In-situ investigation and application of cyano-substituted organic electrode for rechargeable aqueous Na-ion batteries

•A cyano-substituted organic electrode is proposed for aqueous Na-ion batteries.•Cyano groups play an important role in optimizing the electronic properties.•The organic electrode processes a fast, stable, and efficient Na+ storage capability.•Redox characteristics are deeply probed by in-situ investigations and DFT calculations.•A soft-package aqueous Na-ion battery is assembled with exceptional performance.