Do double duty: superior conductive metalloid electrocatalyst for high-rate lithium-selenium batteries

Abstract

Selenium cathodes have gained significant attention due to their higher electrical conductivity and volume specific capacity compared to sulfur cathodes. However, slow conversion reaction kinetics caused by low conductive polyselenides and inescapable shuttle effect lead to poor high-rate capability and cycling performance of lithium-selenium batteries. To surmount these challenges, a high conductive matrix with double duty that metalloid CoTe₂ grown in situ on carbon nanofibers (CoTe₂@CNF) has been proposed and prepared. On the one hand, the electronic and ionic conductivities of free-standing selenium electrodes are effectively enhanced because of high electronic conductive CoTe₂. On the other hand, rapid conversion of polyselenides is achieved because of the high catalytic activity of CoTe₂. Density Functional Theory calculations also prove that CoTe₂ is beneficial for catalytic conversion of polyselenides. Consequently, the Se/CoTe₂@CNF free-standing electrode achieve an impressive initial discharge capacity of 609.5mAh g⁻¹ at 0.5C. Even at 5C, after 1000 cycles, they also maintain a capacity of 298.9mAh g⁻¹ and the attenuation per cycle is less than 0.038 %. This work provides a good approach for preparing high-rate lithium-selenium batteries via superior conductive catalysts to suppress the shuttle effect and accelerate the conversion of polyselenides.