Lithium iron phosphate (LFP) has the chemical formula LiFePO₄. Its safety gene lies in its unique “olivine structure”—like a sturdy armor for lithium ions.
Structure determines destiny
1. Crystal Structure: A “Safe Pathway” for Lithium Ions
Under a microscope, LFP crystals appear olivine-shaped (hexagonal structure). Within this structure:
PO₄³⁻ tetrahedra create a strong framework, like steel bars in buildings. This structure holds up well, even under high heat.
Fe²⁺ ions reside in the interstices of the skeleton, stabilizing the structure;
Li⁺ ions move through the pathways, inserting and deinserting during charge and discharge. This keeps a clear path and stops any deviation.
This structure is much more durable than ternary materials. When the battery faces impacts or high temperatures, the PO₄³⁻ skeleton stays strong. This prevents oxygen from escaping, which can cause combustion in ternary materials. Experiments show that LFP decomposes at over 500°C. In contrast, ternary materials like NCM811 start to break down at 200°C.
2. Charging and Discharging Principle: Gentle “Ion Movement”
The charging and discharging of LFP is like smooth “ion movement.” It differs from the intense reactions seen in ternary materials.
During charging, Li⁺ leaves the positive electrode (LiFePO₄). It moves through the electrolyte to the negative electrode (graphite) and forms LiC₆.
During discharging, Li⁺ moves from the negative electrode to the positive one. At the same time, electrons travel through the external circuit to create current.
The redox reaction between Fe²⁺ and Fe³⁺ is mild. This is unlike the violent reactions in transition metals such as nickel and cobalt. These metals in ternary materials release a lot of heat. LFP has minimal temperature changes during charging and discharging. This is usually less than 20°C.
Performance Introduction: Advantages and Disadvantages of LFP
No battery is perfect. LFP’s performance characteristics can be summarized as “two strengths and two weaknesses.” Understanding these characteristics is crucial to understanding its application scenarios.
1. Two Core Advantages: Safety and Lifespan
Maximum Safety:
LFP has a unique advantage: it doesn’t release oxygen. Plus, it can resist high temperatures. Ternary materials give off oxygen when heated, helping combustion. In contrast, LFP breaks down into non-flammable substances like Fe₂O₃ and P₂O₅. This is also the key to its resistance to ignition during needle penetration and compression tests.
Incredible Cycle Life:
LFP’s olivine structure changes volume by just 3.7% during charge and discharge. In contrast, ternary materials change by 7-10%. This leads to very stable structural stability. Conventional LFP batteries last for 3,000 to 5,000 cycles. However, LFP batteries made for energy storage can go over 10,000 cycles. If you charge and discharge them daily, that’s about 27 years of use.
2. Two Significant Shortcomings: Energy Density and Low-Temperature Performance
Low Energy Density:
The theoretical energy density of LFP is 170 mAh/g. However, mass-produced batteries usually have an energy density of 150-200 Wh/kg. In contrast, ternary materials like NCM811 can achieve 250-300 Wh/kg. LFP batteries have a shorter range for the same weight. For instance, an LFP vehicle with the same battery volume might reach 500 km, while a ternary material vehicle can go 600 km.
Significant “power loss” at low temperatures:
Below 0°C, LFP’s ionic conductivity decreases, compromising charging efficiency and capacity. At -20°C, LFP’s capacity retention is approximately 60%, while ternary materials can reach 75%. This is why users in northern China prefer ternary batteries.
Technological breakthrough: How to make LFP “strengthen its strengths and overcome its weaknesses”?
1. Material Modification: Accelerating LFP Production
Nanoidization and Carbon Coating:
Making LFP particles nanoscale (<100nm) increases their surface area, enabling faster lithium-ion migration. Coating the surface with a layer of carbon (2-5nm thick) increases conductivity by 1,000 times. The modified LFP improves rate performance from 1C to 5C (full charge in 12 minutes).
Metal Ion Doping:
Doping with metal ions like Mg²⁺ and Nb³⁺ improves the crystal structure. It also boosts performance at low temperatures. CATL’s “low-temperature LFP” achieves a capacity retention of 75% at -20°C, approaching the level of ternary materials.
2. Structural Innovation: BYD’s Blade Battery’s “Space Magic”
Traditional LFP batteries use square modules, resulting in a space utilization rate of only 60%. BYD’s Blade Battery uses long, thin cells that are 1.5 meters long and 10 centimeters wide. These cells fit into the battery pack like a “blade.” This design boosts space use to over 90%.
This design lets the LFP system reach an energy density over 180Wh/kg. It also offers a range of 600km and stays puncture-resistant. In 2023, the BYD Han EV with Blade Batteries got a “zero spontaneous combustion” rating in the C-NCAP crash test.
3. System Integration: The “Art of Subtraction” of CTP Technology
CATL’s CTP technology removes the module casing in battery packs. This lets them pack LFP cells tightly. A water-cooled plate manages the temperature. This design:
Reduces weight by 15% and increases energy density by 10%;
Reduces costs by 10% (eliminating module materials and assembly costs).
LFP battery packs with CTP are common in energy storage stations, like Huawei’s 5G base station, and in commercial vehicles, such as Yutong electric buses.
Application Map: Where is LFP’s “home field”?
With its safety and cost advantages, LFP has become a necessity in the following scenarios:
1. New Energy Vehicles: A Counterattack from Low-End to High-End
**Entry-Level Models:** The Wuling Hongguang MINI EV features LFP batteries. This cuts costs by 15%, lowering the price to 30,000 yuan.
**Mid- to High-End Models:** The BYD Han EV and Xiaopeng P5 use Blade Battery/LFP versions. They offer a range of up to 600 km. This setup balances safety and range.
Commercial Vehicles: Buses and logistics vehicles are charged and discharged 2-3 times per day. The long lifespan of LFP (10 years/500,000 kilometers) can reduce overall lifecycle costs.
2. Energy Storage Power Stations: LFP’s “Absolute Home”
70% of global energy storage power stations use LFP batteries for three reasons:
Long cycle life (10,000 cycles), requiring no replacement for 20 years;
Low cost (0.5 yuan/Wh), 30% lower than ternary materials;
High safety prevents fires at energy storage power stations. The 2021 Texas fire was caused by ternary batteries.
China’s “PV + LFP energy storage” projects, like the 100MW station in Haixi Prefecture, Qinghai, have cut costs. Now, the price per kilowatt-hour is just 0.3 yuan. This makes it cheaper than coal-fired power generation.
3. Two-Wheeled Vehicles and Specialty Applications
Electric Bicycles: High-end models from Yadea and Aima use LFP batteries. These batteries keep 80% of their capacity after 500 charges. This means they last three times longer than lead-acid batteries.
Ships and Underground Equipment: In tight spaces like submarines and coal mines, LFP’s non-explosive nature is essential. LFP has been used as an emergency power source for China’s deep-sea probe, the “Struggler.”
LFP went from under 10% market share in 2015 to over 50% in 2023. This growth comes from the new energy industry’s focus on balancing safety and cost. Electric vehicles are becoming “household necessities,” not just “experience tools.” Energy storage is moving from “supplementary energy” to “grid mainstays.” LFP provides stability and reliability as key benefits.
In the future, better solid-state electrolytes and sodium ion doping could boost LFP’s energy density and performance in cold temperatures. No matter how it changes, its main principle of “safety” will keep it successful in the competitive power battery market.
