Preparation And Electrochemical Performance Of Carbon Anode Materials For Potassium Ion Batteries

Benefiting from the a wide range of sources,low cost,environmental friendliness and high stability,carbon materials have been widely used as one of the most promising anode materials for potassium ion batteries(PIBs).However,the structure of carbon materials will swell and collapse during K⁺insertion and extraction process,resulting in a short cycling life,making it difficult for carbon-based materials to be applied in potassium ion batteries.In this thesis,the structure design of carbon material through different preparation methods have been reported,where three carbon-based materials with different structure have been obtained,achieving long cycling stability and high specific capacity.The main research contents of the thesis are as follows:(1)Mesoporous carbon spheres(MCS)with rich porous structure have been prepared with the assistance of an Aerosol-spray Pyrolysis Technology using silica colloids as a template.When used as the negative electrode for potassium ion battery,MCS exhibits good rate capability and excellent cycling stability.Different electrolytes including KP-001,KP-044,and KP-056 are used to explore its electrochemical performance.The results indicate that MCS show excellent electrochemical cycling ability when using KP-044 electrolyte.A high specific capacity of 154.5 mAh g^-1 can be achieved after being cycled for 200 times at a current density of 50 mAg^-1.Furthermore,the specific capacity can reach 105.3 mAh g^-1 after 500 cycles at a current density of 100 mAg^-1.(2)A porous carbon material(NC)with nitrogen atoms doping has been obtained through Polymer Carbonization,where the o-phenylenediamine and silica colloids are mixed under ice bath for polymerization,and then freeze-dried and carbonization.O-phenylenediamine is used as a source of carbon and nitrogen.The nitrogen doping of carbon increases the active sites,and the porous structure produced after etching silica templates enhances the specific surface area.In this thesis,two silica colloid templates with a particle size of 15,30 nm are used,and the NC samples calcined at the temperature of 750?,900?,and 1050?are obtained to explore the effect on electrochemical performance.Meanwhile,two electrolytes of KP-001,KP-044 have been used.The results show that the 30-750-NC sample,which is calcined at 750?with 30 nm Si O₂ colloid as a template,has a higher specific capacity.In KP-044 electrolyte,the charge and discharge specific capacity is 143.1 and 147.6 mAh g^-1 at the current density of 50 mAg^-1 for 200 cycles,when continued to 800 cycles at 100 mAg^-1,and the charge-discharge specific capacity value is 164.5 and 173.2 mAh g^-1,respectively.(3)NiS/C composite material is obtained by the reaction of nickel citrate precursor with carbon disulfide using Vapor deposition.NiS delivers a high theoretical capacity of 590 mAh g^-1 but suffers from a short cycling life.The capacity can be improved effectively by combining with carbon-based materials.The electrochemical performance of NiS/C composite material has been explored to investigate its specific capacity and cycling stability as the negative electrode in potassium ion battery and lithium ion battery.LX-146,KP-068,KP-044electrolytes are used for test in PIBs.The results show that the discharge specific capacity is767.4 mAh g^-1 after 99 cycles at a current density of 50 mAg^-1in lithium-ion battery,and the discharge capacity can reach 737.5 mAh g^-1 with a Coulombic efficiency of 98.67%after 150cycles at a current rate of 100 mAg^-1.In potassium ion batteries,the composites show better cycling stability and higher specific capacity in KP-044.When the current density is 50 mAh g^-1,the specific discharge capacity of is 652.4 mAh g^-1 after 100 cycles,where the capacity retention can maintain 94.99%when compared to the values at the second cycle.Increasing the rate to 100 mAh g^-1,and the specific discharge capacity is still up to 547.6 mAh g^-1.