organic carbon in the organic carbon aqueous solution is selected from one or more of glucose, fructose and citric acid. The mass percentage of the organic carbon in the solid electrolyte is 5% to 15%, which can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any value between 5% and 15%.

[0074] Organic carbon is used to coat the solid electrolyte, which is formed into nanocapsules after high-temperature carbonization. There is a huge cavity between the core and the shell, which enhances the large surface area / pore volume of the mesoporous shell and is beneficial to the diffusion of anions and cations. At the same time, the cavity structure can provide more space for the deposition of lithium salts and calcium phosphate layers, forming a dense coating layer.

[0075] The temperature of the heating reaction is 100-250° C., which can be 100, 150, 200, 250, or any value between 100 and 250° C., and the time is 5-10 hours, which can be 5, 6, 7, 8, 9, 10, or any value between 5 and 10 hours.

[0076] After the heating reaction, the obtained reactant is separated by filtration, washed with water and ethanol, and then calcined.

[0077] The calcination temperature is 500-1000° C., and can be 500, 600, 700, 800, 900, 1000, or any value between 500 and 1000° C. The calcination time is 1-4 hours, and can be 1, 2, 3, 4, or any value between 1 and 4 hours.

[0078] Then, the carbon-coated solid electrolyte, silane coupling agent, silicon source, mesoporous template agent, ammonia water and ethanol are mixed to carry out a first reaction to obtain a solid electrolyte sequentially coated with a carbon layer and a mesoporous silicon dioxide layer.

[0079] The present invention selects mesoporous silica to form a coating layer on the outermost layer of the solid electrolyte, and utilizes its core-shell structure, high specific surface area inner cavity skeleton structure and particles, and nanopores on the surface that are connected to the inner cavity and are similar to ion channels to promote the rapid migration of lithium ions and improve the stability and safety of the material.

[0080] The silane coupling agent is one or more of aminoethylaminopropyl polydimethylsiloxane (AEAPS), KH550 and KH560, and the coupling agent is 1-5wt% of the solid electrolyte, which can be 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, or any value between 1-5wt%;

[0081] The silicon source is one or more of tetraethyl orthosilicate (TEOS), methyl orthosilicate (TMOS) and tetraethoxysilane (TEOSS), and the amount of the silicon source is 3-8wt% of the solid electrolyte, which can be 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt% or any value between 3wt% and 8wt%;

[0082] The mesoporous template agent is one or more of hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), and polyvinylpyrrolidone (PVP), and the amount of the mesoporous template agent is 0.2-1wt% of the solid electrolyte, which can be 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, or any value between 0.2-1wt%;

[0083] The ratio of the solid electrolyte (unaminated) to ethanol is 5g:100-200ml, and can be 5g:100ml, 5g:120ml, 5g:150ml, 5g:160ml, 5g:180ml, 5g:200ml, or any value between 5g:100-200ml.

[0084] The ammonia water is 28% ammonia water. The ratio of the solid electrolyte (unaminated) to the ammonia water is 5g:1-4ml, which can be 5g:1ml, 5g:2ml, 5g:3ml, 5g:4ml, or any value between 5g:1-4ml.

[0085] The time of the first reaction is 1 to 2 hours. The temperature of the reaction is room temperature. In the present invention, the room temperature is defined as 25±5° C. Preferably, magnetic stirring is performed during the reaction.

[0086] The solid electrolyte (SE@C@mSiO2) sequentially coated with a carbon layer and a mesoporous silica layer was washed with water and then dried, and then calcined under air conditions to obtain a solid electrolyte with a cavity formed by removing the carbon layer.

[0087] The calcination temperature is 500-800°C, and can be 500, 600, 700, 800, or any value between 500-800°C, and the calcination time is 3-8h, and can be 3, 4, 5, 6, 7, 8, or any value between 3-8h. During the calcination, the mesoporous template is also removed.

[0088] A lithium salt solution containing phosphate radicals is mixed with a solid electrolyte with a cavity formed by removing a carbon layer, and then dried to obtain a solid electrolyte containing lithium salts containing phosphate radicals in the cavity.

[0089] The present invention introduces lithium phosphate into the solid electrolyte. Since the size of lithium ions is only 0.1-10nm, which is smaller than the size of the mesoporous channel, lithium ions can smoothly pass through the mesoporous channel and enter the inner cavity of the capsule to achieve the effect of pre-lithiation.

[0090] Specifically, a lithium salt containing phosphate is dissolved in ethanol, and then a solid electrolyte with a cavity formed by removing the carbon layer is added and mixed, and ultrasonic dissolution is continued. The sample is placed in an oscillating constant temperature water bath for 12 to 24 hours, and then the obtained sample is placed in an oven for drying to obtain a solid electrolyte with a lithium salt containing phosphate in the cavity.

[0091] Wherein, the lithium salt containing phosphate is one or more of lithium phosphate, lithium dihydrogen phosphate, lithium phosphite and lithium hypophosphite, and the mass of the lithium salt containing phosphate is 0.5-2wt% of the solid electrolyte, which can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, or any value between 0.5 and 2wt%.

[0092] Finally, the solid electrolyte of lithium salt containing phosphate in the cavity, the calcium source compound and water are mixed for a second reaction to obtain a composite solid electrolyte having a first coating layer of a lithium salt layer, a second coating layer of a calcium phosphate layer and a third coating layer of a mesoporous silica layer.

[0093] The present invention selects the surface of the lithium salt layer of the calcium phosphate deposition coating layer. When calcium ions are added, the calcium ions can be more strongly combined with phosphate radicals to form calcium phosphate, which effectively prevents the leakage of lithium ions inside the capsule, thereby achieving loading and blocking.

[0094] Specifically, the solid electrolyte containing lithium salt of phosphate in the cavity is dissolved in ultrapure water, and then a calcium source compound is added dropwise under stirring, and the reaction is carried out under continuous stirring to obtain a reaction product. The calcium source compound is selected from one or more of calcium chloride, calcium nitrate and calcium iodide. The selected stirring speed is 100 to 300 rpm.

