Researchers at the University of St Andrews have published new findings that provide valuable insight into how particle size and electrolyte selection influence the performance of tin anodes in sodium-ion batteries.
The work builds on ongoing research at St Andrews into high-capacity anode materials and further strengthens understanding of the challenges and opportunities associated with tin-based energy storage technologies. The International Tin Association previously visited the University of St Andrews in 2024 as part of its ongoing programme to engage with leading researchers developing new applications for tin.
Tin is attracting significant attention as a sodium-ion battery anode material due to its high theoretical capacity of 847 mAh g⁻¹, more than double that of conventional hard carbon anodes. However, during charging, tin alloys with sodium and can undergo volume expansion of more than 400%, creating mechanical stresses that can lead to electrode degradation and capacity loss over time.
To better understand these challenges, the St Andrews team compared commercially available micron-sized tin particles with laboratory-synthesised nanosized tin materials. The materials were evaluated using both conventional carbonate-based electrolytes and diglyme-based electrolytes.
The study found that electrolyte chemistry played a decisive role in performance. Micron-sized tin operated in a diglyme-based electrolyte delivered stable cycling for more than 150 cycles, retaining approximately 85% of its capacity. Despite the substantial volume changes associated with sodium alloying, the electrolyte formed a stable and flexible solid-electrolyte interphase (SEI) that helped maintain electrode integrity during repeated charge and discharge cycles.
In contrast, all materials tested in conventional carbonate electrolytes showed rapid capacity fading. Detailed microscopy revealed extensive electrolyte decomposition, cracking, and the formation of thick surface layers that isolated the active tin material from the electrochemical reaction. The researchers also observed that nanosized tin particles, while better able to accommodate volume expansion, promoted increased electrolyte decomposition due to their higher surface area. This ultimately resulted in poorer long-term cycling stability.
The findings highlight the importance of considering both particle size and electrolyte chemistry when developing tin-based sodium-ion batteries. Rather than focusing solely on reducing particle size, the research suggests that achieving stable long-term performance requires careful optimisation of the interactions between the tin anode and the electrolyte.
As interest in sodium-ion batteries continues to grow, studies such as this provide valuable guidance for researchers and developers seeking to commercialise high-capacity tin anodes. The work also reinforces the growing body of evidence that tin remains one of the most promising alloy-type anode materials for next-generation sodium-ion battery technologies.
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