Flexible Cathode Materials Enabled by a Multifunctional Covalent Organic Gel for Lithium-Sulfur Batteries with High Areal Capacities

A Stable Triazole-Based Covalent Gel for Long-Term Cycling Zn Anode in Zinc-Ion Batteries

In this work, a functional covalent gel material is developed to resolve the severe dendritic growth and hydrogen evolution reaction toward Zn/electrolyte interface in aqueous zinc-ion batteries (ZIBs). A covalent gel layer with superior durability forms homogeneously on the surface of Zn foil. The covalent gel with triazole functional groups can uniformize the transport of Zn2+ due to the interactions between Zn2+ ions and the triazole groups in the covalent gel. As a consequence, the symmetrical battery with triazole covalent gel maintains stable Zn plating/stripping for over 3000 h at 1 mA cm-2 and 1 mAh cm-2 , and the full cell combined with a V2 O5 cathode operates steadily and continuously for at least 1800 cycles at 5 A g-1 with a capacity retention rate of 67.0%. This work provides a train of thought to develop stable covalent gels for the protection of zinc anode toward high-performance ZIBs.

Triazine-based porous organic polymers with enhanced electronegativity as multifunctional separator coatings in lithium-sulfur batteries

The commercialization of lithium-sulfur batteries is seriously affected by the shuttle behavior and slow conversion kinetics of polysulfides. Herein, a new porous organic polymer (POP) is synthesized and grown on reduced graphene oxide (rGO) in situ to improve battery performance, which serves as an efficient polysulfide adsorber and catalytic promoter for polysulfide conversion. The polar POP shows strong chemisorption to polysulfides, which is confirmed by a series of calculations and experimental results. As a popular conductive substrate, rGO offers an electron transport channel for sulfur and polysulfide conversion. Due to the synergistic functions of composite materials, the batteries with POP@rGO modified separators retain a high specific capacity of 697.3 mA h g-1 and a minimum capacity fading rate of 0.04% per cycle at 1C over 500 cycles. Besides, even at a high sulfur loading of 5 mg cm-2, a high area capacity of 4.27 mA h cm-2 can also be achieved, which shows that it has great potential in promoting the commercialization of lithium-sulfur batteries.

From Fundamental Understanding to Engineering Design of High-Performance Thick Electrodes for Scalable Energy-Storage Systems

The ever-growing needs for renewable energy demand the pursuit of batteries with higher energy/power output. A thick electrode design is considered as a promising solution for high-energy batteries due to the minimized inactive material ratio at the device level. Most of the current research focuses on pushing the electrode thickness to a maximum limit; however, very few of them thoroughly analyze the effect of electrode thickness on cell-level energy densities as well as the balance between energy and power density. Here, a realistic assessment of the combined effect of electrode thickness with other key design parameters is provided, such as active material fraction and electrode porosity, which affect the cell-level energy/power densities of lithium-LiNi_0.6 Mn_0.2 Co_0.2 O₂ (Li-NMC622) and lithium-sulfur (Li-S) cells as two model battery systems, is provided. Based on the state-of-the-art lithium batteries, key research targets are quantified to achieve 500 Wh kg^-1 /800 Wh L^-1 cell-level energy densities and strategies are elaborated to simultaneously enhance energy/power output. Furthermore, the remaining challenges are highlighted toward realizing scalable high-energy/power energy-storage systems.

Corrigendum to "Carbonized cotton fiber supported flexible organic lithium ion battery cathodes" [J. Colloid Interface Sci. 572 (2020) 1-8]

Carbonized cotton fibers (CCFs) were prepared by the carbonization of commercial cottons at 700, 800 and 900 °C. The following characterizations indicated that the properties of the obtained CCFs could be effectively tuned by the carbonization temperatures. Containing both high conductivity and high aspect ratio, the CCFs could be used as the conductive agents for the construction of the integrated organic cathodes in lithium ion batteries (LIBs). With the optimized ratio of CCF from 900 °C, the organic LIB cathodes showed a high specific capacity of 135 mA h g^-1 at a current density of 0.05 A g^-1 and an impressive cyclizing stability by keeping 90.5% of the highest capacity value after 500 cycles at 0.5 A g^-1. The moderate mechanical stability of the CCF supported organic cathode enabled the further fabrication of flexible LIBs, which manifested stable performances at various bent states, confirming the potentials of CCFs in flexible energy storage devices.

Recent Developments of Nanomaterials and Nanostructures for High-Rate Lithium Ion Batteries

Lithium ion batteries have been considered as a promising energy-storage solution, the performance of which depends on the electrochemical properties of each component, including cathode, anode, electrolyte and separator. Currently, fast charging is becoming an attractive research field due to the widespread application of batteries in electric vehicles, which are designated to replace conventional diesel automobiles in the future. In these batteries, rate capability, which is closely linked to the topology and morphology of electrode materials, is one of the determining parameters of interest. It has been revealed that nanotechnology is an exceptional tool in designing and preparing cathodes and anodes with outstanding electrochemical kinetics due to the well-known nanosizing effect. Nevertheless, the negative effects of applying nanomaterials in electrodes sometimes outweigh the benefits. To better understand the exact function of nanostructures in solid-state electrodes, herein, a comprehensive review is provided beginning with the fundamental theory of lithium ion transport in solids, which is then followed by a detailed analysis of several major factors affecting the migration of lithium ions in solid-state electrodes. The latest developments in characterisation techniques, based on either electrochemical or radiology methodologies, are covered as well. In addition, state-of-the-art research findings are provided to illustrate the effect of nanomaterials and nanostructures in promoting the rate performance of lithium ion batteries. Finally, several challenges and shortcomings of applying nanotechnology in fabricating high-rate lithium ion batteries are summarised.

Carbonized cotton fiber supported flexible organic lithium ion battery cathodes

Carbonized cotton fibers (CCFs) were prepared by the carbonization of commercial cottons at 700, 800 and 900 °C. The following characterizations indicated that the properties of the obtained CCFs could be effectively tuned by the carbonization temperatures. Containing both high conductivity and high aspect ratio, the CCFs could be used as the conductive agents for the construction of the integrated organic cathodes in lithium ion batteries (LIBs). With the optimized ratio of CCF from 900 °C, the organic LIB cathodes showed a high specific capacity of 135 mA h g^-1 at a current density of 0.05 A g^-1 and an impressive cyclizing stability by keeping 90.5% of the highest capacity value after 500 cycles at 0.5 A g^-1. The good mechanical stability of the CCF supported organic cathode enabled the further fabrication of flexible LIBs, which manifested stable performances at various bent states, confirming the potentials of CCFs in flexible energy storage devices.

Flexible Porous Organic Polymer Membranes for Protonic Field-Effect Transistors

Artificial transistors represent an ideal means for meeting the requirements in interfacing with biological systems. It is pivotal to develop new proton-conductive materials for the transduction between biochemical events and electronic signals. Herein, the first demonstration of a porous organic polymer membrane (POPM) as a proton-conductive material for protonic field-effect transistors is presented. The POPM is readily prepared through a thiourea-formation condensation reaction. Under hydrated conditions and at room temperature, the POPM delivers a proton mobility of 5.7 × 10^-3 cm² V^-1 s^-1 ; the charge carrier densities are successfully modulated from 4.3 × 10¹⁷ to 14.1 × 10¹⁷ cm^-3 by the gate voltage. This study provides a type of promising modular proton-conductive materials for bioelectronics application.