Search for: All records

Abstract Realizing extreme fast charging (XFC) in lithium‐ion batteries for electric vehicles is still challenging due to the insufficient lithium‐ion transport kinetics, especially in the electrolyte. Herein, a novel high‐performance electrolyte (HPE) consisting of lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF₆) and carbonates is proposed and tested in pilot‐scale, 2‐Ah pouch cells. Moreover, the origin of improved electrochemical performance is comprehensively studied via various characterizations, suggesting that the proposed HPE exhibits high ionic conductivity and excellent electrochemical stability at high charging rate of 6‐C. Therefore, the HPE‐based pouch cells deliver improved discharge specific capacity and excellent long‐term cyclability up to 1500 cycles under XFC conditions, which is superior to the conventional state‐of‐the‐art baseline electrolyte. 

Abstract One of the most challenging aspects of developing high-energy lithium-based batteries is the structural and (electro)chemical stability of Ni-rich active cathode materials at thermally-abused and prolonged cell cycling conditions. Here, we report in situ physicochemical characterizations to improve the fundamental understanding of the degradation mechanism of charged polycrystalline Ni-rich cathodes at elevated temperatures (e.g., ≥ 40 °C). Using multiple microscopy, scattering, thermal, and electrochemical probes, we decouple the major contributors for the thermal instability from intertwined factors. Our research work demonstrates that the grain microstructures play an essential role in the thermal stability of polycrystalline lithium-based positive battery electrodes. We also show that the oxygen release, a crucial process during battery thermal runaway, can be regulated by engineering grain arrangements. Furthermore, the grain arrangements can also modulate the macroscopic crystallographic transformation pattern and oxygen diffusion length in layered oxide cathode materials.