A fabrication process for conformal coating of a thin polymer electrolyte layer on nanostructured electrode materials for three-dimensional micro/nanobattery applications, compositions thereof, and devices incorporating such compositions. In embodiments, conformal coatings (such as uniform thickness of around 20-30 nanometer) of polymer Polymethylmethacralate (PMMA) electrolyte layers around individual Ni—Sn nanowires were used as anodes for Li ion battery. This configuration showed high discharge capacity and excellent capacity retention even at high rates over extended cycling, allowing for scalable increase in areal capacity with electrode thickness. Such conformal nanoscale anode-electrolyte architectures were shown to be efficient Li-ion battery system.