Elevated electrochemical performances enabled by a core–shell titanium hydride coated separator in lithium–sulphur batteries

Abstract

To date, the lithium–sulphur battery is still suffering from fast capacity fade and poor rate performance due to its special electrochemical mechanism. The interlayer or separator with conductive coatings is considered effective in inhibiting the shuttle effect. Here, we proposed a novel metal hydride with high conductivity and preferably chose TiH₂ as the conductive coating because of its low cost, high conductivity, and good stability in air. The TiH₂ powder was prepared by a simple ball-milling method, and the effect of the atmosphere was also investigated. A core–shell heterostructure formed, in which the TiH₂ core acted as an electron transfer pathway, and the titanium oxide nano-shell functioned as the absorber for polysulfides. Thus, with the combination of fast electronic transfer and strong absorption ability, the TiH₂ coated separator could improve the cycling stability, the rate performances, and the self-discharge rate. The TiH₂ separator could increase the capacity of the lower plateau and delay the oversaturation points at high rates, promoting the liquid–solid conversion. It is believed that the promotion resulted from the high conductivity and polysulfide absorption of the TiH₂ separator. Although the preparation process still needs further optimization, the core–shell metal hydride provided a novel strategy for designing the heterostructure, which could provide high conductivity and strong absorption ability toward polysulfides simultaneously.