【作者】 路艳罗；

【导师】 段雪；

【作者基本信息】 北京化工大学 ， 应用化学， 2005， 博士

【摘要】 本论文针对锂离子电池正极材料层状锂锰氧化物结构不稳定的缺点,根据超分子层状结构材料的主客体可调控性特征,分别采用离子交换法、水滑石前体法、水热法等对其进行主体层板调控和客体调控,制备了一系列锂锰氧化物插层组装材料。采用XRD、HT-XRD、ICP、XPS、TG-DTA、TG-MS、EXAFS、TEM和SEM等手段对其进行了详细表征;通过恒流充放电循环、循环伏安等方法对其电化学性能进行了研究,并探讨了影响其结构稳定性和电化学性能的因素。 层状LiMnO₂具有单斜结构,C2/m空间群,SEM表明其具有棒状形貌。由于其结构不稳定,充放电过程中容易发生畸变,Mn由层板迁移至层间,占据Li⁺的嵌入位置,并阻塞其扩散通道,导致其电化学循环性能较差。 通过主体层板调控,制备了一系列O2结构Li[Mn_1-xM_x]O₂（M=Li、Cr、Mg、Al、Fe）和O3结构Li[Co_xNi_yMn_1-x-y]O₂。O2结构Li[Mn_1-xM_x]O₂具有不规则的六方层状形貌,掺杂元素基本能够均匀分布在层板上,充放电过程中保持主客体有序排列,抑制结构畸变,提高电化学循环性能,掺杂一定量的Al对电池的可逆容量影响不大,同时可以有效抑制容量的衰减,对提高电化学性能有利,作为锂离子电池正极材料性能较好。O3结构Li[Co_xNi_yMn_1-x-y]O₂材料具有α-NaFeO₂层状结构,层间距为0.47nm左右。随着Co含量增大嵌锂量增加,而Ni含量增大嵌锂量降低。Ni最容易在表面相稳定存在,Mn次之,而Co易于在体相稳定存在。过渡金属元素在层板上局域结构相似,M—O键长平均化。通过调控主体层板组成,可以提高层板稳定性,抑制过渡金属向层间迁移。当Co/Ni/Mn摩尔比为1/1/1时,主客体排列高度有序,材料首次放电比容量达到118.1mAh·g^-1,循环过程中容量衰减缓慢。随着Co含量增加,材料的可逆比容量有所提高。 对层状锰氧化物进行插层组装,得到M-MnO₂（M=Ba、Sr、ZrO）。与前驱体K_xMnO₂相比,M-MnO₂晶体结构没有变化。MnO₂层板存在Mn缺陷位,柱撑更多还原

【Abstract】 Doped and pillared layered lithium manganese oxides were synthesized by ion-exchange, layered double hydroxides （LDHs） precursor and hydrothermal method, respectively. These materials were characterized by XRD, HT-XRD, ICP, XPS, TG-DTA, TG-MS, EXAFS, TEM and SEM, and the electrochemical properties were studied by charge-discharge cycling and cyclic voltammogram methods. The factors which affect the structural stability and electrochemical properties were investigated.The material LiMnO₂ has a layered structure with the monoclinic space group C2/m. SEM micrograph shows that LiMnO₂ possesses a needle-like morphology. The structure transforms to spinel during charge-discharge cycle, as a result the electrochemical behavior were not satisfying.A series of layered O₂ structure Li[Mn（1-x）M_x]O₂ （M=Li, Cr, Mg, Al, Fe） and 03 strucuture Li[Co_xNi_yMn_1-x-y]O₂ were obtained by varying the composition of the host layers. 02 structure materials Li[Mn_1-xM_x]O₂ have an irregular hexagonal morphology. The XRD patterns can be indexed as a structure hexagonal space group P3ml. The electrochemical properties were influenced by the doped elements. Manganese oxides substituted by Al are prime candidates for the cathode of lithium ion batteries, for the charge-discharge capacity and cycling life were improved simultaneously. Layered 03structure materials Li[Co^NiyMn\.x-y]O2 have the a-NaFeO2 structure. It has been found that the content of lithium was improved with the increase of Co content and decrease of Ni content. The local environment of the transitional metals are rather similar in Li[CoxMni..v]O2. The Co/Ni/Mn molar ratio has a remarkable influence on the electrochemical properties. Among these materials, Li[Coi/3Nii/3Mni/3]O2 possesses high reversible capacity （118.1 mAh-g^’）, and the most stable cycling life. Moreover, the capacity increases as more Co doped in the material.Supramolecular pillared oxides M-MnC?2 （M=BaN Sr^ ZrO） were prepared by intercalating the guest cations into MnO2 host matrix. The materials M-MnO2 have the same structure as the precursor KJvlnO2. For ZrO-MnO2, EXAFS indicates that Zr atom locates between the MnC>2 layers forming a stable structure. The strong interaction between M2+ ions and MnC?2 layers may restrain structure distortion in charge-discharge cycling, and the cycling properties were improved distinctly. Among these pillared materials, （ZrO）nMnO2 has an advanced capacity and long life. Mn^V2Os?H2O containing double sheets of V2O5 layers has been synthesized by a new method - oxidation of VOSO4 with layered MnC>2. XPS indicates that the oxidation state of vanadium and manganese are +5 and +4, respectively. The molar ratio of Mn/V near surface was almost the same as that in the bulk. The electrochemical properties were improved with the decrease of the Mn content. Mno.i4V205.27"l-53H20 has a specific capacity of 200 mAhg ’ between 2.0 and 4.0 V, with the discharge capacity at the 18th cycle remaining as high as 208.3 mAhg"1. It is therefore a potential practical candidate as the cathode material for rechargeable lithium batteries.Four lithium manganese oxide phases have been synthesized for the first time by mild hydrothermal reactions of layered manganese oxide （8-KxMnO2） with different lithium compounds. The four materials obtained are rock salt structure I^MnCb, hollandite structure a-MnC?2, spinel structure LiM^C^, and birnessite structure LiJvlnCh. Of the four lithium manganese oxides, birnessite structure LiJvlnCh demonstrated the most stable cycling behavior with high coulombic efficiency. Its reversible capacity reaches 162.8 mAhg^’, indicating that it is a viable cathode material更多还原