Voltage-prioritized hierarchical assessment of voltage and capacity stability via cutoff-voltage regulation in high-nickel Li-rich all-solid-state batteries

The development of high-energy lithium-rich layered oxide (LLO)-based all-solid-state lithium batteries (LLO-ASSLBs) is hindered by concurrent capacity fade and voltage decay, with the latter posing critical safety risks to battery management systems in practical applications. This study proposes a cutoff-voltage strategy that modulates the depth of discharge (DOD) to establish a voltage-prioritized evaluation framework for optimizing cycling stability. By systematically reducing discharge cutoff voltages from 2.8 V, the relative decay rates of capacity and voltage are actively controlled. The percentage retentions of cycling voltage and cycling capacity are introduced as unified quantitative metrics, enabling direct comparative assessment of these distinct yet equally critical performance parameters. A hierarchical evaluation principle is established wherein voltage stability constitutes the prerequisite criterion, with capacity stability maximized under this constraint. The optimal 2.4 V cutoff achieves the best balance, delivering 89.3% capacity retention and 90.8% voltage retention after 300 cycles. Post-cycling structural characterization reveals that excessive DOD promotes layered-to-spinel phase transformation, transition metal reduction, and lattice distortion, which are identified as the primary drivers of accelerated voltage decay. These findings provide a rigorous diagnostic protocol and operational strategy for optimizing the trade-off between high capacity and cycling stability in LLO-ASSLBs. • Voltage-prioritized hierarchical evaluation: First framework establishing voltage stability as prerequisite while maximizing capacity retention under this constraint. • Unified quantitative metrics: Percentage retentions enable direct comparison and hierarchical optimization of capacity and voltage degradation. • Optimal 2.4 V cutoff: Achieves 90.8% voltage retention and 89.3% capacity retention after 300 cycles, balancing redox activation with structural stability.