AlF_3包覆锂离子电池正极材料Li_(1.2)(Mn_(0.54)Ni_(0.16)Co_(0.08))O_2的制备、表征及电化学性能(英文)

采用溶胶-凝胶法合成锂离子电池正极材料Li1.2(Mn0.54Ni0.16Co0.08)O2,并用Al F3对这种材料进行表面包覆改性。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨率透射电子显微镜(HRTEM)等表征材料的结构和形貌。结果表明,合成的Li1.2(Mn0.54Ni0.16Co0.08)O2具有典型的层状α-Na Fe O2结构,AlF3均匀包覆在Li1.2(Mn0.54Ni0.16Co0.08)O2材料表面,包覆层厚度为5~7 nm。电化学测试表明,包覆Al F3后材料的电化学性能得到提高,在1C倍率下,包覆的AlF3材料的首次放电容量为208.2 m A·h/g,50次循环后容量保持率为72.4%,而未包覆AlF3的材料的首次放电容量和容量保持率分别为191.7 m A·h/g和51.6%。     

Al2O3包覆LiNi0.03Co0.05Mn1.92O4正极材料的制备及其电化学性能

以Al(NO3)3?9H2O为包覆原料,通过燃烧法制备得到LiNi0.03Co0.05Mn1.92O4@Al2O3正极材料。通过X射线衍射(XRD),场发射扫描电子显微镜(FESEM)和透射电镜(TEM)等表征手段对材料的结构和形貌进行分析,并通过恒电流充放电、循环伏安(CV)、交流阻抗(EIS)等测试分析材料的电化学性能。结果表明,Al2O3包覆没有改变LiNi0.03Co0.05Mn1.92O4的尖晶石型结构,包覆层厚度约10.6nm。LiNi0.03Co0.05Mn1.92O4@Al2O3正极材料电化学性能得到了明显改善,1 C和10 C倍率下初始放电比容量分别为119.9 mAh?g-1和106.3 mAh?g-1,充放电循环500次后容量保持率分别为88.4%和78.2%,而未包覆的LiNi0.03Co0.05Mn1.92O4在1 C和10 C倍率下初始放电比容量分别为121.2 mAh?g-1和104.0 mAh?g-1,500次循环后容量保持率分别为84.1%和67.6%。LiNi0.03Co0.05Mn1.92O4@Al2O3活化能为32.92 kJ?mol-1,而未包覆材料的活化能为36.24 kJ?mol-1,包覆有效降低了材料Li+扩散所需克服的能垒,提高了材料的电化学性能。     

高容量正极材料Li[Li0.2Ni0.2Mn0.6]O2的合成及电化学性能

以LiOH.H2O、Ni(OH)2和Mn3O4为原料,采用固相法合成锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2。通过X射线衍射(XRD)、扫描电子显微镜(SEM)对所得样品的结构和形貌进行表征,并测试了该材料的倍率性能和高低温性能。结果表明:900℃下烧结10 h后可获得晶粒细小均匀的层状Li[Li0.2Ni0.2Mn0.6]O2材料,并具有良好的电化学性能,放电容量最高可达235.9 mA.h/g;在50℃下测试时该材料的放电容量高达284.4 mA.h/g,并表现出良好的循环性能,其倍率性能和低温性能还有待进一步改善。     

掺F锂离子电池正极材料Li1.03Co0.10Mn1.90FzO4-z的制备及电化学性能

以Li2CO3、Mn2O3、Co2O3及LiF为原料,采用高温固相法合成了掺F的Li1.03Co0.10Mn1.90FzO4?z锂电池正极材料。通过离子发射光谱(ICP)和电位分析法确定了材料的化学组成,用X-射线衍射(XRD)、扫描电子显微镜(SEM)和电化学测试仪分析了 F 掺杂量对材料结构、形貌和电池性能的影响。结果表明,掺 F 的Li1.03Co0.10Mn1.90FzO4?z正极材料为尖晶石结构,在F掺入量z≤0.10时,随着掺杂量的增加晶胞参数逐渐增加,当F掺杂量继续增加时,晶胞参数的增幅有所减小。适量的F?与金属离子Li+、Co+的复合掺杂提高了材料的放电比容量,同时增强了材料结构的稳定性。电化学性能测试表明,Li1.03Co0.10Mn1.90F0.15O3.85的首次放电比容量达到111.0 mA·h/g,0.2C倍率下30次循环后容量保持率为97.0%。     

