Research Unveils Mechanism in Next-Gen Battery Dissolution

Abstract

Despite numerous studies aimed at solving the detrimental dissolution issue of organic electrode materials (OEMs), a fundamental understanding of their dissolution mechanism has not yet been established. Herein, we systematically investigate how changes in electrolyte composition affect the ion-solvent interactions propagating to OEM dissolution by changing the cation. The cyclability of OEM is significantly different by alkali cations, where the OEM with K is stable even after 300 cycles and that with Li is drastically decayed within 100 cycles. This different behavior is owing to the dissolution of OEM into electrolytes, and the dissolution of OEMs was found to be highly dependent on the cation-solvent interaction. Strong cation-solvent interactions induce cointercalation into the layered structure of the electrode and cause electrode deformation. This behavior allows OEMs to easily detach from their original location, consequently leading to dissolution and severe capacity decay. The cation-solvent interaction-dependent phenomenon is similar to that of OEMs with high-concentration electrolytes, in which fewer cation-solvent pairs exist. The result provides insight into proper electrolyte selection and is expected to set a constructive milestone in the utilization of organic electrodes.

An recent study has revealed significant insights into the intermolecular mechanisms involved in the dissolution of organic electrode materials (OEMs) within electrolytes during battery cycling tests.

Jointly led by Professor Won-Jin Kwak from the Department of Mechanical Engineering at UNIST and Professor Joonmyung Choi from Hanyang University, this research demonstrates the strong cation-solvent interaction energy within the electrolyte induces the accelerated dissolution of OEMs.

Organic batteries represent the next-generation of secondary batteries, replacing traditional metal electrodes, such as lithium and nickel, with cost-effective organic materials that can be manufactured on a continuous basis in industrial settings. However, the short lifespan of these batteries remains a significant barrier to commercialization, primarily due to the severe dissolution of OEMs into the electrolyte. While various studies have sought to address this issue, the underlying causes of dissolution have yet to be clearly identified.

The research indicates that strong cation-solvent interactions promote co-intercalation-a process whereby solvent molecules are incorporated along with cations into the microstructure of the electrode. When cations penetrate the electrode's internal structure, the involvement of solvent molecules causes it to expand, allowing the electrode material to flow out more readily. In contrast, weak interactions facilitate the straightforward insertion of cations without solvent involvement.

The research team arrived at these conclusions by systematically examining and analyzing experimental results with varying cation types, as well as calculating the interaction energy between cations and solvents. Their experiments, which involved lithium, sodium, and potassium ions, revealed that lithium ions produced the most pronounced interactions with solvent molecules, resulting in thinner electrodes with higher interaction energies.

Hyun-Wook Lee, the first author of the study, commented, "While previous research on organic electrodes primarily focused on restructuring materials to combat dissolution, our findings shed light on its root causes."

Professor Kwak added, "This study is the first to demonstrate that the dissolution of electrode materials is not merely a matter of solubility but rather a function of cation-solvent interactions and ensuing mechanistic changes. We also present a targeted electrolyte design strategy."

The findings of this research were published in ACS Nano on January 14, 2025, and were supported by the Ministry of Science and ICT's Nano and Material Technology Development Project.

Journal Reference

Ji-Hee Lee, Youngoh Kim, Hyun-Wook Lee, et al., "Control of Electrolyte Desolvation Energy Suppressing the Cointercalation Mechanism and Organic Electrode Dissolution," ACS Nano, (2025).