Si-C composite material with nanometer micropore gap and preparation method thereof and purposes
Technical field
The present invention relates to nano composite material, a kind of Si-C composite material with nanometer micropore gap and preparation method thereof with
Purposes.
Background technology
Lithium ion battery negative material is generally material with carbon element, such as graphite, needle coke, carbonaceous mesophase spherules, carbon fiber, nano-sized carbon
Fibers etc., the theoretical reversible lithium storage specific capacity having been commercialized application graphite cathode material at present is 372mAh/g.Improve lithium ion
The capacity of battery, depends primarily on the embedding lithium ability of negative material, and the research and development of high-capacity cathode material have become raising lithium
The key of ion battery performance.The theoretical lithium storage content of silicon (Si) material is 4200mAh/g, is a kind of to improve capacity of negative plates
Ideal material.But, the volumetric expansion in process of intercalation of the Si material, up to 300%, will cause destruction and the machine of material structure
Tool is pulverized so that separate between conductive network with silicon particle.The poorly conductive of silicon materials, first charge-discharge efficiency is low, energy
Amount decay is fast, cycle performance extreme difference, is such materials application in high specific energy lithium ion battery key scientific problems urgently to be resolved hurrily.
In order to alleviate alloy material volumetric expansion in charging process, improve its cyclical stability, prepare the silicon grain of nanoscale,
Or carbon/silicon nano composite material is relatively effective method.
Jung etc. use silane cracking prepare 50nm amorphous silicon film, its first capacity up to more than 3000mAh/g, but
After circulating at 20 times, capacity rapid attenuation to 400mAh/g [H.Jung, M.Park, Y.Yoon, et al.Journal of Power
Sources,2003,115:346.].Bourderau uses CVD to be prepared for the Si thin film of 1.2 μm, finds that capacity can first
Reach 1000mAh/g, but after circulating 20 times, capacity decays to the most rapidly about 200mAh/g [S.Bourderau, T.Brousse.
Journal of Power Sources,1999,81:233.].Cui, while preparation Si nano wire, introduces nucleocapsid structure, core
For the Si line that crystal formation is good, play constitutionally stable left and right;Shell is one layer of unformed Si film, play capacity storage effect [L.Cui,
Y.Cui.Nano Letters,2009,9:491.]。
Silicon and carbon are combined and are used for preparing negative material, study hotspot the most in recent years.Researchers be investigated Si and graphite,
Carbonaceous mesophase spherules, CNT, Graphene, many empty carbon, amorphous carbon, carbon aerogels etc. composite at lithium-ion electric
Application in terms of the negative material of pond.Electrostatic spinning technique is the effective ways preparing nanofiber, the polymer precursor of electrospinning carbon,
After oxidation carbonization, the carbon nano-fiber with unique microstructures can be prepared, such as loose structure, hollow structure, embedding nanometer
Grain, nucleocapsid structure, surface abnormity etc. [M.Inagani, Y.Yang, F.Kang.Advanced Materials, 2012,24:2547.].
Polyacrylonitrile (PAN) solution mixing nano-silicon particle is carried out electrostatic spinning by Li etc., after oxidation carbonization, obtains silicon grain embedding
Enter the carbon nano-fiber in carbon base body, and using this as the negative material for lithium ion battery, first capacity up to 1000mAh/g,
After 50 circulations, capacity attenuation to below 700mAh/g, it is primarily due in carbon base body not reserve buffering to the expansion of silicon
Space, limits the raising of material circulation performance;And silicon particle there occurs significantly reunion, substantial amounts of silicon particle is exposed to be received
On the surface of rice carbon fiber [Y.Li, B.Guo, L.Ji, et al.Carbon, 2013,51:185.].Patent CN102623680A is open
A kind of silicon-carbon composite cathode material with three-dimensional preformed hole structure and preparation method thereof, in carbon base body, utilizes silicon dioxide
For template coated Si particle, finally with Fluohydric acid., silicon dioxide is etched away, thus obtains the reserved gap structure on silicon grain surface,
Material reversible capacity first can reach 1190mAh/g, and coulombic efficiency is 78.2%, and circulating the reversible capacity after 100 times is 1056
MAh/g, capability retention is 88.7%.But in this patent, owing to reserved hole is by being formed after etching silicon dioxide,
After silicon dioxide etches away, silicon particle is integrally located in hole thus cannot be fully contacted with carbon base body and (only cause because of gravity
Point cantact), thus cause its electronic transmission performance poor.
