Binder-Free, Thin-Film Ceramic-Coated Separators for Improved Safety of Lithium-Ion Batteries

Abstract

Separators play a crucial role in ensuring the safety of lithium-ion batteries (LIBs). Commercial polyolefin-based separators such as polyethylene (PE) still possess serious safety risks under abuse conditions because of their poor thermal stability. In this work, a novel type of binder-free, thin ceramic-coated separators with superior safety characteristics is demonstrated. A thin layer of alumina (Al 2 O 3 ) is coated on commercial PE separators using the electron-beam physical vapor deposition (EB-PVD) technique. Scanning electron microscopy (SEM), contact angle, impedance spectroscopy, and adhesion test techniques were employed to evaluate structure–property correlations. When compared to commercial slurry-coated separators, the EB-PVD-coated separators display (i) higher thermal stability, (ii) stronger ceramic–polymer adhesion, and (iii) competitive electrochemical performance of full LIB cells. Thermal stability, in terms of improved shutdown and breakdown characteristics of the separator, was studied using the in situ impedance technique up to 190 °C. In addition, the improved adhesion of the ceramic layer deposited on the PE separator was studied following the tape adhesion strength test. We prove that the thin (binder-free) ceramic layer coated by EB-PVD is far more effective in improving separator safety than those made using the conventional thick slurry coating.

A Critical Review on Materials and Fabrications of Thermally Stable Separators for Lithium‐Ion Batteries

“…When the temperature increases further, separator breakdown happens, i.e., large thermal shrinkage and breakage occur, causing an internal short circuit and speeding up thermal runaway of LIBs. [17] This is because films are uniaxially stretched along the machine Li-ion batteries nowadays are widely used as energy storage systems owing to their high power and energy densities. However, the safety of Li-ion batteries has increasingly become a grave concern, and how to effectively mitigate or avoid the thermal runaway of Li-ion batteries, particularly during fast charging/discharging, is a critical issue.…”

“…When the temperature increases further, separator breakdown happens, i.e., large thermal shrinkage and breakage occur, causing an internal short circuit and speeding up thermal runaway of LIBs. [ 17 ] This is because films are uniaxially stretched along the machine direction (MD) in the dry manufacturing process for separators, which results in anisotropic material behaviors at high temperatures. [ 11,18–21 ] In general, the thermal stability of separators can affect their dimensional stability or shrinkage, melt rupture, and puncture resistance.…”

A Nonflammable and Thermally Stable Polyethylene/Glass Fiber−Magnesium Hydroxide/Polyethylene Composite Separator with High Mechanical Strength and Electrolyte Retention to Enhance the Performance of Lithium‐Ion Batteries

“…It is indicated that coating high‐temperature‐resistant materials on polyolefin separators can improve thermal stability and electrolyte wettability of the separator. [ 7–12 ] Cho et al [ 13 ] coated the PE separator with amino‐functionalized SiO 2 particles to reduce the thermal shrinkage of the separator at 130 °C. Chen et al [ 14 ] coated PE separator with zeolitic imidazolate to improve its thermal stability and electrolyte wettability.…”

“…It is indicated that coating high-temperature-resistant materials on polyolefin separators can improve thermal stability and electrolyte wettability of the separator. [7][8][9][10][11][12] Cho et al [13] coated the PE separator with amino-functionalized SiO 2 particles to reduce the thermal shrinkage of the separator at 130 C. Chen et al [14] coated PE separator with zeolitic imidazolate to improve its thermal stability and electrolyte wettability. However, due to the inability of high-temperature-resistant materials to form a self-supporting layer, the improvement of the thermal stability of the commercial separator is very limited.…”

Fabrication and Investigation of PE-SiO2@PZS Composite Separator for Lithium-Ion Batteries

“…A variety of other methods have been developed in recent years to overcome the disadvantages of separators, including polymer composites (a blend of polymer and inorganic fillers) [ 13 , 14 , 15 , 16 , 17 ], inorganic fillers (e.g., SiO 2 , TiO 2 , Al 2 O 3 and zeolite) [ 18 , 19 , 20 , 21 , 22 , 23 ], and polymer blends [ 17 , 24 ]. Remarkably, it has been confirmed that modification of a polyolefin membrane with a blend of polymer and inorganic fillers as a coating may be the most promising approach [ 1 , 25 ].…”