Carbon coating MoS2The preparation method and application of/silicon compositeTechnical field
The invention belongs to technical field of lithium ion, and in particular to a kind of carbon-coated MoS2The system of/silicon compositePreparation Method and its application in lithium ion battery.
Background technology
Currently, commercial lithium ion battery mainly uses graphite negative electrodes material, however the storage lithium gram volume of this materialIt is low, cannot meet the needs of lithium ion battery with high energy density.It is urgent to develop a kind of negative material with high-energy densityIn the eyebrows and eyelashes.
Molybdenum disulfide is a kind of two-dimentional transient metal sulfide having with graphite-like quasi-lamellar structure.Its interlayer mainly hasWeak van der Waals interaction has the covalent bond effect of molybdenum and sulphur atom in layer.Ontology molybdenum disulfide is received by the molybdenum disulfide of multilayerRice piece is constituted.The structure feature of molybdenum disulfide enables it to the material of main part as storage foreign ion and molecule, such as Li+, Mg2+,Na+, K+Deng.Lemmon etc. reports the MoS of (DOI.10.1021/cm101254j) stripping2Nano material, lithium storage content playUp to 1131mAh/g.
As the silicon materials of the same clan with graphite, there is high specific discharge capacity (4200mAh/g).In addition, silicon is also with lowRemoval lithium embedded voltage platform (be less than 0.5V vs Li+/ Li), and it is its rich reserves, cheap, therefore be that current high-energy is closeSpend the research hot topic of negative material.However, due to the characteristic of its own, silicon materials can be along with larger body in cyclic processProduct expansion and contraction, the stress effect thus brought lead to the active material on electrode and easy to produce between active material to splitLine, active material are easily separated from collector, and it is serious to ultimately cause capacity attenuation.
Invention content
The present invention obtains MoS by being introduced into nano-silicon in the solution containing molybdenum source, using liquid phase reduction2/ silicon is compoundMaterial.During liquid-phase reduction, there is the MoS with graphite-like plate like structure2Be grown in nano silicon material surface, formed byMoS2Nano-silicon (the MoS of nanometer sheet protection2/ silicon) composite material.Then it by chemical vapour deposition technique, obtains carbon-coatedMoS2/ silicon composite.Composite material obtained shows high electrochemical lithium storage content and excellent cycle performance.This methodThe carbon coating MoS of preparation2/ silicon composite has potential application prospect in field of lithium ion battery.
The object of the present invention is to provide a kind of high power capacity and the preparation method of the negative material with excellent cycling performance, toolPreparation process is as follows：
(1) nano-silicon is added in the aqueous solution containing molybdenum source, reducing agent is added, MoS is obtained by Liquid reduction reaction process2/Silicon composite；
(2) carbon coating is carried out to the composite material obtained by step (1), obtains carbon-coated MoS2/ silicon composite.
Further, the molybdenum source described in step (1) is sodium molybdate, ammonium thiomolybdate, phosphomolybdic acid, molybdenum pentachloride, three oxidationsOne or more of molybdenum.
Further, the grain size of the nano-silicon described in step (1) is 50-100nm.If the grain size of silicon is too small, i.e. siliconSpecific surface area is too big, then will increase the contact area of electrolyte and material, in charge and discharge process side reaction increase, reduce batteryCoulombic efficiency for the first time；If the grain size of silicon is too big, although can reduce the contact area of electrolyte and material, lithium ion existsThe path migrated in particle increases, and causes lithium ion diffusion rate relatively slow, is unfavorable for the performance of capacity, therefore, the present inventionSelect the grain size of nano-silicon for 50-100nm.
Further, the molar ratio of the nano-silicon described in step (1) and molybdenum source is 0.01-1:1.
Further, the reducing agent described in step (1) is hydrazine hydrate, thiocarbamide, L-cysteine, thioacetamide, hydrochloric acidThe molar ratio of one or more of azanol, reducing agent and molybdenum source is 3:1-6:1.
Further, the Liquid reduction reaction process temperature described in step (1) is 60-120 DEG C, reaction time 3-15h.
