LiNi1-3_Mn1-3Co1-3O2掺杂Mo研究

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原位XRD表征富锂锰基正极材料的结构

原位XRD表征富锂锰基正极材料的结构冯波;王璐璘;马琳鸽;卓锦德【摘要】首次利用原位X射线衍射光谱法(XRD)分析了富锂锰基材料在H2气氛下,温度从25℃逐步升至400℃的过程中结构发生的变化,结果表明:富锂锰基材料最终被还原为MnO和单质Co、Ni,过程中并未出现正交相的LiMnO2,这与三方相(空间群R-3m)的LiMn1/3Ni1/3Co1/3O2还原过程一致,但明显不同于单斜相(空间群C2/m)的Li2MnO3被还原为LiMnO2和MnO的情况,验证了富锂锰基材料的结构为单一的三方相,而非单斜相和三方相的复合相.电化学测试表明:均相结构的三方相富锂锰基材料放电比容量在250 mAh/g左右,充放电循环100次后容量保持率在80％以上.准确地表征富锂锰基材料的三方相结构将有助于改进制备工艺,获得循环性能更好的材料.【期刊名称】《电源技术》【年(卷),期】2019(043)007【总页数】3页(P1097-1099)【关键词】原位XRD;还原;富锂锰基材料;三方相【作者】冯波;王璐璘;马琳鸽;卓锦德【作者单位】北京低碳清洁能源研究所,北京102209;北京低碳清洁能源研究所,北京102209;北京低碳清洁能源研究所,北京102209;北京低碳清洁能源研究所,北京102209【正文语种】中文【中图分类】TM912.9富锂锰基材料xLi2MnO3·(1－x)LiMO2(0＜x＜1,M=Ni,Co,Mn…)的放电比容量和电压平台都比较高(＞250 mAh/g,2.0～4.8 V)，是一种很有潜力的锂电池正极材料，但较差的充放电循环性能限制了其商业化应用。

富锂锰基材料的循环性能由其物相结构决定，许多研究者利用X射线衍射光谱法(XRD)、透射电子显微镜法(TEM)直接分析该材料的结构[1-3]，但至今观点并不一致，主要分为两种：一种认为是单斜相结构(空间群C2/m)，另外一种认为是单斜相和三方相(空间群R-3m)形成的固溶体结构。

LiNi_1_3_Co_1_3_Mn_1省略2_AC混合超级电容器正负极

1 实验
1.1 混合超级电容器的工作原理以 LiNi1/3Co1/3 Mn1/3O2 为正极，活性炭(AC)为负
极的混合超级电容器的工作原理如图 1 所示。其基本过程为：充电吸附的锂离子通过电解液回归正极。与纯双
电层超级电容器相比，由于负极吸附的离子由正极
提供，因此这种混合超级电容器的电解液不需要太
第 30 卷第 1 期 2011 年 1 月
电子元件与材料 ELECTRONIC COMPONENTS AND MATERIALS
研究与试制
LiNi1/3Co1/3Mn1/3O2/AC 混合超级电容器
正负极容量配比研究
吴明霞, 曹小卫, 安仲勋, 杨恩东, 华黎
（上海奥威科技开发有限公司，上海 201203)
Abstract: The supercapacitor using the activated carbon (AC) as the negative electrode, LiNi1/3Co1/3Mn1/3O2 as the positive electrode and 1 mol/L LiBF4/AN as the electrolyte respectively was studied. To optimize the capacity ratio of the positive electrode and the negative electrode, electrochemical performance of charge and discharge ability, various discharge rates and cycle life were investigated. The results show specific energy and specific power of as-prepared supercacpacitors reach 11 Wh/kg and 5 278 W/kg respectively. With the capacity ratio of 4∶1 of the positive electrode and the negative electrode. The capacity maintenance ratio of the supercapacitors keep at 92% after 2 200 cycles. The prepared supercapacitor has high probability of commercialization.

锂离子电池正极材料掺杂和表面包覆研究综述

锂离子电池正极材料掺杂和表面包覆研究综述王栋; 郑莉莉; 杜光超; 张志超; 冯燕; 戴作强【期刊名称】《《储能科学与技术》》【年(卷),期】2019(008)0z1【总页数】6页(P43-48)【关键词】锂离子电池; 正极材料; 掺杂; 表面包覆【作者】王栋; 郑莉莉; 杜光超; 张志超; 冯燕; 戴作强【作者单位】青岛大学机电工程学院; 青岛大学动力集成及储能系统工程技术中心; 电动汽车智能化动力集成技术国家地方联合工程技术中心(青岛) 山东青岛260071【正文语种】中文【中图分类】TM912目前已商业化的锂离子电池正极材料主要有钴酸锂（LiCoO2）、锰酸锂（LiMn2O4）、磷酸铁锂（LiFePO4）和三元材料[Li(Ni,CO,Mn)O2]4种。

其中，钴酸锂LiCoO2材料理论比容量高、循环性能优异、放电平台平稳、工作电压高等优点，但钴元素较为稀缺，且其过充条件下的安全性能存在隐患。

尖晶石型的锰酸锂LiMn2O4材料具有较高容量，同时锰容易获得、价格便宜且环保。

但其合成相比于其他正极材料复杂且涉及多种相变。

橄榄石型LiFePO4结构稳定、化学稳定，但是电子电导率低和锂离子扩散慢。

层状镍钴锰酸锂系列[即三元材料Li(Ni,CO,Mn)O2]具备有以上3种材料的优点，并在一定程度上弥补了它们的不足，成为正极材料最具前景的替代材料之一，但是其容量保持率低、高温循环和安全性能存在一定隐患。

以上缺点限制了这些材料的进一步应用，目前，主要通过掺杂工艺和表面包覆工艺等方法改善上述材料在电化学方面的性能。

1 锂离子电池正极材料掺杂1.1 掺杂机理掺杂是指通过引入某些金属或者元素来增加电极材料的离子导电性，加强结构的稳定性。

最常见的掺杂方式有金属离子掺杂和复合掺杂，掺杂的主要元素有Mg、Al、Ti、Cr、Zr等，掺杂的金属离子可以提供较Ni、Co、Mn（M）等活性过渡金属更强的M—O化学键，通过抑制高电压下晶格氧的析出，提高材料的结构稳定性[1]。

ICP-AES原子发射分析法检测LiNi1／3Co1／3Mn1／3O2中Ni含量

材料研究不断开拓新的方向Ｉ２Ｊ。锂离子电池的优异性能与电池的材料选择，材料的制备工艺等密切相关 “ 。锂离子材料ＬｉＮｉＣｏＭｎ０发展很快，但目前尚没有
系列溶液作工作曲线（由计算机自动绘制）。完成所有预备程序后将仪器进样毛细管插入样品溶液中，仪器将自动完成分析过程，计算机直接报出样品中元素的浓度。
２讨
论
约电池、材料研制成产的缺陷。
２．１酸度的影响
１实验方法及实验仪器
１．１仪器及操作条件
仪器：ＳＰＳ一８０００型原子发射光谱分析仪。
配制Ｎｊ标准溶液浓度为０，２．０×１０
Ｌ，４，０ｘ１０～ｇ／Ｌ，
要求。
关键词：ＩＣＰ — ＡＥＳ；镍钴锰酸锂；镍；测定方法
中图分类号：０６５３
文献标识码：Ａ
文章编号：１００１ — ９６７７（２０１３）０３ — ００９３— ０２
ＤｅｔｅｒｍｉｎａｔｉｏｎｏｆＬｉＣｏｎｔｅｎｔｉｎＬｉＮｉｌ／３Ｃｏ１／３Ｍｎｌ／３０２
ＦＵＸｉａｏ —ｎｉｎｇ，ＬＩＮＲｕ
（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙａｎｄＣｈｅｍｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＸｉｎｘｉａｎｇＣｏｌｌｅｇｅ，ＨｅｎａｎＸｉｎｘｉａｎｇ４５３００７，Ｃｈｉｎａ）

毕业设计任务书 (修改)

1.任务及背景：主要研究锂离子三元正极材料的离子热法制备工艺，锂离子二次电具有高能量密度、重量轻、不污染环境、无记忆效应、工作性能稳定、安全可等特点，自问世以来应用广泛，已成为目前主要的便携式电源，也是大功率动电池的开发重点。
2.成果形式：提交锂离子三元正极材料的离子热法制备的研究设计方案；最终以毕业论文的形式展示出来。
3、主要仪器和设备
电池测试仪，电化学工作站，直流电源（整流器），恒温槽。
4、主要参考文献
1.牛小波.锂离子电池三元复合正极材料的合成及其电化学性能研究.重庆大学硕士论文，中文摘要。2009.
2.禹筱元,余仕僖,周正添.锂离子电池LiNi1/3Co(1/3Mn1/3O2正极材料的性能研究广东化工. 2008(04)
3.着重培养的能力：在查找锂离子三元正极材料的离子热法制备相关论文时培养自己独立解决问题及分析问题的能力，在实验的过程中学会的找到解决问题的方法和途径。不断的在动手实践中形成好的动手和学习能力。
二、应收集的资料及主要参考文献
1.牛小波.锂离子电池三元复合正极材料的合成及其电化学性能研究.重庆大学硕士论文，中文摘要。2009.
毕业设计（论文）任务书
设计（论文）题目锂离子电池三元正极材料的离子热法制备
学院名称化学工程学院
专业（班级）应用化学 09-1班
姓名（学号）艾诚(20093482)
指导教师李学良
系（教研室）负责人邓宁
锂离子三元正极材料的离子热法制备
一、毕业设计（论文）的主要内容及要求（任务及背景、成果形式、着重培养的能力）
2、完成任务的可能思路和方案
1.将Li（1-y）Ni（1/3）Co（1/3）Mn（1/3）O2中Li的值分别取0、0.1、0.2—0.9等值，通过对电池放电曲线及循环周期等参数的测定的比较，分析探究含Li量不同对电化学性能的影响。找出最佳的Li的含量。

