As the demand for large scale batteries has grown, considerations such as earth abundance, cost, and toxicity have assumed a greater importance. Metal oxides are worthy of evaluation as active materials for electrochemical energy storage, particularly those utilizing earth abundant, low cost, environmentally benign metal centers such as iron. For example, magnetite (Fe<sub>3</sub>O<sub>4</sub>), has shown promise due to its high theoretical capacity (926 mAh/g). However, to facilitate broader implementation of metal oxides in batteries, full understanding of the fundamental electrochemical reduction-oxidation mechanisms of the electroactive materials is required, coupled with characterization at the mesoscale to understand the underlying contributors to localized resistance which must be addressed in order to achieve significant improvements to current capability and reversibility. An emerging paradigm for the implementation of close-packed materials in higher current applications is the tuning of the materials crystallite dimensions, where the reduction of crystallite size should minimize the path length for ion transport upon discharge, resulting in a reduction of both internal cell resistance and the resultant structural strain associated with lithium insertion. Opportunities gained through controlled crystallite size reduction of oxide based materials will be described. In addition to the crystallite size of the electroactive material, a complete study of an electroactive nanomaterial in the complex mesoscale environment of a composite battery electrode should also consider the level of electroactive particle agglomeration, and agglomerate distribution within the battery electrode. These factors can influence electronic conductivity as well as access to lithium ions, as can be demonstrated both from empirical studies and mathematical models.

Mesoscale metal-oxide-based composite electrodes: Impact of crystallite size and aggregation on battery electrochemistry

251st National Meeting (2016)

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