Towards extreme fast charging of 4.6 V LiCoO_(2) via mitigating high-voltage kinetic hindrance

High-voltage LiCoO_(2)(LCO) is an attractive cathode for ultra-high energy density lithium-ion batteries(LIBs) in the 3 C markets.However,the sluggish lithium-ion diffusion at high voltage significantly hampers its rate capability.Herein,combining experiments with density functional theory(DFT) calculations,we demonstrate that the kinetic limitations can be mitigated by a facial Mg^(2+)+Gd^(3+)co-doping method.The as-prepared LCO shows significantly enhanced Li-ion diffusion mobility at high voltage,making more homogenous Li-ion de/intercalation at a high-rate charge/discharge process.The homogeneity enables the structural stability of LCO at a high-rate current density,inhibiting stress accumulation and irreversible phase transition.When used in combination with a Li metal anode,the doped LCO shows an extreme fast charging(XFC) capability,with a superior high capacity of 193.1 mAh g^(-1)even at the current density of 20 C and high-rate capacity retention of 91.3% after 100 cycles at 5 C.This work provides a new insight to prepare XFC high-voltage LCO cathode materials.

Recent progress on MOF-derived carbon materials for energy storage

Metal-organic frameworks(MOFs)are of quite a significance in the field of inorganic-organic hybrid crystals.Especially,MOFs have attracted increasing attention in recent years due to their large specific surface area,desirable electrical conductivity,controllable porosity,tunable geometric structure,and excellent thermal/chemical stability.Some recent studies have shown that carbon materials prepared by MOFs as precursors can retain the privileged structure of MOFs,such as large specific surface area and porous structure and,in contrast,realize in situ doping with heteroatoms(eg,N,S,P,and B).Moreover,by selecting appropriate MOF precursors,the composition and morphology of the carbon products can be easily adjusted.These remarkable structural advantages enable the great potential of MOF-derived carbon as high-performance energy materials,which to date have been applied in the fields of energy storage and conversion systems.In this review,we summarize the latest advances in MOF-derived carbon materials for energy storage applications.We first introduce the compositions,structures,and synthesis methods of MOF-derived carbon materials,and then discuss their applications and potentials in energy storage systems,including rechargeable lithium/sodium-ion batteries,lithium-sulfur batteries,supercapacitors,and so forth,in detail.Finally,we put forward our own perspectives on the future development of MOF-derived carbon materials.

Insights into Ti doping for stabilizing the Na_(2/3)Fe_(1/3)Mn_(2/3)O_(2)cathode in sodium ion battery

Iron-and manganese-based layered metal oxides,as cathodes for sodium ion batteries,have received widespread attention because of the low cost and high specific capacity.However,the Jahn-teller effect of Mn^(3+)ions and the resulted unstable structure usually lead to continuously capacity decay.Herein,Titanium(Ti)has been successfully doped into Na_(2/3)Fe_(2/3)Mn_(2/3)O_(2)to suppress the Jahn-Teller distortion and improve both cycling and rate performance of sodium ion batteries.In situ high-energy synchrotron X-ray diffraction study shows that Ti-doped compound(Na_(2/3)Fe_(1/3)Mn_(0.57)Ti_(0.1)O_(2))can maintain the single P2 phase without any phase transition during the whole charging/discharging process.Various electrochemical characterizations are also applied to explore the better kinetics of sodium ions transfer in the Na_(2/3)Fe_(1/3)Mn_(0.5)7 Ti_(0.1)O_(2).This work provides a comprehensive insight into the Ti-doping effects on the performance from both structural and electro kinetic perspectives.

疫情期大学生在线学习满意度混合研究——基于学生参与理论视角

受新冠肺炎疫情影响,全国高校均开启了在线教学模式,在线教育得到了井喷式的发展。基于学生参与理论的视角以四川某医科大学参加在线学习并自愿高质量完成问卷调查的6326名学生为研究对象,采用混合研究的方法对不同特征大学生在线学习满意度差异进行了实证剖析,研究发现除不同专业和性别的学习者总体满意度不存在显著差异,不同性别的学习者学习资源满意度、互动答疑满意度以及课程引导满意度不存在显著差异外,其余学习者特征研究维度在四个满意度维度均存在显著差异,最终提出及时总结经验,做好教学督导;提供优质资源,做好教学设计;适度高效互动,做好教学评测;激发学习内驱,做好教学引导等四条对策建议。

