Study On Improving The Performance Of Lithium-Sulfur Battery With Heteropolyacid-based Complex

High specific energy lithium-sulfur(Li-S)secondary battery has attractive development prospects,and the problem to be solved urgently in their commercialization is poor cycle stability.In view of this,the author designed and prepared a series of heteropoly acid-based complexes to improve the electrochemical performance of Li-S battery.The main research work includes:First,the adsorption capacity of three heteropoly acids(SiW,PW and PMo)on polysulfides was comparatively studied,which proved that SiW and PW could effectively adsorb polysulfides.The heteropoly acid modified separator coating was designed and prepared,and the electrochemical performance of three kinds of heteropoly acid modified separator batteries was investigated,which verified the feasibility of SiW and PW to improve the electrochemical performance of lithium-sulfur batteries.Then,two kinds of heteropoly acids(SiW and PW)were used to react with Cystine in a low-temperature solid-phase reaction,and the heteropoly acid-based complexes(SiW/Cystine and PW/Cystine)were designed and prepared,and the structural composition of the complexes were analyzed.Two kinds of heteropoly acid-based complexes were used to design and prepare separator modified coating.After comparative study of the electrochemical performance,we found that SiW/Cystine shows greater advantage.Finally,the method and mechanism of SiW/Cystine coating to improve the electrochemical performance of lithium-sulfur battery were explored.The research results show that SiW/Cystine could not only effectively adsorb polysulfides through metal ions,but also could adjust the conversion of polysulfides with the help of Cystine’s sulfur-sulfur bond,and accelerate the electrochemical reaction kinetics.While the SiW/Cystine content is 45%,the lithium-sulfur battery using SiW/Cystine modified separator coating could stably cycle for 200 cycles at 0.5 C current density;the discharge specific capacity of battery at 2 C could reach 671.6 mAh g-1 in the rate test.At the same time,it is found that the coating also plays a positive role in protecting the cathode and anode electrodes of the battery,which provides a guarantee for improving the performance of the lithium-sulfur battery.