A binder-driven cathode-electrolyte interphase a displacement reaction for high voltage NaV(PO)F cathodes in sodium-ion batteries

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2023-03, Vol.11 (11), p.554-5547
• Main Authors: Yun, Dae Hui, Song, Jinju, Kim, Jiseong, Seo, Joon Kyo, Kang, Joonhee, Park, Sohyun, Kim, Jaekook, Yoo, Dong-Joo, Choi, Sunghun
• Format: Article
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d2ta07990a

Sodium super ionic conductor (NASICON)-structured Na 3 V 2 (PO 4 ) 2 F 3 (NVPF) is a promising cathode for application in sodium-ion batteries (SIBs) because of its high working potential (3.7 V and 4.2 V vs. Na/Na + ) and structural stability. Nonetheless, interfacial instability deteriorates its electrochemical performance. Therefore, to overcome this limitation, we introduced a sodium polyacrylate (NaPAA) binder for NVPF cathodes. The NaPAA binder effectively suppresses electrolyte decomposition by uniformly covering NVPF particles. Furthermore, the sodium carboxylate group of R-COONa in the NaPAA binder can react with the HPO 2 F 2 intermediate generated by the hydrolysis of NaPF 6 and be converted into R-COOH and NaPO 2 F 2 via the displacement of Na + by H + . This results in the formation of a stable and Na-ion conductive NaPO 2 F 2 -rich cathode-electrolyte interphase (CEI) layer. In addition, the NaPAA-based electrode exhibits desirable cycling and rate performances compared to those of conventional poly(vinylidene difluoride)-based electrodes. This study provides new insights into the design of CEI layers by introducing chemical functional groups in the binder for high-performance SIB cathodes. A sodium polyacrylate (NaPAA) binder induces the formation of a stable and Na-ion conductive NaPO2F2-rich cathode-electrolyte interphase layer via a displacement reaction.