Layered P2-Na2/3Co1/2Ti1/2O2 as a high-performance cathode material for sodium-ion batteries

Abstract

Abstract Layered oxides are regarded as promising cathode materials for sodium-ion batteries. We present Na 2/3 Co 1/2 Ti 1/2 O 2 as a potential new cathode material for sodium-ion batteries. The crystal features and morphology of the pristine powder were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The cathode material is evaluated in galvanostatic charge-discharge and galvanostatic intermittent titration tests, as well as ex-situ X-ray diffraction analysis. Synthesized by a high-temperature solid state reaction, Na 2/3 Co 1/2 Ti 1/2 O 2 crystallizes in P2-type structure with P 6 3 / mmc space group. The material presents reversible electrochemical behavior and delivers a specific discharge capacity of 100 mAh g −1 when tested in Na half cells between 2.0 and 4.2 V (vs. Na + /Na), with capacity retention of 98% after 50 cycles. Furthermore, the electrochemical cycling of this titanium-containing material evidenced a reduction of the potential jumps recorded in the Na x CoO 2 parent phase, revealing a positive impact of Ti substitution for Co. The ex-situ XRD measurements confirmed the reversibility and stability of the material. No structural changes were observed in the XRD patterns, and the P2-type structure was stable during the charge/discharge process between 2.0 and 4.2 V vs. Na + /Na. These outcomes will contribute to the progress of developing low cost electrode materials for sodium-ion batteries.