3D Hierarchically Assembled Porous Wrinkled-Paper-like Structure of ZnCo2O4 and Co-ZnO@C as Anode Materials for Lithium-Ion Batteries

Three dimensional (3D) hierarchically assembled porous transition metal oxide nanostructures are promising materials for next generation rechargeable Li-ion batteries (LIBs). Here, the controlled synthesis of 3D hierarchically porous ZnCo2O4 “wrinkled-paper-like” structure constructed from two-dimensional (2D) nanosheets (∼20 nm thick) through calcination of corresponding mixed metal carbonate intermediate is presented. The mixed metal hydroxy-carbonate intermediate with wrinkled-paper-like structure has been synthesized by a novel organic surfactant and organic solvent free protocol at reflux condition using an aqueous solution of corresponding metal salt and ammonium carbonate. Active-inactive nanocomposites of Co-ZnO@C with similar wrinkled-paper-like morphology with varying carbon content, have also been synthesized through carbonation of hydroxyl-carbonate intermediate followed by calcination (under reducing environment). Calcination of the carbon coated mixed metal carbonate results in phase separated uniform Co metal and ZnO particles embedded on carbon matrix. The results demonstrate that incorporation of ∼23% carbon in the matrix significantly improves the performance as anode material in LIB by exhibiting high specific capacity and enhanced cycling performance. At a current density of 100 mAg–1, it shows an excellent initial specific capacity of 527 mAhg–1, which is maintained up to 50 cycles. In fact, a slight gradual increase in capacity with cycling has been observed.