A negative electrode material, a preparation method therefor, and an application thereof

Abstract

The application discloses a kind of negative electrode material and its preparation method and application, negative electrode material includes: porous Si C, silicon nanometer layer and carbon nanometer layer;Wherein, the layer number of silicon nanometer layer is greater than or equal to 1, the layer number of carbon nanometer layer is greater than or equal to 1;Negative electrode material uses porous Si C as framework, silicon nanometer layer and carbon nanometer layer are spaced distribution in the pore of porous Si C;The pore size of the pore of porous S i C is between 1nm-500nm;The thickness of silicon nanometer layer is between 1nm-50nm;The thickness of carbon nanometer layer is between 1nm-50nm;Lithium battery prepared by using the negative electrode material provided in the embodiment of the application has lower volume expansion rate, higher mass specific capacity, good conductivity and cycle life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery materials, in particular to a negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] Silicon material can reach the highest theoretical capacity of 4200 mAh / g (Li4.4Si) in the complete lithium intercalation state, which is more than 10 times that of graphite material, and even higher than the capacity of 3860 mAh / g of metal lithium negative electrode. Moreover, silicon material also has the properties of rich reserves and environmental protection, and is one of the most promising commercial lithium-ion battery (LIBs) negative electrode materials. However, silicon negative electrode material also has a serious volume expansion problem. In the complete lithium intercalation state, the volume expansion can reach about 300%, and the huge stress generated in the expansion process not only causes the breakage of silicon negative electrode particles, but also destroys the binder network of the electrode, leading to electrode pulverization, loss of active material, and seriously affecting the cycle performance of the silicon negative electrode. In addition, the low conductivity of the silicon negative electrode material further limits the commercial application of the silicon negative electrode material.

[0003] Therefore, it is necessary to develop a negative electrode material which can solve the problems of volume expansion rate and poor conductivity of the silicon negative electrode material and is suitable for commercial application. SUMMARY

[0004] The present application provides a negative electrode material and a preparation method and application thereof. The silicon nanolayer and the carbon nanolayer are sequentially and intermittently distributed in the pores of the porous SiC by the gas deposition method and automatic control of the feeding parameters. The deposition thickness of the silicon layer and the carbon layer intermittently distributed in the pores of the porous SiC is in the nanometer scale, and the conductivity of the carbon nanolayer itself can improve the conductivity of the overall material. The negative electrode material provided by the present application can effectively inhibit the volume expansion of the silicon particles in the silicon nanolayer by the high hardness and high strength of the porous SiC skeleton. Meanwhile, the intermittent carbon nanolayer can not only improve the conductivity of the overall material, but also inhibit the volume expansion of silicon. The volume expansion of silicon is inhibited by the synergistic effect of the skeleton structure of the porous SiC and the carbon nanolayer, so that the negative electrode sheet prepared by the negative electrode material has a relatively optimal volume expansion rate.

[0005] In addition, in the gas deposition process, the method of intermittent deposition is adopted to deposit the silicon nanolayer and the carbon nanolayer in the pores of the porous SiC, which effectively avoids the generation of Si-C bonds at high temperature, thereby avoiding the capacity loss of the material and improving the reversible capacity of the battery. Therefore, the lithium battery prepared by the negative electrode material provided by the present application has a relatively low volume expansion rate, a relatively high mass specific capacity, good conductivity and cycle life.

[0006] In a first aspect, embodiments of the present invention provide a negative electrode material, the negative electrode material comprising: porous SiC, a silicon nanolayer, and a carbon nanolayer;

[0007] Wherein, the number of silicon nanolayers is greater than or equal to 1, and the number of carbon nanolayers is greater than or equal to 1; the negative electrode material uses porous SiC as a framework, and the silicon nanolayers and the carbon nanolayers are distributed alternately in the pores of the porous SiC;

[0008] The pore size of the porous SiC is between 1 nm and 500 nm.

[0009] The thickness of the silicon nanolayer is between 1 nm and 50 nm.

[0010] The thickness of the carbon nanolayer is between 1 nm and 50 nm.

[0011] Preferably, the porous SiC has a particle size Dv50 between 300 nm and 100 μm; and the porous SiC has a porosity between 30% and 95%.

[0012] The silicon nanolayer accounts for 50%-80% of the total mass of the negative electrode material; the carbon nanolayer accounts for 10%-40% of the total mass of the negative electrode material.

[0013] Preferably, the negative electrode material further includes a carbon coating layer; the mass of the carbon coating layer accounts for 0-20% of the total mass of the negative electrode material.

[0014] In a second aspect, embodiments of the present invention provide a method for preparing the negative electrode material described in the first aspect above, the method comprising:

[0015] Step 1: Under an argon atmosphere, porous SiC is placed on a substrate in the deposition chamber of a vapor deposition furnace. Silicon-containing gas is introduced into the deposition chamber through a first carrier gas from the first furnace chamber, causing the silicon to cool and deposit onto the pore walls of the porous SiC to form a silicon nanolayer. The first furnace chamber and the deposition chamber are connected through a first gas inlet. Before introducing the silicon-containing gas, the parameters of the automatic gas inlet valve are adjusted to control the amount of silicon-containing gas introduced.

[0016] Step 2: Carbon-containing gas is introduced into the deposition chamber from the second furnace chamber through the second carrier gas, so that carbon is deposited onto the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. The second furnace chamber and the deposition chamber are connected through the second gas inlet. Before the carbon-containing gas is introduced, the parameters of the automatic gas inlet valve of the second gas inlet are adjusted to control the amount of carbon-containing gas introduced.

[0017] Repeat steps one and two, alternating between introducing a silicon-containing gas and a carbon-containing gas to obtain the negative electrode material.

[0018] The negative electrode material uses porous SiC as a framework, with silicon nanolayers and carbon nanolayers distributed alternately in the pores of the porous SiC; the number of silicon nanolayers is greater than or equal to 1, and the number of carbon nanolayers is greater than or equal to 1.

[0019] The pore size of the porous SiC is between 1 nm and 500 nm.

[0020] The thickness of the silicon nanolayer is between 1 nm and 50 nm.

[0021] The thickness of the carbon nanolayer is between 1 nm and 50 nm.

[0022] The number of times that steps one and two are repeated is greater than or equal to zero.

[0023] Preferably, the process for preparing the silicon-containing gas is as follows: under a protective atmosphere or reduced pressure, the first silicon source material is placed in the first furnace cavity, heated to 500℃-2000℃, and held for 1 hour to 5 hours to allow the first silicon source material to vaporize and dissociate, thereby obtaining the silicon-containing gas; or the second silicon source material is directly introduced and heated to 500℃-2000℃, and held for 20 minutes to 5 hours to obtain the silicon-containing gas.

[0024] The first silicon source material is a solid and / or liquid, specifically including one or more of silicon powder, hexamethyldisilane, and tris(trimethylsilyl)silane;

[0025] The second silicon source material is a gas, specifically including one or more of silane, silane, tetrafluorosilane, and chlorosilane; the gas flow rate of the second silicon source material is 0.1L / min-5L / min.

[0026] Preferably, the process for preparing the carbon-containing gas is as follows: under a protective atmosphere or reduced pressure, the first carbon source material is placed in the second furnace cavity, heated to 500℃-1300℃, and held for 30 minutes to 3 hours to allow the first carbon source material to vaporize and dissociate, thereby obtaining the carbon-containing gas; or the second carbon source material is directly introduced and heated to 500℃-1300℃, and held for 10 minutes to 3 hours to obtain the carbon-containing gas.

