Cement-based batteries with biochar-tuned microporous networks: A solution to infrastructure-integrated energy storage

Cement-based batteries offer a promising pathway for self-powered sensing in remote or infrastructure-limited environments; however, their real-world deployment remains limited due to persistent challenges of early-stage energy decay and long-term instability. This study aims to address this gap by developing a novel cement-based battery system integrating a discrete Zn-embedded cement-based anode (DZCA) with internal steel reinforcement as the cathode. A pore-structure optimization strategy combining foaming agents and porous biochar particles (BCPs) within the anode encapsulating matrix was employed to overcome the electrochemical limitations of cement batteries. The foaming-agent–generated macropores enhanced ionic conductivity and facilitated anodic-product transport, while BCPs acted as internal electrolyte reservoirs capable of storing and gradually releasing alkaline solution at the Zn–matrix interface. Multiple techniques (SEM-ImageJ, BET, and micro-CT) were used to evaluate the pore-structure characteristics of the encapsulating matrix, and a 20-week wet/dry discharge test under chloride-rich conditions was performed to assess the long-term applicability of the prepared cement-based batteries. The results showed that the BCP incorporation markedly regulated the early-stage anode activation and sustained the superior long-term performance of cement-based batteries, which is attributable to the electrolyte-buffering capability of BCPs. EIS, SEM-EDS, and resistivity measurements further verified that slow electrolyte release from BCPs maintained pore-solution continuity, stabilized local alkalinity, and sustained charge-transfer processes. Finally, the prepared batteries with mean pore sizes between 7.5 and 29 μm demonstrated superior energy retention and electrochemical durability under the tested conditions, indicating a critical pore-size window and providing a microstructural design guideline for durable, infrastructure-integrated cement-based energy storage systems.