CN107317012A - A kind of high performance lithium ion secondary battery negative material Si/C composites and preparation method thereof - Google Patents

A kind of high performance lithium ion secondary battery negative material Si/C composites and preparation method thereof Download PDF

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CN107317012A
CN107317012A CN201710508925.0A CN201710508925A CN107317012A CN 107317012 A CN107317012 A CN 107317012A CN 201710508925 A CN201710508925 A CN 201710508925A CN 107317012 A CN107317012 A CN 107317012A
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acid
composites
lithium ion
secondary battery
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CN107317012B (en
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徐立强
侯璇
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Shenzhen Research Institute Of Shandong University
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Shenzhen Research Institute Of Shandong University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The present invention provides a kind of high performance lithium ion secondary battery negative material Si/C composites and preparation method thereof, and it is as follows that the preparation method includes step：Bagasse is soaked in acid solution, is calcined under scrubbed, dry, air atmosphere, obtains SiO2Powder；By SiO2 powder and magnesium powder ground and mixed it is uniform after, under restitutive protection's atmosphere calcine, through in acid solution, hydrofluoric acid aqueous solution soak, it is then scrubbed, dry, obtain Si nano particles；Obtained Si nano particles are added in aqueous ascorbic acid, are stirred at room temperature, then in stirring 0.5 1h at 80 100 DEG C；In being calcined under protective gas atmosphere, Si/C composites are obtained.Raw material used in the present invention is simple and easy to get, environmental protection, cheap and can be mass-produced；Experimental method is simple to operation, low for equipment requirements；Obtained material even aperture distribution, and with excellent chemical property.

Description

A kind of high performance lithium ion secondary battery negative material Si/C composites and its preparation Method
Technical field
The present invention relates to a kind of high performance lithium ion secondary battery negative material Si/C composites and preparation method thereof, category In technical field of lithium ion.
Background technology
Silicon is considered as one of most promising negative material, because its theoretical specific capacity (4200mA h/g) is business More than ten times of graphite negative pole (370mA h/g).However, the problem of silicium cathode material has serious, i.e., in charge and discharge cycles During silicon electrode can undergo sizable volumetric expansion (volumetric expansion can reach 300% during electrochemistry lithiumation), lead Cracking and the crushing of silicon are caused, the capacity for ultimately causing negative material encloses quick heavy losses within charge and discharge cycles several.
Researchers can efficiently solve above mentioned problem, because nano-silicon through exploration discovery using the silicon of nanostructured Between there is spacing distance, it can adapt to the volumetric expansion of silicon as structure cushion space.Experimental result also channel syndrome Bright nano-silicon has superior chemical property really, however, the long circulating performance of silicon is still unsatisfactory.Therefore study Persons are also exploring multiplying power and the long circulating that the suitable structure of design synthesis makes the existing high specific capacity of silicon materials also have Can, silicon is constantly promoted as the commercialization process of potential lithium ion battery negative material.
The research of carbon coated and its associated materials or metal material has also been carried out on silicon materials, by these Amorphous carbon and metal coating can effectively alleviate huge volume of the silicon in electrochemical process as the padded coaming of silicon Mechanical stress caused by change, while electronic conductor can also be served as, and then effectively improves the electric conductivity of material.Such as, in State patent document CN104752691A discloses a kind of Si/C Composite Negative Electrode Material for Lithium Ion Batteries and preparation method thereof.Should Material is made up of the material of graphite framework material, intermediate buffer layer SiOC materials, carbon fiber and coated with carbon, and table The material of face carbon coated is combined by cushion SiOC and carbon fiber with graphite framework material；In the composite, cladding The silicon materials of amorphous carbon in the presence of SiOC and carbon fiber more efficiently with graphite contact, it is to avoid silicon materials itself Reunite and the stripping with graphite；Composite structure design is very novel but preparation process is numerous and diverse, and cost is higher, is unfavorable for work Industry is produced, and chemical property is general, and long circulating performance needs further exploitation；For another example, Chinese patent literature CN104466185A discloses a kind of silicon/carbon compound cathode materials and preparation method thereof, negative electrode of lithium ion battery and lithium-ion electric Pond.Silicon/the carbon compound cathode materials are the nucleocapsid clad structures using silicon nanoparticle as core, by shell of in-situ carbon, and described are received Space is there are between rice silicon grain and the in-situ carbon housing；The preparation method of the negative material includes：Organic carbon source is coated SiO2 composites, to organic carbon source coated Si O2 composites carry out pre-oxidation treatment, to the organic carbon after pre-oxidation treatment Source coated Si O2Composite carries out in-situ carburization and SiO2Magnesiothermic reduction reaction etc. step.Silicon/carbon compound cathode of the invention Material has excellent electric conductivity and structural stability can, its preparation method safety and environmental protection, suitable for industrial production.But prepare Step is cumbersome, and cost is higher, and raw material use the silica for the nanosizing bought, it is necessary to further handle, and electricity Chemical property has much room for improvement.
