A silicon-based negative electrode material for lithium ion batteries and a preparation method thereof, and a lithium ion battery

Abstract

The application relates to the technical field of energy storage materials, and discloses a silicon-based negative electrode material for lithium ion batteries, a preparation method of the silicon-based negative electrode material and a lithium ion battery. x The negative electrode material comprises hollow SiO x balls and nanomaterials uniformly dispersed between the hollow SiO x balls, wherein x is 1-2; the nanomaterials comprise nanosilicon and a carbon shell layer coated on the surface of the nanosilicon, and the carbon shell layer is prepared by carbonizing a saccharide; the saccharide is at least one of glucose, sucrose, fructose, chitosan, agarose, sodium alginate, carboxymethyl cellulose, carboxymethyl chitosan, carboxymethyl agarose and gluconic acid; the inner diameter D x of the hollow SiO 50 ball is greater than the particle size D 50 of the nanosilicon. The lithium ion battery obtained by using the silicon-based negative electrode material has excellent reversible capacity and initial coulomb efficiency, and also has the characteristics of excellent cycle performance.

Description

Technical Field

[0001] This invention relates to the field of energy storage materials technology, specifically to a silicon-based anode material for lithium-ion batteries, its preparation method, and lithium-ion batteries. Background Technology

[0002] With the burning of fossil fuels, global warming and the greenhouse effect are impacting the healthy and sustainable development of human society. The energy crisis and clean energy have become a focus of research. In recent years, the rapid development of electric vehicles and portable devices has led to the widespread application of lithium-ion batteries in these fields due to their high energy density and long cycle life.

[0003] However, with increasing demands, the research on electrode materials has gradually become an important research direction for high-energy-density batteries. Among them, the research on anode materials, as a crucial component of batteries, has also become one of the current research hotspots.

[0004] Currently, the most widely used and technologically mature anode material for lithium-ion batteries is graphite, with a theoretical specific capacity of 372 mAh g. -1 However, due to the carbon intercalation mechanism, that is, the process of lithium ions intercalating into carbon materials, lithium dendrites will form at the negative electrode during cycling, which will then puncture the separator and cause an internal short circuit. Therefore, this intercalation mechanism poses a safety hazard.

[0005] Silicon has a high theoretical specific capacity of approximately 4200 mAh g. -1 It forms a lithium-silicon alloy with lithium ions. This alloying mechanism can effectively avoid lithium deposition and the formation of lithium dendrites, thus fundamentally avoiding safety hazards.

[0006] However, silicon-based anode materials still have the following problems: 1) silicon has poor conductivity; 2) silicon undergoes a 300% volume expansion during the lithiation process; 3) the volume expansion leads to a cycle of rupture-formation-rupture of the solid electrolyte interphase (SEI) between the anode and the electrolyte, which continuously consumes the electrolyte.

[0007] Therefore, it is of great significance to develop a silicon-based anode material with strong conductivity that can alleviate the volume expansion during silicon charging and discharging. Summary of the Invention

[0008] The purpose of this invention is to solve the problem of poor cycle performance of silicon-based anode materials in the prior art due to the easy occurrence of volume expansion.

[0009] To achieve the above objectives, a first aspect of the present invention provides a silicon-based anode material for lithium-ion batteries, the anode material comprising hollow SiO₂. x Spheres and uniformly dispersed in the hollow SiO xNanomaterials between spheres, in the hollow SiO x In the sphere, x is 1-2; the nanomaterial includes nano-silicon and a carbon shell coating the surface of the nano-silicon, and the carbon shell is prepared by carbonization of sugars;

[0010] The sugar is selected from at least one of glucose, sucrose, fructose, chitosan, agarose, sodium alginate, carboxymethyl cellulose, carboxymethyl chitosan, carboxymethyl agarose, and gluconic acid;

[0011] The hollow SiO x The inner diameter D of the ball 50 The particle size D of the nano-silicon is larger than that of the nano-silicon. 50 ;

[0012] Based on the total mass of the negative electrode material, the hollow SiO x The content of the spheres is 10-80 wt%, the content of the nano-silicon is 10-80 wt%, and the content of the carbon shell is 1-30 wt%.

