Negative electrode material and preparation method and application thereof

Abstract

The embodiment of the invention relates to a negative electrode material as well as a preparation method and application thereof. The structure of the negative electrode material comprises an inner core and a shell, the inner core comprises porous carbon, a first solid electrolyte and nano silicon particles; the first solid electrolyte is loaded on the surface of the porous carbon and in the pore structure of the porous carbon; the nano silicon particles are deposited in a pore structure of the porous carbon; the outer surface of the inner core is coated with the shell, and the shell comprises a carbon material and / or a second solid electrolyte. According to the negative electrode material disclosed by the invention, the first solid electrolyte in the inner core is loaded on the surface of the porous carbon, so that silicon carbide without electrochemical activity is prevented from being generated by direct contact between nano silicon particles and the porous carbon, and the actual capacity of a lithium ion battery can be improved; the first coulombic efficiency of the lithium ion battery can be improved through the coating of the shell, and the rate capability and the fast charging performance can also be improved; by adding the first solid electrolyte and the second solid electrolyte, the performance of the lithium ion battery in an extreme environment can be improved.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion battery materials, and particularly to a negative electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] The negative electrode material of a lithium-ion battery is an important component of the lithium-ion battery, mainly responsible for storing and releasing lithium ions. At present, the negative electrode materials of lithium-ion batteries mainly include carbon materials and lithium titanate materials. With the rapid development and continuous iteration of the entire industry, some new negative electrode materials have gradually begun to occupy the market, such as silicon-based negative electrode materials (such as silicon oxide negative electrodes and silicon-carbon negative electrodes) with high specific capacity and rich reserves.

[0003] At present, the silicon-carbon negative electrode material mainly prepared by chemical vapor deposition has shown excellent performance, because vapor deposition reduces the size of nano-silicon particles, effectively alleviates a series of problems brought about by the expansion of nano-silicon particles; in addition, vapor deposition ensures the uniform deposition of nano-silicon particles, inhibits the agglomeration of nano-silicon particles, and improves the cycle performance of the lithium-ion battery.

[0004] However, when preparing the silicon-carbon negative electrode material by chemical vapor deposition, the nano-silicon particles are directly deposited in the pores of the porous carbon. Due to the high activity of the nano-silicon particles, it is easy to generate electrochemically inactive silicon carbide with the carbon in the porous carbon, thereby reducing the capacity of the silicon-carbon negative electrode material. In addition, the fast charging requirement of the battery requires the development of silicon-carbon negative electrode materials with high rate performance. Therefore, more severe challenges are posed for the rapid transmission of electrons and ions in the silicon-carbon negative electrode material. Also, for the use of the battery in extreme environments, such as extreme environments of high / low temperature and high / low pressure, in order to ensure the normal charge and discharge of the battery, requirements are also put forward for the application of the silicon-carbon negative electrode material in extreme environments.

[0005] Therefore, how to solve the problems of generating inactive silicon carbide in the preparation process of the silicon-carbon negative electrode material and how to improve the fast charging of the battery and its performance in extreme environments has become one of the current research hotspots. Summary of the Invention

[0006] The object of the present invention is to provide a negative electrode material, a preparation method thereof, and an application thereof for the defects existing in the prior art. Among them, the negative electrode material has a core-shell structure, and the first solid electrolyte in the core can inhibit the generation of electrochemically inactive silicon carbide, and the carbon material or the first solid electrolyte in the shell can improve the electronic conductivity and ionic conductivity of the negative electrode material.

[0007] To achieve the above object, in the first aspect, the present invention provides a negative electrode material, and the structure of the negative electrode material includes a core and a shell;

[0008] The components of the core include porous carbon, a first solid electrolyte, and nano-silicon particles; the first solid electrolyte is loaded on the surface of the porous carbon and in the pore structure of the porous carbon; the nano-silicon particles are deposited in the pore structure of the porous carbon;

[0009] The outer shell is coated on the outer surface of the core, and the components of the outer shell include a carbon material and / or a second solid electrolyte.

[0010] Preferably, the first solid electrolyte is an oxide solid electrolyte and / or a sulfide solid electrolyte.

[0011] Preferably, the second solid electrolyte is an oxide solid electrolyte and / or a sulfide solid electrolyte.

[0012] Second, the present invention provides a method for preparing the negative electrode material according to any one of the above first aspects, and the preparation method includes:

[0013] Adding a first solid electrolyte raw material and a porous carbon raw material into a solvent and stirring to obtain a slurry;

[0014] Performing heat treatment on the slurry to obtain a porous carbon material loaded with a first solid electrolyte;

[0015] Under an inert atmosphere, performing chemical vapor deposition on the porous carbon material and a silicon source gas to obtain a porous carbon composite material including porous carbon, a first solid electrolyte, and nano-silicon particles;

[0016] Under an inert atmosphere, performing a coating treatment on the porous carbon composite material to obtain an outer shell containing a carbon material and / or a second solid electrolyte, thereby obtaining a negative electrode material.

