Li2FeCSO7 crystallizes in the monoclinic P2_1/m space group. Li(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted LiO4 trigonal pyramids that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one S(1)O4 tetrahedra,  a cornercorner with one Li(1)O4 trigonal pyramid,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Li(1)O4 trigonal pyramid. The corner-sharing octahedral tilt angles are 62°. Fe(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with four equivalent S(1)O4 tetrahedra, corners with two equivalent Li(1)O4 trigonal pyramids, and edges with two equivalent Li(1)O4 trigonal pyramids. C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. S(1) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form SO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra and corners with two equivalent Li(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 42-59°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to two equivalent Li(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted trigonal pyramidal geometry to two equivalent Li(1), one Fe(1), and one C(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Li(1), one Fe(1), and one C(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one S(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one S(1) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Fe(1) and one S(1) atom.
Li2FeCSO7 crystallizes in the monoclinic P2_1/m space group. Li(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted LiO4 trigonal pyramids that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one S(1)O4 tetrahedra,  a cornercorner with one Li(1)O4 trigonal pyramid,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Li(1)O4 trigonal pyramid. The corner-sharing octahedral tilt angles are 62°. The Li(1)-O(1) bond length is 2.01 Å. The Li(1)-O(2) bond length is 2.05 Å. The Li(1)-O(3) bond length is 2.14 Å. The Li(1)-O(4) bond length is 2.16 Å. Fe(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with four equivalent S(1)O4 tetrahedra, corners with two equivalent Li(1)O4 trigonal pyramids, and edges with two equivalent Li(1)O4 trigonal pyramids. The Fe(1)-O(2) bond length is 2.24 Å. The Fe(1)-O(3) bond length is 2.19 Å. The Fe(1)-O(5) bond length is 2.17 Å. The Fe(1)-O(6) bond length is 2.12 Å. Both Fe(1)-O(4) bond lengths are 2.09 Å. C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. The C(1)-O(1) bond length is 1.28 Å. The C(1)-O(2) bond length is 1.31 Å. The C(1)-O(3) bond length is 1.32 Å. S(1) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form SO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra and corners with two equivalent Li(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 42-59°. The S(1)-O(5) bond length is 1.48 Å. The S(1)-O(6) bond length is 1.49 Å. Both S(1)-O(4) bond lengths are 1.49 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to two equivalent Li(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted trigonal pyramidal geometry to two equivalent Li(1), one Fe(1), and one C(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Li(1), one Fe(1), and one C(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one S(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one S(1) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Fe(1) and one S(1) atom.