Preparation Of Lithium Titanate/graphene Composites And Study On Anode Performance Of Li-ion Capacitor

In order to improve the electrochemical performance of LTO for LICs,LTO/graphene composites were synthesized through a facile one-step solid-state reaction.It was found that there is an adding threshold of graphene nanosheets on the formation of LTO/graphene during the solid state reaction.The composite exhibited interweaved structure between graphene nanosheets and LTO particles rather than agglomeration as compared with the bare LTO.The effect of graphene nanosheets on the electrochemical performance of LTO was investigated.The optimized composite with decreased polarization exhibits a specific capacity of 172.5 mAh g^-11 at 0.1 C and still remains 65 mAh g^-11 at 20 C.The LICs full cell was also assembled for the practical evaluation.The LICs full cell with balanced mass ratio of anode to cathode could deliver an energy density of 14 Wh kg^-11 at a power density of2700 W kg^-11 and exhibit superior capacitance retention of 97%after 3000 cycles at a current density of 0.4 A g^-1.The boosts in reversible capacity,rate capability and cycling performance are ascribed to the synergistic effect of graphene nanosheets,which provide short lithium ion diffusion length as well as facile electron conduction channel.Furthermore,porous LTO nanoparticles were prepared by a precursor directed hydrothermal method.The influence of sintering temperature and graphene additives on the microstructure evolution and electrochemical properties of LTO for LICs was investigated.Bare LTO with fine particle and porous microstructure can be obtained under low temperature sintering?600oC?,which can deliver a specific capacity of 65.2 mAh g^-11 at the current rate of 20 C.As raising temperature,the LTO particles are inclined to grow with coarse particle and the agglomerate state,deteriorating the electrochemical performances?14.3 mAh g^-11 at 20 C?.After introduction of graphene additives,LTO can be prepared with increased surface area,pore volume and electrical conductivity,which are beneficial for LTO to contact with electrolyte,shorten the lithium diffusion length and facilitate the electron and ion transport during lithiation/delithiation process,leading to the greatly improved electrochemical performances?102 mAh g^-11 at 20 C?.The LICs full cell using the LTO/graphene anode and activated carbon cathode was also evaluated.The decent energy/power densities(maximum energy/power densities are 44.0 Wh kg^-11 and 7200 W kg^-1,respectively)with excellent cycling stability?capacitance retention of 80%at a current density of 3.2 A g^-11 after 10000 cycles?show the promising application perspective.