Battery Basics
Learning Objectives
1) To state the various parts of the battery and their
functions
2) To indicate the use of the electrochemical series
3) To distinguish between primary and secondary
batteries
4) To indicate the meaning of terms used in the context of
battery technology
Electrochemical Device
Electrode phase
Electrolyte phase
Charge Transfer
Energy Storage device
Electrochemical Device
External circuit
Anode Electrolyte Cathode
Anode Oxidation Loss of electrons
Cathode Reduction Gain of electrons
The Electrochemical Cell
Standard Half Cell and SHE
Standard Electrode
Potential
𝐴𝑢3+ + 3𝑒 − → 𝐴𝑢 + 1.420 𝑉 Standard
𝑃𝑡 2+ + 2𝑒 − → 𝑃𝑡 + 1.200 𝑉 Electrochemical
𝑂2 + 4𝐻 + + 4𝑒 − → 2𝐻2 𝑂 + 1.229 𝑉
Series
𝐴𝑔+ + 𝑒 − → 𝐴𝑔 + 0.800 𝑉
𝐶𝑢2+ + 2𝑒 − → 𝐶𝑢 + 0.340 𝑉
2𝐻 + + 2𝑒 − → 𝐻2 0.000 𝑉
𝑃𝑏 2+ + 2𝑒 − → 𝑃𝑏 − 0. 126 𝑉
𝑁𝑖 2+ + 2𝑒 − → 𝑁𝑖 − 0. 250 𝑉
𝐶𝑑2+ + 2𝑒 − → 𝐶𝑑 − 0. 403 𝑉
𝑍𝑛2+ + 2𝑒 − → 𝑍𝑛 − 0.763 𝑉
𝐿𝑖 + + 𝑒 − → 𝐿𝑖 − 3.401 𝑉
Energy Storage Device:
Fuel and oxidant are stored within
the device.
Energy Conversion Device:
Fuel and oxidant are stored external
to the device
Cell:
A single electrochemical unit; i.e. one
anode, one cathode, and the electrolyte
Battery:
A collection of cells in series or parallel
Primary Cell:
Single use power source
Secondary Cell:
Can be recharged
Thermodynamics
Thermodynamics Cell Voltage
Thermodynamics Cell Voltage
Kinetics
Thermodynamics Cell Voltage
Kinetics Cell Current
Cell characteristics:
Capacity: Total charge in cell
Coulombs or Ah
Voltage
Power = V * I
Current Watts
Time
Power * Time
Energy: Joules or Wh
Conclusions
1) Batteries have specific parts that can have dramatically
opposite functions
2) The electrochemical series is the starting point to
understand Battery voltages
3) Primary and secondary batteries are both commonly
used
Battery Testing and
Performance
Learning Objectives
1) To draw a schematic of the typical battery test process
2) To indicate the significance of C-Rate
3) To be familiar with the typical discharge and charge
curves
4) To indicate the effect of the C-Rate on the charge-
discharge curve
5) To indicate the significance of the polarization curve
Battery Testing
V
Load A
Anode Electrolyte Cathode
The C-Rate
The rate at which the battery is discharge or charged,
relative to its capacity
The C-Rate
The rate at which the battery is discharge or charged,
relative to its capacity
1 C Rate => Discharge or Charge in 1 hour
2 C Rate => Discharge or Charge in ½ hour
5 C Rate => Discharge or Charge in 12 minutes
0.1 C Rate => Discharge or Charge in 10 hours
Terminology associated with use
State of charge: % of maximum capacity that is
remaining unused
Depth of Discharge: % of maximum capacity that has
been discharged
Cycle life: Number of cycles before the battery fails to
meet performance specifications. Affected by Depth of
Discharge
Discharge – Charge curves
Discharge – Charge curves
Discharge – Charge curves
1.5
Voltage (V)
0.0
0.0 5.0 10.0 15.0 20.0
Time (hrs)
Discharge – Charge curves
1.5
Voltage (V)
0.0
0.0 2.5 5.0 7.5 10.0
Time (hrs)
Effect of C-Rate on Discharge
1.5
C/2
Voltage (V)
C
5C 2C
0.0
0.0 5.0 10.0 15.0 20.0
Capacity (Ah)
Polarization curve
Activation losses
1.5
Ohmic losses