The content of the invention
In view of the shortcomings of the prior art, the present invention provides a kind of high performance lithium ion secondary battery negative material Si/C and is combined Material, the composite even aperture distribution and with excellent chemical property.
The present invention also provides a kind of preparation side of above-mentioned high performance lithium ion secondary battery negative material Si/C composites Method, the preparation method is simple to operation, low for equipment requirements, and used raw material is simple and easy to get, environmental protection, cheap, And can be mass-produced.
Technical scheme is as follows：
A kind of high performance lithium ion secondary battery negative material Si/C composites, the composite includes answering for carbon and silicon The mass content of carbon is 10-35% in compound, the compound, and the mass content of silicon is 65-90%；The composite it is microcosmic Pattern is：Si nano grain surfaces are coated with carbon-coating, form carbon silicon nano composite sphere, and be supported on the surface of sheet carbon.
According to currently preferred, the size of the Si nano particles is 15-25nm, and the thickness of carbon-coating is 3-7nm, A diameter of 18-32nm of ball.
According to currently preferred, the Si/C composites are to be prepared using bagasse and ascorbic acid as raw material； First SiO is prepared by raw material of bagasse2, Si nano particles are prepared through reduction；Then again using ascorbic acid as carbon source Prepare.
It is preferred that, the mass ratio of the Si nano particles and ascorbic acid is 1:0.6-5.
A kind of preparation method of high performance lithium ion secondary battery negative material Si/C composites, including step are as follows：
(1) bagasse is soaked under 1-12h in 0.5-2mol/L acid solution, scrubbed, dry, air atmosphere and forged Burn, obtain SiO2Powder；
(2) after the SiO2 powder for preparing step (1) and magnesium powder ground and mixed are uniform, in restitutive protection's gas atmosphere Lower calcining is enclosed, mixture is obtained；Mixture is first soaked in 5-10h in 0.5-2mol/L acid solution, quality is then soaked in again Concentration is 1-10min in 2-8% hydrofluoric acid aqueous solution, scrubbed, dry, obtains Si nano particles；
(3) the Si nano particles for preparing step (2) are added in aqueous ascorbic acid, and 6-10h is stirred at room temperature；So After stirring 0.5-1h at 80-100 DEG C, colloidal sol is obtained；By gained colloidal sol in being calcined under protective gas atmosphere, Si/C composite woods are obtained Material.
According to currently preferred, the quality of sugarcane and the volume ratio of acid solution are described in step (1)：0.1-1g/mL.
According to currently preferred, acid described in step (1) is one kind in hydrochloric acid, sulfuric acid or nitric acid；The acid solution It is the aqueous solution or acid and water and the mixed solution of alcohol of acid.
It is further preferred that the alcohol is absolute ethyl alcohol；In the mixed solution of the acid and water and alcohol, the volume of water and alcohol Than for 0.1-0.5:1.
According to currently preferred, mode of washing described in step (1) is that deionized water and absolute ethyl alcohol are alternately washed respectively Wash.
According to currently preferred, drying mode described in step (1) is to dry 2-12h at 80-120 DEG C.
According to currently preferred, calcining heat is 500-800 DEG C described in step (1), and calcination time is 2-5h, heating Speed is 1-5 DEG C/min.
According to currently preferred, SiO described in step (2)2Powder and the mass ratio of magnesium powder are 0.5-1:1.
According to currently preferred, restitutive protection's gas described in step (2) is that volume ratio is 95：5 Ar/H2 mixing Gas or volume ratio are 95：5 Ar/CO mixed gas.
According to currently preferred, calcining heat described in step (2) is 600-700 DEG C, and calcination time is 6-8h, heating Speed is 2-5 DEG C/min.
According to currently preferred, the quality of mixture described in step (2) and the volume ratio of acid solution are 0.02- 0.15g/mL；The quality of mixture and the volume ratio 0.05-0.375g/mL of hydrofluoric acid aqueous solution.
