In Situ Construction of a LiF-Enriched Interfacial Modification Layer for Stable All-Solid-State Batteries.

All-solid-state batteries (ASSBs), particularly based on sulfide solid-state electrolytes (SSEs), are expected to meet the requirements of high-energy-density energy storage. However, the unstable interface between the ceramic pellets and lithium (Li) metal can induce unconstrained Li-dendrite growth with safety concerns. Herein, we design a carbon fluoride-silver (CFx-Ag) composite to modify the SSEs. As lithium fluoride (LiF) nanocrystals can be in situ formed through electrochemical reactions, this LiF-enriched modification layer with high surface energy can more effectively suppress Li dendrite penetration and interfacial reactions between the SSEs and anode. Remarkably, the all-solid-state symmetric cells using a lithium-boron alloy (LiB) anode can stably work to above 2,500 h under 0.5 mA cm-2 and 2 mAh cm-2 at 60 °C without shorting. A modified LiB||LiNi0.6Mn0.2Co0.2O2 (NMC622) full cell also demonstrates an improved capacity retention and high Coulombic efficiency (99.9%) over 500 cycles. This work provides an advanced solid-state interface architecture to address Li-dendrite issues of ASSBs.

Hydroxypropyl-ß-cyclodextrin improves the removal of polycyclic aromatic hydrocarbons by aerobic granular sludge.

Polycyclic aromatic hydrocarbons (PAHs) as polar organic pollutants, their potential harm to the environment has caused widespread concern. This study describes a simple method to prepare modified aerobic granular sludge (AGS) by hydroxypropyl-ß-cyclodextrin (HP-ß-CD). Using HP-ß-CD modified AGS as the adsorbent, the removal of specific PAHs: Fluoranthene (Fla) reached 95% comparing to 80% of the unmodified AGS. The removal of Fla was related to initial concentration, temperature and ion concentration (Na+, Mg2+). The removal efficiency of Fla reached 96.27%, 94.26% and 93.69%, when initial concentration of Fla was 10, 15 and 20 µmol/L. At temperatures of 15°C, 30°C and 45°C, the removal efficiency of Fla (15 µmol/L) gradually improved from 87.20% to 94.84% and 95.73%. The presence of Na+ and Mg2+ ions led to the deterioration of PAHs removal. With the increase of Na+ and Mg2+ concentrations, the removal efficiency of modified AGS on PAHs decreased by 3.9% and 6.5%, respectively. These findings indicate the potential application of cyclodextrins as the active sites of a complex modified polymer network for PAHs wastewater treatment.

Boosting the Energy Density of Li||CFx Primary Batteries Using a 1,3-Dimethyl-2-imidazolidinone-Based Electrolyte.

Elevating the discharge voltage plateau is regarded as the most effective strategy to improve the energy density of Li||CFx batteries in consideration of the finite capacity of CFx (x ∼ 1) cathodes. Here, an electrolyte, with LiBF4 in 1,3-dimethyl-2-imidazolidinone (DMI)/1,2-dimethoxyethane (DME), is developed for the first time to substantially promote the discharge voltage of CFx without compromising the available discharge capacity. DME possesses the property of low viscosity, while DMI functions to increase the voltage plateau during discharge owing to its moderate nucleophilicity and donor number, which decreases the energy barrier for breaking C-F bonds. The optimized electrolyte exhibits a significantly high average discharge voltage of 2.69 V at a current density of 10 mA g-1, which is 11.6% higher than the control electrolyte (2.41 V). In addition, a high energy density of 2099 Wh kg-1 is achieved in the optimized electrolyte (vs 1905 Wh kg-1 in the control electrolyte), showing great potential for practical applications.

Insights into the vertical distribution of the microbiota in steel plant soils with potentially toxic elements and PAHs contamination after 60 years operation: Abundance, structure, co-occurrence network and functionality.

Both potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) are widely present in soil contaminated by steel industries. This study assessed the vertical variation (at 20 cm, 40 cm, 60 cm, 80 cm, 120 cm, and 150 cm depth) of bacterial abundance, community structure, functional genes related to PAHs degradation, and community co-occurrence patterns in an old steel plant soils which contaminated by PTEs and PAHs for 60 years. The excessive PAHs and PTEs in steel plant soils were benzo (a) pyrene, benzo (b) fluoranthene, dibenzo (a, h) anthracene, indeno (1,2,3-c, d) pyrene, and lead (Pb). The abundance and composition of bacterial community considerably changed with soil depth in two study areas with different pollution degrees. The results of co-occurrence network analysis indicated that the top genera in blast furnace zone identified as the potential keystone taxa were Haliangium, Blastococcus, Nitrospira, and Sulfurifustis. And in coking zone, the top genera were Gaiella. The predictions of bacterial metabolism function using PICRUSt showed that the PAHs-PTEs contaminated soil still had the potential for PAHs degradation, but most PTEs negatively correlated with PAHs degradation genes. The total sulfur (TS), acenaphthene (ANA), and Zinc (Zn) were the key factors to drive development of bacterial communities in the steel plant soils. As far as we know, this is the first investigation of vertical distribution and interaction of the bacterial microbiota in the aging soils of steel plant contaminated with PTEs and PAHs.