[0013] A second aspect of the present invention provides a method for preparing the silicon-based anode material for lithium-ion batteries described in the first aspect, the method comprising:

[0014] (1) In the presence of solvent I, sugars and nano-silicon are first mixed to obtain a first mixture, and the first mixture is then mixed with hollow SiO2. x The balls are mixed a second time to obtain a second mixture;

[0015] (2) The second mixture is subjected to drying and carbonization treatment in sequence.

[0016] A third aspect of the present invention provides a lithium-ion battery comprising the silicon-based anode material for lithium-ion batteries described in the first aspect.

[0017] The lithium-ion battery obtained using the silicon-based anode material provided by the present invention has excellent initial discharge specific capacity and initial coulombic efficiency, as well as excellent cycle performance. In particular, the lithium-ion battery formed using the silicon-based anode material provided by the present invention maintains an initial discharge specific capacity and coulombic efficiency of up to 67% after 50 discharge cycles at 0.2C.

[0018] In addition, the method for preparing silicon-based anode materials for lithium-ion batteries provided by this invention is simple, environmentally friendly, and easy to mass-produce.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] Figure 1This is the XRD pattern of the silicon-based anode material for lithium-ion batteries prepared in Example 3 of this invention;

[0021] Figure 2 This is a SEM image of the silicon-based anode material for lithium-ion batteries prepared in Example 3 of this invention;

[0022] Figure 3 This is a cycle curve of a lithium-ion battery assembled using the lithium-ion battery silicon-based anode material prepared in Example 3 of this invention. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] In this invention, unless otherwise stated, room temperature or normal temperature refers to 25±2℃.

[0025] In this invention, the hollow SiO x The outer diameter of the sphere refers to "hollow SiO2". x The diameter of the outer circumference of a sphere.

[0026] In this invention, the hollow SiO x The inner diameter of the sphere refers to the "hollow SiO2". x The diameter of the inner circle of a hollow sphere.

[0027] As previously described, a first aspect of the present invention provides a silicon-based anode material for lithium-ion batteries, the anode material comprising hollow SiO₂. x Spheres and uniformly dispersed in the hollow SiO x Nanomaterials between spheres, in the hollow SiO x In the sphere, x is 1-2; the nanomaterial includes nano-silicon and a carbon shell coating the surface of the nano-silicon, and the carbon shell is prepared by carbonization of sugars;

[0028] The sugar is selected from at least one of glucose, sucrose, fructose, chitosan, agarose, sodium alginate, carboxymethyl cellulose, carboxymethyl chitosan, carboxymethyl agarose, and gluconic acid;

[0029] The hollow SiO x The inner diameter D of the ball 50 The particle size D of the nano-silicon is larger than that of the nano-silicon. 50 ;

[0030] Based on the total mass of the negative electrode material, the hollow SiO x The content of the spheres is 10-80 wt%, the content of the nano-silicon is 10-80 wt%, and the content of the carbon shell is 1-30 wt%.

[0031] In a preferred embodiment, based on the total mass of the negative electrode material, the hollow SiO₂ x The content of the spheres is 40-60 wt%, the content of the nano-silicon is 20-40 wt%, and the content of the carbon shell is 10-20 wt%. During their research, the inventors discovered that, in this preferred embodiment, a lithium-ion battery with superior cycle performance and initial coulombic efficiency can be obtained.

[0032] In a preferred embodiment, the hollow SiO x The spheres are hollow SiO2 spheres. The inventors unexpectedly discovered that using hollow SiO2 spheres could yield lithium-ion batteries with superior cycle performance and initial coulombic efficiency.

[0033] Preferably, the hollow SiO x The inner diameter D of the ball 50 The wavelength is 200nm-500nm, more preferably 300nm-400nm; the hollow SiO x Sphere outer diameter D 50 The wavelength range is 300nm-1000nm, and more preferably 400nm-900nm.

[0034] Preferably, the particle size D of the nano-silicon is... 50 The wavelength range is 10nm-200nm, and more preferably 40nm-60nm.

