Electrolyte-Induced Morphology Evolution to Boost Potassium Storage Performance of Perylene-3,4,9,10-tetracarboxylic Dianhydride.

Organic materials have attracted extensive attention for potassium-ion batteries due to their flexible structure designability and environmental friendliness. However, organic materials generally suffer from unavoidable dissolution in aprotic electrolytes, causing an unsatisfactory electrochemical performance. Herein, we designed a weakly solvating electrolyte to boost the potassium storage performance of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). The electrolyte induces an in situ morphology evolution and achieves a nanowire structure. The weakly dissolving capability of ethylene glycol diethyl ether-based electrolyte and unique nanowire structure effectively avoid the dissolution of PTCDA. As a result, PTCDA shows excellent cycling stability (a capacity retention of 89.1% after 2000 cycles) and good rate performance (70.3 mAh g-1 at 50C). In addition, experimental detail discloses that the sulfonyl group plays a key role in inducing morphology evolution during the charge/discharge process. This work opens up new opportunities in electrolyte design for organic electrodes and illuminates further developments of potassium-ion batteries.

Weakly Coordinating Diluent Modulated Solvation Chemistry for High-Performance Sodium Metal Batteries.

Diluents have been extensively employed to overcome the disadvantages of high viscosity and sluggish kinetics of high-concentration electrolytes, but generally do not change the pristine solvation structure. Herein, a weakly coordinating diluent, hexafluoroisopropyl methyl ether (HFME), is applied to regulate the coordination of Na+ with diglyme and anion and form a diluent-participated solvate. This unique solvation structure promotes the accelerated decomposition of anions and diluents, with the construction of robust inorganic-rich electrode-electrolyte interphases. In addition, the introduction of HFME reduces the desolvation energy of Na+, improves ionic conductivity, strengthens the antioxidant, and enhances the safety of the electrolyte. As a result, the assembled Na||Na symmetric cell achieves a stable cycle of over 1800 h. The cell of Na||P'2-Na0.67MnO2 delivers a high capacity retention of 87.3 % with a high average Coulombic efficiency of 99.7 % after 350 cycles. This work provides valuable insights into solvation chemistry for advanced electrolyte engineering.

Anion-Reinforced Solvation Structure Enables Stable Operation of Ether-Based Electrolyte in High-Voltage Potassium Metal Batteries.

Electrolytes with anion-dominated solvation are promising candidates to achieve dendrite-free and high-voltage potassium metal batteries. However, it's challenging to form anion-reinforced solvates at low salt concentrations. Herein, we construct an anion-reinforced solvation structure at a moderate concentration of 1.5 M with weakly coordinated cosolvent ethylene glycol dibutyl ether. The unique solvation structure accelerates the desolvation of K+, strengthens the oxidative stability to 4.94 V and facilitates the formation of inorganic-rich and stable electrode-electrolyte interface. These enable stable plating/stripping of K metal anode over 2200 h, high capacity retention of 83.0 % after 150 cycles with a high cut-off voltage of 4.5 V in K0.67MnO2//K cells, and even 91.5 % after 30 cycles under 4.7 V. This work provides insight into weakly coordinated cosolvent and opens new avenues for designing ether-based high-voltage electrolytes.