Voltage fade is a major problem in battery applications for high-energy lithium- and manganese-rich (LMR) layered materials. As a result of the complexity of the LMR structure, the voltage fade mechanism is not well understood. Here we conduct both in situ and ex situ studies on a typical LMR material (Li1.2Ni0.15Co0.1Mn0.55O2) during charge–discharge cycling, using multi-length-scale X-ray spectroscopic and three-dimensional electron microscopic imaging techniques. Through probing from the surface to the bulk, and from individual to whole ensembles of particles, we show that the average valence state of each type of transition metal cation is continuously reduced, which is attributed to oxygen release from the LMR material. Such reductions activate the lower-voltage Mn3+/Mn4+ and Co2+/Co3+ redox couples in addition to the original redox couples including Ni2+/Ni3+, Ni3+/Ni4+ and O2−/O−, directly leading to the voltage fade. We also show that the oxygen release causes microstructural defects such as the formation of large pores within particles, which also contributes to the voltage fade. Surface coating and modification methods are suggested to be effective in suppressing the voltage fade through reducing the oxygen release.
|Number of pages||9|
|Publication status||Published - 2018 Aug 1|
Bibliographical noteFunding Information:
We acknowledge the technical support of the beamline scientists J. Bai of X14A, NSLS and S. N. Ehrlich of X18A, NSLS. The work carried out Brookhaven National Laboratory was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technology Office of the US Department of Energy through the Advanced Battery Materials Research (BMR) Program, including the Battery500 Consortium under contract DE-SC0012704. Use of STEM at the Center for Functional Nanomaterials of Brookhaven National Laboratory was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-SC0012704. The work at the Institute of Physics was supported by funding from the ‘One Hundred Talent Project’ of the Chinese Academy of Sciences, the National Key R&D Program of China (grant no. 2016YFA0202500) and the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (grant no. 51421002). The work carried out at Dongguk University was supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science & ICT (NRF-2017M1A2A2044502). Certain commercial names are mentioned for purposes of illustration and do not constitute an endorsement by the National Institute of Standards and Technology. J.L. and K.A. gratefully acknowledge support from the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office. Argonne National Laboratory is operated for DOE Office of Science by UChicago Argonne, LLC, under contract no. DE-AC02-06CH11357. This research used beamlines X14A, X18A and U7A of the National Synchrotron Light Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract no. DE-AC02-98CH10886.
© 2018, The Author(s).
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Fuel Technology
- Energy Engineering and Power Technology