[0027] The first carbon source material is a liquid, specifically including one or more of the following: liquid asphalt, acetone, anhydrous ethanol, and tetrahydrofuran solution containing phenolic resin;

[0028] The second carbon source material is a gas, specifically including one or more of methane, ethane, ethylene, propane, propylene, acetylene, and natural gas; the gas flow rate of the second carbon source material is 0.1 L / min to 5 L / min.

[0029] Preferably, the parameters of the automatic air intake valve of the first air inlet are as follows: the time for introducing the silicon-containing gas is 1 min to 20 min, the first carrier gas is nitrogen or argon, and the flow rate of the first carrier gas is 0.5 L / min to 5 L / min.

[0030] The parameters for the automatic intake valve of the second intake port are as follows: the time for introducing the carbon-containing gas is 20s-20min, the second carrier gas is nitrogen or argon, and the flow rate of the second carrier gas is 0.5L / min-5L / min.

[0031] The time interval between introducing silicon-containing gas and carbon-containing gas is 5 seconds to 5 minutes.

[0032] Preferably, the preparation method further includes: carbon coating the negative electrode material;

[0033] The carbon coating method includes one of the following: gas phase coating, liquid phase coating or solid phase coating;

[0034] The mass of the carbon coating layer accounts for 0-20% of the total mass of the high-performance silicon-oxygen anode material.

[0035] Thirdly, embodiments of the present invention provide a negative electrode sheet, the negative electrode sheet comprising the negative electrode material described in the first aspect above.

[0036] Fourthly, embodiments of the present invention provide a lithium battery, the lithium battery including the negative electrode sheet described in the third aspect above.

[0037] This invention provides an anode material, its preparation method, and its application. Through vapor deposition and automatic control of feed parameters, silicon nanolayers and carbon nanolayers are sequentially and interspersed within the pores of porous SiC. Since the deposition thickness of the silicon and carbon layers interspersed within the porous SiC pores is at the nanoscale, coupled with the conductivity of the carbon nanolayers themselves, the overall conductivity of the material can be improved. The anode material provided by this invention utilizes the high hardness and strength of the porous SiC framework to effectively suppress the volume expansion of silicon particles in the silicon nanolayers. Simultaneously, the interspersed carbon nanolayers not only improve the overall conductivity of the material but also suppress silicon volume expansion. Through the synergistic effect of the porous SiC framework structure and the carbon nanolayers, the volume expansion of silicon is suppressed, resulting in an anode sheet prepared from the anode material of this invention exhibiting a superior volume expansion rate.

[0038] Furthermore, in the vapor deposition process of this invention, an intermittent deposition method is used to deposit silicon nanolayers and carbon nanolayers separately in the pores of porous SiC, effectively avoiding the formation of Si-C bonds at high temperatures, thereby preventing capacity loss and improving the reversible capacity of the battery. Therefore, the lithium battery prepared using the negative electrode material provided in this invention has a low volume expansion rate, high specific capacity, good conductivity, and cycle life. Attached Figure Description

[0039] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples.

[0040] Figure 1 This is a flowchart of the preparation method of the negative electrode material provided in the embodiments of the present invention;

[0041] Figure 2 This is a schematic diagram of the structure of the negative electrode material provided in an embodiment of the present invention;

[0042] Figure 3 These are charge-discharge curves of a coin cell assembled with the negative electrode material provided in Embodiment 1 of the present invention and a coin cell assembled with the silicon-carbon negative electrode material in Comparative Example 1.

[0043] Figure 4 This is a charge-discharge curve of a coin cell assembled with silicon-based anode material provided in Comparative Example 2 of this invention. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any way, that is, not intended to limit the scope of protection of the present invention.

[0045] This invention provides a negative electrode material comprising: porous SiC, silicon nanolayers, and carbon nanolayers; wherein the negative electrode material uses porous SiC as a framework, and the silicon nanolayers and carbon nanolayers are distributed alternately in the pores of the porous SiC.

[0046] The silicon nanolayer accounts for 50%-80% of the total mass of the anode material, the number of silicon nanolayers is greater than or equal to 1, and the thickness is between 1nm and 50nm.

[0047] The carbon nanolayer accounts for 10%-40% of the total mass of the negative electrode material. The number of carbon nanolayers is greater than or equal to 1, and the thickness is between 1nm and 50nm.

[0048] In optional designs, the anode material also includes a carbon coating layer; the mass of the carbon coating layer accounts for 0-20% of the total mass of the anode material.

[0049] This invention provides a method for preparing the above-mentioned negative electrode material, such as... Figure 1 As shown, the specific steps include:

[0050] Step 110: Under an argon atmosphere, place porous SiC on a substrate in the deposition chamber of a vapor deposition furnace;

[0051] Among them, the pore size of porous SiC is 1nm-500nm, the particle size Dv50 is 300nm-100μm, and the porosity is 30%-95%.

[0052] The temperature in the sedimentation chamber is raised to 600℃-800℃.

[0053] Step 120: Prepare a silicon-containing gas. Under a protective atmosphere or reduced pressure, place the first silicon source material in the first furnace chamber, heat it to 500℃-2000℃, and hold it for 1 hour to 5 hours to allow the first silicon source material to vaporize and dissociate, thereby obtaining the silicon-containing gas. Alternatively, directly introduce the second silicon source material, heat it to 500℃-2000℃, and hold it for 20 minutes to 5 hours to obtain the silicon-containing gas.

[0054] The protective atmosphere in the first furnace chamber is a nitrogen atmosphere or an argon atmosphere, and the flow rate of the protective gas is 0.1L / min-8L / min; the specific pressure reduction condition is: the first furnace chamber is evacuated to 10Pa-250Pa.

[0055] The first silicon source material is a solid and / or liquid, specifically including one or more of silicon powder, hexamethyldisilane, and tris(trimethylsilyl)silane; when the first silicon source material is liquid, it can be placed directly into the first furnace cavity, or the liquid first silicon source material can be introduced into the first furnace cavity by bubbling with carrier gas nitrogen or argon.

[0056] The second silicon source material is a gas, specifically including one or more of the following: silane, silane, tetrafluorosilane, and chlorosilane; the gas flow rate of the second silicon source material is 0.1L / min-5L / min.

[0057] Step 130: Prepare carbon-containing gas. Under a protective atmosphere or reduced pressure, place the first carbon source material in the second furnace chamber, heat it to 500℃-1300℃, and hold it for 30 minutes to 3 hours to allow the first carbon source material to vaporize and dissociate, thereby obtaining the carbon-containing gas. Alternatively, directly introduce the second carbon source material, heat it to 500℃-1300℃, and hold it for 10 minutes to 3 hours to obtain the carbon-containing gas.

[0058] The protective atmosphere in the second furnace chamber is a nitrogen atmosphere or an argon atmosphere, and the flow rate of the protective gas is 0.1L / min-8L / min; the specific pressure reduction condition is: the second furnace chamber is evacuated to 10Pa-250Pa;

[0059] The first carbon source material is a liquid, specifically including one or more of liquid asphalt, acetone, anhydrous ethanol, and tetrahydrofuran solution containing phenolic resin. When the first carbon source material is used, it can be placed directly into the second furnace chamber, or the liquid first carbon source material can be introduced into the second furnace chamber by bubbling with carrier gas nitrogen or argon.

[0060] The second carbon source material is a gas, specifically including one or more of methane, ethane, ethylene, propane, propylene, acetylene, and natural gas; the gas flow rate of the second carbon source material is 0.1 L / min to 5 L / min.

