A binder-driven cathode-electrolyte interphase via a displacement reaction for high voltage Na3V2(PO4)(2)F-3 cathodes in sodium-ion batteries

초록

Sodium super ionic conductor (NASICON)-structured Na3V2(PO4)(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 HPO2F2 intermediate generated by the hydrolysis of NaPF6 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 NaPO2F2-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.

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