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Effect of Pr content in Ml on the electrochemical properties of Ml(NiCoMnAl)5 alloys
Journal of
AK.LOY$ AND COMP©UND5 ELSEVIER
Journal of Alloys and Compounds 231 (1995) 550-552
Effect of Pr content in M1 on the electrochemical properties of M I ( N i - C o - M n - A 1 ) 5 alloys Z . H . C h e n , M . Q . L u , Y.L. W a n g , Z . Q . H u State Key Laboratory of RSA, Institute of Metal Research, Academia Sinica, 110015 Shenyang, China
Abstract
The electrochemical properties of MINi3.sCo0.sMn0.4A10.3 alloys with various Pr contents in MI were studied in this work. It was found that the Pr content in MI obviously affected the electrochemical properties of MI(Ni-Co-Mn-A1)5 alloys. The electrochemical properties were greatly improved if the electrode alloy contained about 20 at.% Pr in MI. The electrode made from this alloy has a higher capacity, better discharge rate characteristics and longer cycle life than that from alloy with less than 10 at.% Pr in MI, as in common misch metal. The AA size cells in which electrode alloy contains about 17 at% Pr in MI are also studied. It was found that these cells have a very long cycle life (1400 cycles) with reasonable capacity (1250 mA h) and rate capability (1100 mA h) when discharged at 5 C). In particular, they have a very superior low temperature capability. For example, their capacity was higher than 1050 mA h when discharged at 1 C and -18 °C. Keywords: Pr; M1; Electrochemical properties; MI-Ni alloys
1. Introduction Extensive work has been carried out on utilizing LaNis-base alloys as a negative electrode [1-10]. The rare earth content obviously affects the electrochemical properties of the MmNi-base alloys [5]. Zhao et al. [10] found that the electrochemical properties of alloy in which lathanum was the main element element was superior to that of the alloy in which cerium is the main element, but little attention has been paid to the effects of Pr on the electrochemical properties of the MINi-base alloys. The content of Pr in the MmNi-base alloys will effect the electrochemical properties. The study of the effects of Pr content in misch metal on the electrochemical properties of negative alloy is very useful for the selection of misch metal for the super capability alloy for M H - N i batteries, In this work, we studied the electrochemical properties of alloys with various Pr contents in misch metal MI (in which lanthanum is the main element). The properties of the A A size battery of which electrode was made from the alloy containing 17 at.% Pr in M1 were also studied. 2. Experimental details The hydrogen-absorbing alloys listed in Table 1 Elsevier Science S.A.
SSDI 0925-8388(95 )01725-9
were prepared by arc melting the constituent elements under an argon atmosphere. The ingot was crushed and ground mechanically to produce powder below 100 mesh. The alloy for preparing the electrode of the M H - N i battery of A A size was prepared by induction melting. The crystal structure was confirmed by X-ray diffraction analysis. The electrodes were made by the following process: the powder was mixed with poly(vinyl alcohol) (PVA), and then impregnated into a foamed nickel matrix. The electrode (200 m A h) was tested in an M H electrode-limited open cell with a sintered nickel positive electrode (600 m A h), separator and electrolyte (5.4 M K O H + 0.6 M L i O H solution). The A A size M H - N i cylinder cell was constructed by sandwiching the MH electrode and sintered Ni electrode, separated by polyamide non-woven cloth.
3. Results and discussion
3.1. Electrochemical properties of (LaNdPr)Ni4.oCoo4Mno.sAlo3 alloys Fig. 1 gives the electrode capacities of D1, D 2, 9 3 and D 4 at the beginning of the charge-discharge cycles. It can be seen that these alloys are easily
Z.H. Chen et al. I Journal of Alloys and Compounds 231 (1995) 550-552 Table 1 Compositions of the alloys Alloy
D1 Dz D3 D4
F1 F2 F3 F5
activated. The capacity increases with the increase in Pr content in M1. The rate capability of the D 4 containing 20 at.% Pr in M1 is much superior to those o f D 1, D z and D 3 for which the Pr contents are less than that in D 4, as shown in Fig. 2.