[0035] Preferably, the thickness of the carbon shell is 10nm-300nm, more preferably 20nm-200nm.

[0036] Preferably, the sugar is selected from at least one of glucose, sucrose, fructose, chitosan, agarose, sodium alginate, carboxymethyl cellulose, carboxymethyl chitosan, carboxymethyl agarose, and gluconic acid.

[0037] According to a particularly preferred embodiment of the present invention, the sugar is carboxymethyl chitosan. The inventors have discovered that, in this preferred embodiment, a lithium-ion battery with superior overall performance can be obtained.

[0038] It should be noted that the present invention does not impose any particular limitation on the method for preparing the silicon-based anode material for lithium-ion batteries described in the first aspect. Those skilled in the art can select methods based on known techniques within the art. However, in order to obtain lithium-ion batteries with better cycle performance, as mentioned above, the second aspect of the present invention provides a method for preparing the silicon-based anode material for lithium-ion batteries described in the first aspect, the method comprising:

[0039] (1) In the presence of solvent I, sugars and nano-silicon are first mixed to obtain a first mixture, and the first mixture is then mixed with hollow SiO2. x The balls are mixed a second time to obtain a second mixture;

[0040] (2) The second mixture is subjected to drying and carbonization treatment in sequence.

[0041] The lithium-ion battery formed by the silicon-based anode material prepared by the method provided in this invention has superior cycle performance.

[0042] Preferably, in step (1), the first mixing operation includes: first dissolving the sugar in the solvent I to obtain a sugar solution, and then mixing the sugar solution with the nano-silicon to obtain the first mixture.

[0043] Preferably, solvent I is water.

[0044] Preferably, in step (1), the concentration of the sugar solution is 10-100 g / L, more preferably 20-40 g / L. During their research, the inventors discovered that by adopting this preferred embodiment, lithium-ion batteries with superior cycle performance can be obtained.

[0045] Preferably, in step (1), the first mixing is performed under ultrasonic conditions, and the conditions for the first mixing include at least: ultrasonic power of 10-200W, temperature of 10-60℃, and time of 0.5-2h.

[0046] Preferably, in step (1), the second mixing method includes: first mixing the first mixture with the hollow SiO2. x The balls were mixed under ultrasonic conditions for 0.5-2 hours, and then mixed at a stirring speed of 300-500 rpm for 20-30 hours.

[0047] In a preferred embodiment, in step (1), the nano-silicon and the hollow SiO x The mass ratio of the spheres used is 0.1-10:1, more preferably 0.5-1.5:1. The inventors have discovered that by adopting this preferred embodiment, lithium-ion batteries with superior cycle performance and higher initial coulombic efficiency can be obtained.

[0048] In a preferred embodiment, in step (2), the drying process is freeze drying or spray drying.

[0049] Preferably, in step (2), the freeze-drying conditions include at least the following: a temperature of -50 to 0°C and a time of 20-30 hours.

[0050] Preferably, in step (2), the conditions for spray drying include at least: a temperature of 90-250°C, an air inlet rate of 70%-100%, a feed rate of 200mL / h-2500mL / h, and a solid content of 5-30wt%.

[0051] According to a particularly preferred embodiment of the present invention, in step (2), the carbonization process is carried out under a protective atmosphere, and the protective atmosphere is selected from at least one of nitrogen, helium, neon, argon, krypton and xenon, or the protective atmosphere is selected from a mixture of at least one of nitrogen, helium, neon, argon, krypton and xenon and hydrogen.

[0052] Preferably, in step (2), the protective atmosphere is a mixture containing hydrogen, and the hydrogen content in the protective atmosphere is 1-30% by volume. The inventors have found that by adopting this preferred embodiment, SiO2 can be reduced better, the content of active material can be increased, and thus the discharge specific capacity of the negative electrode material can be improved.

[0053] Preferably, in step (2), the carbonization treatment conditions include at least the following: temperature of 600-1500℃, heating rate of 1-20℃ / min, and time of 0.5-24h.

[0054] More preferably, in step (2), the carbonization treatment conditions include at least: a temperature of 700-1200℃, a heating rate of 1-5℃ / min, and a time of 1-8h.

