Correlation between Microstructure and Potassium Storage Behavior in Reduced Graphene Oxide Materials

Potassium-ion batteries (PIBs) are considered to be potential alternatives to the conventional lithium-ion batteries (LIBs) due to the similar working mechanism and abundant potassium (K) resource. However, it still remains challenging to directly apply commercial graphite anodes for PIBs owing to the large K ions, which may impede the electrochemical intercalation of K ions into the graphite interlayer and result in a poor cyclic stability and rate capability. Reduced graphene oxide (rGO) has shown remarkable electrochemical performance as an anode material for PIBs due to the fact that rGO possesses more active sites with an enlarged interlayer distance. Understanding the microstructure of rGO is crucial for optimizing its K-ion storage capabilities. Herein, it is revealed that the K-ion storage behavior of rGO is strongly dependent on the thermal treatment temperature on account of the difference in microstructure. rGO graphitized at 2500 degrees C exhibits a superior long-term cyclic stability for 2500 cycles due to the expanded interlayer distance and the unique graphite-like structure in a long range, enabling it to endure the huge volume change during uninterrupted K-ion intercalation/deintercalation processes.