Summary of the invention
The technical problem to be solved is to provide a kind of Si-C composite material with nanometer micropore gap for nano-silicon
While cushion space is reserved in the expansion of grain, it is ensured that the electron transport ability that material is overall.
The present invention also provides for preparation method and its purposes in prepared by ion cathode material lithium of above-mentioned composite.
Think after inventor herein's research: all silicon that can not be fully solved of Si-C composite material are in charge and discharge process at present
Expansion issues, it is critical only that carbon base body therein the most really plays the effect of rock-steady structure;Most researchs are only by the cladding work of carbon
With, suppress the swelling stress of silicon;And provide sufficient cushion space to the expansion of silicon.After discharge and recharge repeatedly, carbon
Finally there is destroying of self structure due to the swelling stress by silicon in matrix, thus reduce the protective effect to silicon and self
Chemical property.Therefore, research has the silicon-carbon nano composite material of the volumetric expansion offer cushion space for silicon, to silica-based
The development of negative material high-capacity lithium ion cell has the biggest impetus.This patent non-solvent based on polymer solution
Induction is separated theory, uses the electrostatic spinning technique PAN(polyacrylonitrile to dopen Nano silicon grain) solution carries out Static Spinning
Silk molding, dynamic analysis of spinning carries out double diffusion between solvent-coagulator and curing molding in coagulating bath, controls curing condition, is had
There is the as-spun fibre of multi-pore structure;Nascent nanofiber is oxidized, after carbonization, obtain internal containing abundant nanometer micropore, receive
Rice silicon embeds the carbon nano-fiber in carbon base body, and is used as the negative material of lithium ion battery.
Specifically, the present invention is by the techniques below means above-mentioned technical problem of solution:
As it is shown in figure 1, a kind of Si-C composite material with nanometer micropore gap structure, including silicon nanoparticle and carbon nano-fiber
Matrix, described silicon nanoparticle is dispersed in described carbon nano-fiber matrix, nano-pore is distributed in described carbon nano-fiber matrix
Hole and the micropore connecting described nano aperture.
Preferably: in described carbon nano-fiber matrix, the average diameter of carbon nano-fiber is 100-600nm, described silicon nanoparticle
Average diameter be 10-60nm.
Preferably: the mass fraction of described silicon particle is 3-67%, the mass fraction of described carbon nano-fiber matrix is 33-97%.
If it is not notable that the content of silicon particle improves effect less than the storage lithium ability of 3% pair of material, then can cause aforementioned if greater than 67%
Structure formation distribution in the material is not ideal enough.
Compared with prior art, the present invention passes through the induced curing molding of non-solvent, electrospinning fibre is carried out pore-creating, finally gives many
Hole nanometer composite Si-C fiber.Silicon is encapsulated in porous filamentous nanocarbon by the Si-C composite material of the present invention, and the embedding of silicon carries
The high overall storage lithium ability of material, carbon base body can help silicon grain to carry out electric charge transmission, the hole in carbon nano-fiber matrix
Can either effectively accommodate silicon volumetric expansion in charge and discharge process with micro hole structure, described micropore is also ion, electric charge
Transmission provides passage easily.The advantage of both silicon-carbons is combined by this composite, and restrained effectively lacking of the two
Point, thus improve the chemical property of material.
The present invention also provides for the preparation method of a kind of Si-C composite material with nanovoids structure, comprises the following steps:
S1, the configuration polyacrylonitrile spinning solution containing silicon nanoparticle;
S2, polyacrylonitrile spinning solution step S1 obtained load in syringe, carry out electrostatic spinning after the match at high-pressure electrostatic,
Dynamic analysis of spinning in atmosphere through 2-10cm spin journey after enter solidified forming in liquid coagulating bath to obtain nascent polyacrylonitrile nano fine
Dimension, nascent polyacrylonitrile nanofiber is placed 1-3h in liquid coagulating bath, is then carried out vacuum drying and obtain polypropylene nano fibre
Dimension, wherein, the voltage of described high-voltage electrostatic field is 5-30kV, and spinning liquid flow is 0.1-1.0mL/h;
S3, step S2 is obtained polyacrylonitrile nanofiber carry out oxidation processes and obtain nanofiber oxide;
S4, described nanofiber oxide is carried out carbonization form described Si-C composite material.
