Beyond Polymerization: In Situ Coupled Fluorination Enables More Stable Interfaces for Solid-State Lithium Batteries
Xunjie Yin, Yong Guo, Sijia Chi, Yiran Jia, Fangbing Li, Jiangshan Qi, Xuerui Yi, Shichao Wu, Quan‐Hong Yang
Abstract
In situ polymerization strategies hold great promise for enhancing the physical interfacial stability in solid-state batteries, yet (electro)chemical degradation of polymerized interfaces, especially at high voltages, remains a critical challenge. Herein, we find interphase engineering is crucial for the polymerization process and polymer stability and pioneer an in situ polymerization-fluorination (Poly-FR) strategy to create durable interfaces with excellent physical and (electro)chemical stabilities, achieved by designing a bifunctional initiator for both polymerization and on-surface lithium donor reactions. The integrated in situ fluorination converts Li 2 CO 3 impurities on LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) surfaces into LiF-rich interphases, effectively inhibiting the aggressive (de)lithiation intermediates and protecting the interface from underlying chemical degradation, thereby surpassing the stability limitations of polymerization alone. Furthermore, the Poly-FR mediated symmetric Li|Li cells achieve an impressive cycling stability of up to 12,000 h. Solid-state cells with NCM811 cathodes and Li metal anodes realize an ultrastable cycling performance of 400 cycles with 83.4% retention at a high voltage of 4.5 V. This work points toward advanced in situ polymerization and beyond.