Density Functional Theory Study Of 2D PC₂ Ion Electrode Material

With the gradual depletion of fossil fuels and the aggravation of environmental pollution,the electric vehicle market has developed explosively.In addition,people’s life today has been inseparable from portable electronic products.All these have brought new challenges to the current battery technology.Batteries of electric vehicles and portable electronic products mainly are Li-ion batteries（LIBs）.At the same time,Na-ion batteries（NIBs）have also attracted extensive attention as a substitute.At present,the main problems of LIBs/NIBs used commercially are low energy density,low power density,low cycle capacity and low safety.The main reason for these problems is the insufficient performance of battery electrode materials.Current researches generally believe that two-dimensional（2D）materials have great potential in the application of electrode materials,because 2D materials have great specific surface area.Therefore,we mainly study the 2D electrode materials in this work.The main research contents of this paper are as follows:In recent years,2D pentagonal（penta）structures have attracted more and more attention in the application of ion battery electrode materials.In this work,we established the models of 60 kinds of 2D penta materials,calculated their electronic characteristics and stability based on density functional theory,and finally selected penta-PC₂as the research object.The results show that penta-PC₂is a potential LIBs/NIBs electrode material.The reasons are as follows:1.Different from most semiconductor penta electrode materials,penta-PC₂shows metallicity.The metal state charge density from C-2pz orbit is evenly and uniformly distributed in the whole penta-PC₂,resulting in excellent conductivity of penta-PC₂.2.In addition to the dynamic stability,we found that 2D penta-PC₂also has thermal and mechanical stability.In particular,it can withstand temperatures up to 1500K.3.Penta-PC₂has ultra-high theoretical storage capacity.The theoretical storage capacity of Li/Na are 1462/1949mahg^-1,which is about 3 and 4 times of graphite.4.For Li/Na adsorption,penta-PC₂shows quite negative adsorption energy（<-0.8ev）and small change of lattice constant（<2%）at both high and low concentrations.5.Li/Na have low and isotropic migration potential barriers（0.21e V/0.28e V）on penta-PC₂.6.For Li/Na adsorption,penta-PC₂shows an appropriate average open circuit voltage（0.75/0.63V）.Based on the above factors,the electrode made of penta-PC₂will show excellent conductivity,outstanding circulation ability,ultra-high ion capacity,fast charge/discharge rate and good safety performance,indicating its potential as LIBs/NIBs electrode material.