Toward Higher-Power Li-Ion Batteries: Unravelling Kinetics and Thermodynamics of MoNb12O33 vs NMC622

Abstract

Wadsley-Roth niobates show promise as anode materials for high-power lithium-ion batteries. This study presents a comprehensive investigation into the kinetics and thermodynamics of Li-ion transport in doped and carbon-coated micron-sized MoNb12O33 (MNO) electrodes, optimizing its performance in high-power cells alongside a LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode. The electrodes and cells were designed with an areal capacity of 1.2 ± 0.2 mAh cm2, 90 wt% active material, and a negative-to-positive capacity ratio of ~1.2. Galvanostatic intermittent techniques and potentiostatic electrochemical impedance spectroscopy (EIS) were employed to elucidate kinetic and thermodynamic electrochemical parameters. MNO exhibited an exchange current density of ~0.012-0.021 mA cm-2 and high lithium diffusion coefficients of ~10-9 cm2 s-1 at 50% state of charge (SOC) and 25°C. Lithiation and delithiation rate tests in MNO//Li and NMC622//MNO cell configurations at 15°C and 0°C highlighted the exceptional rate performance. Rapid charging of full cells was achieved at all tested temperatures, with charging times of 3 minutes to 75% state of charge at 25°C, 6 minutes at 15°C, and 30 minutes at 0°C. Notably, a 6-minute charge (10C rate) at 0°C still provided 50% of the initial capacity. EIS at various SOC levels indicated the formation of an unstable or reversible solid electrolyte interphase (SEI) layer on the MNO anode at 70-100% SOC. This research provides a valuable parameter set for the development of physics-based models and establishes a solid foundation for advancing the application of MoNb12O33 anode materials in high-power lithium-ion batteries, with potential implications for the broader field of energy storage technologies.