尖晶石型Li_4Mn_5O_(12)正极材料的合成

以LiOH·H2O和MnCO3为原料,采用两段固相法制备了亚微米级大小的尖晶石型Li4Mn5O12正极材料.通过充放电测试、X射线衍射、扫描电镜等现代实验方法研究了合成温度对材料的电化学性能的影响.研究表明:500℃烧结制备的样品表现出最佳的电化学性能.在0.2 C倍率电流条件下,第1循环和第30循环的放电容量分别为143.5 mAh·g-1和143.9 mAh·g-1;在2 C倍率电流下,样品的第1循环和第50循环的放电容量分别为109.2 mAh·g-1和126.1 mAh·g-1.     

锂离子电池高电压正极材料LiNi_（0.5）Mn_（1.5）O_4的合成与性能

采用镍锰氢氧化物和碳酸锂为原料,在高温下合成LiNi0.5Mn1.5O4正极材料。系统地研究了不同的退火工艺对LiNi0.5Mn1.5O4结构与电化学性能的影响。研究发现,合成的样品都具有标准的尖晶石结构和规则的八面体外形。电化学测试结果表明,在700℃下退火12h得到的样品电化学性能最佳。首次放电容量达到141mAh/g,40次循环后容量保持率为99.2%,5C放电时容量仍然达到122mAh/g。     

锂离子电池正极材料LiNi_(0.8)Co_(0.2)的掺杂改性研究

采用共沉淀法和成LiNi0.8Co0.2O2,探讨影响锂离子电池正极材料LiNi0.8Co0.2O2电化学性能及结构的因素.为了提高材料的电化学性能,对材料进行了掺杂改性的研究,分别掺入Al、Mn、Mg和Fe四种元素.通过在2.8～4.2V范围内的充放电测试分析,掺入Mn的正极材料LiNi0.8Co0.1Mn0.1O2具有最高的放电比容量以及最低的容量损失,其首次放电容量为168.84 mAh/g,十次循环后的放电容量为166.9 mAh/g.     

Li_(1.52)Ni_(0.30)Mn_(0.78)Co_(0.06)O_(2.00)正极材料的电化学性能

以Li2CO3、Ni(CH3COO)2·2H2O、Mn(CH3COO)2·4H2O、Co(CH3COO)2·4H2O和Na2CO3为原料,通过直接沉淀法制备了具有α-NaFeO2型层状结构的微米Li1.52Ni0.30Mn0.78Co0.06O2.00正极材料.通过X射线衍射、扫描电镜、恒电流充放电、交流阻抗、循环伏安法等方法研究了样品的结构和电化学性能.结果表明:充电截止电压4.6V时样品的充放电性能最佳.在电流200 mAh·g-1时,该样品第1循环和第40循环的放电容量分别为150.2 mAh·g-1、155.0 mAh·g-1;样品的电化学反应受电荷传递阻抗和和Li+扩散的共同控制.     

共沉淀法制备LaF_3表面修饰LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2及性能研究

以LiNi1/3Co1/3Mn1/3O2为正极材料,采用共沉淀合成方法制备LaF3表面修饰LiNi1/3Co1/3Mn1/3O2正极材料,利用X射线衍射(XRD)、扫描电镜(SEM)和电化学测试等方法对合成材料的结构、形貌以及电化学性能进行表征。结果表明:经过LaF3表面修饰的LiNi1/3Co1/3Mn1/3O2材料保持了LiNi1/3Co1/3Mn1/3O2层状结构,其中LaF3表面修饰量为0.59%时,在电压为2.75～4.50V范围内,以0.3mA/cm2电流密度下经恒电流充放电测试,其首次放电比容量为172.7mAh/g,经过50周充放电循环后放电比容量为163.5mAh/g,表现出较高的初始放电比容量和良好的抗过充电性能。     

尖晶石锂锰氧化物的电化学性能研究

以LiOH.H2O和Mn(CH3COO)2.2H2O为原料,用微波烧结和固相烧结相结合合成了尖晶石型Li4Mn5O12正极材料.XRD分析、DTA分析、循环伏安和充放电实验表明,先用300W的微波烧结30min,然后再用380℃后处理48 h可获得具有纯Li4Mn5O12物相的样品.该样品的初始放电容量为176mAh/g,40循环的放电容量为123 mAh/g.     

