What are Lithium ion Batteries & How LFP batteries work?

                               

                                       Figure 1: 48V LFP battery fixed inside a cabinet.

What are Lithium ion Batteries ?

Lithium ion batteries are the rechargable batteries which has Lithium as cathode active material.

There are different types of Lithium ion batteries like LFP,NMC,NCA etc, All these comes under Lithium family batteries and each one has its advantages and disadvantages.

These batteries having better features compared to other lead acid or VRLA batteries because of the Power electronics components avaialbilty to control each and every parameters of the battery.

For example the monitoring section reads and monitor all real time data's from individual cells and sensors connectd in it, means Voltage of individual cells,battery pack,total voltage,cell temperature,Over current or Under current etc...., each and every parameters of the battery including SOH and SOC also tracked using in-build BMS(Battery Monitoring System).

The Lithium ion batteries have high energy density, means the amount of energy stored per unit volume is higher than the traditional Lead acid batteries hence the size of the battery is smaller.

The Li-ion battery can store as much as twice of the power Lead Acid batterycan hold and also environmentally friendly but these batteries are susceptible to 100% discharge so max 90% discharge is recommended.

Working of LFP battery?

                                                   

                                              Figure 2: Shows movement of Ions & Electrons

Like anyother LMO (Lithium Metal Oxide ) batteries, the working of LFP is similar and the only change is the usage of cathode metal oxides.

Incase of LFP the cathode is Lithium (Ferrous Phosphate) Li-(FePO4), for NMC battery the cathode is a mixed of Lithium (Nickel Manganese Cobalt Oxide) Li(NiMnCoO2).

The Negative electrode of Lithium ion battery is graphite/graphene and the positive electrode is lithium iron phosphate, The electrolytes such as LiPF6(lithium hexafluorophosphate) is used.,The Seperator used in the LFP batteries can be Polyethylene (PE) , Polypropylene (PP).

Charging:

While Charging,the lithium atoms leave the metal oxide structure and ionize into Li+ ions under the release of an electron. In this process Li+ ions diffuse to the negative electrode(anode). 

At the surface of the graphite particles the Li+ ions and electrons recombine with each other forming neutral lithium atoms and are reintercalated into the molecular structure of the graphite.

When no more ions will flow, the battery is fully charged and ready to use.

Discharging

During discharge, lithium atoms oxidize by forming Li+ ions and electrons, whereas Li+ ions move to the positive electrode diffusing through the electrolyte and the separator. The electrons flow from the negative electrode to the positive on the external circuitry, where the resulting current flow can be used to run any type of load.

 At the positive electrode the electrons recombine with the Li+ ions and are stored in the molecular structure of the cathode active material,

When all the ions have moved back, the battery is fully discharged hence it needs charge again.