The amorphous GeO x (x <1) was synthesized and investigated its suitability as a Na-ion battery anode. GeO x was synthesized by oxidizing Zintl-phase NaGe with isopropyl alcohol at room temperature. The amorphous GeO x showed good electrochemical Na storage as an anode for Na-ion batteries, with first reversible capacity of 342mAhg−1, high power of 237mAhg−1 (6Ag−1), and cycle performance, retaining a capacity of 216mAhg−1 after 40 cycles.