Silicon with Columnar Microporous Architecture for Ultrahigh Total Energy-Storage Capacity and with Highly Reversible Lithiation Performance
By Vadlamani, B. S.; Jagannathan, M.; Chandran, K. S. Ravi
Published in ACS Applied Energy Materials
2018
Abstract
The continuous miniaturization of microelectronic devices places an ever increasing demand on energy-storage capacities of on-chip Li-ion batteries. The search for positive electrodes for such batteries inevitably leads to Si because of its very high mass specific capacity (?4200 mAh/g for Li4.4Si). Although Si thin films and nanowires can provide very high specific capacities, their storage capacities (measured as coulombs per unit area) are, however, very limited. We report here a new Si electrode architecture, having columnar micropores, which provides a very high mass specific Li-storage capacity (?1212 mAh/g), and the highest total Li-storage capacity (?1.21 mAh/cm2) relative to other Si electrodes. These capacities are sustainable for over 200 cycles. It is shown that columnar microporous Si architecture can store a greater amount of charge (?250%) than solid-Si, due to the increased surface area provided by the columnar pores. Further, the most exciting finding of this study is that the pore walls of the columnar microporous architecture do not appear to crumble even after a large number of cell cycles, mitigating the Si cracking issues. Electron microscopy revealed that the superior performance is due to the accommodation of volume changes, caused by lithiation, within the pores. The present findings reveal a new pathway for architecturing Si electrodes for much larger and highly reversible total charge-storage capacities for on-chip Li-ion cells.