Synthesis, redox potential evaluation and electrochemical characteristics of NASICON-related-3D framework compounds
The framework compounds M 2(SO 4) 3 with M = ( Ti Fe), ( V Fe), Fe and Li x M 2( PO 4) 3 with M = Ti, ( V Fe), Fe, were synthesized and electrochemically characterized by the coin-cell method. Use of larger (XO 4) n− polyanions not only allows fast Li +-ion conduction in an open three-dimensional fr...
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Published in | Solid state ionics Vol. 92; no. 1; pp. 1 - 10 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Amsterdam
Elsevier B.V
01.11.1996
Elsevier Science |
Subjects | |
Online Access | Get full text |
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Summary: | The framework compounds M
2(SO
4)
3 with
M = (
Ti
Fe), (
V
Fe),
Fe and
Li
x
M
2(
PO
4)
3 with
M =
Ti, (
V
Fe),
Fe, were synthesized and electrochemically characterized by the coin-cell method. Use of larger (XO
4)
n− polyanions not only allows fast Li
+-ion conduction in an open three-dimensional framework that is selective for the working alkali ion on discharge; it also stabilizes operative redox potentials
Fe
3+
Fe
2+
,
Ti
4+
Ti
3+
and
V
3+
V
2+
that give open-circuit voltages
V
oc > 2.5 V as well as access to
V
4+
V
3+
,
Ti
3+
Ti
2+
and
Fe
2+
Fe
+
couples. Separation of the
V
4+
V
3+
and
V
3+
V
2+
couples were found to be 2.0 V. Fe
2(SO
4)
3 has both monoclinic and rhombohedral modifications that give a flat open-circuit voltage
V
oc = 3.6 V versus Li and a reversible capacity for ~ 1.8 lithium atoms per formula unit. Li
x
Fe
2(SO
4)
3 shows an abrupt voltage drop occurring for
x > 2 that can be held in check by the addition of buffers such as Li
3Fe
2(PO
4)
3, FeV(SO
4)
3 and LiTi
2(PO
4)
3. Changing the polyanion group from (SO
4)
2− to (PO
4)
3− in these framework compounds decreases the redox potentials from 3.2 to 2.5 V for the
Ti
4+
Ti
3+
couple, 2.5 to 1.7 V for the
V
3+
V
2+
couple and 3.6 to 2.8 V for the
Fe
3+
Fe
2+
couple. Comparative advantages and disadvantages of framework cathodes for Li rechargeable battery applications are discussed. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0167-2738 1872-7689 |
DOI: | 10.1016/S0167-2738(96)00472-9 |