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

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RECHARGEABLE LITHIUM BATTERIES (AMBIENT TEMPERATURE) 34.21

One of the major problems of lithium polymer electrolyte systems is the development of

high interfacial resistance at the lithium/ polymer electrolyte interphase.

This resistance

grows with time and could be as high as 10 k

⍀ cm

⫺

This resistance layer is due to the

reactions of lithium with water, other impurities, and the salt anions. Similar to nonaqueous

electrolytes, the solid electrolyte interphase (SEI) also exists in the lithium/ polymer electro-

lyte systems.

In this case, the solid electrolyte interface (SEI) consists of the inorganic

reduction products of the polymer electrolyte and its impurities.

The capacity of a lithium polymer electrolyte battery decreases gradually on cycling. This

capacity loss is most likely related to degradation at the electrode interfaces due to repeated

plating-stripping cycles at the lithium metal anode and the repeated intercalation-

deintercalation cycles at the composite cathode. The cycling performance of lithium polymer

electrolyte cells can be improved by reducing the lithium passivation phenomena and by

improving the cathode morphology and homogeneity (particle size).

The energy density of the SPE batteries is projected to be close to that of the liquid-

electrolyte lithium rechargeable batteries. The thin cell design, however, usually requires a

larger percentage of materials of construction and nonreactive components, which tend to

lower the energy density. Larger electrode areas are also required for a given cell capacity

than with conventional battery design. The thin separator and larger electrode area could

adversely affect the cycle life, safety, and reliability of the battery by increasing the chance

for internal short circuits, lithium dendrite penetration, and other deleterious effects.

Another potential advantage of the solid polymer battery is that the design lends itself to

manufacture by automatic processes and the capability to be easily fabricated in a variety

of shapes and forms. Very thin batteries for cell phones, PDAs and similar applications can

be manufactured. At the other extreme, large thin plates can be manufactured and assembled

in multiplate prismatic or bipolar batteries.

Solid polymer batteries using lithium metal have not yet been introduced in the market-

place, and most of the performance characteristics are based on laboratory prototypes. The

technology offers several potential advantages compared to the other rechargeable lithium

batteries, including high energy density, low self-discharge rate, improved safety, and thin

cell design. The success of this approach will depend on the ability to achieve these advan-

tages, ﬁrst in small cells and batteries and then to be able to scale up the technology to the

larger-size cells and multicell batteries required, for example, for electric vehicles. Lithium

ion batteries using polymer electrolytes have been introduced to the market in 2000.

Inorganic Electrolyte Batteries. The rechargeable lithium batteries with SO

-based inor-

ganic electrolytes are attractive because they can operate at high charge and discharge rates

due to the high ionic conductivity of the electrolyte. Other advantages are a high energy

density, a low self-discharge rate, the ability to accept limited overcharge and overdischarge,

and a wide electrochemical voltage window (5.0 V versus lithium).

Their drawback is the toxicity of the electrolyte and concern with safety problems. High-

capacity fade and relatively low capacity at low temperatures are other disadvantages.

Several types of batteries have been investigated using the SO

-based electrolyte cells

(with LiAlCl

as a solute) and metallic lithium for the negative electrode. These use either

carbon

or CuCl

for the positive electrode material.

With a high-surface-area carbon black such as Ketjen black, the SO

-based LiAlCl

elec-

trolyte forms a complex which is believed to take part in the discharge-charge process as

34.22 CHAPTER THIRTY-FOUR

During overcharge, more lithium is deposited from the electrolyte solution at the anode, and

the decomposition of AlCl

⫺

occurs at the cathode with the generation of free chlorine. This

free chlorine combines with metallic lithium to form LiCl, which subsequently recombines

with AlCl

and regenerates the electrolyte,

⫹

Li ⫹ e → Li

⫺

–

AlCl → AlCl ⫹ Cl ⫹ e

4322

–

Li ⫹ Cl → LiCl

LiCl ⫹ AlCl → LiAlCl

While this scheme provides an overcharge mechanism, the chloride generated will attack

the separator and compromise safety.