[0017] Preferably, the heat treatment is spray drying and high-temperature calcination;

[0018] The conditions of the spray drying: the inlet air temperature is 150°C - 400°C, and the outlet air temperature is 80°C - 200°C;

[0019] The conditions of the high-temperature calcination: the temperature is 400°C - 800°C, and the time is 1 hour - 5 hours.

[0020] Preferably, the temperature of the chemical vapor deposition is 400°C - 1000°C, and the time is 2 hours - 15 hours.

[0021] Preferably, the coating treatment includes carbon coating and / or second solid electrolyte coating;

[0022] The conditions of the carbon coating are: the temperature is 300°C - 1000°C, and the time is 2 hours - 20 hours;

[0023] The second solid electrolyte coating includes a spray drying stage and a high-temperature calcination stage;

[0024] The conditions of the spray drying stage are as follows: the inlet air temperature is 150°C - 400°C, and the outlet air temperature is 80°C - 200°C;

[0025] The conditions of the high-temperature calcination stage are as follows: the temperature is 400°C - 800°C, and the time is 1 hour - 5 hours.

[0026] Further preferably, the carbon source for the carbon coating is one or more of alkanes, alkenes, and alkynes.

[0027] In a third aspect, the present invention provides a negative electrode sheet, which includes the negative electrode material described in any one of the first aspects or the negative electrode material prepared by the preparation method described in any one of the second aspects.

[0028] In a fourth aspect, the present invention provides a lithium-ion battery, which includes the negative electrode sheet described in the third aspect; the electrolyte of the lithium-ion battery is an aqueous electrolyte or an oil-based electrolyte.

[0029] A negative electrode material provided by an embodiment of the present invention has a core-shell structure composed of a core and a shell. Among them, the first solid electrolyte in the core is loaded on the surface of the porous carbon, avoiding the direct contact between the nano-silicon particles and the porous carbon to generate electrochemically inactive silicon carbide, which can improve the actual capacity of the lithium-ion battery; the coating of the shell can reduce the specific surface area of the negative electrode material, improve the first Coulomb efficiency of the lithium-ion battery, and can also improve the ionic conductivity and ion conductivity, thereby enhancing the rate performance of the lithium-ion battery and improving its fast charging performance; the addition of the first solid electrolyte and the second solid electrolyte is beneficial to improving the performance of the negative electrode material in extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flowchart of the preparation method of the negative electrode material provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments.

[0033] An embodiment of the present invention provides a negative electrode material, and the structure of the negative electrode material includes a core and a shell.

[0034] Among them, the composition of the core may specifically include porous carbon, a first solid electrolyte, and nano-silicon particles. The first solid electrolyte is loaded on the surface of the porous carbon and in the pore structure of the porous carbon. The first solid electrolyte may specifically be an oxide solid electrolyte and / or a sulfide solid electrolyte. Among them, the oxide solid electrolyte may specifically include lithium aluminum titanium phosphate (Li 1.4 Al 0.4 Ti 1.6 (PO4)3, abbreviated as LATP), lithium lanthanum titanium oxide (Li 0.33 La 0.56 Ti03, abbreviated as LLTO), lithium lanthanum zirconium oxide (Li7La3Zr20 12 , abbreviated as LLZO), etc. The sulfide solid electrolyte may specifically include Li3PS4, Li 10 GeP2S 12 , etc.

[0035] When the negative electrode material is applied in a lithium-ion battery, the first solid electrolyte in the core can improve the interfacial transport rate of lithium ions during the electrochemical reaction process, and can also improve the performance of the negative electrode material in extreme environments. Further, the first solid electrolyte is loaded on the surface of the porous carbon and in the pore structure of the porous carbon, so that the nano-silicon particles and the pore structure of the porous carbon do not directly contact, which can inhibit the formation of electrochemically inactive silicon carbide, thereby improving the actual capacity of the lithium-ion battery.

[0036] The composition of the shell may specifically include a carbon material and / or a second solid electrolyte. The second solid electrolyte may specifically include an oxide solid electrolyte and / or a sulfide solid electrolyte. Among them, the oxide solid electrolyte may specifically include lithium aluminum titanium phosphate (Li 1.4 Al 0.4 Ti 1.6 (PO4)3, abbreviated as LATP), lithium lanthanum titanium oxide (Li 0.33 La 0.56 Ti03, abbreviated as LLTO), lithium lanthanum zirconium oxide (Li7La3Zr20 12 , abbreviated as LLZO), etc. The sulfide solid electrolyte may specifically include Li3PS4, Li 10 GeP2S 12etc. The thickness of the outer shell can specifically be 2 nm - 50 nm. The outer shell is coated on the outer surface of the inner core, forming a core-shell structure of the negative electrode material. The carbon material in the outer shell can improve the electronic conductivity of the negative electrode material, and the second solid electrolyte can improve the ionic conductivity of the negative electrode material. At the same time, the coating of the outer shell reduces the specific surface area of the negative electrode material and improves the first Coulomb efficiency of the lithium-ion battery.

