Against the backdrop of global energy transition and the rapid development of the electric vehicle industry, high-energy-density and high-safety battery technologies have become a focus of attention for both scientific research and industry. Traditional lithium-ion batteries, due to the use of liquid electrolytes, face the risk of thermal runaway, limiting their application in higher energy-density scenarios. Solid-state batteries, as a representative of next-generation energy storage technology, are highly anticipated due to their high safety and theoretically high energy density. In this field, LLZTO (lithium lanthanum zirconium tantalum oxide), as a key solid-state electrolyte material, has attracted widespread attention in recent years for maintaining exceptionally low temperatures during battery operation.
In a groundbreaking study recently published in PRX Energy, a research team from the University of California, Riverside has uncovered the intrinsic mechanism by which LLZTO materials maintain low temperatures during charging and discharging cycles. This discovery not only resolves a long-standing scientific question within the academic community but also provides critical theoretical foundations for designing safer, higher-energy-density next-generation lithium batteries.
During battery charge and discharge, the internal electrochemical reactions inevitably generate heat. If this heat cannot be dissipated in time, it will lead to battery performance degradation, shortened cycle life, and even, in extreme cases, thermal runaway, causing fires or explosions. Therefore, thermal management is a crucial aspect of battery system design. LLZTO, as a ceramic-based solid electrolyte, not only possesses high ionic conductivity, supporting higher energy density battery designs, but also exhibits extremely low thermal conductivity, significantly reducing the risk of overheating and combustion.
However, the reason for LLZTO’s low thermal conductivity has remained a mystery. To explore its intrinsic properties, the research team used an advanced “floating zone method” to prepare high-quality LLZTO single-crystal samples. The single-crystal structure eliminates interference from grain boundaries, defects, and other factors, truly reflecting the intrinsic physical properties of the material. The latest experimental results show that LLZTO’s thermal conductivity is only 1.59 W/m·K, approximately 1/250th that of copper, indicating that its low thermal conductivity is an inherent property.
Through a combination of neutron scattering experiments and atomic-scale simulations, researchers further revealed its microscopic mechanism: in solid materials, heat is primarily transferred through “phonons”—the quantized form of collective atomic vibrations. Research has revealed a large number of “optical phonon” modes within the LLZTO lattice. These modes, with high and asynchronous vibrational frequencies, strongly interact with the dominant “acoustic phonons” responsible for heat transfer, leading to intensified phonon scattering and effectively hindering heat conduction.
Elucidating this mechanism not only explains the excellent thermal insulation properties of LLZTO materials but also provides new insights into controlling the thermal transport behavior of materials at the atomic level. Through phonon engineering, it may be possible to develop more novel solid-state electrolytes with controllable thermal conductivity, driving innovation in battery thermal management technology.
From a holistic energy system perspective, this discovery has profound implications. As the proportion of renewable energy continues to increase, large-scale energy storage systems place higher demands on battery safety, lifespan, and energy density. The application of LLZTO-like materials is expected to help build safer solid-state battery systems and improve system reliability in scenarios such as electric vehicles and grid energy storage. Furthermore, this research provides an example of the interdisciplinary integration of materials science and energy engineering, demonstrating the leading role of fundamental mechanism research in technological breakthroughs.
Looking ahead, with a deeper understanding of the thermal behavior of key materials for solid-state batteries, and by combining AI-assisted material screening with multi-scale simulation technology, humanity will be better able to design new battery systems that combine high energy density and intrinsic safety, injecting strong momentum into the global green energy transition.
