(Invited) Mechanically Extreme Batteries: From Flexible to Structural

Batteries with extreme mechanical properties are attractive for unique applications. On the soft side, flexible and stretchable batteries are attractive for wide applications, such as health care and flexible electronics. It is challenging to realize high flexibility/stretchability and high energy density simultaneously. In this talk, I will talk about feasible and scalable strategies to fabricate flexible lithium-ion batteries, which can concurrently have high energy density and high mechanical flexibility, including bendability, foldability, twistability and stretchability. Inspired by the structure of animal spine, the vertebrae-like hard segments with multiple layers of conventional anode/separator/cathode stack to offer energy storage are interconnected by the soft components as marrow with the monolayer stack to provide flexibility. On the other hand, mechanically strong batteries are also important as they may replace structural components in vehicles and aircrafts for lightweighting. I will discuss a scalable and feasible tree-root-like lamination at the electrode/separator interface, which effectively transfers load between different layers of battery components and thus dramatically enhances the flexural modulus of pouch cells from 0.28 to 3.1 GPa. A graphite/LiNi0.5Mn0.3Co0.2O2 full cell with such interfacial lamination delivers a steady discharge capacity of 148.6 mAh g−1 at C/2 and 95.5% retention after 500 cycles. A prototype of “electric wings” is also demonstrated, which allows an aircraft model to fly steadily.