Conversion‐Type Anodes: Challenges, Mitigation Strategies, and Evaluation Guidelines

ABSTRACT

Conversion‐type anode materials enable multi‐electron redox reactions and therefore offer theoretical capacities beyond those of classical insertion‐based anode materials such as graphite. However, their practical implementation is limited by multiple coupled penalties that evolve with cycling and electrode design. This review organizes recent progress in conversion‐type anodes (including transition metal oxides, sulfides, selenides, and phosphides) around five recurring limitations: (i) voltage hysteresis and low round‐trip energy efficiency, (ii) low initial Coulombic efficiency and cyclable‐lithium inventory loss, (iii) interphase instability with continuous electrolyte reduction and dissolution‐mediated cross‐talk, (iv) chemo‐mechanical damage leading to fracture, contact loss, and conductive network degradation, and (v) transport and accessibility limitations that intensify in thick, high‐areal‐loading electrodes under practical electrolyte amounts. We survey mitigation strategies spanning active‐material and microstructure design, composite and processing controls, electrolyte design and formation protocols, and electrode‐architecture design to improve ionic accessibility and reduce concentration polarization in thick electrodes. To reduce mechanistic overinterpretation, this review develops a coupled‐penalty evaluation framework in which each section closes with an integrated interpretation and a validation checklist defining the evidence required for mechanistic claims. Overall, this review provides practical guidelines for distinguishing intrinsic conversion/reconversion pathway changes from electrode‐level accessibility, resistance, interphase, and formation‐history effects in conversion‐type anodes.