Mitigating Strain Accumulation in Li2RuO3 via Fluorine Doping.

Lithium ruthenium oxide (Li2RuO3) is an archetypal lithium rich cathode material (LRCM) with both cation and anion redox reactions (ARRs). Commonly, the instability of oxygen redox activities has been regarded as the root cause of its performance degradation in long-term operation. However, we find that not triggering ARRs does not improve and even worsens its cyclability due to the detrimental strain accumulation induced by Ru redox activities. To solve this problem, we demonstrate that F-doping in Li2RuO3 can alter its preferential orientation and buffer interlayer repulsion upon Ru redox, both of which can mitigate the strain accumulation along the c-axis and improve its structural stability. This work highlights the importance of optimizing cation redox reactions in LRCMs and provides a new perspective for their rational design.

Electric pulse-tuned piezotronic effect for interface engineering.

Investigating interface engineering by piezoelectric, flexoelectric and ferroelectric polarizations in semiconductor devices is important for their applications in electronics, optoelectronics, catalysis and many more. The interface engineering by polarizations strongly depends on the property of interface barrier. However, the fixed value and uncontrollability of interface barrier once it is constructed limit the performance and application scenarios of interface engineering by polarizations. Here, we report a strategy of tuning piezotronic effect (interface barrier and transport controlled by piezoelectric polarization) reversibly and accurately by electric pulse. Our results show that for Ag/HfO2/n-ZnO piezotronic tunneling junction, the interface barrier height can be reversibly tuned as high as 168.11 meV by electric pulse, and the strain (0-1.34‰) modulated current range by piezotronic effect can be switched from 0-18 nA to 44-72 nA. Moreover, piezotronic modification on interface barrier tuned by electric pulse can be up to 148.81 meV under a strain of 1.34‰, which can totally switch the piezotronic performance of the electronics. This study provides opportunities to achieve reversible control of piezotronics, and extend them to a wider range of scenarios and be better suitable for micro/nano-electromechanical systems.

Tartaric Acid Cross-Linking Polyvinyl Alcohol as Degradable Separators for Rechargeable Lithium Ion Batteries.

The escalating focus on environmental concerns and the swift advancement of eco-friendly biodegradable batteries raises a pressing demand for enhanced material design in the battery field. The traditional polypropylene (PP) that is monopolistically utilized in the commercial LIBs is hard to recycle. In this work, we prepare a novel water degradable separators via the cross-linking of polyvinyl alcohol (PVA) and dibasic acid (tartaric acid, TA). Through the integration of non-solvent liquid-phase separation, we successfully produced a thermally stable PVA-TA membrane with tunable thickness and a high level of porosity. These specially engineered PVA-TA separators were implemented in LiFePO4 (LFP)|separator|Li cells, resulting in superior multiplicative performance and achieving a capacity of 88 mAh g-1 under 5 C. Additionally, the straightforward small molecule cross-linking technique significantly reduced the crystalline region of the polymer, thereby enhancing ionic conductivity. Notably, after cycling, the PVA-TA separators can be easily dissolved in 95 °C hot water, enabling its reutilization for the production of new PVA-TA separators. Therefore, this work introduces a novel concept to design green and sustainable separators for recyclable lithium batteries.

Ternary Rotational Polyanion Coupling Enables Fast Li Ion Dynamics in Tetrafluoroborate Ion Doped Antiperovskite Li2OHCl Solid Electrolyte.

