Sulfur-bearing anode composite material, positive plate, Li-S secondary cell and preparation method thereof
Technical field
The present invention relates to a kind of secondary cell and positive plate thereof, positive electrode and preparation method separately, relate in particular to a kind of with secondary cell and positive plate, positive electrode and the preparation method separately of elemental sulfur as positive pole.
Background technology
Li-S secondary cell system based on lithium metal negative pole and sulphur simple substance positive pole is one of combination that energy density is the highest in the known chemical bilateral system.The theoretical energy density of Li-S battery system is 2600Wh/kg and 2800Wh/L, average voltage 2.1V.Compare with TNT equivalent 1280Wh/kg with the theoretical energy density 580Wh/kg of lithium ion battery, the Li-S battery system has quite high energy density.Suppose that 25% theoretical value can realize on actual battery, the energy density of Li-S battery system is 4 times of existing lithium ion battery greatly about 700Wh/kg.Up to the present, the application potential of Li-S battery system has given confirmation by the research of a plurality of research groups.
The theoretical specific capacity that the sulfenyl positive pole can provide is 1680 mAh/g, surpasses the positive electrode of any known secondary cell.But elemental sulfur is an insulator, and because the high impedance and the reactive problem of sulphur, the efficient utilization of Li-S battery system is very difficult.In addition, the discharging product lithium sulphur compound of Li-S battery system is dissolved by electrolyte solution easily, and with lithium metal negative reaction, make circulation volume decay very fast.For the utilance that improves elemental sulfur, common in the world solution is at present: in the manufacture process of positive electrode, a large amount of electronic conductor and ion conductors of adding, high-strength and long time ball milling, solve the nonconducting problem of sulphur, though this can improve the performance of sulfur electrode to a certain extent, the utilance of active material sulphur still remains to be improved, and the adding of inert matter, greatly reduce the specific energy of battery.In electrolyte, dissolve the problem that discharge capacity descends rapidly in the charge and discharge cycles that causes for sulfide, adopt the electrolytical Li-S battery of colloidal state polymer cycle efficieny to increase than the cycle efficieny of liquid state electrolyte battery, its average attenuation rate is about 5%, but adopt the electrolytical prescription positive electrode active material utilization of colloidal state polymer not high, estimate relevantly to the absorption of electrochemical reaction intermediate product with the gel state material, and there is certain difficulty in process in the colloidal state polymer electrolyte membrance in the preparation of industrialization cell process.
From the existing disclosed situation of document, in the research of the dispersiveness of improving Li-S battery positive electrode active material sulphur, the anodal conductivity of raising, existing sublimation process by sulphur, and the preparation technology's report that sulphur and conductive carbon high strength ball milling is prepared the C/S compound, but the utilance increase rate of anodal sulphur is all very limited in the existing technology, the cyclic process capacity attenuation is bigger, still is further improved.
Summary of the invention
The technical problem to be solved in the present invention is to overcome the deficiencies in the prior art, a kind of good conductivity, good dispersion, sulfur-bearing anode composite material that active material utilization is high are provided, and the positive plate that is used for the Li-S secondary cell that comprises this sulfur-bearing anode composite material of a kind of anodal gram volume height, good cycle is provided and comprises the Li-S secondary cell of this positive plate, the corresponding preparation method that sulfur-bearing anode composite material, positive plate and Li-S secondary cell also are provided.
For solving the problems of the technologies described above, the present invention has at first proposed a kind of sulfur-bearing anode composite material, described sulfur-bearing anode composite material is the hud typed structure that shell coats kernel, described kernel is the C/S compound that elemental sulfur and nanometer conductive carbon black are combined into, and described shell is that the organic polymer that contains plasticizer coats rete.
In the above-mentioned sulfur-bearing anode composite material, described organic polymer is selected from the mixture of one or more compositions in polyoxyethylene, polyoxyethylene-polyoxypropylene copolymer, polyethylene glycol, Kynoar, the vinylidene fluoride-hexafluoropropylene copolymer; Described plasticizer is low molecular poly, dibutyl phthalate, tributyl phosphate, butyl borate or polyethylene glycol alkyl ether (for example Polyethylene glycol dimethyl ether etc.).
