Synthesis Of Hollow Carbon Nanospheres To Confine Red Phosphorus For Sodium Ion Batteries

With the increasing demand for portable electronic devices and electric vehicles,the price of lithium-ion batteries has increased rapidly.Sodium ion batteries are expected to replace lithium ion batteries due to their low price,wide distribution and environmental friendliness.Although red phosphorus?RP?has a very high theoretical capacity,its low electrical conductivity and huge volume expansion during charge and discharge severely limit its application for sodium ion batteries.Therefore,in this thesis,mesoporous hollow carbon nanospheres?CS?prepared by sea-urchin-liked silica templates were used to confine red phosphorus for the anode of sodium ion batteries via gas processed encapsulation method and solution processed encapsulation method,respectively.The results of research are listed as follows:?1?The mesoporous hollow carbon nanospheres were prepared by sea-urchin-liked silica template.Based on the rate performance of hollow carbon nanospheres and activated carbon,only by combining the hollow carbon nanospheres with high capacity materials?red phosphorous,RP?can exert its structural advantages.The hollow carbon nanospheres were combined with red phosphorus by gas processed encapsulation method.During the vaporization-condensation process,the secondary annealing post-treatment can promote the removal of unnecessary RP on CS surface,decrease of RP size in conductive networks and efficient confinement of the amorphous RP in CS.The as-prepared RH-3-1-RP/CS composites exhibited much better rate performance and cycling stability than those of 3-1-RP/CS,with a super high capacity of 1027 m A h g^-1even after long-term cycling of 2000 cycles at 4 A g^-1and an excellent capacity retention of 97.5%.?2?Red phosphorus is converted into soluble polyphosphide anions in organic solvents by activating reactions with nucleophilic reagents via solution processed encapsulation method,followed by combination with CS to form PP@CS composites.The inner sea-urchin-liked structure of CS not only improved the electrical conductivity but also created enough interior surface for maximizing phosphorus utilization and shortening the ion's diffusion distance.In addition,the hollow structure also can compensate the volume expansion of polyphosphide.The PP@CS-0.30 electrode displayed a reversible capacity of 536 m Ah g^-1at 2 A g^-1after300 cycles.Its capacity retention rate is 50.7%,and the capacity loss rate per cycle is only 0.1%.