CN110323418A - Si-C composite material and its preparation method and application - Google Patents
Si-C composite material and its preparation method and application Download PDFInfo
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- CN110323418A CN110323418A CN201810749708.5A CN201810749708A CN110323418A CN 110323418 A CN110323418 A CN 110323418A CN 201810749708 A CN201810749708 A CN 201810749708A CN 110323418 A CN110323418 A CN 110323418A
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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
- 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
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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
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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
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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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
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- 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 relates to negative electrode active material fields, and in particular to Si-C composite material and its preparation method and application.The Si-C composite material includes by the second carbon-coating of the first carbon-coating cladding simple substance silicon particle composite particles formed and several composite particles outer claddings；Wherein, there are cavitys between second carbon-coating and the composite particles.Method of the invention is easy to operate, cost is lower, environmentally protective, resulting Si-C composite material chemical property with higher.
Description
Technical field
The present invention relates to negative electrode active material fields, and in particular to Si-C composite material and its preparation method and application.
Background technique
Currently, commercialized lithium ion battery negative material is mainly graphite material, but the theoretical specific volume of graphite material
Low (372mAh/g) is measured, the demand of height ratio capacity lithium ion battery is unable to satisfy.Silicon is because having very high theoretical specific capacity (about
3600mAh/g) receiving more and more attention, it is considered as one of the material of most possible substitution graphite cathode, however
Silicon-based anode is but slowly not up to large-scale production and application.This is because silicon can generate about 300% during Li insertion extraction
Volume change, the dusting that huge volume change will cause silicon electrode are peeled off, are made between silicon particle and between silicon and collector
Electrical contact is lost, the specific capacity of electrode sharply declines even entirely ineffective.
For the serious bulk effect of silicon materials, researchers, which are widely used, is modified to improve cycle performance it,
One of method is exactly to utilize preparing porous silicon by magnesiothermic reduction, and then further progress carbon coating obtains Si-C composite material.
Wei Wang et al. (Silicon and Carbon Nanocomposite Spheres with Enhanced
Electrochemical Performance for Full Cell Lithium Ion Batteries,Scientific
Reports, 2017,7.) first withThen legal system prepared silicon dioxide introduces sodium chloride as slow in magnesium thermit
Thermit powder improves huge heat release problem during magnesium thermit, is successively washed after reaction using deionized water, HCl, HF
Wash removal magnesia and unreacted silica, the porous silicon obtained.Then chemical vapour deposition technique is used, using acetylene as carbon
Source gas coats one layer of carbon-coating in porous silicon surface, so that porous silicon@carbon composite be prepared, second is used in the document
Alkynes gas is as carbon coating gas higher cost.
CN103579596A discloses a kind of preparation method of lithium ion battery negative material, uses the pyrolysis of rice husk solid
Body product then passes through metal powder high temperature reduction as silicon source and carbon source, and reduzate is carried out pickling, i.e., successively passes through
HCl or HNO3Or sulfuric acid scrubbing, it is then handled again with HF, porous silicon-carbon composite can be obtained.But the porous silico-carbo
Composite material cycle performance is poor, under 0.1C electric current, 200 weeks charging and discharging capacities of circulation just in 600mAh/g or so,
Specific capacity is relatively low.
It using diatomite is that raw material prepares porous silicon/graphene composite lithium ion cell and bears that CN106532008A, which is disclosed a kind of,
The method of pole material uses natural diatomaceous earth for silicon source, successively uses alkali cleaning and pickling, obtains purified silicious earth, and and magnesium
Powder carries out magnesium thermit and obtains porous silicon, porous silicon in glucose, starch, table sugar, sucrose, silicon carbide any one
High temperature carbonization is carried out on a catalyst as carbon source mixing back loading, and it is compound that product through pickling can be obtained porous silicon/graphene
Lithium ion battery negative material.Carbon source is at high cost in the preparation of the porous silicon/graphene composite lithium ion battery cathode material, and
Specific capacity is lower over numerous cycles, and cycle performance is poor.
