A nano-silicon embedded silicon oxide / carbon composite negative electrode material and its preparation method
By dispersing nano-SiO2 with asphalt and performing low-temperature molten salt aluminothermic reduction, combined with ball milling treatment, a nano-Si embedded silicon oxide/carbon composite negative electrode material was prepared, which solved the oxidation and structural order problems of Si/C composite materials during the preparation process and achieved high capacity and good electrochemical performance.
Patent Information
- Application Number
- CN202411681602.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-22
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2044-11-22
AI Technical Summary
During the preparation process of existing Si/C composite negative electrode materials, nano-Si is easily oxidized, the capacity is reduced, and the pyrolytic carbon structure has low order, resulting in poor electrochemical performance. In addition, the nano-Si content is low and the capacity is low.
Nano-SiO2 and asphalt are dispersed and then reduced by low-temperature molten salt aluminotherm to form carbon-coated nano-Si embedded in SiOx. Combined with asphalt polymerization accelerator, nano-Si embedded in silicon dioxide/carbon composite negative electrode material is prepared by ball milling.
It effectively avoids the oxidation of nano-Si, improves the specific capacity and electrochemical properties of the material, and the material exhibits excellent cycle stability and reversibility at high current density, making it suitable for large-scale production.
Smart Images
Figure CN119601602B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of lithium ion battery negative electrode materials, and in particular relates to a nano-silicon embedded silicon oxide / carbon composite negative electrode material and a preparation method thereof. Background Art
[0002] Silicon (Si) has the advantages of high theoretical capacity, suitable working potential and high natural abundance, and is a representative negative electrode material for the next generation of lithium-ion batteries. However, due to the inherent large volume expansion (up to 300%) during the lithium insertion / delithiation process, the active Si particles break and pulverize, causing the solid electrolyte interface film (SEI) to be unstable, and ultimately leading to severe capacity decay of the Si negative electrode material. In addition, pure Si material has poor electronic conductivity and is difficult to support high-rate charge and discharge. In order to solve these problems, the combination of nano-sized Si and different carbon materials to form Si / C composite negative electrode materials with different structures has been proven to be a very promising method that can largely overcome the inherent shortcomings of silicon negative electrode materials.
[0003] Asphalt, a byproduct of the petroleum industry, offers advantages such as high aromaticity, a high carbon-to-hydrogen ratio, low cost, and widespread availability. It is a high-quality carbon precursor for silicon-carbon anode materials in lithium-ion batteries. Coating the silicon with asphalt, after heat treatment, forms a carbon coating on the surface. This can buffer volume expansion and form a stable SEI film, thereby improving the cycling performance of the electrode material. Furthermore, the carbon-coated silicon exhibits excellent electrical conductivity, which can enhance the rate capability of the electrode material.
[0004] At present, the common preparation method of commercial Si / C composite negative electrode materials is to uniformly disperse nano-Si and graphite in molten asphalt, or to uniformly disperse nano-Si and graphite in solutions such as asphalt / CCl4 or asphalt / tetrahydrofuran (C4H8O) to obtain asphalt / graphite / Si precursor, and then obtain Si / C composite negative electrode materials by heat treatment in a high-temperature inert atmosphere.
[0005] The above-mentioned method for preparing Si / C composite negative electrode materials has obvious disadvantages: first, nano-Si has extremely high reactivity and easily reacts with oxygen-containing functional groups and water vapor in asphalt during heat treatment, resulting in partial oxidation of nano-Si, causing problems such as reduced coulombic efficiency and capacity of the final Si / C negative electrode material; second, in order to reduce the effect of active Si expansion on the cycle stability of Si / C composite negative electrode materials, the content of nano-Si in the composite material prepared by this method is relatively low (usually 20wt%), resulting in a low maximum specific capacity of the prepared Si / C composite negative electrode material (usually 800mAh g -1); Third, in order to prevent Si from reacting with C to form SiC, the heat treatment temperature of the asphalt / Si precursor cannot exceed 900°C, which results in a low structural order of the asphalt pyrolysis carbon, and ultimately causes the electrochemical reaction reversibility and rate performance of the Si / C composite negative electrode material to be poor. Summary of the Invention
[0006] The purpose of the present invention is to overcome the above problems existing in the conventional technology and provide a nano-silicon embedded silicon oxide / carbon composite negative electrode material and its preparation method. The present invention can achieve the effective reduction of carbon-coated nano-SiO2 to obtain carbon-coated nano-Si embedded SiO2 x The thin flaky asphalt pyrolysis carbon introduced can effectively relieve the stress caused by the volume expansion of Si. The addition of asphalt polymerization accelerator makes the asphalt coated on the surface of the active material still have a high degree of structural order at a temperature below 900℃. x The preparation method of carbon / carbon composite negative electrode material is not only simple in process, high in efficiency, low in cost, environmentally friendly, and easy to achieve large-scale production, but also the prepared lithium-ion battery negative electrode material has excellent comprehensive electrochemical properties.
