A dual-functional matrix with high absorption and electrocatalysis to suppress the shuttle effect in lithium-selenium batteries

Due to the higher conductivity of selenium than sulfur, lithium selenium (Li-Se) batteries have received increasing attention. However, the shuttle effect and the slow conversion kinetics of polyselenides have resulted in poor cycling performance of Li-Se batteries. In this work, a CoTe2 and MOF derived composite (CoTe2-MD) was designed and synthesized. As a dual-functional matrix, the MOF derivative acted as an adsorbent and effectively reduced the dissolution of the polyselenides in ether electrolytes via physical/chemical absorption. CoTe2 acted as an electrocatalyst, which accelerated the conversion reaction of the polyselenides and improved the redox kinetics of the reactions. The results proved that the dual-functional matrix consisting of the adsorbent and electrocatalyst further suppressed the shuttle effect and significantly improved the cycle stability of the Li-Se batteries. At 0.5C, the Se/CoTe2-MD electrode showed 540.4 mA h g-1 of initial discharge capacity. Even after 200 cycles, it still maintained a reversible capacity of 454.1 mA h g-1, with a decay rate of only 0.08% per cycle. A dual-functional matrix as both an adsorbent and an electrocatalyst effectively restrained the shuttle effect and improved the electrochemical performance of Li-Se batteries.