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Electrochemical energy storage devices storage energy by reversibly convert electric energy to chemical energy either by faradic reaction or electric double-layer.The energy density,powder density,reversibility and cycling life are key parameters,which depend primarily on the electrode.Electrochemically active materials whichparticipate faradic reactions in electrode usually suffer from low electron conductivity,especially for the cathode materials for lithium ion batteries and the oxides for supercapacitors,thereby delivering a limited power density.Three-dimensional(3D)network embedded in electrode with electrochemically active materials providesinterconnected paths for efficient charge and ion exchange,which accelerates electrochemical reactions thus the power density.However it is electrochemically inactive,and sacrifices energy density of the electrode.An ideal electrode may consist of electrochemically active materials distributed in a 3D network with high electro conductivity and electrochemical stability,low density and good compatibility with various electrochemical systems.Materials made of sp2-hybridized carbon,for example carbon nanotubes and graphene,are conductive and stable in a variety of electrochemical systems,and has a nominal density of 2.2 g/cm3(graphite),lower than many other conductive materials,therefore has been widely used as conductive fillers in electrode.However the carbon units in electrode form a conduction network by touch each other with van der waals force,thus leave a large barrier for charge transfer.We propose an interconnected freestanding three-dimensional network made by covalently bonded sp2 carbon,and successfully fabricated three types of structures experimentally[1,2,3].All the nano-structure units made of sp2 hybridized carbon are covalently connected thus avoids the ohmicresistivity occurin discrete carbon fillers.The networksare freestanding and light in weight,thus allow for combining with a variety of electrochemically active material for both battery and/or supercapacitor applications with enhanced power density and energy density simultaneously.