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-cell [[lead-acid battery|lead-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 continuous [[trickle 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.{{cn|date=July 2020}}
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-cell [[lead-acid battery|lead-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 continuous [[trickle 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.{{cn|date=July 2020}}
===High peak current/power ratings===
LFP batteries have higher current or peak-power ratings than NMC.<ref>
{{cite news|url=http://www.scientificamerican.com/article.cfm?id=better-battery-lithium-ion-cell-gets-supercharged|title=A Better Battery? The Lithium Ion Cell Gets Supercharged|archive-url=https://web.archive.org/web/20131023213559/http://www.scientificamerican.com/article.cfm?id=better-battery-lithium-ion-cell-gets-supercharged|archive-date=2013-10-23|url-status=live|first=Adam|last=Hadhazy|work=[[Scientific American]]|date=2009-03-11}}</ref>
The lithium iron phosphate battery (LiFePO 4 battery) or LFP battery (lithium ferrophosphate) is a type of lithium-ion battery using lithium iron phosphate (LiFePO 4) as the cathode material, and a graphiticcarbon electrode with a metallic backing as the anode. The energy density of an LFP battery is lower than that of other common lithium ion battery types such as Nickel Manganese Cobalt(NMC) and Nickel Cobalt Aluminum (NCA), and also has a lower operating voltage. Because of its lower cost, low toxicity, long cycle life and other factors, LFP batteries are finding a number of roles in vehicle use, utility scale stationary applications, and backup power.[5] LFP batteries are cobalt-free.[6]
LiFePO 4 is a natural mineral of the olivine family (triphylite). Arumugam Manthiram and John B. Goodenough first identified the polyanion class of cathode materials for lithium ion batteries.[7][8][9]LiFePO 4 was then identified as a cathode material belonging to the polyanion class for use in batteries in 1996 by Padhi et al.[10][11] Reversible extraction of lithium from LiFePO 4 and insertion of lithium into FePO 4 was demonstrated. Because of its low cost, non-toxicity, the natural abundance of iron, 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.[12][13]
MIT introduced a new coating that allows the ions to move more easily within the battery. The "Beltway Battery" utilizes a bypass system that allows the lithium ions to enter and leave the electrodes at a speed great enough to fully charge a battery in under a minute. The scientists discovered that by coating lithium iron phosphate particles in a glassy material called lithium pyrophosphate, ions bypass the channels and move faster than in other batteries. Rechargeable batteries store and discharge energy as charged atoms (ions) are moved between two electrodes, the anode and the cathode. Their charge and discharge rate are restricted by the speed with which these ions move. Such technology could reduce the weight and size of the batteries. A small prototype battery cell has been developed that can fully charge in 10 to 20 seconds, compared with six minutes for standard battery cells.[17]
Negative electrodes (anode, on discharge) made of petroleum coke were used in early lithium-ion batteries; later types used natural or synthetic graphite.[18]
Specifications
Multiple Lithium Iron Phosphate cells are wired in series and parallel to create a 2800Ah 52V battery. Total battery capacity is 145.6 kWh. Note the large, solid tinned copper busbar connecting the cells together. This busbar is rated for 700 amps DC to accommodate the high currents generated in a 48 volt DC system.Lithium Iron Phosphate cells, each 700 Ah amp-hours 3.25 volts. Two cells are wired in parallel to create a single 3.25 V 1400 Ah battery with a capacity of 4.55 kWh.
According to one manufacturer, lithium iron phosphate batteries in an electric car can be charged at a fast charging station to 80% within 15 minutes, and 100% within 40 minutes.[26]
Advantages and disadvantages
The LiFePO 4 battery uses a lithium-ion-derived chemistry and shares many advantages and disadvantages with other lithium-ion battery chemistries. However, there are significant differences.
More abundant constituents with lower human and environmental impact
LFP contain neither nickel[27] nor cobalt, both of which are supply-constrained and expensive. As with lithium, human rights[28] and environmental[29] concerns have been raised concerning the use of cobalt.
