Preparation Of Cathode Materials And Separator Modification Technology For Lithium-Sulfur Battery

In recent years,lithium-sulfur battery has been widely studied by researchers because of their high theoretical specific capacity of 1675 mAh g^-1 and the theoretical specific energy of 2600 Wh kg^-1.Moreover,elemental sulfur has the advantages of abundant reserves,non-toxicity and environmental friendliness,so lithium-sulfur battery is regarded as one of the most promising next-generation secondary battery.However,the commercialization of lithium-sulfur battery is hindered by the insulation of elemental sulfur,the structural destruction of the sulfur positive electrode,and the shuttle effect of long-chain polysulfides.In order to solve these problems,the team take lithium-sulfur battery interlayer?cathode materials and modified separators as research objects.Aiming to enhance the conductivity of sulfur cathodes,improve the physical limitation of the elemental sulfur and chemical adsorption of polysulfides.The interlayer or modified separator was carried out by the following research work to further inhibiting the dissolution and shuttle effect of polysulfides.?1?In order to inhibit the shuttle effect of polysulfides,NSHPC was synthesized by a simple and environmentally friendly one-step strategy,and then NSHPC interlayer was produced by a simple slurry coating methode.The results showed that the NSHPC with a unique honeycomblike micro/mesoporous structure,which owned a high specific surface area(2543.8 m² g^-1)and a large pore volume(2.14 cm³ g^-1).It will facilitate the penetration of the electrolyte.The lithium-sulfur battery using the NSHPC interlayer and the pure sulfur enthode electrode can release a high initial discharge capacity of 1549 mAh g^-1 at0.1 C and high reversible discharge specific capacity of 609 mAh g^-1 was maintained even after 300 cycles at 0.5 C.Those good electrochemical performances were due to the physical confinement of the unique porous structure to sulfur and polysulfides and the co-doping of nitrogen and sulfur resulting in electrostatic repulsion of the carbon material to polysulfides.?2?In order to further inhibit the shuttle effect of polysulfides and improve the performance of lithium-sulfur battery,the holistic design strategy of NMCS@MoS₂/S composite cathode and CNT/CH modified separator was proposed.In the holistic design,NMCS@MoS₂ played an important role in the adsorption of sulfur and polysulfides;CNT/CH modified separator was also invaluable in promoting lithium ion transport and chemical adsorption of polysulfides.NMCS@MoS₂/S-CNT/CH delivered a high reversible capacity of 827 mAh g^-1 after 200 cycles at 0.5 C.The high reversible specific capacity of 501 mAh g^-1 was maintained,and the capacity attenuation per cycle was only0.08%at high current density of 1 C even after 500 cycles.?3?In order to simplify the synthesis process while maintaining good electrochemical performance,the team proposed a simple and efficient one-step hydrothermal synthesis of SnS₂@CNT as the holistic design strategy of sulfur host and modified separator.SnS2@CNT/S-SnS2@CNT releaseed a high initial discharge specific capacity of 1375mAh g^-1 at 0.1 C,which was based on the physical limitation and chemical absorption of polysulfides and the advantages of fast electron/lithium ion transport of SnS₂@CNT.A high reversible specific capacity of 555 mAh g^-1 can be obtained even after 800 cycles at a large current density of 2 C.In addition,a lithium-sulfur battery with a high sulfur loading of 4.8 mg cm^-2 and sulfur content of 88 wt.%can exhibit a reversible region capacity of 4.5 mAh cm^-2 after 50 cycles.Therefore,the holistic design strategy provided a useful exploration for the commercialization of high-performance lithium-sulfur battery.