[0061] Step 140: The silicon-containing gas is introduced into the deposition chamber through the first carrier gas from the first furnace chamber, so that the silicon element is cooled and deposited on the pore walls of the porous SiC to form a silicon nanolayer. The first furnace chamber and the deposition chamber are connected through the first gas inlet. Before the silicon-containing gas is introduced, the parameters of the automatic gas inlet valve of the first gas inlet are adjusted to control the amount of silicon-containing gas introduced.

[0062] The parameters for the automatic intake valve of the first intake port are as follows: the time for introducing silicon-containing gas is 60s-20min, the first carrier gas is nitrogen or argon, and the flow rate of the first carrier gas is 0.5L / min-5L / min.

[0063] Step 150: Carbon-containing gas is introduced into the deposition chamber from the second furnace chamber through the second carrier gas, so that carbon is deposited onto the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. The second furnace chamber and the deposition chamber are connected through the second gas inlet. Before the carbon-containing gas is introduced, the parameters of the automatic gas inlet valve of the second gas inlet are adjusted to control the amount of carbon-containing gas introduced.

[0064] The parameters for the automatic intake valve of the second intake port are as follows: the time for introducing carbon-containing gas is 60s-20min, the second carrier gas is nitrogen or argon, and the flow rate of the second carrier gas is 0.5L / min-5L / min.

[0065] Step 160, repeat steps 140 and 150, and alternately introduce a gas containing silicon and a gas containing carbon to obtain the negative electrode material.

[0066] Among them, the number of times steps 140 and 150 are repeated is greater than or equal to zero; the time interval between introducing silicon-containing gas and carbon-containing gas is 5s-5min.

[0067] In optional embodiments, the preparation method further includes: carbon coating of the anode material; the carbon coating method includes: one of gas phase coating, liquid phase coating or solid phase coating; the mass of the carbon coating layer accounts for 0-20% of the total mass of the high-performance silicon-oxygen anode material.

[0068] A schematic diagram of the structure of the carbon-coated negative electrode material prepared is shown below. Figure 2 As shown, through Figure 2 As can be seen, the anode material with carbon coating uses porous SiC as a framework, with silicon nanolayers and carbon nanolayers distributed alternately in the pores of porous SiC.

[0069] This application proposes that the time interval between introducing silicon-containing gas and carbon-containing gas is 5s-5min. That is, after introducing silicon-containing gas into the deposition chamber, wait 5s-5min to allow the silicon-containing gas in the deposition chamber to be completely deposited, and then introduce carbon-containing gas into the deposition chamber. This allows the silicon nanolayers and carbon nanolayers deposited in the pores of porous SiC to be distributed alternately. The time interval can be, for example, 5s, 10s, 1min, 2min, 5min or any time within the range.

[0070] The negative electrode material prepared by the present invention can be used as an active material for lithium battery negative electrode materials and for preparing lithium battery negative electrode sheets. The negative electrode sheet of this application also includes a negative electrode current collector. This application does not have any particular limitation on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, copper foil, copper alloy foil, nickel foil, stainless steel foil, or composite current collectors.

[0071] Lithium batteries using the negative electrode material of this invention as the negative electrode material can include, but are not limited to, lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries. Lithium batteries prepared using the negative electrode material provided in the embodiments of this invention exhibit low volume expansion, high specific capacity, good conductivity, and long cycle life.

[0072] To better understand the technical solution provided by this invention, the preparation process and characteristics of the negative electrode material of this invention are illustrated below with several specific examples.

[0073] Example 1

[0074] This embodiment provides a preparation process and performance testing of a negative electrode material. The specific preparation process is as follows.

[0075] 1) Under an argon atmosphere at room temperature, 2 kg of porous SiC was placed on a substrate in the deposition chamber of a vapor deposition furnace. The porous SiC had a particle size Dv50 of 300 nm, a pore size distribution between 50 nm and 150 nm, and a porosity of 70%.

[0076] 2) To prepare a silicon-containing gas, the first chamber of the deposition chamber was evacuated to 50 Pa, and silane with a flow rate of 2 L / min was introduced for 5 min. The temperature was then raised to 2000 °C and held for 30 min to obtain a silicon-containing gas.

[0077] 3) To prepare a carbon-containing gas, the second chamber of the deposition chamber was evacuated to 50 Pa, and acetylene was introduced at a flow rate of 3 L / min for 1 min. The temperature was then raised to 1300℃ and held for 10 minutes to obtain a carbon-containing gas.

[0078] 4) The silicon-containing gas is introduced into the deposition chamber through the first gas inlet by nitrogen gas from the first furnace chamber, so that the silicon element is cooled and deposited on the pore walls of the porous SiC to form a silicon nanolayer. Before the silicon-containing gas is introduced, the parameters of the automatic gas inlet valve of the first gas inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 2L / min and the introduction time is 1min, so as to obtain a silicon nanolayer with a thickness of 12nm.

[0079] 5) Carbon-containing gas is introduced into the deposition chamber through the second gas inlet by nitrogen gas from the second furnace chamber, so that carbon elements are deposited on the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. Before introducing the carbon-containing gas, the parameters of the automatic gas inlet valve of the second gas inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 2L / min and the introduction time is 20s, so as to obtain a carbon nanolayer with a thickness of 8nm.

[0080] 6) Repeat steps 5) and 6) 3 times, introducing silicon-containing gas and carbon-containing gas at intervals of 1 minute each time, to obtain the negative electrode material.

[0081] The prepared anode material is carbon coated, specifically: 1 kg of anode material is placed in a rotary furnace and heated to 800°C under a protective atmosphere. Argon and acetylene gas are introduced at a volume ratio of 2:1 for gas phase coating. After holding at this temperature for 110 min, the organic gas source is turned off. After cooling to room temperature, the material is discharged and graded to obtain the anode material with a carbon coating layer.

[0082] The negative electrode sheet was prepared using the carbon-coated negative electrode material prepared in this embodiment, and coin half-cells and full cells were assembled for testing. The specific process is as follows.

[0083] The preparation method of button half-cell is as follows: The negative electrode material containing carbon coating, conductive additive carbon black, and binder (sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:1) are weighed in a mass ratio of 95%:2%:3%, and a slurry is prepared using a pulping machine. After that, the slurry is coated, dried, cut into pieces, and assembled into button half-cells in a glove box.

[0084] The prepared coin cell half-cells were tested using a charge-discharge instrument in constant current charge-discharge mode. The discharge lithium insertion process was a stepped discharge mode: 1C discharge to 5.0mV, 0.5C discharge to 5.0mV, 0.2C discharge to 5.0mV, and 0.1C discharge to 5.0mV; the charging delithiation process was: 1C charging to 2V.

[0085] The initial efficiency and reversible capacity test data of the coin cells prepared in this embodiment are shown in Table 1, and the initial stepped discharge capacity of the coin cells is shown in Table 2.

[0086] The charge-discharge curve of the coin cell assembled with the carbon-coated negative electrode material provided in Embodiment 1 of the present invention is as follows: Figure 3 As shown.

[0087] The preparation method of the full cell is as follows: Preparation of negative electrode sheet: The negative electrode material containing carbon coating layer is prepared with graphite to form a composite with a specific capacity of 450 mAg / h, and then weighed and mixed with conductive additives and binders in a ratio of 95%:2%:3%; at room temperature, the mixed materials and solvent deionized water are put into a slurry machine to prepare a slurry; the prepared slurry is uniformly coated on copper foil at a coating speed between 2.2 m / min and 3.5 m / min, and the temperature of the coating machine drying tunnel is between 70 and 100℃; after double-sided drying in the coating machine, the negative electrode sheet is obtained.

