Research On The Preparation,Modification And Application Of Hard Carbon Materials

Among electrochemical energy storage devices,Lithium-ion capacitors（LICs）are a"double-high"device with both power and energy density.However,the difference of positive and negative storage mechanisms causes difficulties in its capacity and kinetic balance.The positive electrode undergoes a typical non-Faraday bilayer effect with quick kinetic response but low capacity,whereas the negative electrode has a greater capacity but its kinetic rate is limited by ion embedding.Hard carbon has only short-range graphite domains,and the ion embedding depth is shallow,so the reaction rate is faster.The porous hard carbon can offer a sizable active surface for adsorption,resulting in a high energy density.In order to create positive and negative electrode materials that were well matched,fiber hard carbon and porous carbon were modified in this study.（1）In the Na Cl-KCl,porous carbon was prepared by introducing trithiocyanic acid（TA）with petroleum pitch.Besides the doping effect,TA is more important in regulating the pore distribution of porous carbon and is amplified in the molten salt,finally leaving nanosheets of porous carbon.The porous carbon exhibits the best pore distribution and morphology,and shows a large specific capacity of 65 m Ah g^-1 at 10 A g^-1.（2）Applying electrostatic spinning,highly conductive polyacrylonitrile（PAN）nanofibers are produced.Glycerol acts as a"bridge"between PAN fibers,reducing the resistance while reducing the exposure area of the fibers in the electrolyte,which is beneficial for reducing the resistance of the solid electrolyte layer.Meanwhile,PAN acquires hydrophilicity and links with carbon nanotubes,constructing a fast conducting network and exhibit a 300%higher capacity compared to pure PAN fibers at 5 A g^-1.（3）The constructed highly stable LIC can achieve an energy density of 131.48 Wh kg^-1 and have an excellent capacity retention rate（93.5%）over 10,000 cycles at a high power density(6104.6 W kg^-1).Futhermore,prelithiumed anode with ultrathin deposited lithium layers were further explored.The ultrathin lithium layer has a good pre-lithiation effect on hard carbon anode,and the equivalence between the deposited and the supplemented indicates the potential of this method for controlled pre-lithiation.