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The preparation of separators using heat-resistant polymers is an effective approach to improve the safety of lithium-ion batteries (LIBs). However, separators using a single heat-resistant polymer compared with the composite modified polymer have low conductivities, which leads to low battery performances. In this study, for the first time, a heat-resistant separator was successfully prepared using an ion-modified metal–organic framework (MOF) and poly­(aryl ether benzimidazole)­(OPBI). Diversified ion channels were constructed by ion modification combined with phase inversion and physical mixing. The lithium-ion transmission efficiency and safety of the LIBs were effectively improved. The hybrid separator exhibited a satisfactory thermal stability (absence of shrinkage at 200 °C for 1 h), higher ionic conductivity (1.46 mS cm–1), and better electrolyte uptake rate. Moreover, the hybrid separator is conducive to inhibiting the growth of Li dendrites. A cell assembled with the hybrid separator delivered a reversible capacity of 157 mA h g–1 at 0.5 C. The capacity retention of the cell was up to 94% after 200 cycles. Thus, the hybrid membrane is a valuable candidate to enhance the safety and electrochemical properties of LIBs.

Constructing high-density hydrogen bonding networks is crucial to improve the proton conductivity of proton exchange membranes (PEMs) and the single-cell output power of high-temperature fuel cells (HTFCs). In this work, a series of benzimidazole polymers containing a pyridine group in the backbone are successfully synthesized via copolymerization. The high-density hydrogen network is constructed via blending the polyether polybenzimidazole (OPBI) with the bipyridine polybenzimidazole copolymer, and the 1,3,5-triglycidyl isocyanurate that contains nitrogen atoms and hydroxyl groups is used as a cross-linking agent. As a result, the proton conductivity and the output power density of the single cell are significantly enhanced by the high-density hydrogen bonding network. The single-cell performance of 693 mW cm–2 is achieved in the cross-linked OPBI/copolymer blend membranes containing pyridine group under a saturated phosphoric acid (PA) adsorption (284%). Even under the low PA uptake (178%), the proton conductivity (0.050 S cm–1) is 2.1 times that of the OPBI membrane (0.024 S cm–1), and the output power density of the single-cell performance (501 mW cm–2) is 1.4 times that of the OPBI membrane (358 mW cm–2). The results demonstrate that introducing nitrogen sites into polybenzimidazole cross-linked membranes is an effective strategy for preparing high-performance fuel cell PEMs.

Polybenzimidazoles (PBIs) are the most promising binders for the catalyst layer (CL) in high‐temperature proton exchange membrane fuel cells (HT‐PEMFC). However, traditional commercial PBIs are not applied in binders because they do not enhance the electrochemical performance and because the related solvents are not environmentally friendly. In addition, proton transfer channels in PBIs are not investigated at the microscopic and atomic scales to date. In this study, a nitrogen‐rich rigid PBI binder containing pyridine, diazofluorene, and partially grafted nitrile (PBPBI‐3CN) is prepared with a functionalized structure, good thermal stability, and good solubility in an environmentally friendly solvent. A membrane electrode assembly (MEA) is fabricated with the PBPBI‐3CN binder, providing a high peak power density, low resistance, and good stability. The protonation, hydrogen bond networks, and platform for proton transfer are confirmed in the CLs. The protonation of PBPBI‐3CN occurs in two steps. First, some phosphoric acid (PA) molecules bind to nitrogen‐containing acidophilic groups via preliminary protonation; second, multiple PA molecules then interact with nitrogen‐containing acidophilic groups via further protonation. With protonation as the foundation, a sufficient amount of PA molecules form a hydrogen bond network, and proton transfer channels are established.

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