Surface Modification of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 by V2O5- Coating

在采用低温共沉淀-水热-煅烧法合成锂离子电池Fe-Ni-Mn体系正极材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的基础上,对合成的材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6进行V2O5的包覆改性研究,以提高材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的首次放电比容量和循环性能。用XRD、SEM、TEM、ICP光谱和恒流充放电测试研究包覆材料的结构和电化学性能。结果表明,V2O5包覆并没有改变材料的晶体结构,只存在于材料的表面,与未包覆的材料相比,V2O5包覆后的材料具有更好的首次放电容量和容量保持率。50周循环后,添加质量分数3%V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的放电比容量可以维持在200.3 mAh/g,大于未添加V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的194.0 mAh/g。CV测试表明,包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应。     

V_2O_5包覆对Li_(1.6)(Fe_(0.2)Ni_(0.2)Mn_(0.6))O_(2.6)材料的表面改性（英文）

在采用低温共沉淀-水热-煅烧法合成锂离子电池Fe-Ni-Mn体系正极材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的基础上,对合成的材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6进行V2O5的包覆改性研究,以提高材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的首次放电比容量和循环性能。用XRD、SEM、TEM、ICP光谱和恒流充放电测试研究包覆材料的结构和电化学性能。结果表明,V2O5包覆并没有改变材料的晶体结构,只存在于材料的表面,与未包覆的材料相比,V2O5包覆后的材料具有更好的首次放电容量和容量保持率。50周循环后,添加质量分数3%V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的放电比容量可以维持在200.3 mAh/g,大于未添加V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的194.0 mAh/g。CV测试表明,包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应。     

锂离子电池正极材料LiNi0.5Co0.2Mn0.3O2的制备及电化学性能

采用液相共沉淀法和固相烧结法分别制备镍钴锰复合氢氧化物(Ni0.5Co0.2Mn0.3(OH)2)和LiNi0.5Co0.2Mn0.3O2正极材料。通过X射线衍射和电化学性能测试对所得样品的结构及电化学性能进行了表征。结果表明:LiNi0.5Co0.2Mn0.3O2具有很好的α-NaFeO2层状结构,以20 mA/g的电流密度在2.5～4.3 V的电压区间充放电时,最高首次放电比容量达175 mA.h/g,首次库伦效率在89%～90%之间。当首次放电比容量为160～170 mA.h/g时,30循环未见容量衰减。锂含量对其电化学性能影响的结果表明:锂含量(n(Li)/n(Ni+Co+Mn))在1.03～1.09的范围内,随着锂含量的增加,放电比容量略有减小,但循环性能、中值电压以及平台性能都得到提高;当锂含量超过1.09时,循环性能、中值电压以及平台性能开始降低。     

CSTR系统制备高性能Ni0.6Co0.2Mn0.2(OH)2及电化学性能研究

采用共沉淀法在CSTR(连续搅拌反应器系统)工艺体系中批量合成出镍钴锰三元氢氧化物前驱体Ni0.6Co0.2Mn0.2(OH)2 (622),掺入适量的Li2CO3高温焙烧后得到锂离子二次电池正极材料Li[Ni0.6Co0.2Mn0.2]O2。使用扫描电子显微镜(SEM)观察样品形貌,X射线衍射仪(XRD)及透射电子显微镜(TEM)分析合成样品的具体结构,充放电循环测试系统测试其电化学性能。SEM测试表明产物为二次粒子团聚而成类球形颗粒;XRD及TEM结果表明合成的样品具有典型的层状α-NaFeO2结构。在电压范围为2.8 V-4.3 V,0.2 C倍率条件下,首次充放电容量分别为206 mAh g-1 和176 mAh g-1,100次循环后容量保持率达到85%。     

