Facilitating ionic conductivity and interfacial stability via oxygen vacancies-enriched TiO2 microrods for composite polymer electrolytes

Abstract

Composite polymer electrolyte is viewed as one of the most competitive systems for the next generation in electrolytes for solid-state Li-metal batteries, owing to its favorable flexibility, favoring interfacial contact and low cost. However, the composite polymer electrolyte suffers from low ion conductivity and interfacial stability. Herein, we propose morphology and defect control strategies to successfully prepare oxygen vacancies-enriched 1D-structured TiO2 fillers to optimum ionic conductivity and interfacial strength of the CPEs. Various electrochemical characterizations and density functional theory (DFT) calculations reveal that the induced oxygen vacancies on the TiO2 surface help dissociate LiTFSI and produce more free Li ions. Notably, the 1D-structured TiO2 microrods not only act as a solid plasticizer to increase the amorphous phases of PEO matrix but also provide continuous interaction surfaces for strong anion adsorption to promote homogenous environment and ensure interfacial stability. Benefiting from this novel design, the symmetric Li//Li cell exhibits an ultra-long lifespan stable cycling over 1000 h at 0.2 mA cm−2. Besides, solid-state lithium metal batteries with LiFePO4 cathode exhibit superior cyclability (162.4 mAh g−1 at 0.33C after 200 cycles) and rate capability (132 mAh g−1 at 2C). This work provides a promising strategy of conduction structures for delicately designing advanced solid-state electrolytes, demonstrating the promise of developing all-solid-state Li-metal batteries.