Massively Reconstructing Hydrogen Bonding Network and Coordination Structure Enabled by a Natural Multifunctional Co-Solvent for Practical Aqueous Zn-Ion Batteries.

The practical application of aqueous Zn-ion batteries (AZIBs) is hindered by the crazy Zn dendrites growth and the H2O-induced side reactions, which rapidly consume the Zn anode and H2O molecules, especially under the lean electrolyte and Zn anode. Herein, a natural disaccharide, d-trehalose (DT), is exploited as a novel multifunctional co-solvent to address the above issues. Molecular dynamics simulations and spectral characterizations demonstrate that DT with abundant polar -OH groups can form strong interactions with Zn2+ ions and H2O molecules, and thus massively reconstruct the coordination structure of Zn2+ ions and the hydrogen bonding network of the electrolyte. Especially, the strong H-bonds between DT and H2O molecules can not only effectively suppress the H2O activity but also prevent the rearrangement of H2O molecules at low temperature. Consequently, the AZIBs using DT30 electrolyte can show high cycling stability even under lean electrolyte (E/C ratio = 2.95 µL mAh-1), low N/P ratio (3.4), and low temperature (-12 °C). As a proof-of-concept, a Zn||LiFePO4 pack with LiFePO4 loading as high as 506.49 mg can be achieved. Therefore, DT as an eco-friendly multifunctional co-solvent provides a sustainable and effective strategy for the practical application of AZIBs.

Regulating Au coverage for the direct oxidation of methane to methanol.

The direct oxidation of methane to methanol under mild conditions is challenging owing to its inadequate activity and low selectivity. A key objective is improving the selective oxidation of the first carbon-hydrogen bond of methane, while inhibiting the oxidation of the remaining carbon-hydrogen bonds to ensure high yield and selectivity of methanol. Here we design ultrathin PdxAuy nanosheets and revealed a volcano-type relationship between the binding strength of hydroxyl radical on the catalyst surface and catalytic performance using experimental and density functional theory results. Our investigations indicate a trade-off relationship between the reaction-triggering and reaction-conversion steps in the reaction process. The optimized Pd3Au1 nanosheets exhibits a methanol production rate of 147.8 millimoles per gram of Pd per hour, with a selectivity of 98% at 70 °C, representing one of the most efficient catalysts for the direct oxidation of methane to methanol.

Efficient Self-Assembly Preparation of 3D Carbon-Supported Ti3 C2 Tx Hollow Spheres for High-Performance Potassium Ion Batteries.

MXenes are considered a promising negative electrode material for potassium ion batteries (PIBs) in view of their low potassium ion diffusion barrier and excellent electrical conductivity. However, the stacking phenomenon in practical applications severely reduces their active surface and leads to slow K+ diffusion. Herein, a facile composite template method is proposed to construct stacking-resistance 3D carbon-supported Ti3 C2 Tx (3D-C@Ti3 C2 Tx ) hollow spheres. Due to the unique structure, when used as a negative electrode material, as-prepared 3D-C@Ti3 C2 Tx hollow spheres show not only improved rate capability with 160.4 mAh g-1 at 100 mA g-1 and 133.7 mAh g-1 at 500 mA g-1 , but also stable cycling performance with 142.5 mAh g-1 specific capacity remained at 2 A g-1 after 4200 cycles. Furthermore, the full cells with 3D-C@Ti3 C2 Tx anode can operate stably for 1000 cycles at 100 mA g-1 . Moreover, the linear fit analysis demonstrates that 3D-C@Ti3 C2 Tx hollow spheres have a fast and stable capacitive potassium storage mechanism. This method is simple and easy to implement, which provide a feasible path to solve the stacking problem of 2D materials.

Scalable synthesis of N/S co-doped hard carbon microspheres as a high-performance anode material for sodium-ion batteries.

