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

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LITHIUM-ION BATTERIES 35.79

Cycle number

0 100 200 300 400

Capacity, (Ah)

0.00

0.05

0.10

0.15

2C discharge capacities

C/5 discharge

residual capacity at 1C

FIGURE 35.94 Capacity of a 0.136 Ah C / LiCoO

polymer Li-ion battery when

charged at the 1C rate to 4.2 V (CCCV, 90 min.), and discharged at the 1C rate to

2.8 V, with periodic discharge at the 0.2C and 2C rates, at 21⬚C. (Courtesy of

Telcordia.)

Discharge time, h

012345

Voltage, V

2.5

3.0

3.5

4.0

4.5

C/5

280

cycles

FIGURE 35.95 Battery voltage when discharged at the 0.2C, C or 2C rates at

cycle numbers from 20 to 290, at 21⬚C. (Courtesy of Telcordia.)

35.80 CHAPTER THIRTY-FIVE

100

200

300

400

500

600

700

0 100 200 300 400 500

Cycle Number

Discharge Capacity (mAh)

UPF36 3562

FIGURE 35.96 Capacity of a 0.57 Ah polymer Li-ion battery when

charged at 0.57 A in a CCCV regime to 4.2 V (0.028 A cutoff), and

discharged at 0.57 A to 2.57 V. (Courtesy of Sanyo.)

3.4

3.5

3.6

3.7

3.8

3.9

4.0

4.1

0 100 200 300 400 500

Cycle Number

Cell Thickness (mm)

Internal Resistance (mOhms)

UPF363562

Cell Thickness

Internal Resistance

FIGURE 35.97 Battery internal resistance and thickness for a 0.57 Ah

polymer Li-ion battery charged at 0.57 A in a CCCV regime to 4.2 V (0.028 A

cutoff) and discharged at 0.57 A to 2.75 V. (Courtesy of Sanyo.)

Storage Stability of Polymer C /LiCoO

Batteries. Polymer C/ LiCoO

Li-ion batteries can

sustain storage at elevated temperature, as illustrated in Fig. 35.98, for storage at 60

⬚C, and

in Fig. 35.99 for storage at 80

⬚C. In these tests, batteries were cycled at the C/5 rate, stored,

then cycled at either the C/2 or C/5 rates. As shown, after storage at 60

⬚Cor80⬚ C, ap-

proximately 7% capacity loss was observed.

LITHIUM-ION BATTERIES 35.81

Cycle number

0 20406080

Capa city, Ah

0.0

0.1

0.2

0.3

C/5

discharge rate: C/2

storage loss

C/5

FIGURE 35.98 Capacity fade of a C/ LiCoO

polymer Li-ion battery

when cycled at 21⬚C after storage fully charged at 60⬚C for seven days.

(Courtesy of Telcordia.)

Cycle number

020406080

Capacity, (Ah)

0.0

0.1

0.2

0.3

C/5 discharge rate: C/2

storage loss

C/5 C/5

FIGURE 35.99 Capacity fade of a C / LiCoO

polymer Li-ion battery

when cycled at 21⬚C after storage fully charged at 80⬚C for seven days.

(Courtesy of Telcordia.)

35.7.4 Performance of C /LiMn

-type Polymer Li-ion Batteries

The electrical performance of polymer Li-ion batteries that employ the C/LiMn

chemistry

is comparable to other Li-ion batteries. The voltage of a C /LiMn

battery when discharged

at 0.5C then charged in a CCCV regime at the 0.5C rate to 4.2 V is indicated in Fig. 35.100.

As shown, the batteries provide slightly higher average voltage than C/LiCoO

-type batteries,

3.8 V, although their speciﬁc energy and energy density are lower than comparable batteries

35.82 CHAPTER THIRTY-FIVE

0123456

3.0

3.2

3.4

3.6

3.8

4.0

4.2

Charge 4.2V

Constant Voltage

Charge C/2

Constant Current

Rest

Open Circuit

C/2 Discharge

Voltage (Volts)

Test Time (hrs)

FIGURE 35.100 Voltage as a function of time for a 3 Ah C /LiMn

polymer Li-ion battery discharged and charged at the 0.5C rate. (Courtesy

of Valence Technology.)

