Co[sbnd]Fe hydroxyoxalate nanosheets chemically bonded with reduced graphene oxide as High-performance anode for lithium-ion batteries

Abstract

Transition metal layered double hydroxide (LDHs) materials are promising anodes for high-energy lithium-ion batteries (LIBs) due to their high specific capacities. However, the conductivity and the influence of intercalated anions are key issues for improving their electrochemical performances. Herein, a C2O42− intercalated CoFe-LDH nanosheets anchored on reduced graphene oxide (Co0.83Fe0.17(OH)2(C2O4)0.085·0.08H2O/rGO, CFO) composite was successfully synthesized for the first time by a two-step hydrothermal process. Graphene provides abundant nucleation sites for CoFe-LDH and forms the interconnected porous network skeleton. The intercalated C2O42− ions widen the interlayer spacing of CoFe-LDH to 0.92 nm, which can enhance the transportation of lithium ions. The lithium storage mechanism was proved that the CFO was transformed into a heterostructure nanocomposite (metal hydroxide and lithium oxalate) after discharge, and the high-valent carbon in lithium oxalate was electrocatalytically converted into low-valent carbon. This results in fast electrochemical reactions and high capacity. What’s more, the CFO shows a high reversible capacity (1603 mAh g−1 after 120 cycles), and long-term cycle stability under high current density (CFO delivers a reversible capacity of 860 mAh·g−1 after 1000 cycles at 4 A·g−1). This work provides a new anodes material for application in high-energy LIBs.