Easily because local reaction unevenly generates magnesium silicide and part is former when traditional magnesium thermit prepares elemental silicon
Material has neither part nor lot in reaction, and in subsequent HCl treatment step, the magnesium silicide and hydrochloric acid reactant salt of generation generate silane and hydrogen, has
Safety problem, and make the conversion ratio of element silicon in raw material relatively low, unreacted SiO2It needs to remove using hydrofluoric acid, You Haihuan
Border.
Existing Si-C composite material is largely first to prepare elemental silicon, is then taking liquid phase coating, gas phase cladding
The methods of carry out carbon coating again, obtain Si-C composite material；And use carbon source be mostly polystyrene, glucose, phenolic resin,
The higher organic matter of the prices such as dopamine or methane, dangerous gas as acetylene.
Summary of the invention
It is made the purpose of the present invention is to provide a kind of preparation method of novel Si-C composite material and by this method
Si-C composite material and application, method of the invention is easy to operate, cost is lower, environmentally protective, resulting silicon-carbon composite wood
Expect chemical property with higher.
To achieve the goals above, one aspect of the present invention provides a kind of Si-C composite material, the Si-C composite material packet
It includes by the second carbon-coating of the first carbon-coating cladding simple substance silicon particle composite particles formed and several composite particles outer claddings；Wherein,
There are cavitys between second carbon-coating and the composite particles.
Second aspect of the present invention provides a kind of preparation method of Si-C composite material, this method comprises:
(1) under an inert atmosphere, silicon-containing material and magnesium metal are subjected to magnesium thermit, convert magnesium silicide for element silicon
Form；
(2) in carbon dioxide atmosphere, the product of the magnesium thermit is subjected to calcination process；
(3) product of the calcination process is subjected to pickling；
Wherein, the temperature of the magnesium thermit is 500-850 DEG C, and the temperature of the calcination process is 700-1000 DEG C.
Second aspect of the present invention provides Si-C composite material prepared by the above method.
Third aspect present invention provides the cathode including above-mentioned Si-C composite material.
Fourth aspect present invention provides the lithium ion battery including above-mentioned cathode.
The method have the advantages that:
1) SiO is restored with traditional magnesium thermit2It prepares elemental silicon to compare, the method for the present invention overuses magnesium thermit, first
Magnesium silicide is substantially completely converted by element silicon in raw material, then is fully converted to magnesium silicide by magnesium silicide and carbon dioxide reaction
Elemental silicon, so that the conversion ratio of silicon significantly improves.
2) traditional Si-C composite material mostly first prepares elemental silicon, then carries out the cladding of carbon, this hair in simple substance silicon face
Bright method reduces preparation section, in situ while elemental silicon generates to carry out carbon coating on its surface and resulting
Si-C composite material carbon-coating coats even closer, and the chemical property of material greatly improves；
3) since excessive magnesium thermit makes SiO2It is substantially completely converted into magnesium silicide, no silica is remaining, so not
Traditional magnesium heat is same as to need to handle the complete SiO of unreacted using HF2, be conducive to environmental protection；
4) waste utilization is played the role of as carbon-source gas with carbon dioxide, considerably reduces preparation cost.
Detailed description of the invention
Fig. 1 is the X-ray diffractogram (XRD diagram) of process product in embodiment 1.From bottom to top successively are as follows: silica is former
The XRD diagram of material；XRD diagram after magnesium thermit；XRD diagram after logical carbon dioxide gas roasting；Final product XRD after cleaning
Figure.
Fig. 2 is the Raman spectrogram of final product Si-C composite material in embodiment 1.
Fig. 3 is the scanning electron microscope (SEM) photograph of silica material used in embodiment 1.
Fig. 4 is the scanning electron microscope (SEM) photograph of final product Si-C composite material in embodiment 1.
