Application of high-performance lithium-ion batteries with dual-layer separators composed of electron beam irradiated PVDF-HFP/PMMA/AlO(OH) and PVDF-CTFE/PEO/LiTFSI/AlO(OH) in fast charging and discharging

With the rapid advancement of battery technologies, the demand for high-performance lithium-ion batteries (LIBs) has surged, particularly in fast-charging applications. This has driven the exploration of advanced materials to overcome the limitations of commercial separators. In this study, we present a pioneering approach: a dual-layer composite separator comprising Poly(vinylidene fluoride-co-hexafluoropropylene)/ Poly(methyl methacrylate)/ Aluminum oxyhydroxide and Poly(vinylidene fluoride-co-chlorotrifluoroethylene)/ Poly(ethylene oxide)/ Lithium bis(trifluoromethanesulfonyl)imide/ Aluminum oxyhydroxide (PVDF-HFP/PMMA/AlO(OH) and PVDF-CTFE/PEO/LiTFSI/AlO(OH)), modified via electron beam irradiation at varying doses to enhance separator performance, especially in mitigating rapid capacity degradation under fast-charging conditions. Electron beam irradiation induces cross-linking to enhance the material's mechanical strength, chemical stability and thermal stability without compromising its inherent polymer structure. Radiation triggers free radicals, allowing polymers to crosslink at room temperature and preventing membrane deformation. Due to the absence of initiators, the electrical and electrochemical properties of the system are not affected. This constitutes its primary advantage over alternative cross-linking approaches, which typically compromise structural integrity through chemical additives or thermal degradation. The most significant feature of this dual-layer separator is its ability to effectively address interfacial compatibility issues between the cathode and anode. Compared to commercial polypropylene (PP) separators, the dual-layer separator exhibits superior thermal stability, porosity (71 %), electrolyte wettability (421 % uptake), ionic conductivity (1.42 mS cm⁻¹) and electrochemical performance. The optimal formulation, containing 12 wt% boehmite nanoparticles and irradiated at 160 kGy, demonstrated exceptional cycling stability. At a current density of 10C, the battery retained 94.1 % of its initial discharge capacity (108.9 mAh g⁻¹) after 1000 cycles. Even under extreme fast-charging conditions (10C and 15C), the separator maintained >90 % and > 80 % capacity retention after 1000 and 1500 cycles, respectively. These results highlight the dual-layer separator's ability to sustain high energy density while addressing capacity fade, offering a viable pathway for commercializing fast-charging LIBs. The synergistic effects of boehmite-enhanced interfacial compatibility and radiation-induced crosslinking provide a robust framework for next-generation battery separators.