Browsing by Author "Liu, Jue"
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- Effect of the grain arrangements on the thermal stability of polycrystalline nickel-rich lithium-based battery cathodesHou, Dong; Xu, Zhengrui; Yang, Zhijie; Kuai, Chunguang; Du, Zhijia; Sun, Cheng-Jun; Ren, Yang; Liu, Jue; Xiao, Xianghui; Lin, Feng (Springer, 2022-06-15)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.
- Investigating Particle Size-Dependent Redox Kinetics and Charge Distribution in Disordered Rocksalt CathodesZhang, Yuxin; Hu, Anyang; Liu, Jue; Xu, Zhengrui; Mu, Linqin; Sainio, Sami; Nordlund, Dennis; Li, Luxi; Sun, Cheng-Jun; Xiao, Xianghui; Liu, Yijin; Lin, Feng (Wiley-V C H Verlag, 2022-04)Understanding how various redox activities evolve and distribute in disordered rocksalt oxides (DRX) can advance insights into manipulating materials properties for achieving stable, high-energy batteries. Herein, the authors present how the reaction kinetics and spatial distribution of redox activities are governed by the particle size of DRX materials. The size-dependent electrochemical performance is attributed to the distinct cationic and anionic reaction kinetics at different sizes, which can be tailored to achieve optimal capacity and stability. Overall, the local charged domains in DRX particles display random heterogeneity caused by the isotropic delithiation pathways. Owing to the kinetic limitation, the micron-sized particles exhibit a holistic "core-shell" charge distribution, whereas sub-micron particles show more uniform redox reactions throughout the particles and ensembles. Sub-micron DRX particles exhibit increasing anionic redox activities yet inferior cycling stability. In summary, engineering particle size can effectively modulate how cationic and anionic redox activities evolve and distribute in DRX materials.
- Tailoring Disordered/Ordered Phases to Revisit the Degradation Mechanism of High-Voltage LiNi0.5Mn1.5O4 Spinel Cathode MaterialsSun, Huabin; Hu, Anyang; Spence, Stephanie; Kuai, Chunguang; Hou, Dong; Mu, Linqin; Liu, Jue; Li, Luxi; Sun, Chengjun; Sainio, Sami; Nordlund, Dennis; Luo, Wei; Huang, Yunhui; Lin, Feng (Wiley-V C H Verlag, 2022-05)In the spinel oxide cathode family, LiNi0.5Mn1.5O4 (LNMO) shows a high operating voltage (approximate to 4.7 V vs Li/Li+) and excellent Li-ion mobility with stable 3D conducting channels. Ni/Mn cation disordered and ordered phases usually coexist in LNMO materials, and they have distinct structural and electrochemical properties, resulting in different battery performances for LNMO materials with different phase compositions. Identifying the correlation between phase compositions and electrochemical properties is of significance to the improvement of battery performance and understanding of degradation mechanisms. Herein, the disordered/ordered phase compositions in LNMO materials are tailored by post-annealing strategies and their impacts on electrochemical performance and degradation mechanisms from the surface to the bulk are systematically investigated. The ordered phase increases rapidly as Mn3+ is oxidized to Mn4+ through a post-annealing process. LNMO with an intermediate fraction of disordered and ordered phases gives rise to improved cycling stability. This article further reports that a high ordered phase fraction can preferentially protect Ni from dissolution during cycling. However, these results suggest that the transition metal dissolution and surface structural change of LNMO do not exhibit a direct correlation with cycling stability. These results indicate the capacity fading mainly correlates with the bulk structural distortion, leading to decreased Li-ion kinetics.