Chen Zhanjun, Wang Tao, Yang Xianglin, Peng Yangxi, Zhong Hongbin, Hu Chuanyue
Modern Industry School of Advanced Ceramics, Hunan Provincial Key Laboratory of Fine Ceramics and Powder Materials, School of Materials and Environmental Engineering, Hunan University of Humanities, Science and Technology, Loudi 417000, China.
School of Materials Science and Engineering, Dongguan University of Technology, Dongguan 523808, China.
Materials (Basel). 2023 Mar 1;16(5):2049. doi: 10.3390/ma16052049.
The thermal stability of the polyethylene (PE) separator is of utmost importance for the safety of lithium-ion batteries. Although the surface coating of PE separator with oxide nanoparticles can improve thermal stability, some serious problems still exist, such as micropore blockage, easy detaching, and introduction of excessive inert substances, which negatively affects the power density, energy density, and safety performance of the battery. In this paper, TiO nanorods are used to modify the surface of the PE separator, and multiple analytical techniques (e.g., SEM, DSC, EIS, and LSV) are utilized to investigate the effect of coating amount on the physicochemical properties of the PE separator. The results show that the thermal stability, mechanical properties, and electrochemical properties of the PE separator can be effectively improved via surface coating with TiO nanorods, but the degree of improvement is not directly proportional to the coating amount due to the fact that the forces inhibiting micropore deformation (mechanical stretching or thermal contraction) are derived from the interaction of TiO nanorods directly "bridging" with the microporous skeleton rather than those indirectly "glued" with the microporous skeleton. Conversely, the introduction of excessive inert coating material could reduce the ionic conductivity, increase the interfacial impedance, and lower the energy density of the battery. The experimental results show that the ceramic separator with a coating amount of ~0.6 mg/cm TiO nanorods has well-balanced performances: its thermal shrinkage rate is 4.5%, the capacity retention assembled with this separator was 57.1% under 7 C/0.2 C and 82.6% after 100 cycles, respectively. This research may provide a novel approach to overcoming the common disadvantages of current surface-coated separators.
聚乙烯（PE）隔膜的热稳定性对于锂离子电池的安全性至关重要。尽管用氧化物纳米颗粒对PE隔膜进行表面涂层可以提高热稳定性，但仍存在一些严重问题，如微孔堵塞、易脱落以及引入过多惰性物质，这些都会对电池的功率密度、能量密度和安全性能产生负面影响。本文采用TiO纳米棒对PE隔膜表面进行改性，并利用多种分析技术（如扫描电子显微镜、差示扫描量热法、电化学阻抗谱和线性扫描伏安法）研究涂层量对PE隔膜物理化学性能的影响。结果表明，通过用TiO纳米棒进行表面涂层可以有效提高PE隔膜的热稳定性、机械性能和电化学性能，但由于抑制微孔变形（机械拉伸或热收缩）的力源自TiO纳米棒直接与微孔骨架“桥接”的相互作用，而非间接与微孔骨架“胶合”的相互作用，因此改善程度与涂层量并非成正比。相反，引入过多的惰性涂层材料会降低离子电导率、增加界面阻抗并降低电池的能量密度。实验结果表明，TiO纳米棒涂层量约为0.6 mg/cm²的陶瓷隔膜具有平衡良好的性能：其热收缩率为4.5%，用该隔膜组装的电池在7 C/0.2 C下的容量保持率为57.1%，100次循环后为82.6%。本研究可能为克服当前表面涂层隔膜的常见缺点提供一种新方法。
