CN103715399A

CN103715399A - Electrode composite material and preparation method thereof, positive electrode, and battery having positive electrode

Info

Publication number: CN103715399A
Application number: CN201310436893.XA
Authority: CN
Inventors: 陈璞; 张永光; 李晶
Original assignee: Positec Power Tools Suzhou Co Ltd
Current assignee: Positec Power Tools Suzhou Co Ltd
Priority date: 2012-09-29
Filing date: 2013-09-23
Publication date: 2014-04-09
Also published as: WO2014048390A1

Abstract

The present invention relates to an electrode composite material, which contains elemental sulfur, a conductive polymer and graphene or a reduced graphene oxide, and has a layered structure, wherein the graphene or the reduced graphene oxide adopted as a substrate provides an effective electron conduction network and a stable structure for the electrode composite material, such that the electrode composite material has characteristics of good cycle life, good rate performance and high discharge capacity. The present invention further discloses a preparation method for the electrode composite material, a positive electrode applying the electrode composite material, and a battery having the positive electrode.

Description

Electrode composite material and preparation method thereof, positive pole, there is this anodal battery

Technical field

The present invention relates to a kind of electrode composite material.

The invention still further relates to a kind of preparation method of electrode composite material.

The invention still further relates to a kind of positive pole with this electrode composite material.

The invention still further relates to a kind of this anodal battery that has.

Background technology

In recent years, along with scientific and technological development, more and more outstanding to the demand of the especially renewable green energy resource of the energy, battery is just being brought into play irreplaceable effect as storage and the conversion equipment of energy.Lithium ion battery, because it has very high specific energy and volumetric specific energy, has attracted to pay close attention to widely.Low cost, high-energy-density, long circulation life, the secondary cell of environmental protection is the emphasis of current lithium ion battery exploitation.

The LiFePO4 of the lithium transition-metal oxide that current commercial positive electrode is mainly stratiform or spinel structure (as cobalt acid lithium, LiMn2O4) and olivine structural etc.Cobalt acid lithium (LiCoO ₂) theoretical capacity relatively large, 275mAh/g, but its price is high, has certain toxicity, and exothermal decomposition reactions easily occurs this positive electrode when overcharging, and not only makes battery capacity obviously decline, and cell safety is also threatened simultaneously; LiMn2O4 (LiMn ₂o ₄) theoretical capacity be 148mAh/g, actual capacity is lower than 130mAh/g, the stability of this positive electrode is bad, easily causes and cause cycle efficieny on the low side by lattice deformability in charge and discharge process; LiFePO4 (LiFePO ₄) theoretical capacity be 172mAh/g, the poorly conductive of this positive electrode, reduces the reversible capacity of battery.Above-mentioned conventional anode material for lithium-ion batteries capacity is generally not high, all has some problems simultaneously yet, can not meet battery development requirement.

The theoretical specific capacity of elemental sulfur is 1675mAh/g, and the theoretical specific energy that is assembled into battery with lithium metal can reach 2600mAh/g, far above commercial positive electrode at present, becomes the main trend of current battery development.The inorganic sulphide of elemental sulfur and sulfur-bearing, organic sulfur compound, poly-organic disulfide, organic polysulfide, poly-sulfo-compound and carbon-sulphur polymer etc. are extensively concerned as the positive electrode of high power capacity, but these materials still exist some problems.

First, the conductivity of elemental sulfur and sulfide itself is very poor, need add a large amount of conductive agents to increase its conductivity; Secondly, elemental sulfur is during as positive electrode active materials, although the Li of the elementary sulfur existing on positive pole while charging completely and existence while discharging completely ₂s is insoluble in polarity organic bath, but part discharges and recharges the anodal many lithium sulfides that exist, is soluble in polarity organic bath, and in addition, the little molecular sulfur compound producing during polymeric organosulfides electric discharge is also soluble in organic bath, affects the cycle performance of battery.Therefore, how improving the conductivity of material, and solve the problems of dissolution that discharges and recharges intermediate product, improve the cycle performance of battery, is the research emphasis of sulfur-bearing positive electrode.

Summary of the invention

The invention provides a kind of high electrode capacity, electrochemical reversibility is good and the electrode composite material of stable circulation.

The invention provides a kind of electrode composite material, the graphene oxide that described electrode composite material contains elemental sulfur, conducting polymer and Graphene or reduction.

Preferably, described conducting polymer is selected from a kind of in polypyrrole and polyacrylonitrile.

Preferably, described electrode composite material has layer structure.

Preferably, described elemental sulfur is attached to described conducting polymer.

Preferably, the graphene oxide of described Graphene or reduction has nanometer laminated structure, and described elemental sulfur and conducting polymer are attached to the graphene oxide of described Graphene or reduction in the lump.

Preferably, in described electrode composite material, the specific gravity range of described elemental sulfur is 30-90%, and the specific gravity range of described conducting polymer is 9-50%, and the specific gravity range of the graphene oxide of described Graphene or reduction is 1-20%.

Preferably, in described electrode composite material, the mass ratio of the graphene oxide of polyacrylonitrile and reduction is 45:1-10:1.

The present invention also provides a kind of positive pole, and described positive pole comprises electrode composite material as above.

The present invention also provides a kind of battery, comprise positive pole, negative pole and be located at positive pole and negative pole between electrolyte, described positive pole at least comprises electrode composite material as above.

The present invention also provides a kind of preparation method of electrode composite material, and described preparation method comprises the steps:

Acrylonitrile, elemental sulfur, Graphene and initator are dissolved in solvent, under preset temperature, stir, after stirring, wash and be dried, dried product is carried out under protective gas atmosphere to heat treated.

Preferably, described when dry temperature range be 60-80 ℃.

Preferably, described heat treated temperature range is 200-400 ℃.

Preferably, described initator is selected from potassium peroxydisulfate and lauryl sodium sulfate.

Preferably, described solvent is selected from least one in water, methyl alcohol, ethanol, 1-METHYLPYRROLIDONE, dimethyl formamide, acetonitrile.

Preferably, described washing is centrifuge washing, and washing agent during described centrifuge washing is water.

Elemental sulfur, polyacrylonitrile and Graphene are dispersed in dispersant, after mechanical mixture, are dried, dried product is carried out under protective gas atmosphere to heat treated.

Preferably, described when dry temperature range be 60-80 ℃.

Preferably, described heat treated temperature range is 200-400 ℃.

Preferably, described dispersant comprises organic solvent, and described organic solvent is selected from least one in methyl alcohol, ethanol, 1-METHYLPYRROLIDONE, dimethyl formamide, acetonitrile.

Preferably, described mechanical mixture is that ball milling mixes.

Preferably, rotating speed during described ball milling is 500-1000rpm, and Ball-milling Time is 3-9h.

Polyacrylonitrile solution is mixed at weak basic condition with the graphite oxide olefinic oxide suspension of reduction, and deposition, disperses after the product of deposition is leached again, by being dried after dispersion and elemental sulfur mechanical mixture, dried product is carried out to heat treated.

Preferably, be that the graphene oxide of described polyacrylonitrile and reduction is dispersed in methyl alcohol, ethanol, 1-METHYLPYRROLIDONE, dimethyl formamide or acetonitrile again described dispersion again.

Preferably, described when dry temperature range be 60-80 ℃.

Preferably, described heat treated temperature range is 200-400 ℃.

Preferably, described mechanical mixture is that ball milling mixes.

Preferably, described ball milling is wet ball grinding.

The compound of polypyrrole and Graphene is joined in the suspension containing elemental sulfur, dry after mixing, dried product is carried out under protective gas atmosphere to heat treated.

Preferably, the compound of described polypyrrole and Graphene is to prepare by situ aggregation method, comprises the steps:

By in the ultrasonic mixed solvent that is dispersed in methyl alcohol and acetonitrile of Graphene, add pyrroles, in the time of ultrasonic processing, add liquor ferri trichloridi, filtration is precipitated thing, by dry after sediment washing, obtain the compound of polypyrrole and Graphene, polypyrrole is formed on Graphene.

Preferably, described in, be mixed into ultrasonic mixing.

Preferably, described when dry temperature range be 60-80 ℃.

Preferably, described heat treated temperature range is 150-350 ℃.

Preferably, described liquor ferri trichloridi is for dropwise adding.

Preferably, the washing agent in described when washing is deionized water and ethanol.

A kind of electrode composite material provided by the invention, electrode composite material has layer structure, the graphene oxide of Graphene or reduction is as substrate, for sulphur provides an effective electrical conductance path and stable structure, this stable structure can make electrode composite material in charge and discharge process, can be good at bearing change in volume, makes electrode composite material have excellent electric conductivity and stable circulation performance.The present invention also provides the preparation method of this electrode composite material, and preparation method simply, easily goes, and has industrial applications prospect.

Accompanying drawing explanation

Below in conjunction with drawings and embodiments, the invention will be further described.

