Today, there are a large number of batteries with different types of chemistry. The most popular batteries today are lithium-ion. This group also includes lithium-iron-phosphate (ferrophosphate) batteries. While all batteries in this category are broadly similar in technical specifications, lithium iron phosphate batteries have their own unique features that distinguish them from other batteries made using lithium-ion technology.
The story of the discovery of the lithium iron phosphate battery
The inventor of the LiFePO4 battery is John Goodenough, who worked in 1996 at the University of Texas on a new cathode material for lithium-ion batteries. The professor managed to create a material that is more cheap, has less toxicity and high thermal stability. Among the shortcomings of the battery, which used the new cathode, was a lower capacity.
No one was interested in John Goodenough's invention, but in 2003 A 123 Systems decided to develop this technology, considering it quite promising. Many large corporations have become investors in this technology - Sequoia Capital, Qualcomm, Motorola.
Characteristics of LiFePO4 batteries
The voltage of the ferrophosphate battery is the same as that of other lithium-ion technology batteries. The rated voltage depends on the dimensions of the battery (size, form factor). For batteries 18 650 it is 3.7 volts, for 10 440 (little fingers) - 3.2, for 24 330 - 3.6.
For almost all batteries, the voltage gradually drops during discharging. One of the unique features is the voltage stability when working with LiFePO4 batteries. Batteries made using nickel technology (nickel-cadmium, nickel-metal hydride) have voltage characteristics similar to these.
Depending on size, a lithium iron phosphate battery can deliver between 3.0 and 3.2 volts until fully discharged. This property gives more advantages to these batteries when used in circuits, as it practically eliminates the need for voltage regulation.
Full discharge voltage is 2.0 volts, the lowest recorded discharge limit of any lithium technology battery. These batteries are leaders inservice life, which is equivalent to 2000 cycles for charge and discharge. Due to the safety of their chemical structure, LiFePO4 batteries can be charged using a special accelerated delta V method when a large current is applied to the battery.
Many batteries can't withstand this method of charging, causing them to overheat and deteriorate. In the case of lithium-iron-phosphate batteries, using this method is not only possible, but even recommended. Therefore, there are special chargers specifically for charging such batteries. Of course, such chargers cannot be used on batteries with other chemistry. Depending on the form factor, lithium iron phosphate batteries on these chargers can be fully charged in 15-30 minutes.
Recent developments in the field of LiFePO4 batteries offer the user batteries with an improved operating temperature range. If the standard operating range for lithium-ion batteries is -20 to +20 degrees Celsius, then lithium iron phosphate batteries can work perfectly in the range of -30 to +55. Charging or discharging a battery at temperatures above or below those described will severely damage the battery.
Lithium iron phosphate batteries are much less affected by the aging effect than other lithium-ion batteries. Aging is the natural loss of capacity over time, which is independent of whether a battery is used oris on the shelf. By comparison, all lithium-ion batteries lose about 10% capacity each year. Lithium iron phosphate lose only 1.5%.
The downside of these batteries is the lower capacity, which is 14% less (or so) than other lithium-ion batteries.
Ferrophosphate battery safety
This type of batteries is considered one of the safest among all existing types of batteries. LiFePO4 Lithium Phosphate batteries have very stable chemistry, and are able to withstand heavy loads well in discharge (in low resistance operation) and charge (when charging the battery with high currents).
Due to the fact that phosphates are chemically safe, these batteries are easier to dispose of after they have worked out their resource. Many batteries with hazardous chemistry (such as Lithium-Cob alt) have to undergo additional recycling processes in order to eliminate their environmental hazard.
Charging lithium iron phosphate batteries
One of the reasons for the commercial interest of investors in ferrophosphate chemistry was the ability to quickly charge, resulting from its stability. Immediately after the organization of the conveyor release of LiFePO4 batteries, they were positioned as batteries that can be quickly charged.
Special chargers have been produced for this purpose. As already mentioned above, such chargers cannot be used on other batteries, as this will cause them to overheat and will greatly damagethem.
A special charger for these batteries can charge them in 12-15 minutes. Ferrophosphate batteries can also be charged with conventional chargers. There are also combined charger options with both charging modes. The best option, of course, would be to use smart chargers with many options to control the charging process.
Lithium iron phosphate battery device
The lithium-iron-phosphate LiFePO4 battery has no special features in the internal structure compared to its counterparts in chemical technology. Only one element has undergone a change - a cathode made of iron phosphate. The anode material is lithium (all lithium-ion batteries have a lithium anode).
The operation of any battery is based on the reversibility of a chemical reaction. Otherwise, the processes occurring inside the battery are called oxidation and reduction processes. Any battery consists of electrodes - a cathode (minus) and an anode (plus). Also, inside any battery there is a separator - a porous material impregnated with a special liquid - an electrolyte.
When the battery is discharged, lithium ions move through the separator from the cathode to the anode, giving off the accumulated charge (oxidation). When a battery is charged, lithium ions move in the opposite direction from the anode to the cathode, accumulating charge (recovery).
Types of lithium iron phosphate batteries
All types of batteries on this chemistry can be divided into four categories:
- CompleteBattery.
- Large cells in the form of parallelepipeds.
- Small cells in the form of parallelepipeds (prisms - LiFePO4 batteries at 3.2 V).
- Small coin cells (packs).
- Cylindrical batteries.
Lithium Iron Phosphate batteries and cells can have different nominal voltages from 12 to 60 volts. They outperform traditional lead-acid batteries in many ways: the cycle time is much higher, the weight is several times lower, and they are recharged several times faster.
Cylindrical batteries in this chemistry are used both separately and in a chain. The dimensions of these cylindrical batteries are very different: from 14,500 (finger type) to 32,650.
Lithium iron phosphate batteries
Ferrophosphate batteries for bicycles and electric cycles deserve special attention. With the invention of a new iron-phosphate cathode, along with other types of batteries based on this chemistry, special batteries came out, which, due to their improved characteristics and lighter weight, can be conveniently used even on ordinary bicycles. Such batteries immediately gained popularity among fans of upgrading their bikes.
Lithium Iron Phosphate batteries are able to provide several hours of carefree cycling, which is a worthy competition for internal combustion engines, which were also often installed on bicycles in the past. Usually for datapurposes, 48v LiFePO4 batteries are used, but it is possible to purchase batteries for 25, 36 and 60 volts.
Application of ferrophosphate batteries
The role of batteries in this chemistry is clear without comment. Prisms are used for different purposes - LiFePO4 3, 2 v batteries. Larger cells are used as elements of buffer systems for solar energy and wind turbines. Ferrophosphate batteries are actively used in the construction of electric vehicles.
Small flat batteries are used for phones, laptops and tablet PCs. Cylindrical batteries of different form factors are used for airsoft guns, electronic cigarettes, radio-controlled models, etc.
