Structural insights into composition design of Li-rich layered cathode materials for high-energy rechargeable battery

The Li-rich layered oxide is considered as one of the most promising cathode materials for high energy density batteries, due to its ultrahigh capacity derived from oxygen redox. Although incorporating over-stoichiometric Li into layered structure can generate Li₂MnO₃-like domain and enhance the oxygen redox activity thermodynamically, the fast and complete activation of the Li₂MnO₃-like domain remains challenging. Herein, we performed a systematic study on structural characteristics of Li-rich cathode materials to decipher the factors accounting for activation of oxygen redox. We reveal that the activation of Li-rich cathode materials is susceptible to local Co coordination environments. The Co ions can intrude into Li₂MnO₃-like domain and modulate the electronic structure, thereby facilitating the activation of Li-rich layered cathode materials upon first charging, leading to higher reversible capacity. In contrast, Li₂MnO₃-like domain hardly contains any Ni ions which contribute little to the activation process. The optimum composition design of this class of materials is discussed and we demonstrate a small amount of Co/Mn exchange in Li₂MnO₃-like domain can significantly promote the oxygen redox activation. Our findings highlight the vital role of Co ions in the activation of oxygen redox Li-rich layered cathode materials and provide new insights into the pathway toward achieving high-capacity Li-rich layered cathode materials.     

Identifying the Activation Mechanism and Boosting Electrocatalytic Activity of Layered Perovskite Ruthenate

SrRuO₃ as a rare conductive perovskite ruthenate has attracted increasing attention for application in energy conversion. Here, the electrocatalytic activity for the hydrogen evolution reaction (HER) of thermally synthesized layered SrRuO₃ is investigated and shows a considerable activation during cathodic polarization in alkaline solution. The analysis demonstrates the electrode activation is caused by the increased hydrophilicity of SrRuO₃ surface, revealing the influence of the surface properties on HER performance. For further improving the catalytic activity of perovskite ruthenate, the RuO₂/SrRuO₃ (RSRO) heterostructure is fabricated in situ by reducing the thermal decomposition temperature of 1000 °C for SrRuO₃ to 600 °C. The appropriate lattice parameter of SrRuO₃ ensures a good lattice match, which results in a strong interaction between SrRuO₃ and RuO₂. Hence, the RSRO substantially outperforms the corresponding single‐component oxides. In addition, the increased active sites induced by the rapid improvement of hydrophilicity of RSRO surface further highlight its structural advantage for catalytic hydrogen generation. The experimental and theoretical computation results consistently validate the positive synergistic effect among SrRuO₃ and RuO₂ in tuning the atomic and electronic configuration.     

Mechanistic Differences in Cell Death Responses to Metal‐Based Engineered Nanomaterials in Kupffer Cells and Hepatocytes

The mononuclear phagocyte system in the liver is a frequent target for nanoparticles (NPs). A toxicological profiling of metal‐based NPs is performed in Kupffer cell (KC) and hepatocyte cell lines. Sixteen NPs are provided by the Nanomaterial Health Implications Research Consortium of the National Institute of Environmental Health Sciences to study the toxicological effects in KUP5 (KC) and Hepa 1–6 cells. Five NPs (Ag, CuO, ZnO, SiO₂, and V₂O₅) exhibit cytotoxicity in both cell types, while SiO₂ and V₂O₅ induce IL‐1β production in KC. Ag, CuO, and ZnO induced caspase 3 generated apoptosis in both cell types is accompanied by ion shedding and generation of mitochondrial reactive oxygen species (ROS) in both cell types. However, the cell death response to SiO₂ in KC differs by inducing pyroptosis as a result of potassium efflux, caspase 1 activation, NLRP3 inflammasome assembly, IL‐1β release, and cleavage of gasdermin‐D. This releases pore‐performing peptide fragments responsible for pyroptotic cell swelling. Interestingly, although V₂O₅ induces IL‐1β release and delays caspase 1 activation by vanadium ion interference in membrane Na⁺/K⁺ adenosine triphosphate (ATP)ase activity, the major cell death mechanism in KC (and Hepa 1–6) is caspase 3 mediated apoptosis. These findings improve the understanding of the mechanisms of metal‐based engineered nanomaterial (ENM) toxicity in liver cells toward comprehensive safety evaluation.     

In Situ Two‐Step Activation Strategy Boosting Hierarchical Porous Carbon Cathode for an Aqueous Zn‐Based Hybrid Energy Storage Device with High Capacity and Ultra‐Long Cycling Life

Aqueous Zn‐based hybrid energy storage devices (HESDs) exhibit great potential for large‐scale energy storage applications for the merits of environmental friendliness, low redox potential, and high theoretical capacity of Zn anode. However, they are still subjected to low specific capacities since adsorption‐type cathodes (i.e., activated carbon, hard carbon) have limited capability to accommodate active ions. Herein, a hierarchical porous activated carbon cathode (HPAC) is prepared via an in situ two‐step activation strategy, different from the typical one‐step/postmortem activation of fully carbonized precursors. The strategy endows the HPAC with a high specific surface area and a large mesoporous volume, and thus provides abundant active sites and fast kinetics for accommodating active ions. Consequently, pairing the HPAC with Zn anode yields an aqueous Zn‐based HESD, which delivers a high specific capacity of 231 mAh g^?1 at 0.5 A g^?1 and excellent rate performance with a retained capacity of 119 mAh g^?1 at 20 A g^?1, the best result among previously reported lithium‐free HESDs based on carbon cathodes. Further, the aqueous Zn‐based HESD shows ultra‐long cycling stability with a capacity retention of ≈70% after 18 000 cycles at 10 A g^?1, indicating great potential for environmentally friendly, low‐cost, and high‐safety energy storage applications.     

