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Title: Investigation of K modified P2 Na 0.7 Mn 0.8 Mg 0.2 O 2 as a cathode material for sodium-ion batteries
Authors: Sehrawat, D
Cheong, S
Rawal, A
Glushenkov, AM
Brand, HEA
Cowie, BCC
Gonzalo, E
Rojo, T
Naeyaert, PJP
Ling, CD
Avdeev, M
Sharma, N
Keywords: Sodium ions
Electric batteries
X-ray diffraction
Crystal structure
Solid solutions
Phase transformations
Issue Date: 19-Nov-2018
Publisher: Royal Society of Chemistry
Citation: Sehrawat, D., Cheong, S., Rawal, A., Glushenkov, A. M., Brand, H. E. A., Cowie, B., Gonzalo, E., Rojo, T., Naeyaert, P. J. P., Ling, C. D., Avdeev, M., & Sharma, N. (2019). Investigation of K modified P2 Na 0.7 Mn 0.8 Mg 0.2 O 2 as a cathode material for sodium-ion batteries. CrystEngComm, 21(1), 172-181. doi:10.1039/C8CE01532E
Abstract: Sodium-ion batteries (NIBs) are emerging as a potentially cheaper alternative to lithium-ion batteries (LIBs) due to the larger abundance of sodium and in some cases the similar intercalation chemistry to LIBs. Here we report the solid state synthesized K-modified P2 Na0.7Mn0.8Mg0.2O2 which adopts hexagonal P63/mmc symmetry. The second charge/discharge capacity for the as-prepared material is 115/111 mA h g−1 between 1.5–4.2 V at a current density of 15 mA g−1, which reduces to 61/60 mA h g−1 after 100 cycles. Scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (STEM-EDS) analysis shows a heterogeneous distribution of K and solid state 23Na NMR illustrates that the presence of K perturbs the local environment of Na within the P2 Na0.7Mn0.8Mg0.2O2 crystal structure. Larger scale X-ray absorption near-edge structure (XANES) data on the K L-edge also illustrate that K is present on the surface of electrodes in preference to the bulk. In situ synchrotron X-ray diffraction (XRD) data illustrates that the P2 structural motif is preserved, featuring a solid solution reaction for most of charge–discharge except at the charged and discharged states where multiple phases are present. The K-modified sample of P2 Na0.7Mn0.8Mg0.2O2 is compared with the K-free samples in terms of both structural evolution and electrochemical performance. © The Royal Society of Chemistry 2019
ISSN: 1466-8033
Appears in Collections:Journal Articles

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