Due to their exceptional high energy density, lithium-ion batteries are of central importance in many modern electrical devices. A serious limitation, however, is the slow charging rate used to obtain the full capacity. Thus far, there have been no ways to increase the charging rate without losses in energy density and electrochemical performance. Here we show that the charging rate of a cathode can be dramatically increased via interaction with white light. We find that a direct exposure of light to an operating LiMn2O4 cathode during charging leads to a remarkable lowering of the battery charging time by a factor of two or more. This enhancement is enabled by the induction of a microsecond long-lived charge separated state, consisting of Mn4+ (hole) plus electron. This results in more oxidized metal centers and ejected lithium ions are created under light and with voltage bias. We anticipate that this discovery could pave the way to the development of new fast recharging battery technologies.
Bibliographical noteFunding Information:
This work was supported as part of the Center for Electrochemical Energy Science (CEES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. A.L. and C.J. thank J. Blauwkamp and M. Piernas for technical assistance with cell assembly, T. Rajh and E. Rozhkova for lending the Xe lamp and associated power supply, and L. Utschig and A. Ahmed for helpful discussions. We thank Aude Annick Heidet for technical assistance with sputtering. The work of M.V. was supported by the Laboratory Directed Research and Development (LDRD) funding from Argonne National Laboratory, provided by the Director, Office of Science, of the U.S. DOE under Contract No. DE-AC02-06CH11357. We gratefully acknowledge the computing resources provided on Blues, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory. Further resources were provided by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This work was performed, in part, at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility under Contract No. DE-AC02-06CH11357 (R.S. and V.M.). This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences, under contract number DE-AC02-06CH11357 at Argonne National Laboratory (J.N. and O.G.P.).
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