Lithium Inventory Loss and Cathode Stress Induced by Silicon-Graphite Anodes in Cylindrical NCA90 Full Cells

Abstract

Silicon is a promising anode material for lithium-ion batteries due to its high capacity (3,579 mAhg⁻¹), but its severe volume expansion leads to lithium consumption and stability issues. Blending silicon with graphite mitigates these challenges, yet its impact in full-cell configurations, where lithium inventory is limited by the cathode, remains unclear. This study examines 2 wt.% silicon-graphite (SiGr) anodes in 18650 full-cells paired with Ni-rich NCA90 cathodes. In-operando X-ray diffraction (XRD) reveals that silicon alters graphite phase transitions, shifting differential capacity (dQ/dV) peaks to higher voltages. Additionally, XRD of the cathode shows enhanced lattice expansion and contraction, accelerating cathode degradation. This is confirmed by ICP-OES, which quantifies increased transition metal dissolution in SiGr cells. These findings highlight that silicon incorporation in graphite anodes affects both anode and cathode stability, necessitating prelithiation strategies to mitigate lithium loss and enhance cycle life. Additionally, optimizing lithium inventory management and cathode stabilization is crucial for achieving long-term stability in high-energy-density batteries. This study provides new insights into SiGr full-cell interactions, guiding the development of next-generation lithium-ion batteries.