Wang Lei, Yan Jiawei, Zhang Ran, Li Yanfang, Shen Wenzhuo, Zhang Jiali, Zhong Min, Guo Shouwu
Department of Electronic Engineering, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
ACS Appl Mater Interfaces. 2021 Mar 3;13(8):9875-9884. doi: 10.1021/acsami.0c20854. Epub 2021 Feb 19.
Gel electrolytes show certain advantages over conventional liquid and solid electrolytes, but their mechanical strength and surface adhesion to the electrode remain to be improved. To address the challenges, we design and fabricate herein the core-shell nanofiber mats on the LiFePO electrode as matrices for gel electrolytes, in which the core is poly(-phenylene isophthalamide) (PMIA) nanofiber and the shell are composite of AlO nanoparticles and poly(vinylidene fluoride--hexafluoropropylene) (PVdF-HFP). The mechanical property of the core-shell polymeric nanofiber mats and their surface interaction with LiFePO electrode are characterized complementarily using dynamic thermomechanical analysis and scanning electron microscopy. The electrochemical properties of the gel electrolytes based on the as-prepared matrices after being loaded with lithium salt solution are studied systematically on half coin cells. It is found that the ultimate strength of the core-shell PMIA@PVdF-HFP/AlO mat can reach 6.70 MPa, 2 times higher than that of the PVdF-HFP/AlO nanofiber mat. Meanwhile, the shell PVdF-HFP/AlO can ensure manifest surface affinity to the LiFePO electrode and enhance lithium-ion conductance. Thus, the as-assembled LiFePO half coin cells using PMIA@PVdF-HFP/AlO gel electrolyte show good electrochemical performances, especially the long cycle stability with the capacity retention of 96.6% after 600 cycles under 1C.
凝胶电解质相对于传统的液体和固体电解质具有一定优势，但其机械强度和与电极的表面附着力仍有待提高。为应对这些挑战，我们在此设计并制备了以LiFePO电极上的核壳纳米纤维垫作为凝胶电解质的基质，其中核为聚间苯二甲酰间苯二胺（PMIA）纳米纤维，壳为AlO纳米颗粒与聚偏氟乙烯-六氟丙烯（PVdF-HFP）的复合材料。使用动态热机械分析和扫描电子显微镜对核壳聚合物纳米纤维垫的机械性能及其与LiFePO电极的表面相互作用进行了互补表征。在半硬币电池上系统研究了基于所制备基质并负载锂盐溶液后的凝胶电解质的电化学性能。发现核壳PMIA@PVdF-HFP/AlO垫的极限强度可达6.70 MPa，比PVdF-HFP/AlO纳米纤维垫高2倍。同时，壳层PVdF-HFP/AlO可确保对LiFePO电极具有明显的表面亲和力并提高锂离子电导率。因此，使用PMIA@PVdF-HFP/AlO凝胶电解质组装的LiFePO半硬币电池表现出良好的电化学性能，特别是在1C下600次循环后容量保持率为96.6%的长循环稳定性。
