Boosting electrochemical performance by regulating rigid-flexible microphase separation of multiblock copolymers

[Display omitted] •A novel rigid-flexible multiblock copolymer PBC-mb-PBS was successfully synthesized.•Microphase separation structure was modulated by block molar ratio to regulate ionic conductivity.•This rational multiblock copolymer design for QSPEs offers superior overall performance. The growth of lithium dendrites and associated safety issues hinder the further development of liquid lithium metal batteries. A novel rigid-flexible multiblock copolymer PBC-mb-PBS was successfully synthesized based on molecular design. Incorporating crystalline rigid phase polybutylene succinate (PBS) into PBC-mb-PBS significantly enhances its tensile strength and low-temperature toughness through physical crosslinking. The flexible polydibutyl 2-(2-cyanoethyl)malonate (PBC) phase with side-chain cyano groups facilitate ionic conduction, forming a LiN-rich stabilized interfacial layer, thereby improving oxidative stability and high-voltage cathode compatibility. A series of multiblock copolymers with varying segment lengths were synthesized to balance mechanical properties and ionic conductivity by adjusting microphase separation. The quasi-solid-state polymer electrolyte (QSPE), derived from PBC-mb-PBS with the molar block ratio of 0.42, exhibits optimal electrochemical performance with ionic conductivity of 6.20 × 10−5 S cm−1 at 30°C and 4.22 × 10−4 S cm−1 at 60°C. Due to its bicontinuous microphase structure, it also shows excellent mechanical strength and promotes uniform lithium deposition at high current densities. Li//LiFePO4 and Li//LiNi0.83Co0.05Mn0.12O2 cells demonstrate high capacity retention, confirming the potential of this polymer electrolyte in high-voltage applications. This design strategy offers insights for developing quasi-solid-state lithium metal batteries with superior overall performance.