CN104183868B - Perfluor sulfonyl dicyanamide lighium polymer electrolyte preparation method and lithium-sulfur rechargeable battery - Google Patents

Abstract

The invention discloses a method for preparing a perfluorosulfonyl bisnitrile amide lithium polymer electrolyte, comprising: mixing and reacting malononitrile and lithium hydride in the presence of a specific mixed solvent A at an appropriate temperature and an inert atmosphere for not less than 5 hours , to obtain a lithium malononitrile solution; the purified lithium malononitrile solution reacts similarly with the perfluorosulfonyl fluoride resin with an ethoxy side chain, the lithium malononitrile remains in excess, and after the reaction, it is subjected to subsequent treatment, namely A perfluorosulfonyl bis-nitrile amide lithium polymer electrolyte containing a lithium bis-nitrile amide group in the side chain is obtained. The lithium-sulfur secondary battery of the present invention includes a lithium negative electrode, a positive pole piece, an electrolyte membrane, and an organic electrolyte; the electrolyte used in the electrolyte membrane is a perfluorosulfonyl bisnitrile amide lithium polymer electrolyte; the positive pole piece is mainly composed of a current collector and sulfur cathode active materials; the organic electrolyte contains lithium salts and non-aqueous solvents. The lithium-sulfur secondary battery product of the present invention has high gram capacity of active material during charging and discharging, less dissolution and loss of active material, and long cycle life.

Description

Preparation method of perfluorosulfonyl bisnitrile amide lithium polymer electrolyte and lithium-sulfur secondary battery

technical field

The invention relates to the preparation of a functional electrolyte membrane and a corresponding lithium-sulfur battery, in particular to a preparation method of a perfluorosulfonyl bisnitrile amide lithium polymer electrolyte and a lithium-sulfur secondary battery.

Background technique

With the rapid development of current communications, portable electronic devices, electric vehicles and space technology, the performance of energy storage batteries is increasingly demanding. It is important to develop new lithium batteries with high specific energy, low cost and environmental friendliness. meaning.

Li-S secondary batteries based on Li metal anode and sulfur cathode represent one of the highest energy density combinations of known chemically reversible systems. The theoretical energy density of the lithium-sulfur system is 2600Wh/kg, and the actual energy density that can be expected to be achieved is 700Wh/kg, which is three times that of the existing lithium-ion batteries. Although the achievable energy density of lithium-sulfur batteries has reached 300-400Wh/kg, the sulfur positive electrode is not conductive, the electrochemical reaction process is complicated, and the lithium negative electrode has high activity. The intermediate product lithium polysulfide dissolves in the electrolyte during the charging and discharging process of lithium-sulfur batteries. , in the liquid phase diffuses to the negative electrode through the porous diaphragm (that is, the "shuttle effect"), resulting in the consumption of positive active materials and the corrosion and passivation of the negative electrode, which seriously affects the cycle performance of lithium-sulfur batteries.

The existing perfluorosulfonyl bisnitrile amide lithium polymer electrolyte can overcome the above-mentioned defects to a certain extent, but the existing preparation process has low yield and high cost, and is difficult to be applied to industrial production.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and to provide a perfluorinated compound that can block the penetration of anions and organic molecules, has high ionic conductivity and chemical and electrochemical stability, and has a high yield. The preparation method of the sulfonamide lithium polymer electrolyte also provides a lithium-sulfur secondary battery with high gram capacity of active material, less dissolution and loss of active material and long cycle life during charging and discharging.

In order to solve the above-mentioned technical problems, the technical solution proposed by the present invention is a method for preparing a perfluorosulfonyl bisnitrile amide lithium polymer electrolyte with a higher yield (polymer yield can reach more than 90%), comprising the following steps :

(1) Mix and react malononitrile and lithium hydride in the presence of a specific mixed solvent A at an appropriate temperature and an inert atmosphere. The reaction time is not less than 5 hours. After the reaction is completed, unreacted raw materials and precipitated by-products are removed by filtration, that is Lithium malononitrile solution can be prepared;

(2) The above-mentioned malononitrile lithium solution after purification is reacted similarly with the perfluorosulfonyl fluoride resin with the ethoxy side chain, and the malononitrile lithium remains in excess (malononitrile lithium and perfluorosulfonyl fluoride resin The preferred proportioning range is controlled at 5:1-2:1), after the reaction is completed, after the subsequent treatment, the perfluorosulfonyl bisamide lithium polymer electrolyte containing lithium bisamide groups in the side chain can be obtained.

