Abstract
Lithium-sulfur batteries have emerged as extraordinarily favorable energy storage devices due to their high specific capacity and energy density, safety and low cost. Unfortunately, the wide applications of lithium-sulfur batteries are hampered by several issues, such as the low electronic conductivity and slow redox kinetics, serious volumetric expansion and polysulfide “shuttle effect”. To overcome these issues, in our work, we design and synthesize a composite sulfur host material of Co9S8 microspheres and N-doped carbon nanotubes, where the metallic sulfide Co9S8 with a good conductivity enables the immobilization of the polar lithium polysulfides owing to the strong polar chemisorptive capability, and the one dimensional N-doped carbon nanotubes can provide channels for fast electron and lithium-ion transport. As the lithium polysulfides are well confined, and the redox conversions are promoted, the Co9S8@N-CNTs/S-based lithium-sulfur battery possesses a superior energy storage performance, exhibiting a large specific capacity of 1233 mAh g−1 at 0.1 C and an outstanding cyclic performance, with a low decay of 0.045% per cycle and a Coulombic efficiency of more than 99% after 1000 cycles.
Highlights
The increase in the energy consumption and global warming has accelerated research on electrochemical energy storage devices for electric vehicles and electronic equipment [1,2,3,4,5,6]
In our work, we design and synthesize a composite sulfur host material of Co9S8 microspheres and N-doped carbon nanotubes, where the metallic sulfide Co9S8 with a good conductivity enables the immobilization of the polar lithium polysulfides owing to the strong polar chemisorptive capability, and the one dimensional N-doped carbon nanotubes can provide channels for fast electron and lithium-ion transport
As the lithium polysulfides are well confined, and the redox conversions are promoted, the Co9S8@N-CNTs/S-based lithium-sulfur battery possesses a superior energy storage performance, exhibiting a large specific capacity of 1233 mAh g-1 at 0.1 C and an outstanding cyclic performance, with a low decay of 0.045% per cycle and a Coulombic efficiency of more than 99% after 1000 cycles
Summary
The increase in the energy consumption and global warming has accelerated research on electrochemical energy storage devices for electric vehicles and electronic equipment [1,2,3,4,5,6]. Combining the polar compound with nanocarbon to form a host material capable of strong adsorption and with a high conductivity is beneficial to increase the conductivity, improve the electrolyte contact and provide more effective chemical and physical confinements for polysulfides, which will greatly increase the performance of lithium-sulfur batteries [37, 38]. The synthesis process is convenient, and a three-dimensionally interconnected network structure with the Co9S8 microspheres tightly attached to the N-CNTs is formed In this composite, the polar metal sulfide Co9S8 enables a superior lithium polysulfide absorptivity via the polar chemical bond, which decreases polysulfide dissolution and the shuttle effect and increases the specific capacity and cyclic performance, while the N-doped carbon nanotubes can assist to increase the electronic conductivity and enlarge the interface between the electrode and electrolyte to further enhance the rate performance. The unique Co9S8@N-CNTs composite-based sulfur cathode displays an outstanding overall electrochemical performance, making it promising for applications in lithium-sulfur batteries
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