Conventional lithium-ion batteries (LIBs) with liquid electrolytes are challenged by their big safety concerns, particularly used in electric vehicles. All-solid-state batteries using solid-state electrolytes have been proposed to significantly improve safety yet are impeded by poor interfacial solid–solid contact and fast interface degradation. As a compromising strategy, in situ solidification has been proposed in recent years to fabricate quasi-solid-state batteries, which have great advantages in constructing intimate interfaces and cost-effective mass manufacturing. In this work, quasi-solid-state pouch cells with high loading electrodes (≥3 mAh cm⁻²) were fabricated via in situ solidification of poly(ethylene glycol)diacrylate-based polymer electrolytes (PEGDA-PEs). Both single-layer and multilayer quasi-solid-state pouch cells (2.0 Ah) have demonstrated stable electrochemical performance over 500 cycles. The superb electrochemical stability is closely related to the formation of robust and compatible interphase, which successfully inhibits interfacial side reactions and prevents interfacial structural degradation. This work demonstrates that in situ solidification is a facile and cost-effective approach to fabricate quasi-solid-state pouch cells with both excellent electrochemical performance and safety.