Mass Transport losses
Voltage (V)
0.0
0.0 Current density (A/cm2) 1.0
1.5 Polarization curve Power 1.0
Power (W)
Voltage (V)
0.0 0.0
0.0 Current density (A/cm2) 1.0
A comparison between two cells
1.5
Voltage (V)
Cell A
Cell B
0.0
0.0 Current density (A/cm2) 1.0
Conclusions
1) C-Rate indicates the rate at which the battery is being
charged or discharged relative to its capacity
2) Charge – discharge curves typically show steady
performance of the batteries excepting close to the
fully charged and fully discharged conditions
3) The polarization curve enables comparison between
batteries from the perspective of power delivery
Common Battery Structures
and Types
Learning Objectives
1) Become familiar with the different battery
structures
2) Become familiar with common battery types
3) Indicate advantages and disadvantages of these
different battery types
Different Battery Structures
Cylindrical Cell
Button cell
Prismatic cell
Pouch cell
Button cell
Cylindrical cell
Prismatic cell
Pouch cell
Rechargeable
Lead-Acid:
High current density
Pb H2SO4 PbO2
Toxic
𝑃𝑏 𝑠 + 𝐻2 𝑆𝑂4 → 𝑃𝑏𝑆𝑂4 + 2𝐻 + + 2𝑒 −
𝑃𝑏𝑂2 𝑠 + 𝐻2 𝑆𝑂4 + 2𝐻 + + 2𝑒 − → 𝑃𝑏𝑆𝑂4 + 2𝐻2 𝑂
Rechargeable
Ni-Cd (NiCad)
High cycle life (much more than NiMH), reliable
Lower capacity than NiMH, toxic, memory effect
𝐶𝑑 + 2𝑂𝐻 − → 𝐶𝑑(𝑂𝐻)2 + 2𝑒 −
2𝑁𝑖𝑂 𝑂𝐻 + 2𝐻2 𝑂 + 2𝑒 − → 2𝑁𝑖(𝑂𝐻)2 + 2𝑂𝐻 −
Ni-Metal Hydride (NiMH) Rechargeable
Non toxic, replace Alkaline and NiCd, no memory
effect, high capacity, energy density approaches that
of Li ion
Can self discharge
𝑀𝐻 + 𝑂𝐻 − → 𝑀 + 𝐻2 𝑂 + 𝑒 −
𝑁𝑖𝑂 𝑂𝐻 + 𝐻2 𝑂 + 𝑒 − → 𝑁𝑖(𝑂𝐻)2 + 𝑂𝐻 −
Rechargeable
Lithium Ion
Lighter than NiMH, better energy density
May self discharge
𝐿𝑖𝐶6 → 𝐶6 + 𝐿𝑖 + + 𝑒 −
𝐶𝑜𝑂2 + 𝐿𝑖 + + 𝑒 − → 𝐿𝑖𝐶𝑜𝑂2
Non-Rechargeable
Alkaline
Inexpensive
May not deliver as much current
𝑍𝑛 + 2𝑂𝐻 − → 𝑍𝑛𝑂 + 𝐻2 𝑂 + 2𝑒 −
2𝑀𝑛𝑂2 + 𝐻2 𝑂 + 2𝑒 − → 𝑀𝑛2 𝑂3 + 2𝑂𝐻 −
Non-Rechargeable
Carbon-Zinc
Very Inexpensive
Very low energy density
𝑍𝑛 → 𝑍𝑛2+ + 2𝑒 −
2𝑀𝑛𝑂2 + 2𝑁𝐻4 𝐶𝑙 + 2𝑒 − → 𝑀𝑛2 𝑂3 + 2𝑁𝐻3 + 𝐻2 𝑂 + 2𝐶𝑙 −
Conclusions
1) There are a wide range of battery types
2) These batteries differ from each other in terms of
capacity, environmental friendliness, current densities
supported, and cycle life
3) Careful analysis is needed to match a battery with a
specific end use
Non-Rechargeable
Lithium
High energy density, light weight
Expensive
Lithium ion Batteries
Learning Objectives
1) State the advantages of Lithium based battery
chemistry
2) Indicate the hazard with Lithium metal based batteries
3) Indicate how lithium ion batteries overcome the
hazard
4) Describe the process of Intercalation
5) Indicate the relative position of the energy levels
required for stability of the electrolyte
Lithium
One of the most electropositive elements
Light weight (0.53 gm/cm3)
Environmentally friendly
Dendritic growth of Lithium/ SEI
Porous structure that grows on anode with each
recharge cycle
Can result in internal short circuit
Dendritic growth of Lithium
L C
I A
T T
H H
I O
U D
M E
Dendritic growth of Lithium
L C L C
I A I A
T T T T
H H H H
I O I O
U D U D
M E M E
Dendritic growth of Lithium
L C L C L C
I A I A I A
T T T T T T
H H H H H H
I O I O I O
U D U D U D
M E M E M E
Intercalaction
Carbon based host materials
LiC6 Anode
