Structurally Integrated Cathode Materials for High

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					      Structurally Integrated Cathode Materials for
              High-Enegy Li-Ion Batteries

      Ilias Belharouak, H. Deng, H. Wu, and K. Amine
                                                                                                                                Li1.625Ni0.25Mn0.75O2.5625
     Chemical Sciences and Engineering Division, Argonne
        National Laboratory, 9700 South Cass Avenue,
                  Argonne, IL 60439, USA

The search for novel cathode materials whose main                                                                                 Li1.5Ni0.25Mn0.75O2.5
characteristic is to store more and more electricity per
mass and volume has led to several works [1-4]. Of these
materials, Li1.5Ni0.25Mn0.75O2.5 (for convenience, also
written as Li1.2Ni0.2Mn0.6O2) was found to deliver a high
                                                                                                                                Li1.375Ni0.25Mn0.75O2.4375
reversible capacity while being structurally and thermally
stable upon charging to 4.6 V. These properties make this
material an excellent candidate to surmount the energy
                                                                                               Layered C2/m
density shortfall of current lithium-ion batteries and to                                                     Spinel

meet the lower cost and low toxicity requirement targeted                                                                       Li1.25Ni0.25Mn0.75O2.375

by industry.

A two-step synthesis process was adopted to make active
                                                                                          20       30         40         50          60         70           80
materials. The first step consisted of synthesizing a
                                                                                                                            ο
Ni0.25Mn0.75CO3 and Ni0.25Co0.125Mn0.625CO3 carbonate                                                             2 θ, ( )
precursor through a coprecipitation process. Thereafter,
stoichiometric amounts of Li2CO3 were intimately mixed                                                     Fig. 1
with the as-prepared carbonate precursors to prepare the                                        X-ray diffraction patters of
                                                                                            Li1+xNi0.25Mn0.75O(4.5+x)/2 materials
final lithiated phases according to the following formulas:
Li1+xNi0.25Mn0.75O2.25+x/2 and Li1+xNi0.25Co0.125Mn0.625O2.1875+x/2
(where x = 0.25, 0.375, 0.5, and 0.625). For comparison,
similar compositions were made using lithium and
transition metal nitrate precursors.          Calcination was
accomplished by a first treatment at 600oC for 15 hours                                                                 Li1.625Ni0.25Co0.125Mn0.625O2.5
under air to decompose the precursors, followed by 900oC
for 15 hours to obtain the corresponding lithiated
compounds.
The XRD patterns of these samples do not fit the                                                                       Li1.5Ni0.25Co0.125Mn0.625O2.4375
description of a one-layer structural model, namely, the
structural model of α-NaFeO2 (R-3m) or that of Li2MnO3
(C2/m). They are composed of at least these components,
in addition to a third one that was observed with materials
having less lithium content (Fig.1 & 2). Indeed, a close                                                               Li1.375Ni0.25Co0.125Mn0.625O2.375

examination of the pattern of sample with the lowest
lithium amounts shows the presence of an unusual
broadening on the left side of the peaks observed at 36.92o
and 44.58o. This broadening is less pronounced in sample                                                               Li1.25Ni0.25Co0.125Mn0.625O2.3125

with higher lithium contents and visually disappears for
samples with the highest lithium content. Figure 1 shows
the detail of the XRD pattern of samples where the
splitting of the (104) peak is clearly evident. However, it
                                                                                          20       30         40         50          60         70           80
                                                                                                                            ο
was not possible for us to assign this broadening to (R-3m)                                                       2 θ, ( )
or (C2/m) space groups with great confidence. Within
slight peak position variation, the x-ray lines arising from                                             Fig. 2
the space group (R-3m) could easily be hidden/overlapped                                      X-ray diffraction patters of
by the lines arising from space group (C2/m), and the same                            Li1+xNi0.25Co0.125Mn0.625O(4.375+x)/2 materials
could be said for (Fd-3m), for which all lines could be
hidden/overlapped by (R-3m).
Among all the studied materials, the samples with the                       Acknowledgment
lower lithium content exhibited 1) high capacity at high
                                                                            The authors acknowledge the financial support of the U.S. Department of
rate capability, 2) high packing densities that can lead to                 Energy, FreedomCAR & Vehicle Technologies Office, under Contract
higher volumetric energy density, and 3) outstanding                        No. DE-AC02-06CH11357
safety characteristics.

References                                                                  The submitted manuscript has been created by UChicago Argonne, LLC,
                                                                            Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S.
[1] Ohzuku T., and Y. Makimura, Chemistry Letters, 2001, 642.
                                                                            Department of Energy Office of Science laboratory, is operated under
[2] Lu Z., MacNeil D.D., and Dahn J.R., Electrochem. Solid-State Lett.,
                                                                            Contract No. DE-AC02-06CH11357. The U.S. Government retains for
2001, 4 (11), A191.
                                                                            itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable
[3] Johnson C.S., Kim J.S., Lefief C., Li N., Vaughey J.T., and Thackeray
                                                                            worldwide license in said article to reproduce, prepare derivative works,
M.M., Electrochem. Communications, 2004, 6, 1085.
                                                                            distribute copies to the public, and perform publicly and display publicly,
[4] Deng H., Belharouak I., Sun Y.-K., and Amine K., J. Mater. Chem.,
                                                                            by or on behalf of the Government.
2009, 19 (26), 4510.