Multivalent cation exchange in copper telluride nanoparticles induces electrochemical polarization and high energy storage

Abstract

Efficient energy storage forms the backbone of nascent clean technologies, encompassing applications ranging from large-scale grid buffering to nanoscale capacitive systems.Mechanisms such as electrical double-layer formation and polarization-mediated energy storage are well-documented, particularly in classical thin-film ferroelectric capacitors and electrical double-layer supercapacitors. However, the impact of charge polarization resulting from multivalent cation exchange remains poorly explored. Chalcogenide nanoparticles, in particular, represent an attractive platform where atomic rearrangements, multivalent ion incorporation and internal potential gradients intersect, together supporting promising applications for energy storage. Earlier investigations have enhanced our understanding of the structural changes during ion exchange; however, it is necessary to elucidate the electrochemical consequences. To address this point, we used atomistic molecular dynamics (MD) and Monte Carlo (MC) simulations of multivalent cation exchange on Cu 2-x Te nanoparticles, considering models based on density functional theory (DFT). This computational scheme enabled the precise tracking of ionspecific polarization effects, electrostatic potential gradients and energy accumulation, as a function of ion content and distribution. Our findings reveal that specific Cu/Te ratios lead to asymmetric redistribution of exchanged copper and cadmium ions within the chalcogenide nanoparticles, resulting in spatial charge separation and the generation of an internal electric field and dipole moment. Surprisingly, the calculated theoretical gravimetric energy density for these materials is similar to, or even higher than, that of conventional lithium-ion batteries. Moreover, the incorporation of Eu³⁺ ions could enhance the electrochemical polarization and charge storage during initial Cd²⁺ exchange.These discoveries contribute to grasp ion-specific charge accumulation mechanisms in a more complete fashion. Furthermore, they constitute novel energy storage improvement tactics through controlled cation exchange within chalcogenide frameworks.