[0095] 1 ml of a calcium source compound with a concentration of 0.01-0.06 mol / ml was added dropwise under low-speed stirring, and the above steps were repeated 5 to 10 times, and stirring was continued for 12 hours. The obtained reaction product was placed in an oven for drying to obtain a composite solid electrolyte (SE-Li + @CaP@mSiO2).

[0096] The present invention first subjects the solid electrolyte to amino treatment, and then sequentially prepares a carbon layer and a silicon dioxide layer, and then removes the carbon layer by heat treatment to manufacture a hollow silicon dioxide shell containing a solid electrolyte core. Due to the presence of voids in the hollow shell, and the electrostatic attraction between the negatively charged oxygen ions in the solid electrolyte and the lithium ions of the lithium salt, adsorption can also be generated between them through Lewis acid-base interaction. Free lithium ions are adsorbed on the surface of the solid electrolyte to form a lithium salt layer, achieving the function of pre-lithiation. Calcium phosphate is deposited on the surface of the lithium salt, effectively preventing the leakage of lithium ions, thereby achieving loading and blocking of the porous silicon dioxide shell, and strengthening the pre-lithiation effect. The mesoporous silicon dioxide layer acts as a physical barrier, and can also alleviate the interface stability caused by the volume expansion of the solid electrolyte during the cycle and improve the conductivity of the solid electrolyte.

[0097] The present invention also provides a positive electrode material, comprising: a positive electrode material matrix and a first atomic deposition layer and a second atomic deposition layer sequentially compounded on the surface of the positive electrode material matrix, wherein the first atomic deposition layer is obtained by atomic layer deposition of the above-mentioned composite solid electrolyte, and the second atomic deposition layer is obtained by atomic layer deposition of a water source.

[0098] Wherein, the positive electrode material matrix is ​​LiMn2O4, LiCoO2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiFePO4, Li3V2(PO4)3, LiMn x Fe 1-x PO4, where 0≤x≤1, LiVOPO4, LiNiPO4, LiNi 0.5 Mn 1.5 O4、Li x V2O4, wherein 0<x<2, one or more of LiCoPO4, LiNiO2, LiNiO.

[0099] The composite solid electrolyte provided by the present invention is preferably applied to the positive electrode coating, which can optimize the interface compatibility between the positive electrode material and the solid electrolyte, reduce the side reaction between the positive electrode material and the electrolyte, inhibit the dissolution of the transition metal of the positive electrode material, and ensure that the positive electrode exerts good electrochemical performance, thereby improving the capacity, rate performance and cycle life of the battery.

[0100] The present invention also provides a method for preparing the above-mentioned positive electrode material, comprising the following steps:

[0101] The composite solid electrolyte is introduced into the vacuum reaction chamber to perform a first atomic layer deposition on the cathode material substrate, and then nitrogen is purged to obtain a cathode material composited with the first atomic deposition layer;

[0102] After introducing a water source to perform a second atomic layer deposition on the positive electrode material composited with the first atomic deposition layer, nitrogen is purged to obtain the positive electrode material.

[0103] Wherein, the temperature of the composite solid electrolyte is 80-90°C, and the time of the first atomic layer deposition is 2-3s;

[0104] The temperature of the water source was 25°C, and the time for the second atomic layer deposition was 1 to 2 s;

[0105] The temperature in the vacuum reaction chamber is 220-250°C, and can be 220, 230, 240, 250, or any value between 220-250°C.

[0106] The nozzle temperature of the vacuum reaction chamber is 170-180°C.

[0107] The present invention also provides a lithium ion battery comprising the above-mentioned positive electrode material.

[0108] The present invention provides a solid electrolyte with a multiple coating structure, which has excellent ionic conductivity and good interface compatibility, and effectively inhibits its volume expansion, ensuring the stability of the solid electrolyte structure. When the composite solid electrolyte coated positive electrode material prepared by the present invention is used in a lithium battery, it can improve the specific capacity and conductivity of the positive electrode material; increase the amount of available lithium, thereby improving the energy density of the battery. This is not available in other solid electrolytes. The biggest difference from other solid electrolyte applications is that the multiple coating layers can encapsulate the active site or sensitive component in a certain space, reduce its direct contact with the surrounding environment, thereby limiting the range of volume change; it can also increase a certain mechanical support, prevent the internal material from excessively expanding, help maintain the structural stability of the entire system, and reduce the structural damage caused by volume change. In addition, the composite solid electrolyte prepared by the present invention has a low interface impedance, is more stable than the interface of other solid electrolytes, can increase ionic conductivity and lithium transfer number, thereby meeting the needs of modern electronic equipment and electric vehicles for high energy density batteries. This is rarely available in other solid electrolytes.

[0109] In order to further understand the present invention, the composite solid electrolyte provided by the present invention and its preparation method and application are described below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0110] Example 1

[0111] 1. Preparation of solid electrolyte

[0112] 5gLi with a median particle size of 268nm 1.5 Al 0.5 Ti 1.5The (PO4)3 powder was stirred with 2.5 mol APS in 50 ml methanol solution for 12 h, and then the solvent was extracted by evaporation at about 70 ° C to modify the solid electrolyte powder with amino groups. The amino-functionalized LATP was added to a glucose aqueous solution (10% coating, 100 mL) and kept at 150 ° C for 8 h. The obtained powder was separated by filtration, washed with water and ethanol, and heated in vacuum at 800 ° C for 2 hours to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@C.

[0113] The carbon-coated Li 1.5 Al 0.5 Ti 1.5 (PO4)3 was dissolved in 50 ml of ethanol solution containing 0.15 g of AEAPS and stirred at room temperature. The sample treated with AEAPS was placed in a 50 cm 3 Ethanol, 0.011 g CTAB, 0.2 g TEOS, 2 cm 3 Ammonia (28%) and 70cm 3 The suspension was shaken in a mixed solution of water for 2 hours. The product was collected by centrifugation at 10,000 rpm for 10 minutes, washed with water several times, and vacuum dried at 100°C to obtain solid electrolyte particles covered with a carbon layer and a silicon dioxide layer in sequence. Finally, the product was calcined in air at 800°C for 2 hours to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2.