[0037] In summary, the negative electrode material provided by the embodiment of the present invention has a core-shell structure composed of an inner core and an outer shell. Among them, the first solid electrolyte in the inner core is loaded on the surface of the porous carbon, avoiding the direct contact between the nano-silicon particles and the porous carbon to generate electrochemically inactive silicon carbide, which can improve the actual capacity of the lithium-ion battery; the coating of the outer shell can reduce the specific surface area of the negative electrode material, improve the first Coulomb efficiency of the lithium-ion battery, and can also improve the ionic conductivity and ionic conductivity, thereby enhancing the rate performance of the lithium-ion battery and improving its fast charging performance; the addition of the first solid electrolyte and the second solid electrolyte is beneficial to improving the performance of the negative electrode material in extreme environments.

[0038] The embodiment of the present invention also provides a preparation method of the above-mentioned negative electrode material, and the process is as Figure 1 shown, including the following steps:

[0039] Step 110, adding the first solid electrolyte raw material and the porous carbon raw material into a solvent and stirring to obtain a slurry;

[0040] Specifically, the first solid electrolyte raw material can be first added into the solvent and stirred for a certain time to completely dissolve the first solid electrolyte raw material in the solvent, and then the porous carbon raw material is added, and then stirred for a period of time to uniformly mix the first solid electrolyte raw material and the porous carbon raw material. The first solid electrolyte raw material can specifically include an oxide solid electrolyte raw material and a sulfide solid electrolyte raw material. For example, simple substances or compounds containing elements such as lithium, lanthanum, aluminum, titanium, zirconium, phosphorus, oxygen, sulfur, and germanium. The porous carbon raw material can specifically include activated carbon, carbon molecular sieve, activated carbon fiber, etc. The solvent can be deionized water or ethanol. The mass fraction of ethanol can be 50% - 75%.

[0041] Step 120, performing heat treatment on the slurry to obtain a porous carbon material loaded with the first solid electrolyte;

[0042] Specifically, the heat treatment specifically includes two stages of spray drying and high-temperature calcination. Spray drying can make the particle size of the porous carbon material uniform and the particle size smaller. High-temperature calcination can further remove the remaining solvent in the particles obtained by spray drying, etc., improve the purity and dryness, make the particles more uniform and refined, and can also further improve the heat resistance of the material.

[0043] The conditions for spray drying are specifically as follows: the inlet air temperature is 150°C - 400°C, preferably 200°C - 300°C, and the outlet air temperature is 80°C - 200°C, preferably 100°C - 160°C.

[0044] High-temperature calcination can specifically be carried out in a high-temperature furnace. The inert atmosphere for high-temperature calcination can specifically be one or more of nitrogen, argon, and helium. The gas flow rate is 3 L / min - 10 L / min, preferably 5 L / min - 8 L / min. The heating rate of the high-temperature furnace is 2°C / min - 8°C / min, preferably 4°C / min - 6°C / min. The conditions for high-temperature calcination are specifically as follows: the temperature is 400°C - 800°C, preferably 500°C - 700°C; the time is 1 hour - 5 hours, preferably 2.5 hours - 3.5 hours.

[0045] This process mainly involves loading the first solid electrolyte onto the surface of the porous carbon raw material and into the pore structure of the porous carbon raw material.

[0046] Step 130, in an inert atmosphere, perform chemical vapor deposition on the porous carbon material and the silicon source gas to obtain a porous carbon composite material including porous carbon, the first solid electrolyte, and nano-silicon particles;

[0047] Specifically, the inert atmosphere can specifically be one or more of nitrogen, argon, and helium. Chemical vapor deposition can specifically be carried out in a deposition furnace. First, introduce an inert gas into the deposition furnace at a certain gas flow rate to form an inert atmosphere. The inert atmosphere can be one or more of nitrogen, argon, and helium, and the gas flow rate can be 15 L / min. Then, heat the deposition furnace at a heating rate of 2°C / min - 8°C / min, preferably 4°C / min - 6°C / min, to 400°C - 1000°C, preferably 600°C - 800°C, and keep the temperature of the deposition furnace stable at this temperature for 30 min - 40 min. Finally, introduce the silicon source gas and the inert gas into the deposition furnace together at a preset ratio, and keep it for 2 hours - 15 hours, preferably 5 hours - 10 hours, to perform chemical vapor deposition. The preset ratio can be 1:5 - 4:5, preferably 1:2. The silicon source gas can specifically include but is not limited to silane, disilane, and other silicon-containing alkanes. In this way, a porous carbon composite material is obtained as the core of the negative electrode material. Since the first solid electrolyte is loaded on the surface and pore structure of the porous carbon, it blocks the direct contact between the nano-silicon particles and the porous carbon, greatly reducing the generation probability of silicon carbide. When applied to a lithium-ion battery, it can improve the actual capacity of the lithium-ion battery.

