Electrochemically Active Mn-Doped Iron Hexacyanoferrate as the Cathode Material in Sodium-Ion Batteries

Abstract

In this work, for the performance enhancement of iron hexacyanoferrate, an electrochemically active Mn-doped iron hexacyanoferrate cathode is fabricated via a bottom-up approach. It is found that the pre-treatment of interstitial water and appropriate Mn doping are two keys to achieving higher capacity and higher stability. The interstitial water has a trade-off effect between the alleviation of volume expansion upon Na+ (de)­intercalation and the retardation of Na-ion diffusion. The moisture-tailored iron hexacyanoferrate with appropriate Mn doping exhibits a high initial Coulombic efficiency of 94.8%, enhanced capacity and rate performance, and excellent cycling stability. These results benefit from the fact that the extraction/insertion of Na ions from/into the lattice via a solid-solution mechanism correspond to both the slight volume expansion and fast sodium diffusion rate; otherwise, the removal of interstitial water and a higher Mn content might lead to poor cycling stability due to excessive volume expansion resulting from rhombohedral to cubic phase transformation. Finally, the less demand on the control of air humidity for the fabrication of electrodes and the potential for the full cell coupled with hard carbon are also demonstrated, which shows great potential for practical applications.

Promising Cathode Materials for Sodium-Ion Batteries from Lab to Application

“…For Fe-HCF, the low-spin Fe LS redox at the higher voltage is hard to activate due to the existence of [Fe­(CN) 6 ] vacancies. Through divalent Ni, , Zn, Cu, , or Mn doping, the capacity contribution of the low spin Fe LS redox could be elevated to decrease the energy barriers of Na + migration. It was found that 3% Ni substitution in Fe-HCF could increase the low spin Fe LS capacity contribution from 28% (27 mA h g –1 ) to 43% (50 mA h g –1 ) .…”

High-density cathode structure of independently acting Prussian-blue-analog nanoparticles: a high-power Zn–Na-ion battery discharging ∼200 mA cm−2 at 1000C

“…[29][30][31] Recently, it has been hotly debated if mixed metals can mitigate the volume-change strain of MnHCFs. [32][33][34][35][36] In the element strategy, the uneven distribution of scarce metal resources is a great concern for regulating supply and increasing prices. An earth-abundant, low-cost, and nontoxic Zn is endowed with a high volumetric capacity of 5851 mA h cm −3 , compared to those of Li (2062) > Na (1128) > K (591 mA h cm −3 ) 37 and can be stockpiled safely without self-ignition under ambient air.…”

“…29–31 Recently, it has been hotly debated if mixed metals can mitigate the volume-change strain of MnHCFs. 32–36…”

High specific capacity FeFe(CN)6 as the cathode material in aqueous rechargeable zinc–sodium hybrid batteries

“…However, due to changes in the weather, renewable energy is intermittent, such as solar, wind, etc. 1,2 Rechargeable batteries are expected to buffer this challenge, as they can store intermittent energy to be used as electrochemical energy. Lithium-ion batteries (LIBs) are widely used in portable electronic products due to their high specific capacity, long cycle life and high average voltage, 3,4 but the high cost, flammable organic electrolytes and rarity of lithium resources limit their large-scale application.…”