Unlocking the atomic-scale mechanism of structural evolutions during (de)lithiation and negative-fading in CsPbBr3 anodes

Metal halide perovskite materials have attracted extensive research attention for lithium-ion batteries owing to their distinctive electronic and ionic transport properties. However, the atomic-scale mechanism of phase transformations in metal halide perovskites during lithium storage process remains largely unexplored. Herein, the structural evolution of CsPbBr₃ is comprehensively investigated through various in/ex-situ techniques, disclosing the generation of CsBr, LiBr, Pb, and Li₂₂Pb₅ phases via intercalation-conversion-alloying reactions during lithiation and the reversible formation of CsPbBr₃ upon charging process. Furthermore, CsPbBr₃ particles are embedded within conductive carbon nanotubes (o-CNT) to take full advantage of its negative fading phenomenon, which can deliver high specific capacities of 630 mA h g⁻¹ at 0.1 A g⁻¹ over 220 cycles and 376 mA h g⁻¹ at 1.0 A g⁻¹ at the 900^th cycle. Comprehensive experimental and theoretical analysis identify that the upgraded negative fading of CsPbBr₃ originates from the enhanced Li-alloying reaction of residual Pb metal loaded on o-CNT and the improved pseudocapacitive contribution from the reduced size of active material during cycles. Thus, this work not only uncovers the electrochemical (de)lithiation mechanism of CsPbBr₃ but also proposes an effective strategy to boost the additional “negative fading” effect of halide perovskite materials for superior lithium storage performance.