Carbohydrate-derived block copolymers for sustainable zinc microanodes in aqueous 3D microbatteries

• Applicants: Professor Dr. Kai Zhang; Dr. Minshen Zhu, Ph.D.
• Subject Area: Microsystems
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 455635425

The rapid evolution of miniaturized electronic devices demands high-energy-density microbatteries with small footprint areas, which requires the development of an advanced micromachining technology to minimize the footprint area of a microbattery. At the same time, pushing miniaturized electronic devices towards wearables requires high safety standards. The intrinsic safety and high capacity of zinc ion aqueous batteries allow them to emerge as an excellent replacement for lithium ion batteries. By using mildly acidic solutions as electrolytes, the reversibility of zinc ion batteries can be significantly improved. However, the mildly acidic solution leads to the corrosion of the zinc anode, which limits the cycling stability of the microbattery. Therefore, a reliable strategy that resolves corrosion issues and improves reversibility of the zinc anode in aqueous electrolytes is of great importance. In this project, we will address these challenges by integrating a group of carbohydrate-derived block copolymers into a novel 3D microbattery design for the production of high-energy microbatteries. Various copolymers will be synthesized based on glucose, which is modified with functional groups. These functional copolymers act as artificial interphases for the zinc microanode, which can simultaneously create a "zinc blanket" for high cation transport and suppress corrosion. Starting with the glucose-derived monomers, we will investigate the effect of the glucose units and the introduced functional groups on zinc reversibility. In parallel with our research on the preparation of various copolymers, we will integrate the copolymers into rolled-up nanotechnology towards Swiss-roll microelectrodes, which is based on the mechanical transformation of thin-film systems into 3D objects. The mechanical transformation will be well controlled by tuning the force field that is established by the swelling ability of a hydrogel layer. At the same time, the hydrogel layer directly functions as the electrolyte by swelling in the aqueous electrolyte. In terms of structural stability during the fabrication process and subsequent battery tests, the intimate interaction between copolymers and hydrogels is of great importance. Therefore, topological adhesion between copolymers and hydrogels will be investigated. By optimizing copolymers and their adhesion with zinc and hydrogels, we aim to develop a highly reversible zinc Swiss-roll microanode. To fabricate 3D microbatteries, the zinc Swiss-roll microanode will be developed by coupling with a Swiss-roll microcathode based on manganese oxide. The capacity and cycling stability of 3D Swiss-roll microcathodes will be optimized to realize the ultimate goal of this project: a 3D microbattery delivering high energy output (> 10 μWh) with a minimal footprint area (< 2 mm2) and high stability (> 500 stable cycles).

• DFG Programme: Research Grants