Hard carbon is a promising anode material for sodium-ion batteries (SIBs) due to its abundance. However, it exhibits low reversible capacity and slow kinetics if inappropriate microstructural features are developed during synthesis. Herein, N/S co-doped phenolic resin-based hard carbon microspheres are prepared by a scalable strategy, and the electrochemical performance is assessed both in half cells and full cells. We demonstrate that the expanded interlayer spacing, the increased active sites, and the enhanced capacitive behavior result in the enhanced reversible capacity and promoted kinetics for Na+storage. The sample with appropriate doping amount exhibits an initial charge capacity of 536.8 mAh g-1at 50 mA g-1and maintains 445.9 mAh g-1after 1000 cycles at a current density of 1 A g-1in a Na-metal half cell. Coupled with a carbon-coated Na4Fe3(PO4)2P2O7(NFPP) cathode, the full cell exhibits a capacity of 92.5 mAh g-1after 90 cycles, with a capacity retention of 91.6%. This work provides a facile and scalable method for synthesizing high-performance hard carbon anode materials for SIBs.

Black phosphorus stabilized by titanium disulfide and graphite via chemical bonds for high-performance lithium storage.

Black phosphorus (BP) anode has received extensive attentions for lithium-ion batteries (LIBs) due to its ultrahigh theoretical specific capacity (2596 mAh g-1) and superior electronic conductivity (≈102 S m-1). However, the enormous volume variations during lithiation/delitiation processes greatly limit its applications. Herein, a new BP-titanium disulfide-graphite (BP-TiS2-G) nanocomposite composed of BP, titanium disulfide and graphite has been prepared by a facile and scalable high-energy ball milling method. The experimental data proves that PC and PS bonds have been successfully introduced at the interface, which can effectively maintain the structural integrity of the BP-TiS2-G electrode when evaluated as an anode material for LIBs. In addition, lithium-ion diffusion kinetics have been demonstrated to be enhanced from the synergistic effect of PC and PS bonds. As a result, the BP-TiS2-G anode shows outstanding cycling stability (906.2 mAh g-1 after 1300 cycles at 1.0 A g-1) and superior rate performance (313.8 mAh g-1 at 10.0 A g-1). Our work shows the synergistic effects of different chemical bonds to stabilize BP can be a potential strategy for the development of high-performance alloy-type anodes for rechargeable batteries.

Ultra-fine SnO2nanocrystals anchored on reduced graphene oxide as a high-performance anode material for sodium-ion batteries.

SnO2has attracted extensive research attentions as a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, its application is largely hindered by sluggish sodium ion diffusion and drastic volume change during the conversion reaction and alloying process. Herein, ultra-fine SnO2nanocrystals (3-5 nm) anchored on reduced graphene oxide (rGO) is demonstrated as a promising anode material for SIBs. Ultra-fine SnO2nanocrystals are uniformly grown on rGO sheets by a facile one-step hydrothermal process. Nano-scaled SnO2grains tolerate volume expansion and provide shortened diffusion pathway for sodium ions, and meanwhile rGO acts as an excellent conductive matrix, thus endowing the composite electrode with excellent electrochemical performance. More importantly, the ratio of SnO2to rGO in the composite is optimized. The optimized sample delivers an initial charge capacity of 518 mAh g-1at a current density of 50 mA g-1, and 504 mAh g-1after 300 cycles at a current density of 100 mA g-1. Furthermore, a capacity of 287 mAh g-1can be maintained after 1000 cycles at a current density of 1000 mA g-1.

Surface engineered hollow Ni-Co-P@TiO2-x nanopolyhedrons as high performance anode material for sodium storage.

