image: Schematic representation of the MOF glass coating in facilitating facile lithium-ion pre-desolvation and accelerating fast lithium-ion transport of Glass@Graphite electrode.
Credit: ©Science China Press
How do batteries achieve extreme fast charging? While lithium-ion batteries power everything from smartphones to electric vehicles, their widespread adoption is hampered by a critical limitation: slow charging speeds. The bottleneck lies primarily in the graphite anode. During rapid charging, lithium ions struggle to shed their solvent molecules quickly enough—a process known as desolvation—before entering the anode material. This leads to metallic lithium plating and the formation of an unstable solid electrolyte interphase (SEI), causing rapid capacity fade and serious safety risks.
Conventional solutions, such as highly concentrated electrolytes or conventional surface coatings, have only offered partial fixes, often at the expense of rate capability, cost, or manufacturing scalability. A material that can simultaneously accelerate ion desolvation and ensure rapid, stable transport to the graphite has remained a major challenge.
A Glassy Nano-Sieve for Faster Ions
Addressing this challenge, a research team led by Professor Zhi Chang from Central South University and Professor Haoshen Zhou from Nanjing University has developed a transformative coating strategy using a glassy metal-organic framework (MOF). "The key was to design a coating that acts sequentially—first as a selective gatekeeper, then as a superhighway for lithium ions," explains Professor Chang. Their work, published in the National Science Review, demonstrates a uniformly coated graphite anode (Glass@Graphite) that enables unprecedented fast-charging performance.
The breakthrough lies in the coating's dynamic evolution. Initially applied as an ultra-thin (~5 nm), continuous glassy layer, it transforms during the first discharge cycle into a unique dual-layer architecture. The outer layer is a rigid, insulating MOF glass with precisely engineered 2.93 Å-wide pores. These sub-nanometer channels act as a molecular sieve, forcibly stripping solvent molecules from the lithium ions (pre-desolvation) and creating a highly concentrated ionic environment that promotes the formation of a robust, LiF-rich SEI.
Simultaneously, an inner layer rich in Li₃P forms in contact with the graphite. "Li₃P is a superb lithium-ion conductor", notes Professor Chang. "This layer acts as an ion accelerator, enabling the partially desolvated, smaller lithium ions to diffuse ultrafast into the graphite bulk." This synergistic design—decoupling the slow desolvation step from the subsequent transport step—is the core innovation.
Unprecedented Performance in Real Batteries
The electrochemical results are striking. In half-cell tests, the Glass@Graphite anode maintained a high capacity of over 250 mAh/g at an ultra-high current of 5C, outperforming bare graphite by more than fivefold. More importantly, in practical full-cells paired with commercial NCM-811 cathodes, the batteries delivered exceptional stability, retaining 88% of their capacity after 1,000 cycles under a demanding 4C fast-charging regime.
To validate real-world applicability, the team fabricated a 2.36 Ah pouch cell. It achieved a high energy density of 283 Wh/kg and maintained over 80% of its capacity after 300 cycles, underscoring the technology's commercial viability. Post-mortem analysis revealed a clean, dendrite-free graphite surface with a stable crystal structure, confirming the coating's effective protection over long-term cycling.
Prospects for Fast-Charging Batteries
This glassy MOF coating strategy provides a definitive solution to the long-standing desolvation-transport trade-off in graphite anodes. The low-temperature, scalable synthesis process makes it highly attractive for industrial adoption. By engineering a smart interface that manages ion flow with nanoscale precision, this work paves a clear and promising path for the development of next-generation lithium-ion batteries capable of both extreme fast charging and long service life.