[0055] It should be noted that the carbonization temperature refers to the target temperature, that is, the temperature that the carbonization process is intended to achieve at a heating rate of 1-20℃ / min; and the carbonization time refers to the holding time, that is, the time taken from the moment the carbonization process reaches the target temperature of 700-1200℃. For example, when the target temperature of the carbonization process is 800℃, the carbonization time refers to the holding time at the target temperature of 800℃.

[0056] As previously described, a third aspect of the present invention provides a lithium-ion battery comprising the silicon-based anode material for lithium-ion batteries described in the first aspect.

[0057] Compared with the prior art, the present invention also has the following advantages:

[0058] (1) Introducing hollow SiO into silicon-based anode materials x The spheres can alleviate the volume expansion of silicon and silicon dioxide during the lithiation process of the silicon anode, and compress the hollow SiO2 spheres internally to relieve stress and ensure the integrity of the sandwich spheres.

[0059] (2) The carbon shell formed after the carbonization of sugars coats the surface of nano-silicon, which can increase the conductivity of silicon anode and withstand the outward stress caused by volume expansion, further ensuring the integrity of the sphere during the lithiation and delithiation process.

[0060] (3) The preparation method provided by the present invention is simple, green and environmentally friendly, and easy to mass-produce.

[0061] The present invention will be described in detail below through examples. In the following examples, unless otherwise stated, the raw materials and instruments involved are all commercially available products.

[0062] Sugar-1: Carboxymethyl chitosan, purchased from Sinopharm Group Corporation;

[0063] Nano-Silicon-1: Nano-silicon crystal powder, particle size D 50 It is 50nm and was purchased from Anhui Zesheng Technology Co., Ltd.

[0064] Nano-Silicon-2: Nano-silicon crystal powder, particle size D 50 It is 100nm and was purchased from Ningbo Guangxin Nanomaterials Co., Ltd.

[0065] Nano-Silicon-3: Nano-silicon crystal powder, particle size D 50 The material is 10nm and was purchased from Ningbo Guangxin Nanomaterials Co., Ltd.

[0066] Nano-Silicon-4: Nano-silicon crystal powder, particle size D 50 The material is 400nm and was purchased from Ningbo Guangxin Nanomaterials Co., Ltd.

[0067] Nano-Silicon-5: Nano-silicon crystal powder, particle size D 50 The material is 340nm and was purchased from Ningbo Guangxin Nanomaterials Co., Ltd.

[0068] Hollow SiO2 sphere-1: Outer diameter D 50 It is 500nm, with an inner diameter D. 50 The material is 340nm and was purchased from Changxing Materials Industry Co., Ltd.

[0069] Hollow SiO2 sphere-2: Outer diameter D 50 It is 210nm, with an inner diameter D 50 It is 50nm and was purchased from Aibiai New Materials Co., Ltd.

[0070] In the following examples, the X-ray diffractometers were all purchased from Rigaku Corporation of Japan, and the field emission scanning electron microscopes were all purchased from Hitachi Corporation of Japan.

[0071] Example 1

[0072] This embodiment provides a method for preparing silicon-based anode materials for lithium-ion batteries, including the following steps:

[0073] (1) At room temperature, 0.4 g of carboxymethyl chitosan was dissolved in 20 mL of deionized water and stirred until a carboxymethyl chitosan aqueous solution with a concentration of 20 g / L was obtained. 0.14 g of nano-silicon-1 was added to the aforementioned carboxymethyl chitosan aqueous solution and ultrasonically dispersed (ultrasonic power of 40 W) for 1 h to obtain the first mixture. Then, 0.2 g of hollow SiO2 sphere-1 was added to the first mixture and mixed under ultrasonic conditions (ultrasonic power of 40 W) for 1 h. After mixing at 400 rpm for 24 h, the mixture was stirred to obtain the second mixture.

[0074] (2) The second mixture was placed in a freeze dryer at -50°C for 24 hours to freeze dry, and a silicon-based composite material precursor was obtained. The silicon-based composite material precursor was then placed in a tube furnace and heated to 800°C at 4°C / min under the protection of an argon atmosphere. The temperature was then maintained for 2 hours and then cooled with the furnace to obtain silicon-based anode material S1.

