X.F. Li, Kai Huang, Wujun Zhang, Qitao Shi, Yueqi Wang, Yun Huang, Xin Zhao, Hui Xia, Xi Liu, Yanbin Shen, Liwei Chen
High Resolution Image Download MS PowerPoint Slide Layered sodium oxide cathodes form electrochemically unstable Na 2 CO 3 in humid air, causing capacity fade. This work redefines its role in cathode-electrolyte interphase (CEI) evolution. While a thick, loose Na 2 CO 3 layer promotes detrimental side reactions, a controlled layer can be transformed beneficially. Introducing fluoroethylene carbonate (FEC) enables this Na 2 CO 3 to react in situ, forming a NaF-rich CEI with a dual-layer structure: a dense, insulating NaF inner layer and a Na 2 CO 3 outer layer. This effectively suppresses interfacial decomposition, enhancing cycling stability. To minimize initial Na loss, a hydrophobic self-assembled monolayer (SAM) was employed to precisely regulate the Na 2 CO 3 thickness. The resulting composite “NaF/SAM-Na 2 CO 3 ” CEI synergistically delivers high initial capacity and exceptional long-term cyclability, achieving 88.7% capacity retention after 500 cycles. This study reveals Na 2 CO 3 ’s positive function and proposes a “preconstruction in situ transformation” strategy for designing advanced battery interfaces.