Li-rich antiperovskite (LiRAP) hydroxyhalides are emerging as attractive solid electrolyte (SEs) for all-solid-state Li metal batteries (ASSLMBs) due to their low melting point, low cost, and ease of scaling-up. The incorporation of rotational polyanions can reduce the activation energy and thus improve the Li ion conductivity of SEs. Herein, we propose a ternary rotational polyanion coupling strategy to fasten the Li ion conduction in tetrafluoroborate (BF4-) ion doped LiRAP Li2OHCl. Assisted by first-principles calculation, powder X-ray diffraction, solid-state magnetic resonance and electrochemical impedance spectra, it is confirmed that Li ion transport in BF4- ion doped Li2OHCl is strongly associated with the rotational coupling among OH-, BF4- and Li2-O-H octahedrons, which enhances the Li ion conductivity for more than 1.8 times with the activation energy lowering 0.03 eV. This work provides a new perspective to design high-performance superionic conductors with multi-polyanions.

Negative enthalpy alloys and local chemical ordering: a concept and route leading to synergy of strength and ductility.

Solid solutions are ubiquitous in metals and alloys. Local chemical ordering (LCO) is a fundamental sub-nano/nanoscale process that occurs in many solid solutions and can be used as a microstructure to optimize strength and ductility. However, the formation of LCO has not been fully elucidated, let alone how to provide efficient routes for designing LCO to achieve synergistic effects on both superb strength and ductility. Herein, we propose the formation and control of LCO in negative enthalpy alloys. With engineering negative enthalpy in solid solutions, genetic LCO components are formed in negative enthalpy refractory high-entropy alloys (RHEAs). In contrast to conventional 'trial-and-error' approaches, the control of LCO by using engineering negative enthalpy in RHEAs is instructive and results in superior strength (1160 MPa) and uniform ductility (24.5%) under tension at ambient temperature, which are among the best reported so far. LCO can promote dislocation cross-slip, enhancing the interaction between dislocations and their accumulation at large tensile strains; sustainable strain hardening can thereby be attained to ensure high ductility of the alloy. This work paves the way for new research fields on negative enthalpy solid solutions and alloys for the synergy of strength and ductility as well as new functions.

Negative mixing enthalpy solid solutions deliver high strength and ductility.

Body-centred cubic refractory multi-principal element alloys (MPEAs), with several refractory metal elements as constituents and featuring a yield strength greater than one gigapascal, are promising materials to meet the demands of aggressive structural applications1-6. Their low-to-no tensile ductility at room temperature, however, limits their processability and scaled-up application7-10. Here we present a HfNbTiVAl10 alloy that shows remarkable tensile ductility (roughly 20%) and ultrahigh yield strength (roughly 1,390 megapascals). Notably, these are among the best synergies compared with other related alloys. Such superb synergies derive from the addition of aluminium to the HfNbTiV alloy, resulting in a negative mixing enthalpy solid solution, which promotes strength and favours the formation of hierarchical chemical fluctuations (HCFs). The HCFs span many length scales, ranging from submicrometre to atomic scale, and create a high density of diffusive boundaries that act as effective barriers for dislocation motion. Consequently, versatile dislocation configurations are sequentially stimulated, enabling the alloy to accommodate plastic deformation while fostering substantial interactions that give rise to two unusual strain-hardening rate upturns. Thus, plastic instability is significantly delayed, which expands the plastic regime as ultralarge tensile ductility. This study provides valuable insights into achieving a synergistic combination of ultrahigh strength and large tensile ductility in MPEAs.

Ion Sieve Interface Assisted Zinc Anode with High Zinc Utilization and Ultralong Cycle Life for 61 Wh/kg Mild Aqueous Pouch Battery.

The cycling stability of a thin zinc anode under high zinc utilization has a critical impact on the overall energy density and practical lifetime of zinc ion batteries. In this study, an ion sieve protection layer (ZnSnF@Zn) was constructed in situ on the surface of a zinc anode by chemical replacement. The ion sieve facilitated the transport and desolvation of zinc ions at the anode/electrolyte interface, reduced the zinc deposition overpotential, and inhibited side reactions. Under a 50% zinc utilization, the symmetrical battery with this protection layer maintained stable cycling for 250 h at 30 mA cm-2. Matched with high-load self-supported vanadium-based cathodes (18-20 mg cm-2), the coin battery with 50% zinc utilization possessed an energy density retention of 94.3% after 1000 cycles at 20 mA cm-2. Furthermore, the assembled pouch battery delivered a whole energy density of 61.3 Wh kg-1, surpassing the highest mass energy density among reported mild zinc batteries, and retained 76.7% of the energy density and 85.3% (0.53 Ah) of the capacity after 300 cycles.

