Chemical Pretreatment of Prelithiated SiO@C Anodes to Mitigate Alkaline Issues for Aqueous Processing

The practical application of prelithiated SiO anodes is limited by severe gas evolution during aqueous slurry preparation, caused by high alkalinity from dissolved surface lithium salts. This study introduces a chemical pretreatment using HCl, HF, and NH 4 F to neutralize excess alkalinity prior to slurry processing. The treatment shifts the surface chemistry from strongly alkaline to either neutral or mildly alkaline. The mildly alkaline condition proved more advantageous, preserving beneficial Li 2 SiO 3 . The HCl‐treated sample under this condition achieved a first‐cycle Coulombic efficiency (ICE) of 85% at 0.2 C, markedly higher than the neutral counterpart (74.5%). Further analysis showed that NH 4 F pretreatment (SCL‐NH 4 F) successfully incorporated both LiF and Li 2 SiO 3 . It is proposed that LiF strengthens the mechanical robustness of the solid electrolyte interphase (SEI), while Li 2 SiO 3 helps accommodate silicon's volume expansion. Accordingly, the SCL‐NH 4 F anode demonstrated superior electrochemical performance, including an ICE of 88.5%, a high reversible capacity of 1140.1 mAhg −1 , and remarkable cycling stability with 72.3% capacity retention after 200 cycles at 0.2C. Moreover, it maintained a capacity of 526.1 mAh g −1 after 400 cycles, substantially outperforming both the pristine and other pretreated samples.