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

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 similar to 50 degrees 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.

Automated summary

By using the in-situ carbon-encapsulation-induced strain relaxation strategy, the adsorption and catalytic properties of the MoNi4 bimetallic nanoalloy catalyst for lithium-sulfur batteries have been balanced, leading to improved cycling stability.