Perovskite Lithium Lanthanum Titanate-Modified Separator as Both Adsorbent and Converter of Soluble Polysulfides toward High-Performance Li-S Battery

摘要

A novel separator constructed by coating a layer of perovskite lithium lanthanum titanate (LLTO)/Super P (SP) composite over a commercial PE membrane was employed for the first time in the Li-S battery ([email?protected]). It was found that the [email?protected] battery possessed an obviously lower impedance but higher Li-ion diffusion than the Li-S battery employing the uncoated separator ([email?protected]). This enabled the soluble polysulfides to be effectively immobilized and further electrochemically transformed into Li_(2)S via the formation of thiosulfate/polythionate intermediates over the LLTO/SP-coated separator during the discharge of the battery. As a result, the shuttle effect was effectively inhibited, and particularly the passivation of both the cathode and “dead S” over the separator was largely decreased. These properties ensured that the [email?protected] battery displayed a significantly high specific capacity and rate capability as well as good cycling stability. For the [email?protected] battery with a S loading of 2 mg cm~(–2), an initial specific capacity of 1491 mAh g~(–1) at 0.1C and a residual specific capacity of 459 mAh g~(–1) at 1C after 1200 cycles had been achieved, while for the [email?protected] battery with a S loading of 5 mg cm ~(–2), an initial specific capacity of 1046 mAh g ~(–1) and a residual specific capacity of more than 800 mAh g~(–1) at 0.1C after 50 cycles could be delivered.