Synthesis Of 3D Carbon Based Transition Oxides Hybrid Materials For Energy Storage

With the rapid development of economy and the depletion of traditional fossil energy,we will premote development of new energy resources and renewable energy sources.At the same time,the focue was added on the promotion of effective storage devices.Among the current energy storage systems,lithium ion batteries?LIBs?and supercapacitors have devoted to improve the performance of energy storage.However,these two vehicles have different charge-storage mechanisms which show complementary energy-storage features.Therefore,combining the advantages of these two components will be the major challenge in electrical energy storage devices.Inspiringly,a new concept—i.e.lithium ion capacitors?LICs?was recently proposed.It uses a Li-insertion/extraction cathode?such as LiMn2O4?or anode?e.g.,MnO₂,TiO₂,Li4Ti5O12?,and with an adsorption/desorption anode or cathode?particularly a carbonaceous material,e.g.,carbon nanotube,graphene,active carbon,carbon aerogel?in a non-aqueous electrolyte.Generally,it is a major issue to design electrodes that refrain from the kinetics imbalance as well as achieve a high energy density of LICs.In this work,we rational designed and synthesised three-dimensional?3D?hierarchical porous nanostructure through a conventional and green approach.The followings are the main research content and results which are divided into two parts:?1?Design and synthesis of HTPC//AC LICs system: Herein,we designed a three-dimensional?3D?hierarchical porous nanostructure of hydrogen-treated TiO₂ nanoparticles wrapped conducting polymer polypyrrole?PPy?framework with single-walled carbon nanotubes?SWCNTs?hybrid?denoted as,HTPC?anode material for LICs through a conventional and green approach.Such a unique network can offer continuous electron transport and reduce the diffusion length of lithium ions.A greatly lithium storage specific capacity is achieved with reversible discharge capacity 213 mAh/g?based on the mass of TiO₂?over 50 cycles?@ 0.1 A/g?,which is almostly three times compared with raw TiO₂?a commercial TiO₂ nanoparticles powder?.In addition,coupled with commercial activated carbon?AC?cathode,the fully assembled HTPC//AC LICs delivers a maximum energy and power densities of 31.3 Wh/kg and 4 kW/kg,a reasonably good cycling stability? 77.8 % retention after 3000 cycles?within the voltage range of 1.0-3.0 V.?2?Design and synthesis of MnO_x/rGO//AC LICs: Herein,we rational designed and fabricated a three-dimensional?3D?hierarchical mixed-valent manganese oxide nanoparticles/graphene hybrid anode material for LICs through a conventional and green approach.Such unique networks can provide high surface area and porosity to enhance the electrolyte/electrode interaction,reduce the diffusion length of ions.A greatly improved specific capacity is achieved with reversible discharge capacity 750 mAh/g over 50 cycles at the current rate of 0.1 A/g,which is more than two times compared with graphene?theoretically capacity of 372 mAh/g?.In addition,coupled with commercial activated carbon?AC?cathode,the fully assembled MnO_x/rGO//AC LICs delivers a maximum energy density of 45.7 Wh/kg and a maximum power density of 5 kW/kg,a reasonably good cycling stability? 93.8 % retention after 3000 cycles?within the voltage range of 1.0-4.0 V.