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.