Toward Commercially Viable Li-S Batteries: Overall Performance Improvements Enabled by a Multipurpose Interlayer of Hyperbranched Polymer-Grafted Carbon Nanotubes

Shuttle effect and the low utilization of dissolved lithium polysulfides (LiPSs) are two prevailing concerns in Li-S battery (LSB) research. Energy efficiency on the other hand is often overlooked but vital to the commercial deployment of battery technology. In this work, a composite of hyperbranched poly(amidoamine)-modified multiwalled carbon nanotubes (PAMAM-CNTs) is successfully prepared by chemical grafting and employed as an interlayer material in LSBs. The high content and highly dispersed polar functional groups of PAMAM can efficiently adsorb and enhance the redox reaction of LiPSs. The CNTs function as a scaffold and current collector that reduces the internal polarization. The assembled LSB displays a high energy efficiency of 86% and a low capacity fading rate of 0.037% per cycle over 1200 cycles at 2 C. The cell also shows excellent cycle performance, high sulfur utilization, and improved stability at a high areal capacity of 9 mAh cm-2 (achieved at a sulfur loading of 8.7 mg cm-2) and low electrolyte/sulfur ratio of 6.1 mL g-1. This thin (12 μm) and lightweight (0.34 mg cm-2) interlayer has a negligible impact on the overall cell energy density.