锂离子电池富锂材料Li[Li0.2Ni0.2Mn0.6]O2的制备及掺杂改性

以乙酸盐为原料,采用喷雾干燥法制备层状α-NaFeO2结构的富锂正极材料Li[Li0.2Ni0.2Mn0.6]O2及掺杂Cr的Li[Li0.2Ni0.15Cr0.1Mn0.55]O2。采用X射线衍射、扫描电镜、半电池充放电和电化学阻抗谱等方法研究材料的物相、结构、形貌及电化学性能。结果表明:Cr掺杂使材料的颗粒变粗,但不改变材料的结构,而使材料的层状特征更为明显;Cr掺杂后材料的电化学性能得到明显改善,电荷转移阻抗Rct从275.0降低到105.0,循环稳定性和倍率性能均有所改善,Li[Li0.2Ni0.15Cr0.1Mn0.55]O2材料1C倍率下的放电比容量为140.0 mA.h/g,循环50次后放电比容量为133.7 mA.h/g,远高于未掺杂Cr材料的比容量,未掺杂Cr材料在1C倍率下放电比容量为107.1mA.h/g,循环50次后放电比容量为102.1 mA.h/g。     

球形高电压LiNi0.5Mn1.5O4的制备及其电化学性能

以化学共沉淀法制备的球形Ni0.25Mn0.75CO3为前驱体合成高电压正极材料LiNi0.5Mn1.5O4,探讨用前驱体与Li2CO3直接反应和用前驱体分解后的氧化物与Li2CO3反应两种工艺路线对LiNi0.5Mn1.5O4形貌和电化学性能的影响。用扫描电镜(SEM)和X射线衍射(XRD)对Ni0.25Mn0.75CO3前驱体和LiNi0.5Mn1.5O4样品进行表征,用充放电测试和循环伏安法对LiNi0.5Mn1.5O4样品进行电化学性能研究。结果表明:两种方法合成的LiNi0.5Mn1.5O4均具有尖晶石型结构。但以前驱体Ni0.25Mn0.75CO3直接与Li2CO3反应合成的LiNi0.5Mn1.5O4的一次粒子颗粒较大,形貌较差,性能也较差;而以前驱体分解后的氧化物与Li2CO3反应合成的LiNi0.5Mn1.5O4的形貌及性能均较好。在3.0~4.9 V的电压范围内,1C倍率下电池的放电比容量达到136.3 mA.h/g,循环100次仍有126.5 mA.h/g,且材料具有较好的倍率性能;5C倍率下的首次放电比容量高达120.7 mA.h/g。     

Effect of lithium content on electrochemical property of Li1+x(Mn0.6Ni0.2Co0.2)1-xO2 (0≤x≤0.3) composite cathode materials for rechargeable lithium-ion batteries

In order to confirm the optimal Li content of Li-rich Mn-based cathode materials (a fixed mole ratio of Mn to Ni to Co is 0.6:0.2:0.2), Li_1+x(Mn_0.6Ni_0.2Co_0.2)_1-xO₂ (x=0, 0.1, 0.2, 0.3) composites were obtained, which had a typical layered structure with and C2/m space group observed from X-ray powder diffraction (XRD). Electron microscopy micrograph (SEM) reveals that the particle sizes in the range of 0.4-1.1 μm increase with an increase of x value. Li_1.2(Mn_0.6Ni_0.2Co_0.2)_0.8O₂ sample delivers a larger initial discharge capacity of 275.7 mA·h/g at the current density of 20 mA/g in the potential range of 2.0–4.8 V, while Li_1.1(Mn_0.6Ni_0.2Co_0.2)_0.9O₂ shows a better cycle performance with a capacity retention of 93.8% at 0.2C after 50 cycles, showing better reaction kinetics of lithium ion insertion and extraction.     

