A kind of lithium ion battery silicon-carbon cathode material and preparation method thereofTechnical field
The present invention relates to lithium ion battery negative material fields, in particular it relates to a kind of lithium ion battery silicon-carbonNegative electrode material and preparation method thereof.
Background technique
Negative electrode material is to determine one of the key factor of performance of lithium ion battery, currently, commercial lithium-ion batteries cathodeMaterial is mainly graphite-like, is widely used in portable electronic device, energy storage device with lithium secondary battery prepared by these materialsAnd electric car.The theoretical capacity of graphite is only 372mAh/g, with the fast development of New Energy Industry, to high specific energy lithium ionMore stringent requirements are proposed for power battery, and existing graphite cathode material is difficult to meet the requirement of energy density, this requiresA kind of negative electrode material of high-energy density must be developed.Silicon materials are due to its higher theoretical capacity, and de- lithium current potential platformIt is lower, become at present one of the lithium ion battery negative material of most potentiality to be exploited, however due to silicon meeting in charge and discharge processHuge volume change is generated, electrode is caused to fall off in cyclic process with pole fluid, capacity is greatly lowered, and leads to cycle performanceVery poor, oxygen-containing silica-base material especially aoxidizes sub- silicium cathode material, limits its application because coulombic efficiency for the first time is lower.CN102683649A forms the carbon gas with hole configurations in nano silica fume and superfine graphite surface using resorcinol and formaldehydeGel clad, although improving the surface texture and cycle performance of 3 SiC 2/graphite, the material specific surface area is big, and first charge discharge efficiency is inclinedIt is low, limit its application in lithium battery.For CN102769139A using natural spherical plumbago as raw material, the concentrated sulfuric acid is intercalator,Potassium permanganate is oxidant, then carries out expansion process at high temperature and prepares microdilatancy graphite, and nano-silicon and the graphite are mixedIt closes, then carries out carbon source cladding and heat treatment, obtain silicon-carbon composite cathode material, this method prepares microdilatancy graphite in highly acidIn environment, react more demanding.Cold primer-oil, nano silica fume and spherical natural graphite are mixed carbonization system by CN101244814AStandby silicon-carbon cathode material, this method are difficult to uniformly disperse nano silica fume, and the material first charge discharge efficiency prepared is relatively low.
Summary of the invention
For the problems of the prior art, the purpose of the present invention is to provide a kind of lithium ion battery silicon-carbon cathode materials.
The lithium ion battery silicon-carbon cathode material includes that silicon materials, graphite and organic cracking carbon composition, feature existIn in terms of the parts by weight of ingredient each in Si-C composite material, silicon materials are 1-20 parts, and graphite material is 35-120 parts, pyrolytic carbonIt is 20-60 parts.
In the preferred technical solution of the present invention, in terms of the parts by weight of ingredient each in Si-C composite material, silicon materials 5-15Part, graphite powder is 60-80 parts, and pyrolytic carbon is 25-45 parts.
In the preferred technical solution of the present invention, in terms of the parts by weight of ingredient each in Si-C composite material, 1-10 parts of nano-silicon,Sub- 5-20 parts of silicon is aoxidized, graphite powder is 60-80 parts, and pyrolytic carbon is 25-45 parts.
In the preferred technical solution of the present invention, the silicon materials be nano-silicon/oxidation Asia silicon, preferably nano simple substance silicon,Aoxidize sub- silicon particle.
In the preferred technical solution of the present invention, the partial size of the silicon materials is 20-100nm, preferably 30-80nm.
In the preferred technical solution of the present invention, the partial size for aoxidizing sub- silicon is 0.1-30 μm, preferably 10-25 μm.
In the preferred technical solution of the present invention, the graphite is selected from any or its group of natural graphite, artificial graphiteIt closes, preferably artificial graphite.
In the preferred technical solution of the present invention, the median (D50) of the graphite powder is 1-100 μm, preferably 10-40μm, more preferably 10-20 μm.