Amount (at.%)of
the following elements
La
Nd
]?r
Ni
Co
Mn
AI
0.56 0.50 0.48 0.45 0.55
0.44 0.39 0.37 0.35 0.45
0.00 0.11 0.15 0.20 0.00
4.0 4.0 4.0 4.0 3.5
0.4 0.4 0.4 0.4 0.8
0.3 0.3 0.3 0.3 0.4
0.3 0.3 0.3 0.3 0.3
0.50
0.40
0.10
3.5
0.8
0.4
0.3
Fig. 3 show the capacities of alloys F 1, F 2, F3, F 4 and
0.38 0.33
0.32 0.27
t).30 0.40
3.5 3.5
0.8 0.8
0.4 0.4
0.3 0.3
F 5 charge discharged at 0.6 C. The capacity of F 3 which contains 20 at.% Pr in MI is the highest. The capacity of FI, without Pr in MI, is much less than that
0.44
F4
0.36
0.20
3.5
0.8
0.4
0.3
3.2. Properties of (LaNdPr)Ni3.sCoo.sAlo.sMno. 4 alloys
3 0 0 ~
270
~ ¢~ ~<{ E >, o
~
~
.
d
4
250
d3
230 / ~//F
210 190
"
_
.
f3 f4 f5 f2
270
d2
u 0.
551
.c < E
dl
j ~
"~
240 2 I0 -
o Q.
0
O
150
I I
0
I 2
I 3
I 4
I 5
I 6
150 I0
I 25
I 40
n/cycles
180
E
150
"G
120-
700-
o. 90o
0
60 30
\ >, _o
680'
d4
~_
660-
d3
m ~oE ~o
d2 dl
O 0
I 85
Fig. 3. Relationship between capacity and cycle number for MINi3.sCoo.3Mno.4Alo.3 alloys (0.6C).
.%,.
"
I 70
n
Fig. 1. Relationship between capacity and cycle number during activation for M1Ni4.oCo0.4Mn0aAlo 3 alloys (20 °C).
270240
i 55
i
j
I
2
~
....... ~ ',
nx 250 mA
',
.
',
640-
/
:
/ ,,
\ , . _ . . . . . ..~'
I
62C 0
Fig. 2. Relationship between capacity and discharge current for MINi4.oCoo.4Mno.3Alo.3 alloys (20 °C).
/
I I0
) 20
i :30
) 40
P e r c e n t of Pr in M L Fig. 4. Relationship between Vickers hardness and Pr content in MI for M1Ni3.sCoo.3Mno.4Alo.3 alloys.
552
Z.H. Chen et al. / Journal of Alloys and Compounds 231 (1995) 550-552
14 0 O -
sample in the charge-discharge cycles. The capacity of the cell is 600 m A h after 1400 cycles.
1200 I000 8 0 0
E
600 400 200 (30
4. Conclusion
I I I I I I I 2 0 0 4 0 0 6 0 0 8 0 0 I 0 0 0 1200 1400 n /cycles
Fig. 5. Relationship between capacity and cycle number for battery sample AI.
of the alloys containing Pr, but the capacity decreases when the content of Pr in MI increases to 30 at.% (F 4 and Fs). The Vickers hardness of the alloys, which was found related to the cycle life [11], are different, as shown in Fig. 4. We can see that the hardness of the alloy containing 20 or 30 at.% Pr in M1 is lower than those of the other alloys. It can be assumed that these two alloys a r e m o r e durable in the charge-discharge cycles. 3.3. The properties o f A A
size cells
The A A size cylindrical sealed cell were made by utilizing MLNi3.sCO0.8Mn0.aAI0. 3 alloy for which the Pr content in M1 is 17 at.%. The capacity of these cells achieves 1250 m A h. When discharged at 5 C at 20 °C, the capacity also reaches 1100 m A h. In particular, they have a very superior low temperature capability: 1050 m A h when discharged with 1 C at - 1 8 °C. Fig. 5 shows the decrease in the capacity of the cell
In this work, the effects of Pr content in M1 on the electrochemical properties of alloys were studied. It was found that the content of Pr in MI obviously affects the electrochemical properties of alloys. The electrochemical properties of alloys are superior when the Pr content is about 20 at.% in MI.
