Constraining polyselenide formation in ether based electrolytes through confinement of Se in microporous carbon matrix for Li-Se batteries

Abstract

Nitrogen doped carbon tubes (N-CT) of dia 100nm are prepared by carbonization of polyaniline tubes and selenium impregnation into N-CT is carried out by melt diffusion process. The N-CT possess micropores and small mesopores that assist in trapping Se. Interestingly, Se absorption in micropores creates steric hindrance for the formation of long chain polyselendes during electrochemical discharge and hence leads to direct formation of Li2Se. Whereas, the small mesopores ensure proper electrode-electrolyte contact rendering good rate capability. Due to the presence of small mesopores a small quantity of polyselenides may be formed during initial cycles, however the nitrogen present in the carbon matrix can help in controlling their dissolution by creating polarity. Hence, it is observed here that after few initial cycles, the multistep reaction between Li and Se has changed to a single step. This is supported by in-situ electrochemical analysis like differential capacity (dQ/dV) plots, cyclic voltammetry impedance analysis and ex-situ UV–vis spectroscopy.