According to currently preferred, acid solution described in step (2) is hydrochloric acid and water and the mixed solution of alcohol, the mixing Solution reclaimed water and the volume ratio of alcohol are 0.1-0.5:1；It is preferred that, the alcohol is absolute ethyl alcohol.
According to currently preferred, mode of washing described in step (2) is that deionized water and absolute ethyl alcohol are alternately washed respectively Wash.
According to currently preferred, drying mode described in step (2) is to dry 2-12h at 60-100 DEG C.
According to currently preferred, the mass ratio of Si nano particles and ascorbic acid described in step (3) is 1:0.6-5.
According to currently preferred, the molar concentration of aqueous ascorbic acid described in step (3) is 0.01-0.15mol/ L。
According to currently preferred, protective gas described in step (3) is the gaseous mixture of argon gas, nitrogen, argon gas and hydrogen One kind in the mixed gas of body or nitrogen and hydrogen；The volume ratio of argon gas and hydrogen in the mixed gas of the argon gas and hydrogen For 95:5, the volume ratio of nitrogen and hydrogen is 95 in the mixed gas of nitrogen and hydrogen:5.
According to currently preferred, calcining heat described in step (3) is 500-800 DEG C, and calcination time is 2-4h, heating Speed is 1-5 DEG C/min.
The present invention technical characterstic and have the beneficial effect that：
The present invention prepares silica by raw material of natural resources bagasse, and then will be obtained using magnesium reduction process Reducing silica be silicon, through remove product in MgO, Mg2The Si and SiO not being reduced2, obtain size about 20nm Porous nano Si particles, preparation-obtained nano Si particle has quite excellent specific discharge capacity, but long circulating performance It need to be improved；Therefore, selection ascorbic acid, using sol-gal process and subsequent calcination method, is prepared porous as carbon source Si/C composites.It is huge in electrochemical process that the composite effectively alleviates silicon because of its unique microscopic appearance Big volumetric expansion, while the electric conductivity of material is effectively raised, therefore with very excellent chemical property.
Beneficial effects of the present invention are as follows：
(a) raw material used in the present invention is simple and easy to get, environmental protection, cheap, cost are low；Meanwhile, it is of the invention Preparation method is simple to operation, low for equipment requirements, does not have any poisonous and hazardous material generation in preparation process, can high-volume Production, is adapted to industrial applications.
(b) present invention prepares silica by raw material of bagasse, and method is simple, and cost is low, it is easy to industrialize, can So that bagasse to be turned waste into wealth, effective utilization of waste is realized；And it comes from natural resources, green non-pollution and can be again It is raw.It is Nano grade that obtained silica is extracted from bagasse, and purity is very high.
(c) present invention uses ascorbic acid for carbon source, environmental protection, and it well-proportioned can be coated on the surface of silicon, The size of the material of formation is very homogeneous.
(d) Si/C composites pattern produced by the present invention is homogeneous and porous, and with excellent chemical property, first circle is put Electricity and charge specific capacity may be up to 4109 and 2738mA h/g, and first circle coulombic efficiency can reach 66.6%；The 1st circle, the 2nd circle and The specific discharge capacity of 70 circles can reach 4109,2730 and 2125mA h/g, illustrate the excellent chemical property of material；While institute The composite of preparation has preferable invertibity, high rate performance and long circulating performance.
Brief description of the drawings
Fig. 1 is the XRD diffraction spectrograms of Si nano particles prepared by the embodiment of the present invention 1 and Si/C composites；
Fig. 2 is the SEM pictures of Si nano particles prepared by the embodiment of the present invention 1；
Fig. 3 is the SEM pictures of Si/C composites prepared by the embodiment of the present invention 1；
Fig. 4 is the charging and discharging curve figure of Si/C composites prepared by the embodiment of the present invention 1；
Fig. 5 is the high rate performance figure of Si/C composites prepared by the embodiment of the present invention 1；
Fig. 6 is carbon material prepared by Si nano particles, Si/C composites and comparative example 1 prepared by the embodiment of the present invention 1 Cycle performance comparison diagram.
Embodiment
With reference to specific embodiment, the present invention is described further, but not limited to this.
Experimental method described in following embodiments, is conventional method unless otherwise specified simultaneously；The reagent and material Material, unless otherwise specified, is commercially obtained.
