Nature of bismuth and antimony based phosphate nanobundles/graphene for superior potassium ion batteries

A novel architecture with bismuth (Bi) and antimony (Sb) based phosphate nanobundles well dispersed on graphene nanosheet is devised as outstanding anode for potassium-ion batteries (PIBs). The Bi and Sb based (in a ratio of 47:53) phosphate nanobundles can deliver a favourable cycling performance for 400 cycles under 500 mA g−1, obtaining a gravimetric capacity of 288 mAh g−1 with a remarkable capacity maintenance of 99%, in addition to displaying promising voltage plateaus. Meanwhile, it shows a superior performance in the full battery test, reaching an admired capacity of 372 mAh g−1 at 100 mA g−1. Nature of Bi and Sb based phosphate nanobundles during battery operation, including the lattice evolution, chemical bond cleavage, and phase transformation, is revealed. This study is notable for providing a promising anode for PIBs, and unveiling the nature of potassium storage mechanism of bismuth and antimony based phosphate, which is significant for the electrode development in PIBs.