SECONDARY LITHIUM ION MANUFACTURING (LITHIUM ION BATTERY PACK)

A lithium iron phosphate (LFP) battery is a type of lithium-ion battery that is capable of charging and discharging at high speeds compared to other types of batteries. It is a rechargeable battery consisting of LiFePO4 as its cathode material; hence the name.

Lithium iron phosphate batteries have several distinctive features, including:

• Better power density
• Low discharge rate
• Flat discharge curve
• Less heating
• Higher number of charge cycles
• Increased safety

Lithium iron phosphate (LFP) batteries are also known as lithium ferrophosphate batteries.

The first model of the lithium iron phosphate battery was made after the discovery of phosphate as a cathode material for use in li-ion batteries in 1996. Improvements in the coatings and usage of nano-scale phosphate have made this type of battery more efficient.

The major distinction that lithium iron phosphate batteries have from other li-ion batteries is that LFP is capable of delivering a constant voltage and also has a comparatively higher charge cycle, in the range of 2000-3000. LFP batteries are environmentally safe and structurally stable. They have a lower energy density and low discharge rate. They do not heat up easily and are relatively cooler than other batteries. The chemistry of the battery saves it from thermal runaway, and hence it is considered to be safe for home use.

Due to their constant voltage and safe discharge, LFPs have found applications in cars, bicycles and solar devices. They are also used as replacements for costly lead-acid starter batteries. They are well suited for applications that require high-load currents and endurance. They are easy to store and carry due to their light weight and ability to provide huge amounts of energy. They are widely used in portable electronic devices like laptops and mobile phones.

A recent improvement over the original lithium iron phosphate cathode material by MIT has allowed these batteries to be charged up to 100 times faster than the previous speed. An improvised coating of an ion conductor onto the LFP has enabled the acceleration of ions, and thus the charging time has been greatly reduced.

Lithium Iron Phosphate (LiFePO4)

Phosphate based technology possesses superior thermal and chemical stability which provides better safety characteristics than those of Lithium-ion technology made with other cathode materials. Lithium phosphate cells are incombustible in the event of mishandling during charge or discharge, they are more stable under overcharge or short circuit conditions and they can withstand high temperatures without decomposing. When abuse does occur, the phosphate based cathode material will not burn and is not prone to thermal runaway. Phosphate chemistry also offers a longer cycle life.

Advantages:

a. Quick charging
b. Safer performance and large overcharge tolerance
c. Self balance
d. Simplified battery management system and battery charger
e. Four times higher energy density than a Lead-acid battery
f. Runs better at high temperature with 10% enhanced capacity
g. Longer life cycle of up to 2000 cycles

CONSTRUCTION OF LI FERRO PHOSPHATE BATTERY

Lithium ion batteries are made up of one or more generating compartments called cells. Each cell is composed of three components: a positive electrode, negative electrode, and a chemical called an electrolyte in between them.

The positive electrode is made from chemical compound named lithium iron phosphate (LiFePO4).

The negative electrode is made up of carbon (graphite)

The electrolyte varies from one type of battery to another. All lithium ion batteries more or less work in same manner. During charging the battery, lithium based positive electrode withdraws some of its lithium ions, which move through the electrolyte to reach to the negative electrode and remain there. The battery stores energy during this process. When the battery is discharging, the lithium ions move back across the electrolyte to the positive electrode, producing the energy that powers the battery. In both the cases electrons flow in the opposite direction to the ions around the outer circuits. Electrons do not flow through the electrolyte as it tends to be an effective insulating barrier, as far as electrons are concerned. The movement of ions (through the electrolyte) and electrons (around the external circuit, in the opposite direction) are interconnected processes and if any one of them stops and the other also stops. If ions stop moving through the electrolyte because the battery completely discharges and the electrons can’t move through the outer circuit either, so the power is lost. Similarly we switch off whatever the battery was powering, the electron flow stops and so does the flow of ions and the battery stops discharging. Unlike other batteries lithium ion batteries have built in electronic controllers that regulate the charging and discharging in them. They prevent the overcharging and overheating that can cause lithium ion batteries to explode in some unusual circumstances.