A concerted effort is being made at Argonne National Laboratory to stabilize high capacity ‘layered-layered’ xLi₂MnO₃•(1-x)LiMO₂ electrodes, in which M is typically Mn, Ni and Co, when cycled to high potentials.  The strategy being adopted is to marginally reduce the lithium content in ‘layered-layered’ structures in order to induce the formation of a spinel component, thereby introducing stabilizing transition metal ion pillars in the lithium layers of structurally-integrated ‘layered-layered-spinel’ (1-y)[xLi₂MnO₃•(1-x)LiMO₂]•yLi_0.5MO₂ electrodes. This approach, which follows earlier related work on the composite ‘layered-spinel’ system, xLi₂MnO₃•(1-x)LiMn_2-zLi_zO₄ (0≤z≤0.33) [1], has yielded positive results with improvements in first-cycle efficiency, discharge capacity, and cycling stability being reported, particularly when targeting 5-15% of spinel in the electrode structure [2, 3].

In this presentation, the results of structural studies of ‘layered-layered-spinel’ materials using a combination of X-ray and neutron diffraction, transmission electron microscopy techniques, coupled to complementary electrochemical data, will be reported.  One of the major goals of the study is to determine at what value of y do the transition metal ions start to drop into the lithium layers for any given system and composition, and to what extent can a lithium deficiency in the ‘layered-layered’ structure be compensated by changes in the oxidation state of the M cations while keeping the layered configuration intact.

References

1. C. S. Johnson, N. Li, J. T. Vaughey, S. A. Hackney, M. M. Thackeray, Electrochem. Commun., 7, 528 (2005).
2. D. Kim, G. Sandi, J. R. Croy, K. G. Gallagher, S.-H. Kang, E. Lee, M. D. Slater, C. S. Johnson, M. M. Thackeray, J. Electrochem. Soc., 160, A31 (2013).
3. B. R. Long, J. R. Croy, J. S. Park, J. Wen, D. J. Miller, M. M. Thackeray, J. Electrochem. Soc, 161, A2160 (2014).

Acknowledgment

Support for this work from the Office of Vehicle Technologies of the U.S. Department of Energy, in particular, Tien Duong, David Howell and Peter Faguy, is gratefully acknowledged.

The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.