[0114] Weigh 0.048g lithium phosphate and dissolve it in 40ml ethanol. Then add Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2 was placed in an ultrasonic cleaner for continuous ultrasonication, placed in an oscillating constant temperature metal bath for 16 hours, and then the obtained sample was placed at 70°C for drying to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2 capsules.

[0115] The obtained Li-Li 1.5 Al 0.5 Ti 1.5After the (PO4)3@mSiO2 particles were dissolved in 50ml ultrapure water, 1mL of 0.011mol calcium chloride was added dropwise under low-speed stirring at 200rpm. After repeating the above steps 10 times, stirring was continued for 12h. The obtained sample was placed at 70℃ for drying to obtain a composite solid electrolyte (Li 1.5 Al 0.5 Ti 1.5 (PO4)3-Li + @CaP@mSiO2).

[0116] The composite solid electrolyte prepared above was observed by electron microscopy, and the results are shown in Figure 2 , Figure 2 This is a transmission electron microscopy image of the composite solid electrolyte prepared in Example 1. Figure 2 In the figure, the structures from the outside to the inside are mesoporous silica layer, calcium phosphate layer, lithium salt layer, and solid electrolyte.

[0117] 2. Preparation of positive electrode materials

[0118] Two atomic layer deposition cycles were performed on the surface of 20 g LiCoO2. Li was introduced into the vacuum reaction chamber at 80 °C. 1.5 Al 0.5 Ti 1.5 (PO4)3-Li + @CaP@mSiO2 performs the first atomic layer deposition on the positive electrode particles for 2 seconds. After the first atomic layer deposition, the positive electrode particles are purged with nitrogen for 10 seconds, and then a 25°C water source is introduced to perform the second atomic layer deposition on the positive electrode particles for 2 seconds. After the second atomic layer deposition, the positive electrode particles are purged with nitrogen for 10 seconds, and the temperature in the vacuum reaction chamber is always maintained at 230°C. After the completion, a composite film is formed on the surface of the positive electrode particles.

[0119] Example 2

[0120] 1. Preparation of solid electrolyte

[0121] 5gLi with a median particle size of 379nm 1.8 Al 0.8 Ti 1.2 The (PO4)3 powder was stirred with 3.5 mol MEHA in 80 ml methanol solution for 20 h, and then the solvent was extracted by evaporation at about 70 ° C to modify the solid electrolyte powder with amino groups. The amino-functionalized LATP was added to a glucose aqueous solution (15% coating, 100 mL) and kept at 250 ° C for 5 h. The obtained powder was separated by filtration, washed with water and ethanol, and heated in vacuum at 500 ° C for 4 hours to obtain Li 1.8 Al0.8 Ti 1.2 (PO4)3@C.

[0122] The carbon-coated Li 1.8 Al 0.8 Ti 1.2 (PO4)3 was dissolved in 50 ml of ethanol solution containing 0.11 g of KH560 and stirred at room temperature. The sample treated with KH560 was placed in a 80 cm 3 Ethanol, 0.016g CTAB, 0.15g TMOS, 2.8cm 3 Ammonia (28%) and 70cm 3 The suspension was shaken in a mixed solution of water for 2 hours. The product was collected by centrifugation at 10,000 rpm for 10 minutes, washed with water several times, and vacuum dried at 100°C to obtain solid electrolyte particles covered with carbon layers and silicon dioxide layers in sequence. Finally, the product was calcined in air at 800°C for 4 hours to obtain Li 1.8 Al 0.8 Ti 1.2 (PO4)3@mSiO2.

[0123] Weigh 0.097g of lithium dihydrogen phosphate and dissolve it in 40ml of ethanol. Then add Li 1.8 Al 0.8 Ti 1.2 (PO4)3@mSiO2 was placed in an ultrasonic cleaner for continuous ultrasonication, placed in an oscillating constant temperature metal bath for 20 hours, and then the obtained sample was placed at 70°C for drying to obtain Li 1.8 Al 0.8 Ti 1.2 (PO4)3@mSiO2 capsules.

[0124] The obtained Li-Li 1.8 Al 0.8 Ti 1.2 After the (PO4)3@mSiO2 particles were dissolved in 50ml ultrapure water, 1mL of 0.055mol calcium chloride was added dropwise under low-speed stirring at 300rpm. After repeating the above steps 6 times, stirring was continued for 12h. The obtained sample was placed at 70℃ for drying to obtain a composite solid electrolyte (Li 1.8 Al 0.8 Ti 1.2 (PO4)3-Li + @CaP@mSiO2).

[0125] 2. Preparation of positive electrode materials

[0126] Two atomic layer deposition cycles were performed on the surface of 20 g LiNiO2, and 85 °C Li 1.8 Al 0.8 Ti 1.2 (PO4)3-Li + @CaP@mSiO2 was used to deposit the first atomic layer of the positive electrode particles for 3 seconds. After the first atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and then a 25°C water source was introduced to deposit the second atomic layer of the positive electrode particles for 1.5 seconds. After the second atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and the temperature in the vacuum reaction chamber was always maintained at 220°C. After the completion, a composite film was formed on the surface of the positive electrode particles.

[0127] Example 3

[0128] 1. Preparation of solid electrolyte

[0129] 5g of LLZO powder with a median particle size of 281nm was stirred with 3mol APS in 80ml methanol solution for 20h, and then the solvent was extracted by evaporation at about 70℃ to modify the solid electrolyte powder with amino groups. Amino-functionalized LLZO was added to a glucose aqueous solution (10% coating, 100mL) and kept at 180℃ for 6h. The obtained powder was separated by filtration, washed with water and ethanol, and heated in vacuum at 800℃ for 2h to obtain LLZO@C.

