Abstract:

By virtue of their high specific capacity and long service life, lithium ion batteries are popularly installed in mobile electronic equipment, electric vehicles, and energy storage systems. A battery separator is a vital component as it sustains the battery usage at high temperatures. New electric vehicles are increasing the energy density and safety performance demands of lithium ion batteries, placing more stringent requirements on the heat resistance, mechanical properties, and electrolyte infiltration of lithium-ion battery separators. Existing industrial-scale separators are polyolefin porous membranes, which deliver high performance at low cost. However, the poor thermal stability of polyolefins has become the safety bottleneck of high-energy lithium batteries. Excessively high temperatures cause severe thermal contraction, resulting in short-circuiting between the positive and negative electrodes of the battery, and possible burnout or explosion of the battery. In contrast, nonwoven fabric-based separators deliver excellent heat resistance, so they are expected in the next generation of high-energy lithium battery systems. This paper reviews the research progress of nonwoven fabric-based separators in lithium ion batteries. At present, nonwoven composite separators and nonwoven fabric-based separators are formed by the wet-laid process and electrostatic spinning. These fabrication processes are separately described in detail. Nonwoven fabric-based separators in power lithium-ion batteries are still being tested in small-scale trials. To realize their large-scale industrial production and application, we must overcome technical bottlenecks, i.e., the thickness, pore size, and cost control of the separator. Prompt and effective solutions to these problems would help realize safe batteries with high specific capacity.

Key words: lithium ion battery, non-woven fabric, separator