In the preferred technical solution of the present invention, " pyrolytic carbon " refers to (also known as " pyrolysis of pyrolytic carbon precursor organic matterCarbon precursor ") by roasting charing after amorphous carbon.
In the preferred technical solution of the present invention, the pyrolytic carbon precursor organic matter is selected from pitch, coal tar, polyethyleneAlcohol, butadiene-styrene rubber, carboxymethyl cellulose, polystyrene, polyvinyl chloride, polyacrylonitrile, phenolic resin, furfural resin, asphalt mixtures modified by epoxy resinRouge, glucose, sucrose, fructose, citric acid, cellulose, starch any or combinations thereof, preferably phenolic resin, furfural treeRouge, epoxy resin, sucrose, citric acid it is any or combinations thereof.
In the preferred technical solution of the present invention, the pitch is selected from mid temperature pitch, hard pitch, secondary coal tar pitch, petroleumPitch it is any or combinations thereof.
In the preferred technical solution of the present invention, the discharge capacity for the first time of the Si-C composite material is not less than 700 mAh g-1, first charge discharge efficiency is not less than 88%.
In the preferred technical solution of the present invention, the coulombic efficiency of the 50th circulation of the Si-C composite material is not less than90%。
Nano-silicon, the sub- silicon of oxidation are uniformly attached to graphite particle surface in Si-C composite material of the invention, and outer layer is heatSolution carbon uniformly coats, and wherein it is swollen to effectively reduce volume by graphite and pyrolysis carbon material shared for volume expansion caused by siliconIt is swollen；The material has many advantages, such as that specific capacity is high, coulombic efficiency is high for the first time, cycle performance is excellent, at low cost, and preparation process letterIt is single, it is easily operated, it is at low cost, it is pollution-free, it is suitble to industrialized production.
Another object of the present invention is to provide a kind of preparation methods of Si-C composite material, wherein compound with silicon-carbonThe parts by weight meter of each ingredient in material, silicon materials are 1-20 parts, and graphite material is 35-120 parts, and pyrolytic carbon is 20-60 parts, describedPreparation method include the following steps:
1) nano-silicon and graphite powder are placed in dispersing agent, stirring or sonic oscillation, until being uniformly dispersed, remove dispersing agent, is madeSilicon/graphite material composite particles；
2) obtained silicon/graphite material composite particles are mixed with sub- silicon particle is aoxidized, obtains silicon/graphite/oxidation Asia silicon composite woodExpect particle；
3) silicon/graphite made from step 2/oxidation Asia silicon materials composite particles under agitation, are added to body before pyrolytic carbonIn liquid solution, dispersion mixing removes solvent, and under inert gas protection, roasting charing is compound to get carbon-coated silicon-carbon is pyrolyzedMaterial.
In the preferred technical solution of the present invention, the silicon materials be nano-silicon/oxidation Asia silicon, preferably nano simple substance silicon,Aoxidize sub- silicon particle.
In the preferred technical solution of the present invention, the partial size of the silicon materials is 20-100nm, preferably 30-80nm.
In the preferred technical solution of the present invention, the partial size for aoxidizing sub- silicon is 0.1-30 μm, preferably 10-25 μm.
In the preferred technical solution of the present invention, the graphite powder be selected from natural graphite, artificial graphite any or itsCombination, preferably artificial graphite.
In the preferred technical solution of the present invention, the median (D50) of the graphite powder is 1-100 μm, preferably 10-40μm, more preferably 10-20 μm.
In the preferred technical solution of the present invention, the dispersing agent is selected from water, methanol, ethyl alcohol, propyl alcohol, isopropanol, the third twoAlcohol, butanol, butanediol, acetone it is any or combinations thereof, preferably water, methanol, ethyl alcohol it is any or combinations thereof.
In the preferred technical solution of the present invention, " pyrolytic carbon " refers to pyrolytic carbon precursor organic matter by roasting charcoalChange later amorphous carbon.
