Fabrication And Electrochemical Properties Of Natural Cellulose Derived Vanadium-based Composite Materials

As a novel sustainable energy storage system,lithium ion battery has been widely studied.However,there still are many bottlenecks remaining to be solved for the development of lithium ion battery,especially the design and research of high-performance electrode materials.Vanadium oxide-based materials are regarded as prospective electrode materials for lithium ion battery because of their natural abundance,low cost and high theoretical capacity.Whereas the intrinsic poor electric conductivity,low lithium ion diffusion efficiency and poor structural stability of them must be overcome in order to extend their application in the lithium ion battery area.Natural cellulose has a unique hierarchical porous network and can be used as the template or scaffold for the fabrication of electrode material with specific structure.The preparation of the three-dimensional fibrous network utilizing natural cellulose as template and the hybrid of vanadium with other more conductive phases are the two approaches adopted here to improve the electrochemical performance of vanadium oxide.When employed as electrode materials,the obtained samples manifest improved capacities,cycling stability and rate capability.The followings are the main contents:1.A series of SnO2/V2O5 composites with various SnO2 contents are fabricated by facile dipping and calcination process employing natural cellulose substance(e.g.,filter paper)as template.The obtained composites inherit the morphology of the initial cellulose substance on the micrometer scale and consist of intricate microtubes composed of V2O5 nanorods with SnO2 nanoparticles anchored on the surfaces.When employed as cathode material for lithium-ion batteries,the composite with a SnO2 loading content of 12.1 wt%exhibits excellent electrochemical performance and retains a stable discharge capacity of 126 mAh g-1 after 150 discharge/charge cycles at a current density of 0.1 A g-1 due to its three-dimensional network structure and the enhanced conductivity.2.The pure V2O5 microtubes are prepared by the similar dipping method mentioned above.The obtained V2O5 microtubes replicate the three-dimensional network of the initial cellulose substance and are composed of cross-linked V2O5 nanoparticles with lengths of 200-400 nm.When used as anode material for lithium-ion batteries,the V2O5 microtubes displayed superior cycling stability to the commercial V2O5 powder and V2O5 nanorods and retained a discharge capacity of 676.4 mAh g-1 after 150 discharge/charge cycles at a current density of 0.1 A g-1.The enhanced cycling stability of the V2O5 microtubes benefits from the three-dimensional microtubular structure as it can maintain the structural stability of the active material and facilitate the lithium ion diffusion.3.A V2O5/V3O7/C composite is obtained through a two-step heat treatment of the VxOy/cellulose precursor acquired from the above dipping method using filter paper as template.The composite inherits the three-dimensional network structure,in which the V2O5 and V3O7 nanoparticles are wrapped in amorphous carbon matrix and a continuous fibrous structure is formed.When employed as the anode material for lithium-ion batteries,the obtained V2O5/V3O7/C composite shows high capacities,superior cycling stability and rate properties,which is benefited from the high structural stability and good electric conductivity of the continuous structure.A series of vanadium oxide-based composites with unique three-dimensional network structure derived from natural cellulose substance has been prepared,whose electrochemical properties have been improved along with structural stability and electric conductivity.The template synthesis derived from natural substance is helpful for the fabrication of vanadium oxides and vanadium oxide-based composites with specific framework and provide guidance on their applications in the energy-related area.