In embodiment bagasse derive from Jinan market, pick up from south；Ascorbic acid is commercial products, Chinese medicines group Learn reagent Co., Ltd on sale.
Embodiment 1
A kind of high performance lithium ion secondary battery negative material Si/C composites, the composite includes answering for carbon and silicon The mass content of carbon is 30% in compound, the compound, and the mass content of silicon is 70%；The microscopic appearance of the composite It is：Si nano grain surfaces are coated with carbon-coating, form the nano combined bead of carbon silicon, and be supported on the surface of sheet carbon；It is described The size of Si nano particles is 20nm, and the thickness of carbon-coating is 5nm, a diameter of 25nm of bead or so.
The preparation method of above-mentioned high performance lithium ion secondary battery negative material Si/C composites, including step are as follows：
(1) by the 5g bagasse of collection in 50mL 1mol/L HCl/water solution soaking at room temperature 2 hours, it is inorganic to remove Salt impurity, is alternately washed three times respectively with water and absolute ethyl alcohol, and the dry 12h in 80 DEG C of baking oven；Then, in atmosphere 5h is calcined at 600 DEG C, heating rate is set to 1 DEG C/min, obtains the SiO of white puff2Powder；
(2) SiO for preparing 0.5g steps (1)2It is transferred to 0.5g magnesium powders after ground and mixed is uniform in mortar In porcelain boat, Ar/H is then quickly transferred to2(volume ratio is 95：5) in the tube furnace of atmosphere, 6h, heating rate are calcined at 650 DEG C 5 DEG C/min is set to, mixture is obtained；Said mixture is put into 50mL 1mol/L HCl solutions (HCl:H2O:Absolute ethyl alcohol rubs That ratio=0.66:4.72:8.88) soaking at room temperature 6 hours in, after 60 DEG C of dry 3h, then again soaking at room temperature in 20mL HF water 3 minutes in solution (mass concentration is 5%)；With alternately washing three times respectively of deionized water and absolute ethyl alcohol, in 60 DEG C of baking oven After middle dry 4h, Si nano particles are obtained；
(3) the Si nano particles addition 10mL 0.07mol/L prepared 0.05g steps (2) ascorbic acid is water-soluble In liquid, it is stirred at room temperature 6 hours；Then stirred 30 minutes under 90 degree of water-baths, obtain colloidal sol；Obtained colloidal sol is placed on tube furnace In, under the protective atmosphere of argon gas, 600 DEG C of calcining 2h, heating rate is set to 1 DEG C/min, obtains the Si/C composites of black.
The Si nano particles and the XRD spectra of Si/C composites that the present embodiment is prepared are as shown in figure 1, can by Fig. 1 Know, the product that step (2) of the present invention prepares is Si, the product that the present invention is finally prepared is Si/C composites.
The Si nano particles and the SEM pictures of Si/C composites that the present embodiment is prepared as shown in Figure 2,3, by Fig. 2, 3 understand that the average-size of Si nano particles is about 20nm, a diameter of 25nm of the nano combined bead of carbon silicon or so, and is supported on The surface of sheet carbon.
Embodiment 2
A kind of preparation method of high performance lithium ion secondary battery negative material Si/C composites, including step are as follows：
(1) by the 10g bagasse of collection in 50mL 1mol/L HCl/water solution soaking at room temperature 4 hours, it is inorganic to remove Salt impurity, is alternately washed three times respectively with water and absolute ethyl alcohol, and the dry 10h in 90 DEG C of baking oven；Then, in atmosphere 4h is calcined at 650 DEG C, heating rate is set to 2 DEG C/min, obtains the SiO of white puff2Powder；
(2) SiO for preparing 1g steps (1)2Porcelain is transferred to after ground and mixed is uniform in mortar with 1.5g magnesium powders In boat, Ar/H is then quickly transferred to2(volume ratio is 95：5) in the tube furnace of atmosphere, 7h is calcined at 600 DEG C, heating rate is set For 2 DEG C/min, mixture is obtained；Said mixture is put into 50mL 1mol/L HCl solutions (HCl:H2O:Mole of absolute ethyl alcohol Than=0.66:4.72:8.88) soaking at room temperature 8 hours in, after 80 DEG C of dry 2h, then soaking at room temperature is water-soluble in 20mL HF again 5 minutes in liquid (mass concentration is 3%)；With alternately washing three times respectively of deionized water and absolute ethyl alcohol, in 80 DEG C of baking oven Dry after 2h, obtain Si nano particles；
(3) the Si nano particles addition 10mL 0.1mol/L prepared 0.05g steps (2) ascorbic acid is water-soluble In liquid, it is stirred at room temperature 8 hours；Then stirred 40 minutes under 95 degree of water-baths, obtain colloidal sol；Obtained colloidal sol is placed on tube furnace In, under the protective atmosphere of argon gas, 700 DEG C of calcining 3h, heating rate is set to 2 DEG C/min, obtains the Si/C composites of black.