[0088] Preparation of the positive electrode sheet: Lithium nickel cobalt manganese oxide (NMC) ternary positive electrode material, conductive agent and binder are weighed and mixed in a ratio of 96%:2%:2%; at room temperature, the mixed material and solvent N-methylpyrrolidone are put into a slurry machine to prepare a slurry; the prepared slurry is uniformly coated on aluminum foil at a coating speed of 2.0m / min-3.0m / min and a coating machine drying temperature of 90-120℃; after double-sided coating and drying, the positive electrode sheet is obtained.

[0089] Battery fabrication: The positive electrode of the positive electrode sheet is exposed using aluminum tabs, and the negative electrode sheet is exposed using copper-plated nickel tabs. The prepared positive and negative electrodes and separator are wound into a bare cell. The cell is then encapsulated with aluminum-plastic film using a high-frequency sealing process. The moisture in the battery is removed by high-temperature vacuum baking. Then, 1 mole of electrolyte is injected. The electrolyte is a mixed solution of LiPF6 and ethylene carbonate / dimethyl carbonate (EC / DMC). After vacuum sealing, the battery is obtained.

[0090] Testing: Constant current charge and discharge mode tests were conducted using a charge and discharge instrument. The discharge cutoff voltage was 2.75V, and the charging cutoff voltage was 4.2V. Both charge and discharge tests were performed at a 1C current density.

[0091] At 1C, five battery groups were removed at the first full charge cycle, 300 full charge cycles, and 600 full charge cycles, respectively. The negative electrode sheets were then removed, and the thickness of each electrode sheet was measured at 10 different locations using a thickness gauge. The average value was then recorded. Under the same testing conditions, the average thickness of the electrode sheets in their initial state was obtained.

[0092] The calculation formula is: Electrode full charge expansion rate = (Average thickness of electrode with different number of turns when fully charged - Initial average thickness of electrode) / Initial average thickness of electrode.

[0093] The test results of the expansion rate of the negative electrode sheet of the full cell prepared in this embodiment at 1C rate during the first cycle, 300 cycles, and 600 cycles are detailed in Table 1.

[0094] Example 2

[0095] This embodiment provides a preparation process and performance testing of a negative electrode material. The specific preparation process is as follows.

[0096] 1) Under an argon atmosphere at room temperature, 2 kg of porous SiC was placed on a substrate in the deposition chamber of a vapor deposition furnace. The porous SiC had a particle size Dv50 of 1 μm, a pore size distribution between 200 nm and 260 nm, and a porosity of 60%.

[0097] 2) To prepare a silicon-containing gas, the first chamber of the deposition chamber was evacuated to 70 Pa, and silane was introduced at a flow rate of 3 L / min for 8 min. The temperature was then raised to 800 °C and held for 1 hour to obtain a silicon-containing gas.

[0098] 3) To prepare a carbon-containing gas, the second chamber of the deposition chamber was evacuated to 50 Pa, propylene was introduced at a flow rate of 1 L / min for 4 min, the temperature was raised to 1000℃, and the temperature was held for 30 min to obtain a carbon-containing gas.

[0099] 4) The silicon-containing gas is introduced into the deposition chamber through the first gas inlet by nitrogen gas from the first furnace chamber, so that the silicon element is cooled and deposited on the pore walls of the porous SiC to form a silicon nanolayer. Before the silicon-containing gas is introduced, the parameters of the automatic gas inlet valve of the first gas inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 2L / min and the introduction time is 2min, so as to obtain a silicon nanolayer with a thickness of 25nm.

[0100] 5) Carbon-containing gas is introduced into the deposition chamber through the second inlet by nitrogen gas from the second furnace chamber, so that carbon elements are deposited on the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. Before introducing the carbon-containing gas, the parameters of the automatic gas inlet valve of the second inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 2L / min and the introduction time is 1min, so as to obtain a carbon nanolayer with a thickness of 24nm.

[0101] 6) Repeat steps 5) and 6) 4 times, introducing silicon-containing gas and carbon-containing gas at intervals of 2 minutes each time, to obtain the negative electrode material.

[0102] The prepared anode material is carbon coated, specifically as follows: 1 kg of anode material is placed in a rotary furnace and heated to 800°C under a protective atmosphere. A mixture of argon, propane and natural gas is introduced at a volume ratio of 3:2 for gas phase coating, wherein the volume ratio of propane and natural gas is 1:1. After holding at this temperature for 95 min, the organic gas source is turned off, and the material is discharged and graded after cooling to room temperature, thus obtaining the anode material with a carbon coating layer.

[0103] The negative electrode sheet was prepared using the carbon-coated negative electrode material prepared in this embodiment, and coin half-cells and full cells were assembled and tested. The assembly and testing methods were the same as in Example 1.

[0104] The initial efficiency and reversible capacity test data of the coin cells prepared in this embodiment are shown in Table 1, and the initial stepped discharge capacity of the coin cells is shown in Table 2; the test results of the expansion rate of the negative electrode sheet of the full cell at 1C rate for the first cycle, 300 cycles, and 600 cycles are detailed in Table 1.

[0105] Example 3

[0106] This embodiment provides a preparation process and performance testing of a negative electrode material. The specific preparation process is as follows.

[0107] 1) Under an argon atmosphere at room temperature, 2 kg of porous SiC was placed on a substrate in the deposition chamber of a vapor deposition furnace. The porous SiC had a particle size Dv50 of 500 nm, a pore size distribution between 100 nm and 180 nm, and a porosity of 87%.

[0108] 2) To prepare a silicon-containing gas, the first chamber of the deposition chamber was evacuated to 50 Pa, and chlorosilane was introduced at a flow rate of 2 L / min for 5 min. The temperature was then raised to 2000 °C and held for 2 hours to obtain a silicon-containing gas.

[0109] 3) To prepare a carbon-containing gas, natural gas with a flow rate of 3 L / min was introduced into the second furnace chamber of the deposition chamber under an argon atmosphere for 3 min. The temperature was then raised to 700℃ and held for 30 min to obtain the carbon-containing gas.

[0110] 4) The silicon-containing gas is introduced into the deposition chamber through the first gas inlet by nitrogen gas from the first furnace chamber, so that the silicon element is cooled and deposited on the pore walls of the porous SiC to form a silicon nanolayer. Before the silicon-containing gas is introduced, the parameters of the automatic gas inlet valve of the first gas inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 2L / min and the introduction time is 1min, so as to obtain a silicon nanolayer with a thickness of 12nm.

[0111] 5) Carbon-containing gas is introduced into the deposition chamber through the second gas inlet by nitrogen gas from the second furnace chamber, so that carbon elements are deposited on the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. Before introducing the carbon-containing gas, the parameters of the automatic gas inlet valve of the second gas inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 2L / min and the introduction time is 20s, so as to obtain a carbon nanolayer with a thickness of 8nm.

[0112] 6) Repeat steps 5) and 6) twice, introducing silicon-containing gas and carbon-containing gas at intervals of 3 minutes each time, to obtain the negative electrode material.

[0113] The prepared anode material is carbon coated by mixing 1 kg of anode material with asphalt emulsion at a mass ratio of 15:1 and stirring for 8 hours to form a uniform slurry. After drying the slurry, it is placed in a rotary kiln and heated to 900℃ under a protective atmosphere for 90 minutes. After cooling and grading, the anode material with a carbon coating layer is obtained.

