This paper proposes a new electret with high surface potential and high thermal resistance, which is made of nano-porous silicon dioxide (SiO
2). Electrical charge density in the nano-porous SiO
2 is higher than that in a normal (i.e., nonporous) SiO
2 because there are many voids in the nano-porous SiO
2 and the interface between void and SiO
2 traps electrical charges strongly. Therefore, decrease rate of the trapped charge density in the nano-porous SiO
2 is lower than that of normal SiO
2. Since SiO
2 is thermally stable, thermal stability of the electrical charge in nano-porous SiO
2 electret is better than that in a polymer electret. Output power generated by vibration energy harvesting using the nano-porous SiO
2 electret is also larger than that using the normal SiO
2 or polymer electret.
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