CN115133004A - Carbon-coated modified carbon/silicon oxide composite electrode material for lithium ion battery and preparation method thereof - Google Patents
Carbon-coated modified carbon/silicon oxide composite electrode material for lithium ion battery and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a carbon-coated modified carbon/silicon oxide composite electrode material for a lithium ion battery and a preparation method thereof. The method is characterized in that: the carbon-coated modified carbon/silicon oxide composite electrode material is composed of an electrode active component, a conductive agent, a binder and a porous metal foil, wherein the electrode active component is formed by coating a carbon material outside a porous carbon/silicon oxide core shell, and the porous carbon/silicon oxide core shell is prepared by dispersing, mixing and calcining organic silicon and carbide. The carbon/silicon oxide composite electrode material prepared by the invention effectively improves the electrode capacity through reasonable mixing of carbon/silicon oxide components, the first discharge capacity can reach more than 950mAh/g, the first (second circle) coulombic efficiency can reach more than 90 percent, and the capacity retention rate after 300 cycles of charging and discharging under the current of 500mA/g is more than 85 percent.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a carbon-coated modified carbon/silicon oxide composite electrode material for a lithium ion battery and a preparation method thereof.
Background
Compared with the traditional carbon material negative electrode, silicon (Si) is considered as the most promising next-generation commercial electrode material due to the advantages of excellent theoretical specific capacity (about 4200mAh/g and 372mAh/g of graphite), lower de-intercalation lithium potential (about 0.5V), extremely high storage capacity (the second storage capacity in the earth crust), and the like. However, silicon electrode materials suffer from large volume expansion, poor conductivity, and low Initial Coulombic Efficiency (ICE), which has prevented their widespread commercial use.
The silicon electrode has serious volume expansion and contraction during lithium intercalation and deintercalation, so that the material structure is damaged and mechanically crushed, and the electrode shows poor cycle performance, and meanwhile, silicon belongs to a semiconductor material and has poor conductivity. Aiming at the problem of volume expansion of silicon, the most effective method is to carry out silicon nanocrystallization and adopt a porous structure, and through reducing the absolute volume expansion rate of silicon, the collapse of an electrode structure is effectively relieved, and meanwhile, the diffusion distance of lithium ions can be reduced, and the electrochemical reaction rate is improved; the conventional solution to the problem of poor conductivity of silicon is to adopt a method of compounding silicon and a carbon material, and researches show that the cycle performance of silicon can be effectively improved by compounding an electrode material. At present, the preparation process of nano silicon powder is complex, the particle size of the silicon powder applied to the negative electrode of the lithium battery needs to be controlled below 150nm, the main preparation process at the present stage is a physical grinding method, the silicon powder is ground to be in a nano level through a series of grinding processes such as a ball mill, a sand mill and the like, the equipment investment is huge, the process time consumption is long, and the problems of oxidation of the nano silicon powder and easy introduction of inert impurities are difficult to avoid in the grinding process. Therefore, the improvement of the production technology of the lithium battery nanometer silicon powder has very important practical significance.
Patent CN107946556A discloses a preparation method of graphene-based silicon-carbon composite material, firstly dispersing graphene oxide and maleate in a mass ratio of 1-2: 1 into water, stirring, spray drying to obtain powder, and performing high-temperature treatment to obtain spherical graphene microspheres; dispersing nano silicon and spherical graphene microspheres in a solvent, performing ultrasonic and stirring, removing the solvent after uniform mixing, and performing high-temperature treatment under inert gas to obtain a nano silicon/spherical graphene microsphere compound; and dispersing the compound and an organic carbon source in a solvent, performing ultrasonic treatment and stirring, removing the solvent after uniform mixing, and performing high-temperature treatment under inert gas to obtain the graphene-based silicon-carbon composite material. The electrode prepared by the graphene-based silicon-carbon composite material can achieve the first discharge capacity of more than 750mAh/g, the first coulombic efficiency of more than 92 percent, and the capacity retention rate of more than 85 percent after 500 cycles. However, the preparation of the material needs to use relatively more graphene oxide, and the material is subjected to multiple times of dispersion and high-temperature treatment, so that the operation process is complex and the economical efficiency is low. Patent CN111599989A discloses a silicon-based negative electrode plate, and a preparation method and application thereof. The method comprises the following steps: (1) mixing a material containing a silicon-based negative electrode material and an organic carbon source with a solvent to obtain a mixture; (2) and (2) mixing the mixture obtained in the step (1) with a current collector, and carrying out hydrothermal reaction to obtain the silicon-based negative plate. The preparation method adopts a one-step hydrothermal method to prepare the silicon-based negative plate, does not need to use a binder and a coating process, and improves the content and the capacity of active substances of the silicon-based negative plate; and the porous current collector is further adopted to relieve the volume expansion of the silicon-based negative electrode material, more electron transfer channels are provided, the lithium ion transmission distance is shortened, the interface charge exchange is facilitated, the electrochemical reaction rate is improved, and the cycle performance of the silicon-based negative electrode plate is further improved. However, this method is difficult to ensure the flatness of the electrode interface while improving the conductivity and cycle performance, and lacks the first discharge capacity data. Patent CN103915609B discloses a silicon-silicon oxide-carbon composite material, in which primary silicon oxide coated by a first amorphous carbon layer, elemental silicon particles and a second amorphous carbon layer are dispersed in hard carbon particles along the sphere diameter direction, and the silicon-silicon oxide-carbon composite material can be used for preparing a negative electrode material of a lithium ion secondary battery. The lithium ion battery has the characteristics of large charge and discharge capacity, high primary efficiency and high capacity retention rate after long-time cyclic use. However, the method needs to carry out chemical vapor deposition reaction for many times, the first discharge capacity of the prepared cathode material is less than 550mAh/g, the capacity retention rate of 300-week circulation is less than 90%, and the method is far away from the practical application requirement of the lithium battery.
