Catalytically graphitized freestanding carbon foams for 3D Li-ion microbatteries

Abstract

A long-range graphitic ordering in carbon anodes is desirable since it facilitates Li⁺ transport within the structure and minimizes irreversible capacity loss. This is of vital concern in porous carbon electrodes that exhibit high surface areas and porosity, and are used in 3D microbatteries. To date, it remains a challenge to graphitize carbon structures with extensive microporosity, since the two properties are considered to be mutually exclusive. In this article, carbon foams with enhanced graphitic ordering are successfully synthesized, while maintaining their bicontinuous porous microstructures. The carbon foams are synthesized from high internal phase emulsion-templated polymers, carbonized at 1000 °C and subsequently graphitized at 2200 °C. The key to enhancing the graphitization of the bespoke carbon foams is the incorporation of Ca- and Mg-based salts at early stages in the synthesis. The carbon foams graphitized in the presence of these salts exhibit higher gravimetric capacities when cycled at a specific current of 10 mA g⁻¹ (140 mAh g⁻¹) compared to a reference foam (105 mAh g⁻¹), which amounts to 33% increase.