Pt掺杂材料Li2Pt0.125Co0.875SiO4在脱嵌锂离子过程中晶格和电子结构变化的研究

采用基于密度泛函理论的第一性原理计算方法,研究贵金属Pt掺杂的正极材料Li_2Pt_(0.125)Co_(0.875)SiO_4在锂离子脱嵌过程中晶格和电子结构的变化.计算结果表明,掺杂体系在脱嵌锂离子过程中,晶格参数和体积变化不大,充放电过程中循环稳定性保持较好,脱嵌电压也基本保持不变;Li-O键长增大,Li-O间相互作用减弱,锂离子迁移率增大.与纯相Li_2CoSiO_4相比,禁带中出现了掺杂原子Pt的d轨道电子,带隙变窄,从而提高了掺杂材料Li_2Pt_(0.125)Co_(0.875)SiO_4的电子导电性.

Insights into changes of lattice and electronic structure for Pt-doped Li2Pt0.125Co0.875SiO4 by lithium ions insertion/extraction

Transition metal silicate Li₂CoSiO₄ considered as a kind of stable and high energy density of lithium ion battery cathode material, has drawn intense interest, but the poor electrochemical performance limits its industrial applications. Metal doping is expected to be the most effective approach to improve its electrochemical performance. In this work, first-principles studies based on the density functional theory have been carried out to investigate the changes of the lattice and electronic structure in the charging-discharging process for Pt-doped Li₂Pt_0.125Co_0.875SiO₄. The calculation results show that the changes of the lattice parameter and volume are marginal in the process of removing Li ions, which indicates that Pt-doped Li₂Pt_0.125Co_0.875SiO₄ has high cycling stability and the average voltage also remain unchanged. And, Li-O bond length increases, then the interaction between Li-O decreases, which indicates that the lithium ion mobility increases. Compared with pure Li2CoSiO4, d orbital electrons of doped atom Pt emerge in the band gap, yielding narrower band gap, and the electronic conductivity of the Pt-doped Li₂Pt_0.125Co_0.875SiO₄ is increased. Therefore, Pt-doped Li₂Pt_0.125Co_0.875SiO₄ material effectively improves its electrochemical performance in the process of charging-discharging.