Rational Design of Electrode-Electrolyte Interphase and Electrolytes for Rechargeable Proton Batteries

Rechargeable proton batteries have been regarded as a promising technology for next-generation energy storage devices, due to the smallest size, lightest weight, ultrafast diffusion kinetics and negligible cost of proton as charge carriers. Nevertheless, a proton battery possessing both high energy and power density is yet achieved. In addition, poor cycling stability is another major challenge making the lifespan of proton batteries unsatisfactory. These issues have motivated extensive research into electrode materials. Nonetheless, the design of electrode-electrolyte interphase and electrolytes is underdeveloped for solving the challenges. In this review, we summarize the development of interphase and electrolytes for proton batteries and elaborate on their importance in enhancing the energy density, power density and battery lifespan. The fundamental understanding of interphase is reviewed with respect to the desolvation process, interfacial reaction kinetics, solvent-electrode interactions, and analysis techniques. We categorize the currently used electrolytes according to their physicochemical properties and analyze their electrochemical potential window, solvent (e.g., water) activities, ionic conductivity, thermal stability, and safety. Finally, we offer our views on the challenges and opportunities toward the future research for both interphase and electrolytes for achieving high-performance proton batteries for energy storage.

Bifunctional Alloy/Solid-Electrolyte Interphase Layer for Enhanced Potassium Metal Batteries Via Prepassivation

Potassium (K) metal batteries have attracted great attention owing to their low price, widespread distribution, and comparable energy density. However, the arbitrary dendrite growth and side reactions of K metal are attributed to high environmental sensitivity, which is the Achilles' heel of its commercial development. Interface engineering between the current collector and K metal can tailor the surface properties for K-ion flux accommodation, dendrite growth inhibition, parasitic reaction suppression, etc. We have designed bifunctional layers via prepassivation, which can be recognized as an O/F-rich Sn-K alloy and a preformed solid-electrolyte interphase (SEI) layer. This Sn-K alloy with high substrate-related binding energy and Fermi level demonstrates strong potassiophilicity to homogeneously guide K metal deposition. Simultaneously, the preformed SEI layer can effectually eliminate side reactions initially, which is beneficial for the spatially and temporally KF-rich SEI layer on K metal. K metal deposition and protection can be implemented by the bifunctional layers, delivering great performance with a low nucleation overpotential of 0.066 V, a high average Coulombic efficiency of 99.1%, and durable stability of more than 900 h (1 mA cm-2, 1 mAh cm-2). Furthermore, the high-voltage platform, energy, and power densities of K metal batteries can be realized with a conventional Prussian blue analogue cathode. This work provides a paradigm to passivate fragile interfaces for alkali metal anodes.

Wet-Chemical Synthesis of TiO2/PVDF Membrane for Energy Applications

To satisfy the ever-increasing energy demands, it is of the utmost importance to develop electrochemical materials capable of producing and storing energy in a highly efficient manner. Titanium dioxide (TiO₂) has recently emerged as a promising choice in this field due to its non-toxicity, low cost, and eco-friendliness, in addition to its porosity, large surface area, good mechanical strength, and remarkable transport properties. Here, we present titanium dioxide nanoplates/polyvinylidene fluoride (TiO₂/PVDF) membranes prepared by a straightforward hydrothermal strategy and vacuum filtration process. The as-synthesized TiO₂/PVDF membrane was applied for energy storage applications. The fabricated TiO₂/PVDF membrane served as the negative electrode for supercapacitors (SCs). The electrochemical properties of a TiO₂/PVDF membrane were explored in an aqueous 6 M KOH electrolyte that exhibited good energy storage performance. Precisely, the TiO₂/PVDF membrane delivered a high specific capacitance of 283.74 F/g at 1 A/g and maintained capacitance retention of 91% after 8000 cycles. Thanks to the synergistic effect of TiO₂ and PVDF, the TiO₂/PVDF membrane provided superior electrochemical performance as an electrode for a supercapacitor. These superior properties will likely be used in next-generation energy storage technologies.