Further, the carbon coating process described in step (2) is one kind in liquid phase coating, chemical vapor deposition cladding,Preferably chemical vapor deposition coats, and the carbon source used in vapor deposition processes is acetylene gas/nitrogen, acetylene gas/argon gas or acetyleneOne or more in gas/helium, temperature of plate are 400-1000 DEG C, and the cladding time is 1-12h.
Chemical vapor deposition coating equipment is relatively easy, and process is few, and carbon structure is controllable, and covered effect is uniform.
Using the preparation process provides a kind of carbon coating MoS2/ silicon composite, carbon coating MoS obtained2/ siliconComposite material is used as the negative electrode active material of lithium ion battery.
Beneficial effects of the present invention are as follows：
(a) raw material that the present invention uses is simple and easy to get, and preparation method is simple, low for equipment requirements, using chemical vapor depositionArea method has obtained uniform cladding carbon-coating；
(b) present invention forms MoS during liquid-phase reduction in nanometer silicon face2The protective layer of nanometer sheet composition, thenUsing chemical vapor deposition method in MoS2/ silicon composite surface coats amorphous carbon layer, and covered effect is uniform.Amorphous carbonLayer can not only improve MoS2The electric conductivity of/silicon composite, moreover it is possible to as protection medium, further buffer nano Si material and fillVolumetric expansion in discharge process.The carbon coating MoS being prepared2/ silicon composite combines MoS2, silicon and amorphousThe advantages of carbon, shows high power capacity and excellent cycle performance.
Description of the drawings
Fig. 1 is protected using circulation volume when composite material is as lithium ion battery negative pole active materials made from embodiment 5Holdup and cycle-index relational graph.
Specific implementation mode
To make those skilled in the art more fully understand technical scheme of the present invention, With reference to embodiment to thisInvention is described in further detail.
Embodiment 1
12g sodium molybdates are dissolved under conditions of ultrasonic agitation in 120ml deionized waters, 0.7g grain sizes are then slowly added intoFor the nano-silicon of 100nm, continuously adds 24.2g biomolecule L-cysteines and shift acquired solution after it is completely dissolvedInto the round-bottomed flask of 250ml, under stirring conditions in 80 DEG C of back flow reaction 12h.The product for collecting gained, after vacuum dryingObtain MoS2/ silicon composite.The MoS that will be obtained2/ silicon composite is put in tube furnace, is passed through nitrogen as protectiveness gasBody, gas flow rate is 200 ml/mins, and after being warming up to 800 DEG C, it is 1 to be passed through volume ratio:10 acetylene/nitrogen mixed gas is madeFor carbon-coated carbon source, flow control is 50 ml/mins, and the control cladding time is 6h at 800 DEG C.After deposition, obtainTo carbon-coated MoS2/ silicon composite.
Embodiment 2
12g sodium molybdates are dissolved under conditions of ultrasonic agitation in 120ml deionized waters, are then slowly added into 0.84gDiameter is the nano-silicon of 80nm, continuously adds 15g thioacetamides, after it is completely dissolved, acquired solution is transferred to 250ml'sIn round-bottomed flask, under stirring conditions in 80 DEG C of back flow reaction 12h.The product for collecting gained, MoS is obtained after vacuum drying2/Silicon composite.The MoS that will be obtained2/ silicon composite is put in tube furnace, is passed through nitrogen as protective gas, gas streamSpeed is 200 ml/mins, and after being warming up to 800 DEG C, it is 1 to be passed through volume ratio:10 acetylene/nitrogen mixed gas is as carbon coatingCarbon source, flow control be 50 ml/mins, at 800 DEG C control cladding the time be 6h.After deposition, carbon coating is obtainedMoS2/ silicon composite.
Embodiment 3
13g ammonium thiomolybdates are dissolved under conditions of ultrasonic agitation in 120ml deionized waters, are then slowly added into1.12g grain sizes are the nano-silicon of 80nm, continuously add 10g hydrazine hydrates, acquired solution is transferred in the round-bottomed flask of 250ml,Under stirring conditions in 80 DEG C of back flow reaction 8h.The product for collecting gained, MoS is obtained after vacuum drying2/ silicon composite.The MoS that will be obtained2/ silicon composite is put in tube furnace, is passed through nitrogen as protective gas, and gas flow rate is 200 milliliters/Minute, after being warming up to 700 DEG C, it is 1 to be passed through volume ratio:10 acetylene/nitrogen mixed gas is as carbon-coated carbon source, flow control50 ml/mins are made as, the control cladding time 9h at 700 DEG C.After deposition, carbon-coated MoS is obtained2/ silicon composite woodMaterial.