[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:
[0008] The present invention provides a method for preparing a nano-silicon embedded silicon oxide / carbon composite negative electrode material, comprising the following steps:
[0009] 1) Dispersing appropriate amounts of nano-SiO2 and asphalt in CCl4 according to a certain weight ratio, ultrasonically treating the mixture, stirring the mixture at 30-70°C for 5-8 hours, vacuum drying the resulting product, and subsequently heat treating the mixture at a certain temperature in an inert atmosphere for a period of time to obtain carbon-coated nano-SiO2 powder;
[0010] 2) uniformly mixing the carbon-coated nano-SiO2 powder prepared in step 1) with Al powder in a certain molar ratio to obtain a redox reaction system; then uniformly mixing anhydrous AlCl3 with KCl in a certain molar ratio to obtain an AlCl3-KCl binary mixed salt system; uniformly mixing the reaction system and the mixed salt system in a certain weight ratio, and heating them at a certain temperature and in an inert atmosphere for a period of time to obtain a carbon-coated nano-Si embedded SiO2 system. x ;
[0011] 3) In a certain weight ratio, the carbon-coated nano-Si prepared in step 2) is embedded in SiO x Evenly mix with pitch carbon prepared under certain conditions, add appropriate amount of CCl4, fill with inert gas, and perform ball milling under certain conditions;
[0012] 4) The ball-milled product obtained in step 3), asphalt, styrene monomer and imidazoline are mixed in a certain weight ratio, and the mixture is evenly mixed by ball milling in a CCl4 medium. The ball-milled product is reacted for a period of time at a certain temperature in an inert atmosphere, and then heat-treated for a period of time at a certain temperature to obtain a nano-Si embedded SiO x / carbon composite negative electrode materials.
[0013] Furthermore, in step 1), the particle size of the nano-SiO2 is 10 to 50 nm.
[0014] Furthermore, in step 1), the asphalt is an asphalt having a residual carbon content of 15-25% after heat treatment at 1100° C. in an inert atmosphere.
[0015] Furthermore, in step 1), the weight ratio of nano-SiO2 to asphalt is 1:0.25-0.30, the heat treatment temperature is 900-1100°C, and the heat treatment time is 2-4h.
[0016] Furthermore, in step 2), the molar ratio of nano-SiO2 powder to Al powder in the reaction system is 1:1.5~2.5, the molar ratio of anhydrous AlCl3 to KCl in the mixed salt system is 1:0.7~0.8, the weight ratio of the reaction system to the mixed salt system is 1:4.0~5.0, the heating temperature is 350~450℃, and the heating time is 10~12h.
[0017] Furthermore, in step 3), the asphalt carbon is a product of heat treatment of asphalt in an Ar gas atmosphere, the heat treatment temperature is 1000-1200°C, and the heat treatment time is 2-4 hours; the weight ratio of carbon-coated silicon oxide / silicon to asphalt carbon is 1:0.15-0.25, the ball milling speed is 350-450 rpm, the ball milling time is 6-10 hours, and the weight ratio of material in the ball mill jar to grinding balls is 1:60-100.
[0018] Furthermore, in step 4), the weight ratio of the ball mill product to asphalt is 1:0.50-0.60, the weight ratio of asphalt to styrene and imidazoline is 1:0.7:0.002; the ball mill speed is 250-350 rpm, the ball milling time is 2-4 hours, the weight ratio of the material in the ball mill jar to the grinding balls is 1:60-100; the reaction temperature is 140-180°C, the reaction time is 6-10 hours, the heat treatment temperature is 850-950°C, and the heat treatment time is 2-4 hours.
