Advanced Secondary Batteries And
Their Applications for Hybrid and
Electric Vehicles
Su-Chee Simon Wang
IEEE (Dec. 5, 2011)
1

Introduction to batteries
• Equilibrium and kinetics
• Various secondary batteries
Lead acid batteries
Nickel metal hydride batteries
Lithium ion batteries
• Applications
Electric vehicles
Hybrid electric vehicles
2

– Primary and secondary batteries
– Cell voltage (open circuit)
– Positive and negative electrodes
– Cathode and anode
– Power energy and charge
– Battery cell module and pack
– Charge and discharge curves
– Cycle life
3

• Primary Battery: not rechargeable (dry cell)
• Secondary Battery: rechargeable (lithium ion batteries)
E oc
= E+ - E-
• Battery is composed of
– Positive electrode
+
(Cell V) (Half cell V)
Pos
_
E
– Negative electrode
– Electrolyte
– Separator
+
_ electrolyte separator
– Current collectors
P o s
N e g current collector
4

5

• Use half cell reduction potentials (25 °C)
Electrode reaction
Li + + e ↔ Li
Rb + + e ↔ Rb
Less stable
Cs +
K +
+ e ↔ Cs
+ e ↔ K
Ba +2 + 2e ↔ Ba
Sr +2 + 2e ↔ Sr
Ca +2
Na +
+ 2e ↔ Ca
+ e ↔ Na
Mg(OH)
2
Mg +2
+2e ↔
+ 2e ↔ Mg
Mg + 2OH -
Al(OH)
3
Ti +2
+ 3e
+ 2e ↔ Ti
↔ Al + 3OH -
Be +2
Al +3
+ 2e ↔ Be
+ 3e ↔ Al
Zn(OH)
2
+ 2e ↔ Zn + 2OH -
Mn +2 + 2e ↔ Mn
Fe(OH)
2
2H
2
O + 2e ↔ H
2
Cd(OH)
Zn +2
2
+ 2e
+ 2e ↔
↔
Zn
Fe + 2OH
+ 2OH -
-
+ 2e ↔ Cd + 2OH -
Ni(OH)
2
Ga +3
+ 2e ↔
+ 3e ↔ Ga
Ni + 2OH -
S + 2e ↔ S -2
Fe +2 + 2e ↔ Fe
Cd +2 + 2e ↔ Cd
PbSO
4
In +3
+ 2e ↔
+ 3e ↔ In
Pb + SO
4
-2
Tl +
Co
+ e ↔ Tl
+2 +2e ↔ Co
-2.71
-2.69
-2.38
-2.34
-1.75
-1.70
-1.66
-1.25
-1.05
-0.88
E°, V
-3.01
-2.98
-2.92
-2.92
-2.92
-2.89
-2.84
-0.83
-0.81
-0.76
-0.72
-0.52
-0.48
-0.44
-0.40
-0.36
-0.34
-0.34
-0.27
Electrode reaction
Ni +2 + 2e ↔ Ni
Sn +2
Pb +2
+ 2e ↔ Sn
+ 2e ↔ Pb
O
D
2
+
+ H
2
O + 2e
+ e ↔ 1/2D
2
↔ HO
2
+ OH -
H + + e ↔ 1/2H
2
HgO + H
2
O + 2e ↔ Hg + 2OH
CuCl + e ↔ Cu + Cl -
-
AgCl + e ↔ Ag + Cl -
Cu +2 + 2e ↔ Cu
Ag
2
O + H
2
O + 2e ↔ 2Ag + 2OH -
1/2O
2
+ H
2
O + 2e ↔ 2OH -
NiOOH + H
Cu +
2
O + e ↔ Ni(OH)
2
+ e ↔ Cu
+ OH -
I
2
2AgO + H
2
Hg
+ 2e
+2
↔ 2I -
O + 2e
+ 2e ↔ Hg
↔ Ag
2
O + 2OH -
Ag +
Pd +2
+ e ↔ Ag
+ 2e ↔ Pd
Ir +3 + 3e ↔ Ir
Br
2
O
2
MnO
2
Cl
F
2
2
PbO
PbO
+ 2e
+ 4H
2
2
+
↔
+ 4H +
+ SO
2Br
+ 4e ↔ 2H
2
O
+ 4H +
+ 2e ↔ 2Cl -
+ 2e ↔ Pb +2 + 2H
2
4
-2
↔ PbSO
4
+ 2e ↔ 2F -
-
+ 2e ↔ Mn +2 + 2H
2
O
+ 4H + + 2e
+ 2H
2
O
O
More stable
1.69
2.87
0.80
0.83
1.00
1.07
1.23
1.23
1.36
1.46
0.40
0.45
0.52
0.54
0.57
0.80
E°, V
-0.23
-0.14
-0.13
-0.08
-0.003
0.00
0.10
0.14
0.22
0.34
0.35
6

• Half cell reduction potentials are measured as follows:
– Cell voltage is measured between electrode A (Cu) and hydrogen electrode (E oc
= E
A
– E
H2
)
– The potential of hydrogen electrode in “acid” is defined as zero volt (E oc
= E
A
– 0)
– The measured cell voltage is the half cell reduction potential of electrode A
-
E
+
7

