Exploring multi-segment electrolyte design strategies for portable high-energy aqueous batteries

The limited energy density resulting from the suppressed operating voltage of aqueous batteries presents a significant challenge when it comes to practical applications. To address this issue, various strategies have been proposed to expand the electrochemical potential window of aqueous electrolytes, with a primary focus on inhibiting the hydrogen and oxygen evolution. It is crucial to note that these reactions are closely linked to the pH values. Consequently, adopting a pH design that decouples the acidity of anolyte and basicity of catholyte proves to be advantageous in overcoming the thermodynamic limitations associated with water decomposition and achieving a wider electrochemical stability window. Fortunately, this approach of bipolarized pH values optimizes the redox potentials at anode and cathode, resulting in a lower anodic potential and a higher cathodic potential. This optimization leads to an increase in battery's working voltage. Embracing this concept holds great promises for developing portable high-energy aqueous batteries, thus facilitating their practical applications. In this review, we delve into the research surrounding this innovative electrolyte engineering technology. We aim to provide a clear definition, highlight its efficacy, addressing any remaining challenges, propose potential solutions, and present a roadmap for the portable implementation of multi-segment electrolyte technology.