Nanocolumnar germanium thin films as a high-rate sodium-ion battery anode material

Paul R. Abel, Yong Mao Lin, Tania De Souza, Chia Yun Chou, Asha Gupta, John B. Goodenough, Gyeong S. Hwang, Adam Heller, C. Buddie Mullins

Research output: Contribution to journalArticlepeer-review

169 Scopus citations

Abstract

Both nanocolumnar and dense germanium thin films, synthesized by evaporative deposition, were tested as a potential anode material for sodium-ion batteries. The reversible capacity of the nanocolumnar films was found to be 430 mAh/g, which is higher than the theoretical capacity of 369 mAh/g. The nanocolumnar films retained 88% of their initial capacity after 100 cycles at C/5, whereas the dense films began to deteriorate after ∼15 cycles. Additionally, the nanocolumnar films were stable at charge/discharge rates up to 27C (10 A/g). The diffusion coefficient for sodium in germanium was estimated, from impedance analysis of the dense films, to be ∼10-13 cm 2 s-1. Modeling of diffusion in the sodium- germanium system predicts that sodium diffusion in the near-surface layers of the material is significantly faster than in the bulk. These results show that small feature sizes are critical for rapid, reversible electrochemical sodiation of germanium.

Original languageEnglish
Pages (from-to)18885-18890
Number of pages6
JournalJournal of Physical Chemistry C
Volume117
Issue number37
DOIs
StatePublished - 19 Sep 2013

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