Looking into failure mode identification driven by differential capacity in Ni-rich layered cathodes

Nickel-rich layered cathodes are one of the ideal electrode materials for high-energy lithium-ion batteries, yet suffer from capacity decay and structural degradation during cycling. Although the degradation mechanisms of electrode materials are flourishing, the analysis of performance decay and physicochemical properties dynamic evolution during cycling have not been well developed. Here, we propose a coupling analysis strategy based on differential capacity that distinguishes the failure behavior of electrode materials during cycling by the characteristic evolution of the dQ dV^–1 curve recorded cycle-by-cycle. By coupling in-situ electrochemical tests with differential capacity characterization and comparing them with electrochemical characteristics recorded at different aging upper cut-off voltages cycles, the capacity decay mechanism and physicochemical properties evolution of electrode materials can be dynamically analyzed. The potential failure modes include loss of active Li inventory (LALI), loss of active structure integrity (LASI), and various dominant combinations of these factors. In addition, the distinction of aging behavior can also be applied to the failure level classification of spent electrode materials. Our findings demonstrate a general strategy for analyzing the dynamic failure mechanisms of electrode materials, thereby offering valuable insights for subsequent technology route selection in terms of recycling and reuse.