High-Capacity, High-Rate Nanosized Bismuth-Antimony Embedded in N-Doped Carbon Matrix Via Facile Pyrolysis As Anodes for Advanced Li Storage

Abstract

Antimony (Sb) is an attractive anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity (660 mAh g–1). Nevertheless, it suffers from huge volume expansion and severe particle pulverization during lithiation/delithiation processes, which leads to poor cycling performance. Herein, to address this matter, a composite of bismuth-antimony alloy nanoparticles embedded in N doped-carbon coating (BiSb@NC) is fabricated via a simple pyrolysis method. The design of bimetallic Bi-Sb solid solutions is possible at any molar ratio. The coupled pair, metallic Bi itself, does not only provide high volumetric capacity (3765 mAh cm–3) and low working potential (0.8 V hereafter vs. Li+/Li) but could also synergistically buffer the volume fluctuation due to the different working potentials between the two alloys. Nanosized BiSb alloys can enhance the reaction kinetics through shortened Li+-ion diffusion pathways. Additionally, the N-doped carbon coating also effectively cushions the volume changes of BiSb and maintains effective conductive networks during extended alloying/dealloying reactions with Li+ ions. As a result, the BiSb@NC anode achieves a high reversible capacity of 550 mA h g–1 after 100 cycles at 100 mA g–1 and superior high-rate performance of 350 and 220 mA h g–1 at 2 and 5 A g–1, accordingly despite its high BiSb loading (82 wt%).