Binder-free electrodes for advanced potassium-ion batteries: A review

Abstract

Potassium-ion batteries (PIBs) have attracted enormous attention due to the abundance of potassium resources, low cost, fast ionic conductivity of electrolyte and relatively high operating voltage. Despite great efforts and progress, researches on PIBs are still at the initial stage, especially in the emerging field of flexible and wearable PIBs. The inevitable challenges for PIBs include low reversible capacity, unsatisfactory cycling stability and insufficient energy density, the solution to which mostly relies on designing advanced electrodes. Binder-free electrodes have emerged as promising electrode architecture for PIBs. Such electrodes avoid the use of insulating binders, which can be designed with various synergistic functional materials to address the aforementioned PIB issues and be endowed with flexibility/wearability. In this review, we mainly summarize the recent progress on binder-free electrodes for PIBs, with the focus on the methodologies, detailed strategies and functional materials for electrode construction. One strategy for binder-free electrodes is to assemble free-standing architecture with the help of carbon nanotubes (CNTs), graphitic fibers, and other carbon or mechanically robust materials, either alone or in combination. The other effective strategy is current collector substrate-assisted direct growth, including the use of carbon cloth, metal, MXenes and other conductive substrates. Additionally, challenges and research opportunities are put forward at the end as the guidance for future development of binder-free PIB devices.