Fig. 5 is the scanning electron microscope of partial enlargement for Fig. 4 of final product Si-C composite material in embodiment 1
Figure.
Fig. 6 is that broken segment shows sweeping inside Si-C composite material in final product Si-C composite material in embodiment 1
Retouch electron microscope.
Fig. 7 is the high-resolution-ration transmission electric-lens figure for the final product Si-C composite material that embodiment 1 obtains.
Fig. 8 is the high-resolution of partial enlargement for Fig. 7 for the final product Si-C composite material that embodiment 1 obtains
Transmission electron microscope picture.
Specific embodiment
The endpoint of disclosed range and any value are not limited to the accurate range or value herein, these ranges or
Value should be understood as comprising the value close to these ranges or value.For numberical range, between the endpoint value of each range, respectively
It can be combined with each other between the endpoint value of a range and individual point value, and individually between point value and obtain one or more
New numberical range, these numberical ranges should be considered as specific open herein.
One aspect of the present invention provides a kind of Si-C composite material, and the Si-C composite material includes coating list by the first carbon-coating
Second carbon-coating of composite particles and several composite particles outer claddings that matter silicon particle is formed；Wherein, second carbon-coating and described
There are cavitys between composite particles.
According to the present invention, in the Si-C composite material of the invention, the composite particles are to coat simple substance silicon grain by carbon-coating
Son is formed by, and simple substance silicon particle is also with regard to elementary silicon particle, external the first carbon-coating for forming thinner thickness, wherein preferably,
The partial size of the simple substance silicon particle is 10-100nm.Preferably, first carbon-coating with a thickness of 1-5nm.In addition, the silicon-carbon is multiple
Condensation material further includes the second carbon-coating, which is formed in outside composite particles, and can be coated with several composite particles, thus
Form higher volume of Si-C composite material particle.Preferably, second carbon-coating with a thickness of 20-60nm.In the present invention, institute
State between the second carbon-coating and the composite particles that there are between cavity namely the first carbon-coating and the second carbon-coating and non-fully close knots
It closes, it will be appreciated that be formed honeycomb structure (or referred to as three-dimensional porous network shape structure) by second carbon-coating, and each bee
There are several composite particles, and there are still a fixed gaps for the honeycomb hole equipped with composite particles in socket bore.
Preferably, above-mentioned the silicon-carbon that several composite particles are formed is coated by the second carbon-coating to answer in the Si-C composite material
The partial size of condensation material is about 2-20 μm.Here several composite particles for referring to 1 or more, but the second carbon-coating formation simultaneously
May also only have the case where 1 composite particles namely the two situation in honeycomb structure and deposit, this is included in of the invention
In range.
In accordance with the present invention it is preferred that the content of element silicon is 43-70 weight %, carbon in the Si-C composite material
Content be 30-57 weight %.
Second aspect of the present invention provides a kind of preparation method of Si-C composite material, this method comprises:
(1) under an inert atmosphere, silicon-containing material and magnesium metal are subjected to magnesium thermit, convert magnesium silicide for element silicon
Form；
(2) in carbon dioxide atmosphere, the product of the magnesium thermit is subjected to calcination process；
(3) product of the calcination process is subjected to pickling；
Wherein, the temperature of the magnesium thermit is 500-850 DEG C, and the temperature of the calcination process is 700-1000 DEG C.
According to the present invention, in step (1) that the element silicon in silicon-containing material is (practical by the way that magnesium thermit occurs with magnesium metal
On be a kind of excessive magnesium thermit), so that silicon substrate is originally completely converted into magnesium silicide, and part magnesium then exists with magnesia,
The elemental magnesium that part is not reacted completely may be there remains.In step (2), using carbon dioxide as carbon source, by calcination process, so that
Magnesium silicide is converted into simple substance silicon particle, while carbon dioxide is then converted into simple substance carbon and is coated on outside simple substance silicon particle, magnesium then base
This exists in the form of magnesia.In the present invention, form that simple substance silicon particle is synchronous with carbon coating to be carried out, so that silicon and carbon it
Between contact more closely, while resulting Si-C composite material shows more excellent chemical property.
