Hao Junnan, Yang Fuhua, Zhang Shilin, He Hanna, Xia Guanglin, Liu Yajie, Didier Christophe, Liu Tongchao, Pang Wei Kong, Peterson Vanessa K, Lu Jun, Guo Zaiping
Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Wollongong, NSW 2522, Australia.
School of Mechanical, Materials, Mechatronic, and Biomedical Engineering, Faculty of Engineering & Information Sciences, University of Wollongong, Wollongong, NSW 2500, Australia.
Proc Natl Acad Sci U S A. 2020 Feb 11;117(6):2815-2823. doi: 10.1073/pnas.1918442117. Epub 2020 Jan 29.
Existing lithium-ion battery technology is struggling to meet our increasing requirements for high energy density, long lifetime, and low-cost energy storage. Here, a hybrid electrode design is developed by a straightforward reengineering of commercial electrode materials, which has revolutionized the "rocking chair" mechanism by unlocking the role of anions in the electrolyte. Our proof-of-concept hybrid LiFePO (LFP)/graphite electrode works with a staged deintercalation/intercalation mechanism of Li cations and PF anions in a broadened voltage range, which was thoroughly studied by X-ray diffraction, Raman spectroscopy, and neutron powder diffraction. Introducing graphite into the hybrid electrode accelerates its conductivity, facilitating the rapid extraction/insertion of Li from/into the LFP phase in 2.5 to 4.0 V. This charge/discharge process, in turn, triggers the in situ formation of the cathode/electrolyte interphase (CEI) layer, reinforcing the structural integrity of the whole electrode at high voltage. Consequently, this hybrid LFP/graphite-20% electrode displays a high capacity and long-term cycling stability over 3,500 cycles at 10 C, superior to LFP and graphite cathodes. Importantly, the broadened voltage range and high capacity of the hybrid electrode enhance its energy density, which is leveraged further in a full-cell configuration.
现有的锂离子电池技术正难以满足我们对高能量密度、长寿命和低成本储能不断增长的需求。在此，通过对商业电极材料进行直接的重新设计开发出一种混合电极设计，它通过揭示电解质中阴离子的作用彻底革新了“摇椅”机制。我们的概念验证混合磷酸铁锂（LFP）/石墨电极在拓宽的电压范围内通过锂阳离子和PF阴离子的分步脱嵌/嵌入机制工作，这通过X射线衍射、拉曼光谱和中子粉末衍射进行了深入研究。将石墨引入混合电极可提高其导电性，促进锂在2.5至4.0 V下快速从LFP相中脱出/嵌入。反过来，这种充放电过程会触发阴极/电解质界面（CEI）层的原位形成，增强整个电极在高电压下的结构完整性。因此，这种混合LFP/石墨-20%电极在10 C下经过3500次循环显示出高容量和长期循环稳定性，优于LFP和石墨阴极。重要的是，混合电极拓宽的电压范围和高容量提高了其能量密度，这在全电池配置中得到了进一步利用。
