金属-有机框架材料基固态电解质快离子导体的功能化设计及其在锂金属电池中的应用

Functional Design of Metal-Organic Framework Based Solid-State Electrolytes as Superionic Conductors and Their Application in Lithium Metal Batteries

摘要:

固态电池与传统的锂离子电池和液态电池相比，在提高能量密度和安全性方面具有更大的潜力。然而，现有的固态电解质在提升电导率和克服锂枝晶产生等问题时遇到不少挑战。为解决此问题，选用MIL-101(Cr)的金属-有机框架材料（Metal-organic framework，MOF）作为主体材料，将高电导率的有机单体1,3-二氧戊环（DOL）负载在MIL-101(Cr)上，设计制备了一种新型固态电解质。该方法不仅解决了DOL电化学稳定性差的问题，还充分利用了MIL-101(Cr)富含不饱和金属位点的特点，限制了阴离子的自由移动，加速了锂离子的解离过程，从而提升锂离子迁移数。结果表明，MIL-101(Cr)@DOL材料表现出优异的离子电导率（0.92 mS?cm^-1），稳定的电化学窗口（4.65 V）和较高的锂离子迁移数（0.57）。此外，使用MIL-101(Cr)@DOL材料组装的Li//LiFePO₄电池也表现出了优异的倍率和循环性能，在0.2 C下经过140次循环后放电比容量仍然维持在128.9 mAh?g^-1，容量保持率达到82.9%。将有机单体DOL负载在MIL-101(Cr)上合成的新型固态电解质的方法，对于开发新型的固态电解质材料和寻找新的离子传导机制起到了启发的作用，为提升锂金属电池性能提供了新的途径和可能性。

Abstract:

Compared to traditional lithium-ion batteries and liquid batteries， solid-state batteries hold greater potential for enhancing energy density and safety. However， existing solid-state electrolytes face numerous challenges in improving electrical conductivity and overcoming the issue of lithium dendrite formation. To solve this problem， MIL-101（Cr） Metal-organic framework （MOF） was selected as the main material， and the organic monomer 1， 3-dioxane （DOL） with high conductivity was loaded on MIL-101（Cr） to design and prepare a new solid electrolyte. This method not only solves the problem of poor electrochemical stability of DOL， but also makes full use of the characteristics of MIL-101（Cr） rich in unsaturated metal sites， which limits the free movement of anions， accelerates the dissociation process of lithium ions， and thus increases the migration number of lithium ions. The results show that MIL-101（Cr）@DOL exhibits excellent ionic conductivity （0.92 mS?cm^-1）， stable electrochemical window （4.65 V） and high lithium ion migration number （0.57）. In addition， the Li//LiFePO₄ battery assembled with MIL-101（Cr）@DOL also showed excellent rate and cycle performance， maintaining the specific discharge capacity of 128.9 mAh?g^-1 after 140 cycles at 0.2 C， and the capacity retention rate reached 82.9%. The new solid electrolyte synthesized by loading organic monomer DOL on MIL-101（Cr） is proposed in this study， which plays an inspiring role in the development of new solid electrolyte materials and the search for new ion conduction mechanism， and provides a new way and possibility for improving the performance of lithium metal batteries.