Therefore, the development of the lithium battery anode material which has wide raw material source, simple process, high first-time efficiency and good cycle capacity retention rate has practical significance.
Disclosure of Invention
In order to solve the technical problems of low theoretical capacity of graphite and volume expansion caused by lithium intercalation and deintercalation from silicon in the prior art, the invention aims to provide a carbon/silicon oxide composite electrode material and a preparation method thereof.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:
a carbon-coated modified carbon/silicon oxide composite electrode material is characterized in that the carbon-coated modified carbon/silicon oxide composite electrode material is formed by coating a carbon material outside a porous carbon/silicon oxide core shell.
Preferably, the porous carbon/silicon oxide core shell is prepared by mixing and calcining organic silicon and a carbon material; the mixing process comprises at least one of stirring, ultrasonic treatment, crushing, grinding, ball milling, homogenizing and extrusion; the calcination temperature is 200-1200 ℃ in the calcination process, and the calcination time is 2-15 hours.
Preferably, the porous carbon/silicon oxide core shell is prepared by a sol-gel method, a hydrothermal synthesis method, or a solvothermal synthesis method.
Preferably, the film prepared by the porous carbon/silicon oxide core shell by adopting a gel method has a linear expansion rate of less than or equal to 2% before and after drying.
Preferably, the preparation method of the carbon-coated modified carbon/silicon oxide composite electrode material specifically comprises the following steps:
(1) mixing a material containing carbide and organic silicon with a solvent to obtain a mixed system, reacting the mixed system to obtain a mixture A, wherein the mass concentration of the organic silicon in the mixture A is 0.04-0.4 g/mL, and the mass of the material is 100%, and the mass ratio of the carbide: the feeding mass ratio of the organic silicon material is 0.1-50%;
(2) centrifuging, washing with a solvent, washing with water, drying and calcining the mixture A obtained in the step (1) to obtain the porous carbon/silicon oxide core shell;
(3) and (3) adding a coating carbon material into the porous carbon/silicon oxide core shell obtained in the step (2), and performing ball milling or/and ultrasonic treatment to obtain the carbon-coated modified carbon/silicon oxide material.
Preferably, in the carbon-coated modified carbon/silicon oxide material, the mass fraction of silicon and oxides of silicon is 55% to 95%, and the mass fraction of carbon and oxides of carbon is 5% to 45%.
Preferably, the step (1) may further comprise adding a coagulant comprising at least one of ammonia, triethylamine, cyclohexylamine, pyridine, aniline, and benzylamine to the mixed system.
Preferably, step (1) may further comprise adding a surface modifier to the mixed system, wherein the surface modifier comprises at least one of trimethylchlorosilane, hexamethyldisilazane, hexamethyldisiloxane, and other siloxane monomers or polymers containing organic functional groups.
Preferably, the addition amount of the surface modifier is 0-20% by weight percentage.
Preferably, the reaction treatment conditions in the step (1) are that the reaction temperature is 20-200 ℃, the reaction pressure is 0-2 MPa, and the reaction time is 2-80 hours.
The further preferable technical scheme is that the preparation is carried out by adopting a sol-gel method, the reaction temperature is 20-60 ℃, and the reaction time is 2-30 hours.
Preferably, the step (3) further comprises dispersing the porous carbon/silicon oxide core-shell substance and the coating carbon material in a solvent, removing the solvent after ultrasonic treatment and stirring, and carrying out heat treatment at a temperature of more than or equal to 200 ℃.
Preferably, the particle size of the carbon-coated modified carbon/silicon oxide material is 10-50000 nm.
