In Situ Self-Adaptive Structure Evolution Under Volume Fluctuation Toward High-Performance Silicon-Based Anode.

Abstract

Alloy-type anodes have become the most promising candidates for the next-generation energy-dense lithium-ion batteries, but structural collapse caused by intrinsic volume fluctuation is the key bottleneck to their practical applications. Herein, an innovative self-adaptive structural evolution strategy toward electrochemically stable Si-based alloy-type anode is proposed, which breaks the conventional ideas that pursue the immutability of the initial structure. Particularly, interconnected commercial Si nanoparticles are covalently coated by amorphous homogeneous composite SiO_x/C (h-SiO_x/C) layer, forming a "pea-like" core-shell structure. After charge-discharge cycling, as-designed Si@h-SiO_x/C evolves into a more stable micro-sized "spherical-like" particle with Si always well protected by h-SiO_x/C layer. Furthermore, inner SEI microdomains and cavities are also formed, which can provide rapid transport pathways for Li⁺ and accommodation space for volume expansion, respectively. Accordingly, Si@h-SiO_x/C displays excellent performances in both half and full pouch cells. 3D reconstruction, in situ optical microscopy and finite element simulations have been conducted to deeply analyze the structural self-adaptive mechanism. This work provides new insights into optimizing Si-based alloy anodes via dynamically self-adaptive regulation, replacing conventional static structural design paradigms.