In: Electrical Engineering
Write the half-reactions that occur at each electrode when charging a lithium ion battery with a graphite anode and a LiCoO2 cathode. What is the overall reaction for the charging process?
Can you explain as well too please, not just the answer. Thanks!
Figure.1 below shows the structure and operation of lithium ion battery. The reactants in the electrochemical reactions in a lithium polymer battery are the negative and positive electrodes and the electrolyte providing a conductive medium for lithium ions to move between the electrodes. Electrical energy flows out from or into the battery when electrons flow through an external circuit during discharge or charge, respectively.
Both electrodes allow lithium ions to move in and out of their structures with a process called insertion (intercalation) or extraction (deintercalation), respectively. During discharge, the (positive) lithium ions move from the negative electrode (usually graphite = C6) to the positive electrode (forming a lithium compound) through the electrolyte while the electrons flow through the external circuit in the same direction. When the cell is charging, the reverse occurs with the lithium ions and electrons moved back into the negative electrode in a net higher energy state.
When lithium polymer cells are first charged, lithium ions are transferred from the layers of the lithium cobaltite to the carbon material that forms the anode. The overall reaction is given by,
The positive (cathode) electrode half-reaction in the lithium-doped cobalt oxide substrate is:
The negative (anode) electrode half-reaction for the graphite is:
In this the lithium ions are transported to and from the positive or negative electrodes by oxidizing the transition metal, cobalt (Co), in
During discharge, lithium ions (Li+) carry the current within the battery from the negative to the positive electrode, through the electrolyte and separator diaphragm.
During charging, an external electrical power source (the charging circuit) applies a voltage (a higher voltage than the battery produces, of the same polarity), forcing a charging current to flow within the battery from the positive to the negative electrode, i.e. in the reverse direction of a discharge current under normal conditions. The lithium ions then migrate from the positive to the negative electrode, where they become embedded in the porous electrode material in a process known as intercalation.