Bärmann Peer, Winter Martin, Gonzalez-Julian Jesus, Placke Tobias
University of Münster, MEET Battery Research Center, Institute of Physical Chemistry, Corrensstr. 46, 48149, Münster, Germany.
Helmholtz Institute Münster, IEK-12, Forschungszentrum Jülich GmbH, Corrensstr. 46, 48149, Münster, Germany.
Small. 2021 Nov;17(47):e2104130. doi: 10.1002/smll.202104130. Epub 2021 Oct 11.
MXenes attract tremendous research efforts since their discovery in 2011 due to their unique physical and chemical properties, allowing for application in various fields. One of them is electrochemical energy storage due to their pseudocapacitive (=redox) behavior, high electronic conductivity, and charge storage versatility regarding the cationic species (e.g., Li ). MXenes typically display stable charge/discharge cycling behavior over hundreds of cycles in numerous electrolytes, however, a drastic loss of reversible capacity is detectable during the initial cycles. Furthermore, an electrochemical "activation" is also reported in the literature, especially for free-standing electrodes. Here, these electrochemical phenomena are investigated by electrochemical and analytical means to decipher the responsible mechanism by comparing few-layered and multi-layered Ti C T . A change in the pseudocapacitive behavior of MXenes during cycling can be explained by in situ X-ray diffraction studies, revealing solvent co-intercalation in the first cycle for the morphologically different MXenes. This co-intercalation is responsible for the capacity decay detected in the first cycles and is also responsible for the ongoing "activation" occurring in later cycles.
自2011年被发现以来，MXenes因其独特的物理和化学性质吸引了大量的研究工作，使其能够应用于各个领域。其中一个应用领域是电化学储能，这是由于它们具有赝电容（即氧化还原）行为、高电子导电性以及对阳离子物种（如Li）的电荷存储多功能性。MXenes在众多电解质中通常在数百个循环中表现出稳定的充放电循环行为，然而，在初始循环期间可检测到可逆容量的急剧损失。此外，文献中也报道了电化学“活化”现象，特别是对于独立电极。在此，通过电化学和分析手段研究这些电化学现象，通过比较少层和多层Ti₃C₂Tₓ来破译其负责机制。循环过程中MXenes赝电容行为的变化可以通过原位X射线衍射研究来解释，揭示了形态不同的MXenes在第一个循环中溶剂的共嵌入。这种共嵌入是在第一个循环中检测到的容量衰减的原因，也是在后续循环中持续发生的“活化”的原因。