LiNi0.5Mn1.5O4正极材料的γ-Al2O3包覆及其性能

以氢氧化铝溶胶为前驱体在LiNi0.5 Mn1.5 O4正极材料表面制备尖晶石结构γ-Al2 O3包覆层,借助XRD、SEM、TEM及电化学方法对电极材料的主要性能进行了研究。结果表明：LiNi0.5 Mn1.5 O4表面γ-Al2 O3包覆层形成条件为600℃下煅烧0.5 h,较佳包覆量约为3％（摩尔比）;γ-Al2 O3包覆层形貌完整,厚度约为5～10 nm,（311）晶面间距约0.24 nm;γ-Al2O3包覆的LiNi0.5Mn1.5O4正极材料30周充放电循环（0.2 C）后的比容量为112.1 mAh／g,4 C倍率下的比容量为82.0 mAh／g,容量保持率较基体分别提高了约10％和17.2％。因此,γ-Al2 O3包覆层减小了LiNi0.5 Mn1.5 O4与电解液的接触,有效抑制了基体与电解液之间的副反应,其电化学反应可逆性、循环稳定性及倍率性能得到了提高,有望用作动力锂离子电池正极材料。     

LiCoO_2包覆LiNi_(0.78)Co_(0.2)Zn_(0.02)O_2锂离子电池正极材料

采用共沉淀法制备了LiCoO2包覆LiNi0.78Co0.2Zn0.02O2锂离子电池正极材料,对材料进行XRD、SEM的分析结果表明,该材料具类α-NaFeO2(R-3 m)结构,而且微观颗粒大小均匀.电化学测试结果表明,用LiCoO2进行表面包覆后比未包覆材料的初期放电比容量略有降低,但是材料的循环性能明显提高.包覆材料的首次恒流(60 mA.cm2,3.0~4.2 V,vs.Li /Li)充、放电比容量分别为243.63 mAh.g-1和204.58 mAh.g-1,首次循环效率为83.97%,200次循环后比容量仍为197.06 mAh.g-1,不可逆容量损失仅为7.52 mAh.g-1,容量保持率达到96.0%以上,具有很好的循环性能.     

LiCoO2包覆LiNi0.78Co0.02Zn0.02O2锂离子电池正极材料

采用共沉淀法制备了LiCoO2包覆LiNi0.78Co0.2Zn0.02O2锂离子电池正极材料,对材料进行XRD、SEM的分析结果表明,该材料具类α-NaFeO2(R-3 m)结构,而且微观颗粒大小均匀.电化学测试结果表明,用LiCoO2进行表面包覆后比未包覆材料的初期放电比容量略有降低,但是材料的循环性能明显提高.包覆材料的首次恒流(60 mA·cm2,3.0～4.2 V,vs.Li /Li)充、放电比容量分别为243.63 mAh·g-1和204.58 mAh·g-1,首次循环效率为83.97%,200次循环后比容量仍为197.06mAh·g-1,不可逆容量损失仅为7.52 mAh·g-1,容量保持率达到96.0%以上,具有很好的循环性能.     

反应温度对LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2组织结构及电化学性能的影响

在共沉淀法合成Ni0.4Co0.2Mn0.4(OH)2的基础上制备了锂离子电池正极材料LiNi0.4Co0.2Mn0.4O2.通过XRD,SEM和电化学测试对不同反应温度下LiNi0.4Co0.2Mn0.4O2正极材料的结构、形貌及电化学性能进行了测试和表征.测试表明随着反应温度的提高,c/a和I(003)/I(104)值也在增加,表明温度的升高可以减少锂镍离子的混排,使层状结构更加完整,进而电化学性能也更优异.900℃下反应所得到的样品,以0.2C放电,其首次放电容量为148.3mAh/g,库伦效率最高可达9.8%.循环40个周期后容量保持率为93.9%,具有较好的电化学性能.     