Fig. 1 is the TEM figure of RGO in embodiment 1;

Fig. 2 is the SEM of RGO/PAN/S figure after ball milling in embodiment 1;

Fig. 3 is the SEM of RGO/PAN/S figure, wherein RGO:PAN=1:30 after heat treatment in embodiment 1;

Fig. 4 is the SEM of RGO/PAN/S figure, wherein RGO:PAN=1:15 after heat treatment in embodiment 1;

Fig. 5 is Ppy, the infrared spectrogram of Ppy/GNS and S/Ppy/GNS;

Fig. 6 is Ppy, the XRD collection of illustrative plates of S and S/Ppy/GNS;

Fig. 7 is the SEM figure of Ppy/GNS;

Fig. 8 is the SEM figure of S/Ppy/GNS;

Fig. 9 is the figure of the SEM after PAN/S heat treatment in comparative example 1;

Figure 10 be in embodiment 3 and comparative example 2 battery with 0.5C charging/discharging voltage and specific capacity graph of a relation;

Figure 11 be in embodiment 3 and comparative example 2 battery with 0.2C charge-discharge performance figure;

Figure 12 be in embodiment 3 and comparative example 2 battery with 0.5C charge-discharge performance figure;

Figure 13 be in embodiment 3 and comparative example 2 battery to increase progressively rate charge-discharge cycle performance figure;

Figure 14 be in embodiment 3 battery with 0.1C charge-discharge performance figure;

Figure 15 be in comparative example 2 battery with 0.2C charge-discharge performance figure;

Figure 16 is the CV figure of battery in embodiment 4;

Figure 17 be in embodiment 4 battery with 0.1C charge-discharge performance figure;

Figure 18 be in embodiment 4 battery with 0.5C charge-discharge performance figure;

Figure 19 be in embodiment 5 battery with 0.1C charging/discharging voltage and capacity relationship figure;

Figure 20 be in comparative example 3 battery with 0.1C charging/discharging voltage and capacity relationship figure;

Figure 21 be in embodiment 5 and comparative example 3 battery with 0.1C discharge capacity and cycle-index graph of a relation;

Figure 22 is the cycle performance figure of battery under different discharge-rates in embodiment 5;

Figure 23 be in embodiment 6 battery with 0.1C charge-discharge performance figure;

Figure 24 be in embodiment 8 battery with 0.1C charging/discharging voltage and capacity relationship figure;

Figure 25 is the CV figure of battery in embodiment 8;

Figure 26 is the cycle performance figure of battery under different discharge-rates in embodiment 8 and embodiment 9;

Figure 27 is battery 0.1C charge-discharge performance figure in embodiment 8.

Embodiment

A kind of high electrode capacity and the good electrode composite material of electrochemical reversibility.Electrode composite material comprises the graphene oxide of elemental sulfur, conducting polymer and Graphene or reduction.

Preferably, in electrode composite material, the specific gravity range of elemental sulfur is 30-90%, and the specific gravity range of conducting polymer is 9-50%, and the specific gravity range of the graphene oxide of Graphene or reduction is 1-20%.

Preferably, in electrode composite material, the proportion of elemental sulfur is 46%.

Preferably, in electrode composite material, the proportion of the graphene oxide of Graphene or reduction is 10%.

Preferably, in electrode composite material, the proportion of the graphene oxide of Graphene or reduction is 19%.

Preferably, in electrode composite material, the specific gravity range of conducting polymer is 51.5-55%.

Electrode composite material has layer structure, and elemental sulfur (S) is the particle of micron or sub-micron or nano-grade size, and S is attached on conducting polymer.Graphene (GNS, graphene nano-sheet) or reduction graphene oxide (RGO, reduced graphene oxide) be nanometer laminated structure, GNS is monoatomic graphite linings, RGO is generally the graphite linings of 2-3 atom thick, and GNS or RGO have very large specific area and very strong adsorption capacity, and S and conducting polymer are attached on GNS or RGO in the lump, similar sandwich, the conducting polymer that is attached with S is clipped in GNS or RGO between layers.

Elemental sulfur has considerable theoretical specific capacity, but under room temperature, elemental sulfur is the insulator of electronics and ion, and the anodal lithium-sulfur cell forming of the elemental sulfur that is 100% by sulfur content is at room temperature impossible discharge and recharge.Therefore, in sulfenyl positive pole, must add certain electronics and ionic conductor.The present invention is intended to improve the conductivity of sulfur-bearing electrode composite material, and the stability of electrode and cycle performance are improved.

Conducting polymer is selected from a kind of in polyacrylonitrile (PAN) and polypyrrole (Ppy).There is at a certain temperature pyrolytic reaction in PAN, the cyclisation that comprises cyano group, dehydrogenation, conjugation, the process such as crosslinked, generate the conjugation coalescence pyrroles with electric conductivity, and the low temperature pyrogenation performance of PAN provides good carrier for preparing electrode composite material, be introduced in elemental sulfur elemental sulfur S ₈have crown structure, at a certain temperature, elemental sulfur is molten state, and the sulphur of molten state is embedded in PAN, i.e. a S ₈ring is embedded in the PAN ring of 4 dehydrogenations, and S is attached to PAN, forms the compound of S and PAN, thereby improves the conductive capability of S.Ppy is a kind of high conductive polymer, is widely used in electrode face finish and electrode material, and Ppy has very strong adsorption capacity, and it is upper that S can be adsorbed on Ppy, reaches equally the object of the conductive capability that improves elemental sulfur.

Graphene (GNS), claims again mono-layer graphite or two-dimentional graphite, is the Two-dimensional Carbon atomic crystal of monatomic thickness, and it has high specific area, outstanding heat conductivility and mechanical property and electronics transmits performance.Be introduced in electrode composite material, there is the GNS of nanometer laminated structure as substrate, S and conducting polymer are adsorbed on its surface, GNS superposes between layers, obtain the electrode composite material of similar sandwich, S and conducting polymer are clipped between GNS layer, like this, GNS provides an effective electrical conductance path and stable structure for electrode composite material, this stable structure can make electrode composite material in charge and discharge process, can be good at bearing change in volume, electrode composite material electric conductivity and stable circulation performance are improved, cycle performance and the high rate performance of electrode composite material have been improved.

The graphene oxide (RGO) of reduction is nanometer laminated structure, and the graphite linings that contains 2-3 atom thick, by graphite oxidation, peel off to restore and can make RGO.Graphite is in strong oxidizer oxidizing process, in graphite linings, there is the oxy radicals such as carboxyl, phenolic hydroxyl group and epoxy radicals, the graphite oxide interfloor distance obtaining increases, by using any suitable known technology as ultrasonic or mechanical agitation, make graphite oxide peel off into graphene oxide (GO, graphene oxide), but GO thermodynamic instability is mainly due to the unsettled pyrolysis containing oxygen functional group about the 200 ℃ decomposition that occur, in addition, due to oxy radicals numerous on graphene oxide, destroyed the sp of Graphene ²hybrid systems, make the conductivity variation of GO, so, by chemical reduction reaction remove thermodynamic instability containing oxygen functional group, can control by controlling the consumption of reducing agent the reducing degree of GO, thermodynamic stability and electric conductivity that the RGO that so not only makes to obtain has had, simultaneously due to the remaining ionization containing oxygen functional group, RGO is with negative electricity, due to electrostatic repulsion, RGO can well be dispersed in water, simultaneously because RGO has very large specific area and very strong adsorption capacity, S and PAN are attached on RGO uniformly, same, RGO provides an effective electrical conductance path and stable structure for electrode composite material, make electrode composite material there is excellent electric conductivity and stable structure, cycle performance and the high rate performance of electrode composite material have been improved.

Preferably, in electrode composite material, the mass ratio of the graphene oxide RGO of polyacrylonitrile (PAN) and reduction is 45:1-10:1.

Under this ratio, can guarantee fully the contacting of graphene oxide RGO of polyacrylonitrile (PAN) and reduction, avoid the reunion of RGO, and guarantee the effective UNICOM of RGO between referring to, the conductivity of intensifier electrode composite material.

Under a preferred implementation, in electrode composite material, the mass ratio of the graphene oxide RGO of polyacrylonitrile (PAN) and reduction is 13:1-25:1.

Under another preferred implementation, in electrode composite material, the mass ratio of the graphene oxide RGO of polyacrylonitrile (PAN) and reduction is 26:1-44:1.

Electrode composite material provided by the invention, in elemental sulfur, introduce conducting polymer, GNS or RGO, make electrode composite material there is excellent electric conductivity, in addition, GNS or RGO are as substrate, for S provides an effective electrical conductance path and stable structure, this stable structure can make electrode composite material in charge and discharge process, can be good at bearing change in volume, and electrode composite material electric conductivity and stable circulation performance are improved.Electrode composite material layer structure, the conducting polymer that is attached with S is clipped in the GNS of nanometer laminated structure or RGO between layers, suppressed to discharge and recharge the dissolving of the poly-lithium sulfide of intermediate product, improved the utilance of S, reduced the effect of shuttling back and forth, the cycle performance of electrode composite material and high rate performance are obviously promoted.

The present invention also provides a kind of positive pole, and electrode composite material recited above can be used as positive active material, and electrode composite material and plus plate current-collecting body form positive pole in the lump.

The present invention also provides a kind of battery, comprise positive pole, negative pole and be located at positive pole and negative pole between electrolyte.

