Advanced characterization techniques for phosphate cathodes in aqueous rechargeable zinc-based batteries

Aqueous zinc-based batteries are emerging as highly promising alternatives to commercially successful lithium-ion batteries, particularly for large-scale energy storage in power stations. Phosphate cathodes have garnered significant research interest owing to their adjustable operation potential, electrochemical stability, high theoretical capacity, and environmental robustness. However, their application is impeded by various challenges, and research progress is hindered by unclear mechanisms. In this review, the various categories of phosphate materials as zinc-based battery cathodes are first summarized according to their structure and their corresponding electrochemical performance. Then, the current advances to reveal the Zn²⁺ storage mechanisms in phosphate cathodes by using advanced characterization techniques are discussed. Finally, some critical perspectives on the characterization techniques used in zinc-based batteries and the application potential of phosphates are provided. This review aims to guide researchers toward advanced characterization technologies that can address key challenges, thereby accelerating the practical application of phosphate cathodes in zinc-based batteries for large-scale energy storage.