锂离子电池正极材料LiNi_(0.8)Co_(0.2)O_2的制备与表征

用2次干燥化学共沉淀法制得高密度前驱体Ni0.8Co0.2(OH)2,使之与LiOH.H2O混合经过2个恒温阶段烧结(600℃恒温6 h、850℃恒温24 h)得到LiNi0.8Co0.2O2材料,探讨了镍源、Li/(Ni+Co)摩尔比、合成温度、合成时间等因素对产品的影响,从而优化了LiNi0.8Co0.2O2的合成工艺.所得非球形LiNi0.8Co0.2O2粉末振实密度高达2.94 g/cm3,X射线衍射分析表明该材料具有规整的层状NaFeO2结构,充放电测试表明材料具有良好的电化学性能.     

熔融盐法合成球形锂离子电池正极材料LiNi_(0.8)Co_(0.2)O_2

采用热分析法对不同组成的LiOH-LiNO3二元体系进行研究,绘制了具有最低共熔点的该二元体系T-x相图,该体系的最低共熔点为175.7℃.利用低共熔混合物LiNO3-LiOH为锂盐,与前驱体球形Ni0.8Co0.2(OH)2混合烧结制备出了球形锂离子电池正极材料LiNi0.8Co0.2O2.探讨了Li/(Ni+Co)摩尔比、合成温度、合成时间等因素对产品的影响.X射线衍射分析表明合成的材料具有规整的层状NaFeO2结构,SEM表明所得材料为球形.充放电测试表明在3.0~4.3的电压范围内,首次放电比容量可达170 mAh.g-1,充放电效率为95.5%.结果表明采用该工艺可以制备出电化学性能良好的LiNi0.8Co0.2O2正极材料.     

锂离子电池正极材料LiNi_(0.8)Co_(0.15)Al_(0.05)O_2的制备及性能研究

以Ni SO4·6H2O、Co SO4·7H2O和Al2(SO4)3·18H2O为原料,氨水为络合剂,在碱性条件下通过液相共沉淀法制备了前驱体Ni0.8Co0.15Al0.05(OH)2。将前驱体与Li OH·H2O混合均匀后在氧气氛围下煅烧得到锂离子正极材料Li Ni0.8Co0.15Al0.05O2;通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和电化学性能测试仪对样品性能进行了表征。研究结果表明,在2.8~4.3V电压范围内,在0.1C、0.2C和1C的充放电倍率下,首次放电比容量分别为186.6m Ah·g-1、184.8m Ah·g-1和176.7m Ah·g-1;在0.2C倍率下循环10次后,放电比容量为177.6m Ah·g-1,容量保持率为96.1%;在1C倍率下循环40次后,放电比容量为150.1m Ah·g-1,容量保持率为85.0%。     

α-Ni_(0.8)Co_xAl_(0.2-x)(OH)_(2.2-0.5y)(CO_3)_y·zH_2O配位沉淀法合成和电化学性能

为了改善铝代α-Ni(OH)2的电化学性能,用共沉淀法合成了含不同配比Al3+、Co3+的Ni(OH)2.样品经CT、XRD、FTIR、SEM等表征为α-Ni0.8CoxAl0.2-x(OH)2.2-0.5y(CO3)y.zH2O.恒电流充放电和微电极CV等测试表明:Co3+的摩尔分数在0.02~0.04时,合成的样品作为氢镍电池的正极材料,在放电比容量、电极可逆性和稳定性等方面均得到改善.Co3+发挥了稳定α相结构、增强导电性等多重作用.     

Preparation and performance of LiNi_(0.8)Co_(0.2)O_2 cathode material based on Co-substituted α–Ni(OH)_2 precursor

Co-substituted α-Ni(OH)2 was synthesized by a novel microwave homogeneous precipitation method in the presence of urea. LiNi0.8Co0.2O2 cathode material was synthesized by calcining Co-substituted α-Ni(OH)2 precursor and LiOH·H2O at 900℃ for 10 h in flowing oxygen. XRD, FTIR, FESEM and electro- chemical tests were used to study the physical and the electrochemical performances of the materials. The results show that the prepared LiNi0.8Co0.2O2 compound has a good layered hexagonal structure. Moreover, the LiNi0.8Co0.2O2 cathode material demonstrates stable cyclability with a high initial specific discharge capacity of 183.9 mAh/g. The good electrochemical performance could be attributed to the uniform distribution of Ni2 and Co2 ions in the crystal structure and a minimal cation mixing in LiNi0.8Co0.2O2 host structure.     

