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

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13.16 CHAPTER THIRTEEN

FIGURE 13.15 Effect of temperature on voltage—DA675 zinc / air battery. (Courtesy

of Duracell, Inc.)

13.4.9 Storage Life

Four principal mechanisms affect the capacity of zinc /air batteries during storage and op-

erating service. One mechanism, self-discharge of the zinc (corrosion), is an internal reaction;

the other three are caused by gas transfer. The gas transfer mechanisms are direct oxidation

of the zinc anode, carbonation of the electrolyte and electrolyte water gain or loss.

During storage the air access holes of a zinc/ air battery can be sealed to prevent gas

transfer decay. A typical material for sealing a battery is a polyester tape. Note that, unlike

conventional batteries, one of the zinc /air cell’s reactants, oxygen, is sealed outside the cell

during storage. This characteristic gives zinc /air batteries excellent shelf-life performance.

The primary mechanism affecting the shelf-life of a zinc /air battery is the self-discharge

reaction. Zinc is thermodynamically unstable in an alkaline solution (electrolyte) and reacts

to form zinc oxide (discharged zinc) and hydrogen gas. (An additional advantage of zinc/

air batteries is that hydrogen evolved during the reaction is vented through the sealing tape

to prevent the pressure buildup that can cause cell deformation in conventional batteries.)

This reaction is controlled by additives to the zinc. Results of shelf-life evaluation of DA675

zinc/ air batteries at room ambient conditions over a 5-year storage period are presented in

Table 13.4. Capacity retention over this period is 85% of initial capacity, yielding an average

capacity loss per year of less than 3%.

Elevated temperatures will increase the rate of the self-discharge reaction dramatically.

The capacity loss after 28 days of storage at 54

⬚C, averaged about 3%. Storage life at high

temperatures can be optimized through tradeoffs between other performance parameters and

choice of cell and battery design components.

ZINC / AIR BATTERIES—BUTTON CONFIGURATION 13.17

TABLE 13.4 Capacity Retention vs. Storage Time at 20⬚C*—Zinc /Air

Battery, 675-Size

Storage, years

Average

capacity,

mAh

% change from

initial capacity

Average % change

per annum

1.8

5.0

523

497

452

⫺5.0

⫺13.5

⫺2.8

⫺2.7

* 1.8-year data are actual test data: 5-year data are estimates based on actual

studies conducted on larger cell sizes.

13.4.10 Factors Affecting Service Life

The combination of the effects of self-discharge and gas transfer degradation determines the

service life performance of a zinc/air battery. For most applications water transfer is the

dominant factor. However, under some conditions electrolyte carbonation and direct oxida-

tion mechanisms can adversely affect performance.

Carbonation of Electrolyte. Carbon dioxide, which is present in the atmosphere at a con-

centration of approximately 0.04%, reacts with an alkaline solution (electrolyte) to form an

alkali metal carbonate and bicarbonate. Zinc/air batteries can be satisfactorily discharged

using a carbonated electrolyte, but there are two disadvantages of extreme carbonation: (1)

vapor pressure of the electrolyte is increased, aggravating water vapor loss in low-humidity

conditions, and (2) crystals of carbonate formed in the cathode structure may impede air

access, eventually causing cathode damage with subsequent deterioration of cathode per-

formance. As indicated in Fig. 13.16 carbonation must be extreme to be detrimental to cell

performance in most applications.

Direct Oxidation. The zinc anode of a zinc /air battery can be oxidized directly by oxygen

which enters the cell and dissolves in and diffuses through the electrolyte. Measurements of

the effect of direct oxidation on cell capacity have been predicted experimentally,

using

advanced microcalorimetry techniques to predict direct oxidation effects on DA675 type cells

(cells open, not sealed). This research indicates a capacity loss of less than 1.5% of rated

capacity per year at 25

⬚C and less than 5% per year at 37.5⬚C.

The combined effect of oxidation and self-discharge on fresh batteries, open to the am-

bient, yields a predicted capacity loss of less than 4% per year. However, the typical useful

service life for a zinc/air battery as presented in Table 13.2a is about 3 months.

