Hydrogen-bonded organic frameworks (HOFs) have recently emerged as attractive candidates for solid-state electrolytes (SSEs) due to their structurally ordered pores, tunable chemical structures, and solution processability. However, direct application of HOFs as SSEs is challenging because of the lack of mobile Li⁺ and low-energy-barrier transport pathways. Herein, we design and fabricate a HOF-lithium salt array SSE with efficient Li⁺ transport properties through integrating lithium salts (Li-salts) into the hydrogen bond networks of HOF nanosheets as conducting sites. Li-salt anions with different electronegativities (bis(trifluoromethanesulfonyl)imide (TFSI⁻), tetrafluoroborate (BF₄⁻), and hexafluorophosphate (PF₆⁻)) are utilized to investigate their influence on transport environment and Li⁺ conductivity. We demonstrate that the strong hydrogen bond interactions between anions and HOF nanosheets provide a loose coordination environment for Li⁺, enabling efficient Li⁺ transport. Superior ionic conductivity of 1.0 × 10⁻⁴ S·cm⁻¹ at 30 °C and high Li-ion transference number ( $t_{{\text{Li}}^{+}}$) (0.63) are achieved for the optimized SSE. Consequently, the assembled Li|HOF-LiTFSI|Li cell can stably cycle for over 1000 h at 0.5 mAh·cm⁻². The lithium iron phosphate (LFP)|HOF-LiTFSI|Li half-cell exhibits a satisfactory discharge specific capacity of 161.1 mAh·g⁻¹ with a high capacity retention of 99.0% after 300 cycles at 0.5 C and 25 °C. This work highlights the great potential of flexible HOFs as high-performance solid-state electrolyte materials.

Two-dimensional metal-organic frameworks (2D MOFs), coupling the individual advantages of organic polymer with excellent flexibility and processability, as well as inorganic crystal with well-ordered and temperature-independent structure, are emerging solid-state electrolyte (SSE) materials for wide-temperature solid-state lithium batteries. However, present MOFs have seldom been directly utilized as SSEs, due to the insurmountable transport energy barrier and resultant low ionic conductivity. Here, we report a lamellar MOF electrolyte with high ionic conductivity over wide-temperature ranges through confining N,N-dimethylformamide (DMF) solvent into the ordered pore channel of 2D MOF lamellar framework. We demonstrate that, the fine-tuned microstructure of pore walls could induce the rearrangement of DMF solvent layer, forming long-range ordered and stable solvent layer along pore walls. The solvent layer then acts as low-energy-barrier lithium ion transport path, affording MOF SSE high ionic conductivity over wide-temperature ranges (2.87 × 10⁻⁴–1.58 × 10⁻³ S·cm⁻¹ at −20–100 °C), surpassing most of the currently reported solid-state electrolytes. The MOF SSE also exhibits high t_Li+ of 0.81 and low activation energy of 0.106 eV. Consequently, the assembled LiFePO₄|Li half-cell can stably cycle over wide-temperature ranges, retaining high discharge specific capacities of 158.4 mAh·g⁻¹ at −20 °C and 171.2 mAh·g⁻¹ at 60 °C, respectively, after 300 cycles. This work offers an innovative approach for the design of advanced ion conductors towards wide-temperature solid-state lithium batteries.

Ionic liquids (ILs) hold great promise as high-performance electrolyte material due to their unique advantages including nonvolatility, high thermal stability and high ionic conductivity. However, the IL-based electrolytes always suffer from serious ion aggregation and high viscosity at low temperatures, leading to significantly decline in ionic conductivity. Here, hydrogen-bonded organic framework-ionic liquid composite quasi-solid electrolyte (high temperature treatment (HT)-HOF-IL CQSE) was prepared through confining the IL electrolytes (ILEs) into the pore of HOF lamellar framework. The weak hydrogen bonding interactions within HOF nanosheets, together with the generated interactions between ILE and HOF, enable uniform and continuous distribution of ILE in HOF lamellar framework. This effectively inhibits the ion migration of ILE, which meanwhile serves as Li⁺ transfer sites, affording high ionic conductivity of 5.7 × 10⁻⁵ S·cm⁻¹ at −60 °C, with high lithium-ion transference number of 0.69, whereas ILEs usually lose ionic conduction ability at such low temperatures. The assembled Li symmetrical cell can stably cycle at 0.2 mA·cm⁻² and −20 °C for more than 1500 h. The LiFePO₄|HT-HOF-IL CQSE|Li cell shows excellent cycling performance at 0.5 C at a wide temperature range of −20 to 60 °C. This work may pave a new avenue for the development of high-performance IL-based composite electrolytes.

