Recent Development of Polyolefin‐Based Microporous Separators for Li−Ion Batteries: A Review

Abstract

Secondary Li−ion batteries have been paid attention to wide‐range applications of power source for the portable electronics, electric vehicle, and electric storage reservoir. Generally, lithium‐ion batteries are comprised of four components including anode, cathode, electrolyte and separator. Although separators do not take part in the electrochemical reactions in a lithium‐ion (Li−ion) battery, they conduct the critical functions of physically separating the positive and negative electrodes to prevent electrical short circuit while permitting the free flow of lithium ions through the liquid electrolyte that fill in their open porous structure. Hence, the separator is directly related to the safety and the power performance of the battery. Among a number of separators developed thus far, polyethylene (PE) and polypropylene (PP) porous membrane separators have been the most dominant ones for commercial Li−ion batteries over the decades because of their superior properties such as cost‐efficiency, good mechanical strength and pore structure, electrochemical stability, and thermal shutdown properties. However, there are main issues for vehicular storage, such as nonpolarity, low surface energy and poor thermal stability, although the polyolefin separators have proven dependable in portable applications. Hence, in this review, we decide to provide an overview of the types of polyolefin microporous separators utilized in Li−ion batteries and the methods employed to modify their surface in detail. The remarkable results demonstrate that extraordinary properties can be exhibited by mono‐ and multilayer polyolefin separators if they are modified using suitable methods and materials.

Novel Thermotolerant and Flexible Polyimide Aerogel Separator Achieving Advanced Lithium‐Ion Batteries

“…[15,16] In addition to the modification of physical coating, chemical surface coating is another method for improving the thermal stability of separators, such as grafting melamine to PE separators or methyl methacrylate to PVDF separators. [17,18] However, chemical modification processes are usually more complicated and costly, and they are not environmentally friendly. More importantly, excessive chemical reaction processes will damage the structures of separator substrates.…”

Corn‐based Electrochemical Energy Storage Devices

“…The polymers are widely used as the EES-membrane. [165][166][167] The porous membrane of the EES devices can be prepared from the nanocomposite of polymeric media with corn biochar or corn derivatives. [160] This novel issue is not developed appropriately yet and needs more investigations.…”

“…Therefore, the morphology of EES‐membrane has a significant influence on the performance of the EES devices. The polymers are widely used as the EES‐membrane . The porous membrane of the EES devices can be prepared from the nanocomposite of polymeric media with corn biochar or corn derivatives .…”

Resin‐silica composite nanoparticle grafted polyethylene membranes for lithium ion batteries

“…However, the electrolyte wettability of polyolefin separators is still not satisfactory because of the hydrophobic nature of polyolefin materials. 12 In order to enhance the compatibility between separator and electrolyte, many methods 2,13,14 have been proposed, such as the use of high-dielectric constant polymer materials as separators, [15][16][17][18] surface modification of polyolefin separators, [19][20][21][22][23][24][25] using polymer electrolytes, [26][27][28] and so on. Recently, ceramic NPs coating is widely used to enhance the electrolyte wettability as well as promote the thermal stability of separators.…”