Yes, you can power your modules directly with single-cell LiPo/LiFo battery. A single LiPo/LiFo cell is usually between 3.5~4.2V. Thus, you will need to add a diode in series to get ~0.5V voltage drop and to keep the voltage level suitable for the MCUs. This configuration saves the cost and size of powering the module. For more details about powering Hexabitz module, please refer to this article.