It is a tough issue to achieve high electrochemical performance and high sulfur loading simultaneously, which is of important significance for practical Li–S batteries applications. Inspired by the transportation system of the plant root in nature, a biomimetic root-like carbon/titanium nitride (TiN/C) composite nanofiber is designed as a freestanding current collector for the high sulfur loading cathode. Like the plant root which absorbs water and oxygen from soil and transfers them to the trunk and branches, the root-like TiN/C matrix provides high-efficiency polysulfide, electron, and electrolyte transfer for the redox reactions via its three-dimensional-porous interconnected structure. In the meantime, TiN can not only anchor the polysulfides via the polar Ti–S and N–S bond but also further facilitate the redox reaction because of its high catalytic effect. With 4 mg cm–2 sulfur loading, the TiN/C@S cathode delivers a high initial discharge capacity of 983 mA h g–1 at 0.2 C current density; after 300 charge/discharge cycles, the discharge capacity remains 685 mA h g–1, corresponding to a capacity decay rate of ∼0.1%. Even when the sulfur loading is increased to 10.5 mg cm–2, the cell still delivers a high capacity of 790 mA h g–1 and a decent cycle life. We believe that this novel biomimetic root-like structure can provide some inspiration for the rational structure design of the high-energy lithium–sulfur batteries and other composite electrode materials.
The carbon-based interlayers set between the sulfur cathode and the separator have been demonstrated to be a simple but powerful means to promote the electrochemical performances of the Li-S batteries. However, the detailed mechanism has yet been fully understood. In this work, a series of battery configurations have been designed to further analyze the function mechanism of the carbon interlayer. The controlled studies demonstrate that the function of the interlayer as an accessorial current collector to provide and transport electrons plays the most important role in enhancing the dischargeability and reversibility of the sulfur cathode. The fundamental understanding of the function mechanism will provide further insight for the rational design of the interlayer structure in the Li-S battery system.
In addition to tackling the issues of the low sulfur (S) utilization and poor cycle stability caused by the low conductivity of S and the dissolution of the intermediate polysulfides, Li−S system also yearns for a simple and scalable synthetic route for the S‐based cathode material. Here we demonstrate that a facile spray drying method can be successfully applied to prepare the high‐performance KB−S@rGO composite based on easily obtained commercial raw materials. The spray drying process realizes a quasi‐core‐shell structure: the KB−S congeries enrich the core, and the large GO sheets tend to distribute in the shell and therefore package the KB−S core. A simple post heating‐process facilitate the uniform distribution of S and the partial reduction of the GO. The final KB−S@rGO composite achieves a significant enhancement in both S utilization and capacity retention: it reveals a high initial reversible capacity of 1250 mA h g−1 at 0.1 C. After 100 cycles, the cell still remains a reversible capacity of 883 mA h g−1, responding to a cycle decay value of 0.34% per cycle.
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