Sodium Mesoxalate as Sacrificial Salt for Biomass‐Derived Hard Carbon // Polyanionic Cathode Na‐Ion Full Cells

Up to date, research on sodium‐ion batteries (SIBs) has primarily focused on half‐cell configurations, a crucial but preliminary step in evaluating suitable materials for full‐cell SIBs. To date, the literature on hard carbon (HC)‐based full‐cell SIBs remains limited, and the irreversibility associated with the first cycle of HC anodes presents a significant challenge for the commercialization of hard carbon‐based SIBs. This work evaluates sodium mesoxalate as a sacrificial salt (SS) in the cathode to compensate for biomass‐based hard carbon first cycle irreversibility in two full‐cell systems versus Na₃V₂(PO₄)₃@C and Na₃V₂O₂(PO₄)₂F@C. This sacrificial salt is selected due to its nonflammability, low cost, and ease of dehydration. Full‐cell studies utilizing the sacrificial salt‐containing cathodes and biomass‐derived hard carbon anodes demonstrate to achieve outstanding specific capacity and rate capability at low and moderate rates (from 9 to 130 mA g⁻¹) for the fluorophosphate cell chemistry but poorer electrochemical results for the NASICON‐based system. Finally, Life Cycle Assessment methodology is applied to the sacrificial salt containing full‐cells to evaluate and compare the environmental footprint of these SS full‐cells based on a sustainable anode with polyanionic cathode chemistries.