Negative electrode material and preparation method thereof, lithium ion battery and electric device

Abstract

The application relates to the technical field of battery negative electrode materials, in particular to a negative electrode material, a preparation method thereof, a lithium ion battery and an electric equipment. The negative electrode material comprises silicon-based negative electrode material particles, a titanium oxide layer arranged on the surface of the silicon-based negative electrode material particles, and a carbon coating layer arranged on the surface of the titanium oxide layer; the silicon-based negative electrode material particles contain silicon nanocrystal domains, and the average particle size of the silicon nanocrystal domains is less than or equal to 10 nm. The size of the silicon nanocrystal domains in the negative electrode material is small, the titanium oxide layer and the carbon layer can better inhibit the volume expansion of the negative electrode material and improve the transmission capacity of lithium ions, so that the electrochemical performance of the negative electrode material is improved.

Description

Technical Field

[0001] This invention relates to the field of silicon-based anode material technology, specifically to an anode material and its preparation method, a lithium-ion battery, and an electrical device. Background Technology

[0002] Silicon-based anode materials have a theoretical capacity (3579 mAh g). -1 ) is traditional graphite (375mAh g) -1 More than ten times that of Li / Li, and with a suitable voltage plateau (~0.4V vs. Li / Li). + Silicon-based anode materials are promising high-energy-density anode materials. However, the large volume effect and low conductivity of silicon-based anode materials limit their commercial application. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect of poor electrochemical performance of existing silicon-based anode materials, thereby providing an anode material and its preparation method, a lithium-ion battery and an electrical device.

[0004] Therefore, the present invention provides a negative electrode material, comprising silicon-based negative electrode material particles, a titanium oxide layer disposed on the surface of the silicon-based negative electrode material particles, and a carbon coating layer disposed on the surface of the titanium oxide layer;

[0005] The silicon-based anode material particles contain silicon nanocrystal domains, and the average particle size of the silicon nanocrystal domains is less than or equal to 10 nm.

[0006] Optionally, the average particle size of the silicon nanocrystal domains in the silicon-based anode material particles is 4 nm to 10 nm. For example, the average particle size of the silicon nanocrystal domains can be 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or a range consisting of any two of the above values.

[0007] It should be noted that the silicon nanocrystal domains and their dimensions can be obtained from TEM via Fourier transform or by XRD analysis.

[0008] Optionally, the silicon-based anode material particles further contain lithium silicate, which includes at least one of lithium orthosilicate and lithium metasilicate.

[0009] Incorporating lithium silicates (pre-lithiation) into silicon-based anode materials can improve their initial efficiency. However, pre-lithiated silicon-based anode materials generally suffer from uneven surface coating, which makes some lithium silicates within them prone to precipitating as a coating layer in aqueous solvents. This reaction with water generates a large amount of gas, leading to material deactivation. Using titanium dioxide coating can provide a more rigid protective layer, thereby suppressing gas generation during slurry processing.

[0010] Optionally, the average particle size of the silicon-based anode material particles is 2 μm to 15 μm. For example, the average particle size of the silicon-based anode material particles can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a range consisting of any two of the above values.

[0011] Optionally, in the Raman spectrum of the negative electrode material, I D / I G The value is 0.80 to 0.97, where I D This indicates that the Raman displacement is within 1300±50cm. -1 peak intensity, I G This indicates that the Raman displacement is within 1480±50cm. -1 The peak intensity. For example, I in the Raman spectrum of the negative electrode material. D / I G The value can be 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, 0.97, or a range consisting of any two of the above values. The I value in Raman spectroscopy... D / I G The value can characterize the degree of disorder of carbon in a material. When the I value in the Raman spectrum of the negative electrode material is... D / I G When the value is within the above range, the electrochemical performance of the negative electrode material can be further improved.

