(Invited) Microstructure and Capacity Design of Si-Silicide Alloys As a High-Performance Anode for Li Secondary Batteries

Abstract

Si and Si-based alloys considered as the most desired anode material for LIB owing to high gravimetric and volumetric capacity (3579 mAh g-1and 2200 mAh cm-3, corresponding to L15Si4 state). Despite academic and industrial efforts, applied on resolving the poor cycle life caused by the large volume changes upon redox reactions with Li+, the commercial use of silicon as an anode has not yet been implemented. Here, we report a comprehensive study of Si-based binary, ternary and multi alloys prepared by a facile and inexpensive process, melt-spinning. This approach allows to synthesize a proper microstructure by control a certain level of solidification speed (around 103–106 K/s) and known as the most suitable method for the mass production of alloys. In particular, through the control a size of active Si grains, which are well dispersed in the inactive matrix, we have examined electrochemical properties of Si-Ni binary alloys with the different atomic ratio. The gradual change of delithiation curve at 0.3V was observed upon cycling. OCV studies reveal the change of material state and compliment the observation of Chevrier et.al [1]. In our recent studies, we have designed Si–Fe–Al ternary alloys and practically examined the reliability of the proposed capacity prediction approach based on the Lever rule and phase diagram. Accordingly, half-cell electrochemical test results, XRD and TEM investigations revealed fairly good agreement of the calculated and realized capacities of the Si–Fe–Al alloys. Another attempt was applied to design an alloy with nanostructured crystalline Si (active) surrounded by amorphous matrix (inactive). XRD, HR-TEM and DSC results supported the evidence of formation as the designed microstructure. Effect of the amorphous matrix on the electrochemical performance of the Si-alloy as an anode was investigated and will be discussed at the conference. Reference: [1] Chevrier, V. L., Liu, L., Le, D. B., Lund, J., Molla, B., Reimer, K., & Eberman, K. W. (2014). Evaluating Si-based materials for Li-ion batteries in commercially relevant negative electrodes. Journal of The Electrochemical Society, 161(5), A783-A791.