Abstract: The transition toward clean energy systems is accelerating worldwide, driven by global “dual-carbon” targets. As a critical enabling technology for the efficient grid integration and large-scale utilization of renewable energy, large-scale energy storage technology has become a major research focus in the global energy field. Among such emerging technologies, aqueous zinc-ion batteries (AZIBs) have attracted extensive attention owing to their high theoretical specific capacity, low material cost, superior safety, and good environmental compatibility, as well as to the abundance of zinc resources. These features make AZIBs one of the most promising next-generation technologies, providing them with considerable potential to replace conventional lithium-ion batteries in applications such as low-speed electric vehicles and distributed energy storage systems. In this review, the fundamental components and working principles of AZIBs based on the “Zn²⁺ stripping-plating/insertion-extraction” mechanism are systematically summarized, and the key technological breakthroughs achieved during their development are comprehensively reviewed. Furthermore, the critical scientific issues and technical challenges hindering their practical application and industrialization are clearly identified. From the perspective of cathode materials, poor electronic conductivity and sluggish zinc-ion diffusion kinetics often result in a relatively low practical specific capacity and structural instability during long-term cycling. On the anode side, zinc metal generally suffers from severe dendrite growth and insufficient cycling stability, accompanied by parasitic reactions such as hydrogen evolution, zinc corrosion, and passivation layer formation, which significantly shorten the lifespan of batteries. At the electrolyte level, limitations such as a narrow electrochemical stability window, difficulty in regulating ionic conductivity, and poor electrode–electrolyte interfacial compatibility further restrict improvement in energy density and cycling performance. Among the various strategies proposed to enhance the comprehensive performance of AZIBs, the construction and optimization of composite electrolytes have emerged as a research hotspot owing to their operational simplicity, controllable preparation cost, scalability, and pronounced performance enhancement. This review systematically summarizes the progress of recent research on electrolyte additives by considering the core requirements of electrolyte systems in AZIBs. Through an extensive investigation and analysis of relevant literature, electrolyte additives are categorized into three main types: ionic, organic, and inorganic additives. This paper elaborates on the structure–function relationships, working mechanisms, and research progress pertaining to these three distinct types of electrolyte additives, highlighting their crucial roles in improving electrode–electrolyte interfacial compatibility, expanding electrolyte stability windows, suppressing zinc dendrite growth and parasitic reactions, and enhancing cycling stability and rate performance. Based on the current research status, this paper suggests the future developmental directions of electrolyte additives for aqueous zinc-ion batteries (AZIBs). This area can be systematically advanced from two dimensions—the technical and ecological-application dimensions—with the core goal of green recycling. Research should be conducted following the progressive technical chain of “in-situ characterization − theoretical calculation − machine learning”. This comprehensive review and mechanistic analysis not only provide theoretical guidance and technical references for the rational design of advanced composite electrolyte systems but also contribute to significantly improving the overall performance of AZIBs, thereby accelerating the development of next-generation low-cost and high-safety energy storage technologies and supporting the global clean energy transition.