Structure and surface modification of MXene for efficient Li/K-ion storage

In this paper,three-dimensional(3D)hollow Ti_(3)C_(2)T_(x)MXene tubes(HTCTs)with more–O terminal groups and fewer–F groups are successfully prepared via the template-oriented electrostatic self-assembly and the subsequent annealing treatment.The obtained 3D hollow structure with large specific surface area,unique porous structure,and enlarged interlayer spacing could prevent the re-stacking of twodimensional(2D)sheets and shorten the diffusion pathway of ions.Furthermore,density functional theory(DFT)calculations and electrochemical tests reveal that Ti_(3)C_(2)O_(2)MXene possesses higher adsorption ability and lower diffusion barrier for K^(+)and Li^(+)compared to Ti_(3)C_(2)MXene dominated by–F terminal groups.Benefiting from the synergistic effect of the structural design and surface modification,the asprepared 3D HTCTs exhibit excellent electrochemical performance as anodes for K^(+)and Li^(+)storage compared with 2D Ti_(3)C_(2)T_(x)sheets(TCSs).

钠离子电池层状氧化物正极材料的耐高电压性能

钠离子电池具有资源和成本的优势而在大规模储能和低速电动车领域展现出极大的应用前景。其中,层状氧化物正极材料由于其理论容量高且易于合成等受到了广泛研究。然而,层状氧化物正极材料在循环过程中,尤其是高电压情况下容易出现结构不稳定和表面退化等现象,造成电池性能衰退,阻碍了其商业应用。基于此,本文综述了层状氧化物正极材料在高电压下的结构转变、表面退化以及氧损失等机制,分析和探讨了提高层状氧化物正极材料耐高电压性能的策略,以期为具有耐高电压性能的钠离子电池层状氧化物正极材料的设计开发提供参考;最后总结了钠离子电池层状氧化物正极材料在改性方面存在的不足及未来的研究方向。