π-conjugated structures as advanced anion hosts for dual-ion batteries: Mechanistic insights and optimization strategies

<p>Dual-ion batteries (DIBs) have emerged as a promising energy storage technology due to their cost-effectiveness, environmental friendliness, and potential for high energy and power density. A critical component enabling their performance is the development of efficient anion-hosting cathodes. Among various candidates, π-conjugated structures offer unique advantages, including tunable electronic properties, large π-surfaces for multi-electron transfer, and versatile molecular design. This review comprehensively examines the current progress in π-conjugated materials, like graphite and organic materials, as anion hosts for DIBs, emphasizing the interplay between molecular design and electrochemical performance. We discuss key strategies for enhancing capacity, rate performance, and stability, such as functional group optimization, donor-acceptor architectures, and anion-cation co-storage mechanism. The effects of electrolyte composition, including salt type, concentration, and solvent properties, on anion adsorption and charge transfer processes are critically analyzed. Furthermore, the challenges of achieving high mass loading, improving conductivity, and mitigating side reactions are addressed, alongside innovative approaches such as localized high-concentration electrolytes and interfacial engineering. Lastly, we explore emerging applications of π-conjugated materials in aqueous and low-temperature DIBs, highlighting their potential to expand the operational scope of this technology. The review concludes with perspectives on the future development of π-conjugated anion hosts, including advanced characterization techniques and the integration of computational modeling to unravel fundamental mechanisms. By providing a holistic overview of the design principles and mechanistic insights, this work aims to guide the rational development of high-performance DIBs leveraging π-conjugated materials.</p>