Scalable synthesis of Na2MVF7 (M = Mn, Fe, and Co) as high-performance cathode materials for sodium-ion batteries.

In this work, we focused on the interpretation on a nonclassical crystallization route of NaxMn[Fe(CN)6]y·nH2O (0 < x < 2, 0 < y < 1, MnHCF) nanocrystal preparation via a bottom-up approach. Combin...

Interpretation on a Nonclassical Crystallization Route of Prussian White Nanocrystal Preparation

Fluorine substitution enabled superior performance of NaxMn2-xO1.5F0.5 (x = 1.05-1.3) type Na-rich cathode

Effect of sodium addition on lattice structure and tuning performance in sodium rich NaxTm2-xO2 type cathode materials (Tm=Mn and Cr; X=1.05–1.3) - A study

Electrocatalytic nitrogen reduction reaction (NRR) is considered as a promising candidate to achieve ammonia synthesis because of clean electric energy, moderate reaction condition, safe operating process and harmless by-products. However, the chemical inertness of nitrogen and poor activated capacity on catalyst surface usually produce low ammonia yield and faradic efficiency. Herein, the microfluidic technology is proposed to efficiently fabricate enriched iridium nanodots/carbon architecture. Owing to in-situ co-precipitation reaction and microfluidic manipulation, the iridium nanodots/carbon nanomaterials possess small average size, uniform dispersion, high conductivity and abundant active sites, producing good proton activation and rapid electrons transmission and moderate adsorption/desorption capacity. As a result, the as-prepared iridium nanodots/carbon nanomaterials realize large ammonia yield of 28.73 μg h−1 cm−2 and faradic efficiency of 9.14% in KOH solution. Moreover, the high ammonia yield of 11.21 μg h−1 cm−2 and faradic efficiency of 24.30% are also achieved in H2SO4 solution. The microfluidic method provides a reference for large-scale fabrication of nano-sized catalyst materials, which may accelerate the progress of electrocatalytic NRR in industrialization field. 

Microfluidic-Oriented Synthesis of Enriched Iridium Nanodots/Carbon Architecture for Robust Electrocatalytic Nitrogen Fixation

Rapid synthesis of sodium-rich Prussian white for Sodium-ion battery via a bottom-up approach

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.

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

Electrochemical Active Mn Dopped Iron Hexacyanoferrate as Cathode Material in Sodium-Ion Battery

In this work, using electrochemical active Fe as an ion-exchange element (attack side) and the NaxMnFe(CN)6 slurry with a high solid content (MnHCF) as a template (defensive side), a series of binary hexacyanoferrates are prepared via a simple Mn/Fe ion-exchange process, in which NaxFeFe(CN)6 (FeHCF) and solid solution Nax(FeMn)Fe(CN)6 are concentrated on the shell and the core, respectively. The proportions of the two structures are mainly controlled by the competition between the ion-exchange rate in the bulk material and dissolution-reprecipitation rate. Slowing down the attacking rate, such as the use of a chelating agent complexed with the attacker Fe, is advantageous to form a thermodynamically metastable state with homogeneous distribution of elements since the diffusion of Fe2+ in the solid MnHCF is relatively fast. The shell FeHCF could be adjusted by the dissolution-reprecipitation rate, which is driven by the solubility difference. Adding the chelating agent in the defensive side will promote the dissolution of MnHCF and reprecipitation of FeHCF on the surface. Meanwhile, with the increase of Fe sources, the thickness of the shell FeHCF increases, and correspondingly the content of solid solution decreased due to FeHCF is more stable than solid solutions in thermodynamics. Finally, such a design principle in this case study could also be generalized to other ion-exchange processes. Considering the difference of two components in solubility, the larger difference can make the core/shell structure more clear due to the enhancement of dissolution–reprecipitation route.

Yuming Xi

Papers

Rapid synthesis of sodium-rich Prussian white for Sodium-ion battery via a bottom-up approach

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

Electrochemical Active Mn Dopped Iron Hexacyanoferrate as Cathode Material in Sodium-Ion Battery

How Does Ion Exchange Construct Binary Hexacyanoferrate? A Case Study

Mechanochemical synthesis of Fe/Mn-based binary hexacyanoferrate for sodium-ion battery