The above-mentioned technical scheme of the present invention mainly makes breakthroughs from two points in order to achieve a significant increase in product yield: firstly, from the selection and optimization of the reaction solvent, the yield of the product is improved by selecting a specific mixed solvent, which is An important improvement determined by the inventor after trial and error and creative work; in addition, the present invention also guarantees the yield of the product by prolonging the reaction time, and the limited reaction time is not less than 5h, and can be combined with the selection of the aforementioned mixed solvent by prolonging the reaction time and optimization to achieve complementary advantages, so as to greatly improve the yield of the reaction product of the present invention.

Above-mentioned preparation method, preferably, in described step (1), according to the requirement of stoichiometric ratio, lithium hydride and malononitrile react with 2:1 equivalent, but because lithium hydride is the higher reactant of activity, easily A side reaction occurs, so the reaction system should preferably be controlled in excess of lithium hydride in addition to the purification treatment, and the excess ratio is 1% to 80% (the excess ratio of lithium hydride is the mass fraction of the excess part accounting for the theoretical amount), so as to facilitate The dinitrile substitution is complete, and the subsequent reaction obtains a higher polymer yield.

In the above preparation method, preferably, in the step (1), the specific conditions of the mixing reaction are reflux and stirring at 20° C. to 100° C. for 5 h to 40 h. It should be emphasized that it is very important to control the reaction time more than 5h to improve the yield of the polymer, which is also one of the key features of the present invention, and this is mainly based on our following research: The methyl group contains two active hydrogens, and the electrophilic substitution reaction between lithium hydride and it produces hydrogen gas; a small amount of impurities in the raw material and the one-substitution reaction of the methylene group have a faster reaction rate, release hydrogen gas, and generate a large number of bubbles, but if Sufficient substitution requires a long reaction time; if the substitution reaction is insufficient, the yield of the final product will be reduced due to solubility problems, and the performance of the electrolyte membrane will be affected.

The above-mentioned preparation method, preferably, in the step (1), the specific mixed solvent A is a mixed system of anisole and N-methylpyrrolidone, and the mass ratio of anisole and N-methylpyrrolidone is 20:1 to 2:1, the amount of the specific mixed solvent A added is 10 to 50 times the mass of malononitrile. In the present invention, we have finally found that the mixed solvent of anisole and N-methylpyrrolidone has moderate solubility to the intermediate product and final product of the reaction, which is beneficial to the reaction, by repeatedly testing and preparing dozens of solvents. In the process, an appropriate degree of homogeneous reaction is maintained to further increase the yield. This feature is difficult to see when choosing other single solvents or other combination solvents.

In the above-mentioned preparation method, preferably, in the step (2), the specific conditions for the similar transformation reaction are stirring and reflux reaction for 4h-30h under an inert atmosphere at 40°C-120°C.

In the above-mentioned preparation method, preferably, in the step (2), the subsequent treatment refers to that the polymer precipitate generated by the similar conversion reaction is suction filtered and washed (preferably with a mixed solvent containing ethanol, water, etc. for suction filtration) Washing), dry and weigh to calculate the crude yield, or directly add solvent B and stir and dissolve at 30°C to 100°C, then filter out a small amount of insoluble matter to obtain perfluorosulfonyl bisnitrile amide lithium polymer electrolyte solution (clear transparent solution) ; and then concentrated by distillation to obtain a concentrated solution of lithium polymer electrolyte of perfluorosulfonyl bisnitrile amide; generally, it is preferred to distill and concentrate the solution to a concentration of 10% to 30%. The insolubles were weighed after washing and drying, and used to calculate the actual yield of the perfluorosulfonyl bisnitrile amide lithium polymer electrolyte.

In the above preparation method, preferably, the subsequent treatment also includes: coating the prepared polymer electrolyte concentrate with a coating machine, scraping coating with a doctor blade or casting a film, and adding an extractant after initial drying , extract the solution to form a secondary film of the polymer, after vacuum drying, heat treatment at 120 ° C ~ 200 ° C for 0.5 h ~ 4 h, after cooling, the lithium polymer electrolyte membrane of perfluorosulfonyl bisnitrile amide is obtained; the selected extraction agent Ethanol, isopropanol, diethyl ether, propyl ether, tetrahydrofuran, ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, dioxolane, water, dichloromethane, dichloroethane, toluene, at least one of xylenes. The addition of the extractant is beneficial to the complete removal of the volatile matter of the electrolyte membrane, and it is also beneficial to the demoulding of the electrolyte.