[0012] Optionally, the titanium oxide layer contains Ti 4+ With Ti 3+ The molar ratio is 1:(0.5~1.1). For example, Ti in the titanium oxide layer 4+ With Ti 3+ The molar ratio can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, or a range consisting of any two of the above values. Ti in the titanium oxide layer 4+ With Ti 3+ The molar ratio reflects the concentration of oxygen defects in the titanium oxide layer. When the Ti content in the titanium oxide layer... 4+ With Ti 3+ When the molar ratio is within the above range, the conductivity and lithium-ion transport capacity of the titanium oxide layer can be further improved, thereby enhancing the electrochemical performance of the entire anode material.

[0013] It should be noted that Ti 4+ With Ti 3+ The molar ratio can be obtained by the ratio of the peak areas of each valence state after XPS peak splitting.

[0014] Optionally, the silicon-based anode material includes at least one of silicon suboxide, silicon, silicon alloy, and silicon-carbon.

[0015] Optionally, the thickness of the carbon coating layer is 5–15 nm. For example, the thickness of the carbon coating layer can be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, or a range consisting of any two of the above values. This can further improve the electrochemical performance of the anode material.

[0016] Optionally, the thickness of the titanium oxide layer is 15–25 nm. For example, the thickness of the titanium oxide layer can be 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, or 25 nm, or a range consisting of any two of the above values. This further improves the electrochemical performance of the negative electrode material.

[0017] The present invention also provides a method for preparing the above-mentioned negative electrode material, comprising the following steps:

[0018] (1) Mix an alcohol solution, surfactant, pore-forming agent and titanium source of silicon-based anode material particles, dry them and place them under an inert atmosphere, calcine them at 400-700°C, and cool them to obtain silicon-based anode material coated with titanium oxide.

[0019] (2) At room temperature, the silicon-based anode material coated with titanium oxide is subjected to plasma-enhanced chemical vapor deposition using hydrocarbon gas and hydrogen gas to obtain the anode material.

[0020] Compared with conventional high-temperature CVD carbon coating of titanium oxide, the preparation method of the present invention avoids the growth of silicon nanocrystal domains in silicon-based anode materials by controlling the calcination temperature of titanium oxide coating and the temperature of plasma-enhanced chemical vapor deposition, thereby improving the electrochemical performance of anode materials.

[0021] It should be noted that the room temperature mentioned in this application refers to a temperature of 25℃±5℃.

[0022] Optionally, the flow rate of the hydrocarbon gas is 2 to 32 sccm, and the flow rate of the hydrogen gas is 2 to 16 sccm.

[0023] Optionally, the plasma generation power is 50-300W and the time is 5-30min.

[0024] Optionally, the drying conditions include: a drying temperature of 55–65°C and a drying time of 120–180 min.

[0025] Optionally, the inert atmosphere includes at least one of argon and nitrogen.

[0026] Optionally, the titanium source includes isopropyl titanate, the surfactant includes hexadecylamine, and the pore-forming agent includes ammonia.

[0027] Optionally, the weight ratio of the silicon-based anode material, titanium source, surfactant, and pore-forming agent is (50-500):(0.1-5):(0.02-1):(0.004-1).

[0028] Optionally, the hydrocarbon gas is selected from at least one of alkane gases, olefin gases, and alkyne gases.

[0029] The present invention also provides a lithium-ion battery, wherein the lithium-ion battery comprises the above-described negative electrode material or the negative electrode material prepared by the above-described preparation method.

[0030] The present invention also provides an electrical device including the aforementioned lithium-ion battery. The electrical device includes, but is not limited to, electric vehicles and energy storage devices.

