Linden D., Reddy T.B. (eds.) Handbook of batteries
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LITHIUM-ION BATTERIES 35.49
TABLE 35.15 Summary of LEO Test Results and Predicted Cycle
Life. (Courtesy of SAFT.)
Test regime Cycles completed Predicted cycle life
20% DOD, 24 minute 21,000 91,833
20% OD, 44 minute 12,500 137,663
30% DOD, 47 minute 12,000 55,071
35.4.4 Prismatic Li-ion Batteries
Prismatic Li-ion batteries also offer a high level of performance, although design consider-
ations related to the geometry result in differences in performance. For example, current
cylindrical 18650 cells manufactured by Sanyo provide 1.7 Ah and weigh 42 g, thus offer
150 Wh /kg and 380 Wh /L. A comparably sized prismatic battery, such as the UF103450P
product by Sanyo, provides 1.5 Ah and weighs 38 g, thus offers similar specific energy (146
Wh/ kg) but lower energy density (301 Wh/ L). Some of this difference may result from
unused space remaining in the cell case, such as that resulting from the insertion of a wound
electrode stack into a prismatic can, while other differences occur because in cylindrical
designs the cell case may be loaded with hoop stress without deformation, whereas if pressure
is applied to the broad face of a prismatic design, bulging will result.
These factors change when comparing flat-plate to wound prismatic cell designs. As
described below, many of the larger batteries utilize a flat-plate design whereas small cells
almost universally utilize a wound design consistent with commercial cost requirements.
When LiNi
x
Co
1
⫺
x
O
2
-type positive electrode materials are used, the charge and discharge
curves are sloping and a higher battery capacity can be achieved by charging to higher
voltage, although this shortens battery life. The increased capacity is illustrated by the change
in the specific energy or energy density of INCP 61 /16 /78 batteries charged to either 4.2
or 4.1 V as illustrated in Table 35.16 below. After charge to 4.2 V, the cells delivered 145
Wh/ kg and 345 Wh /L, whereas after charge to 4.1 V, the batteries delivered 131 Wh /kg
and 325 Wh/ L. Similarly sized batteries fabricated using lithium manganese oxide spinel
positive electrode material delivered 84 Wh/kg and 168 Wh /L after charge to 4.2 V.
TABLE 35.16 Specific Energy and Energy Density of Prismatic Li-ion Cells.
(Courtesy of Yardney Technical Products, Inc.)
Cell Voltage limits Specific energy Energy density
INCP 61/ 16/ 78 (7 Ah) 4.2 V–2.5 V 145 Wh/ kg 345 Wh /L
INCP 61/ 16/ 78 (6 Ah) 4.1 V–2.5 V 131 Wh/ kg 325 Wh /L
IMP 61 / 16 / 78 (4 Ah) 4.2 V–2.5 V 84 Wh / kg 168 Wh /L
35.50 CHAPTER THIRTY-FIVE
Discharge Rate Capability of Wound Prismatic Batteries. The rate capability of a 1.4 Ah
wound prismatic C/LiCoO
2
battery at 20⬚C is illustrated by the discharge curves shown in
Fig. 35.56. At the 0.2C rate (270 mA), the battery provided 1.4 Ah, at the C rate
(1.35 A), 1.36 Ah, and at the 2C rate (2.7 A), 0.8 Ah. The average voltage at the C /5 rate
was 3.76 V, 3.5 V at the C rate, and 3.35 V at the 2C rate.
Discharge of Wound Prismatic Batteries at High and Low Temperature. The discharge
capability of wound prismatic batteries is indicated by the discharge curves shown in Fig.
35.57 for a 1.4 Ah wound prismatic design. When discharged at 0.945 A (0.7C), at 45
⬚C
and 60
⬚C, the battery delivered 1.4 Ah; at 20⬚C, 1.34 Ah; at 0⬚C, 1.16 Ah; and at ⫺10⬚C,
0.85 Ah. The average voltage at 20
⬚C was 3.56 V; at 0⬚C, 3.43 V and at ⫺10⬚C, 3.2 V.
