Large-Scale Nanofiber Manufacturing| n-plane aligned doping pattern in electrospunPEl/MBene nanocomposites for high-temperaturecapacitive energy storaget

Xi’an Jiaotong University’s Cheng Yonghong & North China Electric Power University’s Fan Sidi: Electrospinning-Controlled MBene-PEI Alignment for High-Temperature Capacitive Energy Storage

Film capacitors have attracted significant attention in advanced power electronic systems due to their high power density, fast charge/discharge rates, long lifespan, and safety, finding applications in electromagnetic energy equipment, new energy vehicles, and grid integration of renewable energy. Currently, commercial biaxially oriented polypropylene (BOPP) suffers from low dielectric constant (2.2), limiting its energy density to 1-2 J·cm⁻³ and hindering device miniaturization and integration. Additionally, dielectric constant and breakdown strength typically exhibit an inverse relationship, posing challenges in achieving both high dielectric constant and high breakdown strength.

Recently, Fan Sidi’s team at North China Electric Power University proposed using electrospinning to achieve in-plane alignment of 2D MBene nanosheets in a polyetherimide (PEI) matrix. The MBene-PEI composite achieved a dielectric constant of 10.7 at 1 kHz with tanδ < 0.0074. The aligned MBene arrangement enhanced the dielectric constant while effectively suppressing high-temperature leakage currents. The MBene-PEI film exhibited a discharge energy density of 8.03 J·cm⁻³ at room temperature and 5.32 J·cm⁻³ at 150°C, with charge/discharge efficiency exceeding 90%. Furthermore, this alignment improved mechanical strength.The study, titled "In-plane aligned doping pattern in electrospun PEI/MBene nanocomposites for high-temperature capacitive energy storage," was published in Materials Horizons.

 (Mo₂/₃Y₁/₃)₂AlB₂ (MAB) bulk material was etched and exfoliated to obtain 2D Mo₄/₃B₂ (MBene) nanosheets. By adjusting electrospinning collector speed, aligned (high-speed) or disordered (low-speed) MBene-PEI structures were obtained. 

 SEM confirmed nanofiber distribution, while TEM revealed MBene alignment within PEI. High-resolution TEM clearly resolved the MBene-PEI interface.

MBene incorporation significantly enhanced dielectric constant via Maxwell-Wagner-Sillars (MWS) polarization, arising from charge accumulation at conductor (MBene)-insulator (PEI) interfaces under electric fields. MBene’s large surface area further amplified interfacial polarization. Aligned MBene-PEI maintained low dielectric loss 

Aligned MBene-PEI maintained low dielectric loss and suppressed leakage currents via "island effects," preserving high breakdown strength at both room and elevated temperatures. The aligned composite achieved 8.03 J·cm⁻³ at 25°C and 5.32 J·cm⁻³ at 150°C, surpassing pure PEI’s room-temperature performance due to synergistic high permittivity and breakdown strength, alongside minimized energy loss.

In summary, aligned MBene-PEI films demonstrated ultrahigh efficiency (>90%) and energy density (8.03 J·cm⁻³ at 25°C, 5.32 J·cm⁻³ at 150°C), attributable to MBene-induced MWS polarization and optimized orientation. The aligned structure increased dielectric constant by 25.9% and reduced loss by 40.3% versus disordered composites. Isolated MBene networks prevented conductive pathways, maintaining PEI’s intrinsic breakdown strength while enhancing mechanical properties. This work provides a novel strategy for designing high-performance polymer dielectrics for flexible energy storage.