Intrinsically Stable Amorphous Phases Unlock Sustainable Potassium Anodes

Non-graphite-based anodes for potassium-ion batteries offer high capacity but suffer from severe structural degradation due to repeated phase transitions during cycling. Here, we introduce an amorphous phase engineering strategy that fundamentally addresses this instability. The intrinsic structural isotropy and open framework of amorphous materials inherently mitigate volume strain, enabling exceptional long-term cycling stability. As a proof of concept, an amorphous (Bi,Sb)@C electrode exhibits an ultralow capacity decay rate of merely 0.005% per cycle over 3200 cycles (equivalent to 1100 days) at 100 mA g^-1. This work establishes amorphous phase engineering as a general design paradigm, opening a decisive pathway toward durable, long-life potassium-ion batteries and potentially other energy storage systems facing similar stability challenges.