Stable lithium storage with strong-grain sustained pinning-reinforced nanocrystalline silicon

Abstract

Crystalline silicon has long been considered inferior to its amorphous form in lithium storage due to the anisotropy and post-cycling extinction of the crystal structure. However, amorphous silicon is actually not satisfactory and is still prone to collapse, while the contribution of the advanced crystal structure to the stabilization of the mechanical and electrochemical behavior in the Si anode is rather neglected. Herein, we have innovatively designed and constructed a strong-grain pinning-reinforced nanocrystalline silicon for the first time, demonstrating far superior stability to conventional crystalline or amorphous Si. After repeated lithiation/delithiation, this reinforced grain remains firmly rooted in the Si substrate without amorphization, driving the outer protective solid electrolyte interphase optimization and stabilizing the electrode. And the mechanism of the strong-grain generation and reinforcement is clarified by comprehensive molecular dynamics simulations. The electrode with 80 wt% of this reinforced Si still possesses a reversible capacity of 2180.9 mA h g⁻¹ after 200 cycles at 0.8 A g⁻¹. Therefore, the actual outstanding mechanical and electrochemical properties signal a bright future for this reinforcement strategy and for crystalline silicon.