[0019] The present invention also provides a nano-silicon embedded silicon oxide / carbon composite negative electrode material, which is prepared by the above-mentioned preparation method.
[0020] The beneficial effects of the present invention are:
[0021] 1. The present invention can efficiently reduce carbon-coated nano-SiO2 to carbon-coated nano-Si@SiO by means of low-temperature molten salt aluminothermic reduction. x , and nano-Si is embedded in SiO x This avoids the problem of oxidation of highly active nano-Si by oxygen-containing functional groups in asphalt and water vapor during the current heat treatment process of Si / C composite material preparation.
[0022] 2. Carbon-coated nano-Si embedded SiO prepared by reduction of the present invention x , among which amorphous SiO as the main component x It provides a relatively considerable specific capacity. At the same time, its volume change during charge and discharge is much smaller than that of Si. The volume change of the electrode material during charge and discharge is significantly reduced. Therefore, the electrode active material Si / SiO in the present invention is x The content can be as high as 67wt% or more, overcoming the problems of low weight proportion of active components and small specific capacity in current Si / C negative electrode materials.
[0023] 3. The present invention physically and uniformly mixes asphalt, styrene and imidazoline by ball milling, thereby promoting asphalt polymerization, overcoming the low degree of carbon order and low content of microcrystalline carbon in the current Si / C composite negative electrode material after low-temperature (900°C) pyrolysis of asphalt, and effectively improving the reversibility and rate performance of the composite material's electrochemical reaction.
[0024] 4. The nano-Si@SiO prepared by the present invention x The / C composite negative electrode material exhibits excellent electrochemical performance, and the preparation method is simple, the equipment is simple, the cost is low, it is environmentally friendly, and it is easy to achieve mass production. The prepared electrode material has a high conductivity at 0.05A g -1 The first cycle discharge / charge capacity is 2552.8 / 1609.4mAh g -1 , the first coulombic efficiency is 63.0%; when the current is increased to 2.0A g -1 The measured reversible capacity is 948.6 mAh g -1 , the capacity retention rate is as high as 54.9%; at 0.50A g -1 After 200 cycles, the electrode material capacity is still as high as 714.4 mAh g -1 , the capacity retention rate is 82.6%.
[0025] Of course, any product implementing the present invention does not necessarily need to achieve all of the above advantages at the same time. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0027] Figure 1 The nano-Si@SiO prepared in Example 1 x / XRD pattern of C negative electrode material;
[0028] Figure 2 The nano-Si@SiO prepared in Example 1 x XPS pattern of / C negative electrode material;
[0029] Figure 3 The nano-Si@SiO prepared in Example 1 x FESEM image of / C negative electrode material;
[0030] Figure 4 The nano-Si@SiO prepared in Example 1 x TEM image of / C negative electrode material;
[0031] Figure 5 This is a test image of a battery sample assembled with the nano-Si@SiOx / C negative electrode material prepared in Example 1;
[0032] Where: (a) is 0.05A g -1 Constant current charge and discharge curves at different current densities, (b) rate curves at different current densities; (c) constant current charge and discharge curves at 0.5A g -1 Cycling performance curves at different current densities. DETAILED DESCRIPTION
[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.
[0034] The present invention uses nano-SiO2 and asphalt as main raw materials, disperses nano-SiO2 and asphalt in CCl4, heats and stirs, and then dries and heat-treats in an inert atmosphere to obtain carbon-coated nano-SiO2; carbon-coated nano-SiO2, Al powder, KCl and anhydrous AlCl3 are uniformly mixed and heat-treated in an inert atmosphere to obtain carbon-coated nano-Si embedded SiO2. x ; Inlaying carbon-coated nano-Si into SiOx The ball milling product was mixed with asphalt pyrolysis carbon, and the ball milling product was evenly mixed with asphalt, styrene and imidazoline in CCl4 medium, and then heat treated in an inert atmosphere to finally obtain a nano-silicon embedded silicon oxide / carbon composite negative electrode material.