Positive pole at least comprises positive active material.Positive active material contains above-mentioned electrode composite material, and electrode composite material accounts for the 50-90% of positive active material total weight, and wherein, positive active material can also comprise conductive agent and binding agent as required.

Conductive agent is selected from but is not limited only to one or more in conducting polymer, active carbon, Graphene, carbon black, carbon fiber, metallic fiber, metal dust and sheet metal.

Binding agent is selected from but is not limited only to mixture and the derivative of a kind of or above-mentioned polymer in polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyimides, polyester, polyethers, fluorinated polymer, poly-divinyl polyethylene glycol, polyethyleneglycol diacrylate, polyethylene glycol dimethacrylate.

In concrete execution mode, positive pole also comprises plus plate current-collecting body, and plus plate current-collecting body is selected from but is not limited only to metallic nickel, metallic aluminium or stainless steel, and wherein the form of metallic nickel can be nickel foam or nickel screen; The form of metallic aluminium can be aluminium foil or aluminium flake; Stainless form can be stainless (steel) wire.

Negative pole comprises negative current collector and negative electrode active material, and negative electrode active material is selected from lithium metal, lithium alloy, lithium carbon, carbon back or silica-base material.Lithium alloy comprises lithium-aluminium alloy, lithium-magnesium alloy or lithium-ashbury metal; Carbon selection in lithium carbon is unrestricted, comprises crystalline carbon, amorphous carbon or its mixture; Carbon-based material includes but are not limited to graphite; Silica-base material is selected from the silicon of elemental silicon, silicon alloy, metallic cover, at least one in metal-doped silicon.Silicon alloy comprises silicon-carbon alloys, silicon-lithium alloy and silicon-manganese alloy.In order to improve the conductivity of material silicon, generally on the surface of silicon coated or in silicon doping metals, metal is selected from but is not limited only to have the copper, tin, silver etc. of good electronic conduction ability.

Negative current collector is selected from but is not limited only to a kind of in Copper Foil, copper mesh, aluminium foil, nickel foam or stainless (steel) wire, and when negative active core-shell material is lithium metal, lithium metal itself also can be used as negative current collector.

In order to guarantee in charge and discharge process, between the positive pole of battery and negative pole, there is the ion deviate from-embed, as lithium ion, the sulfenyl material of selection and silica-base material do not contain to deviate from simultaneously-during the lithium ion that embeds, to positive pole and/or the pre-embedding lithium processing of negative pole.Concrete pre-embedding mode is not limit, and comprises chemical reaction embedding lithium or electrochemical reaction embedding lithium.

In concrete execution mode, electrolyte at least comprises electrolyte lithium salt and mixed organic solvents, and in concrete execution mode, electrolyte is for containing lithium hexafluoro phosphate (LiPF ₆) the mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC).

Electrolyte lithium salt can include but are not limited to lithium hexafluoro phosphate (LiPF ₆), LiBF4 (LiBF ₄), lithium perchlorate (LiClO ₄), trifluoromethyl sulfonic acid lithium (LiCF ₃sO ₃), bis trifluoromethyl sulfimide lithium (LiN (CF ₃sO ₂) ₂).In electrolyte, add lithium salts and can effectively increase electrolytical ionic conductance.

Electrolytical solvent can be common organic solvent, as dimethoxy-ethane (DME), ethene carbonic ether (EC), diethyl carbonic ether (DEC), propylene carbonate (PC), 1,3-dioxolane (DIOX), various ether, glyme, lactone, sulfone, sulfolane or above mixture.Such as adopting 1,3-dioxolane (DIOX); Also can be polymer, as PVDF, Kynoar-polymethyl methacrylate copolymer (PVDF-PMMA), Kynoar-hexafluoropropylene copolymer (PVDF-HFP), polyethylene glycol borate polymer (PEG-borate esters).

Electrolyte is arranged in battery with the form of gel, is conducive to stop the seepage of potential battery electrolyte, avoids to environment the fail safe that has also improved battery simultaneously.The battery that the specific embodiment of the present invention provides, if need to adopt barrier film in battery structure, barrier film is organic porous material or glass fiber material, and the aperture of barrier film is 0.001-100 micron, and porosity is 20-95%.

In concrete execution mode, electrode composite material, conductive agent, binding agent are mixed, add organic solvent as dispersant, make anode sizing agent.Adopt any method that basic uniform coat can be provided on the whole surface of plus plate current-collecting body, the positive active material slurry making is deposited on the surface of plus plate current-collecting body.For example, can pass through scraper for coating method (doctor blade), coiling pull bar method (wired draw rod) method, silk screen printing or additive method.By the evaporation under normal pressure or low pressure and ambient temperature or high temperature, can will in positive active material pulp layer, remove solvent, the speed of removal of solvents is preferably along pulp surface and keeps substantially constant.Subsequently the positive pole making is assembled into battery together with negative pole, electrolyte, barrier film.

The present invention also provides a kind of preparation method of electrode composite material, and preparation method comprises the steps:

Acrylonitrile, sulphur, Graphene and initator are dissolved in solvent, under preset temperature, stir, washing after stirring, dry after washing, dried product is carried out under protective gas atmosphere to heat treated.

Solvent is selected from least one in water, methyl alcohol, ethanol, 1-METHYLPYRROLIDONE, dimethyl formamide, acetonitrile.Concrete, solvent is water.

Under preset temperature, stir is that concrete, preset temperature range is 60-80 ℃ in order to make the acrylonitrile can better polymerization.

Sulphur and Graphene can join in solvent with solid or form of suspension, concrete, the sulphur content of nano-scale can be dispersed in to the suspension that obtains sulfur-bearing in solvent, so that sulphur can be fully, disperse uniformly, solvent includes but are not limited to a kind of in water, methyl alcohol, ethanol, 1-METHYLPYRROLIDONE, dimethyl formamide, acetonitrile; Graphene can be dispersed in to the suspension that obtains graphene-containing in solvent, so that Graphene can be fully, disperse uniformly, same, solvent includes but are not limited to a kind of in water, methyl alcohol, ethanol, 1-METHYLPYRROLIDONE, dimethyl formamide, acetonitrile.

The present invention is by the method for chemical oxidation in-situ polymerization, make polyacrylonitrile or while existing with acrylonitrile monemer just and elemental sulfur fully mix, by initator, make acrylonitrile monemer oxidation polymerization generate polyacrylonitrile again, in order to make to react completely, vigorous stirring 10h at preset temperature 60-80 ℃, particle after stirring is by centrifuge washing, concrete, and the washing agent that washing adopts is water.Initator includes but are not limited to potassium peroxydisulfate and lauryl sodium sulfate.

Thoroughly after washing, by dry, process to remove water, dry can be to carry out in vacuum condition or protective gas atmosphere, and when dry, temperature range is 60-80 ℃, and drying time, scope was 1-5h, thoroughly to remove water.

Dried product is carried out to heat treated, and for fear of introducing impurity and producing unnecessary side reaction, heat treated is carried out in protective gas atmosphere, concrete, and protective gas is inert gas, and inert gas includes but are not limited to argon gas.The temperature range of heat treated is 200-400 ℃, and the time of heat treated is 1-5h, during heating along with temperature raises, elemental sulfur becomes molten state, with polyacrylonitrile generation dehydrogenation reaction, elemental sulfur is embedded in the polyacrylonitrile ring of dehydrogenation, that is to say that elemental sulfur is attached to polyacrylonitrile.Because Graphene has very large specific area and very strong adsorption capacity, the polyacrylonitrile that is attached with elemental sulfur is attached on Graphene, Graphene is nanometer laminated structure, Graphene accompanies the polyacrylonitrile that is attached with elemental sulfur between layers, and the electrode composite material making has layer structure.

Concrete, by acrylonitrile, potassium peroxydisulfate, lauryl sodium sulfate, nano-sulfur suspension and nano-graphene suspension are dissolved in deionized water.For polymerization AN, by said mixture vigorous stirring 10h at 70 ℃, by the particle water obtaining by centrifugal thorough washing, after washing, in vacuum drying chamber, at 60 ℃, be dried 3h to remove aqueous solvent, then heat treatment 3 hours at 350 ℃ in argon atmosphere, tube furnace, makes sulphur fusing, and reacts with polyacrylonitrile, sulphur is embedded in polyacrylonitrile, is then attached on Graphene in the lump.