Effect of Water Vapor Transfer on Service Life. The decay mechanism determining the

useful service life is water vapor transfer. It occurs when a partial pressure difference exists

between the vapor pressure of the electrolyte and the surrounding environment. As indicated

previously, a cell with a typical electrolyte, consisting of 30% concentration of potassium

hydroxide, will lose water when the humidity at room temperature is below 60% and will

gain water at humidities above 60%. Excessive water loss increases the concentration of the

electrolyte and can eventually cause the cell to fail because of inadequate electrolyte to

13.18 CHAPTER THIRTEEN

FIGURE 13.16 Effect of electrolyte carbonation in 675-size zinc/ air cell (KOH electrolyte).

(a) On internal impedance at 20⬚C (4000 Hz). (b) On voltage-current proﬁle at 20⬚C. (From

Ref. 8; courtesy of Duracell, Inc.)

maintain the discharge reaction. Excessive water gain dilutes the electrolyte, which also

reduces conductivity. Furthermore, the catalyst layer of the air cathode will ﬂood under

sustained water gain conditions, reducing electrochemical activity and eventually causing

cell failure.

The design of a zinc/air battery can be optimized to compensate for water transfer for a

speciﬁc set of operating conditions. Tradeoffs can be made between the volume and com-

position of the electrolyte, the amount of zinc, and the degree of gas diffusion regulation to

maximize service life. For most applications and cell types, diffusion control is the most

important variable.

ZINC / AIR BATTERIES—BUTTON CONFIGURATION 13.19

The balance between performance and service life as related to water transfer rates is

addressed in Table 13.5. This table compares the weight loss and impedance changes of four

commercially available 312-size zinc/air batteries, typically used in hearing aids. The bat-

teries were exposed to 14 and 28 days of ambient air storage after which time their water

weight loss and 1-kHz AC impedance were measured. The variation in this table is primarily

related to battery design. Battery A, for example, was designed with a high air diffusion

cathode for better power capability. However, the low barrier to gas diffusion allows for

more rapid water loss from the cell. Subsequently the A battery is not designed for a low-

rate discharge since it will reach end of life earlier due to increased water loss and internal

impedance. On the other hand, battery D is designed for lower gas diffusion rates, which

allows for more of a medium power capability, but will deliver longer service under low-

rate drain conditions as a result of its lower rate of water loss. Batteries B and C in Table

13.5 lie in the midrange of A and D, achieving neither the highest power capability nor the

longest operating life. The speciﬁc performance characteristics for the 312-size zinc /air bat-

teries are useful in matching power capabilities to the ampliﬁcation requirements in common

hearing aids to achieve the best performance level.

TABLE 13.5 Water Weight and Battery Impedance

Changes for Four Commercialy Available 312-Size Zinc /

Air Button Batteries Exposed to Ambient Conditions for

14–28 Days

Cumulative water weight loss, mg

ABCD

Storage time*

14 days

28 days

9.1

12.2

5.9

7.5

7.3

9.3

0.3

1.0

Impedance,

⍀†

Initial

Final (28 days)

2.3

70.8

4.7

18.0

3.8

15.1

4.3

8.8

Relative change

⫻30 ⫻4 ⫻4 ⫻2

* Relative Humidity during storage—55 Ⳳ 5%.

† AC impedance measured at 1000 Hz and 10 mA.

The effect of diffusion control on water vapor transfer rates for three zinc/air battery

sizes is presented in Table 13.6. Actual instantaneous water transfer rates at a given envi-

ronment will vary throughout the life of the battery, depending on the length of exposure.

As a battery gains or loses water, transfer rates will decrease because the electrolyte equi-

librium relative humidity moves toward the ambient relative humidity. The ﬁgures presented

in Table 13.6 represent average rates computed over the indicated exposure period. Actual

average rates over the life of the battery would be lower.

The effect of continued moisture loss or gain from the electrolyte is illustrated in Fig.

13.17. This ﬁgure shows an intermittent discharge of a zinc/ air battery at 30, 60, and 90%

relative humidity. The least amount of moisture transfer occurs at the 60% relative humidity

condition and the battery delivers the maximum service.

Table 13.7 lists data for zinc /air 675-size battery tested after 14 and 28 days of storage,

unsealed and exposed to various relative humidity conditions. The effects of electrolyte loss

at each of these conditions is presented. The batteries had not been discharged prior to the

test. It is evident that high relative humidity is more detrimental to performance retention,

leading to battery capacity degradation.

13.20 CHAPTER THIRTEEN

TABLE 13.6 Relative Degree of

Environmental Tolerance

Relative

humidity

Ⳳ5%, %

Zinc/ air battery type*

230-size 312-size 675-size

⫺0.047

⫺0.057

⫺0.036

⫺0.084

⫺0.027

⫹0.018

* Storage periods 230-Size—21 days; 312-size—28

days; 675-size—30 days.

