Study Of NbN/C Composites For Electrochemical Energy Storage

Lithium-ion hybrid supercapacitors（LIHCs）is a new type of energy storage equipment which combine the advantages of supercapacitor and Li-ion baterry,it is regarded as a device with large potential applications and has been widely disscuss.However,due to the diffifrent storage mechanism,the matching of positive and negative electrodes is the key limitation of the improvement.As an excellent electric double layer material,carbon based materials has been approved for using as a mixed capacitor cathode.Therefore the research focuses on the anode materials of lithium ion hybrid capacitor（LIHC）.Based on this,this thesis mainly foused on the niobium nitride with pseudocapacitive properties,through the impregnation method and stratified filtration method,has prepared Nb N/graphene and Nb N/MWCNTS two composites.Subsequently tested their performance of lithium-ion battery.When applied the Nb N/graphene in the LIHC,the LIHC exhibited excellent rate performance and cycle stability.The main work is divided into the following aspects:1.Graphene oxide paper as the template,by using solution impregnation method,we have obtained Nb N/graphene composite papers.The composite paper was directly cut as the anode of the lithium ion battery.As a freestanding anode for Li-ion batteries,the nanocomposite shows excellent electrochemical properties including a high specific capacity of 450 m Ah g^-1 at 0.1 A g^-1,a high-rate capacity of 100 m Ah g^-1 at a current density of 10 A g^-1,and good cycling stability（10% decay in capacity after 10000 cycles）.The composite papers with excellent performance is suitable for anode material of LIHC.therefore,we use the Nb N/graphene composite as anode and polyaniline based activated carbon（APDC）as cathode to assemble LIHC.Under the voltage window of 1-4V,the Nb N/graphene ∥ APDC LIHC shows an maximum energy density of 136 Wh kg-1,and a power density of 25 k W kg-1.The LIHC also exhibits the favorable cyclic stability with the capacity retention of ⁸4% after 2000 cycles at a high current density of 1 A g^-12.By using one-step ammoniating,we prepared Nb N nanoparticles,then the Nb N and MWCNTS were modified and alternate vacuum filtration,the Nb N/MWCNTS were prepared.When it is applied to a lithium ion battery,the specific capacity can reached 280 m Ah g^-1 at the current density of 0.1A g^-1,and the capacity can still be kept about 80% when it is recycled 5000 times at the current density of 1A g^-1.