The two-dimensional to three-dimensional transition structures of ZnCo2O4 for the application of lithium-ion batteries

Abstract We prepare the transition structure of ZnCo 2 O 4 via transformation from two-dimensional (2D) nanosheets to three-dimensional (3D) microspheres with the solvothermal method. ZnCo 2 O 4 nanocrystallites were produced from the reaction of zinc acetate and cobalt nitrate in the non-aqueous methanol solution. The oriented attachment of ZnCo 2 O 4 nanocrystallites results in the formation of the 2D wrinkled-paper-like structure of ZnCo 2 O 4 . The 2D ZnCo 2 O 4 nanosheet agglomerate spontaneously because there is no appropriate surfactant, and they have weak electrical double layers in the precursor solution. As the stacking of 2D ZnCo 2 O 4 nanosheets increased, the aggregate of ZnCo 2 O 4 nanosheet was transformed into the 3D ZnCo 2 O 4 microspheres. The transition structure of the ZnCo 2 O 4 was composed of the interconnected ZnCo 2 O 4 nanoparticles, which results in a porous structure to accommodate the volume expansion of ZnCo 2 O 4 structure during the charge process. The transition structure of ZnCo 2 O 4 exhibits a remarkably high specific capacity and improved cycle performance. At a current density of 100 mA g −1 , the transition structure of ZnCo 2 O 4 exhibited excellent initial discharge specific capacity of 2094 mA h g −1 . The discharge capacity maintain at 1296.91 mA h g −1 after 200 cycles. Even as current density reached to 2000 mA g −1 , the average specific capacity still showed 606.88 mA hg −1 .