Low-cost synthesis route for high-performance S/C composite with 90% S content

Abstract

Lithium-sulfur (Li-S) batteries offer a high theoretical energy density of 2567 W?h?kg－1 by the multi-electron-transfer cathode reaction between elemental sulfur and lithium ions, and are a focus of post lithium-ion batteries technology1. Yet, there are challenging obstacles standing in the way of the large-scale application of the Li-S technology in the market, which include the potential safety risky of Li- dendrite formation, low electrical conductivity of sulfur (5*10－30 S?cm－1 at 25 °C), the dissolution of the charge/discharge intermediates, polysulfides (Li2Sx, 4 ≤ x ≤ 8) in the electrolyte, and the volume change of the sulfur during lithiation/delithiation (~80%)2. Carbon materials are commonly used as the host to accommodate sulfur to address the issues relevant to the sulfur-cathode owning to their diversity, conductivity, robust stability and chemistry, and their ready abundance and cost3. A carbon host with sulfur nanoparticles adhered can conduct electrons generated by sulfur lithiation/delithiation, limit the dissolution of polysulfides, and withstand the volume change of the sulfur; it therefore can provide an improved specific capacity, rate capability, and cyclic life. However, these improvements are closely connected to both the mass ratio of sulfur in such a sulfur/carbon composite and the areal loading density of sulfur in the cathode. Higher mass ratio and areal loading density of sulfur are favored for practical Li- S battery application, but are usually accompanied by lower‘sulfur utility’that yields reduced specific capacity, rate capability, and cycle life.