钠金属负极人工界面保护层的研究进展

Research progress on sodium metal anode modified by artificial interface layer

钠金属负极由于其高的比容量、低的氧化还原电位以及资源优势被认为是钠电池极佳的负极材料。然而,不稳定的固体电解质界面(SEI)以及钠枝晶生长问题严重阻碍了其实际应用。因此,采用适当的保护策略实现钠金属负极稳定及高效循环是非常必要的。通常在钠金属负极表面构建人工界面层不仅可以有效实现钠均匀沉积/剥离,而且可有效缓解钠金属负极在电化学过程中的体积变化以及抑制钠枝晶生长。为此,该综述归纳总结了人工界面层策略改善钠金属负极的研究进展。首先讨论了自发形成的SEI膜的基本性质,其存在稳定性差、韧性差、机械强度低等问题。针对此,提出构建无机、有机和无机-有机复合人工界面层保护钠金属负极,实现无枝晶钠沉积/剥离。含钠无机材料通常具有高剪切模量、耐腐蚀、结构稳定、高离子电导率等优点,但脆性大;有机材料通常具有结构可设计性、官能团多样性以及高机械韧性特点,但稳定性较弱;无机-有机复合保护膜结合了上述两者的优势,可构建综合性能优异的人工界面层。文中详细阐述了这三种人工界面膜的实施方法与改性效果。最后,建议对人工界面膜持续优化以及采用先进表征技术、理论计算和模拟等深入研究界面稳定性机理。

Sodium metal anode is considered as the superior anode material due to its high specific capacity,low redox potential,and abundant resources.However,the problems of unstable solid electrolyte interface(SEI)and sodium dendritic growth have seriously hindered its practical application.It is thus essential to adopt appropriate strategies to achieve stable and efficient use of sodium metal anode.Generally,the construction of an artificial interface layer on the surface of the sodium metal anode can not only effectively achieve uniform sodium deposition,but also effectively mitigate the volume change and sodium dendrite growth during the electrochemical process.Therefore,this review focuses on the research progress on sodium metal anode modified by artificial interface layer.Firstly,the basic properties of spontaneously formed SEI films are discussed.Generally,they suffer from poor stability,poor toughness and low mechanical strength.To address these issues,the construction of inorganic,organic and inorganic-organic artificial interfacial layers to protect sodium metal anodes for dendrite-free sodium deposition/exfoliation is proposed.Sodium-contained inorganic materials usually have the advantages of high shear modulus,corrosion resistance,structural stability,and high ionic conductivity,but are brittle;organic materials usually have structural designability,functional group diversity,and high mechanical toughness,but are poorly stable;the inorganic-organic composite protective film combines the advantages of the above two and can build an artificial interface layer with excellent comprehensive performance.The implementation methods and modification effects of these three artificial interface films are elaborated in this paper.Finally,it is suggested to continuously optimize the artificial interfacial films as well as to use advanced characterization techniques,theoretical calculations and simulations to study the mechanisms of interfacial stability in depth.