Preparation and application of polyacrylonitrile electrospun nanofiber-based all-solid-state composite electrolyte for lithium metal battery

Abstract

The demand for lithium-ion batteries that are both safe and high-energy is growing. Liquid electrolytes are used in traditional lithium rechargeable batteries, which pose security hazards such as volatilization, flammability, and explosion. Most of the safety problems associated with liquid electrolytes could be addressed by solid-state electrolytes. This research firstly incorporated Li6.4La3Zr1.4Ta0.6O12 (LLZTO) ceramic nanoparticle filler into electrospun polyacrylonitrile (PAN) to obtain a composite nanofiber membrane, and then added it to polyethylene oxide (PEO) polymer as a nano-polymer filler to create an all-solid-state electrolyte. By incorporating the PAN/LLZTO composite nanofiber membrane, the resulting electrolyte gains a sturdy framework that enhances its overall mechanical strength (7.8 MPa) to prevent the growth of lithium dendrites during cycling. In addition, the addition of LLZTO particles can help promote chain segment motion in a PEO matrix by increasing the ratios of amorphous to crystalline phase, which is beneficial for the rapid migration of lithium ions in the electrolyte membrane. At the same time, the interaction between LLZTO and DMF solvent can also generate an alkaline atmosphere and then promotes the cyclization of PAN, thus enhancing the ionic conductivity of the electrolyte (6.5 × 10−5cm−1 at 30 °C). The Li/Li symmetric battery assembled with the PEO-PAN/LLZTO composite electrolyte can stable cycling for 800 h at different current densities, and the Li/LiFePO4 battery can still maintain a high Coulomb efficiency of 99.7% after even 400 cycles under 1C. The research will lead to a promising electrolyte candidate for all-solid-state lithium metal batteries.