Cycling performance of density modulated multilayer silicon thin film anodes in Li-ion batteries

Abstract

The high volumetric expansion/contraction of silicon (Si) anodes in Li-ion batteries by about ∼400% during lithiation/delithiation causes considerably high stress followed by cracking, pulverization, and the loss of electrical contact; and finally results in capacity fading and failing. In this work, we present a new density modulated multilayer Si thin film anode approach, which can provide a robust high capacity electrode for Li-ion batteries. Alternating high and low density layers have been achieved by simply changing the working gas pressure between low and high values, respectively during magnetron sputter deposition of Si thin film anodes. Our results reveal that density modulated Si films can provide a high coulombic efficiency up to 99% and reversible specific capacity as high as ∼1700 mAh g−1 after 50 cycles. Low-density layers are believed to be performing as compliant layers during volume change making the films more durable compared to conventional Si film anodes. The results of this work can lead to Si thin film anode materials with superior capacity and mechanical stability compared to conventional Si anodes.