[0048] Step 140, in an inert atmosphere, perform a coating treatment on the porous carbon composite material to obtain a shell containing a carbon material and / or a second solid electrolyte, thereby obtaining the negative electrode material;

[0049] Specifically, the coating treatment mainly forms the outer shell of the negative electrode material, specifically including carbon coating and / or second solid electrolyte coating. The carbon source for carbon coating is one or more of alkanes, alkenes, and alkynes. The carbon coating treatment can be specifically carried out in a coating furnace. The ratio of inert gas to carbon source can be specifically 1:3 - 4:5, preferably 3:5. The coating temperature can be 300°C - 1000°C, preferably 500°C - 800°C, and the time is 2 hours - 20 hours, preferably 8 hours - 16 hours. The coating thickness can be specifically 2nm - 50nm.

[0050] The second solid electrolyte coating is divided into two stages: spray drying stage and high-temperature calcination stage;

[0051] The conditions for the spray drying stage: the inlet air temperature is 150°C - 400°C, and the outlet air temperature is 80°C - 200°C. The conditions for the high-temperature calcination stage: the temperature is 400°C - 800°C, and the time is 1 hour - 5 hours

[0052] It should be noted that if both carbon coating and second solid electrolyte coating are used simultaneously, there is no restriction on the sequence. Coating can obtain the outer shell of the negative electrode material, improve the electronic conductivity and ionic conductivity of the negative electrode material, and is beneficial to improving the rate performance and fast charging performance of lithium-ion batteries; and coating reduces the specific surface area of the material to a certain extent, which is beneficial to improving the first Coulomb efficiency of lithium-ion batteries.

[0053] A method for preparing a negative electrode material provided by an embodiment of the present invention. First, by means of heat treatment, the first solid electrolyte is loaded on the surface of the porous carbon raw material. When silicon particles are deposited in the pore structure of the porous carbon raw material, the first solid electrolyte can avoid direct contact between the nano-silicon particles and the porous carbon raw material, inhibit the generation of electrochemically inactive silicon carbide, and improve the actual capacity of the lithium-ion battery; through the coating treatment, the electronic conductivity and ionic conductivity of the negative electrode material are further improved, its rate performance and fast charging performance are improved, and at the same time, the specific surface area of the material is reduced, and the first Coulomb efficiency of the lithium-ion battery is improved. The addition of the first solid electrolyte and the second solid electrolyte is beneficial to improving the performance of the lithium-ion battery in extreme environments.

[0054] The negative electrode material provided by the embodiment of the present invention can be applied to the electrode material of a lithium-ion battery.

[0055] To better understand the technical solution provided by the present invention, the following uses multiple specific examples to separately illustrate the specific process of preparing the negative electrode material by using the method provided by the above embodiment of the present invention, and the electrochemical characteristics of the prepared negative electrode material.

[0056] Example 1

[0057] First step: Weigh 18.13 g of lithium acetate, 20.09 g of aluminum nitrate nonahydrate, 69.02 g of ammonium dihydrogen phosphate, and 120.44 g of tetrabutyl titanate as the first solid electrolyte raw materials. Add them to 45 kg of deionized water and stir for 1.5 hours. Then add 7.5 kg of porous carbon raw materials and stir for 3 hours to obtain a slurry.

[0058] Second step: First, perform spray drying on the slurry. The inlet air temperature is 200 °C, and the outlet air temperature is 120 °C to obtain spray particles. Then, under a nitrogen flow rate of 3 L / min, place the spray particles in a high-temperature furnace. Then, heat the high-temperature furnace at a heating rate of 3 °C / min to 550 °C and keep it warm for 2.5 hours to obtain a porous carbon material loaded with LATP. The mass ratio of LATP to the porous carbon raw materials is 1%.

[0059] Third step: Take 2.5 kg of the porous carbon material and place it in a deposition furnace. Pass nitrogen into the deposition furnace at a gas flow rate of 15 L / min for protection, and heat the deposition furnace at a heating rate of 2 °C / min to 600 °C and keep it warm for 35 min. Then, pass a mixed gas of silane and nitrogen into the furnace at a ratio of 10 L / min:50 L / min and continue to keep it warm for 5.5 hours to perform chemical vapor deposition between the porous carbon material and silane, obtaining a porous carbon composite material including porous carbon, LATP, and nano-silicon particles.

[0060] Fourth step: Under a nitrogen atmosphere, place the porous carbon composite material in a coating furnace. Then, pass a mixed gas of nitrogen and methane into the coating furnace at a ratio of 15 L / min:25 L / min, and heat the coating furnace to 650 °C and keep it warm at this temperature for 7.5 hours to form a carbon layer shell, thereby obtaining a negative electrode material with a carbon layer shell and a core.

[0061] After that, use the prepared negative electrode material to prepare the electrode sheet of a lithium-ion battery, and use this electrode sheet to assemble a button-type half-cell for testing, specifically as follows:

[0062] First, take the above-mentioned negative electrode material, conductive agent Super P, and binder sodium carboxymethyl cellulose in a mass ratio of 8:1:1 and add them to a mortar for grinding. Then add deionized water and beat them in a beater to form a slurry, and coat it on a copper foil current collector. After that, dry it in a vacuum oven at 80 °C for 12 hours, and then cut the dried electrode sheet into circular pieces with a diameter of 14 mm as the electrode sheet of the button-type half-cell.

