Soft solid electrolyte enhances battery safety

For lithium-ion battery makers and users, battery safety overrides other considerations, including longevity. Yet, there are instances of explosion in Li-ion batteries. The current semi-liquid, electrolyte-based batteries are prone to fires because of battery overheating or short circuits. One of the ways researchers are addressing this problem is by using solid electrolytes in Li-ion batteries.

In a recent study in Nature Materials (go.nature.com/3O0PE2u), researchers from Temple University, Philadelphia; the Indian Institute of Science Education and Research (IISER) Pune; and their collaborators made a soft solid electrolyte, (Adpn)₂LiPF₆ (Adpn, adiponitrile). This electrolyte is a salt of lithium and is semi-soft in nature. Unlike traditional electrolytes, it exhibits great thermal and electrochemical stability alongside good ionic conductivity. It is also able to overcome the limitations of traditional ceramic and organic electrolytes.

Additionally, the researchers conducted simulation studies to look at battery behaviour and function in large systems and over long timescales. Simulation studies, such as the ones carried out in this study, allow researchers to understand battery behaviour with more granularity. Such studies help researchers understand how a material is decomposing inside a battery and how different type of ions interact with each other and with the solvent inside the battery. They help them see these interactions at a molecular level. "Simulations are like molecular microscopes that help us track atom by atom," says Arun Venkatnathan, Professor of Chemistry at IISER Pune and co-author of the study.

In the adiponitrile battery, molecular simulations helped predict the behaviour of lithium ions on grain boundaries and how they differ from lithium ions elsewhere in the battery. Being able to distinguish between the two types of lithium ions helped researchers understand the mechanism of ion conduction in the battery. They were able to calculate the theoretical ionic conductivity of the electrolyte using simulations and subsequently compare it with the experimental data.

The simulations developed for this study can help other experimental battery researchers choose better salts and solvents, and to better understand the thermodynamic conditions of their batteries, says Venkatnathan. Having focused on electrolytes in this study, the researchers now want to "find out how electrolytes can talk to electrodes and the chemistry involved in the process".