Enhancing interfacial stability of high-voltage LiCoO2 via a zeolite front-face with confined channels for desolvation

A persistent challenge for high-voltage cathodes

Lithium cobalt oxide (LiCoO₂, LCO) is one of the most widely used cathodes in lithium-ion batteries, yet its practical energy density is far from the theoretical limit. Raising the charge cut-off voltage is a straightforward route to higher capacity. However, under high-voltage conditions, the solvent molecules of the electrolyte undergo severe oxidative decomposition at the cathode interface. In addition, a series of issues, including transition metal dissolution, oxygen release, and deteriorated thermal stability, have become bottlenecks that severely restrict its practical application.

A zeolite armor for LiCoO₂

Recently, Prof. Yang Sun (Sun Yat-sen University), Associate Researcher Maolin Yang (Xiamen University), Professors Qiaobao Zhang (Xiamen University), Yu Qiao (Xiamen University), and Academician Shi-gang Sun (Xiamen University) have reported a new strategy to address this challenge. They developed a high-speed solid-phase mechanofusion technique to fabricate a continuous and uniform zeolite coating directly onto LiCoO₂ particles. Unlike conventional wet-chemical methods, this solvent-free process is both simple and scalable, with an estimated annual output of 120 t year^-1 at production scale. The zeolite layer serves as a physical barrier that decouples the lithium-ion desolvation process from the electric-field-driven intercalation. Its sub-nano channels, approximately 4 Å in diameter, allow lithium ions to pass through while excluding solvent molecules. This creates a locally supersaturated electrolyte environment at the cathode surface, which inherently suppresses solvent dehydrogenation.

Multi-scale characterization for mechanistic understanding

To gain mechanistic insights, the team performed a series of characterizations. Molecular dynamics simulations revealed that lithium ions undergo near-complete desolvation at the zeolite interface, with a significantly reduced desolvation energy barrier compared to the bulk electrolyte. Bond valence site energy calculations further confirmed efficient lithium-ion transport within the zeolite channels. Fourier-transform infrared spectroscopy provided experimental evidence that the electrolyte confined within the zeolite reaches a supersaturated state, far exceeding the solubility limit. Time-of-flight secondary ion mass spectrometry and transmission electron microscopy analyses confirmed the absence of a conventional CEI on the cycled Zeolite@LCO cathode, with the zeolite layer itself acting as a robust artificial interphase.

Exceptional performance at ultrahigh voltages

The electrochemical results are striking. At a cut-off voltage of 4.8 V, the Zeolite@LCO cathode delivers approximately 83% capacity retention after 300 cycles — a notable achievement for conventional carbonate-based electrolytes. Even at an extreme 5.0 V, the coated cathode maintains stable operation with about 61% capacity retention after 200 cycles.

Beyond cycling stability, the zeolite coating also imparts significant improvements in thermal safety. Accelerating rate calorimetry tests show delayed onset of self-heating and higher thermal runaway temperatures for Zeolite@LCO. Online electrochemical mass spectrometry reveals substantially reduced oxygen evolution, attributed to the delayed phase transition of the delithiated cathode at elevated temperatures.

A generalizable strategy for cathodes

The applicability of this approach extends beyond LiCoO₂. The team demonstrated that zeolite-coated LiNi_0.8Co_0.1Mn_0.1O₂ also exhibits enhanced cycling stability at high voltages, suggesting a universal strategy for stabilizing nickel-rich layered oxides. This work provides a practical and translatable paradigm for developing high-energy-density lithium-ion batteries with improved safety. This finding was published in Science Bulletin.