A kind of preparation method of nano ceric oxide/graphene/sulphur composite
Technical field
The present invention relates to lithium sulfur battery anode material preparation field, and in particular to a kind of nano-cerium oxide/graphene/sulphur is multiple
The preparation method and application of condensation material.
Background technology
In recent years, with the decline of oil production rate and the aggravation of global environmental pollution, countries in the world are it is well recognized that cleaning
Free of contamination electric vehicle substitution fuel vehicle is the inevitable choice of a national sustainable development.And the power electric of height ratio capacity
Pool technology turn into be pure electric automobile development key.But the ratio of the commercial lithium-ion batteries based on lithium intercalation/deintercalation
Energy is limited by its positive electrode theoretical specific capacity, and current lithium ion battery is difficult more than 200Wh/kg than energy.Positive pole
Material go no further turn into limiting lithium ion cell specific capacity improve bottleneck, therefore need badly exploitation one kind there is higher ratio
The novel lithium battery positive electrode of energy.Lithium-sulfur cell is the high-energy density secondary electricity of great development potentiality and application prospect
Pond.It has height ratio capacity (1675mAh/g) and high-energy-density (2600Wh/kg).In addition, sulphur exists as positive active material
Source, cost and environment-friendly etc. also show incomparable advantage.
But the problems such as active material utilization is low, cycle life is low and security is poor is there is at present, this serious system
About the development of lithium-sulfur cell.But there is that active material utilization is low, cycle life is low and security is poor at present etc. asks
Topic, this seriously governs the development of lithium-sulfur cell.The main reason for causing above mentioned problem has the following aspects:(1) elemental sulfur
Insulating properties.Elemental sulfur is at room temperature electronics and the insulator of ion, and electron conductivity at room temperature is 5 × 10-30S
cm-1, ionic conductance 10-15, cause lithium-sulfur cell internal resistance to increase, active material utilization is low.(2) polysulfides is molten
Solution, intermediate product polysulfide (Li caused by electrochemical reaction2Sn, n > 4) dissolve in the electrolytic solution, diffuse to cathode of lithium and with
React, cause " shuttle effect ".(3) final product Li is reacted2S is equally electronic body, can be deposited on sulfur electrode
On, and lithium ion migration velocity in solid-state lithium sulfide is slow, makes electrochemical reaction kinetic rate slack-off;(4) sulphur and final production
Thing Li2S density is different, and volumetric expansion about 79%, is easily caused Li after sulphur is lithiated2S efflorescence, causes lithium-sulfur cell
Safety problem.
To solve the above problems, Recent study it is most be carrier and conducting matrix grain using conductive carbon material as sulphur
Sulphur carbon composite anode material.The conductive excellent, specific surface area of graphene is big, chemical stability and mechanical performance are strong, solely
Special two-dimentional porous network geometry, electronics and ion transmission path in lithium-sulfur cell can be shortened, improve the electricity of elemental sulfur
Chemism, in charge and discharge cycles, peripheral lamellar graphite alkene structure will wrap to soluble more lithium sulfides of generation
Cover, be limited in inside electrode material, and then shuttle effect can be slowed down, coulombic efficiency is improved, so as to improve the ratio of electrode
Capacity and the cycle life for improving battery.It is reported that Multimetal oxide passes through hydro-thermal, solvent heat, co-precipitation, atomic layer deposition
The synthesis strategies such as product, collosol and gel and preparation method obtain different sizes such as nanoscale and micron order, different-shape such as graininess,
The different dimensions such as bar-shaped, poroid, spherical, stratiform, flower-shaped metal oxide is in a different manner as being embedded in, being involved in, being implanted into modification
Graphene, can be formed the metal oxides of the forms such as layer structure, sandwich structure, hollow core-shell structure and mixed structure-
Graphene complex.This excellent structure causes the physical absorption or chemical phase interaction between composite and more sulphions
With can preferably limit the dissolution of more sulphions, avoid producing " shuttle effect ", so as to playing very well active material (such as sulphur)
Fixation, sulfenyl composite material exhibits is gone out more preferable cyclical stability.
