 A Lithium iron phosphate (LiFePO4) 14500 battery (right) shown next to a battery placeholder (left) | |
| Specific energy | 90–160 Wh/kg (320–580 J/g or kJ/kg)[1] Next gen: 180–205 Wh/kg[2] |
|---|---|
| Energy density | 325 Wh/L (1200 kJ/L)[1] |
| Specific power | around 200 W/kg[3] |
| Energy/consumer-price | 1-4 Wh/US$[4][5] |
| Time durability | > 10 years |
| Cycle durability | 2,500–9,000[6] cycles |
| Nominal cell voltage | 3.2 V |
Thelithium iron phosphate battery (LiFePO
4 battery) orLFP battery (lithium ferrophosphate) is a type oflithium-ion battery usinglithium iron phosphate (LiFePO
4) as thecathode material, and agraphiticcarbon electrode with a metallic backing as theanode. Because of their low cost, high safety, low toxicity, long cycle life and other factors, LFP batteries are finding a number of roles invehicle use, utility-scale stationary applications, andbackup power.[7] LFP batteries are cobalt-free.[8] As of September 2022, LFP type battery market share forEVs reached 31%, and of that, 68% were from EV makersTesla andBYD alone.[9]Chinese manufacturers currently hold a near-monopoly of LFP battery type production.[10] With patents having started to expire in 2022 and the increased demand for cheaper EV batteries,[11] LFP type production is expected to rise further and surpasslithium nickel manganese cobalt oxides (NMC) type batteries.[12]
Thespecific energy of LFP batteries is lower than that of other common lithium-ion battery types such asnickel manganese cobalt (NMC) andnickel cobalt aluminum (NCA). As of 2024, the specific energy ofCATL's LFP battery is claimed to be 205watt-hours per kilogram (Wh/kg) on the cell level.[13]BYD's LFP battery specific energy is 150 Wh/kg. The best NMC batteries exhibit specific energy values of over 300 Wh/kg. Notably, the specific energy of Panasonic's "2170" NCA batteries used inTesla's 2020 Model 3 mid-size sedan is around 260 Wh/kg, which is 70% of its "pure chemicals" value. LFP batteries also exhibit a lower operatingvoltage than other lithium-ion battery types.
LiFePO
4 is a natural mineral known astriphylite.Arumugam Manthiram andJohn B. Goodenough first identified the polyanion class of cathode materials forlithium ion batteries.[14][15][16]LiFePO
4 was then identified as a cathode material belonging to the polyanion class for use in batteries in 1996 by Padhiet al.[17][18] Reversible extraction of lithium fromLiFePO
4 and insertion of lithium intoFePO
4 was demonstrated. Because of its low cost, non-toxicity, the natural abundance ofiron, its excellent thermal stability, safety characteristics, electrochemical performance, and specific capacity (170 mA·h/g, or 610 C/g) it has gained considerable market acceptance.[19][20]
The chief barrier to commercialization was its intrinsically lowelectrical conductivity. This problem was overcome by reducing the particle size, coating theLiFePO
4 particles with conductive materials such ascarbon nanotubes,[21][22] or both. This approach was developed byMichel Armand and his coworkers atHydro-Québec and theUniversité de Montréal in 2015.[23][24][25] Another approach byYet Ming Chiang's group atMIT consisted ofdoping[19] LFP withcations of materials such asaluminium,niobium, andzirconium.
Negative electrodes (anode, on discharge) made ofpetroleum coke were used in early lithium-ion batteries; later types used natural or synthetic graphite.[26]
The LFP battery uses a lithium-ion-derived chemistry and shares many advantages and disadvantages with other lithium-ion battery chemistries. However, there are significant differences.
Iron and phosphates are verycommon in the Earth's crust. LFP contains neithernickel[33] norcobalt, both of which are supply-constrained and expensive. As with lithium, human rights[34] and environmental[35] concerns have been raised concerning the use of cobalt. Environmental concerns have also been raised regarding the extraction of nickel.[36]
A 2020 report published by theDepartment of Energy compared the costs of large scale energy storage systems built with LFP vs NMC. It found that the cost per kWh of LFP batteries was about 6% less than NMC, and it projected that the LFP cells would last about 67% longer (more cycles). Because of differences between the cell's characteristics, the cost of some other components of the storage system would be somewhat higher for LFP, but on balance it still remains less costly per kWh than NMC.[37]
In 2020, the lowest reported LFP cell prices were $80/kWh (12.5 Wh/$) with an average price of $137/kWh,[38] while in 2023 the average price had dropped to $100/kWh.[39]By early 2024,VDA-sized LFP cells were available for less thanRMB 0.5/Wh ($70/kWh), while Chinese automakerLeapmotor stated it buys LFP cells at RMB 0.4/Wh ($56/kWh) and believe they could drop to RMB 0.32/Wh ($44/kWh).[40] By mid 2024, assembled LFP batteries were available to consumers in the US for around $115/kWh.[41]
LFP chemistry offers a considerably longercycle life than other lithium-ion chemistries. Under most conditions it supports more than 3,000 cycles, and under optimal conditions it supports more than 10,000 cycles. NMC batteries support about 1,000 to 2,300 cycles, depending on conditions.[6]
LFP cells experience a slower rate ofcapacity loss (a.k.a. greatercalendar-life) than lithium-ion battery chemistries such as cobalt (LiCoO
2), manganese spinel (LiMn
2O
4),lithium-ion polymer batteries (LiPo battery) orlithium-ion batteries.[42]
Because of the nominal 3.2 V output, four cells can be placed in series for a nominal voltage of 12.8 V. This comes close to the nominal voltage of six-celllead-acid batteries. Along with the good safety characteristics of LFP batteries, this makes LFP a good potential replacement for lead-acid batteries in applications such as automotive and solar applications, provided the charging systems are adapted not to damage the LFP cells through excessive charging voltages (beyond 3.6 volts DC per cell while under charge), temperature-based voltage compensation, equalisation attempts or continuoustrickle charging. The LFP cells must be at least balanced initially before the pack is assembled and a protection system also needs to be implemented to ensure no cell can be discharged below a voltage of 2.5 V or severe damage will occur in most instances, due to irreversible deintercalation of LiFePO4 into FePO4.[43]
