Research On Preparation,Doping And Composite Of Porous Carbon Materials For Electrochemical Energy Storage

Porous carbon materials are widely used in energy storage due to their high specific surface area,high conductivity and low cost.But porous carbon used in supercapacitors,lithium-ion batteries,sodium ion batteries and other areas,the capacity is generally low.Therefore,this work optimizes porous carbon materials from the perspectives of porous carbon micropore structure,heteroatom doping,graphitization degree,etc.,and effectively improves the specific capacity,multiplier and cyclic stability of porous carbon materials.Firstly,an ultrathin porous carbon shell with a thickness of about 10 nm was prepared by using sodium citrate as carbon precursor.The conductivity of this material is up to 7.12s/cm,and it has good multiplier performance when used as the electrode material of supercapacitor without adding any conductive additives.This cross-linked ultra-thin carbon nanosheet structure can effectively shorten the ion transport path,obtain ultra-high multiplier performance,and effectively improve the capacity of porous carbon materials in large current.Secondly,3D graded porous carbon was prepared by direct carbonization with glucose and zinc nitrate as raw materials.The effect of carbonization temperature on the formation of microporous structures was studied.Three-dimensional hierarchical porous carbon structure advantage is very obvious,macroporous repository used as the electrolyte ions,specific surface area of the microporous provide enough to ion adsorption,mesoporous accelerated ion transport,and as a bridge that crosses from the external and internal microporous material,therefore when used for super capacitor,won the high capacity high ratio and good cycle stability.Then,from the perspective of atomic doping,three-dimensional graded porous carbon(P-3DHPCs)co-doped with phosphorus and oxygen was synthesized by direct pyrolysis using glucose,manganese nitrate and sodium hypophosphite as raw materials.Glucose and sodium hypophosphite were used as carbon sources and phosphorus sources respectively.The content of sodium hypophosphite has an important influence on the structural properties and phosphorus content of P-3DHPCs.When used as the electrode material of supercapacitor,the results show that P/O doping introduces pseudocapacitance on the basis of carbon adsorption mechanism,which effectively improves the specific capacity of porous carbon material.Based on the advantages of doping,we synthesized porous carbon materials with layered pore structure and homogeneous nitrogen and sulfur doping.Good pore structure(micropore,mesoporous and macroporous)is conducive to ion adsorption and transport,and doped atoms can introduce electrochemical active sites and increase pseudocapacitance.Therefore,carbon materials have good electrochemical properties as supercapacitor electrodes.The specific energy density of carbon-based supercapacitors is significantly increased.From the perspective of graphitization degree of porous carbon materials,an advanced carbon nanostructure was prepared.Using the catalytic effect of transition metal,part of sp~3 hybrid carbon atoms of porous carbon materials were converted to sp~2 carbon effectively,and at the same time,porous carbon materials with catalytic graphite structure were formed.Due to the low carbonization temperature,short carbonization time,and different catalytic degrees of different metals,a series of expanded graphite-like layer structures of 0.34~0.44 nm with both defect and amorphous and porous carbon structures were obtained.This advanced carbon material,as the anode material of lithium ion battery and sodium ion battery,has obtained excellent electrochemical lithium/sodium storage performance.Finally,carbon/potassium vanadate composite was prepared as the cathode material for aqueous zinc ion battery.Amorphous carbon not only improved the conductivity of the composite,but also provided active sites for the adsorption of zinc ions.The introduction of capacitive behavior greatly improved the rate performance of the composite.In addition,the oxygen defect structure in potassium vanadate also greatly improves the diffusion ability of zinc ions and the reversibility of electrochemical reactions.The synergistic effect of the two facts endows the composite with excellent electrochemical properties.