Cross-linked membranes showed vastly improved alkaline stability, oxidation stability and mechanical properties compared with uncross-linked membranes due to the effective cross-linked structure.

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Lithium batteries are currently the most popular and promising energy storage system, but the current lithium battery technology can no longer meet people's demand for high energy density devices. Increasing the charge cutoff voltage of a lithium battery can greatly increase its energy density. However, as the voltage increases, a series of unfavorable factors emerges in the system, causing the rapid failure of lithium batteries. To overcome these problems and extend the life of high‐voltage lithium batteries, electrolyte modification strategies have been widely adopted. Under this content, this review first introduces the degradation mechanism of lithium batteries under high cutoff voltage, and then presents an overview of the recent progress in the modification of high‐voltage lithium batteries using electrolyte modification strategies. Finally, the future direction of high‐voltage lithium battery electrolytes is also proposed.

A series of ether-bond free polybenzimidazole (PBI) bearing pendant imidazolium groups (HIm-PBI and PIm-PBI) are synthesized via a low cost preparation process under mild reaction conditions. HIm-PBI and PIm-PBI show excellent membrane forming property, and flexible HIm-PBIand PIm-PBI-based membranes are prepared by casting the polymer/dimethyl sulfoxide solution. For a comparison, etherbond free PBI without pendant imidazolium groups (I-PBI) was synthesized and characterized in detail, and I-PBI shows poor membrane forming ability under the same conditions. HIm-PBI-based anion exchange membranes (AEMs) with the longer pendant alkyl side chain exhibit larger ionic clusters than that of PIm-PBI with the shorter one. Both HIm-PBIand PIm-PBI-based AEMs show excellent alkaline stability, and the HIm-PBI-based AEMs show a high conductivity of 63.4 mS cm −1 at 80 °C, while the value for PIm-PBI-based AEMs is 57.6 mS cm −1 . The H 2 /O 2 single-cell assembled with HIm-PBI shows a maximum power density of 444.5 mW cm −2 at 60 °C, which is higher than the one with PIm-PBI (337.5 mW cm −2 ). A feasible approach to the synthesis of ether-bond free PBI-based AEMs is proposed, and these results indicate that the etherbond free PBI-based AEMs are promising materials for fuel cell applications.