Tuning the electrochemical kinetics of bismuth-based conversion-alloying anodes with anion modulation for sodium-ion storage

Sodium-ion batteries (SIBs) have great application potential in large-scale energy storage devices due to their abundant sodium resources and economic effectiveness, whereas the unavailability of graphite and silicon makes it urgent to develop high-performance anode materials to promote the commercialization of SIBs. In this work, a series of bismuth-based conversion-alloying anode materials are comprehensively studied to decouple the electrochemical kinetics essence through modulating the anions. It's confirmed that bismuth telluride reveals the lowest band gap (Eg), E g ), moderate Na-ion adsorption energy (Ea) E a ) and Na-ion diffusion barrier (Eb), E b ), thereby contributing the optimal electron and Na-ion transfer kinetics behavior. Therefore, Bi2Te3 2 Te 3 anode delivers superior rate capability with high specific capacity of 108.4 mAh center dot g-1- 1 at 5000 mh center dot g-- 1 and ultra-long lifespan over 4000 cycles with low-capacity fading rate of 0.015 % per cycle. High angle annular dark field scanning transmission electron microscopy results visually illustrate from the atomic scale that Na-ion insertion and extraction is carried out through conversion-alloying dual-mechanism, in which Bi-ion is responsible for charge compensation verified by X-ray absorption spectroscopy. The assembled Na-ion full batteries demonstrate the practicality of Bi2Te3 2 Te 3 anode, exhibiting high energy density of 230.4 Wh center dot kg-1,- 1 , great rate property and excellent cycling stability with long lifetime over 600 cycles.