[0031] The technical solution of this invention has the following advantages:

[0032] The anode material provided by this invention includes silicon-based anode material particles, a titanium oxide layer coating the surface of the silicon-based anode material particles, and a carbon coating layer coating the surface of the titanium oxide layer. The silicon-based anode material particles contain silicon nanocrystal domains with an average particle size of less than or equal to 10 nm. The small size of the silicon nanocrystal domains in the anode material of this invention, combined with the titanium oxide layer and carbon layer, can effectively suppress the volume expansion of the anode material and improve the lithium-ion transport capability, thereby improving the electrochemical performance of the anode material. Detailed Implementation

[0033] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0034] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0035] Example 1

[0036] This embodiment provides a negative electrode material, prepared by the following method:

[0037] (1) Place 60g of silicon suboxide containing lithium orthosilicate in 6L of ethanol and ultrasonically stir until it is evenly dispersed to obtain the first solution;

[0038] (2) Transfer the first solution obtained in operation (1) to a fume hood, and add 0.95g of hexadecylamine to the first solution while stirring, and keep the solution stirring to obtain the second solution;

[0039] (3) While stirring, add 0.8 mL of ammonia water (99.999% vol) to the second solution in 5 portions using a syringe, seal the container opening, and keep the solution stirring to obtain the third solution;

[0040] (4) Open the container seal, add isopropyl titanate to the third solution in 8 portions while stirring, close the container opening, keep stirring for 10 minutes to obtain the fourth solution;

[0041] (5) The fourth solution was centrifuged for the first time at 8000 rpm. The solid obtained from the first centrifugation was fully resuspended in deionized water and then centrifuged for the second time at 8000 rpm. The solid obtained from the second centrifugation was fully resuspended in ethanol and then centrifuged for the third time at 8000 rpm. The solid obtained from the third centrifugation was taken to obtain the premixed material.

[0042] (6) Place the premixed material obtained in operation (5) in a vacuum oven and dry it at 80°C for 120 min;

[0043] (7) The dried premixed material was placed in a tube furnace and heated to 450°C at a heating rate of 2°C / min in an argon atmosphere and held for 2 hours. After the holding period, it was cooled to room temperature in an argon atmosphere and then taken out to obtain a silicon-based anode material coated with titanium dioxide.

[0044] (8) At room temperature, the titanium dioxide-coated silicon-based anode material obtained in operation (7) is placed in a plasma-enhanced chemical vapor deposition (PECVD) apparatus. The vacuum pump system is turned on to evacuate the apparatus until the intrinsic vacuum level reaches 1.0 × 10⁻⁶. -2 ~1.0×10 -4 After Pa, methane at a flow rate of 16 sccm and hydrogen at a flow rate of 2 sccm were introduced, the plasma generator power was turned on, the plasma generation power was set to 300W, the system was kept running for 20 minutes, and then the entire PECVD system was turned off. The sample was then removed, and the negative electrode material was obtained.

[0045] The anode material provided in this embodiment includes silicon suboxide with a particle size of 8 μm, a titanium oxide layer with a thickness of 20 nm coated on the surface of the silicon-based anode material particles, and a carbon coating layer with a thickness of 15 nm coated on the surface of the titanium oxide layer. The silicon-based anode material particles contain silicon nanocrystal domains with an average particle size of 5 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.7. In the Raman spectrum of the negative electrode material, I... D / I G The value is 0.97.

[0046] Example 2

[0047] The negative electrode material was prepared according to the method of Example 1, except that the PECVD system ran for 10 minutes in operation (8) of this example.

[0048] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 5 nm, the particle size of the silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 5 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.51, and the I in the Raman spectrum of the negative electrode material... D / I G The value is 0.91.

[0049] Example 3

[0050] The negative electrode material was prepared according to the method of Example 1, except that the plasma generation power was 200W in operation (8) of this example.

[0051] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 5 nm, the particle size of silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 15 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.6, and the I in the Raman spectrum of the negative electrode material is... D / I G The value is 0.97.

[0052] Example 4

[0053] The negative electrode material was prepared according to the method of Example 1. The difference is that in this example, the plasma generation power was 200W and the PECVD system running time was 10min in operation (8).

