Sun Xuan, Sun Jinfeng, Guo Lingzhi, Hou Linrui, Yuan Changzhou
School of Materials Science & Engineering, University of Jinan Jinan 250022 P. R. China
RSC Adv. 2020 Sep 28;10(59):35611-35618. doi: 10.1039/d0ra05578f.
The spinel NiCoO and rock-salt NiCoO have been well established as attractive electrodes for supercapacitors. However, what is the intrinsic role of the congenital aspect, , crystal structure and the surface and/or near-surface controlled electrochemical redox behaviors, if the acquired features (, morphology, specific surface area, pore structure, and so on) are wholly ignored? Herein, we purposefully elucidated the underlying influences of unique crystal structures of NiCoO and NiCoO on their pseudocapacitance from mechanism analysis through the density function theory based first-principles calculations, along with the experimental validation. Systematic theoretical calculation and analysis revealed that more charge carriers near the Fermi-level, stronger affinity with OH in the electrolyte, easier deprotonation process, and the site-enriched characteristic for low-index surfaces of NiCoO enable its faster redox reaction kinetics and greater charge transfer, when compared to the spinel NiCoO. The in-depth understanding of crystal structure-property relationship here will guide rational optimization and selection of appropriate electrodes for advanced supercapacitors.
尖晶石型NiCoO和岩盐型NiCoO已被公认为是超级电容器极具吸引力的电极材料。然而，如果完全忽略诸如形态、比表面积、孔结构等后天获得的特性，那么先天性的晶体结构以及表面和/或近表面可控的电化学氧化还原行为的内在作用是什么呢？在此，我们通过基于密度泛函理论的第一性原理计算进行机理分析，并结合实验验证，有针对性地阐明了NiCoO和NiCoO独特晶体结构对其赝电容的潜在影响。系统的理论计算和分析表明，与尖晶石型NiCoO相比，NiCoO在费米能级附近有更多的电荷载流子，与电解质中OH的亲和力更强，去质子化过程更容易，且低指数表面具有位点富集特性，使其具有更快的氧化还原反应动力学和更大的电荷转移。这里对晶体结构-性能关系的深入理解将指导先进超级电容器合适电极的合理优化和选择。