[0075] In the silicon-based anode material S1, the content of hollow SiO2 spheres is 51 wt%, the content of nano-silicon is 35 wt%, and the content of carbon shell (thickness of 20 nm) is 14 wt%.

[0076] Example 2

[0077] This embodiment provides a method for preparing silicon-based anode materials for lithium-ion batteries, including the following steps:

[0078] (1) At room temperature, 0.8 g of carboxymethyl chitosan was dissolved in 20 mL of deionized water and stirred until a carboxymethyl chitosan aqueous solution with a concentration of 40 g / L was obtained. 0.14 g of nano-silicon-1 was added to the aforementioned carboxymethyl chitosan aqueous solution and ultrasonically dispersed (ultrasonic power of 40 W) for 1 h to obtain the first mixture. Then, 0.2 g of hollow SiO2 sphere-1 was added to the first mixture and mixed under ultrasonic conditions (ultrasonic power of 40 W) for 1 h. After mixing at 400 rpm for 24 h, the mixture was stirred to obtain the second mixture.

[0079] (2) The second mixture was placed in a freeze dryer at -50°C for 24 hours to freeze dry, and a silicon-based composite material precursor was obtained. The silicon-based composite material precursor was then placed in a tube furnace and heated to 800°C at 4°C / min under the protection of argon atmosphere. The temperature was then maintained for 2 hours and then cooled with the furnace to obtain silicon-based anode material S2.

[0080] In the silicon-based anode material S2, the content of hollow SiO2 spheres is 52wt%, the content of nano-silicon is 36wt%, and the content of carbon shell (thickness of 200nm) is 12wt%.

[0081] Example 3

[0082] This embodiment provides a method for preparing silicon-based anode materials for lithium-ion batteries, including the following steps:

[0083] (1) At room temperature, 0.6 g of carboxymethyl chitosan was dissolved in 20 mL of deionized water and stirred until a carboxymethyl chitosan aqueous solution with a concentration of 30 g / L was obtained. 0.14 g of nano-silicon-1 was added to the aforementioned carboxymethyl chitosan aqueous solution and ultrasonically dispersed (ultrasonic power of 40 W) for 1 h to obtain the first mixture. Then, 0.2 g of hollow SiO2 sphere-1 was added to the first mixture and mixed under ultrasonic conditions (ultrasonic power of 40 W) for 1 h. After mixing at 400 rpm for 24 h, the mixture was stirred to obtain the second mixture.

[0084] (2) The second mixture was placed in a freeze dryer at -50°C for 24 hours to freeze dry, and a silicon-based composite material precursor was obtained. The silicon-based composite material precursor was then placed in a tube furnace and heated to 800°C at 4°C / min under the protection of argon atmosphere. The temperature was then maintained for 2 hours and then cooled with the furnace to obtain silicon-based anode material S3.

[0085] In the silicon-based anode material S3, the content of hollow SiO2 spheres is 48wt%, the content of nano-silicon is 34wt%, and the content of carbon shell (thickness of 30nm) is 18wt%.

[0086] Example 4

[0087] The silicon-based anode material for lithium-ion batteries was prepared according to the method in Example 1, except that in step (1), 1g of carboxymethyl chitosan was dissolved in 20mL of deionized water and stirred evenly to obtain a carboxymethyl chitosan aqueous solution with a concentration of 50g / L.

[0088] The remaining steps are the same as in Example 1, to obtain silicon-based anode material S4;

[0089] In the silicon-based anode material S4, the content of hollow SiO2 spheres is 49 wt%, the content of nano-silicon is 35 wt%, and the content of carbon shell is 26 wt%.

