New synthesis strategies to improve Co-Free LiNi0.5Mn0.5O2 cathodes: Early transition metal d0 dopants and manganese pyrophosphate coating

JOURNAL OF POWER SOURCES

卷:479

Article

Darbar, Devendrasinh^1,2  Self, Ethan C.¹  Li, Linze³  Wang, Chongmin³  Meyer, Harry M., III⁴  Lee, Changwook⁵  Croy, Jason R.⁶  Balasubramanian, Mahalingam⁵  Muralidharan, Nitin⁷  Bhattacharya, Indranil²  Belharouak, Ilias^7,8  Nanda, Jagjit^1,8 

[1] Oak Ridge Natl Lab, Div Chem Sci, Oak Ridge, TN 37831 USA

[2] Tennessee Technol Univ, Dept Elect & Comp Engn, Cookeville, TN 38505 USA

[3] Pacific Northwest Natl Lab, Environm Mol Sci Lab, Richland, WA 99354 USA

[4] Oak Ridge Natl Lab, Ctr Nanophase Mat Sci, Oak Ridge, TN 37831 USA

[5] Argonne Natl Lab, Xray Sci Div, Adv Photon Source, Argonne, IL 60439 USA

[6] Argonne Natl Lab, Chem Sci & Engn Div, Argonne, IL 60439 USA

[7] Oak Ridge Natl Lab, Energy & Transportat Sci Div, Oak Ridge, TN 37830 USA

[8] Univ Tennessee, Bredesen Ctr Interdisciplinary Res & Grad Educ, Knoxville, TN 37996 USA

关键词: Co-free cathodes;    d(0) cation;    Pyrophosphate coating;    Cation mixing;    Layered oxide cathodes;   

DOI  :  10.1016/j.jpowsour.2020.228591

来源: Elsevier

【 摘 要 】

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.

【 授权许可】

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