3D Silicon Electrode Based on Stainless Steel Metal Fibril Current Collector for Flexible Lithium-Ion Batteries

Although silicon (Si) has been extensively investigated for one of the next high capacity anode materials, large volume changes during cycling and low electric conductivity result in poor cycling and rate capability. As a result, Si/carbon composite materials having Si content less than 10% are being introduced for commercial lithium-ion batteries (LIBs). This cannot be a good way to utilize Si for electrochemical systems. Therefore, as a different point of view, we try to fully use Si capacity by modifying Si electrode structure with metal fibril current collector. Comparing to flat metal current collector, circular-type fibril current collector having the same Si loading value can mitigate volume-changing stress like Fig. 1. Inspired by this promising fact, we try to use stainless steel metal fibril (SF) of a diameter of 10 um as a current collector. And then Si is sputtered upon SF by using radio-frequency sputtering.

The Si coating thickness is controlled to be about 1um equivalent to the loading level of 0.2 mg/cm² (0.6 mAh/cm²), which is considerably high comparing to conventional thin film Si electrode. The Si/SF electrode can not only deliver 3000 mAh/g at a 300mA/g during the initial cycling, but also maintain 1600 mAh/g at a 2000mA/g rate after 200 cycles without delamination of Si from SF current collector. The rate capability is also astonishing to give 1300 mAh/g at a 12000 mA/g. Finally, when the Si/SF electrode is applied for flexible lithium-ion batteries, the cycle performance is well maintained similarly to the original case.

References

[1] D.J. Lee et al, Journal of Materials Chemistry A, 10 (2014) 1039

[2] D.J. Lee et al, Electrochemistry Communications, 34 (2013) 98-101

[3] J.Y. Choi et al, Advanced Funtional Materials, 23 (2013) 2108-2114

Acknowledgements

This work was supported by the IT R&D program of MKE/KEIT. [10041142, Electrolyte Additive for 200Wh/kg High LIB of High Cycle Life]