LFP battery chemistry

LFP is a lithium-ion battery chemistry named after its cathode material. The cathode has an olivine crystal structure, in which strong phosphorus-oxygen bonds form a rigid framework that resists breaking down when the cell is heated. The anode is graphite, as in other lithium-ion cells. LFP contains no cobalt and no nickel.

An LFP cell has a nominal voltage of 3.2V, against 3.6 to 3.7V for nickel manganese cobalt (NMC), the other chemistry common in home batteries. Its energy density is 90 to 172 Wh/kg, with most cells between 120 and 160, lower than NMC’s. LFP is the dominant chemistry in home and grid storage, holding around 85% of the stationary storage market in 2025.

Thermal runaway resistance and off-gassing

LFP resists thermal runaway to a higher temperature than the other common lithium-ion chemistries. Reported onset sits between 270 and 310°C, against roughly 150 to 215°C for NMC and around 150°C for nickel cobalt aluminium oxide (NCA). The spread in the LFP figure reflects different test conditions.

The reason is the cathode structure. The olivine lattice holds onto its oxygen even above 300°C, while the layered oxide cathodes in NMC and NCA release oxygen when heated, and that oxygen feeds the exothermic reactions that drive a runaway. The iron-phosphate bond is stronger than the cobalt-oxygen bond, so the oxygen is harder to strip out under stress. The UK government’s grid-scale storage guidance describes LFP as typically having better thermal stability than NMC.

Better thermal stability does not make LFP straightforwardly safe. When an LFP cell fails it off-gasses more hydrogen than NMC, which can build an explosive atmosphere in an enclosed space more quickly, and it can release hydrogen fluoride (HF) at 3000 to 8000 ppm (parts per million). A single kWh of cell capacity can produce 400 to 6000 litres of gas during thermal runaway, depending on the chemistry and how charged the cell is. LFP cannot simply be called safer than NMC; the two chemistries carry different hazards.

In UK dwellings the fire risk is managed through where the battery goes rather than by chemistry alone. PAS 63100:2024, the Publicly Available Specification for the fire safety of home battery storage, sets fire-safety requirements and restricts siting, keeping batteries out of lofts, sleeping rooms and escape routes among other locations. Those rules apply to LFP as to any lithium chemistry.

Cycle life, calendar life and what shortens them

Long life is the main reason LFP dominates home and grid storage. Manufacturers quote cycle lives from around 2500 to over 10,000 full charge-discharge cycles before the pack falls to 70 to 80% of its original capacity, the point the industry treats as end of life. NMC, by comparison, is usually rated at 1000 to 3000 cycles. A pack that has reached 70 to 80% is not finished; it holds less than it did but can still serve lighter duties.

The range is wide because cycle life depends heavily on how the battery is used. Depth of discharge has a large effect on cycle life. As a rough guide, a cell cycled to 100% depth of discharge might last around 3000 cycles, one cycled to 80% around 5000 and one cycled to 50% 8000 or more, so a battery worked gently lasts far longer than the headline number worked hard.

Temperature and state of charge drive calendar ageing, the slow capacity loss that happens whether or not the battery is cycled. Holding a cell at high charge and warm temperatures speeds the internal side-reactions that gradually consume capacity, so a pack kept full and hot fades faster than one kept cooler and part-charged. LFP is happiest at 20 to 30°C. In real installations calendar life runs to 10 to 15 years, and solar-storage suppliers quote 15 to 20. A small share of cells fail early, around 1% in the first two years, after which the steady failure rate is below 1% a year.

Cold-weather performance and charging below freezing

Cold is where LFP is weakest, and it affects discharging and charging differently.

Discharging in the cold costs capacity temporarily. Between 0 and 10°C a pack typically gives up 20 to 30% of its rated capacity, and between -20 and 0°C the loss can reach 50%. Internal resistance rises as the temperature falls, so more energy is lost as heat and the voltage sags under load. That capacity returns when the battery warms up; it is a reduction in what the cold pack can deliver, not permanent damage.