With CuCl

as the positive electrode material, the discharge-charge process involves a

simple redox reaction. The high reduction potential of SO

(2.9 V versus lithium on carbon

surfaces) limits the selection of positive electrode materials to only those compounds that

reduce at potentials above the reduction potentials of SO

. Thus CuCl

, which has an open-

circuit potential of 3.45 V and discharges at about 3.35 V, corresponding to the reduction

process of

⫹⫹

Cu ⫹ e → Cu

meets the criteria. The second reduction process,

⫹

Cu ⫹ e → Cu

occurs at about 2.5 V. In principle, the discharge of this Li/CuCl

cell in SO

-based elec-

trolytes should not be permitted beyond 2.9 V, below which the CuCl

electrode would be

passivated by the lithium dithionite produced by the reduction of SO

Although the SO

-based inorganic electrolyte system has been investigated for some time,

the toxicity and the corrosivity of the electrolyte present a potential safety hazard, restricting

commercial development. This system is also known to have severe explosive tendencies for

the reason cited above.

34.3.2 Summary of Design and Performance Characteristics

The different types of rechargeable lithium metal batteries operating at ambient temperature

are classiﬁed in four categories (see Table 34.10).

The cell components and the reaction mechanisms of typical cells for each of these

categories are presented in Table 34.11, and their characteristics are summarized in Table

34.12. Typical discharge curves are shown in Fig. 34.11. Detailed electrical and performance

data are presented in Sec. 34.4.

34.23

TABLE 34.11 Chemistry of Rechargeable Lithium Systems

System Anodes Cathodes Electrolytes Separator

Cell reactions

discharge

—— —



———

冉冊



charge

1. Liquid organic electrolyte, solid

cathode cells:

Lithium molybdenum disulﬁde

(Li/ MoS

)

Lithium manganese dioxide

(Li/Li

0.3

MnO

)

Lithium titanium diosulﬁde

(Li/ TiS

)

Lithium niobium selenide

(Li/ NbSe

)

Lithium/ lithiated cobalt oxide

(Li/Li

CoO

)

Lithium/ lithiated nickel oxide

(Li/Li

NiO

)

MoS

0.3

MnO

TiS

NbSe

CoO

NiO

LiAsF

, PC/EC

LiAsF

, DN,

LiAsF

, 2-MeTHF,

THF

LiAsF

, PC/EC

LiAsF

/LiBF

MF/MA

LiAsF

, MF/MA

Polypropylene

xLi

⫹ MoS



Li MoS



x 2

xLi ⫹ MnO



Li MnO



x 2

xLi ⫹ TiS



Li TiS



x 2

xLi ⫹ NbSe



Li NbSe



x 3

xLi ⫹ Li

⫺

CoO



LiCoO



xLi ⫹ Li

⫺

NiO



LiNiO



2. Polymer electrolyte cells:

Lithium/ vanadium oxide

(Li/PEO/VO

)

Lithium/ titanium disulﬁde

TiS

SPE

—

yLi

⫹ VO





xLi ⫹ TiS

TiS





3. Inorganic electrolyte cells:

Lithium/ sulfur dioxide

(Li/SO

)

Li Carbon (Ketjen

black)

LiAlCl

䡠 xSO

Tefzel

LiAlCl

䡠 3SO

⫹ xC ⫹ 3Li





Lithium/ copper chloride

(Li/ CuCl

)

Li CuCl

LiAlCl

䡠 xSO

Tefzel

⫹ CuCl

LiCl ⫹ CuCl





4. Lithium alloy and other coin

cells:

Lithium-aluminum/ manganese

dioxide

(LiAl/ MnO

)

Lithium-aluminum/ vanadium

pentoxide

(LiAl/ V

)

Carbon-lithium cells

Lithium carbon/ vanadium

pentoxide

Lithium-aluminum/ polymer

LiAl

Li/C

LiAl

MnO

Activated carbon

Polypyrrole (PP)

Polyaniline (PA)

LiAsF

EC/ BC/ DME

—

LiClO

—

Polypropylene

LiAl

⫹ MnO

MnO

⫹ Li

⫺





LiAl ⫹ V

⫹ Li

⫺





⫹ nC ⫹ LiClO

LiSn





⫹ C

ClO

C ⫹ V

⫹ Li

⫺





LiAl ⫹ PP Li

PP ⫹ Li

⫺





34.24

TABLE 34.12 Performance Characteristics of Rechargeable Lithium Metal Systems*

System

Midpoint

voltage,

V Size

Weight,

Capacity,

mAh

Speciﬁc

energy

Wh/kg

Energy

density

Wh/L

Self-

discharge† Cycle life‡

Liquid organic

batteries:

Li/ MoS

Li/Li

0.3

MnO

Li/TiS

Li/ NbSe

Li/ LiCoO

Li/ LiNiO

1.75

3.0

2.1

1.95

3.8

3.6

105

600

800

900

1100

500

4500

140

100

155

135

270

235

270

235

325

1–2

1.25

1–2

See Table 34.14

—

200

250

See Fig. 34.20 (b)