Embodiment 4
7.2g molybdenum trioxides are dissolved under conditions of ultrasonic agitation in 120ml deionized waters, 1.4g is then slowly added intoGrain size is the nano-silicon of 60nm, continuously adds 15.2g thiocarbamides, acquired solution is transferred in the round-bottomed flask of 250ml, stirringUnder conditions of in 100 DEG C of back flow reaction 10h.The product for collecting gained, MoS is obtained after vacuum drying2/ silicon composite.WillThe MoS arrived2/ silicon composite is put in tube furnace, is passed through nitrogen as protective gas, gas flow rate is 200 ml/minsClock, after being warming up to 900 DEG C, it is 1 to be passed through volume ratio:10 acetylene/nitrogen mixed gas is as carbon-coated carbon source, flow controlFor 50 ml/mins, the control cladding time 4h at 900 DEG C.After deposition, carbon-coated MoS is obtained2/ silicon composite.
Embodiment 5
12g sodium molybdates are dissolved under conditions of ultrasonic agitation in 120ml deionized waters, 1.4g grain sizes are then slowly added intoFor the nano-silicon of 100nm, 15.2g thiocarbamides are continuously added, acquired solution is transferred in the round-bottomed flask of 250ml, in stirringUnder the conditions of in 90 DEG C of back flow reaction 8h.The product for collecting gained, MoS is obtained after vacuum drying2/ silicon composite.By what is obtainedMoS2/ silicon composite is put in tube furnace, is passed through nitrogen as protective gas, gas flow rate is 200 ml/mins, is risenTemperature is 1 to volume ratio after 800 DEG C, is passed through:10 acetylene/nitrogen mixed gas is as carbon-coated carbon source, flow control 50Ml/min, the control cladding time 8h at 800 DEG C.After deposition, carbon-coated MoS is obtained2/ silicon composite.
Fig. 1 is protected using circulation volume when composite material is as lithium ion battery negative pole active materials made from embodiment 5Holdup and cycle-index relational graph.The data of Fig. 1 show using negative material made from embodiment 5 as negative electrode of lithium ion battery and liveProperty substance when good cycling stability, 100 times cycle after capacity retention ratio still be up to 91.8%.Excellent stability is attributed to SiMaterial surface forms MoS2The protective layer of nanometer sheet composition and the agraphitic carbon of cladding, have effectively buffered silicon materials in charge and dischargeThe Volumetric expansion generated in the process improves the cyclical stability of battery.
Embodiment 6
13g ammonium thiomolybdates are dissolved under conditions of ultrasonic agitation in 120ml deionized waters, are then slowly added into1.12g grain sizes are the nano-silicon of 80nm, continuously add 13.9g thiocarbamides, acquired solution is transferred in the round-bottomed flask of 250ml,Under stirring conditions in 80 DEG C of back flow reaction 8h.The product for collecting gained, MoS is obtained after vacuum drying2/ silicon composite.The MoS that will be obtained2/ silicon composite is put in tube furnace, is passed through nitrogen as protective gas, and gas flow rate is 200 milliliters/Minute, after being warming up to 800 DEG C, it is 1 to be passed through volume ratio:10 acetylene/nitrogen mixed gas is as carbon-coated carbon source, flow controlIt is made as 50 milliliters/min, the control cladding time 6h at 800 DEG C.After deposition, carbon-coated MoS is obtained2/ silicon composite woodMaterial.
Comparative example 1
12g sodium molybdates are dissolved under conditions of ultrasonic agitation in 120ml deionized waters, 0.7g grain sizes are then slowly added intoFor the nano-silicon of 100nm, continuously adds 24.2g biomolecule L-cysteines and shift acquired solution after it is completely dissolvedInto the round-bottomed flask of 250ml, under stirring conditions in 80 DEG C of back flow reaction 12h.The product for collecting gained, after vacuum dryingObtain MoS2/ silicon composite.