With the proposal of carbon peaking and carbon neutrality goals, clean energy storage is attracting more and more attentions. In view of the lack of lithium resource in our earth, sodium-ion batteries are considered as the emerging and promising next-generation energy storage devices. Appropriate high-performance anode materials play a vital role in the development of sodium-ion batteries. Here, a core-shell hollow Ni-Co-P nanopolyhedron interconnected by oxygen defect TiO2 (Ni-Co-P@TiO2-x) is reported, which is synthesized by ion etching-hydrolysis and subsequent phosphatization/hydrogenation treatment using ZIF-67 as template and hybrid carbon source. The achieved Ni-Co-P@TiO2-x material has several distinct advantages including hollow core-shell structure, flexible conductive carbon matrix, stable electroactive coating layer, and efficient pseudocapacitive behavior, resulting in high reversible capacities, remarkable rate capability and excellent cycle stability. The synergetic battery-capacitor characteristic of Ni-Co-P@TiO2-x material makes it become a promising anode for sodium-ion batteries.

Rational Design of LLZO/Polymer Solid Electrolytes for Solid-State Batteries.

Hybrid composite electrolytes incorporate polymer matrixes and garnet filler attract the focus of concern for all-solid-state batteries, which possess high ionic conductivity, superior electrochemical stability, and wide electrochemical window of ceramic electrolyte advantages, and exhibit excellent flexibility and tensile shear strength from polymer electrolyte benefits. Hence, the unique structure design of solid-state electrolytes resolves the existing defects that the use of either single garnet or polymer electrolytes implemented into battery devices. This review summarizes Li7 La3 Zr2 O12 (LLZO)/polymer solid composite electrolytes (SCEs), comprising LLZO/polymer SCEs with various structures and different ratios of LLZO fillers, LLZO/polymer with different kinds of polymers matrix and hybrid lithium-salt, and Li+ transport pathways within the LLZO/polymers SCEs interface. The purpose here is to propose the viewpoints and challenges of LLZO/polymer SCEs to promote the development of next-generation solid electrolytes.

Confining ZnS/SnS2 Ultrathin Heterostructured Nanosheets in Hollow N-Doped Carbon Nanocubes as Novel Sulfur Host for Advanced Li-S Batteries.

Hollow nanostructured hosts are important scaffolds to achieve high sulfur loading, fast charge transfer, and conspicuous restraint of lithium polysulfides (LiPSs) shuttling in lithium-sulfur (Li-S) batteries. However, developing high-efficiency hollow hosts for improving utilization and conversion of aggregated sulfur in the hollow chamber remains a longstanding challenge. Herein, hollow N-doped carbon nanocubes confined petal-like ZnS/SnS2 heterostructures (ZnS/SnS2 @NC) as a conceptually novel host for Li-S batteries are reported. Specifically, compared to consubstantial hollow double-shelled hosts, the ZnS/SnS2 @NC with higher effective active surface area brings dense contact with sulfur and enhances efficient adsorption sites for binding LiPSs and accelerating their conversion. Benefiting from the unique structure and sophisticated composition, the resulting S@ZnS/SnS2 @NC cathodes exhibit 1294 mAh g-1 at 0.2 C, an ultralow capacity decay of 0.016% per cycle over 500 cycles at 1.0 C, and a high area capacity of 4.77 mAh cm-2 at 0.5 C (5.9 mg cm-2 ). Meanwhile, the performance evolution of S@ZnS/SnS2 @NC cathodes under various sulfur loadings is further investigated by using EIS, which provides the beneficial guidance to explore viable strategies further optimizing their performance. This work sheds new insights into the design of hollow nanostructured hosts with a distinguished ability to regulate LiPSs in Li-S batteries.

Ti-substituted O3-type layered oxide cathode material with high-voltage stability for sodium-ion batteries.

O3-type layered transition metal oxides (NaxTMO2) have attracted extensive attention as a promising cathode material for sodium-ion batteries because of their high capacity. However, the irreversible phase transition especially cycled under high voltage remains a concerning challenge for NaxTMO2. Herein, a Ti-substituted NaNi0.5Co0.2Mn0.3O2 cathode with strongly suppressed phase transition and enhanced storage stability is investigated. The Ti substitution effectively inhibits the irreversible phase transition and alleviates the structural change even charged to 4.3 V during the repeated Na+ deintercalation process. After storing in air or water, the original O3 phase structure of the material is integrally maintained without the generation of impurity phase. As a result, the as-prepared material shows excellent long-term cycle stability and rate performance when charged to a high voltage of 4.3 V.

