Application Of Single-atom Catalysts In Lithium-sulfur Batteries

Lithium-sulfur batteries have high theoretical mass-specific capacity(1675m Ah g^-1)and theoretical energy density(2600 Wh kg^-1),while being low-cost and environmentally friendly,so they are considered as strong contenders for next-generation energy storage batteries.However,lithium-sulfur batteries also have some shortcomings that limit their commercial application,such as the insulation between sulfur and the discharge product lithium sulfide,the"shuttle effect"of lithium polysulfide and volume expansion.In order to solve these problems,in this paper,nitrogen-doped carbon loaded with single atoms is prepared,and the following contents are mainly studied:（1）Single-atom Ti were introduced on nitrogen-doped carbon by hydrothermal synthesis-annealing two-step method,and Ti-NC with polyhedral structure and abundant mesopores was prepared.The nitrogen-doped carbon obtained by annealing improves the conductivity of the material,and the introduction of single-atom Ti and nitrogen-doped sites improves the polarity of the material,promotes the catalytic conversion of polysulfides,and enhances the adsorption performance of the material on polysulfides,to limit the shuttle effect of polysulfides.The prepared Ti-NC/S electrode has a discharge specific capacity of 541 m Ah g^-1 at a current density of 3C.Secondly,after 500 charge-discharge cycles,the discharge specific capacity is 567 m Ah g^-1 at a current density of 0.5C,and the average decay rate per cycle is 0.053%.（2）Single-atom Fe catalysts（Fe SAs-NC）were prepared using NC materials as supports,which can promote the kinetic reaction of polysulfides and accelerate the nucleation of Li₂S during discharge.At 3C current density,the discharge specific capacity of Fe SAs-NC/S is 379 m Ah g^-1.After 500 cycles at 0.5C current density,the capacity is 504 m Ah g^-1,and the average decay rate per cycle is 0.065%.