The piezoionic effect refers to the generation of high ionic currents due to ionic polarization caused by the differentiated movement of cations and anions in polymer electrolytes under gradient deformation. This novel power generation mechanism resembles physiological electricity and shows great promise in bio-related applications. The field of piezoionics benefits from the excellent designability of flexible polymeric materials in terms of their functionality and properties. In this review, the universal basic principles of piezoionics are described first. Subsequently, we summarize four strategies for enhancing net ionic flux through advanced material engineering: structural design optimization, interface engineering, phase separation control, and ion selectivity enhancement. Furthermore, we summarize the current applications in sensing and biointerface technology, as well as provide a prospective analysis of existing challenges and technical limitations for future development. Overall, this review aims to demonstrate the comprehensive development of novel piezoionics and accelerate the transition of these materials from basic research to practical applications.