Financial News Agency, December 12 (Editor Huang Junzhi) As current flows through the battery, the materials inside the battery will gradually wear out. The physical forces of stress and strain also play a role in this process, but their exact impact on battery performance and longevity is currently not fully understood.

Therefore, the US Department of Energy's Oak Ridge National Laboratory (ORNL for short) decided to “take a different approach” and developed a framework for designing solid-state batteries (SSB), focusing on mechanical issues rather than electrochemical properties in general research. The results of the latest research have recently been published in the journal “Science”.

“Our goal is to highlight the importance of mechanics in battery performance,” said Sergiy Kalnaus, a scientist in ORnL's Multiphysics Modelling and Flow Group. “Much of the research focuses on chemical or electrical properties, yet ignores their potential mechanical mechanisms.”

According to reports, the team spans several ORNL research fields, including computation, chemistry, and materials science. Their review paints a more cohesive picture of the conditions affecting the SSB through the use of scientific perspectives.

solid electrolytes

In batteries, charged particles flow through a material called an electrolyte. Most of these electrolytes are liquids, such as lithium-ion batteries in electric vehicles, but solid electrolytes are also being developed. These conductors are usually made of glass or ceramic and can provide benefits such as increased safety and strength.

“Real solid-state batteries don't have flammable liquids inside,” Kalnaus said. “This means they're less dangerous than batteries commonly used today.”

The challenge of developing solid-state batteries

However, due to the challenges associated with these new materials, solid electrolytes are still in the early stages of development.

Specifically, SSB components expand and contract during charge and mass transfer, thereby altering the overall system. The electrodes constantly deform during battery operation, creating stratification and gaps at the interface with the solid electrolyte. In today's systems, the best solution is to apply a lot of pressure to keep everything together.

However, these dimensional changes can damage solid electrolytes made of brittle materials, which often break due to stress and pressure. Making these materials more malleable will allow them to withstand stress by flowing rather than breaking. This behavior can be achieved through some techniques that introduce small crystal defects into ceramic electrolytes.

Future planning

It is understood that the electrons leave the system through the anode. In SSB, the component can be made of pure lithium, the metal with the highest energy density, and although this material provides an advantage to the battery's power, it also creates pressure, which damages the electrolyte.

“Uneven coating and lack of stress relief mechanisms can cause stress concentration during charging.” Erik Herbert, head of ORNL's Mechanical Properties and Mechanics Group, said, “To optimize SSB performance and longevity, we need to design the next generation of anodes and solid electrolytes to maintain a mechanically stable interface without damaging the solid electrolyte diaphragm.”

In fact, the team's work is part of ORNL's long history of researching SSB materials. In the early 1990s, a glass-like electrolyte called lithium phosphorus oxide (LiPON) was developed in laboratories.

LiPon has been widely used as an electrolyte for thin-film batteries with lithium metal anodes. This component can withstand many charge-discharge cycles without failure, mainly due to LiPon's malleability. When it experiences mechanical stress, it flows rather than cracking.

The researchers said, “In recent years, we have learned that LiPon has strong mechanical properties to complement its chemical and electrochemical durability. In our paper, we outline the mechanics of solid electrolyte materials and encourage scientists to consider these when designing new batteries.”