Introduction To The Working Principle And Advantages of Lithium Iron Phosphate Battery

The positive electrode of lithium iron phosphate battery consists of LiFePO4 with olivine structure, the negative electrode consists of graphite, and in the middle is a polyolefin PP/PE/PP diaphragm, which is used to isolate the positive and negative electrodes, blocking the electrons while allowing lithium ions to pass through.

When charging, lithium ions are dislodged from the positive electrode through the electrolyte into the negative electrode, while electrons move from the positive electrode to the negative electrode from the external circuit to ensure the charge balance of the positive and negative electrodes, and when discharging, lithium ions are dislodged from the negative electrode and embedded in the positive electrode through the electrolyte. This microstructure makes the lithium iron phosphate battery has a better voltage platform and longer service life: the battery's charging and discharging process, its positive electrode in the rhombohedral crystal system of LiFePO4 and hexagonal crystal system of FePO4 between the two phases of the transition, due to the FePO4 and LiFePO4 below 200 ℃ in the form of solid melts coexist in the process of charging and discharging there is no obvious two-phase turning point, therefore , the charging and discharging voltage platform of the lithium iron phosphate battery is long and smooth; in addition, after the charging process is completed, the volume of anode FePO4 decreases by only 6.81% relative to that of LiFePO4, and the volume of carbon anode expands slightly during the charging process, which serves the purpose of regulating the change in volume and supporting the internal structure. has a long cycle life.

1. What are the advantages of lithium iron phosphate batteries?

Lithium-ion iron phosphate batteries have won the trust of many manufacturers by virtue of their low price and strong safety. The cathode material in lithium-ion battery accounts for more than 40% of the cost of the whole battery, and under the current technical conditions, the energy density of the overall battery depends on the cathode material, so the cathode material is the core development of lithium-ion batteries, research materials, the current mature application of cathode materials including lithium cobalt, lithium nickel cobalt manganese oxide, lithium iron phosphate and lithium manganate.

2. Lithium Cobaltate

There are layer structure and spinel structure, generally commonly used layer structure, its theoretical capacity of 270mAh/g or so, layer structure lithium cobalt oxide is important in mobile phones, aeromodelling, car models, electronic cigarettes, smart wearable digital products. The current energy density and compaction density of lithium cobalt has basically to the limit, its specific capacity and the theoretical capacity compared to the larger room for improvement, but due to the current overall chemical system limitations, especially the electrolyte in the high-voltage system is easy to decompose, so further enhancement of charging cut-off voltage to enhance the specific capacity of the method is subject to certain limitations, followed by a breakthrough in the electrolyte technology once, its energy density There is still room for improvement.

3. Lithium nickel cobalt manganese oxide (LNCMO)

Generally speaking, LiNixMnyCozO2 has the advantages of being green, low cost (only 2/3 of LiCoO2), good safety (safe working temperature up to 170℃), and long cycle life (extended by 45%). The current research on single-crystal lithium nickel cobalt manganese oxide is important to further improve the energy density of the product by continuously improving the nickel content and the charging cut-off voltage, but this puts forward higher requirements on the electrolyte and other related supporting materials as well as the technical capability of lithium-ion battery manufacturers.

4. Lithium manganate

There are spinel structure and layer structure, and spinel structure is commonly used. The theoretical capacity is 148mAh/g, and the actual capacity is between 100 and 120mAh/g. It has the characteristics of better capacity play, stable structure, superior low temperature performance and low cost, etc. However, its crystal structure is prone to distortion. However, its crystal structure is prone to distortion, resulting in capacity decay and short cycle life. It is important to be applied in some markets that require high security and high cost, but have lower energy density and cycle requirements. Such as small communication devices, rechargeable treasure, electric tools and electric bicycles, special scenes (such as coal mines).

5. Lithium iron phosphate

Generally has a stable olivine skeleton structure, discharge capacity can reach more than 95% of the theoretical discharge capacity, excellent safety performance, good tolerance about overcharging, long cycle life, and low price. However, its energy density limitation is difficult to solve, while electric vehicle users continue to improve range demand.