[0063] Secondly, the above-mentioned electrode was assembled into a coin-type half-cell in an argon-filled glove box. Among them, the aqueous electrolyte of the coin-type half-cell was 1 mol / L lithium hexafluorophosphate LiPF6, the solvent of the electrolyte was ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), and the volume ratio of EC, DMC, and DEC was 1:1:1. The counter electrode was a lithium sheet.

[0064] Finally, the test was carried out on a BlueTEC battery test system to evaluate its electrochemical performance. The test conditions were: voltage window 0.01V - 2V.

[0065] Example 2

[0066] First step, weigh 36.27 g of lithium acetate, 39.43 g of aluminum nitrate nonahydrate, 135.47 g of ammonium dihydrogen phosphate, and 236.40 g of tetrabutyl titanate as the first solid electrolyte raw materials, add them to 45 kg of deionized water and stir for 1.5 hours, then add 7.5 kg of porous carbon raw materials and stir for 3 hours to obtain a slurry.

[0067] Second step, first, perform spray drying on the slurry, with the inlet air temperature of 200°C and the outlet air temperature of 120°C to obtain spray particles. Then, under a nitrogen flow rate of 3 L / min, place the spray particles in a high-temperature furnace, and then heat the high-temperature furnace at a heating rate of 3°C / min to 550°C and hold for 2.5 hours to obtain a porous carbon material loaded with LATP. The mass ratio of LATP to the porous carbon raw materials was 2%.

[0068] Third step, take 2.5 kg of the porous carbon material and place it in a deposition furnace, introduce nitrogen into the deposition furnace at a gas flow rate of 15 L / min for protection, and heat the deposition furnace at a heating rate of 2°C / min to 600°C and hold for 35 min. Then, introduce a mixed gas of silane and nitrogen at a ratio of 10 L / min:50 L / min and continue to hold for 5.5 hours to perform chemical vapor deposition of the porous carbon material with silane to obtain a porous carbon composite material including porous carbon, LATP, and nano-silicon particles.

[0069] Fourth step, under a nitrogen atmosphere, place the porous carbon composite material in a coating furnace, then introduce a mixed gas of nitrogen and methane into the coating furnace at a ratio of 15 L / min:25 L / min, and heat the coating furnace to 650°C and hold at this temperature for 7.5 hours to form a carbon layer shell, thereby obtaining a negative electrode material with a carbon layer shell and a core.

[0070] After that, the assembly and testing of the coin-type half-cell were the same as in Example 1.

[0071] Example 3

[0072] First step: Weigh 90.67 g of lithium acetate, 98.58 g of aluminum nitrate nonahydrate, 338.69 g of ammonium dihydrogen phosphate, and 591 g of tetrabutyl titanate as the first solid electrolyte raw materials. Add them to 45 kg of deionized water and stir for 1.5 hours. Then add 7.5 kg of porous carbon raw materials and stir for 3 hours to obtain a slurry.

[0073] Second step: First, perform spray drying on the slurry. The inlet air temperature is 200 °C, and the outlet air temperature is 120 °C to obtain spray particles. Then, under a nitrogen flow rate of 3 L / min, place the spray particles in a high-temperature furnace. Then, heat the high-temperature furnace at a heating rate of 3 °C / min to 550 °C and keep it warm for 2.5 hours to obtain a porous carbon material loaded with LATP. The mass ratio of LATP to the porous carbon raw materials is 5%.

[0074] Third step: Take 2.5 kg of the porous carbon material and place it in a deposition furnace. Pass nitrogen into the deposition furnace at a gas flow rate of 15 L / min for protection, and heat the deposition furnace at a heating rate of 2 °C / min to 600 °C and keep it warm for 35 min. Then, pass a mixed gas of silane and nitrogen into the furnace at a ratio of 10 L / min:50 L / min and continue to keep it warm for 5.5 hours to perform chemical vapor deposition between the porous carbon material and silane, obtaining a porous carbon composite material including porous carbon, LATP, and nano-silicon particles.

[0075] Fourth step: Under a nitrogen atmosphere, place the porous carbon composite material in a coating furnace. Then, pass a mixed gas of nitrogen and methane into the coating furnace at a ratio of 15 L / min:25 L / min, and heat the coating furnace to 650 °C. Keep it warm at this temperature for 7.5 hours to form a carbon layer shell, thereby obtaining a negative electrode material with a carbon layer shell and a core.

[0076] After that, the assembly and testing of the coin-type half-cell are the same as in Example 1.