Comparative example 2
13g ammonium thiomolybdates are dissolved under conditions of ultrasonic agitation in 120ml deionized waters, then proceed to that 10g is addedAcquired solution is transferred in the round-bottomed flask of 250ml by hydrazine hydrate, under stirring conditions in 80 DEG C of back flow reaction 8h.It collectsThe product of gained obtains a nanometer MoS after vacuum drying2Material.The nanometer MoS that will be obtained2Material is put in tube furnace, is passed through nitrogenFor gas as protective gas, gas flow rate is 200 ml/mins, and after being warming up to 700 DEG C, it is 1 to be passed through volume ratio:10 acetylene/Nitrogen mixed gas is 50 ml/mins as carbon-coated carbon source, flow control, the control cladding time 9h at 700 DEG C.It is heavyAfter product, carbon-coated nanometer MoS is obtained2Material.
Comparative example 3
13g ammonium thiomolybdates are dissolved under conditions of ultrasonic agitation in 120ml absolute ethyl alcohols, are then slowly added into1.12g grain sizes are the nano-silicon of 80nm, continuously add 13.9g thiocarbamides, dry under room temperature until solution volatilizees completely.Collect instituteThe product obtained, is put in tube furnace, is passed through nitrogen as protective gas, gas flow rate is 200 ml/mins, is warming up to 800After DEG C, it is 1 to be passed through volume ratio:10 acetylene/nitrogen mixed gas as carbon-coated carbon source, flow control is 50 milliliters/Min, the control cladding time 6h at 800 DEG C.It is combined by thermal reduction and chemical deposition and obtains carbon-coated MoS2/ silicon composite woodMaterial.
It is prepared by negative plate：Slurry is prepared by stirring, then automatic film applicator is used to be coated on copper foil, is done at 80 DEG CIt is dry to form.Slurry solvent is deionized water, and conductive agent is acetylene black, and binder is sodium carboxymethylcellulose, prepared by the present inventionComposite negative pole material is 8 as the weight ratio control of active material, conductive agent, binder:1:1, copper thickness is 10 μm.DryingPole piece first through twin rollers (pressure 15MPa) roll-in, then cut into the sequin of a diameter of 16mm.
Button cell assembles：Using metal lithium sheet as cathode, electrolyte is the EC/DMC (v/v=1/ of the LiPF6 containing 1.0M1) electrolyte, diaphragm use polyethylene diagrams, by anode cover, positive plate, diaphragm, lithium piece, nickel foam, stainless steel in glove boxGasket, negative plate sequence be assembled into button cell.
Battery testing：Using the chemical property of Wuhan indigo plant electrical testing system thinking button cell, charge-discharge magnification is0.1C, charge voltage range 5mV-3.0V.The button prepared as negative material by the composite material of each embodiment and comparative exampleThe charge-discharge performance of formula battery the results are shown in Table 1.
Table 1, embodiment and comparative example buckle electrical test results compared with
1 data result of table shows：The carbon-coated MoS prepared using the method for the present invention2/ silicon composite is due in nanometerSilicon face forms MoS2The protective layer of nanometer sheet composition, then uses chemical vapor deposition method in MoS2/ silicon composite surfaceAmorphous carbon layer is coated, MoS can not only be improved2The electric conductivity of/silicon composite, moreover it is possible to as protection medium, further bufferVolumetric expansion of the nano Si material in charge and discharge process.Pass through carbon coating compared to comparative example, without addingThe composite material for entering silicon materials and thermal reduction and chemical vapor deposition being combined to be prepared, the carbon packet that embodiment is preparedCover MoS2/ silicon composite combines MoS2, silicon and the advantages of amorphous carbon, show high power capacity, high coulombic efficiency for the first time and excellentDifferent cycle performance.The liquid phase reduction reaction condition that the present invention uses is mild, simple for process, and preparing on a large scale, silicon substrate is compoundMaterial Field has potential application prospect.