Studies Explore Mechanics, Materials for Solid-State Batteries

Solid-state batteries (SSBs) are at the forefront of next-generation energy storage solutions, offering higher energy density and enhanced safety than their lithium-ion counterparts. However, the technology still grapples with significant challenges, including mechanical strain and environmental sustainability. 

 

Solid-state battery. Image used courtesy of Adobe Stock

 

Two recent studies offer groundbreaking solutions to these issues. The first, led by Oak Ridge National Laboratory (ORNL), delves into the mechanical aspects of SSBs, highlighting the need for material ductility and pressure management. The second study, a collaborative effort between UNIST and KAIST, introduces Prussian blue Analogs (PBAs) as eco-friendly solid electrolytes, addressing cost and environmental concerns.
 

Mechanics of SSBs

The research team at ORNL is focusing on an often-overlooked aspect of SSBs: the mechanics. 

As compared to conventional lithium-ion batteries, SSBs are considered a significant advancement. However, they face challenges related to mechanical strain, particularly in the solid electrolytes that replace liquid counterparts. These electrolytes are prone to dimensional changes during charge and mass transport, leading to delamination and voids at the interfaces. Such mechanical issues can compromise the structural integrity and, consequently, the performance and longevity of the battery.

 

The ORNL research team focused on SSB mechanics. Image used courtesy of Kalanus et al.

 

The ORNL team developed a comprehensive framework considering mechanical influences on SSBs to address these challenges. One of their key findings is the need for significant pressure to maintain the structural integrity of the battery components. This insight could lead to engineering solutions incorporating pressure management systems within the battery architecture.

Another pivotal aspect of the research is the focus on material ductility. The study suggests that introducing ductility into solid electrolytes could make them more resilient to mechanical stress, thereby preventing cracking and enhancing longevity. The team proposes techniques such as introducing small crystal defects into ceramic electrolytes as potential solutions.

 

Cheaper, Eco-Friendly SSBs

The second study, conducted by researchers from UNIST in collaboration with KAIST, focuses on developing eco-friendly solid electrolytes using Prussian blue analogs. 

Although SSBs have gained more attention and promise, the technology faces challenges such as high manufacturing costs and environmental concerns associated with traditional solid electrolytes. To tackle these issues, the research team turned to PBAs, a class of materials known for their versatile electrochemical properties. The study systematically investigates the electrochemical characteristics of five different N-coordinated transition metal ions—Manganese (Mn), Cobalt (Co), Iron (Fe), Nickel (Ni), and Copper (Cu)—to understand their influence on sodium ion (Na+) conductivity. 

 

The research team investigated the use of PBAs for SSBs. Image used courtesy of Kim et al.

 

In their study, the researchers found that Mn-based PBAs demonstrated the highest Na+ conductivity, attributed to their larger ionic size and lattice parameters. This high conductivity makes Mn-PBA promising for use as a solid electrolyte in all-solid-state sodium batteries. Notably, PBAs also offer a sustainable alternative to solid electrolytes, often involving rare or toxic elements. 

 

A Brighter Future for SSBs

The future of energy storage technologies hinges on overcoming the existing limitations of SSBs, and these two studies make significant strides in that direction. 

ORNL's focus on the mechanical integrity of SSBs addresses an important gap in understanding these batteries, offering engineering solutions that could lead to more resilient and long-lasting energy storage systems. On the other hand, the UNIST-KAIST collaboration opens up new avenues for eco-friendly and cost-effective SSBs by introducing PBAs as a viable alternative to traditional solid electrolytes. 

Together, these studies address the immediate challenges facing SSBs and lay the groundwork for more sustainable and efficient energy storage solutions.