Emerging nanomaterials for energy storage: A critical review of metrics, hotspots, and future directions

The accelerating depletion of fossil resources and the mounting environmental and climate pressures make the development of high-performance electrochemical energy-storage (EES) technologies an urgent priority. Anchored in the tri-axis of materials – mechanisms – hotspots/trends, this review systematically analyses the structure-property-performance relationships of five emerging classes of nanomaterials—COFs, MOFs, MXenes, PCMs and flaccid antiferroelectrics—in battery and capacitor configurations. Drawing on more than 300 recent publications, we construct a unified evaluation framework built around ten intrinsic parameters—pseudocapacitance, structural gradients/disorder, bond-length or interlayer-spacing regulation, high specific surface area, vacancy effects, ion solubility, dielectric breakdown strength, doping effects, electron-transfer effects and high-entropy strategies—and benchmark them against practical engineering metrics such as energy density, power density, cycle stability and safety. Within this framework, we distil five current research hotspots—biochemical energy storage, supercapacitors, dielectric capacitors, information encryption & decryption, and machine learning & programming—and relate them to five emerging trends: (i) anti-corrosion and acid/alkali-resistant materials, (ii) battery operation under extreme conditions, (iii) fast-charging capability, (iv) wearable and flexible energy-storage systems, and (v) next-generation storage batteries. These insights illustrate how evolving application demands are reshaping both material selection and evaluation strategies. Finally, we outline four strategic directions—green scalable synthesis, in-situ high-throughput characterization, data-driven materials design and device-level integration—that can accelerate the optimization and deployment of novel energy-storage nanomaterials. By providing an actionable assessment toolbox and a forward-looking roadmap, this review aims to guide the rational ranking of material candidates and engineering approaches toward the next generation of sustainable EES systems.