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 Na$_3$V$_2$(PO$_4$)$_3$@C and Na$_3$V$_2$O$_2$(PO$_4$)$_2$F@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.