Monday, 30 May 2022
West Ballroom B/C/D (Vancouver Convention Center)
A. Serikkazyyeva (Nazarbayev University), B. Uzakbaiuly, Z. Bakenov (National Laboratory Astana, Nazarbayev University), and A. Mukanova (Nazarbayev University, Institute of Batteries)
Li-ion microbattery (LIMBs) are a hot topic for investigation due to the miniaturization of electronic devices. For better performance of the microbattery, it is really important to achieve good rate capability and stable cyclability of materials. Lithium metal (Li) is the most attractive anode material, which has a high theoretical capacity (3860 mAh/g), low negative potential, and low density. However, the main problem with Li anode is uncontrollable dendritic growth during the charge and discharge process, high reactivity with moisture, and explosion during cycling. Tin is also one of the promising candidates, which has a high theoretical specific capacity (992 mAh/g) to compare with commercial graphite, better retention of capacity, and longer cyclability. However, Sn anodes usually suffer from the high expansion of volume, which leads to the structure collapse and causes capacity attenuation during the discharge/charge process. Lithium-tin (LixSn) alloy can also act as a negative electrode which can reduce the drawbacks of both Li and Sn materials due to the following advantages. Firstly, the LixSn alloy exhibits a much higher theoretical specific capacity of 788 mAh/g than commercial graphite anode. Secondly, LixSny alloy demonstrates much higher initial Coulombic efficiency than Sn anode. Moreover, due to the strong affinity between Li22Sn5 and metallic Li the ultrafast Li diffusion can be enabled. As well as the small difference between the potentials of the Li22Sn5 and Li (0.3 V) served as a driving force of the Li diffusion. This structure of anode material can minimize the volume changes during stripping/plating by demonstrating lower overpotential. To the best of our knowledge, the LixSn alloy was not studied for use in microbatteries. However, the monolithic thin film can still experience the volume change and the amount of lithium is limited. In this point of view, the multilayered structure with the alternating LixSn and Li-rich layers can provide the highly diffusive media, buffer regions, and enough Li for reactions.
This study reports about the new thin-film anode based on LixSn alloy deposited by using magnetron sputtering and thermal evaporation techniques. Several variations of multilayers were investigated, such as Sn/Li/Sn, Sn/Li/Sn/Li/Sn, and also thicknesses of the anode were diversified. The microcells with liquid electrolyte were assembled and studied. According to the characterization results by SEM, the multilayer structure of the thin-film alloy has pores and a more smooth surface to compare with tin. Furthermore, the formation of an alloy was confirmed by XRD characterization. The developed anode with an initial specific capacity of 726 mAh/g and stable cyclability was tested during 100 cycles. The stripping-plating graphs also confirmed the better performance of 1.5 μm Sn/Li/Sn/Li/Sn anode. Finally, it can be concluded that the LixSn alloy-based anode material demonstrated significant results in terms of cyclability and stability, therefore can be promising anode material for next-generation LIMBs.
