Figure 3.

(a) In situ DEMS analysis of oxygen release during the first charge for the Na_2/3Ni_1/3Mn_2/3O₂ electrode. The charge current density is 10 μA mg^–1, and the cut off voltage is 4.3 V. (b) DOS of Na_2/3Ni_1/3Mn_2/3O₂ cathode at 4.2 V (0.33 Na removal) and 4.3 V (0.6 Na removal). The Fermi level is indicated by the dash line. (c) Schematic representation of the energy level versus DOS and the loss of oxygen. (d) Galvanostatic charge/discharge curves of Na_2/3Ni_1/3Mn_2/3O₂ electrode and the irreversible capacity loss for the first cycle at 0.1 C. (e) HRTEM image of Na_2/3Ni_1/3Mn_2/3O₂ at the pristine state. (f) HRTEM image of Na_2/3Ni_1/3Mn_2/3O₂ after one cycle. (g) The calculated structure of the dense surface.