Trace doping of multiple elements enables stable battery cycling of LiCoO2 at 4.6 V

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LiCoO2 is a dominant cathode material for lithium-ion (Li-ion) batteries due to its high volumetric energy density, which could potentially be further improved by charging to high voltages. However, practical adoption of high-voltage charging is hindered by LiCoO2’s structural instability at the deeply delithiated state and the associated safety concerns. Here, we achieve stable cycling of LiCoO2 at 4.6 V (versus Li/Li+) through trace Ti–Mg–Al co-doping. Using state-of-the-art synchrotron X-ray imaging and spectroscopic techniques, we report the incorporation of Mg and Al into the LiCoO2 lattice, which inhibits the undesired phase transition at voltages above 4.5 V. We also show that, even in trace amounts, Ti segregates significantly at grain boundaries and on the surface, modifying the microstructure of the particles while stabilizing the surface oxygen at high voltages. These dopants contribute through different mechanisms and synergistically promote the cycle stability of LiCoO2 at 4.6 V.

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Fig. 1: Morphology and elemental distribution in bare LCO and TMA-LCO.
Fig. 2: Electrochemical characterization of bare LCO and TMA-LCO.
Fig. 3: Structural evolution during the initial charge–discharge process.
Fig. 4: 3D X-ray tomography reconstruction and element distribution in TMA-LCO.
Fig. 5: Revealing the surface chemistry with soft X-ray spectroscopy.
Fig. 6: Density functional theory calculations for Ti substitution that can modify the surface electronic structure.

Data availability

The data that support the plots within this paper and other finding of this study are available from the corresponding author upon reasonable request.


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This work was supported by funding from the National Key R&D Program of China (grant number 2016YFB0100100), National Natural Science Foundation of China (grant numbers 51822211, 11564016 and 11574281) and Foundation for Innovative Research Groups of the National Natural Science Foundation of China (grant number 51421002). The work done at BNL was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technology Office of the US Department of Energy through the BMR Program, including the Battery500 Consortium under contract DE-SC0012704. Use of the National Synchrotron Light Source II is supported by the US Department of Energy, an Office of Science user Facility operated by Brookhaven National Laboratory under contract number DE-SC0012704. The SLAC National Accelerator Laboratory is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under contract number DE-AC02-76SF00515. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under contract number DE-AC02-76SF00515. Soft X-ray spectroscopic data were collected at beamline 8.0.1 of the Advanced Light Source, which is supported by the Director, Office of Science, Office of Basic Energy Sciences of the US Department of Energy under contract number DE-AC02-05CH11231. We gratefully acknowledge help from beamlines BL14W1 and BL08U at Shanghai Synchrotron Radiation Facility.

Author information

X.Y. and H.L. conceived the idea; J.-N.Z. synthesized the materials and performed electrochemistry measurements and X-ray diffraction measurements; C.M. performed the TEM measurements and analysis; Y.L., M.G., Xiaojing.H., S.L. and Y.C. performed the transmission X-ray microscopy measurement and data analysis; Q.L. and W.Y. performed the soft X-ray spectroscopy experiment and data analysis; C.O. and R.X. performed the density functional theory analysis; Q.L., X.Y., J.-N.Z., Y.L. and C.O. wrote the paper with critical inputs from all other authors. All authors edited and approved the manuscript.

Correspondence to Xiqian Yu or Yijin Liu or Hong Li.

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Supplementary Figs. 1–21, Tables 1–9 and references

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