As the global energy landscape transitions toward cleaner and more sustainable sources, the demand for efficient energy storage systems has become increasingly pressing. Lithium-ion batteries (LIBs) are among the most commercially successful electrochemical energy storage technologies due to their high energy density, long cycle life, and relatively low environmental impact, and are widely deployed in consumer electronics, electric vehicles, and grid-scale energy storage systems. As a core component of LIBs, cathode materials largely determine the energy density, cycling stability, and safety of the battery. This review systematically examines the developmental history and recent research progress of five representative LIB cathode materials, including lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, high-nickel ternary materials, and lithium-rich manganese-based materials, addressing the incomplete and outdated perspectives in existing literature. The crystal structures, key scientific challenges, and recent modification strategies, such as surface coating, bulk doping, structural design, and interface engineering, are comprehensively discussed. By integrating multiscale approaches, including in situ characterization techniques and machine-learning-assisted analysis, this review connects historical developments with emerging research frontiers and provides guidance for the rational design of next-generation high-performance, safe, and cost-effective LIB cathode materials.

With the growing global energy demand and the pressing need for a clean energy transition, supercapacitors (SCs) have demonstrated significant application potential in electric vehicles, wearable electronics, and renewable energy storage systems owing to their rapid charge–discharge capability, exceptional power density, and prolonged cycle life. The improvement of their overall performance fundamentally depends on the synergistic design of electrode materials and electrolyte systems, as well as the precise regulation of the electrode-electrolyte interface. This review focuses on the key components of supercapacitors, systematically reviewing the design strategies of high-performance electrode materials, outlining recent advances in novel electrolyte systems, and comprehensively discussing the critical roles of interfacial reinforcement and optimization in enhancing device energy density, power performance, and cycling stability. Furthermore, interfacial engineering strategies and innovations in device architecture are proposed to address interfacial degradation in flexible SCs under mechanical stress. Finally, key future research directions are highlighted, including the development of high-voltage and wide-temperature-range electrolyte systems and the integrated advancement of multiscale in situ characterization techniques and theoretical modeling. This review aims to provide theoretical guidance and innovative strategies for material design, contributing toward the realization of next-generation supercapacitors with enhanced energy density and reliability.