FIGURE 35.56 Performance of a 1.4 Ah wound prismatic CGP345010
C / LiCoO
2
battery at various discharge rates to 3.0 V at 20⬚C, after being charged
at 945
A to 4.2 V followed by a taper charge for 2 hours total at 20⬚C.
FIGURE 35.57 High and low temperature discharge of a 1.4 Ah
CGP345010 C / LiCoO
2
wound prismatic battery at 1350 mA. Charged at
945 mA to 4.2 V followed by taper charge for 2 hours total at 20⬚C. (Courtesy
of Panasonic.)
LITHIUM-ION BATTERIES 35.51
FIGURE 35.58 Discharge at 120 mA to 3.0 V of a wound prismatic 30486 C /
LiCoO
2
battery before and after 4 month storage at 20⬚C. The battery was charged
at 420 mA to 4.1 V on a CCCV regime followed by a taper charge for 2 hours total
at 20⬚C. (Courtesy of Panasonic.)
FIGURE 35.59 Self-discharge performance of a 30486 C / LiCoO
2
battery at 20⬚C.
Charging conditions: Constant voltage / constant current, 4.1 V, 420 mA (max.) 2 hours,
20⬚C. Discharge conditions: Constant current 120 mA to 3.0 V at 20⬚C. (Courtesy of
Panasonic.)
Storage Performance of Wound Prismatic Cells. The storage stability of wound prismatic
C/ LiCoO
2
batteries is indicated by the discharge curves shown in Fig. 35.58. As shown,
after charge to 4.1 V then storage for 4 months at 20
⬚C, the 0.63 mAh battery delivered
0.57 mAh, with a self discharge rate of 2.4%/ month. After being recharged, the battery
delivered 0.63 mAh, demonstrating that no irreversible capacity loss occurred on storage.
The self-discharge performance of the battery is shown in Fig. 35.59. As shown, the self-
discharge rate is typically 2.4%/month and after 6 months storage at 20
⬚C, 90% of the
battery’s capacity was delivered.
35.52 CHAPTER THIRTY-FIVE
Discharge of Flat-Plate Prismatic Spinel Batteries. Low temperature capability has been
demonstrated in prismatic batteries that utilize a manganese-based spinel positive electrode
material. Shown in Fig. 35.60 are discharge curves at 0.8 A (C /5) for a 4 Ah spinel cell at
25
⬚Cto⫺40⬚C. At ⫺20⬚C, the capacity delivered was 96% of that delivered at 25⬚C (4.2
Ah). At
⫺40⬚C, 3.3 Ah was delivered, or 75% of the value at 25⬚C. As is characteristic of
the spinel chemistry, the voltage was higher than designs that employ LiCoO
2
or Li-
Ni
x
Co
1
⫺
x
O
2
.At25⬚C, the average cell voltage was 3.85 V; at ⫺30⬚C, 3.43 V; and at ⫺40⬚C,
3.16 V.
Prismatic cells that utilize the spinel chemistry offer good cycle life at 25
⬚C as illustrated
in Fig. 35.61. Although spinel designs have fade rates typically twice that of cells that use
cobalt-based chemistry, as illustrated, hundreds of cycles can be delivered without significant
fade. However, spinel cells typically have more capacity fade at high temperature than those
that use cobalt-based chemistry.
012345
2.0
2.5
3.0
3.5
4.0
4.5
25
o
C
-20
o
C
-30
o
C
-40
o
C
Cell Voltage (V)
Discharge Capacity (Ah)
FIGURE 35.60 Discharge curves for a 4 Ah prismatic spinel (C / LiMn
2
O
4
) battery when dis-
charged at the 0.8 A rate at several temperatures.
0 25 50 75 100 125
0
1
2
3
4
5
Discharge Capacity (Ah)
Cycle
FIGURE 35.61 Capacity ofa4Ahprismatic spinel cell when
cycled at 0.8 A between 4.2 and 3.0 V at 25⬚C. (Courtesy of
Yardney Technical Products, Inc.)