一步双修饰策略提高富镍层状氧化物正极材料的电化学性能（英文）

提出一种从表面到体相的一步整体改性策略,同步合成Nb掺杂和LiNbO₃包覆的LiNi_0.83Co_0.12Mn_0.05O₂(NCM)正极材料。LiNbO₃包覆层可以调控界面并促进锂离子扩散;更强的Nb—O键能有效抑制Li⁺/Ni²⁺阳离子混排,提高晶体结构稳定性,从而有助于缓解Li⁺脱出/嵌入过程中晶格参数的各向异性变化。结果表明:双修饰材料表现出较好的结构稳定性和优异的电化学性能。最佳样品NCM-Nb2在2.7～4.3 V之间以1C循环100次后,容量保持率为90.78%,而原始样品容量保持率仅为67.90%;同时,在10C下具有149.1 mA·h/g的更高倍率性能,这些结果突显了一步双修饰策略协同提高富镍层状氧化物正极材料电化学性能的可行性。     

Synthesis and electrochemical properties of Li[NixCoyMn1-x-y]O2 （x, y= 2/8, 3/8） cathode materials for lithium ion batteries

The uniform layered Li(Ni_2/8Co_3/8Mn_3/8)O₂, Li(Ni_3/8Co_2/8Mn_3/8)O₂, and Li(Ni_3/8Co_3/8Mn_2/8)O₂ cathode materials for lithium ion batteries were prepared using the hydroxide co-precipitation method. The effects of calcination temperature and transition metal contents on the structure and electrochemical properties of the Li-Ni-Co-Mn-O were systemically studied. The results of XRD and electrochemical performance measurement show that the ideal preparation conditions were to prepare the Li(Ni_3/8Co_3/8Mn_2/8)O₂ cathode material calcined at 900°C for 10 h. The well-ordered Li(Ni_3/8Co_3/8Mn_2/8)O₂ synthesized under the optimal conditions has the I ₀₀₃/I ₁₀₄ ratio of 1.25 and the R value of 0.48 and delivers the initial discharge capacity of 172.9 mA·h·g⁻¹, the discharge capacity of 166.2 mA·h·g⁻¹ after 20 cycles at 0.2C rate, and the impedance of 558 Ω after the first cycle. The decrease of Ni content results in the decrease of discharge capacity and the bad cycling performance of the Li-Ni-Co-Mn-O cathode materials, but the decreases of Mn content and Co content to a certain extent can improve the electrochemical properties of the Li-Ni-Co-Mn-O cathode materials.     

Synthesis of LiNi1/3CO1/3Mn1/3O2 cathode material via oxalate precursor

Using oxalic acid and stoichiometrically mixed solution of NiCl2, CoCl2, and MnCl2 as starting materials, the triple oxalate precursor of nickel, cobalt, and manganese was synthesized by liquid-phase co-precipitation method. And then the LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion battery were prepared from the precursor and LiOH-H2O by solid-state reaction. The precursor and LiNi1/3Co1/3Mn1/3O2 were characterized by chemical analysis, XRD, EDX, SEM and TG-DTA. The results show that the composition of precursor is Ni1/3Co1/3Mn1/3C2O4·2H2O. The product LiNi1/3Co1/3Mn1/3O2, in which nickel, cobalt and manganese are uniformly distributed, is well crystallized with a-NaFeO2 layered structure. Sintering temperature has a remarkable influence on the electrochemical performance of obtained samples. LiNi1/3Co1/3Mn1/3O2 synthesized at 900 ℃ has the best electrochemical properties. At 0.1C rate, its first specific discharge capacity is 159.7 mA·h/g in the voltage range of 2.75-4.30 V and 196.9 mA·h/g in the voltage range of 2.75-4.50 V; at 2C rate, its specific discharge capacity is 121.8 mA·h/g and still 119.7 mA·h/g after 40 cycles. The capacity retention ratio is 98.27%.     

Enhanced cycling stability of La modified LiNi0.8–xCo0.1Mn0.1LaxO2 for Li-ion battery

A series of layered LiNi_0.8–xCo_0.1Mn_0.1La_xO₂ (x=0, 0.01, 0.03) cathode materials were synthesized by combining co-precipitation and high temperature solid state reaction to investigate the effect of La-doping on LiNi_0.8Co_0.1Mn_0.1O₂. A new phase La₂Li_0.5Co_0.5O₄ was observed by XRD, and the content of the new phase could be determined by Retiveld refinement and calculation. The cycle stability of the material is obviously increased from 74.3% to 95.2% after La-doping, while the initial capacity exhibits a decline trend from 202 mA·h/g to 192 mA·h/g. The enhanced cycle stability comes from both of the decrease of impurity and the protection of newly formed La₂Li_0.5Co_0.5O₄, which prevents the electrolytic corrosion to the active material. The CV measurement confirms that La-doped material exhibits better reversibility compared with the pristine material.     

