聚苯胺薄膜在电量可视化超级电容器中的应用——推荐一个综合化学实验

介绍一个研究探索型大学化学综合性实验——聚苯胺薄膜在电量可视化超级电容器中的应用。内容包括聚苯胺的电化学合成,电致变色性能测试,超级电容器器件制备,性能测试及电量可视化研究。通过本实验的实践,使学生在掌握实验理论和实验技能的基础上,进一步提高独立实验能力和创新意识。本实验的开展还可以使学生接触到科研的前沿领域,激发学生对科学研究的兴趣,培养学生的科研探究能力。

Enhancement of electrochemical performance in lithium-ion battery via tantalum oxide coated nickel-rich cathode materials

Nickel-rich cathode materials are increasingly being applied in commercial lithium-ion batteries to realize higher specific capacity as well as improved energy density.However,low structural stability and rapid capacity decay at high voltage and temperature hinder their rapid large-scale application.Herein,a wet chemical method followed by a post-annealing process is utilized to realize the surface coating of tantalum oxide on LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),and the electrochemical performance is improved.The modified Li Ni_(0.88)Mn_(0.03)Co_(0.09)O_(2)displays an initial discharge capacity of~233 m Ah/g at0.1 C and 174 m Ah/g at 1 C after 150 cycles in the voltage range of 3.0 V–4.4 V at 45℃,and it also exhibits an enhanced rate capability with 118 m Ah/g at 5 C.The excellent performance is due to the introduction of tantalum oxide as a stable and functional layer to protect the surface of LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),and the surface side reactions and cation mixing are suppressed at the same time without hampering the charge transfer kinetics.

Probing the improved stability for high nickel cathode via dual-element modification in lithium-ion

One of the major hurdles of nickel-rich cathode materials for lithium-ion batteries is the low cycling stability,especially at high temperature and high voltage,originating from severe structural degradation,which makes this class of cathode less practical.Herein,we compared the effect of single and dual ions on electrochemical performance of high nickel(LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),NMC)cathode material in different temperatures and voltage ranges.The addition of a few amounts of tantalum(0.2 wt%)and boron(0.05 wt%)lead to improved electrochemical performance.The co-modified Li Ni_(0.88)Mn_(0.03)Co_(0.09)O_(2)displays an initial discharge capacity of 234.9 m Ah/g at 0.1 C and retained 208 m Ah/g at 1 C after 100 cycles at 45℃,which corresponds to a capacity retention of 88.5%,compared to the initial discharge capacity of234.1 m Ah/g and retained capacity of 200.5 m Ah/g(85.6%).The enhanced capacity retention is attributed to the synergetic effect of foreign elements by acting as a surface structural stabilizer without sacrificing specific capacity.

锌负极和锂负极在不同温度下的电化学行为

本文研究表明锂金属负极的枝晶问题在较低温度下会加剧,在较高温度下会受到抑制;而对于水系可充电锌基电池中锌金属负极的枝晶演变,温度的影响则恰恰相反.对两种负极的电化学行为的研究结果表明,界面反应速率和离子扩散率的匹配程度以及副反应综合影响了金属负极的枝晶生长和循环寿命.研究发现有机电解质和水电解质在上述影响因素上的不同性质导致相反的温度影响.本文进一步对混合电解质(有机和水性)进行了详细研究,以调节离子扩散率和副反应,同时扩大水系可充锌基电池的工作温度窗口.本文揭示了有机锂金属负极和水系锌基电池完全相反的温度影响,并揭示了潜在的影响机制,有助于加深对金属负极的理解,从而促进水系锌基电池的大规模应用.

Dark matter direct search sensitivity of the PandaX-4T experiment

The Panda X-4T experiment, a 4-ton scale dark matter direct detection experiment, is being planned at the China Jinping Underground Laboratory. In this paper we present a simulation study of the expected background in this experiment. In a 2.8-ton fiducial mass and the signal region between 1-10 keV electron equivalent energy, the total electron recoil background is found to be 4.9 × 10^(-5) kg^(-1) d^(-1) keV^(-1). The nuclear recoil background in the same region is 2.8 × 10^(-7) kg^(-1) d^(-1) keV^(-1). With an exposure of 5.6 ton-years, the sensitivity of Panda X-4 T could reach a minimum spin-independent dark matter-nucleon cross section of 6 × 10^(-48) cm^2 at a dark matter mass of 40 Ge V/c^2.

