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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-CoSe 2 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., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Nanoengineering is one of the most effective methods to promote the lithium storage performance of silicon material, which suffers from huge volume changes and poor reaction kinetics during cycling. However, the commercial application of nanostructured silicon is hindered by its high manufacturing cost and low tap density. Herein, a Si/Ge/graphite@C composite was successfully synthesized by ball-milling with subsequent calcination. By introducing Ge, graphite and an amorphous carbon coating, both tap density and electrochemical performance are improved significantly. Benefiting from the synergetic effects of the above components, the Si/Ge/graphite@C composite delivers a reversibility capacity of 474 mA h g -1 at 0.2 A g -1 and stable capacity retention., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)