Wherein, in step (1), in order to enable the silicon in silicon-containing material can fully be converted into magnesium silicide, it is preferable that institute
The molar ratio for stating the element silicon and magnesium metal in silicon-containing material is 1:4-8, preferably 1:4-6, more preferably 1:4-4.5.It is described
Magnesium thermit is preferably so that in step (1), and in the product of the magnesium thermit, element silicon exists in the form of magnesium silicide, magnesium member
Element exists in the form of magnesium silicide, optional magnesia and optional magnesium metal.It is highly preferred that making the production of the magnesium thermit
Object is made of magnesium silicide, magnesia and optional magnesium metal.
According to the present invention, the silicon-containing material can be from a variety of with element silicon containing being selected in silicon materials, it is preferable that
The silicon-containing material is one of silica, silicate, siliceous mineral and elemental silicon or a variety of.Wherein, silicate is for example
It can be sodium metasilicate, potassium silicate etc., siliceous mineral can be for example orthoclase, crocidolite etc..
Wherein, the granularity of the silicon-containing material can change in a wider range, it is preferable that the granularity of the silicon-containing material
It is 1-50 μm, is preferably 1-30 μm, more preferably 1-20 μm.Above-mentioned silicon-containing material can come for example, by processing modes such as ball millings
Granularity needed for obtaining.
According to the present invention, the magnesium metal provides preferably in the form of magnesium powder, and especially granularity is 1-100 μm of magnesium powder.
According to the present invention, in order to enable silicon-containing material more can adequately be contacted with magnesium metal, magnesium thermit is being carried out
Before, first silicon-containing material and magnesium metal can be mixed, such as by way of ground and mixed, then be sent again hot to magnesium is carried out
Reaction.The temperature of the magnesium thermit is 500-800 DEG C, preferably 600-750 DEG C, more preferably 650-700 DEG C.Preferably, institute
The time for stating magnesium thermit is 1-10h, preferably 2-8h, more preferably 3-6h.
Wherein, the magnesium thermit can carry out in any reactor that can be realized above-mentioned condition, such as can incite somebody to action
Silicon-containing material and magnesium metal are first sealed in reactor, and then reactor is placed in tube furnace and is heated.Preferably, will contain
Silicon raw material and magnesium metal are heated to institute from room temperature (such as 10-30 DEG C) with 2-10 DEG C/min, preferably 3-8 DEG C/min heating rate
State the temperature of magnesium thermit.
Wherein, the inert atmosphere can be provided by the inert gas of this field routine, for example, can for argon gas, helium,
One of neon etc. is a variety of.
According to the present invention, the product of magnesium thermit is carried out calcination process under carbon dioxide atmosphere by step (2), can shape
At simple substance silicon particle and in elemental silicon particle shape at carbon coating layer, including the first carbon-coating for being coated on outside simple substance silicon particle with shape
At composite particles above, and the second carbon-coating of the three-dimensional netted carbon structure in the composite particles outer cladding.Wherein, institute
The temperature for stating calcination process is 700-900 DEG C, preferably 750-850 DEG C.Preferably, the time of the calcination process is 0.1-
5h, preferably 0.1-3h, more preferably 0.5-2h.
Wherein, which can carry out in the instrument that this field routinely uses, such as can be anti-by the magnesium heat
The product answered is put into corundum magnetic boat, is placed in closed tube furnace.
The carbon dioxide atmosphere is preferably provided by carbon dioxide content for 99% or more carbon dioxide containing gas, such as
It is provided for the carbon dioxide containing gas of 99.5-100%.
