Showing papers by "Bing Ding published in 2023"

Covalent Organic Framework Based Lithium–Sulfur Batteries: Materials, Interfaces, and Solid‐State Electrolytes

Abstract: Lithium–sulfur batteries are recognized as one of the most promising next‐generation energy‐storage technologies owing to their high energy density and low cost. Nevertheless, the shuttle effect of polysulfide intermediates and the formation of lithium dendrites are the principal reasons that restrict the practical adoption of current Li–S batteries. Adjustable frameworks, structural variety, and functional adaptability of covalent organic frameworks (COFs) have the potential to overcome the issues associated with Li–S battery technology. Herein, a summary is presented of emerging COF materials in addressing the challenging problems in terms of sulfur hosts, modified separators, artificial solid electrolyte interphase layers, and solid‐state electrolytes. This comprehensive overview focuses on the design and chemistry of COFs used to upgrade Li–S batteries. Furthermore, existing difficulties, prospective remedies, and prospective research directions for COFs for Li–S batteries are discussed, laying the groundwork for future advancements in this class of fascinating materials.

High‐Performance, Highly Stretchable, Flexible Moist‐Electric Generators via Molecular Engineering of Hydrogels

Abstract: Harvesting energy from ubiquitous moisture has emerged as a promising technology, offering opportunities to power wearable electronics. However, low current density and inadequate stretching limit their integration into self‐powered wearables. Herein, a high‐performance, highly stretchable, and flexible moist‐electric generator (MEG) is developed via molecular engineering of hydrogels. The molecular engineering involves the impregnation of lithium ions and sulfonic acid groups into the polymer molecular chains to create ion‐conductive and stretchable hydrogels. This new strategy fully leverages the molecular structure of polymer chains, circumventing the addition of extra elastomers or conductors. A centimeter‐sized hydrogel‐based MEG can generate an open‐circuit voltage of 0.81 V and a short‐circuit current density of up to 480 µA cm−2. This current density is more than ten times that of most reported MEGs. Moreover, molecular engineering improves the mechanical properties of hydrogels, resulting in a stretchability of 506%, representing the state‐of‐the‐art level in reported MEGs. Notably, large‐scale integration of the high‐performance and stretchable MEGs is demonstrated to power wearables with integrated electronics, including respiration monitoring masks, smart helmets, and medical suits. This work provides fresh insights into the design of high‐performance and stretchable MEGs, facilitating their application to self‐powered wearables and broadening the application scenario.

In Situ Electrochemically Oxidative Activation Inducing Ultrahigh Rate Capability of Vanadium Oxynitride/Carbon Cathode for Zinc-Ion Batteries.

Abstract: As a promising candidate for large-scale energy storage, aqueous zinc-ion batteries (ZIBs) still lack cathode materials with large capacity and high rate capability. Herein, a spherical carbon-confined nanovanadium oxynitride with a polycrystalline feature (VNxOy/C) was synthesized by the solvothermal reaction and following nitridation treatment. As a cathode material for ZIBs, it is interesting that the electrochemical performance of the VNxOy/C cathode is greatly improved after the first charging process viain situ electrochemically oxidative activation. The oxidized VNxOy/C delivers a greatly enhanced reversible capacity of 556 mAh g-1 at 0.2 A g-1 compared to the first discharge capacity of 130 mAh g-1 and a high capacity of 168 mAh g-1 even at 80 A g-1. The ex situ characterizations verify that the insertion/extraction of Zn2+ does not affect the crystal structure of oxidized VNxOy/C to promise a stable cycle life (retain 420 mAh g-1 after 1000 cycles at 10 A g-1). The experimental analysis further elucidates that charging voltage and H2O in the electrolyte are curial factors to activate VNxOy/C in that the oxygen replaces the partial nitrogen and creates abundant vacancies, inducing a conversion from VNxOy/C to VNx-mOy+2m/C and then resulting in considerably strengthened rate performance and improved Zn2+ storage capability. The study broadens the horizons of fast ion transport and is exceptionally desirable to expedite the application of high-rate ZIBs.

The Decisive Role of Li2O2 Desorption for Oxygen Reduction Reaction in Li–O2 Batteries

Abstract: Fundamental issues relevant to the oxygen reduction reaction (ORR) mechanism and reaction interface are ambiguous in Li–O2 batteries. Herein, we utilized highly sensitive surface-enhanced Raman spectroscopy (SERS) to reveal the spontaneous desorption behavior of insoluble products of lithium peroxide (Li2O2) from the electrode surface. Furthermore, the electrochemical ORR mechanism is elucidated at the electrode/Li2O2 interface based on a dynamic equilibrium between the generation and desorption of Li2O2. The desorption of adsorbed Li2O2 species (Li2O2*) is crucial to releasing surface sites and maintaining the electrochemical ORR process at the electrode substrate surface instead of the Li2O2/electrolyte interface. The proceeding of Li2O2* desorption can guarantee the stability of Li2O2* concentration and the discharge plateau in the galvanostatic ORR process. The suppression of Li2O2* desorption is proved to induce the termination of Li2O2* generation, which is accompanied by the growth of adsorbed lithium superoxide (LiO2*), leading to rapid potential attenuation.

Post-synthetic Covalent Organic Framework to Improve the Performance of Solid-State Li+ Electrolytes.

Abstract: As a new class of crystalline materials, covalent organic frameworks (COFs) have long-range ordered channels and feasibility to functionalize. The well-arranged pores make it possible to contain and transport ions. Here, we designed a novel functionalized anionic COF-SS-Li by a post-synthetic method utilizing the Povarov reaction of BDTA-COF, anchoring -SO3- groups to the COF backbone and converting the imine linkage to a more stable quinoline unit. The grafted -SO3- groups and directional channels can promote the lithium-ion transport through a hopping mechanism. As a solid-state lithium-ion electrolyte, COF-SS-Li exhibits the conductivities of 9.63 × 10-5 S cm-1 at 20 °C and 1.28 × 10-4 S cm-1 at 40 °C and a wide electrochemical window of 4.85 V. The assembled Li|COF-SS-Li|Li symmetric cell can cycle stably for 600 h at 0.1 mA cm-2. Also, the Li|COF-SS-Li|LiFePO4 cell delivers an initial capacity of 117 mAh g-1 at 0.1 A g-1 and retains a capacity rate of 56.7% after 500 cycles. The research enriches the solid-state electrolytes for lithium-ion batteries.