制备镍_钴_锰复合氢氧化物的热力学分析

基金项目：教育部高等学校骨干教师基金资助项目（２０００年）作者简介：苏继桃（１９７９－），男，湖南省人，博士生。

Ｂｉｏｇｒａｐｈｙ：ＳＵＪｉ－ｔａｏ（１９７９－），ｍａｌｅ，ｃａｎｄｉｄａｔｅｆｏｒｄｏｃｔｏｒ．制备镍、钴、锰复合氢氧化物的热力学分析苏继桃，苏玉长，赖智广（中南大学材料科学与工程学院，湖南长沙４１００８３）摘要：合成化学计量的锂离子电池正极材料ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２的关键在于制备均匀的前驱体。

通过对Ｍ２＋（Ｎｉ２＋，Ｃｏ２＋，Ｍｎ２＋）－ＮＨ３－ＯＨ－－Ｈ２Ｏ体系的热力学分析，获得了Ｍ２＋－ＮＨ３－ＯＨ－－Ｈ２Ｏ体系中不同氨浓度时的ｌｇ［Ｍ］－ｐＨ关系图（其中Ｍ为过渡金属元素），得到了以（ＮＨ４）２ＳＯ４为络合剂，以ＮａＯＨ为沉淀剂，采用共沉淀法制备的锂离子电池正极材料用镍、钴、锰复合氢氧化物，较适宜的氨浓度为０．５ｍｏｌ／Ｌ左右，最佳共沉淀的ｐＨ值为１２．０左右。

在此氨浓度和ｐＨ值条件下通过共沉淀法制备了类球形的镍、钴、锰复合氢氧化物前驱体粉料，所得前驱体组分恒定，粒度分布均匀，中位粒径Ｄ５０为１４．７６μｍ。

关键词：锂离子电池；正极材料；热力学分析；共沉淀中图分类号：ＴＭ９１２．９文献标志码：Ａ文章编号：１００８－７９２３（２００８）０１－００１８－０５ＴｈｅｒｍｏｄｙｎａｍｉｃａｎａｌｙｓｉｓｏｆｐｒｅｐａｒａｔｉｏｎｏｆｍｕｌｔｉｐｌｅｈｙｄｒｏｘｉｄｏｆＮｉ，ＣｏａｎｄＭｎＳＵＪｉ－ｔａｏ，ＳＵＹｕ－ｃｈａｎｇ，ＬＡＩＺｈｉ－ｇｕａｎｇ（ＳｃｈｏｏｌｏｆＭａｔｅｒｉａｌＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙ，Ｃｈａｎｇｓｈａ，Ｈｕｎａｎ４１００８３，Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ：ＴｈｅｐｒｅｐａｒａｔｉｏｎｏｆｕｎｉｆｏｒｍｐｒｅｃｕｒｓｏｒｉｓｔｈｅｋｅｙｔｏｓｙｎｔｈｅｓｉｚｅＬｉ－ｉｏｎｂａｔｔｅｒｙｃａｔｈｏｄｅｍａｔｅｒｉａｌＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２．ＴｈｅｒｍｏｄｙｎａｍｉｃａｎａｌｙｓｉｓｏｆＭ２＋（Ｎｉ２＋，Ｃｏ２＋，Ｍｎ２＋）－ＮＨ３－ＯＨ－－Ｈ２Ｏｓｙｓｔｅｍｗａｓｐｒｏｃｅｅｄｅｄ，ａｎｄｌｇ［Ｍ］－ｐＨｇｒａｐｈｓａｔＭ２＋（Ｎｉ２＋，Ｃｏ２＋，Ｍｎ２＋）－ＮＨ３－ＯＨ－－Ｈ２ＯｓｙｓｔｅｍｗｉｔｈｄｉｆｆｅｒｅｎｔＮＨ３ｃｏｎｃｅｎｔｒａｔｉｏｎｓｗｅｒｅｏｂｔａｉｎｅｄ．ＴｈｅｍｕｌｔｉｐｌｅｈｙｄｒｏｘｉｄｐｏｗｄｅｒｓｏｆＮｉ，Ｃｏ，ＭｎｆｏｒＬｉ－ｉｏｎｂａｔｔｅｒｙｐｏｓｉｔｉｖｅｍａｔｅｒｉａｌｗｅｒｅｐｒｅｐａｒｅｄｂｙｃｏ－ｐｒｅｃｉｐｉｔａｔｉｏｎｍｅｔｈｏｄａｎｄｕｓｉｎｇ（ＮＨ４）２ＳＯ４ａｓｃｏｍｐｌｅｘｉｎｇａｇｅｎｔ，ＮａＯＨａｓｐｒｅｃｉｐｉｔａｎｔ，ａｎｄｗｉｔｈｔｈｅｏｐｔｉｍａｌＮＨ３ｃｏｎｃｅｎｔｒａｔｉｏｎｏｆ０．５ｍｏｌ／Ｌ，ｐＨｏｆａｂｏｕｔ１２．０．Ｔｈｅｓｈａｐｅｏｆｐｒｅｃｕｒｓｏｒｐｏｗｄｅｒｓｗａｓｓｐｈｅｒｅ－ｌｉｋｅｗｉｔｈａｍｉｄｄｌｅｐａｒｔｉｃｌｅｄｉａｍｅｔｅｒＤ５０ｏｆ１４．７６μｍ，ａｎｄｗｉｔｈｕｎｉｆｏｒｍｓｉｚｅｄｉｓｔｒｉｂｕｔｉｏｎ．Ｋｅｙｗｏｒｄｓ：Ｌｉ－ｉｏｎｂａｔｔｅｒｙ；ｐｏｓｉｔｉｖｅｍａｔｅｒｉａｌ；ｔｈｅｒｍｏｄｙｎａｍｉｃａｎａｌｙｓｉｓ；ｃｏ－ｐｒｅｃｉｐｉｔａｔｉｏｎ目前，研究较多的锂离子电池正极材料是具有α－ＮａＦｅＯ２熔盐结构的层状氧化物ＬｉＭＯ２（Ｍ为过渡金属元素）［１］。

