Scientists Redefine Battery Interphase Design To Boost Sodium-Ion Technologies

Researchers in Japan have challenged long-standing assumptions about electrode interphases in sodium- and potassium-ion batteries, a step they say could accelerate the development of cheaper and more sustainable alternatives to lithium-ion technology.

A team led by Changhee Lee and Shinichi Komaba from Tokyo University of Science published a review in Advanced Energy Materials outlining how the solid-electrolyte interphase (SEI) and cathode-electrolyte interphase (CEI) in sodium- and potassium-ion batteries differ fundamentally from those in lithium-ion systems.

Lithium-ion batteries dominate global energy storage but rely on geographically constrained resources, prompting growing interest in sodium- and potassium-ion chemistries as lower-cost, resource-abundant alternatives suited to grid storage, electric vehicles and consumer electronics.

Electrochemical Reactions 

The researchers said performance limitations in sodium- and potassium-ion batteries stem partly from an incomplete understanding of the electrochemical reactions occurring at the electrode-electrolyte interface, which can lead to instability and shorter battery life.

“Our work reconsiders the conventional assumptions about ideal interphases and provides principles for their design,” Lee said in a statement. He added that interphases in sodium- and potassium-ion batteries should be understood differently from lithium-ion systems due to differences in solubility, electrolyte stability and ion transport.

The study argues that interphases should be viewed as dynamic, semi-solid layers rather than static films. It also highlights the role of binders and electrolyte formulation in controlling interphase behaviour, which the authors say could significantly improve battery stability, safety and cycle life.

Dramatic Impact 

Komaba said even small changes to interphase chemistry could have a “dramatic impact” on battery durability and performance.

The review also examined self-discharge, an often overlooked challenge. Although sodium- and potassium-ion batteries operate at lower cathode potentials, weaker CEI formation and electrolyte instability can accelerate self-discharge, the researchers said.

The findings suggest that improved interphase design could enable safer and longer-lasting sodium- and potassium-ion batteries for renewable energy storage, power tools and portable electronics.

The research was partially funded by Japan’s Ministry of Education, Culture, Sports, Science and Technology and several national research programmes and foundations.