As a total technical conceive, the present invention also provides a kind of positive plate of the Li-S of being used for secondary cell, and described positive plate comprises the aluminium collector of being with conductive coating and the above-mentioned sulfur-bearing anode composite material that is coated on this aluminium collector.
As a total technical conceive, the present invention also provides a kind of Li-S secondary cell, described Li-S secondary cell is to be formed by battery battery core and electrolyte assembling back encapsulation, described battery battery core is mainly formed through reeling, suppressing by negative pole assembly, polyalcohol stephanoporate barrier film and above-mentioned positive plate, described negative pole assembly comprises lithium paper tinsel or lithium-aluminium alloy paper tinsel, and described electrolyte comprises organic solvent and the electrolyte lithium salt that is dissolved in this organic solvent.
In the above-mentioned Li-S secondary cell, described organic solvent is preferably the mixture of one or more compositions in dioxolane, triglyme, glycol dimethyl ether, the oxolane.
In each above-mentioned Li-S secondary cell, described electrolyte lithium salt is preferably the mixture of one or more compositions in hexafluoro phosphorus lithium, lithium perchlorate, trifluoromethyl sulfonic acid lithium, lithium nitrate, the trifluoromethyl semi-annular jade pendant imide li.
As a total technical conceive, the present invention also provides a kind of preparation method of above-mentioned sulfur-bearing anode composite material, may further comprise the steps:
(1) (specific area of used conductive nano carbon black is preferably 60m with elemental sulfur and nanometer conductive carbon black
2/ g~1200m
2/ g) according to (1~5): 1 quality mixes than ball milling that (the ball milling time is preferably 15min~4h), then mixture is heated to 120 ℃~160 ℃, general employing inert gas (for example nitrogen or argon gas etc.) protection in the heating process, make described elemental sulfur fusion and compound, obtain dispersiveness, the good C/S compound of conductivity with described nanometer conductive carbon black;
(2) with the C/S compound ball milling or the grinding that obtain in the step (1), add the above-mentioned organic polymer that contains plasticizer then and carry out the emulsification shearing, the consumption of described organic polymer is 0.1%~10% of a C/S compound quality, and described plasticizer dosage is 5%~20% of this organic polymer consumption; Carry out suction filtration (removing unnecessary solvent and polymer feed liquid) after the dispersion, prepare the sulfur-bearing anode composite material of hud typed structure after 50 ℃~80 ℃ vacuumize with the Buchner funnel suction filtration.
The sulfur-bearing anode composite material of above-mentioned employing fusion method preparation can effectively improve anodal conductivity and dispersiveness, and the C/S composite surface structural change through coating helps electrolytical infiltration.
As a total technical conceive, the present invention also provides a kind of preparation method of the above-mentioned positive plate that is used for the Li-S secondary cell, may further comprise the steps: at first, the sulfur-bearing anode composite material that makes with above-mentioned preparation method and adhesive, solvent or dispersant and process auxiliaries ball milling mix, 40~85 parts of sulfur-bearing anode composite materials (being preferably 50~75 parts) wherein, 4~20 parts in adhesive (being preferably 6~15 parts), 3~10 parts of process auxiliaries, the consumption of solvent or dispersant are 40~100 times of binder dosage; Then the mixed material of (general ball milling 1.5h~5h get final product) behind the ball milling is printed on (available silk screen) or is coated on (available coating machine) described aluminium collector, coating layer thickness (single face coating) is controlled at 20 μ m~100 μ m, makes positive plate (positive plate that can prepare double-coated when adopting the coating machine coating).After the positive plate room temperature that makes is dried in the air and is made 24h, cut-parts behind the vacuum oven 12h of 40 ℃~80 ℃ (being preferably 50 ℃~60 ℃), soldering polar ear.
