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

Abstract

Due to higher conductivity of selenium than sulfur, lithium selenium (Li-Se) batteries has received increasing attention. However, shuttle effect and slow conversion kinetics of polyselenides 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 acts as an adsorbent and effectively reduces the dissolution of the polyselenides in the ethers electrolyte via physical/chemical absorption. The CoTe2 acts as an electrocatalyst, which accelerates the conversion reaction of the polyselenides and improves the redox kinetics of the reactions. The results proved the dual-functional matrix consisted of the adsorbent and electrocatalyst further suppressed the shuttle effect and significantly improved the cycle stability of the Li-Se batteries. At 0.5C, Se/CoTe2-MD electrode showed 540.4 mAh g-1 of initial discharge capacity. Even after 200 cycles, it still main-tained a reversible capacity of 454.1 mAh g-1, with a decay rate of only 0.08% per cycle.