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Researchers use shape memory alloy to address capacity fading of tin anodes for Li-ion batteries

Researchers from the South China University of Technology are proposing the use of NiTi shape memory alloys as a simple approach to solving the long-standing problem of capacity fade with tin (Sn)—and other high-capacity metallic—anodes for Li-ion batteries. Tin (like silicon) has a high theoretical specific capacity (992 mAh g-1 for Li22Sn5) and is one of the more attractive materials for potential negative electrodes in lithium-ion batteries.

However, tin (also like silicon) undergoes large volumetric changes with lithiation and delithiation during discharge and charge cycles (e.g., earlier post), leading to structural stresses and capacity fading.

By supporting the Sn anodes with NiTi shape memory alloys, the large volume change of Sn anodes due to lithiation and delithiation can be effectively accommodated, based on the stress-induced martensitic transformation and super-elastic recovery of the NiTi matrix respectively, which leads to a decrease in the internal stress and closing of cracks in Sn anodes.

Accordingly, stable cyclability (630 mAh g−1 after 100 cycles at 0.7C) and excellent high-rate capabilities (478 mAh g−1 at 6.7C) were attained with the NiTi/Sn/NiTi film electrode. These shape memory alloys can also combine with other high-capacity metallic anodes, such as Si, Sb, Al, and improve their cycle performance.

—Hu et al.

A paper on their work is published in Acta Materialia.

Resources

  • Renzong Hu, Min Zhu, Hui Wang, Jiangwen Liu, Ouyang Liuzhang, Jin Zou (2012) Sn buffered by shape memory effect of NiTi alloys as high-performance anodes for lithium ion batteries, Acta Materialia, Volume 60, Issue 12, Pages 4695-4703, doi: 10.1016/j.actamat.2012.05.015

Comments

Davemart

A remarkably simple, and by the sounds of it effective, approach!

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