E ?
Chemical reactions?
Chemical reactions?
Cu Zn
CuSO
4
ZnSO
4
Cell open circuit voltage E oc
= E°
+
- E°
-
Positive electrode: Cu Negative electrode: Zn
E°
+
E°
-
E oc
= 0.34 V
= -0.76 V
= 0.34 – (- 0.76) = 1.1 V ( intrinsic )*
E = 1.1 V
Cu Zn
*Current: extrinsic
8

Table
Half Cell Reduction Potentials (25 °C)
Electrode reaction
Li + + e ↔ Li
Rb + + e ↔ Rb
Cs +
K +
+ e ↔ Cs
+ e ↔ K
Ba +2 + 2e ↔ Ba
Sr +2 + 2e ↔ Sr
Ca +2
Na +
+ 2e ↔ Ca
+ e ↔ Na
Mg(OH)
2
+2e ↔
Mg +2 + 2e ↔ Mg
Mg + 2OH -
Al(OH)
3
Ti +2
+ 3e
+ 2e ↔ Ti
↔ Al + 3OH -
Be +2
Al +3
+ 2e ↔ Be
+ 3e ↔ Al
Zn(OH)
2
Mn +2
+ 2e ↔ Zn + 2OH -
+ 2e ↔ Mn
Fe(OH)
2
2H
2
Cd(OH)
2
+ 2e ↔
Zn +2 + 2e ↔ Zn
Fe + 2OH -
O + 2e ↔ H
2
+ 2OH -
+ 2e ↔ Cd + 2OH -
Ni(OH)
2
Ga +3
+ 2e ↔
+ 3e ↔ Ga
Ni + 2OH -
S + 2e ↔ S -2
Fe +2 + 2e ↔ Fe
Cd +2 + 2e ↔ Cd
PbSO
4
In +3
+ 2e ↔
+ 3e ↔ In
Pb + SO
4
-2
Tl +
Co
+ e ↔ Tl
+2 +2e ↔ Co
E°, V
-3.01
-1.75
-1.70
-1.66
-1.25
-1.05
-0.88
-0.83
-0.81
-0.76
-0.72
-2.98
-2.92
-2.92
-2.92
-2.89
-2.84
-2.71
-2.69
-2.38
-2.34
-0.52
-0.48
-0.44
-0.40
-0.36
-0.34
-0.34
-0.27
Electrode reaction
Ni +2 + 2e ↔ Ni
Sn +2
Pb +2
+ 2e ↔ Sn
+ 2e ↔ Pb
O
2
+ H
2
O + 2e ↔ HO
D + + e ↔ 1/2D
2
2
+ OH -
H + + e ↔ 1/2H
2
HgO + H
2
O + 2e ↔ Hg + 2OH
CuCl + e ↔ Cu + Cl -
-
AgCl + e ↔ Ag + Cl -
Cu +2 + 2e ↔ Cu
Ag
2
O + H
2
O + 2e ↔ 2Ag + 2OH -
1/2O
2
+ H
NiOOH + H
Cu +
2
O + 2e ↔ 2OH -
2
O + e ↔ Ni(OH)
+ e ↔ Cu
2
+ OH -
I
2
+ 2e ↔ 2I -
2AgO + H
2
Hg +2
O + 2e
+ 2e ↔ Hg
↔ Ag
2
O + 2OH -
Ag +
Pd +2
+ e ↔ Ag
+ 2e ↔ Pd
Ir +3 + 3e ↔ Ir
Br
2
+ 2e ↔ 2Br -
O
Cl
2
2
+ 4H
MnO
2
PbO
2
+ + 4e ↔ 2H
2
O
+ 4H + + 2e ↔ Mn +2 + 2H
2
O
+ 2e ↔ 2Cl -
PbO
2
F
2
+ 4H + + 2e ↔ Pb +2 + 2H
2
+ SO
4
-2
↔ PbSO
4
+ 2e ↔ 2F -
+ 4H
+ 2H
2
+ + 2e
O
O
E°, V
-0.23
-0.14
-0.13
-0.08
-0.003
0.00
0.80
0.80
0.83
1.00
1.07
1.23
0.10
0.14
0.22
0.34
0.35
0.40
0.45
0.52
0.54
0.57
1.23
1.36
1.46
1.69
2.87
9

• Hydrogen Fuel Cells (with hydrogen and oxygen electrodes)
O
2
+ 4H + + 4e ↔ 2H
2
O 1.23 V
H + + e ↔ 1/2H
2
0.00 V
E oc
= 1.23 – 0 = 1.23 V
• Lithium Fluorine Battery
F
2
+ 2e ↔ 2F
Li + + e ↔ Li
-
E oc
= 2.87 – (–3.01) =
2.87 V
-3.01 V
5.88 V
10

Strong reducing agents
Strong oxidants
11

• Cathode: the electrode where reduction reaction takes place
• Anode: the electrode where oxidation reaction takes place
Secondary battery
• During charge
– Negative electrode is the cathode
– Positive electrode is the anode
• During discharge
– Positive electrode is the cathode
– Negative electrode is the anode
12

