电化学阻抗谱弛豫时间分布基础

电化学阻抗谱(EIS)是一种高效的原位/非原位电化学表征技术,已在电化学能源领域得到广泛应用,如用于锂离子电池、超级电容器、燃料电池等材料及器件性能的诊断和优化.弛豫时间分布(DRT)是一种不依赖于研究对象先验知识的EIS解析技术,可用于分离和解析EIS中高度重叠的物理化学过程.为了促进DRT解析技术的应用和推广,本文详细阐述了如下问题:1)DRT解析原理、实现算法及重要扩展;2)典型电路基元的DRT解析分析;3)DRT的具体实现及在电化学能源中的典型应用举例;4)DRT解析技术研究进展、存在问题及发展趋势.

磷酸锌改性提高正极材料LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)的电化学性能

富镍正极材料LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)具有低成本、可逆容量大等优势,是一种受到广泛研究的、极具商业化应用潜力的正极材料。然而高的镍含量会使电极表面结构不稳定性加剧,晶面间距降低,从而导致较差的循环性能与倍率性能。在采用共沉淀法制备纯样NCM811正极材料基础上,采用聚乙烯吡咯烷酮(PVP)辅助磷酸锌(Zn_(3)(PO_(4))_(2))包覆NCM811正极材料,XRD图谱表明,ZnO添加量(质量分数)3%时的改性样品(NCM2)的I_((003))/I_((104))值最大,c/a值较纯样的大,具有较低的Li^(+)/Ni^(2^(+))混排程度。同时,Zn^(2^(+))进入电极材料表面晶格,使晶面间距扩大,(003)平面内原子散射能力提升。X射线光电子能谱(XPS)、扫描电镜(SEM)及能谱(EDS)等表征结果表明,Zn_(3)(PO_(4))_(2)均匀包覆在正极材料颗粒表面。NCM2在0.1C电流密度下进行100次循环后的容量为191 mAh·g^(-1),容量保持率为92%,而未改性样品的容量保持率为87%。在5C电流密度下NCM2放电比容量比纯样高43%。循环伏安曲线和电化学阻抗谱结果表明,改性后正极材料电化学极化降低且Li^(+)扩散速率提高,提升了正极材料的循环性能和倍率性能。

Compensation/consumption hierarchical control strategy based on wind-solar-hydrogen coupling grid connection

In the process of grid-connected wind and solar power generation,there are problems of high rate of abandoning wind and light and insufficient energy.In order to solve these problems,we construct a grid-connected wind-solar hydrogen storage(alkaline electrolyzer(AE)-hydrogen storage tank-battery-proton exchange membrane fuel cell(PEMFC))coupled system architecture.A grid-connected compensation/consumption hierarchical control strategy based on wind-solar hydrogen coupling is proposed.During the grid-connected process of wind and solar power generation,the upper-level control allocates power reasonably to the hydrogen energy storage system by dispatching the power of wind and solar power generation.At the same time,the control strategy ensures that the pressure of the hydrogen storage tank is within the safety range limit,and the lower control completes the control of the duty cycle of the converter in the system.Due to the randomness of wind and light,the hydrogen energy storage system is divided into three working conditions,namely compensation,balance and consumption,and five working modes.The simulation results show that the hydrogen energy storage system compensates for 40%of the power shortage,and consumes 27.5%of the abandoned wind and solar energy,which improves the utilization rate of clean energy.