Metal-N4@Graphene as Multifunctional Anchoring Materials for Na-S Batteries: First-Principles Study.

Developing highly efficient anchoring materials to suppress sodium polysulfides (NaPSs) shuttling is vital for the practical applications of sodium sulfur (Na-S) batteries. Herein, we systematically investigated pristine graphene and metal-N4@graphene (metal = Fe, Co, and Mn) as host materials for sulfur cathode to adsorb NaPSs via first-principles theory calculations. The computing results reveal that Fe-N4@graphene is a fairly promising anchoring material, in which the formed chemical bonds of Fe-S and N-Na ensure the stable adsorption of NaPSs. Furthermore, the doped transition metal iron could not only dramatically enhance the electronic conductivity and the adsorption strength of soluble NaPSs, but also significantly lower the decomposition energies of Na2S and Na2S2 on the surface of Fe-N4@graphene, which could effectively promote the full discharge of Na-S batteries. Our research provides a deep insight into the mechanism of anchoring and electrocatalytic effect of Fe-N4@graphene in sulfur cathode, which would be beneficial for the development of high-performance Na-S batteries.

Mn3O4 anchored polypyrrole nanotubes as an efficient sulfur host for high performance lithium-sulfur batteries.

Lithium-sulfur batteries have attracted numerous attentions owing to their high theory discharge specific capacity and energy density. However, sulfur cathode usually suffers from poor cycle stability and slow reaction kinetics, caused by its poor conductivity, excessive volume changes during charge/discharge processes, complex sulfur species conversion reaction and the dissolution of polysulfide intermediates. Here, we present a free-standing framework of Mn3O4 nanoparticles combine with polypyrrole (PPy) nanotubes as host materials for lithium-sulfur batteries to overcome these issues. In this construction, PPy nanotubes serve as the excellent container of sulfur and physical barrier for the excessive volume expansion of sulfur during electrochemical reaction processes, and the nanotubes also provide an efficient conductive network for the rapid transmission of electrons and ions, while Mn3O4 nanoparticles facilitate trapping lithium polysulfides. The coordination of PPy nanotubes and Mn3O4 effectively alleviate the shuttle effect as well as enhance the utilization of sulfur. The obtained PPy@Mn3O4-S sample shows high capacities of 1419.9 and 925.5 mAh g-1 at 0.1 C and 1 C rate, respectively, and exhibits a low capacity fading rate of 0.062% per cycle for 800 cycles at 1 C rate. This work provides a new and effective way for the design of lithium-sulfur batteries with both high rate performance and long cycle stability.

Boosting Lithium Storage in Free-Standing Black Phosphorus Anode via Multifunction of Nanocellulose.

Layer-structured black phosphorus (BP) demonstrating high specific capacity has been viewed as a very promising anode material for future high-energy-density Li-ion batteries (LIBs). However, its practical application is hindered by large volume change of BP and poor mechanical stability of BP anodes by traditional slurry casting technology. Here, a free-standing flexible anode composed of BP nanosheets and nanocellulose (NC) nanowires is fabricated via a facile vacuum-assisted filtration approach. The constructed free-standing BP@NC composite anode offers three-dimensional (3D) mixed-conducting network for Li+/e- transports. The substrate of NC film has a certain flexibility up to 10.2% elongation that can restrain the volume change of BP and electrode during operation. In addition, molecular dynamic (MD) simulation and density function theory (DFT) show the greatly enhanced Li+ diffusion in BP@NC composite where the Li ions receive less repulsive force at the interface of BP interlayer and nanocellulose. Benefiting from above multifunction of nanocellulose, the BP@NC composite exhibits high capacities of 1020.1 mAh g-1 at 0.1 A g-1 after 230 cycles and 994.4 mAh g-1 at 0.2 A g-1 after 400 cycles, corresponding to high capacity retentions of 87.1% and 84.9%, respectively. Our results provide a low-cost and effective strategy to develop advanced electrodes for next-generation rechargeable batteries.

