High-Performance Lithium–Sulfur Batteries with a Cost-Effective Carbon Paper Electrode and High Sulfur-Loading

Abstract

The lithium sulfur (Li–S) battery has attracted much attention due to its high energy density and the low cost of sulfur, but practical applications are still impeded by its short cycle life and low practical energy density due to polysulfide shuttle and low sulfur-loading. Here, we report a novel electrode design to achieve high energy density and long-cycling Li–S batteries, which rely on a cost-effective and well-performed carbon nanofiber-porous carbon paper (CNFPC) electrode. In this design, the CNF substrate with a high electrical conductivity (420 S cm–1) and an extremely low density (∼0.2 g cm–3) is used as a current collector and as a host for high sulfur-loading (∼6.7 mg cm–2), while the carbon black nanoparticles which are well-distributed within the CNF substrate function as electrical bridges for nonconductive sulfur and highly conductive CNF framework. In addition, the densely packed (∼6.6 g cm–3) porous carbon layer (∼5 μm) on the top of CNF acts as a protective layer to inhibit polysulfide shuttle between cathode and anode. As a result, this unique design enables the fabrication of Li–S batteries with a remarkably high reversible capacity exceeding 900 mAh g–1 at 0.2 C, 800 mAh g–1 at 0.5 C, and 700 mAh g–1 at 1 C, while the average coulombic efficiency is greater than 99.5%. Moreover, at a high current rate of 1.5 C, capacity retention from 709 to 302 mAh g–1, corresponding to an areal capacity of >2 mAh cm–2, is obtained over 1000 cycles.