[0035] The present invention can effectively avoid the problems of oxidation of active nano-Si and low specific capacity of Si / C composite materials during heat treatment. This is because, first, when nano-SiO2 is stirred in asphalt / CCl4 solution at a certain temperature, as CCl4 evaporates, asphalt is evenly coated on the surface of nano-SiO2. After treatment in an inert atmosphere, a uniform porous carbon coating is formed on the surface of nano-SiO2. Then, with the help of low-temperature molten salt aluminothermic reduction, a large number of reduced Si atoms are aggregated to form nano-Si. At the same time, unreduced SiO2 undergoes a disproportionation reaction with nano-Si to form SiO x Wrapped on the surface of nano-Si (nano-Si@SiO x ), and the pitch pyrolysis carbon is coated on nano-Si@SiO x The surface effectively blocks water vapor and highly active nano-Si@SiO x The carbon-coated nano-Si embedded in SiO is reduced to avoid the adverse effects of oxidation. x , which is mainly composed of SiO x The volume changes little during the charge and discharge process, and provides a relatively considerable specific capacity, which circumvents the problem of low specific capacity of Si / C composite negative electrode materials caused by low content of nano-Si in current composite materials. The present invention introduces a polymerization promoter into the asphalt, so that the asphalt coated on the surface of the active material still has a high degree of structural order at a thermal decomposition product below 900°C. This is because during the heat treatment process at 140°C, imidazoline can promote the thermal polycondensation reaction of styrene monomer and aromatic compounds in asphalt, so that the planar molecular layer continues to grow larger, and at the same time, a large number of planar molecular layers continue to stack and rearrange, so that the carbonized product has a higher degree of structural order and a higher content of microcrystals, and is coated on the active component nano-Si@SiO x The surface was finally prepared with nano-Si embedded silicon oxide / carbon (nano-Si@SiO x / C) composite negative electrode materials.
[0036] The specific embodiments of the present invention are as follows:
[0037] Example 1
[0038] 1) 3.0005 g of nano-SiO2 and 0.8401 g of asphalt were dispersed in CCl4 at a weight ratio of 1:0.28, and the mixed suspension was stirred on a magnetic stirrer at 50°C for 6 h. The stirred product was vacuum dried and then heat-treated at 1000°C in an Ar atmosphere for 3 h to obtain carbon-coated nano-SiO2.
[0039] 2) According to the molar ratio of nano-SiO2 to Al powder of 1:2.0, 1.0032g of carbon-coated nano-SiO2 was weighed and uniformly mixed with 0.6413g of Al powder. Then, according to the weight ratio of the reaction system to the mixed salt system of 1:4.4298 and the molar ratio of anhydrous AlCl3 to KCl of 1:0.75, 5.6367g of anhydrous AlCl3 and 2.3592g of KCl were weighed and uniformly mixed. The mixed powder was uniformly mixed and placed in a corundum crucible, and heat-treated at 400°C in an Ar gas atmosphere for 10h. Then, it was washed with a 9wt% dilute hydrochloric acid solution and dried to obtain a carbon-coated nano-Si embedded SiO x ;
[0040] 3) The asphalt was heat treated at 1100℃ for 3h in an Ar atmosphere to obtain asphalt pyrolysis carbon, and the carbon-coated nano-Si was embedded in SiO x The weight ratio of carbon to asphalt pyrolysis carbon was 1:0.2009. 0.5056 g of carbon-coated silicon oxide / silicon and 0.1016 g of asphalt carbonization product were weighed, 3 g of CCl4 were added and mixed evenly, and then placed in a polyethylene ball mill with zirconia grinding balls at 400 rpm for 8 h.
[0041] 4) According to the weight ratio of the ball-milled product obtained in step 3) to asphalt of 1:0.5355, and the weight ratio of asphalt to styrene and imidazoline of 1:0.7:0.002, 0.5007g of the ball-milled product, 0.2681g of asphalt, 0.1877g of styrene, and 0.0005g of imidazoline were weighed, 3g of CCl4 was added and mixed evenly, and the mixture was placed in a polyethylene ball mill with zirconia grinding balls at 300 rpm for 3h; then, the mixture was milled at 2°C min in an Ar atmosphere. -1 Heat to 140℃, keep at 140℃ for 8h, then -1 The temperature was raised to 900℃ and heat treated for 3h to obtain a nano-silicon embedded silicon oxide / carbon composite negative electrode material (abbreviated as nano-Si@SiO x / C).