[0114] The negative electrode sheet was prepared using the carbon-coated negative electrode material prepared in this embodiment, and coin half-cells and full cells were assembled and tested. The assembly and testing methods were the same as in Example 1.

[0115] The initial efficiency and reversible capacity test data of the coin cells prepared in this embodiment are shown in Table 1, the initial stepped discharge capacity of the coin cells is shown in Table 2, and the test results of the expansion rate of the negative electrode sheet of the full cell at 1C rate for the first, 300, and 600 cycles are detailed in Table 1.

[0116] Example 4

[0117] This embodiment provides a preparation process and performance testing of a negative electrode material. The specific preparation process is as follows.

[0118] 1) Under an argon atmosphere at room temperature, 2 kg of porous SiC was placed on a substrate in the deposition chamber of a vapor deposition furnace. The porous SiC had a particle size Dv50 of 50 μm, a pore size distribution between 300 nm and 420 nm, and a porosity of 53%.

[0119] 2) To prepare a silicon-containing gas, 1 kg of silicon powder was placed in the first chamber of the deposition chamber, the vacuum was drawn to 80 Pa, the temperature was raised to 2000 °C, and the temperature was maintained for 2 hours. The silicon powder was then vaporized and decomposed to obtain a silicon-containing gas.

[0120] 3) To prepare a carbon-containing gas, the first chamber of the deposition chamber was evacuated to 50 Pa, propane was introduced at a flow rate of 3 L / min for 2 min, and the temperature was raised to 800℃ and held for 20 min to obtain a carbon-containing gas.

[0121] 4) The silicon-containing gas is introduced into the deposition chamber through the first gas inlet by nitrogen gas from the first furnace chamber, so that the silicon element is cooled and deposited on the pore walls of the porous SiC to form a silicon nanolayer. Before the silicon-containing gas is introduced, the parameters of the automatic gas inlet valve of the first gas inlet are adjusted, and the flow rate of the carrier gas argon is set to 2L / min and the introduction time is 5min, so as to obtain a silicon nanolayer with a thickness of 50nm.

[0122] 5) Carbon-containing gas is introduced into the deposition chamber through the second gas inlet by nitrogen gas in the second furnace chamber, so that carbon is deposited on the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. Before introducing the carbon-containing gas, the parameters of the automatic gas inlet valve of the second gas inlet are adjusted, and the flow rate of carrier gas argon is set to 2L / min and the introduction time is 2min, so as to obtain a carbon nanolayer with a thickness of 16nm.

[0123] 6) Repeat steps 5) and 6) 3 times, introducing silicon-containing gas and carbon-containing gas at intervals of 5 minutes each time, to obtain the negative electrode material.

[0124] The negative electrode material prepared in this embodiment was used to prepare negative electrode sheets and assemble coin half cells and full cells for testing. The assembly and testing methods were the same as in Example 1.

[0125] The initial efficiency and reversible capacity test data of the coin cells prepared in this embodiment are shown in Table 1, the initial stepped discharge capacity of the coin cells is shown in Table 2, and the test results of the expansion rate of the negative electrode sheet of the full cell at 1C rate for the first, 300, and 600 cycles are detailed in Table 1.

[0126] Example 5

[0127] This embodiment provides a preparation process and performance testing of a negative electrode material. The specific preparation process is as follows.

[0128] 1) Under an argon atmosphere at room temperature, 2 kg of porous SiC was placed on a substrate in the deposition chamber of a vapor deposition furnace. The porous SiC had a particle size Dv50 of 100 μm, a pore size distribution between 350 nm and 500 nm, and a porosity of 70%.

[0129] 2) To prepare a silicon-containing gas, the first chamber of the deposition chamber was evacuated to 200 Pa. Tris(trimethylsilyl)silane was introduced into the first chamber by bubbling argon gas at a flow rate of 1 L / min for 10 min. The temperature was then raised to 1100 °C and held for 2 hours to obtain a silicon-containing gas.

[0130] 3) To prepare a carbon-containing gas, the second chamber of the deposition chamber was evacuated to 20 Pa. A carrier gas of argon with a flow rate of 1 L / min was bubbled into the second chamber to introduce tetrahydrofuran containing phenolic resin for 10 min. The temperature was then raised to 1000 °C and held for 1 hour to obtain a carbon-containing gas.

[0131] 4) The silicon-containing gas is introduced into the deposition chamber through the first gas inlet by nitrogen gas from the first furnace chamber, so that the silicon element is cooled and deposited on the pore walls of the porous SiC to form a silicon nanolayer. Before the silicon-containing gas is introduced, the parameters of the automatic gas inlet valve of the first gas inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 1L / min and the introduction time is 3min, so as to obtain a silicon nanolayer with a thickness of 20nm.

[0132] 5) Carbon-containing gas is introduced into the deposition chamber through the second inlet by nitrogen gas from the second furnace chamber, so that carbon is deposited on the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. Before introducing the carbon-containing gas, the parameters of the automatic gas inlet valve of the second inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 1L / min and the introduction time is 1min, so as to obtain a carbon nanolayer with a thickness of 4nm.

[0133] 6) Repeat steps 5) and 6) 5 times, introducing silicon-containing gas and carbon-containing gas at intervals of 2.5 min each time, to obtain the negative electrode material.

[0134] The prepared anode material was carbon-coated as follows: 800g of anode material and graphene were dissolved in ethanol at a ratio of 22:1 and stirred for 7 hours to form a uniform slurry. The slurry was then dried directly and placed in a rotary kiln, heated to 850℃ in a protective atmosphere and held for 1.5 hours. After cooling and grading, the carbon-coated anode material was obtained.

[0135] The negative electrode sheet was prepared using the carbon-coated negative electrode material prepared in this embodiment, and coin half-cells and full cells were assembled and tested. The assembly and testing methods were the same as in Example 1.

[0136] The initial efficiency and reversible capacity test data of the coin cells prepared in this embodiment are shown in Table 1, the initial stepped discharge capacity of the coin cells is shown in Table 2, and the test results of the expansion rate of the negative electrode sheet of the full cell at 1C rate for the first, 300, and 600 cycles are detailed in Table 1.

[0137] Example 6

[0138] This embodiment provides a preparation process and performance testing of a negative electrode material. The specific preparation process is as follows.

[0139] 1) Under an argon atmosphere at room temperature, 2 kg of porous SiC was placed on a substrate in the deposition chamber of a vapor deposition furnace. The porous SiC had a particle size Dv50 of 30 μm, a pore size distribution between 100 nm and 260 nm, and a porosity of 80%.

[0140] 2) To prepare a silicon-containing gas, the first chamber of the deposition chamber was evacuated to 30 Pa, and tetrafluorosilane with a flow rate of 0.2 L / min was introduced for 20 min. The temperature was then raised to 500 °C and held for 2 hours to obtain a silicon-containing gas.

[0141] 3) To prepare a carbon-containing gas, place acetone in the second furnace chamber of the deposition chamber, evacuate to 30 Pa, heat to 500 °C, and hold for 30 minutes to obtain a carbon-containing gas.

[0142] 4) The silicon-containing gas is introduced into the deposition chamber through the first gas inlet by nitrogen gas from the first furnace chamber, so that the silicon element is cooled and deposited on the pore walls of the porous SiC to form a silicon nanolayer. Before the silicon-containing gas is introduced, the parameters of the automatic gas inlet valve of the first gas inlet are adjusted, the flow rate of the carrier gas nitrogen is set to 0.5 L / min, and the introduction time is 2 min, so as to obtain a silicon nanolayer with a thickness of 8 nm.

