Abstract: High-entropy materials (HEMs), an innovative class of materials with complex stoichiometry, have recently garnered considerable attention in energy storage applications. While their multi-element compositions (five or more principal elements in nearly equiatomic proportions) confer unique advantages such as high configurational entropy, lattice distortion, and synergistic cocktail effects, the fundamental understanding of structure–property relationships in battery systems remains fragmented across existing studies. This review addresses critical research gaps by proposing a multidimensional design paradigm that systematically integrates synergistic mechanisms spanning cathodes, anodes, electrolytes, and electrocatalysts. We provide an in-depth analysis of HEMs’ thermodynamic/kinetic stabilization principles and structure-regulated electrochemical properties, integrating and establishing quantitative correlations between entropy-driven phase stability and charge transport dynamics. By summarizing the performance benchmarking results of lithium/sodium/potassium-ion battery components, we reveal how entropy-mediated structural tailoring enhances cycle stability and ionic conductivity. Notably, we pioneer the systematic association of high-entropy effects to electrochemical interfaces, demonstrating their unique potential in stabilizing solid-electrolyte interphases and suppressing transition metal dissolution. Emerging opportunities in machine learning-driven composition screening and sustainable manufacturing are discussed alongside critical challenges, including performance variability metrics and cost-benefit analysis for industrial implementation. This work provides both fundamental insights and practical guidelines for advancing HEMs toward next-generation battery technologies.