In the preferred technical solution of the present invention, the pyrolytic carbon precursor organic matter is selected from pitch, coal tar, polyethyleneAlcohol, butadiene-styrene rubber, carboxymethyl cellulose, polystyrene, polyvinyl chloride, polyacrylonitrile, phenolic resin, furfural resin, asphalt mixtures modified by epoxy resinRouge, glucose, sucrose, fructose, citric acid, cellulose, starch any or combinations thereof, preferably phenolic resin, furfural treeRouge, epoxy resin, sucrose, citric acid it is any or combinations thereof.
In the preferred technical solution of the present invention, the pitch is selected from mid temperature pitch, hard pitch, secondary coal tar pitch, petroleumPitch it is any or combinations thereof.
In the preferred technical solution of the present invention, the method for removing dispersing agent or solvent is selected from filtering, centrifugation, dryingIt is any or combinations thereof.
In the preferred technical solution of the present invention, the inert gas be nitrogen, argon gas, hydrogen, helium any or itsCombination.
In the preferred technical solution of the present invention, the roasting carbonization condition is to be heated up with the heating rate of 1-5 DEG C/min500-1600 DEG C, constant temperature 2-24h are warming up to 200-500 DEG C, constant temperature 1-8h, then with the heating rate of 1-10 DEG C/min, coolingTo room temperature；Preferred roasting carbonization condition be warming up to 250-450 DEG C, constant temperature 2-6h with the heating rate of 1-3 DEG C/min, then withThe heating rate of 2-8 DEG C/min is warming up to 600-1200 DEG C, and constant temperature 8-18h is cooled to room temperature.
In the preferred technical solution of the present invention, the discharge capacity for the first time of the Si-C composite material is not less than 700 mAh g-1。
In the preferred technical solution of the present invention, capacity retention ratio is not less than after 50 circulations of the Si-C composite material88%。
The present invention is by silicon materials (wherein, the silicon materials are preferably nano-silicon, aoxidize sub- silicon particle) and graphite material (itsIn, the graphite is preferably any or combinations thereof, more preferably artificial graphite of natural graphite, artificial graphite) powder is placed inIn dispersing agent, stirring or sonic oscillation remove dispersing agent until being uniformly dispersed, and silicon/graphite composite particles are made, then will be obtainedSilicon/graphite composite particles are mixed with sub- silicon particle is aoxidized, and silicon/graphite/oxidation Asia silicon particle are obtained, before being then added to pyrolytic carbonIn body solution, dispersion mixing removes solvent, and under inert gas protection, roasting charing is multiple to get carbon-coated silicon-carbon is pyrolyzedCondensation material.Nano-silicon, the sub- silicon of oxidation are uniformly attached to graphite particle surface in Si-C composite material of the invention, and outer layer is pyrolysisCarbon uniformly coats, and wherein volume expansion caused by silicon effectively reduces volume expansion by graphite and pyrolysis carbon material shared；The material has many advantages, such as that specific capacity is high, coulombic efficiency is high for the first time, cycle performance is excellent, at low cost, and preparation process is simple,It is easily operated, it is at low cost, it is pollution-free, it is suitble to industrialized production, and the initial charge specific capacity under 0.2C discharge-rate is greater than700mAh g-1, coulombic efficiency is not less than 88% for the first time, and the coulombic efficiency of the 50th circulation is 90% or more.
Detailed description of the invention
Fig. 1 is that the SEM of 1 silicon-carbon cathode material of the embodiment of the present invention schemes.
Fig. 2 is the XRD diagram of 1 silicon-carbon cathode material of the embodiment of the present invention.
Fig. 3 is the first charge-discharge curve graph of 1 silicon-carbon cathode material of the embodiment of the present invention.
Fig. 4 is the cycle performance curve of 1 silicon-carbon cathode material of the embodiment of the present invention.
Specific embodiment
Invention is further described in detail with reference to the accompanying drawings and examples.
