A Low‐Cost and Environmentally Friendly Mixed Polyanionic Cathode for Sodium‐Ion Storage

Abstract

Sodium‐ion batteries (NIBs) are the most promising alternatives to lithium‐ion batteries in the development of renewable energy sources. The advancement of NIBs depends on the exploration of new electrode materials and fundamental understanding of working mechanisms. Herein, via experimental and simulation methods, we develop a mixed polyanionic compound, Na2Fe(C2O4)SO4⋅H2O, as a cathode for NIBs. Thanks to its rigid three dimensional framework and the combined inductive effects from oxalate and sulfate, it delivered reversible Na insertion/desertion at average discharging voltages of 3.5 and 3.1 V for 500 cycles with Coulombic efficiencies of ca. 99 %. In situ synchrotron X‐ray measurements and DFT calculations demonstrate the Fe2+/Fe3+ redox reactions contribute to electron compensation during Na+ desertion/insertion. The study suggests mixed polyanionic frameworks may provide promising materials for Na ion storage with the merits of low cost and environmental friendliness.

A fluoroxalate cathode material for potassium-ion batteries with ultra-long cyclability

“…Meanwhile, our attempts in taking highresolution TEM or selected area electron diffraction proved unsatisfactory owing to the sample's sensitivity to intense electron beams, similar to some other oxalate, fluorosulphates and metalorganic frameworks. [54][55][56][57] The thermal behavior of KFeC 2 O 4 F was analyzed by simultaneous thermogravimetric-differential scanning calorimetry and variable-temperature XRD. As shown in Fig.…”

A phosphite-based layered framework as a novel positive electrode material for Na-ion batteries

“…22 In addition, an oxalate sulphate framework material, Na 2 Fe(C 2 O 4 )SO 4 ⋅H 2 O demonstrated 3 V operation as a positive electrode for SIBs. 25 With two distinct channels of 5.907 and 4.126 Å, the material demonstrates facile Na migration and delivered a capacity close to its theoretical value of 88 mAh g −1 and good cycle stability over 500 cycles.…”

A novel low-cost and environment-friendly cathode with large channels and high structure stability for potassium-ion storage

“…Pristine KFOS was first ball-milled with conductive carbon to form a uniform mixture (Fig. S7), similar to other polyanionic electrode materials [42,43]. Galvanostatic cycling experiments were performed on half cells using a fixed rate of 100 mA g 4.5 V likely determined by carbonate electrolyte but not the KFOS, which restrained redox reactions and therefore limited the obtained capacity stated in detail below.…”