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

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LITHIUM BATTERIES 14.85

FIGURE 14.76 Discharge rate vs. capacity of Li/ FeS

and Zn / alkaline / MnO

‘‘AA’’-size batteries at

21⬚C. (Courtesy of Eveready Battery Co, Inc.)

14.10.1 Chemistry

The Li/ FeS

battery uses lithium for the anode, iron disulﬁde for the cathode, and lithium

iodide in an organic solvent blend as the electrolyte. The cell reactions are

⫹

4Li → 4LI ⫹ 4eAnode

⫺

FeS ⫹ 4e → Fe ⫹ 2SCathode

4Li ⫹ FeS → Fe ⫹ 2Li SOverall

Intermediate species are formed during the discharge, but they have not been fully charac-

terized. They are dependent on many variables, including discharge rate and temperature.

Evidence of the intermediate species can be seen in the stepped discharge curve for Li /FeS

batteries on a light drain, as illustrated in Fig. 14.77.

The overall cell reaction for the monosulﬁde electrode is

2Li

⫹ FeS → Fe ⫹ Li S

FIGURE 14.77 Stepped discharge curve of Li / FeS

AA-size batteries on light drain at

21⬚C. 5000-⍀ background with 25-⍀, 1-s / week pulse. (Courtesy of Eveready Battery Co.,

Inc.)

14.86 CHAPTER FOURTEEN

FIGURE 14.78 Cross section and top assembly of Li / FeS

AA-size battery. (Courtesy of Eveready Battery Co., Inc.)

14.10.2 Construction

Li/ FeS

batteries may be manufactured in a variety of designs, including the button and both

bobbin and spiral-wound-electrode cylindrical cells. A bobbin construction is most suitable

for light-drain applications. The spiral-wound-electrode construction is needed for the heav-

ier-drain applications, and it is this design that has been commercialized.

The construction of the spiral-wound cylindrical battery is shown in Fig. 14.78. These

batteries typically have several safety devices incorporated in their design to provide protec-

tion against such abusive conditions as short circuit, charging, forced discharge, and over

heating. Two safety devices are shown in the ﬁgure—a pressure relief vent and a resettable

thermal switch, called a positive thermal coefﬁcient (PTC) device. The safety relief vent is

designed to release excessive internal pressure to prevent violent rupture if the battery is

heated or abused electrically.

LITHIUM BATTERIES 14.87

The primary purpose of the PTC is to protect against external short circuits, though it

also offers protection under certain other electrical abuse conditions. It does so by limiting

the current ﬂow when the cell temperature reaches the PTC’s designed activation temperature.

When the PTC activates, its resistance increases sharply, with a corresponding reduction in

the ﬂow of current and, consequently, internal heat generation. When the battery (and the

PTC) cools, the PTC resistance drops, allowing the battery to discharge again. The PTC will

continue to operate in this manner for many cycles if an abusive condition continues or

recurs. The PTC will not ‘‘reset’’ indeﬁnitely, but when it ceases to do so, it will be in the

high-resistance condition. The characteristics of PTCs (or any other current-limiting devices

in the battery) may place some limitations on performance. These are discussed in more

detail in Sec. 14.10.3.

14.10.3 Performance

Voltage. The nominal voltage of the Li/FeS

system is given as 1.5 V and the open-circuit

voltage of undischarged cells is approximately 1.8 V. The voltage on load drops within

milliseconds, as shown in Fig. 14.79.

Discharge. Li/ FeS

batteries typically have a higher operating voltage and a ﬂatter dis-

charge proﬁle than aqueous zinc /alkaline manganese dioxide 1.5-V batteries. This is illus-

trated in Fig. 14.80, which compares the performance of these two battery systems at rela-

tively light and heavy constant-current discharge rates. These characteristics of the Li /FeS

battery result in higher energy and power output, especially on heavier drains were the

operating voltage differences are greatest.

Typical discharge curves of the AA-size Li/ FeS

battery under constant-resistance, con-

stant-current, and constant-power discharge modes are shown in Figs. 14.81 to 14.83.

Operating Temperature. Li/FeS

batteries are also suitable for use over a broad tempera-

ture range, generally

⫺40 to 60⬚C. As can be seen in Fig. 14.84, service life is improved at

elevated temperatures as it is at room temperature. In some applications there may be further

limits on the maximum discharge temperature due to current limiting, which are part of the

cell or battery device designs. Service life is reduced as the discharge temperature is lowered

below room temperature, though the performance of the Li /FeS

battery is affected much

less by low temperature than are aqueous systems.

