Metal–organic frameworks (MOFs) have attracted intensive study as solid electrolytes (SEs) in recent years. However, MOF particles work separately in SEs and numerous interfaces hinder a high-efficiency ion transport, which lowers the performance of solid-state batteries (SSBs). Herein, continuous ion-conductive paths were constructed by cross-linked MOF chains. Chains of a newly developed MOF (Zr-BPDC-2SO3H) were grown on bacterial cellulose (BC) nanofibers to provide a continuous ion transport network. The cross-linked MOF chains exhibit a high ionic conductivity of 7.88 × 10–4 S cm–1 at 25 °C, single-ion transport ability (t Li +=0.88), a wide electrochemical window up to 5.10 V, excellent interface compatibility, and the capability for suppressing lithium dendrites. Most importantly, the SSB fabricated with the cross-linked MOF chains shows more than 100% improved specific capacity in comparison to an SSB without this design and stable cycling performance at 3 C. This work provides a splendid strategy for developing high-performance SEs with porous ion conductors.

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Metal–organic frameworks (MOFs) have been attracting a great deal of attention as potential solid electrolytes (SEs). However, the interfacial compatibility of MOF-based SEs caused by the physical contact among MOF particles, the polymer binder, and electrodes is not yet fully determined. Herein, a bioinspired design strategy aiming to build ion transport pathways at interfaces was introduced. The MOF-to-MOF transport paths were built via in situ ring opening of epoxide, akin to the protein molecules that transport the ion across the cell walls. After optimization, the obtained SE is endowed with a high ion conductivity of 1.70 × 10–3 S cm–1 at 30 °C, a wide electrochemical window of 4.6 V, a high Li+ transference number of 0.8, and a decreased interface resistance. Consequently, the fabricated quasi-solid metal batteries exhibit higher and more stable cycling performance compared to the performance of those without interface optimization. This strategy for optimizing the interfacial compatibility of MOFs thus exploits a new avenue for developing high-performance SEs for various metal batteries.

Metal-organic frameworks (MOFs) have drawn considerable interest as solid electrolytes (SEs) by virtue of their talents for rational design as ion channels. The crystal interface plays a significant role in ion transport and is thus of vital importance to the performance of solid batteries, however, interface effects of MOFs in SEs are not yet fully understood, especially at the molecular level, and not engineered as well. In this work, MOFs engineered with diverse molecules (Lewis bases) are designed for an optimized interfaces and the impact of interfaces for ion transport is analyzed by using engineered MOFs as SEs. The results show that the ion conductivity of MOFs decorated with a long chain Lewis base (LCLB) has been greatly improved. The interface resistance of the SEs composed of MOFs with LCLB has decreased markedly. Most importantly, the corresponding Li|SE|LiPO 4 solid-state battery (SSB) shows an improved specific capacity of 47% and longer lifetime at 5 C compared with the SSB without interface engineering. Such results shed new light on the understanding of ion transport at interfaces and suggest the feasibility of interface engineered MOFs as advanced SEs.

A highly electronegative carboxyl-decorated anionic metal−organic framework (MOF), (Me 2 NH 2 ) 2 [In 2 (THBA) 2 ]-(CH 3 CN) 9 (H 2 O) 21 (InOF; H 4 THBA = [1,1′:4′,1″-terphenyl]-2′,3,3″,5,5′,5″-hexacarboxylic acid), with high-density electronegative functional sites was designed and constructed. One unit cell of InOF possesses 12 negative sites that originate from the negatively charged secondary building unit [In(COO) 4 ] − and exposed carboxyl groups on the ligand. The abundant electronegative sites can facilitate the hopping of ions in channels and thus result in highly efficient ion conductivities for various metal ions. Our results show that Li + -loaded materials have a remarkably high ion conductivity of 1.49 × 10 −3 S/cm, an ion transference number of 0.78, and a relatively low activation energy of 0.19 eV. The Na + , K + , and Zn 2+ ion conductivities of InOF are 7.97 × 10 −4 , 7.69 × 10 −4 , and 1.22 × 10 −3 S/cm at 25 °C, respectively.