Preferably, the solvent is at least one of water, methanol, ethanol, n-hexane, toluene and carbonate; the organic silicon is at least one of tetraethyl silicate, 3-glycidyl ether oxypropyl triethoxysilane, methyl triethoxysilane, vinyl triethoxysilane, silicon hydroxylate or epoxide; the carbide is at least one of glucose, starch, cane sugar or ash generated after biomass material is combusted, dichloro-N, N '-bis (3-hydrogenated rosin acyl oxide-2-hydroxypropyl) tetramethylethylenediamine and dichloro-N, N' -bis (3-rosin acyl oxide-2-hydroxypropyl) tetramethylethylenediamine; the coated carbon material is at least one of graphite, graphite oxide, graphene oxide, multi-layer graphene, few-layer graphene, saccharides, organic weak acid salts (such as citrate), organic weak acids (such as tannic acid), phenolic resin, a C-containing cross-linking agent and a C-containing conductive agent.
According to another aspect of the present invention, there is provided an electrode for a lithium ion battery, comprising an electrode current collector and a carbon/silicon oxide electrode material coated on the electrode current collector, the carbon/silicon oxide electrode material comprising the above-described carbon/silicon oxide composite electrode material, a conductive agent and a binder.
Preferably, the electrode current collector is at least one of a porous metal foil and a foam metal, preferably a porous copper foil, and is characterized in that: porosity: 20% -90%; pore diameter: 0.01-100 um.
Preferably, the binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethylcellulose, sodium alginate, chitosan, styrene butadiene rubber and LA type binders; the conductive agent is at least one of conductive carbon black, conductive graphite, superconducting carbon black, acetylene black, ketjen black, carbon nanotubes, VGCF and graphene.
According to another aspect of the present invention, there is provided a lithium ion battery comprising the above electrode.
Preferably, the carbon/silicon oxide is SiOx/Cy, wherein x is more than or equal to 0 and less than or equal to 2, and y is more than or equal to 0.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) the carbon-coated modified carbon/silicon oxide electrode material prepared by the invention has a porous carbon/silicon oxide core-shell structure, can effectively inhibit the problem of silica atomization of silicon serving as an electrode material in the charging and discharging processes, provides an effective expansion space for the volume expansion of the silicon material, effectively prevents the problem of thermal runaway caused by the volume expansion of the electrode, and improves the cycling stability and capacity retention rate of the electrode;
(2) the carbon/silicon oxide electrode material prepared by the invention effectively improves the electrode capacity by reasonably mixing the silicon and carbon components, the first discharge capacity can reach more than 950mAh/g, the first coulombic efficiency can reach more than 90 percent, and the capacity retention rate is more than 85 percent after 300 cycles of charge and discharge under the current of 500 mA;
(3) the carbon/silicon oxide electrode and the lithium ion battery have the same advantages as the silicon-based material.
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments.
Example 1
This example provides a method for preparing a carbon-coated modified carbon/silicon oxide electrode material for a lithium battery electrode, and table 1 shows the formula of the components used for preparing the carbon-coated modified carbon/silicon oxide electrode material in this example.
TABLE 1 formulation for preparing carbon-coated modified carbon/silicon oxide electrode material components
The raw materials required for the formulation of the carbon-coated modified carbon/silicon oxide electrode material components were prepared according to table 1 above, and the coated modified carbon/silicon oxide electrode material in this example was prepared as follows:
(1) tetraethyl silicate, dichloro-N, N' -bis (3-hydrogenated rosin acyloxy-2-hydroxypropyl) tetramethylethylenediamine, ethanol and water are stirred and dispersed to obtain a mixed system, the mass concentration of organic silicon in the mixed system is 0.27g/mL, the feeding weight ratio of carbide to organic silicon is 50%, the reaction temperature is controlled at 60 ℃, and the sol-gel method synthesis is carried out for 2 hours;
(2) centrifugally separating a solvent, washing with ethanol, washing with deionized water, tabletting, vacuum drying at 80 ℃ for 12 hours, testing that the linear expansion rate of the dried sheet is less than or equal to 1% compared with that of the sheet before drying, and then calcining at 1200 ℃ for 2 hours to obtain the carbon/silicon oxide composite material;
(3) mechanically crushing the carbon/silicon oxide composite material, adding cane sugar and ethanol for ultrasonic dispersion, drying at 80 ℃, then placing the carbon/silicon oxide composite material in a tubular furnace for roasting at 600 ℃ under the protection of inert gas, cooling, washing with 0.01M hydrochloric acid, washing with deionized water, and drying to obtain the carbon-coated modified carbon/silicon oxide composite material, wherein the composite material is shown to be in a porous core-shell structure through SEM (scanning electron microscope) spectrum, and has uniform size and particle size of 800-1000 nm;
(4) uniformly mixing a carbon-coated modified carbon/silicon oxide material, polyvinylidene fluoride and a conductive agent Super P, adding N-methyl pyrrolidone, and uniformly stirring to prepare slurry; and then coating the slurry on porous copper foil with the aperture of 1-10 mu m and the porosity of 35%, and drying and rolling to obtain the lithium ion battery electrode plate.
Example 2
This example provides a method for preparing a carbon-coated modified carbon/silicon oxide electrode material for a lithium battery electrode, and table 2 shows the formulation of the components used for preparing the carbon-coated modified carbon/silicon oxide electrode material in this example.
