Construction of 3D CoO Quantum Dots/Graphene Hydrogels as Binder-Free Electrodes for Ultra-high Rate Energy Storage Applications

High-capacity, fast-charging and long-life magnesium/black phosphorous composite negative electrode for non-aqueous magnesium battery

Secondary non-aqueous magnesium-based batteries are a promising candidate for post-lithium-ion battery technologies. However, the uneven Mg plating behavior at the negative electrode leads to high overpotential and short cycle life. Here, to circumvent these issues, we report the preparation of a magnesium/black phosphorus (Mg@BP) composite and its use as a negative electrode for non-aqueous magnesium-based batteries. Via in situ and ex situ physicochemical measurements, we demonstrate that Mg ions are initially intercalated in black phosphorus two-dimensional structures, forming chemically stable MgxP intermediates. After the formation of the intermediates, Mg electrodeposition reaction became the predominant. When tested in the asymmetric coin cell configuration, the Mg@BP composite electrode allowed stable stripping/plating performances for 1600 h (800 cycles), a cumulative capacity of 3200 mAh cm-2, and a Coulombic efficiency of 99.98%. Assembly and testing of the Mg@BP | |nano-CuS coin cell enabled a discharge capacity of 398 mAh g-1 and an average cell discharge potential of about 1.15 V at a specific current of 560 mA g-1 with a low decay rate of 0.016% per cycle for 225 cycles at 25 °C.

Lithium Azides Induced SnS Quantum Dots for Ultra-Fast and Long-Term Sodium Storage

Tin sulfide (SnS) is an attractive anode for sodium ion batteries (NIBs) because of its high theoretical capacity, while it seriously suffers from the inherently poor conductivity and huge volume variation during the cycling process, leading to inferior lifespan. To intrinsically maximize the sodium storage of SnS, herein, lithium azides (LiN3 )-induced SnS quantum dots (QDs) are first reported using a simple electrospinning strategy, where SnS QDs are uniformly distributed in the carbon fibers. Taking the advantage of LiN3 , which can effectively prevent the growth of crystal nuclei during the thermal treatment, the well-dispersed SnS QDs performs superior Na+ transfer kinetics and pseudocapacitive when used as an anode material for NIBs. The 3D SnS quantum dots embedded uniformly in N-doped nanofibers (SnS QDs@NCF) electrodes display superior long cycling life-span (484.6 mAh g-1 after 5800 cycles at 2 A g-1 and 430.9 mAh g-1 after 7880 cycles at 10 A g-1 ), as well as excellent rate capability (422.3 mAh g-1 at 20 A g-1 ). This fabrication of transition metal sulfides QDs composites provide a feasible strategy to develop NIBs with long life-span and superior rate capability to pave its practical implementation.

Doped Carbon Quantum Dots Reinforced Hydrogels for Sustained Delivery of Molecular Cargo

Hydrogels have emerged as important soft materials with numerous applications in fields including biomedicine, biomimetic smart materials, and electrochemistry. Because of their outstanding photo-physical properties and prolonged colloidal stability, the serendipitous findings of carbon quantum dots (CQDs) have introduced a new topic of investigation for materials scientists. CQDs confined polymeric hydrogel nanocomposites have emerged as novel materials with integrated properties of the individual constituents, resulting in vital uses in the realm of soft nanomaterials. Immobilizing CQDs within hydrogels has been shown to be a smart tactic for preventing the aggregation-caused quenching effect and also for manipulating the characteristics of hydrogels and introducing new properties. The combination of these two very different types of materials results in not only structural diversity but also significant improvements in many property aspects, leading to novel multifunctional materials. This review covers the synthesis of doped CQDs, different fabrication techniques for nanostructured materials made of CQDs and polymers, as well as their applications in sustained drug delivery. Finally, a brief overview of the present market and future perspectives are discussed.

Universal lithiophilic interfacial layers towards dendrite-free lithium anodes for solid-state lithium-metal batteries

Solid-state lithium-metal batteries (SSLMBs) using garnet Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) as the solid electrolyte are expected to conquer the safety concerns of high energy Li batteries with organic liquid electrolytes owing to its nonflammable nature and good mechanical strength. However, the poor interfacial contact between the Li anode and LLZTO greatly restrains the practical applications of the electrolyte, because large polarization, dendritic Li formation and penetration can occur at the interfaces. Here, an effective method is proposed to improve the wettability of the LLZTO toward lithium and reduce the interfacial resistance by engineering universal lithiophilic interfacial layers. Thanks to the in-situ formed lithiophilic and ionic conductive Co/Li₂O interlayers, the symmetric Li/CoO-LLZTO/Li batteries present much smaller overpotential, ultra-low areal specific resistance (ASR, 12.3 Ω cm²), high critical current density (CCD, 1.1 mA cm^-2), and outstanding cycling performance (1696 h at a current density of 0.3 mA cm^-2) at 25 °C. Besides, the solid-state Li/CoO-LLZTO/LFP cells deliver an excellent electrochemical performance with a high coulombic efficiency of ~100% and a long cycling time over 185 times. Surprisingly, the high-voltage (4.6 V) solid state Li/CoO-LLZTO/Li_1.4Mn_0.6Ni_0.2Co_0.2O_2.4 (LMNC622) batteries can also realize an ultra-high specific capacity (232.5 mAh g^-1) under 0.1 C at 25 °C. This work paves an effective way for practical applications of the dendrite-free SSLMBs.

Fabricating 3D Macroscopic Graphene-Based Architectures with Outstanding Flexibility by the Novel Liquid Drop/Colloid Flocculation Approach for Energy Storage Applications

Inspired by "water ripples" in nature and the flocculation phenomenon in colloid chemistry, a novel liquid drop/colloid flocculation approach is developed to fabricate an extremely flexible and compressible 3D macroscopic graphene-based architecture (hydrogels or aerogels), via a new coagulation-induced self-assembly mechanism. This facile and universal technique can be achieved in a neutral, acidic, or basic coagulation bath, producing microsized hydrogels with various structures, such as mushroom, circle, disc shapes, etc. The method also allows us to introduce various guest materials in the graphene matrix using transition metal salts as the coagulating bath. A mushroom-shaped NiCo oxide/GS hybrid aerogel (diameter: 3 mm) is prepared as an example, with ultrathin NiCo oxide nanosheets in situ grown onto the surface of graphene. By employing as binder-free electrodes, these hybrid aerogels exhibit a specific capacitance of 858.3 F g^-1 at 2 A g^-1, as well as a good rate capability and cyclic stability. The asymmetric supercapacitor, assembling with the hybrid aerogels as cathode and graphene hydrogels as anode materials, could deliver an energy density of 21 Wh kg^-1 at power density of 4500 W kg^-1. The ease of synthesis and the feasibility of obtaining highly flexible aerogels with varied morphologies and compositions make this method a promising one for use in the field of biotechnology, electrochemistry, flexible electronics, and environment applications.