Structural characterization of layered LiNi0.85−xMnxCo0.15O2 with x = 0, 0.1, 0.2 and 0.4 oxide electrodes for Li batteries

We report the synthesis of LiNi_0.85−xCo_0.15Mn_xO₂ positive electrode materials from Ni_0.85−xCo_0.15Mn_x(OH)₂ and Li₂CO₃. XRD and XPS are used to study the effect of Mn-doping on the microstructures and oxidation states of the LiNi_0.85−xCo_0.15Mn_xO₂ materials. The analysis shows that Mn-doping promotes the formation of a single phase. With increasing substitution of Mn ions for Ni ions, the lattice parameter a decreases, while the lattice parameters c and c/a increase. XPS revealed that the oxidation states of Ni, Co and Mn in LiNi_0.85−xCo_0.15Mn_xO₂ compounds (where x = 0.1, 0.2 and 0.4) were +2/+3, +3 and +4. The substitution of Mn ions for Ni ions induces a decrease in the average oxidation state of Ni. Because the substitution of Mn for Ni ions is complex, the extent of the changes between the lattice parameter and L_M-O differ. The occupation of Ni in Li sites is affected by the ordering of Mn⁴⁺ with Ni²⁺ and Mn⁴⁺ with Li⁺.     

Synthesis and electrochemical performances of LiNi0.6Co0.2Mn0.2O2 cathode materials

LiNi_0.6Co_0.2Mn_0.2O₂ was prepared from LiOH·H₂O and MCO₃ (M=Ni, Co, Mn) by co-precipitation and subsequent heating. XRD, SEM and electrochemical measurements were used to examine the structure, morphology and electrochemical characteristics, respectively. LiNi_0.6Co_0.2Mn_0.2O₂ samples show excellent electrochemical performances. The optimum sintering temperature and sintering time are 850 °C and 20 h, respectively. The LiNi_0.6Co_0.2Mn_0.2O₂ shows the discharge capacity of 148 mA·h/g in the range of 3.0?4.3 V at the first cycle, and the discharge capacity remains 136 mA·h/g after 30 cycles. The carbonate co-precipitation method is suitable for the preparation of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials with good electrochemical performance for lithium ion batteries.     

Preparation and electrochemical performance of 2LiFe1–xCoxPO4–Li3V2(PO4)3/C cathode material for lithium-ion batteries

2LiFe_1–xCo_xPO₄–Li₃V₂(PO₄)₃/C was synthesized using Fe_1–2xCo_2xVO₄ as precursor which was prepared by a simple co-precipitation method. 2LiFe_1–xCo_xPO₄–Li₃V₂(PO₄)₃/C samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. All 2LiFe_1–xCo_xPO₄–Li₃V₂(PO₄)₃/C composites are of the similar crystal structure. The XRD analysis and SEM images show that 2LiFe_0.96Co_0.04PO₄–Li₃V₂(PO₄)₃/C sample has the best-ordered structure and the smallest particle size. The charge–discharge tests demonstrate that these powders have the best electrochemical properties with an initial discharge capacity of 144.1 mA·h/g and capacity retention of 95.6% after 100 cycles when cycled at a current density of 0.1C between 2.5 and 4.5 V.     

Synthesis and characterization of layered Li（Ni1/3Mn1/3CO1/3）O2 cathode materials by spray-drying method

Spherical Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 was prepared via the homogenous precursors produced by solution spray-drying method. The precursors were sintered at different temperatures between 600 and 1 000 ℃ for 10 h. The impacts of different sintering temperatures on the structure and electrochemical performances of Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 were compared by means of X-ray diffractometry(XRD), scanning electron microscopy(SEM), and charge/discharge test as cathode materials for lithium ion batteries. The experimental results show that the spherical morphology of the spray-dried powers maintains during the subsequent heat treatment and the specific capacity increases with rising sintering temperature. When the sintering temperature rises up to 900 ℃ , Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 attains a reversible capacity of 153 mA·h/g between 3.00 and 4.35 V at 0.2C rate with excellent cyclability.