NSRRC Activity Report 2023

Energy Science 069 In addition, Hwang’ team has been championing a groundbreaking anode-free rechargeable aqueous hybrid battery design noted for its exceptional safety, eco-friendliness, and affordability. This innovative architecture is initiated through the in situ deposition of tin onto the surface of a copper current collector, with the electrolyte serving solely as the source of zinc ions. 2 The in operando TXM observations enhance our understanding of the mechanisms behind zinc and tin plating and stripping on the copper substrate. In operando TXM imaging has the capability to monitor interfacial phenomena and changes in morphology during the processes of zinc deposition and removal. Notably, the findings indicate that the additive-free electrolyte cannot establish a stable coating. By contrast, adding SnBr 2 to the electrolyte promotes the formation of a copper–tin alloy, leading to effective nucleation, thus achieving a more uniform and consistent layer of zinc deposition. The resulting formation of a uniform and compact layer of zinc implies that the initial nucleation of tin plays a crucial role in ensuring the evenness and smoothness of the zinc layer. The distinct plateau, indicative of Cu/Sn/Zn alloy formation, signifies improved nucleation and homogeneity in zinc deposition. As shown in Fig. 2 , the tin layer aids in creating a smooth, uniform, dense, and dendrite-free zinc layer on the copper, a process enhanced by favorable conditions provided by alloy formation. The formation of the copper–tin alloy stabilizes the zinc plating and removal within the anode-free aqueous hybrid battery, achieving an average coulombic efficiency of approximately 99.1%. This is in stark contrast to the 97.6% efficiency of the electrolyte without any additives. Utilizing an electrolyte enriched with SnBr 2 , the capacity retention rate after 100 charging and discharging cycles increases significantly to 35.2%, a substantial increase from the mere 7.8% observed in the absence of additives. Thus, the addition of SnBr 2 significantly improves zinc deposition and removal processes by encouraging the formation of a Cu/Sn/Zn alloy inside the battery, resulting in a more stable cycle life free from dendritic zinc growth. Moreover, in the realm of battery research, analysis of energy materials’ three-dimensional structure is crucial for improving our understanding of battery performance. Recently, Duncan H. Gregory from the University of Glasgow (United Kingdom) and Yan-Gu Lin from the NSRRC collaborated, utilizing the TXM to investigate these aspects. Their research focused on the three-dimensional characterization of a novel nanoporous silicon (NP-Si) material, which shows promise in replacing conventional graphite anodes in lithium-ion batteries, potentially improving their performance. The viability of NP-Si as a sustainable material is closely related to its production process, which traditionally relies on methods that are harmful to the environment. To address this, the collaborative team developed a more environmentally friendly production technique that efficiently converts SiO 2 into Mg 2 Si using low-powered microwaves in conjunction with magnesium plasma. The microwave- induced metal plasma (MIMP) method (see Fig. 3(a) ) produces a three-dimensional NP-Si structure, characterized using the TXM (as shown in Fig. 3(b) ), that is particularly well-suited for use as an anode in batteries. In summary, the use of synchrotron-based transmission X-ray microscopy for analyzing the three-dimensional tomographies of energy materials, coupled with the observation of structural changes during in situ / in operando electrochemical reactions, provides a crucial visualization of how material structures affect battery performance. This valuable insight has the potential to expedite the development and performance evaluation of new energy materials. Consequently, the TXM has established itself as an essential and irreplaceable tool in the field of energy materials development and research. (Reported by Chun- Chieh Wang) This report features the work of Bing-Joe Hwang and his collaborators published in ACS Energy Lett. 8 , 2817 (2023) and Electrochim. Acta 443 , 141883 (2023), and the work of Duncan H. Gregory and his collaborators published in ACS Appl. Mater. Interface 15 , 36076 (2023). TLS 01B1 X-ray Microscopy • TXM • Energy Materials, Materials Science, Environmental and Earth Sciences, Physics References 1. M. A. Weret, S.-K. Jiang, K. N. Shitaw, C.-Y. Chang, T. M. Tekaligne, J.-C. Chiou, S.-C. Yang, N. T. Temesgen, Y. Nikodi- mos, S.-H. Wu, C.-C. Wang, W.-N. Su, B. J. Hwang, ACS Energy Lett. 8 , 2817 (2023). 2. T. A. Nigatu, H. K. Bezabh, S.-K. Jiang, B. W. Taklu, Y. Nikodimos, S.-C. Yang, S.-H. Wu, W.-N. Su, C.-C. Yang, B. J. Hwang, Electrochim. Acta 443 , 141883 (2023). 3. Z. Fan, W.-R. Liu, L. Sun, A. Nishio, R. Szczęsny, Y.-G. Lin, S. Okada, D. H. Gregory, ACS Appl. Mater. Interface 15 , 36076 (2023).