Volume contractible antimony bromide electrode as negative electrode for long-lasting Li-ion batteries

Antimony is one of the promising anode materials for lithium-ion batteries due to its high volumetric and gravimetric capacity (theoretical specific capacity 660 mAh g ⁻¹) and stable voltage window (0.87–0.91 V vs Li/Li ⁺ ). However, a high-volume expansion ( ∼130%) of Sb on lithiation degrades the electrochemical performance and restricts its application. In this work, a novel strategy is explored to use antimony halide (SbBr ₃) instead of Sb as the starting anode material. In the first step, Li will react with SbBr ₃ to form LiBr and pure Sb, leading to a 78% contraction in volume, and then this pure Sb further lithiates to form Li ₃ Sb expanding the volume (of the lithiated Sb by 130%). LiBr, which is a byproduct of the first reaction, dissolves into the solvent, leaving a porous Sb. In a nutshell, the two-step lithiation process results in a net volume-contacted porous antimony, ideal as an electrode to counter volumetric stress in subsequent charge-discharge cycles. The electrochemical performance of this electrode is much superior when compared with the pure antimony electrode, taking advantage of initial volume reduction and porous scaffold. It achieves a high specific discharge capacity of 345 mAh g ⁻¹ at a rate of 100 mA g ⁻¹ even after the end of the 100th cycle and losing only 20% of its capacity. This shows that this volume contractible technique can be successfully employed for metals and metallic alloys having drastically higher Li-storing capacities than graphite.