Electric Double Layer Regulator Design through a Functional Group Assembly Strategy towards Long-lasting Zinc Metal Batteries.

Regulating the electric double layer (EDL) structure of the zinc metal anode by using electrolyte additives is an efficient way to suppress interface side reactions and facilitate uniform zinc deposition. Nevertheless, there are no reports investigating the proactive design of EDL-regulating additives before the start of experiments. Herein, a functional group assembly strategy is proposed to design electrolyte additives for modulating the EDL, thereby realizing a long-lasting zinc metal anode. Specifically, by screening ten common functional groups, N, N-dimethyl-1H-imidazole-1-sulfonamide (IS) is designed by assembling an imidazole group, characterized by its high adsorption capability on the zinc anode, and a sulfone group, which exhibits strong binding with Zn2+ ions. Benefiting from the adsorption functionalization of the imidazole group, the IS molecules occupy the position of H2O in the inner Helmholtz layer of the EDL, forming a molecular protective layer to inhibit H2O-induced side reactions. Meanwhile, the sulfone group in IS, acting as a binding site to Zn2+, promotes the de-solvation of Zn2+ ions, facilitating compact zinc deposition. Consequently, the utilization of IS significantly extending the cycling stability of Zn||Zn and Zn||NaV3O8·1.5H2O full cell. This study offers an innovative approach to the design of EDL regulators for high-performance zinc metal batteries.

Iron, Tungsten Dual-Doped Nickel Sulfide as Efficient Bifunctional Catalyst for Overall Water Splitting.

Developing low-cost and highly efficient bifunctional catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is a challenging problem in electrochemical overall water splitting. Here, iron, tungsten dual-doped nickel sulfide catalyst (Fe/W-Ni3S2) is synthesized on the nickel foam, and it exhibits excellent OER and HER performance. As a result, the water electrolyze based on Fe/W-Ni3S2 bifunctional catalyst illustrates 10 mA cm-2 at 1.69 V (without iR-compensation) and highly durable overall water splitting over 100 h tested under 500 mA cm-2. Experimental results and DFT calculations indicate that the synergistic interaction between Fe doping and Ni vacancy induced by W leaching during the in situ oxidation process can maximize exposed OER active sites on the reconstructed NiOOH species for accelerating OER kinetics, while the Fe/W dual-doping optimizes the electronic structure of Fe/W-Ni3S2 and the binding strength of intermediates for boosting HER. This study unlocks the different promoting mechanisms of incorporating Fe and W for boosting the OER and HER activity of Ni3S2 for water splitting, which provides significant guidance for designing high-performance bifunctional catalysts for overall water splitting.

Salt Anion Amphiphilicity-Activated Electrolyte Cosolvent Selection Strategy toward Durable Zn Metal Anode.

One effective solution to inhibit side reactions and Zn dendrite growth in aqueous Zn-ion batteries is to add a cosolvent into the Zn(CF3SO3)2 electrolyte, which has the potential to form a robust solid electrolyte interface composed of ZnF2 and ZnS. Nevertheless, there is still a lack of discussion on a convenient selection method for cosolvents, which can directly reflect the interactions between solvent and solute to rationally design the electrolyte solvation structure. Herein, logP, where P is the octanol-water partition coefficient, a general parameter to describe the hydrophilicity and lipophilicity of chemicals, is proposed as a standard for selecting cosolvents for Zn(CF3SO3)2 electrolyte, which is demonstrated by testing seven different types of solvents. The solvent with a logP value similar to that of the salt anion CF3SO3- can interact with CF3SO3-, Zn2+, and H2O, leading to a reconstruction of the electrolyte solvation structure. To prove the concept, methyl acetate (MA) is demonstrated as an example due to its similar logP value to that of CF3SO3-. Both the experimental and theoretical results illustrate that MA molecules not only enter into the solvation shell of CF3SO3- but also coordinate with Zn2+ or H2O, forming an MA and CF3SO3- involved core-shell solvation structure. The special solvation structure reduces H2O activity and contributes to forming an anion-induced ZnCO3-ZnF2-rich solid electrolyte interface. As a result, the Zn||Zn cell and Zn||NaV3O8·1.5H2O cell with MA-involved electrolyte exhibit superior performances to that with the MA-free electrolyte. This work provides an insight into electrolyte design via salt anion chemistry for high-performance Zn batteries.

