Linden D., Reddy T.B. (eds.) Handbook of batteries

Подождите немного. Документ загружается.

LITHIUM-ION BATTERIES 35.59

0 50 100 150 200 250 300

4.1-3.0V, 1A

4.2-3.0V, 1A

4.1-2.5V, 6A

4.2-3.0V, 6A

Discharge Capacity (Ah)

Cycle Number

FIGURE 35.68 Capacity of INCP 160/ 61 / 78 cells when cycled at a constant current of 1

A and 6 A, for charge and discharge, between 4.2 or 4.1 V and 3.0 V or 2.5 V at 25⬚C.

(Courtesy of Yardney Technical Products, Inc.)

TABLE 35.21 Voltage Limits and Fade Rate of INCP 160 /61 /78 Cells

Cycled at 1 A or 6 A at 25

⬚C. (Courtesy of Yardney Technical Products,

Inc.)

Charge

limit

Discharge

limit Rate

Fade rate

cycles 1–300

Fade rate

cycles

⬎300

4.1 V 3.0 V 1.0 A 0.035%/ cycle —

4.2 V 3.0 V 1.0 A 0.092%/ cycle —

4.1 V 2.5 V 6.0 A 0.037%/ cycle 0.017% /cycle

4.2 V 3.0 V 6.0 A 0.056%/ cycle 0.016% /cycle

0 500 1000 1500 2000 2500 3000

4.1-3.0V, 1A

4.2-3.0V, 1A

4.1-2.5V, 6A

Discharge Capacity (Ah)

Cycle Number

FIGURE 35.69 Capacity of INCP 60/ 61 / 78 cells charged to 4.2 V or 4.1 V and discharged

to 3.0 V or 2.5 V at 25⬚C at 1 A or 6 A. The cells cycled at 1 A completed 300 cycles, whereas

the cell cycled at 6 A completed 3000 cycles. (Courtesy of Yardney Technical Products, Inc.)

35.60 CHAPTER THIRTY-FIVE

Charged Stand Performance of 6 Ah Flat-Plate Prismatic Cell. The ability of a 6 Ah

INCP 160/61/78 cell to provide discharge capability after prolonged charged stand is in-

dicated by the data shown in Fig. 35.71. Prior to the test, the cell delivered 6.1 Ah. After a

four month stand at full charge at 25

⬚C, the cell provided 5.3 Ah, thus a self-discharge rate

of 3.5% per month. After recharge, the cell provided 5.8 Ah, or 95% of the capacity provided

four months earlier. When a similar test was performed on a cell stored at 50% DOD, 98%

capacity recovery was observed after four months storage at 25

⬚C.

01234567

2.0

2.5

3.0

3.5

4.0

4.5

0246

2.0

2.5

3.0

3.5

4.0

4.5

Voltage (V )

Capacity (Ah)

Cycle 1

Cycle 250

Cycle 500

Cycle 1000

FIGURE 35.70 Discharge curves for a 6 Ah prismatic Li-ion cell when cycled at 6 A between

4.1 V and 2.5 V at 25⬚C. (Courtesy of Yardney Technical Products, Inc.)

01234567

2.00

2.25

2.50

2.75

3.00

3.25

3.50

3.75

4.00

Prior to Charged Stand

After 4 month, fully charged stand:

Initial discharge (Self Discharge = 3.46%/month)

Recovery after 1 cycle (Capacity fade = 1.24%/month)

Voltage (V)

Discharge Capacity

FIGURE 35.71 Discharge of a 6 Ah INCP 160 /61 /78 cell before and after 4-

month stand fully charged, and discharge after charge, all at 25⬚C. (Courtesy of Yard-

ney Technical Products, Inc.)

LITHIUM-ION BATTERIES 35.61

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

0 5 10 15 20 25 30 35

Capacity (Ah)

Cell Voltage (V)

25 A

50 A

125 A

175 A

250 A

FIGURE 35.72 Discharge curves for a 35 Ah ﬂat-plate prismatic cell at rates from

25Ato250Aat25⬚C. (Courtesy of Yardney Technical Products, Inc.)

20 40 60 80 100 200250 400

Discharge Capacity (Ah)

Discharge Rate (A)

FIGURE 35.73 Rate capability of a 35 Ah ﬂat-plate prismatic cell

at 25⬚C. (Courtesy of Yardney Technical Products, Inc.)