Preparation method provided by the invention is in conjunction with in-situ polymerization and heat treated, first make monomer and the elemental sulfur of polyacrylonitrile fully mix, in the situation that existing, elemental sulfur make acrylonitrile monemer generate polyacrylonitrile in the polymerization of Graphene surface oxidation by initator, together with now a part of sulphur has been strapped in polyacrylonitrile, then in the process of heat treated, make sulphur fusing, elemental sulfur constraint and that fettered reacts with polyacrylonitrile, be embedded in polyacrylonitrile, pass through in-situ polymerization, improved the degree of mixing of polyacrylonitrile and elemental sulfur, and then pass through heat treated, make sulphur and polyacrylonitrile reaction, sulphur is embedded in polyacrylonitrile ring, the polyacrylonitrile with electric conductivity not only improves the conductive capability of sulphur, and in charge and discharge process, guarantee the activity of sulphur, improve the utilance of sulphur.Further, Graphene has nanometer laminated structure, Graphene adhering between layers the polyacrylonitrile that has embedded sulphur.Graphene has the very strong electronic capability of leading, it is as substrate, an effective electrical conductivity network and stable structure framework are provided, not only make electrode composite material can better bear the bulk effect in charge and discharge process, and improved conductive capability and the power-performance of electrode composite material; In addition, embedded the polyacrylonitrile of elemental sulfur, can effectively suppress the dissolving of the many lithium sulfides of charge and discharge cycles process intermediate product, improved the utilance of elemental sulfur, made electrode composite material there is excellent cycle performance.The electrode composite material that preparation method provided by the invention obtains has excellent chemical property, and technique simply, easily go, has industrial applications prospect simultaneously.

Elemental sulfur, polyacrylonitrile and Graphene are dispersed in dispersant according to predetermined ratio, and mechanical mixture, is dried after mixing, dried product is carried out in protective gas atmosphere to heat treated.

Dispersant is selected from but is not limited to organic solvent, and organic solvent includes but not limited to one or more in methyl alcohol, ethanol, acetonitrile, dimethyl formamide (DMF) and 1-METHYLPYRROLIDONE (NMP).Dispersant mainly plays elemental sulfur (S), polyacrylonitrile (PAN) and the well-mixed object of Graphene (GNS), then by mechanical mixture, it is uniformly dispersed, concrete, mechanical mixture includes but are not limited to ball milling and mixes, range of speeds during ball milling is 500-1000rpm, and the time range that ball milling mixes is 3-9h.During ball milling, use zirconia balls to grind in ball grinder, in order not destroy ball grinder, introduce impurity, make simple substance S, PAN and GNS fully be ground and dispersed simultaneously, preferred rotational speed of ball-mill is 800rpm, and Ball-milling Time is 6h.

The mixed gains of ball milling are dried to processing, and to remove dispersant, dry can be to carry out in vacuum condition or protective gas atmosphere, and when dry, temperature range is 60-80 ℃, and drying time, scope was 8-16h, thoroughly to remove dispersant.

Dried product is carried out to heat treated, and heat treated is carried out in protective gas atmosphere, and protective gas is inert gas, and inert gas includes but are not limited to argon gas.The temperature range of heat treated is 200-400 ℃, and heat treated time range is 3-9h, during heating along with temperature raises, elemental sulfur becomes molten state, with polyacrylonitrile generation dehydrogenation reaction, elemental sulfur is embedded in the polyacrylonitrile ring of dehydrogenation, that is to say that elemental sulfur is attached to polyacrylonitrile.

Concrete, simple substance S, PAN and GNS are mixed according to weight ratio 4:1:0.25, using NMP as dispersant, ball milling 6h under rotating speed 800rpm.By the further dry 12h at 60 ℃ of vacuum drying chambers of ball milling gains, to remove dispersant NMP, then heat treated 6h at 350 ℃ in the tube furnace of argon atmosphere, make S fusing and react with PAN, GNS is nanometer laminated structure, has very large specific area and very strong adsorption capacity, and the PAN that has embedded S is attached on GNS, the electrode composite material making has layer structure, clips the PAN that has embedded S between the GNS of nanometer laminated structure.

Preparation method provided by the invention combines ball milling and mixes and heat treated, ball milling mixes mixes each component of electrode composite material, and then pass through heat treated, make sulphur and polyacrylonitrile reaction, sulphur is embedded in polyacrylonitrile ring, and the polyacrylonitrile with electric conductivity not only improves the conductive capability of sulphur, and in charge and discharge process, guarantees the activity of sulphur, improve the utilance of sulphur, finally make the electrode composite material of the sulphur/polyacrylonitrile/Graphene with layer structure.Further, Graphene has nanometer laminated structure, Graphene adhering between layers the polyacrylonitrile that has embedded sulphur.Graphene has the very strong electronic capability of leading, it is as substrate, an effective electrical conductivity network and stable structure framework are provided, make electrode composite material have good holding capacity for the change in volume in charge and discharge process, improved conductive capability and the power-performance of electrode composite material; In addition, embedded the polyacrylonitrile of elemental sulfur, can effectively suppress the dissolving of the many lithium sulfides of charge and discharge cycles process intermediate product, improved the utilance of elemental sulfur, made electrode composite material there is excellent cycle performance.The electrode composite material that preparation method provided by the invention obtains has excellent chemical property, and technique simply, easily go, has industrial applications prospect simultaneously.

Polyacrylonitrile solution is mixed under weak basic condition with the graphene oxide suspension of reduction, after deposition, sedimentation products is disperseed again, by dispersion and elemental sulfur mechanical mixture, dry after mixing, dried product is carried out to heat treated.

In polyacrylonitrile (PAN) solution, solvent can be selected from organic solvent, and organic solvent includes but are not limited to dimethyl formamide (DMF), at temperature range 50-80 ℃ so that polyacrylonitrile can fully dissolve, concrete, at 60 ℃, PAN is dissolved in DMF.

The graphene oxide (RGO) of reduction is dispersed in suitable solvent, as water, methyl alcohol, ethanol, acetonitrile, 1-METHYLPYRROLIDONE or dimethyl formamide, obtains RGO suspension.

RGO adopts improved Hummers legal system standby.First by Hummers method synthetic graphite oxide, peel off again to obtain graphene oxide (GO), yet, GO thermodynamic instability, and poor electric conductivity, GO is mainly due to the unsettled pyrolysis containing oxygen functional group about the 200 ℃ decomposition that occur, and produces thus carbon monoxide, carbon dioxide and water vapour.On the other hand, the thermodynamic stability of RGO is good more than GO.So, further by chemical reduction reaction remove thermodynamic instability in GO containing oxygen functional group, make GO change RGO into, to increase its thermodynamic stability and conductivity.In addition, can control by controlling the consumption of reducing agent the reducing degree of Graphene, the thermodynamic stability and the electric conductivity that so not only make RGO have, simultaneously because the ionization containing oxygen functional group not being reduced makes RGO with negative electricity, due to electrostatic repulsion, RGO can well be dispersed in water.

Concrete, PAN/DMF solution and RGO suspension are mixed under weak basic condition, weakly alkaline environment is in order to make RGO suspension more stable, preferably alkalescent is that pH value is less than 9.The alkalescent reagent of selecting is ammoniacal liquor, concrete, under high degree of agitation, add ammonia spirit, the mass concentration of ammonia spirit is 0.5wt%, continue subsequently vigorous stirring 12-24h, because the polarity of DMF can better be disperseed RGO, PAN tends to be deposited on the RGO surface with layer structure, deposition rate is slower, obtains uniform PAN/RGO compound.

After stirring, deposit PAN and RGO, concrete deposition process is to pass through centrifugal treating, range of speeds when centrifugal is 8000-12000rpm, the time of centrifugal treating is 10min-1h, after deposition, disperse, concrete dispersant includes but are not limited to ethanol, concrete again, PAN/RGO compound is again dispersed in ethanol through ultrasonic after centrifugal, then carries out wet ball grinding with elemental sulfur immediately.Rotating speed during ball milling is 400-800rpm, and in order to make to mix fully, Ball-milling Time is 0.5-2h.

Ball milling is dried processing after mixing, and to remove solvent wherein, dry can be to carry out in vacuum condition or protective gas atmosphere, and baking temperature is 60-80 ℃, and be 1-4h drying time.

Dried product is carried out to heat treated, and for fear of introducing impurity and producing unnecessary side reaction, heat treated is carried out in protective gas atmosphere, concrete, and protective gas is inert gas, and inert gas includes but are not limited to argon gas.The temperature range of heat treated is 200-400 ℃, and the heat treated time is 1-5h, during heating along with temperature raises, elemental sulfur becomes molten state, with polyacrylonitrile generation dehydrogenation reaction, elemental sulfur is embedded in the polyacrylonitrile ring of dehydrogenation, that is to say that elemental sulfur is attached to polyacrylonitrile.Because RGO has very large specific area and very strong adsorption capacity, the polyacrylonitrile that is attached with elemental sulfur is attached on RGO, RGO is nanometer laminated structure, contain 2-3 monatomic graphite linings, RGO accompanies the polyacrylonitrile that is adhering to elemental sulfur between layers, and the electrode composite material making has layer structure.

Concrete, at 60 ℃, by PAN powder dissolution in DMF.Get PAN/DMF solution and mix with the suspension that contains RGO, add 0.5wt% ammonia spirit under high degree of agitation, then vigorous stirring is 24 hours.At rotating speed, be within 10000rpm centrifugal 10 minutes, to obtain gray, with being about to gray and elemental sulfur, carry out wet ball grinding, ethanol is dispersant, rotating speed 600rpm, ball milling 30 minutes.The mixture that ball milling is obtained is dried 2 hours in 60 ℃ of vacuum drying chambers.Then, by dried product heat treated 3 hours in 320 ℃ of pipe furnaces, annealing.Finally, obtain electrode composite material.

