Session: Advances in Electrochemistry:

Lithium ion batteries (LIBs) have extensive applications in portable electronics, portable power tools and electric vehicles due to their impressive stability, safety, energy density and scalability. Although commercial graphite anode can safely store lithium ions without the formation of lithium metal dendrites, its theoretical capacity is relatively low capacity, i.e., 372 mAh/g. Tungsten trioxide (WO3) has a theoretical capacity of 693 mAh/g, which is nearly twice as that of commercial graphite anode. In addition, the volumetric capacity of WO3 is approximately 6 times higher than graphite. However, Tungsten trioxide anode experiences significant volume expansion during lithiation and delithiation, thus causing electrode pulverization, delamination and rapid capacity loss. In this study, we demonstrate a facile method to solve this issue by the use of fibrous asymmetric membranes. First, tungsten trioxide nanoparticles were synthesized through the precipitation reaction between Na2WO4 and HCl at room temperature. Then the WO3 particles were used to fabricate fibrous asymmetric membranes by a straightforward phase inversion method combined with carbonization. Both the WO3 particles and the fibrous asymmetric membranes were characterized using scanning electron microscopy (SEM), energy dispersive x-Ray spectroscopy (EDS), transition electron microscopy (TEM), powder X-ray diffractometer (PXRD), Raman spectroscopy, Thermogravimetric analyzer (TGA), and BET surface area analyzer. The electrochemical performance of WO3 fibrous asymmetric membranes as LIB anodes was evaluated by cyclic voltammetry, rate performance, cycling tests and electrochemical impedance spectroscopy, and the results were compared to the control, WO3 nanoparticle and other literature reports. Dip-coated WO3 fibrous asymmetric membrane anode demonstrated the most outstanding capacity retention of 80% in 50 cycles at ~ 1/5C rate. It was also identified that the choice of polymers for the phase inversion can significantly affect the chemical composition and electrochemical properties of WO3 fibrous asymmetric membranes. The characterization, in combination with the electrochemical performance, confirmed that the fibrous asymmetric membrane structure is efficient in accommodating the large electrode volume change and thus preventing rapid capacity loss during repeated lithiation and delithiation.

Olivia Sheppard

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