Constant Current Discharge Rate Capability of 35 Ah C/ LiNi

ⴚ

Flat-Plate Pris-

matic Cells. The high rate, continuous discharge capability of a 35 Ah C/LiNi

⫺

ﬂat-plate prismatic cells at 25⬚C is indicated by the discharge curves shown in Fig. 35.72

and the plot of discharge capacity versus rate in Fig. 35.73. These cells weigh 870 g and

have outside dimensions of 9.45

⫻ 14.0 ⫻ 2.74 cm. At 50 A, they provide an average

voltage of 3.5 V, at 125 A, 3.3 V, at 175 A, 3.2 V and at 250 A, 3.0 V. As illustrated in

Fig. 35.73, on discharge at up to 50 A the cells offered over 32 Ah and at 125 A, 29 Ah.

At 25 A, they provided 134 Wh /kg and 323 Wh/ L, and at 50 A 130 Wh/ kg and 313

Wh/ L. At 250 A, the voltage plateaued at 3.35 V yielding a speciﬁc power and power

density of 960 W /kg and 2300 W /L.

Larger ﬂat-plate prismatic cells of similar design offer comparable relative performance.

See Fig. 35.76, which describes the capacity of a 35 Ah ﬂat-plate prismatic battery at 0.1C

to C rates at 40

⬚C, 20⬚C and ⫺20⬚C. At the C rate at 20⬚C, the capacity was 12% less than

that at the C /5 rate.

35.62 CHAPTER THIRTY-FIVE

00:00 00:05 00:10 00:15

2.5

3.0

3.5

4.0

4.5

50A 100A75A25A

Voltage (V)

Test Time

00:00 00:05 00:10 00:15

2.5

3.0

3.5

4.0

4.5

100A75A50A25A

Voltage (V)

Test Time

FIGURE 35.74 Cell voltage during 10 second pulse discharge at 25 A, 50 A, 75 A and 100 A at 20⬚C and

⫺20⬚C for a 35 Ah prismatic design.

-50 -40 -30 -20 -10 0 10 20 30 40

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

25 A

50 A

75 A

100 A

End of Pulse Voltage (V)

Temperature (°C)

FIGURE 35.75 Minimum voltage during a 10 second pulse discharge

of a 35 Ah prismatic cell at 25 A, 50 A, 75 A and 100 A.

Pulse Discharge Performance of 35 Ah Prismatic Cells. Flat-plate prismatic cells can

deliver high-rate pulse discharge at temperatures as low as

⫺40⬚C. The voltage of a 35 Ah

prismatic cell during 10 second pulse discharge at 25 A, 50 A, 75 A and 100 A at 20

⬚C and

⫺20⬚C is shown in Fig. 35.74. At 20⬚C, the voltage drop from the open circuit voltage is

0.2 V at 50 A and 0.36 V at 100 A. At

⫺20⬚C, the voltage drop from the open circuit

voltage is 0.84 V at 50 A and 1.24 V at 100 A. The ability to deliver the 10 pulse at

temperatures from 30

⬚Cto⫺40⬚C is illustrated in Fig. 35.75. As shown, the minimum cell

voltage at 100 A at

⫺40⬚C was 1.6 V.

LITHIUM-ION BATTERIES 35.63

C/10 C/5 C/2 C

Discharge Rate

40°C

20°C

-20°C

Discharge Capacity (Ah)

100%

120%

80%

132%

100

120

140

Percent

FIGURE 35.76 Rate capability of a 35 Ah ﬂat-plate prismatic cell at 40⬚C,

20⬚C, and ⫺20⬚C. (Courtesy of Yardney Technical Products, Inc.)

2.5

3.5

4.5

0 5 10 15 20 25

30 35 40

Discharge Capacity (Ah)

Voltage (V)

Discharge at low temperature

Discharge at room temperature

Temperature

- 20

FIGURE 35.77 Discharge of a Yardney 35 Ah prismatic Li-ion battery at

5Aat25⬚C and ⫺20⬚C after charge at 5 A to 4.1 V at 25⬚C. (Courtesy of

Jet Propulsion Laboratory (JPL).)

Continuous Low Temperature Discharge of Flat-Plate Prismatic 35 Ah Cells. Figure

35.76 shows the discharge capacity of a 35 Ah prismatic cell at 40

⬚C, 20⬚C and ⫺20⬚C. As

shown, the cell provided rate capability to 1C at

⫺20⬚C, delivering 80% of the capacity

provided at the C /5 rate. From the 0.1C to the 1C rate, the capacity at

⫺20⬚C was typically

30% less than that at 20

⬚C.

Prismatic 35 Ah cells that employ electrolytes speciﬁcally formulated for low tempera-

tures have demonstrated charge and discharge capability at low temperature. Figure 35.77

shows the discharge of a 35 Ah cell at 25

⬚Cor⫺20⬚C after charge at 25⬚C. When discharged

⫺20⬚C, the battery delivered 24.5 Ah, 72% of that provided at 25⬚C (34.1 Ah). After

charge at

⫺20⬚C, the cell provided 22 Ah when discharged at ⫺20⬚C, 91% of that provided

after charge at 25

⬚C, as shown in Fig. 35.78. After charge at ⫺30⬚C, discharge at ⫺30⬚C

provided 17.7 Ah, as shown in Fig. 35.79, 81% of that delivered after charge at 25

⬚C and

discharge at

⫺30⬚C (21.9 Ah).