共沉淀法合成Ni_(1/3)Co_(1/3)Mn_(1/3)(OH)_2的热力学分析

对Me2+(Me=Ni,Co,Mn)-NH3-OH--H2O共沉淀反应体系进行了热力学分析,采用共沉淀法合成了LiNi1/3Co1/3Mn1/3O2正极材料前驱体Ni1/3Co1/3Mn1/3(OH)2,研究了pH值和氨水浓度[N]对前驱体振实密度的影响.热力学分析表明:以氢氧化钠为沉淀剂、氨水为络合剂,采用共沉淀法合成前驱体的最佳pH值为11,最佳[N]为0.1～0.5mol/L;在此条件下,金属阳离子Ni2+、Co2+和Mn2+的损失最小,分别小于1×10-3、1×10-3和1×10-6mol/L.在pH=11、[N]=0.24mol/L条件下,所合成的前驱体中Ni、Co、Mn的摩尔比为0.324∶0.349∶0.327,与理论设计值1∶1∶1非常接近,其振实密度高达1.32g/cm3.     

片状Co(OH)2的制备及其电化学性能研究

采用柠檬酸前驱体法制备了电活性物质Co(OH)2.首先用硝酸钴与柠檬酸通过溶胶凝胶法制得凝胶体,再在250 ℃下热处理得到红褐色的前驱体,最后将前驱体与KOH溶液反应制得目标产物.用红外光谱(FT-IR)对前驱体的组成进行了分析,用X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)表征了产物的结构和形貌,用循环伏安和恒电流充放电等测试方法对其电化学性能进行了研究.结果表明,具有六方晶相的片状Co(OH)2表现出优良的电化学性能,有望成为超级电容器的电极材料.     

锰含量对LiNi0.85-xCo0.15MnxO2结构及形貌的影响

采用共沉淀法先合成出氢氧化物前驱体Ni0.85-xCo0.15Mnx(OH)2,其中X=0、0.1、0.2和0.4,前驱体与Li2CO3在空气气氛中固相烧结制得正极材料LiNi0.85-xCo0.15MnxO2。用XRD、SEM研究了锰含量对材料结构和形貌的影响。研究发现,LiNi0.85Co0.15O2的X射线衍射图中存在微量第二相,而锰掺杂有利于减小反应过程中锂离子损失和镍离子占据锂位,容易形成有序层状结构材料。随着Mn离子替代Ni离子量的增加,晶胞参数a减小,晶胞参数c、c/a及I003/I104值增大。SEM结果表明前驱体和最终产物形貌均随锰含量增加颗粒均匀性增强,粒子尺寸变小,粒径分布变窄。     

Ni(OH)2的表面修饰对电极性能的影响

采用化学镀的方法在Ni(OH)2粉末表面微包覆一层Co,Ni膜,以此为活性材料 出了与物理掺杂钴方式相比性能更好的Ni(OH)2电极,找出了一种适用于碱性条件下的化学镀活化液。     

La_(0.8)Cu_(0.2)Ni_(1-x)M_xO_3钙钛矿氧化物的制备及催化性能研究

采用柠檬酸络合法制备了一系列La0.8Cu0.2Ni1-xMxO3(M分别为Mn、Fe和Co)钙钛矿复合氧化物.催化性能的测定结果表明:750℃焙烧制得的催化剂La0.8Cu0.2Ni0.8Mn0.2O3显示出良好的三效催化性能,能使贫燃条件下CO、NO和C3H6的起燃温度较低,分别为165℃、295℃和302℃,当温度高于400℃时完全转化.扫描电子显微镜(SEM)和X射线衍射(XRD)的测试分析结果表明:La0.8Cu0.2Ni0.8Mn0.2O3因具有良好的钙钛矿晶型结构,且为纳米级晶体,所以三效催化性能良好.     

Comparative study of LiNiO2, LiNi0.8Co0.2O2 and LiNi0.75Al0.25O2 for lithium-ion batteries

The comparative study of LiNi0.8Co0.2O2 and LiNi0.75Al0.25O2 was carried out by X-ray diffraction (XRD) and electrochemical methods. The results show that Co and Al doping suppress the phase transition during charge-discharge. The experiments indicate that LiNi0.75Al0.25O2 has the better cycle-ability and over-charge resistance comparing with LiNi0.8Co0.2O2. The interfacial behavior was studied by use of electrochemical impedance spectroscopy (EIS). The results show that LiNi0.75Al0.25O2 has a slightly larger polarization character than LiNi0.8Co0.2O2.     

