Penn State Researchers Advance Safer Solid-State Batteries with Cold Sintering Technique

allanbrelon · 2025-04-26T04:06:31Z

Lithium-ion batteries have long been essential for powering modern devices, but the liquid electrolytes they use are unstable, creating risks of fire and safety concerns. Researchers at Penn State are now pursuing a safer energy storage alternative for laptops, smartphones, and electric vehicles: solid-state electrolytes (SSEs).

According to Hongtao Sun, assistant professor of industrial and manufacturing engineering, solid-state batteries—which replace liquid electrolytes with SSEs—are a promising alternative to traditional lithium-ion technology. While there are key differences, both battery types share similar operational principles.

"Rechargeable batteries have two internal electrodes: an anode and a cathode," Sun explained. "The electrolyte connects these two, allowing ions to move between them. In lithium-ion batteries, the electrolyte is liquid, but in solid-state batteries, it’s solid."

Solid-state batteries offer greater stability and safety compared to conventional lithium-ion batteries but present manufacturing and conductivity challenges. One major obstacle is the high temperatures required to fabricate ceramic-based SSEs, which complicates production and practical use.

To address this issue, Sun and his team turned to a technique called cold sintering—a process where powdered materials are treated with a small amount of liquid, gently heated, and then compressed into a dense form. This method operates at much lower temperatures than traditional sintering, relying on pressure and minimal heat rather than extreme temperatures.

The researchers used cold sintering to integrate a highly conductive ceramic-polymer composite SSE known as LATP-PILG. Traditional ceramic SSEs consist of polycrystalline grains separated by grain boundaries, which act as defects that impede ion transport. To improve conductivity, Sun’s team co-sintered a poly-ionic liquid gel (PILG) with LATP ceramics, creating a polymer-in-ceramic composite that enhances stability and conductivity.

The PILG functions as a highly conductive "grain boundary," improving ion transport across engineered interfaces rather than through natural, defect-prone ones. Initial attempts to fabricate the composite using traditional high-temperature sintering failed because the high heat destroyed the polymer components before the ceramic could properly densify.

"One of the main challenges with LATP-based composite SSEs is that conventional sintering temperatures are so high that additives like polymers burn away before the ceramic forms," Sun said. "This is why cold sintering, with much lower temperatures, was necessary."

Cold sintering technology was first developed at Penn State in 2016 by Clive Randall, director of the Materials Research Institute. Its application to solid-state batteries began in 2018, when researchers in Enrique Gomez’s lab successfully cold sintered ceramic composite electrolytes.

Traditional sintering requires temperatures reaching around 80% of a material’s melting point—often between 900 to 1,000 degrees Celsius for ceramics like LATP. In contrast, Sun’s team achieved successful cold sintering at just 150 degrees Celsius.

"This lower temperature enables us to integrate different materials into a dense form without worrying about their distinct processing limits," Sun said.

This advancement could significantly improve the manufacturing of safer, more efficient solid-state batteries, paving the way for their broader use in next-generation electronic devices and vehicles.

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Penn State Researchers Advance Safer Solid-State Batteries with Cold Sintering Technique

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