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 (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 ^oC, 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 ^oC for more than 1500 hours. The LiFePO₄|HT-HOF-IL CQSE|Li cell shows excellent cycling performance at 0.5C at a wide temperature range of -20 to 60 ^oC. 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.