Since the advent of lithium-ion battery has been around it for research, development work has been carried out in the last century the late 90s and developed a lithium-polymer battery, 2002, introduced after the lithium iron phosphate batteries.
Mainly by the internal lithium-ion battery cathode, anode, electrolyte and membrane composition. Positive and negative electrode and electrolyte materials and process differences between different makes batteries have different properties, and have different names. Currently on the market lithium-ion battery cathode material of lithium cobalt oxide is mainly (LiCoO2), plus a few use lithium manganese oxide (LiMn2O4) and lithium nickel oxide (LiNiO2) as cathode materials for lithium-ion battery, the latter two generally positive materials, lithium-ion battery known as the “Lithium manganese battery” and “lithium nickel batteries.” The newly developed lithium iron phosphate power battery is lithium iron phosphate (LiFePO4) battery cathode material for lithium-ion batteries, lithium-ion battery is a new member of the family.
General lithium-ion battery electrolyte is a liquid, but then developed a solid and gel polymer electrolyte, describes this kind of lithium ion battery lithium polymer battery, its performance is better than the liquid electrolyte lithium-ion batteries.
The full name of lithium iron phosphate lithium iron phosphate should be lithium-ion battery, this name is too long, referred to as lithium iron phosphate batteries. Because of its properties, especially suitable for the application of power, then add in the name of the “power” word, that is, lithium iron phosphate batteries. Some people call it “Lithium iron (LiFe) battery.”
Currently used as a cathode material for lithium ion batteries are: LiCoO2, LiMn2O4, LiNiO2 and LiFePO4. The cathode material composition of the metal elements, cobalt (Co) the most expensive, and not much storage, nickel (Ni), manganese (Mn) are cheaper, and iron (Fe) the cheapest. Cathode material prices and the prices of these metals market consistent. Therefore, the use of LiFePO4 cathode material of lithium-ion battery should be made of the cheapest. It is also characterized by environmental pollution.
As the requirements of rechargeable batteries are: high capacity, high voltage, good performance of charge-discharge cycle, the output voltage stability, high current charge and discharge, electrochemical stability, the use of security (will not over charge, over discharge and short circuit caused by improper operation of fire or explosion), the working temperature range, non-toxic or less toxic pollution to the environment. Use of LiFePO4 for lithium iron phosphate cathode performance requirements of these are good, especially in large discharge rate of discharge (5 ~ 10C discharge) and discharge voltage stable, the security (no burning, no explosion), Life on the (number of cycles ), environmental pollution, it is the best, is the best high-current output power battery.
The internal structure of LiFePO4 battery shown in Figure 1. The structure of the left is olivine LiFePO4 as battery anode, the cathode foil connection with the middle of the polymer membrane, which separates the positive and negative, but the lithium ion Li + can not pass the electronic e-the right is carbon (graphite) to form a battery anode, the copper foil and the negative battery connection. Between the top and bottom of the battery cell electrolyte, the battery from the metal shell sealed package.
LiFePO4 battery’s nominal voltage is 3.2 V, terminate the charging voltage is 3.6V, termination of discharge voltage is 2.0V. Because each manufacturer uses the positive and negative electrode material, electrolyte material quality and process is different, its performance will be some differences. For example, the same model (the same package, standard battery), the battery capacity are very different (10% -20%).