Stable cycling and excess capacity of a nanostructured Sn electrode based on Sn(CH3COO)2 confined within a nanoporous...

A high capacity, electrochemically stable, nanostructured Sn electrode for Li ion battery anodes is described. This electrode utilizes a rigid, electrically conductive, nanoporous carbon aerogel scaffold by incorporating tin acetate, Sn(CH3COO)2, into the scaffold pore volume through melt infusion. Incorporation of the Sn(CH3COO)2 by melt infusion ensures a chemically stable contact with the scaffold. The mechanical rigidity of the pore volume confines the Sn to nanometer dimensions without sintering, leading to stable cycling. Separation of the synthesis of the scaffold from the loading with Sn(CH3COO)2 permits optimized division of the scaffold pore volume for expansion and electrolyte access during reaction with Li. Using this design, an electrode based on an aerogel with a 5 nm mode pore size was cycled over 300 times without degradation. In addition, after subtracting the contribution from the carbon scaffold, the capacity exceeded the theoretical capacity for Sn, due to an oxidation reaction occurring at 1.2 V. This excess capacity may be related to the solid-solid or solid-electrolyte interfaces in the electrode, possibly representing a new reversible Li ion reaction.