LITHIUM-ION BATTERIES 35.53
Pulse Discharge Performance of 6 Ah C/ LiNi
1
⫺
x
Co
x
O
2
Flat-Plate Prismatic Cells. Many
applications, including power tools, radios, thermal imaging devices, engine starters, and
medical implants require high-rate pulse discharge capability, although the duty cycles
vary greatly. To indicate the pulse discharge capability of a flat-plate prismatic
C/ LiNi
1
⫺
x
Co
x
O
2
Li-ion battery, Fig. 35.62 shows the cell voltage during 0.2 second pulses
at 50 A (8.3C) to 125 A (20.8C) ona6Ahcell. The positive electrode in these cells had a
geometric area of 2106 cm
2
. As shown, the minimum voltage at 50 A (24 mA /cm
2
)was
2.81 V, at 75 A (36 mA/ cm
2
) 2.45 V, at 100 A (47 mA /cm
2
) 2.11 V and at 125 A (59 mA/
cm
2
), 1.76 V. Thus at 125 A the cell delivered 1170 W /kg and 2933 W /L. A plot of the
minimum voltage versus the discharge rate is shown in Fig. 35.63. As shown, for short,
high-rate pulses, the minimum voltage is linearly related to the discharge rate. Figure 35.64
shows the voltage during a high-rate pulse discharge using a duty cycle of 25 A, 0.1 second
pulses with 7.5 A continuous between pulses. In this regime, the cell delivered 5.28 Ah and
the voltage drop during the pulse was typically less than 0.3 V, again illustrating the ability
of this technology to provide high power.
0.0 0.1 0.2
1.5
2.0
2.5
3.0
3.5
4.0
0.0 0.1 0.20.0 0.1 0.20.0 0.1 0.2
1.5
2.0
2.5
3.0
3.5
4.0
125 A
Time (sec)
100 A
Time (sec)
75 A
Time (sec)
50 A
Cell Voltage
Time (sec)
FIGURE 35.62 Pulse discharge ofa6Ahflat-plate prismatic cell at 50 A to 125 A
for 0.2 seconds at 25⬚C. Prior to the test the cell was aged for 36 weeks at room tem-
perature then charged at 5 A. (Courtesy of Yardney Technical Products, Inc.)
35.54 CHAPTER THIRTY-FIVE
40 50 60 70 80 90 100 110 120 130
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
Minimum Cell Voltage (V)
Discharge Rate (A)
Actual Data
Voltage=-0.0139(Amps) + 3.504 (R=0.99)
FIGURE 35.63 Minimum cell voltage during 0.2 second pulse discharge
of 6 Ah prismatic cell at various rates at 25⬚C. (Courtesy of Yardney Tech-
nical Products, Inc.)
1261 1262
3.0
3.2
3.4
3.6
0100020003000
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
dV=0.28 V
Voltage
Time (Seconds)
5.28 Ah
Voltage
Time (Sec.)
Cell
FIGURE 35.64 Pulse discharge ofa6Ahprismatic cell at 25⬚C using a duty
cycle with 25 A, 0.1 second pulses and 7.5 A between cycles. (Courtesy of
Yardney Technical Products, Inc.)
LITHIUM-ION BATTERIES 35.55
Low-Temperature Discharge of Flat-Plate Prismatic 6 Ah Cells. Flat-plate prismatic cells
can provide improved low temperature performance if they employ a ternary electrolyte
specially formulated to broaden their temperature capability. Discharge curves at 1 A at
temperatures from 25
⬚Cto⫺40⬚C for a 6 Ah cell charged to 4.1 V are shown in Fig. 35.65.
The capacity, energy and average voltage provided by the cell at temperatures from 25
⬚Cto
⫺40⬚C are shown in Table 35.17. At ⫺20⬚C, the product delivered 4.90 Ah and 16.8 Wh,
or 82% of the capacity and 79% of the energy delivered at 25
⬚C, and at ⫺40⬚C, the cell
delivered 4 Ah and 11.6 Wh.
0123456
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Cell Voltage (V)
Discharge Capacity (Ah)
25°C
0°C
-20°C
-30°C
-40°C
FIGURE 35.65 Voltage of a 6 Ah prismatic cell charged to 4.1 V at 25⬚C, then
discharged at 1 A at several temperatures. (Courtesy of Yardney Technical Products,
Inc.)
