Patil Shripad, Koirala Krishna Prasad, Crafton Matthew J, Yang Guang, Tsai Wan-Yu, McCloskey Bryan D, Wang Chongmin, Nanda Jagjit, Self Ethan C
Bredesen Center for Interdisciplinary Research and Education, University of Tennessee Knoxville, Knoxville, Tennessee 37996, United States.
Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States.
ACS Appl Mater Interfaces. 2023 Aug 23;15(33):39253-39264. doi: 10.1021/acsami.3c05619. Epub 2023 Aug 11.
Cobalt-free cation-disordered rocksalt (DRX) cathodes are a promising class of materials for next-generation Li-ion batteries. Although they have high theoretical specific capacities (>300 mA h/g) and moderate operating voltages (∼3.5 V vs Li/Li), DRX cathodes typically require a high carbon content (up to 30 wt %) to fully utilize the active material which has a detrimental impact on cell-level energy density. To assess pathways to reduce the electrode's carbon content, the present study investigates how the carbon's microstructure and loading (10-20 wt %) influence the performance of DRX cathodes with the nominal composition LiMnTiOF. While electrodes prepared with conventional disordered carbon additives (C65 and ketjenblack) exhibit rapid capacity fade due to an unstable cathode/electrolyte interface, DRX cathodes containing 10 wt % graphite show superior cycling performance (e.g., reversible capacities ∼260 mA h/g with 85% capacity retention after 50 cycles) and rate capability (∼135 mA h/g at 1000 mA/g). A suite of characterization tools was employed to evaluate the performance differences among these composite electrodes. Overall, these results indicate that the superior performance of the graphite-based cathodes is largely attributed to the: (i) formation of a uniform graphitic coating on DRX particles which protects the surface from parasitic reactions at high states of charge and (ii) homogeneous dispersion of the active material and carbon throughout the composite cathode which provides a robust electronically conductive network that can withstand repeated charge-discharge cycles. Overall, this study provides key scientific insights on how the carbon microstructure and electrode processing influence the performance of DRX cathodes. Based on these results, exploration of alternative routes to apply graphitic coatings is recommended to further optimize the material performance.
无钴阳离子无序岩盐（DRX）阴极是一类很有前景的下一代锂离子电池材料。尽管它们具有较高的理论比容量（>300 mA h/g）和适中的工作电压（相对于Li/Li约为3.5 V），但DRX阴极通常需要高碳含量（高达30 wt%）才能充分利用活性材料，这对电池级能量密度有不利影响。为了评估降低电极碳含量的途径，本研究调查了碳的微观结构和负载量（10 - 20 wt%）如何影响标称组成为LiMnTiOF的DRX阴极的性能。虽然用传统无序碳添加剂（C65和科琴黑）制备的电极由于阴极/电解质界面不稳定而表现出快速的容量衰减，但含有10 wt%石墨的DRX阴极表现出优异的循环性能（例如，可逆容量约为260 mA h/g，50次循环后容量保持率为85%）和倍率性能（在1000 mA/g时约为135 mA h/g）。使用了一系列表征工具来评估这些复合电极之间的性能差异。总体而言，这些结果表明，基于石墨的阴极的优异性能主要归因于：（i）在DRX颗粒上形成均匀的石墨涂层，该涂层在高充电状态下保护表面免受寄生反应的影响；（ii）活性材料和碳在整个复合阴极中的均匀分散，这提供了一个坚固的电子导电网络，可以承受反复的充放电循环。总体而言，本研究提供了关于碳微观结构和电极加工如何影响DRX阴极性能的关键科学见解。基于这些结果，建议探索应用石墨涂层的替代路线，以进一步优化材料性能。
