A grain-boundary-rich cobalt selenide hollow multi-shelled structure as a highly efficient electrocatalyst for lithium–sulfur batteries

Abstract

Catalytic conversion of polysulfides has been regarded as an effective strategy to suppress the shuttle effect in lithium–sulfur (Li–S) batteries by accelerating the conversion of lithium polysulfides (LiPSs). However, the rational design of high-performance sulfur electrocatalysts still remains a big challenge. In this work, we develop a facile approach to synthesize a grain-boundary-rich cobalt selenide hollow multi-shelled structure (denoted as GB-CoSe HoMS) to serve as a high-efficiency electrocatalyst for Li–S batteries. Such a unique structural design could physically inhibit the diffusion of polysulfide intermediates and effectively accommodate the large volume expansion. Besides, the GB-CoSe HoMS possesses strong chemical adsorption towards LiPSs and superior catalytic activity to accelerate the conversion reaction kinetics, thereby suppressing the shuttle effect of LiPSs and enhancing the sulfur utilization. Owing to the multifarious advantages, the assembled Li–S batteries with GB-CoSe HoMS modified polypropylene separators display a high initial discharge capacity of 1393.3 mA h g⁻¹ at 0.1C, superior rate performance (660.9 mA h g⁻¹ at 3C), and good long-term cycle stability with a low capacity decay rate of 0.046% per cycle after 1000 cycles at 1C. More significantly, even with a high sulfur loading of 5.5 mg cm⁻² and lean electrolyte (E/S ≈ 8.0 μL mg⁻¹), the battery still harvests a high discharge capacity of 977.8 mA h g⁻¹ after 40 cycles at 0.2C, suggesting its great potential for practical applications. The present work demonstrates the importance of engineering the morphology and grain boundary in developing high-performance electrocatalysts for Li–S batteries.