A thin film battery comprises a substrate, anode and cathode current collector layers formed over the substrate, anode and cathode layers formed over and in electrical contact with respective ones of the current collector layers, and an electrolyte layer formed between the anode and cathode layers. The thin film battery further comprises a barrier layer formed from a material such as tin oxide, tin phosphate, tin fluorophosphate, chalcogenide glass, tellurite glass or borate glass. The barrier layer is configured to encapsulate the thin film battery layers and substantially inhibit or prevent exposure of the thin film battery layers to air or moisture.