Electrochemically nanostructured electrodes for Li-ion microbatteries

Abstract: Electrodeposition is a promising technique for fabricating complex nanostructures and coating these with suitable thin films of active materials. The research presented in this thesis aims at the development of new electro- chemical methods for the synthesis of nanostructured electrodes suitable for Li-ion microbatteries. Electrodes based on nanostructured Cu and Al current collectors have been investigated to provide insight into the fabrication of both anodes and cathodes.Coating 3D aluminium current collectors with a vanadium oxide thin film is generally accompanied by aluminium corrosion due to the oxidative environment employed in the electrodeposition. To circumvent this issue a protective intermediate MnOx coating was implemented which suppresses the Al corrosion thereby facilitating subsequent vanadium oxide deposition.3D Cu electrodes with thin Cu2O coatings were fabricated to investigate their electrochemical properties and the mechanism of the Cu2O conversion reaction. Impressive high-rate cycling capabilities and capacity retention were observed with capacities corresponding to 130% of the theoretical capacity obtained after 390 cycles. This capacity gain was linked to electro- chemical milling of the Cu2O particles producing particles smaller than 5 nm. A distribution of particles with different sizes was also observed during the electrochemical analysis. This gave rise to a substantial redox potential distribution and a large electroactive potential window.