Occurrence and seasonal variations of antibiotic micro-pollutants in the Wei River, China.

In this study, a systematic monitoring campaign of 30 antibiotics belonging to tetracyclines (TCs), macrolides (MLs), fluoroquinolones (FQs) and sulfonamides (SAs) was performed in the Xi'an section of the Wei River during three sampling events (December 2021, June 2022, and September 2022). The total concentrations of antibiotics in water ranged from 297 to 461 ng/L with high detection frequencies ranging from 45% to 100% for the various antibiotics. A marked seasonal variation in concentrations was found with total antibiotic concentrations in winter being 1.5 and 2 times higher than those in the summer and autumn seasons, respectively. The main contaminants in both winter and summer seasons were FQs, but in the autumn SAs were more abundant, suggesting different seasonal sources or more effective runoff for certain antibiotics during periods of rainfall. Combined analysis using redundancy and clustering analysis indicated that the distribution of antibiotics in the Wei River was affected by the confluence with dilution of tributaries and outlet of domestic sewage. Ecological risk assessment based on risk quotient (RQ) showed that most antibiotics in water samples posed insignificant risk to fish and green algae, as well as insignificant to low risk to Daphnia. The water-sediment distribution coefficients of SAs were higher than those of other antibiotics, indicating that particle-bound runoff could be a significant source for this class of antibiotics.

Hygroscopic Solutes Enable Non-van der Waals Electrolytes for Fire-Tolerant Dual-Air Batteries.

Thermal safety issues of batteries have hindered their large-scale applications. Nonflammable electrolytes improved safety but solvent evaporation above 100 °C limited thermal tolerance, lacking reliability. Herein, fire-tolerant metal-air batteries were realized by introducing solute-in-air electrolytes whose hygroscopic solutes could spontaneously reabsorb the evaporated water solvent. Using Zn/CaCl2 -in-air/carbon batteries as a proof-of-concept, they failed upon burning at 631.8 °C but self-recovered then by reabsorbing water from the air at room temperature. Different from conventional aqueous electrolytes whose irreversible thermal transformation is determined by the boiling points of solvents, solute-in-air electrolytes make this transformation determined by the much higher decomposition temperature of solutes. It was found that stronger intramolecular bonds instead of intermolecular (van der Waals) interactions were strongly correlated to ultra-high tolerance temperatures of our solute-in-air electrolytes, inspiring a concept of non-van der Waals electrolytes. Our study would improve the understanding of the thermal properties of electrolytes, guide the design of solute-in-air electrolytes, and enhance battery safety.

Photodegradation of hydroxyfluorenes in ice and water: A comparison of kinetics, effects of water constituents, and phototransformation by-products.

The photochemical behavior of organic pollutants in ice is poorly studied in comparison to aqueous photochemistry. Here we report a detailed comparison of ice and aqueous photodegradation of two representative OH-PAHs, 2-hydroxyfluorene (2-OHFL) and 9-hydroxyfluorene (9-OHFL), which are newly recognized contaminants in the wider environment including colder regions. Interestingly, their photodegradation kinetics were clearly influenced by whether they reside in ice or water. Under the same simulated solar irradiation (λ > 290 nm), OHFLs photodegraded faster in ice than in equivalent aqueous solutions and this was attributed to the specific concentration effect caused by freezing. Furthermore, the presence of dissolved constituents in ice also influenced photodegradation with 2-OHFL phototransforming the fastest in 'seawater' ice (k = (11.4 ± 1.0) × 10-2 min-1) followed by 'pure-water' ice ((8.7 ± 0.4) × 10-2 min-1) and 'freshwater' ice ((8.0 ± 0.7) × 10-2 min-1). The presence of dissolved constituents (specifically Cl-, NO3-, Fe(III) and humic acid) influences the phototransformation kinetics, either enhancing or suppressing phototransformation, but this is based on the quantity of the constituent present in the matrixes, the specific OHFL isomer and the matrix type (e.g., ice or aqueous solution). Careful derivation of key photointermediates was undertaken in both ice and water samples using tandem mass spectrometry. Ice phototransformation exhibited fewer by-products and 'simpler' pathways giving rise to a range of hydroxylated fluorenes and hydroxylated fluorenones in ice. These results are of importance when considering the fate of PAHs and OH-PAHs in cold regions and their persistence in sunlit ice.

