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

Advantages of LiFePO₄ Battery Cells VS Lead-Acid Batteries

Lithium Iron Phosphate battery is a lithium-ion battery that uses Lithium Iron Phosphate (LiFePO₄) as the positive electrode material and carbon as the negative electrode material. In contrast, a Lead-acid battery (VRLA) is a type of battery whose electrodes are mainly made of lead and its oxides, and whose electrolyte is sulfuric acid solution.

• (1) Cycle life: The cycle life of cylindrical 26650 LiFePO₄ battery cells from Wiltson Energy can reach 2000 times, while lead-acid batteries typically offer 200 to 300 times.
• (2) Nominal voltage of single unit: Nominal voltage of LiFePO₄ battery is 3.2V; Nominal voltage of lead-acid battery is 2.0V.
• (3) Gravimetric energy: LiFePO₄ cells offer 150Wh/kg, compared to lead-acid batteries at 40Wh/kg.
• (4) Volume/Weight: The volume of LiFePO₄ cells is 2/3 of the volume of lead-acid batteries, while the weight is only 1/3 to 1/4 of lead-acid batteries.
• (5) Durability: LiFePO₄ batteries have strong durability, slow consumption, a cycling life of more than 1,500 times, and a general life of 5-8 years, while lead-acid batteries generally last 1-1.5 years.
• (6) Charging time: LiFePO₄ battery starting current can reach 2C; while the charging time of lead-acid batteries is 8-10 hours under normal charging conditions.
• (7) Environmental protection: LiFePO₄ batteries are considered to be the world's green battery and do not contain any heavy metals. They are pollution-free during the process of production and use, while there is a large amount of lead in lead-acid batteries, which will pollute the environment if not handled properly after disposal.
• (8) Safety: Under intense impact, lead-acid batteries can explode, endangering the life of the user; The decomposition temperature of LiFePO₄ battery is about 600℃, so it's very safe and won't explode even in a violent impact.
• (9) Use and maintenance: Although lead-acid batteries are cheaper to acquire than LiFePO₄ batteries due to their cheap materials, they are less economical than LiFePO₄ batteries in terms of service life and routine maintenance. Practical application results show that the cost-effectiveness of LiFePO₄ batteries is more than 4 times that of lead-acid batteries.