摘要
多元正极材料LiNi_(0.6)Co_(0.1)Mn_(0.3)O_(2)(NCM613)通过提高充电电压,能量密度可以达到高镍材料水平(Ni>80%,NCM811),并且安全性及循环稳定性更优、原料及加工成本更低,是锂离子电池正极材料近年来重要的发展方向之一。但NCM613在高电压充电态下与电解液存在严重的副反应,引起表界面活性降低和稳定性变差,造成电池的容量衰减、产气鼓胀、安全隐患大等一系列问题。通过在正极表面包覆能有效提高锂离子电池界面稳定性,本文常见的氧化物包覆层能够避免电解液与活性材料的界面副反应,减少活性过渡金属离子的溶解,但通常无法解决界面处锂离子的传输问题,造成容量、倍率、循环性能的衰减。为了提高NCM613与电解液界面活性及稳定性,本文以Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP)为包覆剂,采用液相法对NCM613进行改性,研究了包覆量及热处理温度对改性效果的影响。LATP包覆可以有效提高正极材料容量、倍率及循环性能,并且对正极材料在高电压状态下的热稳定性有较明显的改善作用。当包覆量为0.8%、热处理温度为500℃时样品性能最佳:0.1 C放电比容量达到197.2 mA·h·g^(-1),1 C倍率放电容量保持率达到93.1%,1 C循环80周容量保持率96.1%,DSC放热峰温度由基体的271.8℃延后到290.7℃,放热量由459.8 J·g^(-1)降低至306.5 J·g^(-1)。高离子电导率的LATP包覆在正极材料表面可以提高正极/电解液界面活性,提供快速的锂离子传输通道;LATP中结构稳定的P-O键对表面的氧及过渡金属具有较好的锚定作用,抑制氧析出及过渡金属溶出,阻止电解液对材料的侵蚀,提高正极/电解液界面稳定性。
LiNi_(0.6)Co_(0.1)Mn_(0.3)O_(2)(NCM613)is one of the important research directions for lithium-ion battery cathode materials in recent years with acceptable safety performance,good cyclic stability,lower raw material and processing costs,and the ability to achieve energy density comparable to high Ni NCM(Ni>80%,NCM811)by increasing the charging voltage.However,NCM613 suffers from serious side reactions with the electrolyte under high voltage charging state,causing a decrease in interfacial activity and stability,and then resulting in a series of problems such as capacity decay,gas generation,and safety hazards in the battery.Surface coating has been considered as the most effective approach which can effectively improve the interface stability of NCM613/electrolyte.Of the various coating materials,oxide coating layers can prevent interface side reactions between electrolyte and cathode materials,reduce the dissolution of transition metal ions,but typically cannot provide Li^(+)transport channel at the interface,resulting in degradation of capacity,rate,and cycling performance.In order to improve the interfacial activity and stability between NCM613 and electrolyte,Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP)was coated on NCM613 by liquid-phase method and the effects of coating amount and heat treatment temperature were studied.LATP coating effectively improve the capacity,rate,and cycling performance of cathode materials,and significantly enhances their thermal stability for cathode materials under high voltage.NCM613 exhibits optimal performance when the coating amount is 0.8%and the annealed temperature is 500℃:the discharge specific capacity at 0.1 C reaches 197.2 mA·h·g^(-1),capacity retention of discharge specific at 1 C reaches 93.1%and it still maitains 96.1%after 80 cycles compared to the first cycle,which is significantly higher than those of bare material.Additionally,the DSC exothermic peak temperature is delayed from 271.8℃to 290.7℃,and the exothermic heat decreases from 459.8 J·g^(-1)to 306.5 J·g^(-1).Coating LATP with high ionic conductivity on the surface of the cathode material can improve the interfacial activity between the NCM and electrolyte,providing the fast lithium ion transport channel.The stable P-O bond in LATP may exert a pillar effect on surface oxygen and transition metals,preventing side reactions between NCM and electrolyte,and improving the stability of the NCM/electrolyte interface.
作者
邵宗普
刘亚飞
于月光
赵志浩
SHAO Zongpu;LIU Yafei;YU Yueguang;ZHAO Zhihao(BGRIMM Technology Group Co.Ltd.,Beijing 100160,China;Beijing Easpring Material Technology Co.Ltd.,Beijing 100070,China;School of Materials Sclenee and Engineenng,Northeastern University,Shenyang 110167,China;China Iron&Steel Research Institute Group Co.Ltd.,Beijing 100053,China)
出处
《矿冶》
2024年第6期843-851,共9页
Mining And Metallurgy
基金
国家重点研发计划项目(2023YFB2503900)
北京市科技计划项目(Z191100004719001)。
