Towards Durable Fast-Charging All-Solid-State Batteries: Challenges and Mitigation Strategies for High-Loading Composite Cathodes

All-solid-state batteries (ASSBs) are recognized as next-generation energy storage systems capable of delivering high energy density, enhanced safety, and rapid charging. Yet, achieving durable performance at practical areal capacities remains challenging, with the composite cathode acting as a decisive bottleneck. This review critically examines fast-charging ASSBs with an emphasis on the design, degradation, and mitigation of high-loading composite cathodes. We first outline design fundamentals, including cathode architecture, the role of active/inactive phases, and the transport and mechanical characteristics of solid electrolytes. We then analyze coupled chemo-mechanical phenomena, such as volume change-induced stress, interfacial evolution, and pressure/temperature effects, which accelerate impedance growth and capacity fade under fast-charging conditions. Key degradation pathways, including lithium plating, dendrite growth, particle fracture, and current density hotspots, are evaluated for their impact on cycle life. Emerging diagnostic strategies and engineering solutions, such as interface modification, dry electrode processing, and solid electrolyte tuning, are discussed as pathways to scalable, durable performance. By consolidating insights from operando studies and translational projects, this review identifies research gaps and provides a forward looking perspective on enabling high energy, fast-charging ASSBs suitable for electric mobility and grid applications.