LiMn2O4 Cathode
LiPF6 in EC/DEC Electrolyte (Lithium
Hexafluorophosphate in Ethylene
Carbonate and Diethyl Carbonate)
Graphite
Unit Cell
a = b = 2.46 Ao
acc = 1.42 Ao
d002 = 3.35 Ao
Intercalaction
Li+ Li+
Li+
Li+
Li+
Li+ Li+
Li+ Li+ Li+
Li+ Li+
Li+
Li+
Li+
Li+ Li+
Li+
Stage 4 Intercalaction
Li+
Li+ Li+ Li+
Li+ Li+
Li+ Li+
Li+ Li+
Li+ Li+ Li+ Li+
Li+
Li+
Li+
Li+
Li+
Li+ Li+
Li+
Li+ Li+ Li+
Stage 3 Intercalaction
Li+ Li+
Li+ Li+
Li+
Li+ Li+
Li+
Li+
Li+ Li+ Li+ Li+
Li+ Li+
Li+
Li+
Li+ Li+
Li+ Li+
Li+ Li+
Li+
Li+
Stage 2 Intercalaction
Li+ Li+ Li+ Li+
Li+
Li+
Li+ Li+ Li+ Li+
Li+
Li+ Li+
Li+ Li+ Li+ Li+
Li+
Li+
Li+ Li+ Li+
Li+
Li+
Li+
Li+
Li+ Li+ Li+
Stage 1
Intercalaction
Li+ Li+
Li+
Li+ Li+ Li+
Li+
Li+
Li+ Li+
Li+ Li+
Li+ Li+ Li+
Li+
Li+
Li+ Li+
Li+
Li+
Li+ Li+ Li+ Li+
Li+
Li+ Li+
Li+
Li+ Li+ Li+ Li+
Li+
Li+
Li+ Li+
Electrolyte Stability Window
Electrolyte
Anode LUMO
mA
Cathode
mC
HOMO
Conclusions
1) Lithium metal based rechargeable batteries can
develop internal short circuit with repeated cycling.
2) Lithium ion batteries overcome this issue
3) Intecalation and host compounds make Li-ion batteries
safe
4) HOMO and LUMO of electrolyte important in
determining electrolyte stability window
Supercapacitors
Supercapacitors,
Electric Double Layer Capacitor
Ultracapacitor
Learning Objectives
1) What is a Supercapacitor
2) How does it differ from a capacitor
3) What type of applications is it suited for
4) Typical Materials used
Supercapacitor
High capacitance
High energy density
Lower Voltage
High cycle life
Charge and discharge much faster than
batteries
Bridges the gap between capacitors and
rechargeable batteries
Supercapacitor
Regenerative braking
Loading and unloading activities
Start-Stop of electric vehicles
Supercapacitor: Electrical energy, uses ions
Battery: Chemical energy, uses ions
Capacitor: Electrical energy, uses electrons
Capacitor
+ - + -
+ - + -
+
+ +
-
-
+
+
-
- -
+ - + -
+ - + -
+ - + -
+ - + -
Dielectric Material
Capacitor Supercapacitor
Electrolyte
Electrode Material Current Collector
+ - + -
+ - + -
+
+ +
-
-
+
+
-
- - + -
+ - + -
+ - + -
+ - + -
+ - + -
Dielectric Material Separator Material
106
Batteries
Specific Energy (Wh/kg)
Capacitors
101
101 106
Specific Power (W/kg)
Charge-Discharge duration
106
Hours
Batteries
Specific Energy (Wh/kg)
Seconds to Minutes
ms to ms
Capacitors
101
101 106
Specific Power (W/kg)
Charge-Discharge duration
106 Cycle Life
Hours
Thousand
Batteries
Specific Energy (Wh/kg)
Seconds to Minutes
Nearly a million
ms to ms
‘Infinte’
Capacitors
101
101 106
Specific Power (W/kg)
Materials Used:
Electrode:
Activated carbon, Graphene, Carbon nanotubes
Activated Carbon: Natural carbons and polymers heat treated in inert atmosphere
Graphene can restack
Carbon nanotubes – cylindrical surface is used
Materials Used:
Electrolyte:
Aqueous electrolytes: Voltage restricted to 1.23 V
Organic electrolytes: Lower conductivity (Propylene Carbonate)
Ionic liquids: Organic salts with no solvents and melting point
below 100 oC
Conclusions
1) Supercapacitors bridge the gap between
capacitors and batteries
2) High surface area carbon materials used in
electrodes
3) Aqueous, organic as well as ionic liquids
considered as electrolytes