Embodiment 1
(1) silicon/graphite material composite particles preparation
Weigh the nano simple substance Si powder that 0.50g partial size is 30-80nm and the artificial graphite that 10.00g D50 is 20 μm；It will be allegedThe nano simple substance Si powder and artificial graphite taken is placed in the ethanol water that 60ml concentration is 33v/v%, after stirring 30min, thenThe ethanol water (suspension) of nano simple substance silicon obtained and artificial graphite is placed in ultrasonator, ultrasonic disperse 2h,After keeping nano-silicon and artificial graphite evenly dispersed, filtering, 80 DEG C of drying, obtaining silicon/artificial graphite composite particles, (i.e. silicon/carbon is multipleClose particle).
(2) preparation of silicon/graphite composite particles/oxidation Asia silicon particle mixing body mixture
3.00g epoxy resin is weighed, is dissolved in 10ml ethyl acetate；It under agitation, will be obtained in step (1)The sub- silicon of oxidation is added in silicon/artificial graphite composite particles to be mixed, is then added to epoxy resin ethyl acetate solution (to obtain the final productPyrolytic carbon precursor solution) in, continue stir 30min, sonic oscillation disperse 2h after, be dried in vacuo at 80 DEG C, obtain silicon/The mixture (i.e. pyrolytic carbon precursor mixture) of artificial graphite/oxidation Asia silicon composite particles and epoxy resin.
(3) preparation of Si-C composite material
The mixture of silicon/artificial graphite/oxidation Asia silicon composite particles and epoxy resin made from step (2) is put into tube furnaceIn, under protection of argon gas, carry out roasting charing, wherein the roasting carbonization condition is, with the heating rate liter of 1 DEG C/minTemperature is to 400 DEG C, constant temperature 5h；1200 DEG C are warming up to the heating rate of 2 DEG C/min again, constant temperature 12h is cooled to room temperature, grinding, mistake300 meshes to get.
According to detection method of the present invention, silicon/graphite composite particulate material 0.2C prepared by testing example 1 is firstCoulombic efficiency when secondary specific discharge capacity (mAh g-1) and the 50th week circulation, the results are shown in Table 1.
Embodiment 2
(1) silicon/graphite composite particles preparation
Weigh the nano simple substance Si powder that 0.50g partial size is 30-80nm and the artificial graphite that 10.00g D50 is 20 μm；It will be allegedThe nano simple substance Si powder and artificial graphite taken is placed in the methanol aqueous solution that 60ml concentration is 33v/v%, after stirring 30min, thenThe methanol aqueous solution (suspension) of nano simple substance silicon obtained and artificial graphite is placed in ultrasonator, ultrasonic disperse 2h,After keeping nano-silicon and artificial graphite evenly dispersed, filtering, 80 DEG C of drying obtain silicon/artificial graphite composite particles (i.e. silicon/graphiteComposite particles).
(2) silicon/graphite/oxidation Asia silicon particle is mixed with pyrolytic carbon precursor solution
5.00g citric acid is weighed, is dissolved in 50ml water；Under stiring, by silicon/artificial graphite obtained in step (1)The sub- silicon of oxidation is added in composite particles to be mixed, continues to stir 30min, then sonic oscillation disperses 2h, in 80 DEG C of progress vacuumIt is dry, obtain the mixture (i.e. pyrolytic carbon precursor mixture) of silicon/mesocarbon microspheres composite particles and citric acid.
(3) preparation of Si-C composite material
The mixture of silicon/graphite/oxidation Asia silicon composite particles and citric acid made from step (2) is put into tube furnace, in argonUnder gas shielded, roasting charing is carried out, wherein the roasting carbonization condition is to be warming up to 400 with the heating rate of 1 DEG C/minDEG C, constant temperature 5h；1200 DEG C are warming up to the heating rate of 2 DEG C/min again, constant temperature 12h is cooled to room temperature, and 300 mesh are crossed in grindingSieve to get.