Secondary Battery
• During charge
– Negative electrode is the cathode
Zn +2 + 2e Zn
– Positive electrode is the anode
Cu Cu +2 + 2e -
• During discharge
– Positive electrode is the cathode
Cu +2 + 2e Cu
– Negative electrode is the anode
Zn Zn +2 + 2e -
Charge
V e
+ cation
-
Cu
CuSO
4 anion
Zn
ZnSO
4 e
Discharge
Load
+ -
Cu Zn
CuSO
4 anion
ZnSO
4
13

• Power = Voltage * Current
– 1 W (watt) = 1 V (volt) * 1 A (ampere)
– 1 kW = 1000 W
• Energy = Power * Time
– 1 Wh (watt-hour) = 1 W * 1 h (hour)
– 1 kWh = 1000 Wh
– 1 Wh = 3600 J (joules)
• Charge = Current * Time
– 1 Ah = 1 A * 1 h
– 1 kAh = 1000 Ah
– 1 Ah = 3600 C (coulombs)
14

• Specific power : power withdrawn per unit battery weight
– W/kg
• Power density: power withdrawn per unit battery volume
– W/L
• Specific energy : energy stored per unit battery weight
– Wh/kg
• Energy density: energy stored per unit battery volume
– Wh/L
15

• Examples
– AA primary alkaline battery
• 1.5 V (3 Ah)
– Lead acid SLI battery
• 12 V (50 Ah)
– Prius battery
• 202 V (6.5 Ah)
– Lithium ion battery (laptop)
• 10 V (5 Ah)
• Gasoline (tank)
– 600 kWh
4.5 Wh
600 Wh
1300 Wh (1.3 kWh)
50 Wh
16

NiMH Cell
1.2 V
NiMH Module
11 cells
11 x 1.2 = 13.2 V
NiMH Pack for EV1
26 Modules
26 x 13.2 = 343 V
17

Constant current charge (I
1.3
ch
) and discharge (I dis
)
1.1
E ch overpotential: η ch
0.9
E oc overpotential: η dis
E dis
+ (ch)
0.7
0.5
charge overcharge discharge
+
+ (dis) E ch
E oc
E dis
(dis) -
-
(ch) -
0
0
5
SOC (%)
10 15 20 25 30
100 0 DOD (%) 100
18

• Charge voltage E ch
> E oc
• Discharge voltage E dis
< E oc
• Energy efficiency = (voltaic efficiency * coulombic efficiency) = (E dis
/ E ch
) * (I dis
* t dis
/ I ch
* t ch
) < 1
• The voltage drop is caused by cell resistance
– ∆ E dis
– ∆ E ch
= E oc
= E ch
– E dis
- E oc
= η
= η ch dis
= I dis
= I ch
* R ( R: broader resistance
* R (R: extrinsic )
)
Constant current charge (I
1.3
ch
) and discharge (I dis
)
E ch
1.1
charge
E oc
0.9
discharge E dis
0.7
t ch t dis
0.5
0 5 10 20 25 30 19

• Nickel metal hydride electric vehicle battery (~300 W/kg)
Component Resistance Percentage terminals tabs
KOH/separators positive electrode positive substrate negative electrode negative substrate
TOTAL
0.1 mohm
0.6 mohm
3 mohm
1.5 mohm
2.5 mohm
2 mohm
3 mohm
12.7 mohm
0.8 %
4.7 %
23.6 %
11.8 %
19.7 %
15.7 %
23.6 %
100 % 20

• State of charge (SOC, %)
• Depth of discharge (DOD, %)
• SOC + DOD = 100
• Self discharge
• Discharge
– “C” rate
1C, 2C, 1/2C
1.3
1.1
0.9
0.7
E ch charge
0.5
0
0
5
SOC (%)
10
100
E dis
E oc discharge
0
20 25
DOD (%) 100
30
21

• Cycle life is the number of chargedischarge cycles a battery can deliver (has to meet energy and power performance targets)
• Cycle life depends on depth of discharge and temperature
– Examples
• lead acid battery
• nickel cadmium battery
22

• Introduction to batteries
Equilibrium and kinetics, E oc
• Various secondary batteries
> E dis
Lead acid batteries
Nickel metal hydride batteries
Lithium ion batteries
• Applications
Electric vehicles
Hybrid electric vehicles
23

• ∆ G: Free energy change from reactants to products during discharge (J/mole) negative value
• ∆ G = - nFE oc
(nFE oc
: electric work)  Max.
– n: Number of moles of electron transferred
– F: Faraday’s constant (96500 C/mole)
– E oc
: Open circuit cell voltage
• Theoretical Specific energy nFE oc
/ total weight of reactants
24

(Lithium Ion Battery)
• Lithium ion battery half cell reactions
(+) CoO
2
+ Li + + e
Eº = 1 V
↔ LiCoO
2
(-) Li + + C
6
+ e ↔ LiC
Eº ~ -3 V
6 n = 1
Theoretical specific energy = nFE oc
/ total weight of reactants
• Overall reaction during discharge
CoO
2
+ LiC
6
LiCoO
2
+ C
6
E oc
= E + - E = 1 - (-3) = 4 V
E oc
= 4 V
25

