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

Подождите немного. Документ загружается.

SOLID-ELECTROLYTE BATTERIES 15.19

FIGURE 15.17 Discharge data for D-cell diameter Li /I

battery at 25⬚C. (Courtesy of

Catalyst Research Corp.)

15.3.5 Self-Discharge

In addition to the ohmic and nonohmic polarization losses there are two other mechanisms

for capacity loss in the Li/I

battery system. The ﬁrst is self-discharge. It occurs by the direct

combination of lithium and iodine which has diffused through the lithium iodide layer to

reach the lithium anode. The amount of self-discharge observed in these batteries is depen-

dent on the effective thickness of the lithium iodide discharge layer. For this reason the

largest percentage of self-discharge occurs early in the battery’s life when the lithium iodide

layer is very thin. In fact, at a discharge rate of 1 to 2

␮

A/cm

virtually all self-discharge

loss occurs by the time the battery is 25% depleted. Figure 15.18 shows a plot of power lost

FIGURE 15.18 Power (heat) loss due to self-discharge vs. discharge

state for typical Li / I

battery (calorimetric measurements made at

open-circuit voltage). (Courtesy of Medtronic, Inc.)

15.20 CHAPTER FIFTEEN

FIGURE 15.19 Capacity and loss projections for 2.0-Ah stoichiometric capacity

Li/I

battery. a—loss to 1:1 adduct formation: b—loss to iodination reaction: c—

projected loss to self-discharge: d—projected loss to polarization: e—net utilizable

battery capacity. (Courtesy of Medtronic, Inc.)

to self-discharge versus state of discharge for a 2000-mAh stoichiometric capacity Li/I

medical battery at 37⬚C. These measurements were made using a microcalorimeter. The

amount of self-discharge observed in the batteries precoated with a layer of P2VP is a little

greater than in the batteries which do not receive this treatment. This is because the diffusion

path between the cathode depolarizer and the lithium anode is thinner than in the uncoated

batteries. However, the amount of self-discharge in any of these batteries is 10% or less

(depending on the discharge rate) of the rated capacity of the cell over a 10 to 15-year

lifetime and is therefore small compared to most battery systems. Calorimetric measurements

have shown that self-discharge losses are smaller while current is being drawn from the

battery. Most estimates (including that above) are made at open circuit. Therefore they over-

estimate self-discharge losses by as much as 100%.

15.3.6 Other Performance Losses

The total iodine utilization in the Li/I

battery depends on the initial ratio of iodine to donor

material in the cathode depolarizer as well as loss due to self-discharge. The iodine and

amine nitrogen form a very strong 1:1 complex which is not dischargeable at a useful voltage.

For this reason the amount of iodine that can be discharged is limited to that between the

initial starting ratio of the battery material depolarizer and that of the 1:1 complex. In ad-

dition, the P2VP used as a donor material in these batteries is chemically attacked by the

iodine in the battery. The result is that approximately another one-half mole of iodine per

mole of nitrogen atoms in the donor materials becomes unavailable for discharge.

Thus the

maximum amount of discharge capacity is equal to the iodine that lies between the initial

cathode ratio and about a 1.5:1 ﬁnal ratio. This value does not include the self-discharge

and polarization losses discussed.

The effect of all losses upon the available capacity as a function of rate is summarized

in Fig. 15.19 for a battery at 37

⬚C. Here the deliverable capacity is estimated by starting

with the stoichiometric capacity and subtracting the losses and limitations which arise from

the various processes described. This battery had an initial cathode-to-donor ratio of 6.2 mol

iodine per pyridine ring (15:1 weight ratio) in the cathode complex. The maximum utilization

is predicted to be 60% of stoichiometric capacity for this ratio of iodine to P2VP. The mole

ratio of iodine to donor material ranges from 6 to 8 in currently available batteries. The

achievable utilization will depend on this ratio. (Most literature for commercial batteries

gives the initial ratio in terms of weight ratio of iodine to donor material.)