Surface coordination layer passivates oxidation of copper.

Owing to its high thermal and electrical conductivities, its ductility and its overall non-toxicity1-3, copper is widely used in daily applications and in industry, particularly in anti-oxidation technologies. However, many widespread anti-oxidation techniques, such as alloying and electroplating1,2, often degrade some physical properties (for example, thermal and electrical conductivities and colour) and introduce harmful elements such as chromium and nickel. Although efforts have been made to develop surface passivation technologies using organic molecules, inorganic materials or carbon-based materials as oxidation inhibitors4-12, their large-scale application has had limited success. We have previously reported the solvothermal synthesis of highly air-stable copper nanosheets using formate as a reducing agent13. Here we report that a solvothermal treatment of copper in the presence of sodium formate leads to crystallographic reconstruction of the copper surface and formation of an ultrathin surface coordination layer. We reveal that the surface modification does not affect the electrical or thermal conductivities of the bulk copper, but introduces high oxidation resistance in air, salt spray and alkaline conditions. We also develop a rapid room-temperature electrochemical synthesis protocol, with the resulting materials demonstrating similarly strong passivation performance. We further improve the oxidation resistance of the copper surfaces by introducing alkanethiol ligands to coordinate with steps or defect sites that are not protected by the passivation layer. We demonstrate that the mild treatment conditions make this technology applicable to the preparation of air-stable copper materials in different forms, including foils, nanowires, nanoparticles and bulk pastes. We expect that the technology developed in this work will help to expand the industrial applications of copper.

Understanding Protection Mechanisms of Graphene-Encapsulated Silicon Anodes with Operando Raman Spectroscopy.

Carbon-coated silicon micro- and nanostructures have been widely used as composite anodes for lithium-ion batteries combining the benefits of high theoretical capacity of Si and better conductivity of carbon. To optimize structures that allow the Si volume expansion without losing the electrical connection, a detailed carbon protection mechanism is desired. We fabricate a network of interconnected sandwich branches with a silicon thin film encapsulated between a porous 3-dimensional graphene foam and graphene drapes (so-called a graphene ensemble). This prototype binder-free anode, of great mechanical strength and composed of only silicon and few-layer graphene, provides distinct signals under operando Raman spectroscopy. During electrochemical cycles, the graphene G peak shows variation of peak position and intensity, while the 2D peak experiences a negligible shift from limited deformation. Silicon displays excellent structural reversibility under the sandwich protection, validating the functions of graphenic carbon coating. This specific graphene ensemble can also serve as an experimental scaffold for mechanical and chemical analysis of many active materials.

Robust Lithium Metal Anodes Realized by Lithiophilic 3D Porous Current Collectors for Constructing High-Energy Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are attractive candidates for next-generation rechargeable batteries. With the steady development of sulfur cathodes, the recent revival of research on dendrite-free Li metal anodes offers opportunities to improve the stabilities and safety of Li-S batteries. However, the low capacities and low Li utilizations of current Li anodes hinder the improvement of the energy densities of Li-S batteries. Here, we present a facile approach to fabricate lithiophilic three-dimensional porous current collectors by modifying commercial metal foams with yolk-shell structured N-doped porous carbon nanosheets. Benefiting from the structure-based rational design, this current collector is able to generate dendrite-free Li anodes with improved Coulombic efficiencies and life spans, enabling carbon/sulfur cathodes to exhibit significantly enhanced stabilities (e.g., 78.1% of capacity retention after 1400 cycles). More importantly, we successfully constructed a high-areal-capacity Li-S full cell (9.84 mAh cm-2) with 82% Li utilization. This work provides a promising route toward high-energy-density Li-S batteries.

Recent Advances in Hollow Porous Carbon Materials for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are considered as one of the most potential next-generation rechargeable batteries due to their high theoretical energy density. However, some critical issues, such as low capacity, poor cycling stability, and safety concerns, must be solved before Li-S batteries can be used practically. During the past decade, tremendous efforts have been devoted to the design and synthesis of electrode materials. Benefiting from their tunable structural parameters, hollow porous carbon materials (HPCM) remarkably enhance the performances of both sulfur cathodes and lithium anodes, promoting the development of high-performance Li-S batteries. Here, together with the templated synthesis of HPCM, recent progresses of Li-S batteries based on HPCM are reviewed. Several important issues in Li-S batteries, including sulfur loading, polysulfide entrapping, and Li metal protection, are discussed, followed by a summary on recent research on HPCM-based sulfur cathodes, modified separators, and lithium anodes. After the discussion on emerging technical obstacles toward high-energy Li-S batteries, prospects for the future directions of HPCM research in the field of Li-S batteries are also proposed.