How Lithium-Ion Batteries Work
You can find Lithium-ion Batteries in all walks of life these days. The batteries are used in Ipods,
Laptops, Remote Control Cars, and even small Solar Energy Systems. The reason why the batteries are
so popular is because pound for pound they are one of the most effective batteries available.
Each lithium-ion battery is made up of smaller
batteries called cells that are contained within a
plastic container. Each cell is made of five
layers. The cell usually lies vertically but for
simplicity sake we will imagine the cell lying flat.
The bottom layer is made of a pure copper and
the top layer is made of aluminum. Just below
the aluminum plate is a very pure lithium metal
oxide which has a positive charge and is called
the cathode. The more pure the metal oxide the
longer the battery lasts and the higher its
performance. Above the copper plate lies the anode which has a negative charge and is made of
graphite (a layered carbon structure).
Between the cathode and the anode is a liquid medium electrolyte which carries electrons between the
cathode and the anode allowing the batteries charge to flow freely. This electrolyte medium must be
very pure and free of water to ensure efficient charging/discharging of energy inside the battery. The
cathode and anode do not directly touch one another as it would cause a short circuit. Between the two
layers in the electrolyte is another (extremely thin) layer simply called the separator.
When the lithium-ion battery is connected to an outside current and allowed to charge positively-
charged lithium-ions are repelled from the
positively charged cathode layer and are
attracted to the negatively charged anode. The
lithium ions are so small that they are able to
pass through the separator due to the principle
of micro-porosity. The positive ions are stored
in the layered graphite structure of the anode
effectively charging the battery.
When the battery is used and energy is
removed from the cell the charge of the
cathode diminishes attracting the positive ions it originally lost. The ions travel from the anode through
the electrolyte medium and separator back to the cathode. The amount of energy that can be stored in
a battery and how long the battery will last depends heavily on the quality and purity of the materials
used. Companies focus heavily on R&D to increase the purity as well as design of their lithium ion
batteries to better the quality and output of their
Lithium-Ion Batteries are very popular because they
have a number of advantages over the competition.
The materials within the batteries are not only
highly reactive and great at storing energy but they
are much lighter than the comparable materials of
other batteries. The batteries are also very good at
holding their charge. Over a month a lithium-ion
battery will only lose 5 percent of its charge while
other batteries lose up to 20 percent. These
batteries can also withstand hundreds of charge
cycles during their lifetime.
However, the battery also has its drawbacks such as
its sensitivity to high temperatures which can ruin a lithium-battery very quickly (although companies
have been conducting research to better the temperature range the batteries can withstand). If lithium-
batteries are ever completely discharged they cannot be recharged which means that an on-board
computer must be used to manage the charge of the battery. This makes the batteries much more
expensive than their base material cost. Lastly, these batteries degrade quickly. The moment they leave
the factory floor the degradation has already started, making the battery life only a few years. All of
these reasons combined mean that if you installed Helios 260 watt panels on your home for solar energy
lithium-ion is not the battery for you. However, if you are purchasing a new laptop, cellphone, tablet,
etc. there is a high chance you will find a lithium-ion battery inside.
Photo Credit: James Vaughan, Martin Terber, Angus