The above-mentioned preparation method who is used for the positive plate of Li-S secondary cell, described adhesive is preferably the copolymer of Kynoar, polyoxyethylene, polystyrene-poly vinyl acetate co-polymer or biasfluoroethylene-hexafluoropropylene; Described solvent or dispersant are preferably isopropyl alcohol, water, N--methyl pyrrolidone, acetonitrile or butanone; Described process auxiliaries preferably includes conductive agent (for example acetylene black), silicon dioxide, organo montmorillonite or inorganic imvite.
As a total technical conceive, the present invention also provides a kind of preparation method of above-mentioned Li-S secondary cell, may further comprise the steps: earlier a described lithium paper tinsel and a copper polar ear are suppressed (colding pressing or hot pressing) back as the negative pole assembly, then can be with described negative pole assembly in drying room or glove box, polyalcohol stephanoporate barrier film and positive plate are reeled, make battery battery core after repressed, with this battery battery core aluminium plastic packaging bag of packing into, add described electrolyte, described electrolyte adds according to the consumption that every gram active material (sulphur is active material) adds 2g~6g, leave standstill more than the 24h, encapsulation obtains the Li-S secondary cell through secondary.
Above-mentioned each technical scheme of the present invention is based on that following technical thought puts forward: promptly adopt elemental sulfur and nanometer conductive carbon black melting mixing after pre-dispersed earlier, enter the hole of nanometer conductive carbon black by melting process through pre-dispersed elemental sulfur, prepare the C/S compound, form finely dispersed micro-nano-scale thin layer at the nanometer conductive carbon black surfaces externally and internally, coat through organic polymer then, obtain sulfur-bearing anode composite material (it is equivalent to a C/S microreactor), use this sulfur-bearing anode composite material and adhesive again, plasticizer, process auxiliaries etc. carry out ball milling to be mixed, the anode sizing agent of preparation Li-S secondary cell, make positive plate after system film and the drying cut-parts, obtain Li-S secondary cell of the present invention with the assembling of negative pole assembly again.
Compared with prior art, the invention has the advantages that: the invention solves Li-S secondary battery anode active compound conductivity, bad dispersibility, the problem that active material utilization is on the low side, when coat C/S compound formation C/S microreactor with organic polymer after, in the activation process after the battery assembling, organic polymer can receive organic solvent and the lithium salts in the electrolyte to form the thin layer that is similar to gel electrolyte, and then the molten mistake of prevention positive active material (elemental sulfur) and electrochemistry intermediate product (poly-sulphur), preparation-obtained Li-S secondary cell is when its energy density improves, and cycle performance all has a more substantial increase.The anodal gram volume of the Li-S secondary cell that the present invention's assembling obtains is higher than 1200mAh/g, positive electrode active material utilization surpasses 70%(generally can reach 75%), energy content of battery density is greater than 320Wh/kg, 50 capacity of C/20 charge and discharge cycles remain on more than the 1000mAh/g, conservation rate is higher than 80%, and efficiency for charge-discharge is greater than 90%.To sum up, the present invention has improved the dispersiveness of positive active material, has effectively improved anodal gram volume and cycle performance of battery simultaneously.
Description of drawings
Fig. 1 is the positive plate discharge curve of the Li-S secondary cell of preparation in the embodiment of the invention 1.
Fig. 2 is the Li-S secondary cell cycle charge-discharge curve chart repeatedly of preparation in the embodiment of the invention 1.
Embodiment
Embodiment 1
A kind of sulfur-bearing anode composite material of the present invention, this sulfur-bearing anode composite material are the hud typed structure that shell coats kernel, and kernel is the C/S compound that elemental sulfur and nanometer conductive carbon black are combined into, and shell is the coated with polyethylene glycol rete of homemade plasticizer-containing.
