Balancing Act: Optimizing SiOx specific surface area for enhanced cycling stability and rate capability in practical 350 Wh/kg lithium-ion batteries

To improve the cycle stability of 350 Wh/kg high-energy-density lithium-ion batteries, we systematically investigated four SiO x samples with distinct specific surface areas using lithium half-cells and high-energy-density pouch cells. Through comparative evaluation, we revealed how varying specific surface areas of SiO x particles affect electrochemical performance in pouch cell configurations. Contrary to conventional understanding that higher surface area provides increased reactive sites, our findings demonstrate that SiO x with elevated surface area failed to significantly extend pouch cell cycle life. Through comprehensive evaluation of silicon negative electrode expansion phenomena and solid electrolyte interphase (SEI) parasitic reactions, we identified optimal performance in SiO x with 1.3393 m 2 g −1 specific surface area. Compared to maximum and minimum surface area counterparts, this material exhibited 25.38 % and 195 % enhancements in long-term cycling stability, respectively. Furthermore, electrochemical analysis revealed a positive correlation between SiO x surface area and cell rate capability, attributable to expanded lithium-ion diffusion pathways that facilitate rapid charge/discharge processes. This work establishes critical design criteria for balancing cycle stability and rate performance in silicon-negative electrode lithium-ion batteries while advancing practical implementation of high-energy-density (≥350 Wh/kg) battery systems. • Optimal SiO x surface area boosts cycle life by 195 % in 350 Wh/kg batteries. • An appropriate SiO x SSA balance SEI formation and silicon expansion. • Insufficient SSA can't buffer Si volume changes, hastening electrode degradation. • High-surface-area SiOx boosts 3C capacity by 4.5 % via low-tortuosity Li + pathways. • Pouch cell validation overcomes half-cell limitations for practical anode design.