In situ X-ray diffraction study on the formation of α-Sn in nanocrystalline Sn-based electrodes for lithium-ion batteries

Oehl N, Schmuelling G, Knipper M, Kloepsch R, Placke T, Kolny-Olesiak J, Plaggenborg T, Winter M, Parisi J

Abstract

In situ X-ray diffraction (XRD) was performed to study the formation of the α-Sn structure in nanocrystallineSn-based electrodes during electrochemical lithium insertion and extraction at room temperature. Therefore,pure β-Sn nanoparticles were synthesised and further processed into electrodes. The lithiation andde-lithiation process of the β-Sn nanoparticles follows the formation of discrete lithium–tin phases whichperfectly fits the voltage plateaus in the charge/discharge diagram. However, unlike bulk electrodes, whereno α-Sn is formed, we observed the formation of the semiconducting α-modification at 870 mV vs. Liwithin the first de-lithiation process. This observation explains earlier reports of an increasing internal resistanceof such an electrode. Additionally, our study supports earlier suggestions that predominantly small tincrystallites are transformed from the β-Sn phase into the α-Sn phase, while larger crystallites retain theirmetallic β-Sn structure.