South Korea's leading electric vehicle (EV) battery manufacturer, SK On, has recently unveiled a groundbreaking development in the realm of battery technology.
They have successfully collaborated with Professor Park Hee Jung's research team from Dankook University's Department of Materials Science and Engineering to create an innovative oxide-based solid electrolyte.
This electrolyte exhibits exceptional lithium-ion conductivity, which refers to how quickly lithium ions can move within the battery. Faster ion movement translates to improved battery performance and rapid charging capabilities. SK On anticipates that this breakthrough will enhance its competitiveness in the domain of all-solid-state batteries.
The research findings concerning this oxide-based solid-state electrolyte have garnered widespread recognition, with their publication as a cover article in the esteemed academic journal "Advanced Functional Materials" (Impact Factor 19.9). Furthermore, SK On and Dankook University's joint research team has completed patent applications for this technology both domestically and internationally.
What sets this newly developed solid-state electrolyte apart is not only its remarkable enhancement of lithium-ion conductivity but also its exceptional air stability. The team achieved a 70% increase in lithium-ion conductivity, reaching the world's highest level at 1.7 millisiemens per centimeter (1.7 mS/cm), by adjusting the additive material in the oxide-based solid-state electrolyte known as Li-La-Zr-O (Lithium-Lanthanum-Zirconium-Oxygen or LLZO).
Typically, an increase in lithium-ion conductivity can compromise stability. However, the research team effectively addressed this challenge by meticulously controlling the microstructure of LLZO. Solid-state electrolytes are typically susceptible to moisture (H2O) and carbon dioxide (CO2), which can degrade their functionality over time. In contrast, this particular solid-state electrolyte demonstrates outstanding stability under prolonged exposure to atmospheric conditions.
Although oxide-based solid-state electrolytes generally exhibit lower ionic conductivity compared to their sulfide-based counterparts, they offer superior chemical stability. This minimizes reactivity with anode materials and can prevent the formation of lithium dendrites—a tree-branch-like crystalline structure that can accumulate on the cathode's surface during charging and discharging. If these dendrites penetrate the separator and reach the anode, internal short-circuits and the risk of fire can occur.
Moreover, the use of oxide-based solid-state electrolytes can elevate the maximum operating voltage of batteries from the conventional 4.3V to an impressive 5.5V. This theoretical increase could result in a 25% boost in battery capacity.
This advanced solid-state electrolyte is not limited to NCM cathode-based solid-state batteries but can also be applied to next-generation batteries, including lithium-sulfur and lithium-air batteries. Currently, these next-generation batteries use liquid electrolytes, but the application of this solid-state electrolyte can transform them into all-solid-state batteries.
Additionally, this material can be integrated into SK On's high-molecular-oxide-based composite solid-state batteries, which are currently in development. Since oxide-based solid-state electrolytes possess superior mechanical properties compared to high-molecular alternatives, this application can effectively overcome the limitations associated with high-molecular all-solid-state batteries, such as dendrite formation.
As a result, this new electrolyte holds the potential to meet the demands for both fire safety and extended driving range in next-generation batteries.
Choi Kyoung-hwan, Head of SK On Next Generation Battery R&D Office, said, “This solid-state electrolyte, which has both ionic conductivity and atmospheric stability, will have a substantial ripple effect as an innovative technology for creating high-quality all-solid-state batteries.” He added, “Based on our superb future technological competitiveness, SK On will continue to forge growth opportunities in the field of next-generation batteries.”
Meanwhile, SK On is actively developing two types of all-solid-state batteries: high-molecular-oxide composite batteries and sulfide-based batteries. The company aims to produce early prototypes of both types by 2026 and plans to commercialize them by 2028. The construction of a next-generation battery pilot plant at the Daejeon Battery Research Institute is also underway and is expected to be completed next year.
