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.

中文翻译：

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具有优异锂离子传输性能的羧化聚酰亚胺隔膜，适用于高功率密度锂离子电池†

锂离子传输性能的改善，以及对高功率密度的不断增长的需求，是推动锂离子电池发展的关键。这里，我们提出一个新的类的羧化聚酰亚胺（PI）的分离器，其可以制造通过基于碱处理的表面改性。提出了具有未共享电子对的–COOH基团有助于锂离子的去溶剂化和锂离子传输速率的增加。值得注意的是，这种修饰并没有破坏PI隔膜的微观结构，因此，在这项工作中清楚地证明了–COOH基团对锂离子传输性能的影响。结果表明，羧化的PI隔板有利于提高锂离子转移数（最高为0.87），是原始PI隔板的四倍。更重要的是，首次将–COOH基团计算出的锂离子传输速率提高了六倍以上。得益于其高锂离子转移数和略微增加的离子电导率，