An enhanced polyethylene/polyetherimide composite separator for high-performance lithium-sulfur battery

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ORIGINAL PAPER

An enhanced polyethylene/polyetherimide composite separator for high-performance lithium-sulfur battery Jiuqing Liu 1 & Yang Xi 1 & Qihou Li 1 & Jie Li 1 & Meng Liu 1 & Cheng Wang 1 & Zikun Hong 1 & Feifei Song 1 & Lishun Bai 1 & Fanli Zeng 1 Received: 13 March 2020 / Revised: 18 June 2020 / Accepted: 25 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract The high performance and safety of lithium-sulfur (Li-S) batteries are the focus of research in recent years. The separator is an important part of the battery, whose performance stability directly affects the performance of the battery. What’s more, there are still many defects in the commercial polyolefin separator. In this work, a polyethylene/polyetherimide (PE/PEI) composite separator is designed by surface coating and non-solvent-induced phase separation (NIPS) method. The film breakage temperature and anti-puncture strength of the PE/PEI composite separator (181.96 °C, 7.90 N) are higher than those of the commercial PE separator (153.00 °C, 6.20 N), which will greatly ensure the safety problems caused by internal self-heating and external short circuit of Li-S batteries. The PE/PEI composite separator–based Li-S battery delivers a high initial specific capacity of 1265 mAh g−1 at 0.2 C and exhibits excellent rate capability compared with the commercial PE separator. Therefore, the PE/ PEI composite separator is a candidate separator for the high-performance and high-safety Li-S battery. Keywords Polyethylene/polyetherimide composite separator . Film breakage temperature . Anti-puncture strength . Safety . Li-S batteries

Introduction The lithium-sulfur (Li-S) battery has the advantages of high capacity density (1675 mAh g−1), high energy density (2600 Wh kg−1), wide source of sulfur material, low cost, and good environmental compatibility [1, 2], and it is considered to be one of the most promising candidates for nextgeneration high-energy density secondary battery [3–5]. As an important component of the Li-S battery, the stability of the separator performance directly affects the performance of the battery [6, 7]. At present, there are still more defects in the commercial Li-S battery separator with the polyolefin material. In the process of high-power discharge, the local temperature of the battery rises rapidly, and when the battery temperature is close to the starting point of the melting of the separator, the thermal shrinkage of the separator will make the

* Jiuqing Liu [email protected] 1

School of Metallurgy and Environment, Central South University, Changsha 410083, Hunan, China

cathode and anode contact, and the instantaneous heat generation is a great potential danger for the battery’s safety. The polyolefin separator itself has a hydrophobic property and poor wettability to the electrolyte. In the long-term charging and discharging process of the battery, the separator should be stable in the cathode and anode, and the slight poor contact can lead to an increase of the battery’s internal resistan