Synthesis And Characterizations Of Cathode Materials For Li-Se Batteries

Selenium is an attractive cathode material owing to high electronic conductivity and high theoretical volumetric capacity density.However,the biggest problem facing selenium is shuttle effect,which hinders the electrochemical performance.Focusing on the problem,we systematically investigate the effects of hybrid cathode and diaphragm modification on the electrochemical performance for Li-Se batteries.Firstly,we synthesis of porous carbon,and selenium is mixed with the porous carbon to form Se/Porous carbon composites by the melt diffusion process.Characterization methods show that selenium is embedded into the porous carbon and the hybrid exhibits reversible discharge capacity of 220 m Ah/g at 0.5 C（1 C = 675 m Ah/g）after 1000 cycles,which shows good electrochemical stability.Then,we make carbon using paper as source through thermal process and induce it as interlayer for Li-Se battery.Characterizations show that under the current density of 0.5 C over 60 cycles,the discharge specific capacity with no interlayer is only 62 m Ah/g,however,the discharge specific capacity with two interlayers is 138 m Ah/g,the discharge specific capacity with four interlayers is 302 m Ah/g.It illustrates that the linear relationship between the number of interlayers and electrochemical performance.Additionally,we also analysis the charge-discharge curves and the result shows adding interlayer play a role in hurdling the shuttle effect.Finally,we fabricate Se-TiO₂/NFF cathode material with TiO₂ nanofibers and NFF interlayer.Selenium was first mixed with the TiO₂ nanofibers to form Se-TiO₂ composites by the melt diffusion process.Next,electronically conductive nickel foam foil（NFF）is introduced as interlayer placed between the electrode and the separator.Se-TiO₂/NFF exhibits reversible discharge capacity of 600.4 m Ah/g at 0.5 C after 200 cycles,and delivers a discharge capacity as high as 321.3 m Ah/g even at 30 C.The superior electrochemical performance can be ascribed to the synergetic effects of TiO₂ and NFF.More interestingly,we have found a redox reaction happened in NFF during the process of charging and discharging.In conclusion,in this paper,synthesis of hybrid compound conducting carbon and modification of interlayer are used to improve the electrochemical performance of Li-Se batteries.This article provides a theoretical and technical basis for the research of Li-Se battery.