Lithium sulfide (Li₂S) has drawn much attention owing to its super-high theoretical specific capacity and energy density, as well as its compatibility with lithium-free anode materials. However, the commercialization of Li₂S cathode is severely hindered by its poor rate capability and short cyclic life arising from its poor electrical conductivity, high activation energy barrier and shuttle effect of polysulfide intermediates. Many approaches have been reported, mainly focusing on the development of host for Li₂S cathode as well as electrolyte engineering, which have achieved great progress. This review firstly provides an in-depth discussion of the challenges encountered Li₂S cathode, subsequently discusses the host design for Li₂S cathode and electrolyte engineering, focusing on the fundamental mechanism underlying the host or electrolyte engineering for improving the reaction kinetics and interface stability. Finally, the remaining challenges and future directions of Li₂S cathode are discussed to further improve the performance of Li₂S cathode materials and promote their practical application.

Developing noble-metal-free oxygen evolution reaction (OER) electrocatalysts with stable performance at large working current is an imperative and yet formidable challenge for practical large scale water splitting. In this study, by inheriting hierarchical nanostructure and elemental homogeneity of Prussian blue analogues, a series of medium entropy transition metal phosphides (METMP) OER catalysts with high cost-effectivity, efficiency and stability were precisely prepared. Specifically, the METMP-based ((FeCoNi)P/Ni₂P-NF) catalyst demonstrates exceptional performance with an overpotential of only 232 mV at 50 mA·cm⁻² and a Tafel slope of 52.7 mV·dec⁻¹, significantly superior to its less entropy counterparts and commercial RuO₂. Moreover, it even maintains stability at the industrial standard current density of 500 mA·cm⁻² for over 200 h. Density functional theory (DFT) calculations indicates that the synergistic effect of Fe, Co, Ni modulates electronic structure of METMPs, which effectively reduces the energy barrier for the rate-determining HOO* formation step, thereby considerably enhancing catalytic activity. This work not only contributes to the fundamental understanding of the role of medium/high entropy in catalysis but also paves the way for the development of next-generation electrocatalysts for energy-related applications.