Severe burn injury alters intestinal microbiota composition and impairs intestinal barrier in mice

Background:The intestinal barrier integrity is crucial for maintaining intestinal homeostasis,and the mechanisms of intestinal barrier disruption induced by burn injury remain obscure.This study was aimed to investigate the changes of intestinal microbiota and barrier function in burned mice to further comprehend the mechanisms of burn-induced intestinal barrier dysfunction.Methods:Samples were from mice inflicted with 30%total body surface area(TBSA)full-thickness burns.The intestinal permeability,tight junction proteins expressions,zonula occludens-1(ZO-1)localization,inflammatory cytokines expressions,and short-chain fatty acids(SCFAs)contents were determined.The microbial community was assessed via 16S rDNA Illumina sequencing.Results:The intestinal permeability was increased after severe burn injury,peaking at 6 h post-burn,with approximately 20-folds of the control(p<0.001).The expression of tight junction proteins(ZO-1,occludin,claudin-1,and claudin-2)was significantly altered(p<0.05).The ZO-1 morphology was dramatically changed following burn injury.The fecal SCFAs’contents(acetate,propionate,butyrate,isobutyrate,and isovalerate)were noticeably declined after burn injury(p<0.05).The expressions of pro-inflammatory cytokines(interleukin(IL)-1βand IL-6)in ileal mucosa were increased,whereas the expressions of anti-inflammatory cytokines(IL-4 and IL-13)were decreased following burn injury(p<0.05).In addition,burned mice showed an alteration of intestinal microbial community,such as decreased diversity,reduced Bacteroidetes abundance,and increased Firmicutes abundance.Conclusions:The severe burn-induced intestinal barrier dysfunction is along with the alterations of microbial community.

Sub-cytotoxic concentrations of ionic silver promote the proliferation of human keratinocytes by inducing the production of reactive oxygen species

Silver-containing preparations are widely used in the management of skin wounds, but the effects of silver ions on skin wound healing remain poorly understood. This study investigated the effects of silver ions （Ag^＋） on the proliferation of human skin keratinocytes （HaCaT） and the production of intracellular reactive oxygen species （ROS）. After treating HaCaT cells with Ag^＋ and/or the active oxygen scavenger N-acetyl cysteine （NAC）, cell proliferation and intracellular ROS generation were assessed using CCK-8 reagent and DCFH-DA fluorescent probe, respectively. In addition, 5-bromo-2-deoxyUridine （BrdU） incorporation assays, cell cycle flow cytometry, and proliferating cell nuclear antigen （PCNA） immunocytochemistry were conducted to further evaluate the effects of sub-cytotoxic Ag^＋ concentrations on HaCaT cells. The proliferation of HaCaT cells was promoted in the presence of 10^-6 and 10^-5s mol/L Ag^＋at 24, 48, and 72 h. Intracellular ROS generation also significantly increased for 5 60 min after exposure to Ag^＋ The number of BrdU-positive cells and the presence of PCNA in HaCaT cells increased 48 h after the addition of 10^-6 and 10^-5 mol/L Ag^＋, with 10^-5 mol/L Ag^＋ markedly increasing the cell proliferation index. These effects of sub-cytotoxic Ag^＋ concentrations were repressed by 5 mmol/L NAC. Our results suggest that sub-cytotoxic Ag^＋ concentrations promote the proliferation of human keratinocytes and might be associated with a moderate increase in intracellular ROS levels. This study provides important experimental evidence for developing novel silver-based wound agents or dressings with few or no cytotoxicity.

A Case of New Variant COVID-19 First Emerging in South Africa Detected in a Security Guard at the Isolation Point—Shenzhen,China,January 23,2021

On January 22,2021,a 34-year-old male,who served as a security guard at the isolation point in Shenzhen,tested positive for coronavirus disease 2019(COVID-19)during the every-three-day routine test.After the nasopharyngeal swab was further confirmed as positive for COVID-19 by Shenzhen CDC,the patient was transferred to the Third People’s Hospital of Shenzhen and was diagnosed as a COVID-19 asymptomatic infection.On January 25,2021,Shenzhen CDC identified the 20H/501.Y.V2(B.1.351)variant,which was a variant of COVID-19 virus first emerging in the South Africa.