Synthesis of LiNi0.8Co0.2O2 in Air Atmosphere and its Characterization

The commercialized lithium secondary cells need the electrode materials with high speeific capacity, lower pollution and lower price. Certain industrial materials ( NiSO_4, CoSO_4 , LiOH·H_2O)were used to synthesize Ni_(0.8)Co_(0.2)(OH)_2 of a stratified structure, when various synthesis conditions such as pH, reaction temperature et al. were controlled strictly. After LiOH·H_2O and Ni_(0.8)Co_(0.2) (OH)_2were calcinated in air atmosphere, LiNi_(0.8)Co_(0.2)O_2 positive electrode materials with good layered crystal structure was obtained. Tests showed that the optimal calcination temperature in air atmosphere was about at 720℃ and LiNi_(0.8)Co_(0.2)O_2 synthesized in the above conditions had good electrochemical properties and a low cost. The first specific: discharge capacity of the material was 186 mAh/g, and the specific discharge capacity was 175 mAh/g after 50 cycles at a 0.2C rate, between 3.0～4.2 V with a discharge deterioration ratio of 0.22% each cycle. Tests showed that LiNi_(0.8)Co_(0.2)O     

尖晶石型锰酸锂制备及其电化学性能

锰酸锂被认为是取代商品锂离子电池正极材料的LiCoO2候选材料.以二氧化锰、醋酸锰及氢氧化锂为原料,蒸馏水为分散剂,在空气气氛下进行分段烧结,控制烧结温度和时间,制备了锂离子电池正极材料锰酸锂.用X射线衍射仪,电子扫描电镜对产物的结构特征、微观表面形貌和恒流充放电性能进行了表征.结果表明:所制得正极材料为尖晶石型锰酸锂,结晶度高,无杂质相,材料颗粒的粒径均匀,首次放电比容量为117.3 mAh/g(0.5 mA/cm2,2.8~4.4 V,vs.Li+/Li);50次循环后,放电比容量为107.9 mAh/g,不可逆容量损失为9.4 mAh/g,比容量保持率为92.0%.得到了很好的综合电化学性能.     

Effects of different iron sources on the performance of LiFePO_4/C composite cathode materials

Olivine LiFePO4/C composite cathode materials were synthesized by a solid state method in N2 + 5vo1% H2 atmosphere.The effects of different iron sources,including Fe(OH)3 and FeC2O4·2H2O,on the performance of as-synthesized cathode materials were investigated and the causes were also analyzed.The crystal structure,the morphology,and the electrochemical performance of the prepared samples were characterized by X-ray diffractometry (XRD),scanning electron microscopy (SEM),laser particle-size distribution measurement,and other electrochemical techniques.The results demonstrate that the LiFePO4/C materials obtained from Fe(OH)3 at 800℃ and FeCeO4·2H2O at 700℃ have the similar electrochemical performances.The initial discharge capacities of LiFePO4/C synthesized from Fe(OH)3 and FeC2O4·2H2O are 134.5 mAh·g-1 and 137.4 mAh.g-1 at the C/5 rate,respectively.However,the tap density of the LiFePO4/C materials obtained from Fe(OH)3 are higher,which is significant for the improvement of the capacity of the battery.     