[0042] The negative electrode materials prepared in the above steps were assembled into a half-cell and tested at 0.05A g -1 The first cycle discharge / charge capacity is 2552.8 / 1609.4mAh g -1, the first coulombic efficiency is 63.0%; when the current is increased to 2.0A g -1 The measured reversible capacity is 948.6 mAh g -1 , the capacity retention rate is as high as 54.9%; at 0.50A g -1 After 200 cycles, the electrode material capacity is still as high as 714.4 mAh g -1 , the capacity retention rate is 82.6%.
[0043] Example 2
[0044] 1) 3.0005 g of nano-SiO2 and 0.7513 g of asphalt were dispersed in CCl4 at a weight ratio of 1:0.25, and the mixed suspension was stirred on a magnetic stirrer at 50°C for 6 h. The stirred product was vacuum dried and then heat-treated at 1000°C in an Ar atmosphere for 3 h to obtain carbon-coated nano-SiO2.
[0045] 2) According to the molar ratio of nano-SiO2 to Al powder of 1:2.0, 1.0032g of carbon-coated nano-SiO2 was weighed and uniformly mixed with 0.6449g of Al powder. Then, according to the weight ratio of the reaction system to the mixed salt system of 1:5.0 and the molar ratio of anhydrous AlCl3 to KCl of 1:0.75, 5.6685g of anhydrous AlCl3 and 2.3725g of KCl were weighed and uniformly mixed. The mixed powder was uniformly mixed and placed in a corundum crucible, and heat-treated at 400°C for 10h in an Ar gas atmosphere. Then, it was washed with a 9wt% dilute hydrochloric acid solution and dried to obtain a carbon-coated nano-Si embedded SiO x ;
[0046] 3) The asphalt was heat treated at 1100℃ for 3h in an Ar atmosphere to obtain asphalt pyrolysis carbon, and the carbon-coated nano-Si was embedded in SiO x The weight ratio of carbon to asphalt pyrolysis carbon was 1:0.25. 0.5056 g of carbon-coated silicon oxide / silicon and 0.1264 g of asphalt carbonization product were weighed, 3 g of CCl4 were added and mixed evenly, and then placed in a polyethylene ball mill with zirconia grinding balls at 400 rpm for 8 h.
[0047] 4) According to the weight ratio of the ball-milled product obtained in step 3) to asphalt of 1:0.50, and the weight ratio of asphalt to styrene and imidazoline of 1:0.7:0.002, 0.5007g of the ball-milled product, 0.2504g of asphalt, 0.1752g of styrene, and 0.0005g of imidazoline were weighed, 3g of CCl4 was added and mixed evenly, and the mixture was placed in a polyethylene ball mill with zirconia grinding balls at 300 rpm for 3h; then, the mixture was milled in an Ar atmosphere at 2°C min -1 Heat to 140℃, keep at 140℃ for 8h, then-1 The temperature was raised to 900℃ and heat-treated for 3h to obtain a nano-silicon embedded silicon oxide / carbon composite negative electrode material (abbreviated as SiO x / Si@C).
[0048] The negative electrode materials prepared in the above steps were assembled into a half-cell and tested at 0.05A g -1 The first cycle discharge / charge capacity is 2507.3 / 1557.0mAh g -1 , the first coulombic efficiency is 62.1%; when the current is increased to 2.0A g -1 The reversible capacity was measured to be 833.0 mAh g -1 , the capacity retention rate is as high as 52.7%; at 0.50A g -1 After 200 cycles, the electrode material capacity is still as high as 698.1 mAh g -1 , the capacity retention rate is 80.4%.
[0049] Example 3
[0050] 1) 3.0005 g of nano-SiO2 and 0.9002 g of asphalt were dispersed in CCl4 at a weight ratio of 1:0.30, and the mixed suspension was stirred on a magnetic stirrer at 50°C for 6 h. The stirred product was vacuum dried and then heat-treated at 1000°C in an Ar atmosphere for 3 h to obtain carbon-coated nano-SiO2.
