Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1998-04-07
2001-06-05
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S231100
Reexamination Certificate
active
06242132
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to anode compositions for lithium-ion batteries, and more particularly to compositions which comprise a silicon-tin oxynitride glassy material.
DESCRIPTION OF THE INVENTION
In “lithium” type batteries, the anode comprises lithium metal. Such systems are generally characterized by disadvantages such as:
1. The service temperature of the battery is generally <100° C., preferably <70° C., due to the high reactivity of lithium with any protective battery coating and owing to the low melting point thereof (180.5° C.), which makes lithium metal creep long before this temperature is reached. This problem has been mitigated by alloying the lithium with a suitable solute element to raise the melting point of the anode. See U.S. Pat. No. 5,705,293 issued on Jan. 6, 1998 to Hobson.
2. Cell fabrication requires thermal evaporation of lithium in vacuum below 10
−6
mbar and subsequent handling in an argon filled glove box.
3. Battery integration into electronic modules requires in many cases temperatures as high as 250° C. which would melt the anode. In “lithium-ion” batteries, however, the anode comprises a host matrix filled with the electroactive lithium species having an electrochemical lithium activity lower than unity, i.e. lithium metal is not present. Among the best host matrices for anode application are lithium alloys, various kinds of carbon, and transition metal oxides. However, lithium alloys are known to lose considerable capacity upon cycling, transition metal oxides such as Li
4
Ti
5
O
12
discharge well above 1 V vs. Li
+
/Li thereby significantly reducing the specific energy of the battery, and thin-film amorphous lithium-carbon anodes show at best moderate specific discharge capacities and are typically highly resistive to lithium ion transport.
A silicon-tin oxynitride anode in accordance with the present invention does not require handling in a glove-box. After being heated at 250° C. for 1 hr in air, a silicon-tin oxynitride/lithium phosphorous oxynitride/LiCoO
2
battery, which can be prepared totally by sputtering, shows an increased reversible discharge capacity of about 10% in the range of 4.2V to 2.7V. The corresponding anode potential in this range is 0-1.0 V vs. Li
+
/Li. The battery can deliver a volumetric discharge capacity (discharge capacity per volume) of more than 260 &mgr;Ah/cm
2
×&mgr;m in this voltage range at 1 mA/cm
2
. This is more than 5 times higher than the volumetric discharge capacity of the lithium-carbon anode, which gives 56 &mgr;Ah/cm
2
×&mgr;m between 0-1.3 V vs. Li
+
/Li at only 10 &mgr;A/cm
2
. Moreover, long-term cycling tests (>3000 cycles) reveal that the battery's discharge capacity fades by only 0.001% per cycle. For further information on the behavior of the lithium-carbon anode, refer to R. B. Goldner et al.,
Development of a Thin Film Li
1-y
CoO
2
/Li
x
C
6
Rocking
-
Chair Battery, Thin Film Ionic Devices and Materials,
J. B. Bates, Editor, p. 173,
The Electrochemical Society Proceedings Series.
Vol. 95-22, Pennington, N.J. (1996).
The crystallization and decomposition of SnO-SiO
2
glasses, including SnSiO
3
glass, is well known and reported in the technical literature.
The use of Sn (crystalline), SnO (crystalline), SnO
2
(crystalline), Li
2
SnO
3
(crystalline), and SnSiO
3
(glassy) as anodes in lithium-ion batteries has recently been described by I. A. Courtney et al. in
Electrochemical and In
-
Situ X
-
ray Diffraction Studies of the Reaction of Lithium with Tin Oxide Composites, J. Electrochem. Soc.,
Vol. 144, No. 6, p. 2045-2052, June, 1997.
U.S. Pat. No. 5,618,640 issued on Apr. 8, 1997 to Idota et al. describes the materials which are suitable for negative bulk electrodes (anodes) in nonaqueous secondary (rechargeable) batteries: Tin-silicon oxides, tin-silicon-phosphorous oxides, tin-silicon-phosphorous-aluminum oxides, and tin-silicon oxyfluorides. Excellent cycling capabilities are reported, but no figures on battery performance are provided. No oxynitrides are mentioned therein. Idota et al. is further discussed hereinbelow.
U.S. Pat. No. 5,395,711 issued on Mar. 7, 1995 to Tahara et al. relates to Li
x
SiO
y
(x≧0 and 2>y>0) as a negative bulk electrode in nonaqueous secondary batteries. No more than discharge-charge cycles are disclosed. No oxynitrides are mentioned therein.
All anodes in the above-listed literature contain conductive agents and binders.
U.S. Pat. No. 4,957,883 issued on Sep. 18, 1990 to Kobayashi et al. describes an oxynitride glass and a process for preparing same and a fiber thereof. The composition of the glass is represented by Si—M
1
—M
2
—O—N and contains SiO
2
, Si
3
N
4
and M
1
O in amounts which, as mole %, satisfy the following equations (a) and (b):
(
SiO
2
+3
Si
3
N
4
+M
1
O
)×100/(100+2
Si
3
N
4
)=65
to less than
100 (a)
(
SiO
2
+3
Si
3
N
4
)/
M
1
O=
0.7
to
2.3 (b)
wherein M
1
is Ca, or Ca and Mg; M
2
is at least one of the metals selected from the group consisting of Al, Sr, La, Ba, Y, Ti, Zr, Ce, Na, K, Sb, B, Cr, Pb, V and Sn. The glass contains 0-40 mole % SiO
2
, 26-70 mole % CaO, 0-20 mole % MgO, and over 0 to not more than 22 at. % M
2
. Kobayashi is discussed further hereinbelow.
Accordingly, objects of the present invention include the provision of lithium-ion batteries which can withstand service temperatures of at least 250° C. without degrading, do not require glove-box handling during fabrication, and are not degraded by high-temperature device assembly processes. Further and other objects of the present invention will become apparent from the description contained herein.
In accordance with one aspect of the present invention, the foregoing and other objects are achieved by a composition of matter which includes Ca-free Si
a
Sn
b
O
y
N
z
wherein a+b=2, y≦4, and 0<z≦3.
In accordance with another aspect of the present invention, a thin-film battery includes a cathode and an anode, the anode including Si
a
Sn
b
O
y
N
z
wherein a+b=2, y≦4, and 0<z≦3.
REFERENCES:
patent: 4008950 (1977-02-01), Chapman et al.
patent: 5322825 (1994-06-01), Leung et al.
patent: 5445887 (1995-08-01), Casti
patent: 5474861 (1995-12-01), Bito et al.
patent: 5512387 (1996-04-01), Ovshinsky
patent: 6-290782A (1994-10-01), None
patent: 11-102705 (1999-04-01), None
patent: WO 98/47196 (1998-10-01), None
Bates John B.
Neudecker Bernd J.
Chaney Carol
Craig George L.
Marasco Joseph A.
UT-Battelle LLC
LandOfFree
Silicon-tin oxynitride glassy composition and use as anode... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Silicon-tin oxynitride glassy composition and use as anode..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silicon-tin oxynitride glassy composition and use as anode... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2506827