Constructing a Highly Functional Oxygen Defect NaTi 2 (PO 4– y ) 3 –TiO 2 –PAN 3D Nanofibrous Network for High-Rate and Durable Quasi-Solid-State FeS 2 Batteries

Solid-state batteries are increasingly regarded as a key future energy storage option because they are highly safe and exhibit increased energy density, enabling them to address the drawbacks of traditional liquid lithium-ion batteries. Nevertheless, their industrial deployment is still hindered by obstacles, including significant interfacial resistance, limited ionic conductivity, and inadequate interface stability. To address these limitations, this work introduces a combined approach that employs defect modulation alongside rational structural design. A three-dimensional nanofibrous network composite solid electrolyte (NATP-TiO2-PAN) was fabricated via electrospinning, incorporating Al3+-doped oxygen-deficient NaTi2(PO4)3 (NATP) and TiO2 into a polyacrylonitrile (PAN) polymer matrix. Defect engineering via Al3+ doping introduces oxygen vacancies into the NATP framework. These vacancies broaden the electrochemical window and decrease the activation energy for Li+ transport, thereby enhancing Li+ mobility. Computational results indicate that the (110) crystal plane of NATP is strongly compatible with lithium metal, promoting stable Li+ adsorption and the formation of a passivated interface, thereby suppressing lithium dendrite growth. The NATP-TiO2-PAN composite electrolyte demonstrates a high ionic conductivity of 1.06 × 10-4 S cm-1 at 60 °C and a wide electrochemical stability window of 4.5 V. The assembled Li|NATP-TiO2-PAN|Li symmetric cell maintains stable cycling for more than 1100 h with minimal polarization, confirming effective dendrite suppression. Benefiting from the stabilized interface and mitigation of volume expansion, the assembled quasi-solid-state Li|NATP-TiO2-PAN|FeS2 battery delivers excellent cycling stability, retaining 350 mAh g-1 after 800 cycles at 500 mA g-1 and maintaining more than 50% capacity retention after 1500 cycles at 1000 mA g-1. This work provides a promising material design strategy and experimental foundation for developing highly safe, high-performance quasi-solid-state lithium-ion batteries (QSSBs).