In the above preparation method, preferably, the solvent B is anisole, N-methylpyrrolidone, N-ethylpyrrolidone, dichloroethane, dimethyl sulfoxide, sulfolane, water, triglyme , tetraethylene glycol dimethyl ether, etc., or a mixture of two.

In the above-mentioned preparation method, preferably, part of the components of the specific mixed solvent A and solvent B can be the same, and both solvent A and solvent B are a mixed solvent system containing anisole, and after adding solvent B, the solid content therein reaches 4% to 50%. In the above two-step reaction, the use of the same solvent system can avoid the cumbersome operation of solvent removal treatment, reduce the loss of products in the subsequent treatment process and the possible side reactions caused by high-temperature distillation and concentration. In addition, the mixed solvent system comprising one or two ethers and other types of solvents can meet the requirements of increasing the reaction temperature and reducing the volatilization of solvents in the above two-step reaction, and is easy to realize the purification of the main products of the two-step reaction.

The above-mentioned preparation method of the present invention mainly adopts a polymer analogous transformation method to prepare an electrolyte with a carbon chain structure substituted by perfluoro as the main chain and an ethoxy side chain end containing a lithium sulfonyl bisnitrile amide group; the system relies on the main chain The dense crystalline structure, the charge effect and volume effect of the side chain inhibit the migration of anions and organic solvent molecules in the electrolyte, thereby obtaining a single cation migration.

As a general technical concept, the present invention also provides a lithium-sulfur secondary battery, comprising a lithium negative electrode, a positive electrode sheet, an electrolyte membrane, and an organic electrolyte;

The electrolyte used in the electrolyte membrane is the perfluorosulfonyl bisnitrile lithium polymer electrolyte obtained by the above-mentioned preparation method of the present invention;

The lithium negative electrode mainly includes a negative electrode active material composed of lithium metal or a lithium-containing alloy (it may also include conductive materials and binders, etc.);

The positive pole piece is mainly composed of a current collector (preferably aluminum foil or aluminum mesh) that conducts current, and a positive active material coated on the current collector, a conductive agent and a binder; the positive active material is sulfur element, organic At least one of sulfide, carbon-sulfur polymer; the conductive agent is a carbon-based conductive agent, such as one or more of preferred conductive carbon black, acetylene black or graphite powder; the binder is preferably Polyethylene oxide, styrene-butadiene rubber, polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene copolymer, etc. Wherein, the mass percentages of the positive electrode active material, the conductive agent and the binder are preferably 50%-80%, 15%-30% and 5%-20%, respectively.

The organic electrolytic solution comprises a lithium salt and a non-aqueous solvent, and the lithium salt is selected from lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium perchlorate (LiClO ₄ ), lithium trifluoromethanesulfonyl imide (LiN(CF ₃ SO ₂ ) ₂ ), lithium trifluoromethanesulfonate (LiSO ₃ CF ₃ ), lithium nitrate, lithium polysulfide of different valence states at least A kind; Described non-aqueous solvent comprises acetonitrile, cyclohexane, cyclohexanone, isopropanol, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, Diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, ethyl butyrate, Dimethoxyethane, 1,3-dioxolane, diglyme (dimethoxyethyl ether), triglyme, tetraglyme, ethylene glycol di At least one of methyl ether, sulfolane, dimethyl sulfoxide, and dimethyl sulfone. The added non-aqueous solvent has a certain activation effect on the electrolyte membrane, and the electrolyte membrane will absorb the non-aqueous solvent in the electrolyte. After reaching a certain balance, it will play a good role in the lithium-sulfur secondary battery with high ion conductivity. Lithium ions and inhibit the mutual migration and diffusion of anions and organic molecules between the positive and negative electrodes. The type of solvent has a certain influence on the conductivity of the electrolyte membrane. By adjusting the type and concentration of the non-aqueous solvent in the organic electrolyte, the ion conductivity of the electrolyte membrane can be adjusted within a certain range, and the cycle of the lithium-sulfur secondary battery can be improved. performance.

