Organic-inorganic Hybrid Perovskite-Based Light-Assisted Li-oxygen Battery with Low Overpotential.

Organic-inorganic hybrid perovskites have emerged in the last decade as promising semiconductors due to the excellent optoelectronic properties. This kind of perovskites exhibited respectable photocatalytic activities toward potential application in battery; however, the instability issue still hindered their practical use. Herein, a hybrid perovskite material, 4,4'-ethylenedipyridinium lead bromide [(4,4'-EDP)Pb2 Br6 ], was assembled onto the carbon materials to function as photoelectrode of the Li-oxygen battery. The strong cation-π interactions between the A-site cations enabled this hybrid perovskite to endure the cycling process as well as the exposure to battery electrolyte and oxygen. Benefitting from the photo-generated carriers of the photoelectrode under illumination, the formation/decomposition of the discharge product was accelerated, thus leading to a reduced overpotential from 1.3 V to an optimized 0.5 V compared to the Li-oxygen battery without illumination. The overpotential could be maintained lower than 0.9 V after cycling for 170 h. Furthermore, when exposed to the sunlight, the charging voltage was reduced by over 0.2 V. The intrinsic stability and strong light absorption of perovskites together with the optimized perovskite/carbon cathode interfaces contributed to the improved performance under different light sources without complex material design, which shed light on the exploration of organic-inorganic hybrid perovskites in Li-oxygen battery applications.

Carbon Nanotube-Coupled Seaweed-like Cobalt Sulfide as a Dual-Functional Catalyst for Overall Water Splitting.

Preparation of high-efficiency dual-functional catalysts remains the bottleneck for electrochemical water splitting. To prepare a non-precious metal catalyst with high activity and stability, here, we present a seaweed-like structure consisting of transition-metal sulfide nanoplates self-assembled on carbon nanotube sponge networks (SW-CoS@CNT). By adjusting the key parameters during synthesis (e.g., the loading amount and ratio of Co and S precursors), the microstructure can be tailored in a wide range, and sulfur defects can be introduced into the nanoplates by thermal annealing. The resulting SW-CoS@CNT serves as a freestanding dual-functional catalytic electrode, showing low overpotentials of 105 and 218 mV for the hydrogen evolution reaction and the oxygen evolution reaction, respectively, which are superior to most reported transition-metal-sulfide-based catalysts in alkaline solution. Rational design of this hierarchical biomimetic structure may be useful in developing high-performance electrochemical catalysts in renewable energy and environmental fields.

Dual Network Sponge for Compressible Lithium-Ion Batteries.

Compressible energy devices have received increasing attention with the rapid development of flexible electronics and wearable devices due to their size adaptability and functional stability. However, it is hard to simultaneously achieve satisfactory energy density and mechanical stability for electrodes. Here an open-porous dual network sponge (DNS) with two networks of highly conductive carbon nanotubes and Li+ -intercalating TiO2 -B nanowires is synthesized and employed as compressible lithium ion battery electrodes. All 1D components inside the DNS mutually penetrate with each other to form two physically distinct but functionally coupling networks, endowing DNS excellent compressibility and stability. A prototype compressible lithium-ion battery (C-LIB) is also demonstrated, in which the DNS exhibits a specific capacity of >238 mAh g-1 under static 50% strain, and further in situ measurements show that under 1000 times of cyclic strains, DNS can charge and discharge normally maintaining a high capacity of 240 mAh g-1 and exhibits robustness to fast strain rates up to 500% min-1 . The dual network structure can be extended to design high-performance compliant electrodes that are promising to serve in future compressible and deformable electronics and energy systems.

Application-Driven Carbon Nanotube Functional Materials.

