Preparation And Properties Of Flexible C/MoO₂ Composite Nanofiber Membranes As Binder-Free Anodes For Lithium-Ion Batteries

Lithium-ion batteries?LIBs?are widely used for portable electronic devices,such as cell phones and laptop computers,because of their high energy density,long lifetime and non-pollution.Nevertheless,the energy densities of commercial batteries are still not sufficient for the practical applications of LIBs.As a key component of LIBs,electrode material dominates the electrochemical properties.Molybdenum dioxide?MoO2?has attracted a lot of attentions in lithium ion batteries field due to its high electrical conductivity,good structure stability and high capacity.However,the cycle performance of MoO2 suffer from the formation of Li0.98MoO2 with poor conductivity and the huge volume expansions during the lithiation and delithiation processes.Carbon nanofiber membranes can effectively alleviate volume swing effect,improve electrical conductivity,increase the specific surface and the salt content and enhance the electrochemical properties.In this paper,porous carbon composite nanofiber membranes with MoO2 particles were obtained via electrospinning as a self-standing anodes for lithium ion battery.The influences of the MoO2 content and porous structure on the microstructure,phase of structure and electrochemical properties of composite nanofibers were studied.The main research results of this paper include:?1?The effect of MoO₂ content on composite fiber membrane.When the heat treatment condition was under 600?for 5 h,MoO₂ had good crystallinity and the composite nanofiber membranes maintained good flexibility.With the increase of MoO2 content,the graphitization of membranes and the size of MoO2 nanoparticles were increasing,the capacity of the membranes presented a trend of increasing first and then decreasing,and the impedance showed the trend of decreasing first and then increasing.The membrane had the best electrochemical performance when the content of MoO2 was 35.6 wt%.The discharged capacity at a current density of 100 mA/g was 809 mAh/g after 50 cycles,the coulombic efficiency was about 100%.?2?The effect of pore structure on composite nanofiber membrane.With the increase of PMMA content,the graphitization of membranes was decreasing,the volume of pore was increasing,and the specific surface area and the capacity of the membranes presented a trend of increasing first and then decreasing.The electrochemical properties of The porous nanofiber membrane electrode was best at the PMMA and PAN ratio of 2:8.The discharge capacity of the membrane electrode was 1073 mAh/g at current density of 100 mA/g after 60cycle,the remaining capacity was 716 mAh/g and 447 mAh/g at higher current density of 1000mA/g and 2000 mA/g.It was found that the electrochemical properties of electrode materials were effectively improved by the porous structure.