Multi-electron Reaction Materials for High-Energy-Density Secondary Batteries: Current Status and Prospective

Abstract: To address increasing energy supply challenges and allow for the effective utilization of renewable energy sources, transformational and reliable battery chemistry are critically needed to obtain higher energy densities. Here, significant progress has been made in the past few decades in energetic battery systems based on the concept of multi-electron reactions to overcome existing barriers in conventional battery research and application. As a result, a systematic understanding of multi-electron chemistry is essential for the design of novel multi-electron reaction materials and the enhancement of corresponding battery performances. Based on this, this review will briefly present the advancements of multi-electron reaction materials from their evolutionary discovery from lightweight elements to the more recent multi-ion effect. In addition, this review will discuss representative multi-electron reaction chemistry and materials, including ferrates, metal borides, metal oxides, metal fluorides, lithium transition metal oxides, silicon, sulfur and oxygen. Furthermore, insertion-type, alloy-type and conversion-type multi-electron chemistry involving monovalent Li⁺ and Na⁺ cations, polyvalent Mg²⁺ and Al³⁺ cations beyond those of alkali metals as well as activated S²⁻ and O²⁻ anions are introduced in the enrichment and development of multi-electron reactions for electrochemical energy storage applications. Finally, this review will present the ongoing challenges and underpinning mechanisms limiting the performance of multi-electron reaction materials and corresponding battery systems. Graphic Abstract: [Figure not available: see fulltext.]