Ni/Co比例对LiCoxNi1-xO2电化学性能的影响

采用固相反应法合成了一系列LiCoxNi1-xO2(0≤x≤1)材料,用XRD和电化学实验方法研究了Co3+取代Ni3+对LiNiO2材料电化学性能的影响.结果表明,当Ni/Co比例为8:2时材料具有最好电化学性能,比容量可以达到170～180mAh/g,并且具有好的抗过充性能.     

AlPO4包覆LiNi1/3Co1/3Mn1/3O2的制备与电化学性能

采用高温固相法制备LiNi_1/3Co_1/3Mn_1/3O₂,溶胶-凝胶法制备AlPO₄包覆LiNi_1/3Co_1/3Mn_1/3O₂材料(AlPO₄-coated LiNi_1/3Co_1/3Mn_1/3O₂).并用XRD、SEM检测等对材料进行了表征,用X-射线衍射、扫描电镜分析以及电化学测试等手段对样品的微观结构、表面形貌和电化学性能进行了研究.结果表明：在AlPO₄-coated LiNi_1/3Co_1/3Mn_1/3O₂中,AlPO₄以无定形态包覆于的表面;AlPO₄的存在,阻止了电极与电解质溶液之间的副反应,降低了电极的表面膜阻抗和电荷转移阻抗,加快了锂离子的扩散速度,使得LiNi_1/3Co_1/3Mn_1/3O₂的循环性能和倍率性能显著改善.     

Tuning Li3PO4 modification on the electrochemical performance of nickel-rich LiNi0.6Co0.2Mn0.2O2

Surface deterioration occurs more easily in nickel-rich cathode materials with the increase of nickel content. To simultaneously pre-vent deterioration of active cathode materials and improve the electrochemical performance of the nickel-rich cathode material, the surface of nickel-rich LiNi0.6Co0.2Mn0.2O2 cathode material is decorated with the stable structure and conductive Li3PO4 by a facile method. The LiNi0.6Co0.2Mn0.2O2–1wt％, 2wt％, 3wt％Li 3PO4 samples deliver a high-capacity retention of more than 85％ after 100 cycles at 1 C under a high voltage of 4.5 V. The effect of different coating amounts (0–5wt％) for the LiNi0.6Co0.2Mn0.2O2 cathode is analyzed in detail. Results show that 2wt％ coating of Li3PO4 gives better performance compared to other coating concentrations. Detailed analysis of the structure of the samples during the charge?discharge process is performed by in-situ X-ray diffraction. It is indicated that the modification for LiNi0.6Co0.2Mn0.2O2 cathode could protect the well-layered structure under high voltages. In consequence, the electrochemical performance of modified samples is greatly improved.     

LiNi0.85-xCoxMn0.15O2电化学性能的第一性原理研究

采用基于密度泛函理论的第一性原理平面波赝势方法计算了空间群为R-3M,具有层状结构的LiNi0.85-xCoxMn0.15O2的带隙、分波态密度、嵌锂形成能和晶胞体积.计算结果表明LiNi0.65Co0.2Mn0.15O2具有较高的可逆容量,又具有较好的电池性能,为该系列金属氧化物中较为理想的锂离子电池正极材料,与文献的结果相比较,我们发现理论计算结果与实验结果有较好的一致性.本文采用CASTEP中原子混合实现镍钴含量的变化后,分析了LiNi0.85-xCoxMn0.15O2的物理性质及电化学性质.揭示了镍钴含量变化对材料作为锂离子电池正极材料的性能的影响,进而为寻找新的正极三元材料提供理论指导.     

Optimizing the Synthetic Conditions of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 from a Carbonate Co-precipitation Method

1 Introduction As a promising cathode material for lithium ion batteries,LiNi1/3Co1/3Mn1/3O2 attracted intensive attentions.Owing to high specific capacity,long circle life and excellent safety,it may be an alternative candidate for LiCoO2.As a complex composite,however,it is difficult to synthesize phase-pure LiNi1/3Co1/3Mn1/3O2 by a simple mixed calcination method[1].From this concern,carbonate co-precipitation method,which can prepare homogeneous LiNi1/3Co1/3Mn1/3O2 with typical layered structure,bec...