Progress of 3D conductive framework for Na metal anode

Sodium is considered an ideal anode material for high-energy batteries because of its low cost, high natural abundance, low redox potential (−2.71 V vs SHE), and high theoretical specific capacity (1166 mA·h·g⁻¹). However, due to the high reactivity, sodium rapidly reacts with the electrolyte to form an unstable solid electrolyte interface (SEI) layer during stripping/plating cycling. In addition, due to the large size change of sodium, the SEI layer repeatedly breaks and reassembles, resulting in the continuous consumption of sodium and electrolyte, as well as low coulombic efficiency and rapid capacity loss. Simultaneously, due to an uneven electric field distribution on sodium, numerous sodium dendrites generate during the repeated plating/stripping cycles. The growing Na dendrites easily pierce the separator, causing a short circuit and a series of safety issues. The above issues lead to the deterioration of battery performance and safety risks, thus considerably hindering the application of sodium metal batteries. Various studies have been conducted to solve these issues, including electrolyte engineering, artificial SEI layers, current collector and interlayer engineering, solid-state electrolyte engineering, and three-dimensional (3D) frameworks for sodium metal. Among various improvement strategies, the construction of a 3D conductive framework can effectively reduce the local current density, decrease nuclear energy, inhibit Na dendrite growth, and impede volume expansion, thus having a great potential in future applications. In this study, the current research progress in using various 3D conductive frameworks to improve the cycling stability of a sodium metal battery is reviewed, including carbon-based, metal-based, and MXene-based frameworks. Simultaneously, the pros and cons of different 3D conductive framework technologies in recent years are summarized and classified, and the electrochemical performance parameters of different 3D conductive frameworks for sodium metal batteries are compared. Finally, the development prospect and direction of 3D conductive frameworks in sodium metal anodes are discussed from basic research and practical applications. This review provides deeper insights into building more comprehensive and efficient sodium metal anodes. The 3D conductive framework technology can remarkably improve the cycle life and safety of a sodium metal battery. Multistrategy joint research methods will facilitate the practical applications of a sodium metal battery. Further exploration of the deposition behavior of sodium metal is required in the future, and we believe that it can definitely achieve commercial applications with continuous efforts.