Scalable Binder-Free Freestanding Electrodes Based on a Cellulose Acetate-Assisted Carbon Nanotube Fibrous Network for Practical Flexible Li-Ion Batteries

Herein, a freestanding cellulose acetate–carbon nanotube (CA–CNT) film electrode is presented to achieve highly flexible, high-energy lithium-ion batteries (LIBs). CA serves as a dispersing agent of CNTs and a binder-free network former. A straightforward washing can remove CA in the electrode almost completely, while the fibrous CNT network within the electrode is sustained. Furthermore, the facile fabrication enables the large-scale production of the film electrode because the CA–CNT film is processed by a conventional casting method and not by the area-limited vacuum filtration. The superior electrochemical performance and high flexibility of the full cell assembled with CA–CNT-based electrodes are maintained even at a high active material loading, which has been proven difficult to accomplish in the conventional configuration LIBs. In addition, by simply stacking six sheets of the freestanding film electrode, a capacity as high as 5.4 mA h cm–2 is achieved. The assembled pouch battery operates stably under extreme deformation. We demonstrate that the rational design of the electrode could extend the flexibility to a higher energy than that achieved with the conventional configuration. We believe that the low production cost, high flexibility, and superior electrochemical performance of the proposed freestanding film electrode can expedite the implementation of wearable gears in daily life.