TABLE 2 formulation for preparing carbon-coated modified carbon/silicon oxide electrode material compositions
The raw materials required for the formulation of the carbon-coated modified carbon/silicon oxide electrode material components were prepared according to table 2 above, and the coated modified carbon/silicon oxide electrode material in this example was prepared as follows:
(1) tetraethyl silicate, hexamethyldisiloxane, dichloro-N, N' -bis (3-hydrogenated rosin acyloxy-2-hydroxypropyl) tetramethylethylenediamine, ethanol and water are stirred and dispersed to obtain a mixed system, the mass concentration of organic silicon in the mixed system is 0.26g/mL, the feeding weight ratio of carbide to organic silicon is 50%, the reaction temperature is controlled at 60 ℃, and the reaction time is 2 hours to carry out sol-gel synthesis;
(2) centrifugally separating a solvent, washing with ethanol, washing with deionized water, tabletting, vacuum drying at 80 ℃ for 12 hours, testing that the linear expansion rate of the dried sheet is less than or equal to 1% compared with that of the sheet before drying, and then calcining at 1200 ℃ for 2 hours to obtain the carbon/silicon oxide composite material;
(3) mechanically crushing the carbon/silicon oxide composite material, adding cane sugar and ethanol for ultrasonic dispersion, drying at 80 ℃, then placing the carbon/silicon oxide composite material in a tubular furnace for roasting at 600 ℃ under the protection of inert gas, cooling, washing with 0.01M hydrochloric acid, washing with deionized water, and drying to obtain the carbon-coated modified carbon/silicon oxide composite material, wherein the composite material is shown to be in a porous core-shell structure through SEM (scanning electron microscope) spectrum, and has uniform size and particle size of 600-800 nm;
(4) uniformly mixing a carbon-coated modified carbon/silicon oxide material, polyvinylidene fluoride and a conductive agent Super P, adding N-methyl pyrrolidone, and uniformly stirring to prepare slurry; and then coating the slurry on porous copper foil with the aperture of 1-10 mu m and the porosity of 35%, and drying and rolling to obtain the lithium ion battery electrode plate.
Example 3
This example provides a method for preparing a carbon-coated modified carbon/silicon oxide electrode material for a lithium battery electrode, and table 3 shows the formulation of the components for preparing the carbon-coated modified carbon/silicon oxide electrode material in this example.
TABLE 3 formulation for preparing carbon-coated modified carbon/silicon oxide electrode material compositions
The raw materials required for the formulation of the carbon-coated modified carbon/silicon oxide electrode material components were prepared according to table 3 above, and the coated modified carbon/silicon oxide electrode material in this example was prepared as follows:
(1) methyl triethoxysilane, vinyl triethoxysilane, trimethylchlorosilane, glucose, ethanol and ammonia water, stirring and dispersing to obtain a mixed system, wherein the mass concentration of organic silicon in the mixed system is 0.33g/mL, the feeding weight ratio of carbide to organic silicon is 0.1%, controlling the reaction temperature at 20 ℃, and carrying out sol-gel synthesis for 30 hours;
(2) centrifugally separating a solvent, washing with ethanol, washing with deionized water, tabletting, vacuum drying at 80 ℃ for 12 hours, testing that the linear expansion rate of the dried front sheet is less than or equal to 2 percent compared with that of the dried front sheet, and then calcining at 200 ℃ for 15 hours to obtain the carbon/silicon oxide composite material;
(3) adding graphite into the carbon/silicon oxide composite material, performing ball milling, pickling with 0.01M hydrochloric acid, washing with deionized water, and drying to obtain a carbon-coated modified carbon/silicon oxide composite material, wherein the composite material is shown to be in a porous core-shell structure through an SEM (scanning electron microscope) spectrum, and the particle size is 600-1000 nm;
(4) uniformly mixing the carbon-coated modified carbon/silicon oxide material, polytetrafluoroethylene and carbon nano tubes, adding N-methylpyrrolidone, and uniformly stirring to prepare slurry; and then coating the slurry on porous copper foil with the aperture of 50-100 um and the porosity of 90%, and drying and rolling to obtain the lithium ion battery electrode plate.
Example 4
This example provides a method for preparing a carbon-coated modified carbon/silicon oxide electrode material for a lithium battery electrode, and table 4 shows the formulation of the components for preparing the carbon-coated modified carbon/silicon oxide electrode material in this example.
