Chloro-Functionalized Ether-Based Electrolyte for High-Voltage and Stable Potassium-Ion Batteries.

Ether-based electrolyte is beneficial to obtaining good low-temperature performance and high ionic conductivity in potassium ion batteries. However, the dilute ether-based electrolytes usually result in ion-solvent co-intercalation of graphite, poor cycling stability, and hard to withstand high voltage cathodes above 4.0 V. To address the aforementioned issues, an electron-withdrawing group (chloro-substitution) was introduced to regulate the solid-electrolyte interphase (SEI) and enhance the oxidative stability of ether-based electrolytes. The dilute (~0.91 M) chloro-functionalized ether-based electrolyte not only facilitates the formation of homogeneous dual halides-based SEI, but also effectively suppress aluminum corrosion at high voltage. Using this functionalized electrolyte, the K||graphite cell exhibits a stability of 700 cycles, the K||Prussian blue (PB) cell (4.3 V) delivers a stability of 500 cycles, and the PB||graphite full-cell reveals a long stability of 6000 cycles with a high average Coulombic efficiency of 99.98 %. Additionally, the PB||graphite full-cell can operate under a wide temperature range from -5 °C to 45 °C. This work highlights the positive impact of electrolyte functionalization on the electrochemical performance, providing a bright future of ether-based electrolytes application for long-lasting, wide-temperature, and high Coulombic efficiency PIBs and beyond.

Weak Cation-Solvent Interactions in Ether-Based Electrolytes Stabilizing Potassium-ion Batteries.

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 potassium-metal 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||graphite cell operates 200 cycles with 86.6 % capacity retention), the potassium metal shows highly stable plating/stripping (K||Cu cell delivers 550 cycles with average Coulombic efficiency of 98.9 %) and dendrite-free (symmetric K||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 high-performance electrolytes and beyond.

Cyclic-anion salt for high-voltage stable potassium-metal batteries.

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-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.

Prospects of Electrode Materials and Electrolytes for Practical Potassium-Based Batteries.

Potassium-ion batteries (PIBs) have attracted tremendous attention because of 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.

Rational Design of a Polyimide Cathode for a Stable and High-Rate Potassium-Ion Battery.

Potassium has similar chemical characteristics compared with lithium while it is more abundant and of low cost, resulting in widespread research attention on potassium-ion batteries (PIBs). Developing organic polymer cathodes has garnered extensive attention because of their merits of environmental friendship and structure diversity, while confronted with inferior cycle stability and low rate performance. In this paper, we utilize the low-cost graphite nanosheets to stabilize polyimide (PI@G) for PIBs. Additionally, the potassium storage mechanism of PI@G was further evaluated; the highly reversible chemical bonds (C═O) of PI@G are responsible to its long-term stability. Consequently, the PI@G exhibits a maximal capacity of 142 mA h g-1 at the current density of 100 mA g-1 and maintains a capacity of 118 mA h g-1 after 500 cycles (corresponding to a capacity fade of 0.034% per cycle). Moreover, the full battery based on the PI@G cathode also reveals promisingly electrochemical performance. This study may have great significance to the application prospect of the organic cathode for PIBs.