| 摘要: | 鋰離子電池（LIBs）商業化以來，其能量密度高、體積小、重量輕的優點使之在電子產品和電動車中廣泛應用。然而，聚乙烯（PE）和聚丙烯（PP）等商用隔離膜的熱穩定性差導致了安全性問題。此外，PP的電解質的親和力較差，阻礙了鋰離子的傳遞，降低了鋰離子電池的性能。為了解決這些問題，一些研究使用X射線或電漿來活化隔離膜表面，然後透過逐層自組裝引入官能基或無機粒子。然而，此類方法成本高且複雜。相較之下，本研究採用簡單的刮刀塗佈方法，將極性官能基和無機粒子引入PP的表面改善了LIBs的性能及安全性。
在本研究中，我們製備了一種藉由簡單的刮刀塗佈法製備之修飾隔離膜。首先，我們將氧化鎂（MgO）無機粒子、聚偏二氟乙烯（PVDF）和聚丙烯酸（PAA）混合形成漿料，接著，將其塗佈於PP表面。我們研究了不同漿料比例塗佈製備的修飾隔離膜之鋰離子遷移數、離子電導率和電化學窗口的影響。藉由調整PAA和PVdF的比例，我們獲得了最佳的漿料組成，即80% MgO、5% PVdF和15% PAA，稱為15A5V80Mg。在熱穩定性測試中，15A5V80Mg在160 °C下持續1小時的熱處理，未觀察到明顯的熱收縮。電解質含有率從110%增至382%，並且電解質接觸角由35.46°下降到0°，顯著提高了電解質的親和性。此外，它顯示出較高的鋰離子轉移數（0.71）和1.458（mS/cm）的離子電導率。在0.5 mA/cm2電流密度下進行的鋰沉積和剝落測試中，持續超過820小時才短路。結果表明，塗層在隔離膜/鋰界面的穩定作用，減少了鋰枝晶引起的熱失控風險。與PP相比，LiFePO4（LFP）||15A5V80Mg||Li電池在0.2 C下能表現出155 mAh/g的容量。在長循環測試中，LFP||15A5V80Mg||Li電池在2.0 C下經過600次充放電後仍保持92.54%的放電容量，而PP隔離膜僅保持23.77%。這顯示了15A5V80Mg隔離膜優異的循環穩定性。這些發現有助於LIBs的發展和安全性的改善，快速且低成本的製備方式也有助於大規模生產。
;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. |