[0143] 5) Carbon-containing gas is introduced into the deposition chamber through the second inlet by nitrogen gas from the second furnace chamber, so that carbon is deposited on the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. Before introducing the carbon-containing gas, the parameters of the automatic gas inlet valve of the second inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 2L / min and the introduction time is 1min, so as to obtain a carbon nanolayer with a thickness of 8nm.

[0144] 6) Repeat steps 5) and 6) 3 times, introducing silicon-containing gas and carbon-containing gas at intervals of 2 minutes to obtain the negative electrode material.

[0145] The prepared anode material is carbon coated, specifically as follows: 1 kg of anode material is placed in a rotary furnace and heated to 950°C under a protective atmosphere. Argon gas mixed with acetylene and ethylene gas is introduced at a volume ratio of 2:1 for gas phase coating, wherein the volume ratio of acetylene and ethylene is 1:1. After holding at this temperature for 75 min, the organic gas source is turned off. After cooling to room temperature, the material is discharged and graded to obtain the anode material with a carbon coating layer.

[0146] The negative electrode sheet was prepared using the carbon-coated negative electrode material prepared in this embodiment, and coin half-cells and full cells were assembled and tested. The assembly and testing methods were the same as in Example 1.

[0147] The initial efficiency and reversible capacity test data of the coin cells prepared in this embodiment are shown in Table 1, the initial stepped discharge capacity of the coin cells is shown in Table 2, and the test results of the expansion rate of the negative electrode sheet of the full cell at 1C rate for the first, 300, and 600 cycles are detailed in Table 1.

[0148] Example 7

[0149] This embodiment provides a preparation process and performance testing of a negative electrode material. The specific preparation process is as follows.

[0150] 1) Under an argon atmosphere at room temperature, 2 kg of porous SiC was placed on a substrate in the deposition chamber of a vapor deposition furnace. The porous SiC had a particle size Dv50 of 800 nm, a pore size distribution between 80 nm and 160 nm, and a porosity of 95%.

[0151] 2) To prepare a silicon-containing gas, the first chamber of the deposition chamber was evacuated to 150 Pa, and silane with a flow rate of 0.8 L / min was introduced for 15 min. The temperature was then raised to 1700 °C and held for 30 min to obtain a silicon-containing gas.

[0152] 3) To prepare a carbon-containing gas, the first chamber of the deposition chamber was evacuated to 50 Pa, and ethane was introduced at a flow rate of 1 L / min for 18 min. The temperature was then raised to 1300℃ and held for 20 min to obtain a carbon-containing gas.

[0153] 4) The silicon-containing gas is introduced into the deposition chamber through the first gas inlet by nitrogen gas from the first furnace chamber, so that the silicon element is cooled and deposited on the pore walls of the porous SiC to form a silicon nanolayer. Before the silicon-containing gas is introduced, the parameters of the automatic gas inlet valve of the first gas inlet are adjusted, the flow rate of the carrier gas nitrogen is set to 1L / min, and the introduction time is 2.5min, so as to obtain a silicon nanolayer with a thickness of 17nm.

[0154] 5) Carbon-containing gas is introduced into the deposition chamber through the second inlet by nitrogen gas from the second furnace chamber, so that carbon is deposited on the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. Before introducing the carbon-containing gas, the parameters of the automatic gas inlet valve of the second inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 1L / min and the introduction time is 30s to obtain a carbon nanolayer with a thickness of 5nm.

[0155] 6) Repeat steps 5) and 6) 5 times, introducing silicon-containing gas and carbon-containing gas at intervals of 4 minutes each time, to obtain the negative electrode material.

[0156] The prepared anode material was carbon-coated as follows: 800g of silicon-based anode material and graphene were dissolved in ethanol at a ratio of 22:1 and stirred for 7 hours to form a uniform slurry. The slurry was then dried directly and placed in a rotary kiln, heated to 850℃ in a protective atmosphere and held for 1.5 hours. After cooling and grading, the carbon-coated anode material was obtained.

[0157] The negative electrode sheet was prepared using the carbon-coated negative electrode material prepared in this embodiment, and coin half-cells and full cells were assembled and tested. The assembly and testing methods were the same as in Example 1.

[0158] The initial efficiency and reversible capacity test data of the coin cells prepared in this embodiment are shown in Table 1, the initial stepped discharge capacity of the coin cells is shown in Table 2, and the test results of the expansion rate of the negative electrode sheet of the full cell at 1C rate for the first, 300, and 600 cycles are detailed in Table 1.

[0159] Example 8

[0160] This embodiment provides a preparation process and performance testing of a negative electrode material. The specific preparation process is as follows.

[0161] 1) Under an argon atmosphere at room temperature, 2 kg of porous SiC was placed on a substrate in the deposition chamber of a vapor deposition furnace. The porous SiC had a particle size Dv50 of 600 nm, a pore size distribution between 150 nm and 280 nm, and a porosity of 85%.

[0162] 2) To prepare a silicon-containing gas, the first chamber of the deposition chamber was evacuated to 40 Pa, and chlorosilane was introduced at a flow rate of 1.5 L / min for 9 min. The temperature was then raised to 1300 °C and held for 30 min to obtain a silicon-containing gas.

[0163] 3) To prepare a carbon-containing gas, anhydrous ethanol solution was placed in the first chamber of the deposition chamber, evacuated to 40 Pa, heated to 600 °C, and held for 10 minutes to obtain a carbon-containing gas.

[0164] 4) The silicon-containing gas is introduced into the deposition chamber through the first gas inlet by nitrogen gas from the first furnace chamber, so that the silicon element is cooled and deposited on the pore walls of the porous SiC to form a silicon nanolayer. Before the silicon-containing gas is introduced, the parameters of the automatic gas inlet valve of the first gas inlet are adjusted, the flow rate of the carrier gas nitrogen is set to 2L / min, and the introduction time is 1.5min, so as to obtain a silicon nanolayer with a thickness of 16nm.

[0165] 5) Carbon-containing gas is introduced into the deposition chamber through the second inlet by nitrogen gas from the second furnace chamber, so that carbon is deposited on the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. Before introducing the carbon-containing gas, the parameters of the automatic gas inlet valve of the second inlet are adjusted, and the flow rate of the carrier gas nitrogen is set to 2L / min and the introduction time is 20s, so as to obtain a carbon nanolayer with a thickness of 9nm.

[0166] 6) Repeat steps 5) and 6) twice, introducing silicon-containing gas and carbon-containing gas alternately, with each interval being 10 minutes, to obtain the negative electrode material.

[0167] The prepared anode material is carbon coated by mixing 1 kg of anode material with petroleum asphalt at a mass ratio of 18:1, placing it in a high-temperature furnace, holding it at 850℃ for 105 min under a protective atmosphere, and then discharging and classifying it after cooling to room temperature to obtain the anode material with a carbon coating layer.

[0168] The negative electrode sheet was prepared using the carbon-coated negative electrode material prepared in this embodiment, and coin half-cells and full cells were assembled and tested. The assembly and testing methods were the same as in Example 1.

[0169] The initial efficiency and reversible capacity test data of the coin cells prepared in this embodiment are shown in Table 1, the initial stepped discharge capacity of the coin cells is shown in Table 2, and the test results of the expansion rate of the negative electrode sheet of the full cell at 1C rate for the first, 300, and 600 cycles are detailed in Table 1.

[0170] To better illustrate the effects of the embodiments of the present invention, a comparative example is provided to be made with the embodiments described above.