According to the present invention, after due to calcination process, it is mainly Si-C composite material and magnesia in the product of formation, is
This, post-processing mainly removes magnesia.Magnesia is mainly formed in elemental silicon particle periphery in roasting process, for this purpose, step
Suddenly magnesia is removed, can to form gap between the second carbon-coating and composite particles by pickling in (3).To here
Pickling can be using the acid of magnesia can be removed, without hydrofluoric acid.Such as the acid solution that the pickling uses
For hydrochloric acid, concentration is preferably 1-5mol/L.
According to the present invention, the dosage of the acid solution can change in a wider range, it is preferable that relative to described in 1g
The product of calcination process, the dosage of the acid solution are 50-100mL.
According to the present invention, it in order to obtain more pure Si-C composite material, can be washed after pickling, alcohol is washed simultaneously
It is dry.Wherein, washing can for example wash for centrifugal water mode then carries out centrifugation alcohol and washes, then will until supernatant pH is about 7
Solid phase dry 1-48h (preferably 10-20h) under 50-140 DEG C (preferably 60-100 DEG C).
Second aspect of the present invention provides Si-C composite material prepared by the above method.
As described above, method of the invention can easy to operate, cost chemical property is made lower, environmentally protectively
High, particularly high cycle performance Si-C composite material, the Si-C composite material are as described above.Wherein, carbon-coating master
It to be agraphitic carbon.
Third aspect present invention provides the cathode including above-mentioned Si-C composite material.
According to the present invention, above-mentioned Si-C composite material is distributed mainly in the negative electrode material layer of cathode as negative electrode active material
Material.
Wherein, the cathode mainly includes negative current collector and the negative electrode material layer that is formed thereon.
The negative electrode material layer usually contains negative electrode active material, conductive agent and binder, wherein the negative electrode material is this
The above-mentioned Si-C composite material of invention, and conductive agent and binder all use in negative electrode material layer using this field is conventional
Conductive agent and binder, for example, the conductive agent can be one of acetylene black, electrically conductive graphite, conductive black etc. or more
Kind.The binder for example can be with one of PVDF, carboxymethyl cellulose, sodium carboxymethylcellulose, butadiene-styrene rubber etc. or more
Kind.Wherein, the weight ratio of negative electrode active material, conductive agent and binder is preferably 70:5-15:15-25.
Wherein, negative current collector can be for example copper foil, copper mesh etc..
Fourth aspect present invention provides the lithium ion battery including above-mentioned cathode.
According to the present invention, the lithium ion battery can be the construction of the lithium ion battery of this field routine, as long as including
Above-mentioned cathode, there is no any restrictions for the other component of the lithium ion battery by the present invention.
The present invention will be described in detail by way of examples below.
Embodiment 1
The present embodiment is for illustrating Si-C composite material and preparation method thereof of the invention.
(1) by 2g silica dioxide granule (its partial size be 1-20 μm, the same below) and 3.3g magnesium powder (granularity is 1-100 μm) into
It after row ground and mixed is uniform, is put into closed reactor, is sealed and placed in the tube furnace of the argon gas full of purity 99.9%, with
The rate of 5 DEG C/min heats up from room temperature to 675 DEG C and keeps 5h to carry out magnesium thermit；
(2) product of magnesium thermit is placed in the tube furnace of carbon dioxide gas closed and filled with purity 99.9%
It is interior, then in 800 DEG C of reaction 2h to carry out calcination process, cooled to room temperature；
(3) product after opening tube furnace calcination process is in the 1mol/L dilute hydrochloric acid (calcination process relative to 1g
Product, the dosage of dilute hydrochloric acid is 100mL) in carry out soaking and washing；It then washes and using supercentrifuge at 3900 revs/min
It is centrifuged 3 minutes under the revolving speed of clock, removes supernatant and washes centrifugation, so circulation is three times 7 to supernatant pH value, is then used
Ethanol washing is once centrifuged afterwards, and the sample being collected into is placed 70 DEG C of dry 12h in a vacuum drying oven；It is multiple to obtain silicon-carbon
Condensation material Si@C-1, the content of element silicon are 70 weight %.
