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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, and electric toys. The reason why the batteries are so popular is because pound for pound they are one of the most effective batteries available.

The Materials

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.

The Chemistry

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 product.


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.

Coin Cell Battery - 24.5mm (PTH LIR2477)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.