High Ionic Conductivity Motivated by Multiple Ion‐Transport Channels in 2D MOF‐Based Lithium Solid State Battery

Abstract

Metal‐organic frameworks (MOFs) have been proposed as novel fillers for constructing polymer solid electrolytes based composite electrolytes. However, MOFs are generally used as passive fillers, in‐depth revealing the binding mode between MOFs and polyethylene oxide (PEO), the critical role of MOFs in facilitating Li+ transport in solid electrolytes is full of challenges. Herein, inspired by density functional theory (DFT) the 2D‐MOF with rich unsaturated metal coordination sites that can bind the O atom in PEO through the metal–oxygen bond, anchor TFSI− to release Li+, resulting in a remarkable Li+ transference number of 0.58, is reported according well with the experimental results and molecular dynamics (MD) simulation. Impressively, after the introduction of the 2D‐MOF, the Li+ can rapidly hop along the benzene ring center within the 2D‐MOF plane, and the interface between the benzene ring and PEO can also serve as a fast Li+ migration pathway, delivering multiple ion‐transport channels, which present a high ion conductivity of 4.6 × 10−5 S cm−1 (25 °C). The lithium symmetric battery is stable for 1300 h at 60 °C, 0.1 mA cm−2. The assembled lithium metal solid state battery maintains high capacity of 162.8 mAh g−1 after 500 cycles at 60 °C and 0.5 C. This multiple ion‐transport channels approach brings new ideas for designing advanced solid electrolytes.

Regulating Metal Centers of MOF-74 Promotes PEO-Based Electrolytes for All-Solid-State Lithium-Metal Batteries

“…16,22,28 It should be noted that MOF materials were usually vacuum heat-treated to expose open metal sites before use. 33,38,44 SEM images (Figure S2) reveal that the morphologies of 15%Cu-MOF/P−Li and 15%Ni-MOF/P−Li are flat and smooth, similar to P−Li, and Cu/Ni elements are uniformly distributed on the surface of SCEs, confirming the uniform dispersion of MOF-74 particles in the PEO matrix. 37 We found that excessive Cu-MOF-74 causes particle aggregation, which degrades the Li-ion transport efficiency.…”

“…Solution casting was used to prepare the PEO-based SCEs as shown in Figure a. ,, It should be noted that MOF materials were usually vacuum heat-treated to expose open metal sites before use. ,, SEM images (Figure S2) reveal that the morphologies of 15%Cu-MOF/P–Li and 15%Ni-MOF/P–Li are flat and smooth, similar to P–Li, and Cu/Ni elements are uniformly distributed on the surface of SCEs, confirming the uniform dispersion of MOF-74 particles in the PEO matrix …”

“…The bands at 1143.49, 1091.08, and 1058.71 cm −1 in the FT-IR spectrum (Figure 2e) of PEO powders are assigned to the asymmetric stretching C−O−C, and a red shift of the FT-IR spectrum of the P−Li was observed due to the induction effect of the C−F bond after LiTFSI dissolution. 51,52 The addition of Cu-MOF-74 causes the blue shift for the stretching vibration peaks of the C−O and C−F groups, which can be attributed to the chelation between Cu(II) and etheroxygen groups containing lone pair electrons in the PEO molecular chain; 44,48,53 the corresponding absorption shifted from 1134.77, 1095.97, and 1055.38 cm −1 to 1135.70, 1096.23, and 1055.99 cm −1 from 1185.84 to 1186.51 cm −1 , severally. 54,55 On the contrary, there were no noticeable shifts in the FT-IR spectra of 15%Ni-MOF/P−Li (Figure S5a), indicating that the interaction between Ni-MOF-74 and the PEO matrix is weaker than that of Cu-MOF-74.…”

Toward Enhancing Performance of Electromagnetic Wave Absorption for Conductive Metal–Organic Frameworks: Nanostructure Engineering or Crystal Morphology Controlling

“…Metal−organic frameworks (MOFs), a new type of periodic porous crystal material, possessing large specific surface area, high porosity, and controllable chemical compositions and structures, have potential applications in many fields such as ion conduction, 14,15 energy storage, 16 and EMW absorption. 17−20 However, the electrical insulation of most MOFs hinders their application in EMW absorption materials.…”

“…Metal–organic frameworks (MOFs), a new type of periodic porous crystal material, possessing large specific surface area, high porosity, and controllable chemical compositions and structures, have potential applications in many fields such as ion conduction, , energy storage, and EMW absorption. − However, the electrical insulation of most MOFs hinders their application in EMW absorption materials. To improve the EMW absorption ability of MOF-based materials, high-temperature calcination in an inert atmosphere is usually adopted to convert the MOF template into a porous carbon-based material containing metal/metallic compounds .…”