Compared with the prior art, the present invention has the advantages of:

1. The perfluorosulfonyl bisnitrile amide lithium polymer electrolyte prepared by the above-mentioned preparation method of the present invention has a highly crystalline main chain to form a dense barrier layer, and the side chains have anion fixed charges, which jointly block the penetration of anions and organic molecules. The main chain of the polymer electrolyte is a perfluorinated carbon-carbon chain, and the anions fixed in the side chains are sulfonyl bisamide anions with a large volume, and have high ion conductivity and chemical and electrochemical stability.

2. The preparation method of the present invention adopts perfluorosulfonyl fluoride resin as a raw material, and prepares it through a similar conversion reaction with lithium malononitrile. The product mixture prepared by the synthesis steps and process conditions of the present invention can be purified at room temperature to 100 After stirring and dissolving at ℃, filtering to obtain a high-purity polymer solution, the whole preparation process is simple, the yield of the product polymer is high, and the yield of the finally prepared single lithium ion polymer is higher than 90%.

3. The lithium-sulfur secondary battery of the present invention mainly suppresses the interdiffusion of polysulfide anions, alkoxide anions and organic solvents between the positive and negative electrodes through the functional polymer electrolyte membrane prepared by the present invention. It is shown to prevent the diffusion of polysulfide anion and alkoxy anion in the electrolyte and the side reaction with the lithium metal anode, and has a high ionic conductivity, so as to ensure that the active material exerts a high gram capacity during the charging and discharging process of the battery, and at the same time Reduce the dissolution and loss of active materials and improve the cycle life of the lithium-sulfur secondary battery (the capacity of the lithium-sulfur secondary battery is kept above 80% after 100 cycles).

Generally speaking, the preparation process of the present invention has simple steps, excellent product performance and high product yield, and can be well applied in industrial practice.

Description of drawings

FIG. 1 is a sample of a single lithium ion polymer electrolyte membrane prepared in Example 1 of the present invention.

Fig. 2 is the fluorine nuclear magnetic spectrum of the single lithium ion polymer prepared in Example 1 of the present invention.

FIG. 3 is a cycle performance curve of a lithium-sulfur battery using a polymer electrolyte membrane in Example 1 of the present invention.

Fig. 4 is the 0.1C charge and discharge capacity and internal resistance curves of the lithium-sulfur battery using the polymer electrolyte membrane in Example 2 of the present invention.

detailed description

In order to facilitate the understanding of the present invention, the following will describe the present invention more fully and in detail in combination with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The terminology used herein is only for the purpose of describing specific embodiments, and is not intended to limit the protection scope of the present invention.

Unless otherwise specified, the various reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

Example 1:

A preparation method of perfluorosulfonyl bisnitrile amide lithium polymer electrolyte of the present invention, comprises the following steps:

(1) Dissolve 1.69g of malononitrile in a mixed solvent composed of 20g of anisole and 5g of N-methylpyrrolidone, then drop it into a 250ml single-necked flask containing 0.71g of lithium hydride, and stir under reflux at 30°C under a nitrogen atmosphere After reacting for 5 hours, a mixed solution containing lithium malononitrile was prepared, and the unreacted raw material lithium hydride and precipitated by-products were removed by filtration to obtain a light red, clear and transparent lithium malononitrile solution.

(2) Add 25g perfluorosulfonyl fluoride resins with ethoxy side chains to the purified above-mentioned lithium malononitrile solution, the ion exchange capacity of the perfluorosulfonyl fluoride resin used is 0.91mmol/100g, Stirring and reflux reaction at 70° C. for 15 hours to obtain a solution of lithium polymer electrolyte of perfluorosulfonyl bisamide lithium polymer electrolyte containing bisamide lithium group in the side chain.

(3) The solution system obtained after the similar conversion reaction in step (2) is subjected to suction filtration to obtain a solid polymer crude product, and the solid polymer is then dried by suction filtration and washing with a mixed solvent containing ethanol and water to obtain 23.5 g of a solid product . Add 280g of dimethyl sulfoxide, stir and dissolve at 70°C, and filter out a small amount of insoluble matter with a 60-mesh screen to obtain a clear and transparent solution, which is the perfluorosulfonyl bisnitrile lithium polymer electrolyte solution. Concentrate by distillation to a concentration of about 10% to obtain a perfluorosulfonyl bisnitrile amide lithium polymer electrolyte concentrate for use. The insoluble matter was weighed after washing and drying, and the weight was about 1 g, and the polymer yield was 90% (calculated according to the mass of the sulfonyl fluoride resin raw material).