Preferably, described step S1 includes: polyacrylonitrile powder adds stirring and dissolving in organic solvent, is subsequently adding nano-silicon
Granule continues stirring more than 24h, and ultrasound wave dispersion more than 1h, obtains the described polyacrylonitrile spinning containing silicon nanoparticle
Solution.
Preferably, described step S2 includes:
Preferably, described step S3 includes: described oxidation processes is carried out in atmosphere, controls oxidizing temperature with 1-10 DEG C/min
Programming rate be progressively warming up to 250-300 DEG C from room temperature, and after constant temperature 1-3h take out obtain described nanofiber oxide.
Preferably, described carbonization is carried out in high temperature carbonization furnace, in argon gas atmosphere, with the programming rate of 1-20 DEG C/min from room
Temperature is progressively warming up to 600-1500 DEG C, and constant temperature 1-3h, takes out and obtain described Si-C composite material after being cooled to room temperature.
Preferably, the solvent of described polyacrylonitrile spinning solution is dimethylformamide.
Preferably, in the dimethyl formamide solution of described polyacrylonitrile, the mass fraction of polyacrylonitrile is 6-15wt%, nano-silicon
Granule is 1:50-1:1 with the mass ratio of polyacrylonitrile.
Compared with prior art, the method for the present invention carries out electrostatic spinning one-tenth to mixing the polyacrylonitrile mixed liquor having silicon nanoparticle
Type, dynamic analysis of spinning because occurring non-solvent induction to be separated and curing molding, forms PAN-Si nanometer as-spun fibre in solidification.?
In solidification process, fibrocortex is first solidifying, and solvent progressively to external diffusion, forms substantial amounts of hole at fibrous inside from fibrous inside
Hole structure.Through subsequent oxidation, carbonisation, PAN gradually forms the network structure of carbon, and silicon nanoparticle is covered by carbon base body
In, big pore space structure is retained in carbon base body, simultaneously because non-carbon cracks removing with the form of gas molecules,
Form the micro hole structure being interconnected in carbon base body, finally give the silicon-carbon nano composite material with built-in multi-pore structure.
Preparation technology of the present invention is simple, raw material sources extensive, and prepared silicon-carbon nano composite material is used for lithium ion battery negative material
Time physical dimension is stable, reversible specific capacity high, cycle performance is excellent, and.
The Si-C composite material with nanometer micropore gap structure described in aforementioned any one is in preparing lithium ion battery negative material
Application, it is possible to increase negative material reversible capacity in charge and discharge process and cyclical stability.
Accompanying drawing explanation
Fig. 1 is the structural representation of the Si-C composite material of the specific embodiment of the invention 1.
Detailed description of the invention
Below against accompanying drawing and combine preferred embodiment the invention will be further described.
A kind of Si-C composite material with nanometer micropore gap structure, including silicon nanoparticle and carbon nano-fiber matrix, described in receive
Rice silicon grain is dispersed in described carbon nano-fiber matrix, nano aperture is distributed and described in connecting in described carbon nano-fiber matrix
The micropore of nano aperture.In carbon nano-fiber matrix, the average diameter of carbon nano-fiber is 100-600nm, described silicon particle
Average diameter is 10-60nm.The mass content of described silicon nanoparticle is 3-67%, and the quality of described carbon nano-fiber matrix contains
Amount is 33-97%, and the aperture of described nano aperture is preferably 50-100nm, and the aperture of described micropore is preferably smaller than 10nm.
