Constructing fast electron and ion conductive framework for Li2S as advanced lithium sulfur battery

Abstract

Lithium sulfide (Li2S) cathode is considered as a prospective substitution for sulfur-based cathode for as its high specific capacity. Despite this, the poor electron and lithium ion transportation for Li2S impedes its further development. Herein, a great electron and lithium ion pathway is constructed for Li2S by a facile spray-dried technology. In this composite, the nano-sized Li2S is well imbedded in framework composed by the nitrogen/oxygen dual doped carbon nanotube/carbon (Li2S/CNT/C-N/O). The electrochemical tests show that the prepared Li2S/CNT/C-N/O cathode exhibits great cycling stability and rate capacity. A high initial discharge capacity of 1014 mAh g−1 is achieved with 671 mAh g−1 capacity remained at 200 mA g−1 after 200 cycles. Impressively, a stable capability is still exhibited from 200 to 3000 mA g−1 during rate testing. In-situ electrochemical impedance spectra test is further used to get insightful understanding about the improvements. The result reveals that decreased resistance and increased lithium-ion diffusion can be achieved for the Li2S/CNT/C-N/O, especially at the initial charging stage of polysulfides nucleation, which shed light on the improved reactive kinetics and active material utilization.