In the crystal structure of LiFePO4, oxygen atoms are arranged in a hexagonal close packing. PO43-tetrahedrons and FeO6 octahedra constitute the spatial framework of the crystal. Li and Fe occupy the octahedral voids, while P occupies the tetrahedral voids. Fe occupies the corner positions of the octahedra, and Li occupies the edge positions of the octahedra. FeO6 octahedra are interconnected on the bc plane of the crystal, and the LiO6 octahedra in the b-axis direction are interconnected to form a chain structure. One FeO6 octahedron shares an edge with two LiO6 octahedra and one PO43-tetrahedron. [3] Because the FeO6 edge-sharing octahedral network is discontinuous, it cannot form electronic conductivity; at the same time, the PO43-tetrahedron restricts the volume change of the lattice, affecting the insertion and extraction of Li+ and electron diffusion, resulting in extremely low electronic conductivity and ion diffusion efficiency of LiFePO4 cathode material. [3] The theoretical specific capacity of LiFePO4 battery is relatively high (about 170 mAh/g), and the discharge plateau is 3.4 V. Li+ ions move back and forth between the positive and negative electrodes to achieve charging and discharging. During charging, an oxidation reaction occurs, and Li+ ions migrate out of the positive electrode and are inserted into the negative electrode through the electrolyte. Iron changes from Fe2+ to Fe3+, and an oxidation reaction occurs.
Lithium iron phosphate (LFP) batteries are a type of lithium-ion battery that uses lithium iron phosphate as the positive electrode material. They are characterized by high safety and stability, high-temperature resistance, and good cycle performance. Similar to ternary lithium-ion batteries, LFP batteries have a theoretical lifespan exceeding 2000 charge-discharge cycles, meaning they can last for over five years even with daily charging. Generally, with daily household use and charging every three days, they can last around eight years. However, due to their poor low-temperature performance, LFP batteries tend to have a longer lifespan in southern regions.
Advantages of lithium iron phosphate batteries
1. High energy density. Lithium iron phosphate batteries have a high energy storage density, currently reaching 460-600 Wh/kg, which is about 6-7 times that of lead-acid batteries;
2. Long service life: Lithium iron phosphate battery packs can last for more than 6 years;
3. High additional voltage (single cell operating voltage is 3.7V-3.2V), approximately equal to the series voltage of three nickel-cadmium or nickel-metal hydride rechargeable batteries, facilitating the construction of battery power packs;
4. It has high power acceptance capability. The lithium iron phosphate batteries used in electric vehicles can achieve a charge-discharge rate of 15-30C, which facilitates high-intensity start-up acceleration.
5. Low self-discharge rate, which is one of the most outstanding advantages of this battery. It can now be achieved as low as 1%/month, which is much lower than 25-30% for Ni-Cd and 30-35% for Ni and MH.
6. Lightweight: Lithium iron phosphate batteries weigh approximately 1/5 to 1/6 of lead-acid batteries of the same volume.
7. It has strong adaptability to both upper and lower temperatures, and can be used in environments ranging from -20°C to 60°C. With process treatment, it can also be used in environments as low as -45°C.
Lithium iron phosphate (LiFePO4) batteries are lithium-ion batteries that use lithium iron phosphate as the positive electrode material. Lithium iron phosphate batteries have advantages such as high operating voltage, high energy density, long cycle life, good safety performance, low self-discharge rate, and no memory effect. So, what are the main applications of lithium iron phosphate batteries?
Application of electric vehicles
LiFePO4 batteries are widely used in passenger cars, buses, logistics vehicles, and low-speed electric vehicles due to their advantages in safety and cost. Although ternary copolymer batteries once dominated the new energy passenger vehicle market due to their energy density advantage, influenced by national new energy vehicle subsidy policies, lithium iron phosphate batteries still hold an irreplaceable advantage in buses and logistics vehicles. Latest data shows that lithium iron phosphate batteries account for half of total battery shipments.
Applications of power supplies
In addition to the characteristics of lithium-ion batteries, lithium iron phosphate batteries also offer instantaneous power output capabilities. Lithium-ion batteries with a capacity of less than one kilowatt-hour replace traditional lead-acid batteries, and BSG motors replace traditional starter motors and generators. It not only features slow start-stop functionality but also functions such as engine shutdown, coasting, regenerative braking, acceleration power, and electric cruise control.
Application of energy storage systems
LiFePO4 batteries possess a series of unique advantages, including high operating voltage, high energy density, long cycle life, low self-discharge rate, no memory effect, environmental friendliness, and support for stepless capacity expansion, making them suitable for large-scale energy storage. They show promising application prospects in areas such as safe grid connection of renewable energy power plants, grid peak shaving, distributed power stations, UPS power supplies, and emergency power supply systems.
