二维石墨氮化碳材料中锂和钠存储的第一性原理研究（英文）

A first-principles study of lithium and sodium storage in two-dimensional graphitic carbon nitride

由于氮原子和均匀孔隙的存在,二维石墨氮化碳被认为可用于电池电极材料。作为一种新型的多孔结构,g-C_2N材料在电池电极材料方面应用的研究甚少。本文通过第一性原理计算研究了单层g-C_2N上锂和钠的吸附和存储情况。基于单层g-C_2N的锂离子电池的容量可以达到596 mAh/g(LiC_2N),而相应的钠离子容量只能达到276 mAh/g (NaC_4N_2)。平均锂结合能相对于孤立的锂原子高达2. 39 e V,这表明g-C_2N上获得的锂电池容量在循环过程中可能不会持续。通过改变C和N原子之间的比例,在C∶N为5∶1的情况下,平均锂结合能可以降低到1. 69 e V,这说明在保持可逆电池容量的同时,循环性能显著改善。所有这些理论计算表明,具有均匀孔隙的石墨碳氮化物可能是一种具有高容量和锂迁移率的电极材料。

Two-dimensional carbon nitride is considered a very good battery electrode material owing to its uniform-size pores and the presence of nitrogen atoms.First-principles calculations were used to investigate the adsorption and storage of lithium and sodium on monolayer g-C 2N.The capacities of lithium and sodium ion batteries for monolayer g-C 2N are 596(LiC 2N)and 276(NaC 4N 2)mAh/g,respectively.The average Li binding energy reaches 2.39 eV relative to isolated Li atoms,which suggests that the lithium capacity achieved on g-C 2N might not be sustained during cycling.By varying the ratio of C to N atoms,it is found that the average Li binding energy is reduced to only 1.69 eV for C∶N^5∶1,indicating a significant improvement in cycling performance while maintaining the reversible capacity.The mobility barrier energies to Li ion diffusion between two layers in bulk structures with AA and AB stacking sequences are 0.25 and 1.23 eV,respectively,indicating that high Li ion conductivity could be achieved in bulk g-C 2N with AA stacking.These calculations demonstrate that graphitic carbon nitride with uniform-size pores can be used as an electrode material with high capacity and high lithium mobility.