High-Performance Li-CO2 Battery Based on Carbon-Free Porous Ru@QNFs Cathode.

Lithium-carbon dioxide (Li-CO2 ) batteries have attracted much attention due to their high theoretical energy density. However, due to the existance of lithium carbonate and amorphous carbon in the discharge products that are difficult to decompose, the battery shows low coulombic efficiency and poor cycle performance. Here, by adjusting the adsorption of carbon dioxide (CO2 ) on ruthenium (Ru) catalysts surface, this work reports an ultralow charge overpotential and long cycle life Li-CO2 battery that consists of typical lithium metal, ternary molten salt electrolyte (TMSE), and Ru-based cathode. Experimental results show that the Ru catalysts deposited on quartz nanofiber (QF) can suppress the four-electron conversion of CO2 to lithium carbonate (Li2 CO3 ). As a result, the battery shows a long-cycle-life of over 457 cycles at 1.0 A g-1 with a limited capacity of 500 mAh g-1 Ru . Remarkably, a recorded low discharge potential of ≈3.0 V has been achieved after 35 cycles at 0.5 A g-1 , with a charge potential retention of over 99%. Moreover, the battery can operate over 25 A g-1 and recover 96% potential. This battery technology paves the way for designing high-performance rechargeable Li-CO2 batteries with carbon neutrality.

A stable solid-state lithium-oxygen battery enabled by heterogeneous silicon-based interface.

Solid-state lithium-metal batteries using inorganic solid-state electrolyte (SSE) instead of liquid-electrolyte, especially lithium-oxygen (Li-O2) battery, have attracted much more attention due to their high-energy density and safety. However, the poor interface contact between electrodes and SSEs makes these batteries lose most of their capacity and power during cycling. Here we report that by coating a heterogeneous silicon carbide on lithium metal anode and Li1.5Al0.5Ge1.5P3O12(LAGP)-SSE, a good interface contact is created between the electrode and electrolyte that can effectively reduce the interface impedance and improve the cycle performance of the assembled battery. As a result, the solid-sate Li-O2battery demonstrates a cycle lifespan of ∼78 cycles being at least 3-times higher than the solid-state Li-O2battery without silicon carbide with a capacity limitation of 1000 mAh g-1at 250 mA g-1. The characterization of discharge products indicates a typical two-electron convention of oxygen-to-lithium oxide for the solid-state Li-O2battery system. This work paves a way for developing high-energy long-cycle solid-state lithium-metal battery. The work provides insights into the interface between the Li-metal and SSE to develop high-energy long-cycle all solid-state Li-metal batteries.

Discovery of Type II Interlayer Trions.

In terms of interlayer trions, electronic excitations in van der Waals heterostructures (vdWHs) can be classified into Type I (i.e., two identical charges in the same layer) and Type II (i.e., two identical charges in the different layers). Type I interlayer trions are investigated theoretically and experimentally. By contrast, Type II interlayer trions remain elusive in vdWHs, due to inadequate free charges, unsuitable band alignment, reduced Coulomb interactions, poor interface quality, etc. Here, the first observation of Type II interlayer trions is reported by exploring band alignments and choosing an atomically thin organic-inorganic system-monolayer WSe2 /bilayer pentacene heterostructure (1L + 2L HS). Both positive and negative Type II interlayer trions are electrically tuned and observed via PL spectroscopy. In particular, Type II interlayer trions exhibit in-plane anisotropic emission, possibly caused by their unique spatial structure and anisotropic charge interactions, which is highly correlated with the transition dipole moment of pentacene. The results pave the way to develop excitonic devices and all-optical circuits using atomically thin organic-inorganic bilayers.

High-energy silicon-sulfurized poly(acrylonitrile) battery based on a nitrogen evolution reaction.

The practical application of high-energy lithium-sulfur battery is plagued with two deadly obstacles. One is the "shuttle effect" originated from the sulfur cathode, and the other is the low Coulombic efficiency and security issues arising from the lithium metal anode. In addressing these issues, we propose a novel silicon-sulfurized poly(acrylonitrile) full battery. In this lithium metal-free system, the Li source is pre-loaded in the cathode, using a nitrogen evolution reaction (NER) to implant Li+ into the silicon/carbon anode. Sulfurized poly(acrylonitrile) based on a solid-solid conversion mechanism can fundamentally circumvent the "shuttle effect". Meanwhile, the silicon/carbon anode can achieve more efficient utilization and higher security when compared with the Li metal anode. The full cell used in this technology can deliver a capacity of 1169.3 mAh g-1, and it can be stabilized over 100 cycles, implying its excellent electrochemical stability. Furthermore, the practical pouch cell with a high sulfur loading of 4.2 mg cm-2 can achieve a high specific energy of 513.2 Wh kg-1. The mechanism of the NER in cathode has also been investigated and analyzed by in situ methods. Notably, this battery design completely conforms to the current battery production technology because of the degassing of gasbag, resulting in a low manufacturing cost. This work will open the avenue to develop a lithium metal-free battery using the NER.

