#South Korea #EV Batteries #Solid-State Batteries #Hanyang University #Gyunggi-do

Recent Research on Solid-State EV Batteries

Researchers from Hanyang University have made a groundbreaking discovery regarding solid-state electric vehicle (EV) batteries, specifically sulfide-based all-solid-state batteries (ASSBs). These innovative batteries manage to utilize solid electrolytes instead of common liquid ones, presenting a promising solution to the limitations associated with traditional lithium-ion batteries. As exciting as this prospect may be, one significant hurdle remains: the necessity to ensure strong chemical compatibility at the interface between the cathode active materials (CAMs) and the sulfide-based solid electrolytes.

To tackle this issue, experts have proposed creating a thin protective layer on the surface of the cathode materials. This protective barrier can effectively reduce direct interactions between the cathode and the electrolyte, thereby minimizing the occurrence of detrimental side reactions. Prior investigations have indicated that successful application depends on maintaining the protective layer's thickness below 5 nanometers. However, the specific minimum thickness needed for optimal performance has remained ambiguous until now.

A dedicated team led by Professor Tae Joo Park from the Department of Materials Science and Chemical Engineering at Hanyang University undertook the task of defining this critical measurement. As Professor Park elaborates, “Our study innovatively moves beyond the traditional concept of optimal thickness, establishing a firm quantitative foundation for thickness-dependent interface design.” The results of their research have been published in Volume 86 of the journal Energy Storage Materials, dated March 8, 2026.

The experimental approach employed lithium niobium oxide (LNO) as a model substance for the protective layer. Utilizing a rotary-type powder atomic layer deposition (ALD) system, the researchers deposited LNO layers of varied thicknesses onto NCM811 powders, chosen for their widespread use in sulfide-based ASSBs. A unique technique called the supercycle method facilitated the precise regulation of both thickness and composition, where lithium and niobium were deposited in alternating cycles, combined with ozone (O₃).

For the study, ASSBs constructed with NCM811 powders received LNO layers measured at 1.0 nm, 2.5 nm, and 5.0 nm. Electrochemical performance evaluation unveiled clear trends linked to layer thicknesses. The LNO-1 cell initially performed outstandingly, boasting a discharge capacity of 229 mAh g⁻¹, as opposed to 216 mAh g⁻¹ for the LNO-2.5 and 207 mAh g⁻¹ for the LNO-5 cells. As expected, a gradual decline in capacity was noted with increased layer thickness.

Notably, while the LNO-1 displayed the least cycle life, around 28% longer cycle life was observed for both the LNO-2.5 and LNO-5 cells compared to the LNO-1. Enhancing interfacial resistance to ion transport was significant too, with the LNO-1 exhibiting a 59% greater resistance than the LNO-2.5 and LNO-5. Furthermore, the base cell was found to endure 43% shorter cycles and had a whopping 145% higher interfacial resistance than the one with the 2.5 nm layer.

Further microscopic and spectroscopic investigations confirmed that substantial suppression of interfacial reactions was only effective when the coating reached a minimum threshold of 2.5 nm. “Our study confirms that the minimal effective thickness for the LNO protective layer is indeed 2.5 nanometers,” Professor Park states. This finding serves as a practical guideline for enhancing cathode-electrolyte interface design in the next generation of solid-state batteries.

Such design insights are crucial not only for improving ASSBs' longevity for electric vehicles but may also lead to extended driving ranges for consumers. Despite remaining challenges related to integrating this precise powder-ALD procedure within full-scale gigafactories, the method holds promise for scalable manufacturing towards commercial viability. The research signifies a vital stride towards developing robust, high-energy solid-state batteries, which could redefine the landscape of electric vehicle performance and usage.

For more insights and detailed reading, please refer to the published study titled Minimum effective thickness of cathode protective layers for sulfide-based all-solid-state batteries via powder-atomic layer deposition in the journal Energy Storage Materials.