Lithium ion battery negative electrode material, preparation method thereof and lithium ion battery

Abstract

The application provides a lithium ion battery negative electrode material, a preparation method thereof and a lithium ion battery. The lithium ion battery negative electrode material comprises tungsten oxide, the surface of the tungsten oxide is coated with a carbon-based material, and the carbon-based material comprises nitrogen-doped carbon. After the tungsten oxide is compounded with the carbon material, the surface of the tungsten oxide is coated with the carbon-based material, and the carbon can effectively alleviate the huge stress of the tungsten oxide during charging and discharging, reduce the volume change of the tungsten oxide, thereby improving the cycle stability of the tungsten oxide and enabling the battery to have a more stable and durable service life. The application further provides a preparation method of the lithium ion battery negative electrode material and a lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a lithium-ion battery anode material, its preparation method, and a lithium-ion battery. Background Technology

[0002] With finite fossil fuel reserves and environmental degradation, research on generating electricity using renewable energy is rapidly becoming a global research hotspot. Renewable energy can be better utilized through energy storage devices. Among various electrochemical energy storage devices, lithium-ion batteries have been extensively studied due to their advantages such as high energy density, long cycle life, and low pollution. Currently, graphite-based carbon anode materials are widely used in commercial lithium-ion batteries. However, the theoretical specific capacity of graphite (372 mAh·g) is limited. -1 The specific capacity of anode materials is relatively low, making it impossible to achieve the high energy density required by some modern electronic devices. The exploration and development of anode materials with high specific capacity and high safety has become a research hotspot in the field of lithium-ion batteries.

[0003] Some transition metal oxides, such as Fe₂O₃, TiO₂, SnO₂, MnO₂, and ZnO, possess high theoretical capacity and rapid power generation capabilities, and are considered viable alternatives to graphite. Tungsten-based oxides (WO₂) 3-x In addition to its high theoretical capacity (693mAh·g) -1 Abundant mineral resources, environmental friendliness, and high stability are also reasons why tungsten oxide is a candidate material for anode materials. However, WO 3-x Metal oxides undergo significant volume changes during conversion reactions, leading to the collapse of their crystal structure and a rapid decline in specific capacity. Furthermore, the poor electrical conductivity of tungsten oxides also limits their practical applications.

[0004] Therefore, there is a need to develop a new lithium-ion battery anode material. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides a lithium-ion battery anode material that can improve the cycle stability of tungsten oxide, enabling the battery to have a more stable and longer lifespan.

[0006] This invention also provides a method for preparing a lithium-ion battery anode material.

[0007] The present invention also provides a lithium-ion battery.

[0008] A first aspect of the present invention provides a lithium-ion battery anode material comprising tungsten oxide, wherein the surface of the tungsten oxide is coated with a carbon-based material, wherein the carbon-based material comprises nitrogen-doped carbon.

[0009] One of the technical solutions of the present invention concerning lithium-ion battery anode materials has at least the following beneficial effects:

[0010] The lithium-ion battery anode material of the present invention, after tungsten oxide and carbon material are combined, the surface of tungsten oxide is coated with carbon-based material. Carbon, as a support, can effectively alleviate the huge stress of tungsten oxide during charging and discharging, reduce the volume change of tungsten oxide, thereby improving the cycle stability of tungsten oxide and enabling the battery to have a more stable and longer lifespan.

[0011] When carbon-based materials are combined with tungsten oxides, they can act as a bridge for electron transfer, improving the conductivity of tungsten oxides, effectively increasing the charge transfer rate during charging and discharging, and enhancing electrochemical performance.

[0012] Experimental results show that carbon-based tungsten oxide coatings, when used as anode materials for lithium-ion batteries, exhibit good cycle stability and rate performance.

[0013] According to some embodiments of the present invention, the morphology of the lithium-ion battery negative electrode material is nanoflower-like.