[0051] 2) According to the molar ratio of nano-SiO2 to Al powder of 1:2.0, 1.0032g of carbon-coated nano-SiO2 and 0.6338g of Al powder were weighed and preliminarily evenly mixed, and then according to the weight ratio of the reaction system to the mixed salt system of 1:4.4298 and the molar ratio of anhydrous AlCl3 to KCl of 1:0.75, 5.6154g of anhydrous AlCl3 and 2.3503g of KCl were weighed and evenly mixed, and the mixed powder was evenly mixed and placed in a corundum crucible, and heat-treated at 400°C in an Ar gas atmosphere for 10h, and then washed with 9wt% dilute hydrochloric acid solution and dried to obtain carbon-coated silicon dioxide / silicon;
[0052] 3) The asphalt was heat treated at 1100℃ for 3h in an Ar atmosphere to obtain asphalt pyrolysis carbon, and the carbon-coated nano-Si was embedded in SiO x The weight ratio of carbon to asphalt pyrolysis carbon was 1:0.15. 0.5056 g of carbon-coated silicon oxide / silicon and 0.0758 g of asphalt carbonization product were weighed, 3 g of CCl4 were added and mixed evenly, and then placed in a polyethylene ball mill with zirconia grinding balls at 400 rpm for 8 h.
[0053] 4) According to the weight ratio of the ball-milled product obtained in step 3) to asphalt of 1:0.60, and the weight ratio of asphalt to styrene and imidazoline of 1:0.7:0.002, 0.5007g of the ball-milled product, 0.3004g of asphalt, 0.2103g of styrene, and 0.0006g of imidazoline were weighed, 3g of CCl4 was added and mixed evenly, and the mixture was placed in a polyethylene ball mill with zirconia grinding balls at 300 rpm for 3h; then, the mixture was milled in an Ar atmosphere at 2°C min -1 Heat to 140℃, keep at 140℃ for 8h, then -1 The temperature was raised to 900°C and heat treated for 3 hours to obtain a nano-silicon embedded silicon oxide / carbon composite negative electrode material (abbreviated as nano-Si@SiOx / C).
[0054] The negative electrode materials prepared in the above steps were assembled into a half-cell and tested at 0.05A g -1 The first cycle discharge / charge capacity is 2498.7 / 1534.2mAh g -1 , the first coulombic efficiency is 61.4%; when the current is increased to 2.0A g -1 The measured reversible capacity is 821.4 mAh g -1 , the capacity retention rate is as high as 52.1%; at 0.50A g -1 After 200 cycles, the electrode material capacity is still as high as 691.4 mAh g -1 , the capacity retention rate is 81.2%.
[0055] Comparative Example 1
[0056] Step 1) in Example 1 is omitted, the surface of the nano-silica is coated in advance, and the nano-silica is directly reduced by aluminothermic reduction. The subsequent steps are exactly the same as in Example 1.
[0057] The negative electrode materials prepared according to the above steps were assembled into a half-cell, and the electrochemical performance was measured as follows:
[0058] At 0.05A g -1 The first cycle discharge / charge capacity is 2120.3 / 1189.5mAh g -1 , the first coulombic efficiency is 56.1%; when the current is increased to 2.0A g -1 The measured reversible capacity is 401.2 mAh g -1 , the capacity retention rate is 35.7%; at 0.50A g -1 After 200 cycles, the electrode material capacity is 430.2 mAh g -1 , the capacity retention rate is 55.3%.
[0059] Comparative Example 2
[0060] Steps 1) and 2) in Example 1 were carried out, step 3) was omitted, and the subsequent steps were exactly the same as in Example 1.
[0061] The negative electrode materials prepared according to the above steps were assembled into a half-cell, and the electrochemical performance was measured as follows:
[0062] At 0.05A g -1 The first cycle discharge / charge capacity is 2442.3 / 1699.1mAh g -1 , the first coulombic efficiency is 69.5%; when the current is increased to 2.0A g -1 The measured reversible capacity is 7797.9 mAh g -1 , the capacity retention rate is 50.2%; at 0.50A g -1 After 200 cycles, the electrode material capacity is 684.2 mAh g -1 , the capacity retention rate is 69.7%.
[0063] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.
