Although nanostructuring provides undeniable benefits, there are still issues that need to be addressed. For transition metal oxides, which are primarily insulators or wide bandgap semiconductors, there is the need to increase electronic conduction by doping, through partial reduction, and by creating good electrical contact between nanoparticles and conductive additives. The restacking of 2D layers, if not carried out properly, can impede ion access to the redox-active sites. This behaviour becomes of greater concern with increasing electrode thickness. Another potential limitation is that the packing density of nanoparticles is low and conventional rolling or doctor-blade electrode manufacturing techniques produce electrode films with a low density. As a result, electrodes comprised of just nanotubes or nanowires may not achieve satisfactory volumetric characteristics.