According to detection method of the present invention, silicon/graphite composite particulate material XRD prepared by testing example 2,SEM, 0.2C first discharge specific capacity (mAh g-1) and circulation the 50th week when coulombic efficiency, the result is shown in Figure 1, Fig. 2, Fig. 3 and figure4。
By Fig. 2 (XRD diagram) as it can be seen that there is the diffraction maximum of Si in composite material, illustrate that the material is Si-C composite material；By scheming1(SEM figure) as it can be seen that the centre of Si-C composite material is graphite particle, the little particle of superficial white is silicon nanoparticle, illustrates thisThe silicon invented in Si-C composite material obtained is uniformly attached to graphite particle surface, and outer layer uniformly coats pyrolytic carbon.
Embodiment 3
(1) silicon/graphite composite particles preparation
Weigh the nano simple substance Si powder that 0.50g partial size is 30-80nm and the natural graphite that 10.00g D50 is 20 μm；It will be allegedThe nano simple substance Si powder and natural graphite taken is placed in the aqueous acetone solution that 60ml concentration is 33v/v%, after stirring 30min, thenThe aqueous acetone solution (suspension) of nano simple substance Si powder obtained and natural graphite is placed in ultrasonator, ultrasonic disperse2h, after keeping nano-silicon and natural graphite evenly dispersed, filtering, 80 DEG C of drying obtain silicon/natural graphite composite particles (i.e. silicon/stoneBlack composite particles).
(2) silicon/graphite/oxidation Asia silicon composite particles are mixed with pyrolytic carbon precursor solution
8.00g sucrose is weighed, is dissolved in 50ml water；Under stiring, by compound, silicon/graphite obtained in step (1)Grain is added in aqueous sucrose solution, is then added and is aoxidized sub- silicon, continues to stir 30min, then sonic oscillation disperses 2h, 80 DEG C intoRow vacuum drying, obtains the mixture (i.e. pyrolytic carbon precursor mixture) of silicon/graphite/oxidation Asia silicon composite particles and sucrose.
(3) preparation of Si-C composite material
The mixture of silicon/graphite/oxidation Asia silicon composite particles and sucrose made from step (2) is put into tube furnace, in argon gasUnder protection, roasting charing is carried out, wherein the roasting carbonization condition is to be warming up to 400 DEG C with the heating rate of 1 DEG C/min,Constant temperature 5h；1200 DEG C are warming up to the heating rate of 2 DEG C/min again, constant temperature 12h is cooled to room temperature, and grinding crosses 300 meshes, i.e.,?.
According to detection method of the present invention, silicon/graphite composite particulate material 0.2C prepared by testing example 3 is firstSecondary specific discharge capacity (mAh g-1) and circulation the 50th week when coulombic efficiency, the results are shown in Table 1.
Embodiment 4
Embodiment 4 difference from example 1 is that, the dosage of nano simple substance silicon powder is 1.00g, and graphite used is D50For 20 μm of natural graphite.
According to detection method of the present invention, silicon/graphite composite particulate material 0.2C prepared by testing example 4 is firstSecondary specific discharge capacity (mAh g-1) and circulation the 50th week when coulombic efficiency, the results are shown in Table 1.
Comparative example 1
(1) prepared by graphite and the mixture of pyrolytic carbon
3g epoxy resin is dissolved in 10g ethyl acetate, under stiring, 10g artificial graphite is added to the second of epoxy resinIn acetate solution, continue to stir 30min, then sonic oscillation dispersion 2h obtains artificial graphite and epoxy in 80 DEG C of vacuum dryingsThe mixture of resin.
(2) preparation of carbon composite is coated
The mixture of artificial graphite obtained in step (1) and epoxy resin is put into tube furnace, under protection of argon gas, with 1DEG C/heating rate of min is warming up to 400 DEG C, constant temperature 5h；1200 DEG C, constant temperature 12h are warming up to the heating rate of 2 DEG C/min again,Be cooled to room temperature, grind, cross 300 meshes to get.