(Lithium Ion Battery)
• Free energy change ( ∆ G) during discharge
∆ G = -nFE oc
= -1 * 96500 * 4 = - 386000 J
= -386 kJ = -107.2 Wh/mole
• Total weight of reactants
CoO
2
CoO
2
+ LiC
6
LiCoO
91 grams
2
+ C
6
Li C
6
7 + 12 * 6 = 79 grams
Total weight 170 grams (0.17 kg)/mole
• Theoretical specific energy
107.2 Wh/ 0.17 kg = 630.6 Wh/kg
• Theoretical energy density
107.2 Wh/0.055 L = 1949 Wh/L
26

• Practical specific energy of a battery is significantly lower than the theoretical value (~30%) ~ 190 Wh/kg for lithium battery (USABC target for EV > 150
Wh/kg)
– Lower discharge voltage ( E dis
< E
• Voltage losses ( broader resistance ) oc
)
– Extra material weight
• Current collectors
• Terminals
• Battery case
• Separators
Theoretical specific energy = nFE oc
/ total weight of reactants =
630.6 Wh/kg
27

• Battery current collectors and terminals
– Collect current from electrodes and interconnect to next battery cells
– Use materials with high electric conductivity and good heat transfer coefficient
• Battery case
– Contain all battery components
– Use materials inert with electrolyte and electrodes
– Need safety release valve with sealed cells
• Separator
– Separate positive and negative electrodes (prevent short circuit)
– Made of insulating materials with high porosity
28

• Practical specific energy of a battery is significantly lower than the theoretical value (<30%)
– Lower discharge voltage (E dis
• Activation polarization losses
< E oc
)
• Ohmic losses
• Concentration polarization losses
– Extra material weight
• Current collectors
• Terminals
• Battery case
• Separators
29

• Source of voltage losses ( broader resistance )
– Electrode activation polarization losses ( η a
)
• Butler-Volmer equation
– Depends on electrode reactions
– Ohmic losses ( η
Ω
)
• Ohm’s law ( Ohmic resistance )
– Electronic resistance (electrode current collector, tabs. and terminals)
– Ionic resistance (electrolyte and separator)
– Temperature effects
– Concentration polarization losses ( η c
)
• Nernst equation
– Depends on diffusion in electrolyte and solid state
30

Constant current charge (I
1.3
ch
) and discharge (I dis
)
1.1
E ch overpotential: η ch
0.9
η dis
= η a
+ η
Ω
+ η c
E oc overpotential: η dis
E dis
+
η +
+ (dis)
0.7
charge overcharge discharge
E oc
E dis
(dis) -
η -
-
0.5
0
0
5
SOC (%)
10 15 20 25 30
100 0 DOD (%) 100
31

• Sources of voltage losses (E oc
– E dis
):
– Electrode activation polarization losses
• Butler-Volmer equation
P < Po
– Ohmic losses
Po
• Ohm’s law
– Electronic resistance (electrode current collector, tabs. and terminals)
– Ionic resistance (electrolyte and separator)
– Concentration polarization losses
• Nernst equation
P
P’
P’ < P Po’
32

( Butler-Volmer Equation) i
i
0
[ e
( 1 − α ) η F / RT
e − αη F / RT
]
• Current density i (electrochemical reaction at electrode/electrolyte interface) is a function of:
– η a
: Activation polarization loss
– i
0
: Exchange current density
– α : The symmetry factor
– F : Faraday’s constant
– R : Molar gas constant
– T : Temperature
+ e
Cu
Discharge
-
Zn
CuSO
Cu
+2
+ 2e
-
4 anion
ZnSO
4
Cu Zn Zn
+2
+ 2e
-
33

C/8 Rate
2-C Rate i = i
0
[ e
( 1 − α ) η F / RT
− e − αη F
Higher current higher η a
/ RT
]
Concentration polarization losses
34

(Nernst Equation)
• During discharge
– Reaction at the positive electrode:
Cu +2 + 2e Cu
– Reaction at the negative electrode:
Zn Zn +2
– Cell reaction:
+ 2e -
Zn + Cu +2 Cu + Zn +2
η c
+
Cu
Discharge
V
-
Zn
• Nernst equation
RT
E oc , real
=
E oc , table
+ nF
– A: Concentration of Cu +2
– B: Concentration of Zn +2
– a and b (= 1): factor for Cu +2 and Zn +2
– R : Molar gas constant
– T : Temperature
E oc , real
Ln
=
– F : Faraday’s constant
(
(
A )
B ) a b
CuSO
4
ZnSO
4
E oc , table
+
RT nF
Ln
( Cu + 2
)
( Zn +
2
)
(If Zn +2 = Cu +2 =1M)
35

