The Doping Modification Research Of Cathode Materials For Advanced Lithium-sulfur Battery

Lithium-sulfur batteries possess a high theoretical capacity and a high energy density,which are expected to be one of the most advanced energy storage equipment at present.In addition,as an active substance,sulfur possesses the virtue for rich in natural resources and bargain price.However,the commercialization of lithium-sulfur batteries is severely hindered by several key challenges,such as the poor electronic conductivity of sulfur and Li₂S₂/Li₂S as well as the shuttle effect of polysulfides.Here,this article is based on cathode materials for the research objects.Polar materials are selected as a substrate for modified research,and polysulfides catalytic conversion mechanism is discussed to alleviate the shuttle effect and accelerate the reaction kinetics.The heteroatom doping for cathode material is carried out a series of research work and specific studies are as follows:（1）In order to alleviate the shuttle effect of polysulfides,an efficient Fe/Co-C₃N₄/C catalyst is prepared by simple sol-gel method and high temperature calcination method.Fe/Co-C₃N₄/C as a catalyst has large specific surface area and high conductivity,which can effectively adsorb polysulfides and promote the electrochemical redox kinetics.The Fe/Co-C₃N₄/C/S shows a high initial capacity of949 m Ah g^-1with a low fading rate of 0.156%per cycle at 0.2 C after 135 cycles.（2）A highly efficient catalyst P_0.1-Mo_0.9Ni_0.1S₂/CNT is synthesized by simple high temperature hydrothermal method and annealing calcination method.It is found that the introduction of nickel can promote the transformation of 2H phase into 1T metallic phase and improve the conductivity of Mo S₂.P_0.1-Mo_0.9Ni_0.1S₂/CNT has the ability to rapidly promote the deposition of lithium sulfide and improve the reaction kinetics.P_0.1-Mo_0.9Ni_0.1S₂/CNT/S can release a high initial capacity of 742 m Ah g^-1with a low fading rate of 0.075%per cycle at 1 C and still retain a high discharge capacity of 463 m Ah g^-1at the 500^thcycle.（3）Mn/Co-Ni O/C is synthesized by simple template-free hydrothermal method and annealing calcination method.The composition and structure of Ni O are optimized on the whole.The matrix is prepared by in-situ pyrolyzation/carbonization of urea,thus improving the electrical conductivity of electrode.By metallic ions(Mn²⁺,Co²⁺)doping,the formation of oxygen vacancy in the lattice is induced,which can promote the diffusion of Li⁺ions in the lattice as well as the electrochemical kinetics of the electrode.The microsphere of Mn/Co-Ni O/C can adsorb polysulfides better and relieve the shuttle effect.The Mn/Co-Ni O/C/S can release a high initial capacity of 1000 m Ah g^-1at 1 C and still retain a high discharge capacity of 778 m Ah g^-1at the 200^thcycle,the capacity retention rate is 78%.