Effects of Current-Limiting Devices. Some current-limiting devices, such as fuses and

PTCs, are designed to respond to high temperatures. Both the ambient temperature and

internal cell heating can affect these devices, so any of the following factors may play a

role:

Surrounding air temperature

Thermal insulating properties of battery container

Heat generated by equipment components during use

Cumulative heating effects of multicell batteries

Discharge rates and durations

Frequency and duration of rest periods

It may be necessary to consult the manufacturer or conduct testing to determine limitations

in speciﬁc applications.

14.88 CHAPTER FOURTEEN

FIGURE 14.79 On-load voltage of Li / FeS

AA-size cells. (Courtesy of Eveready Battery Co.,

Inc.)

FIGURE 14.80 Performance of Li / FeS

and Zn / alkaline / MnO

‘‘AA’’-size batteries at 50 and 750

mA continuous discharge at 21⬚C. (Courtesy of Eveready Battery Co, Inc.)

LITHIUM BATTERIES 14.89

FIGURE 14.81 Constant resistance continuous discharge of Li/ FeS

‘‘AA’’-size batteries at 21⬚C(Courtesy

of Eveready Battery Co, Inc.)

Minutes

Voltage

FIGURE 14.82(a) and (b) Constant current continuous discharge of Li/ FeS

‘‘AA’’-size batteries at 21⬚C.

(Courtesy of Eveready Battery Co.)

14.90 CHAPTER FOURTEEN

FIGURE 14.83 Constant power continuous discharge of Li/ FeS

‘‘AA’’-size batteries at 21⬚C. (Courtesy

of Eveready Battery Co, Inc.)

FIGURE 14.84 Performance of Li / FeS

‘‘AA’’-size batteries on a 1000 mA continuous discharge at various temperatures.

(Courtesy of Eveready Battery Co.)

LITHIUM BATTERIES 14.91

TABLE 14.23 Characteristics of Li/ FeS

AA-Size Battery

Dimensions, mm

Height 50

Diameter 14

Weight g 15

Voltage, V

Nominal classiﬁcation 1.5

Open-circuit 1.8

Capacity, at 20

⬚C, Ah

to 0.9 V

1000 mA 2.8

300 mA 2.4

30 mA 2.6

0.3 mA 2.6

Energy density, Wh/ L

1000 mA 324

300 mA 436

30 mA 500

0.3 mA 540

1-kHz impedance,

⍀ 0.18

Source: Eveready Battery Co., Inc.

Impedance. AC impedance is an electrical characteristic that is frequently used as an in-

dicator of performance for aqueous batteries. The correlation is only poor at best with

Li/ FeS

batteries. There is a protective ﬁlm that forms on the surface of the lithium anode.

This ﬁlm is an important factor in the excellent shelf life of the Li /FeS

cell. As the cell

ages, this protective ﬁlm increases with age. As the ﬁlm increases, the impedance does as

well. However, this ﬁlm is easily disrupted when the battery is put on load, making impe-

dance inappropriate as an indicator of expected Li/FeS

battery performance, especially after

storage.

Storage Temperature. Storage at high temperature will reduce the service life of Li/ FeS

batteries, as it will with other systems. However, because of the very low levels off impurities

in the materials used and the high degree of seal effectiveness required in lithium batteries,

service maintenance of Li/FeS

batteries after high-temperature storage is better than ex-

pected with aqueous systems. The typical storage temperature range of Li/FeS

batteries is

⫺40 to 60⬚C, though relatively short excursions above 60⬚C may be possible. In such cases

the temperature at which the pressure relief vent will operate, and the effect of temperature

on cell and battery cases and insulating materials should be understood.

14.10.4 Cell Types and Applications

Table 14.23 lists the characteristics of the cylindrical Li/FeS

AA-size battery that is cur-

rently available commercially. This battery has better high-drain and low-temperature per-

formance than the conventional zinc cells and is intended to be used in applications that

have a high current drain requirement, such as cameras, computers, and cellular phones. An

example of the advantage of the lithium cell, compared to the Zn /alkaline /MnO

battery is

shown in Fig. 14.85, which plots the number of ﬂashes obtained with an autoﬂash SLR

camera. The lithium battery outperforms the alkaline battery by delivering more ﬂashes with

a more rapid recycle time. See Fig. 6.12 for additional comparative data on the use of several

battery types in photoﬂash use.

