<p>Biochar is considered as key anode material for alkali metal (lithium, sodium, and potassium) ion batteries (AIBs) owing to its rich microstructural features, high specific surface area, active sites, excellent conductivity, and mechanical strength. The multidimensional structures and diverse functional groups of biochar make it enable easy modification to improve ion transport, interface deposition behavior, and electrolyte stability. In addition, biochar-based derivatives, such as silicon/biochar composite anode materials, combine the advantages of high-energy density and low lithiation potential of silicon materials, as well as the superior conductive ability and outstanding mechanical qualities of biochar. In this review, the microstructure, properties, and synthesis methods of biochar materials are systematically clarified, and then, their applications in AIBs are presented followed by summarizing the energy storage mechanism and advanced physicochemical characterizations. Common structural configurations and preparative technique for biochar/silicon-based composites are summarized, such as core–shell, yolk–shell, and embedded coating structures with improved electrochemical and mechanical stability. Finally, toward practical application of biochar and biochar-based derivatives in future AIBs, the issues and challenges are outlined.</p> Graphical abstract <p></p>