A hierarchical channel structured separator with regulated ion transport and high thermal stability for lithium-ion batteries

The separator plays an important role in transporting ions and preventing thermal runaway, which affects the safety of lithium-ion batteries (LIBs). Herein, a novel aluminum oxide-modified polyethylene terephthalate-based track-etched membrane (Al₂O₃/PETTEM) separator is fabricated through a combination of heavy-ion track etching and vacuum filtration methods to regulate lithium-ion transport and improve the safety of LIBs. The separator features a hierarchical nanochannel structure composed of the vertically aligned channels in PETTEM and the gaps between Al₂O₃ nanoparticles on the PETTEM surface, which facilitates the rapid transport and uniform deposition of lithium ions. As a result, the Li||Li cell with the Al₂O₃/PETTEM separator achieves an extended cycle lifespan of up to 1000 h at 0.5 mA cm⁻². The LFP||Li cell with the Al₂O₃/PETTEM separator exhibits a high initial discharge specific capacity of 143 mA h g⁻¹ and maintains 94 % capacity after 200 cycles at room temperature. Additionally, after being modified with Al₂O₃ nanoparticles, the separator exhibits enhanced thermal stability, enabling stable battery operation at an elevated temperature of up to 120 °C and retaining 93.3 % capacity after 200 cycles. This work can offer promising strategies for developing high-safety LIBs.