Carbon nanotube functional materials (CNTFMs) represent an important research field in transforming nanoscience and nanotechnology into practical applications, with potential impact in a wide realm of science, technology, and engineering. In this review, we combine the state-of-the-art research activities of CNTFMs with the application prospect, to highlight critical issues and identify future challenges. We focus on macroscopic long fibers, thin films, and bulk sponges which are typical CNTFMs in different dimensions with distinct characteristics, and also cover a variety of derived composite/hierarchical materials. Critical issues related to their structures, properties, and applications as robust conductive skeletons or high-performance flexible electrodes in mechanical and electronic devices, advanced energy conversion and storage systems, and environmental areas have been discussed specifically. Finally, possible solutions and directions are proposed for overcoming current obstacles and promoting future efforts in the field.

Dislocation-Strained IrNi Alloy Nanoparticles Driven by Thermal Shock for the Hydrogen Evolution Reaction.

Designing high-performance and low-cost electrocatalysts is crucial for the electrochemical production of hydrogen. Dislocation-strained IrNi nanoparticles loaded on a carbon nanotube sponge (DSIrNi@CNTS) driven by unsteady thermal shock in an extreme environment are reported here as a highly efficient hydrogen evolution reaction (HER) catalyst. Experimental results demonstrate that numerous dislocations are kinetically trapped in self-assembled IrNi nanoparticles due to the ultrafast quenching and different atomic radii, which can induce strain effects into the IrNi nanoparticles. Such strain-induced high-energy surface structures arising from bulk defects (dislocations), are more likely to be resistant to surface restructuring during catalysis. The catalyst exhibits outstanding HER activity with only 17 mV overpotential to achieve 10 mA cm-2 in an alkaline electrolyte with fabulous stability, exceeding state-of-the-art Pt/C catalysts. These density functional theory results demonstrate that the electronic structure of as-synthesized IrNi nanostructure can be optimized by the strain effects induced by the dislocations, and the free energy of HER can be tuned toward the optimal region.

Porous-Carbon Aerogels with Tailored Sub-Nanopores for High Cycling Stability and Rate Capability Potassium-Ion Battery Anodes.

Developing advanced electrode materials for potassium-ion batteries (PIBs) is an emerging research area in recent years; so far, several strategies such as heteroatom doping into carbon, increasing interlayer spacing, or creating amorphous region in graphite have been investigated. Here, we studied the effect of sub-nanopores in a porous-carbon aerogel with a pore size distribution centered at around 0.8 nm and achieved outstanding PIB performance including long cycling stability (particularly at small current densities for prolonged charge/discharge period) and high rate capability with enhanced retentions. Mechanism studies reveal very high contribution from surface capacitive potassium (K)-ion storage (more than 90%) to the total capacity, and theoretical calculations show that 0.8 nm sub-nanopores lead to substantially low barrier for K-ion transport and storage, with ultrasmall diffusion energy and negligible lattice change. Sub-nanopore engineering, as demonstrated here, may be adopted to develop highly efficient and stable porous-carbon-based structures for applications in advanced energy storage systems and electrochemical catalysis.

Highly Dispersed Catalytic Co3S4 among a Hierarchical Carbon Nanostructure for High-Rate and Long-Life Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are next-generation energy storage systems with high energy density, and the rate performance is a very important consideration for practical applications. Recent approaches such as introducing catalytic materials to facilitate polysulfide conversion have been explored, yet the results remain unsatisfactory. Here, we present an optimized Li-S electrode featured by a large amount of highly dispersed Co3S4 nanoparticles (∼10 nm in size) throughout a hierarchical carbon nanostructure hybridized from ZIF-67 and carbon nanotube (CNT) sponge. This enables homogeneous distribution and close contact between infiltrated sulfur and Co3S4 nanoparticles within the ZIF-67-derived N-doped carbon nanocubes, leading to effective chemical interaction with polysulfides, maximum catalytic effect and enhanced lithium ion diffusion, while the built-in three-dimensional CNT network ensures high electrical conductivity of the electrode. As a consequence, the Li-S battery exhibits both extraordinary rate performance by maintaining a capacity of ∼850 mAh g-1 at very high charge/discharge rate (5 C) and long-term cycling stability with 85% retention after 1000 cycles at 5 C (an average capacity fading rate of only 0.0137% per cycle).