[0014] According to some embodiments of the present invention, the particle size of the nanoflower is 1 μm to 2 μm.

[0015] The nanoflower structure of carbon-based tungsten oxide anode material has a large specific surface area, which is beneficial to accelerating the chemical reaction rate and improving electrochemical performance.

[0016] According to some embodiments of the present invention, the nanoflower is formed by the self-assembly of nanosheets with a thickness of 20 nm to 40 nm.

[0017] "Self-assembly" refers to the process during the growth of nanosheets, where, as the reaction time increases, the nanosheets undergo thermal induction, accompanied by curling and self-aggregation, eventually forming a final flower-like aggregate at the end of the reaction time.

[0018] A second aspect of the present invention provides a method for preparing a lithium-ion battery anode material, the method comprising reacting a carbon source, a nitrogen source and a tungsten source under the action of a crosslinking agent through a solvothermal reaction to generate the tungsten oxide and crosslinked carbon, followed by annealing treatment, wherein the crosslinked carbon coats the tungsten oxide to form the lithium-ion battery anode material.

[0019] One technical solution of the present invention relating to a method for preparing a negative electrode material for lithium-ion batteries has at least the following beneficial effects:

[0020] The preparation process of this invention is simple and low-cost, and it has good application prospects.

[0021] According to some embodiments of the present invention, the carbon source includes at least one of formaldehyde, acetaldehyde, and glyoxal.

[0022] According to some embodiments of the present invention, the nitrogen source includes at least one of melamine, ethylenediamine, and dopamine hydrochloride.

[0023] According to some embodiments of the present invention, the molar ratio of the nitrogen source to the carbon source is 1:1 to 10.

[0024] The nitrogen source can be melamine, and the carbon source can be formaldehyde. Melamine can be dissolved in 30 mL of ethanol, stirred continuously for 20-30 min, and a small amount of formaldehyde solution can be added and stirred for 1-2 h to obtain a mixed solution.

[0025] According to some embodiments of the present invention, the tungsten source includes at least one of tungsten hexachloride, sodium tungstate, ammonium metatungstate, sodium metatungstate, potassium metatungstate, ammonium paratungstate, sodium paratungstate, and potassium paratungstate.

[0026] According to some embodiments of the present invention, the crosslinking agent includes at least one of citric acid, p-toluenesulfonic acid, and polyethylene glycol.

[0027] According to some embodiments of the present invention, the mass ratio of the tungsten source to the crosslinking agent may be 1:0.5 to 5.

[0028] According to some embodiments of the present invention, the temperature of the solvothermal reaction is 160°C to 200°C.

[0029] According to some embodiments of the present invention, the solvothermal reaction time is 8h to 10h.

[0030] According to some embodiments of the present invention, the annealing temperature is 500°C to 800°C.

[0031] According to some embodiments of the present invention, the annealing treatment time is 1 hour to 5 hours.

[0032] Under high-temperature annealing, carbon materials and tungsten oxides form a strong bond, thereby improving the conductivity and stability of tungsten oxides.

[0033] According to some embodiments of the present invention, the preparation method may be:

[0034] Step 1: Dissolve melamine in 30 mL of ethanol, stir continuously for 20-30 min, add a small amount of formaldehyde solution and stir for 1-2 h to obtain mixture A;

[0035] Step 2: Dissolve the tungsten source in 30 mL of ethanol, add citric acid and stir for 30-40 min, then add the solution obtained in Step 1, continue stirring for 1-2 h, and then transfer to a high-pressure reactor. Place the reactor in a forced-air dryer and react at 160-200℃ for 8-10 h. Wash the obtained product thoroughly and dry it in a vacuum drying oven at 60℃ for 8-12 h to obtain powder sample B;

[0036] Step 3: Place the powder sample B obtained in Step 2 into a tube furnace and anneal it under an Ar atmosphere to obtain a composite material of carbon-based material coated with tungsten oxide.

[0037] In steps 1 and 2, the stirring temperature can be 20℃~25℃.

