The high-pressure behavior of Li 2 CO 3 is studied up to 25 GPa with synchrotron angle-dispersive powder X-ray diffraction in diamond anvil cells and synthesis using a multi-anvil apparatus. A new non-quenchable hexagonal polymorph ( P 6 3 / mcm , Z =2) occurs above 10 GPa with carbonate groups in a staggered configuration along the c -axis— a =4.4568(2) Å and c =5.1254(6) Å at 10 GPa. Two columns of face-shared distorted octahedra around the Li atoms are linked through octahedral edges. The oxygen atoms are coordinated to one carbon atom and four lithium atoms to form a distorted square pyramid. Splittings of X-ray reflections for the new polymorph observed above about 22 GPa under non-hydrostatic conditions arise from orthorhombic or monoclinic distortions of the hexagonal lattice. The results of this study are discussed in relation to the structural features found in other Me 2 CO 3 carbonates ( Me : Na, K, Rb, Cs) at atmospheric conditions.