Structural battery composites: interface engineering, multifunctional architectures, and the path from material innovation to system-level energy storage

Structural battery composites combine electrochemical energy storage and mechanical load-bearing within a common material architecture. Their practical development depends on controlling interactions among carbon-fiber electrodes, structural electrolytes, separators, interphases, and protective layers. This review examines the relationships between constituent architecture, interfacial transport, mechanical–electrochemical coupling, damage evolution, manufacturing processes, and validation maturity. Particular attention is given to the influence of fiber microstructure, electrode coatings, electrolyte morphology, and interfacial adhesion on multifunctional performance. The literature shows simultaneous energy storage and structural functionality, but differences in specimen geometry, normalization basis, testing conditions, and reporting quality limit direct comparisons. This review evaluates evidence from constituent experiments, integrated cells, laminates, and validated models based on experimental scope. The analysis identifies persistent limitations in coupled durability testing, interfacial stability, manufacturing repeatability, environmental protection, and reporting of quantitative evidence. Progress toward engineering application requires standardized mechanical–electrochemical characterization, reliable performance-retention measurements, and component-level validation under representative service conditions.