XRD qualification result: respectively to the product of starting silica particle, magnesium thermit, the product of calcination process and most
Resulting Si-C composite material Si C-1 carries out X-ray diffraction eventually, as a result as shown in Figure 1, wherein distinguish from the bottom to top in Fig. 1
Be silica dioxide granule, the product of magnesium thermit, calcination process product and final resulting Si-C composite material Si@C-1
XRD spectrum；As can be seen that the product of magnesium thermit is mainly made of magnesium silicide and magnesia；The product of calcination process mainly by
Magnesia and silicon composition, without the peak of magnesium silicide, it was demonstrated that the process is mainly magnesium silicide aoxidizes in carbon dioxide gas
Magnesia and elemental silicon are generated, carbon dioxide reduction generates simple substance carbon, fails the peak for seeing simple substance carbon in x-ray diffraction spectra,
It is because what is generated is agraphitic carbon；2 θ of XRD spectrum of Si-C composite material Si@C-1 has high-visible within the scope of 10-80 °
Diffraction maximum, the Si (JPCDS 77-2111) that all diffraction maximums can refer to be designated as cube.
Raman spectrum qualification result: analyzing Si-C composite material Si@C-1 using Raman spectrometer, as a result such as Fig. 2
Shown in, wherein 521cm-1With 970cm-1It is the peak of elemental silicon, 1340cm-1With 1600cm-1Be respectively carbon the peak D and the peak G, by
Figure, which can obtain, contains simple substance carbon and I in materialD/IG=1.06 illustrate the carbon degree of disorder with higher in Si-C composite material.
SEM electron microscope: using scanning electron microscope to starting silica particle (its SEM schemes as shown in Figure 3) and most
Resulting Si-C composite material (its SEM figure is as shown in Fig. 4, Fig. 5 and Fig. 6) is analyzed eventually；Wherein, final resulting silicon-carbon is multiple
The SEM of condensation material Si@C-1 schemes it for interior three-dimensional porous network shape structure (Fig. 6), and partial size is about 10 μm.
HRTEM electron microscope: final resulting Si-C composite material is analyzed using high-resolution-ration transmission electric-lens, (its
HRTEM figure is as shown in Fig. 7 and Fig. 8), the elemental silicon grain diameter of the Si-C composite material is 10-100nm and its is surface coated
First layer carbon layers having thicknesses are about 3nm (Fig. 8), second layer carbon layers having thicknesses 40nm (Fig. 7).
Embodiment 2
The present embodiment is for illustrating Si-C composite material and preparation method thereof of the invention.
According to method described in embodiment 1, the difference is that,
In step (1), the dosage of magnesium powder is 3.2g, in 650 DEG C and keeps 3h in tube furnace to carry out magnesium thermit；
In step (2), in 750 DEG C of reaction 2h to carry out calcination process in tube furnace；It is final to obtain Si-C composite material
Si@C-2, the content of element silicon are 69 weight %.
Embodiment 3
The present embodiment is for illustrating Si-C composite material and preparation method thereof of the invention.
According to method described in embodiment 1, the difference is that,
In step (1), the dosage of magnesium powder is 3.4g, in 700 DEG C and keeps 4h in tube furnace to carry out magnesium thermit；
In step (2), in 850 DEG C of reaction 0.5h to carry out calcination process in tube furnace；It is final to obtain silicon-carbon composite wood
Expect Si@C-3, the content of element silicon is 67 weight %.
Embodiment 4
The present embodiment is for illustrating Si-C composite material and preparation method thereof of the invention.
According to method described in embodiment 1, unlike, in step (1), the dosage of magnesium powder is 4.5g, in tube furnace in
660 DEG C and 6h is kept to carry out magnesium thermit；Final to obtain Si-C composite material Si@C-4, the content of element silicon is 57 weights
Measure %.
Embodiment 5
The present embodiment is for illustrating Si-C composite material and preparation method thereof of the invention.