可参考红外

Novel mixed hydroxy-carbonate precursor assisted synthetic techniquefor LiNi1/3Mn1/3Co1/3O2cathode materialsP.Manikandan,P.Periasamy*Lithium Batteries,Electrochemical Power Sources Division,CSIR–Central Electrochemical Research Institute,Karaikudi630006,India1.IntroductionCurrently,LiCoO2is widely commercialized as a cathodematerial for Li-ion batteries.Since it suffers from high cost andtoxicity of Co[1],there is a quest to synthesize an alternatecheaper,higher capacity and safer layered cathode materials[2].Amongst the potential layered compounds,LiNi1/3Mn1/3Co1/3O2[3]has attracted signiﬁcant attention in this context.It has highcapacity,structural and thermal stability and excellent cyclingperformance[4,5].Accordingly,considerable efforts have beenmade to develop LiNi1/3Mn1/3Co1/3O2with different morphologies[6–9],while most of them are disordered agglomerations[8,9].Thematerial has been synthesized by different methods like solid-state[10],sol–gel[11],molten salt[9]and rheological phase method[12],etc.Unfortunately,due to disorder of Li+and Ni2+site,thecathode properties of LiNi1/3Mn1/3Co1/3O2are sensitively depen-dent on distribution of transition metal and the particlemorphology.As a result,it is difﬁcult to prepare this material ofits potential performance and the rate capability of this materialdepends on the synthetic route which has greater inﬂuence on theparticle morphology.Therefore,it is important to select suitablepreparation method for synthesis of LiNi1/3Mn1/3Co1/3O2cathodematerials.Most research groups have adopted the solid-statereaction process to prepare LiNi1/3Mn1/3Co1/3O2powders[4,10,13].However,LiNi1/3Mn1/3Co1/3O2derived from the solid-state methodsuffers from the problem of signiﬁcant irreversible charge–discharge behavior.The irreversible capacity problem can beovercome in two ways:one is to alter the source materials and theother is to employ alternate synthesis methods.Furthermore toimprove the electrochemical performance of LiNi1/3Mn1/3Co1/3O2,there are several important factors,such as starting raw materials,precursor,preparation method and conditions.Caballero et al.[14]developed a simple solvent-free method forpreparing nanometric cathode materials.The method is based onthe preparation of oxalate precursor by one-step solid-statemetathesis reactions of various hydrated salts in the presence ofhydrated oxalic acid[15,16].In the solid-state metathesisprocedure,no solvent is added which could effectively avoid theoccurrence of concentration gradient in precursor and simplify thepreparation process.A disadvantage of the method is limitation ofthe raw materials.Some of them are comparatively expensive.Thus,the reproductively is very difﬁcult to accomplish.Hence,ithas become necessary to develop precursors.The preparation ofprecursor with atomic scale-mixing of Ni,Co,and Mn ions,is one ofthe most important steps[17].Hydroxide co-precipitation method[4]has been traditionally used to synthesize LiNi1/3Mn1/3Co1/3O2cathode materials.The co-precipitation method yields phase-pureoxide products and high tap-density spherical powders withuniform distribution.With this in mind,it turns out that the novelMaterials Research Bulletin50(2014)132–140A R T I C L E I N F OArticle history:Received16May2013Received in revised form5August2013Accepted3October2013Available online12October2013Keywords:yered compoundsC.Infrared spectroscopyC.X-ray diffractionD.Electrochemical propertiesA B S T R A C TNovel mixed hydroxy-carbonate(MHC)precursors were used to synthesis technique of LiNi1/3Mn1/3Co1/3O2cathode material.The powder X-ray diffraction(XRD)pattern of the synthesized LiNi1/3Mn1/3Co1/3O2cathode materials exhibited a hexagonal cell with a=2.8535A˚and c=14.2040A˚.Fourier transforminfrared spectroscopy(FT-IR)spectrum of MHC and LiNi1/3Mn1/3Co1/3O2consistent with vibrationmodes of functional group.Presence of sub-micrometer particle size(200nm)and highly crystallinemorphology conﬁrmed using scanning electron microscopy(SEM).X-ray photoelectron spectroscopy(XPS)suggested that oxidation state of the transition metals;Ni in+2,Mn in+4and Co in+3states,respectively in LiNi1/3Mn1/3Co1/3O2cathode materials.Cyclic voltammograms(CV)revealed only onemajor redox couple at4V and suggested the absence of structural transitions from hexagonal tomonoclinic structure.The Li vs.LiNi1/3Mn1/3Co1/3O2cell delivered an initial discharge capacity of175mAh gÀ1in the voltage range2.5–4.6V@0.1C.ß2013Elsevier Ltd.All rights reserved.*Corresponding author.Tel.:+914565241421;fax:+914565227713.E-mail addresses:periasamylibatt@,psamy31@(P.Periasamy).Contents lists available at ScienceDirectMaterials Research Bulletinj o u rn a l h om e p a g e:w w w.e l s e v i e r.c o m/l o c a t e/m a t r e s b u0025-5408/$–see front matterß2013Elsevier Ltd.All rights reserved.doi:10.1016/j.materresbull.2013.10.010toxic free MHC[M2(OH)2CO3;M=Ni,Mn,Co]precursors can lead to oxidic cathode products having high dispersibility[18]owing to evolution of non-toxic gases viz.,water and carbon dioxide upon decomposition.The stacking sequence of MHC precursors contains M(OH)6octahedra layers(A)and(CO3)2Àanion interlayer(B), which constitute the layered structure as depicted in Fig.1.The layered structure of M2(OH)2CO3is A-B-A-B-A-B...stacking arrangement with(OH)Àions lie at the apices of octahedra where M cations[M=Ni,Mn,Co]are hidden at their centers[19]. Therefore MHC precursors assisted synthetic technique is exhib-ited to yield oxide products with high dispersity due to(CO3)2Àanion interlayer between M(OH)6octahedra layers.In the present study,MHC precursors were synthesized by precipitation of hydroxy-carbonate furthermore LiNi1/3Mn1/3Co1/ 3O2cathode material obtained through MHC method.The phase purity,structural properties,morphology and electrochemical properties of the synthesized LiNi1/3Mn1/3Co1/3O2cathode materi-als were investigated.2.Experimental2.1.Synthesis of MHC precursor and LiNi1/3Mn1/3Co1/3O2cathode materialsIn this report the cathode material has been synthesized through a MHC method comprising two steps with(i)synthesis of precursor underlying precipitation of hydroxy-carbonate of Ni,Mn and Co ions followed by(ii)optimized calcination of the precursor yielding the oxidic cathode products for being used in Li-ion battery application.Ni2(OH)2CO3precursor was synthesized using stoichiometric aqueous solution of Ni(NO3)2.6H2O(2mole,Merck AR grade).This aqueous solution was slowly added using buret to a mixture of NaOH(2mole)and Na2CO3(1mole)aqueous solution at408C through stirring until the complete precipitation appear-ing as light green gelatinous precipitate,which wasﬁltered, washed using distilled water and ethanol followed by drying at 608C for24h resulting in the MHC precursors.Mn2(OH)2CO3(light brown)and Co2(OH)2CO3(brownish black)precursors were prepared separately under similar conditions.Then,stoichiometric amounts of Ni,Mn,Co MHC precursors and Li2CO3were homogenized and ground well for1h using FRITSCH pulverisette 7instrument at400rpm.After the homogenization step this blend was calcined at600,700,800and9008C for12h to obtain LiNi1/3Mn1/3Co1/3O2cathode materials for further investigation.Li2CO3þ1=3ðNiÞ2ðOHÞ2CO3þ1=3ðMnÞ2ðOHÞ2CO3þ1=3ðCoÞ2ðOHÞ2CO3þ1=2O2À!Dð600À900 CÞ2LiNi1=3Mn1=3Co1=3O2þ2CO2"þH2O"Upon calcination,the thermal decomposition of the startingmaterials blend of MHC and Li2CO3can be visualized through thefollowing reaction:2.2.Characterization techniquesThe powder samples were used to analyze the phase formationby X-ray diffraction(Bruker D8Advance X-ray diffractometer)using Cu K a radiation.The FT-IR spectrum was recorded by aBRUKER Optik GmbH MODEL TENSOR27FT-IR Spectrometer witha detector RT DLaTGS using a KBr pellet in the range of400–4000cmÀ1and the results summarized on co-addition of64scanswith a resolution of4cmÀ1and scanner velocity of10kHz.Morphological examinations were made by SEM(HitachiS-3000H).XPS studies were conducted using a Thermoscientiﬁc,UK Multilab2000electron spectroscope with Al K a radiation andat a scan range of0–1200eV binding energy(BE).Electronparamagnetic resonance(EPR)studies were carried out with aBruker EMX plus X-band spectrometer.CV recorded@0.1mV sÀ1in the range2.5–4.6V using an Autolab electrochemical worksta-tion(PGSTAT30).Electrochemical performance was investigatedusing Arbin multichannel charge–discharge instrument(BT2000).Coin cells of the CR-2032conﬁguration were assembled using Lifoil(750m m)as the anode and LiNi1/3Mn1/3Co1/3O2as the cathode.The area and thickness of the electrode was1.54cm2and50–75m m for Li vs.LiNi1/3Mn1/3Co1/3O2cell.A1M solution of LiPF6in1:1(v/v)EC–DMC mixture was used as the electrolyte.The cathodewas fabricated by blade-coating slurry of80wt.%LiNi1/3Mn1/3Co1/3O2,15wt.%SP-carbon(Timcal)and5wt.%PVdF in NMP onaluminum foil.The cells were assembled in an argon-ﬁlled glovebox(mBRAUN MB200G)with oxygen and moisture levels less than0.1ppm.Galvanostatic charge–discharge studies were conductedin the range2.5–4.6V@0.1C,0.2C,0.5C,1C and2C.3.Results and discussionPrecursors Ni2(OH)2CO3[20],Mn2(OH)2CO3[18]andCo2(OH)2CO3[21]were synthesized as spongy form by precipita-tion of hydroxy-carbonate.These precursors facilitate homoge-neous distribution with Li2CO3to obtain phase purity in the MHCmethod rather than conventional solid-state method entailing incoarser particles shows lower electrochemical performance incomparison toﬁner particles synthesized through wet-chemicalroute(s).Additionally,this route requiring shorter milling time($1h)has an edge over conventional solid state route in terms ofsize tunability,homogeneous product without formation ofsecondary phases facilitating higher electrochemical capacity.3.1.Physical characterization3.1.1.Structural parameters through XRDThe powder XRD patterns of the MHC precursors(a)Ni2(OH)2CO3,(b)Mn2(OH)2CO3and(c)Co2(OH)2CO3and LiNi1/3Mn1/3Co1/3O2materials obtained by calcinations at differenttemperatures for12h are shown in Figs.2and3respectively.Thebroad peaks observed in the case of the material calcined at6008Cindicate that the material is poorly crystalline.It can also be seenthat the crystallinity of material improves with increasingcalcination temperatures.All the peaks could be indexed basedon the a-NaFeO2type structure(space group R3m).TheoxygenFig. 