Approaching the Lithiation Limit of MoS2 While Maintaining Its Layered Crystalline Structure to Improve Lithium Storage.

MoS2 holds great promise as high-rate electrode for lithium-ion batteries since its large interlayer can allow fast lithium diffusion in 3.0-1.0 V. However, the low theoretical capacity (167 mAh g-1 ) limits its wide application. Here, by fine tuning the lithiation depth of MoS2 , we demonstrate that its parent layered structure can be preserved with expanded interlayers while cycling in 3.0-0.6 V. The deeper lithiation and maintained crystalline structure endows commercially micrometer-sized MoS2 with a capacity of 232 mAh g-1 at 0.05 A g-1 and circa 92 % capacity retention after 1000 cycles at 1.0 A g-1 . Moreover, the enlarged interlayers enable MoS2 to release a capacity of 165 mAh g-1 at 5.0 A g-1 , which is double the capacity obtained under 3.0-1.0 V at the same rate. Our strategy of controlling the lithiation depth of MoS2 to avoid fracture ushers in new possibilities to enhance the lithium storage of layered transition-metal dichalcogenides.

Comparing the photodegradation of typical antibiotics in ice and in water: Degradation kinetics, mechanisms, and effects of dissolved substances.

New antibiotic contaminants have been detected in both surface waters and natural ice across cold regions. However, few studies have revealed distinctions between their ice and aqueous photochemistry. In this study, the photodegradation and effects of the main dissolved substances on the photolytic kinetics were investigated for sulfonamides (SAs) and fluoroquinolones (FQs) in ice/water under simulated sunlight. The results showed that the photolysis of sulfamethizole (SMT), sulfachloropyridazine (SCP), enrofloxacin (ENR) and difloxacin (DIF) in ice/water followed the pseudo-first-order kinetics with their quantum yields ranging from 4.93 × 10-3 to 11.15 × 10-2. The individual antibiotics experienced disparate photodegradation rates in ice and in water. This divergence was attributed to the concentration-enhancing effect and the solvent cage effect that occurred in the freezing process. Moreover, the main constituents (Cl-, HASS, NO3- and Fe(III)) exhibited varying degrees of promotion or inhibition on the photodegradation of SAs and FQs in the two phases (p < 0.05), and these effects were dependent on the individual antibiotics and the matrix. Extrapolation of the laboratory data to the field conditions provided a reasonable estimate of environmental photolytic half-lives (t1/2,E) during midsummer and midwinter in cold regions. The estimated t1/2,E values ranged from 0.02 h for ENR to 14 h for SCP, which depended on the reaction phases, latitudes and seasons. These results revealed the similarities and differences between the ice and aqueous photochemistry of antibiotics, which is important for the accurate assessment of the fate and risk of these new pollutants in cold environments.

Boosting Solid-State Reconversion Reactivity to Mitigate Lithium Trapping for High Initial Coulombic Efficiency.