改性棉秆吸附Cr(Ⅵ)工艺研究

以棉花秸秆为原料,在超声波作用下用二硫化碳进行化学改性,制得改性棉秆吸附剂。通过正交试验确定了各因素影响次序和最佳工艺水平组合。结果表明:在pH=1.61、吸附时间为138.47min、吸附剂用量为0.27g、温度为51.61℃条件下,最高吸附效率为99.99%,其中pH在影响改性棉秆吸附过程中表现最为敏感,温度其次;准二级动力学方程拟合效果最好,吸附过程为放热自发反应。利用扫描电子显微镜对改性前后棉秆进行分析,证明改性方法有利于吸附的进行。     

Reaction kinetics of fly ash geopolymerization: Role of particle size controlled by using ball mill

Fly ash is milled for 0, 30 and 90?min and used to study the role of particle size on the kinetics of geopolymer formation. The increase in particle fineness is very prominent in the initial milling stage, and then slows down due to agglomeration effect of finer fraction. The fly ash geopolymerization kinetics and its mechanism is determined using heat of reaction data measured by isothermal conduction calorimeter. The improvement in reaction rate with milling is correlated with the median particle size of the fly ash. The apparent activation energy decreases with size reduction because finer fractions are more prone to alkali activation. Although the kinetics changes with particle fineness, but no alternation is detected in the reaction mechanism, governed by nucleation and growth. The apparent activation energy evaluated by rate method is showing three major steps of geopolymerization such as dissolution, gel formation and restructuring.     

Effect of Co on the microstructure evolution of modified HR3C austenitic heat-resistant steels during long-term ageing

The modified HR3C austenitic heat-resistant steels were aged at 650°C and 700°C for up to 3000 h. The effect of Co on microstructure evolution during long-term ageing was investigated using scanning electron microscope and transmission electron microscope. The experimental results showed that a large amount of σ phase precipitated within the grain during long-term ageing. The growth and coarsening of the σ phase were greatly influenced by the temperature. The variation of micro-hardness can be well understood in terms of volume fraction of the σ phase. The activation energy of forming σ phase was calculated by the Johnson–Mehl–Avrami equation and Arrhenius equation. It was found that Co addition can suppress the precipitation of the σ phase. The related mechanism of Co effect is discussed.     

同步热分析法研究超级铝热剂Al/MnO2的热安定性

为研究超级铝热剂Al/MnO_2的热安定性,利用水热法制备纳米级MnO_2,采用透射电子显微镜(TEM)对纳米Al粉的氧化层厚度进行表征,计算出Al粉中纯Al的质量分数,从而确定更优配比.采用超声共混法制备得到超级铝热剂Al/MnO_2,利用X射线衍射技术(XRD)和场发射扫描电子显微镜(FE-SEM)对超级铝热剂Al/MnO_2的晶型和形貌进行表征,采用热重-差示扫描同步热分析技术(TG-DSC)在不同升温速率条件下研究了超级铝热剂Al/MnO_2的非等温热行为,通过微分Kissinger法和积分Ozawa法计算样品的活化能,对活化能计算结果进行对比.结果表明:水热法制备得到的纳米级MnO_2呈短棒状,晶型为α型,球状Al粉氧化层厚度约5 nm,纯Al质量分数约64.5%,超级铝热剂Al/MnO_2铝热反应的温度区间为540～570℃,放热量约930 J/g;利用Kissinger法和Ozawa法拟合相关性较高,计算得到的活化能分别为429.1和421.9 kJ/mol.两种方法计算得到的活化能结果相近且数值较高,表明超级铝热剂Al/MnO_2具有较好的热安定性,安全性能良好.     

Poly(Sarcosine) Surface Modification Imparts Stealth‐Like Properties to Liposomes

Circulation lifetime is a crucial parameter for a successful therapy with nanoparticles. Reduction and alteration of opsonization profiles by surface modification of nanoparticles is the main strategy to achieve this objective. In clinical settings, PEGylation is the most relevant strategy to enhance blood circulation, yet it has drawbacks, including hypersensitivity reactions in some patients treated with PEGylated nanoparticles, which fuel the search for alternative strategies. In this work, lipopolysarcosine derivatives (BA‐pSar, bisalkyl polysarcosine) with precise chain lengths and low polydispersity indices are synthesized, characterized, and incorporated into the bilayer of preformed liposomes via a post insertion technique. Successful incorporation of BA‐pSar can be realized in a clinically relevant liposomal formulation. Furthermore, BA‐pSar provides excellent surface charge shielding potential for charged liposomes and renders their surface neutral. Pharmacokinetic investigations in a zebrafish model show enhanced circulation properties and reduction in macrophage recognition, matching the behavior of PEGylated liposomes. Moreover, complement activation, which is a key factor in hypersensitivity reactions caused by PEGylated liposomes, can be reduced by modifying the surface of liposomes with an acetylated BA‐pSar derivative. Hence, this study presents an alternative surface modification strategy with similar benefits as the established PEGylation of nanoparticles, but with the potential of reducing its drawbacks.