A Salt‐Templated Strategy toward Hollow Iron Selenides‐Graphitic Carbon Composite Microspheres with Interconnected Multicavities as High‐Performance Anode Materials for Sodium‐Ion Batteries

Abstract

In this work, a facile salt‐templated approach is developed for the preparation of hollow FeSe2/graphitic carbon composite microspheres as sodium‐ion battery anodes; these are composed of interconnected multicavities and an enclosed surface in‐plane embedded with uniform hollow FeSe2 nanoparticles. As the precursor, Fe2O3/carbon microspheres containing NaCl nanocrystals are obtained using one‐pot ultrasonic spray pyrolysis in which inexpensive NaCl and dextrin are used as a porogen and carbon source, respectively, enabling mass production of the composites. During post‐treatment, Fe2O3 nanoparticles in the composites transform into hollow FeSe2 nanospheres via the Kirkendall effect. These rational structures provide numerous conductive channels to facilitate ion/electron transport and enhance the capacitive contribution. Moreover, the synergistic effect between the hollow cavities within FeSe2 and the outstanding mechanical strength of the porous carbon matrix can effectively accommodate the large volume changes during cycling. Correspondingly, the composite microsphere exhibits high discharge capacity of 510 mA h g−1 after 200 cycles at 0.2 A g−1 with capacity retention of 88% when calculated from the second cycle. Even at a high current density of 5.0 A g−1, a high discharge capacity of 417 mA h g−1 can be achieved.

Conversion Reaction Mechanism for Yolk‐Shell‐Structured Iron Telluride‐C Nanospheres and Exploration of Their Electrochemical Performance as an Anode Material for Potassium‐Ion Batteries

“…[12,19] In the initial cathodic process, an obvious peak is observed at 1.3 V, corresponding to the conversion of FeTe 2 into metallic Fe in the potassium telluride matrix and the formation of a solid-electrolyte interface (SEI) film. [12,27] The subsequent broad reduction peak at 0.1 V is attributed to the intercalation of K-ions into a hollow carbon shell. [28] In the anodic process, one broad peak at ≈0.3 V and two obvious peaks at 1.7 and 2.1 V appear.…”

“…The former peak is assigned to the extraction of K + from the carbon shell and the latter two peaks are attributed to the formation of FeTe 1.1 /potassium telluride (1.7 V) and metalloid Te (2.1 V), respectively. [12,27,29] The slightly shifted cathodic peak in the subsequent scans indicates the reduction of FeTe 1.1 and metalloid Te to metallic Fe and potassium telluride. To support the mechanism of the reaction of FeTe 2 with K + , CV measurements of FeTe@C nanospheres prepared at a high tellurization temperature of 700 °C were performed at the potential range, and scan rate shown in Figure S6, Supporting Information.…”

Recent Advances in Aerosol‐Assisted Spray Processes for the Design and Fabrication of Nanostructured Metal Chalcogenides for Sodium‐Ion Batteries

“…Choi et al. introduced a salt‐templated approach to form interconnected multicavities within hollow iron selenide/graphitic carbon microspheres (H‐FeSe 2 /GC) . Numerous cavities were formed by the removal of NaCl nanocrystals, and hollow FeSe 2 nanospheres were formed by the Kirkendall effect during post‐treatment (Figure g–j).…”

“…g) The formation of H‐FeSe 2 /GC, and the corresponding h)–j) TEM images and k) cycling performance. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…Choi et al introduced as alt-templated approach to form interconnected multicavitiesw ithin hollow iron selenide/graphitic carbon microspheres (H-FeSe 2 /GC). [91] Numerous cavities were formed by the removal of NaCl nanocrystals, and hollow FeSe 2 nano-spheres were formed by the Kirkendall effectd uring post-treatment (Figure 11g-j). These characteristicf eatures contributed to enhanced electrochemical performance, with stable cycling performance over 200 cycles and ar eversible capacity retention of 88 % ( Figure 11k).…”