[0130] The carbon-coated LLZO was dissolved in 50 ml of ethanol solution containing 0.18 g of AEAPS and stirred at room temperature. 3 Ethanol, 0.035 g TTAB, 0.3 g TEOSS, 3.3 cm 3 Ammonia (28%) and 70cm 3 The suspension was shaken in a mixed solution of water for 3 hours. The product was collected by centrifugation at 10,000 rpm for 10 minutes, washed with water several times, and vacuum dried at 100°C to obtain solid electrolyte particles covered with a carbon layer and a silicon dioxide layer in sequence. Finally, the product was calcined in air at 600°C for 6 hours to obtain LLZO@mSiO2 with a cavity structure.

[0131] Weigh 0.11g lithium phosphate and dissolve it in 40ml ethanol, then add LLZO@mSiO2 to the above solution, place it in an ultrasonic cleaner for continuous ultrasound, place it in an oscillating constant temperature metal bath for 22h, and then place the obtained sample at 70℃ for drying to obtain LLZO@mSiO2 capsules with built-in lithium salt.

[0132] After dissolving the obtained Li-LLZO@mSiO2 particles in 50ml ultrapure water, 1mL of 0.041mol calcium chloride was added dropwise under low-speed stirring at 250rpm. After repeating the above steps 8 times, stirring was continued for 12h. The obtained sample was placed at 70℃ for drying to obtain a composite solid electrolyte (LLZO-Li + @CaP@mSiO2).

[0133] 2. Preparation of positive electrode materials

[0134] Two atomic layer deposition cycles were performed on the surface of 20 g LiCoO2, and LLZO-Li at 90 °C was introduced into the vacuum reaction chamber. + @CaP@mSiO2 was used to deposit the first atomic layer of the positive electrode particles for 3 seconds. After the first atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and then a 25°C water source was introduced to deposit the second atomic layer of the positive electrode particles for 2 seconds. After the second atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and the temperature in the vacuum reaction chamber was always maintained at 220°C. After the completion, a composite film was formed on the surface of the positive electrode particles.

[0135] Example 4

[0136] 1. Preparation of solid electrolyte

[0137] 5gLi with a median particle size of 312nm 6.25 La3Zr2Al 0.25 O 12 The powder was stirred with 1.5 mol DEA in 40 ml methanol solution for 12 h, and then the solvent was extracted by evaporation at about 70 ° C to modify the solid electrolyte powder with amino groups. The amino-functionalized solid electrolyte was added to a fructose aqueous solution (5% coating, 100 mL) and kept at 200 ° C for 6 h. The obtained powder was separated by filtration, washed with water and ethanol, and heated in vacuum at 600 ° C for 3 hours to obtain Li 6.25 La3Zr2Al 0.25 O 12 @C.

[0138] The carbon-coated Li 6.25 La3Zr2Al 0.25 O 12 Dissolve 0.25g of KH550 in 50ml of ethanol solution and stir at room temperature. 3 Ethanol, 0.019g DTAB, 0.35g TEOS, 1.5cm 3 Ammonia (28%) and 70cm3 The suspension was shaken in a mixed solution of water for 1.5 hours. The product was collected by centrifugation at 10,000 rpm for 10 minutes, washed with water several times, and vacuum dried at 100°C to obtain solid electrolyte particles covered with a carbon layer and a silicon dioxide layer in sequence. Finally, the product was calcined in air at 600°C for 4 hours to obtain Li 6.25 La3Zr2Al 0.25 O 12 @mSiO2.

[0139] Weigh 0.034 g of lithium phosphite and dissolve it in 40 ml of ethanol. Then add Li 6.25 La3Zr2Al 0.25 O 12 @mSiO2, placed in an ultrasonic cleaner for continuous ultrasonication, placed in an oscillating constant temperature metal bath for 14 hours, and then dried at 70°C to obtain Li 6.25 La3Zr2Al 0.25 O 122 @mSiO2 capsules.

[0140] The obtained Li-Li 6.25 La3Zr2Al 0.25 O 122 @mSiO2 particles were dissolved in 50ml ultrapure water, and 1mL of 0.015mol calcium chloride was added dropwise under low-speed stirring at 150rpm. The above steps were repeated 9 times, and stirring was continued for 12h. The obtained sample was placed at 70℃ for drying to obtain a composite solid electrolyte (Li 6.25 La3Zr2Al 0.25 O 12 -Li + @CaP@mSiO2).

[0141] 2. Preparation of positive electrode materials

[0142] Two atomic layer deposition cycles were performed on the surface of 20 g LiCoO2. Li was introduced into the vacuum reaction chamber at 85 °C. 6.25 La3Zr2Al 0.25 O 12 -Li +@CaP@mSiO2 was used to deposit the first atomic layer of the positive electrode particles for 2 seconds. After the first atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and then a 25°C water source was introduced to deposit the second atomic layer of the positive electrode particles for 1.5 seconds. After the second atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and the temperature in the vacuum reaction chamber was always maintained at 240°C. After the completion, a composite film was formed on the surface of the positive electrode particles.

[0143] Example 5

[0144] 1. Preparation of solid electrolyte

[0145] 5gLi with a median particle size of 237nm 6.8 Ln3Z 1.8 Ta 0.2 O 12 The powder was stirred with 2.3 mol TEPA in 50 ml methanol solution for 18 h, and then the solvent was extracted by evaporation at about 70 ° C to modify the solid electrolyte powder with amino groups. The amino-functionalized solid electrolyte was added to a citric acid aqueous solution (15% coating, 100 mL) and kept at 250 ° C for 5 h. The obtained powder was separated by filtration, washed with water and ethanol, and heated in vacuum at 500 ° C for 4 hours to obtain Li 6.8 Ln3Z 1.8 Ta 0.2 O 12 @C.

[0146] The carbon-coated Li 6.8 Ln3Z 1.8 Ta 0.2 O 12 Dissolve 0.13 g of KH560 in 50 ml of ethanol solution and stir at room temperature. 3 Ethanol, 0.036g TTAB, 0.18g TEOSS, 3cm 3 Ammonia (28%) and 70cm 3 The suspension was shaken in a mixed solution of water for 1.5 hours. The product was collected by centrifugation at 10,000 rpm for 10 minutes, washed with water several times, and vacuum dried at 100°C to obtain solid electrolyte particles covered with a carbon layer and a silicon dioxide layer in sequence. Finally, the product was calcined in air at 600°C for 4 hours to obtain Li 6.8 Ln3Z 1.8 Ta 0.2 O 12 @mSiO2.