Embodiment 3
A kind of preparation method of high performance lithium ion secondary battery negative material Si/C composites, including step are as follows：
(1) by the 15g bagasse of collection in 50mL 1mol/L HCl/water solution soaking at room temperature 6 hours, it is inorganic to remove Salt impurity, is alternately washed three times respectively with water and absolute ethyl alcohol, and the dry 8h in 100 DEG C of baking oven；Then, in atmosphere 3h is calcined at 700 DEG C, heating rate is set to 5 DEG C/min, obtains the SiO of white puff2Powder；
(2) SiO for preparing 1g steps (1)2Porcelain boat is transferred to after ground and mixed is uniform in mortar with 2g magnesium powders In, then it is quickly transferred to Ar/H2(volume ratio is 95：5) in the tube furnace of atmosphere, 6.5h is calcined at 700 DEG C, heating rate is set For 5 DEG C/min, mixture is obtained；Said mixture is put into 50mL 1mol/L HCl solutions (HCl:H2O:Mole of absolute ethyl alcohol Than=0.66:4.72:8.88) soaking at room temperature 8 hours in, after 90 DEG C of dry 2h, then soaking at room temperature is water-soluble in 20mL HF again 6 minutes in liquid (mass concentration is 4%)；With alternately washing three times respectively of deionized water and absolute ethyl alcohol, in 100 DEG C of baking oven Dry after 2h, obtain Si nano particles；
(3) the Si nano particles for preparing 0.05g steps (2) add 10mL 0.035mol/L Vitamin C sour water In solution, it is stirred at room temperature 6 hours；Then stirred 30 minutes under 100 degree of water-baths, obtain colloidal sol；Obtained colloidal sol is placed on pipe In formula stove, under the protective atmosphere of argon gas, 750 DEG C of calcining 2h, heating rate is set to 2 DEG C/min, obtains the Si/C composite woods of black Material.
Embodiment 4
A kind of preparation method of high performance lithium ion secondary battery negative material Si/C composites, including step are as follows：
(1) by the 25g bagasse of collection in 50mL 1mol/L HCl/water solution soaking at room temperature 8 hours, it is inorganic to remove Salt impurity, is alternately washed three times respectively with water and absolute ethyl alcohol, and the dry 6h in 110 DEG C of baking oven；Then, in atmosphere 2h is calcined at 800 DEG C, heating rate is set to 5 DEG C/min, obtains the SiO of white puff2Powder；
(2) SiO for preparing 2g steps (1)2Porcelain boat is transferred to after ground and mixed is uniform in mortar with 3g magnesium powders In, then it is quickly transferred to Ar/H2(volume ratio is 95：5) in the tube furnace of atmosphere, 6h is calcined at 650 DEG C, heating rate is set to 5 DEG C/min, obtain mixture；Said mixture is put into 50mL 1mol/L HCl solutions (HCl:H2O:The mol ratio of absolute ethyl alcohol =0.66:4.72:8.88) soaking at room temperature 10 hours in, after 100 DEG C of dry 2h, then soaking at room temperature is water-soluble in 20mL HF again 8 minutes in liquid (mass concentration is 2%)；With alternately washing three times respectively of deionized water and absolute ethyl alcohol, in 80 DEG C of baking oven Dry after 2h, obtain Si nano particles；
(3) the Si nano particles addition 10mL 0.14mol/L prepared 0.05g steps (2) ascorbic acid is water-soluble In liquid, it is stirred at room temperature 10 hours；Then stirred 40 minutes under 95 degree of water-baths, obtain colloidal sol；Obtained colloidal sol is placed on tubular type In stove, under the protective atmosphere of argon gas, 800 DEG C of calcining 2h, heating rate is set to 5 DEG C/min, obtains the Si/C composites of black.
