The invention relates to a battery unit (1) comprising: a plurality of electrically interconnected electrochemical cells (2), each of said cells having an electrode arrangement (3), in particular a lithium-based electrode arrangement (3) with a cathode contact element (4) and an anode contact element (5); and an outer sheathing (7) surrounding a chamber (6) in which the electrochemical cells (2) are arranged. The outer sheathing (7) is designed as a humidity barrier and as a chemical barrier. Each individual electrochemical cell (2) of the battery unit (1) comprises an electrically insulating sheathing (8) which surrounds the respective electrode arrangement (3). The invention also relates to a battery module comprising a plurality of electrically interconnected battery units (1) designed according to the invention.