Constructing a sandwich-structured interlayer with strong polysulfides adsorption ability for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) battery represents one of the most promising candidates for next-generation energy storage devices due to its superhigh energy density. However, its practical utilization is seriously hampered by shuttle effect of lithium polysulfides (LiPSs). In this work, sandwich-structured Ti4O7-carbon nanofibers/Ti4O7/Ti4O7-carbon nanofibers (TC/T/TC) is developed as a functional interlayer to efficiently inhibit shuttle effect for high-performance Li-S batteries. The free-standing TC/T/TC interlayer with favourable flexibility is fabricated through alternately adopting electrospinning and spraying technique, then followed by in-situ high temperature carbonization and reduction. The resulting interlayer presents excellent physical-blocking and chemical-trapping effects for LiPSs since it has a dense middle layer of polar and conductive Ti4O7 with sufficient physicochemical sites for LiPSs trapping and conversion. Besides, the porous surface layers of Ti4O7-carbon nanofibers can provide enough space to restrain volume expansion and recycle the cathode fragments. Furthermore, the highly conductive interlayer can serve as a front current collector to reduce resistance and accelerate redox process. When applied to Li-S battery, CMK3/S cathode (sulfur areal density, 2 mg/cm(2)) with the TC/T/TC interlayer exhibits decent cycling capability and rate performance. It delivers an initial specific capacity of 1129 mAh g(-1) and its capacity remains at 686 mAh g(-1) after 500 cycles at 1 C rate. More excitingly, its initial specific capacity reaches 738 mAh g(-1) at 3 C rate, and the capacity maintains at 481 mAh g(-1) even after 3500 ultra-long cycles, with a high capacity retention of 65.2% and extremely low capacity decay of 0.00995% per cycle. The new type of interlayer will possess a great promise to find its practical application in Li-S batteries. (C) 2019 Elsevier Ltd. All rights reserved.