The Design, Preparation Of Nano-materials And Its Research On Energy Storage Application

The ever-growing demand for large-scale energy storage applications in electricvehicles has triggered significant research efforts on long cycle life, high-capacity, and highpower lithium-ion batteries (LIBs). The commercial LIBs cannot meet these challenges dueto their low energy density. There is a consensus that the breakthrough could be achieved bymoving from classical intercalation reaction to conversion reaction. However, theformidable capacity degradation and poor rate performance still seriously hamper thepractical application of conversion-based materials in LIBs.To meet these challenges, downsizing the electrode materials to nanoscale andconstructing hybrid materials with highly electrical conductive materials have beenproposed to be one of the most promising strategies. Based on the above ideas, we prepareelectrode materials with different nano-structure and study their lithium storage mechanism.Firstly, we report the fabrication of a new hybrid nanostructure composed ofthree-dimensionally ordered macroporous (3DOM) FeF3and homogenous coating ofPEDOT, and its superior electrochemical lithium storage performance. Surprisingly, theadvantageous combination of3DOM structure and homogenous coating of PEDOT endowsthe as-prepared hybrid nanostructures a stable and high reversible discharge capacity up to210mAh g-1above2.0V at room temperature, and good rate capability of120mAh g-1at ahigh current density of1A g-1, which indicate that the special nanostructure couldeffectively buffer the volume change during charge-discharge.Based on the above result, we report a effective strategy to synthesizethree-dimensionally macroporous (3DM) graphene@Fe3O4(3GF) hybrid composite.Benefiting from this advantageous of the3DM structure, the hybrid composite exhibitsexcellent Li+storage performance, delivering a high reversible capacity of980mA h g-1atthe current density of4A g-1even after470cycles, and a good rate capability of293mA hg-1even at20A g-1. Secondly, we present a simple, cheap, and easily scaled-up synthetic procedure for thepreparation of ultrathin GeO2-RGO sheets (GeO2-RGO) through a freeze drying methodThe as-prepared GeO2-RGO show non-aggregated graphene sheets and homogeneouslydispersed GeO2NPs. Such a hybrid structure is an ideal electrode material for LIBs. TheGeO2-RGO show much improved specific capacity (1200mA h g-1at current density of100mA g-1), cycling performance, and rate capability, used as an anode material for LIBs.The past two decades have witnessed LIBs capture the portable electronic markets.However, we shall always be prepared for the exhaustion of limited and unevenlydistributed lithium resources. In response, room-temperature sodium-ion batteries (NIBs)have aroused interest recently as an attractive alternative technology because sodiumresources are practically inexhaustible and ubiquitous. However, due to the intrinsicallymuch larger ionic radius of sodium ion than that of lithium ion, there is still only limitednumber of potential cathode materials for NIBs. The development of suitable cathodematerials is urgently desirable but remains a challenging issue.FeF3is potential cathode materials for NIBs, due to their high theoretical capacity, lowcost, abundant sources, low toxicity, and high safety, which are crucial for large-scaleelectrochemical energy storage. Unfortunately, it is notorious for intrinsically poorelectronic conductivity due to the large band gap induced by the highly ionic character ofthe metal-halogen bond, resulting in a very low actual capacity and fast capacity fading,which had almost kept them away from the radar screen in the search for improvedelectrodes materials for NIBs.A strategy for enabling highly insulated FeF3as high performance cathode materialsfor NIBs is proposed and realized, through constructing metallic Fe and reduced grapheneoxide (RGO) double enhancement conducting matrix, wherein both the metallic Fe andactive FeF3are in situ electrochemically generated from one FeF2grain (as precursor ofFeF3) to ensure their desired homogenous and intimate contact. The efficacy of this conceptis demonstrated by the superior electrochemical performance of the generatedFeF3-Fe-RGO composite including high capacity of150mA h g-1at a current density of50 mA g-1, good cycle stability, and high power capability at room temperature. The strategy issimple yet very effective and also because of its versatility, it may be easily extended toother next generation high-capacity electrode materials while with low electricalconductivity.