According to method described in embodiment 1, unlike, in step (1), in tube furnace in 600 DEG C and keep 8h with into
Row magnesium thermit；In step (2), in 700 DEG C of reaction 1h to carry out calcination process in tube furnace；It is final to obtain silicon-carbon composite wood
Expect Si@C-5, the content of element silicon is 66 weight %.
Embodiment 6
The present embodiment is for illustrating Si-C composite material and preparation method thereof of the invention.
According to method described in embodiment 1, unlike, in step (1), in tube furnace in 750 DEG C of reaction 2h with into
Row magnesium thermit；In step (2), in 900 DEG C of reaction 3h to carry out calcination process in tube furnace；It is final to obtain silicon-carbon composite wood
Expect Si@C-6, the content of element silicon is 62 weight %.
Embodiment 7
The present embodiment is for illustrating Si-C composite material and preparation method thereof of the invention.
According to method described in embodiment 1, unlike, in step (1), in tube furnace in 500 DEG C and keep 10h with into
Row magnesium thermit；In step (2), in 950 DEG C of reaction 4h to carry out calcination process in tube furnace；It is final to obtain silicon-carbon composite wood
Expect Si@C-7, the content of element silicon is 59 weight %.
Embodiment 8
The present embodiment is for illustrating Si-C composite material and preparation method thereof of the invention.
According to method described in embodiment 1, unlike, in step (1), in tube furnace in 850 DEG C and keep 1h with into
Row magnesium thermit；In step (2), in 1000 DEG C of reaction 5h to carry out calcination process in tube furnace；Final acquisition silicon-carbon is compound
Material Si@C-8, the content of element silicon are 55 weight %.
Comparative example 1
According to method described in embodiment 1, the difference is that, in step (1), the dosage of magnesium powder is 2.4g；It is final to obtain silicon
Carbon composite D1.
Comparative example 2
According to method described in embodiment 1, the difference is that, in step (1), the dosage of magnesium powder is 1.6g；And without
The product of step (1) resulting magnesium thermit is directly carried out the pickling of step (3) by step (2)；It is final to obtain simple substance silicon materials
D2。
Test case
The preparation of battery:
(1) cathode is prepared: respectively using the resulting Si-C composite material of above-mentioned example as negative electrode active material and acetylene
Black (purchased from Sichuan open source Hui Neng new material Science and Technology Ltd.), carboxymethyl cellulose are (purchased from Sichuan open source Hui Neng new material section
Skill Co., Ltd) and butadiene-styrene rubber (purchased from Sichuan increase income Hui Neng new material Science and Technology Ltd.) according to weight ratio 70:10:10:
10 are uniformly hybridly prepared into negative electrode material slurry in water, and then it is coated in copper foil current collector, dry in 80 DEG C of vacuum
Dry 10h back roller is pressed into cathode pole piece in case.
It (2) is to electrode with metal lithium sheet, diaphragm is using Celgard2400 diaphragm (beauty using cathode pole piece as working electrode
State), electrolyte is the LiPF for being added to 10 weight % fluorinated ethylene carbonates (FEC)6(solvent is the mixed solution of (1mol/L)
The mixed solvent of the EC (ethylene carbonate) of volume ratio 1:1:1, DMC (dimethyl carbonate) and DEC (diethyl carbonate)).In UN-
Lab type glove box (O2< 1ppm, H2O < 1ppm) in be assembled into button cell.Si-C composite material Si@C- is respectively adopted as a result,
1 to Si-C composite material Si@C-8 as negative electrode active material by obtained button cell C1-C8, using Si-C composite material D1 and
Simple substance silicon materials D2 is as negative electrode active material by obtained button cell DC1 and DC2.
