Cs2O2 is alpha boron-derived structured and crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Cs is bonded in a 6-coordinate geometry to six equivalent O atoms. There are four shorter (2.98 Å) and two longer (3.20 Å) Cs–O bond lengths. O is bonded in a 7-coordinate geometry to six equivalent Cs and one O atom. The O–O bond length is 1.52 Å.