Abstract Organic‐inorganic composite solid electrolytes consisting of garnet fillers dispersed in polyvinylidene difluoride (PVDF) frameworks have shown promise to enable high‐energy solid‐state Li‐metal batteries. However, the air‐sensitive garnets easily form poorly‐conductive residues, which hinders fast Li‐ion exchange at the garnet‐polymer interface and results in low ionic conductivity. The highly alkaline residues trigger instant dehydrofluorination of PVDF to form unsaturated CC bonds, which are unstable against high‐voltage cathode materials. Here it is shown that, by applying a 10‐nm polydopamine coating on the residue‐removed garnet surface, the modified garnet filler becomes air‐stable and does not generate alkaline residues, so PVDF remains an intact structure. Surface characterizations reveal substantial metal‐nitrogen bonding between the La atoms of garnet and the amino groups of polydopamine, which can invite stronger adsorption of Li ions at the heterointerface. A new interparticle Li‐ion conduction mechanism is disclosed for the composite electrolyte, in which Li ions preferably migrate through the garnet‐polydopamine interface, forming an efficient ion‐percolation network. As a result, the composite electrolyte demonstrates an effective room‐temperature Li + conductivity of 1.52 × 10 –4 S cm –1 and a high cutoff voltage of up to 4.7 V versus Li + /Li to support stable operation of all‐solid‐state Li‐LiCoO 2 batteries.
In this work, a facile soft template-assisted water-bath method was adopted to synthesize pure phase single-crystalline β-cobalt hydroxide. Using polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG) and cetyltrimethyl ammonium bromide (CTAB) as soft templates, β-Co(OH)2 with hexagonal, disc-like and flower-like morphologies was successfully fabricated. It was found that all of the nanostructures exhibited preferentially oriented crystal growth along the (001) plane. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the soft templates had an important role in guiding the crystal growth and determining the final structure of β-Co(OH)2. Cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements indicated that the flower-like structures had superior electrochemical properties over hexagonal and disc-like β-Co(OH)2. A four-step growth mechanism of β-Co(OH)2 was proposed based on time-dependent morphological evolution results. The results reveal the potentiality of soft templates in fine-tuning the morphology of single crystal β-Co(OH)2 nanomaterials.
Platinum group metal-free catalysts (e.g., Fe–N–C and Co–N–C) are used as hydrogen peroxide reduction reaction (PRR) catalysts in direct borohydride fuel cells (DBFCs). Fe–N–C is more active in the PRR and demonstrates high performance at the beginning of the DBFC test, whereas Co–N–C exhibits more stability in long-term operation. In the DBFC-accelerated durability test, Fe–N–C displays an activity decline of 18.6%, whereas Co–N–C exhibits a more stable performance, with an activity decrease of only 6.7%. In addition, the active site of Fe–N–C degrades more rapidly than that of Co–N–C in terms of demetalation of the central atom, as revealed by X-ray photoelectron spectroscopy. Furthermore, density functional theory simulations indicate that Co–N–C is more stable than Fe–N–C in both O2 and H2O2 environments. Overall, this study demonstrates that non-noble transition metal catalysts can fully replace platinum group metal catalysts at the cathode and anode in liquid-fuel-powered DBFC systems.
Understanding the evolution of chemosynthetic communities and environmental changes near fluid seepages in the deep sea requires in-situ long-term observation data. However, in-situ detection or sampling for the investigation of cold seeps, hydrothermal vents, and nearby chemosynthetic ecosystems, by manned submersibles and remotely operated vehicles (ROVs), has great restrictions in terms of time. The observation parameters of a free-fall mode Lander cannot be adjusted in real time because there is no communication channel once the Lander is separated from the vessel. A long-term ocean observation platform (LOOP), that uses a new controllable mode for launching and recovery with the aid of a research vessel and submarine vehicles, has been developed and used in the cold seep area of the South China Sea. The LOOP can be operated in an online real-time control mode allowing landing site selection and adjustment of observation parameters during the launching process, with subsequent switched to an offline stand-alone operation mode for long-term, continuous observation. The effective observation times were 375 days and 414 days, respectively, during the 2016 and 2018 deployments in the cold seep area in the South China Sea. Results of these deployments show that salinity and dissolved oxygen parameters have strong spatial heterogeneity in both the horizontal and vertical directions within the cold seep vent. The spatial heterogeneity of environmental parameters may be one of the main driving factors for the uneven spatial distribution of chemosynthetic communities in cold seep areas. Overall, the LOOP provides an innovative and controllable launching and recovery mode and is expected to become a universal underwater observation platform for in-situ, long-term, and continuous data acquisition.
Lithium-ion capacitors (LICs) consist of a capacitor-type cathode and a lithium-ion battery-type anode, incorporating the merits of both components. Well-known for their high energy density, superior power density, prolonged cycle life, and commendable safety attributes, LICs have attracted enormous interest in recent years. However, the construction of high-performance LIC devices faces significant constraints due to the inherent kinetic imbalances between the battery-type and the capacitor-type electrode materials and the trade-off between energy density, power density, and cycle stability. Hence, many efforts have been made to develop high-performance LICs. This review mainly focuses on the recent progresses in LICs, particularly containing the cathode and anode active materials, anode prelithiation technologies, conductive additives, and nonaqueous electrolytes. Finally, a summary and outlook are presented to highlight some future challenges for hybrid LICs.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)