Design And Preparation Of Novel Carbon-based Electrode Nanomaterials And Energy Storage Applications

With the rapid development of electric vehicles and portable electronic devices,the demand for energy devices with large capacity and fast charging characteristics has become urgent.Therefore,it is important to design high-performance electrode materials for energy storage devices,such as supercapacitors and secondary batteries.This dissertation focuses on the design,preparation and energy storage properties of novel carbon-based nanomaterials based on a thorough understanding of the mechanisms and existing problems for the electrode materials of the supercapacitors,Li-ion batteries and Li-ion capacitors.The main research contents are summarized as follows:1.Recycling PM2.5 carbon nanoparticles generated by diesel vehicle engine for supercapacitors and oxygen reduction reaction.Particulate matter(PM)pollution has become a serious environmental problem,particularly,PM2.5(aerodynamic diameter ? 2.5 ?m)particles are extremely harmful,because they can enter the human respiratory system and even penetrate into circulatory system.Herein,we demonstrate an effective strategy to recycle PM2.5 carbon nanoparticles generated by diesel vehicle engine for the applications of clean energy.After thermal treatment and purification,the PM2.5 derived carbon nanoparticles show a of 25-40 nm,a mesoporous structure with an average pore size of?3.3 nm,and nitrogen content of?1.1 at.%.The PM2.5 derived N-doped mesoporous carbon nanoparticles were used as an advanced electrode material in supercapacitors,exhibiting high specific capacity(134.4 F g-1 at 0.1 A g-1)in 6 M L-1 KOH electrolyte and superb stability over 5,000 cycles.Moreover,the recycled PM2.5 carbon nanoparticles show outstanding electrocatalytic properties for oxygen reduction reaction.2.Pine needle-derived microporous carbon frameworks for supercapacitors.In this work,we successfully prepared microporous heteroatom-doped carbon frameworks from pine needles.The preparation procedure is based on the carbonization of pine needles and the following KOH activation at the temperature of 700-1000 ?.The resultant nitrogen-doped carbon materials possess abundant micropores and high specific surface area of 2433 m2 g-1.When served as electrode material for supercapacitors,the pine needles derived carbon shows high specific capacitance of 236 F g-1 at 0.1 A g-1,remarkable rate capability of 183 F g-1 at 20 A g-1 and good long-term stability.The specific capacitance at 2.0 A g-1 increased from 205 to 227 F g-1 after 5,000 cycles,owing to the further activation and wetting of the electrodes.3.Walnut-like multi-core-shell MnO@NC nanocapsules as anode electodes for Li-ion batteries.Metal oxides-based nanomaterials have shown promise as high-energy-density anode materials for lithium-ion batteries.However,the fast capacity degradation due to the large volume expansion upon lithiation hinders their practical application.In this work,we report the preparation of walnut-like multicore-shell MnO encapsulated nitrogen-doped carbon(MnO@NC)nanocapsules via a facile and environmentally friendly process for long-cycling Li-ion batteries.In this hybrid structure,MnO nanoparticles are uniformly dispersed inside carbon nanoshells,which can simultaneously act as a conductive framework and also a protective buffer layer to restrain the volume expansion.The MnO@NC nanocapsules show remarkable electrochemical performances for lithium-ion batteries,exhibiting high reversible capability as high as 762 mAh g-1 at 100 mA g-1 and stable cycling life(624 mAh g-1 after 1000 cycles at 1000 mA g-1).Moreover,the soft-packed full batteries based on MnO@NC nanocapsules anodes and commercial LiFePO4 cathodes present good flexibility and cycling stability.4.Metal carbides and micropores carbon as electrode mateials for hybrid lithium-ion capacitors(HLICs).Hybrid lithium-ion capacitors are promising energy devices,because they can integrate the high energy density of lithium ion batteries and the high power density of supercapacitors,with their low cost and long cycling-life.However,the development of HLICs is usually limited by the kinetics mismatch between the battery-type anode and capacitor-type cathode.Herein,we synthesized hierarchical Co3ZnC nanoparticle encapsulated mesoporous nitrogen-doped carbon nanopolyhedra(Co3ZnC@NC)by a one-step pyrolysis of bimetallic-organic-frameworks.The obtained material was used as anode material for HLICs,showing high lithium storage capacity and excellent rate performance.Moreover,heteroatom-doped microporous.carbon(MPC)derived from nature-abundant biomass(pine needles)are employed as cathode material,demonstrating good rate capability and long cycle stability.As a result,the as-prepared Co3ZnC@NC?MPC HLICs deliver high energy densities of 141.4 Wh kg-1,high power densities of 10.3 kW kg-1 and long cycle life within the wide operating voltage range(1.0-4.5 V).