An initial Coulombic efficiency (ICE) higher than 90% is crucial for industrial lithium-ion batteries, but numerous electrode materials are not standards compliant. Lithium trapping, due to i) incomplete solid-state reaction of Li+ generation and ii) sluggish Li+ diffusion, undermines ICE in high-capacity electrodes (e.g., conversion-type electrodes). Current approaches mitigating lithium trapping emphasize ii) nanoscaling (<50 nm) to minimize Li+ diffusion distance, followed by severe solid electrolyte interphase formation and inferior volumetric energy density. Herein, this work accentuates i) instead, to demonstrate that the lithium trapping can be mitigated by boosting the solid-state reaction reactivity. As a proof-of-concept, ternary LiFeO2 anodes, whose discharged products contain highly reactive vacancy-rich Fe nanoparticles, can alleviate lithium trapping and enable a remarkable average ICE of ≈92.77%, much higher than binary Fe2 O3 anodes (≈75.19%). Synchrotron-based techniques and theoretical simulations reveal that the solid-state reconversion reaction for Li+ generation between Fe and Li2 O can be effectively promoted by the Fe-vacancy-rich local chemical environment. The superior ICE is further demonstrated by assembled pouch cells. This work proposes a novel paradigm of regulating intrinsic solid-state chemistry to ameliorate electrochemical performance and facilitate industrial applications of various advanced electrode materials.

Deshielding Anions Enable Solvation Chemistry Control of LiPF6-Based Electrolyte toward Low-Temperature Lithium-Ion Batteries.

Severe capacity decay under subzero temperatures remains a significant challenge for lithium-ion batteries (LIBs) due to the sluggish interfacial kinetics. Current efforts to mitigate this deteriorating interfacial behavior rely on high-solubility lithium salts (e.g., Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium bis(fluorosulfonyl)imide (LiFSI))-based electrolytes to construct anion participated solvation structures. However, such electrolytes bring issues of corrosion on the current collector and increased costs. Herein, the most commonly used Lithium hexafluorophosphate (LiPF6) instead, to establish a peculiar solvation structure with a high ratio of ion pairs and aggregates by introducing a deshielding NO3 - additive for low-temperature LIBs is utilized. The deshielding anion significantly reduces the energy barrier for interfacial behavior at low temperatures. Benefiting from this, the graphite (Gr) anode retains a high capacity of ≈72.3% at -20 °C, which is far superior to the 32.3% and 19.4% capacity retention of counterpart electrolytes. Moreover, the LiCoO2/Gr full cell exhibits a stable cycling performance of 100 cycles at -20 °C due to the inhibited lithium plating. This work heralds a new paradigm in LiPF6-based electrolyte design for LIBs operating at subzero temperatures.

Trophic transfer of polycyclic aromatic hydrocarbons through the food web of the Fildes Peninsula, Antarctica.

The Antarctic ecosystem is characterized by few consumer species and simple trophic levels (TLs), rendering it an ideal setting to investigate the environmental behavior of contaminants. The paper aims to assess the presence, sources and biomagnification behavior of polycyclic aromatic hydrocarbons (PAHs) of the Antarctic food web and is the first study of biomagnifications of PAHs in the Fildes Peninsula in Antarctica. Nine representative species from the Fildes Peninsula in Antarctica were sampled and evaluated for PAH presence. PAH concentrations ranged from 477.41 to 1237.54 ng/g lipid weight (lw) in the sampled Antarctic biota, with low molecular weight PAHs (naphthalene, acenaphthylene, acenaphthene, and fluorene) comprising the majority of the PAHs. PAHs concentrations were negatively correlated with TLs. Further, the food web magnification factor (FWMF) of ∑PAHs was 0.63, suggesting biodilution of PAHs along the TLs. Source analyses revealed that the PAHs mainly originated from petroleum contamination and the combustion of fossil fuels.

Relative activity of 15 bacterial strains against the larvae of Helicoverpa armigera, Spodoptera exigua, and Spodoptera litura (Lepidoptera: Noctuidae).