• E oc
– E dis
= Total voltage losses (
Activation losses ( η a
) + Ohmic losses ( η
Concentration losses ( η c
)
η dis
, extrinsic) =
Ω
) +
Voltage Los s es in Fuel Cell
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Polarization curve
1.23 V
Activation polarization losses in electrodes
Ohmic losses
Concentration polarization losses
η dis
= E oc
- E dis
~ I dis
* R (broader resistance)
0 500 1000
Current density (mA /cm2)
1500
36

Model: Porous Electrode Theory
• Porous electrode theory
– Butler-Volmer equation
– Ohm’s law
For a battery cell
Power = f (1/R)
R = f (1/surface area)
Current flow
Current flow
Electrode
Current collector decreasing
Pores
(electrolyte)
37

38

13
12
Experimental Results
V.S. MATLAB Model
Marine Lead Acid Battery (12V, 32 Ah)
C/2 Test
1C Test
2C Test
C/2 Model
1 C Model
2 C Model
11
10
9
0.00
0.25
0.50
0.75
Time (Hours)
1.00
1.25
1.50
39

• Introduction to batteries
• Equilibrium and kinetics
Various secondary batteries
Lead acid batteries
Nickel metal hydride batteries
Lithium ion batteries
• Applications
Electric vehicles
Hybrid electric vehicles
40

• Invented by Planté in 1860
• Lead acid starter batteries are enabling technology for gasoline powered IC engine cars
• Almost all vehicles use lead acid batteries for starter lighting and ignition (SLI) systems
• It is 20 billion dollars industry (total battery industry ~ 30 billion dollars)
41

• Positive electrodes
– PbO
2
• Negative electrodes
– Pb
• Current collectors
– Lead (or alloy) grids
• Separators
– Porous or glass mat
• Electrolyte
– 5M H
2
SO
4 aqueous solution
Expanded metal
Cast
1. Positive
2. Negative
3. Separator
4. Tab
5. Bus bar
6. Terminal
42

• Lead acid battery half cell reactions
PbO
2
+ SO
4
2+ 4 H + + 2 e ↔ PbSO
4
E°= 1.69 V
+ 2 H
2
0
PbSO
4
+ 2 e ↔ Pb + SO
4
2-
E°= -0.36 V
• Overall reaction during discharge
PbO
2
+ Pb + 2H
2
SO
4
V oc
= V
+
- V
-
2 PbSO
4
+ 2 H
2
0
= 1.69 – (-0.36) = 2.05 V
43

• Free energy change ( ∆ G) during discharge
∆ G = -nFE = -2 * 96500 * 2.05 = -395700 J
= -395.7 kJ = -109.9 Wh/mole
• Total weight of reactants
PbO
2
PbO
2
+ Pb + 2H
2
SO
4
239 grams
Pb 207 grams
2 PbSO
4
+ 2 H
2
0
2H
2
SO
4
98 *2 = 196 grams
Total weight 642 grams (0.642 kg)/mole
• Theoretical specific energy
109.9 Wh/ 0.642 kg = 171 Wh/kg
• Theoretical energy density
109.9 Wh/0.1 L = 1099 Wh/L
44

• Practical specific energy < 20 % theoretical specific energy (171 Wh/kg) ~ 34 Wh/kg due to:
– Voltage losses (up to 10%)
– Inactive weight (~75%)
• Current collectors
• Tabs and terminals
• Solvent (water) in electrolyte
– Low utilization of active material
USABC target for EV applications: > 150 Wh/kg
45

• During charge:
– 2 PbSO
4
+ 2 H
2
0 PbO
2
+ Pb + H
2
SO
4
(2.05 V)
– Competing reaction : 2H
2
O O
2
+ 2H
2
(1.23 V)
H
2 evolution
Pb
Lead acid battery voltage
2.05 V
PbO
2
O
2 evolution
Water decomposition voltage
1.23 V
-1
-0.36
0 1
Voltage (V)
1.23
1.69
2
46

2
4
• Overall reaction during charge
2 PbSO
4
+ 2 H
2
0 PbO
2
+ Pb + H
2
SO
4
The concentration of sulfuric acid increases to 5 M
• Overall reaction during discharge
+ Pb + H
2
SO
4
2 PbSO
4
+ 2 H
2
0
Diffusion!
PbO
2
The concentration of sulfuric acid decreases
Power?
e discharge e
V
+ anion
Pb
O
2
H
2
SO
4 cation
-
Pb
H
2
SO
4
Cation: H +
Anion: SO
4
-2
47

4.59
Ah
5.10
Ah
5.6
Ah
6.00
Ah
48

• Positive electrode
– Lead grid corrosion
PbO
2
+ Pb + H
2
SO
4
– Shedding
2 PbSO
4
• 70% volume change from PbO
2
• Negative electrode
+ 2 H
2
0 to PbSO
4
(discharge)
– Sulfation (the formation of PbSO
4
)
• Cycle life depends on DOD and temperature
Active material
PbSO
4
Grid
Number of cycles
49

• Introduction to batteries
• Equilibrium and kinetics
• Various secondary batteries
Lead acid batteries
Nickel metal hydride batteries
Lithium ion batteries
• Applications
Electric vehicles
Hybrid electric vehicles
50