[0147] Weigh 0.075g of lithium phosphite and dissolve it in 40ml of ethanol. Then add Li 6.8Ln3Z 1.8 Ta 0.2 O 12 @mSiO2, placed in an ultrasonic cleaner for continuous ultrasonication, placed in an oscillating constant temperature metal bath for 20 hours, and then dried at 70°C to obtain Li 6.8 Ln3Z 1.8 Ta 0.2 O 12 @mSiO2 capsules.

[0148] The obtained Li-Li 6.8 Ln3Z 1.8 Ta 0.2 O 12 @mSiO2 particles were dissolved in 50ml ultrapure water, and 1mL of 0.025mol calcium chloride was added dropwise under low-speed stirring at 250rpm. The above steps were repeated 7 times, and stirring was continued for 12h. The obtained sample was placed at 70℃ for drying to obtain a composite solid electrolyte (Li 6.8 Ln3Z 1.8 Ta 0.2 O 12 -Li + @CaP@mSiO2).

[0149] 2. Preparation of positive electrode materials

[0150] In 20 g LiNi 0.8 Co 0.15 Al 0.05 Two atomic layer deposition cycles were performed on the O2 surface, and 85°C Li 6.8 Ln3Z 1.8 Ta 0.2 O 12 -Li + @CaP@mSiO2 was used to deposit the first atomic layer of the positive electrode particles for 2.5 seconds. After the first atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and then a 25°C water source was introduced to deposit the second atomic layer of the positive electrode particles for 2 seconds. After the second atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and the temperature in the vacuum reaction chamber was always maintained at 250°C. After the completion, a composite film was formed on the surface of the positive electrode particles.

[0151] Example 6

[0152] Solid electrolyte preparation

[0153] 5gLi with a median particle size of 234nm 6.4 La3Zr2Al0.2 O 12 The powder was stirred with 1.2 mol MDEA in 30 ml methanol solution for 15 h, and then the solvent was extracted by evaporation at about 70 ° C to modify the solid electrolyte powder with amino groups. The amino-functionalized solid electrolyte was added to a citric acid aqueous solution (15% coating, 100 mL) and kept at 250 ° C for 2 h. The obtained powder was separated by filtration, washed with water and ethanol, and heated in vacuum at 500 ° C for 4 hours to obtain Li 6.4 La3Zr2Al 0.2 O 12 @C.

[0154] The carbon-coated Li 6.4 La3Zr2Al 0.2 O 12 Dissolve 0.09 g of KH560 in 50 ml of ethanol solution and stir at room temperature. 3 Ethanol, 0.011g PVP, 0.33g TEOS, 1.3cm 3 Ammonia (28%) and 70cm 3 The suspension was shaken in a mixed solution of water for 1 hour. The product was collected by centrifugation at 10,000 rpm for 10 minutes, washed with water several times, and vacuum dried at 100°C to obtain solid electrolyte particles covered with carbon layers and silicon dioxide layers in sequence. Finally, the product was calcined in air at 700°C for 6 hours to obtain Li 6.4 La3Zr2Al 0.2 O 12 @mSiO2.

[0155] Weigh 0.085g of lithium phosphite and dissolve it in 40ml of ethanol. Then add Li 6.4 La3Zr2Al 0.2 O 12 @mSiO2, placed in an ultrasonic cleaner for continuous ultrasonication, placed in an oscillating constant temperature metal bath for 18 hours, and then dried at 70°C to obtain Li 6.4 La3Zr2Al 0.2 O 12 @mSiO2 capsules.

[0156] The obtained Li-Li 6.4 La3Zr2Al 0.2 O 12@mSiO2 particles were dissolved in 50ml ultrapure water, and 1mL of 0.032mol calcium chloride was added dropwise under low-speed stirring at 180rpm. The above steps were repeated 9 times, and stirring was continued for 12h. The obtained sample was placed at 70℃ for drying to obtain a composite solid electrolyte (Li 6.4 La3Zr2Al 0.2 O 12 -Li + @CaP@mSiO2).

[0157] 2. Preparation of positive electrode materials

[0158] In 20 g LiNi 0.8 Co 0.15 Al 0.05 Two atomic layer deposition cycles were performed on the O2 surface, and 85°C Li 6.4 La3Zr2Al 0.2 O 12 -Li + @CaP@mSiO2 was used to deposit the first atomic layer of the positive electrode particles for 2.5 seconds. After the first atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and then a 25°C water source was introduced to deposit the second atomic layer of the positive electrode particles for 2 seconds. After the second atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and the temperature in the vacuum reaction chamber was always maintained at 250°C. After the completion, a composite film was formed on the surface of the positive electrode particles.

[0159] Example 7

[0160] 1. Preparation of solid electrolyte

[0161] 5gLi with a median particle size of 200nm 1.5 Al 0.5 Ti 1.5 The (PO4)3 powder was stirred with 4 mol APS in 50 ml methanol solution for 12 h, and then the solvent was extracted by evaporation at about 70 ° C to modify the solid electrolyte powder with amino groups. The amino-functionalized LATP was added to a glucose aqueous solution (5% coating, 100 mL) and kept at 100 ° C for 5 h. The obtained powder was separated by filtration, washed with water and ethanol, and heated in vacuum at 500 ° C for 1 hour to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@C.

[0162] The carbon-coated Li 1.5 Al 0.5 Ti 1.5(PO4)3 was dissolved in 50 ml of ethanol solution containing 0.05 g of AEAPS and stirred at room temperature. The sample treated with AEAPS was placed in a 50 cm 3 Ethanol, 0.011 g DTAB, 0.4 g TEOS, 1 cm 3 Ammonia (28%) and 70cm 3 The suspension was shaken in a mixed solution of water for 1 hour. The product was collected by centrifugation at 10,000 rpm for 10 minutes, washed with water several times, and vacuum dried at 100°C to obtain solid electrolyte particles covered with a carbon layer and a silicon dioxide layer in sequence. Finally, the product was calcined in air at 500°C for 3 hours to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2.