[0171] Comparative Example 1

[0172] This comparative example provides a preparation process and performance testing of silicon-carbon anode materials prepared by a traditional spray drying method. The specific preparation process is as follows:

[0173] 1) Add 51% silicon powder, 24% carbon source precursor pitch, 24% graphite and 1% antioxidant by total mass to ethanol solvent, and then sand mill to obtain a dispersion.

[0174] 2) The dispersion was spray-dried at 1000℃ under an argon atmosphere to obtain silicon-carbon anode material.

[0175] The prepared silicon-carbon anode material is carbon coated by placing 1 kg of silicon-carbon anode material in a rotary furnace and heating it to 850°C under a protective atmosphere. Argon and acetylene gas are introduced at a volume ratio of 2:1 for gas phase coating. The temperature is maintained for 1.5 hours, the organic gas source is turned off, and the material is discharged and graded after cooling to room temperature to obtain silicon-carbon anode material with carbon coating.

[0176] The silicon-carbon anode material with a carbon coating prepared in this comparative example was used to fabricate a negative electrode sheet and assemble a battery for testing. The specific process was the same as in Example 1. Test data are detailed in Tables 1 and 2.

[0177] The charge-discharge curves of the coin half-cell assembled from the silicon-carbon anode material with a carbon coating provided in Comparative Example 1 of this invention are as follows: Figure 3 As shown.

[0178] Comparative Example 2

[0179] This comparative example provides a preparation process and performance testing of a silicon-based anode material. Unlike the previous examples, this comparative example only deposits nano-silicon within the pores of porous SiC. The specific preparation process is as follows:

[0180] 1) Place 2 kg of porous SiC on the substrate in the deposition chamber of the vapor deposition furnace;

[0181] 2) Place 3.3 kg of silicon powder in the first chamber of the vapor deposition furnace, evacuate to 20 Pa, and heat to 2000 °C to vaporize and dissociate the silicon powder to obtain a silicon-containing gas.

[0182] 3) The silicon-containing gas obtained above is introduced into the deposition chamber by carrier argon gas, and it is cooled and deposited in the pores of porous SiC to nucleate and grow to the nanoscale to obtain silicon-based anode material. The flow rate of carrier argon gas is 3L / min.

[0183] The prepared silicon-based anode material was carbon-coated as follows: 1 kg of silicon-based anode material was placed in a rotary furnace and heated to 1050 °C under a protective atmosphere. A mixture of argon, acetylene, and natural gas was introduced at a volume ratio of 3:2 for gas phase coating, wherein the volume ratio of acetylene and natural gas was 1:1. After holding at this temperature for 80 min, the organic gas source was turned off. After cooling to room temperature, the material was discharged and graded to obtain the silicon-based anode material with a carbon coating layer.

[0184] The silicon-based anode material with a carbon coating prepared in this embodiment was used to prepare anode sheets and assemble coin half-cells and full cells for testing. The specific process is the same as in Example 1, and the test data are detailed in Tables 1 and 2.

[0185] The charge-discharge curves of the coin half-cell assembled from the silicon-based anode material with a carbon coating provided in Comparative Example 2 of this invention are as follows: Figure 4 As shown.

[0186] Comparative Example 3

[0187] This comparative example provides a preparation process and performance testing of a silicon-carbon composite material. Unlike the previous examples, this comparative example uses conventional chemical vapor deposition to deposit a mixture of silicon and carbon elements into the pores of porous SiC. The specific preparation process is as follows:

[0188] 1) Place 2 kg of porous SiC on the substrate in the deposition chamber of the vapor deposition furnace;

[0189] 2) Place 3.3 kg of silicon powder in the first chamber of the vapor deposition furnace, evacuate to 20 Pa, and heat to 2000 °C to vaporize and dissociate the silicon powder to obtain a silicon-containing gas.

[0190] 3) Then, acetylene gas with a flow rate of 2 L / min is introduced into the first chamber of the vapor deposition furnace and mixed thoroughly with the silicon-containing gas obtained above to obtain a mixed gas;

[0191] 4) The mixed gas obtained above is introduced into the deposition chamber by carrier argon gas, and the mixture is cooled and deposited in the pores of porous SiC to nucleate and grow to the nanoscale to obtain silicon-carbon composite material. The flow rate of carrier argon gas is 3L / min.

[0192] The prepared silicon-carbon composite material was carbon-coated as follows: 1 kg of silicon-carbon composite material was placed in a rotary kiln and heated to 1050 °C under a protective atmosphere. Argon gas, acetylene and natural gas were introduced in a volume ratio of 3:2 for gas phase coating, wherein the volume ratio of acetylene and natural gas was 1:1. After holding at this temperature for 80 min, the organic gas source was turned off. After cooling to room temperature, the material was discharged and graded to obtain the silicon-carbon composite material with a carbon coating layer.

[0193] The silicon-carbon composite material with carbon coating prepared in this embodiment was used to prepare negative electrode sheets and assembled into coin half cells and full cells for testing. The specific process is the same as in Example 1, and the test data are detailed in Tables 1 and 2.

[0194] Table 1 shows the test data of batteries assembled from the materials prepared in Examples 1-8 and Comparative Examples 1-3, including the initial efficiency and reversible capacity of the coin half-cells, and the expansion rate test of the negative electrode sheet in the first, 300, and 600 cycles of the full cell.

[0195]

[0196] Table 1

[0197] As can be seen from the comparison of the test data in Table 1, the expansion rate of the negative electrode sheets prepared in Examples 1-8 is much smaller than that of the negative electrode sheet prepared in Comparative Example 1. This is because Examples 1-8 of the present invention, by sequentially and interleaving silicon nanolayers and carbon nanolayers within the pores of porous SiC, utilize the high hardness and high strength of the porous SiC framework to effectively suppress the volume expansion of silicon particles in the silicon nanolayers. At the same time, the interleaved carbon nanolayers not only improve the overall conductivity of the material but also suppress the volume expansion of silicon. Through the synergistic effect of the porous SiC framework structure and the carbon nanolayers, the volume expansion of silicon is suppressed, resulting in the superior expansion rate of the negative electrode sheets in Examples 1-8 of the present invention.

[0198] The reversible capacity of the coin cells in Examples 1-8 is greater than that of the coin cells assembled from silicon-carbon composite materials prepared by the silicon-carbon mixed deposition method in Comparative Example 3. This is because the embodiments of the present invention, through the use of an intermittent deposition method during the vapor phase deposition process, deposit silicon nanolayers and carbon nanolayers separately in the pores of porous SiC, effectively avoiding the formation of Si-C bonds at high temperatures. In contrast, Comparative Example 3, due to the use of silicon-carbon mixed deposition, forms a large number of Si-C bonds at high temperatures, consuming some Si and leading to a decrease in the material's capacity. The reason why the reversible capacity of Comparative Examples 1 and 2 is higher than that of Examples 1-8 is because the silicon content in Comparative Examples 1 and 2 is higher. The silicon-carbon anode material prepared by the conventional spray drying method in Comparative Example 1 itself uses high-quality silicon, while only silicon is deposited in the pores of the porous SiC in Comparative Example 2.

[0199] Table 2 shows the step discharge test data of the coin half-cells prepared in Example 1 and Comparative Example 2.

