Layered-columnar cathode materials for sodium-ion batteries

The advancement of cathode materials possessing high-rate capability and extended cycle life is crucial for the viability of large-scale energy storage in sodium-ion batteries. A layered-columnar material NaFe[O₃PCH(OH)CO₂] is designed with 2D grid-like channels for sodium ion migration. Operating on the Fe²⁺/Fe³⁺ redox reaction, NaFe[O₃PCH(OH)CO₂] exhibits a reversible specific capacity of 106.1 mAh g^-1 after 50 cycles within the voltage range of 1.5-4.2 V, reaching 93.4% of the theoretical specific capacity. Experimental and theoretical investigations show that NaFe[O₃PCH(OH)CO₂] exhibits low-strain characteristics during discharge and charge processes. The presence of stable C-P covalent bonds between organic layers and inorganic columns ([FeO₆] and [CPO₃]) plays a pivotal role in achieving its long cycle life. Even under high current density of 240 mA g^-1, it maintains satisfactory capacities, delivering 61.6 mAh g^-1 after the 1000th cycles, indicating a capacity retention rate of 92.2% with only 0.0078% loss per cycle. This study indicates that layered-columnar structure design offers a viable strategy for the development of high-performance positive electrode material for sodium-ion batteries.