Hybrid All‐in‐One Power Source Based on High‐Performance Spherical Triboelectric Nanogenerators for Harvesting Environmental Energy

With the development of the Internet of Things (IoTs), widely distributed electronics in the environment require effective in situ energy harvesting technologies, which is made challenging by the unstable supply and severe conditions in some environments. In this work, a hybrid all‐in‐one power source (AoPS) is demonstrated for widely adaptive environmental energy harvesting. With a novel structure, the AoPS hybridizes high‐performance spherical triboelectric nanogenerators (TENGs) with solar cells, enabling the harvesting of most typical environmental energies from wind, rain drops, and sun light, for complementary supply. The spherical TENG units with a packaged structure can work robustly to collect energy from fluid. Nearly continuous direct current and a high average power of 5.63 mW can be obtained by four TENG units, which is further complemented by solar cells. Typical application scenarios are also demonstrated, achieving self‐powered soil moisture control, forest fire prevention and pipeline monitoring. The work realizes the concept of an environmental power source that can be deployed in the environment with high adaptability to make use of all kinds of surrounding energies for powering electronics in all‐weather conditions, providing a reliable foundation for the era of the IoTs.     

Networks of High Performance Triboelectric Nanogenerators Based on Liquid–Solid Interface Contact Electrification for Harvesting Low‐Frequency Blue Energy

Blue energy harvested from the ocean is an important and promising renewable energy for the sustainable development of society. Triboelectric nanogenerators (TENGs) are considered one of the most promising approaches for harvesting blue energy. In this work, a liquid–solid‐contact triboelectric nanogenerator (LS TENG) is fabricated to enhance the friction and magnify energy output by 48.7 times, when compared with the solid–solid‐contact TENG with the same area. The buoy‐like LS TENG can harvest energy from different types of low‐frequency vibration (including up–down, shaking, and rotation movements). Moreover, the outputs of the LS TENGs network can reach 290 µA, 16 725 nC, and 300 V, and the LS TENGs network can directly power hundreds of LEDs and drive a radio frequency emitter to form a self‐powered wireless save our souls (SOS) system for ocean emergencies. This work renders an innovative and effective approach toward large‐scale blue energy harvesting and applications.     

Challenges of Spinel Li4Ti5O12 for Lithium‐Ion Battery Industrial Applications

Rechargeable lithium‐ion batteries (LIBs) offer the advantages of having great electrical energy storage and increased continuous and pulsed power output capabilities, which enable their applications in grid energy storage and electric vehicles (EVs). For safety, high power and durability considerations, spinel Li₄Ti₅O₁₂ is one of the most appealing potential candidate as an anode material for power LIBs due to its excellent cycling stability and thermal stability. However, there are still a number of challenges remaining for Li₄Ti₅O₁₂ battery applications. Herein, an updated overview of the latest advances in Li₄Ti₅O₁₂ research is provided and key challenges for its future development (i.e., fast‐charging, specific capacity, swelling, interface chemistry, matching cathode and electrolyte as well as batteries design and manufacturing) are highlighted.     

Ultrathin Li4Ti5O12 Nanosheet Based Hierarchical Microspheres for High‐Rate and Long‐Cycle Life Li‐Ion Batteries

Ultrathin Li₄Ti₅O₁₂ nanosheet based hierarchical microspheres are synthesized through a three‐step hydrothermal procedure. The average thickness of the Li₄Ti₅O₁₂ sheets is only ≈(6.6 ± 0.25) nm and the specific surface area of the sample is 178 m² g^?1. When applied into lithium ion batteries as anode materials, the hierarchical Li₄Ti₅O₁₂ microspheres exhibit high specific capacities at high rates (156 mA h g^?1 at 20 C, 150 mA h g^?1 at 50 C) and maintain a capacity of 126 mA h g^?1 after 3000 cycles at 20 C. The results clearly suggest that the utility of hierarchical structures based on ultrathin nanosheets can promote the lithium insertion/extraction reactions in Li₄Ti₅O₁₂. The obtained hierarchical Li₄Ti₅O₁₂ with ultrathin nanosheets and large specific surface area can be perfect anode materials for the lithium ion batteries applied in high power facilities, such as electric vehicles and hybrid electric vehicles.     