35.64 CHAPTER THIRTY-FIVE

2.5

3.5

4.5

0 5 10 15 20 25 30

Discharge Capacity (Ah)

Voltage (V)

Temperature

- 20

90.7 %

25°C Charge

Low temperature

charge

(-20

FIGURE 35.78 Discharge of a Yardney 35 Ah prismatic Li-ion cell at 5 A at ⫺20⬚ C after

charge at 5 A to 4.1 V at either 25⬚Cor⫺20⬚C. (Courtesy of JPL.)

2.5

3.5

4.5

0 5 10 15 20 25

Discharge Capacity (Ah)

Voltage (V)

25 C Charge

-30 C Charge

FIGURE 35.79 Discharge of a Yardney 35 Ah prismatic Li-ion cell at ⫺30⬚C at 2.5 A after

charge at 2.5 A at 25⬚Cor⫺30⬚C. (Courtesy of JPL.)

LITHIUM-ION BATTERIES 35.65

The 35 Ah cells also provide high rate capability at low temperatures, as indicated by

discharge curves at 40

⬚C, shown in Fig. 35.80, those at ⫺20⬚C, shown in Fig. 35.81, and at

⫺30⬚C, shown in Fig. 35.82. When charged and discharged at 40⬚C, the discharge curves

for rates from 2.5 A to 12.5 A are very similar, the delivered capacity ranged from 35.8 Ah

to 34.4 Ah. The discharge voltages were also comparable. At

⫺20⬚C, the delivered capacity

ranged from 25.2 Ah to 21.2 Ah for these rates. The average voltage at the 2.5 A rate, 3.5

V, was 0.22 V higher than that at 12.5 A, 3.27 V. After charge at

⫺30⬚C, discharge at ⫺30⬚C

at 2.5 A yielded 17.9 Ah, and 9.8 Ah at 12.5 A. The average voltage at

⫺30⬚C and 2.5 A

was 3.29 V, 0.06 V higher than at the 12.5 A rate at

⫺30⬚C (3.23 V). The capacity data is

summarized in Fig. 35.83, which compares the discharge capacity on charge and discharge

at 40

⬚C, ⫺20⬚C and ⫺30⬚C, at rates from 2.5 A to 12.5 A.

Storage Stability of 20 Ah Flat-Plate Prismatic Batteries. The ability of ﬂat-plate prismatic

batteries to retain capacity on storage is indicated by the data presented in Table 35.22 which

lists capacity retention after storage at 0

⬚C, 40⬚C, and 50⬚C at either 50% or 100% state of

charge for 8 or 16 weeks. These cells were on the C/LiCo

⫺

chemistry and used a

ternary carbonate electrolyte. At or below 40

⬚C, the batteries retained over 97% of their

capacity. At 50

⬚C, storage at 100% DOD resulted in 81% capacity retention, while storage

at a 50% state of charge resulted in 91% capacity retention.

2.5

3.5

4.5

0 5 10 15 20 25 30 35 40

Discharge Capacity (Ah)

Voltage (V)

2.5 Amp Discharge Current (C/10)

5.0 Amp Discharge Current (C/5)

7.5 Amp Discharge Current (C/3.3)

12.5 Amp Discharge Current (C/2)

FIGURE 35.80 Rate capability of a Yardney 35 Ah prismatic Li-ion cell when charged at

2.5Ato4.1Vat40⬚C and discharged at 40⬚C. (Courtesy of JPL.)

35.66 CHAPTER THIRTY-FIVE

2.5

3.5

4.5

0 5 10 15 20 25 30

Discharge Capacity (Ah)

Voltage (V)

2.5 Amp Discharge Current (C/10)

5.0 Amp Discharge Current (C/5)

7.5 Amp Discharge Current (C/3.3)

12.5 Amp Discharge Current (C/2)

FIGURE 35.81 Rate capability of 35 Ah prismatic Li-ion cells when charged at

2.5Ato4.1Vat⫺20⬚C and discharged at ⫺20⬚C. (Courtesy of JPL.)

2.5

3.5

4.5

0 5 10 15 20

Discharge Capacity (Ah)

Voltage (V)

2.5 Amp Discharge Current (C/10)

5.0 Amp Discharge Current (C/5)

7.5 Amp Discharge Current (C/3.3)

12.5 Amp Discharge Current (C/2)

FIGURE 35.82 Rate capability of 35 Ah prismatic Li-ion cells when charged at

2.5Ato4.1Vat–30⬚C and discharged at ⫺30⬚C. (Courtesy of JPL.)

