Research Of Carbyne Polysulfide As Cathode Material In Rechargeable Lithium Batteries

Sulfur and organic sulfides cathode materials have been attracted as ecological resources because of its large energy density,low cost and innocuity.However,they exhibited low utilization and poor cycle performance due to the electrically and ionically nonconductive nature and the loss active material in the form of soluble polysulfide reaction products the soluble polysulfide reaction products.In order to improve the conductivity and cycling performance of Organic sulfides,we have prepared Carbyne polysulfide by co-heating carbine(obtained from dehydrohalogenation of PVDC)analog and element sulfur.Carbyne polysulfide had the structure of main-chain providing electric conductivity and-Sx-(x＞2)side-chain functioning as the electrochemical redox component.It also showed that in this material,conducting polymer carbyne was used as stable backbones to provide electric conducting channels to offer good electric conductivity,and polysulfide lines as side lines offer high specific capacity.In this paper,carbyne polysulfides at 300℃.350℃.400℃.450℃temperature was characterized by Raman.XRD.XPS.SEM.elemental analysis,heating analysis to be proved that the product contained C-S and S-S linked on the sp hybridized carbon backbones.Carbyne polysulfide showed different chemical characters in aether and ester electrolytes.In the 1M LiClO₄/DOL+DME electrolyte,carbyne polysulfide behaved typical elemental sulfur discharge curve with 2.4V and 2.1V two platform,and the capacity fade fast with 747mAh·g^-1at the 1^st cycle and 237.5mAh·g_-1at the 60_thcycle;in the IM LiPF₆/ EC+DEC electrolyte,carbyne polysulfide did not has a platform just has a degressive area,and the capacity fade slowly,the cycle performance was improved. The battery had better characters with 800mAh/g at the 1^stcycle and 520mAh·g^-1at the 60^thcycle,the capacity retention was 65%,the efficiencies were almost 100%.The charge-discharge mechanisms in the two electrolytes were discussed by XRD.XPS.AC impedance.It was resulted that the products in the two electrolyte were all Li₂S,so the charge-discharge mechanisms were same that the charge-discharge were completed by the reaction between lithium and sulfur.The reason was possibly that the solubility in the ester electrolytes was very low mostly not at all,the low solubility was propitious to stabilization of structure and restraining moving of active materials,and the characters can be enhanced.