Constructing Dynamic Anode/Electrolyte Interfaces Coupled with Regulated Solvation Structures for Long-Term and Highly Reversible Zinc Metal Anodes.

Aqueous zinc ion batteries (AZIBs) show a great potential for next-generation energy storage due to their high safety and high energy density. However, the severe side reactions of zinc negative electrode largely hinder the further application of AZIBs. Herein, trace tris(hydroxymethyl)aminomethane (Tris) additive with rich lone-pair-electrons and zincophilic sites is firstly introduced to achieve long-term and highly reversible Zn plating/stripping. Specifically, Tris not only regulates the solvation structure of Zn2+, but is also adsorbed vertically on the Zn anode surface with a changed coordination intensity during the plating/stripping process of Zn to generate an in situ dynamic adsorption layer for the first time. The dynamic adsorption layer could successively attract the solvated Zn2+ and then promote the de-solvation of the solvated Zn2+ owing to the orientation polarization with regularly-changed applied electric field, the volume rejection effect, and strong intermolecular force towards H2O of the vertically-adsorbed Tris. Therefore, an improved Zn2+-transport kinetics as well as the inhibition of side reactions of Zn anode are successfully realized. Accordingly, the Zn||Zn symmetric cell provides an ultra-long cycle life of 2600 h. Furthermore, the Zn||MnO2 full cell with Tris could demonstrate a high capacity and structural stability for practical applications.

Constructing Hydrophobic Interface with Close-Packed Coordination Supramolecular Network for Long-Cycling and Dendrite-Free Zn-Metal Batteries.

Commercialization of aqueous zinc-metal batteries remains unrealistic due to the substantial dendrite growth and side reaction issues on the zinc anodes. It is highly demanded to develop easy-to-handle approaches for constructing stable, dense, as well as homogeneous solid anode/electrolyte interfaces. Herein, the authors construct the zinc anode interface with a close-packed Zn-TSA (TSA = thiosalicylate) coordination supramolecular network through the facile and up-scalable wet-chemical method. The hydrophobic Zn-TSA network can block solvated water and establish a solid-state diffusion barrier to well-distribute the interfacial Zn2+ , thus inhibiting hydrogen evolution and zinc dendrite growth on the anode. Meanwhile, the Zn-TSA network induces the formation of a uniform and stable solid electrolyte interphase composed of multiple inorganic-organic compounds. This denser structure can accommodate and self-heal the crack/degradation of the anode interphase associated with the repeated volume changes, and suppress the generation of detrimental by-product, Znx (OTF- )y (OH)2x-y ·nH2 O. Such a rationally fabricated anode/electrolyte interface further endows the assembled symmetric cells with superior plating/stripping stability for over 2000 h without dendrite formation (at 1 mA cm-2 and 1 mAh cm-2 ). Furthermore, this zinc anode has practical application in the Zn-MoS2 and Zn-V2 O5 full cells. This study provides a new train of thought for constructing the dense interface of zinc-metal anode.

Double Ionic-Electronic Transfer Interface Layers for All-Solid-State Lithium Batteries.

Large-scale implementation of all-solid-state lithium batteries is impeded by the physical limitations of the interface between the electrode and solid electrolyte; specifically, high resistance and poor stability, as well as poor compatibility with Li+ migration. We report double ionic-electronic transfer interface layers grown at electrode-electrolyte interfaces by in situ polymerization of 2,2'-bithiophene in polyethylene oxide (PEO) electrolyte. For all-solid-state LiFePO4 ∥PT-PEO-PT∥Li cells, the formation of a conductive polythiophene (PT) layer at the cathode-electrolyte interface resulted in an at least sevenfold decrease in interface resistance, and realized a capacity retention of about 94 % after 1000 cycles along with a lower polarization voltage under a rate of 2 C. The mixed ionic-electronic conductive layers imparted superior interface stability and contact while keeping good compatibility with the Li anode.

Establishing Multifunctional Interface Layer of Perovskite Ligand Modified Lead Sulfide Quantum Dots for Improving the Performance and Stability of Perovskite Solar Cells.

