Large‐Scale Separators Based on Blends of Aromatic Polyethers with PEO for Li‐Ion Batteries: Improving Thermal Shrinkage and Wettability Behavior

Abstract

The development of large‐scale separators with tuned microporous structures and surface areas up to 0.56 m2 are demonstrated for application to Li‐ion batteries. The different separators developed are based on blends composed of aromatic polyethers containing different functional groups that can interact with lithium cations and poly(ethylene oxide) (PEO). The porous structures that are prepared after the partial removal of PEO by water treatment can be fine‐tuned by manipulating the blend composition and aromatic polyether structure. In particular, the miscibility effect on pore formation is thoroughly studied. The prepared separators are highly porous (38–63 %), show good air permeability (comparable Gurley values to commercially available polyolefin separators), and increased wettability to conventional liquid electrolytes. In addition, these separators show improved thermal shrinkage behavior and high thermal stability compared to the commercially available polyolefin separators. LiFePO4/C cells using the novel separators show good performance and retain 93 % of their initial discharge capacity after 166 cycles, thus offering excellent stability for long‐term operation. The aromatic‐polyether‐based chemistry of the prepared separators plays a key role in providing the separator with the aforementioned advantageous characteristics, enabling them to be an interesting alternative to conventional polyolefin‐based separators.

Porous membrane with high curvature, three-dimensional heat-resistance skeleton: a new and practical separator candidate for high safety lithium ion battery

“…Meanwhile, the thermal stability of the PEI based membrane at 180°C weighs against that of the PI separator. This confirms the superior heat resistance of the PEI base membrane and the successful realization of the concept of the 3D heat-resistant skeleton, implying a promising contribution to enhance the thermal safety of lithium ion batteries when used as the separator 21 .…”

A Thermally Stable, Combustion‐Resistant, and Highly Ion‐Conductive Separator for Lithium‐Ion Batteries Based on Electrospun Fiber Mats of Crosslinked Polybenzoxazine

“…After 1min, the liquid electrolyte wets the CR-PBz-FbMs eparator to ah eight of 17 mm compared to 3mmf or Celgard 2300. The high compatibility of the CR-PBz-FbM separator with the utilizedl iquid electrolytes is attributedt ot he high ion conductivity.S imilar to other separators based on thermally stable polymers (cellulose,p olyimide,p olybenzoxazole), [22][23][24][25][26][27] the polar groups (ÀOH and tertiary amine) of CR-PBz-FbM contribute to the high compatibilityo ft he separator andt he electrolyte. Moreover, the dominant interaction between the CR-PBz-FbM separatora nd the electrolyte could be hydrogen bonding.P olybenzoxazine polymers have high tendency to form inter-a nd intrachain hydrogen bonds.…”

“…[9] Thef ailureo ft he separators might result in combustiono ft he battery materials and serious safety problems.T oi mprove the thermal stability of the polyolefin-and other thermoplastic-polymerbased separators,t he additiono fn anoparticles to the separators [10,11] and surface modification of the separators [12][13][14][15][16][17] have been reported. Consequently,s ome polymers with higher melting points andf usion temperatures,s uch as polyacrylonitrile, [18,19] poly(ethylene terephthalate), [20] poly(phthalazinone ether sulfone ketone), [21] Nylon 6,6, [22] poly(butylene terephthalate), [23] and aromatic polyethers, [24] have been reported as raw materials for the preparation of separators to improve their abuse tolerance.N evertheless,t he above-mentioned separators are alls hutdown-typem aterials and could still encounter certain problemsi ns eries-connected cells.…”

Synthesis of Imidazolium based PILs and Investigation of Their Blend Membranes for Gas Separation

“…Additionally, aromatic polyether based pyridinium PILs for use as CO 2 /CH 4 gas separation membranes have been developed [10] that show high glass transition temperature, excellent thermal stability, enhanced solubility and outstanding film forming ability [21][22][23][24][25]. Since the CO 2 permeability at ambient temperature is very low but their selectivity for the CO 2 /CH 4 gas pair is quite favorable (with values up to~50), a further increase of CO 2 permeability while at the same time maintaining the satisfactory CO 2 /CH 4 selectivity, could make these membranes promising candidates for natural gas and biogas purification.…”