[0054] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 5 nm, the particle size of the silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 3 nm. The titanium oxide layer contains Ti... 4+ With Ti3+ The molar ratio is 1:0.53, and the I in the Raman spectrum of the negative electrode material is... D / I G The value is 0.94.

[0055] Example 5

[0056] The negative electrode material was prepared according to the method of Example 1, except that the plasma generation power was 100W in operation (8) of this example.

[0057] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 5 nm, the particle size of the silicon suboxide particles is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 7 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.5, and the I in the Raman spectrum of the negative electrode material D / I G The value is 0.84.

[0058] Example 6

[0059] The negative electrode material was prepared according to the method of Example 1. The difference is that in operation (8) of this example, the plasma generation power is 100W and the running time of the PECVD system is 10min.

[0060] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 5 nm, the particle size of the silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 5 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.7, and the I in the Raman spectrum of the negative electrode material is... D / I G The value is 0.95.

[0061] Example 7

[0062] The negative electrode material was prepared according to the method of Example 1. The difference is that in operation (8) of this example, the plasma generation power is 50W and the running time of the PECVD system is 5min.

[0063] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 5 nm, the particle size of the silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 5 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.51, and the I in the Raman spectrum of the negative electrode material... D / I G The value is 0.86.

[0064] Example 8

[0065] The negative electrode material was prepared according to the method of Example 1. The difference is that in operation (8) of this example, the plasma generation power is 50W and the running time of the PECVD system is 30min.

[0066] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 5 nm, the particle size of the silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 8 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.72, and the I in the Raman spectrum of the negative electrode material is... D / I G The value is 0.89.

[0067] Example 9

[0068] The negative electrode material was prepared according to the method of Example 1, except that in operation (8) of this example, the flow rate of methane was 32 sccm and the flow rate of hydrogen was 16 sccm.

[0069] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 5 nm, the particle size of the silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 12 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.56, and the I in the Raman spectrum of the negative electrode material is... D / I G The value is 0.94.

[0070] Example 10

[0071] The negative electrode material was prepared according to the method of Example 1, except that in operation (8) of this example, the flow rate of methane was 2 sccm and the flow rate of hydrogen was 2 sccm.

[0072] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 5 nm, the particle size of the silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 3 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.28, and the I in the Raman spectrum of the negative electrode material is... D / I G The value is 0.81.

[0073] Example 11

[0074] The negative electrode material was prepared according to the method of Example 1, except that the temperature of heat preservation in operation (7) of this example is 700°C.

[0075] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 10 nm, the particle size of the silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 15 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.72, and the I in the Raman spectrum of the negative electrode material is... D / I G The value is 0.95.

[0076] Example 12

[0077] The negative electrode material was prepared according to the method of Example 1, except that the temperature for heat preservation in operation (7) of this example is 550°C.

[0078] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 6 nm, the particle size of silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 15 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.81, and the I in the Raman spectrum of the negative electrode material... D / I G The value is 0.83.

[0079] Example 13

[0080] The negative electrode material was prepared according to the method of Example 1, except that in operation (8) of this example, methane was replaced with ethylene.

[0081] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 4 nm, the particle size of the silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 5 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.81, and the I in the Raman spectrum of the negative electrode material... D / I G The value is 0.94.

[0082] Example 14

[0083] The negative electrode material was prepared according to the method of Example 1, except that in operation (8) of this example, methane was replaced with acetylene.

[0084] In the negative electrode material of this embodiment, the size of the silicon nanocrystal domains is 4 nm, the particle size of silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 7 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.51, and the I in the Raman spectrum of the negative electrode material... D / I G The value is 0.87.

[0085] Example 15

[0086] The negative electrode material was prepared according to the method of Example 1, except that the PECVD system ran for 30 minutes in operation (8) of this example.

