A fuel cell converts chemical energy from a fuel into electricity through a reaction with oxygen or another oxidizing agent. Hydrogen is commonly used as a fuel but other fuels like natural gas can also be used. Fuel cells provide continuous power as long as fuel is supplied, unlike batteries which have a limited storage capacity. They produce water, heat, and small amounts of pollution as byproducts. Individual fuel cells produce low voltages so they are stacked to increase output. Fuel cells have efficiencies between 40-85% and are used in various applications including transportation, backup power, and utilities.

2.  A fuel cell is a device that converts the
chemical energy
from a fuel into electricity through a
chemical reaction
with oxygen or another oxidizing agent .
Hydrogen is the most common fuel into
electricity but hydrocarbon such as natural
gas and methanol are used
sometimes as alternative .

3.  In secondary batteries, the chemical energy is
stored in their electrodes . But in the fuel cells , the
oxidants and the fuels are stored outside the cell.
 Also they require constant source of fuel and
oxygen to sustain the chemical reaction .This is the
advantage of fuel cell over storage batteries
because itb is possible to supply the fuels
continously from outside and keep the fuel cell
working practically forever.

4.  Fuel cells produce water heat and a small
quantity of nitrogen di oxide .
 Individual fuel cells can produce about 0.7
volts . So they are stacked together to
increase output of the cell.
 They have an energy efficiency of 40-60% and
it can be increased upto 85%.
 First fuel cell was produced in 1838.

5.  Back up power
 Portable power
 Transportation
 Speciality vehicles
 Military and space
 Electric utility
 Auxillary power
 Distributed generation

6.  Lithium is the lightest of metals and it can float on water.
 The electrochemical properties of lithium are excellent
and it is also a highly reactive material.
 These properties gives Lithium the potential to achieve
very high energy and power densities in high-density
battery applications such as automotive and standby
power.
 Lithium batteries are primary batteries in which lithiun
metal (or) lithium compound acts as a Anode. A lithuim
cell can produce voltage from 1.5 V to about 3 V based
on the types of materials used.

7.  1. Lithium batteries
 2. Lithium-ion batteries
 In lithium batteries, a pure lithium metallic
element is used as anode. These types of
batteries are not rechargeable.
 In lithium-ion batteries, lithium compounds are
used as anode.
 These batteries are known as re-chargeable
batteries. Therefore, Lithium ion batteries are
considered as best than pure Lithium based
batteries.

8.  Li-ion batteries are secondary batteries.
 The battery consists of a anode of Lithium,
dissolved as ions, into a carbon.
 The cathode material is made up from Lithium
liberating compounds, typically the three
electro-active oxide materials,
 Lithium Cobalt-oxide (LiCoO2 )
 Lithium Manganese-oxide (LiMn2 O4 )
 Lithium Nickel-oxide (LiNiO2)

9.  They have high energy density than other
rechargeable batteries
 They are less weight.
 They produce high voltage out about 4 V
as compared with other batteries.
 They have improved safety, i.e. more
resistance to overcharge
 No liquid electrolyte means they are
immune from leaking.
 Fast charge and discharge rate.

10.  They are expensive
 They are not available in standard cell types.
 Lithium batteries cannot be recharged. Once the
battery runs out, it has to be replaced. When
lithium batteries are used in large number, the
fact that they are not rechargeable can add to the
cost.
 These batteries can also be difficult to replace if
they are embedded in electronics and may
necessitate professional repair, or even
replacement of the whole electronic item.