Preparation method provided by the invention, adopts centrifugal and ball milling, and each component of electrode composite material is fully mixed.RGO is nanometer laminated structure, contain 2-3 monatomic graphite linings, on RGO, contain carboxyl, the oxy radical such as phenolic hydroxyl group and epoxy radicals, ionization due to these groups, RGO is with negative electricity, due to electrostatic repulsion, RGO can well be dispersed in water, simultaneously because RGO has very large specific area and very strong adsorption capacity, sulphur and polyacrylonitrile are attached on RGO, then pass through heat treated, make sulphur fusing, react with PAN, be embedded in PAN, the electrode composite material finally making has layer structure, RGO is attached with the PAN that has embedded sulphur between layers.

The polyacrylonitrile with electric conductivity not only improves the conductive capability of sulphur, and in charge and discharge process, guarantees the activity of sulphur, improves the utilance of sulphur.Further, RGO has very strong electronic capability and the thermal stability led, and it provides an effective electrical conductivity network and stable structure framework as substrate, has improved conductive capability and the power-performance of electrode composite material; In addition, embedded the polyacrylonitrile of elemental sulfur, can effectively suppress the dissolving of the many lithium sulfides of charge and discharge cycles process intermediate product, improved the utilance of elemental sulfur, made electrode composite material there is excellent cycle performance.The electrode composite material that preparation method provided by the invention obtains has excellent chemical property, and technique simply, easily go, has industrial applications prospect simultaneously.

The compound of polypyrrole and Graphene is joined in the suspension of sulfur-bearing, dry after mixing, dried product is carried out under protective gas atmosphere to heat treated.

Concrete, the sulphur content of nano-scale is dispersed in to the suspension that obtains sulfur-bearing in dispersant, make sulphur can be fully, disperse uniformly, dispersant includes but are not limited to water.

Concrete; be mixed into ultrasonic mixing; after ultrasonic; the suspension of the compound of the polypyrrole mixing and Graphene and sulfur-bearing is dried; to remove solvent wherein; dry can be to carry out in vacuum condition or protective gas atmosphere, and baking temperature scope is 60-80 ℃, and drying time, scope was 1-5h.Concrete, baking temperature is 65 ℃, be 3h drying time.

Dried product is carried out to heat treated, and for fear of introducing impurity and producing unnecessary side reaction, heat treated is carried out in protective gas atmosphere, concrete, and protective gas is inert gas, and inert gas includes but are not limited to argon gas.The temperature range of heat treated is 150-350 ℃, and the heat treated time is 1-5h, and during heating, along with temperature raises, elemental sulfur becomes molten state, and polypyrrole has very strong adsorption capacity, and elemental sulfur is adsorbed onto in polypyrrole, that is to say that elemental sulfur is attached to polypyrrole.Because Graphene has very large specific area and very strong adsorption capacity, the polypyrrole that is attached with elemental sulfur is attached on Graphene, Graphene is nanometer laminated structure, and Graphene accompanies the polypyrrole that is attached with elemental sulfur between layers, and the electrode composite material making has layer structure.

Concrete, the compound of polypyrrole and Graphene is by situ aggregation method (in situ) preparation, comprises the steps:

In order to control reaction speed, liquor ferri trichloridi is for dropwise adding, on Graphene, there is polymerization in pyrroles, after pyrroles's polymerization, filter and be precipitated thing polypyrrole/multi-walled carbon nano-tubes, sediment is washed by deionized water and ethanol, dry after washing, dry can carrying out in vacuum drying chamber, baking temperature scope is 60-80 ℃, drying time, scope was 5-12h.Concrete, at 70 ℃, vacuumize is spent the night.

Concrete, by chemical oxidation of gold, use FeCl ₃as initator, by the synthetic polypyrrole of pyrrole monomer.By in-situ polymerization pyrroles on Graphene, make the Graphene that is attached with polypyrrole.First, at room temperature by Ultrasound Instrument, Graphene is dispersed in methyl alcohol and acetonitrile mixed solvent (volume ratio 1:1) to ultrasonic processing 2h.Pyrroles is joined in above-mentioned solution, after stirring 0.5h, dropwise add FeCl ₃solution, and at room temperature continue ultrasonic.Finally by isolated by filtration, obtain final Ppy/GNS, more thoroughly wash by deionized water, ethanol, 70 ℃ of dried overnight under vacuum environment.

The Ppy/GNS making is joined in the suspension that contains nano-sulfur, ultrasonic processing 0.5h is uniformly dispersed mixture, then mixture is placed in to vacuum drying oven, and at 65 ℃, dry 3h is to remove solvent.Finally, under Ar atmosphere, mixture is heated to 150 ℃, and keeps 3h, obtain the electrode composite material with layer structure.

The surface that is dispersed in Ppy/GNS compound of the S height of nano-scale, due to the electronic conductivity of GNS excellence and good lithium ion migration path, makes sulfenyl electrode composite material have excellent large multiplying power discharging capacity.The Ppy in addition with loose structure can not only hold and bears change in volume larger in charge and discharge process, and in obstruction, discharges and recharges the poly-lithium sulfide of intermediate product and play a key effect from the diffusion problem of electrode.

The preparation method of electrode composite material provided by the invention combines ultrasonic processing, in-situ polymerization and heat treated, each component of electrode composite material can be disperseed more uniformly, the electrode composite material obtaining by this preparation method there is layer structure, the polypyrrole that is attached with elemental sulfur is attached on the Graphene of layer structure, and the polypyrrole that has sulphur is adsorbed in adhering between layers of Graphene.Graphene has the very strong electronic capability of leading, and it provides an effective electrical conductivity network and stable structure framework as substrate, has improved conductive capability and the power-performance of electrode composite material; In addition, absorption has the polypyrrole of sulphur, can effectively suppress the dissolving of the many lithium sulfides of charge and discharge cycles process intermediate product, improves the utilance of elemental sulfur, makes electrode composite material have excellent cycle performance.The electrode composite material that preparation method provided by the invention obtains has excellent chemical property, and technique simply, easily go, has industrial applications prospect simultaneously.

Below by embodiment, the present invention will be further described.

Embodiment 1

1g graphite and 50g sodium chloride are ground 10 minutes in agate mortar, remove the pollutant on graphite, and by its porphyrize.Then by distilled water washing for the mixture of graphite and sodium chloride for several times, and vacuum filtration is to remove sodium chloride, 0.2 micron, filter membrane aperture.After filtration, graphite is put into vacuum drying chamber, dry 20min, removes remaining moisture at 70 ℃.After dry, the solid of gained is mixed in the round-bottomed flask of 250ml to uninterrupted stirring 24 hours at 25 ℃ with the 23ml concentrated sulfuric acid.In above-mentioned dispersion liquid, add 100mg sodium nitrate, stir 5min and make its dissolving.Then, flask is placed in to ice bath, temperature remains on below 20 ℃, in suspension, adds 3g potassium permanganate, is then heated to 40 ℃, keeps 30min, adds 3ml ultra-pure water, after 5min, then adds 3ml ultra-pure water, after 5min, adds 40ml ultra-pure water.Afterwards, suspension is heated to 100 ℃ and maintenance reaction 15min, then adds 140ml ultra-pure water and 10ml hydrogen peroxide (H ₂o ₂, 30wt%), stop reaction.Continue stirred suspension 5min, then use 5% hydrochloric acid centrifuge washing 2 times, ultra-pure water centrifuge washing for several times, the sediment obtaining is distributed in 150ml ultra-pure water, ultrasonic 30min, obtain a kind of brown, uniform suspension, finally suspension is dialysed to remove remaining salt and acid completely, obtain graphite oxide.

The graphite oxide of acquisition is diluted to 0.05wt% by ultra-pure water, by ultrasonic processing 30min, peels off and obtain graphene oxide, then under 5000rpm centrifugal 15min, remove remaining unstripped graphite oxide.Subsequently, get the uniform suspension of 100ml, 100ml ultra-pure water, 100 μ l hydrazine solutions (35wt%, Aldrich) and 0.7ml ammonia spirit (28wt%) mixes in the round-bottomed flask of 250ml.The mass ratio of hydrazine and graphene oxide is about 7:10.After vigorous agitation 5min, round-bottomed flask is immersed in oil bath and heats 1h, temperature remains on 95 ℃ of left and right.In order to obtain stable suspension, after reduction reaction, by dialysis in the ammonia spirit of 0.5wt%, further remove unnecessary hydrazine, the light black obtaining divides suspension, i.e. the graphene oxide (RGO) of reduction, pass through again the ultrasonic processing of 30min, to control the lateral length of RGO lamella.

At 60 ℃, by 5g polyacrylonitrile powder dissolution in the dimethyl formamide solution (DMF) of 850ml.Get respectively 64mlPAN/DMF solution and mix with the RGO solution of 33.3ml, 50ml, 100ml, high degree of agitation 15min.The mass ratio of RGO and PAN is respectively 1:45,1:30 and 1:15.Then to beaker, add 0.5wt% ammonia spirit, until it reaches 500ml, follow vigorous stirring 24h.Then, under 10000rpm, centrifugal 10min obtains grey compound, with being about to grey compound and 1.6g sulphur, carries out wet ball grinding, and dispersant is ethanol, and drum's speed of rotation is 600rpm, ball milling 30min.By the mixture obtaining dry 2h in 60 ℃ of vacuum drying chambers.Then, the dried product of 0.7g is heated to 3h in 320 ℃ of pipe furnaces, annealing.Finally, obtain the electrode composite material of RGO/PAN/S.Wherein the content of sulphur records by elemental analyser.

