Insight into the effect of thick graphite electrodes towards high-performance cylindrical Ni-rich NCA90 Li-ion batteries

Abstract

This study explored the complex effect of graphite tortuosity on the electrochemical performance of Ni-rich NCA90 Li-ion batteries (LIBs). Different levels of graphite anode tortuosity were analyzed, revealing that low-tortuosity electrodes had better graphite utilization. The in-plane tortuosities of the graphite anode electrodes examined were 1.70, 1.94, 2.05, and 2.18, while their corresponding through-plane tortuosities were 4.74, 6.94, 8.19, and 9.80. In-operando X-ray diffraction and differential electrochemical mass spectrometry were employed to investigate the charge storage mechanism and gas evolution. The study revealed that while graphite electrode tortuosity impacted the amount of Li present in the lithiated graphite phase due to diffusion constraints, it did not affect gas generation. The Li-ion utilization in low-tortuosity electrodes was higher than that in high-tortuosity electrodes because of solid-diffusion limitations. Additionally, the galvanostatic intermittent titration technique (GITT) was employed to investigate a lithium-ion diffusion coefficient. Our results indicate that the lithium-ion diffusion coefficient exhibits a significant difference only during LiC6 phase transition. We also observed that the use of a lower tortuosity electrode leads to improved lithium-ion insertion. Consequently, graphite utilization is influenced by the porous electrode design. Safety tests adhering to UN38.3 guidelines verified battery safety. The study demonstrated the practical application of optimized NCA90 LIB cells with diverse graphite electrode tortuosities in a high-performance Lamborghini GoKart, paving the way for further advancements in Ni-rich LIB technology.