James M. Mosby and Amy L. Prieto
We describe the direct single potential electrodeposition of crystalline Cu2Sb, a promising anode material for lithium-ion batteries, from aqueous solutions at room temperature. The use of citric acid as a complexing agent increases the solubility of antimony salts and shifts the reduction potentials of copper and antimony toward each other, enabling the direct deposition of the intermetallic compound at pH 6. Electrodeposition of Cu2Sb directly onto conducting substrates represents a facile synthetic method for the synthesis of high quality samples with excellent electrical contact to a substrate, which is critical for further battery testing.
James M. Mosby, Derek C. Johnson, and Amy L. Prieto
Cu2Sb was electrodeposited onto transmission electron microscopy (TEM) grids to investigate changes in morphology, composition, and crystal structure during the early stages of nucleation and growth. Multiple transitions were observed within the first second of the deposition, leading to the formation of crystalline Cu2Sb. These transitions were analyzed using TEM, scanning electron microscopy, selected area electron diffraction, and energy-dispersive X-ray spectroscopy. The nucleation sites are initially polycrystalline antimony with amorphous copper, which then transition through a polycrystalline copper intermediate containing some antimony before forming crystalline Cu2Sb. These analyses provide direct evidence that Cu2Sb does not deposit directly from solution but deposits by induced underpotential deposition. This is indicative of the electrodeposition of a typical alloy initially, but what is unusual is that the deposit at longer time scales is a highly crystalline intermetallic. This investigation is unique because TEM grids allow the interface between the deposited material and the substrate to be investigated. This is possible because the composite carbon film on the TEM grid behaves as a transparent substrate. This approach can be extended to other systems, allowing the development of a comprehensive understanding of the electrodeposition of intermetallic compounds.
Timothy S. Arthur, Daniel J. Bates, Nicolas Cirigliano, Derek C. Johnson, Peter Malati, James M. Mosby, Emilie Perre, Matthew T. Rawls, Amy L. Prieto, and Bruce Dunn
Three-dimensional (3D) battery architectures have emerged as a new direction for powering micro-electromechanical systems and other small autonomous devices. Although there are few examples to date of fully functioning 3D batteries, these power sources have the potential to achieve high power density and high energy density in a small footprint. This overview highlights the various architectures proposed for 3D batteries, the advances made in the fabrication of components designed for these devices, and the remaining technical challenges. Efforts directed at establishing design rules for 3D architectures and modeling are providing insight concerning the energy density and current uniformity achievable with these architectures. The significant progress made on the fabrication of electrodes and electrolytes designed for 3D batteries is an indication that a number of these battery architectures will be successfully demonstrated within the next few years.