Disclosed herein is a tubular re-chargeable Li-air battery cell comprising a Li-based garnet-type Li6.5La2.5Bao.5ZrTaOi2 (LLBZT) electrolyte and the like. The Li-rich LLBZT is adjacent to a ceramic tubular wall which in turn, is adjacent to a porous or dense cathode which in turn, is adjacent to a porous or dense current- collecting layer. Two or more tubular re-chargeable Li-air battery cells comprising LLBZT may be connected in series. The barium component of the LLBZT may be substituted or doped with an alkaline rare earth metal, for example one of beryllium, magnesium, calcium, strontium, and radium. The tantalum component of LLBZT may be substituted or doped with niobium or lanthanum.