Cadmium (Cd), a highly toxic heavy metal, adversely affects human and animal health. Quercetin (Que) is a kind of flavonoid that can protect many tissues from the toxic effect of heavy metals. ...Although many studies have explored the adverse effects of cadmium on rats and other animals, the mechanism of Cd-induced testicular autophagy and the antagonistic effect of Que on cadmium remain unclear. In this study, Sprague–Dawley rats were treated with Cd, Que or Cd, and Que supplements to explore the mechanisms of Que-alleviated testis injury caused by Cd exposure. The rat body weight and relative testicular weight were measured. Morphological changes in testes and indices of oxidative stress were also examined. The expression levels of autophagy-related genes were detected as well. Results showed that Cd decreased the rat body weight and relative testicular weight and induced pathological changes in testes. Conversely, Que alleviated these changes. We also found that Cd increased the malondialdehyde content and decreased the contents of total superoxide dismutase, glutathione peroxidase, catalase, and glutathione. Moreover, the protein expression levels of P62 and LC3-II increased under Cd exposure conditions. Conversely, Que obviously alleviated these toxic activities induced by Cd. Overall, this study showed that Cd accumulated in rat testes, leading to oxidative stress and autophagy. Que can reduce cadmium toxicity by reducing oxidative stress and inhibiting autophagy. The specific mechanism of Que antagonizing Cd toxicity can provide new insights into countering cadmium toxicity.
The mechanisms and effects of three typical chelating agents, namely glucose, citric acid and sucrose on the sol-gel synthesis process, electrochemical degradation and structural evolution of ...0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 (LLMO) materials are systematically compared for the first time. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analysis indicate that the sample synthesized from sucrose owns well structure, homogenous distribution, low Ni3+ concentration and good surface structural stability during cycling, respectively. Electrochemical tests further prove that the LLMO material obtained from sucrose maintains 258.4mAhg−1 with 94.8% capacity retention after 100 cycles at 0.2C. The superior electrochemical performance can be ascribed to the exceptional complexing mechanism of sucrose, compared to those of the glucose and citric acid. Namely, one mole sucrose can be hydrolyzed into two different monosaccharides and further chelates three M (Li, Ni, Co and Mn) ions to form a more uniform ion-chelated matrix during sol-gel process. This discovery is an important step towards understanding the selection criterion of chelating agents for sol-gel method, that chelating agent with excellent complexing capability is beneficial to the distribution, structural stability and electrochemical properties of advanced lithium-rich layered materials.
The garnet Li
La
Zr
O
(LLZO) has been widely investigated because of its high conductivity, wide electrochemical window, and chemical stability with regards to lithium metal. However, the usual ...preparation process of LLZO requires high-temperature sintering for a long time and a lot of mother powder to compensate for lithium evaporation. In this study submicron Li
La
Zr
Nb
O
(LLZNO) powder-which has a stable cubic phase and high sintering activity-was prepared using the conventional solid-state reaction and the attrition milling process, and Li stoichiometric LLZNO ceramics were obtained by sintering this powder-which is difficult to control under high sintering temperatures and when sintered for a long time-at a relatively low temperature or for a short amount of time. The particle-size distribution, phase structure, microstructure, distribution of elements, total ionic conductivity, relative density, and activation energy of the submicron LLZNO powder and the LLZNO ceramics were tested and analyzed using laser diffraction particle-size analyzer (LD), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Electrochemical Impedance Spectroscopy (EIS), and the Archimedean method. The total ionic conductivity of samples sintered at 1200 °C for 30 min was 5.09 × 10
S·cm
, the activation energy was 0.311 eV, and the relative density was 87.3%. When the samples were sintered at 1150 °C for 60 min the total ionic conductivity was 3.49 × 10
S·cm
, the activation energy was 0.316 eV, and the relative density was 90.4%. At the same time, quasi-solid-state batteries were assembled with LiMn
O
as the positive electrode and submicron LLZNO powder as the solid-state electrolyte. After 50 cycles, the discharge specific capacity was 105.5 mAh/g and the columbic efficiency was above 95%.
Lithium-rich layered oxides, xLi2MnO3·(1−x)LiMO2(M = Ni, Mn, Co), have been under intense investigation as high-performance cathode materials for lithium ion batteries due to their high discharge ...capacity, low cost and environmental benignity. Unfortunately, the commercialized application of these cathode materials have so far been hindered by their severe capacity and voltage fading during high voltage cycling (>4.5 V vs. Li/Li+). In an attempt to overcome these problems, herein, highly crystalline Al2O3 layer from the hydrolysis of aluminum isopropoxide are coated on 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 with controlling the growth of Al2O3 crystals. The coin cell with bare cathode material delivers a high discharge capacity over 268.2 mAh g−1 between 2.0 V and 4.8 V, while the Al2O3 coated cathode material shows the excellent cycling stability corresponding to 98% capacity retention after 100 cycles at 1C. More importantly, the highly crystalline Al2O3 coated cathode materials exhibit a significantly lower discharge voltage decay compared to the bare cathode materials, which could be ascribed to the suppression of the layered-to-spinel transformation by compact and highly crystalline Al2O3 layer. The results here will shed light on developing cathode materials with special structures and superior electrochemical properties for high-performance lithium ion batteries.
Illustration of highly crystalline Al2O3 coating layer and coating process of alumina coated lithium-rich layered oxide cathode material. Display omitted
•The 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 has been synthesized via sol–gel method.•Highly crystalline Al2O3 crystals coating layer is covered on the surface of 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 particles.•The bare cathode material delivers a high discharge capacity of 268.2 mAh g−1 at 0.1C between 2.0 V and 4.8 V.•The highly crystalline Al2O3 coated material has 98% capacity retention after 100 cycles at 1C.
