Recent Progress and Prospects of Layered Cathode Materials for Potassium‐ion Batteries

Abstract

Layered materials with two‐dimensional ion diffusion channels and fast kinetics are attractive as cathode materials for secondary batteries. However, one main challenge in potassium‐ion batteries is the large ion size of K+, along with the strong K+−K+ electrostatic repulsion. This strong interaction results in initial K deficiency, greater voltage slope, and lower specific capacity between set voltage ranges for layered transition metal oxides. In this review, a comprehensive review of the latest advancements in layered cathode materials for potassium‐ion batteries is presented. Except for layered transition metal oxides, some polyanionic compounds, chalcogenides, and organic materials with the layered structure are introduced separately. Furthermore, summary and personal perspectives on future optimization and structural design of layered cathode materials are constructively discussed. We strongly appeal to the further exploration of layered polyanionic compounds and have demonstrated a series of novel layered structures including layered K3V2(PO4)3.

Suppressing the Jahn–Teller Effect in Mn‐Based Layered Oxide Cathode toward Long‐Life Potassium‐Ion Batteries

“…[ 1–4 ] Nonetheless, the shortage of high‐performance cathode materials is one of the essential barriers for developing next generation high‐power and high‐energy‐density PIBs. [ 5–8 ] Compared to other cathode materials, K + ‐contained layered transition metal oxides (K x TMO 2 ; TM = Mn, Co, Fe, Ni, Mg, Ti, etc.) are of great fascination due to the high theoretical capacities, suitable voltage platforms, and expedient synthesis process.…”

Layered Oxide Cathodes Promoted by Crystal Regulation Strategies for Potassium‐Ion Batteries

“…The typical formula of K‐based layered oxides is K x MO 2 (0< x <1; M=V, Fe, Co, Ni, Mn, Cr, etc. ), which consists of edge‐sharing MO 6 layers and K + ions layers [21] . Compared with Li + and Na + , K + which has a larger ionic radius is more likely to change lattice structure of layered transition metal oxides during the intercalation/deintercalation process, contribution to low reversible capacity and multilevel phase transitions [22] .…”

“…), which consists of edgesharing MO 6 layers and K + ions layers. [21] Compared with Li + and Na + , K + which has a larger ionic radius is more likely to change lattice structure of layered transition metal oxides during the intercalation/deintercalation process, contribution to low reversible capacity and multilevel phase transitions. [22] Worse still, numerous studies demonstrate that K + ions between transition metal layers possess strong mutual repulsion and K + /vacancy arrangement, which play critical roles in inferior potassium content and structural instability.…”

Recent Developments and Challenges of Vanadium Oxides (VxOy) Cathodes for Aqueous Zinc‐Ion Batteries

“…ion batteries. [8][9][10][11][12][13][14][15] Among them, zinc ion batteries (ZIBs) have been developed remarkably in recent years owing to their reasonable economic efficiency, convenient production, high safety, and eco-friendliness. Not only that, the high theoretical capacity of Zn 2 + /Zn (820 mAh g À 1 ), low redox potential (À 0.76 V vs. SHE), and the closest ionic radius to Li (Figure 1) have contributed to the enthusiasm for zinc.…”