Dendritic growth of lithium (Li) on lithium metal anodes has hobbled the practical application of Li-metal batteries, despite their theoretical benefits such as high capacity and low redox potential.

Now, researchers at the University of Illinois at Chicago, with colleagues at Texas A&M University, have used a 3D conformal graphene oxide nanosheet (GOn) coating, confined into the woven structure of a glass fiber separator, which permits facile transport of Li-ions throughout its structure, while inhibiting lithium dendrite formation.

In a paper in the journal Advanced Functional Materials, they reported a “remarkably enhanced” cycle life and stability of the Li-metal anode. Ab initio molecular dynamics (AIMD) simulations suggest that lithium ions initially get adsorbed to the lithiophilic GOn and then diffuse through defect sites. This delayed Li transfer eliminates the “tip effect” leading to a more homogeneous Li nucleation.

Meanwhile, the rupture of C—C bonds observed in the GO during AIMD simulations creates more pathways for faster lithium ion transport. In addition, phase-field modeling demonstrates that mechanically rigid GOn coating with proper defect size (smaller than 25 nm) can physically block the anisotropic growth of Li. The team suggested that their work represents a significant step toward the employment of 2D materials for regulating the Li deposition.

Schematics of Li deposition mechanism in case of GO-modified samples. A–F) Adsorption of Li-ions to the lithiophilic GOn coating and controlled on-site delivery of Li-ions to the metal surface, leading to a more uniform Li deposition. Further suppression of Li dendrites will be obtained by high mechanical stability of GOn acting as physical barrier. Foroozan et al. Click to enlarge.

We believe that the best design to prevent the uncontrolled Li deposition is the use of a light, cost effective, and scalable coating, which allows for Li-ions transport, is mechanically stable to suppress Li dendrites, and provides uniform charge distribution on the electrode surface. Carbon materials are in the spotlight for their outstanding physical and mechanical properties, which makes them a great candidate for hindering the dendritic deposition of Li metal anodes.

Herein, we propose that graphene oxide nanosheet (GOn), spray coated on the surface of glass fiber (GF) separator, can be widely used to stabilize the surface of the Li-metal anodes due to its ease of synthesis, lithiophilicity, ultrahigh mechanical strength (Young’s modulus approaching 300 GPa), super exibility (bending modulus approaching 1 kT), defective structure, and electrically insulating nature.

—Foroozan et al.

This research was funded by grant DMR-1620901 from the National Science Foundation and grant DE-EE0007766 from the US Department of Energy.

Resources

• T. Foroozan, F. A. Soto, V. Yurkiv, S. Sharifi-Asl, R. Deivanayagam, Z. Huang, R. Rojaee, F. Mashayek, P. B. Balbuena, R. Shahbazian-Yassar (2018) “Synergistic Effect of Graphene Oxide for Impeding the Dendritic Plating of Li” Adv. Funct. Mater. 1705917. doi: 10.1002/adfm.201705917