Revealing the enhancement mechanism of carbon-encapsulated surface-strained MoNi4 bimetallic nanoalloys toward high-stability polysulfide conversion with a wide temperature range

Abstract

Bimetallic alloy catalysts, due to their more adsorption sites, more abundant electronic structures, and higher catalytic properties than single-metal ones, have attracted much interest in the field of lithium–sulfur batteries (LSBs). However, many LSBs with bimetallic alloys often suffered from their low cycling stability, which was caused by the over-strong adsorption and the bad chemical stability of the catalysts. Herein, in-situ carbon-encapsulation-induced strain relaxation strategy has been adopted to balance the adsorption and catalytic properties of the MoNi4 bimetallic nanoalloy catalyst for LSBs. As a result, the cathode with strained-MoNi4 embedded carbon nanofibers (CNF@s-MoNi4) delivers a high capacity (1632.5 mAh g−1 at 0.1 C), a superior rate capability (retaining 832.4 mAh g–1 at 5.0 C) and excellent cycling stability (decaying rate of 0.0204% per cycle over 520 cycles at 1.0 C). Even at high rates, the CNF@s-MoNi4 can keep a stable cycling capacity (827.5 mAh g–1 and 447.7 mAh g–1 after 250 cycles at 5.0 C and 10.0 C, respectively). Besides, the CNF@s-MoNi4 LSB also exhibits an excellent wide-temperature-range adaptability (-30 ∼ 50°C) and a superior dynamic bending stability. This study would provide a feasible method for developing high-capacity and long-life LSBs with a wide temperature range demand.