| dc.description.abstract | Since the commercialization of lithium-ion batteries (LIBs), they have been widely used in electronic products and electric vehicles due to their high energy density, small size, and light weight. However, commercial separators like polyethylene (PE) and polypropylene (PP) suffer from poor thermal stability, leading to safety issues. Additionally, poor electrolyte affinity of PP hinders lithium ion transport, reducing the performance of LIBs. To solve these problems, some studies have used X-rays or plasma to activate the separator surface, then introduced functional groups or inorganic particles through layer-by-layer self-assembly. However, these methods are costly and complex. In contrast, this study employs a simple blade coating method to introduce polar functional groups and inorganic particles onto the surface of PP, enhancing both the performance and safety of LIBs.
In our study, we made a modified separator, prepared by blade-coating method. We mixed the slurry composed of magnesium oxide (MgO) inorganic particles, poly(vinylidene difluoride) (PVDF) and poly(acrylic acid) (PAA) as adhesives. Then, the slurry was coated on PP surface. The influence of lithium ion transference number, ionic conductivity, and electrochemical window was investigated. By adjusting the ratio of PAA to PVdF, we obtained the optimal slurry composition, which is 80% MgO, 5% PVdF, and 15% PAA, referred to as 15A5V80Mg. No significant thermal shrinkage in thermal stability tests were observed on 15A5V80Mg at 160 °C for 1 hour. The electrolyte uptake increased from 110% to 382% and electrolyte contact angle decreased from 35.46° to 0°, significantly enhancing electrolyte affinity. Moreover, it exhibited a high lithium ion transference number (0.71) and ion conductivity of 1.458 (mS/cm). Lithium plating and stripping tests at a current density of 0.5 mA/cm2 were conducted, it lasted close to 820 hours before short-circuiting. The result illustrated the stabilizing effect of coating on the separator/lithium interface, reducing the risk of thermal runaway caused by lithium dendrites. Compared to PP, the LiFePO4 (LFP)||15A5V80Mg||Li cells can demonstrate the capacity of 155 mAh/g under 0.2 C. During the long cycle test, the LFP||15A5V80Mg||Li cell maintained a 92.54% capacity retention after 600 charge and discharge process at 2.0 C, whereas the PP separator only retained 23.77%. This demonstrates the excellent cycling stability of the 15A5V80Mg separator. These findings are beneficial for the development and improved safety of LIBs. In addition, low-cost and fast preparation methods also has the advantage of facilitating large-scale production. | en_US |