[0038] In step 2, the drying temperature can also be 60℃~80℃.

[0039] The solvents used for washing in step 2 are ultrapure water and ethanol.

[0040] In step 3, the annealing temperature is 500℃~800℃, the heating rate is 2-10℃ / min, and the annealing time can be 1h~5h.

[0041] A third aspect of the present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is prepared from the lithium-ion battery negative electrode material of the present invention.

[0042] One of the technical solutions of the present invention concerning lithium-ion batteries has at least the following beneficial effects:

[0043] The lithium-ion battery of the present invention has good cycle stability and rate performance.

[0044] According to some embodiments of the present invention, the negative electrode further includes a conductive agent and a binder, wherein the mass ratio of the negative electrode material, the conductive agent and the binder is 7:2:1 or 8:1:1. Attached Figure Description

[0045] Figure 1 This is a SEM image of the lithium battery anode material prepared in Example 1 of the present invention.

[0046] Figure 2 This is a charge-discharge curve of the lithium battery anode material prepared in Example 1 of the present invention as the anode of a lithium-ion battery.

[0047] Figure 3 This is a charge-discharge curve of the lithium battery anode material prepared in Comparative Example 1 of the present invention as a lithium-ion battery anode.

[0048] Figure 4This is a cycle performance test diagram of the lithium battery anode material prepared in Example 1 and Comparative Example 1 of the present invention as a lithium-ion battery anode.

[0049] Figure 5 This is a rate performance test diagram of the lithium battery anode material prepared in Example 1 and Comparative Example 1 of the present invention as a lithium-ion battery anode. Detailed Implementation

[0050] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0051] In a first aspect, some embodiments of the present invention provide a lithium-ion battery anode material comprising tungsten oxide, wherein the surface of the tungsten oxide is coated with a carbon-based material, wherein the carbon-based material comprises nitrogen-doped carbon.

[0052] It is understood that in the lithium-ion battery anode material of the present invention, after tungsten oxide and carbon material are combined, the surface of tungsten oxide is coated with carbon-based material. Carbon, as a support, can effectively alleviate the huge stress of tungsten oxide during charging and discharging, reduce the volume change of tungsten oxide, thereby improving the cycle stability of tungsten oxide and enabling the battery to have a more stable and longer lifespan.

[0053] It should be noted that the combination of carbon-based materials and tungsten oxide can act as a bridge for electron transfer, improving the conductivity of tungsten oxide, effectively increasing the charge transfer rate during charging and discharging, and enhancing electrochemical performance.

[0054] Experimental results show that carbon-based tungsten oxide coatings, when used as anode materials for lithium-ion batteries, exhibit good cycle stability and rate performance.

[0055] In conjunction with the first aspect, in some embodiments of the present invention, the morphology of the lithium-ion battery anode material is nanoflower-like.

[0056] In conjunction with the first aspect, in some embodiments of the present invention, the particle size of the nanoflowers is 1 μm to 2 μm.

[0057] The nanoflower structure of carbon-based tungsten oxide anode material has a large specific surface area, which is beneficial to accelerating the chemical reaction rate and improving electrochemical performance.

[0058] In conjunction with the first aspect, in some embodiments of the present invention, the nanoflowers are formed by the self-assembly of nanosheets with a thickness of 20 nm to 40 nm.

[0059] "Self-assembly" refers to the process during the growth of nanosheets, where, as the reaction time increases, the nanosheets undergo thermal induction, accompanied by curling and self-aggregation, eventually forming a final flower-like aggregate at the end of the reaction time.

[0060] In a second aspect, some embodiments of the present invention provide a method for preparing a lithium-ion battery anode material, the method comprising reacting a carbon source, a nitrogen source, and a tungsten source through a solvothermal reaction under the action of a crosslinking agent to generate the tungsten oxide and crosslinked carbon, followed by annealing treatment, wherein the crosslinked carbon coats the tungsten oxide to form the lithium-ion battery anode material.

