Yunya Zhang

Cotton-textile-enabled flexible self-sustaining power packs via roll-to-roll fabrication

With rising energy concerns, efficient energy conversion and storage devices are required to provide a sustainable, green energy supply. Solar cells hold promise as energy conversion devices due to their utilization of readily accessible solar energy; however, the output of solar cells can be non-continuous and unstable. Therefore, it is necessary to combine solar cells with compatible energy storage devices to realize a stable power supply. To this end, supercapacitors, highly efficient energy storage devices, can be integrated with solar cells to mitigate the power fluctuations. Here, we report on the development of a solar cell-supercapacitor hybrid device as a solution to this energy requirement. A high-performance, cotton-textile-enabled asymmetric supercapacitor is integrated with a flexible solar cell via a scalable roll-to-roll manufacturing approach to fabricate a self-sustaining power pack, demonstrating its potential to continuously power future electronic devices.

Cotton-Textile-Enabled, Flexible Lithium-Ion Batteries with Enhanced Capacity and Extended Lifespan

Activated cotton textile (ACT) with porous tubular fibers embedded with NiS2 nanobowls and wrapped with conductive graphene sheets (ACT/NiS2-graphene) was fabricated by a simple two-step heat treatment method. When used as a binder-free electrode, the ACT/NiS2-graphene electrode exhibited an exceptional electrochemical performance including ultrahigh initial discharge capacity (∼1710 mAh g(-1) at 0.01 C), magnificent rate performance (the discharge capacitance retained at ∼645 mAh g(-1) at 1 C after 100 cycles) and excellent cyclic stability (the discharge capacitance recovered to ∼1016 mAh g(-1) at 0.1 C after 400 cycles).

Cotton textile enabled, all-solid-state flexible supercapacitors

A hierarchical NiCo2O4@NiCo2O4 core/shell nanostructure was grown on flexible cotton activated carbon textiles (ACTs) to fabricate NiCo2O4@NiCo2O4/ACT electrodes. After dipping with PVA/KOH polymer gel which served as both the solid state electrolyte and separator, the flexible NiCo2O4@NiCo2O4/ACT hybrid electrode exhibited an exceptional combination of electrochemical and mechanical properties in terms of specific capacitance (1929 F g−1, based on the mass of NiCo2O4), energy density (83.6 Wh kg−1), power density (8.4 kW kg−1), cycling stability, and mechanical robustness (the tensile strength is 6.4 times higher than that of pure ACT). The outstanding electrochemical performance is ascribed to the unique core/shell nanostructure with high active-surface area, morphological stability, and short ion transport path. Such hierarchical core/shell nanostructure of the same material on a cotton-enabled flexible substrate should inspire us to develop flexible solid-state textile energy storage devices for future wearable electronics.

Biomass-derived renewable carbon materials for electrochemical energy storage

ABSTRACT Electrochemical energy storage devices, such as supercapacitors and batteries, have been proven to be the most effective energy conversion and storage technologies for practical application. However, further development of these energy storage devices is hindered by their poor electrode performance. Carbon materials used in supercapacitors and batteries are often derived from nonrenewable resources under harsh environments. Naturally abundant biomass is a green, alternative carbon source with many desired properties. This review article presents state of the art of renewable carbon materials derived from natural biomasses with an emphasis on their applications in supercapacitors and lithium–sulfur batteries. GRAPHICAL ABSTRACT IMPACT STATEMENT This review paper provides a comprehensive understanding for obtaining renewable carbons from natural biomass precursors via various activation methods for electrochemical energy storage application, especially for supercapacitor and lithium sulfur battery.

Capillarity Composited Recycled Paper/Graphene Scaffold for Lithium–Sulfur Batteries with Enhanced Capacity and Extended Lifespan

An effective strategy to tackle the twin crises of global deforestation and fossil fuel depletion is to recycle biomass materials for energy storage devices. This study reports a unique and innovative solution to capitalize on a currently overlooked resource to produce high-performance lithium-sulfur (Li-S) batteries from recycled paper. The recycled paper fibers are creatively composited with graphene oxide sheets via a capillary adsorption method. The recycled paper/graphene oxide hybrid is then converted to activated paper carbon/reduced graphene oxide (APC/graphene) scaffold for sulfur infiltration. The assembled Li-APC/graphene/S battery exhibits a superior lifespan of 620 cycles with an excellent capacity retention rate of 60.5%. An APC interlayer is sandwiched between the Li anode and the separator to suppress the degradation of Li anode by preventing the nonhomogeneous growth of mossy Li whiskers, stretching the battery lifespan up to 1000 cycles with a capacitance retention rate of 52.3%. The capillary adsorption method coupled with the porous carbonaceous anode interlayer configuration creates a new opportunity for the development of batteries derived from porous biomass materials.

Bioinspired, Multiscale Reinforced Composites with Exceptionally High Strength and Toughness

Natures multiscale reinforcing mechanisms in fabricating composite armors, such as seashells, provide lessons for engineering materials design and manufacturing. However, it is still a challenge to simultaneously add both micro- and nanoreinforcements in a matrix material since nano-fillers tend to agglomerate, decreasing their reinforcing effects. In this study, we report a new type of micro/nano hybrid filler, synthesized by an unconventional cotton aided method, which has B4C microplatelet as the core and radially aligned B4C nanowires as the shell. To enhance the bonding between the B4C fillers and epoxy, the B4C micro/nano-fillers were coated with a layer of polyaniline (PANI). With a low concentration of the PANI functionalized B4C micro/nano-fillers (1 wt %), this B4C/epoxy composite exhibited an exceptional combination of mechanical properties in terms of elastic modulus (∼3.47 GPa), toughness (2026.3 kJ/m3), and fracture strain (>3.6%). An analytical mechanics model was established to show that such multiscale reinforcement design remarkably enhanced the load carrying efficiency of the B4C fillers, leading to the overall improved mechanical performance of the composites. This new design concept opens up a new path for developing lightweight, yet high-strength and tough materials with multiscale reinforcing configurations.