[0077] Comparative Example 1

[0078] First step: Take 2.5 kg of the porous carbon raw materials and place them in a deposition furnace. Pass nitrogen into the deposition furnace at a gas flow rate of 15 L / min for protection, and heat the deposition furnace at a heating rate of 2 °C / min to 600 °C and keep it warm for 35 min. Then, pass a mixed gas of silane and nitrogen into the furnace at a ratio of 10 L / min:50 L / min and continue to keep it warm for 5.5 hours to perform chemical vapor deposition between the porous carbon raw materials and silane, obtaining a porous carbon composite material including porous carbon and nano-silicon particles.

[0079] Step 4: Under a nitrogen atmosphere, place the porous carbon composite material in a coating furnace. Then, introduce a mixed gas of nitrogen and methane into the coating furnace at a ratio of 15 L / min:25 L / min, and heat the coating furnace to 650 °C. Keep it at this temperature for 7.5 hours to form a carbon layer shell, thereby obtaining a negative electrode material with a carbon layer shell and a core.

[0080] After that, the assembly and testing of the coin-type half-cell were the same as in Example 1.

[0081] Comparative Example 2

[0082] Step 1: Take 2.5 kg of porous carbon raw material and place it in a deposition furnace. Introduce nitrogen into the deposition furnace at a gas flow rate of 15 L / min for protection, and heat the deposition furnace to 600 °C at a heating rate of 2 °C / min. Keep it at this temperature for 35 min, and then introduce a mixed gas of disilane and nitrogen at a ratio of 10 L / min:50 L / min. Keep it at this temperature for another 5.5 hours to perform chemical vapor deposition of the porous carbon raw material with silane, thereby obtaining a porous carbon composite material including porous carbon and nano-silicon particles.

[0083] Step 4: Under a nitrogen atmosphere, place the porous carbon composite material in a coating furnace. Then, introduce a mixed gas of nitrogen and methane into the coating furnace at a ratio of 15 L / min:25 L / min, and heat the coating furnace to 650 °C. Keep it at this temperature for 7.5 hours to form a carbon layer shell, thereby obtaining a negative electrode material with a carbon layer shell and a core.

[0084] After that, the assembly and testing of the coin-type half-cell were the same as in Example 1.

[0085] Table 1 shows the rate performance test data of the coin-type half-cells prepared in Examples 1-3 and Comparative Examples 1-2.

[0086]

[0087]

[0088] Table 1

[0089] As can be seen from Table 1, compared with Comparative Examples 1 and 2, the coin-type half-cells of the embodiments of the present invention exhibit excellent rate performance. This is because the core of the negative electrode material of the present application is loaded with LATP, which can effectively inhibit the formation of silicon carbide, improve the interfacial transport rate during the electrochemical reaction of the battery, and avoid the loss of specific capacity during the charge and discharge process of the battery.

[0090] Table 2 shows the comparative data of the capacity retention rate of the coin-type half-cells prepared in Examples 1-3 and Comparative Examples 1-2 after 100 cycles at a current density of 0.1C and a temperature of 80 °C.

[0091] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Capacity retention rate 84.8％ 86.9％ 82.7％ 45.9％ 46.4％

[0092] Table 2

[0093] As can be seen from Table 2, compared with Comparative Examples 1 and 2, the cycle retention rate of the button half-cell of the embodiment of the present invention under this test condition remains above 80%. This is because the core of the negative electrode material of the present application is loaded with LATP, which can improve the cycle stability of the lithium-ion battery under higher temperature conditions.

[0094] Example 4

[0095] First step, weigh 68.96 g of lithium nitrate, 232.68 g of lanthanum nitrate, and 481.28 g of tetrabutyl titanate as the first solid electrolyte raw materials, add them to 50 kg of ethanol and stir for 2 hours, then add 7.5 kg of porous carbon raw materials and stir for 4 hours to obtain a slurry.

[0096] Second step, first, perform spray drying on the slurry, with the inlet air temperature being 150 °C and the outlet air temperature being 100 °C to obtain spray particles. Then, under an argon flow rate of 10 L / min, place the spray particles in a high-temperature furnace, and then heat the high-temperature furnace at a heating rate of 2 °C / min to 400 °C and hold for 5 hours to obtain a porous carbon material loaded with LLTO. The mass ratio of LLTO to the porous carbon raw materials is 3%.

[0097] Third step, take 2.5 kg of the porous carbon material and place it in a deposition furnace, introduce helium into the deposition furnace at a gas flow rate of 15 L / min for protection, and heat the deposition furnace at a heating rate of 8 °C / min to 400 °C and hold for 40 min. Then, introduce a mixed gas of disilane and helium at a ratio of 40 L / min:50 L / min and continue to hold for 2 hours to perform chemical vapor deposition of the porous carbon material with disilane to obtain a porous carbon composite material including porous carbon, LLTO, and nano-silicon particles.

[0098] Fourth step, mix the porous carbon composite material and LLTO slurry and perform spray drying, with the inlet air temperature being 150 °C and the outlet air temperature being 100 °C to obtain spray particles. Then, under an argon flow rate of 10 L / min, place the spray particles in a high-temperature furnace, and then heat the high-temperature furnace at a heating rate of 2 °C / min to 400 °C and hold for 5 hours to form an LLTO layer shell, thereby obtaining a negative electrode material with an LLTO layer shell and a core.

