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Composite bipolar plates composed of conductivity fillers and resins are widely employed in stationary proton exchange membrane fuel cell (PEMFC) due to their high corrosion resistance in acidic environments. Phenol-formaldehyde resin is a commonly used adhesive in composite bipolar plates; while numerous benzene rings in phenol-formaldehyde resin result in the poor flexibility of composite bipolar plates. Embedding the flexible segment (–CHOH–CH 2 -O-) in the resin network structure of phenol-formaldehyde resin by copolymerization with epoxy resin is an effective method for improving the defects of phenol-formaldehyde resin. In this contribution, to tailor flexible-segment-rich (–CHOH–CH 2 -O-) resin network structure, the co-polymerization mechanism of phenol-formaldehyde resin and epoxy resin is investigated in detailed by in-situ Fourier Transform Infrared (FTIR), based on which an Alter-T strategy is proposed for flexible-segment-rich (–CHOH–CH 2 -O-) resin network structure during composite bipolar plates fabrication process. The obtained composite bipolar plates consisted of graphite and flexible-segment-rich resin network structure delivers improved flexural strength (86.97 MPa), electrical conductivity (203.22 S cm−1) and areal resistance (3.41 mΩ cm2) in comparison to previously reported composite bipolar plates with same components, which are also over the technical standard of the DOE. It is further demonstrated that enriching the flexible segment for improving the poor flexibility of resin network structure is of great importance to enhance the performance of the composite bipolar plates. A two-step alteration of temperature (Alter-T) strategy was proposed to tailor flexible-segment-rich (–CHOH–CH 2 -O-) in the resin network structure during polymerization, for improving the performance of CBP including mechanical properties and electrical conductivity. This approach provides a new insight of improving CBP performance by regulating resin network structure. [Display omitted] • Epoxy is embedded in the resin network structure of Phenol-Formaldehyde. • The resin network structure flexibility is improved by embedding flexible-segment. • The composite bipolar plates exhibit improved comprehensive performance. [ABSTRACT FROM AUTHOR]