Lithium Ion Battery

Lithium ions are added to a carbon electrode instead of using metallic lithium as the anode.

Lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging.

Schematic of a generic lithium ion battery arrangement shown during discharge

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.

Graphite Anode

A commercial 2600 mAh 18650 Li-ion cell today uses around 10g of graphite anode material.

Seperator

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

Silicon Anode

A commercial 2600 mAh 18650 Li-ion cell today uses around 10g of graphite anode material - just 2.6g of structured silicon can replace graphite.

See also: Battery, Battery Separator, Equivalent Lithium Content, Lithium Metal Anode Battery, Lithium Polymer Battery, Lithium Sulphur Battery.

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Subjects: Electrochemistry Electronics