An efficient electrolyte additive of 1,3,6-hexanetricarbonitrile for high performance aqueous zinc-ion batteries.

The growth of Zn dendrites and parasitic side reactions between electrode and electrolyte are major obstacles to the development of rechargeable aqueous zinc-ion batteries. To address these critical issues, the use of nitrile organic compounds as electrolyte additives holds great promise. Herein, for the first time, we prepared a small volume concentration (x) of 1,3,6-Hexanetricarbonitrile (HTCN-x) as additives into zinc trifluoromethanesulphonate (Zn(OTF)2) electrolyte and studied their electrochemical properties in Zn||ZnxV2O5·nH2O (Zn||ZVO) cells. It was found that the strong interaction between H2O and HTCN could significantly reduce the population of solvated H2O outside the solvation sheath, leading to reduced side reactions in the aqueous Zn(OTF)2 electrolyte. Moreover, the HTCN additive also facilitates the formation of strong and stable solid electrolyte interphase (SEI) film on the surface of the Zn anode, which effectively prevents the growth of Zn dendrites and the anode corrosion caused by the electrolyte. As a result, the HTCN-x (x = 0.3) electrolyte enabled the symmetrical Zn||Zn cell to cycle over 950 h at a current of 1 mA cm-2 with a limited capacity of 1 mAh cm-2. When the HTCN-0.3 electrolyte was used in Zn||ZVO cell, the cell delivered a high initial capacity of 355.6 mAh g-1 at 0.1 A g-1 and maintained a high capacity of 330.0 mAh g-1 at 1 A g-1 after 465 cycles.

Super-resolved dynamics of isolated zinc formation during extremely fast electrochemical deposition/dissolution processes.

The development of zinc-air batteries with high-rate capability and long lifespan is critically important for their practical use, especially in smart grid and electric vehicle application. The formation of isolated zinc (i-Zn) on the zinc anode surface, however, could easily lead to deteriorated performance, such as rapid capacity decay. In particular, under the fast charging/discharging conditions, the electrochemical activities on the anode surface are complicated and severely suppressed. Thus, it is highly desirable to deeply understand the formation mechanism of i-Zn and its relationship with the electrochemical performance during extremely high-rate cycling. Herein, we employed a super-resolution dark-field microscope to in situ analyze the evolution dynamics of the electrolyte-Zn interface during the extremely fast electrochemical deposition/dissolution processes. The unique phenomenon of nanoscopic i-Zn generation under the condition is unveiled. We discovered that the rapid conversion of nanoscopic i-Zn fragments into passivated products could greatly exacerbate the concentration polarization process and increase the overpotential. In addition, the role of large-sized i-Zn fragments in reducing the coulombic efficiency is further elucidated. This information could aid the rational design of highly effective anodes for extremely high-rate zinc-based batteries and other battery systems.

Carbonyls from commercial, canteen and residential cooking activities as crucial components of VOC emissions in China.

Cooking in China supply the large population with nutrition and, as a commercial activity, it also promotes the economic growth of Chinese society. The specific cooking styles in China can produce complex volatile organic compound (VOC) emissions. The resulting adverse effects on the environment and human health of carbonyls from cooking should not be ignored. We quantitatively evaluated the contribution of carbonyls to common VOCs (carbonyl/VOC ratio) from cooking activities in China through the establishment and comparison of the source profiles, emission factors (EFs), emission amount and ozone formation potential (OFP). It was found that carbonyls are crucial components of VOCs from commercial, canteen and residential cooking activities (COC, CAC and REC, respectively). The carbonyl/VOC ratio from cooking activities in China had EFs, emissions, and a total OFP of 22-65 %, 23-34 %, and 49-104 %, respectively. The high OFP was due to the high OFP emissions intensity (OFPEI) and maximum incremental reactivity (MIR) values of carbonyls. This indicates that to alleviate O3 pollution, OFP-based control measures that target carbonyls might be more efficient than measures that target common VOCs. Priority should be given to emission controlling COC emissions, specifically those from medium- and large-scale catering. Formaldehyde, acetaldehyde, and hexanal were the key carbonyl species that form O3 in the environment. Our findings imply that cooking-emitted carbonyls should not be overlooked in investigations of O3 formation and that these compounds should be subject to strict regulations.

