Non-metallic ion batteries beyond convention: fundamentals, material innovations, and pathways to sustainable energy storage

Abstract

The global shift towards renewable energy sources necessitates the progress of safe, sustainable, and high-performance energy storage technologies. Traditional metal-ion batteries, although dominant in current applications, face significant limitations, including resource scarcity, high costs, environmental impact, and safety risks. In response, non-metal ion batteries (NMIBs) have emerged as a promising class of energy storage systems that utilize non-metallic charge carriers, including protons (H⁺), hydronium (H₃O⁺), ammonium (NH₄⁺), halide ions (Cl⁻, Br⁻), and organic ions, as alternatives to metal ions. These systems offer numerous advantages, including fast ion diffusion, biocompatibility, design flexibility, and a reduced ecological footprint. This review presents a comprehensive overview of NMIBs, detailing their fundamental working principles, classification, electrode and electrolyte materials, electrochemical performance, and the distinct mechanisms underlying their operation. Special emphasis is placed on recent advances in advanced functional materials, such as MXenes, MOFs, and redox-active organics, that enhance ionic conductivity and cycle stability. The review also outlines current challenges and research gaps while providing strategic insights into the future direction of this emerging field. By highlighting the potential of NMIBs as viable successors to traditional technologies, this work contributes to the broader vision of achieving sustainable and scalable energy storage solutions.