In-Situ Study of Multistep Lithium-Bismuth Alloying Mechanisms

Abstract

With the high energy density, anode materials storing energy based on alloying mechanisms are promising anode candidate in rechargeable lithium ion batteries. Here, we target bismuth (Bi) nanostructures (theoretical volumetric capacity ~3800mAh/cm−3 with formation of Li3Bi) and explore the (de)alloying mechanisms upon insertion/extractiong of Li+. Real-time synchrotron XRD and in situ TEM of the (de)alloying kinetics of Bi working as a LIB anode are carried out, which reveals the reaction mechanism at both bulk level and at single-nanoparticle level. As analyzed by both two methods, the Li-Bi (de)alloying proceeds via a reversible two-step mechanmism featuring two two-phase reactions, where Li1Bi is identified as the intermediate phase. A preferred alloying pathway along Bi-(012) lattice during the Bi-Li1Bi transitioning stage is revealed and further studied by DFT. We expect such fundamentals discussed here to direct the design of alloying electrode materials with enhanced battery performance.