Today, there are a large number of batteries with various 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 generally similar to each other in technical specifications, lithium-iron-phosphate batteries have their own unique features that distinguish them from other batteries made using lithium-ion technology.
History of the discovery of lithium iron phosphate battery
The inventor of the LiFePO4 battery is John Goodenough, who worked in 1996 at the University of Texas to create new material for the cathode for lithium-ion batteries. The professor was able to create a material with greater cheapness, having less toxicity and high heat resistance. Among the shortcomings of the battery in which the new cathode was used was a lower capacity.
Nobody was interested in the invention of John Goodenough, but in 2003, A 123 Systems decided to develop this technology, considering it quite promising. Investors of this technology have become many large corporations - Sequoia Capital, Qualcomm, Motorola.
Characteristics of LiFePO4 batteries
The voltage of the ferrophosphate battery is the same as that of other batteries related to lithium-ion technology. The rated voltage depends on the dimensions of the battery (size, form factor). For batteries, 18,650 is 3.7 volts, for 10,440 (pinky) - 3.2, for 24,330 - 3.6.
In almost all batteries, the voltage gradually decreases during the discharge process. One of the unique features is the voltage stability during operation with LiFePO4 batteries. Voltage characteristics similar to these have batteries made using nickel technology (nickel-cadmium, nickel-metal hydride).
Depending on the size, the lithium-iron-phosphate battery is capable of delivering from 3.0 to 3.2 volts up to a full discharge. This property gives more advantages for these batteries when used in circuits, since it practically negates the need for voltage regulation.
The voltage at full charge is 2.0 volts, which is the lowest recorded discharge limit among all lithium technology batteries. These batteries are leaders in the service life, which is equivalent to 2000 cycles per charge and discharge. Due to the safety of its chemical structure, LiFePO4 batteries can be charged using the special accelerated Delta V method when a large current is supplied to the battery.
Many batteries can not withstand charging by this method, which leads to excessive heating and damage. In the case of lithium-iron-phosphate batteries, using this method is not just possible, but even recommended. Therefore, especially for charging such batteries, there are special chargers. Of course, such chargers cannot be used on batteries with other chemistry. Depending on the form factor, lithium-iron-phosphate batteries on such chargers can fully charge 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 range for lithium-ion batteries is -20 to +20 degrees Celsius, then lithium-iron-phosphate batteries can work perfectly in the range from -30 to +55. Charging or discharging the battery at temperatures above or below those described will greatly damage the battery.
Lithium iron phosphate batteries are much less susceptible to aging compared to other lithium-ion batteries. Aging is a natural loss of capacity over time, which does not depend on whether the battery is used or on a shelf. For comparison: all lithium-ion batteries lose about 10% of their capacity each year. Lithium-iron-phosphate, on the other hand, lose only 1.5%.
Of the minuses of these batteries, it is worth highlighting a lower capacity, which is 14% less (or so) than other lithium-ion batteries.
Ferrophosphate Battery Safety
This type of battery 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 large loads when discharged (when working with low resistance) 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 exhausted their life. Many hazardous chemistry batteries (such as lithium-cobalt) have to be subjected to additional recycling processes in order to nullify their environmental hazard.
Charging lithium iron phosphate batteries
One of the reasons for investors' commercial interest in ferrophosphate chemistry was the possibility of fast charging, resulting from its stability. Immediately after the organization of the conveyor production of LiFePO4 batteries, they were positioned as batteries that can be quickly charged.
For this purpose, special chargers began to be produced. As already mentioned above, such chargers can not be used on other batteries, as this will cause them to overheat and will greatly damage them.
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 the use of smart chargers with many options that regulate the charging process.
Lithium iron phosphate battery device
The lithium-iron-phosphate LiFePO4 battery has no features in the internal device 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 batteries on lithium-ion technology 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 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 up the accumulated charge (oxidation). When charging the battery, 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 for this chemistry can be divided into four categories:
- Full battery.
- Large cells in the form of parallelepipeds.
- Small cells in the form of parallelepipeds (prismatic - 3.2V LiFePO4 batteries).
- Small flat batteries (packs).
- Cylindrical batteries.
Lithium-iron-phosphate batteries and cells can have different nominal voltages from 12 to 60 volts. They are much ahead of traditional lead-acid batteries: the cycle is much higher, the weight is several times lower, and they recharge several times faster.
Cylindrical batteries in this chemistry are used both separately and in a circuit. The dimensions of these cylindrical batteries are very different: from 14,500 (finger-type) to 32,650.
Lithium iron phosphate battery
Ferrophosphate batteries for bicycles and electric cycles deserve special attention. With the invention of the new iron-phosphate cathode, along with other types of batteries, special batteries were also developed for this chemistry, which, due to their improved characteristics and lower weight, can be conveniently used even on ordinary bicycles. Such batteries immediately gained popularity among fans of upgrading their bikes.
Lithium-iron-phosphate batteries can provide several hours of carefree cycling, which is worthy of competition with internal combustion engines, which were also often used on bicycles before. Typically, LiFePO4 48v batteries are used for these purposes, but it is possible to purchase batteries with 25, 36 and 60 volts.
The use of ferrophosphate batteries
The role of batteries in this chemistry is understandable without comment. For different purposes, prismatic devices are used - LiFePO4 3.2 v batteries. Larger cells are used as elements of buffer systems for solar energy and wind generators. Ferrophosphate batteries are widely used in the construction of electric vehicles.
Small flat batteries are used for phones, laptops and tablets. Cylindrical batteries of various form factors are used for airsoft guns, electronic cigarettes, radio-controlled models, etc.