FIGURE 35.101 Polymer C/ LiMn

Li-ion batteries. (Courtesy of Valence Technology.)

that employ a cobalt-based chemistry. The batteries also provide a low self discharge rate,

2.5% per month at 23

⬚C and 6% per month at 40⬚C. The manganese-based cathode materials

these batteries employ are regarded as environmentally more benign than their cobalt or

nickel-based analogs, and the batteries are claimed to offer improved safety properties. Figure

35.101 is an illustration of several polymer C /LiMn

Li-ion batteries.

LITHIUM-ION BATTERIES 35.83

Discharge Rate Capability. The rate capability of a C/ LiMn

batteries charged in a

CCCV regime at the 0.5C rate to 4.2 V is illustrated in Fig. 35.102. As shown, the batteries

provide 98% of their capacity at the 0.5C rate, and 85% at the 1C rate. Also, these batteries

provide a ﬂat voltage proﬁle with average voltage of 3.8 V at low rates (0.2C); at higher

rates (1C) the average voltage is lower, typically 3.6 V.

FIGURE 35.102 Rate capability of a C / LiMn

polymer Li-ion battery charged

at the 0.5C rate to 4.2 V in a CCCV regime at 23⬚C. (Courtesy of Valence Technology.)

High and Low Temperature Discharge Capability. The ability of C/LiMn

polymer Li-

ion batteries to provide 0.2C discharge capability at temperatures from 60

⬚Cto⫺20⬚Cis

illustrated in Fig. 35.103. As shown, at temperatures at or above 23

⬚C, the battery voltage

and capacity was little changed. At 0

⬚C, the battery provided over 95% of its capacity; at

⫺10⬚ the battery provided 86% of its capacity, and at ⫺20⬚C the battery provided 46% of

the capacity delivered at 23

⬚C. At ⫺20⬚C the average voltage was 3.5 V, 0.3 V lower than

provided at 23

⬚C. The ability of a C /LiMn

polymer Li-ion cell to provide 1C discharge

capability at temperatures from 23

⬚Cto⫺20⬚C is indicated by the data shown in Fig. 35.104.

As shown, at 0

⬚C the 0.6 Ah cell provided 40% of its capacity, and at ⫺10⬚C, 23%.

Voltage (V)

FIGURE 35.103 Voltage of a 0.6 Ah C / LiMn

polymer Li-ion battery when dis-

charged at the 0.2C rate at temperatures from 60⬚Cto⫺20⬚C. The battery was charged in

a CCCV regime at 0.5C to 4.2 V at 23⬚C. (Courtesy of Valence Technology.)

35.84 CHAPTER THIRTY-FIVE

Cycle Life. Polymer C/LiMn

batteries also provide long cycle life, as illustrated in Fig.

35.105 for a battery cycled at the 0.5C rate. As shown, the battery provided 90% of its initial

capacity after 300 cycles, and 84% after 600 cycles.

0.5

1.5

2.5

3.5

4.5

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Capacity [%]

Voltage [V]

1C Discharge at 23°C

1C Discharge at 0°C

1C Discharge at -10°C

1C Discharge at -20°C

FIGURE 35.104 Voltage of a 0.6 Ah C / LiMn

polymer Li-ion battery when discharged at the 1C rate

at temperatures from 23⬚Cto⫺20⬚C. The battery was charged in a CCCV regime at 0.5C to 4.2V at 23⬚C.

(Courtesy of Valence Technology.)

FIGURE 35.105 Capacity of a C / LiMn

polymer Li-ion battery when charged in a CCCV regime

at the 0.5C rate to 4.2 V and discharged to 3.0 V at the 0.5C rate, at 23⬚C. (Courtesy of Valence

Technology.)