Microstructure-dependent CO2-responsive microemulsions for deep-cleaning of oil-contaminated soils.

CO2-responsive microemulsion (ME) is considered a promising candidate for deep-cleaning and oil recovery from oil-contaminated soils. Understanding the responsive nature of different microstructures (i.e., oil-in-water (O/W), bicontinuous (B.C.) and water-in-oil (W/O)) is essential for unlocking the potential and mechanisms of CO2-responsive emulsions in complex multiphase systems and providing comprehensive guidance for remediation of oil-contaminated soils. Herein, the responsiveness of microstructures of ME to CO2 trigger was investigated using experimental designs and coarse-grained molecular dynamic simulations. MEs were formed for the first time by a weakly associated pseudo-Gemini surfactant of indigenous organic acids (naphthenic acids, NAs are a class of natural surface-active molecules in crude oil) and tetraethylenepentamine (TEPA) through fine tuning of co-solvent of dodecyl benzene sulfonic acid (DBSA) and butanol. The O/W ME exhibited an optimal CO2-responsive character due to easier proton migration in the continuous aqueous phase and more pronounced dependence of configuration on deprotonated NA ions. Conversely, the ME with W/O microstructure exhibited a weak to none responsive characteristic, most likely attributed to its high viscosity and strong oil-NA interactions. The O/W ME also showed superior cleaning efficiency and oil recovery from oil-contaminated soils. The results from this study provide insights for the design of CO2-responsive MEs with desired performance and guidance for choosing the favorable operating conditions in various industrial applications, such as oily solid waste treatment, enhanced oil recovery (EOR), and pipeline transportation. The insights from this work allow more efficient and tailored design of switchable MEs for manufacturing advanced responsive materials in various industrial sectors and formulation of household products.

Phytic acid cross-linked and Hofmeister effect strengthened polyvinyl alcohol hydrogels for zinc ion storage.

It is a big challenge to retain the water and thus reduce the charge impedance for solid electrolytes used in flexible and wearable zinc ion batteries. Here, we propose novel phytic acid (PA) cross-linked polyvinyl alcohol (PVA) hydrogels as high-performanced solid electrolytes strengthened by the Hofmeister effect. In this approach, freeze-thawing followed by a salting-out procedure via anions to induce the Hofmeister effect can greatly improve the tensile strain and flexibility of the hydrogels. The PA addition dramatically enhances the ionic conductivity and increases the affinity between the electrolyte and zinc plate. Consequently, the PVA/PA hydrogels exhibit remarkable electrochemical performances with stable full-cell cycling in zinc ion storage and capability in inhibiting Zn dendrite growth.

Deciphering Electrolyte Dominated Na+ Storage Mechanisms in Hard Carbon Anodes for Sodium-Ion Batteries.

Although hard carbon (HC) demonstrates superior initial Coulombic efficiency, cycling durability, and rate capability in ether-based electrolytes compared to ester-based electrolytes for sodium-ion batteries (SIBs), the underlying mechanisms responsible for these disparities remain largely unexplored. Herein, ex situ electron paramagnetic resonance (EPR) spectra and in situ Raman spectroscopy are combined to investigate the Na storage mechanism of HC under different electrolytes. Through deconvolving the EPR signals of Na in HC, quasi-metallic-Na is successfully differentiated from adsorbed-Na. By monitoring the evolution of different Na species during the charging/discharging process, it is found that the initial adsorbed-Na in HC with ether-based electrolytes can be effectively transformed into intercalated-Na in the plateau region. However, this transformation is obstructed in ester-based electrolytes, leading to the predominant storage of Na in HC as adsorbed-Na and pore-filled-Na. Furthermore, the intercalated-Na in HC within the ether-based electrolytes contributes to the formation of a uniform, dense, and stable solid-electrolyte interphase (SEI) film and eventually enhances the electrochemical performance of HC. This work successfully deciphers the electrolyte-dominated Na+ storage mechanisms in HC and provides fundamental insights into the industrialization of HC in SIBs.