The preparation method of the sulfur-bearing anode composite material of present embodiment may further comprise the steps:
(1) (specific area is 1200m with elemental sulfur and nanometer conductive carbon black
2/ g) according to 2.33: 1 quality than ball milling mixing 0.5h, then mixture is joined in the there-necked flask of 1000ml, be heated to 150 ℃ under the nitrogen protection, insulation 2h, make elemental sulfur fusion and compound, obtain dispersiveness, the good C/S compound of conductivity with nanometer conductive carbon black;
(2) get the C/S compound 30g ball milling (or grinding) that obtains in the step (1), join 60g concentration then and be in polyethylene glycol/acetonitrile/water solution of 5%, this mixture is carried out emulsification to be sheared, the consumption that coats with polyethylene glycol is 0.5% of a C/S compound quality, coat and select low molecular poly for use with plasticizer in the polyethylene glycol, consumption is 5% of a polymer poly ethylene glycol consumption, emulsifying mixture shear-mixed 20min(2min~30min all can), with 50 ℃ of vacuumize 2h behind the Buchner funnel suction filtration, prepare the above-mentioned sulfur-bearing anode composite material of hud typed structure.
A kind of positive plate that is used for the Li-S secondary cell of the present invention, this positive plate comprise the aluminium collector of being with conductive coating and are coated on the sulfur-bearing anode composite material of the above-mentioned present embodiment on this aluminium collector.
The above-mentioned preparation method who is used for the positive plate of Li-S secondary cell, may further comprise the steps: at first, the sulfur-bearing anode composite material 20g that present embodiment is made and adhesive Kynoar 2.1g, solvent butanone 90g and process auxiliaries 3g(comprise acetylene black 2g, organo montmorillonite 1g) mixes, ball milling mixing 4h, then the mixed material behind the ball milling is coated on the aluminium collector of band conductive coating, the single face coating layer thickness is controlled at 40 μ m, makes the positive plate of double-coated.After the positive plate room temperature that makes hung 24h, cut-parts behind 60 ℃ vacuum oven 12h were tailored the positive plate into long 40cm, wide 5.3cm, soldering polar ear.
A kind of Li-S secondary cell of the present invention, this Li-S secondary cell is to be formed by battery battery core and electrolyte assembling back encapsulation, battery battery core is mainly formed through reeling, suppressing by negative pole assembly, polyalcohol stephanoporate barrier film and positive plate, the negative pole assembly comprises the lithium paper tinsel, electrolyte is that the trifluoromethyl semi-annular jade pendant imide li of concentration 1M is dissolved in the solution that forms behind the organic solvent, and organic solvent is the mixed solvent that glycol dimethyl ether and dioxolane are formed.
The preparation method of the Li-S secondary cell of present embodiment, may further comprise the steps: earlier with after lithium paper tinsel and the copper polar ear hot pressing as the negative pole assembly, then polyalcohol stephanoporate barrier film, negative pole assembly and positive plate are reeled in glove box, make battery battery core (long 47cm, wide 5.5cm) after repressed, with this battery battery core aluminium plastic packaging bag of packing into, and adding 1M trifluoromethyl semi-annular jade pendant imide li/glycol dimethyl ether/dioxolane electrolyte 3g, leave standstill more than the 24h after the encapsulation, encapsulation obtains the Li-S secondary cell through secondary, tests its electrical property.
The positive plate discharge curve of the Li-S secondary cell of present embodiment preparation as shown in Figure 1, as seen from Figure 1, the anodal gram volume of the Li-S secondary cell that present embodiment prepares surpasses 1300mAh/g, positive electrode active material utilization reaches 75%; Repeatedly the cycle charge-discharge curve chart is as shown in Figure 2 for the Li-S secondary cell of present embodiment preparation, as seen from Figure 2, the Li-S secondary cell C/20 charge-discharge energy density for preparing is 300Wh/kg, 20 energy densities of charge and discharge cycles reduce by 10%, 50 times circulating energy density remains on more than 80% of initial value, and efficiency for charge-discharge is higher than 90%.
