Incorporating Fe into Bismuthic Anode Systems: A Smart "Merits Combination/Complementation" Route to Build Better Ni-Bi Batteries.

The advancement of Ni-Bi batteries has turned sluggish because of impenetrable barriers related to physicochemical instability of bismuthic species under thermal conditions. This directly makes Bi-based anodes impossible to hybridize with graphitic carbons for a longer-term cyclic lifespan. To break this constraint, we herein propose an effective strategy by incorporating Fe into bismuthic systems to form multielement anodes. The smart Bi/Fe merits combination/complementation can drastically promote the tolerable temperature of Bi-containing nanomaterials over 500 °C, enabling carbon encapsulation without altering their geometric properties and in the meantime endowing the anodes with inherited electrochemical superiorities. The as-built BiFeO3@carbon anodes exhibit prominent electrode performances with excellent electrochemical activity (both Bi- and Fe-based components act as faradaic redox reaction sites), excellent rate capabilities, and impressive capacity retention (∼83.4% after 2000 cycles). We further unveil the anodic phase conversions of "BiFeO3 → Bi2O3/Fe2O3" (via the transition state of Bi2O3(222)) based on the real-time characterizations/post-analysis at distinct cyclic stages. The packed full cells exhibit max. energy/power densities of ∼90.72 W h kg-1/∼1.3 kW kg-1. Our study may offer a promising engineering route to promote the development of safe and applicable Ni-Bi batteries in near-future applications.