• Became commercially available around
1992
• Metal hydride is actually a solid phase hydrogen intercalation electrode
• Nickel metal hydride battery has high power and good cycle life for HEV applications
• It is > 1 billion dollars industry (total battery industry ~ 30 billion dollars)
51

• Positive electrodes
– Nickel hydroxide pasted onto nickel foam or sheet substrate
• Negative electrodes
– Most common material is A B
5 or Mm Ni
3.55
Co
0.75
Al
0.2
Mn
0.5
where Mm is misch metal, an alloy consisting of 50% cerium, 25% lanthanum, 15% neodymium, and 10% other rare-earth metals and iron
• Separators
– Polymer with submicron pores
• Electrolyte
– 30% KOH aqueous solution
52

• Nickel metal hydride battery half cell reactions
NiOOH + H
2
O + e ↔ Ni(OH)
2
Eº = 0.45 V
+ OH -
M + H
2
O + e ↔ MH + OH -
Eº = -0.83 V
• Overall reaction during discharge
NiOOH + MH Ni(OH)
2
E oc
= E
+
- E
-
+ M
= 0.45 –(-0.83) = 1.28 V
53

• Free energy change ( ∆ G) during discharge
∆ G = -nFE = -1 * 96500 * 1.28 = - 123520 J
= -123.5 kJ = -34.3 Wh/mole
• Total weight of reactants
NiOOH + MH Ni(OH)
2
NiOOH 92 grams
+ M
MH 70 grams
Total weight 162 grams (0.162 kg)/mole
• Theoretical specific energy
34.3 Wh/ 0.162 kg = 212 Wh/kg
• Theoretical energy density
34.3 Wh/0.02 L = 1715 Wh/L
54

• Practical specific energy up to 45% theoretical specific energy (212
Wh/kg) up to 90 Wh/kg due to:
– Voltage losses (up to 10%)
– Less inactive weight (~50%)
• Current collectors
• Tabs and terminals
• Solvent (water) in electrolyte
– High utilization of active material (~90%)
55

Effects of Discharge Rate on Capacity
• Capacity least affected by discharge rate among commonly used batteries (best abuse tolerance)
Flat discharge voltage curve
C/8 rate
2C rate
4.6 Ah
5.1 Ah
5.6 Ah 6 Ah
56

• Introduction to batteries
• Equilibrium and kinetics
• Various secondary batteries
Lead acid batteries
Nickel metal hydride batteries
Lithium ion batteries
• Applications
Electric vehicles
Hybrid electric vehicles
57

• Invented by Dr. Goodenough at U. Texas in
1982 and became commercially available in
1991 (Sony)
• Both lithium cobalt oxide and carbon electrodes are intercalation electrodes
• Have safety issues for applications in HEV and plug-in HEV
• It is 5 billion dollars industry for applications in portable electronics (total battery industry ~ 30 billion dollars)
58

• Positive electrodes
– Layered lithium metal oxide (LiMO
2
, M = cobalt , nickel, manganese, aluminum, or combination of two to three metals), spinel lithium manganese oxide
(LiMn
2
O
4
), and lithium iron phosphate (LiFePO aluminum current collector
4
) on
• Negative electrodes
– Carbon or graphite on copper current collector
• Separators
– Celgard microporous, polyethylene, or ceramic separators
• Electrolyte
– LiPF
6 dissolved in ethylene carbonate (EC)
• Solvent with high dielectric constant (89.6 at 40°C)
• Lithium salt with high conductivity
• 0.005 S/cm as compared to 0.5 S/cm for aqueous electrolyte

• Prevent lithium metal deposition (or formation of lithium dendrite )
– Lithium metal deposition could still happen during rapid charge when Temp < 5°C
– Dendrite could cause short circuit and thermal runaway
Negative electrode
Electrolyte
Positive electrode
Li metal
Dendrite
60

65 mm
18 mm
Lithium ion battery18650
3.6 V, 2 Ah
7.2 Wh
Alkaline AA battery
1.5 V, 1.5 Ah
2.25 Wh
61

• Lithium ion battery half cell reactions
CoO
2
+ Li + + e ↔ LiCoO
2
Eº = 1 V
Li + + C
6
+ e ↔ LiC
6
Eº ~ -3 V
Li metal
Dendrite
• Overall reaction during discharge
CoO
2
+ Li C
6
E oc
= E
+
LiCoO
2
- E
-
+ C
6
= 1 - (-3.01) = 4 V
62

• Free energy change ( ∆ G) during discharge
∆ G = -nFE = -1 * 96500 * 4 = - 386000 J
= -386 kJ = -107.2 Wh/mole
• Total weight of reactants
CoO
2
CoO
2
+ LiC
6
LiCoO
91 grams
2
+ C
6
Li C
6
79 grams
Total weight 170 grams (0.17 kg)/mole
• Theoretical specific energy
107.2 Wh/ 0.17 kg = 630.6 Wh/kg
• Theoretical energy density
107.2 Wh/0.055 L = 1949 Wh/L
63