FIGURE 13.17 Zinc / air battery discharged at 21⬚C at various

levels of relative humidity. (Courtesy of Duracell, Inc.)

TABLE 13.7 Weight and Capacity Changes as a Function of Storage at Normal and Extreme Relative Humidity

Conditions—675-size Zinc/ Air Battery

Relative

humidity,

Weight loss or gain, mg

0 days 10 days 30 days

Delivered capacity, mAh

0 days 10 days 30 days

⫺152

0.99

3.28

⫺2.51

1.56

3.54

500

465

490

176

283

410

ZINC / AIR BATTERIES—BUTTON CONFIGURATION 13.21

The conditions of use of a battery also affect its performance. Batteries enclosed in a

sealed battery compartment (with allowance for air access) or other enclosure undergo less

performance loss due to water vapor transmission than batteries exposed in the open air.

Batteries exposed to daily indoor and outdoor relative humidity conditions will undergo water

vapor transmission cycling which tends to average out the effects of both environments.

Indoor relative humidities tend to be closer to the conditions for recommended use (40 to

60% RH).

Note that the larger batteries such as the 675-size have greater tolerance to the detrimental

effects of water gain or loss. This is typical in a comparison of batteries of different sizes.

Larger batteries have more electrolyte and also a greater anode-free volume, making them

more tolerant to water loss and gain conditions, respectively.

The operational life of zinc /air battery is most dependent on the control of gas transmis-

sion into and out of the cell. It is evident that water vapor transmission is the key factor in

extending the service life for these batteries. A key area for research and development relating

to zinc /air batteries is focused on membrane technology. A selectively permeable gas dif-

fusion membrane, which allows air diffusion into the cell but excludes or greatly reduces

water vapor transmission, will greatly broaden the range of application for zinc/ air batteries.

Papers and patent disclosures over the last few years have discussed a series of new materials

under study.

18–20

REFERENCES

1. G. W. Elmore and H. A. Tanner, U.S. Patent 3,419,900.

2. A. M. Moos, U.S. Patent 3,267,909.

3. R. G. Biddick, U.S. Patent 4,129,633.

4. E. Yeager, ‘‘Electrochemical Catalysis for Oxygen Electrodes,’’ Rep. LBL-25817, Lawrence Berkeley

Lab., Calif. 1988.

5. C. Warde and A. D. Glasser, U.S. Patent 3935027.

6. B. Szczesniak, et al., Abstract Number 280, Joint International Meeting of ECS and ISE, Paris, 1997.

7. M. Ohashi, H. Watabe, and H. Ogata, Japanese Patent Kokai 9-289045.

8. T. Saeki, T. Watabe, and S. Kobayashi, Japanese Patent Kokai 8-338836 and 8-315870.

9. K. Yoshida and M. Watabe, U.S. Patent 4,380,567.

10. R. Dopp, J. Ottman and J. Passanti, U.S. Patent 5,650,246.

11. A. Borbely and J. Molla, U.S. Patent 4,894,296.

12. A. Ohta, Y. Morita, et al., ‘‘Manganese Oxide as a Catalyst for Zinc-Air Cells,’’ Proc. Battery

Material Symp., 1985.

13. J. Passanti and R. Dopp, U.S. Patent 5,308,711.

14. J. Ottman, B. Dopp and J. Burns, U.S. Patent 5,567,538.

15. H. Konishi and T. Yokoyama, ‘‘Air Cells for Pagers,’’ National Tech. Rep., vol. 37, no. 1, JEC Press,

Cleveland, Ohio, 1991.

16. J. W. Cretzmeyer, H. R. Espig, and J. C. Hall, ‘‘Commercial Zinc-Air Batteries,’’ Power Sources,

Vol. 6, Oriel Press, Newcastle-upon-Tyne, U.K., 1977.

17. S. Bender, J. W. Cretzmeyer, and J. C. Hall, ‘‘Long Life Zinc-Air Cells as a Power Source for

Consumer Electronics, in Progress in Batteries and Solar Cells, vol. 2, JEC Press, Cleveland, Ohio,

1979.

18. T. Takamura, Y. Sato, M. Susuki, T. Nakamura, and K. Sasaki, ‘‘High Performance Zn-Air Cell

Using Gas-Selective Membranes,’’ Proc. Int. Power Sources Symp., Brighton, U.K., The Paul Press,

London, 1985.

