| Lithium ion battery has been widely used because of its advantages such as high working voltage,high energy density,long cycle life and no memory effect.However,the lithium resources in the earth’s crust are limited,and the cost of lithium ion batteries is increasing as the scale of lithium ion batteries expands.Sodium,at the same element family with lithium,is abundant,distributed and cheap,while sodium and lithium have similar physical and chemical properties.Therefore,sodium ion battery is expected to replace lithium ion battery in large-scale energy storage area and has a promising application prospect.Our research work mainly incudes three aspects on the topic of phosphorus based materials.Firstly,we take commercial red phosphorus(P),carbon black(C)and grapheme(G)as raw materials,use ball milling method to prepare P/C and P/G composite material respectively,and explore the influence of milling parameter to improve the electrochemical property of electrode materials.Secondly,we use a high energy milling method to synthesis pure GeP5.Then we combine GeP5 with carbon through the same method and the composite anode material show better electrochemical performance.In the end,we prepare Ni-P nanoparticles by solvothermal method and high temperature thermal reduction method,then load them upon reduced grapheme oxide to prepare Ni-P@RGO composite material,and the composite own better cyclic performance and rate performance。(1)We obtain P/C and P/G composite through a simple milling method,and then explore the influence of milling parameter to improve the electrochemical property of electrode materials.The electrochemical test results show when the P/G composite material prepared by 16 h ball milling at speed of 400 rpm own best electrochemical performance:Its first discharge capacity is 857.9 mAh g-1 and the first charge capacity is 503.5 mAh g-1 at a current density of 1 A g-1,after 50 cycles the reversible capacity of P/G composite material still maintain 385.2 mAh g-1 the capacity retention is 76.5%.The improved electrochemical performance of P/G composite material can be explained in the following two aspects:(ⅰ)the size of red P particles have been reduced to nanoscale after long-time and high speed ball milling,which is benefited to the extraction and insertion of Na+;(ⅱ)good conductivity of graphene could improve the conductivity of P/G composite materials.(2)We synthesize GeP5 nanoparticles through a high energy ball milling method and obtain 50～200 nm pure-phased GeP5 nanoparticles after a 4 h of high energy milling,and then combine GeP5 nanoparticles with carbon black by a same milling method to prepare the GeP5/C composite material.The results reflect the GeP5/C composite material possesses better capacity,cyclic performance:The discharge capacity is 408.7 mAh g-1 after 30 cycles at an ultrahigh current density of 5 Ag-1.The improved electrochemical performance of Ge composite material can be ascribed to better conductivity of GeP5/C composite material,relatively smaller volume change between cycling and the more stable surface of working electrode.(3)We synthesize a new type of Ni-P nanoparticle through solvothermal method and high temperature thermal reduction method,and then using solvothermal method to load it upon on reduced grapheme oxide to prepare Ni-P@RGO composite material.The results show the addition of RGO could improve the electrochemical performance of Ni-P nanoparticle:the capacity of Ni-P@RGO composite material is 200.1 mAh g-1 after 50 cycles at a current density of 100 mA g-1 and even under a high current density of 2 A g-1 the reversible capacity of Ni-P@RGO composite material could reach 105 mAh g-1.The improved electrochemical performance of Ni-P@RGO composite material can be mainly attributed to the graphene have big specific surface area and could upload the Ni-P nanoparticles,which can improve both the electronic conductivity of Ni-P nanoparticles and the transport and diffusion of Na+. |
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