(4) Apply the concentrated polymer electrolyte solution prepared in step (3) with a coating machine and a scraper to form a film, add the extractant ethanol/water (1:2) mixed solution to soak after initial drying, Substitute dimethyl sulfoxide for secondary film formation, vacuum dry after demoulding, heat treatment at 140°C for 0.5h, and obtain the perfluorosulfonyl bisnitrile amide lithium (single lithium ion) polymer electrolyte membrane as shown in Figure 1 after cooling , and its fluorine NMR spectrum is shown in Figure 2.

The above-mentioned preparation method of this embodiment mainly adopts the polymer similar transformation method to prepare an electrolyte membrane with a perfluorinated carbon chain structure as the main chain and an ethoxy side chain end containing a lithium sulfonyl bisamide group; the system uses The dense crystalline structure of the main chain, the charge effect and volume effect of the side chain inhibit the migration of anions and organic solvent molecules in the electrolyte, thereby obtaining a single cation migration.

A lithium-sulfur secondary battery of this embodiment, comprising a lithium negative electrode, a positive electrode sheet, an electrolyte membrane, and an organic electrolyte; the electrolyte membrane is the perfluorosulfonyl bisnitrile lithium polymer electrolyte obtained by the preparation method of the above-mentioned embodiment membrane;

The lithium negative electrode mainly includes lithium metal;

The positive electrode sheet is mainly composed of a current collector (preferably aluminum foil or aluminum mesh) that conducts current and a positive active material coated on the current collector, a conductive agent and a binder; the positive active material is a carbon-sulfur polymer; the conductive agent is Carbon-based conductive agent, such as preferred conductive carbon black, acetylene black or graphite powder; binder is polyvinylidene fluoride; wherein, the mass percentages of positive electrode active material, conductive agent and binder are respectively 70%, 19% and 11% %; mix the positive active material, conductive agent and binder by ball milling for 3h to 4h, use a coating machine to prepare a double-sided coated positive electrode sheet, the positive active material load is 6mg/cm ² , and it is cut into a length of 10cm , 5cm wide positive pole piece, vacuum dried at 60°C for 12h;

The positive pole piece, perfluorosulfonyl bisamide lithium polymer electrolyte membrane, and lithium foil are wound in a glove box to prepare a battery cell. The thickness of the lithium foil used is 100 μm, and then 1M lithium hexafluorophosphate/DME/DOL electrolyte is added. Place it for 24 hours after packaging, and test its electrical performance.

The Li-S secondary battery prepared in this example was tested for C/10 charge and discharge performance, and the voltage was limited to 2.5V-1.5V at room temperature, and the current was 0.75mA/cm ² . Based on the discharge capacity of the 5th cycle, the energy capacity of 110 charge-discharge cycles is maintained at 81.4% (see FIG. 3 ).

Example 2:

A preparation method of perfluorosulfonyl bisnitrile amide lithium polymer electrolyte of the present invention, comprises the following steps:

(1) 1.5g malononitrile was dissolved in a mixed solvent of 25g anisole and 5g N-methylpyrrolidone, then dropped into a 250ml single-necked flask equipped with 0.71g lithium hydride, and reacted at reflux at 30°C under a nitrogen atmosphere for 6 Hours, a mixed solution containing lithium malononitrile was obtained, and the unreacted raw material lithium hydride and precipitated by-products were removed by filtration to obtain a light red, clear and transparent lithium malononitrile solution.

(2) Add 25g perfluorosulfonyl fluoride resins with ethoxy side chains to the purified above-mentioned lithium malononitrile solution, the ion exchange capacity of the perfluorosulfonyl fluoride resins used is 1.0mmol/100g, in a nitrogen atmosphere Stirring and reflux reaction at 70° C. for 15 hours to obtain a solution of lithium polymer electrolyte of perfluorosulfonyl bisamide lithium polymer electrolyte containing bisamide lithium group in the side chain.