SOLID-ELECTROLYTE BATTERIES 15.21

15.3.7 Effect of Temperature

Since the majority of these batteries has been used as power sources for heart pacemakers,

most experience with them is at body temperature (37

⬚C). However, testing has been done

at temperatures between

⫺10 and 60⬚C. These results are more important for the nonmedical

batteries. Figure 15.20 shows the variation of maximum continuous current for the CRC D

battery as a function of temperature. Hard data exist between

⫺10 and 50⬚C. Performance

at the lower temperature is reduced due to the low conductivity of the depolarizer and LiI.

At 60

⬚C, self-discharge is increased along with the rate of other parasitic reactions, although

the battery is usable at this temperature. Manufacturers give operating temperature ranges

for nonmedical batteries between

⫺20 or 0 and 50⬚C. The temperature at which best per-

formance can be expected is between room temperature and 40

⬚C.

FIGURE 15.20 Maximum continuous-current capability of Li /I

battery vs. temperature. (Courtesy of Catalyst Research Corp.)

15.22 CHAPTER FIFTEEN

TABLE 15.7 Solid-State Ag/ I

Batteries*

Ag/Me

Single-cell voltage, V 0.662 0.650

Battery open-circuit voltage, V 3.31 3.25

Internal resistance,

⍀ 30 35

* 1.27 cm diameter ⫻ 1.9 cm height; capacity ⫽ 40 mAh.

FIGURE 15.21 Discharge of Ag/ Me

battery,

21.5-k⍀ constant load. (From Topics in Applied Phys-

ics, vol. 21, reprinted by permission of the publisher,

Springer-Verlag.)

FIGURE 15.22 Discharge of Ag/ Me

battery.

(From Topics in Applied Physics, vol. 21, reprinted by

permission of the publisher, Springer-Verlag.)

15.4 Ag/RbAg

/Me

C BATTERIES

These solid-electrolyte batteries are based on rubidium silver iodide (RbAg

) as the elec-

trolyte. This material exhibits an unusually high ionic conductivity of 0.26

⍀

⫺

䡠 cm

⫺

⬚C.

This permits battery discharge at much higher current drains than those available with

LiI-based batteries. The initial characteristics of small 40-mAh ﬁve-cell batteries are shown

in Table 15.7. Both tetramethylammonium pentaiodide and enneaiodide have been evaluated

as active cathode agents.

These batteries demonstrated efﬁcient discharge capability at tem-

peratures ranging from

⫺40 to 71⬚C. Constant-load discharge curves are shown in Figs.

15.21 and 15.22.

The two cathodes behave similarly. The Me

cathode has the higher

iodine content and activity, which results in higher energy density and rate capability. The

lower iodine activity of the Me

cathode gives rise to a lower rate of self-discharge and,

therefore, better long-term storage characteristics. The batteries were tested after nearly 20

years of storage.

Discharge curves for the nominal 23⬚C stored batteries are shown in Figs.

15.23 and 15.24. These ﬁve-cell batteries delivered about 36 mAh of capacity to a 2-V

cutoff, equal to 90% of their initial capacity as measured in 1972. The capacity is plotted

in Fig. 15.25 as a function of storage time for the tests that were performed at a constant

resistive load of 64.9 k

⍀ after storage times of 0, 10, and 20 years. Additional tests were

conducted after 25 years of storage at 25

⬚C and ⫺15⬚C. The performance obtained this

storage period was similar to that reported above after 20 years of storage. The average

capacity loss rate was less than 0.5% per year after storage and discharge at room temper-

atures.

SOLID-ELECTROLYTE BATTERIES 15.23

FIGURE 15.23 64.9-k⍀ constant load discharge of Ag/ RbAg

/Me

batteries after 20

years of storage at 25⬚C. Discharge temperature: solid curve—25⬚C, dashed curve—60⬚C.

(From Ref. 29.)

FIGURE 15.24 64.9-k⍀ constant-load discharge of Ag / RbAg

/Me

batteries after 20

years of storage at 25⬚C. Discharge temperature: solid curve—25⬚C: dashed curve—60⬚C.

(From Ref. 29.)

15.24 CHAPTER FIFTEEN

FIGURE 15.25 Capacity of Ag/ RbAg

/Me

batteries as a function

of storage time. (From Ref. 29.)

