Synthesis of peanut-like hierarchical manganese carbonate microcrystals via magnetically driven self-assembly for high performance asymmetric supercapacitors

Abstract

To construct a suitable structure for both electronic conduction and ionic transport towards supercapacitors, peanut-like hierarchical manganese carbonate (MnCO₃) microcrystals assembled with floss-like nanowires are synthesized via a hydrothermal process and primarily used as an active material for supercapacitors. The formation mechanism is illustrated by means of a dissolution–recrystallization process and magnetically driven self-assembly. The electrode with peanut-like hierarchical MnCO₃ microcrystals exhibits a high specific capacitance of 293.7 F g⁻¹ and a superior cycle stability of 71.5% retention after 6000 cycles, which are higher than those of the reported Mn-based active materials in alkaline electrolytes. The asymmetric supercapacitor, assembled with the peanut-like MnCO₃ electrode as the positive electrode and a home-made porous carbon electrode as the negative electrode, exhibits an energy density of 14.7 W h kg⁻¹ at a power density of 90.2 W kg⁻¹ and an energy density of up to 11.0 W h kg⁻¹ at 3.3 kW kg⁻¹. An as-assembled all-solid-state supercapacitor series can light up a LED indicator for 10 min, indicating a promising practical application of peanut-like MnCO₃ microcrystals.