B-site engineered medium-entropy perovskite as a dual-purpose material enabling piezoelectric energy harvester and supercapacitor electrode applications

Abstract

This work focused on the synthesis of B-site-engineered medium-entropy perovskite oxides (MEPOs) with a general equimolar composition of La(Ti_0.25Mn_0.25Fe_0.25Co_0.25)O₃ (LTMFC), along with non-equimolar compositions in the B-site to explore the effect of cation disorder on structural and electrochemical performance. X-ray diffraction studies confirm the formation of a single-phase orthorhombic perovskite structure with the pbnm space group for both equimolar and non-equimolar compositions. The non-equimolar La(Ti_0.15Mn_0.15Fe_0.35Co_0.35)O₃ (TM-0.15) exhibits lattice expansion induced by oxygen vacancies, accompanied by partial reduction of Ti⁴⁺ to Ti³⁺, as verified by X-ray photoelectron spectroscopy. Compared with the equimolar LTMFC, non-equimolar TM-0.15 exhibits higher conductivity and faster ion diffusion, resulting in a specific capacitance of 526 F g⁻¹ at 1 A g⁻¹, exceeding that of the equimolar LTMFC (486 F g⁻¹) under identical conditions. Binder-free electrophoretic deposition enables uniform coating over Ni foam with excellent interfacial contact. TM-0.15 was incorporated into poly(vinylidene fluoride) (PVDF) to fabricate a piezoelectric nanogenerator (PENG) that charges the charge-storing devices. 5 wt% of TM-0.15 in PVDF exhibits a higher piezoelectric output voltage of 5 V at 1.5 kgf and is capable of charging a 2.2 µF capacitor to 1.45 V within 25 s. This study suggests that non-equimolar B-site engineering in MEPOs offers a viable strategy to outperform equimolar counterparts, enabling synergistic energy storage and harvesting.