Advanced energy storage performance based on a hairly hydrangea-like Co3-xMnxO4 with high absorption capacity

Abstract

Structural design and regulation of absorption capacity play important roles for improving energy storage performance of bimetallic oxides in supercapacitors (SCs). Herein, three-dimensional Co3-xMnxO4 (0 < x < 3) with different Co/Mn molar ratios are synthesized by hydrothermal method. Scanning electron microscopy (SEM) demonstrates the changes of the morphology of Co3-xMnxO4 (0 < x < 3) with different Co/Mn molar ratios, in which the Co3-xMnxO4 (x = 1.09) exhibits a hairly hydrangea-like morphology and thus provides a reduced contact resistance and an effective ion transition ability proved by the electrochemical measurements. Meanwhile, by theoretical calculations we prove that the addition of Mn adequately improves the absorption capacity of OH−on Co3-xMnxO4 and thereby boosts the reaction activity. Therefore, when the Co3-xMnxO4 (x = 1.09) is used as a SCs electrode, it performs a high specific capacitance of 326 F g−1 at a current density of 1 A g−1. Moreover, an assembled asymmetric supercapacitor (Co3-xMnxO4(x = 1.09)@NF//AC@NF) demonstrates enhanced performances, such as an energy density of 17.77 Wh Kg−1 at a power density of 400 W Kg−1, an outstanding cycling stability with 83.3% retention over 10,000 cycles at a current density of 2 A g−1 and so on. Related studies indicate the potential applications of Co3-xMnxO4 in the future smart micro/nano energy storage devices.