LITHIUM-ION BATTERIES 35.85

35.7.5 Conclusions: Polymer Li-ion Batteries

Polymer Li-ion batteries offer speciﬁc performance comparable to cylindrical and prismatic

Li-ion batteries within a unique, thin form factor. In addition to providing a thin form factor,

the batteries offer many properties desirable for commercial applications including good rate

capability, low self-discharge, long storage stability and the ability to safely sustain physical

or electrical abuse. These products are now being produced in high volume and are being

used in increasing quantities in cell phones and PDAs.

35.8 THIN-FILM, SOLID-STATE Li-ION BATTERIES

A specialized type of Li-ion battery developed for semi-conductor and printed circuit board

(PCB) applications are thin-ﬁlm, solid-state devices. These batteries which employ ceramic

negative, solid electrolyte and positive electrode materials, can sustain high temperatures

(250

⬚C), and can be fabricated by high volume manufacturing techniques on silicon wafers

which are viable as on-chip or on-board power sources for microelectronics.

97,98

Batteries of

this type can be very small, 0.04 cm

⫻ 0.04 cm ⫻ 2.0

␮

m. For microelectronics applications,

all components must survive solder re-ﬂow conditions, nominally 250

⬚C in air or nitrogen

for 10 minutes. Cells with liquid or polymer electrolytes cannot sustain these conditions

because of the volatility or thermal stability of organic components. Further, cells that employ

lithium metal also fail as solder re-ﬂow conditions exceed the melting point of lithium

(180.5

⬚C).

A schematic drawing of a thin-ﬁlm, solid-state Li-ion cell is shown in Fig. 35.106. These

cells are fabricated by sequential layer deposition of the cell components using rf magnetron

sputtering, except for the metallic current collector components which are deposited by DC

magnetron sputtering. The deposition conditions for LiCoO

and lithium phosphorous ox-

ynitride (LiPON) electrolyte are reported in the literature.

The cells are fabricated on a

substrate, typically alumina, quartz, soda-lime glass, or silicon. Positive current collectors of

gold or platinum (0.1

␮

mto0.3

␮

m), over a layer of cobalt (0.01

␮

m to 0.05

␮

m, to

improve adhesion), have been used. Cells using either LiCoO

or LiMn

positive electrode

materials have been fabricated. The positive electrode layer of laboratory test cells is typically

0.05

␮

mto5

␮

m thick and 0.04 cm

to 25 cm

in area, depending on the capacity required

by the application. The electrolyte layer, LiPON, is typically 0.7

␮

mto2

␮

m thick.

Cells with and without negative electrode materials have been fabricated.

100

In cells with

a negative electrode material, SiSn

0.87

1.20

1.72

(SiTON), SnN

, InN

or Zn

have been

used. To accommodate the difference in volumetric capacity of positive and negative elec-

trode materials, the thickness of the negative electrode is typically 7% of the positive elec-

trode. Negative current collectors of copper, titanium, or titanium nitride (0.1

␮

mto0.3

␮

are typical. To enhance the hermeticity of the cell, protective overlayers of LiPON (1

␮

or parylene (6

␮

m) and titanium or aluminum (0.1

␮

m) have been used.

Alternatively, the negative electrode materials may be omitted. A schematic diagram of

this type of cell prior to and after initial charge is illustrated in Fig. 35.107. In these cells,

lithium metal is plated onto the negative current collector when the cell is charged. The

lithium plating-stripping process is efﬁcient with this technology. Thus cells with a negative

electrode material are typically engineered to oversaturate the negative electrode material, or

the negative electrode material is omitted completely.

35.86 CHAPTER THIRTY-FIVE

FIGURE 35.106 Schematic drawing of the construction of a thin-ﬁlm,

solid-state Li-ion cell after an initial charge that lithiates the negative elec-

trode material. (Courtesy of Oak Ridge National Laboratory.)

FIGURE 35.107 Schematic diagram of a thin-ﬁlm ‘‘lithium free’’ solid-state battery prior to and after initial

charge. (Courtesy of Oak Ridge National Laboratory. Reproduced by permission of The Electrochemical Society,

Inc. From Ref. 100.)

