Rechargeable magnesium batteries (RMBs) are gaining attention due to their high energy density, use of abundant materials, and safe metal anodes. However, the lack of suitable cathode materials remains a key challenge. This review discusses the interfacial chemistry between cathodes and electrolytes in RMBs, focusing on the solvation behavior of Mg²⁺, which significantly affects interfacial reactions. Strategies to enhance Mg²⁺ desolvation and intercalation are explored, along with efforts to improve cathode-electrolyte compatibility through electrolyte development and interfacial engineering. The review highlights the importance of a stable interface and fast interfacial chemistry for RMBs. It also discusses the role of chloride species in facilitating Mg²⁺ insertion and the formation of interfacial layers that enhance performance. The review emphasizes the need for further research on cathode materials and interfacial engineering to overcome challenges in RMB development. Key challenges include the high energy barrier for Mg²⁺ transport, the need for efficient electrolytes, and the development of stable interfacial layers. The review concludes with perspectives on future research directions for RMBs.Rechargeable magnesium batteries (RMBs) are gaining attention due to their high energy density, use of abundant materials, and safe metal anodes. However, the lack of suitable cathode materials remains a key challenge. This review discusses the interfacial chemistry between cathodes and electrolytes in RMBs, focusing on the solvation behavior of Mg²⁺, which significantly affects interfacial reactions. Strategies to enhance Mg²⁺ desolvation and intercalation are explored, along with efforts to improve cathode-electrolyte compatibility through electrolyte development and interfacial engineering. The review highlights the importance of a stable interface and fast interfacial chemistry for RMBs. It also discusses the role of chloride species in facilitating Mg²⁺ insertion and the formation of interfacial layers that enhance performance. The review emphasizes the need for further research on cathode materials and interfacial engineering to overcome challenges in RMB development. Key challenges include the high energy barrier for Mg²⁺ transport, the need for efficient electrolytes, and the development of stable interfacial layers. The review concludes with perspectives on future research directions for RMBs.