Above-mentioned Si-C composite material can be prepared by following method:
Silicon nanoparticle and polyacrylonitrile are dissolved in solvent and are prepared as blend spinning liquid, then blend spinning liquid is carried out Static Spinning
Silk, dynamic analysis of spinning curing molding in coagulating bath obtains many spaces PAN-Si nano-composite fiber;Carry out oxidation processes the most successively
And carbonization treatment, obtain the aforementioned Si-C composite material with nanometer micropore gap structure.Wherein, the voltage of electric field of electrostatic spinning is excellent
Electing 5-30kV as, the flow velocity of spinning liquid is preferably 0.1-1.0Ml/h, it is preferred to use molecular weight MwPAN for 15-20 ten thousand makees
For carbon source, in polyacrylonitrile solution, the mass fraction of polyacrylonitrile is preferably the matter of 6-15wt%, silicon nanoparticle and polyacrylonitrile
Amount ratio preferably 1:50 1:1.Oxidation processes is carried out the most in atmosphere, controls the oxidizing temperature intensification speed with 1-10 DEG C/min
Degree is progressively warming up to 250-300 DEG C from room temperature, and after constant temperature 1-3h, taking-up obtains described nanofiber oxide.Carbonization treatment is excellent
It is selected in high temperature carbonization furnace and carries out, in argon gas atmosphere, be progressively warming up to 600-1500 from room temperature with the programming rate of 1-20 DEG C/min
DEG C, and constant temperature 1-3h, take out after being cooled to room temperature and obtain described Si-C composite material.
Below in conjunction with more specific embodiment, technical scheme is explained:
Comparative example 1
The first step: the preparation of spinning liquid.Weigh 9g molecular weight MwThe PAN powder of=150000, adds the DMF to 96mL
In, stir 24h at 65 DEG C and dissolve, the PAN-DMF solution of preparation mass fraction 9%;Weighing 2.25g mean diameter is
The nano-silicon particle of 20-40nm adds to the DMF solution of PAN, continues stirring 24h, and ultrasonic disperse 1h at 65 DEG C,
Obtain Si homodisperse mixed liquor in the DMF solution of PAN.
Second step: the PAN nanofiber of electrostatic spinning preparation doping Si.The mixed solution first step prepared loads syringe
In, with the flow of 0.3mL/h, spinning liquid to be extruded, electrostatic spinning under the high voltage electric field of 18kV, spinning head is to receptor
Distance is 15cm, and dynamic analysis of spinning desolvation curing molding in atmosphere, as-spun fibre is collected on aluminium foil, obtains
PAN-Si composite nano fiber.
3rd step: the oxidation processes of nascent nanofiber.Second step obtains nanofiber carry out in the oxidation furnace of temperature programmed control
Oxidation processes, oxidizing atmosphere is air, with the programming rate of 5 DEG C/min from room temperature to 200 DEG C, then with 2 DEG C/min liter
Temperature, to 270 DEG C, is taken out after constant temperature 1h, prepares to process for high temperature cabonization.
4th step: the carbonization of nanofiber oxide and the formation of nano-silicone wire/carbon composite material.Through snperoxiaized nanofiber at height
Temperature carbide furnace carries out carbonization treatment, under high-purity argon gas (purity > 99.999%) protection, with the programming rate of 10 DEG C/min
800 DEG C progressively it are warming up to from room temperature, and constant temperature 1h, take out sample after being cooled to room temperature, obtain silicon-carbon nano-composite fiber.
5th step: the preparation of silicon-carbon nano composite anode material and electrochemical property test.According to silicon-carbon nano composite material, lead
Electrical carbon is black, the mass ratio of binding agent Kynoar (PVDF) three is that 80:10:10 mix homogeneously makes electrode slice, with metal
Lithium sheet is as to electrode and reference electrode, and Clegard2500 makees barrier film, and electrolyte is the ethylene carbonate (EC) of 1mol/L LiPF6
+ diethyl carbonate (DMC) solution (volume ratio of EC Yu DMC is 1:1), assembles in the glove box of full high-purity argon gas
Become 2032 type button cells.Utilize Land battery test system that above-mentioned half-cell at room temperature carries out constant current charge-discharge performance
Test, charge-discharge magnification is 100mA/g, and charging/discharging voltage scope is 0.01-3.0V.
Obtaining silicon-carbon composite Nano negative material reversible capacity first by above-mentioned steps operation is 1074mAh/g, and coulombic efficiency is 77
%, circulating the reversible capacity after 50 times is 698mAh/g, and capability retention is 65%.