Crystal toxins produced by different strains of entomopathogenic Bacillus thuringiensis (Bt) have been characterized and widely applied as commercial biological pesticides owing to their excellent insecticidal properties. This study aimed to identify novel bacterial strains effective in controlling Spodoptera exigua Hübner, Helicoverpa armigera Hübner, and Spodoptera litura Fabricius. Fifteen culturable bacterial strains were isolated from 60 dead larvae (H. armigera and S. exigua) collected in the field. The biochemical characteristics and 16S rRNA sequences of these strains indicated that one strain (B7) was Lysinibacillus sp., 12 strains (B1, B3, B4, B5, B6, B8, P2, P3, P4, P5, P6, and DW) were Bt kurstaki, and P2-2 and B2 were Bacillus velezensis subsp. Laboratory bioassays indicated that strains B3, P6, B6, and P4 showed high toxicity to second-instar larvae of S. exigua, with LC50 values of 5.11, 6.74, 205.82, and 595.93 µg/ml, respectively; while the strains P5, B5, B6, and P6, were the most efficient against second-instar larvae of H. armigera with LC50 values of 725.82, 11,022.72, 1,282.90, 2,005.28, respectively, and strains DW, P3, P2, and B4 had high insecticidal activity against second-instar larvae of S. litura with LC50 values of 576.69, 1,660.96, 6,309.42, and 5,486.10 µg/ml, respectively. In conclusion, several Bt kurstaki strains with good toxicity potential were isolated and identified in this study. These strains are expected to be useful for biointensive integrated pest management programs to reduce the use of synthetic insecticides.

Apoptosis or Antiapoptosis? Interrupted Regulated Cell Death of Host Cells by Ascovirus Infection In Vitro.

Ascoviruses are insect-specific viruses thought to utilize the cellular apoptotic processes of host larvae to produce numerous virion-containing vesicles. In this study, we first determined the biochemical characteristics of ascovirus-infected, in vitro-cultured insect cells and the possible antiapoptotic capacity of ascovirus-infected insect cells. The results indicated that the ascovirus infection in the first 24 h was different from the infection from 48 h to the later infection stages. In the early infection stage, the Spodoptera exigua host cells had high membrane permeability and cleaved gasdermin D (GSDMD) but uncleaved Casp-6 (SeCasp-6). In contrast, the later infection stage had no such increased membrane permeability and had cleaved SeCasp-6. Four different chemicals were used to induce apoptosis at different stages of ascovirus infection: hydrogen peroxide (H2O2) and actinomycin D (ActD) had similar effects on the ascovirus-infected cells, whereas cMYC inhibitors and tumor necrosis factor alpha (TNF-α) plus SM-164 apoptosis inducers (T/S) had similar effects on infected cells. The former two inducers inhibited viral DNA replication in most situations, while the latter two inducers inhibited viral DNA replication in the early stage of infection but promoted viral DNA replication in the later infection stage. Furthermore, immunoblotting assays verified that T/S treatment could increase the expression levels of viral major capsid protein (MCP) and the host inhibitor of apoptosis protein (SeIAP). Coimmunoprecipitation assays revealed interaction between SeIAP and SeCasps, but this interaction was disturbed in ascovirus-infected cells. This study details the in vitro infection process of ascovirus, indicating the utilization of pyroptosis for antiapoptosis cytopathology. IMPORTANCE Clarifying the relationship between different types of viral infections and host regulation of cell death (RCD) can provide insights into the interaction between viruses and host cells. Ascoviruses are insect-specific viruses with apoptosis-utilizing-like infection cytopathology. However, RCD does not only include apoptosis, and while in our previous transmission electron microscopic observations, ascovirus-infected cells did not show typical apoptotic characteristics (unpublished data), in this study, they did show increased membrane permeability. These results indicate that the cytopathology of ascovirus infection is a complex process in which the virus manipulates host RCD. The RCD of insect cells is quite different from that of mammals, and studies on the former are many fewer than those on the latter, especially in the case of RCD in lepidopteran insects. Our results will lay a foundation for understanding the RCD of lepidopteran insects and its function in the process of insect virus infection.

[Critical Review on Environmental Occurrence and Photochemical Behavior of Substituted Polycyclic Aromatic Hydrocarbons].

