Nickel-plated sulfur nanocomposites for electrochemically stable high-loading sulfur cathodes in a lean-electrolyte lithium-sulfur cell

An electrochemical sulfur cathode is attractive due to its high theoretical charge-storage capacity, low cost, and natural abundance. For practical viability, a high-performance sulfur cathode with a sufficient sulfur loading/ content and stable electrochemical utilization must be developed. However, the satisfaction of these two essential requirements has been proven to be in opposition to each other due to the insulating nature of sulfur and the repeated conversion between solid-/liquid-state active materials that damage the electrochemical efficiency and reversibility. To address these problems, in this work we demonstrate the chemical plating of conductive and electrocatalytic nickel onto sulfur particles to form an electroless-nickel-plated sulfur nanocomposite. This cathode material features a lightweight nickel nanoshell on the surface of the sulfur particles, which enables high electrochemical utilization and kinetics with a high charge-storage capacity (1,008 mA.h g-1) and excellent rate performance (C/20-C/2). The nickel nanoshell chemically traps and catalyzes the liquidstate active material, resulting in stable long-term cyclability for 200 cycles at various rates. These improved electrochemical characteristics are realized by the enhanced battery properties simultaneously reaching up to a high sulfur loading (14 mg cm-2) and a high sulfur content (74 wt%) with a low electrolyte-to-sulfur ratio (7 mu L mg-1). With the capability to utilize and stabilize such a high amount of sulfur, the electroless-nickel-plated sulfur cathode demonstrates enhanced areal/gravimetric capacities along with high energy densities (13-28 mW.h cm-2) that are comparable to those of the current available lithium-ion oxide cathodes (10-14 mW.h cm-2).