Hydrothermal fabrication of MnCO_3@rGO: A promising anode material for potassium-ion batteries

摘要

A simple one-step hydrothermal method is used for the fabrication of MnCO3 nanorods@rGO composite without any further heat treatment. MnCO3 nanorods with size of similar to 5-10 nm in diameter are anchored well on the surface of rGO sheets. The sheet-like nature of rGO is well maintained in the composites. The MnCO3 nanorods@rGO composite provides high surface area (122.6 m(2) g(-1)) for conversion reaction and delivers high capacity and superior long-term cycling performance for potassium-ion batteries. The composite delivers a high capacity of 841 mAhg(-1) and retains 88% capacity at the current density of 200 mAg(-1) after 500 cycles. Even at the high current density of 2000 mAg(-1), the material still delivers a stable capacity 98 mAhg(-1) and maintains over in subsequent cycles. From the ex-situ TEM analysis, we confirmed that the morphology and structure of the composite is preserved after 500 cycles. This further confirms that rod-like morphology on rGO sheets acts as a stable template for reversible potassium intercalation/deintercalation. Moreover, rGO sheets accommodate the volume expansion during cycling and provide structural stability for MnCO3 nanorods.