The content of the invention
Technical scheme is used by the present invention solves the technical problem:The present invention is directed to lithium-sulphur cell positive electrode active material
A kind of the problem of utilization rate is low, high rate performance is poor and cycle life is short, there is provided nano ceric oxide/graphene/sulphur composite wood
The preparation method of material.This method it is innovative graphene oxide is reduced, nano-metal-oxide is adulterated with sulfur loaded solvent heat
Step completion is reacted, improves reaction efficiency, preparation technology is simple, overcomes lithium-sulphur cell positive electrode active material profit in the prior art
With the shortcomings that rate is low, high rate performance is poor, cycle life is short, reaction efficiency is low, preparation technology is complicated.Prepared simultaneously using this method
Nano ceric oxide/graphene/sulphur composite as lithium sulfur battery anode material excellent electrochemical performance, in 0.1C multiplying powers
Under, the discharge capacity first of the material is up to 1400mAh/g.
The technical scheme is that:
A kind of preparation method of nano ceric oxide/graphene/sulphur composite, comprises the following steps:
The first step:Nano sulfur powder is dissolved in carbon disulfide, is made into 2-30mg/mL carbon disulfide/sulphur solution;
Second step:It is added separately to by graphene oxide and nano ceric oxide in deionized water, at normal temperatures using super
Sound separating apparatus is disperseing 1-3h to solution ultrasonic wave, obtains graphene oxide/nano ceric oxide mixing suspension;
Wherein, quality compares graphene oxide:Nano ceric oxide=1:1-20, graphene oxide and nano ceric oxide
Quality sum:Deionized water quality=0.001-0.03:1;
3rd step:Take carbon disulfide/sulphur solution of above-mentioned configuration to be added to above-mentioned graphene oxide/nano ceric oxide to mix
Close in suspension, stir 1-3h under normal temperature, obtain graphene oxide/nano ceric oxide/sulphur mixed solution, by the mixed solution
It is fitted into stainless steel cauldron, the hydro-thermal reaction 5-24h at 100-200 DEG C;Then obtained hydrogel deionization will be reacted
Water cleans 2-6 times at 60-110 DEG C, by obtained product at -45 DEG C vacuum freeze drying 5-12h, that is, obtain nano-silica
Change cerium/graphene/sulphur composite;
Wherein, quality compares graphene oxide:Sulphur=1:1-5.
The power of ultrasonic disperse instrument is 35-60kHz in described second step.
Vacuum drying vacuum in the 3rd described step is 20Pa.
Above-mentioned nano-cerium oxide/graphene/sulphur composite material and preparation method thereof, wherein involved raw material pass through business
Purchase obtains, and equipment used and technique are known to those skilled in the art.
Compared with prior art, the inventive method has the substantive distinguishing features of protrusion as follows:
In the preparation method of the present invention, nano ceric oxide is prepared using the precipitation method, technique is simple, production cost is low, easy
Industrialized in realizing, and the nano-particle that particle is small, purity is high can be made.Using nano ceric oxide to conventional graphite
The improvement that the preparation technology and material modification of alkene/sulphur composite are carried out, the aggregation that effectively prevent between graphene sheet layer are asked
Topic, effectively suppress the dissolving of polysulfide in the electrolytic solution in charge and discharge process, improve utilization rate and the discharge and recharge of active sulfur
Chemical property.
The useful achievement of the present invention:
(1) composite positive pole prepared by the present invention adsorbs sulphur in the three-dimensional grapheme grid containing metal oxide
Between, the polysulfide that effectively can prevent from being formed during circulating battery is dissolved in electrolyte, battery is had good follow
Ring stability.
(2) positive pole prepared by positive electrode provided by the invention is applied in lithium-sulfur cell, has capacity height, cycle performance
Well, the advantages that raw material sources are extensive, cost is low, green non-pollution.Nano ceric oxide is in charge and discharge process in the present invention
Polysulfide produces suction-operated, significantly reduces the dissolving of polysulfide during the course of the reaction so that prepared lithium sulphur electricity
Pond positive electrode electrochemical performance, first charge-discharge capacity are still maintained at up to 1400mAh/g after circulating 100 times
1000mAh/g or so, there is good chemical property.
(3) low in raw material price of positive material for lithium-sulfur battery provided by the invention is pollution-free, and preparation method is simple, raw
Efficiency high is produced, is adapted to large-scale production.
Brief description of the drawings
Fig. 1 is the XRD of nano ceric oxide/graphene/sulphur composite made from embodiment 1;
Fig. 2 is the thermal multigraph of nano ceric oxide/graphene/sulphur composite made from embodiment 1;
Fig. 3 is the chemical property figure of nano ceric oxide/graphene/sulphur composite made from embodiment 1.