Charging below 0°C is the process that does lasting harm. Below freezing, lithium tends to deposit as metal on the surface of the graphite anode instead of slotting into it, which is called lithium plating. The plated lithium permanently reduces capacity and raises internal resistance, and it can grow needle-like dendrites that pierce the separator and cause an internal short. The damage is cumulative and often silent. In one set of tests a single 1C charge (a rate that would fill the pack in about an hour) at 0°C caused 3.6% irreversible capacity loss, and charging at 0.5C at -10°C lost 25% of capacity over 40 cycles, showing up later as reduced runtime, swelling or early shutdowns.

This is why the BMS blocks or limits charging in the cold. A common cutoff is around 0°C, below which the BMS refuses charge; between 0 and 10°C some batteries reduce the charge current, and above 10°C most charge normally. The exact thresholds are set by the manufacturer, so the datasheet is the authority. Where the battery and inverter communicate over a CAN (Controller Area Network) or RS485 data link, the battery can tell the inverter to cut or reduce charging itself.

Some batteries are built to charge in the cold anyway. A few include heating pads run by the BMS, which warm the cells from solar or grid power before charging begins. EcoFlow’s PowerOcean carries an auto-heating pad and is rated to -20°C. Others use a cold-weather electrolyte: EarthX states its cells reach close to full-rate charging at -30°C.

There is genuine disagreement about charging below freezing. Most manufacturers take the conservative line: do not charge an LFP battery below 0°C, because plating causes permanent damage. Specialist manufacturers and some installers argue that reduced-rate charging below 0°C is acceptable, and that the damage is proportional to the charge rate rather than triggered simply by crossing freezing point. BYD, for one, allows full-rate charging above 5°C and a reduced 0.1C rate down to -10°C. The resolution comes down to the specific battery. A standard consumer LFP pack not rated for low-temperature charging should not be charged below freezing. A battery with a cold-weather electrolyte, a built-in heater or a manufacturer-specified reduced-rate profile can charge below 0°C within the range its maker sets.

LFP compared with NMC

LFP and NMC are the two lithium chemistries used in home storage, and choosing between them is a set of trade-offs rather than one being better outright.

Property	LFP	NMC
Nominal cell voltage	3.2V	3.6 to 3.7V
Energy density	90 to 172 Wh/kg	150 to 250 Wh/kg
Cycle life	2500 to 10,000	1000 to 3000
Thermal runaway onset	270 to 310°C	150 to 215°C
Cobalt and nickel	None	Yes

LFP lasts three to five times as many cycles and tolerates heat and abuse better. It uses no cobalt or nickel, which sidesteps the supply-chain and ethical concerns attached to those metals. The longer life makes it cheaper per kWh over its service life, and its production carries an estimated 15 to 25% lower carbon footprint than NMC.

The costs are physical. For the same stored energy an LFP pack is heavier and bulkier, because it holds about 30% less energy per kilogram. It performs worse in sub-freezing conditions, with charge rates falling away below -20°C. Its voltage stays nearly flat across most of the charge range, which makes state of charge harder to read from voltage alone and puts more work on the BMS to estimate charge and keep the cells balanced. For home storage, weight and size matter less than they do in a vehicle, so the bulk and lower energy density cost little in practice while the longer life and thermal margin count for a lot.

LFP in UK home batteries

Most home batteries sold in the UK use LFP. EcoFlow’s PowerOcean and the SolarEdge Home Battery are current examples. The withdrawn GivEnergy range also used LFP, from 5.12 and 9.5 kWh low-voltage units to larger high-voltage stacks, so those specifications remain relevant to installed systems. GivEnergy Ltd ceased trading in April 2026. The same chemistry runs much of grid-scale storage and is increasingly used in EVs as well.

Related entries

• NMC battery chemistry
• BMS
• Thermal runaway containment
• Usable battery capacity
• PAS 63100 domestic battery fire specification
• Battery warranty throughput limits