The irreversible phase transition of LiNi
0.5
Co
0.2
Mn
0.3
O
2
(NCM523) cathode materials easily occurs in high voltage (> 4.5 V) charging processes, which aggravates the corrosion of electrolyte on ...the materials and seriously affects the safety and cycling performance of lithium-ion batteries. In this paper, K and Cl ions were dual-doped into NCM523 by a high-temperature solid state method, and then Al
2
O
3
was coated on the surface of the NCM523 by a hydrothermal method to obtain the modified cathode materials. The crystal structure, morphology and surface state of the modified materials were analyzed, and the electrochemical performance was tested under high cut-off voltage (4.6 V). The results show that when the content of K and Cl dual-doping and Al
2
O
3
coating are 1 mol.% and 2 wt.%, respectively, the comprehensive properties of the materials are excellent. The first discharge capacity of 0.1 C is 210 mAh g
−1
, and the irreversible capacity loss is reduced. Compared with pristine materials, the specific discharge capacity at 5 C was increased by 26 mAh g
−1
, and the capacity retention rate was improved by 16% after 100 cycles at 1 C. The dual-doping of K and Cl ions can inhibit the mixing of cations, enhance the bond strength between transition metal cations and O
2−
, and improve the structural stability and the Li
+
transport rate. The Al
2
O
3
coating separates the cathode materials from the electrolyte and inhibits the corrosion of the electrolyte to the cathode materials. Therefore, the electrochemical properties of the modified cathode materials are significantly improved.
Lithium iron phosphate (LiFePO sub(4)) is a potentially high efficiency cathode material for lithium ion batteries, but the low electronic conductivity and one-dimensional diffusion channel for ...lithium ions require small particle size and shape control during the synthesis. In this paper, well-crystallized and morphology-controlled LiFePO sub(4) cathode material for lithium-ion batteries is successfully synthesized via a soluble starch-assisted hydrothermal method at 180 degreesC for 5 h, followed by calcining with phenolic resin at 750 degreesC for 6 h. In this study, we investigate the effect of five different concentrations of starch solution on controlling morphology of LiFePO sub(4). Interestingly, the nano-sized LiFePO sub(4) particles obtained in 0.075 mol L super(-1) starch solution exhibit a spheroidal microstructure, while the platelet shape LiFePO sub(4) particles are synthesized in lower or higher concentration of starch solution. The mechanism and process of forming such spheroidal microstructure is discussed. These unique structural and morphological properties of LiFePO sub(4) lead to high specific capacity and stable cycling performance. Analysis of the electrochemical impedance spectroscopy reveals that nano-sized carbon/polyacene coated LiFePO sub(4) cathode materials play an critical role in achieving excellent electrochemical performance.
To address increasingly prominent energy problems, lithium-ion batteries have been widely developed. The high-nickel type nickel–cobalt–manganese (NCM) ternary cathode material has attracted ...attention because of its high energy density, but it has problems such as cation mixing. To address these issues, it is necessary to start from the surface and interface of the cathode material, explore the mechanism underlying the material's structural change and the occurrence of side reactions, and propose corresponding optimization schemes. This article reviews the defects caused by cation mixing and energy bands in high-nickel NCM ternary cathode materials. This review discusses the reasons why the core-shell structure has become an optimized high-nickel ternary cathode material in recent years and the research progress of core-shell materials. The synthesis method of high-nickel NCM ternary cathode material is summarized. A good theoretical basis for future experimental exploration is provided.
Lithium-rich layered oxide is one of the most promising candidates for the next-generation cathode materials of high-energy-density lithium ion batteries because of its high discharge capacity. ...However, it has the disadvantages of uneven composition, voltage decay, and poor rate capacity, which are closely related to the preparation method. Here, 0.5Li
MnO
·0.5LiMn
Ni
Co
O
was successfully prepared by sol-gel and oxalate co-precipitation methods. A systematic analysis of the materials shows that the 0.5Li
MnO
·0.5LiMn
Ni
Co
O
prepared by the oxalic acid co-precipitation method had the most stable layered structure and the best electrochemical performance. The initial discharge specific capacity was 261.6 mAh·g
at 0.05 C, and the discharge specific capacity was 138 mAh·g
at 5 C. The voltage decay was only 210 mV, and the capacity retention was 94.2% after 100 cycles at 1 C. The suppression of voltage decay can be attributed to the high nickel content and uniform element distribution. In addition, tightly packed porous spheres help to reduce lithium ion diffusion energy and improve the stability of the layered structure, thereby improving cycle stability and rate capacity. This conclusion provides a reference for designing high-energy-density lithium-ion batteries.
Carbon-coated and doped mesoporous silicon/carbon (m-Si/C) composites were successfully prepared via carbon coating and molten magnesiothermic reduction by using mesoporous silica (SBA-15) and ...dopamine as raw materials. Experimental results were theoretically verified by first-principles calculation. The obtained m-Si/C composites exhibited a high initial Coulombic efficiency of 73% at 0.1 A g
−1
and an excellent cycling stability with 617.5 mAh g
−1
capacity after 100 cycles at 0.1 A g
−1
. This excellent performance was attributed to the combination of carbon and the mesoporous structure of SBA-15 to form a mesoporous carbon framework which could improve the stability and conductivity of the material. The oxygen defects that formed after molten magnesiothermic reduction could effectively alleviate the change in the volume of the Si core and shorten the diffusion path of Li
+
in the Si core. Graphene layers could effectively reduce the energy of the system and the band gap, the embedding of Li
+
would lead to the expansion and distortion of Si, and the carbon layer with elasticity and hardness could buffer the volume expansion of m-Si/C composites. Consistent with experimental results, theoretical results demonstrated that graphene-coated composites positively affected the Li storage of Si.
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