[0163] Weigh 0.025 lithium phosphate and dissolve it in 40 ml of ethanol. Then add Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2 was placed in an ultrasonic cleaner for continuous ultrasonication, placed in an oscillating constant temperature metal bath for 12 hours, and then the obtained sample was placed at 70°C for drying to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2 capsules.

[0164] The obtained Li-Li 1.5 Al 0.5 Ti 1.5 After the (PO4)3@mSiO2 particles were dissolved in 50ml ultrapure water, 1mL of 0.01mol calcium chloride was added dropwise under low-speed stirring at 100rpm. After repeating the above steps 10 times, stirring was continued for 12h. The obtained sample was placed at 70℃ for drying to obtain a composite solid electrolyte (Li 1.5 Al 0.5 Ti 1.5 (PO4)3-Li + @CaP@mSiO2).

[0165] 2. Preparation of positive electrode materials

[0166] Two atomic layer deposition cycles were performed on the surface of 20 g LiCoO2. Li was introduced into the vacuum reaction chamber at 80 °C. 1.5 Al 0.5 Ti 1.5 (PO4)3-Li +@CaP@mSiO2 performs the first atomic layer deposition on the positive electrode particles for 2 seconds. After the first atomic layer deposition, the positive electrode particles are purged with nitrogen for 10 seconds, and then a 25°C water source is introduced to perform the second atomic layer deposition on the positive electrode particles for 2 seconds. After the second atomic layer deposition, the positive electrode particles are purged with nitrogen for 10 seconds, and the temperature in the vacuum reaction chamber is always maintained at 220°C. After the completion, a composite film is formed on the surface of the positive electrode particles.

[0167] Example 8

[0168] 1. Preparation of solid electrolyte

[0169] 5gLi with a median particle size of 500nm 1.5 Al 0.5 Ti 1.5 The (PO4)3 powder was stirred with 4 mol APS in 50 ml methanol solution for 24 h, and then the solvent was extracted by evaporation at about 70 ° C to modify the solid electrolyte powder with amino groups. The amino-functionalized LATP was added to a glucose aqueous solution (15% coating, 100 mL) and kept at 250 ° C for 10 h. The obtained powder was separated by filtration, washed with water and ethanol, and heated in vacuum at 1000 ° C for 4 hours to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@C.

[0170] The carbon-coated Li 1.5 Al 0.5 Ti 1.5 (PO4)3 was dissolved in 150ml ethanol solution containing 0.25g AEAPS and stirred at room temperature. The sample treated with AEAPS was placed in a solution containing 50cm3 ethanol, 0.05g PVP, 0.25g TEOS, 4cm 3 Ammonia (28%) and 70cm 3 The suspension was shaken in a mixed solution of water for 1 hour. The product was collected by centrifugation at 10,000 rpm for 10 minutes, washed with water several times, and vacuum dried at 100°C to obtain solid electrolyte particles covered with a carbon layer and a silicon dioxide layer in sequence. Finally, the product was calcined in air at 800°C for 8 hours to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2.

[0171] Weigh 0.1g lithium phosphate and dissolve it in 40ml ethanol. Then add Li 1.5 Al 0.5 Ti 1.5(PO4)3@mSiO2 was placed in an ultrasonic cleaner for continuous ultrasonication, placed in an oscillating constant temperature metal bath for 24 hours, and then the obtained sample was placed at 70°C for drying to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2 capsules.

[0172] The obtained Li-Li 1.5 Al 0.5 Ti 1.5 After the (PO4)3@mSiO2 particles were dissolved in 50ml ultrapure water, 1mL of 0.06mol calcium chloride was added dropwise under low-speed stirring at 300rpm. After repeating the above steps 10 times, stirring was continued for 12h. The obtained sample was placed at 70℃ for drying to obtain a composite solid electrolyte (Li 1.5 Al 0.5 Ti 1.5 (PO4)3-Li + @CaP@mSiO2).

[0173] 2. Preparation of positive electrode materials

[0174] Two atomic layer deposition cycles were performed on the surface of 20 g LiCoO2. Li at 90 °C was introduced into the vacuum reaction chamber. 1.5 Al 0.5 Ti 1.5 (PO4)3-Li + @CaP@mSiO2 performs the first atomic layer deposition on the positive electrode particles for 3 seconds. After the first atomic layer deposition, the positive electrode particles are purged with nitrogen for 10 seconds, and then a 25°C water source is introduced to perform the second atomic layer deposition on the positive electrode particles for 3 seconds. After the second atomic layer deposition, the positive electrode particles are purged with nitrogen for 10 seconds, and the temperature in the vacuum reaction chamber is always maintained at 250°C. After the completion, a composite film is formed on the surface of the positive electrode particles.

[0175] Example 9

[0176] 1. Preparation of solid electrolyte

[0177] 5gLi with a median particle size of 300nm 1.5 Al 0.5 Ti 1.5The (PO4)3 powder was stirred with 4 mol APS in 50 ml methanol solution for 18 h, and then the solvent was extracted by evaporation at about 70 ° C to modify the solid electrolyte powder with amino groups. The amino-functionalized LATP was added to a glucose aqueous solution (10% coating, 100 mL) and kept at 200 ° C for 8 h. The obtained powder was separated by filtration, washed with water and ethanol, and heated in vacuum at 800 ° C for 3 hours to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@C.

[0178] The carbon-coated Li 1.5 Al 0.5 Ti 1.5 (PO4)3 was dissolved in 100 ml of ethanol solution containing 0.21 g of AEAPS and stirred at room temperature. The sample treated with AEAPS was placed in a solution containing 40 cm3 of ethanol, 0.045 g of TTAB, 0.38 g of TMOS, 3 cm 3 Ammonia (28%) and 70cm 3 The suspension was shaken in a mixed solution of water for 1 hour. The product was collected by centrifugation at 10,000 rpm for 10 minutes, washed with water several times, and vacuum dried at 100°C to obtain solid electrolyte particles covered with a carbon layer and a silicon dioxide layer in sequence. Finally, the product was calcined in air at 600°C for 4 hours to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2.