References [1] H.H. Ewe, E.W. Justi and K. Stephen, Energy Convers, 13 (1973) 109. [2] G. Branod, J. Savradin, M. Bonnemany, A. Percher onGuegan, J.C. Achard and L. Schlapbach, Int. J. Hydrogen Energy, (1976) 1251.
[3] M.H.J.Van Rijswick, in A.F. Adresen and A.J. Maeland (eds.), Hydrides for Energy Storage, Pergamon, Oxford, 1978, p. 261.
[41 T.L. Markin, N.J. Bridger, R. Benett and R.M. Dell, 28th Powder Sources Syrup., Atlantic City, N J, 12-15 June, 1978. [5] T. Sakai, T. Hazama, N. Kuriyamg, A. Kato and H. Ishikawa, J. Less-Common Met., 172-174 (1991) 1175. [6] T. Sakai, II. Yoshinaga, H. Miyamura, N. Kuriyama and Ishikawa, J. Alloys Compd., 180 (1992) 37.
[7] L. Schlaphach, A. Seiler, F. Stuki and H.C. Siegamann, J. Less-Common Met., 73 (1980) 145. [8] J.J.G. Willems and K.H. Buahow, J. Less-Common Met., 129 (1987) 13. [9] A. Percheron-Guegan, C. Lartigue, J.C. Achard, P. Germi and F. Tasset, J. Less-Common Met., 74 (1980) 1.
[10] D.J. Zhao et al., Chin. J. Power Sources, 2 (1993) 21. [11] T. Sakai, K. Oguro and H. Ishikawa, J. Less-Common Met., 161
(1990) 193.
AK.LOY$ AND COMP©UND5 ELSEVIER
Journal of Alloys and Compounds 231 (1995) 550-552
Effect of Pr content in M1 on the electrochemical properties of M I ( N i - C o - M n - A 1 ) 5 alloys Z . H . C h e n , M . Q . L u , Y.L. W a n g , Z . Q . H u State Key Laboratory of RSA, Institute of Metal Research, Academia Sinica, 110015 Shenyang, China
Abstract
The electrochemical properties of MINi3.sCo0.sMn0.4A10.3 alloys with various Pr contents in MI were studied in this work. It was found that the Pr content in MI obviously affected the electrochemical properties of MI(Ni-Co-Mn-A1)5 alloys. The electrochemical properties were greatly improved if the electrode alloy contained about 20 at.% Pr in MI. The electrode made from this alloy has a higher capacity, better discharge rate characteristics and longer cycle life than that from alloy with less than 10 at.% Pr in MI, as in common misch metal. The AA size cells in which electrode alloy contains about 17 at% Pr in MI are also studied. It was found that these cells have a very long cycle life (1400 cycles) with reasonable capacity (1250 mA h) and rate capability (1100 mA h) when discharged at 5 C). In particular, they have a very superior low temperature capability. For example, their capacity was higher than 1050 mA h when discharged at 1 C and -18 °C. Keywords: Pr; M1; Electrochemical properties; MI-Ni alloys
1. Introduction Extensive work has been carried out on utilizing LaNis-base alloys as a negative electrode [1-10]. The rare earth content obviously affects the electrochemical properties of the MmNi-base alloys [5]. Zhao et al. [10] found that the electrochemical properties of alloy in which lathanum was the main element element was superior to that of the alloy in which cerium is the main element, but little attention has been paid to the effects of Pr on the electrochemical properties of the MINi-base alloys. The content of Pr in the MmNi-base alloys will effect the electrochemical properties. The study of the effects of Pr content in misch metal on the electrochemical properties of negative alloy is very useful for the selection of misch metal for the super capability alloy for M H - N i batteries, In this work, we studied the electrochemical properties of alloys with various Pr contents in misch metal MI (in which lanthanum is the main element). The properties of the A A size battery of which electrode was made from the alloy containing 17 at.% Pr in M1 were also studied. 2. Experimental details The hydrogen-absorbing alloys listed in Table 1 Elsevier Science S.A.
