Molecular composite electrolytes of polybenzimidazole/polyethylene oxide with enhanced safety and comprehensive performance for all-solid-state lithium ion batteries

Polyethylene oxide (PEO)-based solid polymer electrolyte (SPE) is recognized as the most promising candidate in the commercialization process of all solid lithium ion battery (LIB). However, the crystallization of PEO results in low ionic conductivity, and the poor mechanical property and flammable feature of PEO lead to potential safety hazards in practical use. Here, we propose a cost-efficient, scalable, and facile approach for safe and high -performance SPE based on molecular composite of aromatic polybenzimidazole (PBI) and PEO. The strong intermolecular interactions effectively inhibit the crystallization of PEO, and significantly improve the modulus, strength, and ionic conductivity of PEO electrolyte by 16.6, 11.4, and 3.1 times with the addition 20% PBI. The thermal stability and flame retardancy are also simultaneously improved thanks to the outstanding heat-resistance and noninflammability of PBI. The PBI/PEO electrolyte exhibits excellent interfacial stability to lithium negative electrodes (500 h at 0.3 mA cm(-2)), and the LiFePO4//Li cell with PBI/PEO electrolyte shows a high-rate performance (152 mAh g(-1) at 0.2 C) as well as cycling performance (100 cycles at 0.2 C) at 60 ?. We believe that the PBI/PEO molecular composite electrolytes hold great promising for practical application in safe and high-performance all-solid-state LIB.

Automated summary

A solid polymer electrolyte (SPE) based on a molecular composite of aromatic polybenzimidazole (PBI) and PEO is proposed to address the issues of low ionic conductivity and potential safety hazards in PEO-based electrolytes. The strong intermolecular interactions effectively inhibit PEO crystallization and significantly improve the modulus, strength, and ionic conductivity of the electrolyte. Additionally, thermal stability and flame retardancy are also enhanced, making the PBI/PEO electrolyte a promising candidate for safe and high-performance all-solid-state lithium ion batteries.