1.Structure of MHC precursors such as Ni2(OH)2CO3,Mn2(OH)2CO3andCo2(OH)2CO3.P.Manikandan,P.Periasamy/Materials Research Bulletin50(2014)132–140133sub-lattice in the a -NaFeO 2type structure forms an fcc lattice with a distortion in the c direction,resulting in a clear splitting of the (006)/(102)and (108)/(110)peaks.If this distortion (in the c direction)is absent (or if the structure is totally cubic),the (006)/(102)and (108)/(110)peaks merge into single peaks,as observed with the sample calcined at 6008C.A good resolution of the (006)/(102)and the (108)/(110)reﬂection pairs is typical of an ideal layered structure [22].Clear separation of the (006)/(102)peaks as well as of the (108)/(110)peaks can be noticed in the patterns of the materials calcined at 9008C.The hexagonal doublets such as (006)/(102)and (108)/(110)are seen with better splitting than those reported in the literature,which conﬁrms that the synthesized LiNi 1/3Mn 1/3Co 1/3O 2com-pound has superior crystallinity,good hexagonal ordering and better layered characteristics [23].Absence of impurity phases like NiO and MnO 2conﬁrm the stoichiometric ratio of the synthesized precursors.The crystallite size (143nm)is obtained using the Scherrer equation for LiNi 1/3Mn 1/3Co 1/3O 2cathode materials.The structural parameters of LiNi 1/3Mn 1/3Co 1/3O 2calcined at different temperatures are illustrated in Table 1.The obtained lattice parameter are lesser (9008C)than the values observed by Ohzukuand Makimura (a =2.867A˚,c =14.246A ˚)[3].The ratio of the lattice constants,c /a is above 4.9and hence it is inferred that the synthesized materials have a well-deﬁned layered structure [10].The c /a ratio of the sample calcined at 9008C is 4.9777,which means it has the best layer properties and least cation mixing [24].The observed lattice parameters of a and c are only marginallydifferent from the corresponding values of 2.8606A˚and 14.2273A ˚reported for a similar compound prepared from precursors formed in ethanol [17].Also,the sample has smaller lattice parameters viz .,a ,c compared to those reported [3]inclusive of a sample prepared by rheological phase method [12].The observed larger triangle distortion,c /a ,is similar to results of Reddy et al.[9].These differences in lattice parameters might have arisen from different preparation conditions and methods.Moreover,Reddy et al.[9]considered these smaller lattice parameters might be due to smaller cation mixing and better ordering of the transition metal ions in the metal-layer.The increases in lattice volume with increasing temperature are in agreement with the elemental crystal growth theory [25].Also the lattice volume is marginally less as compared to that of LiNi 0.6Co 0.2Mn 0.2O 2[25].In lithium battery cathode materials,the oxygen sub lattice and transition metal ions form the host materials of lithium storage,allowing the reversible lithium insertion and extraction from them [26].Thus the local structure of light elements plays a very important role on their physical properties and the electrochemical performance of Li-ion batteries [27,28].The intensity ratio of I (003)/I (104)is a sensitive parameter to determine the cation distribution in lattice [29],the higher this ratio the lower is the degree of the cation mixing.Since the value of I (003)/I (104)depends on the degree of the displacement between ions located at the 3(a )and 3(b )sites in a space group of R3m,this value is a measure of the reactivity of lithium insertion materials for a series of LiNiO 2families.The sample calcined at 9008C has the highest value for I (003)/I (104)(1.6984),while it is the least for the one calcined at 6008C (0.9938).The observed value on calcinations at 9008C is considerably higher than the corresponding value of 1.387reported for the same type of compound prepared by a method based on homogeneous precursors in ethanol [17].The intensity ratio value of I (003)/I (104)is even higher than the value of 1.5645for a layered compound reported by us earlier [30].The degree of cation mixing decreases with increasing calcinations temperature.The degree of cation mixing is much less than that in samples synthesized by the solid-state reaction as the reported I (003)/I (104)value is only 1.01[31].The values are comparable with the values of about 1.39reported in samples prepared with sol–gel method [32].Also the value is higher than 1.26reported with solid state technique [33].In addition,lower value for R =(I 006+I 102)/I 101corresponding to the sample calcined at 9008C (0.3187)over sample calcined at 8008C (0.3963)conﬁrmsFig.2.Powder X-ray diffraction pattern of MHC precursors (a)Ni 2(OH)2CO 3,(b)Mn 2(OH)2CO 3and (c)Co 2(OH)2CO 3.Fig. 3.Powder X-ray diffraction patterns of LiNi 1/3Mn 1/3Co 1/3O 2using MHC precursors,calcined at (a)6008C,(b)7008C,(c)8008C and (d)9008C for 12h.Table 1XRD structural parameters of LiNi 1/3Mn 1/3Co 1/3O 2materials calcined at 600–9008C.Calcined temperatureCrystallite size (nm)a (A˚)c (A˚)c /aV (A ˚)3I 003104R ¼I 006þI 1021016008C 43 2.857414.1279 4.944399.890.9938–7008C 62 2.848114.1504 4.968399.40 1.4462–8008C 89 2.846014.0859 4.949399.80 1.64800.39639008C1432.853514.20404.9777100.151.69840.3187P.Manikandan,P.Periasamy /Materials Research Bulletin 50(2014)132–140134again higher hexagonal ordering for the former eventually paving way for better electrochemical performance [34,35].These results indicate that the sample calcined at 9008C has the best hexagonal ordering in the preparation technique.3.1.2.Insights on (OH)À,(CO 3)2Àand (MO 6)FT-IR spectroscopy investigations were made for conﬁrming the hydroxy-carbonate group and also to study the local environments of cations in cubic close packed oxygen array of the LiNi 1/3Mn 1/3Co 1/3O 2lattices (Fig.4a–d).As seen in Fig.4a–c insert,the precursor material exhibits characteristic frequencies corresponding to stretching n (O–H)at 3400cm À1over lapped with stretching vibration n (O–H)of H 2O mode of vibration indicating that a single broad band for all hydroxy groups in the hydroxy-carbonates (Fig.4a–c inset)in good agreement with literature reports [18].The broad band observed around 1630cm À1indicate the presence bending d (O–H)vibration for adsorbed H 2O in the materials based on perfect agreement with literature reports [36].Broad band appearing around 620cm À1indicates bending d (O–H)vibration for hydroxy group presented in this MHC precursors [18].Also in this MHC precursors,carbonate group signatures revealed through 4modes of vibrations viz.,n 1(CO 32Àsymmetric stretching vibration)around 1050cm À1,n 2(CO 32Àout-of-plane deformation vibration)around 835cm À1,n 3(CO 32Àasymmetric stretching vibration)around 1400cm À1and n 4(CO 32Àin-plane deformation vibration)around 734cm À1are consistent with reports [18,37]on carbonate group FT-IR data (Fig.4a–c).Turning to the spectral data on cathode material (9008C)hydroxy,carbonate groups are totally absent due to the complete thermal decomposition of the precursor material.However we observed clear proof for the occurrence of metal oxygen M–O bond vibrations under different characteristic modes:asymmetric stretching n (MO 6)at 597cm À1[38]and bending vibrations d (O–M–O)at 543cm À1[39]thereby conﬁrming chemical integrity of the intended LiNi 1/3Mn 1/3Co 1/3O 2cathode material in Fig.4d.3.1.3.Surface examination using SEMTurning to explain the uniqueness of results of MHC method,marginal differences are observed in the morphologies between the MHC precursors and LiNi 1/3Mn 1/3Co 1/3O 2material (9008C)as depicted in Fig.5.Precursors in spongy form (Fig.5a–c)may facilitate homogeneous distribution with Li 2CO 3and also due to the generation of H 2O vapors,CO 2gases upon decomposition of the precursor permeating throughout the volume of the reactants can lead to achieving well dispersed LiNi 1/3Mn 1/3Co 1/3O 2particles as product (Fig.5d).It is well known that particle shape and size of cathode materials can affect the energy density in practical use and therefore controlling particle morphology is crucial [40].Synthe-sized LiNi 1/3Mn 1/3Co 1/3O 2materials display a highly crystalline particle with size in the range of 200nm (Fig.5d).The well shaped particle-agglomerated morphology is in agreement with literature reports [41].It can be seen that individual particles are of submicron size and some of them aggregate to form big particles.Such morphology is quite similar to that of the powder synthesized using low temperature solid state reaction [31]and inverse micro-emulsion route [41].3.1.4.XPS studiesXPS measurements carried out to determine the oxidation states of the transition metals in these materials since the oxidation states of Ni,Mn and Co are crucial for electrochemical performance.Fig.6shows the C 1s,Li 1s,Ni 2p,Mn 2p,Co 2p and O 1s XPS core level spectra for the prepared LiNi 1/3Mn 1/3Co 1/3O 2samples.The C 1s emission peak is observed around 284.96eV,which is used as the reference in the present XPS measurements.The binding energy (BE)of the Li 1s emission peak is positioned at 54.70eV and appears as a broad signal.The Ni 2p XPS spectrum in Fig.6c shows the characteristic broad satellite peak with the binding energy at 865.05eV due to the multiple splitting of energy level as usually observed in nickel oxide systems [42].The presence of the satellite