Construction of Mn–Zn binary carbonate microspheres on interconnected rGO networks: creating an atomic-scale bimetallic synergy for enhancing lithium storage properties

Abstract

Transition metal carbonates (TMCs), as promising anode materials for high-performance lithium ion batteries, possess the advantages of abundant natural resources and high electrochemical activity; however, they suffer from poor Li⁺/e⁻ conductivities and serious volume changes during the charge/discharge process. Constructing multicomponent carbonates by introducing binary metal atoms, as well as designing a robust structure at the micro and nanoscales, could efficiently address the above problems. Therefore, single-phase Mn_xZn_1−xCO₃ microspheres anchored on 3D conductive networks of reduced graphene oxide (rGO) are facilely synthesized via a one-pot hydrothermal method without any structure-directing agents or surfactants. Due to the well-designed architecture and atomic-scale bimetallic synergy, the Mn_xZn_1−xCO₃/rGO composites show superior lithium storage capacity, good rate capability and ultra-long cycling performance. Specifically, the Mn_2/3Zn_1/3CO₃/rGO composites could deliver a high capacity of 1073 mA h g⁻¹ at 200 mA g⁻¹. After 1700 cycles at a high rate of 2000 mA g⁻¹, a stable capacity of 550 mA h g⁻¹ can be maintained with the capacity retention approaching 88.6%. Density functional theory (DFT) calculations indicate that the partial Zn substitution in MnCO₃ could significantly decrease the band gap of the crystal, resulting in great improvement of electric conductivity. Moreover, the commercial potential of the Mn_xZn_1−xCO₃/rGO composites is investigated by assembling full cells, suggesting good practical adaptability of the composite anodes. This work would provide a feasible and cost-efficient method to develop high-performance anodes and stimulate many more related research studies on TMC-based electrodes.