The results of the tests conﬁrm the long-term stability of solid-electrolyte batteries with

respect to self-discharge losses. However, the batteries stored at

⫺15⬚C suffered from elec-

trolyte disproportionation and the concurrent resistance increase. This disproportionation was

readily reversed by heating the batteries at 60

⬚C for less than 30 min. Following this thermal

treatment, the internal resistances returned to their normal values, and standard discharge

behavior was observed.

The Ag/I

batteries were inherently deﬁcient in two signiﬁcant areas, voltage and size.

The low cell voltage and high equivalent weights and volumes restricted these batteries to

very low energy densities and speciﬁc energies (0.08 Wh /cm

or 13 Wh /kg). Consequently

no commercial application resulted.

REFERENCES

1. B. B. Owens and P. M. Skarstad, ‘‘Ambient Temperature Solid State Batteries,’’ Solid State Ionics

43:665 (1992).

2. B. B. Owens, ‘‘Solid Electrolyte Batteries,’’ in C. W. Tobias (ed.), Advances in Electrochemistry and

Electrochemical Engineering, vol. 8, Wiley, New York, 1971, chap. 1, pp. 1–62.

3. B. B. Owens, J. E. Oxley, and A. F. Sammells, ‘‘Applications of Halogenide Solid Electrolytes,’’ in

S. Geller (ed.), Solid Electrolytes, Topics in Applied Physics, vol. 21, Springer-Verlag, New York,

1977, chap. 4, pp. 67–104.

4. C. C. Liang, ‘‘Solid-State Batteries,’’ Appl. Solid State Sci. 4:95–135 (1974).

5. T. Takahaski, Denki Kagoku 36:402–412, 481–490 (1968).

6. B. B. Owens and P. M. Skarstad, ‘‘Ambient Temperature Solid-State Batteries,’’ in P. Vashishta, J.

N. Mundy, and G. K. Shenoy (eds.), Fast Ion Transport in Solids, Elsevier-North Holland, New

York, 1979, pp. 61–68.

SOLID-ELECTROLYTE BATTERIES 15.25

7. M. Gauthier, A. Belanger, B. Kapfer, and G. Vassort, ‘‘Solid Polymer Electrolyte Lithium Batteries,’’

in J. R. MacCallum and C. A. Vincent (eds.), vol. 2, Polymer Electrolyte Reviews, Elsevier Applied

Science, London, 1989.

8. C. F. Holmes, ‘‘Lithium/ Halogen Batteries,’’ in B. B. Owens (ed.) Batteries for Implantable Bio-

medical Devices, Plenum, New York, 1986.

9. C. A. C. Sequira and A. Hooper, (eds.), Solid State Batteries, NATO ASI ser. 101, Nijhoff Publishers,

Dordrecht, The Netherlands, 1985.

10. B. V. R. Chowdari and S. Radhakrishna (eds.), Materials for Solid State Batteries, Proc. Regional

Workshop, World Scientiﬁc Publ. Co., Singapore, 1986.

11. R. C. Weast (ed.), Handbook of Chemistry and Physics, 59th ed., Chemical Rubber Publishing Co.,

West Palm Beach, Fla., 1978–1979.

12. C. C. Liang, J. Electrochem. Soc. 120:1289 (1973).

13. C. C. Liang and L. H. Barnette, J. Electrochem. Soc. 123:453–458 (1976).

14. J. R. Rea, L. H. Barnette, C. C. Liang, and A. V. Joshi, ‘‘A New High Energy Density Battery

System,’’ in B. B. Owens and N. Margalit (eds.), Proc. Symp. on Biomedical Implantable Applica-

tions and Ambient Temperature Lithium Batteries, vol. 80-4, Electrochemical Society, Princeton,

N.J., 1980, pp. 245–253.