peak has been observed byotherFig.4.FT-IR spectra of MHC precursors (a)Ni 2(OH)2CO 3,(b)Mn 2(OH)2CO 3,(c)Co 2(OH)2CO 3and (d)LiNi 1/3Mn 1/3Co 1/3O 2,calcined at 9008C for 12h.P.Manikandan,P.Periasamy /Materials Research Bulletin 50(2014)132–140135researchers and has been ascribed to the multiple splitting of the nickel oxide energy levels [43].The BE value of Mn 2p 3/2peak at 642.13eV is typical for Mn 4+oxidation state as depicted in Fig.6[4,44].The Co 2p XPS spectrum Fig.6e shows a well-deﬁned proﬁle with the 2p 3/2and 2p 1/2components at 780.02and 795.18eV.These values are very close to those for Co 3+(2p 3/2and 2p 1/2–780.1,794.9eV)in LiNi 1/3Co 1/3Mn 1/2O 2[45].O 1s spectra showed an interesting succession with the preparation method.The BE value of the O 1s component is located at 531.33eV,originating from Ni–O,Mn–O and Co–O in the synthesized material.The analysis of contents of metal ions from XPS also suggests that binding energies located at 859.14,642.13and 780.02eV are due to the presence of,Ni in +2,Mn in +4and Co in +3states,respectively.Obviously,XPS results revealed the molar ratios of metal elements in the prepared samples with good agreement based on their stoichiometric proportion.3.1.5.Paramagnetic center in LiNi 1/3Mn 1/3Co 1/3O 2cathode materialsEPR spectroscopy provides additional information on the local electronic structure of paramagnetic species having unpaired spin components in LiNi 1/3Mn 1/3Co 1/3O 2cathode materials.It turns out that of the constituents LiNi 1/3Mn 1/3Co 1/3O 2cathode Mn 4+having 3d 3electronic conﬁguration generates intense paramagnetic signal.Furthermore,it has been used for the determination of the cationic distribution in layered compounds [46]as the Co 3+ions adopt low-spin conﬁguration with S =0.The apparent g factor is insensitive to the Co content with a value g =2.033for all LiNi 1/3Mn 1/3Co 1/3O 2materials [47].The electrochemical performance of these electrode materials is strongly sensitive toward the synthesis procedure [48],which has been shown to affect the cationic distribution in oxides [49].LiNi 1/3Mn 1/3Co 1/3O 2contains two magnetic ions,Ni 2+and Mn 4+.Ni 2+is a non-Kramers ion since it has even number of d-electrons and its EPR spectra is very sensitive to the interactions with the environment.Hence the EPR signal of Ni 2+can also be detected only when this ion is present as a residual impurity [50].When the concentration of these ions is large,as in the present case,the distribution of crystal ﬁelds and strains on the different sites smear out the resonance spectra that are no longer are detected.This is the reason why Ni 2+does not contribute to the EPR spectrum.The paramagnetic resonance detected is attributed to the presence of Mn 4+ions that carry a half-integer spin (S =3/2)and are then EPR-active.The EPR spectra of the LiNi 1/3Mn 1/3Co 1/3O 2prepared by MHC method are shown in Fig.7.The EPR spectrum of sample consists of only one signal with a Lorentzian line shape and is indicative of the ordered nature of the sample [51].The position of the center of the signal is close to 3480G.We do not expect the contribution from Ni 3+to be large,because,in the present case,Ni 3+is in the low-spin state [46].Since there is no smearing of EPR resonance,Ni 3+is absent.The cationic distribution in the layer was determined using conventional (9.23GHz)EPRFig.5.SEM image of MHC precursors (a)Ni 2(OH)2CO 3,(b)Mn 2(OH)2CO 3,(c)Co 2(OH)2CO 3and (d)LiNi 1/3Mn 1/3Co 1/3O 2,calcined at 9008C for 12h.P.Manikandan,P.Periasamy /Materials Research Bulletin 50(2014)132–140136spectroscopy [52].EPR results support the proposed model for local cationic distribution in the layered LiNi 1/3Mn 1/3Co 1/3O 2compound.3.2.Electrochemical characterization3.2.1.Cyclic voltammetric investigationsCyclic voltammograms of Li vs .LiNi 1/3Mn 1/3Co 1/3O 2cell is cycled between 2.5and 4.6V at the scan rate of 0.1mV s À1as depicted in Fig.8.The anodic peaks occur at 4.0V and 4.58V which corresponds to the Ni 2+/Ni 4+and Co 3+/Co 4+redox processes.Which is in good agreement with literature reports [4,52].Cyclic voltammograms have already conﬁrmed that Mn 4+is providing stability to the host structure [53].The absence of any peak around 3V suggests that there is no evidence for the Mn 3+/Mn 4+redox process and conﬁrms absence of Mn 3+[54,55]in the samples.An anodic peak at 4.0V and a corresponding cathodic peak at 3.5V can be noted.These redox peaks are also signatures of hexagonal phase in such layered compounds and indicate perfect reversibility.The peaks could be assigned to the Ni 2+/Ni 4+couple.ThefaintlyFig.6.X-ray photoelectron spectroscopy for LiNi 1/3Mn 1/3Co 1/3O 2materials,calcined at 9008C for 12h (a)C 1s,(b)Li 1s,(c)Ni 2p,(d)Mn 2p,(e)Co 2p and (f)O1s.Fig.7.EPR spectrum of LiNi 1/3Mn 1/3Co 1/3O 2materials at room temperature and the position of the center of the signal is close to 3480G as expected for uncorrelated spins with the gyromagnetic factor g =2.033,for the microwave frequency (9.86GHz).P.Manikandan,P.Periasamy /Materials Research Bulletin 50(2014)132–140137detectable high voltage hump exhibited by LiNi 1/3Mn 1/3Co 1/3O 2is similar to observations noted earlier [56]and could be attributed to Co 3+/Co 4+redox couple of the samples.The cathodic peak around 3.5V corresponds to the voltage plateau of the discharge processes of the cell used.The broad anodic and cathodic peaks observed with this material are in contrast with the sharp peaks observed with LiNiO 2,which shows three distinct phase transitions [57].The absence of such multi-phase reactions can mean a lower level of structural degradation upon cycling in LiNi 1/3Mn 1/3Co 1/3O 2cathode materials.Earlier,both Li et al.[58]and Shaju et al.[4]have observed that two peaks appeared in Li vs .LiNi 1/3Mn 1/3Co 1/3O 2cell.One is broad and centered at about 3.75V,the other is smaller and centered at about 4.5V.Shaju et al.[4]have assigned the smaller peak at higher voltage to the Co 3+/Co 4+redox couple while Li et al.[58]suggested that it comes from the solid solution of Li–Ni–Co–Mn–O with Li 2MnO 3because of the presence of residual NiO in the sample.The appearance of only one couple of peaks in the investigated cell between 2.5and 4.6V means that no structural transitions exist from hexagonal to monoclinic,which is believed to limit the reversible charge–discharge capacity in the synthesized materials.The difference D w p between anodic peak potential w pa and cathodic peak potential w pc is a measure of the reversibility of the (de)intercalation process with low value of D w p =0.5V enhancing the reversibility of redox process.The shift observed in the anodic peak can be rationalized by considering active electrolyte decomposition,passive ﬁlm formation processes during ﬁrst anodic scan.Summing up of results of CV studies,barring the initial cycle anodic scan there is perfect overlap of CV traces in 2nd–4th scans indicating excellent reversibility for (de)intercala-tion of Li species [56].This indicates the excellent reversible (de)intercalation of Li ions in the synthesized material.Also the absence of obvious extra redox peak ensures chemical phase singularity of the synthesized cathode in corroboration with XRD studies.It must be noted that samples have been shown to exhibit marked fading compared to the 2nd and 3rd scan [56].However,the absence of such marked fading compared to the 2nd and 3rd scan in the synthesized sample using MHC precursors is a further evidence of phase purity.The CVs are reversible over several cycles,thereby suggesting good reversibility for the electrode processes.These results suggest that the cycle retention during consequent scans is far more superior comparable with other synthesis techniques.This behavior implies that structural degradation is not expected during the (de)intercalation of Li species in the synthesized material.3.2.2.Charge–discharge studiesCharge–discharge study constitutes the most important step in evaluating the performance of designed electrochemical system and feasibility for useful application.Accordingly,voltage vs .capacity performance of Li vs .LiNi 1/3Mn 1/3Co 1/3O 2cell is presented in the voltage range from 2.5to 4.6V @0.1C as shown in Fig.9(1M LiPF 6in 1:1EC–DMC solvents).There is only one major voltage plateau appearing in particular charge–discharge proﬁles.This is consistent with the results of CV experiments.The discharge characteristics have a certain gradient slope,allowing the cell to maintain good performance to the end of discharging and making it easy to monitor capacity.The discharge capacity decay upon cycling is small (on an average 1.2mAh g À1per cycle during the ﬁrst ﬁve cycle),which progressively reduces with cycling (on an average 0.3mAh g À1per cycle between cycle numbers 46and 50).Signiﬁcantly,the coulombic efﬁciency rises from 90%at 1st cycle to 99%at the 50th cycle.The LiNi 1/3Mn 1/3Co 1/3O 2electrode is delivered an initial discharge capacity of 175mAh g À1with an irreversible capacity loss of 20mAh g À1during the 1st discharge cycle.The charge and discharge capacities on the 50th cycle are 153and 152mAh g À1,respectively.The capacity retention at the 50th cycle was 87%.The galvanostatic cycling performance of Li vs .LiNi 1/3Mn 1/3Co 1/3O 2cell is depicted @0.1C and 0.2C up to50Fig.8.Cyclic voltammograms of Li vs .LiNi 1/3Mn 1/3Co 1/3O 2cell in the voltage range from 2.5to 4.6V at 0.1mV s À1(1M LiPF 6in 1:1EC–DMCsolvents).Fig.9.Voltage vs .capacity performance of Li vs .LiNi 1/3Mn 1/3Co 1/3O 2cell in the voltage range from 2.5to 4.6V @0.1C (1M LiPF 6in 1:1EC–DMCsolvents).Fig.10.Capacity vs .cycle number performance of Li vs .LiNi 1/3Mn 1/3Co 1/3O 2cell in the voltage range from 2.5to 4.6V @(a)0.1C and (b)0.2C.P.Manikandan,P.Periasamy /Materials Research Bulletin 50(2014)132–140138。