Polymer electrolyte

batteries:

Li/SPE/VO

— — — — 97 110 — —

Li/ SPE/ S-based

polymer

950 310 350 10–15 200

Inorganic electrolyte

batteries:

Li/SO

3.0 AA 20 500 75 200 0.1 ⬎50

Li/ CuCl

3.2 AA 21 500 75 220 0.1 ⬎100

Lithium alloy batteries:

LiAl/ MnO

LiAl/ V

LiAl/ C

LiTiO

/LiMn

2.5

1.8

2.4

1.5

2430

2320

1620

4.0

2.8

1.3

1.5

1.6

120

100

5.4

0.4

0.2

—

See Tables 34.19,

34.20

See Table 34.21

See Fig. 34.45,

Table 34.22

See Table 34.23

* Some data on experimental cells; see text.

† Self-discharge—% capacity loss per month at 20

⬚C (value-dependent on charge/ discharge conditions and cycling).

‡ Cycle life—to 80% capacity, 100% depth of discharge.

RECHARGEABLE LITHIUM BATTERIES (AMBIENT TEMPERATURE) 34.25

FIGURE 34.11 Typical discharge curves for rechargeable

lithium batteries.

34.4 CHARACTERISTICS OF SPECIFIC RECHARGEABLE LITHIUM

METAL BATTERIES

34.4.1 Liquid Organic Electrolyte, Solid-Cathode Batteries

These rechargeable batteries were attractive because they can deliver the highest energy

densities of all of the ambient-temperature lithium rechargeable batteries. They use a metallic

lithium anode, a liquid aprotic organic electrolyte, and one of several different cathode ma-

terials. Most of the development of these batteries has focused on the cylindrical spirally

wound construction and ﬂat-plate prismatic designs in order to optimize rate capability. The

properties of these batteries, in cylindrical AA or comparable sizes, are compared in Table

34.12. A plot comparing the energy density and power density of the different rechargeable

batteries and lithium/manganese dioxide primary batteries is given in Fig. 34.12. Although

several of these batteries were introduced commercially, they have not been viable in the

battery market.

Lithium/ Molybdenum Disulﬁde (Li/ MoS

) Batteries. The Li/ MoS

system was the ﬁrst

rechargeable lithium battery to be manufactured when it was introduced in the mid-1980s

in a cylindrical AA-size.

The cell used thin lithium metal anodes (125

␮

m), with a stoi-

chiometric excess of about three times, and MoS

on a thin aluminum foil (150

␮

m) for the

cathode. A spirally wound construction, as illustrated in Fig. 34.13, was used. The electrolyte

was 1M LiAsF

dissolved in a 50:50 mixture of propylene carbonate and ethylene carbonate.

Two types of batteries were manufactured. Table 34.12 describes the more advanced of the

two.

The discharge characteristics of the battery at various discharge loads temperatures are

shown in Fig. 34.14. The sloping voltage proﬁle makes it necessary to discharge the battery

over a wide voltage range to obtain full capacity. However, because of this characteristic,

34.26 CHAPTER THIRTY-FOUR

FIGURE 34.12 Comparison of liquid organic electro-

lytes, solid cathode batteries.

FIGURE 34.13 Construction of the Li / MoS

cell. (Cour-

tesy Moli Energy, Ltd.)

RECHARGEABLE LITHIUM BATTERIES (AMBIENT TEMPERATURE) 34.27

FIGURE 34.14 Discharge characteristics of Li / MoS

battery. Bat-

tery charged at 20⬚C, 60 mA to 2.4 V. (a) Discharge characteristics

at 20⬚C. (b) Discharge characteristics at 120 mA. (From Moli Energy

Ltd.)

the voltage can be used as a state-of-charge indicator. The performance of the battery and

its cycle life depend on the manner in which it is discharged as shown in Table 34.13.

Discharging the cells to 0 V could result in irreversible damage due to a phase change of

the cathode material, and low-voltage cutoff circuitry is recommended. The self-discharge

characteristics of the cell as a function of temperature are shown in Fig. 34.15. A constant-

current charge at the C/ 10 rate to a voltage limit of 2.2 or 2.3 V is the recommended charging

procedure. These batteries were withdrawn from the market after several safety incidents

occurred.

Lithium/ Manganese Dioxide (Li/Li

0.3

MnO

) Batteries. Rechargeable spirally wound cy-

lindrical AA-size cells using the Li/MnO

chemistry have also been developed.

