A Dual-Insertion Type Sodium-Ion Full Cell Based on High-Quality Ternary-Metal Prussian Blue Analogs

Prussian blue analogs (PBAs) are especially investigated as superior cathodes for sodium-ion batteries (SIBs) due to high theoretical capacity (approximate to 170 mA h g(-1)) with 2-Na storage and low cost. However, PBAs suffer poor cyclability due to irreversible phase transition in deep charge/discharge states. PBAs also suffer low crystallinity, with considerable [Fe(CN)(6)] vacancies, and coordinated water in crystal frameworks. Presently, a new chelating agent/surfactant coassisted crystallization method is developed to prepare high-quality (HQ) ternary-metal NixCo1-x[Fe(CN)(6)] PBAs. By introducing inactive metal Ni to suppress capacity fading caused by excessive lattice distortion, these PBAs have tunable limits on depth of charge/discharge. HQ-NixCo1-x[Fe(CN)(6)] (x = 0.3) demonstrates the best reversible Na-storage behavior with a specific capacity of approximate to 145 mA h g(-1) and a remarkably improved cycle performance, with approximate to 90% capacity retention over 600 cycles at 5 C. Furthermore, a dual-insertion full cell on the cathode and NaTi2(PO4)(3) anode delivers reversible capacity of approximate to 110 mA h g(-1) at a current rate of 1.0 C without capacity fading over 300 cycles, showing promise as a high-performance SIB for large-scale energy-storage systems. The ultrastable cyclability achieved in the lab and explained herein is far beyond that of any previously reported PBA-based full cells.