Modulation of Radical Intermediates in Rechargeable Organic Batteries.

Organic materials have been considered as promising electrodes for next-generation rechargeable batteries in view of their sustainability, structural flexibility, and potential recyclability. The radical intermediates generated during the redox process of organic electrodes have profound effect on the reversible capacity, operation voltage, rate performance, and cycling stability. However, the radicals are highly reactive and have very short lifetime during the redox of organic materials. Great efforts have been devoted to capturing and investigating the radical intermediates in organic electrodes. Herein, this review summarizes the importance, history, structures, and working principles of organic radicals in rechargeable batteries. More importantly, challenges and strategies to track and regulate the radicals in organic batteries are highlighted. Finally, further perspectives of organic radicals are proposed for the development of next-generation high-performance rechargeable organic batteries.

Decoding the Mechanisms of Reversibility Loss in Rechargeable Zinc-Air Batteries.

Attaining high reversibility of the electrodes and electrolyte is essential for the longevity of secondary batteries. Rechargeable zinc-air batteries (RZABs), however, encounter drastic irreversible changes in the zinc anodes and air cathodes during cycling. To uncover the mechanisms of reversibility loss in RZABs, we investigate the evolution of the zinc anode, alkaline electrolyte, and air electrode through experiments and first-principles calculations. Morphology diagrams of zinc anodes under versatile operating conditions reveal that the nanosized mossy zinc dominates the later cycling stage. Such anodic change is induced by the increased zincate concentration due to hydrogen evolution, which is catalyzed by the mossy structure and results in oxide passivation on electrodes and eventually leads to low true Coulombic efficiencies and short life spans of batteries. Inspired by these findings, we finally present a novel overcharge-cycling protocol to compensate for the Coulombic efficiency loss caused by hydrogen evolution and significantly extend the battery life.

Ultrafast Strategy to Fabricate Sulfur Cathodes for High-Performance Lithium-Sulfur Batteries.

Based on the different dielectric properties of materials and the selective heating property of microwaves, the ultrafast (30 s) preparation of S-NiS2@SP@Bitu as a cathode material for lithium-sulfur batteries was achieved using bitumen, sulfur, Super P, and nickel naphthenate as raw materials for the first time, under microwave treatment. NiS2@SP@Bitu forms Li-N, Li-O, Li-S, and Ni-S bonds with polysulfide, which contributes to promoting the adsorption of polysulfide, reducing the precipitation and decomposition energy barrier of Li2S, and accelerating the catalytic conversion of polysulfide, as result of inhibiting the "shuttle effect" and improving the electrochemical performance. S-NiS2@SP@Bitu as the sulfur cathode material demonstrates outstanding rate performance (518.6 mAh g-1 at 4C), and stable cycling performance. The lithium-sulfur battery with a sulfur loading of 4.8 mg cm-2 shows an areal capacity of 4.6 mAh cm-2. Based on the advantages of microwave selective and rapid heating, this method creatively realized that the sulfur carrier material was prepared and sulfur was fixed in it at the same time. Therefore, this method would have implications for the preparation of sulfur cathode materials.

Precisely manipulated π-π stacking of catalytic exfoliated iron polyphthalocyanine/reduced graphene oxide hybrid via pyrolysis-free path.