[0179] Weigh 0.08g lithium phosphate and dissolve it in 40ml ethanol. Then add Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2 was placed in an ultrasonic cleaner for continuous ultrasonication, placed in an oscillating constant temperature metal bath for 20 hours, and then the obtained sample was placed at 70°C for drying to obtain Li 1.5 Al 0.5 Ti 1.5 (PO4)3@mSiO2 capsules.

[0180] The obtained Li-Li 1.5 Al 0.5 Ti 1.5After (PO4)3@mSiO2 particles were dissolved in 50ml ultrapure water, 1mL of 0.04mol calcium chloride was added dropwise under low-speed stirring at 250rpm. After repeating the above steps 10 times, stirring was continued for 12h. The obtained sample was placed at 70℃ for drying to obtain a composite solid electrolyte (Li 1.5 Al 0.5 Ti 1.5 (PO4)3-Li + @CaP@mSiO2).

[0181] 2. Preparation of positive electrode materials

[0182] Two atomic layer deposition cycles were performed on the surface of 20 g LiCoO2. Li was introduced into the vacuum reaction chamber at 85 °C. 1.5 Al 0.5 Ti 1.5 (PO4)3-Li + @CaP@mSiO2 was used to deposit the first atomic layer of the positive electrode particles for 2.5 seconds. After the first atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and then a 25°C water source was introduced to deposit the second atomic layer of the positive electrode particles for 2.5 seconds. After the second atomic layer deposition, the positive electrode particles were purged with nitrogen for 10 seconds, and the temperature in the vacuum reaction chamber was always maintained at 240°C. After the completion, a composite film was formed on the surface of the positive electrode particles.

[0183] Comparative Example 1

[0184] Compared with implementation 1, Li 1.5 Al 0.5 Ti 1.5 (PO4)3@C@mSiO2 does not undergo high-temperature calcination to remove the carbon layer, and the rest is the same.

[0185] Comparative Example 2

[0186] Compared with Example 1, the addition method of calcium chloride was changed. Instead of adding dropwise, the total calcium chloride was directly poured into the reaction system. The rest was the same.

[0187] Comparative Example 3

[0188] Compared with Example 1, nitrogen purging was not performed during the two atomic deposition processes, and the rest was the same.

[0189] Comparative Example 4

[0190] Compared with Example 3, uncoated LLZO is used to directly coat LiCoO2, and the rest is the same.

[0191] Comparative Example 5

[0192] Compared with Example 7, no amination treatment was performed, and the rest was the same.

[0193] Comparative Example 6

[0194] Compared with Example 7, lithium phosphate and calcium chloride were not added, and the rest were the same.

[0195] Comparative Example 7

[0196] Compared with Example 7, the lithium phosphate was replaced with lithium chloride (0.039 g) in the same molar amount as the lithium phosphate, and the rest was the same.

[0197] The positive electrode materials prepared according to the preparation methods of Examples 1-9 and Comparative Examples 1-7 were respectively mixed with conductive graphite and binder PVDF in a mass ratio of 93.5:4:2.5 with NMP as solvent, and then evenly coated on aluminum foil and dried at 120°C for 12 hours. The plates were punched into 12 mm plates, the diaphragm was polypropylene (PP), and the electrolyte was 1 mol / L (LiPF6) and ethylene carbonate (EC) / dimethyl carbonate (DMC) (the volume ratio of EC and MC was 1:1) solution. In an argon-protected glove box (O2<1ppm, H2O<1ppm), lithium sheets were used as negative electrodes to assemble CR2032 button batteries, and the batteries were tested for electrical performance at rates of 0.1C, 0.2C, 0.5C, and 1C, respectively, and cycled 100 times at a rate of 1C in the voltage range of 2.7-4.3V.

[0198] Table 1

[0199]

[0200]

[0201] In the above test results, Examples 1-9 show obvious differences from Comparative Examples 1-4. From the perspective of initial capacity, the embodiments are generally higher than the comparative examples. For example, Example 7 reaches 208.4 mAh / g at a rate of 0.1C, while Comparative Example 4 is only 166.8 mAh / g. In terms of first effect, the embodiments are also mostly better than the comparative examples. The first effect of the experimental group is as high as 94.5%, while the first effects of Comparative Examples 3 and 4 are both lower than 86%. This is because the composite solid electrolyte strengthens the effect of pre-lithiation, improves the initial capacity of the battery, and reduces the loss of lithium ions, ensuring the stability of battery performance. In terms of capacity performance at different rates, the embodiments perform better overall, while the capacity attenuation of the comparative examples at high rates is more serious. In terms of retention rate after 100 cycles, the retention rate of the embodiments is generally above 80%, while the retention rates of Comparative Examples 1-3 are all below 62%, and Comparative Example 4 is as low as 42.7%. In general, the embodiments are significantly better than the comparative examples in various performance indicators. This is because the solid electrolyte, as a good protective layer, can resist the adverse effects of external factors on the positive electrode material, enhance the safety and stability of the battery, and help optimize the charge and discharge efficiency and overall performance of the battery. Compared with comparative examples 5-7, Example 7 has the best performance, with a capacity of 208.4 mAh / g at 0.1C and a first efficiency of 94.5%. The capacity is well maintained at different rates, with a 1C capacity of 189.6 mAh / g and a retention rate of 89.7%. In summary, the amination treatment, the deposition of a calcium phosphate coating on the surface of the silica inner shell, and the deposition of lithium salts and calcium phosphate on the surface of the solid electrolyte all have a significant effect on improving the performance of the solid electrolyte.

