第一性原理设计阳离子掺杂H-Nb2O5负极材料及其电化学性能研究

First-principles design of cation-doped H-Nb2O5 negative electrode material and its electrochemical performance investigation

  • 摘要: 铌基氧化物负极材料因具有优异的锂离子扩散速率而备受关注,但铌基氧化物导电性较差,严重限制了其大规模应用。本研究运用第一性原理计算方法,采用VASP软件包结合Hubbard修正的广义梯度近似(GGA + U)计算了不同阳离子掺杂对H-Nb2O5的态密度带隙的影响,结果表明,掺杂Ni2+、Co2+、Ag+能改善H-Nb2O5电子结构,将其带隙由纯相H-Nb2O5的0.35 eV分别降低至0、0.1、0.17 eV。在此基础上,采用固相法分别制备了掺杂Ni2+、Co2+、Ag+的H-Nb2O5,并对其结构及电化学储锂机理进行了研究。其中,Ni2+掺杂H-Nb2O5展现出较优的电化学性能,在2.5 C条件下放电比容量达203 mAh/g;在50 C条件下容量仍保持在89 mAh/g;25 C条件下3 000次循环中每次容量损失率仅为0.002 1% 。锂离子迁移势垒计算结果表明,Ni2+掺杂H-Nb2O5的迁移势垒为0.674 eV,远低于纯相H-Nb2O5的0.847 eV。

     

    Abstract: Niobium-based oxide negative electrode materials have attracted much attention because of their excellent lithium-ion diffusion rate, but their poor electrical conductivity severely limits their large-scale application. In this study, the effects of different cationic doping on the bandgap of H-Nb2O5 state density were calculated by using the VASP software package and Hubbard modified generalized gradient approximation (GGA + U). The results show that Ni, Co and Ag can improve the electronic structure of H-Nb2O5 and reduce the band gap compared to pure phase H-Nb2O5 from 0.35 eV to 0, 0.13 and 0.17 eV, respectively. On this basis, H-Nb2O5 doped with Ni, Co and Ag was prepared using the solid phase method, and its structure and electrochemical lithium storage mechanism were studied, respectively. The experimental results show that Ni-doped H-Nb2O5 exhibits the best electrochemical performance among the doped H-Nb2O5 anodes. The specific discharge capacity reaches 203 mAh/g at 2.5 C. The capacity remains at 89 mAh/g at 50 C. The capacity loss rate per 3000 cycles is only 0.002 1% under the 25 C condition. The calculation results show that the migration barrier of Ni-doped H-Nb2O5 is 0.674 eV, much lower than 0.847 eV of pure H-Nb2O5.

     

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