[0061] It is understood that the preparation process of this invention is simple, the cost is low, and it has good application prospects.

[0062] In conjunction with the second aspect, in some embodiments of the present invention, the carbon source includes at least one of formaldehyde, acetaldehyde, and glyoxal.

[0063] In conjunction with the second aspect, in some embodiments of the present invention, the nitrogen source includes at least one of melamine, ethylenediamine, and dopamine hydrochloride.

[0064] In conjunction with the second aspect, in some embodiments of the present invention, the molar ratio of nitrogen source to carbon source is 1:1 to 10.

[0065] The nitrogen source can be melamine, and the carbon source can be formaldehyde. Melamine can be dissolved in 30 mL of ethanol, stirred continuously for 20-30 min, and a small amount of formaldehyde solution can be added and stirred for 1-2 h to obtain a mixed solution.

[0066] In conjunction with the second aspect, in some embodiments of the present invention, the tungsten source includes at least one of tungsten hexachloride, sodium tungstate, ammonium metatungstate, sodium metatungstate, potassium metatungstate, ammonium paratungstate, sodium paratungstate, and potassium paratungstate.

[0067] In conjunction with the second aspect, in some embodiments of the present invention, the crosslinking agent includes at least one of citric acid, p-toluenesulfonic acid, and polyethylene glycol.

[0068] In conjunction with the second aspect, in some embodiments of the present invention, the mass ratio of tungsten source to crosslinking agent may be 1:0.5 to 5.

[0069] In conjunction with the second aspect, in some embodiments of the present invention, the temperature of the solvothermal reaction is 160°C to 200°C.

[0070] In conjunction with the second aspect, in some embodiments of the present invention, the solvothermal reaction time is 8h to 10h.

[0071] In conjunction with the second aspect, in some embodiments of the present invention, the annealing temperature is 500°C to 800°C.

[0072] In conjunction with the second aspect, in some embodiments of the present invention, the annealing time is 1 hour to 5 hours.

[0073] Under high-temperature annealing, carbon materials and tungsten oxides form a strong bond, thereby improving the conductivity and stability of tungsten oxides.

[0074] In conjunction with the second aspect, in some embodiments of the present invention, the preparation method may be:

[0075] Step 1: Dissolve melamine in 30 mL of ethanol, stir continuously for 20-30 min, add a small amount of formaldehyde solution and stir for 1-2 h to obtain mixture A;

[0076] Step 2: Dissolve the tungsten source in 30 mL of ethanol, add citric acid and stir for 30-40 min, then add the solution obtained in Step 1, continue stirring for 1-2 h, and then transfer to a high-pressure reactor. Place the reactor in a forced-air dryer and react at 160-200℃ for 8-10 h. Wash the obtained product thoroughly and dry it in a vacuum drying oven at 60℃ for 8-12 h to obtain powder sample B;

[0077] Step 3: Place the powder sample B obtained in Step 2 into a tube furnace and anneal it under an Ar atmosphere to obtain a composite material of carbon-based material coated with tungsten oxide.

[0078] In steps 1 and 2, the stirring temperature can be 20℃~25℃.

[0079] In step 2, the drying temperature can also be 60℃~80℃.

[0080] The solvents used for washing in step 2 are ultrapure water and ethanol.

[0081] In step 3, the annealing temperature is 500℃~800℃, the heating rate is 2-10℃ / min, and the annealing time can be 1h~5h.

[0082] In a third aspect, some embodiments of the present invention provide a lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is prepared from the lithium-ion battery negative electrode material of the present invention.

[0083] It is understood that the lithium-ion battery of the present invention has good cycle stability and rate performance.

[0084] In conjunction with the third aspect, in some embodiments of the present invention, the negative electrode further includes a conductive agent and a binder, wherein the mass ratio of the negative electrode material, the conductive agent and the binder is 7:2:1 or 8:1:1.

