Fine-tuning intrinsic and doped hydrogenated amorphous silicon thin-film anodes deposited by PECVD for enhanced capacity and stability in lithium-ion batteries

Abstract

Silicon is a promising alternative to graphite as an anode material in lithium-ion batteries,

thanks to its high theoretical lithium storage capacity. Despite these high expectations, silicon anodes

still face significant challenges, such as premature battery failure caused by huge volume changes

during charge–discharge processes. To solve this drawback, using amorphous silicon as a thin film

offers several advantages: its amorphous nature allows for better stress mitigation and it can be

directly grown on current collectors for material savings and improved Li-ion diffusion. Furthermore,

its conductivity is easily increased through doping during its growth. In this work, we focused

on a comprehensive study of the influence of both electrical and structural properties of intrinsic

and doped hydrogenated amorphous silicon (aSi:H) thin-film anodes on the specific capacity and

stability of lithium-ion batteries. This study allows us to establish that hydrogen distribution in the

aSi:H material plays a pivotal role in enhancing battery capacity and longevity, possibly masking the

significance of the conductivity in the case of doped electrodes. Our findings show that we were able

to achieve high initial specific capacities (3070 mAhg-1 at the 10th cycle), which can be retained at

values higher than those of graphite for a significant number of cycles (>120 cycles), depending on

the structural properties of the aSi:H films. To our knowledge, this is the first comprehensive study of

the influence of these properties of thin films with different doping levels and hydrogen distributions

on their optimization and use as anodes in lithium-ion batteries