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

Abstract

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.