Electrolytes with high-efficiency lithium-ion transfer and reliable safety are of great importance for lithium battery. Although having superior ionic conductivity (10⁻³–10⁻² S·cm⁻¹), traditional liquid-state electrolytes always suffer from low lithium-ion transference number ( $t_{{\mathrm{L}\mathrm{i}}^{+}}$, < 0.4) and thus undesirable battery performances. Herein, the deep eutectic solvent (DES) is vacuum-filtered into the ~ 1 nm interlayer channel of vermiculite (Vr) lamellar framework to fabricate a quasi-solid electrolyte (Vr-DES QSE). We demonstrate that the nanoconfinement effect of interlayer channel could facilitate the opening of solvation shell around lithium-ion. Meanwhile, the interaction from channel wall could inhibit the movement of anion. These enable high-efficiency lithium-ion transfer: 2.61 × 10⁻⁴ S·cm⁻¹ at 25 °C. Importantly, the $t_{{\mathrm{L}\mathrm{i}}^{+}}$ value reaches 0.63, which is 4.5 times of that of bulk DES, and much higher than most present liquid/quasi-solid electrolytes. In addition, Vr-DES QSE shows significantly improved interfacial stability with Li anode as compared with DES. The assembled Li symmetric cell can operate stably for 1000 h at 0.1 mA·cm⁻². The lithium iron phosphate (LFP)|Vr-DES QSE|Li cell exhibits high capacity of 142.1 mAh·g⁻¹ after 200 cycles at 25 °C and 0.5 C, with a capacity retention of 94.5%. The strategy of open solvation shell through nanoconfinement effect of lamellar framework may shed light on the development of advanced electrolytes.

Solid polymer electrolytes (SPEs) hold great application potential for solid-state lithium metal battery because of the excellent interfacial contact and processibility, but being hampered by the poor room-temperature conductivity (~ 10⁻⁷ S·cm⁻¹) and low lithium-ion transference number ( $t_{{\mathrm{L}\mathrm{i}}^{+}}$). Here, a lamellar composite solid electrolyte (Vr-NH₂@polyvinylidene fluoride (PVDF) LCSE) with β-conformation PVDF is fabricated by confining PVDF in the interlayer channel of –NH₂ modified vermiculite lamellar framework. We demonstrate that the conformation of PVDF can be manipulated by the nanoconfinement effect and the interaction from channel wall. The presence of –NH₂ groups could induce the formation of β-conformation PVDF through electrostatic interaction, which serves as continuous and rapid lithium-ion transfer pathway. As a result, a high room-temperature ionic conductivity of 1.77 × 10⁻⁴ S·cm⁻¹ is achieved, 1–2 orders of magnitude higher than most SPEs. Furthermore, Vr-NH₂@PVDF LCSE shows a high $t_{{\mathrm{L}\mathrm{i}}^{+}}$ of 0.68 because of the high dielectric constant, ~ 3 times of that of PVDF SPE, and surpassing most of reported SPEs. The LiNi_0.8Co_0.1Mn_0.1O₂||Li cell assembled by Vr-NH₂@PVDF LCSE obtains a discharge specific capacity of 137.1 mAh·g⁻¹ after 150 cycles with a capacity retention rate of 93% at 1 C and 25 °C. This study may pave a new avenue for high-performance SPEs.

