Cubic Perovskite Fluoride as Open Framework Cathode for Na‐Ion Batteries

Abstract

Exploring novel structure prototype and mineral phase, especially open framework material, is crucial to developing high-performance Na-ion battery cathodes in view of potentially faster intrinsic diffusion of Na + in lattices. Perovskite phases have been widely applied in solar cells, fuel cells, and electrocatalysis; however, they are rarely attempted as energy storage electrode materials. This study proposes pre-expanding perovskite iron fluoride (KFeF 3 ) framework by stuffing large-sized K + as a channel filler, which is advantageous over Na + , NH 4 + , and H 2 O molecule filler in terms of structure robustness, symmetry, and connectivity. K + stuffing leads to the preservation of a more "regular" cubic phase with fast isotropic 3D diffusion as a consequence of no distortion of FeF 6 octahedra during K-Na electrochemical exchange and following Na-insertion cycling. High-rate Na-storage is achievable with a reversible capacity of 110, 70, and 40 mAh g −1 at 0.1, 2, and 10 C, respectively, for this open framework fluoride cathode, benefiting from solid solution electrochemical behavior and high intrinsic diffusion coefficient. It is thought that this rate performance is currently the best among Na-storage fluoride materials.

Rechargeable potassium-ion batteries with honeycomb-layered tellurates as high voltage cathodes and fast potassium-ion conductors

“…K-based compounds have also found their niche application in energy storage as host frameworks for reversible reinsertion of Li and Na electrodes. Such compounds include lepidocrocite K 0.8 Li 0.27 Ti 1.73 O 4 14 , K 2 Ti 6 O 13 15 , KFeF 3 16 , K A SO 4 F ( A  = Fe, Co) 17 , KVPO 4 F 18 , fedotovite K 2 Cu 3 O(SO 4 ) 3 19 , K 2 [(VO) 2 (HPO 4 ) 2 (C 2 O 4 )] 20 , KV 3 O 8 21 , K 1.33 Fe 11 O 17 22 , K 2 D 2 (SO 4 ) 3 ( D  = Cu, Fe) 19 , K x V 2 O 5 21 , Prussian analogues 23 , amongst others. Indeed, a great variety of K-based minerals and compounds have been documented, and most have yet to have their electrochemical properties studied.…”

Ultrahigh rate binder-free Na3V2(PO4)3/carbon cathode for sodium-ion battery

“…Among different cathode materials, such as layered transitional metal oxides [13][14][15] , ferrocyanides [16][17][18][19] , transition metal fluoride [20] , polyanionic compounds [12,21,22] , Na 3 V 2 (PO 4 ) 3 (NVP) attracts increasing attentions as a superionic conductor of Na + in virtue of its durable 3D NASICON framework, suitable interstitial channels for Na + transportation and high theoretical capacity [23][24][25][26][27][28] . NVP shows two potential plateaus at 3.4 V and 1.6 V, the higher plateau represents two Na + reversible insertion/extraction, corresponding to V 3 + /V 4 + redox couple, which is very suitable for accommodating Na + at high voltage zone [29,30] .…”

Bimetallic Co‐Mn Perovskite Fluorides as Highly‐Stable Electrode Materials for Supercapacitors

“…; B=Fe, Mn, Ni, Co, Cu, etc.) have been demonstrated as potential electrode materials for Li/Na‐ion rechargeable batteries . The perovskite phase exhibits the merits of intrinsic 3D diffusion channels and a robust architecture with intersectional tetragonal cavity chains .…”