金属有机骨架材料在金属锂电池界面的应用

Application of Metal-Organic Frameworks to the Interface of Lithium Metal Batteries

金属锂电池是下一代高能量密度电池体系的代表。然而,高比能金属锂电池的发展受到界面诸多问题的限制,如:金属锂负极枝晶生长、隔膜界面兼容性、正极界面不稳定等,影响了金属锂电池的界面传质传荷过程,并导致金属锂界面环境恶化、电池的容量衰减、安全性能下降等问题。金属有机骨架(MOF)是一种具有稳定多孔结构的有机无机杂化材料,近年来在高比能金属锂电池领域受到广泛关注。其多孔结构与开放的金属位点(OMs)提供了优异的离子电导率,稳定的空间结构提供了较高的机械强度,多样的官能团与金属节点带来丰富的功能性。本文分析了金属锂电池界面的主要挑战,结合金属锂界面的成核模型,总结了MOF及其衍生材料在解决锂金属负极界面、隔膜界面、以及正负极界面稳定性相互作用等方面的研究进展和作用机理,为解决高比能金属锂电池界面失稳问题提供了解决途径,并展望了MOF基材料的设计与发展方向。

Lithium metal batteries(LMBs) are representative systems for high-energy-density batteries. The design of LMBs with high capacity and high cycle stability is imperative. However, the development of LMBs is hindered by typical interface-related problems such as lithium dendrite growth, incompatible separator interfaces, and unstable cathode interfaces because of the inhomogeneous ionic flux and composition distribution. The intrinsic instability significantly hinders electron/ion transfer at the interface, causing serious issues such as dendrite growth, volume changes, low coulombic efficiency, dead lithium, interface deterioration, capacity degradation, and loss of safety. Metal-organic frameworks(MOFs) are organic-inorganic hybrid materials with a stable highly porous structure, which can allow for highlyefficient gas adsorption, separation and purification, catalysis, etc., in addition to facilitating their application in nanomedicine and other fields. In recent years, MOFs have attracted much attention in the field of LMBs as a possible solution to the typical interface problems abovementioned. The porous structure and open metal sites(OMs) of MOFs provide an excellent interface structure for uniform and high ionic conductivity. As additional bonus, the stable structure provides high mechanical strength with different functional groups and metal sites, resulting in significant versatility of functionality for interface stabilization. MOFs are usually synthesized by hydrothermal/solvothermal, microwave-assisted, electrochemical, and spray-drying methods. The excellent properties of MOFs have prompted researchers to pursue their rational design and modification. Much progress has been made in this direction, and exemplary investigations have been performed to solve the abovementioned interfacial problems encountered with LMBs. Consequently, metallic lithium deposition frameworks, artificial solid electrolyte interface films, electrolyte additives, separator materials, cathode materials for lithium-sulfur batteries, and lithium-air batteries have been developed. However, there is a long way to go before the commercialization of batteries based on MOF materials. In practical, more complex electrochemical reactions occur at the lithium-metal interface, and the operating conditions(temperature, over charging/discharging, external stress, etc.) vary widely. Moreover, MOFs as electrode materials have intrinsic drawbacks, including structural collapse, pore blockage, and low inherent conductivity during the cycles. Based on these interfacial challenges, in LMBs, it introduces the structural characterization and optimization of MOFs and the key chemical components that determines the MOFs of structure(central atom, organic ligand, etc.). Subsequently, we summarized the growth mechanism of lithium dendrites and discussed the applications of MOFs and their derivatives to battery cathodes, separators, anodes, and electrolytes.The manuscript contents would be a guide to solve the problem of unstable interfaces in LMBs by the use of MOFs. Furthermore, the prospects and rational design of MOF-based materials are discussed.