<p>To address the challenge of passivation of magnesium metal anodes within conventional organic electrolytes, the potential of bamboo biochars (BCs) to facilitate Mg-ion transport opens a new avenue for the development of Mg metal batteries. In this work, BCs with a natural hierarchical structure and a three-dimensional (3D) interconnected network are designed and fabricated via one-step carbonization, followed by a pressure infiltration process to prepare a 3D-BCs/Mg composite. This structure enabled a 3D encapsulation and protection of the Mg metal by the BCs framework. Further investigations revealed that the interconnected 3D-BC skeleton significantly increased the number of ion transport channels and improved ion transport efficiency, while effectively mitigating the reductive decomposition of the electrolyte on the Mg metal surface, as compared to randomly distributed particulate BCs (P-BCs). In a Mg||Mg symmetric cell and a Mg||V₂O₅ full cell, the BCs/Mg composite anode featuring a 3D ion-conductive protective interface exhibited remarkable performance enhancements. Moreover, the pressure infiltration process provides a cost-effective and simplified fabrication strategy for Mg metal anodes, which promotes the scalable utilization of plant-derived materials to develop environmentally friendly electrode systems. This approach also holds great potential for application in other metal battery systems requiring interfacial protection.</p> Graphical abstract <p></p>