Photolithographic Structuring of Ordered Silicon Micropillar Electrodes for Lithium-Ion Batteries and Electrochemical Performance

Abstract

Ordered and vertically oriented silicon (Si) micropillar structures, when optimally designed, can accommodate the lithiation-induced volumetric expansion that is limiting the implementation of Si as negative electrodes in Li-ion batteries. As there is not much work in this area, this study is focused on evaluating systematically the potential of Si micropillar electrodes prepared by photolithographic structuring of Si. The specific objective is to determine the effect of micropillar length and the free space around the pillars on the electrochemical performance of the electrode. The Si micropillar electrode with the pillar length of 14 μm showed a high specific capacity (2600 mAh/g) and a high areal capacity (3 mAh/cm2), which were stable for over 100 cycles. However, there was significant capacity degradation in 32 and 48 μm-long Si pillar electrodes due to cracking and electrode damage during cycling. In the 32 μm Si micropillar electrode, a small change in porosity from 69 to 86% caused a substantial increase in specific capacity from 1400 to 2000 mAh/g over 100 cycles, with the areal capacity decreasing from 3 to 2 mAh/cm2. The findings also show the directions for further work for the optimization of Si micropillar electrodes.