While organic-inorganic halide perovskite solar cells (PSCs) show great potential for realizing low-cost and easily fabricated photovoltaics, the unexpected defects and long-term stability against moisture are the main issues hindering their practical applications. Herein, a strategy is demonstrated to address the main issues by introducing lead sulfide quantum dots (QDs) on the perovskite surface as the multifunctional interface layer on perovskite film through establishing perovskite as the ligand on PbS QDs. Meanwhile, the multifunctions are featured in three aspects including the strong interactions of PbS QDs with perovskites particularly at the grain boundaries favoring good QDs coverage on perovskites for ultimate smooth morphology; an inhibition of iodide ions mobilization by the strong interaction between iodide and the incorporated QDs; and the reduction of the dangling bonds of Pb2+ by the sulfur atoms of PbS QDs. Finally, the device performances are highly improved due to the reduced defects and non-radiative recombination. The results show that both open-circuit voltage and fill factor are significantly improved to the high values of 1.13 V and 80%, respectively in CH3 NH3 PbI3 -based PSCs, offering a high efficiency of 20.64%. The QDs incorporation also enhances PSCs' stability benefitting from the induced hydrophobic surface and suppressed iodide mobilization.

2D Conjugated Polyelectrolytes Possessing Identical Backbone with Active-Layer Polymer as Cathode Interlayer for Organic Solar Cells.

A 2D conjugated polyelectrolyte (CPE), PBDTTh-TT-NBr, having the same backbone as the highly efficient donor polymer PTB7-Th and the quaternary ammonium pendant, is synthesized as a cathode interlayer (CIL) material for PTB7-Th-based fullerene and non-fullerene solar cells. The quaternary ammonium group is connected to the 2D conjugated backbone by a long, flexible alkyl chain, facilitating the modification of cathode via forming interface dipoles. Moreover, compared with another CPE analogue to PTB7, PBDT-TT-NBr, without the 2D conjugated backbone, the PBDTTh-TT-NBr presents a higher similarity in polymer structure to the donor polymer PTB7-Th. This feature makes it more compatible with the PTB7-Th-based active-layer film, improving the electron transport. With the PBDTTh-TT-NBr as the CIL, devices afford higher performances than those using the PBDT-TT-NBr in both fullerene and non-fullerene systems. This work offers guidance on choosing the CIL material that ought to possess a highly similar structure to the active-layer component.

Organic Solar Cell Materials toward Commercialization.

Bulk-heterojunction organic solar cells (OSCs) have received considerable attention with significant progress recently and offer a promising outlook for portable energy resources and building-integrated photovoltaics in the future. Now, it is urgent to promote the research of OSCs toward their commercialization. For the commercial application of OSCs, it is of great importance to develop high performance, high stability, and low cost photovoltaic materials. In this review, a comprehensive overview of the fundamental requirements of photoactive layer materials and interface layer materials toward commercialization is provided, mainly focusing on high performance, green manufacturing, simplifying device fabrication processes, stability, and cost issues. Furthermore, the perspectives and opportunities for this emerging field of materials science and engineering are also discussed.

An advanced MoS2 /carbon anode for high-performance sodium-ion batteries.

Molybdenum disulfide (MoS2 ) is a promising anode for high performance sodium-ion batteries due to high specific capacity, abundance, and low cost. However, poor cycling stability, low rate capability and unclear electrochemical reaction mechanism are the main challenges for MoS2 anode in Na-ion batteries. In this study, molybdenum disulfide/carbon (MoS2 /C) nanospheres are fabricated and used for Na-ion battery anodes. MoS2 /C nanospheres deliver a reversible capacity of 520 mAh g(-1) at 0.1 C and maintain at 400 mAh g(-1) for 300 cycles at a high current density of 1 C, demonstrating the best cycling performance of MoS2 for Na-ion batteries to date. The high capacity is attributed to the short ion and electron diffusion pathway, which enables fast charge transfer and low concentration polarization. The stable cycling performance and high coulombic efficiency (∼100%) of MoS2 /C nanospheres are ascribed to (1) highly reversible conversion reaction of MoS2 during sodiation/desodiation as evidenced by ex-situ X-ray diffraction (XRD) and (2) the formation of a stable solid electrolyte interface (SEI) layer in fluoroethylene carbonate (FEC) based electrolyte as demonstrated by fourier transform infrared spectroscopy (FTIR) measurements.

New Method for Preparing ZnO Layer for Efficient and Stable Organic Solar Cells.

Owing to outstanding optoelectronic properties and simple preparation, zinc oxide (ZnO) has widely been used in organic solar cells (OSCs). Although versatile cathode interface materials have been designed in past, ZnO remains indispensable owing to its excellent overall performance. Therefore, solving the persistent problem of residual amine reacting with non-fullerene acceptors will make ZnO superior over other materials, and thus improve the performance and energy budget of OSCs. Herein, a simple, effective, and economical method for removing residual amine in ZnO without distorting ZnO is reported. By accurately comparing the alkalinities of ZnO and residual amine, boric acid (BA) is selected as the amine-removing agent because of its suitable acidic dissociation constant. Moreover, the high water solubility of BA ensures that the post-cleaning process can be easily performed. The work function, electron extraction, and stability of cathode interface layer are optimized through rinsing them with BA. Consequently, the power conversion efficiency (PCE) and stability of OSCs under long-term illumination are significantly improved. The optimal 0.04 and 1.00 cm2  single-junction OSCs are based on PBDB-TF:HDO-4Cl:BTP-eC9 bulk heterojunction output 18.40% and 17.42% efficiencies, respectively. Furthermore, tandem OSCs based on the BA-treated ZnO exhibit a 19.56% PCE, demonstrating the reliability of this method.

