Synergistic electronic and ionic enhancement of nickel hexacyanoferrate for robust sodium-ion battery performance under extreme conditions

Sodium-ion batteries (SIBs) often face performance limitations under stringent conditions, such as low temperatures and overcharge/overdischarge scenarios, primarily due to the inadequacies of cathode materials. Nickel hexacyanoferrate (NiHCF) has emerged as a promising candidate due to its zero-strain ion-insertion characteristic and efficient ionic diffusion pathways. However, its practical application is hindered by inadequate ionic and electronic conductivity. In this study, we address these challenges by enhancing the electronic conductivity of NiHCF through the incorporation of multi-walled carbon nanotubes (MWCNTs). This strategic integration not only leverages NiHCF’s zero-strain ion-insertion property but also significantly improves electron and ion transport. As a result, the modified NiHCF/MWCNT composite demonstrates superior electrochemical performance, exhibiting enhanced robustness and efficiency, making it suitable for large-scale energy storage applications. Under a current density of 10 A g⁻¹ at 25 ℃, the NiHCF/MWCNT composite maintains stable cycling for up to 5000 cycles, with a notable specific capacity of 59.33 mAh g⁻¹. Even at −20 ℃, it continues to deliver robust cycling for 5000 cycles at 10 A g⁻¹. Remarkably, after overcharging to 4.25 V and overdischarging to 1.2 V at both 25 ℃ and −20 ℃, the NiHCF/MWCNT electrode still maintains robust cycling performance. This advancement not only addresses the current limitations of electrode materials under extreme conditions but also offers a scalable and practical approach to improving sustainable energy storage technologies.