High-performance aqueous asymmetric supercapacitor based on hierarchical wheatear-like LiNi0.5Mn1.5O4 cathode and porous Fe2O3 anode

The cobalt-free spinel LiNi0.5Mn1.5O4 is actively explored as a cost-effective energy storage material. Herein, we report a low-temperature lithiation method to synthesize hierarchical wheatear-like LiNi0.5Mn1.5O4 anchored on active carbon cloth (LNMO@ACC). The LNMO@ACC electrode exhibits a high areal capacitance (1468 mF cm−2 at 1 mA cm−2), superior rate performance (1000 mF cm−2 at 10 mA cm−2), and outstanding cycling stability (82.5% retention after 4000 cycles). The mechanism of Li ions adsorption and diffusion on (111) and (400) lattice planes of LiNi0.5Mn1.5O4 is explained by density functional theory (DFT) calculations. The asymmetric supercapacitor (ASC) assembled by LNMO@ACC cathode and porous Fe2O3@ACC anode in 1 M LiNO3 electrolyte achieves a wide potential window of 1.8 V, superior areal capacitance of 851 mF cm−2, high energy density of 5.87 mWh cm−3 at a power density of 14.17 mW cm−3 and excellent cycle stability (retention of 88.6% after 8000 cycles at 20 mA cm−2). This work contributes a new method for preparing high-performance electrode materials and an effective strategy for high energy and power density supercapacitors by matching cathode and anode materials.