(3) The solution system obtained after the similar conversion reaction in step (2) is subjected to suction filtration to obtain a solid polymer crude product, and the solid polymer is then dried by suction filtration and washing with a mixed solvent containing ethanol and water to obtain 23.65g of a solid product . Add 280g of dimethyl sulfoxide, stir and dissolve at 70°C, and filter out a small amount of insoluble matter with a 60-mesh screen to obtain a clear and transparent solution, which is the perfluorosulfonyl bisnitrile lithium polymer electrolyte solution. Concentrate by distillation to a concentration of about 10% to obtain a perfluorosulfonyl bisnitrile amide lithium polymer electrolyte concentrate for use. The insoluble matter was weighed after washing and drying, and the weight was about 0.8 g. The polymer yield was 91.2% (calculated based on the mass of the sulfonyl fluoride resin raw material).

(4) Apply the concentrated polymer electrolyte solution prepared in step (3) with a coating machine and a scraper to form a film, add the extractant ethanol/water (1:2) mixed solution to soak after initial drying, Substitute dimethyl sulfoxide for secondary film formation, vacuum dry after demoulding, heat treatment at 140°C for 0.5h, and obtain perfluorosulfonyl bisnitrile amide lithium polymer electrolyte membrane after cooling.

The above-mentioned preparation method of this embodiment mainly adopts the polymer similar transformation method to prepare an electrolyte membrane with a perfluorinated carbon chain structure as the main chain and an ethoxy side chain end containing a lithium sulfonyl bisamide group; the system uses The dense crystalline structure of the main chain, the charge effect and volume effect of the side chain inhibit the migration of anions and organic solvent molecules in the electrolyte, thereby obtaining a single cation migration.

A lithium-sulfur secondary battery of this embodiment, comprising a lithium negative electrode, a positive electrode sheet, an electrolyte membrane, and an organic electrolyte; the electrolyte membrane is the perfluorosulfonyl bisnitrile lithium polymer electrolyte obtained by the preparation method of the above-mentioned embodiment membrane;

The lithium negative electrode mainly includes lithium metal;

The positive electrode sheet is mainly composed of a current collector (preferably aluminum foil or aluminum mesh) that conducts current and a positive active material coated on the current collector, a conductive agent and a binder; the positive active material is a carbon-sulfur polymer; the conductive agent is Carbon-based conductive agent, such as preferred conductive carbon black, acetylene black or graphite powder; binder is polyvinylidene fluoride; wherein, the mass percentages of positive electrode active material, conductive agent and binder are respectively 70%, 19% and 11% %; mix the positive active material, conductive agent and binder by ball milling for 3h to 4h, use a coating machine to prepare a double-sided coated positive electrode sheet, the positive active material load is 6mg/cm ² , and it is cut into a length of 10cm , 5cm wide positive pole piece, vacuum dried at 60°C for 12h;

The positive pole piece, perfluorosulfonyl bisamide lithium polymer electrolyte membrane, and lithium foil are wound in a glove box to prepare a battery cell. The thickness of the lithium foil used is 100 μm, and then 1M lithium hexafluorophosphate/DME/DOL electrolyte is added. Place it for 24 hours after packaging, and test its electrical performance.

The Li-S secondary battery prepared in this example was tested for C/10 charge and discharge performance, and the voltage was limited to 2.5V-1.5V at room temperature, and the current was 0.75mA/cm ² . Based on the discharge capacity of the 5th cycle, the energy capacity of 101 charge-discharge cycles remains 81.4% (see FIG. 4 ).

Claims (7)

1. a perfluor sulfonyl dicyanamide lighium polymer electrolyte preparation method, comprises the following steps:

(1) by Cyanoacetyl-Cyacetazid and lithium hydride in the presence of specific blend solvent orange 2 A under proper temperature and inert atmosphere hybrid reaction, the response time is no less than 5h, prepares Cyanoacetyl-Cyacetazid lithium solution；Described specific blend solvent orange 2 A is the mixed system of methyl phenyl ethers anisole and N-Methyl pyrrolidone, and the mass ratio of methyl phenyl ethers anisole and N-Methyl pyrrolidone is 20: 1～2: 1, addition is Cyanoacetyl-Cyacetazid quality 10～50 times of described specific blend solvent orange 2 A；