LITHIUM-ION BATTERIES 35.67

24681012.520

Discharge Capacity (Ah)

Discharge Rate (A)

40°C

-20°C

-30°C

FIGURE 35.83 Summary of the rate capability of Yardney 35 Ah prismatic Li-ion

cells when charged and discharged at 40⬚C, ⫺20⬚C and ⫺30⬚C. (Courtesy of Yardney

Technical Products, Inc.)

TABLE 35.22 Storage Stability of 20 Ah Prismatic Li-ion Batteries. (Courtesy of

JPL.)

Storage temperature State of charge Storage time

Reversible capacity

retention

0⬚C (32⬚F) 50% 8 weeks 98%

⬚C (32⬚F) 100% 8 weeks 97%

⬚C (104⬚F) 50% 8 weeks 99%

⬚C (104⬚F) 100% 8 weeks 98%

⬚C (122⬚F) 100% 16 weeks 81%

⬚C (122⬚F) 50% 16 weeks 91%

35.5 CHARGE CHARACTERISTICS OF Li-ION BATTERIES

Li-ion cells are fabricated in the discharged state and thus must be charged before use. Li-

ion cells are typically charged using either a constant current (CC) or constant current,

constant voltage with a taper charge (CCCV) regime. This charge regime is accomplished

through the use of battery management circuitry. At low rates (C /5), the CC regime ap-

proximates the CCCV regime as the cell is fully charged when the upper voltage limit is

attained.

Li-ion cells are typically charged to either 4.1 V or 4.2 V. While LiCoO

is structurally

stable at both potentials,

the cutoff voltage affects cell performance when LiNi

⫺

used.

When charged to 4.2 V, cells with LiNi

⫺

positive electrode material can offer

higher capacity, but with reduced cycle life and storage stability, relative to cells charged to

4.1 V. The capacity of C /LiNi

⫺

cells charged to 4.1 V or 4.2 V is illustrated in Fig.

35.66 for constant current discharge; delivered energy on constant power discharge is illus-

trated in Fig. 35.67. At low rates (C/10), cells charged to 4.2 V delivered about 14% more

capacity than those charged to 4.1 V, whereas at high rates (2C), typically 18% more capacity

was delivered when the higher charge voltage was used. Although the cells charged to

35.68 CHAPTER THIRTY-FIVE

0.0 0.5 1.0 1.5 2.0 2.5

0.0

0.5

1.0

1.5

2.0

Charge Current

Charge Time (hours)

0.0 0.5 1.0 1.5 2.0 2.5

100

Percent Charge

0.0 0.5 1.0 1.5 2.0 2.5

3.0

3.5

4.0

LiMn

LiCoO

Voltage

LiCoO

LiMn

FIGURE 35.84 Voltage, state of charge and current for C / LiMn

and C/ LiCoO

18650 cells in

a 2.5h CCCV charge proﬁle with 1.4 A (C/ LiMn

) or 1.65 A (C / LiCoO

) maximum current and

and 4.2 V maximum voltage. (Courtesy of NEC Moli Energy.)

4.2 V delivered more capacity, their capacity fade was higher. The capacity of the cells when

cycled at constant current is illustrated in Fig. 35.68 and Fig. 35.69. As shown, even though

the capacity fade rate of cells charged to 4.2 V was higher, up to 300 cycles they delivered

greater capacity. Only when cycled for more than 500 cycles did cells charged to 4.1 V

outperform cells charged to 4.2 V. Also illustrated by this data is the performance of Li-ion

cells on high rate (6 A, C rate) or low rate (1 A, C /6 rate) charge. As shown, cells charged

at the lower rate did offer higher capacity, although this difference was reduced after 300

cycles. Further, the capacity fade rates of the cells was comparable.

The voltage, percent charged and current proﬁle for the CCCV charging of a C/LiMn

18650 cell at 1.4 A with a voltage limit of 4.2 V, and a C/ LiCoO

cell at 1.65 A and 4.2

V, is shown in Fig. 35.84. Initially, as the cells are charged at constant current, the state of

charge increases linearly while the cell voltage asymptotically approaches 4.2 V. In the

constant voltage portion of the charge, the current decays as the cell approaches full charge.

Li-ion cells have high coulombic efﬁciency, typically 99.9%, and high energy efﬁciency,

typically 95 to 98%. Because of the absence of parasitic processes, such as the gas forming

reactions common in aqueous systems, more complex charge methodologies, such as pulse

charging, offer little additional beneﬁt.