Lithium batteries are one of many types of batteries, and most people have some understanding of them. But are you familiar with lithium iron phosphate batteries? Do you know the difference between lithium iron phosphate batteries and lithium batteries? If you want to find the answers to these questions, please read on.
I. Lithium iron phosphate batteries
(I) Introduction
Lithium iron phosphate (LFP) batteries are lithium-ion batteries that use lithium iron phosphate as the positive electrode material. The main positive electrode materials for lithium-ion batteries include lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, ternary materials, and lithium iron phosphate. Among these, lithium cobalt oxide is currently the most widely used positive electrode material in lithium-ion batteries.
(II) Advantages
1. Lithium iron phosphate batteries have a long lifespan, with a cycle life exceeding 2000 cycles. Under the same conditions, lithium iron phosphate batteries can be used for 7 to 8 years.
2. Safe to use. Lithium iron phosphate batteries have undergone rigorous safety testing and will not explode even in a traffic accident.
3. Fast charging. Using a dedicated charger, the battery can be fully charged in 40 minutes at 1.5C.
4. Lithium iron phosphate batteries are resistant to high temperatures; their heat resistance can reach 350 to 500 degrees Celsius.
5. Lithium iron phosphate batteries have a large capacity.
6. Lithium iron phosphate batteries have no memory effect.
7. Lithium iron phosphate batteries are green and environmentally friendly, non-toxic, and pollution-free. The raw materials are widely available and inexpensive.
(III) Disadvantages
1. The tap density of the positive electrode in lithium iron phosphate batteries is low, typically between 0.8 and 1.3. They also have a large volume.
2. Poor conductivity, slow lithium-ion diffusion rate, and low actual specific capacity during high charge and discharge cycles.
3. Lithium iron phosphate batteries have poor low-temperature performance.
4. A single lithium iron phosphate battery has a long lifespan, around 2000 cycles, but a lithium iron phosphate battery pack has a short lifespan, generally around 500 cycles.
(iv) Application Areas
Large electric vehicles: buses, electric cars, sightseeing vehicles, and hybrid vehicles, etc.;
Light electric vehicles: electric bicycles, golf carts, small flatbed electric carts, forklifts, cleaning vehicles, electric wheelchairs, etc.;
Power tools: electric drills, chainsaws, lawnmowers, etc.;
Remote control cars, boats, airplanes, and other toys;
Energy storage devices for solar and wind power generation;
UPS, emergency lights, warning lights, and mining lamps (for the highest safety);
Replaces the 3V disposable lithium battery and the 9V nickel-cadmium or nickel-metal hydride rechargeable battery in cameras (identical in size);
Small medical instruments and portable devices, etc.
II. Lithium Batteries
(I) Introduction
Lithium-ion batteries are a type of battery that uses lithium metal or lithium alloys as the negative electrode material and a non-aqueous electrolyte solution. Due to the highly reactive chemical properties of lithium metal, its processing, storage, and use require very strict environmental controls. Therefore, lithium-ion batteries were not widely used for a long time. However, with the development of science and technology, lithium-ion batteries have now become the mainstream technology.
(II) Advantages
1. High energy density. It has a high energy storage density, reaching 460-600Wh/kg, which is about 6-7 times that of lead-acid batteries;
2. Long service life, up to 6 years or more. Batteries with lithium iron phosphate as the positive electrode have a record of 10,000 charge/discharge cycles at 1C (100% DOD).
3. High rated voltage (single cell operating voltage is 3.7V or 3.2V), approximately equal to the voltage of three nickel-cadmium or nickel-metal hydride rechargeable batteries in series, facilitating the formation of battery power packs; lithium batteries can be adjusted to 3.0V using a new type of lithium battery voltage regulator technology, making them suitable for use in small electrical appliances;
4. It has high power handling capacity. The lithium iron phosphate lithium-ion batteries used in electric vehicles can achieve a charge-discharge capacity of 15-30C, which is convenient for high-intensity start-up acceleration;
5. The self-discharge rate is very low, which is one of the most outstanding advantages of this battery. It can generally be below 1% per month, less than 1/20 of that of nickel-metal hydride batteries.
6. Lightweight, weighing approximately 1/6 to 1/5 of lead-acid products for the same volume;
7. It has strong adaptability to high and low temperatures and can be used in environments ranging from -20℃ to 60℃. With processing modifications, it can be used in environments as low as -45℃.
8. Green and environmentally friendly, it does not contain or produce any toxic or harmful heavy metal elements and substances such as lead, mercury, and cadmium, whether in production, use, or disposal.
9. Production consumes virtually no water, which is highly advantageous for water-scarce my country. Specific energy refers to the energy per unit weight or unit volume. Specific energy is expressed in Wh/kg or Wh/L. Wh is a unit of energy; W is watt, h is hour; kg is kilogram (unit of weight), L is liter (unit of volume).