Substituted polycyclic aromatic hydrocarbons (SPAHs) are a type of emerging pollutant that widely exist in the environment, which also exhibit carcinogenicity, mutagenicity, and teratogenicity. These pollutants belong to toxic pollutants because of their similar structures to polycyclic aromatic hydrocarbons (PAHs). Their environmental behavior and ecological risk have attracted increasing attention. Based on a literature review, we found a new breakthrough in the source, distribution, behavior, and risk of SPAHs with comparison to traditional pollutants PAHs. This paper reviewed the current research progress on the environmental occurrence and photochemical behavior of SPAHs. Their sources, formation mechanisms, and distribution characteristics in the multimedia environment were highlighted, and the photochemical transformation kinetics, pathways, and affecting factors of SPAHs in water, ice, and other media were discussed. Furthermore, the research prospects about the environmental behavior and risk of SPAHs were proposed.

Feeding Spodoptera exigua larvae with gut-derived Escherichia sp. increases larval juvenile hormone levels inhibiting cannibalism.

Feed quality influences insect cannibalistic behavior and gut microbial communities. In the present study, Spodoptera exigua larvae were fed six different artificial diets, and one of these diets (Diet 3) delayed larval cannibalistic behavior and reduced the cannibalism ratio after ingestion. Diet 3-fed larvae had the highest gut bacterial load (1.396 ± 0.556 × 1014 bacteria/mg gut), whereas Diet 2-fed larvae had the lowest gut bacterial load (3.076 ± 1.368 × 1012 bacteria/mg gut). The gut bacterial composition and diversity of different diet-fed S. exigua larvae varied according to the 16S rRNA gene sequence analysis. Enterobacteriaceae was specific to the Diet 3-fed larval gut. Fifteen culturable bacterial isolates were obtained from the midgut of Diet 3-fed larvae. Of these, ten belonged to Escherichia sp. After administration with Diet 1- or 2-fed S. exigua larvae, two bacterial isolates (SePC-12 and -37) delayed cannibalistic behavior in both tested larval groups. Diet 2-fed larvae had the lowest Juvenile hormone (JH) concentration and were more aggressive against intraspecific predation. However, SePC-12 loading increased the JH hormone levels in Diet 2-fed larvae and inhibited their cannibalism. Bacteria in the larval midgut are involved in the stabilization of JH levels, thereby regulating host larval cannibalistic behavior.

A Figure of Merit for Fast-Charging Li-ion Battery Materials.

Rate capability is characterized necessarily in almost all battery-related reports, while there is no universal metric for quantitative comparison. Here, we proposed the characteristic time of diffusion, which mainly combines the effects of diffusion coefficients and geometric sizes, as an easy-to-use figure of merit (FOM) to standardize the comparison of fast-charging battery materials. It offers an indicator to rank the rate capabilities of different battery materials and suggests two general methods to improve the rate capability: decreasing the geometric sizes or increasing the diffusion coefficients. Based on this FOM, more comprehensive FOMs for quantifying the rate capabilities of battery materials are expected by incorporating other processes (interfacial reaction, migration) into the current diffusion-dominated electrochemical model. Combined with Peukert's empirical law, it may characterize rate capabilities of batteries in the future.

Occurrence, spatial distributions, and ecological risk of pyrethroids in coastal regions of South Yellow and East China Seas.

Pyrethroids are increasingly receiving attention as aqueous micropollutants, but their presence has been reported only in a few small coastal areas. In this study, we investigated the distribution, sources, and risks of nine pyrethroids in large marine zones. The 40 seawater samples were collected from the South Yellow Sea (SYS) and East China Sea (ECS) in China, during the spring of 2020, using a high-volume, solid-phase extraction method. The total pyrethroid concentrations ranged from 0.72 to 1.82 ng L-1 in the SYS and from 0.02 to 11.0 ng L-1 in the ECS. We used cluster analysis to classify pollutant sources into five categories, and discussed the influence of sources on the transport and distribution of pyrethroids in each group. Ecological risk assessment indicated that pyrethroids pose a high risk to crustaceans and a negligible risk to others. These results are important for understanding the behavior of pyrethroids in marine environments.