Semi-Immobilized Ionic Liquid Regulator with Fast Kinetics toward Highly Stable Zinc Anode under -35 to 60 °C.

Aqueous zinc ion batteries (ZIBs) have been extensively investigated as a next-generation energy storage system due to their high safety and low cost. However, the critical issues of irregular dendrite growth and intricate side reactions severely restrict the further industrialization of ZIBs. Here, a strategy to fabricate a semi-immobilized ionic liquid interface layer is proposed to protect the Zn anode over a wide temperature range from -35 to 60 °C. The immobilized SiO2 @cation can form high conjugate racks that can regulate the Zn2+ concentration gradient and self-polarizing electric field to guarantee uniform nucleation and planar deposition; the free anions of the ILs can weaken the hydrogen bonds of the water to promote rapid Zn2+ desolvation and accelerate ion-transport kinetics simultaneously. Because of these unique advantages, the cycling performance of the symmetric Zn batteries is greatly enhanced, evidenced by a cycling life of 1800 h at 20 mA cm-2 , and a cycle lifespan of 2000 h under a wide temperature window from -35 to 60 °C. The efficiency of this semi-immobilizing strategy is well demonstrated in various full cells including pouch cells, showing high performance at large current (20 A g-1 ) and wide temperatures with extra-long cycles up to 80 000 cycles.

All-Solid-State Batteries with a Limited Lithium Metal Anode at Room Temperature using a Garnet-Based Electrolyte.

Metallic lithium (Li), considered as the ultimate anode, is expected to promise high-energy rechargeable batteries. However, owing to the continuous Li consumption during the repeated Li plating/stripping cycling, excess amount of the Li metal anode is commonly utilized in lithium-metal batteries (LMBs), leading to reduced energy density and increased cost. Here, an all-solid-state lithium-metal battery (ASSLMB) based on a garnet-oxide solid electrolyte with an ultralow negative/positive electrode capacity ratio (N/P ratio) is reported. Compared with the counterpart using a liquid electrolyte at the same low N/P ratios, ASSLMBs show longer cycling life, which is attributed to the higher Coulombic efficiency maintained during cycling. The effect of the species of the interface layer on the cycling performance of ASSLMBs with low N/P ratio is also studied. Importantly, it is demonstrated that the ASSLMB using a limited Li metal anode paired with a LiFePO4 cathode (5.9 N/P ratio) delivers a stable long-term cycling performance at room temperature. Furthermore, it is revealed that enhanced specific energies for ASSLMBs with low N/P ratios can be further achieved by the use of a high-voltage or high mass-loading cathode. This study sheds light on the practical high-energy all-solid-state batteries under the constrained condition of a limited Li metal anode.

10 µm-Thick High-Strength Solid Polymer Electrolytes with Excellent Interface Compatibility for Flexible All-Solid-State Lithium-Metal Batteries.

An ultrathin solid polymer electrolyte (SPE) consisting of modified polyethylene (PE) as the host and poly(ethylene glycol) methyl ether acrylate and lithium salts as fillers is presented. The porous poly(methyl methacrylate)-polystyrene interface layers closely attached on both sides of the PE effectively improve the interface compatibility among electrolytes and electrodes. The resultant 10 µm-thick SPEs possess an ultrahigh ionic conductance of 34.84 mS at room temperature and excellent mechanical properties of 103.0 MPa with elongation up to 142.3%. The Li//Li symmetric cell employing an optimized solid electrolyte can stably cycle more than 1500 h at 60 °C. Moreover, the LiFePO4 //Li pouch cell can stably cycle over 1000 cycles at 1 C rate and with a capacity retention of 76.4% from 148.9 to 113.7 mAh g-1 at 60 °C. The LiCoO2 //Li pouch cell can stably operate at 0.1 and 0.2 C rate for each 100 cycles. Furthermore, the LiFePO4 //Li pouch cell can work stably after curling and folding, which proves its excellent flexibility and safety simultaneously. This work offers a promising strategy to realize ultrathinness, excellent compatibility, high strength, as well as safe solid electrolytes for all-solid-state lithium-metal batteries.

