Active Material Interfacial Chemistry and Its Impact on Composite Magnetite Electrodes

Rational design of battery systems with specific performance characteristics are needed to meet the growing, diverse needs of energy storage as batteries penetrate a range of sectors from automobiles to consumer electronics, among others. Here, we surface modified magnetite particles with distinct molecular entities containing different electronic and ionic conductivities and investigated how the local surface environment affected key battery characteristics such as capacity retention, rate capability, and electrode impedance. Herein, direct covalent attachment of poly [3-(4-carboxypropyl)thiophene] onto magnetite nanoparticles via a Fischer esterification scheme was shown to create robust anodes with low charge transfer resistances, excellent charge capacity retention at 0.3 C, and robust charge capabilities/specific capacities. The functionalization strategies used here rely on manipulating the native hydroxide layer of the active material, and thus can be applied to various conversion-type electrode materials. This work contributes to the growing toolset of chemical techniques to modify active materials to create battery systems with specific performance characteristics.