Next‐Generation Carbon‐Based Anodes for Alkali Metal‐Ion Batteries: Recent Progress on Biphenylene and Emerging Materials

The pursuit of high‐performance anode materials for next‐generation metal‐ion batteries is vital for advancing sustainable energy storage technologies. This review presents a comprehensive overview of carbon‐based anodes, tracing their evolution from conventional materials, like graphite, hard/soft carbon, and graphene to emerging carbon frameworks, including graphyne, graphullerene, biphenylene, and their derivatives. Among these, biphenylene, a recently synthesized 2D carbon allotrope comprising 4‐, 6‐, and 8‐membered rings, has attracted attention for its unique structural, electronic, and mechanical properties, which are well‐suited for alkali metal (Li, Na, K) storage. We compare the synthetic strategies developed for biphenylene with those of other novel carbon allotropes, emphasizing key physicochemical properties, including high surface area, tunable conductivity, intrinsic porosity, structural flexibility, and fast ion transport that make biphenylene and its derivatives promising anode candidates. Recent computational and experimental advances in biphenylene‐based anodes are critically assessed, with a focus on heteroatom doping, functionalization, and morphological engineering, which are essential for optimizing performance. Finally, we discuss the challenges, knowledge gaps, and future research directions toward the rational design of next‐generation biphenylene‐based anodes as promising materials for metal‐ion batteries.