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Author: Arnold, Stefanie × Start date: 2018 × DDC: 600 × Version: publishedVersion × WGL Institute: INM ×

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    Unraveling the Electrochemical Mechanism in Tin Oxide/MXene Nanocomposites as Highly Reversible Negative Electrodes for Lithium-Ion Batteries
    (Weinheim : Wiley-VCH, 2023) Gentile, Antonio; Arnold, Stefanie; Ferrara, Chiara; Marchionna, Stefano; Tang, Yushu; Maibach, Julia; Kübel, Christian; Presser, Volker; Ruffo, Riccardo
    Lithium-ion batteries are constantly developing as the demands for power and energy storage increase. One promising approach to designing high-performance lithium-ion batteries is using conversion/alloying materials, such as SnO2. This class of materials does, in fact, present excellent performance and ease of preparation; however, it suffers from mechanical instabilities during cycling that impair its use. One way to overcome these problems is to prepare composites with bi-dimensional materials that stabilize them. Thus, over the past 10 years, two-dimensional materials with excellent transport properties (graphene, MXenes) have been developed that can be used synergistically with conversion materials to exploit both advantages. In this work, a 50/50 (by mass) SnO2/Ti3C2Tz nanocomposite is prepared and optimized as a negative electrode for lithium-ion batteries. The nanocomposite delivers over 500 mAh g−1 for 700 cycles at 0.1 A g−1 and demonstrates excellent rate capability, with 340 mAh g−1 at 8 A g−1. These results are due to the synergistic behavior of the two components of the nanocomposite, as demonstrated by ex situ chemical, structural, and morphological analyses. This knowledge allows, for the first time, to formulate a reaction mechanism with lithium-ions that provides partial reversibility of the conversion reaction with the formation of SnO.
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    Three-Dimensional Cobalt Hydroxide Hollow Cube/Vertical Nanosheets with High Desalination Capacity and Long-Term Performance Stability in Capacitive Deionization
    ([Beijing] : China Association for Science and Technology, 2021) Xiong, Yuecheng; Yu, Fei; Arnold, Stefanie; Wang, Lei; Presser, Volker; Ren, Yifan; Ma, Jie
    Faradaic electrode materials have significantly improved the performance of membrane capacitive deionization, which offers an opportunity to produce freshwater from seawater or brackish water in an energy-efficient way. However, Faradaic materials hold the drawbacks of slow desalination rate due to the intrinsic low ion diffusion kinetics and inferior stability arising from the volume expansion during ion intercalation, impeding the engineering application of capacitive deionization. Herein, a pseudocapacitive material with hollow architecture was prepared via template-etching method, namely, cuboid cobalt hydroxide, with fast desalination rate (3.3 mg (NaCl)·g-1 (h-Co(OH)2)·min-1 at 100 mA·g-1) and outstanding stability (90% capacity retention after 100 cycles). The hollow structure enables swift ion transport inside the material and keeps the electrode intact by alleviating the stress induced from volume expansion during the ion capture process, which is corroborated well by in situ electrochemical dilatometry and finite element simulation. Additionally, benefiting from the elimination of unreacted bulk material and vertical cobalt hydroxide nanosheets on the exterior surface, the synthesized material provides a high desalination capacity ( mg (NaCl)·g-1 (h-Co(OH)2) at 30 mA·g-1). This work provides a new strategy, constructing microscale hollow faradic configuration, to further boost the desalination performance of Faradaic materials.