[0099] After that, use the prepared negative electrode material to prepare the electrode sheet of the lithium-ion battery, and use this electrode sheet to assemble a button half-cell for testing, specifically as follows:

[0100] First, take the above-mentioned negative electrode material, conductive agent Super P, and binder sodium carboxymethyl cellulose in a mass ratio of 8:1:1 and add them to a mortar for grinding. Then, add deionized water and beat them in a beater to form a slurry, which is coated on a copper foil current collector. After that, dry it in a vacuum oven at 80 °C for 12 hours, and then cut the dried electrode sheet into circular pieces with a diameter of 14 mm as the electrode sheets of the coin-type half-cell.

[0101] Secondly, assemble the above-mentioned electrode sheets into a coin-type half-cell in an argon-filled glove box. Among them, the solvent of the oil-based electrolyte of the coin-type half-cell is N-methylpyrrolidone (NMP). The counter electrode is a lithium sheet.

[0102] Finally, test it on a BlueTEC battery test system to evaluate its electrochemical performance. The test conditions are: voltage window 0.01 V - 2 V.

[0103] Example 5

[0104] In the first step, weigh 59.89 g of lithium hydroxide, 349.19 g of lanthanum oxide, and 88.04 g of zirconium oxide as the first solid electrolyte raw materials, add them to 45 kg of deionized water and stir for 2 hours, then add 7.5 kg of porous carbon raw materials and stir for 5 hours to obtain a slurry.

[0105] In the second step, first, perform spray drying on the slurry, with the inlet air temperature being 400 °C and the outlet air temperature being 160 °C to obtain spray particles. Then, place the spray particles in a high-temperature furnace under an argon flow rate of 5 L / min, and then heat the high-temperature furnace at a heating rate of 8 °C / min to 800 °C and hold for 1 hour to obtain a porous carbon material loaded with LLZO. The mass ratio of LLZO to the porous carbon raw materials is 4%.

[0106] In the third step, take 2.5 kg of the porous carbon material and place it in a deposition furnace. Pass argon into the deposition furnace at a gas flow rate of 15 L / min for protection, and heat the deposition furnace at a heating rate of 4 °C / min to 1000 °C and hold for 30 min. Then, pass a mixed gas of silane and argon into the deposition furnace at a ratio of 10 L / min:20 L / min and continue to hold for 5 hours to perform chemical vapor deposition of the porous carbon material with silane to obtain a porous carbon composite material including porous carbon, LLZO, and nano-silicon particles.

[0107] In the fourth step, under a nitrogen atmosphere, place the porous carbon composite material in a coating furnace, then pass a mixed gas of nitrogen and ethylene into the coating furnace at a ratio of 40 L / min:50 L / min, and heat the coating furnace to 1000 °C and hold at this temperature for 2 hours to form a carbon layer shell, thereby obtaining a negative electrode material with a carbon layer shell and a core.

[0108] Example 6

[0109] In the first step, weigh 318.30 g of lithium chloride, 77.52 g of phosphorus, and 321.07 g of sulfur as the first solid electrolyte raw materials, add them to 50 kg of ethanol and stir for 1.5 hours, then add 7.5 kg of porous carbon raw materials and stir for 3.5 hours to obtain a slurry.

[0110] In the second step, first, perform spray drying on the slurry, with the inlet air temperature being 300 °C and the outlet air temperature being 80 °C to obtain spray particles. Then, under a helium flow rate of 8 L / min, place the spray particles in a high-temperature furnace, and then heat the high-temperature furnace to 500 °C at a heating rate of 4 °C / min and hold for 3.5 hours to obtain a porous carbon material loaded with Li3PS4. The mass ratio of Li3PS4 to the porous carbon raw materials is 6%.

[0111] In the third step, take 2.5 kg of the porous carbon material and place it in a deposition furnace. Pass argon into the deposition furnace at a gas flow rate of 15 L / min for protection, and heat the deposition furnace to 800 °C at a heating rate of 6 °C / min and hold for 32 min. Then, pass a mixed gas of disilane and argon into the deposition furnace at a ratio of 20 L / min:30 L / min and continue to hold for 15 hours to perform chemical vapor deposition of the porous carbon material with disilane to obtain a porous carbon composite material including porous carbon, Li3PS4, and nano-silicon particles.

[0112] In the fourth step, under an argon atmosphere, place the porous carbon composite material in a coating furnace, then pass a mixed gas of argon and propyne into the coating furnace at a ratio of 10 L / min:30 L / min, and heat the coating furnace to 500 °C and hold at this temperature for 16 hours to form a carbon layer shell, thereby obtaining a negative electrode material with a carbon layer shell and a core.

[0113] Example 7

[0114] In the first step, weigh 234.45 g of lithium sulfide, 226.81 g of phosphorus pentasulfide, and 139.57 g of germanium disulfide as the first solid electrolyte raw materials, add them to 45 kg of ethanol and stir for 2 hours, then add 7.5 kg of porous carbon raw materials and stir for 4 hours to obtain a slurry.

