The improvement of lithium ion transport properties, along with the ever-increasing demand for high-power density, is key to boosting the development of lithium-ion batteries. Here, we present a new class of carboxylated polyimide (PI) separator, which can be fabricated via an alkali treatment-based surface modification. The –COOH groups with unshared electron pairs were proposed to contribute to the desolvation of lithium ions and an increase in the lithium ion transport rate. Notably, the modification did not destroy the microstructure of the PI separator, and thus the effect of –COOH groups on the lithium ion transport properties was clearly demonstrated in this work. The result showed that the carboxylated PI separator was conducive to improving the lithium ion transference number (up to 0.87), which is four times higher than that for the original PI separator. More importantly, for the first time, the –COOH group was calculated to increase the lithium ion transport rate by more than six times. Benefiting from its high lithium ion transference number and slightly increased ionic conductivity, the cell assembled with the carboxylated PI separator achieved a better cycle performance and higher rate capability than that with the original PI separator.

This study reviews the recent developments and the characteristics of polymeric separators used for lithium ion batteries.

Bacterial infections and biofilm-associated antibiotic resistance continue to pose significant challenges in biomedical applications, often resulting in device-related complications and therapeutic failures. To address these concerns, the development of antibacterial surface-engineered biomaterials has become a major research focus, offering localized, non-systemic strategies to combat microbial contamination. This review provides a comprehensive overview of recent advances in antibacterial surfaces, with a focus on their mechanisms of action, design principles, and functional performance. Strategies are discussed within the widely recognized categories of active, passive, and hybrid systems. Active surfaces function through agent release or contact-mediated killing, while passive surfaces inhibit bacterial adhesion by modulating surface topography or chemistry. Hybrid systems integrate both mechanisms to achieve synergistic effects. The review also highlights current and emerging applications in medical implants, wound care, and hygienic textiles. Finally, key limitations and future opportunities are critically examined, offering insights into the rational design and clinical translation of next-generation antibacterial biomaterials.