Can I charge a lipo battery using piezoeletric energy harvesting?
In principle, any source of voltage/current can be used to provide power. In the case of piezoelectrics, the devil is in the details: PZTs simply don't produce much.

Especially in this case, you are looking at a losing cause. Consider that your esp8266 draws 75 mA at 3.3 volts, or 247 mW. Meanwhile, according to your illustration, the PZT produces 5.36 mW. I'm sure you see the problem.

If you were to make a dedicated micropower controller, you could produce a unit which transforms the high-voltage/low current PZT output to a usable level. The controller would turn off the 8266 most of the time, and direct the transformed PZT output to a battery charger. At regular intervals, the controller would turn the 8266 on and allow it to make a measurement, then turn it off again. You would, of course, need to account for the power draw of the controller, but dedicated simple logic can be built in CMOS with very low power draw.

In the best possible case, the duty cycle of the 8266 would be about 5.36/247, or about 2%. This would assume perfect efficiency both in the transformation/charging process, and in the 3.3 regulator. And you won't get that in either case. Regulators can operate in the 90% efficiency range if you know what you're doing, but battery charging is notoriously inefficient, especially as you approach full charge. I'd estimate that you might hope for something on the order of a factor of 5 - 10 worse than the ideal.