(2) be there is similar transformation reaction to the perfluor sulfonyl fluororesin of band ethoxy side chain in above-mentioned Cyanoacetyl-Cyacetazid lithium solution after purification, Cyanoacetyl-Cyacetazid lithium keeps excess, through subsequent treatment after having reacted, described subsequent treatment refers to that the polymer described similar transformation reaction generated precipitates after filtering and washing, add solvent B stirring and dissolving at 30 DEG C～100 DEG C, then filter insoluble matter and obtain perfluor sulfonyl dicyanamide lighium polymer electrolyte solution；Obtain perfluor sulfonyl dicyanamide lighium polymer electrolyte concentrated solution through distillation and concentration again, namely obtain the side chain perfluor sulfonyl dicyanamide lighium polymer electrolyte containing dicyanamide lithio group；Described solvent B is one or both the mixing in methyl phenyl ethers anisole, N-Methyl pyrrolidone, N-ethyl pyrrolidone, dichloroethanes, dimethyl sulfoxide, sulfolane, triethylene glycol dimethyl ether., tetraethylene glycol dimethyl ether.

Preparation method the most according to claim 1, it is characterised in that: in described step (1), lithium hydride reacts with the mol ratio equivalent of 2:1 with Cyanoacetyl-Cyacetazid, and control lithium hydride should be excessive, and excess ratio is 1%～80%.

Preparation method the most according to claim 1, it is characterised in that: in described step (1), the actual conditions of hybrid reaction is reaction 5h～40h under the conditions of 20 DEG C～100 DEG C of return stirrings.

4. according to the preparation method according to any one of claims 1 to 3, it is characterised in that: in described step (2), the actual conditions of similar transformation reaction is to be stirred at reflux reaction 4h～30h under the inert atmosphere of 40 DEG C～120 DEG C.

Preparation method the most according to claim 4, it is characterized in that: described subsequent treatment also includes: by prepared polymer dielectric concentrated solution coating machine coating, coater blade coating film forming or casting film-forming, extractant two-step film forming is added after the most dry, after vacuum drying, 120 DEG C～200 DEG C of heat treatment 0.5h～4h, after cooling, i.e. obtain perfluor sulfonyl dicyanamide lighium polymer dielectric film；Selected extractant is at least one in ethanol, isopropanol, ether, propyl ether, oxolane, ethylene carbonate, Allyl carbonate, diethyl carbonate, Ethyl methyl carbonate, dioxolane, water, dichloromethane, dichloroethanes, toluene, dimethylbenzene.

6. according to the preparation method according to any one of claims 1 to 3, it is characterized in that: described specific blend solvent orange 2 A is identical with the fractions of solvent B, and specific blend solvent orange 2 A is, with solvent B, the mixed solvent system comprising methyl phenyl ethers anisole, after adding solvent B, solids content therein is made to reach 4%～50%.

7. a lithium-sulfur rechargeable battery, comprises cathode of lithium, anode pole piece, dielectric film, organic electrolyte；It is characterized in that:

The electrolyte that described dielectric film is used is the perfluor sulfonyl dicyanamide lighium polymer electrolyte that preparation method according to any one of claim 1～6 obtains；

Described cathode of lithium mainly includes lithium metal or the negative active core-shell material of lithium alloys composition；

Described anode pole piece is mainly made up of the collector and coating positive electrode active materials, conductive agent and binding agent on a current collector conducting electric current；Described positive electrode active materials is at least one in sulfur simple substance, organic sulfur compound, carbon-sulfur polymer；

Described organic electrolyte comprises lithium salts and nonaqueous solvent, and described lithium salts is selected from least one in the polysulfide lithium of lithium hexafluoro phosphate, LiBF4, hexafluoroarsenate lithium, lithium perchlorate, lithium trifluoromethanesulp,onylimide, trifluoromethyl sulfonic acid lithium, lithium nitrate, different valence state；Described nonaqueous solvent includes acetonitrile, hexamethylene, Ketohexamethylene, isopropanol, oxolane, 2-methyltetrahydrofuran, ethylene carbonate, Allyl carbonate, butylene, dimethyl carbonate, diethyl carbonate, Ethyl methyl carbonate, methyl propyl carbonate, methyl formate, Ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, ethyl n-butyrate., dimethoxy-ethane, 1, 3-dioxolane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether., tetraethylene glycol dimethyl ether, glycol dimethyl ether, sulfolane, dimethyl sulfoxide, at least one in dimethyl sulfone.