Embodiment
Embodiment 1
(1) graphene oxide is prepared using Hummers methods:First by 1g graphite (325 mesh), 0.5gNaNO3It is dense with 23mL
Sulfuric acid is poured into 250mL beakers, is added in above-mentioned beaker 3g KMnO4 under ice bath state, is then stirred 30min, Zhi Hou
30mL deionized waters are added under stirring, continue to stir 15min.Then 50mL deionized waters are added again, are finally being mixed
30ml H are added in solution2O2, graphite oxide solution is obtained (containing a large amount of H+).Gone being added in the graphite oxide solution of preparation
Ionized water, centrifugation (6000 turns/min of rotating speed) in centrifuge tube is placed in, supernatant in centrifuge tube is removed after centrifugation, and add go again
Ionized water, centrifuge (6000 turns/min of rotating speed), repeat this operation, until pH value of solution=7, it is molten to finally give neutral alumina graphite
Liquid.By the graphite oxide solution of preparation, using ultrasonic disperse instrument, ultrasonic wave disperses 2h under 50kHz at normal temperatures, obtains aoxidizing stone
Black alkene solution, it is subsequently placed at 60 DEG C of drying box dry 24h and obtains graphene oxide powder.;
(2) a certain amount of Ce (N0 are weighed3)3·6H2O is made into 0.4mol/L solution, and ammoniacal liquor is added dropwise to pH=10.Continue
2h is stirred, after standing 4h, filtering, with distillation water washing, is subsequently placed in 90 DEG C of baking oven and dries 12h;
(3) dried sediment is ground slightly, or is directly loadable into mortar, is put into Muffle furnace, and 4h is calcined at 400 DEG C,
Obtain nano ceric oxide (particle size range 9-32nm);
(4) the nano sulfur powder (purity 99.99%) for weighing certain mass is dissolved in carbon disulfide that (purity is
99.5%), it is made into 20mg/mL solution;
(5) according to mass ratio 1:9 ratio weighs the graphene oxide of first step preparation, nano ceric oxide, according to mixed
Compound (i.e. nano ceric oxide and graphene oxide) is 0.01 with deionized water quality ratio:1 ratio, is added mixture to
In deionized water, 1h is disperseed to said mixture ultrasonic wave in 50kHz using ultrasonic disperse instrument at normal temperatures, obtains graphite oxide
The uniform mixing suspension of alkene/nano ceric oxide;
(6) take carbon disulfide/sulphur solution of above-mentioned configuration to be added to above-mentioned graphene oxide/nano ceric oxide uniformly to mix
Closing suspension, (wherein graphene oxide, sulphur mass ratio are 1:1) in, 1h is stirred under normal temperature, obtains graphene oxide/nano-silica
Change cerium/sulphur mixed solution, the mixed solution is loaded into stainless steel cauldron hydro-thermal reaction 10h at 180 DEG C;
(7) hydrogel that reaction obtains is cleaned 3 times repeatedly with deionized water at 90 DEG C, by obtained product subzero
45 DEG C, vacuum freeze drying 12h under the conditions of vacuum 20Pa, that is, obtain nano ceric oxide/graphene/sulphur composite.
Fig. 1 is the X-ray diffractogram of nano ceric oxide/graphene/sulphur composite obtained by the present embodiment.Respectively
Show nano ceric oxide, the X ray diffracting spectrum of nano ceric oxide/graphene/sulphur composite.Can from figure
Go out, diffracting spectrum unanimously occurs without miscellaneous peak, and the center of area that the nano ceric oxide sample for illustrating to prepare comprises only fluorite structure is stood
The crystal of side.
Fig. 2 is the thermogravimetric curve figure of nano ceric oxide/graphene/sulphur composite obtained by the present embodiment.From figure
In as can be seen that nano ceric oxide/graphene/sulphur composite in sulphur weight/mass percentage composition about 65%, show that this is compound
Material three-dimensional structure is excellent, there is big specific surface area, is advantageous to the storage of sulphur.
Nano ceric oxide/graphene/sulphur the composite prepared by the method for above-described embodiment 1, in lithium-sulfur cell just
Applied in the material of pole.Nano ceric oxide/graphene/sulphur composite that embodiment 1 is obtained and conductive agent Super P and glue
Agent Kynoar (PVDF) is tied with mass ratio 8:1:1, which is fully ground mixing, is made into slurry, and even application is in aluminum foil current collector
On, coating layer thickness 0.3mm, 12h is dried at 60 DEG C.Dry positive plate is cut into a diameter of 1.5cm disk, will just
Pole piece assembles to obtain button chargeable lithium ion battery with lithium cathode sheet.Chemical property analysis is carried out to prepared sample
(BTS-5V5mA, new prestige).
