Lithium Ion Cell

In a rechargeable lithium ion battery lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging.

The cathode is a lithium transition metal oxide, eg manganese or cobalt or a combination of transitional metals. The anode is a graphite-based material, which can intercalate or release lithium.

When discharge begins the lithiated carbon releases a Li⁺ ion and a free electron.

Electrolyte, that can readily transports ions, contains a lithium salt that is dissolved in an organic solvent. The Li⁺ ion, which moves towards the electrolyte, replaces another Li + ion from the electrolyte, which moves towards the cathode. At the cathode/electrolyte interface, Li⁺ ions then become intercalated into the cathode and the associated electron is used by the external device.

When charging takes place, the lithium metal oxide is delithiated and the reverse process ensues.

• The operational voltage is set by the choice of Cathode and Anode.
• The capacity of the cell is determined by the area and thickness of the cathode and anode.
• The power is determined by: thickness of anode and cathode, electrical resistance and ability to extract heat.

The following video explains this all with fabulous 3D photorealistic animation.

Separator: a porous membrane placed between electrodes of opposite polarity, permeable to ionic flow but preventing electric contact of the electrodes.

Lithium Ion Chemistry

There are many variations on the lithium ion chemistry. The cathode is a lithium transition metal oxide, eg manganese or cobalt or a combination of transitional metals. The anode is a graphite-based material, which can intercalate or release lithium.