چكيده به لاتين
Graphite is the most common material used in the anode of lithium-ion batteries (LIBs). In spite of its advantages, graphite low specific capacity hinder its application in future technologies such as electric vehicles and off-peak energy storage .The most promising candidates for graphite replacement are Si, Sn, and Ge elements.
In this research, new graphene and silicon-based nanostructures have been explored computationally as the anode of LIBs. Firstly, Structural and electronic properties of phosphrus and nitrogen codoped graphenes (PN-graphenes) have been calculated. Lithium adsorption energy and diffusion barrier on pyridinic PN-graphene obtained to be 2.189 and 2.466 eV, respectively. These values show the advantages of pyridinic PN-graphene as LIBs anode over pristine and other PN-graphenes. Then, the adsorption of maleic anhydride (MA) on Al-doped graphene was calculated. The calculated adsoprtion energy (-1.95 eV) suggests that Al-doped graphene could be a suitable substrate for MA and preventing MA dissolution in electrolyte. Our results indicated that Li sotrage capability of MA/Al-graphene complex is twice of bare Al-graphene or MA. Diffusion barrier of Li across MA/Al-graphene complex calculated to be 1.99 eV which make Li motion not to be so easy on this complex.
Also, the adsorption and diffusion of lithium on pristine and boron, nitrogen, aluminium and phosphorus-doped silicenes were studied. Li storage in all doped silicene systems is more than pristine silicene. Diffusion barrier of Li across of N-doped silicene obtained to be 0.05 eV (0.32 eV for pristine silicene) and perpendicular diffusion of Li on Al-doped silicene calculated to be 1.47 eV (1.67 for pristine silicene). These results show the potential of doped silicenes for LIBs anode. Calculations showed that formation of 5559 and 5105 defects on silicene is more easier in comparison with graphene. These defective silicenes could adsorb Li up to 50% concentration without the formation of Li clusters. Diffusion barrier of Li on 5559 and 5105 silicenes obtained to be 0.252 and 0.069 eV. Based on these data, it can be concluded that creation of defects is a good strategy to enhance performance of silicene as LIBs anode.