35.8.1 Electrical Performance of Thin-ﬁlm, Solid-state Li-ion Batteries

SiTON/LiCoO

Batteries. The rate capability of a SiTON/LiCoO

battery before any ther-

mal treatment is illustrated in Fig. 35.108. As shown, the battery provided a discharge current

density up to 5 mA/ cm

, comparable to cylindrical Li-ion batteries, within a voltage range

of 4.2 V to 2.7 V. The utilization of the negative electrode material (anode) was high, 600

mAh/g at 2 mA/cm

These batteries are designed for use in microelectronics applications where all components

must sustain solder reﬂow processes, typically a heat treatment at 250

⬚C for 10 minutes. To

demonstrate the ability to sustain these conditions, Figure 35.109 shows discharge curves

before and after heat treatment at 250

⬚C for 10 minutes or 1 hour. As shown, the capacity

of the battery increased by 20% as a result of the 10 minute treatment, indicating that solder

re-ﬂow processes improve battery performance. This improvement has been suggested to

result from improved ionic conductivity and decreased charge transfer resistance of the

LiPON electrolyte as a result of the heat treatment.

Heat treatment also improved the rate

capability of the battery, as illustrated in Fig. 35.110. As shown, at 5 mA/ cm

, between 4.2

V and 2.7 V, the utilization of the SiTON was 450 mAh/g, 30% higher that observed before

heat treatment. In addition, discharge at 10 mA /cm

and 20 mA/cm

was demonstrated.

LITHIUM-ION BATTERIES 35.87

FIGURE 35.108 Rate capability of a SiTON / LiPON / LiCoO

bat-

tery. Speciﬁc capacity and volumetric capacity are based on the as-

deposited mass and volume of SiTON. (Courtesy of Oak Ridge Na-

tional Laboratory. Reproduced from the Journal of Power Sources, Vol.

81, 1999, with permission from Elsevier Science.)

FIGURE 35.109 Voltage of a SiTON/ LiCoO

battery when discharged

at 25⬚Cat1mA/cm

before and after heat treatment at 250⬚C for 10

minutes or 1 hour. (Courtesy of Oak Ridge National Laboratory. Repro-

duced from the Journal of Power Sources, Vol. 81, 1999, with permission

from Elsevier Science.)

35.88 CHAPTER THIRTY-FIVE

FIGURE 35.110 Rate capability of a SiTON/ LiPON/ LiCoO

battery after treatment at 250⬚C in air for 1 hour. Speciﬁc capacity

and volumetric capacity are based on the as-deposited mass and

volume of SiTON. (Courtesy of Oak Ridge National Laboratory.

Reproduced from the Journal of Power Sources, Vol. 81, 1999, with

permission from Elsevier Science.)

Solid-state SiTON/ LiCoO

batteries offer high cycle life, as illustrated in Fig. 35.111 for

a cathode heavy cell cycled initially between 3.93 V and 2.7 V for 3000 cycles, then between

4.1 V and 2.7 V for 10,000 cycles, all at 0.08 mA/cm

at 25⬚C. When the upper voltage

limit was set to 3.93 V, no Li-plating occurred, whereas with the upper voltage limit set to

4.1 V, 30% of the capacity occurred while the negative electrode was at 0 V vs. lithium. In

the initial 3000 cycles, the capacity fade rate was 0.001% per cycle, whereas with the higher

upper voltage limit, the capacity fade rate was 0.002% per cycle while the cell capacity was

initially increased over 40%.

FIGURE 35.111 SiTON speciﬁc capacity when cycled in a SiTON/

LiCoO

battery between either 3.93 V and 2.7 V or 4.1 V and 2.7 V,

at 0.08 mA / cm

at 25⬚C. (Courtesy of Oak Ridge National Labora-

tory. Reproduced from the Journal of Power Sources, Vol. 81, 1999,

with permission from Elsevier Science.)