• Practical specific energy up to 30% theoretical specific energy (630.6
Wh/kg) ~ 190 Wh/kg due to:
– Voltage losses (up to 10%)
– Less inactive weight (~35%)
• Current collectors
• Tabs and terminals
• Electrolyte
• Carbon in negative electrode
– Utilization of active material (~50%)
• Intercalation electrodes
64

• Lithium batteries cannot use aqueous electrolyte
Lithium batteries with aqueous electrolyte
Lithium ion battery
~ 4 V
H
2 evolution
Water decomposit ion voltage
1.23 V
O
2 evolution
-3.2 -2.7 -2.2 -1.7 -1.2 -0.7 -0.2 0.3 0.8 1.3 1.8
Voltage (V)
65

• Overall reaction during charge
LiCoO
2
+ C
6
CoO
2
+ LiC
6
Charge
Li + + e Li
Carbon LiCoO
2
Lithium
Lithium ion
66

• Positive electrode is oxidized and oxygen released (exothermic reaction)
67

• Overall reaction during discharge
CoO
2
+ LiC
6
LiCoO
2
+ C
6
Discharge
Li Li + + e
Carbon LiCoO
2
Lithium
Lithium ion
68

• Overcharge
– Exothermic reaction of oxidized positive electrode material with electrolyte
• High ambient temperature
– SEI (solid electrolyte interphase) decomposition at temperature 90 to 120 °C
• Short circuit
– Internal
– External
• High charge or discharge current
69

• Lithium ion battery is assembled inside a dry room (does not need a dry box w/inert atmosphere) with lithium ions impregnated in the positive electrode (the smaller electrode)
• During the first charge, lithium ions are transferred from the positive to the negative electrode and form lithium metal
Enlarged graphite particle
-
Graphite
(or C) particles
CoO
2 particles
+
Enlarged
CoO2 particle
Capacity determined by the positive electrode

• The electrolyte, ethylene carbonate ( EC ), is not thermodynamically stable with lithium metal
• SEI is formed on carbon or graphite particles during the first charge (Li active material wasted)
• SEI properties
– SEI has porous structure (more porous if SEI formation steps are not optimized)
– SEI is ionic conductor (electronic insulator)
SEI
( Li
+ EC) pores
Li-C ethylene carbonate
Li+ (during charge)
Li+ (during
Li + + C
6
+ e ↔ LiC
6 discharge)
71

• Charge discharge cycles
– Volume changes in the carbon or graphite particles crack SEI and expose fresh Li to electrolyte (EC)
• Storage (calendar life)
– Ethylene carbonate (EC) diffuse through SEI
(pores) and react with Li inside SEI ethylene carbonate
SEI
Li-C
Li + EC thicker SEI
(capacity loss & high impedance rate capability loss) pores
72

• Advantages
– Very high energy and power
– Excellent charge retention
• Disadvantages
– Safety concerns
– High cost (control systems)
– Lithium deposition during charge at low temperature
– Short calendar life
73

(Positive Electrode)
Structure Material
Layered oxides (2D)
LiCoO
2
Li(Co-Ni)O
2
LiCo
1/3
Ni
1/3
Mn
1/3
O
2
(L-333)
Spinel (3D) LiMn
2
O
4
E oc
3.6 to
3.7
Capacity Safety Cost
151 Ah/kg Acceptable high
3.7
119 Ah/kg good Low
Olivine (1D) LiFePO
4
3.4
161 Ah/kg best Low
– Spinel is more proven than olivine except a high temperature
– Spinel has relatively lower capacity (119 vs.150 or 160
Ah/kg for other materials) and solubility problems
– Olivine has very low conductivity
74

New Lithium Iron Phosphate Cells
(CALB, Thunder Sky, GBS)
75

(Negative Electrode)
• Spinel negative electrode (Altair)
– Lithium titanate (Li
4
Ti
5
O
12
)
• Advantages
– At lower voltage (~ 2.5 V) lithium is thermodynamically stable in electrolyte no SEI
– Rapid charge and discharge
– Extremely long cycle life (> 20,000 )
• Disadvantages
– Lower voltage (2.5 V)
– Low electronic coductivity (additives)
A supercapacitor!
76

Gasoline
77

30
25
20
15
Supercapacitors VS. Lithium Batteries
Apower Cap
Commercial supercaps
Nickel-Carbon supercap
Graphene-Based supercap
CALB iron phosphate battery
Altair ( 国轩 ) titanate battery
Fuji Hybrid
10
5
0
0
Power Sys
20 40 60 80
Spesific energy (Wh/kg)
100 120
78

• Lead acid battery
– Low energy, < 40 Wh/kg
– Moderate power, > 200 W/kg
– Short life (deep discharge cycle), ~ 400 EV cycles
– Low cost, ~ $150/kWh
• Nickel metal hydride battery
– Moderate energy, < 100 Wh/kg
– High power, > 1000W/kg
– Long life, ~ 2000 EV cycles
– High cost, ~ $1000/kWh (cell)
• Lithium ion battery
– High energy, < 200Wh/kg
– High power, > 1000W/kg
– Long life, ~ 2000 EV cycles
– High cost, ~ $ 400/kWh (control system)
79