Metal macrocycles with well-defined molecular structures are ideal platforms for the in-depth study of electrochemical oxygen reduction reaction (ORR). Structural integrity of metal macrocycles is vital but remain challenging since the commonly used high-temperature pyrolysis would cause severe structure damage and unidentifiable active sites. Herein, we propose a pyrolysis-free strategy to precisely manipulate the exfoliated 2D iron polyphthalocyanine (FePPc) anchored on reduced graphene oxide (rGO) via π-π stacking using facile high-energy ball milling. A delocalized electron shift caused by π-π interaction is firstly found to be the mechanism of facilitating the remarkable ORR activity of this hybrid catalyst. The optimal FePPc@rGO-HE achieves superior half-wave potential (0.90 V) than 20 % Pt/C. This study offers a new insight in designing stable and high-performance metal macrocycle catalysts with well-defined active sites.

Green synthesis of mesoporous and biodegradable iron silicide nanoparticles for photothermal cancer therapy.

Photothermal nanomaterials have shown great potential for photothermal therapy. In this study, we developed a simple green method of magnesiothermic co-reduction for the synthesis of mesoporous, magnetic and biodegradable iron silicide nanoparticles (FeSi NPs) as applied to photothermal therapy (PTT). Starting from biogenic tabasheer extracted from bamboo and Fe2O3, the resultant FeSi NPs with a much lower band gap exhibited excellent optical absorption with a photothermal conversion efficiency of 76.2%, indicating a good photothermal performance. The weight extinction coefficient was measured to be 13.3 L g-1 cm-1 at 1064 nm (second near-infrared window, NIR-II), which surpassed the performance of other competitive Si-based and Fe-based photothermal agents. Results of the cell viability assay showed that cells could be killed by NIR-II laser irradiation with the synthesized FeSi NPs. In vivo results on mice showed clearly an efficient suppression of tumour growth by photothermal treatment with FeSi NPs. FeSi NPs were found to be biodegradable in simulated body fluids. The results from our work indicate that FeSi NPs are a new class of promising photothermal agents (PTAs) for application in cancer therapy.

Two-Step Redox in Polyimide: Witness by In Situ Electron Paramagnetic Resonance in Lithium-ion Batteries.

Organic materials are promising candidates for future rechargeable batteries, owing to their high natural abundance and rapidly redox reaction. Elaborating the charge/discharge process of organic electrode is critical to unveil the fundamental redox mechanism of lithium-ion batteries (LIBs), but monitoring of this process is still challenging. Here, we report a nondestructive electron paramagnetic resonance (EPR) technique to real-time detect the electron migration step within polyimide cathode. From in situ EPR tests, we vividly observe a classical redox reaction along with two-electron transfer which only shows one pair of peaks in the cyclic voltammetry curve. The radical anion and dianion intermediates are detailed delineation at redox sites in EPR spectra, which can be further confirmed through density functional theory calculations. This approach is especially crucial to elaborate the correlation behind electrochemical and molecular structure for multistep organic-based LIBs.

Realizing High-Performance Cathodes with Cationic and Anionic Redox Reactions in High-Sodium-Content P2-Type Oxides for Sodium-Ion Batteries.

P2-type layered transition-metal oxides with anionic redox reactions are promising cathodes for sodium-ion batteries. In this work, a high-sodium-content P2-type Na7/9Li1/9Mg1/9Cu1/9Mn2/3O2 (NLMC) cathode material is prepared by substituting Li/Mg/Cu for Mn sites in Na2/3MnO2. The Li/Mg ions trigger the anionic redox reaction, while the Cu ions enhance the structure stability during electrochemical cycling. As a result, the oxide has a high reversible capacity of 225 mAh g-1 originating from both cationic and anionic redox activities with a capacity retention of 77% after 100 cycles. The migration energy barrier and Na ion diffusion kinetics are studied using density functional theory (DFT) calculations and the galvanostatic intermittent titration technique. Furthermore, X-ray diffraction, DFT, scanning electron microscopy, and transmission electron microscopy are applied to reveal the structural evolution and charge compensation of NLMC, providing a thorough understanding of the structural and morphology evolution of Na-deficient oxides during cycling. The results are inspiring for the design of a high-Na content P2-type layered oxide cathode for sodium-ion batteries.

