| specific energy | 90–110 Wh/kg (320–400 J/g) |
|---|---|
| energy density | 220 Wh/L (790 kJ/L) |
| specific power | >300 W/kg |
| Energy/consumer-price | 0.5-2.5 Wh/US$ (US$0.11–0.56/kJ) |
| Time durability | >10 years |
| Cycle durability | 2,000 cycles |
| Nominal cell voltage | 3.3 V |
The lithium iron phosphate (LiFePO4) battery, also called LFP battery, is a type of rechargeable battery, specifically a lithium-ion battery, which uses LiFePO4 as a cathode material.
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LiFePO4 was discovered by John Goodenough's research group at the University of Texas in 1996,[1][2] as a cathode material for rechargeable lithium batteries. Because of its low cost, non-toxicity, the high abundance of iron, its excellent thermal stability, safety characteristics, good electrochemical performance, and high specific capacity (170 mA·h/g, or 610 C/g) it gained some market acceptance.[3][4]
The key barrier to commercialization was its intrinsically low electrical conductivity. This problem, however, was then overcome partly by reducing the particle size and effectively coating the LiFePO4 particles with conductive materials such as carbon, and partly by employing the doping[3] approaches developed by Yet-Ming Chiang and his coworkers at MIT using cations of materials such as aluminium, niobium, and zirconium. It was later shown that most of the conductivity improvement was due to the presence of nanoscopic carbon originating from organic precursors.[5] Products using the carbonized and doped nanophosphate materials developed by Chiang are now in high volume mass production and are used in industrial products by major corporations including Black and Decker's DeWalt brand, the Fisker Karma, Daimler, Cessna and BAE Systems.
Most lithium-ion batteries (Li-ion) used in consumer electronics products are lithium cobalt oxide batteries (LiCoO2). Other varieties of lithium-ion batteries include lithium manganese oxide (LiMn2O4) and lithium nickel oxide (LiNiO2). The batteries are named after the material used for their cathodes; the anodes are generally made of carbon and a wide variety of electrolytes are used.
The LiFePO4 battery uses a lithium-ion-derived chemistry and shares many of its advantages and disadvantages with other Lithium-ion battery chemistries.
However, one key advantage over other lithium-ion batteries is the superior thermal and chemical stability, which provides better safety characteristics than lithium-ion batteries with other cathode materials.[6] Due to significantly stronger bonds between the oxygen atoms in the phosphate (compared to the cobalt), oxygen is not readily released, and as a result, lithium iron phosphate cells are virtually incombustible in the event of mishandling during charge or discharge, and can handle high temperatures without decomposing.[6]
Lithium iron phosphate chemistry also offers a longer cycle life over standard lithium-ion cells.[6]
The use of phosphates also reduces the cost and environmental concerns of Cobalt cells, particularly in regards of cobalt entering the environment through improper disposal,[6] with considerably increased safety over the cobalt chemistry type of lithium battery cell, particularly when compared to LiPo battery cells commonly used in the aeromodeling hobby.
One of the other major advantages for LiFePO4 when compared with LiCoO2 is higher current or peak-power rating.[7]
LFP batteries have some drawbacks:
While LiFePO4 cells have lower voltage and energy density than LiCoO2 Li-ion cells, this disadvantage is offset over time by the slower rate of capacity loss (aka greater calendar-life) of LiFePO4 when compared with other lithium-ion battery chemistries (such as LiCoO2 cobalt or LiMn2O4 manganese spinel based lithium-ion polymer batteries or lithium-ion batteries).[10][11] For example:
LiFePO4 is an intrinsically safer cathode material than LiCoO2 and manganese spinel. The Fe-P-O bond is stronger than the Co-O bond, so that when abused, (short-circuited, overheated, etc.) the oxygen atoms are much harder to remove. This stabilization of the redox energies also helps fast ion migration.
As lithium migrates out of the cathode in a LiCoO2 cell, the CoO2 undergoes non-linear expansion that affects the structural integrity of the cell. The fully lithiated and unlithiated states of LiFePO4 are structurally similar which means that LiFePO4 cells are more structurally stable than LiCoO2 cells.
No lithium remains in the cathode of a fully charged LiFePO4 cell—in a LiCoO2 cell, approximately 50% remains in the cathode. LiFePO4 is highly resilient during oxygen loss, which typically results in an exothermic reaction in other lithium cells.[4]
LFP batteries were featured on the November 5, 2008 episode of Prototype This!. They were used as the power source for a hexapod (walking) vehicle. Lithium Technology Corp. announced in May 2007, that they had developed a new Lithium Iron Phosphate battery with cells large enough for use in hybrid cars, claiming they are "the largest cells of their kind in the world.".[14] While they may be large enough for such uses, there remain limitations to the use of this particular Lithium battery technology which may make their use contraindicated. See Advantage and Disadvantages above for details.
This battery is used in the electric cars made by Aptera[15] and QUICC.[16]
Killacycle, the worlds fastest electric motorcycle, uses lithium iron phosphate batteries.[17]
Roehr Motorcycle Company, uses a 5.8 kW·h capacity LFP battery pack to power its supersport electric motorcycle.
This type of battery technology is used on the One Laptop per Child (OLPC) project.[18] OLPC batteries are manufactured by BYD Company of Shenzhen, China, the world's largest producer of Li-ion batteries. BYD, also a car manufacturer, plans to use its lithium iron phosphate batteries to power its PHEV, the F3DM and F6DM (Dual Mode), which will be the first commercial dual-mode electric car in the world. It plans to mass produce the cars in 2009.[19]
One Laptop per Child uses LFP batteries in its XO laptops because they contain no toxic heavy metals in compliance with the European Union's Restriction of Hazardous Substances Directive.[20]
LFP batteries are gaining popularity now in the world of hobby-grade R/C, due to the benefits over the ever-popular LiPo batteries. They can be recharged much faster and for more cycles, are not prone to catching fire or exploding while recharging, and are more robust than the LiPo type.
LFP batteries are used by electric vehicles manufacturer Smith Electric Vehicles to power its products.
Used by Minneapolis Electric Bike and Chicago Electric Bicycles.
Some electronic cigarette modifications also use these types of batteries.