Optimization of prismatic type layered electrode materials for high performance sodium battery

Abstract

The prismatic and octahedral type layered cathode materials can provide enhanced performance in sodium-ion batteries, due to low potential barrier during the intercalation. Among them, the prismatic layered Na-Ni-Mn-O system is the most preferable electrode with a high theoretical capacity of 173 mAhg−1. The P2-type phase could be attained only by satisfying the conditions of alkali, and transition metal ratio 0.5 ≤ x ≤ 1. The P2-type layered structure in the Na-Ni-Mn-O system has been studied via optimizing the alkali and transition metals in two phases. Here, the vacuum assisted solid-state preparation method was carried out to avoid NiMnO4 impurities. From diffraction analysis and refinement data, the structural changes were analyzed, then the optimal ratio for perfect P2-structure has been confirmed. The perfect P2-structure was obtained only for the samples Na0.66Ni0.3Mn0.7O2, Na0.66Ni0.33Mn0.67O2. The prepared materials showed the initial discharge capacity of 194 mAhg−1 at 0.1C. Highlights Prismatic type layered Na-Ni-Mn-O electrodes synthesized via simple solid-state reaction. The prepared electrode delivered initial capacity of 194 mAh g−1 at 0.1 C. Mn richness maintains the low potential barrier for Na-ion during cycling. This enhances the electrochemical performances of the material. Increment of Nickel concentration enhance the unite cell volume.