One important advantage over other lithium-ion chemistries is thermal and chemical stability, which improves battery safety.[44][35][better source needed]LiFePO
4 is an intrinsically safer cathode material thanLiCoO
2 andmanganese dioxidespinels through omission of thecobalt, whose negativetemperature coefficient ofresistance can encouragethermal runaway. TheP–O bond in the(PO
4)3−
ion is stronger than theCo–O bond in the(CoO
2)−
ion, so that when abused (short-circuited,overheated, etc.), the oxygen atoms are released more slowly. This stabilization of the redox energies also promotes faster ion migration.[45][better source needed]
As lithium migrates out of the cathode in aLiCoO
2 cell, theCoO
2 undergoesnon-linear expansion that affects the structural integrity of the cell. The fully lithiated and unlithiated states ofLiFePO
4 are structurally similar which means thatLiFePO
4 cells are more structurally stable thanLiCoO
2 cells.[citation needed]
No lithium remains in the cathode of a fully charged LFP cell. In aLiCoO
2 cell, approximately 50% remains.LiFePO
4 is highly resilient during oxygen loss, which typically results in an exothermic reaction in other lithium cells.[20] As a result,LiFePO
4 cells are harder to ignite in the event of mishandling (especially during charge). TheLiFePO
4 battery does notdecompose at high temperatures.[35]
Theenergy density (energy/volume) of a new LFP battery as of 2008 was some 14% lower than that of a newLiCoO
2 battery.[46] Since discharge rate is a percentage of battery capacity, a higher rate can be achieved by using a larger battery (moreampere hours) if low-current batteries must be used.
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Enphase pioneered LFP along with SunFusion Energy Systems LiFePO4 Ultra-Safe ECHO 2.0 and Guardian E2.0 home or business energy storage batteries for reasons of cost and fire safety, although the market remains split among competing chemistries.[47] Though lower energy density compared to other lithium chemistries adds mass and volume, both may be more tolerable in a static application. In 2021, there were several suppliers to the home end user market, including SonnenBatterie andEnphase.Tesla Motors continued to useNMC batteries in its home energy storage products until the release of the Power Wall 3 in 2023. Tesla utility-scale batteries switched to using LFP in 2021.[48] According to EnergySage the most frequently quoted home energy storage battery brand in the U.S. is Enphase, which in 2021 surpassedTesla Motors andLG.[49]
Higher discharge rates needed for acceleration, lower weight and longer life makes this battery type ideal for forklifts, bicycles and electric cars. Twelve-volt LiFePO4 batteries are also gaining popularity as a second (house) battery for a caravan, motor-home or boat.[50]
Tesla Motors uses LFP batteries in all standard-rangeModels 3 andY made after October 2021[51] except for standard-range vehicles made with 4680 cells starting in 2022, which use anNMC chemistry.[52]
As of September 2022, LFP batteries had increased its market share of the entire EV battery market to 31%. Of those, 68% were deployed by two companies, Tesla and BYD.[53]
Lithium iron phosphate batteries officially surpassed ternary batteries in 2021 with 52% of installed capacity. Analysts estimate that its market share will exceed 60% in 2024.[54]
The first vehicle to use LFP batteries was the Chevrolet Spark EV in 2014 only. The batteries were made by A123 Systems. In February 2023, Ford announced that it will be investing $3.5 billion to build a factory in Michigan that will produce low-cost batteries for some of its electric vehicles. The project will be fully owned by a Ford subsidiary, but will use technology licensed from Chinese battery company Contemporary Amperex Technology Co., Limited (CATL).[55]
Lithium iron phosphate (LiFePO4) batteries, known for their stable operating voltage (approximately 3.2V) and high safety, have been widely used insolar lighting systems. Compared to traditional nickel-cadmium (NiCd) or nickel-metal hydride (NiMH) batteries, LiFePO4 batteries offer a longer cycle life and superior thermal stability, making them well-suited for solar applications that require frequent charging and discharging.[56][57]
In addition, LiFePO4 batteries exhibit a high tolerance to overcharging during the charging process, allowing them to be connected directly tosolar panels without the need for complex charge control circuitry. This makes them an ideal energy source for solar garden lights,streetlights, and other outdoor lighting systems.[58]
By 2013, better solar-chargedpassive infrared motion detector security lamps emerged.[59] As AA-sized LFP cells have a capacity of only 600 mAh (while the lamp's bright LED may draw 60 mA), the units shine for at most 10 hours. However, if triggering is only occasional, such units may be satisfactory even charging in low sunlight, as lamp electronics ensure after-dark "idle" currents of under 1 mA.[60]
Someelectronic cigarettes use these types of batteries. Other applications include marine electrical systems[61] and propulsion, flashlights,radio-controlled models, portable motor-driven equipment, amateur radio equipment, industrial sensor systems[62] andemergency lighting.[63]
Current test projecting excellent calendar life: 17%impedance growth and 23% capacity loss in 15 years at 100%SOC, 60 °C.
The proposed lighting device has an ultra-low standby power consumption of only 0.007 W.
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