In、Bi、Sb掺杂SnO2锂化的第一性原理研究

采用基于密度泛函理论（DFT）的第一性原理平面波赝势(USPP)法，以In、Bi、Sb掺杂SnO2为主要研究对象，构建了M1-XSnxO2二维片状材料模型并模拟其锂化过程，获得Li+饱和浓度曲线；构建M1-XSnxO2三维晶体结构并计算其能带结构、态密度，分子轨道和布居；使用过渡态搜索（TS search）方法评估了Li+扩散的能垒；结果表明，M1-XSnxO2锂化至饱和状态时锂浓度分别为Li0.47SnO2、Li0.47In0.3Sn0.7O2、Li0.47Bi0.3Sn0.7O2、Li0.59Sb0.3Sn0.7O2；SnO2、In-SnO2、Bi-SnO2、Sb-SnO2的带隙分别为1.23eV、1.72 eV、1.47 eV、0.23 eV，其中Sb-SnO2态密度在费米能级处脉冲峰的展宽范围扩大到-2 eV ~ 6 eV，这表明Sb原子的掺杂使得原子间的耦合作用增强，带隙减小，轨道范围变大，电子的非局域性变强；掺杂In、Bi、Sb原子后SnO2离子键的键级由0.33分别转变为0.22、0.03、0.02，离子性依次增强，其中Sb-SnO2的离子性最强，Sn-O键强度最低。同样的路径下Li+在SnO2、In-SnO2、Bi-SnO2、Sb-SnO2中扩散所需的最大能量分别为1.1eV 、0.75 eV、 1.03 eV、0.56 eV；金属元素Sb掺杂SnO2可有效增强其锂化能力。

First-principles study on the lithiation of In, Bi, and Sb-doped SnO2

Using the first-principles plane wave pseudopotential (USPP) method based on density functional theory (DFT) and taking In, Bi and Sb doped SnO2 as the main research object, a two-dimensional sheet model of M1-XSnxO2 was constructed in CASTEP and its lithiation process was simulated to obtain Li+ saturation concentration curve. The three-dimensional crystal structure of M1-XSnxO2 was constructed and its band structure, density of states, molecular orbital and population were calculated. The energy barrier of Li+ diffusion was evaluated using the transition state search (TS search) method. The results show that the lithium concentrations of M1-XSnxO2 are Li0.47SnO2, Li0.47In0.3Sn0.7O2, Li0.47Bi0.3Sn0.7O2 and Li0.59Sb0.3Sn0.7O2, respectively. The band gaps of SnO2, In-SnO2, Bi-SnO2 and Sb-SnO2 are 1.23 eV, 1.72 eV, 1.47 eV and 0.23 eV, respectively. The pulse peak of Sb-SnO2 state density at Fermi level is broadened to-2 eV ~ 6 eV. The results show that the doping of Sb atoms enhances the coupling between atoms, decreases the band gap, increases the orbital range, and enhances the nonlocality of electrons. After doping with In, Bi and Sb atoms, the bond order of SnO2 ionic bond changes from 0.33 to 0.22, 0.03 and 0.02, respectively, and the ionicity is enhanced in turn, among which Sb-SnO2 has the strongest ionicity and its Sn-O bond strength is the lowest. The maximum energy required for Li+ diffusion in SnO2, In-SnO2, Bi-SnO2 and Sb-SnO2 is 1.1 eV, 0.75 eV, 1.03 eV and 0.56 eV, respectively. The metal element Sb doped SnO2 can effectively enhance its lithiation ability.