期刊
JOURNAL OF POWER SOURCES
卷 479, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.jpowsour.2020.228591
关键词
Co-free cathodes; d(0) cation; Pyrophosphate coating; Cation mixing; Layered oxide cathodes
资金
- Energy Efficiency and Renewable Energy (EERE)
- DOE Office of Science [DE-AC02-06CH11357]
- DOE's Office of Biological and Environmental Research
- US Department of Energy (DOE) [DE-AC05-00OR22725]
- Vehicle Technologies Office (VTO)
In this work, we report solution-based doping and coating strategies to improve the electrochemical performance of the Co-free layered oxide cathode LiNi0.5Mn0.5O2 (NM-50/50). Small amounts of d(0) dopants (e.g., Mo(6+)and Ti4+, 0.5-1 at. %) increase the cathode's specific capacity, cycling stability, and rate capability. For example, a Mo-doped cathode with the nominal composition LiNi0.495Mn0.495Mo0.01O2 exhibits a high reversible capacity of 180 mA h/g at 20 mA/g compared to only 156 mA h/g for undoped NM-50/50. Effects of 1 at.% Mo dopant on the cathode structure were studied using a suite of characterization tools including X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Xray absorption spectroscopy. These measurements demonstrate that Mo6+ dopant is enriched near the particle surface and improves the electrochemical performance of LiNi0.5Mn0.5O2 by: (i) reducing Li+/Ni2+ cation mixing which facilitates Li+ transport, (ii) mitigating undesirable phase transformations near the cathode surface, and (iii) altering the cathode/electrolyte interfacial chemistry. This work also reports the use of an inorganic Mn2P2O7 coating which enhances the cycling stability of Mo-doped NM-50/50, presumably through formation of a stable cathode electrolyte interphase (CEI) layer. Overall, the synthesis approaches reported herein are quite general and can potentially be expanded to other high voltage Li-ion battery cathodes.
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