CeO2对锂离子电池正极材料LiMn1 3Co1 3Ni1 3O2的包覆改性

中国科学 E辑: 技术科学 2009年第39卷第4期: 809~813 《中国科学》杂志社SCIENCE IN CHINA PRESSCeO2对锂离子电池正极材料LiMn1/3Co1/3Ni1/3O2的包覆改性王萌, 吴锋, 苏岳锋*, 陈实北京理工大学化工与环境学院, 国家高技术绿色材料发展中心, 北京 100081* E-mail: suyuefeng@收稿日期: 2008-06-03; 接受日期: 2008-07-23国家重点基础研究发展计划(“973”计划)(批准号: 2002CB211800)和国家高技术研究发展计划(“863”计划)(批准号: 2006AA11A165, 2007AA11A104)资助项目摘要采用溶胶凝胶法对LiMn1/3Co1/3Ni1/3O2表面包覆了1.0 wt%的CeO2. 采用X射线衍射(X R D),扫描电镜(S E M),循环伏安(C V)和恒流充放电对包覆和未包覆的LiMn1/3Co1/3Ni1/3O2进行了结构表征与性能测试分析. 研究显示, CeO2并没有改变电极材料的晶体结构, 仅在电极材料表面形成均匀的包覆层. 包覆1.0 wt% CeO2后的材料的放电容量和循环性能均明显优于未包覆的材料. 在20 mA·g−1的电流密度下, 包覆1.0 wt% CeO2后的材料的放电容量为182.5 mAh·g−1而未包覆的材料仅为165.8 mAh·g−1. 包覆1.0 wt% CeO2后的材料在3.0 C下循环12周后的容量保持率达93.2%, 而未包覆的材料的容量保持率仅为86.6%. CV测试表明, CeO2包覆层可以有效的防止正极材料与电解液的直接接触, 抑制了材料结构的转变或抑制了与电解液的副反应, 从而提高了材料的电化学性能. 关键词LiMn1/3Co1/3Ni1/3O2 CeO2包覆锂离子电池自Ohzuku[1]首次发表关于LiMn1/3Co1/3Ni1/3O2材料的研究后, 这种材料引起了广大研究者的关注. 虽然与其他材料相比, LiMn1/3Co1/3Ni1/3O2具有较高的放电容量, 优良的倍率性能和热稳定性. 但是, 这种材料在较高截止电压和较大电流下的电化学性能还有待提高[2~4]. Kageyama等人[5]的研究表明, 材料在高截止电压和大电流下的容量的衰减主要是由于电极材料与电解液间的表面层不稳定所导致. 改善方法之一是在材料表面包覆一层氧化物膜, 可以提高材料的循环性能, 但关于其中的机理目前尚在研究中[6]. 在所有正极材料中, 关于LiMn1/3Co1/3Ni1/3O2的包覆研究较少. 一些研究表明, 在LiMn1/3Co1/3Ni1/3O2表面包覆C, ZrO2, TiO2, Al2O3, Al(OH)3[7~9]能改善材料的电化学性能. 近年来研究显示, 采用CeO2对锂离子电池正极材料LiCoO2, LiMn2O4和LiNi0.8Co0.2O2进行包覆改性, 可以明显改善材料的电化学性能[10~12]. 本文采用溶胶凝胶法在LiMn1/3Co1/3Ni1/3O2材料表面上包覆了一层CeO2. 通过一系列测试, 讨论了包覆层对材料结构和电化学性能的影响.1 实验1.1 CeO2包覆LiCo1/3Ni1/3Mn1/3O2正极材料的制备采用商用LiMn1/3Co1/3Ni1/3O2正极材料作为包覆对象, Ce(NO3)3·6H2O(分析纯)为包覆原料, 制备包覆量为1.0 wt%, 3.0 wt% CeO2的正极材料. 分别取计量比的Ce(NO3)3·6H2O(热分解温度为723 K[13])溶于去809王萌等: CeO2对锂离子电池正极材料LiMn1/3Co1/3Ni1/3O2的包覆改性离子水中, 搅拌溶解后, 加入一定量的柠檬酸溶解. 再取 3.0 g的LiMn1/3Co1/3Ni1/3O2加入混合溶液中, 搅拌70~80℃加热蒸发水分至凝胶状. 将凝胶在100℃下真空干燥6 h, 再在700℃下热处理5 h, 得到包覆量为1.0 wt%, 3.0 wt% CeO2的LiMn1/3Co1/3Ni1/3O2正极材料.1.2制备及电池组装将包覆后的材料与乙炔黑按一定比例混合均匀, 加入5.0 wt%聚偏氟乙烯溶液(三者的物质量比为85:10:5), 再次混合均匀, 涂于光滑平整的铝箔, 55℃下真空干燥12 h, 以8 MPa的压力压片, 制成电极以金属锂片为对电极, Celgard 2300为隔膜, 以 1.0 mol/L LiPF6/EC+DMC(体积比为1:1)为电解液, 在氩气手套箱内组装成CR2025扣式电池.1.3 材料分析及电池电化学性能测试材料的微观结构采用日本理学D Max-RD12 kW 旋转阳极衍射仪进行XRD分析, 测试条件: CuKα辐射, 40 kV管电压, 150 mA管电流, 扫速为8º·min-1; 材料形貌分别采用S-3500N日立公司扫描电镜和JEM2010透射电镜进行SEM和TEM分析.电池组装完毕后, 静置陈化12 h, 然后在室温下, 采用CT2001A Land电池测试仪进行恒流充放电测试. 进行电化学测试时, 电池以0.2 C充电后, 分别以0.2,1.0,2.0,3.0C放电, 充放电区间为2.8~4.5 V.2 结果与讨论2.1 包覆材料的X射线衍射分析(XRD)图1是未包覆和包覆1.0 wt% CeO2的LiCo1/3Ni1/3 Mn1/3O2的XRD谱图. 从图1看出, 两种样品均具有良好的α-NaFeO2层状结构, CeO2的包覆并没有对材料XRD谱图产生明显影响, 图中几乎观察不到CeO2的衍射峰, 这可能是由于CeO2的包覆量较小. 包覆后晶体的参数2θ和I(003)/I(004)比值几乎没有改变. 因此, 以上分析表明, 金属元素Ce没进入母体的晶格内, 并未改变材料的晶体结构, 仅在表面形成包覆层, 这在接下来的TEM测试中得到进一步证明.图1 LiCo1/3Ni1/3Mn1/3O2 XRD谱图(a)未包覆; (b)包覆1.0wt% CeO22.2 包覆材料的扫描电镜(SEM)和透射电镜(TEM)分析图2是未包覆和包覆1.0 wt% CeO2后的LiCo1/3Ni1/3 Mn1/3O2的扫描电镜图. 可以发现, 未包覆的材料表面是光滑的; 包覆1.0 wt% CeO2的材料表面有一些细小的颗粒, 且颗粒间变得更加紧密. 分析其原因是由于大部分CeO2在材料表面形成了包覆层, 增大了颗粒的体积, 从而减少了颗粒间的空隙. 图3是包覆1.0 wt%图2 LiCo1/3Ni1/3Mn1/3O2 SEM图(a) 未包覆; (b)包覆1.0 wt% CeO2810中国科学 E 辑: 技术科学 2009年第39卷第4期CeO 2的材料的透射电镜图, 可以发现CeO 2在LiCo 1/3Ni 1/3Mn 1/3O 2的表面形成一层包覆层. 为了确定CeO 2的包覆量, 又对包覆后的颗粒表面作微区EDX 成分分析, 见图4, 发现颗粒表面上的CeO 2的含量为0.96%.图3 包覆1.0 wt% CeO 2的LiCo 1/3Ni 1/3Mn 1/3O 2 TEM 图图4 包覆1.0 wt% CeO 2的LiCo 1/3Ni 1/3Mn 1/3O 2 EDX 图2.3 CeO 2包覆LiCo 1/3Ni 1/3Mn 1/3O 2的电化学性能图5是未包覆和分别包覆1.0 wt%, 3.0 wt% CeO 2的LiCo 1/3Ni 1/3Mn 1/3O 2在电流密度为20 mA ·g −1下的初始充放电曲线比较. 由图5可见, 与未包覆的材料相比, 包覆量为1.0 wt%的材料的充电平台有所降低, 放电平台明显提高, 容量也相应提高. 未包覆的LiCo 1/3 Ni 1/3Mn 1/3O 2的初始放电容量为165.8 mAh ·g −1, 充放电效率为85.5%. 而包覆1.0 wt% CeO 2的LiCo 1/3Ni 1/3Mn 1/3O 2的初始放电容量达182.5 mAh ·g −1, 充放电效率为85.7%, 放电容量和库伦效率高于未包覆的材料. 此结论与Ha 等人[10]的研究结果相似. 但当包覆量达3.0 wt%时, 材料的放电容量和库伦效率均有所降低, 分别为159.0 mAh ·g −1和82.6%. 这是由于Ce 4+不具有电化学活性, 过多的CeO 2包覆反而会降低材料的放电容量[11]. 可见, 1.0 wt% CeO 2包覆可以提高LiCo 1/3Ni 1/3 Mn 1/3O 2的放电容量和充放电效率.为了研究CeO 2包覆对材料LiCo 1/3Ni 1/3Mn 1/3O 2循环稳定性的影响, 图6对比了未包覆和包覆1.0 wt%CeO 2的LiCo 1/3Ni 1/3Mn 1/3O 2在不同放电倍率下的循环性能. 从图6中可以看出, 包覆后的材料在0.2 C 下的放电容量随着循环次数的增加略微有所提高, 循环12周后的容量与初始容量相比, 提高了1.1%. 这可能与包覆后的材料未完全活化有关. 当放电倍率为图5 LiCo 1/3Ni 1/3Mn 1/3O 2的首次充放电曲线(a) 未包覆CeO 2; (b) 包覆1.0 wt% CeO 2; (c) 包覆3.0 wt% CeO2图6 LiCo 1/3Ni 1/3Mn 1/3O 2分别在不同倍率下的循环性能(a) 未包覆; (b) 包覆1.0 wt% CeO 2811王萌等: CeO 2对锂离子电池正极材料LiMn 1/3Co 1/3Ni 1/3O 2的包覆改性1.0 C 时, 循环12周后包覆1.0 wt% CeO 2的材料的容量保持率为98.5%, 明显高于未包覆的材料的容量保持率(97.6%). 这种包覆后材料循环性能提高的现象随着电流密度的增加而更加显著. 当放电电流达到3.0 C , 包覆后的材料12周后的容量保持率为93.2%, 而未包覆的材料的容量保持率仅为86.6%. 由此可见, CeO 2的包覆能显著提高材料的循环性能. LiCo 1/3Ni 1/3Mn 1/3O 2容量衰减的原因是由于颗粒结构的转变和表面形态的变化所引起的电荷转移电阻的增大时[9]. Ha 等人[10~12]认为CeO 2包覆层的存在可以避免活性物质直接与电解液的接触, 提高界面稳定性, 抑制Mn 和Co 元素的溶解. 从而显著提高了材料的循环稳定性.由于锂离子电池的充电时间取决于锂离子在正极材料中的嵌入/脱出速率, 因此电池的倍率性能是评价电池性能的一个重要指标. 图7表示的是未包覆和包覆1.0 wt% CeO 2的LiCo 1/3Ni 1/3Mn 1/3O 2在不同放电倍率下的放电容量图. 可以看出, 当放电电流为0.2 C 时, 未包覆材料的放电容量为156.9 mAh ·g −1; 当电流密度增加到2.0 C 时, 容量减小到120.6 mAh ·g −1, 仅为电流密度0.2 C 时容量的76.9%. 而包覆1.0 wt% CeO 2的LiCo 1/3Ni 1/3Mn 1/3O 2在2.0 C 时的放电容量达136.5 mAh ·g −1, 是0.2 C 时容量的84.3%. 因此, 1.0 wt% CeO 2包覆能有效提高LiCo 1/3Ni 1/3Mn 1/3O 2在不同倍率下的放电容量. 包覆后的材料在大电流下性能的提高是由于包覆层促进了锂离子在CeO 2和LiCo 1/3Ni 1/3Mn 1/3O 2颗粒间的迁移.2.4 循环伏安测试图8是由未包覆和包覆的材料在室温下的循环图7 LiCo 1/3Ni 1/3Mn 1/3O 2 分别在电流密度为0.2, 1.0, 2.0和3.0 C 下的放电曲线比较(a) 未包覆; (b) 包覆1.0 wt% CeO 2图8 LiCo 1/3Ni 1/3Mn 1/3O 2的循环伏安谱图(a) 未包覆; (b) 包覆1.0 wt% CeO 2812中国科学E辑: 技术科学 2009年第39卷第4期伏安图. 扫描速度为0.1 mV·S−1, 电位范围为2.5~4.8 V,扫描3周. 两种样品的首次循环伏安图与接下来的第2, 3周不同. 对于未包覆的材料来说, 第一个阳极扫描有2个氧化峰, 一个主峰在3.64 V, 一个小峰在4.60 V; 还原峰分别在4.06和4.73 V. 在接下来的循环中, 氧化峰位置没有太大变化, 但是还原锋却一直向低电位移. 而对于包覆1.0 wt% CeO2的LiCo1/3Ni1/3 Mn1/3O2来说, 第1周的氧化峰在3.67和4.59 V, 还原峰在3.94和4.71 V, 极化现象明显小于未包覆的材料. 在第2周和第3周扫描中, 氧化峰和还原峰的位置没有太大变化. 另外, 主峰的强度降低程度较小, 从而表明容量的衰减得到有效抑制. 这表明CeO2的包覆能有效抑制循环过程中材料结构的转变或抑制与电解液的负反应, 从而使材料具有较好的电化学循环性能.3 总结材料表面包覆金属氧化物是一种提高材料电化学性能有效的方法. 本文采用溶胶凝胶法合成了包覆为1.0 wt% CeO2的LiMn1/3Co1/3Ni1/3O2. 电化学测试表明, 包覆后的材料循环性能优于未包覆的材料, 且随着电流密度的增大, 包覆后材料的循环性能提高更加明显. 经分析表明, 包覆层的存在可以有效防止活性物质跟电解液间的直接接触, 因此减小了活性物质跟电解液间的副反应, 提高了材料的电化学性能.参考文献1 Ohzuku T, Makimura Y. Layered lithium insertion material of LiCo1/3Ni1/3Mn1/3O2 for lithium-ion bateries.Chem Lett, 2001, 30(7):642—643[DOI]2 Yabuuchi N, Ohzuku T. Novel lithium insertion material of LiCo1/3Ni1/3Mn1/3O2 for advanced lithium-ion batteries.J Power Sources,2003, 119-121: 171—174[DOI]3 Hwang B J, Tsai Y W, Carlier D, et al. A combined computational/experimental study on LiNi1/3Co1/3Mn1/3O2. Chem Mater, 2003,15(19): 3676—3682[DOI]4 Li D C, Muta T, Zhang L Q, et al. Effect of synthesis method on the electrochemical performance of LiNi1/3Mn1/3Co1/3O2. J PowerSources, 2004, 132(1): 150—155[DOI]5 Kageyama M, Li D, Kobayakawa K, et al. Structural and electrochemical properties of LiNi1/3Mn1/3Co1/3O2−x F x prepared by solid statereaction. J Power Sources, 2006, 157(2): 494—500[DOI]6 Myung S T, Izumi K, Komaba S, et al. Functionality of oxide coating for Li[Li0.05Ni0.4Co0.15Mn0.4]O2 as positive electrode materials forlithium-ion secondary batteries. J Phys Chem C, 2007, 111(10): 4061—4067[DOI]7 Jang S B, Kang S H, Amine K, et al. Synthesis and improved electrochemical performance of Al(OH)3-coated Li[Ni1/3Mn1/3Co1/3]O2cathode materials at elevated temperature. Electrochimica Acta, 2005, 50(20): 4168—4173[DOI]8 Kim Y, Kim H S, Martin S W. Synthesis and electrochemical characteristics of Al2O3-coated LiNi1/3Co1/3Mn1/3O2 cathode materialsfor lithium ion batteries. Electrochimica Acta, 2006, 52(3): 1316—1322[DOI]9 Li D, Kato Y, Kobayakawa K, et al. Preparation and electrochemical characteristics of LiNi1/3Mn1/3Co1/3O2 coated with metal oxidescoating. J Power Sources, 2006, 160(2): 1342—1348[DOI]10 Ha H W, Jeong K H, Yun N J, et al. Effects of surface modification on the cycling stability of LiNi0.8Co0.2O2 electrodes by CeO2 coat-ing. Electrochimica Acta, 2005, 50(18): 3764—3769[DOI]11 Ha H W, Yun N J, Kim K. Improvement of electrochemical stability of LiMn2O4by CeO2coating for lithium-ion batteries.Electrochimica Acta, 2007, 52(9): 3236—3241[DOI]12 Ha H W, Yun N J, Kim M H, et al.Enhanced electrochemical and thermal stability of surface-modified LiCoO2 cathode by CeO2coating. Electrochimica Acta, 2006, 51(16): 3297—3302[DOI]13 Ying C, Zuoren N, Meiling Z, et al. Effects of Y2O3 and CeO2 on processing and characteristics of tungsten electrodes. Trans Non-ferrous Met Soc China, 1999, 9(2): 322—326813。