A Stable Rechargeable Aqueous Zn-Air Battery Enabled by Heterogeneous MoS2 Cathode Catalysts.

Aqueous rechargeable zinc (Zn)−air batteries have recently attracted extensive research interest due to their low cost, environmental benignity, safety, and high energy density. However, the sluggish kinetics of oxygen (O2) evolution reaction (OER) and the oxygen reduction reaction (ORR) of cathode catalysts in the batteries result in the high over-potential that impedes the practical application of Zn−air batteries. Here, we report a stable rechargeable aqueous Zn−air battery by use of a heterogeneous two-dimensional molybdenum sulfide (2D MoS2) cathode catalyst that consists of a heterogeneous interface and defects-embedded active edge sites. Compared to commercial Pt/C-RuO2, the low cost MoS2 cathode catalyst shows decent oxygen evolution and acceptable oxygen reduction catalytic activity. The assembled aqueous Zn−air battery using hybrid MoS2 catalysts demonstrates a specific capacity of 330 mAh g−1 and a durability of 500 cycles (~180 h) at 0.5 mA cm−2. In particular, the hybrid MoS2 catalysts outperform commercial Pt/C in the practically meaningful high-current region (>5 mA cm−2). This work paves the way for research on improving the performance of aqueous Zn−air batteries by constructing their own heterogeneous surfaces or interfaces instead of constructing bifunctional catalysts by compounding other materials.

Enhanced Broadband Plasmonic Absorbers with Tunable Light Management on Flexible Tapered Metasurface.

The growing attention in solar energy has motivated the development of highly efficient solar absorbers, and a metasurface absorber with broadband optical absorption is one of the main research interests. In this study, we developed an efficient metasurface absorber on a flexible film with a simple fabrication process. It consists of a polyimide nanocone substrate coated with gold and tungsten layers, exhibiting over 96% optical absorption in the visible range and a tunable absorption performance in the long wave range. From the analysis of experiment and simulation, the enhanced optical absorption is attributed to the synergistic effects of localized nanoparticle plasmon resonance and cavity plasmon resonance, and tunable light management comes from the strong infrared reflection of a gold layer and intrinsic absorption of variable tungsten layers. Meanwhile, the polarization-independent and omnidirectional optical absorption properties are demonstrated in the fabricated absorbers. Furthermore, this absorber shows the robustness against bending, maintaining the stable and excellent absorption performance after hundreds of bending tests. Our work offers a low-cost and straightforward tactic to design and fabricate flexible solar absorbers, and this metasurface absorber is a promising candidate for many exciting applications, such as emissivity control and flexible energy-related devices.

Highly cross-linked Cu/a-Si core-shell nanowires for ultra-long cycle life and high rate lithium batteries.

Seeking long cycle lifetime and high rate performance are still challenging aspects to promote the application of silicon-loaded lithium ion batteries (LIBs), where optimal structural and compositional design are critical to maximize a synergistic effect in composite core-shell nanowire anode structures. We here propose and demonstrate a high quality conformal coating of an amorphous Si (a-Si) thin film over a matrix of highly cross-linked CuO nanowires (NWs). The conformal a-Si coating can serve as both a high capacity storage medium and a high quality binder that joins crossing CuO NWs into a continuous network. And the CuO NWs can be reduced into highly conductive Cu cores in low temperature H2 annealing. In this way, we have demonstrated an excellent cycling stability that lasts more than 700 (or 1000) charge/discharge cycles at a current density of 3.6 A g(-1) (or 1 A g(-1)), with a high capacity retention rate of 80%. Remarkably, these Cu/a-Si core-shell anode structures can survive an extremely high charging current density of 64 A g(-1) for 25 runs, and then recover 75% initial capacity when returning to 1 A g(-1). We also present the first and straightforward experimental proof that these robust highly-cross-linked core-shell networks can preserve the structural integrity even after 1000 runs of cycling. All these results indicate a new and convenient strategy towards a high performance Si-loaded battery application.

Substantial Improvement of Short Wavelength Response in n-SiNW/PEDOT:PSS Solar Cell.

We report herein on the effects of silicon nanowire with different morphology on the device performance of n-SiNW/PEDOT:PSS hybrid solar cells. The power conversion efficiency (PCE) and external quantum efficiency (EQE) of the SiNW/PEDOT:PSS hybrid solar cells can be optimized by varying the length of the silicon nanowires. The optimal length of silicon nanowires is 0.23 µm, and the hybrid solar cell with the optimal length has the V oc of 569 mV, J sc of 30.1 mA/cm(2), and PCE of 9.3 %. We fabricated more isolated silicon nanowires with the diluted etching solution. And the J sc of the hybrid solar cell with more isolated nanowires has a significant enhancement, from 30.1 to 33.2 mA/cm(2). The remarkable EQE in the wavelength region of 300 and 600 nm was also obtained, which are in excess of 80 %. Our work provides a simple method to substantially improve the EQE of hybrid solar cell in the short wavelength region.