A moisture-controlled Prussian white/CNT composite high energy cathode for next-generation sodium-ion batteries

Abstract

In this study, we present a Prussian white (Na₂MnFe(CN)₆)–carbon nanotube (PW–CNT) composite material with a carbon conductive network as a promising high energy cathode for sodium-ion batteries (SIBs). This cathode, which is prepared by a chelating-agent-assisted precipitation method to regulate defect crystallization, is showcased as a promising solution to the bottlenecks of high lattice defects, irreversible phase transitions, the resulting structural instability and hence unstable cycling usually present in the PW cathode for SIBs. Precisely, the PW–CNT composite formation highlights the effectively controlled moisture content achieved through the strategic integration of CNTs and a chelating agent during the material synthesis. Moreover, the electrochemical behavior and performance of PW–CNT composites, particularly in sodium-ion batteries, are explored within the context of controlled moisture environments. The intricate interplay between PW, CNTs, and the chelating agent, as well as their synergistic influence on moisture management and subsequent electrochemical performance, is thoroughly examined. At an extreme rate of 10C, the PW–CNT composite cathode exhibited a high reversible capacity of 133 mA h g⁻¹, very close to the theoretical value (∼140 mA h g⁻¹), and almost 30% higher than that of the PW (∼103 mA h g⁻¹) and 1.2 times greater than that of a conventional Prussian blue (PB) cathode (∼58 mA h g⁻¹), respectively. A coin-type full-cell configuration with a hard carbon (HC) anode exhibited ∼58% capacity retention after 1500 cycles at 1C thereby underscoring the potential of the PW–CNT composite cathode to advance the real-time applications for energy storage applications including SIBs.