A novel acid-base composite membrane consisting of acidic carboxyl-containing polyimide (PI-COOH) and basic polybenzimidazole (OPBI) was fabricated and employed as a high-temperature proton exchange membrane (HT-PEM). PI-COOH was used to prepare HT-PEMs for the first time. The PBI-based acid-base composite membranes and ordinary composite membranes were investigated to elucidate the correlation between the polymer structure and membrane properties, especially in situations where phosphoric acid (PA) is used. The results show that OPBI-xPI-COOH composite membranes (x represents the weight percentage of PI-COOH in the entire membrane) deliver high proton conductivities and superior PA retention due to the continuous hydrogen bond network between OPBI and PI-COOH. The OPBI-50PI-COOH composite membrane revealed a proton conductivity of 89 mS cm⁻¹ under low PA uptake (109%). Compared to the linear OPBI and OPBI-40PI composite membrane, a single cell with a low PA-doped OPBI-50PI-COOH composite membrane presented superior durability and power density (463 mW cm⁻²) at 160 °C and 0% relative humidity. In a short-term durability test of 369 h, the voltage attenuation rate was only 119 μV h⁻¹. These outstanding outcomes indicate that the obtained acid-base composite membranes can be considered as capable candidates for HT-PEMs with enhanced performance.

The electrolyte of high concentration LiTFSI dimethyl sulfoxide (DMSO), polytetrafluoroethylene (PTFE) and nickel foam are applied to help preserve electrolyte and achieve a record-breaking cycle stability for Li–CO ₂ batteries.

As a traditional high-temperature proton exchange membrane (HT-PEM), phosphoric acid (PA)-doped polybenzimidazole (PBI) is often subject to severe mechanical strength deterioration owing to the “plasticizing effect” of a large amount of PA. In order to address this issue, we fabricated the HT-PEMs with a crosslinked network of poly (arylene ether ketone) to confine polybenzimidazole in semi-interpenetration network using self-synthesized amino-terminated PBI (PBI-4NH₂) as a crosslinker. Compared with the pristine linear poly [2,2′-(p-oxdiphenylene)-5,5′-benzimidazole] (OPBI) membrane, the designed HT-PEMs (semi-IPN/xPBI), in the semi-IPN means that the membranes with a semi-interpenetration structure and x represent the combined weight percentage of PBI-4NH₂ and OPBI. In addition, they also demonstrate an enhanced anti-oxidative stability and superior mechanical properties without the sacrifice of conductivity. The semi-IPN/70PBI exhibits a higher proton conductivity than OPBI at temperatures ranging from 80 to 180 °C. The HT-PEMFC with semi-IPN/70PBI exhibits excellent H₂/O₂ single cell performance with a power density of 660 mW cm⁻² at 160 °C with flow rates of 250 and 500 mL min⁻¹ for dry H₂ and O₂ at a backpressure of 0.03 MPa, which is 18% higher than that of OPBI (561 mW cm⁻²) under the same test conditions. The results indicate that the introduction of PBI containing crosslinked networks is a promising approach to improve the comprehensive performance of HT-PEMs.