SSDI 0925-8388(95 )01725-9
were prepared by arc melting the constituent elements under an argon atmosphere. The ingot was crushed and ground mechanically to produce powder below 100 mesh. The alloy for preparing the electrode of the M H - N i battery of A A size was prepared by induction melting. The crystal structure was confirmed by X-ray diffraction analysis. The electrodes were made by the following process: the powder was mixed with poly(vinyl alcohol) (PVA), and then impregnated into a foamed nickel matrix. The electrode (200 m A h) was tested in an M H electrode-limited open cell with a sintered nickel positive electrode (600 m A h), separator and electrolyte (5.4 M K O H + 0.6 M L i O H solution). The A A size M H - N i cylinder cell was constructed by sandwiching the MH electrode and sintered Ni electrode, separated by polyamide non-woven cloth.
3. Results and discussion
3.1. Electrochemical properties of (LaNdPr)Ni4.oCoo4Mno.sAlo3 alloys Fig. 1 gives the electrode capacities of D1, D 2, 9 3 and D 4 at the beginning of the charge-discharge cycles. It can be seen that these alloys are easily
Z.H. Chen et al. I Journal of Alloys and Compounds 231 (1995) 550-552 Table 1 Compositions of the alloys Alloy
D1 Dz D3 D4
F1 F2 F3 F5
activated. The capacity increases with the increase in Pr content in M1. The rate capability of the D 4 containing 20 at.% Pr in M1 is much superior to those o f D 1, D z and D 3 for which the Pr contents are less than that in D 4, as shown in Fig. 2.
Amount (at.%)of
the following elements
La
Nd
]?r
Ni
Co
Mn
AI
0.56 0.50 0.48 0.45 0.55
0.44 0.39 0.37 0.35 0.45
0.00 0.11 0.15 0.20 0.00
4.0 4.0 4.0 4.0 3.5
0.4 0.4 0.4 0.4 0.8
0.3 0.3 0.3 0.3 0.4
0.3 0.3 0.3 0.3 0.3
0.50
0.40
0.10
3.5
0.8
0.4
0.3
Fig. 3 show the capacities of alloys F 1, F 2, F3, F 4 and
0.38 0.33
0.32 0.27
t).30 0.40
3.5 3.5
0.8 0.8
0.4 0.4
0.3 0.3
F 5 charge discharged at 0.6 C. The capacity of F 3 which contains 20 at.% Pr in MI is the highest. The capacity of FI, without Pr in MI, is much less than that
0.44
F4
0.36
0.20
3.5
0.8
0.4
0.3
3.2. Properties of (LaNdPr)Ni3.sCoo.sAlo.sMno. 4 alloys
3 0 0 ~
270
~ ¢~ ~<{ E >, o
~
~
.
d
4
250
d3
230 / ~//F
210 190
"
_
.
f3 f4 f5 f2
270
d2
u 0.
551
.c < E
dl
j ~
"~
240 2 I0 -
o Q.
0
O
150
I I
0
I 2
I 3
I 4
I 5
I 6
150 I0
I 25
I 40
n/cycles
180
E
150
"G
120-
700-
o. 90o
0
60 30
\ >, _o
680'
d4
~_
660-
d3
m ~oE ~o
d2 dl
O 0
I 85
Fig. 3. Relationship between capacity and cycle number for MINi3.sCoo.3Mno.4Alo.3 alloys (0.6C).
.%,.