Highly durable aqueous Zn ion batteries based on a Zn anode coated by three-dimensional cross-linked and branch-liked bismuth-PVDF layer.

Rechargeable aqueous Zn ion batteries have been regarded as one of the most promising candidates for next-generation energy storage devices due to their low cost, non-toxicity and high safety. However, the dendrite growth of Zn anode and severe undesired side-reactions largely limited their practical application. Here, we developed a bismuth (Bi)-PVDF layer with unique 3D cross-linked and branch-liked structures as a protective layer on the Zn surface (Zn@Bi-PVDF) to suppress the formation of Zn dendrites and side-reactions, leading to the uniform plating and stripping of Zn during the cycles. Consequently, the symmetric cell with Zn@Bi-PVDF electrodes exhibits long cycling life over 2400 h at a current density of 1 mA cm-2 with a fixed capacity of 1 mAh cm-2. When the Zn@Bi-PVDF anode is paired with a NaV3O8·1.5H2O (NVO) cathode, the fabricated Zn@Bi-PVDF//NVO cell maintains a high reversible capacity of 175.5 mAh g-1 at 1 A g-1 after 500 cycles with an initial capacity retention of 64.1%.

[Industrial Volatile Organic Compounds (VOCs) Emission Inventory in China].

An industrial volatile organic compounds (VOCs) emission inventory was developed in China in 2018. It was based on the emission factors method, using a revised and updated source classification system and emission factors of key industrial sources. Results showed that the total industrial VOCs emission in China in 2018 reached as high as 12698 kt. Processes using products containing VOCs were the largest contributors, accounting for 59% of the total emission. The industrial coating industry, printing, the basic organic chemical industry, gasoline storage and transport, and the oil refinery industry were the five largest emitters, accounting for 54% of the total emission. Guangdong, Shandong, Zhejiang, and Jiangsu were the four largest emission contributors, contributing to 41% of the total emission. Hainan, Ningxia, Tibet, Heilongjiang, and Xinjiang showed the largest VOCs emission intensities, with more than 80 t·(100 million yuan)-1. Processes using products containing VOCs were the main emission contributors in most provinces. The uncertainty for the total industrial VOCs emission in 2018, based on a Monte Carlo simulation, was[-32%, 48%] at the 95% confidence interval.

Improved emissions inventory and VOCs speciation for industrial OFP estimation in China.

Ozone (O3) pollution is becoming increasingly serious in China. Reactivity-based control of volatile organic compounds (VOCs) is an efficient method of alleviating O3 pollution. In this study, an improved industrial VOCs emissions inventory for China from 2011 to 2018 and local source profiles for six specific industries were developed to improve estimation of ozone formation potential (OFP). The results indicated that average annual growth rate for industrial VOCs emissions during 2015-2018 was lower than 2011-2014, which could be related to China's industrial structural upgrade and implementation of VOCs source control during the 13th Five-Year Plan period. The industrial coating, printing, basic organic chemical, gasoline storage and transport, and oil refinery industries were the key sources of VOCs emissions. M/p-xylene, toluene, ethyl benzene, propene, o-xylene, ethene, 1,2,4-trimethylbenzene, m-ethyl toluene, isopentane, and 1-butene were the top 10 species in terms of OFP. The top 20 species based on OFP accounted for an estimated 85% of total OFP and only 59% of emissions. The industrial coating, printing, basic organic chemical, oil refinery industries and other five sectors were the top 10 sources in terms of OFP, which together contributed 81% of total OFP. Priority should be given to the top 20 or more species with high reactivity and the top 10 sources based on OFP for future O3 reductions in China.