Claims
1. A method for preparing a nano-silicon embedded silicon oxide / carbon composite negative electrode material, characterized in that: The steps include: 1) Dispersing appropriate amounts of nano-SiO2 and asphalt in CCl4 according to a certain weight ratio, ultrasonically treating the mixture, stirring the mixture at 30-70°C for 5-8 hours, vacuum drying the resulting product, and subsequently heat treating the mixture at a certain temperature in an inert atmosphere for a period of time to obtain carbon-coated nano-SiO2 powder; 2) uniformly mixing the carbon-coated nano-SiO2 powder prepared in step 1) with Al powder in a certain molar ratio to obtain a redox reaction system; then uniformly mixing anhydrous AlCl3 with KCl in a certain molar ratio to obtain an AlCl3-KCl binary mixed salt system; uniformly mixing the reaction system and the mixed salt system in a certain weight ratio, and heating them at a certain temperature and in an inert atmosphere for a period of time to obtain a carbon-coated nano-Si embedded SiO2 system. x ; 3) In a certain weight ratio, the carbon-coated nano-Si prepared in step 2) is embedded in SiO x Evenly mix with pitch carbon prepared under certain conditions, add appropriate amount of CCl4, fill with inert gas, and perform ball milling under certain conditions; 4) The ball-milled product obtained in step 3), asphalt, styrene monomer and imidazoline are mixed in a certain weight ratio, and the mixture is evenly mixed by ball milling in a CCl4 medium. The ball-milled product is reacted for a period of time at a certain temperature in an inert atmosphere, and then heat-treated for a period of time at a certain temperature to obtain a nano-Si embedded SiO x / carbon composite negative electrode materials.
2. The method for preparing the nano-silicon embedded silicon oxide / carbon composite negative electrode material according to claim 1, characterized in that: In step 1), the particle size of the nano-SiO2 is 10 to 50 nm.
3. The method for preparing the nano-silicon embedded silicon oxide / carbon composite negative electrode material according to claim 1, characterized in that: In step 1), the asphalt is an asphalt having a residual carbon content of 15-25% after heat treatment at 1100° C. in an inert atmosphere.
4. The method for preparing the nano-silicon embedded silicon oxide / carbon composite negative electrode material according to claim 1, characterized in that: In step 1), the weight ratio of nano-SiO2 to asphalt is 1:0.25-0.30, the heat treatment temperature is 900-1100°C, and the heat treatment time is 2-4 hours.
5. The method for preparing the nano-silicon embedded silicon oxide / carbon composite negative electrode material according to claim 1, characterized in that: In step 2), the molar ratio of nano-SiO2 powder to Al powder in the reaction system is 1:1.5-2.5, the molar ratio of anhydrous AlCl3 to KCl in the mixed salt system is 1:0.7-0.8, the weight ratio of the reaction system to the mixed salt system is 1:4.0-5.0, the heating temperature is 350-450°C, and the heating time is 10-12h.
6. The method for preparing the nano-silicon embedded silicon oxide / carbon composite negative electrode material according to claim 1, characterized in that: In step 3), the asphalt carbon is a product of heat treatment of asphalt in an Ar gas atmosphere, the heat treatment temperature is 1000-1200°C, and the heat treatment time is 2-4 hours; the weight ratio of carbon-coated silicon oxide / silicon to asphalt carbon is 1:0.15-0.25, the ball milling speed is 350-450 rpm, the ball milling time is 6-10 hours, and the weight ratio of the material in the ball mill jar to the grinding balls is 1:60-100.
7. The method for preparing the nano-silicon embedded silicon oxide / carbon composite negative electrode material according to claim 1, characterized in that: In step 4), the weight ratio of the ball mill product to asphalt is 1:0.50-0.60, the weight ratio of asphalt to styrene and imidazoline is 1:0.7:0.002; the ball mill speed is 250-350 rpm, the ball milling time is 2-4 h, the weight ratio of the material in the ball mill jar to the grinding balls is 1:60-100; the reaction temperature is 140-180°C, the reaction time is 6-10 h, the heat treatment temperature is 850-950°C, and the heat treatment time is 2-4 h.
8. A nano-silicon embedded silicon oxide / carbon composite negative electrode material, prepared by the preparation method according to any one of claims 1 to 7.