Aging Analysis of High-Capacity Graphite/NMC811 Lithium-Ion Battery Using Incremental Capacity and Electrochemical Impedance Spectroscopy

Abstract A high capacitive Graphite/NMC811 lithium-ion cell was investigated using incremental capacity analysis (IC) and electrochemical impedance spectroscopy (EIS) techniques to evaluate behaviour and aging mechanism in a standard electrolyte comprising lithium hexafluorophosphate salt (LiPF6) dissolved in carbonate solvents. IC measurements were conducted at a very low C-rate (C/50) to minimize thermodynamics and kinetics disturbances, particularly at 100% Depth of Discharge, while EIS was performed across a wide frequency range from 10 kHz to 10 mHz at different States of Charge (SoC) and cycles. When subjected to aging, the cell retained approximately 60% of its initial capacity (8 Ah) after 1600 cycles highlighting significant degradation. Key parameters such as the characteristic H2  H3 phase transition of the NMC811 cathode, internal cell resistance and capacity retention were systematically measured at different states of health (SoH) using these non-destructive methods (IC and EIS). The evolution of these electrochemical signatures as a function of cycling provides critical insight into the aging mechanism affecting nickel-rich NMC cell, contributing to a deeper understanding of performance loss in high-energy lithium-ion batteries.