Ma Le Anh, Palm Rasmus, Nocerino Elisabetta, Forslund Ola Kenji, Matsubara Nami, Cottrell Stephen, Yokoyama Koji, Koda Akihiro, Sugiyama Jun, Sassa Yasmine, Månsson Martin, Younesi Reza
Department of Chemistry, Ångström Laboratory, Uppsala, Sweden.
Department of Applied Physics, KTH Royal Institute of Technology, SE-10691 Stockholm, Sweden.
Phys Chem Chem Phys. 2021 Nov 3;23(42):24478-24486. doi: 10.1039/d1cp03115e.
Sodium transition metal oxides with a layered structure are one of the most widely studied cathode materials for Na-ion batteries. Since the mobility of Na in such cathode materials is a key factor that governs the performance of material, electrochemical and muon spin rotation and relaxation techniques are here used to reveal the Na-ion mobility in a P2-type NaMgNiMnO ( = 0, 0.02, 0.05 and 0.07) cathode material. Combining electrochemical techniques such as galvanostatic cycling, cyclic voltammetry, and the galvanostatic intermittent titration technique with μSR, we have successfully extracted both self-diffusion and chemical-diffusion under a potential gradient, which are essential to understand the electrode material from an atomic-scale viewpoint. The results indicate that a small amount of Mg substitution has strong effects on the cycling performance and the Na mobility. Amongst the tested cathode systems, it was found that the composition with a Mg content of = 0.02 resulted in the best cycling stability and highest Na mobility based on electrochemical and μSR results. The current study clearly shows that for developing a new generation of sustainable energy-storage devices, it is crucial to study and understand both the structure as well as dynamics of ions in the material on an atomic level.
具有层状结构的钠过渡金属氧化物是钠离子电池中研究最为广泛的阴极材料之一。由于钠离子在这类阴极材料中的迁移率是决定材料性能的关键因素，因此本文采用电化学以及μ子自旋旋转与弛豫技术来揭示P2型NaMgNiMnO（x = 0、0.02、0.05和0.07）阴极材料中的钠离子迁移率。通过将恒电流循环、循环伏安法以及恒电流间歇滴定技术等电化学技术与μSR相结合，我们成功地提取了在电位梯度下的自扩散和化学扩散，这对于从原子尺度理解电极材料至关重要。结果表明，少量的镁取代对循环性能和钠离子迁移率有显著影响。在测试的阴极体系中，基于电化学和μSR结果发现，镁含量为x = 0.02的组成具有最佳的循环稳定性和最高的钠离子迁移率。当前的研究清楚地表明，对于开发新一代可持续储能装置而言，在原子水平上研究和理解材料中离子的结构以及动力学至关重要。