Fig. 3 is the chemical property curve of nano ceric oxide/graphene/sulphur composite obtained by the present embodiment.
It may be seen that under 0.1C multiplying powers, the discharge capacity first of the material is up to 1400mAh/g, and battery performance is good.
Embodiment 2
(1) prepare graphene oxide using Hummers methods (with embodiment 1);
(2) a certain amount of Ce (N03) is weighed3·6H2O is made into 1mol/L solution, and ammoniacal liquor is added dropwise to pH=10.Continue to stir
3h is mixed, after standing 6h, filtering, with distillation water washing, is subsequently placed in 100 DEG C of baking oven and dries 12h;
(3) dried sediment is ground slightly, or is directly loadable into mortar, is put into Muffle furnace, and 6h is calcined at 300 DEG C,
Obtain nano ceric oxide;
(4) the nano sulfur powder (purity 99.99%) for weighing certain mass is dissolved in carbon disulfide that (purity is
99.5%), it is made into 20mg/mL solution;
(5) according to mass ratio 1:15 ratio weighs the graphene oxide of first step preparation, nano ceric oxide, according to mixed
Compound is 0.01 with deionized water quality ratio:1 ratio, is added mixture in deionized water, at normal temperatures using ultrasound
Separating apparatus disperses 2h in 50kHz to said mixture ultrasonic wave, obtains the uniform mix suspending of graphene oxide/nano ceric oxide
Liquid;
(6) take above-mentioned configuration carbon disulfide/sulphur solution (wherein graphene oxide, sulphur mass ratio be 1:1) it is added to
State in the uniform mixing suspension of graphene oxide/nano ceric oxide, 1h is stirred under normal temperature, obtain graphene oxide/nanometer two
Cerium oxide/sulphur mixed solution, the mixed solution is loaded into stainless steel cauldron hydro-thermal reaction 12h at 180 DEG C;
(7) hydrogel that reaction obtains is cleaned 3 times repeatedly with deionized water at 90 DEG C, by obtained product subzero
45 DEG C, vacuum freeze drying 12h under the conditions of vacuum 20Pa, that is, obtain nano ceric oxide/graphene/sulphur composite.
Embodiment 3
(1) prepare graphene oxide using Hummers methods (with embodiment 1);
(2) a certain amount of Ce (N03) is weighed3·6H2O is made into 2mol/L solution, and ammoniacal liquor is added dropwise to pH=10.Continue to stir
5h is mixed, after standing 8h, filtering, with distillation water washing, is subsequently placed in 110 DEG C of baking oven and dries 12h;
(3) dried sediment is ground slightly, or is directly loadable into mortar, is put into Muffle furnace, and 8h is calcined at 450 DEG C,
Obtain nano ceric oxide;
(4) the nano sulfur powder (purity 99.99%) for weighing certain mass is dissolved in carbon disulfide that (purity is
99.5%), it is made into 20mg/mL solution;
(5) according to mass ratio 1:9 ratio weighs the graphene oxide of first step preparation, nano ceric oxide, according to mixed
Compound is 0.01 with deionized water quality ratio:1 ratio, is added mixture in deionized water, at normal temperatures using ultrasound
Separating apparatus disperses 1h in 50kHz to said mixture ultrasonic wave, obtains the uniform mix suspending of graphene oxide/nano ceric oxide
Liquid;
(6) take above-mentioned configuration carbon disulfide/sulphur solution (wherein graphene oxide, sulphur mass ratio be 1:2) it is added to
State in the uniform mixing suspension of graphene oxide/nano ceric oxide, 1h is stirred under normal temperature, obtain graphene oxide/nanometer two
Cerium oxide/sulphur mixed solution, the mixed solution is loaded into stainless steel cauldron hydro-thermal reaction 24h at 150 DEG C;
(7) hydrogel that reaction obtains is cleaned 3 times repeatedly with deionized water at 90 DEG C, by obtained product subzero
45 DEG C, vacuum freeze drying 12h under the conditions of vacuum 20Pa, that is, obtain nano ceric oxide/graphene/sulphur composite.
Unaccomplished matter of the present invention is known technology.