The solid lithium negative electrode has been a cause of problems with this type of cell,
namely safety difficulties and sometimes a decrease in performance due to passivation.
Thus these cells have been largely superseded by the lithium ion battery.
The lithium polymer battery uses lithium metal for the negative electrode and a transition
metal intercalation oxide for the positive one. In the resulting chemical reaction the lithium
combines with the metal oxide to form a lithium metal oxide and release energy. When the
battery is recharged the chemical reaction is reversed. The lithium is thus both a reactant
and the mobile ion that moves through the electrolyte.
A lithium ion battery is a rechargeable battery in which lithium ions move between the
anode and cathode, creating a flow of electricity. Lithium in the anode (carbon material)
is ionised and emitted to the electrolyte. Lithium ions move through a porous plastic
separator and into the cathode. At the same time, electrons are released from the anode.
This becomes an electric current travelling to an outside electric circuit. During charging,
lithium ions go from the cathode to the anode through the separator. Since this is a
reversible chemical reaction, the battery can be recharged.
The three primary functional components of a lithium ion battery are the anode, cathode
and electrolyte. The anode of a conventional lithium ion cell is made from carbon, the
cathode is a metal oxide, and the electrolyte is a lithium salt in an organic solvent.
The electrolyte is typically a mixture of organic carbonates. Depending on the choice
of materials, the voltage, capacity, life and safety of a lithium ion battery can change
dramatically. Recently, novel architectures using nanotechnology have been employed to
Pure lithium reacts vigorously with water so that a non-aqueous electrolyte is used, and
a sealed container rigidly excludes water from the battery pack.
Lithium ion batteries are more expensive than NiCad batteries but operate over a wider
temperature range with higher energy densities, while being smaller and lighter. They are
fragile and so need a protective circuit to limit peak voltages.
Initially used for consumer electronics, the lithium ion battery (LIB) is growing in pop-ularity for EV applications. Research is yielding a stream of improvements to traditional
LIB technology, focusing on energy density, durability, cost and safety.
An important point about
LIBs is that accurate control of voltage is needed when charging lithium cells. If it is
slightly too high it can damage the battery; too low and the battery will be insufficiently
charged. Suitable commercial chargers are being developed along with the battery.
The LIB has a considerable weight advantage over other battery systems and this
makes it a highly attractive candidate for EVs. The specific energy, for example, is
about three times that of lead acid batteries, and this could give a car a very reasonable
range. However, large batteries have until recently been prohibitively expensive, though
the price has now dropped to the point where the LIB is the preferred battery for EVs.
With recent developments and improved specific energies large companies have set up