New Interface Strategy Enhances Ion Flow in Solid-State Batteries

Lithium-ion batteries have become the global standard. Today, it is the most popular and widely used type of battery, with its market size estimated to be valued at about $65 billion in 2023.

But, of course, they are not without drawbacks, including temperature sensitivity, safety concerns, and limited lifespan.

To make Li-ion batteries safer and more powerful, liquid electrolytes are being replaced with solid ones to create solid-state batteries, whose market is projected to grow at a CAGR of 41.6% between 2024 and 2032.

A Shift to Solid-State Batteries (SSBs)

In a battery, the electrolyte is the material that makes it possible for ions to move through the device to generate power.

So, a battery that has a solid electrolyte is a solid-state battery, which provides higher energy density, faster charging, temperature resilience, longer timespan, and enhanced safety.

Despite their promise, SSBs also face several challenges, including complex manufacturing and potential safety concerns related to dendrite formation. Also, they can experience interfacial delamination, limiting their performance and lifespan. Together, these limitations are hindering the widespread adoption of SSBs.

To overcome these challenges, researchers and companies around the world are actively working on advancing the tech.

For instance, Samsung SDI is targeting an energy density of 900 Wh/L through its proprietary solid electrolyte and anode-less technologies, 40% higher than its current batteries.

Chinese giants CATL and BYD are also making significant strides in SSB tech, with the former working on a hybrid “condensed state battery” and the latter researching oxide- and sulfide-based solid electrolytes, both targeting an energy density of 500 Wh/kg.

In the EU, Volkswagen has partnered with QuantumScape (QS ). Its battery unit, PowerCo, has also secured a licensing deal to mass-produce solid-state cells with an initial capacity of 40 GWh annually, 30% more range, and ultra-fast charging.

Nissan is planning to begin mass production of its first solid-state cells before the decade is over, while LG is targeting 2030 for commercialization. Solid Power, meanwhile, has partnered with Ford (F ), BMW, and SK Innovation to accelerate the commercialization of all-solid-state battery technology with a focus on sulfide-based solid electrolytes for EVs.

Earlier this month, German multinational automotive company Mercedes-Benz Group AG (formerly Daimler) unveiled the first car powered by a lithium-metal SSB on the road. The prototype SSB was integrated into an EQS late last year.

The SSB in an EQS-based vehicle can increase the driving range by 25%, noted the company.

So, while in progress, the commercialization of SSBs is still several years away. In the meantime, a team of researchers from the University of Texas at Dallas has discovered a way to boost the performance of solid-state batteries.

Enhancing Ionic Conductivity in SSBs

Published in ACS Energy Letters, the latest study details the discovery of an enhanced ionic conductivity upon mixing a solid electrolyte with another solid.

This increased ionic conductivity is caused by the formation of a space charge layer at the interface, providing a new strategy for developing fast ionic conductors for SSBs. The ‘space charge layer’, as a result of the mixing of small particles between two solid electrolytes, is an accumulation of electric charge at the interface between the two materials.

What happens is that when the solid electrolyte materials, which are separate, make physical contact, a layer is formed at their boundary. At the boundary, charged particles accumulate because of differences in the chemical potential of each material.

The layer then helps create pathways that make it easier for these charged particles or ions to move across the interface. According to the study’s co-corresponding author, Dr. Laisuo Su, who is an assistant professor of materials science and engineering in the Erik Jonsson School of Engineering and Computer Science:

“Imagine mixing two ingredients in a recipe and unexpectedly getting a result that is better than either ingredient alone.”