MoS2/Mayenite Electride Hybrid as a Cathode Host for Suppressing Polysulfide Shuttling and Promoting Kinetics in Lithium–Sulfur Batteries

The commercial viability of emerging lithium-sulfur batteries (LSBs) remains greatly hindered by short lifespans caused by electrically insulating sulfur, lithium polysulfides (Li₂S_n; 1 ≤ n ≤ 8) shuttling, and sluggish sulfur reduction reactions (SRRs). This work proposes the utilization of a hybrid composed of sulfiphilic MoS₂ and mayenite electride (C12A7:e^-) as a cathode host to address these challenges. Specifically, abundant cement-based C12A7:e^- is the most stable inorganic electride, possessing the ultimate electrical conductivity and low work function. Through density functional theory simulations, the key aspects of the MoS₂/C12A7:e^- hybrid including electronic properties, interfacial binding with Li₂S_n, Li⁺ diffusion, and SRR have been unraveled. Our findings reveal the rational rules for MoS₂ as an efficient cathode host by enhancing its mutual electrical conductivity and surface polarity via MoS₂/C12A7:e^-. The improved electrical conductivity of MoS₂ is attributed to the electron donation from C12A7:e^- to MoS₂, yielding a semiconductor-to-metal transition. The resultant band positions of MoS₂/C12A7:e^- are well matched with those of conventional current-collecting materials (i.e., Cu and Ni), electrochemically enhancing the electronic transport. The accepted charge also intensifies MoS₂ surface polarity for attracting polar Li₂S_n by forming stronger bonds with Li₂S_n via ionic Li-S bonds than electrolytes with Li₂S_n, thereby preventing polysulfide shuttling. Importantly, MoS₂/C12A7:e^- not only promotes rapid reaction kinetics by reducing ionic diffusion barriers but also lowers the Gibbs free energies of the SRR for effective S₈-to-Li₂S conversion. Beyond the reported applications of C12A7:e^-, this work highlights its functionality as an electrode material to boost the efficiency of LSBs.