19. M. Yoshino, S. Noya, and M. Yanagihara, Japanese patednt Kokai 2-216755 and 2-216756.

20. N. Yoshino, S. Noya, A. Hanabusa, and N. Yangihara, Japanese Patent Kokai 3-108255, 3-108256,

and 3-108257.

14.1

CHAPTER 14

LITHIUM BATTERIES

David Linden and Thomas B. Reddy

14.1 GENERAL CHARACTERISTICS

Lithium metal is attractive as a battery anode material because of its light weight, high

voltage, high electrochemical equivalence, and good conductivity. Because of these outstand-

ing features, the use of lithium has dominated the development of high-performance primary

and secondary batteries during the last two decades. (See Chap. 34 and 35 covering lithium

secondary batteries.)

Serious development of high-energy-density battery systems was started in the 1960s and

concentrated on nonaqueous primary batteries using lithium as the anode. The lithium bat-

teries were ﬁrst used in the early 1970s in selected military applications, but their use was

limited as suitable cell structures, formulations, and safety considerations had to be resolved.

Lithium primary cells and batteries have since been designed, using a number of different

chemistries, in a variety of sizes and conﬁgurations. Sizes range from less than 5 mAh to

10,000 Ah; conﬁgurations range from small coin and cylindrical cells for memory backup

and portable applications to large prismatic cells for standby power in missile silos.

Lithium primary batteries, with their outstanding performance and characteristics, are

being used in increasing quantities in a variety of applications, including cameras, memory

backup circuits, security devices, calculators, watches, etc. Nevertheless, lithium primary

batteries have not attained a major share of the market as was anticipated, because of their

high initial cost, concerns with safety, the advances made with competitive systems and the

cost-effectiveness of the alkaline/manganese battery. World-wide sales of lithium primary

batteries for 1999 have been estimated at $1.1 billion.

14.1.1 Advantages of Lithium Cells

Primary cells using lithium anodes have many advantages over conventional batteries. The

advantageous features include the following:

1. High voltage: Lithium batteries have voltages up to about 4 V, depending on the cathode

material, compared with 1.5 V for most other primary battery systems. The higher voltage

reduces the number of cells in a battery pack by a factor of at least 2.

2. High speciﬁc energy and energy density: The energy output of a lithium battery (over

200 Wh /kg and 400 Wh /L) is 2 to 4 or more times better than that of conventional zinc

anode batteries.

14.2 CHAPTER FOURTEEN

3. Operation over a wide temperature range: Many of the lithium batteries will perform

over a temperature range from about 70 to

⫺40⬚C, with some capable of performance to

150

⬚C or as slow as ⫺80⬚C.

4. Good power density: Some of the lithium batteries are designed with the capability to

deliver their energy at high current and power levels.

5. Flat discharge characteristics: A ﬂat discharge curve (constant voltage and resistance

through most of the discharge) is typical for many lithium batteries.

6. Superior shelf life: Lithium batteries can be stored for long periods, even at elevated

temperatures. Storage of up to 10 years at room temperature has been achieved and

storage of 1 year at 70

⬚C has also been demonstrated. Shelf lives over 20 years have been

projected from reliability studies.

The performance advantages of several types of lithium batteries compared with conven-

tional primary and secondary batteries, are shown in Secs. 6.4 and 7.3. The advantage of

the lithium cell is shown graphically in Figs. 7.2 to 7.9, which compare the performance of

the various primary cells. Only the zinc/air, zinc/mercuric oxide, and zinc/silver oxide cells,

which are noted for their high energy density, approach the capability of the lithium systems

at 20

⬚C. The zinc /air cell, however, is very sensitive to atmospheric conditions; the others

do not compare as favorably on a speciﬁc energy basis nor at lower temperatures.

14.1.2 Classiﬁcation of Lithium Primary Cells

Lithium batteries use nonaqueous solvents for the electrolyte because of the reactivity of

lithium in aqueous solutions. Organic solvents such as acetonitrile, propylene carbonate, and

dimethoxyethane and inorganic solvents such as thionyl chloride are typically employed. A

compatible solute is added to provide the necessary electrolyte conductivity. (Solid-state and

molten-salt electrolytes are also used in some other primary and reserve lithium cells; see

Chaps. 15, 20, and 21.) Many different materials were considered for the active cathode

material; sulfur dioxide, manganese dioxide, iron disulﬁde, and carbon monoﬂuoride are now

in common use. The term ‘‘lithium battery,’’ therefore, applies to many different types of

chemistries, each using lithium as the anode but differing in cathode material, electrolyte,

and chemistry as well as in design and other physical and mechanical features.