An overview of amphoteric ion exchange membranes for vanadium redox flow batteries

Vanadium redox flow battery(VRB),as the most promising large-scale electrical energy storage units,has attracted extensive attention.Amphoteric ion exchange membrane(AIEM),as the core part of VRB,separates electrolyte on both sides of electrolytic tank and conducts H+.The AIEM with cation and anion groups possesses excellent performances,such as high ion conductivity(σ),low vanadium ion permeability(Pvn+),relative stability and low cost.However,the performance of AIEM directly depends on the chemical structure of polymers.In addition to ensuring foundational physical performance,ion selectivity of AIEM is significant since the crossover of vanadium ion with various valences may reduce the battery capacity.In this paper,AIEMs for VRB and their chemical structures as well as synthesis approaches to realize all kinds of high-performing AIEMs are reviewed.The current trend and future direction of prospective materials for the VRB separators are documented in detail as well.

Building durable aqueous K-ion capacitors based on MXene family

Obtaining stable aqueous K-ion capacitors is still challenging due to the cathode materials tended to structurally collapse after long-term cycling during large-radius K-ion insertion/extraction.In this work,three different typical MXene electrodes,i.e.,Nb_(2)C,Ti_(2)C,and Ti_(3)C_(2) were individually investigated upon their electrochemical behaviors for potassium-ion(K-ion)storage.All these MXene materials exhibited pseudocapacitive-dominated behaviors,fast kinetics,and durable K-ion storage,delivering superior performance compared with other K-ion host materials.According to the experimental results,it could be ascribed to the intrinsically large interlayer distance for K-ion transport and the superb structural stability of MXene even subjected to long-term potassiation/depotassiation process.

Self-supported porous heterostructure WC/WO_(3−x)ceramic electrode for hydrogen evolution reaction in acidic and alkaline media

Tungsten carbide(WC)-based materials are widely considered as the hydrogen evolution reaction(HER)process catalysts due to their“Pt-like”electronic structure.Nonetheless,traditional powder electrodes have a high cost,and display problems related to the process itself and the poor stability over operation time.This paper presented a self-supported asymmetric porous ceramic electrode with WO_(3-x)whiskers formed in situ on the walls of the finger-like holes and membrane surface,which was prepared by combining phase inversion tape-casting,pressureless sintering,and thermal treatment in a CO_(2) atmosphere.The optimized ceramic electrode displayed good catalytic HER activity and outstanding stability at high current densities.More specifically,it demonstrated the lowest overpotentials of 107 and 123 mV and the lowest Tafel slopes of 59.3 and 72.4 mV·dec^(-1)at 10 mA·cm^(-2)in acidic and alkaline media,respectively.This superior performance was ascribed to the structure of the ceramic membrane and the charge transfer efficiency,which was favored by the in situ developed WC/WO_(3-x)heterostructure and the oxygen vacancies.

Engineering practice of mechanical soil aeration for the remediation of volatile organic compound-contaminated sites in China： Advantages and challenges

In recent years, many industrial enterprises located in the urban centers of China have been relocated owing to the rapid increase in urban development. At the sites abandoned by these enterprises, volatile organic compounds have frequently been detected, sometimes at high concentrations, particularly at sites abandoned by chemical manufacturing enterprises. With the redevelopment of sites and changes in land-use tvpe associated with these sites, substantial amounts of contaminated soils now require remediation. ＂Since China is a developing country, soil remediation warrants the usage of techniques that are suitable for addressing the unique challenges faced in this country. Land shortage is a common problem in China; the large numbers of contaminated sites, tight development schedules, and limited financial resources necessitate the development of .cost-effective methods for land reclamation.Mechanical soil aeration is a simple, effective, and low-cost soil remediation tectm^que mat is particularly suitable for the remediation of large volatile organic compound-contaminated sites. Its effectiveness has been confirmed by conducting laboratory studies, pilot tests, and full-scale projects.This study reviews current engineei-ing practice and developmental trends of mechanical soil aeration and analyzes the advantages and disadvantages of this technology for application in China as an emerging soil remediation market. The findings of this study might aid technology development in China, as well as assist other developing countries in the assessment and implementation of costeffective hazardous waste site soil remediation programs.