Mechanistic insights into the electrochemical Li/Na/K-ion storage for aqueous bismuth anode

Bismuth (Bi) was evaluated recently as an alloy-type anode material for aqueous alkali-metal ion batteries (ARABs) on account of its high theoretical capacity (385 mAh g−1), low redox potential (∼ −0.8 V vs. SCE), dendrite-free and absence of memory effects. However, it remains challenging for clarifying and pinpointing the intrinsic interaction mechanism between Bi and alkali metal ions (Li+, Na+ and K+), which is significant to reveal the potential and limitation of Bi electrode for future applications in ARABs. Herein, we gain the insights into the similarity and divergence of the (de)alloying mechanism of aqueous Bi electrode for AM ions (Li+, Na+ and K+) storage by ex-XANES, SXES, HRTEM and DFT. As a result, Bi shows superior specific capacities for Na+ and K+ storage but the lowest capacity for Li+ storage. Large adsorption energy makes Li+ dealloy from Bi matrix irreversibly, causing inferior rate performance and cycling stability. The largest radius of K+ triggers large volume expansion, which is responsible for the poor cycling stability for K+ storage. Bi exhibits superior performance for Na+ storage owning to the appropriate interaction strength between Bi and Na+. Our work can provide a proof-of-concept to universally pinpoint interactions between electrode and charge carriers for a wide range of metal electrodes.