Embodiment 5
A kind of preparation method of high performance lithium ion secondary battery negative material Si/C composites, including step are as follows：
(1) by the 35g bagasse of collection in 50mL 1mol/L HCl/water solution soaking at room temperature 10 hours, to remove nothing Machine salt impurity, is alternately washed three times respectively with water and absolute ethyl alcohol, and the dry 4h in 120 DEG C of baking oven；Then, in air In calcine 2h at 800 DEG C, heating rate is set to 2 DEG C/min, obtains the SiO of white puff2Powder；
(2) SiO for preparing 2.5g steps (1)2Porcelain is transferred to after ground and mixed is uniform in mortar with 5g magnesium powders In boat, Ar/H is then quickly transferred to2(volume ratio is 95：5) in the tube furnace of atmosphere, 8h is calcined at 650 DEG C, heating rate is set For 5 DEG C/min, mixture is obtained；Said mixture is put into 50mL 1mol/L HCl solutions (HCl:H2O:Mole of absolute ethyl alcohol Than=0.66:4.72:8.88) soaking at room temperature 10 hours in, after 100 DEG C of dry 2h, then again soaking at room temperature in 20mL HF water 10 minutes in solution (mass concentration is 5%)；With alternately washing three times respectively of deionized water and absolute ethyl alcohol, in 60 DEG C of baking oven After middle dry 4h, Si nano particles are obtained；
(3) the Si nano particles for preparing 0.05g steps (2) add 10mL 0.0175mol/L Vitamin C sour water In solution, it is stirred at room temperature 6 hours；Then stirred 40 minutes under 95 degree of water-baths, obtain colloidal sol；Obtained colloidal sol is placed on tubular type In stove, under the protective atmosphere of argon gas, 600 DEG C of calcining 2h, heating rate is set to 1 DEG C/min, obtains the Si/C composites of black.
Comparative example 1
A kind of preparation method of carbon material, including step are as follows：
0.12g ascorbic acid is placed in tube furnace, under the protective atmosphere of argon gas, 600 DEG C are calcined 2h, heating rate 1 DEG C/min is set to, carbon material is obtained.
Test example 1
Properties of product are tested
Carbon material made from Si nano particles made from embodiment 1 and Si/C composites and comparative example 1 is used as lithium Ion secondary battery negative material, electrode is prepared using rubbing method.
By active material, Super P (conductive carbon black) and sodium alginate (binding agent) in mass ratio 60:30:10 mixing point Dissipate in deionized water, slurry is made after being ground uniformly in mortar, slurry is coated on copper foil, in an oven 60 DEG C of vacuum After drying 3 hours, a diameter of 12mm circular pole piece is cut into.Using lithium metal as to electrode, barrier film uses Celgard 2300 macromolecule membranes, electrolyte is by LiPF6It is dissolved in the sub- second of diethyl carbonate (DEC)/dimethyl carbonate (DMC)/carbonic acid (volume ratio is 1 to ester (EC)：1：1) in mixed liquor, LiPF in mixed liquor6Concentration be 1mol/L.Charge/discharge curve and circulation Test is carried out at 25 DEG C on Land-CT2001A battery test systems, and voltage is set between 0.01-2.0V.
Fig. 4 is the charging and discharging curve figure of Si/C composites made from embodiment 1, and Fig. 4 illustrates material in voltage model Enclose for 0.01-2V, current density is the 1st circle under 0.1A/g, the 2nd circle and the 70 lower charging and discharging curves of circle circulation, first circle discharges and filled Electric specific capacity is respectively 4109 and 2738mA h/g, and first circle coulombic efficiency can reach 66.6%；In first lap, the 2nd circle and 70 circles Specific discharge capacity be respectively 4109,2730 and 2125mA h/g, illustrate the excellent chemical property of material.
Fig. 5 is the high rate performance figure of Si/C composites made from embodiment 1, and composite is shown in Figure 5 not With the high rate performance under current density 0.1,0.2,0.5,1,2 and 3A/g, 2680,2456,2187,1487 Hes are shown respectively 1420mA h/g reversible specific capacity.In addition, after low current 0.1A/g is again restored to after high current density has been tested, Reversible specific capacity remains to return to 2200mA h/g, and specific capacity is not obvious in the circulation of 10 circles under each current density Decay, show the excellent invertibity of Si/C composites and high rate performance.
