1.C] Explain the construction and working of Li-ion battery, mention its applications.
Answer:
Construction:
Lithium metal is an attractive anode material because of its lightweight, high voltage, very low electrode potential, high electrical equivalence and good conductivity. A lithium cell can produce voltage from 1.5 V to 3.5V based on the types of materials used. There are two types of lithium-based batteries are available.
Schematic diagram of Lithium Metal Battery is shown in Figure 1.11 and Lithium-ion Battery is shown in Figure 1.12.
Construction and working of Li-Ion Batteries:
The cell is represented as, C, Li+│Li+│LiMn2O4
It consists of:
- Anode: is made of graphite (C6)
- Cathode: The cathode material is made of intercalated lithium compound, such as multi layered lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), lithium manganese oxide(LiMn2O4) etc.
- Electrolyte: A non-coordinating electrolyte salt such as LiPF6 or lithium hexafluoroarsenate monohydrate (LiAsF6) or lithium tetrafluoroborate (LiBF4) is dissolved in an organic solvent like ethylene carbonate or diethyl carbonate etc. Since lithium reacts violently with water, a non-aqueous electrolyte must be used.
- Separator: Polypropylene soaked with electrolyte.
Working:
During charging; an external load forces the Li+ ions to travel from cathode (lithium compound of LiMn2O4) to anode and accumulates on the surface of graphite. During discharge; Li+ spontaneously starts migrating back to lithium compound (LiMn2O4) at cathode and electrons flow through the external circuit. The probable cell reactions are given below,
Applications:
- Light weight and compact, low maintenance
- High voltage and high energy density
- Used in mobile phones, tabs, laptops, wireless communication devices etc.
- Used in medical devices, electric cars, auto mobiles etc.