Fig. 1 is transmission electron microscope (TEM) picture of the RGO of preparation in embodiment 1, as can be seen from the figure by ultrasonic processing, graphite oxide is realized to peeling off well of graphene oxide.

Fig. 2 is the scanning electron microscopy of RGO/PAN/S (SEM) picture after ball milling in embodiment 1, from inferring figure that PAN/RGO composite surface is covered by S after wet ball grinding, and through heat treated, i.e. annealing, S and PAN react, the excessive sulphur in surface is evaporated simultaneously.

Fig. 3 and Fig. 4 are the scanning electron microscopy of RGO/PAN/S (SEM) pictures after heat treatment in embodiment 1, RGO:PAN=1:30 in Fig. 3, RGO:PAN=1:15 in Fig. 4.Fig. 3 shows that polyacrylonitrile is deposited on RGO surface uniformly, when increasing the content of RGO, as shown in Figure 4, some RGO are not covered by PAN/S, from the cross section, edge of blocky-shaped particle, can significantly find out the layer structure of electrolysis composite material, the thickness of thin layer is in 10nm left and right.

Embodiment 2

By chemical oxidation of gold, use FeCl ₃as initator, by the synthetic polypyrrole of pyrrole monomer (Aldrich, purity 98%).By in-situ polymerization pyrroles on Graphene, make the Graphene (Ppy/GNS) that polypyrrole adheres to.First, at room temperature by Ultrasound Instrument (Fisher Scientific, FB120) Graphene of 0.1g (US research nano-materials Inc) is dispersed in the methyl alcohol of 40mL and acetonitrile mixed solvent (volume ratio 1:1) to ultrasonic processing 2h.0.2g pyrroles is joined in solution, stir 0.5h, subsequently by 15mL, the FeCl of 0.5mol/L ₃dropwise join in above-mentioned solution, and at room temperature lasting ultrasonic, by isolated by filtration, obtain Ppy/GNS, more thoroughly wash by deionized water, ethanol, 70 ℃ of dried overnight under vacuum environment.

The Ppy/GNS making is joined and contains 6g nano-sulfur (US research nano-materials Inc, in suspension 10wt%), by the ultrasonic 0.5h of Ultrasound Instrument, mixture is uniformly dispersed, then mixture is placed in to vacuum drying oven, at 65 ℃, dry 3h is to remove solvent.Finally, under Ar atmosphere, mixture is heated to 150 ℃, and keep 3h, obtain S/Ppy/GNS electrode composite material, by chemical analyzer (CHNS, Vario Micro Cube, Elementar) content that records elemental sulfur in electrode composite material is 41%.

By fourier transform infrared spectroscopy (FTIR, 520, Nicolet) study Ppy, the chemical constitution of Ppy/GNS and S/Ppy/GNS.Fig. 5 is Ppy, the infrared spectrogram of Ppy/GNS and S/Ppy/GNS.Characteristic peak correspondence=CH plane vibration of I indication in figure, the corresponding C-N stretching vibration of II, the corresponding pyrrole ring fundamental vibration of III.Fig. 5 shows that the present invention successfully makes Ppy by in-situ polymerization, and the characteristic peak of Ppy appears in the infrared spectrum of Ppy/GNS and S/Ppy/GNS equally, and just the intensity at peak decreases.

By X-ray diffractometer (XRD, D8Dis-cover, Bruker), detect the crystal structure of sample.Fig. 6 is the Ppy of preparation, the XRD collection of illustrative plates of S and S/Ppy/GNS.As can be seen from the figure, Ppy is unbodied, elemental sulfur is Fddd rhombic system, in S/Ppy/GNS, being positioned at the broad peak of locating in 2 θ=24.5 ° and 2 θ=42.8 ° can be owing to the characteristic peak of Graphene, in S/Ppy/GNS, do not observe the characteristic peak of S, the S that shows nano-scale is good being adsorbed in compound.

Fig. 7 and Fig. 8 are respectively the SEM picture of Ppy/GNS and S/Ppy/GNS.Fig. 7 shows after polymerization, and Ppy forms and be fixed on GNS surface, and pyrrole monomer is coughed up singly-bound by π, and hydrogen bond and Van der Waals force are adsorbed on the GNS with bigger serface.In Fig. 8, can obviously find out that the S/Ppy/GNS of staggered nano-sheet is stacked brokenly, and there is coarse surface, be coated with intensive sulfur granules.This can have very strong adsorption capacity to S owing to Ppy.Fig. 7 and Fig. 8 have proved the layer structure of electrolysis composite material of the present invention.

Comparative example 1

At 60 ℃, 5g polyacrylonitrile powder and 1.6g sulphur are carried out to wet ball grinding, dispersant is ethanol, and drum's speed of rotation is 600rpm, ball milling 30min.By the mixture obtaining dry 2h in 60 ℃ of vacuum drying chambers.Then, dried product is heated to 3h in 320 ℃ of pipe furnaces, annealing.Finally, obtain PAN/S composite material.

SEM figure after the composite material PAN/S heat treatment that Fig. 9 provides for comparative example 1.With Fig. 2 comparison, in Fig. 9, composite material is mainly ellipticity particle, and agglomeration is obvious, and in Fig. 9, electrode composite material particle size is all relative even with dispersion.

Embodiment 3

By assembling button cell, CR2032 studies the chemical property of S/PAN/RGO electrode composite material.

By electrode composite material S/PAN/RGO, conductive agent Ketjen black KB600 and binding agent PVDF according to weight ratio 8:1:1, in NMP, mix and make slurry, subsequently slurry is coated on the nickel foam collector of 12 millimeters of diameters, at 80 ℃, be dried and make work electrode in 12 hours, in electrode composite material, the weight ratio of RGO and PAN is 1:30.Lithium metal is as to electrode, and electrolyte is the LiPF that contains 1M ₆vinyl carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) (volume ratio 1:1:1) solution, barrier film is ENTEK ET20-26, assembles CR2032 button cell in being full of the glove box of argon gas.Then by New Ware battery testing system, at room temperature with certain current density, battery is carried out to charge-discharge test, open circuit voltage scope is 1-3V.

Comparative example 2

In comparative example 2, composite material is PAN/S, and all the other batteries compositions and assemble method are with embodiment 3.

The battery that Figure 10 provides for embodiment 3 and comparative example 2 is with charging/discharging voltage under 0.5C multiplying power and specific capacity graph of a relation, the battery average charge that comparative example 2 provides and discharge voltage are respectively 2.3V and 1.7V, shown very strong electrochemical polarization, and the introducing of Graphene has reduced this electrochemical polarization greatly, in embodiment 3, battery discharge voltage rises to 1.8V from 1.7V, and charging voltage has dropped to 2.25V from 2.3V.Figure 11 and 12 is respectively battery charge-discharge performance figure under 0.2C and 0.5C multiplying power that embodiment 3 and comparative example 2 provide.As can be seen from the figure: in comparative example 2 battery circulation 40 times after specific capacity decay fast, and battery rear specific capacity of circulation several times before experience reaches stable in embodiment 3, and keep always, the capability retention circulating 60 times time approaches 95%, show that the electrode composite material with layer structure is distributed between layers soluble middle polysulfide, improved the utilance of sulphur, and this layer structure cycle life and the stability of battery have been strengthened to a certain extent.

The performance test of the battery that Figure 13 provides for embodiment 3 and comparative example 2 under the multiplying power progressively increasing.Battery circulates after 10 times with the multiplying power of 0.2C, and current density is increased to 0.5C gradually, and then 1C, and 2C reduce to 0.2C.For battery in embodiment 3, the stable capacity that 0.2C, 0.5C, 1C and 2C are corresponding is about respectively 1333,1249,1166,800mAh/g, and only has 440mAh/g with the specific capacity of battery 2C multiplying power in comparative example under condition 2, is probably its half.This phenomenon shows that the existence of Graphene has promoted the high rate performance of electrode composite material really.

Figure 14 and 15 be respectively battery that embodiment 3 and comparative example 2 provide under 0.1C and 0.2C multiplying power charging and discharging capacity and coulomb efficiency with the graph of a relation of cycle-index.In Figure 14, the initial specific capacity of battery is 1827mAh/g, because side reaction makes it higher than theoretical specific capacity, circulate after 10 times and be reduced to gradually a metastable value 1352mAh/g, specific discharge capacity conservation rate through 90 circulations with respect to the tenth time is 90%, illustrates that PAN/RGO/S electrode composite material has good cyclical stability.In Figure 15, after circulating battery 200 times, specific capacity still has 1050mAh/g, with respect to the tenth specific discharge capacity conservation rate, is 82%, and reversible specific discharge capacity conservation rate is 77% for the first time.The electrode composite material that shows layer structure can absorb polysulfide between the layers, contributes to improve cycle life and the power-performance of battery.

