Hydrothermal fabrication of MnCO₃@rGO: A promising anode material for potassium-ion batteries

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 ~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 m² 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.