Synthesis and characterization of lithium iron phosphate nanowires from sago pith waste cellulose nanofibril aerogel

Abstract

This project aimed to produce highly crystalline lithium iron phosphate coated aerogel (LiFePO4 nanowires) via coating and sintering LiFePO4 on the surface of an aerogel template prepared from cellulose nanofibril (SPCNF) extracted from sago pith waste (SPW). The effects of SPCNF aerogel quantity (Xq), sintering duration (Xt) and sintering temperature (XT) on the quality of LiFePO4 were studied. Specifically, SPCNF were first extracted from SPW through combined chemical and mechanical treatments, followed by a freeze-drying step to produce an aerogel. The resulting white and spongy SPCNF aerogel was characterized to elucidate its morphology, crystallinity, and thermal resistance using field-emission scanning electron microscopy, powder x-ray diffraction (PXRD) and thermogravimetric analysis, respectively. Results showed that the morphology of SPCNF aerogel resembled that of a web-liked structure with the diameters of each SPCNF measured to be within 15-30 nm. The degree of crystallinity of the aerogel was approximately 88.38% and its thermal degradation temperature was in the range of 260-350 °C. The aerogel was then coated with LiFePO4 through direct coating on aerogel by applying a uniform solution containing Li+, Fe2+ and PO43- in 1:1:1 molar ratio and followed by calcination and sintering. The final product, LiFePO4 nanowires had wire-liked structure with the diameters between 15-30 nm, and the PXRD and transmission electron microscopy verified the nanowires were covered with LiFePO4. Results from design of experiment of full-factorial design showed that the three parameters are significant and the coating quality, Y can be correlated with the following equation: Y = 5.662 + 7.23875Xq + 7.23875Xt + 5.60125XT + 7.23875XqXt + 5.60125XqXT + 5.60125 XtXT + 5.60125 XqXtXT.