Al^（3＋）掺杂α-Ni（OH）2复合CNTs电极材料的高温性能

采用化学共沉淀法制备Al^（3＋）掺杂α-Ni（OH）2粉体,将其复合碳纳米管（CNTs）制成镍电极材料并研究其在高温下的电化学性能。结果表明：以混合CNTs（w=0.5%）的Al掺杂α-Ni（OH）2样品材料为活性物质制成镍电极,由其组装的MH-Ni电池在65℃高温环境下,采用0.2和1.0 C充放电制度的放电比容量分别为391.1和366.4 mAh·g^-1;经40次充放电循环,放电比容量衰减率分别为6.8%、11.98%,表现出较好的高温环境电化学性能。     

锂离子电池正极材料LiNi0.8Co0.2O2的合成及性能研究

以硝酸盐和淀粉为原料,采用溶胶-凝胶方法合成LiNi_0.8Co_0.2O₂锂离子电池正极材料,利用X射线衍射（XRD）、扫描电镜(SEM)和电化学测试等方法对合成材料的结构、形貌以及电化学性能进行表征。结果表明,合成材料为单一晶相的α-NaFeO₂型层状结构,颗粒小且分布均匀,在电压为2.75~4.50 V (vs. Li+/Li) 范围内,以0.2 mA/cm2电流密度下经恒电流充放电测试,其首次放电比容量为183.1 mAh/g,经过50周充放电循环后放电比容量为171.3 mAh/g,表现出较大的初始放电比容量和良好的循环性能。     

纳米絮状Li_4Ti_5O_(12)的水热法合成及性能的研究

为解决高温烧结制备的锂离子电池负极材料Li4Ti5O12易团聚、形貌差的问题,采用水热低温烧结法,以钛酸丁酯、氢氧化锂分别为钛源和锂源,异丙醇为溶剂,制备纯相Li4Ti5O12。用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和比表面测试仪对样品进行表征,采用恒流充放电法对钛酸锂进行电化学性能评价。结果表明,在400℃低温煅烧后可得到单一纯相尖晶石型Li4Ti5O12,所制备样品为具有大比表面积的纳米絮状粉体,表现出良好的电化学性能,在常温条件下,以0.1C倍率进行充放电,首次放电容量达到155.7mA·h/g,经50次循环后容量仍保持约143mA·h/g,容量保持率达到91.8%。     

锂离子电池正极材料锰掺杂LiNi_（0.8）Co_（0.2）O_2的合成及其性能

采用共沉淀法对LiNi0.8Co0.2O2进行Mn元素的掺杂改性,考察不同掺杂量对LiNi0.8Co0.2O2材料的结构和电化学性能的影响,并对LiNi0.8-xMnxCo0.2O2（0≤x≤3）进行X射线衍射和扫描电镜分析以及循环伏安测试。充放电测试结果显示：未掺杂Mn的LiNi0.8Co0.2O2材料的初始放电比容量为164.32 mAh/g,50次循环以后为161.86 mAh/g。经掺Mn后LiNi0.8Co0.2O2材料的初始放电比容量为163.13 mAh/g,并且50次循环以后还能保持在162.33 mAh/g左右,效率达到99%以上。研究表明,掺Mn后的LiNi0.8Co0.2O2材料具有更加稳定的层状结构,并且其循环性能得到很大程度的提高。     

Synthesis and electrochemical characterization of LiNi0.78Co2Al0.02O2 cathode material in a novel co-precipitation method

LiNi0.78Co2Al0.02O2 cathode materials were prepared with a novel co-precipitation method followed by heat-treating. The properties of the materials were characterized. XRD patterns showed that no secondary phase appeared and the hexagonal lattice parameter c of LiNi0.78Co2Al0.02O2 was larger than that of LiNi0.8Co0.2O2. The SEM images indicated that the powders of the material were submicron size. The results of the ICP-AES analysis proved that elemental compositions of the material were similar to those of the targeted one. Cyclic voltammetry (3.0-4.2 V) illustrated that the new material had good lithium-ion intercalation/de-intercalation performance. The results of galvanostatic cycling showed that the initial specific discharge capacity of the prepared ma-terial was 181.4 mAh/g, and the specific discharge capacity was 177.3 mAh/g after 100 cycles (0.2C,3.0-4.2 V, vs. Li /Li) with the capacity retention ratio of 97.7%.