Insight Into the Failure Mechanism of Conversion‐Alloy Anode Materials in Potassium‐Ion Batteries: A Case Study of Bi 2 Te 3

ABSTRACT Conversion‐alloy‐type anodes have attracted considerable attention in potassium‐ion batteries due to their high theoretical capacities, but the inferior stability hinders their potential applications. Generally, the failure mechanism of conversion‐alloy anodes is ascribed to volume expansion or the shuttle effect, which, however, fails to adequately explain their characteristic electrochemical behavior: an initial rapid drop and then a gradual decline in capacity. Herein, by combining electrochemical characterizations with multi‐scale microscopies, spectroscopy, and theoretical calculations, we systematically analyze the failure mechanism of Bi 2 Te 3 , a typical conversion‐alloy anode. The failure processes and mechanisms are identified into two stages: (1) the rapid capacity fading dominated by the shuttle effect in the first several cycles and (2) the gradual material deactivation and capacity decline due to solid‐electrolyte interphase accumulation in the following cycles. Furthermore, in response to these failure mechanisms, an elaborate design of Bi 2 Te 3 ‐based electrode featuring ultrafine nanoparticles and carbon encapsulation is presented, which exhibits prominent capability in avoiding the above negative effects and substantially enhancing cycling stability. This study reveals the failure mechanism of conversion‐alloy anode throughout its entire life cycle, and the gained insight may lead to targeted optimization strategies for stable high‐capacity electrodes.