A lithium-ion battery or Li-ion battery (abbreviated as LIB) is a type of rechargeable battery in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging.
Li-ion battery is mainly composed of positive electrode, negative electrode, electrolyte and diaphragm. Chemistry, performance, cost and safety characteristics vary across LIB types. Electrolytes are all liquid. The biggest difference for various Li-ion battery is the anode materials.
Six Cathode materials and their application.
Next we’ll simply introduce 6 cathode materials and their application.
- Lithium Cobalt Oxide ( LiCoO2) , used for Hand-held electronics . Offers high energy density but presents safety risks, especially when damaged.
2. Lithium Ion Manganese Oxide Battery (LiMn2O4, Li2MnO3, or LMO)
3. Lithium iron phosphate (LiFePO4)
4. Lithium Titanate (Li4Ti5O12 or LTO)
5. Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2 or NMC) .Such batteries are widely used for electric tools, medical equipment, and other roles. NMC in particular is a leading contender for automotive applications. Offer lower energy density but longer lives and less likelihood of fire or explosion.
6. Lithium nickel cobalt aluminum oxide (LiNiCoAlO2 or NCA)
“Anode” sends electrons through a wire
Just like the cathode, the anode substrate is also coated with active material.
The anode’s active material performs the role of enabling electric current to flow through the external circuit while allowing reversible absorption/emission of lithium ions released from the cathode.
When the battery is being charged, lithium ions are stored in the anode and not the cathode.
At this point, when the conducting wire connects the cathode to the anode (discharge state), lithium ions naturally flow back to the cathode through the electrolyte, and the electrons (e-) separated from lithium ions move along the wire generating electricity.
For anode graphite which has a stable structure is used, and the anode substrate is coated with active material, conductive additive and a binder.
Thanks to graphite’s optimal qualities such as structural stability, low electrochemical reactivity, conditions for storing much lithium ions and price, the material is considered suitable to be used for anode.
“Electrolyte” allows the movement of ions only
a. What is electrolyte?
Lithium ions move through the electrolyte and electrons move through the wire.
This is the key in enabling the use of electricity in a battery.
If ions flow through the electrolyte, not only can’t we use electricity but safety will be jeopardized.
Electrolyte is the component which plays this important role.
It serves as the medium that enables the movement of only lithium ions between the cathode and anode.
For the electrolyte, materials with high ionic conductivity are mainly used so that lithium ions move back and forth easily.
b. Component of Electrolyte
The electrolyte is composed of salts, solvents and additives.
The salts are the passage for lithium ions to move, the solvents are organic liquids used to dissolve the salts, and the additives are added in small amounts for specific purposes.
Electrolyte created in this way only allows ions to move to the electrodes and doesn’t let electrons to pass.
In addition, the movement speed of lithium ions depends on the electrolyte type.
Thus, only the electrolytes that meet stringent conditions can be used.
“Separator”, the absolute barrier between cathode and anode.
While the cathode and anode determine the basic performance of a battery, electrolyte and separator determine the safety of a battery.
The separator functions as a physical barrier keeping cathode and anode apart.
It prevents the direct flow of electrons and carefully lets only the ions pass through the internal microscopic hole.
Therefore, it must satisfy all the physical and electrochemical conditions.
Commercialized separators we have today are synthetic resin such as polyethylene (PE) and polypropylene (PP).