"
I 70
n
Fig. 1. Relationship between capacity and cycle number during activation for M1Ni4.oCo0.4Mn0aAlo 3 alloys (20 °C).
270240
i 55
i
j
I
2
~
....... ~ ',
nx 250 mA
',
.
',
640-
/
:
/ ,,
\ , . _ . . . . . ..~'
I
62C 0
Fig. 2. Relationship between capacity and discharge current for MINi4.oCoo.4Mno.3Alo.3 alloys (20 °C).
/
I I0
) 20
i :30
) 40
P e r c e n t of Pr in M L Fig. 4. Relationship between Vickers hardness and Pr content in MI for M1Ni3.sCoo.3Mno.4Alo.3 alloys.
552
Z.H. Chen et al. / Journal of Alloys and Compounds 231 (1995) 550-552
14 0 O -
sample in the charge-discharge cycles. The capacity of the cell is 600 m A h after 1400 cycles.
1200 I000 8 0 0
E
600 400 200 (30
4. Conclusion
I I I I I I I 2 0 0 4 0 0 6 0 0 8 0 0 I 0 0 0 1200 1400 n /cycles
Fig. 5. Relationship between capacity and cycle number for battery sample AI.
of the alloys containing Pr, but the capacity decreases when the content of Pr in MI increases to 30 at.% (F 4 and Fs). The Vickers hardness of the alloys, which was found related to the cycle life [11], are different, as shown in Fig. 4. We can see that the hardness of the alloy containing 20 or 30 at.% Pr in M1 is lower than those of the other alloys. It can be assumed that these two alloys a r e m o r e durable in the charge-discharge cycles. 3.3. The properties o f A A
size cells
The A A size cylindrical sealed cell were made by utilizing MLNi3.sCO0.8Mn0.aAI0. 3 alloy for which the Pr content in M1 is 17 at.%. The capacity of these cells achieves 1250 m A h. When discharged at 5 C at 20 °C, the capacity also reaches 1100 m A h. In particular, they have a very superior low temperature capability: 1050 m A h when discharged with 1 C at - 1 8 °C. Fig. 5 shows the decrease in the capacity of the cell
In this work, the effects of Pr content in M1 on the electrochemical properties of alloys were studied. It was found that the content of Pr in MI obviously affects the electrochemical properties of alloys. The electrochemical properties of alloys are superior when the Pr content is about 20 at.% in MI.
References [1] H.H. Ewe, E.W. Justi and K. Stephen, Energy Convers, 13 (1973) 109. [2] G. Branod, J. Savradin, M. Bonnemany, A. Percher onGuegan, J.C. Achard and L. Schlapbach, Int. J. Hydrogen Energy, (1976) 1251.
[3] M.H.J.Van Rijswick, in A.F. Adresen and A.J. Maeland (eds.), Hydrides for Energy Storage, Pergamon, Oxford, 1978, p. 261.
[41 T.L. Markin, N.J. Bridger, R. Benett and R.M. Dell, 28th Powder Sources Syrup., Atlantic City, N J, 12-15 June, 1978. [5] T. Sakai, T. Hazama, N. Kuriyamg, A. Kato and H. Ishikawa, J. Less-Common Met., 172-174 (1991) 1175. [6] T. Sakai, II. Yoshinaga, H. Miyamura, N. Kuriyama and Ishikawa, J. Alloys Compd., 180 (1992) 37.
[7] L. Schlaphach, A. Seiler, F. Stuki and H.C. Siegamann, J. Less-Common Met., 73 (1980) 145. [8] J.J.G. Willems and K.H. Buahow, J. Less-Common Met., 129 (1987) 13. [9] A. Percheron-Guegan, C. Lartigue, J.C. Achard, P. Germi and F. Tasset, J. Less-Common Met., 74 (1980) 1.
[10] D.J. Zhao et al., Chin. J. Power Sources, 2 (1993) 21. [11] T. Sakai, K. Oguro and H. Ishikawa, J. Less-Common Met., 161
(1990) 193.