Li4Ti5O12 Nanoparticles Embedded in a Mesoporous Carbon Matrix as a Superior Anode Material for High Rate Lithium Ion Batteries

A mesoporous Li₄Ti₅O₁₂/C nanocomposite is synthesized by a nanocasting technique using the porous carbon material CMK‐3 as a hard template. Modified CMK‐3 template is impregnated with Li₄Ti₅O₁₂ precursor, followed by heat treatment at 750 °C for 6 h under N₂. Li₄Ti₅O₁₂ nanocrystals of up to several tens of nanometers are successfully synthesized in micrometer‐sized porous carbon foam to form a highly conductive network, as confirmed by field emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, and nitrogen sorption isotherms. The composite is then evaluated as an anode material for lithium ion batteries. It exhibits greatly improved electrochemical performance compared with bulk Li₄Ti₅O₁₂, and shows an excellent rate capability (73.4 mA h g^?1 at 80 C) with significantly enhanced cycling performance (only 5.6% capacity loss after 1000 cycles at a high rate of 20 C). The greatly enhanced lithium storage properties of the mesoporous Li₄Ti₅O₁₂/C nanocomposite may be attributed to the interpenetrating conductive carbon network, ordered mesoporous structure, and the small Li₄Ti₅O₁₂ nanocrystallites that increase the ionic and electronic conduction throughout the electrode.     

Integrated Intercalation‐Based and Interfacial Sodium Storage in Graphene‐Wrapped Porous Li4Ti5O12 Nanofibers Composite Aerogel

Sodium storage in both solid–liquid and solid–solid interfaces is expected to extend the horizon of sodium‐ion batteries, leading to a new strategy for developing high‐performance energy‐storage materials. Here, a novel composite aerogel with porous Li₄Ti₅O₁₂ (PLTO) nanofibers confined in a highly conductive 3D‐interconnected graphene framework (G‐PLTO) is designed and fabricated for Na storage. A high capacity of 195 mA h g^?1 at 0.2 C and super‐long cycle life up to 12 000 cycles are attained. Electrochemical analysis shows that the intercalation‐based and interfacial Na storage behaviors take effect simultaneously in the G‐PLTO composite aerogel. An integrated Na storage mechanism is proposed. This study ascribes the excellent performance to the unique structure, which not only offers short pathways for Na⁺ diffusion and conductive networks for electron transport, but also guarantees plenty of PLTO–electrolyte and PLTO–graphene interfacial sites for Na⁺ adsorption.     

Amorphous Carbon Coated High Grain Boundary Density Dual Phase Li4Ti5O12‐TiO2: A Nanocomposite Anode Material for Li‐Ion Batteries

This work introduces an effective, inexpensive, and large‐scale production approach to the synthesis of a carbon coated, high grain boundary density, dual phase Li₄Ti₅O₁₂‐TiO₂ nanocomposite anode material for use in rechargeable lithium‐ion batteries. The microstructure and morphology of the Li₄Ti₅O₁₂‐TiO₂‐C product were characterized systematically. The Li₄Ti₅O₁₂‐TiO₂‐C nanocomposite electrode yielded good electrochemical performance in terms of high capacity (166 mAh g^?1 at a current density of 0.5 C), good cycling stability, and excellent rate capability (110 mAh g^?1 at a current density of 10 C up to 100 cycles). The likely contributing factors to the excellent electrochemical performance of the Li₄Ti₅O₁₂‐TiO₂‐C nanocomposite could be related to the improved morphology, including the presence of high grain boundary density among the nanoparticles, carbon layering on each nanocrystal, and grain boundary interface areas embedded in a carbon matrix, where electronic transport properties were tuned by interfacial design and by varying the spacing of interfaces down to the nanoscale regime, in which the grain boundary interface embedded carbon matrix can store electrolyte and allows more channels for the Li+ ion insertion/extraction reaction. This research suggests that carbon‐coated dual phase Li₄Ti₅O₁₂‐TiO₂ nanocomposites could be suitable for use as a high rate performance anode material for lithium‐ion batteries.     