29–35

The

same construction was used as with the Li/MoS

cells. A specially heat-treated Li

MnO

was used as the positive electrode material with carbon black. Commercial cells used an

electrolyte of 1M LiAsF

in dioxolane with added tributylamine as a stabilizer.

34.28 CHAPTER THIRTY-FOUR

TABLE 34.13 Performance Characteristics of Li / MoS

AA-Size Batteries

User

mode

Voltage

limits

10th cycle

Capacity,

Average

energy,

Cycle life,

number of cycles

To 80% of

10th-cycle

capacity

To 50% of

10th-cycle

capacity

High capacity 2.6–1.1 0.82 1.52 100 110

2.4–1.1 0.70 1.23 180 200

Normal 2.4–1.3 0.60 1.10 400 500

High cycle life 2.1–1.6 0.40 0.74 800 1000

1.95–1.75 0.15 0.27 1800 3000

Source: Moli Energy Ltd.

FIGURE 34.15 Self-discharge characteristics of Li/ MoS

AA-

size battery. (From Moli Energy, Ltd.)

Some of the performance characteristics of this AA-size battery are listed in Table 34.12

and are plotted in Fig. 34.16. The discharge proﬁle is fairly ﬂat with a midpoint voltage, at

moderate discharge rates, close to 3 V. The cell can be discharged at current levels of up to

about 2A, to a 2.0 V cut-off. The self-discharge rate is low, and is typical of the self-discharge

rate of many of the lithium metal /organic electrolyte rechargeable cells. Two hundred cycles

were obtained with a C /3 discharge and a C /12.5 charge rate when cycled to 100% depth

of discharge (DOD). Three hundred to 350 cycles can be obtained to 65% of initial capacity

at 100% DOD when discharged at 250 mA and changed at 80 mA to 3.40 V.

These AA-size batteries with lithium metal anodes were introduced into the consumer

market, with claims of safe performance under abusive electrical conditions due to an in-

trinsic shut-down mechanism involving polymerization of the electrolyte which protects the

cell under short circuit and overcharge (shutdown at 4.0 V).

33,34

RECHARGEABLE LITHIUM BATTERIES (AMBIENT TEMPERATURE) 34.29

FIGURE 34.16 Performance characteristics of Li / LiO

0.3

MnO

re-

chargeable AA-size battery. (a) Charge and discharge curves. I

⫽

250 mA; I

⫽ 250 mA (cycle no. 5). (b) Capacity vs. cycle number.

⫽ 60 mA; I

⫽ 250 mA (100% DOD). (c) Capacity vs. discharge

rate. (d ) Short-circuit behavior after 50 cycles. (From Tadiran Elec-

tronic Industries, Inc.).

34.30 CHAPTER THIRTY-FOUR

These AA-size batteries have been withdrawn from the commercial market because it has

been found that, at high charging rates, lithium deposition produces small grains which react

with the electrolyte in spite of the passivating tendency of the LiAsF

-dioxolane-tributylam-

ine electrolyte. The amount of electrolyte is limited in spiral-wound construction and is

spread in a thin layer within the electrode structure. During cycling, the lithium-electrolyte

reaction depletes the amount of electrolyte so that only a part of the active material continues

to function, leading to a pronounced increase in internal resistance and ultimate failure as a

result of the high internal impedance and reduced amount of active material. Another failure

mechanism is the high current densities which develop as the area of active material de-

creases, leading to dendritic short circuits.

Lithium/ Titanium Disulﬁde (Li /TiS

) Cells. This rechargeable battery system was ﬁrst

developed as a button cell for use in watches with a lithium-aluminum alloy anode. This

product never achieved commercial success due to fragmentation of the alloy anode on

cycling which limited cycle life. Later the battery was investigated in cylindrical and pris-

matic designs of up to about 5-Ah capacity.

36–39

Its advantageous characteristics are a rela-

tively ﬂat discharge and high energy density.

Figure 34.17a compares the discharge characteristics of the Li/TiS

battery, which used

an electrolyte composed of 1.5M LiAsF

in a mixture of 2-methyl tetrahydrofuran and te-

trahydrofuran, with that of the Li/MoS

cell. Figure 34.17b shows the discharge-charge

characteristics of a 2-Ah battery.

More than 250 cycles were achieved with a speciﬁc energy

of about 100 Wh/kg.

FIGURE 34.17 (a) Comparative performance of AA-size batter-

ies. Discharge rate ⫽ 200 mA; 20⬚C. (b) Successive cycles of a 2-

Ah Li/ TiS

battery. The battery is overcharged at the end of each

cycle, with the overcharge plateau time-limited to be at ⬃0.4 Ah.