The team, led by Prof. Chen Guohua, Chair Professor of the Department of Chemical and Biological Engineering at HKUST, developed a cartilage-inspired polymer nanocoating that suppresses the degradation and wear of battery cathode materials where it begins: at the internal grain boundaries of individual cathode particles. The work, carried out with Dr. Liu Qiang, a Research Assistant Professor in the same department, and Dr. Liu Yutong, a postdoctoral fellow who began the research during her PhD at The Hong Kong Polytechnic University, demonstrates that a coating only about fourteen nanometers thick can act as a dynamic shock absorber inside battery particles, holding capacity at exceptionally high levels after thousands of charge-discharge cycles.

The problem the coating addresses is known as intergranular cracking, and it is the central obstacle standing between laboratories and the commercial deployment of next-generation nickel-rich layered cathodes. These nickel-rich materials are attractive because they pack more energy into the same volume, which is exactly what manufacturers of electric vehicles and consumer electronics want. But during cycling, the lithium ions that shuttle in and out of the cathode cause repeated volume changes in the material. Those changes generate severe dynamic internal stress, and because layered cathode particles are polycrystalline aggregates built from many smaller primary particles, the stress concentrates along the boundaries between those grains. Cracks propagate, the electrical and ionic pathways inside the particle are severed, isolated fragments stop contributing to capacity, and the cathode degrades cycle by cycle.

The HKUST team’s solution came from an unlikely teacher: the human knee. Cartilage in human joints performs a remarkable mechanical function, deforming under load and dissipating external stress so that the brittle bones beneath it are protected from damage. Replicating that biological strategy at the nanoscale, the researchers designed a crosslinked shape-memory polymer with the chemical designation p(BA-V4D4). The material is engineered to balance two properties that normally pull against each other: deformability, which lets it absorb and redistribute mechanical stress, and strength, which keeps it from simply being squeezed out of the way. When placed between adjacent primary particles inside a cathode, the optimized copolymer behaves, in the team’s own description, like cartilage between bones.

Getting a polymer into the interior of a battery particle is not straightforward, and this is where the team’s process innovation matters as much as the material itself. The researchers used initiated Chemical Vapor Deposition, or iCVD, a gas-phase technique previously developed in Chen’s laboratory. In iCVD, monomer vapors are delivered to the substrate and polymerize in situ on its surface, requiring no liquid solvents. Because the reactants travel as vapor, they can penetrate spaces that liquid coatings cannot reach. In this work, the monomer vapor penetrated deep into the electrode’s secondary particles, reaching the vulnerable internal boundaries between primary particles through nanosized channels just ten to twenty nanometers wide and roughly four thousand nanometers deep, and polymerized there to form a resilient, highly uniform stress-absorbing layer roughly fourteen nanometers thick.

Dr. Liu Qiang, a co-corresponding author of the study, explained the mechanism in the university’s announcement. By deploying a shape-memory polymer as an adaptive stress dissipator, he said, the team can suppress intergranular cracking through a solid stress delocalization mechanism, and the polymer structure was engineered to achieve an optimal balance between deformability and strength. He credited the laboratory’s earlier CVD technology for enabling the coating to be integrated into grain boundaries through those incredibly narrow nanosized channels. Dr. Liu Yutong, a co-first author, added that traditional methods cannot penetrate the grain boundaries of cathode materials or allow researchers to tune the mechanical properties of the polymer easily, whereas the iCVD method transports reactants into those boundaries to form a protective coating via in-situ polymerization. She noted that the team has successfully applied the technology to nickel-rich NCM cathodes and to commercial LiFePO4 materials, demonstrating its universal applicability across different cathode chemistries.

The shape-memory character of the polymer is what elevates it beyond a passive binder. A conventional coating might cushion a particle once, but under the repeated cyclic loading of thousands of charge-discharge cycles, a passive layer would fatigue and fail. A shape-memory polymer, by contrast, can deform under stress and recover its configuration, delocalizing stress dynamically rather than merely absorbing a single impact. In effect, the coating converts the sharp, localized stress concentrations that would otherwise nucleate cracks into distributed, manageable deformation across the particle’s interior. That is precisely the role cartilage plays in a joint, and it is why the researchers describe their material as biomimetic rather than simply protective.

For Prof. Chen, the achievement is the culmination of a research thread that began two decades ago. He recalled that the idea of applying CVD polymer coatings to energy storage materials took shape during his sabbatical at MIT in 2005, where CVD polymers were being applied to pharmaceutical particles for controlled drug release. His laboratory has since been, in his words, the first to successfully apply the technology to lithium-ion battery materials, and it previously demonstrated that CVD can coat conductive polymers in research published in Nature Energy in 2019. The new p(BA-V4D4) work extends that platform to a broader range of functional polymeric materials, positioning iCVD as a general tool for engineering the mechanical environments inside energy storage devices rather than only their surfaces.

The implications reach beyond conventional liquid-electrolyte cells. Prof. Chen said the team is now exploring the application of the technology to solid-state batteries, where mechanical stress at interfaces is an even more acute problem and where the coating could help address critical challenges related to both high-energy density and safety. Solid-state designs replace the flammable liquid electrolyte of conventional cells with a solid medium, but maintaining stable contact and managing stress between rigid solid components remains one of the field’s hardest problems, making an adaptive stress-dissipating interlayer an appealing candidate. Meanwhile, the team is scaling up the iCVD process to produce coated cathode particles at the 1,000-kilogram scale, enough to manufacture large batteries for industrial applications spanning consumer electronics, electric vehicles, and electric vertical takeoff and landing aircraft, a category of aircraft whose viability depends heavily on battery energy density and cycle life.

The research was a collaborative effort involving experts from universities and institutions across Hong Kong and the Chinese Mainland, contributing materials synthesis, characterization, and data science. Co-first authors alongside Dr. Liu Yutong are Prof. Zuo Wenhua of Xiamen University and Dr. Wang Wei, a PhD graduate of The Hong Kong Polytechnic University. Key contributors include Dr. Yu Hailong and Prof. Huang Xuejie of the Institute of Physics at the Chinese Academy of Sciences, Prof. Liu Xiang of Beihang University, Prof. Ruan Haihui and Dr. Lin Cong of PolyU, Dr. Zhang Kai of the Institute of High Energy Physics at the Chinese Academy of Sciences, Prof. Du Ke of Central South University, and Prof. Pan Feng of Peking University Shenzhen Graduate School. The study, titled Dynamic delocalization of stress in brittle battery positive electrode active materials by shape-memory polymer nanocoating, was published in Nature Nanotechnology on 23 July 2026. If the scale-up succeeds, the humble engineering lesson embedded in human joints, that resilient, deformable layers protect brittle structures from repeated stress, may soon be running inside the batteries of phones, cars, and aircraft, quietly extending the working life of the devices that depend on them.

Subject of Research: A biomimetic shape-memory polymer nanocoating that suppresses intergranular cracking in lithium-ion battery cathode materials.

Article Title: HKUST develops novel cartilage-inspired polymer nanocoating to substantially extend battery lifespan

Article References: HKUST develops novel cartilage-inspired polymer nanocoating to substantially extend battery lifespan. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: lithium-ion batteries, cathode materials, nanocoating, shape-memory polymer, initiated chemical vapor deposition, nickel-rich cathodes, intergranular cracking, biomimetic materials, solid-state batteries, HKUST, Nature Nanotechnology, battery degradation