[0200]

[0201] Table 2

[0202] As can be seen from the comparison of the test data in Table 2, although Comparative Example 2 has a higher reversible specific capacity compared to the Example, the discharge capacity of the coin half-cell in Comparative Example 2 is higher at lower current densities of 0.1C and 0.2C during the stepped discharge process, but the discharge capacity is very small at current densities of 0.5C and 1C, and obvious polarization occurs. This indicates that the silicon-based anode material in Comparative Example 2, which only has silicon deposited in the porous SiC pores, has poor performance in the high-current discharge process. In contrast, the anode material in the Example of this invention, in which silicon nanolayers and carbon nanolayers are deposited alternately in the porous SiC pores, has better performance in the high-current discharge process than Comparative Example 2.

[0203] This invention provides an anode material, its preparation method, and its application. Through vapor deposition and automatic control of feed parameters, silicon nanolayers and carbon nanolayers are sequentially and interspersed within the pores of porous SiC. Since the deposition thickness of the silicon and carbon layers interspersed within the porous SiC pores is at the nanoscale, coupled with the conductivity of the carbon nanolayers themselves, the overall conductivity of the material can be improved. The anode material provided by this invention utilizes the high hardness and strength of the porous SiC framework to effectively suppress the volume expansion of silicon particles in the silicon nanolayers. Simultaneously, the interspersed carbon nanolayers not only improve the overall conductivity of the material but also suppress silicon volume expansion. Through the synergistic effect of the porous SiC framework structure and the carbon nanolayers, the volume expansion of silicon is suppressed, resulting in an anode sheet prepared from the anode material of this invention exhibiting a superior volume expansion rate.

[0204] Furthermore, in the vapor deposition process of this invention, an intermittent deposition method is used to deposit silicon nanolayers and carbon nanolayers separately in the pores of porous SiC, effectively avoiding the formation of Si-C bonds at high temperatures, thereby preventing capacity loss and improving the reversible capacity of the battery. Therefore, the lithium battery prepared using the negative electrode material provided in this invention has a low volume expansion rate, high specific capacity, good conductivity, and cycle life.

[0205] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A negative electrode material, characterized in that, The negative electrode material includes: porous SiC, silicon nanolayers, and carbon nanolayers; The silicon nanolayer has a layer number greater than or equal to 1, and the carbon nanolayer has a layer number greater than or equal to 1; the negative electrode material uses porous SiC as a framework, with the silicon nanolayer and the carbon nanolayer distributed alternately in the pores of the porous SiC; The pore size of the porous SiC is between 1 nm and 500 nm. The thickness of the silicon nanolayer is between 1 nm and 50 nm. The thickness of the carbon nanolayer is between 1 nm and 50 nm.

2. The negative electrode material according to claim 1, characterized in that, The porous SiC has a particle size Dv50 between 300 nm and 100 μm; the porous SiC has a porosity between 30% and 95%. The silicon nanolayer accounts for 50%-80% of the total mass of the anode material; the carbon nanolayer accounts for 10%-40% of the total mass of the anode material.

3. The negative electrode material according to claim 1, characterized in that, The negative electrode material further includes a carbon coating layer; the mass of the carbon coating layer accounts for 0-20% of the total mass of the negative electrode material.

4. A method for preparing the negative electrode material according to any one of claims 1-3, characterized in that, The preparation method includes: Step 1: Under an argon atmosphere, porous SiC is placed on a substrate in the deposition chamber of a vapor deposition furnace. Silicon-containing gas is introduced into the deposition chamber through a first carrier gas from the first furnace chamber, causing the silicon to cool and deposit onto the pore walls of the porous SiC to form a silicon nanolayer. The first furnace chamber and the deposition chamber are connected through a first gas inlet. Before introducing the silicon-containing gas, the parameters of the automatic gas inlet valve are adjusted to control the amount of silicon-containing gas introduced. Step 2: Carbon-containing gas is introduced into the deposition chamber from the second furnace chamber through the second carrier gas, so that carbon is deposited onto the silicon nanolayer in the pores of porous SiC to form a carbon nanolayer. The second furnace chamber and the deposition chamber are connected through the second gas inlet. Before the carbon-containing gas is introduced, the parameters of the automatic gas inlet valve of the second gas inlet are adjusted to control the amount of carbon-containing gas introduced. Repeat steps one and two, alternating between introducing a silicon-containing gas and a carbon-containing gas to obtain the negative electrode material. The negative electrode material uses porous SiC as a framework, with silicon nanolayers and carbon nanolayers distributed alternately in the pores of the porous SiC; the number of silicon nanolayers is greater than or equal to 1, and the number of carbon nanolayers is greater than or equal to 1. The pore size of the porous SiC is between 1 nm and 500 nm. The thickness of the silicon nanolayer is between 1 nm and 50 nm. The thickness of the carbon nanolayer is between 1 nm and 50 nm. The number of times that steps one and two are repeated is greater than or equal to zero.

5. The preparation method according to claim 4, characterized in that, The specific process for preparing the silicon-containing gas is as follows: Under a protective atmosphere or reduced pressure, the first silicon source material is placed in the first furnace cavity, heated to 500℃-2000℃, and held for 1 hour-5 hours to allow the first silicon source material to vaporize and dissociate, thereby obtaining the silicon-containing gas; or the second silicon source material is directly introduced and heated to 500℃-2000℃, and held for 20 minutes-5 hours to obtain the silicon-containing gas. The first silicon source material is a solid and / or liquid, specifically including one or more of silicon powder, hexamethyldisilane, and tris(trimethylsilyl)silane; The second silicon source material is a gas, specifically including one or more of silane, silane, tetrafluorosilane, and chlorosilane; the gas flow rate of the second silicon source material is 0.1L / min-5L / min.

6. The preparation method according to claim 4, characterized in that, The specific process for preparing the carbon-containing gas is as follows: Under a protective atmosphere or reduced pressure, the first carbon source material is placed in the second furnace chamber, heated to 500℃-1300℃, and held at that temperature for 30 minutes to 3 hours. After the first carbon source material is vaporized and dissociated, the carbon-containing gas is obtained. Alternatively, the second carbon source material is directly introduced and heated to 500℃-1300℃, and held at that temperature for 10 minutes to 3 hours to obtain the carbon-containing gas. The first carbon source material is a liquid, specifically including one or more of the following: liquid asphalt, acetone, anhydrous ethanol, and tetrahydrofuran solution containing phenolic resin; The second carbon source material is a gas, specifically including one or more of methane, ethane, ethylene, propane, propylene, acetylene, and natural gas; the gas flow rate of the second carbon source material is 0.1 L / min to 5 L / min.

7. The preparation method according to claim 4, characterized in that, The parameters for the automatic intake valve of the first intake port are as follows: the time for introducing the silicon-containing gas is 1 min to 20 min, the first carrier gas is nitrogen or argon, and the flow rate of the first carrier gas is 0.5 L / min to 5 L / min. The parameters for the automatic intake valve of the second intake port are as follows: the time for introducing the carbon-containing gas is 20s-20min, the second carrier gas is nitrogen or argon, and the flow rate of the second carrier gas is 0.5L / min-5L / min. The time interval between introducing silicon-containing gas and carbon-containing gas is 5 seconds to 5 minutes.

8. The preparation method according to claim 4, characterized in that, The preparation method further includes: carbon coating the negative electrode material; The carbon coating method includes one of the following: gas phase coating, liquid phase coating or solid phase coating; The mass of the carbon coating layer accounts for 0-20% of the total mass of the negative electrode material.

9. A negative electrode sheet, characterized in that, The negative electrode sheet comprises the negative electrode material described in any one of claims 1-3.

10. A lithium battery, characterized in that, The lithium battery includes the negative electrode sheet as described in claim 9.

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