Amorphous MnO2-Modified FeOOH Ternary Composite with High Pseudocapacitance As Anode for Lithium-Ion Batteries

Abstract

The development of high-capacity anodes that are stable at high rates is of immediate interest as a potential alternative to the commercial graphite anode in lithium-ion batteries (LIBs). Conversion-based transition metal oxides, known for their high theoretical capacities, have been extensively studied in this regard. In this work, a ternary FeOOH-rGO-MnO2 composite has been suitably designed to address the limitations of the bare FeOOH anode arising from poor conductivity and volume expansion. A simple low-temperature synthesis method was employed to obtain a uniform distribution of FeOOH nanorods over the rGO matrix, which was further modified with a buffer layer of amorphous MnO2 nanosheets. While cycling at high rates, the modified composite anode delivered capacities of 956, 842, and 688 mAh g–1 at 1, 2, and 5 A g–1, respectively, for 200 cycles along with a cycling stability of 900 mAh g–1 at 1 A g–1 for 100 cycles. Various electrochemical techniques were used to analyze the superior performance of the ternary composite anode. The carbon matrix effectively provides favorable pathways for electron conduction and aids in the stable SEI formation, while the amorphous MnO2 sustains the structural integrity of the electrode by controlling volume expansion. Further, the exceptional stability of the anode at high rates was attributed to the marked increase in capacitive contribution in the FeOOH-rGO-MnO2 ternary composite anode, paving the way for faster electrode kinetics.