[0087] In the negative electrode material of this embodiment, the average particle size of silicon nanocrystal domains is 5 nm, the particle size of silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 20 nm, and the thickness of the carbon coating layer is 20 nm. The titanium oxide layer contains Ti... 4+ and Ti 3+ The molar ratio is 1:1.1, and the Raman spectrum of the negative electrode material contains I. D / I G The value is 1.00.

[0088] Comparative Example 1

[0089] The negative electrode material was prepared according to the method of Example 1, except that the temperature of heat preservation in operation (7) of this example is 800°C.

[0090] In the negative electrode material of this comparative example, the average particle size of silicon nanocrystal domains is 15 nm, the particle size of silicon suboxide is 8 μm, the thickness of the titanium oxide layer is 19 nm, and the thickness of the carbon coating layer is 15 nm. The titanium oxide layer contains Ti... 4+ With Ti 3+ The molar ratio is 1:0.69, and the I in the Raman spectrum of the negative electrode material is... D / I G The value is 0.95.

[0091] Performance testing

[0092] Coin cells and CR2032 and 3Ah pouch cells were prepared using the negative electrode materials of Examples 1-15 and Comparative Example 1, respectively, and the electrical performance of each cell was tested.

[0093] The coin cell battery consists of the following components:

[0094] Negative electrode: A slurry was prepared by mixing negative electrode material, conductive agent SP and modified polyacrylic acid in a weight ratio of 93:3:4, and then coated onto an 8μm copper foil current collector to prepare the negative electrode.

[0095] Positive electrode: Lithium metal.

[0096] Electrolyte: 1.2 mol / L LiPF6, solvent is EC / DMC with a molar ratio of 1:1 plus 10 wt% FEC (EC: ethylene carbonate, DMC: dimethyl carbonate, FEC: fluoroethylene carbonate).

[0097] Diaphragm: Celgard 2500.

[0098] The components of a pouch battery are as follows:

[0099] Negative electrode: 12wt% negative electrode material + 88wt% artificial graphite are used as negative electrode active material. A slurry is prepared according to the weight ratio of negative electrode active material, conductive agent SP and modified polyacrylic acid 93:3:4. The slurry is coated on an 8μm copper foil current collector to prepare the negative electrode.

[0100] Positive electrode: High nickel cobalt manganese oxide lithium NCM811 is used as the positive electrode material. A slurry is prepared according to the weight ratio of positive electrode material, conductive agent SP and binder PVDF of 97:2:1, and coated on aluminum foil current collector to prepare the positive electrode.

[0101] Electrolyte: 1.2 mol / L LiPF6, solvent is EC / DMC with a molar ratio of 1:1 plus 10 wt% FEC (EC: ethylene carbonate, DMC: dimethyl carbonate, FEC: fluoroethylene carbonate).

[0102] Diaphragm: Celgard 2500.

[0103] The electrical performance testing methods are as follows:

[0104] (1) Test of the first discharge capacity of the negative electrode of the button cell: first discharge capacity mAh / mass of negative electrode active material g;

[0105] (2) Coulombic efficiency of button cell in the first cycle: first charge capacity / first discharge capacity * 100%;

[0106] (3) Specific capacity of button cell battery during first charge: First charge capacity / mass of active material (mAh / g);

[0107] (4) Test on the 4C rate discharge capacity retention of soft-pack batteries: 4C discharge capacity / 1C discharge capacity;

[0108] (5) DC internal resistance DCR test of soft pack battery: divide the battery capacity and adjust it to 50% SOC, discharge at 5C for 10s, test the discharge resistance, resistance DCR=(V0-V10) / I, where V0 is the potential before discharge, V10 is the potential at the 10th second of discharge, and I is the discharge current 5C.