Lithium primary batteries can be classiﬁed into several categories, based on the type of

electrolyte (or solvent) and cathode material used. These classiﬁcations, examples of mate-

rials that were considered or used, and the major characteristics of each are listed in Table

14.1.

Soluble-Cathode Cells. These use liquid or gaseous cathode materials, such as sulfur di-

oxide (SO

) or thionyl chloride (SOCl

), that dissolve in the electrolyte or are the electrolyte

solvent. Their operation depends on the formation of a passive layer on the lithium anode

resulting from a reaction between the lithium and the cathode material. This prevents further

chemical reaction (self-discharge) between anode and cathode or reduces it to a very low

rate. These cells are manufactured in many different conﬁgurations and designs (such as

high and low rate) and with a very wide range of capacities. They are generally fabricated

in cylindrical conﬁguration in the smaller sizes, up to about 35 Ah, using a bobbin construc-

tion for the low-rate cells and a spirally wound (jelly-roll) structure for the high-rate designs.

Prismatic containers, having ﬂat parallel plates, are generally used for the larger cells up to

10,000 Ah in size. Flat or ‘‘pancake-shaped’’ conﬁgurations have also been designed. These

soluble cathode lithium cells are used for low to high discharge rates. The high-rate designs,

using large electrode surface areas, are noted for their high power density and are capable

of delivering the highest current densities of any active primary cell.

14.3

TABLE 14.1 Classiﬁcation of Lithium Primary Batteries*

Cell

classiﬁcation

Typical

electrolyte

Power

capability Size, Ah

Operating

range,

⬚C

Shelf

life,

years

Typical

cathodes

Nominal

cell

voltage,

Key

characteristics

Soluble cathode

(liquid or gas)

Organic or

inorganic

(w/ solute)

Moderate to

high power,

0.5 to 10,000

⫺80 to 70 5–20 SO

SOCl

3.0

3.6

3.9

High energy

output, high power

output, low-

temperature

operation, long

shelf life

Solid cathode Organic

(w/ solute)

Low to

moderate

power, mW-W

0.03 to 33

⫺40 to 50 5–8 V

AgV

5.5

CrO

MnO

O(PO

)

(CF)

CuS

FeS

CuO

3.3

3.2

3.1

3.0

2.6

1.7

1.5

High energy output

for moderate

power

requirements,

nonpressurized

cells

Solid

electrolyte (see

Chap. 15)

Solid state Very low

power,

␮

0.003 to 0.5 0 to 100 10–25 PbI

/PbS/Pb

(P2VP)

1.9

2.8

Excellent shelf life,

solid state—no

leakage, long-term

microampere

discharge

*For reserve batteries; see Chaps. 20 and 21.

14.4 CHAPTER FOURTEEN

Solid-Cathode Cells. The second type of lithium anode primary cells uses solid rather than

soluble gaseous or liquid materials for the cathode. With these solid cathode materials, the

cells have the advantage of not being pressurized or necessarily requiring a hermetic-type

seal, but they do not have the high-rate capability of the soluble-cathode systems. They are

designed, generally, for low- to medium-rate applications such as memory backup, security

devices, portable electronic equipment, photographic equipment, watches and calculators,

and small lights. Button, ﬂat, and cylindrical-shaped cells are available in low-rate and the

moderate-rate jelly-roll conﬁgurations. A number of different solid cathodes are being used

in lithium primary cells, as listed in Table 14.1. The discharge of the solid-cathode cells is

not as ﬂat as that of the soluble-cathode cells, but at the lower discharge rates and ambient

temperature their capacity (energy density) may be higher than that of the lithium/ sulfur

dioxide cell.

Solid-Electrolyte Cells. These cells are noted for their extremely long storage life, in excess

of 20 years, but are capable of only low-rate discharge in the microampere range. They are

used in applications such as memory backup, cardiac pacemakers, and similar equipment

where current requirements are low but long life is critical (see Chap. 15).

In Fig. 14.1 the size or capacity of these three types of lithium cells (up to the 30-Ah

size) is plotted against the current levels at which they are typically discharged. The ap-

proximate weight of lithium in each of these cells is also shown.

FIGURE 14.1 Classiﬁcation of lithium primary cell types.