【作者】 尹召强；

【导师】 张兰； 巫湘坤；

【作者基本信息】 合肥学院 ， 材料与化工（专业学位）， 2023， 硕士

【摘要】 发展可持续能源是改善环境问题和推动绿色发展的重要举措,可再生能源的间歇性和不可控性使其难以直接应用于能源系统中。因此,需要大力发展储能技术,将可再生能源大规模应用于电力系统。锂浆料电池将电极活性材料和导电剂分散于电解液中形成固液混合悬浮液浆料,以悬浮液浆料作为流体电极组成电池。这种电池综合了液流电池和锂离子电池两者的优点,是一种新型的电化学储能技术。目前,锂浆料电池处于基础研发阶段,电极浆料还存在一些问题,比如浆料电极的稳定性、电子电导率、电极界面副反应等。本文针对浆料电池以上问题,开展正极浆料电极的工艺和配方优化、流动浆料电极内阻分析以及浆料电池充电机制优化等研究工作,主要研究进展如下:(1)将活性物质镍钴锰酸锂(NCM622)、导电添加剂科琴黑(KB)和碳纳米管(CNT)以及碳酸酯类电解液制备成正极浆料电极,研究了不同设备、不同搅拌时间、不同固含量以及不同导电添加剂以及含量对浆料电极性能的影响。结果发现,配方为30%NCM622、导电剂为1%KB+1%CNT和68%的电解液,使用脱泡机搅拌10 min的浆料性能更优,在充放电循环30周期放电比容量仍有103.3 mAh/g。(2)研究了流动对浆料电极内阻的影响。首先测试了KB和NCM622材料颗粒电导率,然后测试了不同流速对浆料电极的离子传输阻抗和电子传输阻抗的影响,以及浆料反应器电池在静态和流动模式下的充放电循环。结果表明,KB具有远高于NCM622的电导率,是浆料电极中电子传导的主要路径。浆料流动高流速提高了离子扩散,离子传输阻抗随流速增加而减小;在导电剂形成完整的导电渗透网络浆料中,流速对电子传输影响较小;浆料反应器电池在静止状态下性能最好,在流动模式下,由于浆料电极中固体颗粒存在对流、分散与再团聚等运动,固体颗粒之间的连通状态是动态变化的,导致电池体系不稳定,影响电池性能。(3)通过恒电流间歇滴定技术(GITT)制定了6级充电协议(SS-CC),分析了恒流充电(CC)、恒流恒压充电(CC-CV)、脉冲充电(PP-CC)以及SS-CC对浆料电池性能的影响。研究表明,SS-CC充电协议存在更高的容量保持率和较低阻抗,并且通过循环后负极锂表面形貌表征可知,SS-CC充电协议存在更少的锂枝晶和副反应,该充电策略提高了浆料电池循环稳定性和能量效率。更多还原

【Abstract】 The development of sustainable energy is an important measure to solve environmental problems and promote green development.The intermittency and uncontrollability of renewable energy make it difficult to directly apply in the energy system.Therefore,it is necessary to develop energy storage technology and apply renewable energy to power system on a large scale.The lithium slurry battery is a new electrochemical energy storage technology that combines the benefits of flow batteries and lithium ion batteries.It is made up of a solid-liquid mixed suspension slurry that disperses electrode active material and conductive agent in electrolyte,and suspension slurry is used as a fluid electrode to form a battery.At present,lithium slurry batteries are in the basic research and development stage,and there are still some issues with electrode slurry,such as stability,electronic conductivity,electrode interface side reactions,etc.In order to solve the above problems of slurry batteries,this paper carried out research on the optimization of positive slurry electrode process and formula,analysis of internal resistance in flowable slurry electrode and optimization of charging strategy in slurry battery.The main research progress are as follows:(1)Active material lithium nickel cobalt manganese oxides cathode(NCM622),conductive additives Ketjen black(KB),carbon nanotubes(CNT)and carbonate electrolyte were used to prepare the positive slurry electrode.The effects of different equipment,different stirring time,different solid content,different conductive additives,and their contents on the performance of slurry electrode were studied.The results show that the slurry with 30%NCM622,1%KB+1%CNT as conductive additives,and 68%electrolyte,stirred with a defoaming machine for 10 minutes,exhibit better performance.After 30 cycles,the discharge specific capacity was still 103.3 mAh/g.(2)The influence of flow on the internal resistance of slurry electrode was studied.This paper first tested the particle conductivity of KB and NCM622 materials,and then investigated the impact of different flow rates on the ion and electron transport impedance of the slurry electrode.The study also examined the charge and discharge cycles of the slurry reactor battery in both static and flow modes.The results show that the conductivity of KB is much higher than that of NCM622,which is the main path of electron conduction in slurry electrode.The high flow rate of slurry improves ion diffusion,and the ion transport impedance decreases with the increase of flow velocity.In the slurry with complete conductive permeation network formed by the conductive agent,the effect of velocity on electron transport is small.The slurry reactor battery has the best performance in the static state.In the flow mode,due to the movement of solid particles in the slurry electrode,such as convection,dispersion and reagglomeration,the connectivity between the solid particles changes dynamically,which leads to the instability of the battery system and affects the battery performance.(3)Firstly,a six-stage charging protocol(SS-CC)was developed by constant-current intermittent titration(GITT),and the effects of constant-current charging(CC),constant-current and constant-voltage charging(CC-CV),pulse charging(PP-CC)and SS-CC on the performance of slurry batteries were analyzed.The research shows that the SS-CC charging protocol has higher capacity retention rate and lower impedance,and the surface morphology of cathode lithium after cycling shows that the SS-CC charging protocol has fewer lithium dendrites and side reactions.This charging strategy improves the cycle stability and energy efficiency of the slurry battery.更多还原