Lithium–Lithium Titanate Composite Anode for Semi-Solid-State Lithium–Sulfur Batteries

Lithium-sulfur batteries have attracted significant attention recently as sulfur is one of the most abundant elements in the earth's crust, low-cost, has a non-toxic nature, multi-electron transfer property coupled with its remarkable theoretical specific capacity of 1672 mAh g^-1 and energy density of 2600 Wh kg^-1. However, lithium-deficient sulfur cathodes associated with lithium metal anodes together to face challenges, such as significant volume expansion during cycling, dendrite formation, and polysulfide shuttling effect from the sulfur cathodes, leading to corrosion, all of which negatively impact the cycle lifespan of the battery. On the other hand, moving away from liquid to solid-state garnet-based solid electrolytes is highly aided for lithium-sulfur batteries because of their high ionic conductivity of 10^-3 S cm^-1_, stability with lithium metal, lithium-based alloys and moreover in mitigating the polysulfide issues. The particular lithium-sulfur solid-state batteries still possess intense lithium metallic anode issues. Utilizing a composite anode constructively addresses the significant interfacial resistance arising from the solid-solid contact issues, making it an excellent solution for the interfacial issues and helps in minimizing the volume expansion of the lithium metal during the charge-discharge. Successful attempts have been made on associating the lithium metal with lithium titanate composite anodes, but its full potential can be expected with high-capacity cathodes, like sulfur, as such combinations have not yet been explored. Here a full cell study using a polyacrylonitrile sulfur (PANS) cathode with a lithium-lithium titanate (Li-LTO) composite anode was compared to a pure lithium-metal-based anode at 0.2 C for more than 150 cycles with an improved discharge capacity retention observed over these cycles for a Li-LTO composite-based cell, whereas the pure lithium-sulfur (Li-S) cell loses complete discharge capacity at around 100 cycles.