Smoothing the Surface and Improving the Electrochemical Properties of NaxMnO2 by a Wet Chemical Method.

NaxMnO2 (NMO) is treated by a wet chemical method in this paper. The treated NMO can form a copper oxide coating layer, and some of the coating layer can be peeled off, smoothing the surface of particles. Electrochemical measurement shows that treated NMO can maintain 72.6% of its specific capacity after 300 cycles, which is better than the 58.7% specific capacity of untreated NMO materials. Additionally, the ratio of capacity remaining rate can be improved from an initial 87% to 99.5%. So, this wet chemical method is available to smooth the electrode surface and reduce the internal impedance, and thus to effectively improve electrochemical performance during the battery cycle.

Antimony Nanorod Encapsulated in Cross-Linked Carbon for High-Performance Sodium Ion Battery Anodes.

Antimony- (Sb) based materials have been considered as one of promising anodes for sodium ion batteries (SIBs) owing to their high theoretical capacities and appropriate sodium inserting potentials. So far, the reported energy density and cycling stability of the Sb-based anodes for SIBs are quite limited and need to be significantly improved. Here, we develop a novel Sb/C hybrid encapsulating the Sb nanorods into highly conductive N and S codoped carbon (Sb@(N, S-C)) frameworks. As an anode for SIBs, the Sb@(N, S-C) hybrid maintains high reversible capacities of 621.1 mAh g-1 at 100 mA g-1 after 150 cycles, and 390.8 mAh g-1 at 1 A g-1 after 1000 cycles. At higher current densities of 2, 5, and 10 A g-1, the Sb@(N, S-C) hybrid also can display high reversible capacities of 534.4, 430.8, and 374.7 mAh g-1, respectively. Such impressive sodium storage properties are mainly attributed to the unique cross-linked carbon networks providing highly conductive frameworks for fast transfer of ions and electrons, alleviating the volume expansion and preventing the agglomeration of Sb nanorods during the cycling.

Defects in metal triiodide perovskite materials towards high-performance solar cells: origin, impact, characterization, and engineering.

The rapid development of solar cells (SCs) based on organic-inorganic hybrid metal triiodide perovskite (MTP) materials holds great promise for next-generation photovoltaic devices. The demonstrated power conversion efficiency of the SCs based on MTP (PSCs for short) has reached over 20%. An MTP material is a kind of soft ionic solid semiconductor. The intrinsic optoelectronic properties of MTP are greatly determined by several factors, such as the crystalline phase, doping type, impurities, elemental composition, and defects in its crystal structure. In the development of PSCs, a good understanding and smart engineering of the defects in MTP have been demonstrated to be a key factor for the fabrication of high-efficiency PSCs. In this review, we start with a brief introduction to the types of defects and the mechanisms for their formation in MTP. Then, the positive and negative impacts of defects on the important optoelectronic features of MTP are presented. The optoelectronic properties mainly include charge recombination, charge transport, ion migration, and structural stability. Moreover, commonly used techniques for the characterization of the defects in MTP are systematically summarized. Recent progress on the state-of-the-art defect engineering approaches for the optimization of PSC devices is also summarized, and we also provide some perspectives on the development of high-efficiency PSCs with long-term stability through the optimization of the defects in MTP.

Manipulating the Architecture of Atomically Thin Transition Metal (Hydr)oxides for Enhanced Oxygen Evolution Catalysis.

Graphene-like nanomaterials have received tremendous research interest due to their atomic thickness and fascinating properties. Previous studies mainly focus on the modulation of their electronic structures, which undoubtedly optimizes the electronic properties, but is not the only determinant of performance in practical applications. Herein, we propose a generalized strategy to incrementally manipulate the architectures of several atomically thin transition metal (hydr)oxides, and study their effects on catalytic water oxidation. The results demonstrate the obvious superiority of a wrinkled nanosheet architecture in both catalytic activity and durability. For instance, wrinkled Ni(OH)2 nanosheets display a low overpotential of 358.2 mV at 10 mA cm-2, a high current density of 187.2 mA cm-2 at 500 mV, a small Tafel slope of 54.4 mV dec-1, and excellent long-term durability with gradually optimized performance, significantly outperforming other nanosheet architectures and previously reported catalysts. The outstanding catalytic performance is mainly attributable to the 3D porous network structure constructed by wrinkled nanosheets, which not only provides sufficient contact between electrode materials and current collector, but also offers highly accessible channels for facile electrolyte diffusion and efficient O2 escape. Our study provides a perspective on improving the performance of graphene-like nanomaterials in a wide range of practical applications.