15. C. C. Liang, A. V. Joshi, and N. E. Hamilton, J. Appl. Electrochem. 8:445–454 (1978).

16. D. E. Ginnings and T. E. Phipps, J. Am. Chem. Soc. 52:1340 (1930).

17. B. J. H. Jackson and D. A. Young, J. Phys. Chem. Solids 30:1973–1976 (1969).

18. C. R. Schlaijker and C. C. Liang, ‘‘Solid-State Batteries and Devices,’’ in W. Van Gool (ed.), Fast

Ion Transport in Solids, North Holland, Amsterdam, 1973, pp. 689–694.

19. C. C. Liang, U.S. Patent 3,713,897 (1973).

20. A. M. Stoneham, E. Wade, and J. A. Kilner, Mater. Res. Bull. 14:661–666 (1979).

21. J. R. Rea, DOE Battery and Electrochemical Contractors’ Conf, Arlington, Va., vol. 11, session VII,

Dec. 1979.

22. S. J. Garlock, ‘‘Characteristics of Lithium Solid State Batteries in Memory Circuits,’’ Wescon 81,

San Francisco, Calif., Professional Program Session Rec. 29, Electronic Conventions, Inc., El Se-

gundo, Calif., Sept. 1981.

23. G. M. Phillips and D. F. Untereker, ‘‘Phase Diagram for the Poly-2-vinylpyridine and Iodine Sys-

tem,’’ in B. B. Owens and N. Margalit (eds.), Proc. Symp. on Biomedical Implantable Applications

and Ambient Temperature Lithium Batteries, vol. 80-4, Electrochemical Society, Princeton, N.J.,

1980.

24. P. M. Skarstad, B. B. Owens, and D. F. Untereker, ‘‘Volume Changes on Discharge in Lithium-

Iodine (Poly-2-vinylpyridine) Cells,’’ 152d Electrochem. Soc. Meeting, Atlanta, Oct. 1977, abstract

23.

25. K. R. Brennen and D. F. Untereker, ‘‘Iodine Utilization in Li / I

(Poly-2-vinylpyridine) Batteries,’’

in B. B. Owens and N. Margalit (eds.), Proc. Symp. on Biomedical Implantable Applications and

Ambient Temperature Lithium Batteries, vol. 80-4, Electrochemical Society, Princeton, N.J., 1980.

26. J. P. Phipps, T. G. Hayes, P. M. Skarstad, and D. Untereker, Solid State Ionics 18, 19:1073 (1986).

27. C. L. Schmidt and P. M. Skarstad, ‘‘Development of a Physically-Based Model for the Lithium /

Iodine Battery,’’ in T. Keily and B. W. Baxter (eds.), Power Sources, vol. 13, International Power

Sources Committee, Leatherhead, England, 1991, pp. 347–361.

28. D. L. Warburton, R. F. Bis, and B. B. Owens, ‘‘Five-Year Storage Tests of Solid-State Ag / 1

Batteries,’’ 28th Power Sources Symp., Atlantic City, N.J., June 12–15, 1978.

29. B. B. Owens and J. R. Bottelberghe, ‘‘Twenty Year Storage Test of Ag /RbAg

Solid State

Batteries,’’ Solid State Ionics 62:243 (1993).

30. D. L. Warburton, et al., ‘‘Twenty-ﬁve Year Shelf-life of an Active Primary Battery.’’ Proc. 38th

Power Sources Conf. pp. 89–92 (1998). Cherry Hill, N.J.

P • A • R • T • 3

RESERVE BATTERIES

16.3

CHAPTER 16

RESERVE BATTERIES—

INTRODUCTION

David Linden

16.1 CLASSIFICATION OF RESERVE BATTERIES

Batteries, which use highly active component materials to obtain the required high energy,

high power, and /or low-temperature performance, are often designed in a reserve construc-

tion to withstand deterioration in storage and to eliminate self-discharge prior to use. These

batteries are used primarily to deliver high power for relatively short periods of time after

activation in such applications as radiosondes, fuzes, missiles, torpedoes, and other weapon

systems. The reserve design also is used for batteries required to meet extremely long or

environmentally severe storage requirements.

In the reserve structure, one of the key components of the cell is separated from the

remainder of the cell until activation. In this inert condition, chemical reaction between the

cell components (self-discharge) is prevented, and the battery is capable of long-term storage.