TABLE 4 formulation for preparing carbon-coated modified carbon/silicon oxide electrode material compositions
The raw materials required for the formulation of the carbon-coated modified carbon/silicon oxide electrode material components were prepared according to table 4 above, and the coated modified carbon/silicon oxide electrode material in this example was prepared as follows:
(1) tetraethyl silicate, poly (dimethylsiloxane), rice hull ash and ethanol are subjected to ultrasonic dispersion, then triethylamine and water are added to obtain a mixed system, the mass concentration of organic silicon in the mixed system is 0.08g/mL, the feeding weight ratio of carbide to organic silicon is 10 percent, the reaction temperature is controlled at 40 ℃, and the sol-gel method synthesis is carried out after the reaction time is 20 hours;
(2) centrifugally separating a solvent, washing with ethanol, washing with deionized water, tabletting, vacuum drying at 80 ℃ for 12 hours, testing that the linear expansion rate of the dried sheet is less than or equal to 1 percent compared with that of the sheet before drying, and then calcining at 400 ℃ for 12 hours to obtain the carbon/silicon oxide composite material;
(3) adding multilayer graphene into a carbon/silicon oxide composite material, performing ball milling, adding ethanol, performing ultrasonic dispersion, drying at 80 ℃, then placing in a tubular furnace at 250 ℃ for roasting, cooling, washing with 0.01M hydrochloric acid, washing with deionized water, and drying to obtain a carbon-coated modified carbon/silicon oxide composite material, wherein the composite material is shown to be in a porous core-shell structure through an SEM (scanning electron microscope) spectrum, and the particle size is 600-1000 nm;
(4) uniformly mixing the carbon-coated modified carbon/silicon oxide material, LA133 and graphene, adding N-methylpyrrolidone, and uniformly stirring to prepare slurry; and then coating the slurry on porous copper foil with the aperture of 0.01-1 um and the porosity of 20%, and drying and rolling to obtain the lithium ion battery electrode plate.
Example 5
This example provides a method for preparing a carbon-coated modified carbon/silicon oxide electrode material for a lithium battery electrode, and table 5 shows the formulation of the components for preparing the carbon-coated modified carbon/silicon oxide electrode material in this example.
TABLE 5 formulation for preparing carbon-coated modified carbon/silicon oxide electrode material compositions
The raw materials required for the formulation of the carbon-coated modified carbon/silicon oxide electrode material components were prepared according to table 5 above, and the coated modified carbon/silicon oxide electrode material in this example was prepared as follows:
(1) stirring and dispersing epoxy butyl trimethoxy silane, vinyl triethoxy silane, dichloro-N, N' -bis (3-hydrogenated rosin acyloxy-2-hydroxypropyl) tetramethylethylenediamine, ethanol and water to obtain a mixed system, wherein the mass concentration of organic silicon in the mixed system is 0.40g/mL, the feeding weight ratio of carbide to organic silicon is 33%, ultrasonically dispersing the mixed system, transferring the mixed system to a high-pressure reaction kettle, and carrying out hydrothermal synthesis reaction for 2 hours under the condition that the reaction temperature is 200 ℃ and the system pressure is 2.0 MPa;
(2) centrifugally separating a solvent, washing with ethanol, washing with deionized water, tabletting, vacuum drying at 80 ℃ for 12 hours, testing that the linear expansion rate of the dried sheet is less than or equal to 1 percent compared with that of the sheet before drying, and then calcining at 700 ℃ for 5 hours to obtain the carbon/silicon oxide composite material;
(3) adding sodium citrate into the carbon/silicon oxide composite material, grinding, adding ethanol, performing ultrasonic dispersion, drying at 80 ℃, then placing in a tubular furnace at 400 ℃ for roasting, cooling, washing with 0.01M hydrochloric acid, washing with deionized water, and drying to obtain a carbon-coated modified carbon/silicon oxide composite material, wherein the composite material is shown to be in a porous core-shell structure through an SEM (scanning electron microscope) spectrum, and the particle size is 300-500 nm;
(4) uniformly mixing the carbon-coated modified carbon/silicon oxide material, sodium carboxymethylcellulose, styrene butadiene rubber and conductive carbon black, adding N-methyl pyrrolidone, and uniformly stirring to prepare slurry; and then coating the slurry on porous copper foil with the aperture of 10-40 um and the porosity of 65%, and drying and rolling to obtain the lithium ion battery electrode plate.
Example 6
This example provides a method for preparing a carbon-coated modified carbon/silicon oxide electrode material for a lithium battery electrode, and table 6 shows the formulation of the components for preparing the carbon-coated modified carbon/silicon oxide electrode material in this example.
