Triboelectric nanogenerators (TENGs) have attracted increasing attention because of their excellent energy conversion efficiency, the diverse choice of materials, and their broad applications in energy harvesting devices and self‐powered sensors. New materials have been explored, including green materials, but their performances have not yet reached the level of that for fluoropolymers. Here, a high‐performance, fully green TENG (FG‐TENG) using cellulose‐based tribolayers is reported. It is shown that the FG‐TENG has an output power density of above 300 W m−2, which is a new record for green‐material‐based TENGs. The high performance of the FG‐TENG is due to the high positive charge density of the regenerated cellulose. The FG‐TENG is stable after more than 30 000 cycles of operations in humidity of 30%–84%. This work demonstrates that high‐performance TENGs can be made using natural green materials for a broad range of applications.

Electric double-layer capacitors (EDLCs) or supercapacitors (SCs) are fast energy storage devices with high pulse efficiency and superior cyclability, which makes them useful in various applications including electronics, vehicles and grids. Aqueous SCs are considered to be more environmentally friendly than those based on organic electrolytes. Because of the corrosive nature of the aqueous environment, however, expensive electrochemically stable materials are needed for the current collectors and electrodes in aqueous SCs. This results in high costs for a given energy-storage capacity. To address this, we developed a novel low-cost aqueous SC using graphite foil as the current collector and a mix of graphene, nanographite, simple water-purification carbons and nanocellulose as electrodes. The electrodes were coated directly onto the graphite foil by using casting frames and the SCs were assembled in a pouch cell design. With this approach, we achieved a material cost reduction of greater than 90% while maintaining approximately one-half of the specific capacitance of a commercial unit, thus demonstrating that the proposed SC can be an environmentally friendly, low-cost alternative to conventional SCs.

The number of applications based on graphene, few-layer graphene, and nanographite is rapidly increasing. A large-scale process for production of these materials is critically needed to achieve cost-effective commercial products. Here, we present a novel process to mechanically exfoliate industrial quantities of nanographite from graphite in an aqueous environment with low energy consumption and at controlled shear conditions. This process, based on hydrodynamic tube shearing, produced nanometer-thick and micrometer-wide flakes of nanographite with a production rate exceeding 500 gh-1 with an energy consumption about 10 Whg-1. In addition, to facilitate large-area coating, we show that the nanographite can be mixed with nanofibrillated cellulose in the process to form highly conductive, robust and environmentally friendly composites. This composite has a sheet resistance below 1.75 Ω/sq and an electrical resistivity of 1.39×10-4 Ωm and may find use in several applications, from supercapacitors and batteries to printed electronics and solar cells. A batch of 100 liter was processed in less than 4 hours. The design of the process allow scaling to even larger volumes and the low energy consumption indicates a low-cost process.

Graphene and porous carbon materials are widely used as electrodes in supercapacitors. In order to form mechanically stable electrodes, binders can be added to the conducting electrode material. However, most binders degrade the electrical performance of the electrodes. Here we show that by using nanofibrillated cellulose (NFC) as a binder the electrical properties, such as capacitance, were enhanced. The highest capacitance was measured at an NFC content of approximately 10 % in ratio to the total amount of active material. The NFC improved the ion transport in the electrodes. Thus, electrodes made of a mixture of nanographite and NFC achieved larger capacitances in supercapacitors than electrodes with nanographite only. In addition to electrical properties, NFC enhanced the mechanical stability and wet strength of the electrodes significantly. Furthermore, NFC stabilized the aqueous nanographite dispersions, which improved the processability. Galvanostatic cycling was performed and an initial transient behaviour of the supercapacitors during the first cycles was observed. However, stabilized supercapacitors showed efficiencies of 98–100%.

To increase the energy storage density of lithium-ion batteries, silicon anodes have been explored due to their high capacity. One of the main challenges for silicon anodes are large volume variations during the lithiation processes. Recently, several high-performance schemes have been demonstrated with increased life cycles utilizing nanomaterials such as nanoparticles, nanowires, and thin films. However, a method that allows the large-scale production of silicon anodes remains to be demonstrated. Herein, we address this question by suggesting new scalable nanomaterial-based anodes. Si nanoparticles were grown on nanographite flakes by aerogel fabrication route from Si powder and nanographite mixture using polyvinyl alcohol (PVA). This silicon-nanographite aerogel electrode has stable specific capacity even at high current rates and exhibit good cyclic stability. The specific capacity is 455 mAh g−1 for 200th cycles with a coulombic efficiency of 97% at a current density 100 mA g−1.