The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smtd.202101131. Potassium-ion batteries (PIBs) have attracted tremendous attention becauseof their high energy density and low-cost. As such, much effort has focused on developing electrode materials and electrolytes for PIBs at the material levels. This review begins with an overview of the high-performance electrode materials and electrolytes, and then evaluates their prospects and challenges for practical PIBs to penetrate the market. The current status of PIBs for safe operation, energy density, power density, cyclability, and sustainability is discussed and future studies for electrode materials, electrolytes, and electrode-electrolyte interfaces are identified. It is anticipated that this review will motivate research and development to fill existing gaps for practical potassium-based full batteries so that they may be commercialized in the near future.

Conventional ether-based electrolytes exhibited a low polarization voltage in potassium-ion batteries, yet suffered from ion-solvent co-intercalation phenomena in a graphite anode, inferior potassiummetal performance, and limited oxidation stability.Here, we reveal that weakening the cation-solvent interactions could suppress the co-intercalation behaviour, enhance the potassium-metal performance, and improve the oxidation stability. Consequently, the graphite anode exhibits K + intercalation behaviour (K j j graphite cell operates 200 cycles with 86.6 % capacity retention), the potassium metal shows highly stable plating/stripping (K j j Cu cell delivers 550 cycles with average Coulombic efficiency of 98.9 %) and dendritefree (symmetric K j j K cell operates over 1400 hours) properties, and the electrolyte exhibits high oxidation stability up to 4.4 V. The ion-solvent interaction tuning strategy provides a promising method to develop highperformance electrolytes and beyond.

Electrolyte anions are critical for achieving high-voltage stable potassium metal batteries (PMBs). However, the common anions cannot simultaneously prevent the formation of ‘dead K’ and the corrosion of Al current collector, resulting in poor cycling stability. Here, we demonstrate cyclic-anion of hexafluoropropane-1,3-disulfonimide (HFDF−) based electrolytes that can mitigate the ‘dead K’ and remarkably enhance the high voltage stability of PMBs. Particularly, even using low salt concentration (0.8 M) and additive-free carbonate-based electrolytes, the PMBs with a high voltage polyanion cathode (4.4 V) also exhibit excellent cycling stability of 200 cycles with a good capacity retention of 83%. This noticeable electrochemical performance is due to the highly-efficient passivation ability of the cyclic anions on both anode and cathode surfaces. This cyclic anion-based electrolyte design strategy is also suitable for lithium and sodium metal battery technologies.

Organic electrode materials are extensively applied for alkali metal (lithium, sodium, and potassium)‐ion batteries (LIBs, SIBs, and PIBs) due to their sustainability and low cost. As a typical organic cathode, poly(2,6‐anthraquinonyl sulfide) (PAQS) shows high theoretical capacity, yet its electrochemical behavior and mechanisms in alkali‐metal‐ion batteries still require clarification. Herein, PAQS microspheres are synthesized and applied as cathodes for LIBs, SIBs, and PIBs. When using traditional low‐concentration electrolytes, the reduction voltage and the initial discharge capacity of PAQS electrode in LIB, SIBs, PIBs are 2.11 V/103 mAh g−1, 1.76/1.30 V/134 mAh g−1, 1.94/1.54 V/198 mAh g−1 at 100 mA g−1, respectively, while the cycling stability of PAQS is in the order of LIBs > SIBs > PIBs. To further promote the practical application of PIBs, a facile method is demonstrated to improve the cycle stability of PAQS for PIBs by using a novel high‐concentration electrolyte. The cycling stability of PIBs with PAQS can be improved significantly to 1200 cycles with a capacity decay of 0.031% per cycle. This work may provide guidelines for developing innovative organic materials used in applicable metal‐ion batteries demonstrates the impact of electrolyte optimization on improving the cycling stability.

Electrolytes are critical for the safety and long-term cyclability of potassium ion batteries. Here, a low-concentration, non-flammable, and weakly solvating electrolyte enables the cycling stability of K||graphite cell for over 2 years.