TABLE 6 formulation for preparing carbon-coated modified carbon/silicon oxide electrode material compositions
The raw materials required for the formulation of the carbon-coated modified carbon/silicon oxide electrode material components were prepared according to table 6 above, and the coated modified carbon/silicon oxide electrode material in this example was prepared as follows:
(1) carrying out ultrasonic dispersion on tetraethyl silicate, starch, trimethylchlorosilane and ethanol, then adding aniline and water to obtain a mixed system, wherein the mass concentration of organic silicon in the mixed system is 0.22g/mL, the feeding weight ratio of carbide to organic silicon is 50%, transferring the mixed system into a high-pressure reaction kettle to carry out hydrothermal synthesis reaction, and controlling the reaction temperature to be 100 ℃ and the system pressure to be 0.1MPa for 30 hours;
(2) centrifugally separating a solvent, washing with ethanol, washing with deionized water, tabletting, vacuum-drying at 80 ℃ for 12 hours, testing that the linear expansion rate of the dried front sheet is less than or equal to 2 percent, and calcining at 700 ℃ for 5 hours to obtain the carbon/silicon oxide composite material;
(3) adding polyaniline into a carbon/silicon oxide composite material, grinding, adding ethyl carbonate, performing ultrasonic dispersion, drying, then placing in a tubular furnace at 800 ℃ for roasting, cooling, performing 0.01M hydrochloric acid washing, deionized water washing, and drying to obtain a carbon-coated modified carbon/silicon oxide composite material, wherein the composite material is shown to be in a porous core-shell structure through an SEM (scanning electron microscope) spectrum, and the particle size is 100-150 nm;
(4) uniformly mixing a carbon-coated modified carbon/silicon oxide material, sodium carboxymethylcellulose, styrene butadiene rubber and conductive carbon black, adding N-methyl pyrrolidone, and uniformly stirring to prepare slurry; and then coating the slurry on porous copper foil with the aperture of 1-10 mu m and the porosity of 45%, and drying and rolling to obtain the lithium ion battery electrode plate.
Example 7
This example provides a method for preparing a carbon-coated modified carbon/silicon oxide electrode material for a lithium battery electrode, and table 7 shows the formulation of the components for preparing the carbon-coated modified carbon/silicon oxide electrode material in this example.
TABLE 7 formulation for preparing carbon-coated modified carbon/silicon oxide electrode material compositions
The raw materials required for the formulation of the carbon-coated modified carbon/silicon oxide electrode material components were prepared according to table 7 above, and the coated modified carbon/silicon oxide electrode material in this example was prepared as follows:
(1) carrying out ultrasonic dispersion on tetraethyl silicate, dichloro-N, N' -bis (3-hydrogenated rosin acyloxy-2-hydroxypropyl) tetramethylethylenediamine, trimethylchlorosilane and methanol, then adding ammonia water to obtain a mixed system, wherein the mass concentration of organosilicon in the mixed system is 0.13g/mL, the feeding weight ratio of carbide to organosilicon is 33%, transferring the mixed system to a high-pressure reaction kettle to carry out hydrothermal synthesis reaction, and reacting for 20 hours at the reaction temperature of 150 ℃ and the system pressure of 0.4 MPa;
(2) separating the solvent, washing with methanol, washing with deionized water, tabletting, vacuum drying at 80 ℃ for 12 hours, testing that the linear expansion rate of the dried front sheet is less than or equal to 2 percent compared with that of the dried front sheet, and then calcining at 700 ℃ for 5 hours to obtain the carbon/silicon oxide composite material;
(3) adding polyaniline into a carbon/silicon oxide composite material, grinding, adding ethyl carbonate, performing ultrasonic dispersion, drying, then placing in a tubular furnace at 800 ℃ for roasting, cooling, performing 0.01M hydrochloric acid washing, deionized water washing, and drying to obtain a carbon-coated modified carbon/silicon oxide composite material, wherein the composite material is shown to be in a porous core-shell structure through an SEM (scanning electron microscope) spectrum, and the particle size is 10-50 nm;
(4) uniformly mixing a carbon-coated modified carbon/silicon oxide material, sodium carboxymethylcellulose, styrene butadiene rubber and conductive carbon black, adding N-methyl pyrrolidone, and uniformly stirring to prepare slurry; and then coating the slurry on porous copper foil with the aperture of 1-10 mu m and the porosity of 45%, and drying and rolling to obtain the lithium ion battery electrode plate.
Comparative example 1
The present comparative example provides a carbon/silicon oxide electrode material for a lithium battery electrode.
(1) Silicon oxide (SiO) 0.9 ) Adding ethanol into the powder and sucrose, stirringDispersing, drying at 80 ℃, and then calcining at 600 ℃ for 5 hours to obtain a carbon/silicon oxide composite material 1;
(2) adding graphite into the carbon/silicon oxide composite material 1, performing ball milling, pickling with 0.01M hydrochloric acid, washing with deionized water, and drying to obtain a carbon/silicon oxide composite material 2, wherein the particle size of the composite material is 10-20 um as shown by an SEM (scanning electron microscope) map;
(3) uniformly mixing the carbon/silicon oxide material 2, polytetrafluoroethylene and carbon nano tubes, adding N-methylpyrrolidone, and uniformly stirring to prepare slurry; and then coating the slurry on porous copper foil with the aperture of 1-10 mu m and the porosity of 45%, and drying and rolling to obtain the electrode plate of the lithium ion battery.
