Developing new methods to prepare pseudocapacitive materials with high pseudocapacitance/electronic conductivity is of great interest for hybrid supercapacitors. Recently, the exfoliation/restacking of manganese and cobalt layered transition metal oxides was proposed. Despite improved electrochemical performance of such Mn-Co composites, their bulk organization (i.e. the scale at which the stacking occurs) and structure (i.e. porosity horizontal ellipsis ) remains to be elucidated so far. To tackle this issue, here, SEM and Auger analysis with a nanoscale resolution, coupled to cross-section preparation is proposed. A good correlation between the restacking method, the nanoscale organization/structure of composites and resulting electrochemical performance is obtained. Importantly, the combination of cross-section with Auger analysis allows revealing the nanoscale stacking of the Mn and Co phases. Also, the porosity of the nano-composites, revealed by the cross-section preparation, is correlated to the speed of the restacking process. A fast flocculation step forms aggregates with a porous bulk structure while a slow flocculation step leads to a dense and closed bulk structure of the aggregates. These results highlight that a better control/understanding of the organization/structure of such nano-composites can lead to further improvement. Overall, the innovative cross-section Auger approach proposed in this study should also benefit to the understanding of other nano-composites. (c) 2021 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.
Cross-Section Auger Analysis to Study the Bulk Organization/Structure of Mn-Co Nano-Composites for Hybrid Supercapacitors
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