高镍三元正极材料LiNi0.8Co0.1Mn0.1O2的合成与改性

LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2是一种具有高能量密度的锂离子电池正极材料,但实际应用中的循环性能不佳、热稳定性差等缺陷亟待改善。本研究通过高温固相反应法制备了LiNi_(0.8)-Co_(0.1)Mn_(0.1)O_2材料,并采用H_3BO_3对其进行包覆改性。扫描电镜(SEM)显示包覆热处理后正极材料表面形成了一层不均匀絮状包覆物,X射线光电子能谱(XPS)测试显示该包覆物为LiBO_2和Li_2B_4O_7的混合物。电化学测试表明包覆物有效减缓了循环过程中的阻抗增加,显著提升了正极材料的容量与循环性能,其中0.5%包覆的正极材料0.2 C首次放电容量达到195.9 mAh·g~(-1),1 C循环100周后容量保持率达到88.7%。     

LiNi0.6Co0.1Mn0.3O2材料的制备及其Nb2O5包覆改性

高镍层状LiNixCoyMn1-x-yO2（x≥0.6）三元材料具有较高的能量密度,但因锂镍混排、结构稳定性不佳等问题限制了其在锂离子电池中的应用。因此,采用Nb2O5包覆对三元材料LiNi0.6Co0.1Mn0.3O2（NCM613）进行改性,并考察了不同包覆量对NCM613的形貌结构和电化学性能的影响,得出了最佳工艺条件的包覆量为0.75%。首先,采用共沉淀法制备了前驱体Ni0.6Co0.1Mn0.3(OH)2;然后利用高温固相法制备了裸样LiNi0.6Co0.1Mn0.3O2（NCM613）;最后加入不同物质的量的Nb2O5粉末,通过球磨后高温烧结回火法制备了不同比例包覆量的Nb2O5@NCM613样品。XRD分析结果表明,各包覆样品与裸样NCM613的晶体结构相似,都具有完整的α-NaFeO2层状结构,阳离子混排程度较低;SEM分析结果表明,包覆样品和裸样NCM613均为1.0~1.5 μm的类球状粒子,且Ni、Co、Mn和Nb元素均匀分布在类球状材料表面;TEM分析结果表明,0.75Nb2O5@NCM613样品的Nb2O5包覆层厚度约为10~20 nm;材料电化学性能研究结果表明,在2.7~4.3 V、0.2C的电流密度条件下NCM613和0.75Nb2O5@NCM613的首圈放电比容量分别为208.11, 237.39 mA·h/g,1.0C循环100圈后,0.75Nb2O5@NCM613的放电比容量为176.43 mA·h/g,容量保持率高达86%。与裸样相比,在100圈循环后0.75Nb2O5@NCM613的阻抗明显降低,电化学极化降低,可逆性增强,这是因为Nb2O5包覆能提高材料的结构稳定性和电化学性能。可见,Nb2O5包覆高镍三元材料有利于推动高镍层状正极材料的工业化生产。     

锂离子电池正极材料LiNi0.5Mn0.5O2的合成

以Ni(OH)2、LiOH.H2O和MnO2为原料,采用机械活化-高温固相反应法在空气中合成了具有α-NaFeO2型层状有序结构的LiNi0.5Mn0.5O2,研究了合成产物的成分、物相、结构和形貌,以及物料在球磨和煅烧过程中的物理化学变化。采取高能球磨对原料进行机械活化,可提高物料的混合程度和反应活性,促进产物生成。合成的最佳工艺条件:高能球磨8 h,950℃下煅烧20 h,锂过量10%(摩尔比)。     

锂离子电池正极材料锰掺杂LiNi0.8Co0.2O2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。     

空气中合成锂离子电池正极材料LiNi1-xTixO2

以N i(OH)2、TiO2和LiOH.H2O为原料,采用固相反应法在空气中合成了LiN i1-xTixO2(x=0.025、0.050、0.100),用XRD研究了合成材料的物相和结构,用SEM研究了合成材料的形貌,用电池性能测试仪研究了合成材料的电化学性能.结果表明,原料中的n(Ti)/n(N i Ti)值对合成材料的结构和电化学性能影响很大.少量的钛可以进入LiN iO2的晶格形成LiN i1-xTixO2固溶体,而钛含量过大则会出现杂相.n(Ti)/n(N i Ti)值为0.050的样品结构有序度最高,充放电容量最大.     

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。     

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.     

