Carbon nanotube/zirconia composite-coated separator for a high-performance rechargeable lithium-sulfur battery

Abstract

The shuttle effect caused by polysulfides remains a major issue hindering the application of lithium-sulfur (Li-S) batteries. In this work, a composite of organically modified carbon nanotube (CNT) and zirconia (ZrO2) nanoparticles is synthesized and used as a surface coating on a commercial Celgard separator to restrain the shuttle effect and improve battery performance. Electrolyte uptake and water contact angle measurements show that the CNT/ZrO2 composite-coated separator has an enhanced electrolyte wettability. Thermal shrinkage results reveal an improvement in the stability of the coated separators, especially at high temperatures. Electrochemical measurements also show the effectiveness of the CNT/ZrO2 composite-coated separator in a Li-S battery. The initial discharge capacity is improved after coating, as is the capacity retention rate. In addition, a battery with a CNT/ZrO2 composite-coated separator attains an impressive capacity reversibility as high as 91.7% in a rate performance test from 0.1 to 2 C. The composite coating restrains the shuttle effect effectively and improves the thermal shrinkage properties of the separator. Thus, the use of a CNT/ZrO2 composite-coated separator should improve the prospects for practical application of Li-S batteries.