Charging and discharging capacity test: land battery test system is used, with the current density of 0.2A/g, respectively to above-mentioned button
The initial charge specific capacity of formula battery, coulombic efficiency measures for the first time, charge specific capacity and corresponding library after 100 circulations
Human relations efficiency measures, and calculates capacity retention ratio of the circulation after 100 weeks；The results are shown in Table 1.
Table 1
It can be seen that Si-C composite material of the invention with excellent chemical property, Neng Gouzuo by the result of table 1
For negative electrode active material use.
The preferred embodiment of the present invention has been described above in detail, and still, the present invention is not limited thereto.In skill of the invention
In art conception range, can with various simple variants of the technical solution of the present invention are made, including each technical characteristic with it is any its
Its suitable method is combined, and it should also be regarded as the disclosure of the present invention for these simple variants and combination, is belonged to
Protection scope of the present invention.
Claims (13)
1. a kind of Si-C composite material, which is characterized in that the Si-C composite material includes coating simple substance silicon grain by the first carbon-coating
Second carbon-coating of composite particles and several composite particles outer claddings that son is formed；Wherein, second carbon-coating and compound described
There are cavitys between grain.
2. Si-C composite material according to claim 1, wherein the partial size of the simple substance silicon particle is 10-100nm；
Preferably, first carbon-coating with a thickness of 1-5nm；
Preferably, second carbon-coating with a thickness of 20-60nm.
3. Si-C composite material according to claim 1 or 2, wherein in the Si-C composite material, the content of element silicon
For 43-70 weight %, the content of carbon is 30-57 weight %.
4. a kind of preparation method of Si-C composite material, which is characterized in that this method comprises:
(1) under an inert atmosphere, silicon-containing material and magnesium metal are subjected to magnesium thermit, convert element silicon to the shape of magnesium silicide
Formula；
(2) in carbon dioxide atmosphere, the product of the magnesium thermit is subjected to calcination process；
(3) product of the calcination process is subjected to pickling；
Wherein, the temperature of the magnesium thermit is 500-850 DEG C, and the temperature of the calcination process is 700-1000 DEG C.
5. according to the method described in claim 4, wherein, in step (1), element silicon and magnesium metal in the silicon-containing material
Molar ratio is 1:4-8, preferably 1:4-6, more preferably 1:4-4.5.
6. method according to claim 4 or 5, wherein in step (1), the silicon-containing material is silica, silicic acid
One of salt, siliceous mineral and elemental silicon are a variety of；
Preferably, the granularity of the silicon-containing material is 1-50 μm, is preferably 1-30 μm, more preferably 1-20 μm；
Preferably, it is 1-100 μm of magnesium powder that the magnesium metal, which is granularity,.
7. method according to any one of claims 4 to 6, wherein in step (1), the temperature of the magnesium thermit is
500-800 DEG C, preferably 600-750 DEG C, more preferably 650-700 DEG C；
Preferably, the time of the magnesium thermit is 1-10h, preferably 2-8h, more preferably 3-6h.
8. the method according to any one of claim 4-7, wherein in step (1), the product of the magnesium thermit
In, element silicon exists in the form of magnesium silicide, and magnesium elements are deposited in the form of magnesium silicide, optional magnesia and optional magnesium metal
?.
9. the method according to any one of claim 4-8, wherein in step (2), the temperature of the calcination process is
700-900 DEG C, preferably 750-850 DEG C；
Preferably, the time of the calcination process is 0.1-5h, preferably 0.1-3h, more preferably 0.5-2h；
Preferably, the carbon dioxide atmosphere is provided by carbon dioxide content for 99% or more carbon dioxide containing gas.
10. the method according to any one of claim 4-9, wherein the acid solution that the pickling uses for hydrochloric acid,
Concentration is 1-5mol/L；
Preferably, the product relative to the calcination process of 1g, the dosage of the acid solution are 50-100mL.
11. Si-C composite material made from the method as described in any one of claim 4-10.
12. including the cathode of Si-C composite material described in any one of claim 1-3 and 11.
13. including the lithium ion battery of cathode described in claim 12.
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