Lithium iron phosphate battery

The lithium iron phosphate battery (LiFePO4 battery) or LFP battery (lithium ferrophosphate) is a type of lithium-ion battery using lithium iron phosphate (LiFePO4) as the cathode material, and a graphitic carbon electrode with a metallic backing as the anode. Because of their low cost, high safety, 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.

The specific energy of LFP batteries is lower than that of other common lithium ion battery types such as nickel manganese cobalt (NMC) and nickel cobalt aluminum (NCA). The specific energy of CATL's LFP battery is currently 125 Watt-hours per kilogram (Wh/kg) and up to possibly 160 Wh/kg with improved packing technology. 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 in Tesla’s 2020 Model 3 is around 260 Wh/kg, which is 70% of its "pure chemicals" value. LFP batteries also exhibit a lower operating voltage than other lithium-ion battery types.

History

LiFePO4 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.

The chief barrier to commercialization was its intrinsically low electrical conductivity. This problem was overcome by reducing the particle size, coating the LiFePO4 particles with conductive materials such as carbon nanotubes,

Negative electrodes (anode, on discharge) made of petroleum coke were used in early lithium-ion batteries; later types used natural or synthetic graphite.

Specifications

Comparison with other battery types

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.

Resource availability

Iron and phosphates are very common in the Earth's crust. LFP contains neither nickel

Cost

A 2020 report published by the Department 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 in balance it still remains less costly per kWh than NMC.

In 2020, the lowest reported LFP cell prices were $80/kWh (12.5Wh/$) with an average price of $137/kWh,

Better aging 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.

LFP cells experience a slower rate of capacity loss (a.k.a. greater calendar-life) than lithium-ion battery chemistries such as cobalt (LiCoO2) or manganese spinel (LiMn2O4) lithium-ion polymer batteries (LiPo battery) or lithium-ion batteries.

Viable alternative to lead-acid batteries

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, due to irreversible deintercalation of LiFePO4 into FePO4.

Safety

One important advantage over other lithium-ion chemistries is thermal and chemical stability, which improves battery safety.

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 LFP cell. In a LiCoO2 cell, approximately 50% remains. LiFePO4 is highly resilient during oxygen loss, which typically results in an exothermic reaction in other lithium cells.

Lower energy density

The energy density (energy/volume) of a new LFP battery is some 14% lower than that of a new LiCoO2 battery.

Uses

Home energy storage

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.

Vehicles

Higher discharge rates needed for acceleration, lower weight and longer life makes this battery type ideal for forklifts, bicycles and electric cars. 12 V LiFePO4 batteries are also gaining popularity as a second (house) battery for a caravan, motor-home or boat.

Tesla Motors uses LFP batteries in all standard-range Models 3 and Y made after October 2021

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.

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.

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).

Solar-powered lighting systems

Single "14500" (AA battery–sized) LFP cells are now used in some solar-powered landscape lighting instead of 1.2 V NiCd/NiMH.

LFP's higher

By 2013, better solar-charged passive infrared motion detector security lamps emerged.

Other uses

Some electronic cigarettes use these types of batteries. Other applications include marine electrical systems