Preparation of spherical and dense LiNi0.8Co0.2O2 lithium-ion battery particles by spray pyrolysis

With citric acid as a polymeric agent layered LiNi0.8Co0.2O2 materials were synthesized by a spray pyrolysis method. The LiNi0.sCo0.2O2 particles were characterized by means of XRD, SEM and TEM. The electrochemical performances of LiNi0.8Co0.2O2 particles were studied in a voltage window of 3.00-4.35 V and at a current density of 30 mA/g. The results show that in the pilot-scale spray pyrolysis process, the morphology of particles is dependent upon the precursor concentration and flux of carrier gas. The initial discharge capacity of the LiNi0.8Co0.2O2particles at 720 ℃ for 12 h is 187.3 mA.h/g, and the capacity remains 96.8% with excellent cycleability after 30 cycles. The LiNi0.8Co0.2O2 samples synthesized under the optimized conditions by the spray pyrolysis method shows a good electrochemical performance.     

Synthesis and electrochemical characterization of LiNi0.78Co0.2Al0.02O2 cathode material in a novel co-precipitation method

LiNi0.78 Co0.2 Al0.02O2 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.rsCoo.2AI~0202 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 material 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%.     

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%.     

Na+掺杂对LiNi1/3Co1/3Mn1/3O2结构和电化学性质的影响

采用高温固相法成功制备了不同Na+掺杂浓度的Li_1-xNa_xNi_1/3Co_1/3Mn_1/3O₂锂离子电池正极材料,探究了Na元素掺杂对层状氧化物正极材料结构以及电化学性能的影响。通过X射线粉末衍射仪和扫描电子显微镜表征了材料的结构和形貌,结果表明,当x≤0.3时,样品不会出现其它杂相;当x＞0.3时,样品中会出现NaNi_1/3Co_1/3Mn_1/3O₂的杂相。同时随着掺杂浓度的增加,样品的阳离子混排度逐渐增加。电化学性能结果表明,少量Na+的掺入可以提高LiNi_1/3Co_1/3Mn_1/3O₂在0.2C,0.5C下的放电比容量并增强其循环稳定性,但会损坏材料的倍率性能。     

正极材料LiNi_（0.4）Mn_（0.4）Co_（0.2）O_2的制备和性能

采用草酸共沉淀法合成了锂离子正极材料LiNi0.4Mn0.4Co0.2O2。用XRD、SEM和充放电实验对合成产物的结构、形貌和电化学性能进行了表征;用DSC对合成产物在不同充电状态下的热稳定性进行了研究。结果表明,采用草酸共沉淀法合成的正极材料LiNi0.4Mn0.4Co0.2O2具有α-NaFeO2型层状结构,阳离子有序度高,粒度均匀适中,电化学性能良好,首次放电比容量达到158.7 mAh/g,30次循环后放电比容量还有144.8 mAh/g;过充电状态下具有良好的热稳定性。     

Comparative experiment on layered Li（Ni1/3Co1/3Mn1/3）O2 as the alternative material for LiCoO2

This work was financially supported by the National Natural Science Foundation of China （No.50472093）.     

球形正极材料LiNi0.8-xCo0.2AlxO2的合成与表征

以LiNO3、Al(NO3)3.9H2O、Co(NO3)2.6H2O和球形Ni(OH)2为原料,采用熔盐包裹法在空气中合成了LiNi0.8-xCo0.2AlxO2.采用XRD、SEM和电池性能测试仪研究了合成产物的结构、形貌和电化学性能.考察了合成温度、合成时间、掺铝量和锂过量对合成产物结构的影响.实验表明,采用熔盐包裹法在空气中合成的LiNi0.8-xCo0.2AlxO2具有α-NaFeO2型层状有序结构和球状形貌,并具有良好的电化学性能,其中LiNi0.7Co0.2Al0.1O2的最大放电比容量达到157.7 mAh/g.在空气中合成LiNi0.8-xCo0.2AlxO2的最佳工艺条件为合成温度750℃,合成时间16 h,锂过量10%(摩尔分数).     

水热法制备LiNi_(0.5)Mn_(1.5)O_4及其电化学性能的研究

以LiOH·H2O、MnSO4·H2O和NiSO4·6H2O等为原料,采用水热法合成尖晶石LiNi0.5Mn1.5O4材料.利用扫描电子显微镜、粉末X-射线衍射仪、电化学测试分别对材料形貌、结构和电化学性能进行表征.研究加入不同锂量和热处理对尖晶石LiNi0.5Mn1.5O4材料的初始容量、放电平台以及循环性能的影响.结果表明:经过850℃热处理所合成的材料分布均匀、结晶和电化学性能良好.当LiOH溶液为0.162 g·mL-1时,尖晶石LiNi0.5Mn1.5O4材料在1 C倍率电流(140 mAh g-1)条件下,首次放电比容量为111.0 mAh·g-1.且该样品的循环性能优越:经150充放电循环后的容量衰减率仅为4.5%.