Comparative example 2
The first step: the preparation of spinning liquid.Weigh 9g molecular weight MwThe PAN powder of=150000, adds the DMF to 96mL
In, stir 24h at 65 DEG C and dissolve, the PAN-DMF solution of preparation mass fraction 9%;Weighing 0.47g mean diameter is
The nano-silicon particle of 20-40nm adds to the DMF solution of PAN, continues stirring 24h, and ultrasonic disperse 1h at 65 DEG C,
Obtain Si homodisperse mixed liquor in the DMF solution of PAN.
Second step: the PAN nanofiber of electrostatic spinning preparation doping Si.Spinning condition is identical with the second step in comparative example 1.
3rd step: the oxidation processes of nascent nanofiber.Oxidation processes condition is identical with the 3rd step in comparative example 1.
4th step: the carbonization of nanofiber oxide and the formation of nano-silicone wire/carbon composite material.Carbonization Conditions and comparative example 1 the
Four steps are identical.
5th step: the preparation of silicon-carbon nano composite anode material and electrochemical property test.Material preparation with method of testing with compare
The 5th step in example 1 is identical.
Obtaining silicon-carbon composite Nano negative material reversible capacity first by above-mentioned steps operation is 605mAh/g, and coulombic efficiency is 83
%, circulating the reversible capacity after 50 times is 466mAh/g, and capability retention is 77%.
Comparative example 3
The first step: the preparation of spinning liquid.Weigh 9g molecular weight MwThe PAN powder of=150000, adds the DMF to 96mL
In, stir 24h at 65 DEG C and dissolve, the PAN-DMF solution of preparation mass fraction 9%;Weighing 6.0g mean diameter is 20-40
The nano-silicon particle of nm adds to the DMF solution of PAN, continues stirring 24h, and ultrasonic disperse 1h, obtain at 65 DEG C
Si is homodisperse mixed liquor in the DMF solution of PAN.
Second step: the PAN nanofiber of electrostatic spinning preparation doping Si.Spinning condition is identical with the second step in comparative example 1.
3rd step: the oxidation processes of nascent nanofiber.Oxidation processes condition is identical with the 3rd step in comparative example 1.
4th step: the carbonization of nanofiber oxide and the formation of nano-silicone wire/carbon composite material.Carbonization Conditions and comparative example 1 the
Four steps are identical.
5th step: the preparation of silicon-carbon nano composite anode material and electrochemical property test.Material preparation with method of testing with compare
The 5th step in example 1 is identical.
Obtaining silicon-carbon composite Nano negative material reversible capacity first by above-mentioned steps operation is 1463mAh/g, and coulombic efficiency is 67
%, circulating the reversible capacity after 50 times is 717mAh/g, and capability retention is 49%.
Embodiment 1
Compare with comparative example 1.
The first step: the preparation of spinning liquid.The preparation method of spinning liquid is identical with the first step in comparative example 1 with condition, obtains Si
Homodisperse mixed liquor in the DMF solution of PAN.
Second step: the PAN nanofiber of electrostatic spinning preparation doping Si.The mixed solution first step prepared loads syringe
In, with the flow of 0.3mL/h, spinning liquid to be extruded, electrostatic spinning under the high voltage electric field of 18kV, spinning liquid is through a segment distance
Air after, enter curing molding in coagulating bath.Air section distance between spinning head and coagulating bath is 3cm, and coagulating bath is normal
Tepidarium, setting time is 2h, and as-spun fibre is vacuum dried 12h at 60 DEG C, obtains concrete dynamic modulus PAN-Si composite Nano fine
Dimension.
3rd step: the oxidation processes of nascent nanofiber.Oxidation processes condition is identical with the 3rd step in embodiment 1.
4th step: the carbonization of nanofiber oxide and the formation of nano-silicone wire/carbon composite material.Carbonization Conditions and comparative example 1 the
Four steps are identical.As it is shown in figure 1, obtain having abundant micro hole structure, with carbon nano-fiber 100 as matrix, nano-silicon
The nano-silicone wire/carbon composite material that granule 200 is embedded, is distributed nano aperture 300 and the phase of 50-100nm in this material
The micropore 400 less than 10nm, the intercommunicated aperture.
5th step: the preparation of silicon-carbon nano composite anode material and electrochemical property test.Material preparation with method of testing with compare
The 5th step in example 1 is identical.
Obtaining silicon-carbon composite Nano negative material reversible capacity first by above-mentioned steps operation is 1124mAh/g, and coulombic efficiency is 81
%, circulating the reversible capacity after 50 times is 934mAh/g, and capability retention is 83%.