From Straw to Device Interface: Carboxymethyl-Cellulose-Based Modified Interlayer for Enhanced Power Conversion Efficiency of Organic Solar Cells.

Advanced interface materials made from petrochemical resources have been extensively investigated for organic solar cells (OSCs) over the past decades. These interface materials have demonstrated excellent performances in OSC devices. However, the limited resources, high-cost, and non-ecofriendly nature of petrochemical-based interface materials restrict their commercial applications. Here, a facile and effective approach to prepare cellulose and its derivatives as a cathode interface layer for OSCs with enhanced performance from rice straw of agroforestry residues is demonstrated. By employing this carboxymethyl cellulose sodium (CMC) into OSCs, a highly efficient inverted OSC is constructed, and a power conversion efficiency (PCE) of 12.01% is realized using poly[(2,6-(4,8-bis(5-(2-ethyl-hexyl)-thiophen-2-yl)-benzo[1,2-b:4,5-b'] dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7-bis(2-ethylhexyl)benzo[1',2'-c: 4',5'-c']dithiophene-4,8-dione): 3,9-bis(2-methylene-((3-(1, 1-dicyanomethylene)-6/7-methyl)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d: 2',3'-d']-s-indaceno[1,2-b: 5, 6-b']dithiophene as the active layer, which shows over 9.4% improvement in PCE compared to that of a device without the CMC layer (PCE = 10.98%), especially the enhancement in short-circuit current. The improved current densities and PCEs are attributed to the reduced work function, enhanced absorption, and improved interfacial contact by using CMC and ZnO as co-interface. This approach of fabricating interface materials from biorenewable sources for OSCs is simple, scalable, and cost-effective, representing a promising direction for the development of smart interface and green electronics.

Impact of Interface Layers on Luminescence Imaging of Organic Solar Cells: Discriminating ETL from HTL Defects.

Over the last two decades, organic photovoltaic (OPV) devices have seen their efficiency increase, while long-term stability and upscaling have been demonstrated for first-generation modules. Since the maturity level of this technology has now improved, techniques for rapid quality control have become relevant. Imaging techniques such as photo- and electroluminescence have already been used for this purpose. However, defects could only be localized either in the active layer or in interface layers, without being able to distinguish between defects located in the ETL from those within the HTL. Here, we present a simple method to unambiguously discriminate between ETL and HTL defects. Furthermore, we demonstrate the strong impact of HTL thickness on the detected photoluminescence signal. Our approach will help avoid misinterpretations in luminescence experiments and gain an understanding of device failure during processing or aging.

Constructing Multifunctional Metallic Ni Interface Layers in the g-C3N4 Nanosheets/Amorphous NiS Heterojunctions for Efficient Photocatalytic H2 Generation.

The construction of exceptionally robust and high-quality semiconductor-cocatalyst heterojunctions remains a grand challenge toward highly efficient and durable solar-to-fuel conversion. Herein, novel graphitic carbon nitride (g-C3N4) nanosheets decorated with multifunctional metallic Ni interface layers and amorphous NiS cocatalysts were fabricated via a facile three-step process: the loading of Ni(OH)2 nanosheets, high-temperature H2 reduction, and further deposition of amorphous NiS nanosheets. The results demonstrated that both robust metallic Ni interface layers and amorphous NiS can be utilized as electron cocatalysts to markedly boost the visible-light H2 evolution over g-C3N4 semiconductor. The optimized g-C3N4-based photocatalyst containing 0.5 wt % Ni and 1.0 wt % NiS presented the highest hydrogen evolution of 515 µmol g-1 h-1, which was about 2.8 and 4.6 times as much as those obtained on binary g-C3N4-1.0%NiS and g-C3N4-0.5%Ni, respectively. Apparently, the metallic Ni interface layers play multifunctional roles in enhancing the visible-light H2 evolution, which could first collect the photogenerated electrons from g-C3N4, and then accelerate the surface H2-evolution reaction kinetics over amorphous NiS cocatalysts. More interestingly, the synergetic effects of metallic Ni and amorphous NiS dual-layer electron cocatalysts could also improve the TEOA-oxidation capacity through upshifting the VB levels of g-C3N4. Comparatively speaking, the multifunctional metallic Ni layers are dominantly favorable for separating and transferring photoexcited charge carriers from g-C3N4 to amorphous NiS cocatalysts owing to the formation of Schottky junctions, whereas the amorphous NiS nanosheets are mainly advantageous for decreasing the thermodynamic overpotentials for surface H2-evolution reactions. It is hoped that the implantation of multifunctional metallic interface layers can provide a versatile approach to enhance the photocatalytic H2 generation over different semiconductor-cocatalyst heterojunctions.