[0090] Example 5

[0091] This embodiment provides a method for preparing silicon-based anode materials for lithium-ion batteries, including the following steps:

[0092] (1) At room temperature, 0.6 g of carboxymethyl chitosan was dissolved in 20 mL of deionized water and stirred until a carboxymethyl chitosan aqueous solution with a concentration of 30 g / L was obtained. 0.28 g of nano-silicon-1 was added to the aforementioned carboxymethyl chitosan aqueous solution and ultrasonically dispersed (ultrasonic power of 40 W) for 1 h to obtain the first mixture. Then, 0.2 g of hollow SiO2 sphere-1 was added to the first mixture and mixed under ultrasonic conditions (ultrasonic power of 40 W) for 1 h. After mixing, the mixture was stirred at 400 rpm for 24 h to obtain the second mixture.

[0093] (2) The second mixture was placed in a freeze dryer at -50°C for 24 hours to freeze dry, and a silicon-based composite material precursor was obtained. The silicon-based composite material precursor was then placed in a tube furnace and heated to 800°C at 4°C / min under the protection of an argon atmosphere containing 10% hydrogen by volume. The temperature was then maintained for 2 hours and then cooled with the furnace to obtain silicon-based anode material S5.

[0094] In the silicon-based anode material S5, the content of hollow SiO2 spheres is 68 wt%, the content of nano-silicon is 23 wt%, and the content of carbon shell is 9 wt%.

[0095] Example 6

[0096] The silicon-based anode material for lithium-ion batteries was prepared according to the method of Example 1, except that in step (1), nano-silicon-1 was replaced with an equal mass of nano-silicon-2.

[0097] The remaining steps are the same as in Example 1, and silicon-based anode material S6 is obtained;

[0098] In the silicon-based anode material S6, the content of hollow SiO2 spheres is 51 wt%, the content of nano-silicon is 35 wt%, and the content of carbon shell is 14 wt%.

[0099] Example 7

[0100] The silicon-based anode material for lithium-ion batteries was prepared according to the method of Example 1, except that in step (1), nano-silicon-1 was replaced with an equal mass of nano-silicon-3.

[0101] The remaining steps are the same as in Example 1, and silicon-based anode material S7 is obtained;

[0102] In the silicon-based anode material S7, the content of hollow SiO2 spheres is 49 wt%, the content of nano-silicon is 35 wt%, and the content of carbon shell is 16 wt%.

[0103] Example 8

[0104] The silicon-based anode material for lithium-ion batteries was prepared according to the method of Example 1, except that in step (1), 0.6 g of nano-silicon-1 was used.

[0105] The remaining steps are the same as in Example 1, to obtain silicon-based anode material S8;

[0106] In the silicon-based anode material S8, the content of hollow SiO2 spheres is 81 wt%, the content of nano-silicon is 14 wt%, and the content of [missing information] is 5 wt%.

[0107] Comparative Example 1

[0108] The silicon-based anode material for lithium-ion batteries was prepared according to the method in Example 4, except that hollow SiO2 spheres were not added.

[0109] The specific preparation process is as follows:

[0110] (1) At room temperature, 0.6 g of carboxymethyl chitosan was dissolved in 20 mL of deionized water and stirred until homogeneous to obtain a carboxymethyl chitosan aqueous solution with a concentration of 30 g / L. 0.14 g of nano-silicon-1 was added to the aforementioned carboxymethyl chitosan aqueous solution and ultrasonically dispersed (ultrasonic power of 40 W) for 1 h to obtain the first mixture. Then, the mixture was stirred at 400 rpm for 24 h to obtain the second mixture.

[0111] (2) The second mixture was placed in a freeze dryer at a temperature of -50℃ and freeze-dried for 24h to obtain a silicon-based composite material precursor. The silicon-based composite material precursor was then placed in a tube furnace and heated to 800℃ at a rate of 4℃ / min under the protection of an argon atmosphere. The temperature was then maintained for 2h and then cooled with the furnace to obtain the silicon-based anode material DS1.

[0112] In the silicon-based anode material DS1, the content of nano-silicon is 86 wt%, and the content of carbon shell is 14 wt%.

[0113] Comparative Example 2

[0114] The silicon-based anode material for lithium-ion batteries was prepared according to the method of Example 1, except that in step (1), nano-silicon-1 was replaced with an equal mass of nano-silicon-4.

