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Sodium/Potassium (Na/K) metal anodes have been considered as the promising anodes for next-generation Na/K secondary batteries owing to their ultrahigh specific capacity, low redox potential and low cost. However, their practical application is still hampered due to unstable solid electrolyte interphase, infinite volume change, and dendrite growth. Herein, we design a 3D-Na₃Bi/3D-K₃Bi alloy host which enables the homogeneous and heterogeneous nucleation growth of Na/K metal. The unique structure with periodic alternating of electron and ion conductivity improves the mass transfer kinetics and prevents the volume expansion during cycling. Meanwhile, the sodiophilicity of Na₃Bi/potassiophilicity of K₃Bi framework can avoid dendritic growth. Cycling lifespans over 700 h with 1 mAh cm⁻² for 3D-Na₃Bi@Na electrode and about 450 h with 1 mAh cm⁻² for 3D-K₃Bi@K electrode are achieved, respectively …