Study On Synthesis Of Heteroatom Doping Porous Carbon And Electrochemistry Of Potassium Storage

Carbonaceous materials are one of the most promising anode materials for Potassium-ion batteries?PIBs?,because of their abundance,stability,and safe usage.However,the practical application of carbon materials is hindered by poor specific capacity and insuffcient cycling life.The design of porous structure and doping with heteroatoms are two simple and effective methods to promote the potassium storage performance.Nitrogen,being able to generate defect sites and enhance the electronic conductivity,is considered as one of the most promising dopants for carbonaceous anode materials.Besides,compared with undoped carbon,N-doped carbonaceous material features expanded interlayer space,thus facilitating the ion insertion and extraction,improving the electrochemical performances.Phosphorus doping is another significant modified approach,which is beneficial to modifying the electronic properties,accelerating electron transfer,and increasing partial reactivity,due to its electron-donating ability and strong n-type behavior.Herein we demonstrate a facile and scalabl carbonization strategy to prepare heteroatom doped,porous carbon as an anode material for high-performance PIBs.?1?A simple and green carbonization process in molten salt is used to synthesize nitrogen/oxygen co-doped hierarchically porous carbon?NOPC?for PIBs by using cyanobacteria as the carbon source.It exhibits highly reversible capacities and ultra-long cycling stability,retaining a capacity of 266 mAh g^-1 at 50 mA g^-1?100 cycles?and presenting a capacity of 104 mAh g^-1 at 1000 mA g^-1?1000 cycles?.Besides,kinetics analysis reveals that the potassium ion storage of NOPC is dominated controlled by a capacitive process,which plays a crucial role in the excellent rate performance and superior reversible ability.The high proportion of capacitive behavior can be ascribed to the hierarchically porous structure and enhanced conductivity resulting from nitrogen and oxygen doping.?2?The high N-doped hollow carbon materials are synthesized via carbonizing polyurethane which exhibits hollow interconnected architecture,a shape similar to the neuroncell network.An ultrahigh pyridinic N-content-doped porous carbon monolith is reported,and the content of pyridinic N reaches up to 16%in overall material?51.4%out of 31%N content?,being higher than most of previously reported N-doping carbonaceous materials,which exhibit greatly improved electrochemical performance for potassium storage,especially in term of superior cycling stability(no obvious fadingover 200 cycles at 100 mA g^-1).Pyridinic N is highly effective in creating active ion storage sites and can enhance the electron transportation,thus being mainly responsible for thus high capacity.?3?N/P Dual-Doped porous carbon?NPDPC?was successfully synthesized via a facile self-template method,which is easy and effcient methods.Combination of open porous structures of NPDPC,the large interlayer spacing can not only facilitate the diffusion of K⁺,but also enhance the reversible capacity of K⁺storage.When applied as anode materials for PIBs,NPDPC exhibits excellent rate capability(120 mAh g^-1 at2000 mA g^-1)and high reversible capacity(301 mAh g^-1 at a low current density of 50mA g^-1).The enhanced potassium ion storage performance is attributed to the synergistic effect of the porosity and the dual-doping of nitrogen and phosphorus.