Lüchtefeld Janik, Lee Ming-Yu, Hemmelmann Hendrik, Wachs Susanne, Behling Christopher, Mayrhofer Karl J J, Elm Matthias T, Berkes Balázs B
Non-Aqueous Electrochemistry, Electrocatalysis Department, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Cauerstr. 1, 91058 Erlangen, Germany.
Department of Chemical and Biological Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 1, 91058 Erlangen, Germany.
ACS Omega. 2023 Aug 25;8(36):32606-32614. doi: 10.1021/acsomega.3c03173. eCollection 2023 Sep 12.
A fundamental understanding of aging processes in lithium-ion batteries (LIBs) is imperative in the development of future battery architectures for widespread electrification. Herein, dissolution of transition metals from cathode active materials of LIBs is among the most important degradation processes. Research has demonstrated that elevated operating temperatures accelerate battery degradation. However, the exact mechanism of transition-metal dissolution at elevated temperatures has still to be clarified. Current literature suggests that the reaction rate of dissolution increases with increasing temperature; moreover, the decomposition of electrolytes results in products that also accelerate dissolution processes. Most studies focus on ex situ analyses of thermally treated full cells. This approach is not appropriate to get detailed insights and to distinguish between different contributions. In this work, with the help of real-time dissolution analysis using an electroanalytical flow cell (EFC) coupled to an inductively coupled plasma mass spectrometer (ICP-MS), we present novel details of the temperature effects on in situ dissolution at the cathode electrolyte interface. With fresh electrolytes, we find increased Mn dissolution even at open-circuit conditions as well as with constant voltage polarization when the electrode sample is heated at constant temperatures between 50 and 80 °C. The release of transition metals also responds in a nuanced manner when applying temperature transients. Utilizing electrolytes preheated at 60 and 100 °C, we demonstrate that decomposition products in the bulk electrolyte have no influence on transition-metal (TM) dissolution when constantly flushing the cell with the thermally aged electrolyte samples. Only when keeping the cathode temperature at 60 °C, the dissolution increases by a factor of 2-3. Our findings highlight the interplay between the cathode and electrolyte and provide new insights into the dissolution mechanism of cathode materials.
要开发适用于广泛电气化的未来电池架构，深入了解锂离子电池（LIBs）的老化过程至关重要。在此，锂离子电池正极活性材料中过渡金属的溶解是最重要的降解过程之一。研究表明，升高的工作温度会加速电池降解。然而，高温下过渡金属溶解的确切机制仍有待阐明。当前文献表明，溶解反应速率随温度升高而增加；此外，电解质的分解会产生加速溶解过程的产物。大多数研究集中在对热处理后的全电池进行非原位分析。这种方法不适用于获得详细的见解以及区分不同的影响因素。在这项工作中，借助与电感耦合等离子体质谱仪（ICP-MS）联用的电分析流动池（EFC）进行实时溶解分析，我们展示了温度对阴极电解质界面原位溶解影响的新细节。使用新鲜电解质时，我们发现即使在开路条件下以及当电极样品在50至80°C的恒定温度下加热并进行恒压极化时，锰的溶解也会增加。施加温度瞬变时，过渡金属的释放也会有细微的响应。利用在60°C和100°C预热的电解质，我们证明当用热老化的电解质样品持续冲洗电池时，本体电解质中的分解产物对过渡金属（TM）溶解没有影响。只有当阴极温度保持在60°C时，溶解增加2至3倍。我们的研究结果突出了阴极与电解质之间的相互作用，并为阴极材料的溶解机制提供了新的见解。