Synthesis and photoluminescence characteristics of Sm3+‐doped Bi4Si3O12 red‐emitting phosphor

A series of novel red‐emitting Sm³⁺‐doped bismuth silicate phosphors, Bi₄Si₃O₁₂:xSm³⁺ (0.01 ≤ x ≤ 0.06), were prepared via the sol–gel route. The phase of the synthesized samples calcinated at 800 °C is isostructural with Bi₄Si₃O₁₂ according to X‐ray diffraction results. Under excitation with 405 nm light, some typical peaks of Sm³⁺ ions centered at 566, 609, 655 and 715 nm are found in the emission spectra of the Sm³⁺‐doped Bi₄Si₃O₁₂ phosphors. The strongest peak located at 609 nm is due to ⁴G_5/2–⁶H_7/2 transition of Sm³⁺. The luminescence intensity reaches its maximum value when the Sm³⁺ ion content is 4 mol%. The results suggest that Bi₄Si₃O₁₂:Sm³⁺ may be a potential red phosphor for white light‐emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd.     

A High‐Crystalline NaV1.25Ti0.75O4 Anode for Wide‐Temperature Sodium‐Ion Battery

Sodium‐ion batteries with abundant and low‐cost sodium resources is a promising alternative to Li‐ion batteries in large‐scale energy applications. While the anode materials, due to their insufficient cycling life and insecure voltage, could not still satisfy the market demands, especially in the wide‐temperature fields, here, a high‐crystallinity anode material with post‐spinel structure, namely NaV_1.25Ti_0.75O₄, which always maintains excellent electrochemical performance at the widely variable temperatures, is reported. The results indicate that this anode delivers a high‐safety and ultrastable room‐temperature performance (i.e., an average output voltage of 0.7 V vs Na⁺/Na and the ultralong cycling life over 10 000 cycles) and good wide‐temperature performance (below 9% capacity variation at 60 and ?20 °C compared to that at 25 °C). These excellent achievements could benefit from the long durability and stability of 1D channels and superfast ion diffusion in a temperature‐dependent range. This finding provides a promising strategy to construct the safe and stable full‐cell prototypes and promotes the wide‐temperature application of sodium‐ion batteries.     

Hollow NiCo2S4 Nanospheres Hybridized with 3D Hierarchical Porous rGO/Fe2O3 Composites toward High‐Performance Energy Storage Device

Hierarchical hollow NiCo₂S₄ microspheres with a tunable interior architecture are synthesized by a facile and cost‐effective hydrothermal method, and used as a cathode material. A three‐dimensional (3D) porous reduced graphene oxide/Fe₂O₃ composite (rGO/Fe₂O₃) with precisely controlled particle size and morphology is successfully prepared through a scalable facile approach, with well‐dispersed Fe₂O₃ nanoparticles decorating the surface of rGO sheets. The fixed Fe₂O₃ nanoparticles in graphene efficiently prevent the intermediates during the redox reaction from dissolving into the electrolyte, resulting in long cycle life. KOH activation of the rGO/Fe₂O₃ composite is conducted for the preparation of an activated carbon material–based hybrid to transform into a 3D porous carbon material–based hybrid. An energy storage device consisting of hollow NiCo₂S₄ microspheres as the positive electrode, the 3D porous rGO/Fe₂O₃ composite as the negative electrode, and KOH solution as the electrolyte with a maximum energy density of 61.7 W h kg^?1 is achieved owing to its wide operating voltage range of 0–1.75 V and the designed 3D structure. Moreover, the device exhibits a high power density of 22 kW kg^?1 and a long cycle life with 90% retention after 1000 cycles at the current density of 1 A g^?1.     

High‐Performance Ultrathin Co3O4 Nanosheet Supported PdO/CeO2 Catalysts for Methane Combustion

Efficient utilization of methane via catalytic complete combustion is a very important pathway to realize energy efficiency and pollution reduction. From the viewpoint of structural design, herein a green water‐phase route is developed to prepare ultrathin Co(OH)₂ nanosheet supported Pd catalysts. As a platform, the as‐obtained Pd/Co(OH)₂ nanosheets are able to be further used to load CeO₂ nanoparticles to form 2D nanostructured Pd/CeO₂/Co(OH)₂ multicomponent hybrids, and further calcination can result in the final well‐crystallized ultrathin Co₃O₄ nanosheet supported PdO/CeO₂ catalysts. Catalytic tests on methane combustion reveal that CeO₂ as a catalytic assistant greatly boosts the catalytic performance of PdO/Co₃O₄ via strong synergetic effects with Pd species and Co₃O₄ components. The best sample of PdO/CeO₂‐0.1/Co₃O₄ exhibits surprisingly enhanced light‐off activity, indicating that such 2D Co₃O₄ nanosheet supported nanocatalysts might show promising prospect for heterogeneous catalysis.     

