In situ synthesis of Cu(ii) dicarboxylate metal organic frameworks (MOFs) and their application as battery materials†
New materials for battery electrodes are paramount to ensuring future battery supply can meet the ever-increasing demand for energy storage. Furthermore, detailed investigation on the various physical and chemical aspects of these materials is required to allow the same level of nuanced microstructural and electrochemical tuning that is available for conventional electrode materials. Here a comprehensive investigation is undertaken on the poorly understood in situ reaction between dicarboxylic acids and the copper current collector that occurs during electrode formulation, using a series of simple dicarboxylic acids. Specifically, we focus on the relationship between the extent of the reaction and the properties of the acid. Additionally, the extent of the reaction was demonstrated to affect both the electrode microstructure and the electrochemical performance. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and small and ultra-small angle neutron scattering (U/SANS) are used to provide unprecedented detail on the microstructure ultimately leading to a deeper understanding of formulation based performance enhancing techniques. Ultimately, it was determined that the copper-carboxylates are the active material, not the parent acid, and in some cases i.e., copper malate, capacities as high as 828 mA h g−1 were achieved. This work lays the foundation for future studies that use the current collector as an “active” component in electrode formulation and function rather than simply an inactive component of a battery.