Kondracki Łukasz, Niemelä Janne-Petteri, Baster Dominika, El Kazzi Mario, Utke Ivo, Trabesinger Sigita
PSI Center for Energy and Environmental Sciences, Paul Scherrer Institute, Forschungsstrasse 111, Villigen CH-5232, Switzerland.
Laboratory for Mechanics of Materials and Nanostructures, Empa, Feuerwerkerstrasse 39, Thun CH-3602, Switzerland.
ACS Appl Energy Mater. 2024 Oct 14;7(20):9336-9348. doi: 10.1021/acsaem.4c01862. eCollection 2024 Oct 28.
Maintaining the electrochemically and mechanically stable solid electrolyte interphase (SEI) is of highest importance for the performance of high-capacity anode materials such as silicon (Si). Applying flexible Li-ion permeable coatings to the electrode surface using molecular layer deposition (MLD) offers a strategy to improve the properties of the SEI and greatly contributes to an increase in the cycle life and capacity retention of Si electrodes. In this study, the long-term cycling of Si electrodes with an MLD alucone coating is investigated in the context of more stable SEI formation. When the joined strategy introducing both MLD coating and anFEC electrolyte additive was realized, high performance of Si anodes was achieved, capable of delivering more than 1500 mAh g even after 400 cycles. The reason for the significantly improved longevity is the ability of the alucone layer to react with HF present in LiPF-based electrolytes already under OCV-like conditions, fluorinating most of the available -OH groups in the alucone structure. This reaction not only partially scavenges hydrofluoric acid but also does not disturb the confining effect of alucone-like fluorinated artificial SEI. This study shows the significance of searching for synergetic solutions, such as a combination of electrode surface modification and electrolyte composition, for maximizing the capacity retention of Si as an active material or as a capacity-enhancing additive to graphite electrodes, and as well can be applied to other high-energy battery materials with large volume changes during cycling.
对于硅（Si）等高容量负极材料的性能而言，维持电化学和机械稳定的固体电解质界面（SEI）至关重要。使用分子层沉积（MLD）在电极表面施加柔性锂离子可渗透涂层，提供了一种改善SEI性能的策略，并极大地有助于提高硅电极的循环寿命和容量保持率。在本研究中，在更稳定的SEI形成的背景下，研究了具有MLD铝酮涂层的硅电极的长期循环性能。当实现了引入MLD涂层和氟代碳酸乙烯酯（FEC）电解质添加剂的联合策略时，实现了硅负极的高性能，即使在400次循环后仍能提供超过1500 mAh g的容量。寿命显著提高的原因是，即使在类似开路电压（OCV）的条件下，铝酮层也能够与基于LiPF的电解质中存在的HF反应，使铝酮结构中大部分可用的-OH基团氟化。该反应不仅部分清除了氢氟酸，而且不会干扰类似铝酮的氟化人工SEI的限制作用。本研究表明，寻找协同解决方案（如电极表面改性和电解质组成的组合）对于最大化硅作为活性材料或作为石墨电极容量增强添加剂的容量保持率具有重要意义，并且也可应用于其他在循环过程中发生大体积变化的高能电池材料。