[0115] The remaining steps are the same as in Example 1, to obtain silicon-based anode material DS2;

[0116] In the silicon-based anode material DS2, the content of hollow SiO2 spheres is 52wt%, the content of nano-silicon is 36wt%, and the content of carbon shell is 12wt%.

[0117] Comparative Example 3

[0118] The silicon-based anode material for lithium-ion batteries was prepared according to the method of Example 1, except that in step (1), nano-silicon-1 was replaced with an equal mass of nano-silicon-5.

[0119] The remaining steps are the same as in Example 1, and silicon-based anode material DS3 is obtained;

[0120] In the silicon-based anode material DS3, the content of hollow SiO2 spheres is 53 wt%, the content of nano-silicon is 37 wt%, and the content of carbon shell is 10 wt%.

[0121] Comparative Example 4

[0122] The silicon-based anode material for lithium-ion batteries was prepared according to the method of Example 1, except that in step (1), hollow SiO2 spheres-1 were replaced with hollow SiO2 spheres-2 of equal mass.

[0123] The remaining steps are the same as in Example 1, to obtain silicon-based anode material DS4;

[0124] In the silicon-based anode material DS4, the content of hollow SiO2 spheres is 49 wt%, the content of nano-silicon is 35 wt%, and the content of carbon shell is 16 wt%.

[0125] Test case

[0126] The lithium-ion battery silicon-based anode material prepared in the examples and comparative examples was mixed with conductive carbon black (Super-P), carboxymethyl cellulose (CMC), and styrene-butadiene latex (SBR) in a mass ratio of 8:1:0.5:0.5 to form a slurry, which was then coated onto copper foil. After vacuum drying at 80°C and rolling, the anode was formed.

[0127] Electrode performance testing: Performance testing was conducted on a coin cell. The battery assembly method is as follows: a lithium sheet was used as the counter electrode, and the electrolyte was a 1 mol / L LiPF6 solution dissolved in a mixed solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (volume ratio 1:1:1), with 10 wt% fluorinated ethylene carbonate as an additive; Celgard 2325 was used as the separator, and the cells were assembled into CR2025 coin cells.

[0128] Cyclic performance testing method: The Blue Battery Testing System (Wuhan Jinno Electronics Co., Ltd.) was used to conduct constant current charge-discharge tests at a current density of 200 mAh / g, with the charge-discharge voltage limited to between 0-1.5V. Specific test results are shown in Table 1.

[0129] The formula for calculating the capacity retention rate after 50 cycles is: (discharge specific capacity after 50 cycles / initial discharge specific capacity) × 100%.

[0130] Table 1

[0131]

[0132] As can be seen from the results in the table above, the lithium-ion battery obtained by using the silicon-based anode material provided by the present invention has excellent initial discharge specific capacity and initial coulombic efficiency, as well as excellent cycle performance, with a capacity retention rate of up to 67% after 50 cycles.

[0133] This invention provides, by way of example, XRD and SEM images of the lithium-ion battery silicon-based anode material prepared in Example 3, and cycle curves of a lithium-ion battery assembled using the lithium-ion battery silicon-based anode material prepared in Example 3 of this invention, as shown in the figures. Figures 1-3 .

[0134] Figure 1 This is the XRD pattern of the silicon-based anode material for lithium-ion batteries prepared in Example 3 of this invention. Figure 1 In the diagram, Si-PDF#77-2108 is the standard card for silicon, and SiO2-PDF#99-0038 is the standard card for silicon dioxide. From... Figure 1 As can be seen from the above, the negative electrode material prepared by the method of the present invention contains hollow SiO2 spheres and nano-silicon.

[0135] Figure 2 This is a SEM image of the silicon-based anode material for lithium-ion batteries prepared in Example 3 of this invention. From... Figure 2 As can be seen, in the negative electrode material prepared by the method of the present invention, the nano-silicon particles can be uniformly wrapped around the hollow SiO2 spheres.

[0136] Figure 3 This is a cycle curve diagram of a lithium-ion battery assembled using the silicon-based anode material prepared in Example 3 of this invention. From... Figure 3 As can be seen from the results, the electrochemical performance of the negative electrode material prepared in Example 3 is stable, and its discharge specific capacity can be stabilized at 600 mAh / g.

