Understanding the influence of crystal packing density on electrochemical energy storage materials

Crystal structure determines electrochemical energy storage characteristics; this is the underlying logic of material design. To date, hundreds of electrode materials have been developed to pursue superior performance. However, it remains a great challenge to understand the fundamental structure–performance relationship and achieve quantitative crystal structure design for efficient energy storage. In this review, we introduce the concept of crystal packing factor (PF), which can quantify crystal packing density. We then present and classify the typical crystal structures of attractive cathode/anode materials. Comparative PF analyses of different materials, including polymorphs, isomorphs, and others, are performed to clarify the influence of crystal packing density on energy storage performance through electronic and ionic conductivities. Notably, the practical electronic/ionic conductivities of energy storage materials are based on their intrinsic characteristics related to the PF yet are also affected by extrinsic factors. The PF provides a novel avenue for understanding the electrochemical performance of pristine materials and may offer guidance on designing better materials. Additional approaches involve size regulation, doping, carbon additives, and other methods. We also propose extended PF concepts to understand charge storage and transport behavior at different scales. Finally, we provide our insights on the major challenges and prospective solutions in this highly exciting field

Characterization of circSEC11A as a novel regulator of Iodine-125 radioactive seed-induced anticancer effects in hepatocellular carcinoma via targeting ZHX2/GADD34 axis

Abstract Iodine-125 (I-125) radioactive seed implantation is used for the local treatment of hepatocellular carcinoma (HCC), but the molecular mechanisms regulating its anticancer effects remain incompletely understood. In this study, we report that hsa_circ_0000647 (circSEC11A) is highly expressed after I-125 treatment in HCC cell lines and tissues and is a key regulator of I-125-induced anticancer effects. CircSEC11A acts as a competing endogenous RNA (ceRNA) to sponge miR-3529-3p, promoting the expression of zinc fingers and homeoboxes 2 (ZHX2) and enhancing I-125-induced anticancer effects. Dual-luciferase reporter assay, RNA pull-down, RNA immunoprecipitation, and fluorescence in situ hybridization were thereafter performed to verify the interaction among the molecules. Anticancer effects were detected using CCK-8, flow cytometry, TUNEL, EdU, transwell, and wound healing assays. Furthermore, ZHX2 transcriptionally inhibits GADD34, a negative regulator of endoplasmic reticulum stress (ERS), to enhance I-125- induced anticancer effects in vivo and in vitro. In conclusion, we characterized circSEC11A as a novel regulator of I-125-induced anticancer effects in HCC via miR-3529-3p/ZHX2/GADD34 axis-mediated ERS. Thus, circSEC11A may act as a potential therapeutic target for I-125 implantation in the clinic

Tunable Synthesis of Colorful Nitrogen-Doped Titanium Oxide and Its Application in Energy Storage

The one-pot synthesis of titania with diverse degrees of oxygen vacancies and nitrogen dopants through arc-discharge and nitridation process is first reported. The series of TiO_2–<i>x</i>:N samples are prepared by tuning the ratio of CO₂/H₂ in the chamber. The chemical composition, microstructure, and valence state of TiO_2–<i>x</i>:N are characterized by a variety of measurements. Specifically, the as-prepared samples achieve the highest specific capacitance (210 F g^–1 at 2 mV s^–1), which is much higher than that of TiO_2–<i>x</i> and commercial P25. Moreover, it exhibits good cycling stability with 9% attenuation of capacitance after 10,000 cycles. The capacitive enhancement can be attributed to more active pseudocapacitive properties and improved electrical conductivity due to oxygen vacancies and nitrogen dopants. This work provides another feasible path to simplify the tunable synthesis of titania with different oxygen defects, and further optimize the degree of nitrogen dopants in order to realize better performance in the future

Electrodes with Electrodeposited Water-excluding Polymer Coating Enable High-Voltage Aqueous Supercapacitors

Aqueous supercapacitors are powerful energy sources, but they are limited by energy density that is much lower than lithium-ion batteries. Since raising the voltage beyond the thermodynamic potential for water splitting (1.23 V) can boost the energy density, there has been much effort on water-stabilizing salvation additives such as Li2SO4 that can provide an aqueous electrolyte capable of withstanding ~1.8 V. Guided by the first-principles calculations that reveal water can promote hydrogen and oxygen evolution reactions, here, we pursue a new strategy of covering the electrode with a dense electroplated polymerized polyacrylic acid, which is an electron insulator but a proton conductor and proton reservoir. The combined effect of salvation and coating expands the electrochemical window throughout pH 3 to pH 10 to 2.4 V for both fast and slow proton-mediated redox reactions. This allows activated carbon to quadruple the energy density, a kilogram of nitrogen-doped graphene to provide 127 Watt-hour, and both to have improved endurance because of suppression of water-mediated corrosion. Therefore, aqueous supercapacitors can now achieve energy densities quite comparable to that of a lithium-ion battery, but at 100 times the charging/discharging speed and cycle durability

Controlled Phase Evolution from Co Nanochains to CoO Nanocubes and Their Application as OER Catalysts

One-dimensional materials favoring efficient charge transfer have attracted enormous attentions. Here cobalt nanochains are prepared by a direct-current (DC) arc-discharge method under the gaseous mixture of He and H₂. The Co nanochains can range up to several micrometers. When H₂ is replaced by CO₂, the sample shows a phase evolution from Co nanochains to CoO nanocubes. The ratio of CoO/Co can be effortlessly altered by varying the partial pressure of CO₂ in the reaction gas mixture. CoO nanocubes are attained in the pure CO₂. The prepared samples are explored as catalyst for oxygen evolution reaction (OER). The catalytic activity is highly dependent on the phase proportion of Co and CoO. The sample prepared under CO₂:He = 1:7 unveils the optimal OER performance with an onset point of 1.50 V versus reversible hydrogen electrode (RHE) and an overpotential of 350 mV at 10 mA cm^–2. The high OER performance can be attributed to synergistic effect and charge transfer process between Co and CoO. Co can inject electrons into CoO, which manipulates the work function of CoO to make it more suitable for oxygen evolution. The good OER performance can also be ascribed to the defective structure of CoO. The CoO/Co composite shows good robustness with less than 8% current loss throughout the long-term test