Novel Binder Improves Ion Diffusion in Sodium-Ion Batteries

Researchers at the Japan Advanced Institute of Science and Technology (JAIST) have focused on polymeric binders to enhance the performance and stability of electrodes in Sodium-ion batteries (SIBs). They developed a novel, highly functionalized, water-soluble poly(ionic liquid) called poly(oxycarbonylmethylene 1-allyl-3-methylimidazolium) (PMAI) and investigated its effectiveness in binding both lithium-ion batteries (LIBs) and SIBs. The study was published in Advanced Energy Materials.

The global market for electronic devices and electric vehicles is expected to grow and diversify in the coming years. To meet this rising demand, stronger batteries with enhanced performance, safety, and efficiency are essential.

For over 30 years, LIBs have dominated the secondary ion battery market. However, concerns over costly extraction methods, unethical distribution practices, and unsustainable extraction processes have led to a steady decline in the lithium supply.

As a result, industry players and researchers are exploring alternatives to LIBs. SIBs offer a promising alternative due to sodium's natural abundance, affordability, and considerable electrochemical potential. However, several challenges must be addressed before SIBs can be used for commercial applications.

Firstly, sodium's larger ionic radius compared to lithium leads to slower ion kinetics and more complex phase stability and interphase formation. Secondly, the development of electrodes that provide high performance and compatibility with both LIBs and SIBs remains a challenge. While carbon-based materials present some limitations, they also show promise as electrodes for both battery types.

In this study, Professor Noriyoshi Matsumi and doctoral student Amarshi Patra from the JAIST were involved in developing the PMAI-based anodic-half cell, which demonstrated excellent cyclic stability and electrochemical performance.

There has been a worldwide increase in demand for materials enabling fast charge-discharge and resolving the slow kinetics issue of sodium-ion diffusion. This polymer-based binder with dense ionic liquid functional groups acts as a component of high-performing electrode systems in SIBs.

Noriyoshi Matsumi, Professor, Japan Advanced Institute of Science and Technology

The researchers tested the efficacy of the new PMAI material by using it as a hard carbon anode binder in SIBs and a graphite anode binder in LIBs. The electrochemical evaluation results showed remarkable performance in the PMAI-based anodic-half cell. It demonstrated high capacities (297 mAhg^-1 at 1C for LIBs and 250 mAhg^-1 at 60 mAg^-1 for SIBs) and excellent cycle stability, retaining 96 % of capacity after 200 cycles for SIBs and 80 % after 750 cycles for LIBs.

Due to the formation of a functionalized solid electrolyte interphase through binder reduction and the presence of densely polar ionic liquid groups, the experimental results also demonstrated improved ion diffusion coefficients, lower resistance, and activation energy.

The full-cell examination confirmed improved performance and stability when PMAI was used as the anode binder, highlighting its potential as a binder material for secondary ion battery applications.

“This class of materials will be adopted in fast-charging energy storage systems for commercial applications, as this binder promotes improved sodium-ion diffusion. This study will encourage the development of more advanced materials, paving the way for new sodium-ion powered electronic devices and electric vehicles,” concluded Prof. Matsumi.

The developed novel poly(ionic liquid) is a novel class of material. Poly(ionic liquid)s have been intensely studied for a variety of applications such as energy storage devices, biochemical applications, sensing applications, catalytic applications, etc. Our novel densely ionic liquid functionalized polymer has potential utility for above-mentioned various research field.

Noriyoshi Matsumi, Professor, Japan Advanced Institute of Science and Technology

Journal Reference:

Patra, A., et al. (2024) Densely Imidazolium Functionalized Water Soluble Poly(Ionic Liquid) Binder for Enhanced Performance of Carbon Anode in Lithium/Sodium-Ion Batteries. Advanced Energy Materials. doi.org/10.1002/aenm.202403071