Recent Progress in Graphite Intercalation Compounds for Rechargeable Metal (Li, Na, K, Al)-Ion Batteries.

Lithium-ion batteries (LIBs) with higher energy density are very necessary to meet the increasing demand for devices with better performance. With the commercial success of lithiated graphite, other graphite intercalation compounds (GICs) have also been intensively reported, not only for LIBs, but also for other metal (Na, K, Al) ion batteries. In this Progress Report, we briefly review the application of GICs as anodes and cathodes in metal (Li, Na, K, Al) ion batteries. After a brief introduction on the development history of GICs, the electrochemistry of cationic GICs and anionic GICs is summarized. We further briefly summarize the use of cationic GICs and anionic GICs in alkali ion batteries and the use of anionic GICs in aluminium-ion batteries. Finally, we reach some conclusions on the drawbacks, major progress, emerging challenges, and some perspectives on the development of GICs for metal (Li, Na, K, Al) ion batteries. Further development of GICs for metal (Li, Na, K, Al) ion batteries is not only a strong supplement to the commercialized success of lithiated-graphite for LIBs, but also an effective strategy to develop diverse high-energy batteries for stationary energy storage in the future.

Metal-Free Carbon Materials for CO2 Electrochemical Reduction.

The rapid increase of the CO2 concentration in the Earth's atmosphere has resulted in numerous environmental issues, such as global warming, ocean acidification, melting of the polar ice, rising sea level, and extinction of species. To search for suitable and capable catalytic systems for CO2 conversion, electrochemical reduction of CO2 (CO2 RR) holds great promise. Emerging heterogeneous carbon materials have been considered as promising metal-free electrocatalysts for the CO2 RR, owing to their abundant natural resources, tailorable porous structures, resistance to acids and bases, high-temperature stability, and environmental friendliness. They exhibit remarkable CO2 RR properties, including catalytic activity, long durability, and high selectivity. Here, various carbon materials (e.g., carbon fibers, carbon nanotubes, graphene, diamond, nanoporous carbon, and graphene dots) with heteroatom doping (e.g., N, S, and B) that can be used as metal-free catalysts for the CO2 RR are highlighted. Recent advances regarding the identification of active sites for the CO2 RR and the pathway of reduction of CO2 to the final product are comprehensively reviewed. Additionally, the emerging challenges and some perspectives on the development of heteroatom-doped carbon materials as metal-free electrocatalysts for the CO2 RR are included.

Chevrel Phase Mo6 T8 (T = S, Se) as Electrodes for Advanced Energy Storage.

With the large-scale applications of electric vehicles in recent years, future batteries are required to be higher in power and possess higher energy densities, be more environmental friendly, and have longer cycling life, lower cost, and greater safety than current batteries. Therefore, to develop alternative electrode materials for advanced batteries is an important research direction. Recently, the Chevrel phase Mo6 T8 (T = S, Se) has attracted increasing attention as electrode candidate for advanced batteries, including monovalent (e.g., lithium and sodium) and multivalent (e.g., magnesium, zinc and aluminum) ion batteries. Benefiting from its unique open crystal structure, the Chevrel phase Mo6 T8 cannot only ensure rapid ion transport, but also retain the structure stability during electrochemical reactions. Although the history of the research on Mo6 T8 as electrodes for advanced batteries is short, there has been significant progress on the design and fabrication of Mo6 T8 for various advanced batteries as above mentioned. An overview of the recent progress on Mo6 T8 electrodes applied in advanced batteries is provided, including synthesis methods and diverse structures for Mo6 T8 , and electrochemical mechanism and performance of Mo6 T8 . Additionally, a briefly conclusion on the significant progress, obvious drawbacks, emerging challenges and some perspectives on the research of Mo6 T8 for advanced batteries in the near future is provided.