Embodiment 4

By assembling CR2025 button cell, study the chemical property of S/Ppy/GNS electrode composite material.

Battery comprises: the polypropylene diaphragm of lithium an-ode, S/Ppy/GNS positive pole, micropore and infiltration are at two (fluoroform sulphonyl) imine lithium (LiTFSI of 1M, Aldrich, purity 96%) tetraethyleneglycol dimethyl ether (Aldrich, purity 99%) electrolyte.Anodal preparation process is: by 80wt%S/Ppy/GNS, the binding agent PVDF (Kynar, HSV900) of 10wt% and the conductive agent acetylene black of 10wt% (MTI, purity 99.5%) are at NMP (NMP, Sigma-Aldrich, purity >=99.5%) middle mixing make anode sizing agent.

The anode sizing agent making is laid in the circular nickel foam that diameter is 1cm, in vacuum drying chamber, at 60 ℃, is dried after 12h, for dry rear positive electrode is contacted with nickel foam well, anodal with the compacting of 8Mpa pressure by hydraulic press.In being full of the Braun glove box of argon gas, assemble button cell, by multichannel cell tester (BT-2000), under different current densities, battery is carried out to constant current charge-discharge, voltage range is 1-3V, by potentiostat (VMP3, Bio-logic) carry out cyclic voltammetric (CV) test, voltage range is 1-3V, and sweep speed is 0.5mV/s.All electro-chemical tests all at room temperature carry out.

Figure 16 is the CV figure of the battery that provides of embodiment 4, as can be seen from Figure, in cyclic process, the voltage at negative electrode and anode peak and peak current change less, show the good capability retention of electrode composite material, CV result shows that the problem that Ppy/GNS spreads from electrode at the poly-lithium sulfide of obstruction plays very important effect.

Figure 17 is discharge capacity and coulomb efficiency vs. cycle-index figure that battery that embodiment 4 provides discharges and recharges with 0.1C.Battery has shown lower coulomb efficiency 91.8% at circulation time first, and further circulation coulomb efficiency increases, and because remaining S contacts well with the Ppy of porous, makes the reversibility raising of battery.Coulomb efficiency in circulation after 50 times reaches 99.5%, namely along with the cycle-index increase effect minimizing of shuttling back and forth.On the other hand, battery has shown good cycle performance, and the reversible capacity after circulating battery 50 times maintains 715.8mAh/g, than the S/Ppy composite material that there is no GNS, reversible specific capacity has at least improved 200mAh/g, and is under the charge-discharge magnification of twice.The raising of reversibility shows that S/Ppy/GNS that GNS provides an effective electrical conductance path and had a layer structure provides very stable structure for sulphur.

Figure 18 is battery charge-discharge performance figure under 0.5C multiplying power in embodiment 4, and battery capacity is 875.1mAh/g, circulates after 50 times, and capacity still has 597mAh/g, shows the good stable circulation performance of battery, and the attenuation rate of each circulation is 0.64%.Under 1C multiplying power, obtained better cycle performance of battery, the attenuation rate of each circulation is 0.54%, this result can ascribe to and under higher current density, fly the reduction of shuttle effect.

Embodiment 5

By S (Sigma-Aldrich, powder particle size 100 orders), polyacrylonitrile (PAN, Sigma-Aldrich) and Graphene (GNS, US research nano-materials Inc) according to weight ratio 4:1:0.25, mix, ball milling 6h under rotating speed 800rpm, NMP is as dispersant.After ball milling at 60 ℃ of vacuum drying chambers dry 12h, to remove solvent, then heat treated 6h at 350 ℃ in the tube furnace of argon atmosphere, makes S fusing and reacts with PAN.

By electrode composite material S/PAN/GNS, conductive agent acetylene black and binding agent PVDF according to weight ratio 8:1:1, in NMP, mix and make slurry, subsequently slurry is coated on the nickel foam collector of diameter 1cm, at 60 ℃, vacuumize makes work electrode for 12 hours, for positive electrode contacts well with nickel foam collector, by electrode, by hydraulic press roll-in, pressure is 8MPa.By accurate weighing, press and control geometry and make the weight of electrode of preparation identical with thickness.Lithium metal is as to electrode, and electrolyte is the LiPF that contains 1M ₆vinyl carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) (volume ratio 1:1:1) solution, barrier film is polypropylene, assembles CR2032 button cell in being full of the glove box of argon gas.

By multichannel cell tester (BT-2000, Arbin Instruments), under different current densities, battery is carried out to constant current charge-discharge, voltage range is 1-3V.

Comparative example 3

In comparative example 3, electrode material is S/PAN, and in addition, the preparation process of S/PAN, the formation of battery and method of testing are with embodiment 5.

Figure 19 and Figure 20 are battery charging/discharging voltage and capacity relationship figure under 0.1C multiplying power in embodiment 5 and comparative example 3, as can be seen from the figure: with comparative example 3, compare, in embodiment 5, the polarization that discharges and recharges of battery obviously reduces, and shows that in charge and discharge process, voltage difference reduces.The electrode composite material dynamics of having added Graphene improves, and polarization reduces, thereby the energy of battery and power density improve.

Figure 21 is battery discharge capacity and cycle-index graph of a relation under 0.1C multiplying power in embodiment 5 and comparative example 3, and in embodiment 5, the chemical property of battery obviously improves, and shows that the effect of shuttling back and forth in battery is inhibited.In comparative example 3, capacity attenuation is very fast for battery, and after discharging and recharging 50 times, battery capacity relatively initially reduces by 38%.

Figure 22 is the cycle performance figure of battery under different discharge-rates in embodiment 5.The high magnification capacity of battery excellence is because electrode composite material Graphene has excellent electrical conductivity performance, especially, with the circulation of 1C and 2C rate charge-discharge initially several times after, discharge capacity increases gradually, in 100 processes that circulate, almost not decay of capacity, shows that battery has highly stable cycle performance.

Embodiment 6

By 0.62mL acrylonitrile (ACROS, purity 99%), 10mg potassium peroxydisulfate (EMD, purity 99%), 0.1g lauryl sodium sulfate (Sigma-Aldrich, purity >=99%), 19.72g nano-sulfur suspension (USresearch nano-materials Inc, percentage by weight 10wt%) and 0.616g nano-graphene suspension (US research nano-materials Inc, percentage by weight 2wt%) be dissolved in 20mL deionized water.For polypropylene nitrile, by mixture vigorous stirring 10h at 70 ℃, then water is by centrifugal thorough washing.By washed product in vacuum drying chamber at 60 ℃ dry 3h to remove solvent, then in tube furnace under argon atmosphere, heat treatment 3 hours at 350 ℃, make sulphur fusing, and react with PAN, obtain having the S/PAN/GNS of layer structure.

Further, using the S/PAN/GNS electrode composite material making as positive electrode active materials assembled battery.All the other formations of battery and method of testing are with embodiment 5.

Figure 23 is battery charge-discharge performance figure under 0.1C multiplying power that embodiment 6 provides.Specific capacity when battery discharges first reaches 1588.9mAh/g, almost not decay of capacity in 100 processes of battery charging and discharging circulation, and coulomb efficiency is about 100%, the effect of shuttling back and forth that shows to contain in battery is inhibited, and has further verified that the electrode composite material that preparation method provided by the invention obtains has excellent cycle performance.

Embodiment 7

1g graphite and 50g sodium chloride are ground to 10min in agate mortar, remove the pollutant on graphite, and by its porphyrize.Then by distilled water washing for the mixture of graphite and sodium chloride for several times, and vacuum filtration is to remove sodium chloride, 0.2 micron, filter membrane aperture.After filtration, graphite is put into vacuum drying chamber, dry 20min, removes remaining moisture at 70 ℃.After dry, the solid of gained is mixed in the round-bottomed flask of 250ml to uninterrupted stirring 24 hours at 25 ℃ with the 23ml concentrated sulfuric acid.In above-mentioned dispersion liquid, add 100mg sodium nitrate, stir 5min and make its dissolving.Then, flask is placed in to ice bath, temperature remains on below 20 ℃, in suspension, adds 3g potassium permanganate, is then heated to 40 ℃, keeps 30min, adds 3ml ultra-pure water, after 5min, then adds 3ml ultra-pure water, after 5min, adds 40ml ultra-pure water.Afterwards, suspension is heated to 100 ℃ and maintenance reaction 15min, then adds 140ml ultra-pure water and 10ml hydrogen peroxide (H ₂o ₂, 30wt%), stop reaction.Continue stirred suspension 5min, then use 5% hydrochloric acid centrifuge washing 2 times, ultra-pure water centrifuge washing for several times, the sediment obtaining is distributed in 150ml ultra-pure water, ultrasonic 30min, obtain a kind of brown, uniform suspension, finally suspension is dialysed to remove remaining salt and acid completely, obtain graphite oxide.

