Chemical bonding boosts nano-rose-like MoS2 anchored on reduced graphene oxide for superior potassium-ion storage
The abundant and low-cost potassium resources promote potassium-ion batteries (KIBs) as promising energy storage devices, thus accelerating the investigation of ideal electrode materials to accommodate the large-size K-ions. Here, a nano-rose-like MoS2 confined in reduced graphene oxide (MoS2@rGO) is evaluated as anode material to boost K-ion storage. The MoS2@rGO hybrid not only features large specific surface area for excellent electron conductivity and facile K-ions diffusion, but also provides a robust three-dimension (3D) network with stable interfacial connection through strong chemical bonds (Mo-C and Mo-O-C) between MoS2 and rGO, which can alleviate the mechanical stress to guarantee the structure stability during cycling. It is also confirmed that both intercalation and conversion reaction mechanisms, based on four-electrons-transfer, play an important role in K-ions insertion/extraction. Hence, the initial capacity of 438.5 mAh·g−1 with excellent cycling stability (capacity retention of 95.0% after 200 cycles) at 100 mA g−1 and the remarkable rate capability (196.8 mAh·g−1 at 2 A g−1) among many reported anodes are achieved for MoS2@rGO. No obvious fading at 500 mA g−1 can be observed over ultra-long lifespan of 1000 cycles. Finally, the K-ion full cells are assembled with K2Fe[Fe(CN)6] cathode to demonstrate the practical application.