[0109] (6) Capacity retention test of soft-pack battery: ① Charging: Charge at a constant current density of 1C to 4.2V and then let stand for 10min; ② Discharging: Discharge at a constant current density of 1C to 2.5V and let stand for 0min. The discharge capacity is recorded as Qn (n=1,2,3……400); ③ Repeat "①, ②" for 400 cycles; The capacity retention rate of the soft-pack battery after 400 cycles is: Q400 / Q1;

[0110] (7) Test of volume expansion rate of soft pack battery: 400 cycles, disassembled with full charge, the thickness of the micrometer caliper is d2, the thickness of the fresh electrode sheet is d1, the expansion rate of the soft pack battery after 400 cycles of full charge is calculated as: (d2-d1) / (d1-8).

[0111] (8) Lithium plating test of soft pack battery: ① Charging: constant current charging at a current density of 2.4C to 4.2V, and resting for 10min; ② Discharging: constant current discharging at a current density of 1C to 2.5V, and resting for 10min; after 10 cycles, constant current charging at a current density of 1.6C to 4.2V for full charge, disassembly and observation of the negative electrode interface.

[0112] The test results are shown in Tables 1 and 2.

[0113] Table 1. Test results of electrical performance of each button cell

[0114]

[0115]

[0116] Table 2. Electrical performance test results of each soft-pack battery

[0117]

[0118]

[0119] As shown in Tables 1 and 2, the electrochemical performance of the batteries assembled using the negative electrode materials described in Examples 1 to 15 is significantly better than that of the batteries assembled using the negative electrode materials described in Comparative Example 1. This indicates that by controlling the size of the silicon nanocrystal domains in the negative electrode material to be less than or equal to 10 nm, and combining them with titanium oxide and carbon layers, the volume expansion of the negative electrode material can be effectively suppressed and the lithium-ion transport capacity can be improved, thereby improving the electrochemical performance of the negative electrode material.

[0120] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A negative electrode material, characterized in that, It includes silicon-based anode material particles, a titanium oxide layer disposed on the surface of the silicon-based anode material particles, and a carbon coating layer disposed on the surface of the titanium oxide layer; The silicon-based anode material particles contain silicon nanocrystal domains, and the average particle size of the silicon nanocrystal domains is less than or equal to 10 nm; the titanium oxide layer contains Ti 4+ With Ti 3+ The molar ratio is 1:(0.5~1.1). The method for preparing the negative electrode material includes the following steps: (1) Mix the alcohol solution, surfactant, pore-forming agent and titanium source of silicon-based anode material particles, dry them and place them under an inert atmosphere, calcine them at 400~700°C, and cool them to obtain silicon-based anode material coated with titanium oxide; (2) At room temperature, the silicon-based anode material coated with titanium oxide is subjected to plasma-enhanced chemical vapor deposition using hydrocarbon gas and hydrogen gas to obtain the anode material; the flow rate of the hydrocarbon gas is 16~32 sccm, the plasma generation power is 100~300W, and the time is 10~20min.

2. The negative electrode material according to claim 1, characterized in that, The silicon-based anode material particles also contain lithium silicate, which includes at least one of lithium orthosilicate and lithium metasilicate.

3. The negative electrode material according to claim 1, characterized in that, In the Raman spectrum of the negative electrode material, I D / I G The value is 0.8~0.97, where I D This indicates that the Raman displacement is within 1300±50cm. -1 peak intensity, I G This indicates that the Raman displacement is within 1480±50cm. -1 Peak intensity.

4. The negative electrode material according to claim 1, characterized in that, The silicon-based anode material includes at least one of silicon suboxide, silicon, silicon alloy, and silicon-carbon.

5. The negative electrode material according to claim 1, characterized in that, The thickness of the carbon coating layer is 5~15nm.

6. The negative electrode material according to claim 1, characterized in that, The flow rate of the hydrogen gas is 2~16 sccm.

7. A lithium-ion battery, comprising a negative electrode sheet, said negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of said negative electrode current collector, characterized in that, The negative electrode active material layer comprises the negative electrode material according to any one of claims 1 to 6.

8. An electrical appliance, characterized in that, Includes the lithium-ion battery as described in claim 7.

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