Unblocking the Robust Na⁺ Charge Storage  Behavior on Pb Nanocrystals in Porous Carbon Framework

Lead (Pb), with low average discharge plateau, large volumetric capacity, low cost (2000USD/MT) and high recycling rate (99%), is deemed as an optimal anode for sodium-ionbatteries/capacitors. However, several issues including short cycling life and poor ratecapability, stemming from amazing volume expansion (over 486%) and insulatingintermediates of Pb44- based “Zintl phases” during the sodiation, hinder the wide use of Pb.Herein, amorphous carbon coated discrete Pb nanocrystals (Pb@C) with highly porousstructure are prepared by sintering a compacted mixture composed of polyvinylpyrrolidone and lead citrate. This Pb@C nanocomposite achieves high levels of Na+storage with the robust rate capability and cycling stability. Furthermore, a sodium-ioncapacitor based on this Pb@C anode possesses the merits of high energy/power outputsand durable cycling life (> 12,000 cycles). The principal benefit arises from Pb-embeddedporous carbon structure with the functions of the increased electron connectivity, buffered2volume expansion and shortened Na+ diffusion path/barrier as confirmed by the theoreticalsimulations and in-situ/ex-situ structural analyses.Keywords: Sodium-ion capacitor; Pb anode; Alloying reaction; Na+ storage mechanism Composite