Encapsulating segment-like antimony nanorod in hollow carbon tube as long-lifespan, high-rate anodes for rechargeable K-ion batteries

K-ion battery (KIB) is a new-type energy storage device that possesses potential advantages of low-cost and abundant resource of potassium. To develop advanced electrode materials for accommodating the large size and high activity of potassium ion is of great interests. Herein, a segment-like antimony (Sb) nanorod encapsulated in hollow carbon tube electrode material (Sb@HCT) was prepared. Beneficial from the virtue of abundant nitrogen doping in carbon tube, one-dimensional and hollow structure advantages, Sb@HCT exhibits excellent potassium storage properties: in the case of potassium bis(fluorosulfonyl)imide (KFSI) electrolyte, Sb@HCT displays a reversible capacity of up to 453.4 mAh·g^-1 at a current density of 0.5 A·g^-1 and good rate performance (a capacity of 211.5 mAh·g^-1 could be achieved at an ultrahigh rate of 5 A·g^-1). Additionally, Sb@HCT demonstrates excellent long-cycle stability at a current density of 2 A·g^-1 over 120 cycles. Meanwhile, electrolyte optimization is an effective strategy for greatly improving electrochemical performance. Through ex-situ characterizations, we disclosed the potassiation of Sb anode is quite reversible and undergoes multistep processes, combining solid solution reaction and two-phase reaction.