The notorious growth of sodium dendrites and significant volume fluctuations have posed substantial challenges to the practical application of sodium metal anodes. In this work, an aerogel composed of MgF₂ nanoparticles (NPs) onto a three-dimensional (3D) printed reduced graphene oxide (rGO) (MgF₂/rGO) monolith was employed as a scaffold for sodium metal anodes. During the initial discharge process, the MgF₂ NPs underwent an electrochemical in-situ conversion into NaF and sodiophilic Mg NPs, which act as the Na metal nucleation centers and contribute to the formation of a stable solid electrolyte interface (SEI) layer. Benefiting from these synergistic effects, the 3D printed MgF₂/rGO electrode exhibits a high Coulombic efficiency of 99.49% after 1200 cycles at 0.5 mA·cm⁻² with 1 mAh·cm⁻². It also shows a long cycle lifespan of 2500 h with a high capacity of 10 mAh·cm⁻² at 5 mA·cm⁻². Moreover, when assembled into a full cell with a Na@MgF₂/rGO anode and a Na₃V₂(PO₄)₃@C-rGO cathode, the cell delivers an extended cycle life of 3500 cycles at 1 C, preserving a reversible capacity of 86.98 mAh·g⁻¹. This work paves the way for utilization of 3D printed metal-fluorides to enhance the electrochemical performance of the sodium metal anodes.

Aqueous zinc-ion batteries (AZIBs) are an appealing battery system due to their low cost, intrinsic safety, and environmental-friendliness, while their application is plagued by the obstacles from the cathode, electrolyte, and zinc anode. Summarizing the design principles and strategies toward the optimization of cathode, electrolyte, and zinc anode is crucial for the development of AZIBs. Herein, we present a comprehensive analysis of the design principles and promising strategies toward the improvement of AZIBs. Firstly, the various reaction mechanisms are summarized and the existing issues associated with the cathode, electrolyte, and zinc anode are discussed to guide the rational design of AZIBs. Subsequently, we provide an in-depth and comprehensive discussion on the design principles and strategies for the electrodes/electrolyte/separator optimization, and analyze the advantages and disadvantages of various strategies. Importantly, the design principles and strategies of the newly appeared conversion-type AZIBs, such as Zn-S battery and Zn-Se battery, are also discussed and analyzed. The effect of design strategies on the electrochemical performance and the relationship between the current issues and strategies are also unveiled in detail. Finally, some research trends and perspectives are provided for designing better AZIBs.