The electrolyte is the component that is usually isolated, although in some water-activated

batteries the electrolyte solute is contained in the cell and only water is added.

The reserve batteries can be classiﬁed by the type of activating medium or mechanism

that is involved in the activation:

Water-activated batteries: Activation by fresh- or seawater.

Electrolyte-activated batteries: Activation by the complete electrolyte or with the electro-

lyte solvent. The electrolyte solute is contained in or formed in the cell.

Gas-activated batteries: Activation by introducing a gas into the cell. The gas can be

either the active cathode material or part of the electrolyte.

Heat-activated batteries: A solid salt electrolyte is heated to the molten condition and

becomes ionically conductive, thus activating the cell. These are known as thermal bat-

teries.

Activation of the reserve battery is accomplished by adding the missing component just

prior to use. In the simplest designs, this is done by manually pouring or adding the elec-

trolyte into the cell or placing the battery in the electrolyte (as in the case of seawater-

activated batteries). In more sophisticated applications the electrolyte storage and the acti-

vation mechanism are contained within the overall battery structure, and the electrolyte is

brought automatically to the active electrochemical components by remotely activating the

16.4 CHAPTER SIXTEEN

activation mechanism. The trigger for activation can be a mechanical or electrical impulse,

the shock and spin accompanying the ﬁring of a shell or missile, and so on. Activation can

be completed very rapidly if required, usually in less than one second. The penalty for

automatic activation is a substantial reduction in the speciﬁc energy and/or energy density

of the battery due to the volume and weight of the activating mechanism. It is therefore not

general practice to rate these batteries in terms of speciﬁc energy or energy density.

The gas-activated batteries are a class of reserve batteries which are activated by intro-

duction of a gas into the battery system. There are two types of gas-activated batteries: those

in which the gas serves as the cathodic active material and those in which the gas serves to

form the electrolyte. The gas-activated batteries were attractive because they offered the

potential of a simple and positive means of activation. In addition, because the gas is non-

conductive, it can be distributed through a multicell assembly without the danger of short-

circuiting the battery through the distribution system. Gas-activated batteries are no longer

in production, however, because of the more advantageous characteristics of other systems.

The thermal or heat-activated battery is another class of reserve battery. It employs a salt

electrolyte, which is solid and, hence, nonconductive at the normal storage temperatures

when the battery must be inactive. The battery is activated by heating it to a temperature

sufﬁciently high to melt the electrolyte, thus making it ionically conductive and permitting

the ﬂow of current. The heat source and activating mechanism, which can be set off by

electrical or mechanical means, can be built into the battery in a compact conﬁguration to

give very rapid activation. In the inactive stage the thermal battery can be stored for periods

of 10 years or more.

16.2 CHARACTERISTICS OF RESERVE BATTERIES

Reserve batteries have been designed using a number of different electrochemical systems

to take advantage of the long unactivated shelf life achieved by this type of battery design.

Relatively few of these have achieved wide usage because of the lower capacity of the reserve

structure (compared with a standard battery of the same system), poorer shelf life after

activation, higher cost, and generally acceptable shelf life of active primary batteries for most

applications. For the special applications that prompted their development, nevertheless, the

reserve structure offers the needed advantageous characteristics.

In recent years, however, the use of reserve batteries has declined because of the improved

storability of active primary batteries and the limited number of applications requiring ex-

tended storage. Most of these applications are for special military weapon systems.

The reserve batteries are usually designed for speciﬁc applications, each design optimized

to meet the requirements of the application. A summary of the major types of reserve bat-

teries, their major characteristics and advantages, disadvantages, and key areas of application

is given in Table 16.1.

Conventional Systems. Reserve batteries employing the conventional electrochemical sys-

tems, such as the Leclanche´ zinc-carbon system, date back to the 1930–1940 period. This

structure, in which the electrolyte is kept in a separate vial and introduced into the cell at

the time of use, was employed as a means of extending the shelf life of these batteries,

which was very poor at that time. Later similar structures were developed using the zinc-

alkaline systems. Because of the subsequent improvement of the shelf life of these primary

batteries and the higher cost and lower capacity of the reserve structure, batteries of this

type never became popular.