2D Frameworks of C2 N and C3 N as New Anode Materials for Lithium-Ion Batteries.

Novel layered 2D frameworks (C3 N and C2 N-450) with well-defined crystal structures are explored for use as anode materials in lithium-ion batteries (LIBs) for the first time. As anode materials for LIBs, C3 N and C2 N-450 exhibit unusual electrochemical characteristics. For example, C2 N-450 (and C3 N) display high reversible capacities of 933.2 (383.3) and 40.1 (179.5) mAh g-1 at 0.1 and 10 C, respectively. Furthermore, C3 N shows a low hypothetical voltage (≈0.15 V), efficient operating voltage window with ≈85% of full discharge capacity secured at >0.45 V, and excellent cycling stability for more than 500 cycles. The excellent electrochemical performance (especially of C3 N) can be attributed to their inherent 2D polyaniline frameworks, which provide large net positive charge densities, excellent structural stability, and enhanced electronic/ionic conductivity. Stable solid state interface films also form on the surfaces of the 2D materials during the charge/discharge process. These 2D materials with promising electrochemical performance should provide insights to guide the design and development of their analogues for future energy applications.

Highly Rechargeable Lithium-CO2 Batteries with a Boron- and Nitrogen-Codoped Holey-Graphene Cathode.

Metal-air batteries, especially Li-air batteries, have attracted significant research attention in the past decade. However, the electrochemical reactions between CO2 (0.04 % in ambient air) with Li anode may lead to the irreversible formation of insulating Li2 CO3 , making the battery less rechargeable. To make the Li-CO2 batteries usable under ambient conditions, it is critical to develop highly efficient catalysts for the CO2 reduction and evolution reactions and investigate the electrochemical behavior of Li-CO2 batteries. Here, we demonstrate a rechargeable Li-CO2 battery with a high reversibility by using B,N-codoped holey graphene as a highly efficient catalyst for CO2 reduction and evolution reactions. Benefiting from the unique porous holey nanostructure and high catalytic activity of the cathode, the as-prepared Li-CO2 batteries exhibit high reversibility, low polarization, excellent rate performance, and superior long-term cycling stability over 200 cycles at a high current density of 1.0 A g-1 . Our results open up new possibilities for the development of long-term Li-air batteries reusable under ambient conditions, and the utilization and storage of CO2 .

Recent Progress in the Design of Advanced Cathode Materials and Battery Models for High-Performance Lithium-X (X = O2 , S, Se, Te, I2 , Br2 ) Batteries.

Recent advances and achievements in emerging Li-X (X = O2 , S, Se, Te, I2 , Br2 ) batteries with promising cathode materials open up new opportunities for the development of high-performance lithium-ion battery alternatives. In this review, we focus on an overview of recent important progress in the design of advanced cathode materials and battery models for developing high-performance Li-X (X = O2 , S, Se, Te, I2 , Br2 ) batteries. We start with a brief introduction to explain why Li-X batteries are important for future renewable energy devices. Then, we summarize the existing drawbacks, major progress and emerging challenges in the development of cathode materials for Li-O2 (S) batteries. In terms of the emerging Li-X (Se, Te, I2 , Br2 ) batteries, we systematically summarize their advantages/disadvantages and recent progress. Specifically, we review the electrochemical performance of Li-Se (Te) batteries using carbonate-/ether-based electrolytes, made with different electrode fabrication techniques, and of Li-I2 (Br2 ) batteries with various cell designs (e.g., dual electrolyte, all-organic electrolyte, with/without cathode-flow mode, and fuel cell/solar cell integration). Finally, the perspective on and challenges for the development of cathode materials for the promising Li-X (X = O2 , S, Se, Te, I2 , Br2 ) batteries is presented.