In one aspect, a battery cell including: an electrode assembly, wherein the electrode assembly includes a first electrode plate, a second electrode plate, and a separator disposed between the first electrode plate and the second electrode plate; electrode tabs connected to the electrode plate and the second electrode plate, and extending from one side of the electrode assembly; a case for sealing the electrode assembly and an electrolyte; and a reinforcing material disposed in at least a region between the electrode assembly and the case, and comprising ceramic material and a polymer gel is provided.