The electrolyte serves as the "blood" of lithium batteries, directly determining the battery's cycle life, charging and discharging efficiency, and usage safety. With the upgrading of the power battery and energy storage battery industries, end manufacturers have become increasingly strict with the purity standards of electrolyte. In the entire process of electrolyte purification, ingredient mixing, and repeated filling, the filtration stage is of crucial importance. Currently, the leading electrolyte manufacturers in the industry have gradually phased out traditional filter elements such as pp pleated filter cartridge and PES, and have adopted hydrophilic PTFE folded filter elements as the standard consumable for electrolyte filtration, which has become the mainstream choice in the lithium battery industry to replace defective PP filter cartridge.
At its core, the special chemical properties of the electrolyte impose extremely high requirements on the folding filter element. Lithium battery electrolyte is mainly composed of lithium salts, organic solvents, and various functional additives, with complex components and strong solubility and corrosiveness. Traditional polypropylene pleated filter element, nylon, and PES filter elements have obvious shortcomings: they are easily eroded and swollen by polar organic solvents, not only causing the pleated membrane filter element to break and fail but also causing the precipitation of fibers, impurities, and metal ions, resulting in secondary pollution of the electrolyte; at the same time, they cannot effectively intercept gel impurities and ultra-fine particles, failing to meet the production standards of high-end batteries.
PTFE material, with its "plastic king" level physical and chemical properties, perfectly suits the strict filtration conditions of electrolyte. Firstly, PTFE has excellent chemical inertness and does not react with carbonate solvents, lithium salt raw materials, etc., and has a corrosion resistance far exceeding conventional pp pleated filter cartridge materials. It will not swell, deform, or age when immersed in electrolyte for a long time, fundamentally avoiding material impurity issues and ensuring the purity of the electrolyte, which cannot be realized by ordinary PP filter cartridge.
Secondly, the hydrophilic modified PTFE filter membrane has uniform pore size and high porosity, with a filtration accuracy of up to 0.22 μm, capable of precisely intercepting metal microparticles, carbon powder, gelous precipitates, and precipitated crystals produced during the production process. These fine impurities are the core causes of battery self-discharge, increased internal resistance, and cycle degradation. Using high-performance folding filter element made of PTFE for filtration can significantly reduce the defective rate and stabilize the electrochemical performance of the battery. At the same time, the folded structure design expands the effective filtration area, has a small operating pressure difference, and a large flow rate, suitable for large-scale industrial continuous production, effectively improving production efficiency compared with traditional polypropylene pleated filter element.
In addition, the no-glue heat sealing process is another core advantage. High-quality PTFE folded filter elements are formed by full heat fusion welding, eliminating the risk of chemical glue layer solubility and release, meeting the ultra-high cleanliness requirements of electronic-grade electrolyte. Moreover, the pleated membrane filter element has excellent temperature resistance, suitable for the full production range of electrolyte from room temperature to medium temperature, with a lifespan that is over 30% higher than that of ordinarypp pleated filter cartridge and polypropylene pleated filter element, helping enterprises reduce material replacement and downtime maintenance costs.
Nowadays, hydrophilic PTFE folded filter elements are widely used in the coarse filtration of electrolyte, terminal fine filtration, and finished product filling in all processes, suitable for liquid lithium salts and various additive solution filtration. In the context of the continuous expansion of the production capacity of energy storage batteries and power batteries, high-purity filtration has become an industry necessity. In summary, the multiple advantages of adapting to corrosive media, high-precision impurity removal, low impurity release, and high cost performance are precisely the core reasons why PTFE folded folding filter element become the optimal solution for lithium battery electrolyte filtration, outperforming conventional PP filter cartridge and other common pleated membrane filter element products on the market.