Bio-based furan aramid/ceramic-coated lithium-ion battery separators with high ionic conductivity, wettability and safety via in situ lithium compensation strategy

The structural design and performance characteristics of the diaphragm have a decisive impact on the safety and electrochemical performance of lithium-ion batteries (LIBs). However, traditional polyolefin diaphragms still face challenges in simultaneously improving the ion transport efficiency and thermal stability. Here, we report an in situ dynamic lithium compensation strategy for manufacturing a bio-based furan aramid/ceramic diaphragm (BAS) with higher thermal stability and ion transport efficiency. Specifically, exchangeable carboxyl groups (–COOH) are introduced into the bio-based furan aramid (BA) framework, which are in situ converted into –COOLi groups to form lithium ions (Li+) transport channels, achieving dynamic compensation of active Li+. The dual transmission system of ion exchange and physical pore channels synergistically enhances the ionic conductivity of BAS to 1.536 mS cm−1. The high polarity structure of the furan ring and the electrolyte have excellent compatibility, significantly reducing the solid–liquid interfacial energy, making BAS have extremely high electrolyte wettability (contact angle of 0°). The BA amide group forms a multi-scale bonding network with the nano-ceramics. The BAS prepared by the water-coating process exhibits excellent thermal stability (with a thermal shrinkage rate of less than 1 % after 1 h at 150 °C). The LiFePO4|Li half-cell assembled with BAS shows a capacity retention rate of up to 91.7 % after 280 cycles at 1C, with a Coulomb efficiency of 99 %, demonstrating excellent cycling stability. This design and development based on bio-materials provides a new approach for high safety and high energy density battery systems.