Comparative example 2
This comparative example provides a method for preparing a carbon/silicon oxide electrode material for a lithium battery electrode, which is different from example 1 in the ratio of the amount of the carbide to the amount of the silicone, wherein the amounts of the carbide (N, N' -bis (3-hydrogenated abietyloxy-2-hydroxypropyl) tetramethylethylenediamine dichloride) and the silicone (tetraethyl silicate) are 100% by weight, and the remaining steps are the same as example 1.
Comparative example 3
This comparative example provides a carbon/silicon oxide electrode material for a lithium battery electrode, which differs from example 2 in that step (3) is not carried out, the carbon/silicon oxide composite obtained in step (2) is used instead of the carbon-coated modified carbon/silicon oxide material used in step (4), and the remaining steps are the same as example 2.
Comparative example 4
This comparative example provides a carbon/silicon oxide electrode material for a lithium battery electrode, which is different from example 2 in that the reaction temperature in step (2) is 80 ℃, the reaction time is 6 hours, and the remaining steps are the same as example 2.
Comparative example 5
This comparative example provides a carbon/silicon oxide electrode material for a lithium battery electrode, which is different from example 6 in that the reaction temperature in step (2) is 60 ℃, the system pressure is 0, and the remaining steps are the same as example 6.
Test example
Assembling and testing performance of the lithium ion battery: a lithium plate is taken as a counter electrode, a microporous polypropylene membrane is taken as a diaphragm, 1mol/L LiPF6 (the solvent is dimethyl carbonate and dipropyl carbonate with equal volume) is taken as electrolyte, and the electrode plate to be tested prepared in the embodiment and the comparative example and the electrode plate to be tested are assembled into a CR2032 button lithium ion battery in an argon-filled glove box. And (3) after the lithium ion battery is kept stand for 24 hours, performing charge and discharge tests under 500mA g & lt-1 & gt, wherein the charge and discharge interval is between 0.01 and 3.0V.
1. Electrochemical performance test
The assembled battery was charged and discharged at a current of 500mA/g, and the obtained capacity and capacity retention rate were measured at turns 2 and 300, and the results are shown in Table 8.
2. Pole piece expansion ratio test
The assembled battery was charged and discharged at a current of 500mA/g for 300 weeks, and then disassembled after being fully charged, and the thickness expansion rate of the prepared electrode sheet was measured, and the results are shown in table 8.
Table 8 Experimental test results of the charge and discharge test capacity, the capacity retention rate and the pole piece expansion rate of the lithium batteries of examples 1 to 7 and comparative examples 1 to 4
It can be seen from table 8 that the electrode prepared from the carbon-coated modified carbon/silicon oxide provided by the invention has high charge-discharge specific capacity, high first efficiency, good stability, good cycle capacity retention rate and low pole piece expansion rate.
The electrochemical performance of the electrodes prepared from the carbon-coated modified carbon/silicon oxide prepared in examples 1 to 7 of the invention is obviously superior to that of comparative examples 1 to 5. Specifically, the preparation method of the carbon/silicon oxide electrode material provided by the invention is not only superior to the preparation method of the existing silicon-carbon electrode plate, but also combines the sol-gel reaction and hydrothermal reaction operation modes defined by the method with the materials, proportion, temperature, pressure and operation steps defined by the invention to prepare the carbon-coated modified carbon/silicon oxide electrode plate, and has the effects of high specific charge-discharge capacity, high primary efficiency, good stability, good cycle capacity retention rate and low electrode plate expansion rate.
The carbon/silicon oxide composite materials are synthesized by adopting a sol-gel method in examples 1 to 4, the carbon/silicon oxide composite materials are synthesized by adopting a hydrothermal synthesis method in examples 5 to 7, and as can be seen from table 1, the first discharge capacity of the electrode slice prepared by the two synthesis methods is more than 950mAh/g, the first (second turn) coulombic efficiency is more than 90%, the capacity retention rate is more than 85% after 300 cycles of charge and discharge under the current of 500mA/g, and the expansion rate of the silicon-carbon electrode slice is less than 140% after 300 cycles. The use of the surface modifier is increased in the embodiment 2 compared with the embodiment 1, and the data in the table 1 show that the introduction of the surface modifier has obvious effects on improving the charge-discharge capacity, improving the charge-discharge cycle capacity retention rate of the pole piece and inhibiting the expansion of the pole piece.
Comparative example 1 uses silicon oxide (SiO) 0.9 ) The powder replaces organic silicon to prepare the carbon/silicon oxide composite material, and because the silicon oxide powder can not form an effective porous core-shell structure to limit the expansion of the silicon material in charge-discharge cycles and provide an effective space for the expansion of the silicon material, the expansion rate of the pole piece is improved by 20 percent after 300 charge-discharge cycles, and the charge-discharge cycle stability is also reduced. The material ratio of the comparative example 2 is 4:1, which exceeds the parameter setting range, the comparative example 3 does not carry out carbon coating treatment, the comparative example 4 carries out sol-gel method, the reaction temperature exceeds the range, and the reaction temperature and pressure of the comparative example 5 do not reach the parameter limiting requirements, as can be seen from the table 1, the comparative examples do not reach the embodiment effect in the aspects of coulomb efficiency and capacity retention rate, and the important functions of the material ratio and the process parameters on achieving the technical effect of the invention are shown; the electrode sheet expansion rate of the comparative example is obviously higher than that of the example after the electrode sheet expansion rate is cycled for 300 times, which shows that the electrode prepared by the porous carbon/silicon oxide core-shell external coating carbon material prepared by the material proportion, the process parameters and the process can effectively inhibit the volume of the silicon material in the charge-discharge cycle processThe expansion effect is favorable for long-term circulation, and the service efficiency of the lithium ion battery is improved.
Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. The carbon-coated modified carbon/silicon oxide composite electrode material is characterized by consisting of a porous carbon/silicon oxide core shell and an external coating carbon material.
2. The carbon-coated modified carbon/silicon oxide composite electrode material according to claim 1, wherein: the porous carbon/silicon oxide core shell is prepared by mixing and calcining organic silicon and a carbon material; the mixing process comprises at least one of stirring, ultrasonic treatment, crushing, grinding, ball milling, homogenizing and extrusion; the calcination temperature in the calcination process is 200-1200 ℃, and the calcination time is 2-15 hours.
3. The carbon-coated modified carbon/silicon oxide composite electrode material according to claim 1, wherein the preparation method specifically comprises the following steps:
(1) mixing a material containing carbide and organic silicon with a solvent to obtain a mixed system, wherein the mass concentration of the organic silicon in the mixed system is 0.04-0.4 g/mL, and the mass concentration of the carbide: the feeding mass ratio of the organic silicon material is 0.1-50%, and a mixture A is obtained after the mixed system is subjected to reaction treatment;
(2) centrifuging, washing with a solvent, washing with water, drying and calcining the mixture A obtained in the step (1) to obtain the porous carbon/silicon oxide core shell;
(3) and (3) adding a coating carbon material into the porous carbon/silicon oxide core shell obtained in the step (2), and performing ball milling or/and ultrasonic treatment to obtain the carbon-coated modified carbon/silicon oxide material.
4. The method according to claim 3, wherein the step (1) further comprises adding a coagulant comprising at least one of ammonia, triethylamine, cyclohexylamine, pyridine, aniline, and benzylamine to the mixture;
preferably, the step (1) may further include adding a surface modifier to the mixed system, wherein the surface modifier includes at least one of trimethylchlorosilane, hexamethyldisilazane, hexamethyldisiloxane, and other siloxane monomers or polymers containing organic functional groups.
5. The method for preparing the carbon-coated modified carbon/silicon oxide composite electrode material according to claim 3, wherein in the step (1), the reaction conditions include a reaction temperature of 20 to 200 ℃, a reaction pressure of 0 to 2MPa, and a reaction time of 2 to 80 hours;
preferably, the step (3) may further include dispersing the porous carbon/silicon oxide core-shell substance and the coated carbon material in a solvent, removing the solvent after ultrasonic treatment and stirring, and performing heat treatment at a temperature of not less than 200 ℃.
6. The method according to claim 3, wherein the solvent is at least one of water, methanol, ethanol, n-hexane, toluene, and carbonate; the organic silicon is at least one of tetraethyl silicate, 3-glycidyl ether oxypropyl triethoxysilane, methyl triethoxysilane, vinyl triethoxysilane, silicon hydroxylate or epoxide; the carbide is at least one of ash content after glucose, starch, cane sugar or biomass materials are combusted, dichloro-N, N '-bis (3-hydrogenated rosin acyl oxide-2-hydroxypropyl) tetramethylethylenediamine and dichloro-N, N' -bis (3-rosin acyl oxide-2-hydroxypropyl) tetramethylethylenediamine; the coating carbon material is at least one of graphite, graphite oxide, graphene oxide, multi-layer graphene, few-layer graphene, saccharides, organic weak acid salts (such as citrate), organic weak acids (such as tannic acid), phenolic resin, a C-containing cross-linking agent and a C-containing conductive agent.
7. An electrode for a lithium ion battery, which is characterized by comprising an electrode current collector and a carbon/silicon oxide electrode material coated on the electrode current collector, wherein the carbon/silicon oxide electrode material comprises the carbon/silicon oxide composite electrode material, a conductive agent and a binder according to claims 1-6.
8. The electrode according to claim 7, wherein the electrode current collector is at least one of a porous metal foil and a metal foam, preferably a porous copper foil, and is characterized in that: porosity: 20 to 90 percent; pore diameter: 0.01-100 um.
9. The electrode of claim 7, wherein the binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethylcellulose, sodium alginate, chitosan, styrene butadiene rubber, and LA-type binders; the conductive agent is at least one of conductive carbon black, conductive graphite, superconducting carbon black, acetylene carbon black, ketjen black, carbon nanotubes, VGCF and graphene.
10. A lithium ion battery comprising the electrode of claim 7.
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