Sodium‐Ion Battery Anodes Comprising Carbon Sheets: Stable Cycling in Half‐ and Full‐Pouch Cell Configuration

Abstract In this work, carbon sheets derived from starch packing peanuts were evaluated for their viability as sodium‐ion anodes in both half‐cell and full‐pouch cell configurations. The carbon sheets are ≈1 μm thick and 5–50 μm wide in dimensions with hard carbon structuring. The carbon sheets have a surface area of 430 m 2 g −1 with 92.5 % micropores (<2 nm) and 7.5 % mesopores (2–6 nm). Moreover, the carbon sheets contain a native Na 2 CO 3 layer on the surface that could act as stable artificial solid–electrolyte interphase (SEI). The carbon sheet anode delivers 153 mAh g −1 of reversible capacity at 50 mA g −1 and 55 mAh g −1 at 1000 mA g −1 with good cycling stability (92 % capacity retention) after 150 cycles. Post‐diagnostic analysis of the cycled carbon sheet electrode reveals that sheet‐like morphology of the carbon remains preserved after one hundred discharging–charging cycles and no excessive SEI formation is observed. The carbon sheet anodes, when paired with a Na a Ni 1− x − y − z Mn x M1 y M2 z O 2 cathode (M1 and M2 are transition metals) by Faradion Limited (UK), exhibit an average discharge voltage of 3.15 V. Stable cycling is demonstrated in full‐cells with 90 % capacity retention after 200 cycles and 84 % retention after 300 cycles in pouch cells. This excellent long‐term cycling stability with an average coulombic efficiency of 99.8 % is among the best reported for sodium‐ion full‐cells in the literature and is attributed to the material's stable SEI formation.