Getting respectively 64ml concentration is that the PAN/DMF solution of 5.88g/L and the RGO solution of different amounts mix, and makes the mass ratio of RGO and PAN be respectively 1:16 and 1:32; High degree of agitation 15min.Then to beaker, add water, until it reaches 600ml, follow vigorous stirring 24h.Then, under 10000rpm, centrifugal 10min obtains grey compound, with being about to grey compound and 1.6g sulphur, carries out wet ball grinding, and dispersant is ethanol, and drum's speed of rotation is 600rpm, ball milling 30min.By the mixture obtaining dry 2h in 60 ℃ of vacuum drying chambers.Then, by the dried product of 0.7g 150 ℃ of heating 1h in pipe furnace, 320 ℃ of heating 3h annealing.Finally, obtain the electrode composite material of S/PAN/RGO, be denoted as respectively S/PAN/RGO-16, S/PAN/RGO-32.Wherein, the sulfur content in both is recorded and is about 44wt% by elemental analyser.

Embodiment 8

By assembling button cell, CR2032 studies the chemical property of electrode composite material S/PAN/RGO-16.

By electrode composite material S/PAN/RGO-16, conductive agent Ketjen black KB600 and binding agent PVDF according to weight ratio 8:1:1, in NMP, mix and make slurry, subsequently slurry is coated on the nickel foam collector of 12 millimeters of diameters to the dry work electrode that makes for 12 hours at 80 ℃.Lithium metal is as to electrode, and electrolyte is the LiPF that contains 1M ₆vinyl carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) (volume ratio 1:1:1) solution, barrier film is ENTEK ET20-26, assembles CR2032 button cell in being full of the glove box of argon gas.Then by New Ware battery testing system, at room temperature with certain current density, battery is carried out to charge-discharge test, open circuit voltage scope is 1-3V.

Embodiment 9

As different from Example 8, with S/PAN/RGO-32, substitute S/PAN/RGO-16, the chemical property of electrode composite material S/PAN/RGO-32 is studied.

Figure 24 is that the battery of embodiment 8 is with the graph of a relation of charging/discharging voltage and specific capacity under 0.1C multiplying power.As can be seen from Figure 24, the discharge capacity first of compound S/PAN/RGO-16 be about be greater than the calculating gained of 1800mAh/g(based on sulphur).This is far longer than the theoretical capacity 1672mAh/g of sulphur, and this is because irreversible lithium inserts in the PAN skeleton of conjugated pi system.In the 2nd circulation, this compound shows the reversible capacity of 1470mAh/g, and the utilance of the sulphur of this expression approximately reaches 90%.

From Figure 24, it can also be seen that, in the 1st circulation, at 2.35V, have a little voltage platform (arrow points place in Figure 24), at 1.65V, have a large voltage platform simultaneously.These two voltage platforms are difficult to be distinguished and arrive in the 2nd time and later circulation, and in fact, unique voltage platform is at about 1.8V.In addition, from the 1st time to the 10th time, charge and discharge platform is converted into higher value.

Figure 25 is the CV curve of the battery of embodiment 8, and sweep speed is 0.1mV/s.In the 1st circulation, at 2.35V, there is little negative electrode peak (arrow points place in Figure 25), at 1.21V, there is large negative electrode peak.This shows the two-step reaction between lithium and sulphur.At 2.4V, there is a large anode peak, for lithium ion is deviate from LiS _n.After circulation in, the negative electrode peak of 2.35V disappears, the negative electrode peak of 1.21V obviously shifts simultaneously, in the 10th circulation, goes to 1.69V.In addition the very little displacement in anode peak.This is consistent with Figure 24.

Figure 26 is embodiment 8 and the performance test of the battery of embodiment 9 under the multiplying power progressively increasing.Battery with the multiplying power circulation of 0.2C 10 times after, 0.5C circulation 10 times, 1C circulation 10 times, and 2C circulation 10 times, then reduce to 0.2C recirculation 10 times.As can be seen from Figure 26, the stable capacity that battery 0.2C, 0.5C, 1C and the 2C of embodiment 8 are corresponding is about respectively 1353mAh/g, 1292mAh/g, 1180mAh/g, 828mAh/g.This shows that embodiment 8 batteries have more excellent high rate performance.

In addition, embodiment 8 batteries also have good capacity restoration performance, and after high rate cyclic, 0.2C can also have 96% initial capacity conservation rate, and this shows that composite material S/PAN/RGO-16 has highly stable structure.

Figure 27 is battery 0.1C charge-discharge performance figure in embodiment 8 and comparative example 2.As can be seen from Figure 27, the capacity characteristic of comparative example 2 in front 20 cyclic processes is basic similar to embodiment 8, and after 40 circulations, capacity starts fast-descending, after 100 circulations, almost drops to 0mAh/g, and this shows active material inactivation substantially.The basic reason that causes active material inactivation is the dissolving of polysulfide and flies shuttle effect.And embodiment 8 is after 10 circulations, can obtain the reversible specific capacity of about 1385mAh/g.After 200 circulations, still remain on 1100mAh/g, can reach 80% the capability retention of stablizing capacity.In addition, after 20 circulations, its coulomb of efficiency approaches 100%.This explanation composite material S/PAN/RGO-16 has very excellent cycle performance, and it has effectively suppressed the dissolving of polysulfide and has flown shuttle effect.

Although inventor has done more detailed elaboration and has enumerated technical scheme of the present invention, be to be understood that, to those skilled in the art, above-described embodiment is modified and/or flexible or to adopt the replacement scheme being equal to be obvious, all can not depart from the essence of spirit of the present invention, the term occurring in the present invention, for to the elaboration of technical solution of the present invention and understanding, can not be construed as limiting the invention.

Claims

1. an electrode composite material, is characterized in that: the graphene oxide that described electrode composite material contains elemental sulfur, conducting polymer and Graphene or reduction.

2. electrode composite material according to claim 1, is characterized in that: described conducting polymer is selected from a kind of in polypyrrole and polyacrylonitrile.

3. electrode composite material according to claim 1, is characterized in that: described electrode composite material has layer structure.

4. electrode composite material according to claim 3, is characterized in that: described elemental sulfur is attached to described conducting polymer.

5. electrode composite material according to claim 3, it is characterized in that: the graphene oxide of described Graphene or reduction has nanometer laminated structure, described elemental sulfur and conducting polymer are attached to the graphene oxide of described Graphene or reduction in the lump.

6. electrode composite material according to claim 1, it is characterized in that: in described electrode composite material, the specific gravity range of described elemental sulfur is 30-90%, and the specific gravity range of described conducting polymer is 9-50%, and the specific gravity range of the graphene oxide of described Graphene or reduction is 1-20%.

7. electrode composite material according to claim 2, is characterized in that: in described electrode composite material, the mass ratio of the graphene oxide of polyacrylonitrile and reduction is 45:1-10:1.

8. a positive pole, is characterized in that: described positive pole comprises as the electrode composite material as described in any one in claim 1-7.

9. a battery, comprise positive pole, negative pole and be located at positive pole and negative pole between electrolyte, described positive pole at least comprises as the electrode composite material as described in any one in claim 1-7.

10. a preparation method for electrode composite material, is characterized in that: described preparation method comprises the steps:

Acrylonitrile, elemental sulfur, Graphene and initator are dissolved in solvent, under preset temperature, stir,

After stirring, wash and be dried, dried product is carried out under protective gas atmosphere to heat treated.

11. preparation methods according to claim 10, is characterized in that: described preset temperature range is 60-80 ℃.

The preparation method of 12. 1 kinds of electrode composite materials, is characterized in that: described preparation method comprises the steps:

Elemental sulfur, polyacrylonitrile and Graphene are dispersed in dispersant, after mechanical mixture, are dried,

Dried product is carried out under protective gas atmosphere to heat treated.

The preparation method of 13. 1 kinds of electrode composite materials, is characterized in that: described preparation method comprises the steps:

Polyacrylonitrile solution is mixed under weak basic condition with the graphene oxide suspension of reduction; after deposition; the product of deposition is leached and disperseed, will after dispersion and elemental sulfur mechanical mixture, be dried, dried product is carried out under protective gas atmosphere to heat treated.

14. according to the preparation method described in claim 12 or 13, it is characterized in that: described mechanical mixture is that ball milling mixes.

15. according to the arbitrary described preparation method of claim 10-14, it is characterized in that: described heat treated temperature range is 200-400 ℃.

The preparation method of 16. 1 kinds of electrode composite materials, is characterized in that: described preparation method comprises the steps:

The compound of polypyrrole and Graphene is joined in the suspension containing elemental sulfur, dry after mixing,

Dried product is carried out under protective gas atmosphere to heat treated.

17. preparation methods according to claim 16, is characterized in that: the compound of described polypyrrole and Graphene is prepared by situ aggregation method, comprises the steps:

By in the ultrasonic mixed solvent that is dispersed in methyl alcohol and acetonitrile of Graphene, add pyrroles, in the time of ultrasonic processing, add liquor ferri trichloridi, filter and be precipitated thing, by dry after sediment washing, obtain polypyrrole/graphene, polypyrrole is formed on Graphene.

18. preparation methods according to claim 16, is characterized in that: described heat treated temperature range is 150-350 ℃.

19. according to the arbitrary described preparation method of claim 10-16, it is characterized in that: described when dry temperature range be 60-80 ℃.