Preparation Of Porous Carbon And Carbon Based Nanodots Composites And Study On The Properties Of Ion Battery Anode

Lithium-ion batteries(LIBs)have been widely used because of their high energy density,excellent stability and no memory effect.However,the development and application of lithium-ion batteries are severely restricted by the limited and uneven distribution of lithium resources and the complicated and highly polluted lithium recovery process.Sodium-ion batteries(SIBs)and potassium ion batteries(PIBs)have broad application prospects in the field of large-scale energy storage due to the abundant Na/K resources.As the most commonly used anode material of lithium-ion,graphite has the advantages of low cost and good stability.However,its low capacity and poor rate performance cannot meet the needs of electric vehicles and other products with long endurance and high power.In addition,incompatibilities often arise when graphite is used for SIBs and PIBs.In this paper,we used several methods to synthesize the anode material of lithium-ion,sodium ion and potassium ion batteries with high capacity and good rate performance,such as morphology and structure control,element doping and transition metal compound embedding.The main research contents of this paper are as follows:(1)N-doped porous carbon materials were synthesized though high-temperature pyrolysis and template removal process by using waste bamboo leaves rich in silicon compounds as carbon source.The as-prepared N-doped porous carbon materials show excellent performance as the anode of LIBs and SIBs.For LIBs,the sample has a capacity of 450 m Ah g^-1after 500 cycles at 0.2 A g^-1.As the anode of SIBs,the capacity is 180 m Ah g^-1 after 300 cycles at 0.1 A g^-1.The performance is far superior to that of commercial graphite anode.(2)The composites composed of FeP nanodots and N,P co-doped graphene was synthesized by high-temperature heat treatment of graphene oxide,Fe salt,melamine and phytic acid.Graphene oxide has strong electrostatic interaction with Fe³⁺,which could make sure the uniform distribution of FeP nanodots.When the composites was used as the anode of Li Bs,it shows high reversible capacity(up to 1000 m Ah g^-1 after100 cycles at 0.1 A g^-1),excellent cycle stability(314 m Ah g^-1 after 2000 cycles at 5 A g^-1)and outstanding rate performance(439 m Ah g^-1 at 10 A g^-1).FeP@NPC has a broad application prospect in the field of rapid charge and discharge.(3)N-doped porous carbon(N-C)with large specific surface area and abundant pore and defect structure was synthesized by a two-activator strategy using chitosan as raw material,iron nitrate and sodium nitrate as activators.This carbon material shows excellent electrochemical performance in both PIBs and potassium ion capacitors.When applied to the anode of potassium ion battery,the reversible capacity i s 325 m Ah g^-1 at the current density of 0.1 A g^-1,and 148 m Ah g^-1 after 1000 cycles at 1.0 A g^-1.(4)MoP nanodots-porous carbon composites were synthesized by high temperature carbothermal reduction using ammonium phosphomolybdate as the precursor.when it was used as the anode of PIBs,the reversible capacities could reach up to 240 m Ah g^-1and 161 m Ah g^-1 after 1000 cycles at 1 A g^-1and 5 A g^-1,respectively.Besides,the results also show that the K⁺storage process of the material meets the transformation reaction mechanism,and the MoP nanodots have excellent structural stability during the long-term cycling process.(5)Monodispersed Ni₂P nanodots embedded N,P co-doped porous carbon composites were synthesized by high temperature carbonization process using biomass gelatin as carbon/nitrogen source and strong chelation of Ni²⁺,phytic acid as phosphorus source.When it was used as the anode of PIBs,it could keep a capacity of 212 m Ah g^-1 after 5000 cycles at 1 A g^-1.The structure changes of Ni₂P nanodots after cycling and the storage mechanism of K⁺were studied by TEM technology,the results show that the reaction of Ni₂P with K⁺meets the transformation reaction mechanism.(6)FeS nanodots embedded S doped porous carbon(FeS@SPC)composites were synthesized through high temperature carbonization and secondary vulcanization,using sodium citrate as carbon source,pore-forming agent and complexing agent,S powder as sulfur source.As the anode of PIBs,the sample keeps the capacity of 309 m Ah g^-1after 100 cycles at 0.1 A g^-1.Even after 3000 cycles at 1 A g^-1,the specific capacity still remained 232 m Ah g^-1.Besides,the theoretical calculation results reveal that FeS@SPC has higher adsorption energy for K⁺compared with SPC,suggesting FeS@SPC has better K⁺storage capacity.