Sodium Storage and Transport Properties in Layered Na2Ti3O7 for Room‐Temperature Sodium‐Ion Batteries

Layered sodium titanium oxide, Na₂Ti₃O₇, is synthesized by a solid‐state reaction method as a potential anode for sodium‐ion batteries. Through optimization of the electrolyte and binder, the microsized Na₂Ti₃O₇ electrode delivers a reversible capacity of 188 mA h g^?1 in 1 M NaFSI/PC electrolyte at a current rate of 0.1C in a voltage range of 0.0–3.0 V, with sodium alginate as binder. The average Na storage voltage plateau is found at ca. 0.3 V vs. Na⁺/Na, in good agreement with a first‐principles prediction of 0.35 V. The Na storage properties in Na₂Ti₃O₇ are investigated from thermodynamic and kinetic aspects. By reducing particle size, the nanosized Na₂Ti₃O₇ exhibits much higher capacity, but still with unsatisfied cyclic properties. The solid‐state interphase layer on Na₂Ti₃O₇ electrode is analyzed. A zero‐current overpotential related to thermodynamic factors is observed for both nano‐ and microsized Na₂Ti₃O₇. The electronic structure, Na⁺ ion transport and conductivity are investigated by the combination of first‐principles calculation and electrochemical characterizations. On the basis of the vacancy‐hopping mechanism, a quasi‐3D energy favorable trajectory is proposed for Na₂Ti₃O₇. The Na⁺ ions diffuse between the TiO₆ octahedron layers with pretty low activation energy of 0.186 eV.     

Molten salt synthesis and luminescence of Dy3+‐doped Y3Al5O12 phosphors

Dy³⁺‐doped Y₃Al₅O₁₂ phosphors were prepared at a relatively low temperature using molten salt synthesis. The phase of the prepared Dy³⁺‐doped Y₃Al₅O₁₂ phosphors was confirmed using X‐ray powder diffraction. Results indicated that Dy³⁺ doping did not change the Y₃Al₅O₁₂ phase. Following excitation at 352 nm, emission spectra of the Dy³⁺‐doped Y₃Al₅O₁₂ phosphors consisted of blue, yellow, and red emission bands. The influence of Dy³⁺ concentration and excitation wavelength on emission was investigated. The ratio of yellow light to blue light varied with change in Dy³⁺ doping concentration, due to changes in the structure around Dy³⁺. Emission intensities also changed when the excitation wavelength was changed. This variation is luminescence generated a system for tunable white light for Dy³⁺‐doped Y₃Al₅O₁₂ phosphors.     

The Fine Line between a Two‐Phase and Solid‐Solution Phase Transformation and Highly Mobile Phase Interfaces in Spinel Li4+xTi5O12

Phase transitions play a crucial role in Li‐ion battery electrodes being decisive for both the power density and cycle life. The kinetic properties of phase transitions are relatively unexplored and the nature of the phase transition in defective spinel Li_4+xTi₅O₁₂ introduces a controversy as the very constant (dis)charge potential, associated with a first‐order phase transition, appears to contradict the exceptionally high rate performance associated with a solid–solution reaction. With the present density functional theory study, a microscopic mechanism is put forward that provides deeper insight in this intriguing and technologically relevant material. The local substitution of Ti with Li in the spinel Li_4+xTi₅O₁₂ lattice stabilizes the phase boundaries that are introduced upon Li‐ion insertion. This facilitates a subnanometer phase coexistence in equilibrium, which although very similar to a solid solution should be considered a true first‐order phase transition. The resulting interfaces are predicted to be very mobile due to the high mobility of the Li ions located at the interfaces. This highly mobile, almost liquid‐like, subnanometer phase morphology is able to respond very fast to nonequilibrium conditions during battery operation, explaining the excellent rate performance in combination with a first‐order phase transition.