Lithium-rich transition metal oxide (Li1+XM1−XO2) cathodes have high energy density above 900 Wh kg−1 due to hybrid anion- and cation-redox (HACR) contributions, but critical issues such as oxygen release and voltage decay during cycling have prevented their application for years. Here we show that a molten molybdate-assisted LiO extraction at 700 °C creates lattice-coherent but depth (r)-dependent Li1+X(r)M1−X(r)O2 particles with a Li-rich (X ≈ 0.2) interior, a Li-poor (X ≈ −0.05) surface and a continuous gradient in between. The gradient Li-rich single crystals eliminate the oxygen release to the electrolyte and, importantly, still allow stable oxygen redox contributions within. Both the metal valence states and the crystal structure are well maintained during cycling. The gradient HACR cathode displays a specific density of 843 Wh kg−1 after 200 cycles at 0.2C and 808 Wh kg−1 after 100 cycles at 1C, with very little oxygen release and consumption of electrolyte. This high-temperature immunization treatment can be generalized to leach other elements to avoid unexpected surface reactions in batteries.
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The data that support the plots in this paper and other findings of this study are available from the corresponding author upon reasonable request.
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We acknowledge the support from NSF ECCS-1610806 and Wuxi Weifu High-Technology Group Co., Ltd. This research used resources of the Center for Functional Nanomaterials and the 23-ID-2 (IOS) beamline of the National Synchrotron Light Source II, both of which are US Department of Energy Office of Science user facilities at Brookhaven National Laboratory, under contract DE-SC0012704. Also, this work was performed in part at the Center for Nanoscale Systems, a member of the National Nanotechnology Coordinated Infrastructure Network supported by the National Science Foundation under NSF award no. 1541959.
The authors declare no competing interests.
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Zhu, Z., Yu, D., Yang, Y. et al. Gradient Li-rich oxide cathode particles immunized against oxygen release by a molten salt treatment. Nat Energy 4, 1049–1058 (2019). https://doi.org/10.1038/s41560-019-0508-x
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