Dynamic mechanical equilibrium of silicon anodes for lithium-ion batteries enabled by surface hydroxyl-rich bonding

Abstract

Severe volume expansion of silicon (Si) leads to unstable solid electrolyte interface (SEI) rupture and electrode structure collapse, ultimately causing poor cycling stability of lithium-ion batteries. Herein, we engineered a hydroxyl-rich silicon surface, enhancing the interface forces by increasing hydrogen bonding sites with carboxymethyl cellulose (CMC), thereby maintaining a mechanical balance during dynamic volume change. Furthermore, theoretical calculations indicate that the augmentation of hydroxyl groups promotes the charge transfer between the CMC molecule and the surface and enhances the interface adsorption energy. As a result, the obtained Si-C₂H₆O anode exhibits a high specific capacity of 2483 mA h g⁻¹ at 0.2 A g⁻¹ after 100 cycles, with a capacity retention of 81.2%. In addition, it exhibits a durable specific capacity of above 1200 mA h g⁻¹ at 2 A g⁻¹ after 1000 cycles with a coulombic efficiency of over 99.5%. The assembled full cells based on the Si-C₂H₆O anode achieve a high areal capacity of 2.68 mA h cm⁻² at 0.2 C. The success of this strategy effectively addresses the issue of volume expansion in Si anodes, further enhancing the cycling performance and facilitating their wide-scale commercial applications.