An ammonia-induced universal synthesis approach for manganese based layered oxides.

Manganese-rich layered transition-metal oxides are of great interests as positive electrodes for sodium-ion batteries considering their high specific capacity and operating voltage. However, it remains challenging to synthesize layered transition-metal oxides with high stability and rapid ion-migration kinetics. Herein, we develop a straightforward and universal synthesis approach for P2-type layered transition-metal oxides by simply updating the conventional solid-state reaction with only additional dicyandiamide introduced. We reveal the ammonia released successfully restrains the irreversible oxygen redox for stabilizing cationic migration and decreases the crystallization temperature for high-quality structure formation. The effectively suppressed Jahn-Teller distortion and facilitated Na+ transport kinetics therefore endow Na1/2MnO2 with overall performance enhancement, including a 6.7-fold improvement in rate capability and enhanced cycling stability. Similar performance enhancements are also found in other manganese-based layered transition-metal oxides, presenting great strategy universality. This work marks a key step forward in the synthesis-by-design of high-performance sodium-ion batteries electrode materials.