Study on xLiVPO4F·yLi3V2(PO4)3/C Composite for High-Performance Cathode Material for Lithium-Ion Batteries.

Cathode materials made of xLiVPO4F·yLi3V2(PO4)3/C (x:y = 1:0, 2:1, 0:1) are synthesized via a feasible sol-gel method for high-performance lithium-ion batteries. The structures, morphology, and electrochemical properties of the composites are thoroughly investigated. The results show that LiVPO4F/C, Li3V2(PO4)3/C, and 2LiVPO4F·Li3V2(PO4)3/C can be synthesized under 750°C without the formation of impurities. Meanwhile, the unique morphology of the 2LiVPO4F·Li3V2(PO4)3/C composite, which is porous, with nanoflakes adhering to the surface, is revealed. This composite integrates the advantages of LiVPO4F and Li3V2(PO4)3. There are four discharge plateaus near 4.2, 4.1, 3.7, and 3.6 V, and the cathode material delivers high capacities of 143.4, 141.6, 133.2, 124.1, and 117.6 mAh g-1 at rates of 0.1, 0.2, 0.5, 1, and 2 C, respectively. More importantly, the discharge capacity can be almost fully recovered when the discharge rate returns to 0.1 C. The study is highly promising for the development of cathode material for LIBs.

Spherical Li4Ti5O12/NiO Composite With Enhanced Capacity and Rate Performance as Anode Material for Lithium-Ion Batteries.

Compositing with metal oxides is proved to be an efficient strategy to improve electrochemical performance of anode material Li4Ti5O12 for lithium-ion batteries. Herein, spherical Li4Ti5O12/NiO composite powders have been successfully prepared via a spray drying method. X-ray diffraction and high-resolution transmission electron microscopy results demonstrate that crystal structure of the powders is spinel. Scanning electron microscopy results show that NiO uniformly distributes throughout Li4Ti5O12 matrix. It is found that compositing with NiO increases both discharge platform capacity and rate stability of Li4Ti5O12. The as-prepared Li4Ti5O12/NiO (5%) exhibits a high initial discharge capacity of 381.3 mAh g-1 at 0.1 C, and a discharge capacity of 194.7 mAh g-1 at an ultrahigh rate of 20 C.

Spray-Drying Synthesis of LiFeBO3/C Hollow Spheres With Improved Electrochemical and Storage Performances for Li-Ion Batteries.

LiFeBO3/C cathode material with hollow sphere architecture is successfully synthesized by a spray-drying method. SEM and TEM results demonstrate that the micro-sized LiFeBO3/C hollow spheres consist of LiFeBO3@C particles and the average size of LiFeBO3@C particles is around 50-100 nm. The thickness of the amorphous carbon layer which is coated on the surface of LiFeBO3 nanoparticles is about 2.5 nm. LiFeBO3@C particles are connected by carbon layers and formed conductive network in the LiFeBO3/C hollow spheres, leading to improved electrical conductivity. Meanwhile, the hollow structure boosts the Li+ diffusion and the carbon layers of LiFeBO3@C particles protect LiFeBO3 from moisture corrosion. Consequently, synthesized LiFeBO3/C sample exhibits good electrochemical properties and storage performance.

PPy-encapsulated SnS2 Nanosheets Stabilized by Defects on a TiO2 Support as a Durable Anode Material for Lithium-Ion Batteries.