[0085] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0086] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0087] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0088] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0089] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0090] Example 1

[0091] This embodiment first prepares a lithium-ion battery anode material, and then uses it to prepare the anode. The specific steps are as follows:

[0092] (1) Preparation method of carbon-based tungsten oxide composite material

[0093] Step 1: Dissolve 10 mmol of melamine in 30 mL of ethanol, stir continuously for 30 min, add 3 mL of formaldehyde solution and stir for 1 h to obtain mixture A;

[0094] Step 2: Dissolve 2 mmol WCl6 in 30 mL of ethanol, add 1 mmol citric acid and stir for 30 min, then add solution A obtained in Step 1, continue stirring for 1 h, and then transfer to a high-pressure reactor. Place the reactor in a forced-air dryer and react at 200 °C for 10 h. Wash the obtained product with water and ethanol, then place it in a vacuum drying oven and dry at 60 °C for 8 h to obtain powder sample B;

[0095] Step 3: Place the powder sample B obtained in Step 2 in a tube furnace and anneal it under an Ar atmosphere at a temperature of 750℃ and a heating rate of 5℃·min. -1 The annealing time is 2 hours, and the final product is WO3. 3-x / NC composite materials.

[0096] (2) Preparation method of carbon-based material coated tungsten oxide anode

[0097] The WO prepared in (1) 3-x / NC composite material is used as the negative electrode active material for lithium-ion batteries, acetylene black as a conductive agent, polyvinylidene fluoride as a binder, and N-methylpyrrolidone as a solvent. The active material, conductive agent, and binder are mixed evenly at a mass ratio of 7:2:1, and a uniform slurry is formed through prolonged stirring. This slurry is then coated onto copper foil using a scraper. After drying in a vacuum drying oven at 120℃ for 12 hours, it is cut into circular pieces with a diameter of 12mm.

[0098] Example 2

[0099] This embodiment first prepares a lithium-ion battery anode material, and then uses it to prepare the anode. The specific steps are as follows:

[0100] (1) Preparation method of carbon-based tungsten oxide composite material

[0101] Step 1: Dissolve 5 mmol of melamine in 30 mL of ethanol, stir continuously for 30 min, add 1.5 mL of formaldehyde solution dropwise and stir for 1 h to obtain mixture A;

[0102] Step 2: Dissolve 2 mmol WCl6 in 30 mL of ethanol, add 1 mmol citric acid and stir for 30 min, then add solution A obtained in Step 1, continue stirring for 1 h, and then transfer to a high-pressure reactor. Place the reactor in a forced-air dryer and react at 200 °C for 10 h. Wash the obtained product with water and ethanol, then place it in a vacuum drying oven and dry at 60 °C for 8 h to obtain powder sample B;

[0103] Step 3: Place the powder sample B obtained in Step 2 in a tube furnace and anneal it under an Ar atmosphere at a temperature of 750℃ and a heating rate of 5℃·min. -1 The annealing time is 2 hours, and the final product is WO3. 3-x / NC composite materials.

[0104] (2) Preparation method of carbon-based material coated tungsten oxide anode

[0105] The WO prepared in (1) 3-x / NC composite material is used as the negative electrode active material for lithium-ion batteries, acetylene black as a conductive agent, polyvinylidene fluoride as a binder, and N-methylpyrrolidone as a solvent. The active material, conductive agent, and binder are mixed evenly at a mass ratio of 7:2:1, and a uniform slurry is formed through prolonged stirring. This slurry is then coated onto copper foil using a scraper. After drying in a vacuum drying oven at 120℃ for 12 hours, it is cut into circular pieces with a diameter of 12mm.

