Ni-CoSe2 heterojunction coated by N-doped carbon for modified separators of high-performance Li-sulfur batteries

Functional separators modified by transition metal compounds have been proven to be effective in suppressing the shuttle effect of polysulfides and accelerating sluggish electrode dynamics in lithium-sulfur batteries (LSBs). However, the behaviors of heterojunctions composed of transition metals and their compounds in LSBs are still rarely studied. Herein, we report a novel Ni-CoSe2 heterostructure coated with nitrogen-doped carbon. Compared to homogeneous cobalt diselenide, it exhibits much stronger adsorption and catalytic conversion abilities towards polysulfides. With the modified separators, the lithium-sulfur batteries exhibit significantly improved capacity retention and reduced polarization during cycling.

Fast Heat Transport Inside Lithium-Sulfur Batteries Promotes Their Safety and Electrochemical Performance

Lithium-sulfur batteries are paid much attention owing to their high specific capacity and energy density. However, their practical applications are impeded by poor electrochemical performance due to the dissolved polysulfides. The concentration of soluble polysulfides has a linear relationship with the internal heat generation. The issue of heat transport inside lithium-sulfur batteries is often overlooked. Here, we designed a functional separator that not only had a high thermal conductivity of 0.65 W m⁻¹ K⁻¹ but also alleviated the diffusion of dissolved active materials to the lithium anode, improving the electrochemical performance and safety issue. Lithium-sulfur batteries with the functional separator have a specific capacity of 1,126.4 mAh g⁻¹ at 0.2 C, and the specific capacity can be remained up to 893.5 mAh g⁻¹ after 100 cycles. Pouch Cells with high sulfur loading also showed a good electrochemical performance under a lean electrolyte condition of electrolyte/sulfur (E/S) = 3 μL mg⁻¹.

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Fast heat transport inside Li-S batteries was designed by a simple method

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Pouch cells showed a good electrochemical performance under a lean electrolyte condition

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In situ 2D XANES was conducted to explore the mechanism of Li-S batteries

Reduced graphene oxide/TiO2(B) nanocomposite-modified separator as an efficient inhibitor of polysulfide shuttling in Li-S batteries

The shutting effect in lithium–sulfur (Li–S) batteries hinders their widespread application, which can be restrained effectively by a modified separator. In this work, a composite of reduced graphene oxide and beta-phase TiO₂ nanoparticles (RGO/TiO₂(B)) is designed as a separator modification material for improving the electrochemical behavior of Li–S batteries. The TiO₂(B) nanoparticles are in situ prepared and tightly adhere to the RGO layer. A series of examinations demonstrated that the RGO/TiO₂(B)-coated separator efficiently inhibits the polysulfide shuttling phenomenon by the cooperative effect of physical adsorption and chemical binding. Specifically, as modified separators, a comparison between TiO₂(B) and anatase TiO₂(A) each composited with RGO has been conducted. The TiO₂(B) sample not only exhibits a superior blocking character of migrating polysulfides, but also enhances battery electrochemical kinetics by fast Li ion diffusion.

Beta-phase TiO₂ nanoparticles were adhered onto RGO in situ to fabricate a multi-functional separator for high-performance lithium–sulfur (Li–S) batteries.