锂电池实验报告

篇一：锂离子电池的制备合成及性能测定实验报告实验二锂离子电池的制备合成及性能测定一.实验目的1.熟悉锂离子电极材料的制备方法，掌握锂离子电极材料工艺路线；2.掌握锂离子电池组装的基本方法；3.掌握锂离子电极材料相关性能的测定方法及原理；4.熟悉相关性能测试结果的分析。

二.实验原理锂离子电池的结构与工作原理：所谓锂离子电池是指分别用二个能可逆地嵌入与脱嵌锂离子的化合物作为正负极构成的二次电池。

人们将这种靠锂离子在正负极之间的转移来完成电池充放电工作的，独特机理的锂离子电池形象地称为“摇椅式电池”，俗称“锂电”。

以licoo2为例：⑴电池充电时，锂离子从正极中脱嵌，在负极中嵌入，放电时反之。

这就需要一个电极在组装前处于嵌锂状态，一般选择相对锂而言电位大于3v且在空气中稳定的嵌锂过渡金属氧化物做正极，如licoo2、linio2、limn2o4、lifepo4。

⑵为负极的材料则选择电位尽可能接近锂电位的可嵌入锂化合物，如各种碳材料包括天然石墨、合成石墨、碳纤维、中间相小球碳素等和金属氧化物，包括sno、sno2、锡复合氧化物snbxpyoz(x=0.4～0.6，y=0.6～0.4，z=(2＋3x＋5y)/2)等。

三.实验装置及材料1.实验装置：恒温槽，冰箱，搅拌器，管式电阻炉，真空干燥箱，鼓风干燥箱，铁夹，分液漏斗，研钵，烧杯，ph试纸，循环水真空泵，漏斗，抽滤瓶，滤纸，玻璃皿，温度计；2.实验材料：乙醇，醋酸镍，醋酸钴，醋酸锰，碳酸钠，去离子水，氨水，乙炔黑，pvdf，nmp，lioh；四.实验内容及步骤1.样品的制备及准备碳酸盐共沉淀法制备lini1/3co1/3mn1/3o2：分别称取摩尔比为1：1：1的醋酸镍(ni(ch3coo)2·4h2o)、醋酸钴 (co(ch3coo)2·4h2o)、醋酸锰 (mn(ch3coo)2·4h2o)，用去离子水溶解，溶液金属离子总浓度为1mol·l-1。

锂离子电池电极材料综述(精)

锂离子电池电极材料综述一、引言从上世世纪70年代起锂离子电池的研究至第一个可充式锂-二硫化钼电池于1979年研究成功，再到1991年SONY公司首次推出商品化锂离子电池产品算起，锂离子电池的发展至今已有30多年的时间。

锂离子电池是以Li+嵌入化合物为正负极的二次电池，实际上是一个锂离子浓差电池，正负极由两种不同的锂离子嵌入化合物组成。

与其它蓄电池相比，锂离子电池具有开路电压高、循环寿命长、能量密度高、安全性能高、自放电率低、无记忆效应、对环境友好等优点。

目前，锂离子电池已经被广泛应用于移动通讯、便携式笔记本电脑、摄像机、便携式仪器仪表等领域。

随着这些电器的高能化，轻量化，对锂离子电池的需求也越来越迫切。

同时被看作是未来电动汽车动力电源的重要候选者之一，并在空间技术、国防工业等大功率电源方面展示出广阔的应用前景二、工作原理锂离子电池通常正极采用锂化合物，负极采用锂－碳层间化合物。

电介质为锂盐的有机电解液。

充电时，Li+从正极脱嵌经过电解质嵌入负极，正极处于贫锂态，同时电子的补偿从外电路供给到碳负极，保证负极的电荷平衡。

放电时， Li+从负极脱嵌经过电解质嵌入正极，正极处于富锂态。

在正常充放电过程中， Li+在层状结构的碳材料和层状结构的金属氧化物的层间嵌入和脱出，一般只引起层面间距变化，不破坏晶体结构。

三、电极材料（1）电极材料的性能要求简单来说，电池主要包括正极、负极、电解质与隔膜四个部分。

正极材料通常是一种嵌入化合物，在外电场作用下化合物中的锂可逆的嵌入和嵌出；负极材料一般是层状结构的碳材料。

锂离子电池正极材料在改善电池容量方而起着非常重要的作用。

理想的正极材料应具备以下品质：点位高、比能量大、电池充放电速率快、充放电循环寿命长、密度（包括重量能量密度和体积能量密度）大、导电率高、无环境污染、成本低、易制成电极和低温性能好等。

选取负极材料的依据是锂在其中可逆容量、反应电位、扩散速率等。

理想的负极材料应具有电位低、比能量大、电池充放电速率快、充放电循环寿命长、密度（包括重量能量密度和体积能量密度）大、导电率高和低温性能好等优良品质。

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2006年第64卷化学学报 Vol. 64, 2006 第17期, 1854～1858 ACTA CHIMICA SINICA No. 17, 1854～1858

* E-mail: yuanht@nankai.edu.cn Received November 25, 2005; revised March 9, 2006; accepted May 15, 2006. 国家973项目基础研究基金(No. 2002 CB 211800)和天津市自然科学基金资助项目.