Embodiment 2
Compare with comparative example 1.
The first step: the preparation of spinning liquid.The preparation method of spinning liquid is identical with the first step in embodiment 1 with condition, obtains Si
Homodisperse mixed liquor in the DMF solution of PAN.
Second step: the PAN nanofiber of electrostatic spinning preparation doping Si and PVC.The mixed solution first step prepared loads
In syringe, being extruded by spinning liquid with the flow of 0.3mL/h, electrostatic spinning under the high voltage electric field of 18kV, spinning liquid is through one
After the air of segment distance, enter curing molding in coagulating bath.Air section distance between spinning head and coagulating bath is 3cm, solidification
Bath is room temperature dehydrated alcohol, and setting time is 2h, and as-spun fibre is vacuum dried 12h at 60 DEG C, obtains concrete dynamic modulus PAN-Si
Composite nano fiber.
3rd step: the oxidation processes of nascent nanofiber.Oxidation processes condition is identical with the 3rd step in embodiment 1.
4th step: the carbonization of nanofiber oxide and the formation of nano-silicone wire/carbon composite material.Carbonization treatment condition and embodiment 1
In the 4th step identical.
5th step: the preparation of silicon-carbon nano composite anode material and electrochemical property test.Material preparation and method of testing and enforcement
The 5th step in example 1 is identical.
Obtaining silicon-carbon composite Nano negative material reversible capacity first by above-mentioned steps operation is 1166mAh/g, and coulombic efficiency is 84
%, circulating the reversible capacity after 50 times is 991mAh/g, and capability retention is 85%.
Embodiment 3
Compare with comparative example 2.
The first step: the preparation of spinning liquid.The preparation method of spinning liquid is identical with the first step in comparative example 2 with condition.
Second step: the PAN nanofiber of electrostatic spinning preparation doping Si.Spinning condition is identical with the second step in embodiment 1.
3rd step: the oxidation processes of nascent nanofiber.Oxidation processes condition is identical with the 3rd step in comparative example 2.
4th step: the carbonization of nanofiber oxide and the formation of nano-silicone wire/carbon composite material.Carbonization Conditions and comparative example 2 the
Four steps are identical.
5th step: the preparation of silicon-carbon nano composite anode material and electrochemical property test.Material preparation with method of testing with compare
The 5th step in example 2 is identical.
Obtaining silicon-carbon composite Nano negative material reversible capacity first by above-mentioned steps operation is 625mAh/g, and coulombic efficiency is 86
%, circulating the reversible capacity after 50 times is 546mAh/g, and capability retention is 87%.
Embodiment 4
Compare with comparative example 3.
The first step: the preparation of spinning liquid.The preparation method of spinning liquid is identical with the first step in comparative example 3 with condition.
Second step: the PAN nanofiber of electrostatic spinning preparation doping Si.Spinning condition is identical with the second step in embodiment 2.
3rd step: the oxidation processes of nascent nanofiber.Oxidation processes condition is identical with the 3rd step in comparative example 3.
4th step: the carbonization of nanofiber oxide and the formation of nano-silicone wire/carbon composite material.Carbonization Conditions and comparative example 3 the
Four steps are identical.
5th step: the preparation of silicon-carbon nano composite anode material and electrochemical property test.Material preparation with method of testing with compare
The 5th step in example 3 is identical.
Obtaining silicon-carbon composite Nano negative material reversible capacity first by above-mentioned steps operation is 625mAh/g, and coulombic efficiency is 86
%, circulating the reversible capacity after 50 times is 546mAh/g, and capability retention is 87%.
Obtaining silicon-carbon composite Nano negative material reversible capacity first by above-mentioned steps operation is 1638mAh/g, and coulombic efficiency is 75
%, circulating the reversible capacity after 50 times is 1113mAh/g, and capability retention is 68%.
Above content is to combine concrete preferred implementation further description made for the present invention, it is impossible to assert the present invention
Be embodied as be confined to these explanations.For those skilled in the art, without departing from the present invention
On the premise of design, it is also possible to make some equivalents and substitute or obvious modification, and performance or purposes are identical, all should be considered as belonging to
In protection scope of the present invention.