Revolutionary Cathode Material Enables High

Scientists have made significant advancements in addressing the air/water-instability and structural-cum-electrochemical instability of Sodium-transition-metal-oxide-based cathode materials for Sodium-ion batteries. These new developments have resulted in the creation of stable, high-performance cathode materials that exhibit excellent electrochemical cyclic stability and remain stable when exposed to air and water. This breakthrough is crucial for the development of cost-effective and sustainable energy storage systems for various applications, including consumer electronics, grid energy storage, renewable energy storage, and electric vehicles.

With the increasing importance of battery-driven electric vehicles due to environmental concerns, the development of a cost-effective, safe, and sustainable alkali metal-ion battery system beyond Lithium-ion is essential. India, in particular, possesses abundant sodium sources, making the upcoming Sodium-ion battery system highly significant in the Indian context. Sodium-ion cells consist of cathode and anode active materials that enable the reversible insertion and removal of Na-ions during charge and discharge. The performance of these cells depends on the stability of the electrodes, Na-transport kinetics, and various dynamic resistances.

Although Sodium-ion batteries offer many advantages, the electrochemical behavior and stability of the layered Na-transition-metal-oxide-based cathode materials need improvement for widespread usage in Na-ion battery systems. The lack of stability makes handling and storing Na-transition-metal-oxides challenging and negatively impacts their electrochemical performance. Furthermore, their water instability necessitates the use of toxic and expensive chemicals like N-Methyl-2-pyrrolidone (NMP) for electrode preparation, instead of water-based slurries.

Professor Amartya Mukhopadhyay's group at IIT Bombay has made significant progress in developing environmentally stable and high-performance cathodes for Sodium-ion batteries. By introducing "interslab" spacing through tuning the TM-O bond covalency, they have proposed a universal design criterion for successful and widespread development of these cathodes. Adjusting the degree of covalency affects the net charge on the O-ions, influencing the electrostatic attraction between Na- and O-ions as well as the repulsions between O-ions across the Na-layer.

The research demonstrates that reducing TM-O covalency results in stronger Na-O bonds and improved air/water stability, while increasing TM-O covalency leads to weaker Na-O bonds and enhanced Na-transport kinetics, allowing for higher power density. Additionally, by increasing TM-O bond covalency, the group stabilized the prismatic O-coordination of Na-ions, enabling higher Na-storage capacity and improved air/water stability.

These advancements hold immense practical significance and are expected to facilitate the widespread development of high-performance and cost-effective Sodium-ion battery systems through eco-friendly electrode processing methods.