Price
In 2020, the lowest reported LFP cell prices were $80/kWh (12.5Wh/$) .[30]
Better ageing and cycle-life characteristics
LFP chemistry offers a considerably longer cycle 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. [4]
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-cell lead-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 continuous trickle 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.[citation needed]
Safety
One important advantage over other lithium-ion chemistries is thermal and chemical stability, which improves battery safety.[29]LiFePO 4 is an intrinsically safer cathode material than LiCoO 2 and manganese dioxidespinels through omission of the cobalt, with its negative temperature coefficient of resistance that can encourage thermal runaway. The P–O bond in the (PO 4)3− ion is stronger than the Co–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.[32]
As lithium migrates out of the cathode in a LiCoO 2 cell, the CoO 2 undergoes non-linear expansion that affects the structural integrity of the cell. The fully lithiated and unlithiated states of LiFePO 4 are structurally similar which means that LiFePO 4 cells are more structurally stable than LiCoO 2 cells.[citation needed]
No lithium remains in the cathode of a fully charged LiFePO 4 cell. (In a LiCoO 2 cell, approximately 50% remains.) LiFePO 4 is highly resilient during oxygen loss, which typically results in an exothermic reaction in other lithium cells.[13] As a result, LiFePO 4 cells are harder to ignite in the event of mishandling (especially during charge). The LiFePO 4 battery does not decompose at high temperatures.[29]
Lower energy density
The energy density (energy/volume) of a new LFP battery is some 14% lower than that of a new LiCoO 2 battery.[33] Also, many brands of LFPs, as well as cells within a given brand of LFP batteries, have a lower discharge rate than lead-acid or LiCoO 2.[citation needed] Since discharge rate is a percentage of battery capacity, a higher rate can be achieved by using a larger battery (more ampere hours) if low-current batteries must be used. Better yet, a high-current LFP cell (which will have a higher discharge rate than a lead acid or LiCoO 2 battery of the same capacity) can be used.
Enphase pioneered LFP home storage batteries for reasons of cost and fire safety, although the market remains split among competing chemistries.[34] The lower energy density compared to other lithium chemistries is 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 and Enphase. Tesla Motors continues to use NMC batteries in its home energy storage products, but in 2021 switched to LFP for its utility-scale battery product.[35] The most quoted home energy storage battery in the U.S. is the Enphase, which in 2021 surpassed Tesla Motors and LG.[36]
Transportation
Higher discharge rates needed for acceleration, lower weight and longer life makes this battery type ideal for forklifts, bicycles and electric cars. 12V LiFePO4 batteries are also gaining popularity as a second (house) battery for a caravan, motor-home or boat.
Tesla Motors currently uses LFP batteries in certain vehicles, including its Chinese-made Standard Range Models 3 and Y, and some Model 3 units in the United States beginning around August 2021.[37] In October 2021, Tesla announced that all standard-range Models 3 and Y will begin using LFP battery chemistry.[38]
LFP's higher (3.2 V) working voltage lets a single cell drive an LED without circuitry to step up the voltage. Its increased tolerance to modest overcharging (compared to other Li cell types) means that LiFePO 4 can be connected to photovoltaic cells without circuitry to halt the recharge cycle. The ability to drive an LED from a single LFP cell also obviates battery holders, and thus the corrosion, condensation and dirt issues associated with products using multiple removable rechargeable batteries.[citation needed]
By 2013, better solar-charged passive infrared security lamps emerged.[39] 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.[citation needed]
Other uses
Many home EV conversions use the large format versions as the car's traction pack. With the advantageous power-to-weight ratios, high safety features and the chemistry's resistance to thermal runaway, there are few barriers for use by amateur home "makers". Motorhomes are often converted to lithium iron phosphate because of the high draw.
^Manthiram, A.; Goodenough, J. B. (1987). "Lithium insertion into Fe2(MO4)3 frameworks: Comparison of M = W with M = Mo". Journal of Solid State Chemistry. 71 (2): 349–360. Bibcode:1987JSSCh..71..349M. doi:10.1016/0022-4596(87)90242-8.
^"LiFePO 4: A Novel Cathode Material for Rechargeable Batteries", A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, Electrochemical Society Meeting Abstracts, 96-1, May, 1996, pp 73
^"Phospho-olivines as Positive-Electrode Materials for Rechargeable Lithium Batteries" A. K. Padhi, K. S. Nanjundaswamy, and J. B. Goodenough, J. Electrochem. Soc., Volume 144, Issue 4, pp. 1188-1194 (April 1997)
^"ANR26650M1". A123Systems. 2006. Archived from the original on 2012-03-01. ...Current test projecting excellent calendar life: 17% impedance growth and 23% capacity loss in 15 [fifteen!] years at 100% SOC, 60 deg. C...