Realizing High-Performances Sb Anodes for K-Ion Batteries

Abstract

Alloy anodes have long been considered promising alternatives to carbon counterparts for high-energy K-ion batteries (KIBs) as they could uptake several ions per K atom through alloying reactions, delivering exceptional capacities at low voltage. However, alloy electrodes usually undergo severe volume expansion upon large K ion insertion, which will trigger the pulverization of active particles and the breakage of solid electrolyte interphase (SEI), leading to rapid capacity degradation. Instead of fabricating nanostructured materials, novel electrolyte formulations can be used to realize stable cycling of high-capacity anodes in KIBs. Sb is a promising low-cost anode material for KIBs, possessing a high theoretical capacity of 660 mAh g-1 at average voltage of about 0.5V toward K+/K. However, it shows rapid capacity degradation in conventional carbonate-based electrolytes. To stabilize the Sb anodes, novel ether-based KIB electrolytes are designed to replace the conventional ones, enabling a high reversible capacity over 180 cycles. It is found that a thinner and amorphous SEI, with abundant oligomer-like species, is built in ether base electrolytes. Such SEI is more elastic, and can effectively wrap the Sb particles to accommodate repeated volumetric changes, and preventing copious electrolytes decomposition. These findings allow us to develop crucial fundamental knowledge to design ideal SEIs for stabilizing alloy anodes to boost the energy densities of today’s alkali-metal ion batteries.