[0106] Example 3

[0107] This embodiment first prepares a lithium-ion battery anode material, and then uses it to prepare the anode. The specific steps are as follows:

[0108] (1) Preparation method of carbon-based tungsten oxide composite material

[0109] Step 1: Dissolve 10 mmol of melamine in 30 mL of ethanol, stir continuously for 30 min, add 3 mL of formaldehyde solution and stir for 1 h to obtain mixture A;

[0110] Step 2: Dissolve 2 mmol WCl6 in 30 mL of ethanol, add 2 mmol citric acid and stir for 30 min, then add solution A obtained in Step 1, continue stirring for 1 h, and then transfer to a high-pressure reactor. Place the reactor in a forced-air dryer and react at 200 °C for 10 h. Wash the obtained product with water and ethanol, then place it in a vacuum drying oven and dry at 60 °C for 8 h to obtain powder sample B;

[0111] Step 3: Place the powder sample B obtained in Step 2 in a tube furnace and anneal it under an Ar atmosphere at a temperature of 750℃ and a heating rate of 5℃·min. -1 The annealing time is 2 hours, and the final product is WO3. 3-x / NC composite materials.

[0112] (2) Preparation method of carbon-based material coated tungsten oxide anode

[0113] The WO prepared in (1) 3-x / NC composite material is used as the negative electrode active material for lithium-ion batteries, acetylene black as a conductive agent, polyvinylidene fluoride as a binder, and N-methylpyrrolidone as a solvent. The active material, conductive agent, and binder are mixed evenly at a mass ratio of 8:1:1, and a uniform slurry is formed through prolonged stirring. This slurry is then coated onto copper foil using a scraper. After drying in a vacuum drying oven at 120℃ for 12 hours, it is cut into circular pieces with a diameter of 12mm.

[0114] Example 4

[0115] This embodiment first prepares a lithium-ion battery anode material, and then uses it to prepare the anode. The specific steps are as follows:

[0116] (1) Preparation method of carbon-based tungsten oxide composite material

[0117] Step 1: Dissolve 10 mmol of melamine in 30 mL of ethanol, stir continuously for 30 min, add 3 mL of formaldehyde solution and stir for 1 h to obtain mixture A;

[0118] Step 2: Dissolve 2 mmol WCl6 in 30 mL of ethanol, add 1 mmol citric acid and stir for 30 min, then add solution A obtained in Step 1, continue stirring for 1 h, and then transfer to a high-pressure reactor. Place the reactor in a forced-air dryer and react at 200 °C for 10 h. Wash the obtained product with water and ethanol, then place it in a vacuum drying oven and dry at 60 °C for 8 h to obtain powder sample B;

[0119] Step 3: Place the powder sample B obtained in Step 2 in a tube furnace and anneal it under an Ar atmosphere at a temperature of 500℃ and a heating rate of 5℃·min. -1 The annealing time is 2 hours, and the final product is WO3. 3-x / NC composite materials.

[0120] (2) Preparation method of carbon-based material coated tungsten oxide anode

[0121] The WO3 / NC composite material prepared in (1) was used as the negative electrode active material for lithium-ion batteries, acetylene black as the conductive agent, polyvinylidene fluoride as the binder, and N-methylpyrrolidone as the solvent. The active material, conductive agent, and binder were mixed uniformly at a mass ratio of 7:2:1, and a homogeneous slurry was formed through prolonged stirring. This slurry was then coated onto copper foil using a scraper. The slurry was dried in a vacuum drying oven at 120°C for 12 hours and then cut into circular pieces with a diameter of 12 mm.

[0122] Comparative Example 1

[0123] This comparative example prepared a lithium-ion battery anode material, which differs from Example 1 in that it does not contain carbon materials. Specific steps are as follows:

[0124] (1) A method for preparing tungsten oxide anode material

[0125] Step 1: Dissolve 1 mmol WCl6 in 30 mL of ethanol and stir for 1 h. Then transfer the solution to a high-pressure reactor and place the reactor in a forced-air dryer. React at 200 °C for 10 h. Wash the resulting product with water and ethanol and then dry it in a vacuum drying oven at 60 °C for 8 h to obtain a powder sample.

