Transient implantable medical bionics offer great promise in the field of smart controlled release and tissue regeneration. On-board energy storage is the ideal power system to drive them. In this work, a critical component of such a device, a biodegradable polymer electrolyte (silk fibroin-choline nitrate) has been developed. The efficiency of this electrolyte is demonstrated when deployed in a biodegradable thin-film magnesium battery. The battery, encapsulated in silk, offers a specific capacity of 0.06 mAh cm-2. The enzymatic degradation of the whole device occurs over 45 days in the buffered protease XIV solution. A programmed battery lifetime can be achieved using silk protection layers. This battery system provides a new avenue for an on-board biodegradable power source for next-generation transient medical bionics.
Flexible freestanding electrodes are highly desired to realize wearable/flexible batteries as required for the design and production of flexible electronic devices. Here, the excellent electrochemical performance and inherent flexibility of atomically thin 2D MoS 2 along with the self-assembly properties of liquid crystalline graphene oxide (LCGO) dispersion are exploited to fabricate a porous anode for high-performance lithium ion batteries. Flexible, free-standing MoS 2 -reduced graphene oxide (MG) film with a 3D porous structure is fabricated via a facile spontaneous self-assembly process and subsequent freeze-drying. This is the first report of a one-pot self-assembly, gelation, and subsequent reduction of MoS 2 /LCGO composite to form a flexible, high performance electrode for charge storage. The gelation process occurs directly in the mixed dispersion of MoS 2 and LCGO nanosheets at a low temperature (70 °C) and normal atmosphere (1 atm). The MG film with 75 wt% of MoS 2 exhibits a high reversible capacity of 800 mAh g −1 at a current density of 100 mA g −1 . It also demonstrates excellent rate capability, and excellent cycling stability with no capacity drop over 500 charge/discharge cycles at a current density of 400 mA g −1 .
High performance supercapacitors coupled with mechanical flexibility are needed to drive flexible and wearable electronics that have anesthetic appeal and multi-functionality. Two dimensional (2D) materials have attracted attention owing to their unique physicochemical and electrochemical properties, in addition to their ability to form hetero-structures with other nanomaterials further improving mechanical and electrochemical properties. After a brief introduction of supercapacitors and 2D materials, recent progress on flexible supercapacitors using 2D materials is reviewed. Here we provide insights into the structure-property relationships of flexible electrodes, in particular free-standing films. We also present our perspectives on the development of flexible supercapacitors.
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