Stable Cycling of BiSbSe1.5Te1.5 Conversion-Alloying Anodes

Abstract

Conversion-alloying anodes based on metal-selenides/tellurides have been explored extensively during the past decade for usage in lithium-ion batteries (LIBs), in order to increase cell energy density.1,2 Due to the large expansion and contraction during (de)lithiation, however, deterioration due to pulverization is a main hurdle to overcome for stable cycling. Strategies such as nano-structuring and composites have been applied to improve the mechanical stability, but no silver-bullet has yet been found.Here we present proof-of-concept for a conversion-alloying based anode BiSbSe1.5Te1.5, a medium high-entropy alloy (MHEA). The main idea is that the increased entropy can enhance the mechanical properties via solid solution strengthening. The MHEA was synthesized using high-energy ball milling to get a single phase (R3m), which was subsequently used as the anode active material, and this without compositing with any carbon material, in contrast to previously reported Se/Te-based alloys.3,4 As a result, our half-cells (Li//MHEA) were able to attain stable cycling with high capacity (420 mAh g-1), agreeable capacity retention (84%), and coulombic efficiency (>99%) for 100 cycles at C/5 rate (Figure 1).5 The formation of a stable solid electrolyte interphase (SEI) was inferred by electrochemical impedance spectroscopy (EIS) data, showing reduced charge transfer resistance with cycling. Furthermore, operando XRD showed reversibility of the initial phases during (de)lithiation. We furthermore believe that moving from MHEAs to “proper” HEAs might further enhance the mechanical properties and stabilize the structure for even longer duration.Figure 1: a) Charge-discharge curves and b) galvanostatic cycling of Li//BiSbSe1.5Te1.5. References Li, L., Zhao, J., Zhao, H. & Mao, J. Bi2Se0.5Te2.5/S, N-doped reduced graphene oxide as anode materials for high-performance lithium ion batteries. J. Alloys Compd. 920, 166003 (2022).Fan, H. et al. Recent advances of metal telluride anodes for high-performance lithium/sodium-ion batteries. Mater. Horizons 9, 524–546 (2022).Zhang, Z., Zhao, X. & Li, J. SnSe/carbon nanocomposite synthesized by high energy ball milling as an anode material for sodium-ion and lithium-ion batteries. Electrochim. Acta 176, 1296–1301 (2015).Wei, Y. et al. Wrapping Sb2Te3 with a Graphite Layer toward High Volumetric Energy and Long Cycle Li-Ion Batteries. ACS Appl. Mater. Interfaces 12, 16264–16275 (2020).Alvi, S. et al. To be submitted. (2023). Figure 1