Exploring calcium pillaring of O3-type NaNi$_{0.9}$Ti$_{0.1}$O$_2$ cathodes to advance Na-ion battery technology
Year: 2025
Type: article
Abstract: NaNi$_{0.9}$Ti$_{0.1}$O$_2$ (NNTO), a promising sodium-ion cathode material, is capable of delivering high specific capacities but is compromised by structural degradation at high potentials and poor redox stability. Herein, we introduced varying amounts of Ca$^{2+}$ as pillaring ions into the intercalation sites of NNTO to examine their effect on structure and electrochemical performance. Laboratory X-ray diffraction and charge/discharge testing identified Na$_{0.95}$Ca$_{0.025}$Ni$_{0.9}$Ti$_{0.1}$O$_2$ (CaNNTO) as the optimal composition in terms of interlayer spacing, rate capability, and cycling stability. Specifically, the capacity retention after 200 cycles improved from 27 to 48 %. To elucidate the role of Ca$^{2+}$, synchrotron X-ray diffraction was performed, revealing that CaNNTO undergoes only about 3 % volume change in the initial cycle, compared to about 30 % for NNTO. This reduced volume variation was confirmed by cross-sectional electron microscopy and acoustic emission measurements. Hard and soft X-ray absorption spectroscopy further indicated a more reversible nickel redox (Ni$^{2+}$/Ni$^{3+}$/Ni$^{4+}$) in CaNNTO, and differential electrochemical mass spectrometry demonstrated that Ca$^{2+}$ incorporation helps suppress oxygen loss from the lattice, thereby directly stabilizing the cathode|electrolyte interface. Overall, calcium pillaring is found to effectively mitigate structural collapse and redox instabilities, making CaNNTO a more viable candidate for practical sodium-ion battery applications.
Authors: An, Siyu, Karger, Leonhard, Müller, Philipp, Lin, Jing, Vasala, Sami, Baran, Volodymyr, Dreyer, Sören L., Zhang, Ruizhuo, Ulusoy, Fatih, Kondrakov, Aleksandr, Janek, Juergen, Brezesinski, Torsten
Institution: Deutsches Elektronen-Synchrotron DESY
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7077157958
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