[0126] Step 2: Place the powder sample obtained in Step 1 in a tube furnace and anneal it under an Ar atmosphere at a temperature of 750℃ and a heating rate of 5℃·min. -1 The annealing time is 2 hours, and WO3 material is finally obtained.

[0127] (2) A method for preparing a tungsten oxide lithium-ion battery negative electrode

[0128] The WO prepared in (1) 3-x This material serves as the negative electrode active material for lithium-ion batteries. Acetylene black is used as a conductive agent, polyvinylidene fluoride as a binder, and N-methylpyrrolidone as a solvent. The active material, conductive agent, and binder are mixed evenly at a mass ratio of 7:2:1 and stirred for an extended period to form a uniform slurry. This slurry is then coated onto copper foil using a scraper. After drying in a vacuum oven at 120°C for 12 hours, it is cut into 12mm diameter discs.

[0129] Comparative Example 2

[0130] This comparative example prepared a lithium-ion battery anode material, which differs from Example 1 in that it does not contain tungsten oxide (WO3). 3-x Specific steps:

[0131] (1) A method for preparing carbon material for lithium-ion battery anode

[0132] Step 1: Dissolve 10 mmol of melamine in 30 mL of ethanol, stir continuously for 30 min, add 3 mL of formaldehyde solution and stir for 1 h to obtain mixture A;

[0133] Add 1 mmol of citric acid to solution A obtained in step 1 and stir for 1 h. Then transfer the solution to a high-pressure reactor and place the reactor in a forced-air dryer. React at 200 °C for 10 h. Wash the resulting product with water and ethanol and then dry it in a vacuum drying oven at 60 °C for 8 h to obtain powder sample B.

[0134] Step 2: Place the powder sample obtained in Step 1 in a tube furnace and anneal it under an Ar atmosphere at a temperature of 750℃ and a heating rate of 5℃·min. -1 The annealing time is 2 hours, and the final result is NC material, which is a single carbon-based material nitrogen-doped carbon.

[0135] (2) A method for preparing a carbon material anode

[0136] NC, prepared in (1), was used as the negative electrode active material for lithium-ion batteries, acetylene black as the conductive agent, polyvinylidene fluoride as the binder, and N-methylpyrrolidone as the solvent. The active material, conductive agent, and binder were mixed uniformly at a mass ratio of 7:2:1, and a homogeneous slurry was formed through prolonged stirring. This slurry was then coated onto copper foil using a scraper. The slurry was dried in a vacuum drying oven at 120°C for 12 hours and then cut into circular pieces with a diameter of 12 mm.

[0137] Methods for preparing lithium-ion batteries

[0138] Using the front electrode as the working electrode, glass fiber (Whatman GF / F) as the diaphragm, lithium sheet as the counter electrode, and a 1:1 mixture of ethylene carbonate and dimethyl carbonate as the solvent, a 1 mol L... -1 Using LiPF6 as the electrolyte, 2032 coin cells were assembled in an argon-filled glove box, and their electrochemical performance was tested after standing in a 25°C constant temperature chamber for 10 hours.

[0139] Electrochemical performance testing methods

[0140] Electrochemical performance tests were all conducted in a 25°C constant temperature chamber. Charge-discharge tests were performed on a LAND CT2001A instrument, with constant current voltage cutoff values ​​of 0.01V and 3V, respectively.

[0141] Test case

[0142] This experimental example uses scanning electron microscopy to test the carbon-based material-coated tungsten oxide anode material from Example 1. The test results are as follows: Figure 1 As shown.

[0143] The basic morphology of carbon-based tungsten oxide coating is nanosheets with a thickness between 20-40 nm. In addition, these nanosheets self-assemble into flowers with a thickness of 1-2 μm.

[0144] This experiment tested the constant current charge-discharge performance of the negative electrode materials of Example 1 and Comparative Example 1. The test results are as follows: Figure 2 , Figure 3 , Figure 4 As shown.

