PNNL

Abstract

High gravimetric/volumetric capacity and low working potential make Si as one of the ideal candidate anode materials for lithium ion batteries. However, the large volume change of Si upon lithiation/delithiation poses a critical challenge for stable battery operations. Here, we introduce a novel designing concept, which takes advantage of such a deformation and ensures the structural stability of the material by developing a 2D Si nanosheet coated with a thin carbon layer (2DSi@C). Upon electrochemical cycling, this 2DSi@C exhibits unique deformation patterns, featuring accommodation of deformation in the thickness direction upon lithiation, while forming ripples upon delithiation, as consistently demonstrated by in-situ TEM observation and chemomechanical simulation. The ripple formation presents a unique mechanism for releasing the cycling induced stress, rendering the 2DSi@C chemomechanically much more stable and durable than the bare 2DSi counterparts. This work demonstrates a general principle as how to take the advantage of the large deformation materials for designing high capacity electrode.