Materials Design and Mechanistic Understanding of Tellurium and Tellurium–Sulfur Cathodes for Rechargeable Batteries

ConspectusThe market demand for lithium-ion batteries (LIBs) has been proliferating in wide applications, from portable electronics and electric vehicles to renewable energy storage, due to their advantages of high energy density and reliable life cycles. Currently, further development of LIBs is hindered by the limited specific/volumetric capacity and high cost of conventional intercalation-type cathode materials. In this context, sulfur (S) has gained intensive attention as a conversion-type cathode because of its abundance, low cost, and high theoretical capacity (1675 mAh g^-1). However, the insulating nature of S causes severe issues of sluggish redox kinetics, low S utilization, and unsatisfactory practical capacity. So far, extensive efforts have been devoted to boosting Li-S redox kinetics and enhancing cycling stability by inhibiting the shuttle effect, including developing functional electrolyte additives, introducing redox catalysts, and tailoring the S cathode structure. Partially substituting S atoms in S₈ rings with high-electrical-conductivity elements (e.g., selenium, 1 × 10^-3 S m^-1) at the molecular level proves to be an effective strategy for tackling the above-mentioned challenges in Li-S batteries. It is noteworthy that tellurium (Te), with remarkable electrical conductivity (2 × 10² S m^-1) and high density (6.24 g cm^-3), is a promising battery electrode material that can realize fast electron transport and deliver volumetric capacity comparable to that of S or Se. Additionally, Te-S molecular regulation is one facile strategy to reshape Li-S chemistry, accelerate redox kinetics, and manipulate the lithiation/delithiation behaviors. Te is an effective eutectic accelerator that prevents polysulfide dissolution in Li-S batteries under the dissolution-deposition mechanism. Meanwhile, the Li-Te electrochemistry can contribute to reversible capacity in Li-Te_xS_y batteries through Te-Li₂Te conversion and enhance the materials utilization of Te_xS_y.This Account highlights state-of-the-art advancements in applying Te or Te_xS_y as high-capacity cathodes for rechargeable batteries. First, battery configuration and reaction pathways in Li-Te batteries are discussed, followed by the introduction of cathode design strategies to improve cathode structure stability. The limitations of this Te-only cathode are outlined in terms of the abundance, cost, and energy density. Second, the role of Te in Li-S chemistry is clarified by the analysis of the crystal structure, electrochemical behaviors, solid electrolyte interphase composition, and energy profiles. Third, recent progresses on quasi-solid-state Li-Te batteries have been introduced, focusing on flexible gel polymer electrolytes with adjustable ionic conductivity. Afterward, advancements in interface engineering by the atomic layer deposition technique in metal-Te batteries are highlighted. Additionally, mechanistic analysis in emerging zinc-Te_xS_y batteries with outstanding areal capacity is demonstrated. Finally, we provide insightful perspectives on the future directions of material design in Te-based energy storage technologies. This Account is expected to deepen the fundamental understanding of metal-Te/Te_xS_y chemistry and offer inspiration for the further development of Te-based high-energy-density rechargeable batteries.