Suppression of O3/P3 Phase Transition for Nanosize NaCrO2 with Enriched Domain Boundaries in Individual Particle

Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)


Rechargeable Na batteries are promising to realize sustainable energy development in the future because of the material abundance, and many electrode materials have been actively researched in the world. O3-type NaCrO21, 2 is known to show excellent cycle performance and thermal stability3. Additionally, O3 NaCrO2 shows second highest operating voltage among O3-type layered oxides, next to O3 NaFeO2. O3-type layered oxides translate into P3-type layered structure after removing Na from the layered structure. Such phase transitions result in large volume changes associated with increase in interlayer distance because of large repulsive interaction between MeO2 layers. The deterioration of cyclability associated with O3/P3 transitions is, therefore, anticipated as electrode materials.

In this study, nanosize NaCrO2 with enriched domain boundaries in individual particle was synthesized from nanosize cation-disordered rocksalt-type NaCrO2 prepared by mechanical milling. The sample delivers large reversible capacity without voltage plateaus associated with phase transitions as shown in Figure 1a. Ex-situ XRD data clearly indicates that the O3/P3 phase transition is effectively suppressed on charge/discharge processes. High-resolution TEM imaging shows that micrometer-size secondary particles consist of highly crystalline nanosize NaCrO2 particles. These nanosize domains are randomly aligned in the individual particle. We propose that randomly aligned particles with many grain boundaries cancel and suppress gliding of transition metal layers. Moreover, nanosize NaCrO2 shows better capacity retention in Na cells (Figure 1b) on the long-term cycle test.

From these results, we will further discuss the factors affecting phase transitions for O3-type layered structure as positive electrode materials of rechargeable Na batteries for more details.


This study was in part granted by MEXT program “Elements Strategy Initiative to Form Core Research Center”, MEXT; Ministry of Education Culture, Sports, Science and Technology, Japan. High-resolution TEM work was carried out with the support from Deakin Advanced Characterization Facility. A.M.G. acknowledges the funding support from Australian Research Council Discovery grant DP160101178.


[1] J. J. Braconnier, C. Delmas, and P. Hagenmuller, Materials Research Bullentin, 17, 993 (1982).

[2] S. Komaba et al., Electrochemistry Communications, 12, 355 (2010).

[3] X. Xia, J. R. Dahn, Electrochem. Solid-State Lett., 15 , A1 (2011).

[4] N Yabuuchi, K Kubota, M Dahbi, S Komaba, Chemical Reviews, 114, 11636 (2014).