With the rapid and ever increasing growth in portable electronics, such as smartphones and tablet computers, and the growing need for safer and longer range electric and hybrid powered vehicles, there has never been a more prevalent demand for light weight, high performance batteries with high power and energy densities. Commercial Li-ion batteries are just about keeping up with advancements in electronics. However, the limited performance of today’s commercial batteries is common knowledge, with the majority of hand held electronic devices requiring charging every day. Identifying and preparing battery materials which are capable of high performance, fast charging, and stable, safe capacity retention during operation would significantly advance portable device power technology.

Germanium based anode materials have attracted a lot of attention due to the high theoretical capacity of Ge (1384 mAh/g) with various nanostructures such as nanowires, nanotubes and nanoparticles being investigated as anode materials. (1-3) However the cost of preparing pure Ge nanostructures can be quite high due to the use of expensive anhydrous precursors such as diphenylgermane and the need to perform synthesis under an inert atmosphere. These factors would also impede scaling up the synthesis of these materials for industrial applications. To circumvent these issues we are investigating the electrochemical performance of GeO₂ with an inverse opal (IO) morphology, which can be prepared in air using cheaper precursors.

In this work we detail the preparation of GeO₂ IOs with application as anode materials for Li-ion batteries. The IO samples are initially structurally characterised via electron microscopy, electron diffraction and X-ray diffraction. We demonstrate the electrochemical evaluation of our GeO₂ IO samples with cyclic voltammetry, rate capability testing and long cycle life (>1000 cycles) galvanostatic testing. Previous reports on the electrochemical performance of GeO₂ as an anode material have indicated that the capacity values obtained from the oxide are lower than those obtained from pure Ge. However, we demonstrate that by preparing a highly ordered, porous, three dimensionally interconnected network of GeO₂ in the form of an IO, we can obtain capacity values which are comparable to the highest values previously reported for pure Ge.

Acknowledgements

This work was also supported by Science Foundation Ireland (SFI) through an SFI Technology Innovation and Development Award under contract no. 13/TIDA/E2761. This publication has also emanated from research supported in part by a research grant from SFI under Grant Number 14/IA/2581.

References

1. T. Kennedy, E. Mullane, H. Geaney, M. Osiak, C. O’Dwyer and K. M. Ryan, Nano Lett., 14, 716 (2014).

2. L.-F. Cui, R. Ruffo, C. K. Chan, H. Peng and Y. Cui, Nano Lett., 9, 491 (2009).

3. D.-J. Xue, S. Xin, Y. Yan, K.-C. Jiang, Y.-X. Yin, Y.-G. Guo and L.-J. Wan, ‎J. Am. Chem. Soc., 134, 2512 (2012).