Lithium iron phosphate batteries are a type of battery in the lithium battery family. The positive electrode material is mainly lithium iron phosphate. Compared with traditional lead-acid batteries, lithium-ion batteries have significant advantages in terms of working voltage, energy density, and cycle life.
I. Advantages and disadvantages of square and cylindrical lithium iron phosphate batteries
Cylindrical lithium iron phosphate battery
Advantages: Cylindrical lithium iron phosphate batteries were the earliest mature industrialized lithium battery product. After more than 20 years of development, the production process of cylindrical lithium batteries is now mature, with high production efficiency and relatively low cost. Therefore, the cost of PACK is also relatively low. The yield of lithium batteries is higher than that of square lithium batteries and soft-pack lithium batteries, and their consistency and safety are also excellent.
Disadvantages: Cylindrical lithium iron phosphate batteries are generally packaged in steel shells, which makes them relatively safe, but also makes them heavier, resulting in a relatively lower specific energy of the lithium battery pack.
Square lithium iron phosphate battery
Advantages: The packaging shell of square lithium iron phosphate batteries is mostly made of materials such as aluminum alloy and stainless steel. The internal structure of the battery adopts a winding or stacking process, which provides better protection for the cell than pouch lithium batteries. The safety of the cell is also greatly improved compared to cylindrical lithium batteries.
Disadvantages: While square lithium iron phosphate battery packs can be customized to fit specific product dimensions, this results in a wide variety of square lithium battery models on the market. Too many different models make it difficult to standardize manufacturing processes, leading to low levels of automation, significant individual cell variations, and potentially causing the lifespan of entire square lithium battery packs to be far shorter than that of individual cells.
II. Differences in characteristics between square and cylindrical shapes
1. Battery shape: Square lithium batteries can be any size, while pouch batteries can be made thinner, which is something cylindrical batteries cannot do.
2. Rate characteristics: Due to the limitations of the process of welding multiple tabs to cylindrical lithium batteries, the rate characteristics are slightly worse than those of square multi-tab designs.
3. Discharge platform: Since the same positive electrode material, negative electrode material and electrolyte are used, the discharge platform is theoretically the same. However, the internal resistance of square batteries is slightly higher, so the discharge platform is slightly higher.
4. Product quality: Cylindrical lithium battery technology is very mature, and the probability of secondary cutting defects in the electrode sheets is low. Moreover, the winding process is more mature and automated than the stacking process. The stacking process is still using a semi-manual method, which has an adverse effect on the quality of the battery.
5. Electrode welding: Cylindrical lithium battery electrodes are easier to weld than square lithium battery electrodes, which are prone to poor welding, affecting battery quality.
6. Pack assembly: Round batteries are relatively easier to use, so the packing scheme is simple and the heat dissipation is good. When packing square batteries, the heat dissipation problem must be solved.