Fig. 6 is carbon material prepared by Si nano particles, Si/C composites and comparative example 1 prepared by the embodiment of the present invention 1 Cycle performance comparison diagram, show Si/C composites in Fig. 6, the cyclicity of carbon material and Si nano particles in 0.5A/g Can, Si/C composites show optimum cycle performance, and the cyclical stability of material can effectively be improved by indicating carbon coating, and And effectively suppress the rapid decay of capacity.

Claims (10)

1. a kind of high performance lithium ion secondary battery negative material Si/C composites, it is characterised in that the composite includes The mass content of carbon is 10-35% in the compound of carbon and silicon, the compound, and the mass content of silicon is 65-90%；This is combined The microscopic appearance of material is：Si nano grain surfaces are coated with carbon-coating, form silicon-carbon nano composite sphere, and be supported on sheet carbon Surface；
The size of the Si nano particles is 15-25nm, and the thickness of carbon-coating is 3-7nm, a diameter of 18-32nm of ball.
2. high performance lithium ion secondary battery negative material Si/C composites according to claim 1, it is characterised in that The Si/C composites are to be prepared using bagasse and ascorbic acid as raw material；First prepared by raw material of bagasse SiO2, Si nano particles are prepared through reduction；Then prepared again by carbon source of ascorbic acid；
It is preferred that, the mass ratio of the Si nano particles and ascorbic acid is 1:0.6-5.
3. the preparation of the high performance lithium ion secondary battery negative material Si/C composites as described in claim any one of 1-2 Method, including step are as follows：
(1) bagasse is soaked under 1-12h in 0.5-2mol/L acid solution, scrubbed, dry, air atmosphere and calcined, obtained SiO2Powder；
(2) SiO for preparing step (1)2After powder and magnesium powder ground and mixed are uniform, under restitutive protection's atmosphere Calcining, obtains mixture；Mixture is first soaked in 5-10h in 0.5-2mol/L acid solution, mass concentration is then soaked in again For 1-10min in 2-8% hydrofluoric acid aqueous solution, scrubbed, drying obtains Si nano particles；
(3) the Si nano particles for preparing step (2) are added in aqueous ascorbic acid, and 6-10h is stirred at room temperature；Then in 0.5-1h is stirred at 80-100 DEG C, colloidal sol is obtained；By gained colloidal sol in being calcined under protective gas atmosphere, Si/C composites are obtained.
4. the preparation method of high performance lithium ion secondary battery negative material Si/C composites according to claim 3, Characterized in that, the quality of sugarcane and the volume ratio of acid solution are described in step (1)：0.1-1g/mL；
It is preferred that, acid described in step (1) is one kind in hydrochloric acid, sulfuric acid or nitric acid；The acid solution be acid the aqueous solution or Acid and water and the mixed solution of alcohol；
It is further preferred that the alcohol is absolute ethyl alcohol；In the mixed solution of the acid and water and alcohol, the volume ratio of water and alcohol is 0.1-0.5:1。
5. the preparation method of high performance lithium ion secondary battery negative material Si/C composites according to claim 3, Characterized in that, calcining heat is 500-800 DEG C described in step (1), calcination time is 2-5h, heating rate is 1-5 DEG C/ min。
6. the preparation method of high performance lithium ion secondary battery negative material Si/C composites according to claim 3, Characterized in that, SiO described in step (2)2Powder and the mass ratio of magnesium powder are 0.5-1:1.
7. the preparation method of high performance lithium ion secondary battery negative material Si/C composites according to claim 3, Characterized in that, calcining heat described in step (2) is 600-700 DEG C, calcination time is 6-8h, heating rate is 2-5 DEG C/ min。
8. the preparation method of high performance lithium ion secondary battery negative material Si/C composites according to claim 3, Characterized in that, acid solution described in step (2) is hydrochloric acid and water and the mixed solution of alcohol, the mixed solution reclaimed water and alcohol Volume ratio is 0.1-0.5:1；It is preferred that, the alcohol is absolute ethyl alcohol.
9. the preparation method of high performance lithium ion secondary battery negative material Si/C composites according to claim 3, Characterized in that, the mass ratio of Si nano particles and ascorbic acid described in step (3) is 1:0.6-5；
It is preferred that, the molar concentration of aqueous ascorbic acid described in step (3) is 0.01-0.15mol/L.
10. the preparation method of high performance lithium ion secondary battery negative material Si/C composites according to claim 3, Characterized in that, calcining heat described in step (3) is 500-800 DEG C, calcination time is 2-4h, heating rate is 1-5 DEG C/ min。
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