A battery system comprising: an anode composed of a non-toxic biocompatible metal; a first printable carbon-based current collector comprising biocompatible multiple few layer graphene (FLG) sheets in electrical contact with and extending from the anode; a three-dimensional (3D) hierarchical mesoporous carbon-based cathode including an open porous structure configured to catalyze an active material via gas diffusion; a polymer-based barrier film deposited on the 3D hierarchical mesoporous carbon-based cathode, the polymer-based barrier film configured to prevent oxygen from entering the open porous structure while deposited on the 3D hierarchical mesoporous carbon-based cathode; a second printable carbon-based current collector comprising biocompatible multiple few layer graphene (FLG) sheets in electrical contact with and extending from the cathode; and an electrolyte layer disposed between the anode and the cathode, the electrolyte layer configured to activate the battery system when released into one or both of the anode and the cathode.