·研究简报· Li[Ni1/3Mn1/3Co1/3]O2掺杂Mo研究王丽琴焦丽芳袁华堂* 郭建李海霞

章明王永梅 (南开大学新能源材料化学研究所天津 300071)

摘要采用高温固相合成法制备了Li[Ni(1－x)/3Mn(1－x)/3Co(1－x)/3Mox]O2 (x＝0, 0.005, 0.01, 0.02). 对它们进行了XRD,

SEM, 循环伏安及充放电容量测试, 结果发现, 掺杂x＝0.01 Mo的样品具有较高的嵌锂容量和良好的循环稳定性, 在20 mA/g放电电流密度和2.3～4.6 V的电压范围内具有211.6 mAh/g的首次放电比容量, 循环50周后放电比容量仍能达到185.9 mAh/g, 容量损失为12.1%. 关键词锂电池; MoO3; 掺杂; 正极材料

The Study on Mo-Doped Li[Ni1/3Mn1/3Co1/3]O2

WANG, Li-Qin JIAO, Li-Fang YUAN, Hua-Tang* GUO, Jian LI, Hai-Xia ZHANG, Ming WANG, Yong-Mei (Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071)

Abstract Layered Li[Ni(1－x)/3Mn(1－x)/3Co(1－x)/3Mox]O2 materials (x＝0, 0.005, 0.01, 0.02) were prepared by

a solid-state pyrolysis method. Experiments of XRD, SEM, cyclic voltammetry and charge/discharge cycling were carried out. It indicated that when x＝0.01, the sample showed the highest first discharge capacity of 211.6 mAh•g－1 at a current density of 20 mA/g in the voltage range 2.3～4.6 V, and stable cycleability by possessing 185.9 mAh•g－1 after 50 cycles, and the capacity fade was only 12.1%. The Mo-doped samples exhibited higher discharge capacity and better cycleability at room temperature. Keywords Li battery; MoO3; doping; cathode material

近年来, 层状Li-Ni-Co-Mn-O系列化合物, 因其具有较好的电化学性能和稳定的结构, 受到人们的广泛关注[1～6]. 尤其是Li[Ni1/3Mn1/3Co1/3]O2正极材料, 具有较高的充放电容量和热稳定性, 倍受广大研究者的青睐, 以期能替代目前已商业化但价格昂贵且容量较低的LiCoO2正极材料[7～11]. 但是Li[Ni1/3Mn1/3Co1/3]O2正极材料也存在着明显的不足, 如合成制备批量产品存在困难, 样品高倍率放电性能较差, 振实密度低, 循环稳定性有待提高等. 基于此, 国内外研究者们对此进行了表面修饰和金属掺杂[11].如最近Jang等[12]用Al(OH)3对Li[Ni1/3Mn1/3Co1/3]O2进行表面修饰, 但首次循环容量没有提高, 只是略微提高了循环稳定性. 目前文献报道的掺杂元素主要有: Co, Cr, Al, Ni, Mg, Cu以及过量的Li等, 基本都集中在单元或二元掺杂, 仅从某一方面改善电极的性能, 但却以放电容量的大幅降低为代价[13].

目前, 对Li[Ni1/3Mn1/3Co1/3]O2正极材料进行MoO3

掺杂尚未见报道, 本文使用MoO3对其进行掺杂, 并研

究了不同的掺杂比例对材料性能和结构的影响. No. 17 王丽琴等：Li[Ni1/3Mn1/3Co1/3]O2掺杂Mo研究 1855

1 实验部分 1.1 Li[Ni(1－x)/3Mn(1－x)/3Co(1－x)/3Mox]O2正极材料的制备 Li[Ni(1－x)/3Mn(1－x)/3Co(1－x)/3Mox]O2 (x＝0, 0.005, 0.01, 0.02)正极材料采用固相合成法制备. 以Li(OAc)•2H2O, Mn(OAc)2•4H2O, Co(OAc)2•4H2O, Ni(OAc)2•4H2O, (nLi∶nNi∶nMn∶nCo＝1.1∶[(1－x)/3]∶[(1－x)/3]∶[(1－

x)/3], x＝0, 0.005, 0.01, 0.02)为原料, 混合研磨, 然后分别按照nMo/(nMn＋nNi＋nCo＋nMo)＝0, 0.005, 0.01, 0.02的

比例, 分别加入MoO3, 混合均匀并研磨. 把样品放入

120 ℃烘箱内48 h, 得到前驱物, 然后在800 ℃下焙烧24 h, 得到系列样品. 1.2 合成产物的结构表征样品的X衍射分析在D/max IIIA 型X射线衍射仪(日本理学)上进行, 测试条件: Cu Kα辐射, 石墨单色器, 50 kV 管压, 150 mA 管流; 日立S-3500型扫描电子显微镜得到SEM图. 1.3 合成产物的电化学性能以m样品∶m乙炔黑∶mPTFE＝85105 ∶∶的质量比制取

正极片, 负极采用金属锂, 集流体采用铜箔. 电解液为1 mol/L LiPF6 (VPC∶VEC∶VDMC＝103060). ∶∶电池组

装在充满氩气的无水无氧的手套箱内进行. 组装好的电池在Land 电池测试系统测试电池循环寿命, 充放电电流为0.1 C (20 mA/g), 充放电电压范围为2.3～4.6 V; 循环伏安测试在CHI660B型电化学工作站(上海华辰仪器公司)上进行.

2 结果与讨论 2.1 X射线衍射分析(XRD) 图1是Li[Ni(1－x)/3Mn(1－x)/3Co(1－x)/3Mox]O2 (x＝0,

0.005, 0.01, 0.02)样品的XRD谱图, 从图中可以看出, 样品属六方晶系, R-3m空间群, 具有α-NaFeO2层状结构. 所有的样品均具有尖锐的衍射峰, 几乎没有杂质峰, 尤其是x＝0.01时, 样品没有任何杂质峰, 这说明样品晶化程度较高. 图中显示样品(006)和(102)及(108)和(110)两种衍射峰明显分离, 表明层状结构的规整度高且材料中阳离子的无序度低. 此外, (006)/(102)和(018)/(110)峰分裂明显, 这与LiCoO2和 LiNiO2的层状

结构特征峰相符合[14～17], 说明样品应具有类似钴酸锂

的良好电化学活性. 以上分析表明, Mo元素的掺杂并没有改变原材料的层状结构, Mo元素很好地掺入到原材料里面. I003/I104的峰强度比分别是1.07, 1.56, 1.78, 1.61, 从文献中[18]可知, I003/I104的峰强度比值表明阳离子在晶格中的有序程度, 比值越高, 说明材料的电化学性能越

好. 由此可推知x＝0.01时材料应具有最佳的电化学活性, 在下面的电化学性能测试中将证实这一结论.

图1 Li[Ni(1－x)/3Mn(1－x)/3Co(1－x)/3Mox]O2 (x＝0, 0.005, 0.01,

0.02)样品的XRD谱图 Figure 1 XRD patterns of Li[Ni(1－x)/3Mn(1－x)/3Co(1－x)/3Mox]O2

(x＝0, 0.005, 0.01, 0.02) samples

表1列出了材料相关的晶胞参数. 掺杂Mo元素后, 晶胞参数a, c及晶胞体积有所变大, 这是因为掺杂的Mo6＋半径(0.062 nm)比Mn3＋ [r(Mn3＋)＝0.068 nm]小, 但是大于Co3＋ [r(Co3＋)＝0.0545 nm], Ni3＋ [r(Ni3＋)＝

0.056 nm]. 但c/a没有改变, 这说明材料的六方结构并没有因为Mo元素的掺杂而改变, 二维结构稳定, 层状结构好. 随着掺杂量的增加, 材料的体积进一步增大, 这将会降低材料的电化学性能.

表1 Li[Ni(1－x)/3Mn(1－x)/3Co(1－x)/3Mox]O2材料晶胞参数 Table1 Lattice parameters of Li[Ni(1－x)/3Mn(1－x)/3Co(1－x)/3 Mox

O2 materials

x a/nm c/nm c/a V/nm3 I003/

I104

Specific surface area/(m2•g−1)

0 0.284961.420454.98 0.10089 1.078.3 0.0050.286711.424434.97 0.10141 1.569.1 0.01 0.286841.425474.97 0.10157 1.7812.6 0.02 0.286711.426894.98 0.10158 1.618.5

2.2 扫描电镜(SEM) SEM分析表明, 所有样品粒径较小, 但也存在很大的不同. 未掺杂Mo的样品颗粒均匀但团聚现象严重, 使材料的比表面积相对较小. 掺杂量为0.5% Mo的材料有一部分颗粒粒径有所增大, 粒径大小不一, 且分散性不好. 掺杂1% Mo的材料颗粒均匀, 表面光滑, 分散性好. 掺杂2% Mo的材料颗粒团聚现象又加剧, 粒径大小不均. 这与比表面积测试结果一致(如表1). 可知, 当掺杂量小于1%时, 少量的Mo元素能减少Li[Ni1/3-