Exploration of CrPO4@N-doped carbon composite as advanced anode material for potassium-ion batteries

Metal phosphates are attracting great attention as anode materials for alkali-ion batteries due to their chemical stability, low working voltage, and high theoretical capacity. However, there are few reports on the application of metal phosphate as potassium-ion batteries (PIBs) anode material, and the potassium storage mechanism remains mysterious. Herein, a core–shell chromium phosphate@N-doped carbon (denoted as CrPO 4 @NC) composite is newly synthesized and demonstrated as conversion-type anode material for PIBs. The N-doped carbon coating layer effectively relieves the mechanical strain and improves electrical conductivity during repetitive cycling. The formed P–C bonding between CrPO 4 core and nitrogen-doped carbon shell can help to maintain structural integrity and accelerate charge transfer. As a consequence, the CrPO 4 @NC composite exhibits a decent capacity (304.6 mAh g −1 at 50 mA g −1 ), good rate capability (135.1 mAh g −1 at 500 mA g −1 ), and superior stability (133.2 mAh g −1 at 200 mA g −1 after 100 cycles). Particularly noteworthy, we also provide experimental evidence that a conversion reaction occurs at CrPO 4 @NC electrode with metallic Cr and K 3 PO 4 formed during the potassiation process. This work illustrates that CrPO 4 may be a kind of anode material for applications in energy storage systems.