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Lithium Ion Cells
Historically, lead-acid, nickel-cadmium (Ni-Cd), and nickel-metal hydride
(Ni-MH) batteries have been the conventional choice for small-sized rechargeable
batteries. Nowadays, rechargeable batteries are required to provide higher energy
density to meet the needs of customers.
Moreover, the attention being focused on protecting the environment has
resulted in demand for products that are environmentally friendly.
Features of different cell types
A. High Energy Density
The weight of a lithium ion battery is approximately one half compared to a
nickel-cadmium or nickel-metal hydride battery of similar capacity. Moreover,
the volume of the lithium ion battery is 40 to 50% smaller than that of a
nickel-cadmium and 20 to 30% smaller than that of a nickel-metal hydride
battery.
B. High Voltage
A single lithium ion cell has a voltage of 3.7V (mean value), which is equal
to either three nickel-cadmium or nickel-metal hydride cells connected in
series.
C. Pollution-free
The lithium ion battery does not contain any polluting substances such as
cadmium, lead, mercury, etc.
D. Non-metal Lithium
The lithium ion battery does not employ any lithium metal. It is not governed
by aircraft transportation rules relating to carrying lithium batteries in
passenger airplanes.
E. Long Cycle Life
Under normal conditions, the lithium ion battery has a life of more than 500
charge/discharge cycles.
F. No Memory Effect
The lithium ion battery is free from the so-called memory effect, a
phenomenon seen in nickel-cadmium in which the apparent battery capacity
decreases when shallow charge and discharge cycles are repeated.
G. Fast Charge Capacity
The lithium ion battery can be fully charged in 1 to 2 hours, using a
constant-current / constant-voltage (CC/CV) type dedicated charger with a rated
voltage of 4.2V per cell.
Applications
The rechargeable lithium ion battery shows great promise as a battery to meet
such requirement. This battery technology has excellent features, such as: high
energy density, high voltage and cycle life characteristics. These batteries are
widely used for High capacity multi-cell applications (e.g. electric bike,
electric wheelchair, electric golf car, electric motor-cycle, electric car,
etc.) High-rate discharge applications (e.g. power tools, e-scooter, electric
golf car, electric motor-cycle, electric car, etc.)
Comparison of Lithium Cobalt (LiCoO2), Lithium Manganese Oxide (LiMn2O4), Lithium Nickel Manganese Cobalt (LiNiMnCoO2) and Lithium Ferrous Phosphate (LiFePO4).
| Cell Chemistries |
LiCoO2 |
LiMn2O4 |
LiNiMnCoO2 |
LiFePO4 |
| Rate Voltage |
3.7V |
3.8V |
3.6V |
3.2V |
| Charging Voltage |
4.2V |
4.2V |
4.2V |
3.7V |
| Dischargiing end Voltage |
3.0V |
2.5V |
2.5V |
2.0V |
| Energy Density (Wh/L) |
447 |
253 |
327 |
222 |
| Energy Density (Wh/Kg) |
140-145 |
105-115 |
140-155 |
90-110 |
| Cycle Life |
>700 |
>500 |
>700 |
>1800 |
| Self-Discharge Rate
(Month) |
1% |
5% |
1% |
0.05% |
High Temperature
Performance
(55+/-2  ) |
Good |
Acceptable |
Good |
Excellent |
Low Temperature
Performance
(-20+/-2 ) |
Good |
Good |
Good |
Good |
| High-rate Discharge (10C) |
N/A |
Good |
Good |
Excellent |
| Safety & Environmental
Concern |
Bad |
Good |
Good |
Excellent |
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