Synthesis, crystal structure of a lithium - zinc bimetal coordination polymer and its graphene composite as anode materials for lithium ion battery

Abstract A new bimetal coordination polymer composed of Li + , Zn 2+ and 4,5‑imidazole dicarboxylic acid (idca) with a molecular formula of Li 5 Zn 6 C 25 H 11 N 10 O 24 (LiZn1) was prepared via a simple hydrothermal method. The single crystal structure shows that LiZn1 has a 3-D framework consisting of three independent four coordinated Li + and three independent five coordinated Zn 2+ cations, respectively. Topological study indicates the network of LiZn1 is 9-nodal, 3,3,3,3,3,4,5,5,6-connected net, with a point symbol of {4.6.7} 2 {4.6 2 } 4 {4 2 .6 2 .7 2 .9 3 .11}{4 2 .6} 2 {4 3 .6 3 .7 2 .8 5 .9 2 } 2 {4 3 .6 3 } 2 {6 2 .8}{6 5 .7 2 .8.9 2 } 2 . The graphene composite (LiZn1/gr, gr stands for graphene.) was prepared via a sonication treatment of the mixture of LiZn1 and graphene. LiZn1 was employed as the anode of a lithium ion battery, the initial discharge capacity was obtained for 558 mAh/g, after 100 cycles the discharge capacity was decreased to around 75 mAh/g. However, the graphene composite (LiZn1/gr) has improved very much the performance with the initial discharge capacity of 1090 mAh/g and after 100 cycles the discharge capacity could remain about 133 mAh/g.