Nanostructured-alloy-type anodes have received great interest for high-performance lithium-ion batteries (LIBs). However, these anodes experience huge volume fluctuations during repeated lithiation/delithiation and are easily pulverized and subsequently form aggregates. Herein, an efficient method to stabilize alloy-type anodes by creating defects on the surface of the metal oxide support is proposed. As a demonstration, PPy-encapsulated SnS2 nanosheets supported on defect-rich TiO2 nanotubes were produced and investigated as an anode material for LIBs. Both experimental results and theoretical calculations demonstrate that defect-rich TiO2 provides more chemical adhesions to SnS2 and discharge products, compared to defect-poor TiO2 , and then effectively stabilizes the electrode structure. As a result, the composite exhibits an unprecedented cycle stability. This work paves the way to designing durable and active nanostructured-alloy-type anodes on oxide supports.

Controllable Synthesis of Na3V2(PO4)3/C Nanofibers as Cathode Material for Sodium-Ion Batteries by Electrostatic Spinning.

Na3V2(PO4)3/C nanofibers are prepared by a pre-reduction assisted electrospinning method. In order to maintain the perfect fibrous architecture of the Na3V2(PO4)3/C samples after calcining, a series of heat treatment parameters are studied in detail. It is found that the heat treatment process shows important influence on the morphology and electrochemical performance of Na3V2(PO4)3/C composite nanofibers. Under the calcining conditions of 800°C for 10 h with a heating rate of 2.5°C min-1, the well-crystallized uniform Na3V2(PO4)3/C nanofibers with excellent electrochemical performances are successfully obtained. The initial discharge specific capacities of the nanofibers at 0.05, 1, and 10C are 114.0, 106.0, and 77.9 mAh g-1, respectively. The capacity retention still remains 97.0% after 100 cycles at 0.05C. This smooth, uniform, and continuous Na3V2(PO4)3/C composite nanofibers prepared by simple electrospinning method, is expected to be a superior cathode material for sodium-ion batteries.

Longitudinal Study of the Effects of Environmental pH on the Mechanical Properties of Aspergillus niger.

The regulation of environmental pH is key to the health of an ecosystem, influencing the metabolic activity, growth, and development of organisms within it. Although pH values can be measured by a wide range of readily available technologies ranging from fluorescent dyes and nanosensors, these cannot reveal the history of environmental pH from before monitoring begins. This information is sometimes crucial for piecing together what has happened to an ecosystem, and our long-term goal is therefore to develop technologies capable of obtaining it. Here, we propose monitoring environmental pH over time by tracking mechanical properties of a common fungus. As a first step toward obtaining a time history of pH, we evaluate the effect of pH upon the effective indentation modulus of spores and hyphae of Aspergillus niger. We report that the indentation modulus of this phosphorus-solubilizing fungus, obtained through atomic force microscopy and nanoindentation, correlated with environmental acidity. We observed a significant, monotonic increase in moduli over the course of incubation in an acidic environment, but no change in moduli over time for incubation in a neutral environment. Results show promise for using our scheme to detect and track environmental pH over time, and more broadly for using a microorganism's mechanical properties as a biomarker for environmental detection.

Electrocatalytic activity of anodic biofilm responses to pH changes in microbial fuel cells.

This study investigates the effects of anodic pH on electricity generation in microbial fuel cells (MFCs) and the intrinsic reasons behind them. In a two-chamber MFC, the maximum power density is 1170 ± 58 mW m(-2) at pH 9.0, which is 29% and 89% higher than those working at pH 7.0 and 5.0, respectively. Electrochemical measurements reveal that pH affects the electron transfer kinetics of anodic biofilms. The apparent electron transfer rate constant (k(app)) and exchange current density (i(0)) are greater whereas the charge transfer resistance (R(ct)) is smaller at pH 9.0 than at other conditions. Scanning electron microscopy verifies that alkaline conditions benefit biofilm formation in MFCs. These results demonstrate that electrochemical interactions between bacteria and electrodes in MFCs are greatly enhanced under alkaline conditions, which can be one of the important reasons for the improved MFC output.