[0137] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A silicon-based anode material for lithium-ion batteries, characterized in that, The anode material includes hollow SiO₂. x Spheres and uniformly dispersed in the hollow SiO x Nanomaterials between spheres, in the hollow SiO x In the sphere, x is 1-2; the nanomaterial includes nano-silicon and a carbon shell coating the surface of the nano-silicon, and the carbon shell is prepared by carbonization of sugars; The sugar is selected from at least one of glucose, sucrose, fructose, chitosan, agarose, sodium alginate, carboxymethyl cellulose, carboxymethyl chitosan, carboxymethyl agarose, and gluconic acid; The hollow SiO x The inner diameter D of the ball 50 The particle size D of the nano-silicon is larger than that of the nano-silicon. 50 ; Based on the total mass of the negative electrode material, the hollow SiO x The content of the spheres is 10-80 wt%, the content of the nano-silicon is 10-80 wt%, and the content of the carbon shell is 1-30 wt%.

2. The negative electrode material according to claim 1, wherein, Based on the total mass of the negative electrode material, the hollow SiO x The content of the spheres is 40-60 wt%, the content of the nano-silicon is 20-40 wt%, and the content of the carbon shell is 10-20 wt%.

3. The negative electrode material according to claim 1 or 2, wherein, The hollow SiO x The inner diameter D of the ball 50 The wavelength is 200nm-500nm, and the hollow SiO₂ x Sphere outer diameter D 50 The range is 300nm-1000nm.

4. The negative electrode material according to claim 3, wherein, The hollow SiO x The inner diameter D of the ball 50 The wavelength is 300nm-400nm, and the hollow SiO₂ is... x Sphere outer diameter D 50 The range is 400nm-900nm.

5. The negative electrode material according to claim 1 or 2, wherein, The particle size D of the nano-silicon 50 The range is 10nm-200nm.

6. The negative electrode material according to claim 5, wherein, The particle size D of the nano-silicon 50 The wavelength range is 40nm-60nm.

7. The negative electrode material according to claim 1 or 2, wherein, The thickness of the carbon shell is 10nm-300nm.

8. The negative electrode material according to claim 7, wherein, The thickness of the carbon shell is 20nm-200nm.

9. A method for preparing the silicon-based anode material for lithium-ion batteries according to any one of claims 1-8, characterized in that, The method includes: (1) In the presence of solvent I, sugars and nano-silicon are first mixed to obtain a first mixture, and the first mixture is then mixed with hollow SiO2. x The balls are mixed a second time to obtain a second mixture; (2) The second mixture is subjected to drying and carbonization treatment in sequence.

10. The method according to claim 9, wherein, In step (1), the nano-silicon and the hollow SiO x The mass ratio of the balls used is 0.1-10:

1.

11. The method according to claim 9 or 10, wherein, In step (1), the nano-silicon and the hollow SiO x The mass ratio of the balls used is 0.5-1.5:

1.

12. The method according to claim 9 or 10, wherein, In step (2), the drying process is freeze drying or spray drying.

13. The method according to claim 12, wherein, In step (2), the freeze-drying conditions include at least: a temperature of -50 to 0°C and a time of 20-30 hours; and / or In step (2), the conditions for spray drying include at least the following: temperature of 90-250℃, air inlet rate of 70%-100%, feed rate of 200 mL / h-2500 mL / h, and solid content of 5-30 wt%.

14. The method according to claim 9 or 10, wherein, In step (2), the carbonization process is carried out under a protective atmosphere, and the protective atmosphere is selected from at least one of nitrogen, helium, neon, argon, krypton and xenon, or the protective atmosphere is selected from at least one of nitrogen, helium, neon, argon, krypton and xenon and a mixture of hydrogen.

15. The method according to claim 9 or 10, wherein in step (2), the conditions for the carbonization treatment include at least: The temperature is 600-1500℃, the heating rate is 1-20℃ / min, and the time is 0.5-24h.

16. A lithium-ion battery, characterized in that, The lithium-ion battery includes the silicon-based anode material for lithium-ion batteries as described in any one of claims 1-8.

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