According to detection method of the present invention, silicon/carbon composite particulate material 0.2C prepared by test comparison example 1 is for the first timeSpecific discharge capacity (mAh g-1) and 50 circulation volumes and capacity retention ratio, the results are shown in Table 1.Using following methods to implementationThe negative electrode material of example 1~4 and comparative example 1 is tested:
Electronic scanner microscope (SEM) test of the present invention is seen using Rigaku JSM-6700F electronic scanner microscopeExamine the characteristics such as surface topography, the granular size of sample, wherein emitting voltage 5KV carries out vacuum metal spraying to powder surface2min scans inspired secondary electron, times scattered electron, transmission by the high-power electron beam for obtaining aggregation on sampleElectronics, the reception for absorbing the physical signals such as electronics, visible light and X-ray, amplification and display imaging obtain sample to analyze sampleThe various information of pattern.
XRD spectrum of the present invention tests to obtain using X-ray diffraction analysis method, and XRD test uses Cu-Ka spokeSource, Guan Liuwei 40mA are penetrated, pipe pressure is 40KV, and 12 °/min of scanning speed, 10-90 ° of scanning range, step-length is 0.020 °.
Charge-discharge performance test of the present invention carries out simulated battery using LAND CT2001A battery test systemConstant current charge-discharge test, voltage tester scope 0-1.8V.The production of simulated battery includes the following steps: according to silicon-carbon composite woodMaterial: conductive carbon black: the mass ratio of Kynoar (PVDF) is 85: 5: 10, weighs required Si-C composite material, conductive carbon blackAnd PVDF, Si-C composite material and conductive carbon black are ground in mortar, it is uniformly mixed, is added to the N- methyl pyrrole of PVDFIt in pyrrolidone (NMP) solution, stirs evenly, slurry is made, then slurry is coated on copper foil, pole piece is made in drying, rolling.Made with metal lithium sheet to electrode, Celgard2400 is diaphragm, 1mol/L LiPF6/EC(ethylene carbonate)+DMC(carbonic acid diformazanRouge)+EMC(methyl ethyl carbonate rouge) (volume ratio 1: 1: 1) be electrolyte, is assembled into simulated battery in the glove box of logical argon gas, it is quietIt is tested after setting 12h.
Unless otherwise indicated, the present invention relates to when the percentage between liquid and liquid, the percentage is volume/bodyProduct percentage；The present invention relates to when percentage between liquid and solid, the percentage is volume/weight percentage；This hairWhen the bright percentage being related between solid and liquid, the percentage is weight/volume percent；Remaining is w/w hundredDivide ratio.
The Electrochemical results of silicon-carbon cathode material prepared by embodiment 1-4 and comparative example 1 are as shown in table 1.
The Electrochemical results of 1 silicon-carbon cathode material of table
As shown in Figure 1, particle is uniform from SEM figure it is found that 1 silicon-carbon cathode material of the embodiment of the present invention is the spherical shape of rule；Such as figureShown in 2, from XRD diagram it is found that 1 silicon-carbon cathode material of the embodiment of the present invention can be amorphous structure, 002 peak at 24 ° or so, andDiffraction maximum is wider, the interlamellar spacing D of 002 crystal face002Between 0.340~0.375nm.As shown in figure 3,1 silicon-carbon of the embodiment of the present inventionNegative electrode material, when charging and discharging currents density is 1C, initial charge specific capacity is 763.6mAh/g, and coulombic efficiency is for the first time88.68%.As shown in figure 4,1 silicon-carbon cathode material of the embodiment of the present invention, coulombic efficiency when recycling the 50th week is 99.7%.By withUpper result is it is found that reversible capacity is big for the first time using the silicon-carbon cathode material of the method for the invention preparation, and coulombic efficiency is high for the first time,Have both excellent cycle performance simultaneously.
The Applicant declares that the present invention illustrates method detailed of the invention by embodiment described above, but the present invention is simultaneouslyIt is not limited to above-mentioned method detailed, this means that the invention must rely on the above detailed methods to implement.Technical fieldTechnical staff it will be clearly understood that any improvement in the present invention, to the equivalence replacement and auxiliary element of each raw material of product of the present inventionAddition, the selection of concrete mode etc., all fall in protection scope of the present invention and the open scope.