Embodiment 2
A kind of sulfur-bearing anode composite material of the present invention, this sulfur-bearing anode composite material is the hud typed structure that shell coats kernel, kernel is the C/S compound that elemental sulfur and nanometer conductive carbon black are combined into, and shell is that the Kynoar of homemade plasticizer-containing coats rete.
The preparation method of the sulfur-bearing anode composite material of present embodiment may further comprise the steps:
(1) (specific area is 1200m with elemental sulfur and nanometer conductive carbon black
2/ g) according to 4: 1 quality than ball milling mixing 0.5h, then mixture is joined in the there-necked flask of 1000ml, be heated to 150 ℃ under the nitrogen protection, insulation 2h, make elemental sulfur fusion and compound, obtain dispersiveness, the good C/S compound of conductivity with nanometer conductive carbon black;
(2) get the C/S compound 20g ball milling (or grinding) that obtains in the step (1), join 70g concentration then and be in Kynoar/butanone solution of 4%, this mixture is carried out emulsification to be sheared, the consumption that coats with Kynoar is 2% of a C/S compound consumption, coat and select Polyethylene glycol dimethyl ether for use with plasticizer in the Kynoar, consumption is 10% of a polymer poly vinylidene consumption, emulsifying mixture shear-mixed 20min(2min~30min all can), with 50 ℃ of vacuumize 2h behind the Buchner funnel suction filtration, prepare the above-mentioned sulfur-bearing anode composite material of hud typed structure.
A kind of positive plate that is used for the Li-S secondary cell of the present invention, this positive plate comprise the aluminium collector of being with conductive coating and are coated on the sulfur-bearing anode composite material of the above-mentioned present embodiment on this aluminium collector.
The above-mentioned preparation method who is used for the positive plate of Li-S secondary cell, may further comprise the steps: at first, the sulfur-bearing anode composite material 20g that present embodiment is made comprises silicon dioxide 0.8g and acetylene black 2g with polystyrene-poly vinyl acetate co-polymer 2g, aqueous solvent 80g and process auxiliaries 2.8g() mix, ball milling 4h, be coated on the mixed material behind the ball milling on the aluminium collector of band conductive coating with coating machine then, the single face coating layer thickness is controlled at 80 μ m, makes the positive plate of double-coated.After the positive plate room temperature that makes was dried in the air and made 24h, cut-parts behind 60 ℃ vacuum oven 12h were tailored the positive plate into long 40cm, wide 5.3cm, soldering polar ear.
A kind of Li-S secondary cell of the present invention, this Li-S secondary cell is to be formed by battery battery core and electrolyte assembling back encapsulation, battery battery core is mainly formed through reeling, suppressing by negative pole assembly, polyalcohol stephanoporate barrier film and positive plate, the negative pole assembly comprises the lithium paper tinsel, electrolyte is that the trifluoromethyl semi-annular jade pendant acid lithium of concentration 1M is dissolved in the solution that forms behind the organic solvent, and organic solvent is the mixed solvent that glycol dimethyl ether and dioxolane are formed.
The preparation method of the Li-S secondary cell of present embodiment, may further comprise the steps: earlier with lithium paper tinsel (the wide 55mm of lithium paper tinsel, thickness is 100 μ m) with copper polar ear hot pressing after as the negative pole assembly, then with the polyalcohol stephanoporate barrier film, negative pole assembly and positive plate are reeled in glove box, make battery battery core (long 47cm after repressed, wide 5.5cm), with this battery battery core aluminium plastic packaging bag of packing into, and adding 1M trifluoromethyl semi-annular jade pendant acid lithium/glycol dimethyl ether/dioxolane electrolyte 3g, leave standstill more than the 24h after the encapsulation, encapsulation obtains the Li-S secondary cell through secondary, tests its electrical property.
The Li-S secondary cell C/20 charge-discharge energy density that present embodiment prepares is 300Wh/kg, 20 energy densities of charge and discharge cycles are constant substantially, 50 times circulating energy density remains on more than 80% of initial value, and 100 times cyclic discharge capacity keeps more than 60% of initial value.