A research team from The Chinese University of Hong Kong (CUHK) has developed a novel interface engineering strategy by designing and assembling a tailored molecular layer on the surface of battery positive electrode materials, successfully modulating the chemical environment at the electrode-electrolyte interface. This strategy significantly enhances the stability and cycling performance of high-voltage lithium metal batteries, offering a new pathway toward safer, more stable, and higher-energy lithium metal batteries for the future. It also helps enhance the safety and driving range of electric vehicles and energy storage devices. The research findings have been published in the leading journal Nature Nanotechnology.
The hidden threat of high-voltage batteries: the interface we cannot see
Lithium metal batteries are widely regarded as a promising technology for next-generation electric vehicles and energy storage systems because of their exceptionally high energy density. Compared to current lithium-ion batteries, they offer the potential for longer driving ranges and lighter battery packs. However, when these batteries operate at high voltages, a hidden challenge emerges: what happens in the thin, invisible region where the electrode meets the electrolyte often determines whether the battery can function reliably. At this interface, electrolyte molecules can undergo oxidative decomposition, and the resulting byproducts gradually accumulate, leading to rapid performance decay and even battery failure. This challenge is difficult to address because it cannot be solved by improving electrode materials alone or by adjusting the electrolyte composition alone.
Smart molecular coating changes the game
The research team, led by Professor Lu Yi-Chun of the Department of Mechanical and Automation Engineering at CUHK’s Faculty of Engineering, proposed a novel approach: rather than passively enduring interfacial reactions, they chose to actively reshape the chemical environment at the interface. They assembled an ultrathin yet functionally precise molecular layer on the surface of the battery positive electrode material. This molecular coating changes how electrolyte molecules behave as they approach the surface. Some molecules in this layer are more welcoming and attract electrolyte molecules closer, while others are more reserved and keep them away. By tuning these molecular characteristics, the researchers can regulate the interfacial chemical environment, much like adjusting temperature. Through this delicate balance of attraction and repulsion, the team identified the optimal condition, forming a protective layer that suppresses harmful side reactions without interfering with the normal operation of the battery interface.
In experiments, the modified positive electrode maintained 80% of its initial capacity after 200 cycles under harsh high-voltage and elevated-temperature conditions (60°C), while unmodified electrodes showed much faster performance degradation. This improvement does not come from increasing the complexity of the electrode or electrolyte system but from a precise and controllable chemical modification at the interface. This suggests that the method could be integrated into existing battery manufacturing processes without requiring a complete system overhaul.
Professor Lu said: “This research reveals the molecular-level mechanisms at the electrode-electrolyte interface. We not only provide new scientific insights but also demonstrate a new pathway for interface design. Although the current validation has been carried out in laboratory-scale coin cells, in principle this method should be applicable to larger-scale battery systems. We hope this work will provide scientific guidance for the development of next-generation lithium metal batteries with both high energy density and high stability, accelerating their practical application and driving the electric vehicle and energy storage industries into a new phase of development.”
Molecular coating regulates the electrode-electrolyte interface and improves high-voltage lithium metal battery stability.
a. Schematic illustration of the electrical double layer with an ultrathin molecular coating anchored on the NMC811 positive electrode surface. The molecular layer is positioned close to the electrode surface and modulates the local chemical and electrostatic environment where electrolyte molecules approach the high-voltage electrode. Blue and pink circles represent electrolyte anions and cations, respectively, while white circles denote solvent molecules.
b. Long-term cycling performance of lithium metal coin cells at a high cut-off potential of 4.7 V. Compared with the pristine electrode, the molecular-coating-modified electrode shows markedly improved cycling stability and maintains 80% of its initial capacity after 200 cycles, demonstrating the effectiveness of interfacial molecular design in suppressing harmful side reactions.
Dr Wang Huwei, first author of the study and Postdoctoral Researcher in the Department of Mechanical and Automation Engineering, CUHK.
Professor Lu Yi-Chun
CUHK Press Release: CUHK develops molecular coating to enhance lithium metal battery stability, a key technological breakthrough for the electric vehicle industry