[0115] In the second step, first, perform spray drying on the slurry, with the inlet air temperature being 260 °C and the outlet air temperature being 200 °C to obtain spray particles. Then, under a helium flow rate of 7 L / min, place the spray particles in a high-temperature furnace, and then heat the high-temperature furnace to 700 °C at a heating rate of 6 °C / min and hold for 3 hours to obtain a porous carbon material loaded with 10 Li 12 GeP2S 10 Li 12It accounts for 8% of the mass of the porous carbon raw material.

[0116] In the third step, take 2.5 kg of the porous carbon material and place it in a deposition furnace. Pass argon into the deposition furnace at a gas flow rate of 15 L / min for protection, and heat the deposition furnace to 700 °C at a heating rate of 5 °C / min. Keep it at this temperature for 38 min. Then, pass a mixed gas of disilane and argon into the furnace at a ratio of 10 L / min:25 L / min, and continue to keep it at this temperature for 10 hours, so that the porous carbon material undergoes chemical vapor deposition with disilane to obtain a porous carbon composite material including porous carbon, Li 10 GeP2S 12 and nano-silicon particles.

[0117] In the fourth step, under a nitrogen atmosphere, place the porous carbon composite material in a coating furnace. Then, pass a mixed gas of nitrogen and butene into the coating furnace at a ratio of 10 L / min:20 L / min, and heat the coating furnace to 800 °C. Keep it at this temperature for 8 hours to form a carbon layer shell; then, mix the porous carbon composite material with the carbon layer shell and Li 10 GeP2S 12 slurry and conduct spray drying treatment. The inlet air temperature is 400 °C, and the outlet air temperature is 200 °C to obtain spray particles. Then, place the spray particles in a high-temperature furnace under a helium flow rate of 7 L / min, and heat the high-temperature furnace to 400 °C at a heating rate of 6 °C / min. Keep it at this temperature for 5 hours to form a Li 10 GeP2S 12 layer shell, thereby obtaining a negative electrode material with a carbon layer, a Li 10 GeP2S 12 layer shell and a core.

[0118] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A negative electrode material, characterized in that, The structure of the negative electrode material includes a core and a shell; The composition of the core includes porous carbon, a first solid electrolyte, and nano-silicon particles; the first solid electrolyte is loaded on the surface of the porous carbon and in the pore structure of the porous carbon; the nano-silicon particles are deposited in the pore structure of the porous carbon; The shell coats the outer surface of the core, and the composition of the shell includes a carbon material and / or a second solid electrolyte.

2. The negative electrode material according to claim 1, wherein The first solid electrolyte is an oxide solid electrolyte and / or a sulfide solid electrolyte.

3. The negative electrode material according to claim 1, wherein, The second solid electrolyte is an oxide solid electrolyte and / or a sulfide solid electrolyte.

4. A method for preparing the negative electrode material according to any one of claims 1-3 above, characterized in that, The preparation method includes: Adding a first solid electrolyte raw material and a porous carbon raw material into a solvent and stirring to obtain a slurry; Performing heat treatment on the slurry to obtain a porous carbon material loaded with a first solid electrolyte; Under an inert atmosphere, subjecting the porous carbon material to chemical vapor deposition with a silicon source gas to obtain a porous carbon composite material including porous carbon, a first solid electrolyte, and nano-silicon particles; Under an inert atmosphere, performing a coating treatment on the porous carbon composite material to obtain a shell containing a carbon material and / or a second solid electrolyte, thereby obtaining the negative electrode material.

5. The preparation method according to claim 4, wherein The heat treatment is spray drying and high-temperature calcination; The conditions for spray drying: inlet air temperature 150°C - 400°C, outlet air temperature 80°C - 200°C; The conditions for high-temperature calcination: temperature 400°C - 800°C, time 1 hour - 5 hours.

6. The preparation method according to claim 4, characterized in that, The temperature for chemical vapor deposition is 400°C - 1000°C, and the time is 2 hours - 15 hours.

7. The preparation method according to claim 4, wherein The coating treatment includes carbon coating and / or second solid electrolyte coating; The conditions for carbon coating are: temperature 300°C - 1000°C, time 2 hours - 20 hours; The second solid electrolyte coating includes a spray drying stage and a high-temperature calcination stage; The conditions for the spray drying stage: inlet air temperature 150°C - 400°C, outlet air temperature 80°C - 200°C; The conditions for the high-temperature calcination stage: temperature 400°C - 800°C, time 1 hour - 5 hours.

8. The preparation method according to claim 7, characterized in that, The carbon source for carbon coating is one or more of alkanes, alkenes, and alkynes.

9. A negative electrode sheet, characterized in that, The negative electrode sheet includes the negative electrode material according to any one of claims 1 - 3 or the negative electrode material prepared by the preparation method according to any one of claims 4 - 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode sheet according to claim 9; the electrolyte of the lithium-ion battery is an aqueous electrolyte or an oil-based electrolyte.

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