| 摘要 |
The present invention provides a sodium ion secondary battery and a lithium ion secondary battery capable of reversible high-capacity electrical discharge. The sodium ion secondary battery and lithium ion secondary battery comprise a positive electrode, a negative electrode and an electrolyte. The active substances in the positive electrodes and negative electrodes of these secondary batteries are single-phase polycrystalline materials represented by the chemical formula NaxTi4O9 (2 ≤ x ≤ 3), preferably Na2Ti4O9, having a one-dimensional tunnel-type structure and belonging to the monoclinic crystal system. These polycrystalline materials are produced by filling a container comprising a material such as molybdenum with raw materials including a sodium compound, and a titanium compound and/or metallic titanium, and firing at a temperature of from 800°C to 1600°C inclusive. |