• Introduction to batteries
• Equilibrium and kinetics
• Various secondary batteries
• Lead acid batteries
• Nickel metal hydride batteries
• Lithium ion batteries
Applications
Electric vehicles
Hybrid electric vehicles
80

• History of electric vehicles
– Electric motor demonstrated in 1832
– Planté invented lead acid batteries in 1860
– Electric vehicles were more popular than vehicles with internal combustion engines early 20 th century (from 1900 to 1912)
• 30,000 electric vehicles in US
• 200,000 electric vehicle worldwide
– The invention of battery powered starter
(1911) wiped out electric vehicles after 1920
81

• Ayrton & Perry EV
(1882)
– Ten lead acid battery cells (200 pounds)
– Peak power output
400 Watts
– Range 10 ~ 25 miles
– Speed 10 mph
82

Jenatzy electric race car sets world speed record at 61 mph
(1899-1902)
83

• Renewed interests on electric vehicles
– Uncertainties on the supply of petroleum based fuels
– High price of petroleum based fuels
– Improved technologies on batteries
• Global opportunities
– More opportunities in countries such as China and India
• Less or no crude oil reserves compared to the US
• More city driving
• Shorter range requirements
84

Tesla
85

Build Your Dreams (BYD)
86

Years in development:
4
Battery range:
40 miles
Supplemented by onboard gas generator
Passengers: 4
Price: $40000
87

Years in development: 4
Battery range:
100 miles (100% electric, 0 emissions)
Passengers: 4
Price: $32780
88

89

90

91

HEV
Prius
Chevy
Volt
EV
92

(with the same capacity)
High Specific Power
Cell terminal
1 tab
+ + + -
2 tabs
+ + -
High Specific Energy
Cell terminal terminal
+ -
2 tabs terminal
1 tab
93

High Specific Power High Specific Energy ( Range )
•Bias power at the cost of energy
•Smaller particles, lower density
•Thinner electrodes
IR)
• Bias energy at the cost of power
• Larger particles, higher density
• Thicker electrodes active material)
94

• Method I: Estimate force required to move the vehicle
F = mg*C r
+ ½ ρ C
D
Av 2 + ma + mg*sin( θ )
C r
: coefficient of rolling resistance
C
D
: Coefficient of air drag
ρ : Density of air
A: Cross section of the vehicle
θ : Slope of the road
• Calculate power and energy required to drive the vehicle for 200 km
Power P = F * v (velocity)
Energy = ∫ P dt
(integration from time t = 0 to T for driving 200 km)
Total energy (Wh) required for the battery pack to drive
200 km
95

• Use the empirical equation
Range (km) = ( Є /e) * F b
Є
: Usable battery specific energy (Wh/kg) e: Specific weight consumption (Wh/(kg*km))
(e = 0.11 for a normal car driving on flat terrain)
F b
: Battery fraction
• For the battery pack
Є
= 150 Wh/kg (lithium ion battery)
F b
= 250 / 1500 = 0.167
Range = (150 / 0.11) * 0.167 = ~ 220 km
(150 Wh/kg * 250 kg = 37.5 kWh )
96

• Specific weighted consumption
“e” CONDITIONS
0.06
Well designed, low acceleration rail vehicles, and level conditions
0.07
GM prototype impact with superior aerodynamics but impractical features
0.09
Stop, start, low acceleration, slow speed bus on level roads, good weather, stops every 300 m
0.11
For a normal car with all-season tires, generally flat terrain
0.15
Smooth freeway driving, good weather, level terrain
0.20
Hilly terrain
97

• Energy: ~ 40 kWh for 200 km range
• Power (acceleration): ~ 100 kW , 250kg (400 W/kg)
• Power (regenerative braking): ~ 40 kW (160 W/kg)
• The efficiency of city driving is higher than that of highway driving
• Weight: battery fraction F b vehicle weight)
= 0.167 (less than 1/3
• Life: 10 years and 100,000 miles
• Cost: competitive with internal combustion drive train
98

• Introduction to batteries
• Equilibrium and kinetics
• Various secondary batteries
• Lead acid batteries
• Nickel metal hydride batteries
• Lithium ion batteries
• Applications
Electric vehicles
Hybrid electric vehicles
99

• Hybrid electric vehicle types
Types Main Attributes
Micro-1 Stop, power for idle loads, crank ICE
Battery
VRLA
Micro-2 Micro-1 plus regenerative braking
Mild-1 Micro-2 plus lunch assist
VRLA
VRLA
Mild-2 Mild-1 plus limited power assist VRLA, NiMH
Moderate Mild-2 plus full power assist NiMH
Strong Moderate plus extended power assist (limited electric drive)
Strong plus extended electric drive Plug-in
HEV
VRLA: Valve regulated lead acid battery
NiMH
NiMH , Li-ion
NIMH: Nickel metal hydride battery
100

• Thinner electrodes and separators
• More electrodes in parallel
• Shorter aspect ratio
• Thicker and heavier current collectors
• Conductive additives mixed with active materials in electrodes
101