N, S-doped graphene derived from graphene oxide and thiourea-formaldehyde resin for high stability lithium-sulfur batteries.

ABSTRACT

Although lithium-sulfur (Li-S) batteries with a high theoretical energy density and low cost have attracted extensive research attention, their commercialization is still unsuccessful due to the poor cycle life caused by the dissolution of polysulfides. It is the key challenge to overcome polysulfide shuttling for achieving long-term cycling stability in Li-S batteries. Here we report a novel strategy for the synthesis of N, S-doped graphene with high nitrogen and sulfur contents via in situ self-assembly of graphene oxide and thiourea-formaldehyde resin and calcination. The N, S-doped graphene serves as a conductive agent and a chemosorbent for suppressing polysulfide shuttling and preventing the Li-metal from corrosion, leading to a high reversible capacity and superior cycling stability. The Li-S batteries with the N, S-doped graphene can achieve an excellent cycling life (622 mA h g-1 after 500 cycles at 1C) and a slow capacity decay rate (0.049% per cycle over 500 cycles at 1C). The proposed strategy has the potential to enhance the high electrochemical properties of Li-S batteries.