Zhaojin Li,Jialin Ren,Huilan Sun,Di Zhang,Qiujun Wang,Qujiang Sun,Bo Wang
Lithium-rich manganese-based cathode materials (LNCM) have garnered tremendous attention for the superior reversible capacity. However, the inherently unstable structure and low diffusion kinetics of Li + hamper their commercialization process. Recent studies have shown that void defects within grains are the main cause of oxygen release and voltage drop during cycling. Therefore, highly crystallinity small particles are the ideal structure for high power density and cycling stability of LNCM. However, improving the crystallinity of materials often means increasing the sintering temperature, which can easily cause material aggregation and grain growth. In this paper, by adopting the electrostatic spinning technology, nanowire shaped precursor are constructed, which facilitates the direct contact between the hot gas flow and the precursor during sintering, thus promoting ion diffusion and material crystallinity. Besides, the electronic and chemical environment in the modified LNCM sample have regulated simultaneously, accompanying with a significant increase in O vacancies, Mn 4+ and Ni 3+ ions. Adjustments from morphology to molecular structure increased the contact area between the material and electrolyte, improved the diffusion ability of Li + , and enhanced structural stability of the material, resulting in improved rate performance and cycling stability. This study expands our understanding of adopting electrospinning technology to prepare high-performance materials.
This study reports an eco-friendly waterborne epoxy (WBE) coating with excellent corrosion resistance by adding ammonium grafted graphene oxide (AGO) as co-dispersant. AGO, as a co-dispersant, addresses the problem of a lot of micro-defects caused by the intrinsic mismatch between epoxy resin and amine curing agents during the formation of aqueous epoxy resin. Also, the compatibility of GO in the epoxy resin matrix is also improved by the ammonium modification. The ammonium modification process was systematically studied using Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) spectra, UV–vis spectra, Raman spectra and X-ray photoelectron spectra (XPS). Scanning electron microscope (SEM) images show that AGO sheets has successfully inhibited the formation of micro-pores and micro-defects, forming a more compact WBE/AGO composite coating . As a result, the corrosion resistance of the coating has been greatly improved as investigated by the potentiodynamic polarization test. The corrosion rate of WBE/AGO is decreased by three orders of magnitude compared to pure WBE coating. The corrosion protection mechanism of the WBE/AGO coating is studied via Electrochemical impedance spectroscopy (EIS) test, and equivalent electrical circuits are applied to fitting the EIS results and reveal the effect of AGO in the composite coating.
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