Preparation and characterization of regenerated cellulose-based lithium-ion battery electrodes

In this work, the lithium iron phosphate (LiFePO₄) /multi-walled carbon nanotubes (MWCNTs)/ketjen black (KB)/regenerated cellulose (RC) freestanding composite electrodes were prepared by using 1-ethyl-3-methylimidazolium diethyl phosphate ([Emim]DEP) /dimethyl sulfoxide (DMSO) as the solvent system for the application of lithium-ion battery cathode. The electrodes were characterized and analyzed by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscope (EIS), and constant-current charge/discharge. The results indicate that the electrodes possess a three-dimensional layered network structure comprising RC and MWCNTs intertwined and lapped. The LiFePO₄ and KB particles can be inlaid and distributed on the surface of the network structure or among the pores, which enhances the multi-directionality and conduction rate of electron conduction, as well as the utilization efficiency of LiFePO₄. The electrode comprising a 3:1 ratio of MWCNTs to KB and a LiFePO₄ loading of 40 wt% performed best overall, with initial discharge specific capacities of 177.12, 143.02, and 127.12 mAh·g⁻¹ at rates of 0.1, 2, and 5 C, respectively. Moreover, the capacity retention was 99.82% after 50 cycles at 0.1 C and 94.58% after 200 cycles at 2 C. The Coulombic efficiency remained above 97% during 50 cycles at 0.1 C and above 98% during 200 cycles at 2 C. The electrodes exhibit favorable electrochemical performance and flexibility, which hopefully match the evolution of electrochemical energy storage devices toward lightweight and flexibility.