Three-Dimensional, Submicron Porous Electrode with a Density Gradient to Enhance Charge Carrier Transport.

Rapid charging capability is a requisite feature of lithium-ion batteries (LIBs). To overcome the capacity degradation from a steep Li-ion concentration gradient during the fast reaction, electrodes with tailored transport kinetics have been explored by managing the geometries. However, the traditional electrode fabrication process has great challenges in precisely controlling and implementing the desired pore networks and configuration of electrode materials. Herein, we demonstrate a density-graded composite electrode that arises from a three-dimensional current collector in which the porosity gradually decreases to 53.8% along the depth direction. The density-graded electrode effectively reduces energy loss at high charging rates by mitigating polarization. This electrode shows an outstanding capacity of 94.2 mAh g-1 at a fast current density of 59.7 C (20 A g-1), which is much higher than that of an electrode with a nearly constant density gradient (38.0 mAh g-1). Through these in-depth studies on the pore networks and their transport kinetics, we describe the design principle of rational electrode geometries for ultrafast charging LIBs.

Enabling the High-Voltage Operation of Layered Ternary Oxide Cathodes via Thermally Tailored Interphase.

Layered ternary oxides LiNix Mny Coz O2 are promising cathode candidates for high-energy lithium-ion batteries (LIBs), but they usually suffer from the severe interfacial parasitic reactions at voltages above 4.3 V versus Li+ /Li, which greatly limit their practical capacities. Herein, using LiNi1/3 Mn1/3 Co1/3 O2 (NMC111) as the model system, a novel high-temperature pre-cycling strategy is proposed to realize its stable cycling in 3.0-4.5 V by constructing a robust cathode/electrolyte interphase (CEI). Specifically, performing the first five cycles of NMC111 at 55 °C helps to yield a uniform CEI layer enriched with fluorine-containing species, Li2 CO3 and poly(CO3 ), which greatly suppresses the detrimental side reactions during extended cycling at 25 °C, endowing the cell with a capacity retention of 92.3% at 1C after 300 cycles, far surpassing 62.0% for the control sample without the thermally tailored CEI. This work highlights the critical role of temperature on manipulating the interfacial properties of cathode materials, opening a new avenue for developing high-voltage cathodes for Li-ion batteries.

Hygroscopic Chemistry Enables Fire-Tolerant Supercapacitors with a Self-Healable "Solute-in-Air" Electrolyte.

High-temperature-induced fire is an extremely serious safety risk in energy storage devices; which can be avoided by replacing their components with nonflammable materials. However; these devices are still destroyed by the high-temperature decomposition; lacking reliability. Here, a fire-tolerant supercapacitor is further demonstrated that recovers after burning with a self-healable "solute-in-air" electrolyte. Using fire-tolerant electrodes and separator with a semiopen device configuration; hygroscopic CaCl2 in the air ("CaCl2 -in-air") is designed as a self-healable electrolyte; which loses its water solvent at high temperatures but spontaneously absorbs water from the air to recover by itself at low temperatures. The supercapacitor is disenabled at 500 °C; while it recovers after cooling in the air. Especially; it even recovers after burning at around 647 °C with enhanced performance. The study offers a self-healing strategy to design high-safety; high-reliability; and fire-tolerant supercapacitors; which inspires a promising way to deal with general fire-related risks.

Strain-Driven Auto-Detachable Patterning of Flexible Electrodes.