[0145] from Figure 2 It can be seen that the negative electrode material provided in Example 1 achieved a first-cycle discharge specific capacity of 1007.9 mAh g. -1 The charge-discharge curves from the tenth to the hundredth cycle almost overlap, indicating that the carbon-based tungsten oxide anode material has good cycle stability; when cycled to the hundredth cycle, the coulombic efficiency is 99.46%, which indicates that the energy loss is small.

[0146] from Figure 3 It can be seen that the first-cycle discharge specific capacity of the negative electrode material provided in Comparative Example 1 is 930.8 mAh g. -1 As charging and discharging proceed, the discharge specific capacity continues to decrease, resulting in poor stability. The coulombic efficiency after the 100th cycle is 98.03%, and the energy loss is higher than that of the negative electrode material in Example 1.

[0147] like Figure 4As shown, the reversible specific capacity of the anode material provided in Comparative Example 1 eventually stabilized at 226.3 mAh g-1, while the reversible specific capacity of the anode material provided in Example 1 eventually stabilized at 463.9 mAh g-1. Compared with the anode material in Comparative Example 1, the anode material provided in Example 1 showed a significant improvement in cycle stability and a marked improvement in final electrochemical performance.

[0148] Rate performance tests were also conducted on the negative electrode materials of Example 1 and Comparative Example 1, such as... Figure 5 As shown, at current densities of 200, 500, 1000, and 2000 mA g -1 The corresponding specific capacities were 396.4, 254.3, 156.8, and 96.6 mAh g, respectively. -1 And when the current density returns to 100 mA g -1 The continuous decay of specific capacity indicates that the anode material in Comparative Example 1 has poor electron transport capability and poor rate performance. In contrast, the electron transport capability of the carbon-based tungsten oxide coating is enhanced, ensuring electrochemical performance and significantly improving rate performance. Specifically, the anode materials in Example 1 have specific capacities of 200, 500, 1000, and 2000 mAg. -1 The corresponding specific capacities were 459.7, 398.9, 355.3, and 310.6 mAh g, respectively. -1 The carbon-based tungsten oxide coating exhibits excellent rate performance.

[0149] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a lithium-ion battery anode material, wherein the lithium-ion battery anode material comprises tungsten oxide, the surface of the tungsten oxide is coated with a carbon-based material, the carbon-based material comprises nitrogen-doped carbon, and the morphology of the lithium-ion battery anode material is nanoflowers, the particle size of the nanoflowers being 1µm~2µm, characterized in that, The preparation method includes the following steps: under the action of a crosslinking agent, carbon source, nitrogen source and tungsten source are reacted by a solvothermal reaction to generate tungsten oxide and crosslinked carbon, and after annealing treatment, the crosslinked carbon coats the tungsten oxide to form the lithium-ion battery anode material; The temperature of the solvothermal reaction is 160℃~200℃; The solvothermal reaction time is 8h~10h; The annealing temperature is 500℃~800℃; The annealing process takes 1 to 5 hours.

2. The preparation method according to claim 1, characterized in that, The nanoflowers are formed by the self-assembly of nanosheets with a thickness of 20 nm to 40 nm.

3. The preparation method according to claim 1, characterized in that, The carbon source includes at least one of formaldehyde, acetaldehyde, and glyoxal.

4. The preparation method according to claim 1, characterized in that, The nitrogen source includes at least one of melamine, ethylenediamine, and dopamine hydrochloride.

5. The preparation method according to claim 1, characterized in that, The tungsten source includes at least one of tungsten hexachloride, sodium tungstate, ammonium metatungstate, sodium metatungstate, potassium metatungstate, ammonium paratungstate, sodium paratungstate, and potassium paratungstate.

6. The preparation method according to claim 1, characterized in that, The crosslinking agent includes at least one of citric acid, p-toluenesulfonic acid, and polyethylene glycol.

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