Revealing the accelerated reaction kinetic of Ni-rich cathodes by activated carbons for high performance lithium-ion batteries

Activated carbons (AC) play a key role in enabling the reaction kinetic of cathodes in lithium ion batteries (LIBs). However, the charge transfer dynamics and reaction kinetics mechanism of AC composited cathodes along their thickness direction are still poorly understood. Herein, we systematically compare the internal reactive process evolutions of AC modified LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes and pristine NCM622 cathodes at high C-rates. The charge transfer dynamic is revealed by the time of flight secondary ion mass spectrometry and X-ray photoelectron spectra analyzes. The addition of AC endows the NCM622 cathode regions close to the current collector possess higher lithium ion concentrations, meanwhile more Ni2+ can be converted into Ni3+. The results of COMSOL Multiphysics simulations based on the porous electrode theory is analyzed to explore reaction ki-netics mechanism. AC in NCM622 cathodes homogenizes the reaction distributions, contributing to the boosted reaction kinetic, eventually, resulting in the high utilization of active materials. These findings provide a direct way to reduce solid-state diffusion resistances and accelerate reaction kinetics of electrodes, which is critical for developing batteries with long cycle stability and rate performance at high rates.

Automated summary

Activated carbons have been found to play a crucial role in lithium-ion batteries by improving the reaction kinetics of cathodes. In this study, the internal reactive process evolutions of activated carbon modified LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes were compared to pristine NCM622 cathodes. The addition of activated carbon resulted in higher lithium ion concentrations and increased conversion of Ni2+ to Ni3+. COMSOL Multiphysics simulations showed that activated carbon homogenized the reaction distributions in cathodes, leading to improved reaction kinetics and higher utilization of active materials. These findings are important for developing batteries with long cycle stability and high rate performance.