TABLE 35.17 Capacity and Energy of a 6 Ah Cell at Low
Temperatures
Temperature (⬚C) Capacity (Ah) Energy (Wh) V
avg
(V)
25 5.97 21.35 3.57
0 5.15 18.34 3.56
⫺20 4.90 16.78 3.42
⫺30 4.64 14.92 3.22
⫺40 4.06 11.57 2.85
Discharge Rate Capability of 7 Ah Flat-Plate Prismatic Cells. Flat-plate prismatic cells
can provide higher rate capability than common wound products, as illustrated below for
7 Ah cells. This cell employs a different electrode configuration from the 6 Ah unit in
the same case. The high rate capability is attributable to the cell design as flat-plate prismatic
designs have many current collector tabs, versus the single or small number of tabs typical
in wound units, minimizing ohmic polarization. These cells utilized the LiNi
1
⫺
x
Co
x
O
2
-type
positive electrode materials and have a sloping charge curve, characteristic of Li-ion cells
that use this material. As a result, cells can be charged to higher voltage, yielding higher
capacity, although this typically adversely affects cell life. To illustrate the effect of charge
voltage, data for cells charged to either 4.1 V or 4.2 V are compared.
35.56 CHAPTER THIRTY-FIVE
012345678
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
012345678
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
012345678
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
012345678
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
012345678
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
012345678
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
012345678
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
012345678
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0.36A
24A
.36 A
.72 A
1.5 A
3.0 A
6.0 A
12.0 A
18.0 A
24.0 A
Cell Voltage (V)
Capacity (Ah)
012345678
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
012345678012345678012345678012345678012345678012345678012345678
0.36A24A
Cell Voltage (V)
Discharge Capacity (Ah)
0.36 A
0.72 A
1.5 A
3.0 A
6.0 A
12 A
18 A
24 A
(a)
(b)
FIGURE 35.66 Voltage vs. capacity fora7AhINCP 61 / 16 / 78
cell when discharged at constant current at 25⬚C after charging to
(a) 4.1 V or (b)4.2Vat1A.(Courtesy of Yardney Technical Prod-
ucts, Inc.)
Constant-current discharge curves for cells charged to either 4.1 V or 4.2 V at 1 A at
25
⬚C are shown in Fig. 35.66. At 0.36 A, the unit charged to 4.1 V delivered 6.8 Ah and
24.3 Wh, 10.5% less capacity and 12.2% less energy than the unit charged to 4.2 V. Both
delivered high-rate capability; here discharge at rates up to 24 A (3.4C) are shown. For the
cell charged to 4.2 V, the average voltage during the 24 A discharge was 3.24 V, 0.4 V less
than that at 0.36 A (3.64 V).
The performance characteristics of this 7 Ah prismatic cell as a function of discharge rate
after charging to 4.2 V are summarized in Table 35.18.
At constant power, more significant differences in cell performance are observed between
units charged to 4.1 V or 4.2 V. Constant power discharge curves for INCP 611678 cells
are shown in Fig. 35.67; the energy delivered by these products is tabulated in Table 35.19
and Table 35.20. As illustrated, at rates up to the 1 E rate (22.5 W), the batteries delivered
energy comparable to that delivered at the lowest rate evaluated. For example, at 22.5 W,
the unit charged to 4.2 V delivered 90% of the energy delivered at 1.35 W, and at 22.5 W
the unit charged to 4.1 V delivered 86% of the energy delivered at 1.35 W. However, the
unit charged to 4.2 V offered better performance at high rates. At 90 W (4 E), the cell
charged to 4.2 V delivered 21.9 Wh, or 78% of the value delivered at 1.35 W, whereas the
cell charged to 4.1 V delivered 12.3 Wh at 90 W, or 50% of the value delivered at 1.35 W.
This performance improvement for prismatic batteries charged to a higher voltage is
achieved, however, at the expense of reduced cycle life. It must be emphasized that charging
to higher voltages must be controlled to avoid lithium plating on the negative electrode,
particularly at lower temperatures.
LITHIUM-ION BATTERIES 35.57
TABLE 35.18 The Capacity and Energy Delivered bya7AhCell Upon Constant Current Discharge When Charged
to 4.2 V at 1 A. (Courtesy of Yardney Technical Products, Inc.)
