Advanced Li2 S/Si Full Battery Enabled by TiN Polysulfide Immobilizer.

ABSTRACT

Lithium sulfide (Li2 S) is a promising cathode material with high capacity, which can be paired with nonlithium metal anodes such as silicon or tin so that the safety issues caused by the Li anode can be effectively avoided. However, the Li2 S full cell suffers from rapid capacity degradation due to the dissolution of intermediate polysulfides. Herein, a Li2 S/Si full cell is designed with a Li2 S cathode incorporated by titanium nitride (TiN) polysulfide immobilizer within parallel hollow carbon (PHC). This full cell delivers a high initial reversible capacity of 702 mAh gLi2S -1 (1007 mAh gsulfur -1 ) at 0.5 C rate and excellent cyclability with only 0.4% capacity fade per cycle over 200 cycles. The long cycle stability is ascribed to the strong polysulfide anchor effect of TiN and highly efficient electron/ion transport within the interconnected web-like architecture of PHC. Theoretical calculations, self-discharge measurements, and anode stability experiments further confirm the strong adsorption of polysulfides on the TiN surface. The present work demonstrates that the flexible Li2 S cathode and paired Si anode can be used to achieve highly efficient Li-S full cells.