The rapid development of E-Skin has attracted researchers’ attention to portable wearable devices. However, it is a great challenge to achieve high-output performance and high-environmental protection simultaneously. Polyhydroxybutyrate (PHB) has excellent electron-withdrawing ability and biodegradability, but its stretching ability is poor, which limits its application in portable wearable devices. In this paper, the biocompatible poly(lactide-co-caprolactone) (PLCL) was innovatively selected to modify the properties of the PHB electrospun membranes, and PHB/PLCL composite membranes with different contents of PLCL were constructed. Then, the expanded polytetrafluoroethylene (ePTFE) membranes and PHB/PLCL electrospun membranes were used as the friction layers to construct a flexible triboelectric nanogenerator (TENG). With the increase of PLCL contents, the elastic recovery rate of the composite membranes increased to 68% of tension at 40% strain. The toughness of the composite membrane was increased by 546%, which exhibits ultratoughness and stretchable properties. Based on the ultratoughness and high elasticity electrospun membranes with 50% PLCL, a stretchable and large deformation sensing device was made. The PHB/PLCL-ePTFE TENG could distinguish pingpong and badminton accurately, as well as their various postures such as forehand, backhand, smash poses, etc., which provided a new idea for large deformation monitoring of TENGs.