两性分子掺杂自支撑单离子传导聚合物电解质及其锂金属二次电池

Zwitterion-doped self-supporting single-ion conducting polymer electrolyte membrane for dendrite-free lithium metal secondary batteries

制备高离子电导率的自支撑单离子传导聚合物电解质仍然面临挑战.本文中,我们通过聚[4,4’(二苯醚基)-5,5’-联苯并咪唑]侧链化学接枝丙烷磺酰(三氟甲基磺酰)亚胺锂,得到自支撑聚合物电解质(PBIg-LiPSI).PBI-g-LiPSI具有优异的成膜性能,实验发现,掺杂两性分子1-甲基-3-丙烷磺酰(三氟甲基磺酰)亚胺咪唑内盐(MeImPSI)后,离子电导率和^(7)Li核磁共振峰的化学位移都随着掺杂两性分子的质量分数呈线性递增.PBI-g-LiPSI/MeImPSI(25 wt%)凝胶自支撑单离子传导聚合物电解质的室温离子电导率是0.68 mS cm^(-1),锂离子迁移数是0.95.使用该电解质隔膜的金属锂对称电池在±0.5 mA cm^(-2)@2 mA h cm^(-2)运行2100小时未发生短路,金属锂二次电池可在1C下稳定循环500圈.本工作开发了一种用于金属锂二次电池的两性分子掺杂自支撑单离子传导聚合物电解质.

Exploring self-supporting polymer electrolyte membranes that exhibit both high ionic conductivity and cation transference poses a challenge for lithium metal secondary batteries.In this research,we utilized poly(4,4'-(diphenyl ether)-5,5'-bibenzimidazole)(O-PBI)and grafted it with lithium propanesulfonyl(trifluoromethyl sulfonyl)imide(PBIg-LiPSI)through a nucleophilic substitution reaction involving sodium 3-iodopropanesulfonyl(trifluoromethyl sulfonyl)imide(NaIPSI)and pre-activated O-PBI with lithium hydride.This process was followed by a lithium-ion exchange.The excellent leaving ability of the iodine substituent in NaIPSI allowed for a grafting ratio close to 100%,resulting in the highest possible lithium content.Moreover,the strong π-π interaction among the aromatic polybenzimidazole facilitated the formation of a self-supporting polymer electrolyte membrane,even when doped with zwitterionic 1-propanesulfonyl(trifluoromethyl sulfonyl)imide-3-methylimidazolium(MeImPSI).The ionic conductivities and ^(7)Li nuclear magnetic resonance chemical shifts of MeImPSI-doped PBI-g-LiPSIs showed a linear increase with the doping mass fraction of zwitterion.This finding confirmed that the zwitterion can act as a dipole,reducing the electrostatic attraction between the lithium cation and immobilized bis(sulfonyl)imide anion.Among different doping ratios,a 25-wt% MeImPSI-doped PBI-g-LiPSI exhibited the highest ionic conductivity of 0.68 mS cm^(-1) at room temperature,along with a lithium transference number of 0.95.To assess the performance of the electrolyte as well as separator,a lithium symmetric cell was assembed using the 25-wt%MeImPSI-doped PBI-g-LiPSI.The cell exhibited stable performance during galvanostatic cycling at ±0.5 mA cm^(-2) with a charge-discharge capacity of 2 mA h cm^(-2),for an impressive duration of 2100 h.Additionally,we successfully demonstrated the application of single-ion conducting lithium metal secondary batteries.The film-forming property of PBI,combined with the enhanced ionic mobility provided by the zwitterion contributed to the overall excellent performance of the single-ion conducting polymer electrolyte system.