A battery is a transducer that converts chemical energy into electrical energy. They are the source of energy which can be stored and also mobile. Batteries which can be used only once are called as primary batteries while which are rechargeable and used more than one time are called as rechargeable or secondary batteries.
Lithium is used in both primary as well as secondary batteries but the term lithium ion batteries is generally used for secondary batteries. They come in various shapes (coin, cylindrical and pouch) and sizes depending upon the energy density and the area of applications.
Note: Batteries is a commonly used for cells also but it is
specifically known for a pack. The pack may contain one or more cells.
Developments
Recent
developments of lithium-ion (Li-ion) batteries based on new and
improved chemistries have resulted in batteries with high performance,
long lifetime and increased safety. It not only became the ultimate
choice for any portable power equipment but also in standalone systems
like UPS and energy grid for power backup. Thanks to the decrease in
cell prices with advances in research, which makes it affordable for
everyone and everything.
Nevertheless, there are some issues
Majorly the efficiency and life depends on temperature, load current and state of charge.
High input cost for industrial production.
Even
though the competitors at present in market, i,e Lead Acid Batteries
which can overcome these issues to some extent but the portability with
high energy density factor cannot be replaced. Therefore, LIB rules the
market at present and the near future.
Importance
With
rise of electronic gadgets, the need of batteries has grown from high
power to portable high energy density. We have been addicted to gadgets
in every activity, whether it is for leisure, work or for essential
activities like health control and monitoring. Lithium ion batteries are
always the favorite because of the two aspects portability and high
energy storage. Yet issues of fire explosion due to flammable
electrolyte is a concern for many. Older battery technologies are still
equipped because of this fire safety issue and of course they are
cheaper. The hunger of energy storage whether its for your pocket or
home or electric grid, LIB's has the answer. In mobiles and hand held
devices there is no replacement for LIB's, energy storage for home is
not a viable option since its slightly costlier than older technologies
while for the power grid LIB's has a definite answer and its already
been installed in some places.
Battery Life:
While
using a battery we have a decrease in maximum capacity it can hold at
100% charge these are due to parasitic and other reactions inside the
cell. A battery which can hold 10% charge is really impractical to use
since it gives a backup for a very less time. The capacity of a battery
for a device is generally designed by the manufacturer and they only
defined the useful capacity till which the battery is good to use, i.e.,
80%. The number of cycles a battery can charge and discharge till the
loss of capacity to 80% is called as battery life. In our daily life we
do not charge a battery till it completely drains out and therefore we
cant track the battery life properly. In laboratory, the cells are
tested to charge and discharge at a constant rate continuously till they
reach to 80% of its capacity. This life is generally called as calendar
life.
Chemistry:
Battery are made of number of
components among them only three components are of great interest viz.,
cathode, anode and electrolyte.
Among the three, cathode is the
one which is talked about mostly among both researchers as well as
manufacturers. Cathode is called to be the limiting factor in defining
capacity since it is lower than the carbon anode which is mostly used
while the electrolytes is used to facilitate the movement of ions.
Researchers
have found quite a many chemistry in cathode and it is difficult for a
normal mind to keep track all the properties of it, especially the
voltage part which is very important. A wrong charger with a wrong
battery would either or both decrease the life of a battery or explode.
An NMC chemistry battery has a maximum voltage of 4.2 while LFP has 3.3
V.
Voltage:
The voltage of any cell depends on the
combination of the cathode and anode material is used. A combination of
NMC//Graphite cell has a nominal of 3.7V while NMC//Si-Graphite cell has
3.6.
Charging and discharging:
Generally, LIB's
have carbon material as anode and they do not have any lithium in them.
While charging, under the application of voltage, the lithium ions
migrate from cathode to anode through electrolyte (electrons flow in the
reverse direction outside the battery). In this process (for charging a
battery), the positive terminal is anode while negative terminal is
cathode. The lithium ions are stored in the cages of carbon like
prisoner with gates closed, and they wait to be released.
When
discharging, the positive terminal is cathode and negative terminal is
anode. The reverse migration of lithium ions from anode to cathode takes
place without any intervention of any external source while itself
acting as a voltage source.
Cell are charged in two methods:
constant voltage (CV) and constant current (CC), At low charge CV method
is used to increase the voltage of the battery to some extent and from
there when we have some charge in the battery, CC method is used.
Rate of Charge/Discharge:
The flow of lithium ions or electrons can be tuned with the load while voltage (typically~4.2-3) depends upon the state of charge. As a convention, if the cell discharges with a rate that it exhausts in a hour then it is called as 1C rate. If it takes half an hour to exhaust then the rate is called as 2C and 10 min then 6C similarly a cell can take long time to discharge like if it takes 6hrs then the rate is C/6. the same convention is applied to charge the cell.
More:
Introduction
to batteries | History of batteries | Lithium ion batteries | Working
Principle | How ecofriendly are they | Need for batteries | Cost of
Batteries | Formation Cycle | Effect of Temperature | Voltage | C Rate
and Fast Charging | Other Secondary Batteries | Primary Vs Secondary |
Ragone Plot | Forms and Sizes | Battery Packs | Thermal Engineering |
Transportation | Recycling | Glossary | Electric Vehicles | Energy
Storage | Different LIB | Safety | Testing
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