Amphiphile Confined Water Electrolyte Enables Facilitated Cation Transport through Nanometric Water Channels

The prevalence of bulky cation hydration shells in aqueous electrolytes often leads to sluggish cation transport and aggressive interfacial reactions. Here, we propose an amphiphile confined water electrolyte in which the aqueous phase reorganizes into nanoscale domains within an amphiphilic matrix, resulting in decoupling of the cation transport in water channels from the inert amphiphile phase. To achieve this, molecular screening converged on linear n-alkanols that combine one hydroxyl head (-OH) with a hydrophobic n-alkyl [-R(CH₂)-CH₃] tail. The hydrophilic head effectively binds with the water molecules residing around the cations and disrupts the water hydrogen-bond network, whereas the hydrophobic tails pack into a continuous matrix that expels excess water from the bulk phase. Via further tuning of the water-to-amphiphile ratio, nanometric water channels at a size of ∼1.8 nm are formed, yielding a Zn²⁺ transference number of 0.79. The Zn||KFeMnHCF full cell was able to cycle for 15,000 cycles with a capacity retention of 78.4%, and a discharge capacity of 68.4 mAh/g can be delivered even at -60 °C. This work demonstrates a successful application of amphiphile-driven structuring to confine the aqueous phase in an electrolyte, providing a viable route to mitigate cation migration penalties and reduce water parasitic reactions.