Structural and Electrochemical Properties of Layered P2-Na 0.8 Co 0.8 Ti 0.2 O 2 Cathode in Sodium-Ion Batteries

Björn Pohle, Mikhail V. Gorbunov, Qiongqiong Lu, Amin Bahrami, Kornelius Nielsch and Daria Mikhailova
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Björn Pohle: Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V., Helmholtzstr. 20, D-01069 Dresden, Germany
Mikhail V. Gorbunov: Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V., Helmholtzstr. 20, D-01069 Dresden, Germany
Qiongqiong Lu: Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V., Helmholtzstr. 20, D-01069 Dresden, Germany
Amin Bahrami: Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V., Helmholtzstr. 20, D-01069 Dresden, Germany
Kornelius Nielsch: Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V., Helmholtzstr. 20, D-01069 Dresden, Germany
Daria Mikhailova: Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V., Helmholtzstr. 20, D-01069 Dresden, Germany

Energies, 2022, vol. 15, issue 9, 1-16

Abstract: Layered Na 0.8 Co 0.8 Ti 0.2 O 2 oxide crystallizes in the ?-RbScO 2 structure type (P2 modification) with Co(III) and Ti(IV) cations sharing the same crystallographic site in the metal-oxygen layers. It was synthesized as a single-phase material and characterized as a cathode in Na- and Na-ion batteries. A reversible capacity of about 110 mA h g ?1 was obtained during cycling between 4.2 and 1.8 V vs. Na + /Na with a 0.1 C current density. This potential window corresponds to minor structural changes during (de)sodiation, evaluated from operando XRD analysis. This finding is in contrast to Ti-free Na x CoO 2 materials showing a multi-step reaction mechanism, thus identifying Ti as a structure stabilizer, similar to other layered O3- and P2-Na x Co 1?y Ti y O 2 oxides. However, charging the battery with the Na 0.8 Co 0.8 Ti 0.2 O 2 cathode above 4.2 V results in the reversible formation of a O2-phase, while discharging below 1.5 V leads to the appearance of a second P2-layered phase with a larger unit cell, which disappears completely during subsequent battery charge. Extension of the potential window to higher or lower potentials beyond the 4.2–1.8 V range leads to a faster deterioration of the electrochemical performance. After 100 charging-discharging cycles between 4.2 and 1.8 V, the battery showed a capacity loss of about 20% in a conventional carbonate-based electrolyte. In order to improve the cycling stability, different approaches including protective coatings or layers of the cathodic and anodic surface were applied and compared with each other.

Keywords: cation design of Na-cathodes; structural transition in layered Na-oxides; Na-metal protective strategy; Na-cathode protective strategy (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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