《Bifunctional Li2Se Mediator to Accelerate Sulfur Conversion and Lithium Deposition Kinetics in Lithium−Sulfurized Polyacrylonitrile Batteries》
Lithium-sulfur batteries are expected to become the next generation of high-energy-density rechargeable batteries due to their ultra-high theoretical energy density and low cost. Vulcanized polyacrylonitrile (SPAN) is a promising sulfur cathode material due to its unique chemical structure and good conductivity. However, the application of Li-SPAN batteries is severely limited by the slow sulfur dynamics and uncontrollable lithium deposition problems, resulting in poor electrochemical performance in ether electrolytes. In this work, we propose a bifunctional electrolyte additive, lithium selenide (Li2Se). On the side of the sulfur cathode, Li2Se will continuously attack the S-S bond of the polysulfide to form a higher reactive S-Se bond, reduce the reaction energy barrier, and accelerate the sulfur cathode kinetics. On the lithium anode side, Li2Se contributes to the transport and diffusion of Li+, forming a stable selenium-containing organic-inorganic composite SEI, reducing the nucleation overpotential of lithium metal and increasing the exchange current density of lithium deposition. Therefore, Li-SPAN cells with Li2Se exhibited high discharge specific capacity, excellent cycle stability, and high rate performance (500 cycles at 2C, and 1331 mAh g−1 at high rate 3C). In addition, under practical conditions (SPAN loading=12.0 mg cm-2, E/S=5 μL/mg), a high areal capacity of 10.3 mAh cm-2 was achieved. This work provides a new strategy for the construction of practical high-energy-density Li-SPAN batteries.
https://pubs.acs.org/doi/full/10.1021/acsaem.3c00815