Manganese Local Environment Modulation via SiO4 Substitution to Boost Sodium Storage Performance of Na4 MnCr(PO4 )3.

Manganese-based Na superionic conductors (NASICONs) Na4 MnCr(PO4 )3 with three-electron reaction are attractive cathode materials for sodium-ion batteries. However, the irreversible distortion of Mn local structure leads to sluggish electrode kinetics, voltage hysteresis, and poor cycling stability. Here, SiO4 is introduced to substitute PO4 to modulate the local environment of Mn to activate the redox activity and stabilize the reversibility of Na4 MnCr(PO4 )2.9 (SiO4 )0.1 (NMCP-Si). A combined experimental and theoretical investigation have been undertaken to reveal the evolution of electronic structures and Na storage properties associated with SiO4 substitution. The NMCP-Si exhibits much-enhanced rate capability and cycling stability, being attributed to the unique Jahn-Teller distortion (Mn3+ ) that facilitates sodium de/insertion kinetics by optimizing the Na ion diffusion channels. This work addresses the challenge of stabilizing the structure of Mn-based NASICONs and represents a breakthrough in understanding how to improve the Na+ conductivity by regulating local structure.

Electronic Perturbation of Copper Single-Atom CO2 Reduction Catalysts in a Molecular Way.

Fine-tuning electronic structures of single-atom catalysts (SACs) plays a crucial role in harnessing their catalytic activities, yet challenges remain at a molecular scale in a controlled fashion. By tailoring the structure of graphdiyne (GDY) with electron-withdrawing/-donating groups, we show herein the electronic perturbation of Cu single-atom CO2 reduction catalysts in a molecular way. The elaborately introduced functional groups (-F, -H and -OMe) can regulate the valance state of Cuδ+ , which is found to be directly scaled with the selectivity of the electrochemical CO2 -to-CH4 conversion. An optimum CH4 Faradaic efficiency of 72.3 % was achieved over the Cu SAC on the F-substituted GDY. In situ spectroscopic studies and theoretical calculations revealed that the positive Cuδ+ centers adjusted by the electron-withdrawing group decrease the pKa of adsorbed H2 O, promoting the hydrogenation of intermediates toward the CH4 production. Our strategy paves the way for precise electronic perturbation of SACs toward efficient electrocatalysis.

Single-Atom Yttrium Engineering Janus Electrode for Rechargeable Na-S Batteries.

The development of rechargeable Na-S batteries is very promising, thanks to their considerably high energy density, abundance of elements, and low costs and yet faces the issues of sluggish redox kinetics of S species and the polysulfide shuttle effect as well as Na dendrite growth. Following the theory-guided prediction, the rare-earth metal yttrium (Y)-N4 unit has been screened as a favorable Janus site for the chemical affinity of polysulfides and their electrocatalytic conversion, as well as reversible uniform Na deposition. To this end, we adopt a metal-organic framework (MOF) to prepare a single-atom hybrid with Y single atoms being incorporated into the nitrogen-doped rhombododecahedron carbon host (Y SAs/NC), which features favorable Janus properties of sodiophilicity and sulfiphilicity and thus presents highly desired electrochemical performance when used as a host of the sodium anode and the sulfur cathode of a Na-S full cell. Impressively, the Na-S full cell is capable of delivering a high capacity of 822 mAh g-1 and shows superdurable cyclability (97.5% capacity retention over 1000 cycles at a high current density of 5 A g-1). The proof-of-concept three-dimensional (3D) printed batteries and the Na-S pouch cell validate the potential practical applications of such Na-S batteries, shedding light on the development of promising Na-S full cells for future application in energy storage or power batteries.