What are LFP Batteries?

Lithium Iron Phosphate battery (LiFePO₄, LFP, “lifer”) is a type of lithium-ion battery where the cathode is made of lithium ferrophosphate (orthophosphoric acid salt, LiFePO₄), and the anode is made of graphite on a copper foil substrate.

Due to their lower cost, enhanced safety, low toxicity, and long service life, LFP batteries are widely used in vehicles, stationary batteries, and backup power systems. Notably, LFP batteries do not contain cobalt, a material often associated with ethical and environmental concerns.

Market Impact and Production

As of September 2022, the market share of LFP batteries for electric vehicles reached 31%. A significant portion of this, 68%, was attributed to Tesla and Chinese electric vehicle manufacturer BYD alone. Chinese manufacturers currently hold a near-monopoly on the production of LFP batteries. However, with patents expiring in 2022, demand and production of these cheaper, mass-produced batteries are expected to increase globally.

History of LFP Technology

LiFePO₄ was first discovered in 1996 by Professor John Goodenough of the University of Texas, as a cathode material for lithium-ion batteries. This material was notable for its significantly lower cost, reduced toxicity, and greater heat resistance compared to traditional LiCoO₂. Its primary disadvantage at the time was a smaller capacity.

Until 2003, this technology saw little development until A123 Systems took it on. The history of A123 Systems began in late 2000 in the laboratory of Professor Jiang Ye-Ming from the Massachusetts Institute of Technology (MIT). Jiang's team initially worked on a different battery concept, but when research stalled in 2003, they shifted focus to lithium iron phosphate batteries. Global corporations such as Motorola, Qualcomm, and Sequoia Capital became investors in the newly formed company.

Key Characteristics

• Specific energy density: 90-160 W•h/kg (320-580 kJ/kg)
• Volumetric energy density: 220–350 W•h/dm³ (790 kJ/dm³)
• Volumetric density of the structure: 2 kg/dm³
• Number of charge-discharge cycles before losing 20% of capacity: 2000-7000. The lifespan heavily depends on charge and discharge current (e.g., at 0.25C and 100% depth of discharge, it exceeds 6000 cycles; at 1C, it drops to 3000). It also varies with discharge depth (e.g., at 1C and 80% discharge depth, it's 4500 cycles; at 60%, it's 10000 cycles).
• Shelf life: up to 15 years
• Self-discharge at room temperature: 3-5% per month
• Voltage:
• Maximum per cell: 3.65 V (fully charged)
• Midpoint: 3.3 V
• Minimum: 2 V (fully discharged)
• Working: 3.0-3.3 V
• Minimum operating voltage (discharge): 2.5 V
• Specific power: >6.6 W/g (discharge current 60C)
• Operating temperature range:
• During discharge: from −30 °C to +55 °C
• When charging: 0 °C to 40 °C