As a new class of porous material, polymer-metal-organic framework (polyMOF) has attracted tremendous interests owing to their combined advantages of polymer and crystalline MOF. However, the poor film-forming ability of polyMOF limits its widespread application, especially in membrane separation area. Herein, for the first time, we demonstrate the fabrication of free-standing polyMOF membrane. The polyMOF nanosheets are synthesized by a polymer-assisted self-inhibition crystal growth strategy. Followed by self-assembly through vacuum filtration, a 20 μm-thick free-standing polyMOF membrane is constructed. Benefiting from the inclusion of polymer with hydrophobic backbone and the continuously distributed non-coordinated hydrophilic groups along polymer chain, the polyMOF membrane attains excellent structure stability against water, as well as superior proton transfer property. Proton conductivity as high as 112 and 25.6 mS·cm^–1 is obtained by this polyMOF membrane at 100% and 20% relative humidity (RH), respectively, which are two orders of magnitude higher than those of pristine MOF. The conductivity under low humidity (20% RH) is even over 8 times higher than that of commercial Nafion membrane (3 mS·cm^–1). This study may provide some guidance on the development of polyMOF membranes.

Porous laminar membranes hold great promise to realize ultrafast ion transfer if efficient and stable transfer channels are constructed in vertical direction. Here, metal-organic framework (MOF) nanosheets bearing imidazole molecules in the pores were designed as building blocks to assemble free-standing MOF laminar membrane. Then, Nafion chains were threaded into the pores induced by electrostatic attraction from imidazole molecules by slowly filtering dilute Nafion solution. We demonstrate that the threaded Nafion chains lock adjacent MOF nanosheets, affording highly enhanced structural stability to the resultant laminar membrane with almost no water swelling. Significantly, abundant acid-base pairs are formed in the pores along Nafion chains, working as efficient, continuous conduction pathways in vertical direction. Proton conductivities as high as 110 and 46 mS·cm^–1 are obtained by this membrane under 100% and 40% relative humidity (RH), respectively, which are two orders of magnitude higher than that of pristine MOF membrane. The conductivity under low humidity (40% RH) is even over 2 times higher than that of commercial Nafion membrane, generating the maximum power density of 1,100 mW·cm^–2 in hydrogen fuel cell (vs. 291 mW·cm^–2 of Nafion membrane). Besides, the influence of water state on proton transfer in confined space is investigated in detail.

Developing laminar composite solid electrolyte with ultrathin thickness and continuous conduction channels in vertical direction holds great promise for all-solid-state lithium batteries. Herein, a thin, laminar solid electrolyte is synthesized by filtrating –NH₂ functionalized metal-organic framework nanosheets and then being threaded with poly(ethylene oxide) chains induced by the hydrogen-bonding interaction from –NH₂ groups. It is demonstrated that the threaded poly(ethylene oxide) chains lock the adjacent metal-organic framework nanosheets, giving highly enhanced structural stability (Young’s modulus, 1.3 GPa) to 7.5-μm-thick laminar composite solid electrolyte. Importantly, these poly(ethylene oxide) chains with stretching structure serve as continuous conduction pathways along the chains in pores. It makes the non-conduction laminar metal-organic framework electrolyte highly conductive: 3.97 × 10⁻⁵ S cm⁻¹ at 25 ℃, which is even over 25 times higher than that of pure poly(ethylene oxide) electrolyte. The assembled lithium cell, thus, acquires superior cycling stability, initial discharge capacity (148 mAh g⁻¹ at 0.5 C and 60 ℃), and retention (94% after 150 cycles). Besides, the pore size of nanosheet is tailored (24.5–40.9 Å) to evaluate the mechanisms of chain conformation and ion transport in confined space. It shows that the confined pore only with proper size could facilitate the stretching of poly(ethylene oxide) chains, and meanwhile inhibit their disorder degree. Specifically, the pore size of 33.8 Å shows optimized confinement effect with trans-poly(ethylene oxide) and cis-poly(ethylene oxide) conformation, which offers great significance in ion conduction. Our design of poly(ethylene oxide)-threaded architecture provides a platform and paves a way to the rational design of next-generation high-performance porous electrolytes.