Flexible electrodes that are multilayer, multimaterial, and conformal are pivotal for multifunctional wearable electronics. Traditional electronic circuits manufacturing requires substrate-supported transfer printing, which limits their multilayer integrity and device conformability on arbitrary surfaces. Herein, a "shrinkage-assisted patterning by evaporation" (SHAPE) method is reported, by employing evaporation-induced interfacial strain mismatch, to fabricate auto-detachable, freestanding, and patternable electrodes. The SHAPE method utilizes vacuum-filtration of polyaniline/bacterial cellulose (PANI/BC) ink through a masked filtration membrane to print high-resolution, patterned, and multilayer electrodes. The strong interlayer hydrogen bonding ensures robust multilayer integrity, while the controllable evaporative shrinking property of PANI/BC induces mismatch between the strains of the electrode and filtration membrane at the interface and thus autodetachment of electrodes. Notably, a 500-layer substrateless micro-supercapacitor fabricated using the SHAPE method exhibits an energy density of 350 mWh cm-2 at a power density of 40 mW cm-2 , 100 times higher than reported substrate-confined counterparts. Moreover, a digital circuit fabricated using the SHAPE method functions stably on a deformed glove, highlighting the broad wearable applications of the SHAPE method.

Mechano-Graded Electrodes Mitigate the Mismatch between Mechanical Reliability and Energy Density for Foldable Lithium-Ion Batteries.

Flexible lithium-ion batteries (LIBs) with high energy density are highly desirable for wearable electronics. However, difficult to achieve excellent flexibility and high energy density simultaneously via the current approaches for designing flexible LIBs. To mitigate the mismatch, mechano-graded electrodes with gradient-distributed maximum allowable strain are proposed to endow high-loading-mass slurry-coating electrodes with brilliant intrinsic flexibility without sacrificing energy density. As a proof-of-concept, the up-graded LiNi1/3 Mn1/3 Co1/3 O2 cathodes (≈15 mg cm-2 , ≈70 µm) and graphite anodes (≈8 mg cm-2 , ≈105 µm) can tolerate an extremely low bending radius of 400 and 600 µm, respectively. Finite element analysis (FEA) reveals that, compared with conventionally homogeneous electrodes, the flexibility of the up-graded electrodes is enhanced by specifically strengthening the upper layer and avoiding crack initiation. Benefiting from this, the foldable pouch cell (required bending radius of ≈600 µm) successfully realizes a remarkable figure of merit (FOM, energy density vs bending radius) of 121.3 mWh cm-3 . Moreover, the up-graded-electrodes-based pouch cells can deliver a stable power supply, even under various deformation modes, such as twisting, folding, and knotting. This work proposes new insights for harmonizing the mechanics and electrochemistry of energy storage devices to achieve high energy density under flexible extremes.

Dielectric Polarization in Inverse Spinel-Structured Mg2 TiO4 Coating to Suppress Oxygen Evolution of Li-Rich Cathode Materials.

High-energy Li-rich layered cathode materials (≈900 Wh kg-1 ) suffer from severe capacity and voltage decay during cycling, which is associated with layered-to-spinel phase transition and oxygen redox reaction. Current efforts mainly focus on surface modification to suppress this unwanted structural transformation. However, the true challenge probably originates from the continuous oxygen release upon charging. Here, the usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li-rich material is reported, using Mg2 TiO4 as a proof-of-concept material. The creation of a reverse electric field in surface layers effectively restrains the outward migration of bulk oxygen anions. Meanwhile, high oxygen-affinity elements of Mg and Ti well stabilize the surface oxygen of Li-rich material via enhancing the energy barrier for oxygen release reaction, verified by density functional theory simulation. Benefited from these, the modified Li-rich electrode exhibits an impressive cyclability with a high capacity retention of ≈81% even after 700 cycles at 2 C (≈0.5 A g-1 ), far superior to ≈44% of the unmodified counterpart. In addition, Mg2 TiO4 coating greatly mitigates the voltage decay of Li-rich material with the degradation rate reduced by ≈65%. This work proposes new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high-energy-density rechargeable batteries.