Poly­(ethylene oxide) (PEO)-based polymer electrolytes have shown extraordinary promise for all-solid-state lithium batteries; however, the practical application was severely restricted by their low ionic conductivity. In this work, the robust pores of HKUST-1­(Cu) were first filled by a lithium-containing ionic liquid (Li-IL) to form ion-conductive Li-IL@HKUST-1. Subsequently, flexible composite polymer electrolytes (CPEs) were constructed via a solution-casting approach upon the incorporation of Li-IL@HKUST-1 with PEO. The as-synthesized CPE membrane showed a high ionic conductivity of 1.20 × 10–4 S cm–1 at 30 °C compared to 9.76 × 10–6 S cm–1 for the PEO-only electrolyte. Furthermore, the assembled LiFePO4/Li solid-state batteries delivered a stable reversible capacity of 136.2 mAh g–1 with a capacity retention of 92% after 100 cycles at a high current density of 1 C (60 °C). The excellent electrochemical performance was mainly attributed to the combination of Li-IL@HKUST-1 and the PEO matrix, which effectively reinforced the polymer matrix and facilitated the fast transport of lithium ions. The present research provides an effective strategy for building high-performance all-solid-state lithium batteries.

As a superconductive metal-organic framework (MOF) material, Cu-BHT (BHT: benzenehexathiol) can demonstrate outstanding electrochemical properties owing to the potential redox reactions of the cuprous ions, sulfur species and benzene rings...

Recently, carboxylate metal‐organic framework (MOF) materials were reported to perform well as anode materials for lithium‐ion batteries (LIBs); however, the presumed lithium storage mechanism of MOFs is controversial. To gain insight into the mechanism of MOFs as anode materials for LIBs, a self‐supported Cu‐TCNQ (TCNQ: 7,7,8,8‐tetracyanoquinodimethane) film was fabricated via an in situ redox routine, and directly used as electrode for LIBs. The first discharge and charge specific capacities of the self‐supported Cu‐TCNQ electrode are 373.4 and 219.4 mAh g−1, respectively. After 500 cycles, the reversible specific capacity of Cu‐TCNQ reaches 280.9 mAh g−1 at a current density of 100 mA g−1. Mutually validated data reveal that the high capacity is ascribed to the multiple‐electron redox conversion of both metal ions and ligands, as well as the reversible insertion and desertion of Li+ ions into the benzene rings of ligands. This work raises the expectation for MOFs as electrode materials of LIBs by utilizing multiple active sites and provides new clues for designing improved electrode materials for LIBs.

Metal-organic frameworks (MOFs) have recently been considered as potential electrodes for lithium-ion batteries. However, there are only a few reports of pristine MOFs as high-performance electrode materials; whereas, in other cases, their overall specific capacities and cycle stabilities are insufficient. In this work, Cu-BTC (BTC = 1,3,5-trimesic acid) is taken as an example to systematically explore the effects of polymer binder, activation temperature, and synthesis method on the electrochemical properties of MOFs. Through the optimization of these conditions, the electrochemical properties of Cu-BTC can be significantly improved. With carboxymethyl cellulose (CMC) as the binder, the activated Cu-BTC (synthesized with the precooling method) displays a stable specific capacity of 626.4 mAh g À 1 after 100 cycles of charge and discharge at a current density of 100 mA g À 1. Besides, the mechanism study shows that both the copper species and organic ligands of Cu-BTC take part in the redox chemistry contributing to the lithium storage capability.

In recent years, metal‐organic frameworks (MOFs) have been widely used in the fields of hydrogen storage, gas separation, catalysts, and so on. It is inspiring to apply MOFs in the field of electrochemistry, whereas the intrinsic low electric conductivity of MOFs limits their promising future. Herein, a new approach to improve the electronic conductivity of Cu‐MOF (CuBTC) is developed, by adopting LiTCNQ solution as the reductant to generate CuTCNQ@CuBTC (BTC=1,3,5‐benzenetricarboxylic acid; TCNQ=7,7,8,8‐tetracyanoquinodimethane) core‐shell nanoparticles with conductive CuTCNQ as the shell and non‐conductive CuBTC as the core, and the reaction conditions are optimized. Mutually validated data indicate that conductive CuTCNQ shell grows thicker with a higher temperature (60 °C) and prolonged time (24 h). With this method, the conductivity of the CuBTC material is effectively improved from 3.84×10−9 to 2.94×10−7 S cm−1.

Despite the high capacity of metal−organic framework (MOF) electrodes for Li-ion batteries (LIBs), the low initial Coulombic efficiency (ICE) due to irreversible and massive consumption of lithium ions in the initial cycle hinders their practical application. Nanoscale transition metal oxides (TMOs) can activate the electrochemically stable Li−O bonds and therefore improve the ICE. Hence, copper benzene-1,3,5-tricarboxylate (Cu-BTC) rods with encapsulated supernano CuO were synthesized in a straightforward way using CuO and H 3 BTC as the metal source and organic ligand, respectively. By altering the reaction temperature, the size of CuO crystals can be adjusted from 6.98 to 2.72 nm. The CuO-doped Cu-BTC (40 °C) anode delivers an optimal capacity of 990.7 mA h g −1 (under 0.2 A g −1 ) after 100 cycles and the highest ICE of 61.84%, which exceeds the other counterparts. Such superior electrochemical properties are closely related to the size and content of CuO. This strategy introduces supernano CuO into Cu-BTC, which can be generalized to construct other in situ-formed TMO-doped MOF compounds as efficient lithium storage materials.

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Metal–organic frameworks (MOFs) have drawn intensive attention for their prospect as electrode materials of lithium‐ion batteries. However, MOFs with high capacity usually suffer from poor cycling stability, due to the volume fluctuation during cycles. Herein, based on the structure tenability of MOFs, copper phthalate (Cu‐oBDC), copper isophthalate (Cu‐mBDC), and copper terephthalate (Cu‐pBDC) with the same active sites for lithium storage are chosen as target materials and investigated as anodes for LIBs. The three MOF materials display different cycle stability in the galvanostatic charge–discharge test. Cu‐mBDC and Cu‐pBDC show obvious performance attenuation in cycles, while Cu‐oBDC with the largest interplanar spacing (13.02 Å) is eventually stabilized, and the solid electrolyte interface membrane is formed in the later cycling. At a current density of 100 mA g−1, the Cu‐oBDC delivers a reversible specific discharge capacity of 683.6 mAh g−1 after 250 cycles, outperforming the other two counterparts. This work adjusts the crystal structure of MOFs toward the improvement of cycle stability and provides a strategy to optimize the electrochemical performances of MOFs.