[0202] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite solid electrolyte, characterized in that From inside to outside, it includes: solid electrolytes; a lithium salt layer coated on the surface of the solid electrolyte; a calcium phosphate layer coated on the surface of the lithium salt layer; A mesoporous silica layer is coated on the surface of the calcium phosphate layer.

2. The composite solid electrolyte according to claim 1, characterized in that The size of the solid electrolyte is 100-800 nm; the pore diameter of the mesopores of the mesoporous silica shell is 2-50 nm.

3. A method for preparing a composite solid electrolyte, characterized in that: The following steps are involved: A) modifying the solid electrolyte with an amino compound to obtain an amino-functionalized solid electrolyte; B) mixing the amino-functionalized solid electrolyte with an organic carbon aqueous solution for a heating reaction, and calcining the heating reaction product under vacuum conditions to obtain a carbon-coated solid electrolyte; C) mixing the carbon-coated solid electrolyte, a silane coupling agent, a silicon source, a mesoporous template agent, aqueous ammonia, and ethanol to perform a first reaction to obtain a solid electrolyte sequentially coated with a carbon layer and a mesoporous silica layer; D) calcining the solid electrolyte sequentially coated with the carbon layer and the mesoporous silica layer in air to obtain a solid electrolyte with the carbon layer removed to form a cavity; E) mixing a lithium salt solution containing phosphate radicals with a solid electrolyte having a cavity formed by removing the carbon layer, and drying the mixture to obtain a solid electrolyte containing a lithium salt containing phosphate radicals in the cavity; F) mixing a solid electrolyte containing a lithium salt of phosphate radicals, a calcium source compound and water in the cavity to perform a second reaction to obtain a composite solid electrolyte having a first coating layer of a lithium salt layer, a second coating layer of a calcium phosphate layer and a third coating layer of a mesoporous silica layer.

4. The preparation method according to claim 1, characterized in that The solid electrolyte is selected from NASICON type solid electrolyte Li 1+x Al x Ti 2-x (PO4)3, 0≤x<1, Garnet-type solid electrolyte Li 3x La 2 / 3-x TiO3, Li 7-x La3Zr 2- x M x O 12 , M is one or more of Nb, Al or Ta, 0≤x<1, and the particle size D50 of the solid electrolyte is 200nm~500nm.

5. The preparation method according to claim 1, characterized in that The amino compound is selected from N-(2-hydroxyethyl)caprolactam (MEHA), diethanolamine (DEA), methyldiethanolamine (MDEA), tetraethylenepentamine (TEPA), and 3-aminopropyltrimethoxysilane (APS); The ratio of the solid electrolyte to the amino compound is 5 g: (1-4) mol; The modification is carried out at room temperature and the modification time is 12 to 24 hours.

6. The preparation method according to claim 1, characterized in that In step B), the organic carbon in the organic carbon aqueous solution is selected from one or more of glucose, fructose and citric acid; The heating reaction temperature is 100-250°C and the time is 5-10 hours; The calcination temperature is 500-1000°C and the time is 1-4 hours; The mass percentage of the organic carbon in the solid electrolyte is 5% to 15%.

7. The preparation method according to claim 1, characterized in that In step C), the silane coupling agent is one or more of aminoethylaminopropyl polydimethylsiloxane, KH550 and KH560, and the amount of the coupling agent is 1 to 5 wt% of the solid electrolyte; The silicon source is one or more of ethyl orthosilicate, methyl orthosilicate and tetraethoxysilane, and the amount of the silicon source is 3-8 wt% of the solid electrolyte; The mesoporous template agent is one or more of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and polyvinylpyrrolidone, and the amount of the mesoporous template agent is 0.2-1 wt% of the solid electrolyte; The first reaction time is 1 to 2 hours.

8. The preparation method according to claim 1, characterized in that In step D), the calcination temperature is 500-800° C. and the calcination time is 3-8 hours.

9. The preparation method according to claim 1, characterized in that In step E), the lithium salt containing phosphate is one or more of lithium phosphate, lithium dihydrogen phosphate, lithium phosphite and lithium hypophosphite, and the mass of the lithium salt containing phosphate is 0.5-2 wt% of the solid electrolyte.

10. The preparation method according to claim 1, characterized in that In step F), the calcium source compound is selected from one or more of calcium chloride, calcium nitrate and calcium iodide; The stirring speed of the second reaction is 100-300 rpm.

11. A positive electrode material, characterized in that include: A positive electrode material matrix and a first atomic deposition layer and a second atomic deposition layer sequentially compounded on the surface of the positive electrode material matrix, wherein the first atomic deposition layer is obtained by atomic layer deposition of the composite solid electrolyte according to claim 1 or 2, and the second atomic deposition layer is obtained by atomic layer deposition from a water source.

12. The positive electrode material according to claim 11, characterized in that The positive electrode material matrix is ​​LiMn2O4, LiCoO2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiFePO4, Li3V2(PO4)3, LiMn x Fe 1-x PO4, where 0≤x≤1, LiVOPO4, LiNiPO4, LiNi 0.5 Mn 1.5 O4、Li x One or more of V2O4, wherein 0<x<2, LiCoPO4, LiNiO2, and LiNiO.

13. A method for preparing a positive electrode material according to claim 11 or 12, characterized in that: The following steps are involved: The composite solid electrolyte according to claim 1 or 2 is introduced into a vacuum reaction chamber to perform a first atomic layer deposition on a cathode material substrate, followed by nitrogen purge to obtain a cathode material composited with the first atomic deposition layer; A water source is introduced to perform a second atomic layer deposition on the positive electrode material composited with the first atomic deposition layer, and then nitrogen is purged to obtain the positive electrode material.

14. The preparation method according to claim 13, characterized in that The temperature of the composite solid electrolyte is 80-90°C, and the time for the first atomic layer deposition is 2-3s; The temperature of the water source was 25°C, and the time for the second atomic layer deposition was 1–2 s; The temperature in the vacuum reaction chamber is 220-250°C; The nozzle temperature of the vacuum reaction chamber is 170-180°C.

15. A lithium ion battery, characterized in that: Comprising the positive electrode material according to claim 11 or 12.

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