Discharge rate
(A) Capacity (Ah) Energy (Wh)
Energy density
(Wh/L)
Specific energy
(Wh/ kg)
Average
voltage (V)
0.36 7.60 27.63 324 147 3.64
3.00 7.38 26.36 309 140 3.57
6.00 7.23 25.55 300 136 3.53
12.00 7.23 24.79 291 132 3.43
24.00 7.02 22.76 267 121 3.24
0 5 10 15 20 25
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
1.35 W
2.70 W
5.63 W
11.3 W
22.5 W
45.0 W
67.5 W
90.0 W
Cell Voltage (V)
E
Cell Voltage (V)
E
Cell Voltage (V)
E
Cell Voltage (V)
E
Cell Voltage (V)
E
Cell Voltage (V)
E
Cell Voltage (V)
E
Cell Voltage (V)Cell Voltage (V)Cell Voltage (V)Cell Voltage (V)Cell Voltage (V)Cell Voltage (V)Cell Voltage (V)Cell Voltage (V)Cell Voltage (V)
Energy (Wh)
0 5 10 15 20 25 30
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25 30
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25 30
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25 30
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25 30
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25 30
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25 30
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 5 10 15 20 25 30
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
EEEEEEE
1.35 W
2.70 W
5.63 W
11.3 W
22.5 W
45.0 W
67.5 W
90.0 W
Energy (Wh)
(a)
(b)
FIGURE 35.67 Voltage vs. energy for a 7 Ah INCP 60/ 16 / 78 cell upon
discharge at constant power at 25⬚C after charging to (a) 4.1 V or (b) 4.2
V at 1 A. (Courtesy of Yardney Technical Products, Inc.)
35.58 CHAPTER THIRTY-FIVE
TABLE 35.19 Energy Delivered bya7AhINCP 160/ 61/ 78 Cell on
Constant Power Discharge after Charging to 4.1 V at 1 A at 25
⬚C.
(Courtesy of Yardney Technical Products, Inc.)
Power (W) Energy (Wh)
Energy density
(Wh/L)
Specific energy
(Wh/ kg)
1.35 24.39 286 130
11.3 21.90 256 116
22.5 20.92 245 111
45.0 18.82 221 100
90.0 12.25 144 65
TABLE 35.20 Energy Delivered bya7AhINCP 160/ 61/ 78 Cell on
Constant Power Discharge after Charging to 4.2 V at 1 A at 25
⬚C.
(Courtesy of Yardney Technical Products, Inc.)
Power (W) Energy (Wh)
Energy density
(Wh/L)
Specific energy
(Wh/ kg)
1.35 28.13 329 149
11.3 26.62 312 141
22.5 25.45 298 135
45.0 23.53 276 125
90.0 21.90 257 116
Cycle Life of Flat-Plate Prismatic Cells. Prismatic Li-ion cells offer high cycle life and
can be cycled continuously at high rates. The capacity of INCP 60 /61 /78 cells cycled at
the 1 A or 6 A rate for charge and discharge, with charge limited at either 4.2 V or 4.1 V
and discharge limited to 3.0 V or 2.5 V is illustrated in Fig. 35.68. The average fade rate
over the initial 300 cycles is listed in Table 35.21. As shown, the cells cycled at
1 A demonstrated better capacity retention than cells cycled at 6 A, and the cells cycled to
4.1 V demonstrated better capacity retention than those cycled to 4.2 V. However, in all
cases the fade rate is low. For example, the cell cycled at 6 A (1C rate) between 4.2 V and
3.0 V delivered 5.2 Ah on the 300th cycle, or 83% of its initial capacity, and the cell cycled
at 1 A between 4.1 V and 3.0 V delivered 5.8 Ah on the 300th cycle, or 90% of the initial
value. To illustrate the cycle life of these cells over longer periods, Fig. 35.69 shows data
from this test to 3000 cycles. As shown, after 300 cycles the fade rate of a cell cycled at
6 A was linear at 0.017%/cycle. As the cell was cycled, the average voltage decreased as
resistance increased, as illustrated by the discharge curves in Fig. 35.70.