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

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 approximate to 1 mu m thick and 5-50 mm 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 Na2CO3 layer on the surface that could act as stable artificial solid-electrolyte interphase (SEI). The carbon sheet anode delivers 153 mAhg(-1) of reversible capacity at 50 mAg(-1) and 55 mAhg(-1) at 1000 mAg(-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.