High‐Performance Cathode Materials for Potassium‐Ion Batteries: Structural Design and Electrochemical Properties

Abstract

Due to the obvious advantage in potassium reserves, potassium‐ion batteries (PIBs) are now receiving increasing research attention as an alternative energy storage system for lithium‐ion batteries (LIBs). Unfortunately, the large size of K+ makes it a challenging task to identify suitable electrode materials, particularly cathode ones that determine the energy density of PIBs, capable of tolerating the serious structural deformation during the continuous intercalation/deintercalation of K+. It is therefore of paramount importance that proper design principles of cathode materials be followed to ensure stable electrochemical performance if a practical application of PIBs is expected. Herein, the current knowledge on the structural engineering of cathode materials acquired during the battle against its performance degradation is summarized. The K+ storage behavior of different types of cathodes is discussed in detail and the structure–performance relationship of materials sensitive to their different lattice frameworks is highlighted. The key issues facing the future development of different categories of cathode materials are also highlighted and perspectives for potential approaches and strategies to promote the further development of PIBs are provided.

Cardanol-Derived Epoxy Resins as Biobased Gel Polymer Electrolytes for Potassium-Ion Conduction

“…Our group has recently started working on potassium-ion batteries (KIBs), given the cheap and abundant raw material (2.09 wt % in Earth’s crust), its favorable geographical distribution, and its intriguing electrochemical properties (K + /K has a potential of −2.93 V vs standard hydrogen electrode, a value close to that of Li + /Li, −3.04 V). 39 − 41 Also, potassium ions show a weaker Lewis acidity than that of lithium-based counterparts, accompanied by a much smaller Stokes’ radius (i.e., 3.6 vs 4.8 Å) in propylene carbonate, thus guaranteeing a higher ionic conductivity in the liquid electrolyte. 42 − 44 Overall, potassium ions can be successfully used as charge carriers between the anode and cathode in KIBs, following the same “rocking-chair” mechanism that has brought lithium-ion battery to the current worldwide success.…”

Interphases in the electrodes of potassium ion batteries

“…As a protective interphase layer, a CEI should possess decent rigidity and flexibility as mechanical support to the cathode structure. At the same time, as an ionic bridge interconnecting the cathode and the electrolyte, a CEI adds kinetic hindrances for K-ion transfer and therefore, a thin CEI is considered favourable for fast K-ion transport [71,75,76]. A trade-off between mechanical strength and ionic conductivity should be considered in CEI design.…”

A Low‐Strain Phosphate Cathode for High‐Rate and Ultralong Cycle‐Life Potassium‐Ion Batteries

“…Thep ositive electrode plays ap ivotal role in the energy density and power density of the full battery,particularly the elevated potential positive electrode.U nfortunately,o nly af ew types of positive electrodes for PIBs have been successfully designed and synthesized, including Prussian blue analogues, [12,13] organic materials, [14,15] layered transitionmetal oxides, [16,17] and phosphate compounds. [18,19] Among diverse kinds of cathode materials for PIBs,p hosphate compounds have received widespread investigations with high capacity and good cyclic performance on account of their large interstitial channels and robust three-dimensional frameworks,w hich are favorable for obtaining superfast K + migration kinetics and low-strain potassium-ion storage mechanism.…”