Abstract: The global energy and environmental problems caused by the extensive use of fossil fuels have significantly impac-ted on the human’s production and livelihoods, which can be expected to well address via developing and utilizing various clean energy sources, such as solar energy, water energy and wind energy, etc. Efficient energy conversion and storage technologies are the key and basics of the large-scale use of clean energy due to their regional and intermittent characteristics. Lithium-ion batteries, as green energy storage devices, are widely used in mobile phones, laptops, cameras and other portable electronic devices. In recent years, lithium-ion batteries have begun to be applied in the field of power batteries such as electric vehicles. However, the electric vehicles suffer from inferior cruise-ability, frequent charging and high cost because of their relatively low energy density. The energy density (2 600 Wh·kg-1) of lithium-sulfur batteries, composed of lithium metal as anode and sulfur as cathode, is much higher than that of state-of-the-art lithium-ion batteries. Additionally, the sulfur cathode material is abundant, nontoxic, cost effectiveness and environmental friendliness. Hence, lithium-sulfur batteries are considered as one of the most promising secondary batteries. However, the poor CE and limited cycle life, caused by the fundamental defects of sulfur cathode such as low ionic/electronic conductivities, large volumetric expansion and shuttle effect, hamper the widespread application of Li-S battery. So far, considerable studies have focused on enhancing the conductivity, inhibiting or eliminating the shuttle effect and stabilizing the microstructure of electrode material during repeated cycles. It has been demonstrated that the S/C composite cathode materials with special microstructure, prepared by compositing sulfur and carbon with different morphology, exhibit significantly improved conductivity, decreased shuttle effect of lithium polysulfide and less volume change during lithium intercalation/deintercalation. These improvements lead to better rate performance, cycling stability and charge-discharge efficiency. Moreover, the introduction of heterogeneous element-doped carbon materials, metal oxides and conductive polymers in the sulfur cathode material can achieve effective chemical adsorption of lithium polysulfide. Excellent electrochemical lithium storage performance of sulfur cathode can also be achieved by the combination of these various modification me-thods. In this review, the main problems and recent research progress in sulfur cathode materials are summarized and commented upon based on the principle of lithium-sulfur batteries. Meanwhile, it also gives brief suggestions and outlooks on the future research directions in lithium-sulfur batteries.
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