14.92 CHAPTER FOURTEEN

Button-type Li/FeS

batteries are no longer manufactured. Batteries using the Li/ FeS

system have not been manufactured for commercial use.

FIGURE 14.85 Comparison of number of ﬂashes in automatic camera

for zinc-alkaline and Li /FeS

AA-size batteries. One ﬂash every 30 s with

camera in manual mode. (Courtesy of Eveready Battery Co., Inc.)

14.11 LITHIUM/COPPER OXIDE (Li/CuO) AND LITHIUM/COPPER

OXYPHOSPHATE [Li/Cu

O(PO

)

] CELLS

The lithium /copper oxide (Li /CuO) system is characterized by a high speciﬁc energy and

energy density (about 280 Wh /kg and 650 Wh /L) as copper oxide has one of the highest

volumetric capacities of the practical cathode materials (4.16 Ah /cm

). The battery has an

open-circuit voltage of 2.25 V and an operating voltage of 1.2 to 1.5 V, which makes it

interchangeable with some conventional batteries. The battery system also features long

storability with a low self-discharge rate and operation over a wide temperature range.

Li/ CuO batteries have been designed in button and cylindrical conﬁgurations up to about

3.5 Ah in size, mainly for use in low- and medium-drain, long-term applications for elec-

tronic devices and memory backup. Higher-rate designs as well as hermetically sealed bat-

teries with glass-to-metal seals have also been manufactured.

Figure 14.86 compares the performance of a Li/ CuO AA-size cylindrical battery with

the zinc/alkaline/MnO

battery. The Li/CuO cell has a signiﬁcant capacity advantage at low

discharge rates, but loses this advantage at higher discharge rates.

LITHIUM BATTERIES 14.93

FIGURE 14.86 Comparison of Li / CuO and

Zn / alkaline / MnO

AA-size batteries at 20⬚C.

14.11.1 Chemistry

The discharge reaction of the Li/CuO cell is

2Li

⫹ CuO → Li O ⫹ Cu

The discharge proceeds stepwide, CuO → Cu

O → Cu, but the detailed mechanism has not

been clariﬁed.

1,44

A double-plateau discharge has been observed at high-temperature (70⬚C)

discharges at low rates, which blends into a single plateau under more normal discharge

conditions.

14.11.2 Construction

The construction of the Li /CuO button-type battery shown in Fig. 14.87a is similar to other

conventional and lithium/solid-cathode cells. Copper oxide forms the positive electrode and

lithium the negative. The electrolyte consists of lithium perchlorate in an organic solvent

(dioxolane).

The cylindrical batteries (Fig. 14.87b) use an inside-out bobbin construction. A cylinder

of pure porous nonwoven glass is used as the separator, nickel-plated steel for the case, and

a polypropylene gasket for the cell seal. The can is connected to the cylindrical copper oxide

cathode and the top to the lithium anode.

14.94 CHAPTER FOURTEEN

FIGURE 14.87 Lithium / copper oxide batteries (a) Button conﬁguration. (Courtesy

of Panasonic, Division of Matsushita Electric Corp. of America.)(b) Cylindrical battery,

bobbin construction. (Courtesy of SAFT America, Inc.)

14.11.3 Performance

Button Battery. The performance of the 60-mAh Li/ CuO button cell under various dis-

charge conditions and temperatures is shown in Fig. 14.88.

Cylindrical Bobbin Li/ CuO Battery. Typical discharge curves for this system are shown

in Fig. 14.89. After a high initial load voltage, the discharge proﬁle is ﬂat at the relatively

light loads. The bobbin construction does not lend itself to high-rate discharges and the

battery capacity is signiﬁcantly lowered with increasing discharge rates. The Li /CuO cylin-

drical battery operates over a wide temperature range, typically from

⫺20 to 70⬚C, although

the battery can operate outside these limits, but with changes in the discharge proﬁle or load

capability. Discharge curves at several different temperatures are shown in Fig. 14.90. The

performance of the battery at temperatures from

⫺40 to 70⬚C and at various loads is sum-

marized in Fig. 14.91. The high capacity of the battery at the lighter loads falls off sharply

with increasing load and decreasing temperatures.