Coaxially Coated Vertical Carbon Nanofiber Arrays as 3D Multifunctional Electrodes for Battery-Supercapacitor Hybrids

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This award provides funding for the study and development of materials and methods for the creation of a set of hierarchical nanostructured electrodes. The approach combines dissimilar functional nanomaterials into a unique three-dimensional architecture based on vertical nanowire arrays. The targeted electrode comprises a ternary nanostructure consisting of: 1) a coaxial coating of a thin film of a lithium storage material such as a metal oxide (for cathode use) or silicon (for anode use) layered on 2) a brush-like carbon template (i.e., a vertically aligned carbon nanofiber array grown on a copper foil) onto which 3) an electrically conductive polymer layer is further deposited as an outer sheath. The highly conductive carbon nanofiber core serves both as a reliable current collector and as a stable structural support, enabling fast lithium reactions with the storage materials (metal oxides or silicon) for applications in supercapacitors and Li-ion batteries. The combination of the stable carbon nanofiber core and conductive polymer sheath makes it possible for the sandwiched lithium storage materials to accommodate the inherent large volumetric expansion and contraction during charge-discharge cycles. If successful, the results of this research will lead to Li-ion based battery-supercapacitor hybrids with significantly improved power density, greater energy capacity, and prolonged cycle life, overcoming drawbacks that limit the utility of many other such electrical energy storage devices. The ternary composites can be used as either cathodes or anodes through the deposition of appropriate lithium storage materials. The approach to fabricating these materials is based on scalable processing technologies that are suitable for industrial manufacturing. This research addresses high-performance electrical energy storage solutions that form an essential part of the development and utilization of renewable energy resources.