Ag/C包覆对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响

运用共沉淀和元素化学沉积相结合的方法,制备出了具有Ag/C包覆层的层状富锂固溶体材料Li [Li0.2Mn0.54Ni0.13Co0.13]O2.通过X射线衍射(XRD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、恒流充放电、循环伏安(CV),电化学阻抗谱(EIS)和X射线能量散射谱(EDS)方法,研究了Ag/C包覆层对Li[Li0.2Mn0.54Ni03Co013]O2电化学性能的影响.结果表明,Ag/C包覆层的厚度约为25 nm,Ag/C包覆在保持了固溶体材料α-NaFeO2六方层状晶体结构的前提下,显著地改善了Li[Li0.0Mn054Ni0.13Co013]O2的电化学性能.在2.0-4.8 V (vs Li/Li+)的电压范围内,首次放电(0.05C)容量由242.6 mAh·g-1提高到272.4 mAh·g-1,库仑效率由67.6％升高到77.4％;在0.2C倍率下,30次循环后,Ag/C包覆的电极材料容量为222.6 mAh·g-1,比未包覆电极材料的容量高出14.45％;包覆后的电极材料在1C下的容量仍为0.05C下的81.3％.循环伏安及电化学交流阻抗谱研究表明,Ag/C包覆层抑制了材料在充放电过程中氧的损失,有效降低了Li[Li02Mn0.54Ni0.13Co013]O2颗粒的界面膜电阻与电化学反应电阻.     

Ag/C包覆对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响

运用共沉淀和元素化学沉积相结合的方法,制备出了具有Ag/C包覆层的层状富锂固溶体材料Li[Li0.2Mn0.54Ni0.13Co0.13]O2.通过X射线衍射(XRD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、恒流充放电、循环伏安(CV),电化学阻抗谱(EIS)和X射线能量散射谱(EDS)方法,研究了Ag/C包覆层对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响.结果表明,Ag/C包覆层的厚度约为25 nm,Ag/C包覆在保持了固溶体材料α-NaFeO2六方层状晶体结构的前提下,显著地改善了Li[Li0.2Mn0.54Ni0.13Co0.13]O2的电化学性能.在2.0-4.8 V(vs Li/Li+)的电压范围内,首次放电(0.05C)容量由242.6 mAh·g-1提高到272.4 mAh·g-1,库仑效率由67.6%升高到77.4%;在0.2C倍率下,30次循环后,Ag/C包覆的电极材料容量为222.6 mAh·g-1,比未包覆电极材料的容量高出14.45%;包覆后的电极材料在1C下的容量仍为0.05C下的81.3%.循环伏安及电化学交流阻抗谱研究表明,Ag/C包覆层抑制了材料在充放电过程中氧的损失,有效降低了Li[Li0.2Mn0.54Ni0.13Co0.13]O2颗粒的界面膜电阻与电化学反应电阻.     

锂离子电池正极材料Li[Li0.2Mn0.54Ni0.13Co0.13]O2的合成及电化学性能研究

以LiOH•H₂O, Ni₂O₃, Co₃O₄和MnO₂为原料, 经过机械活化后在空气气氛下经高温烧结, 合成了锂离子电池正极材料Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂. 通过X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学性能测试对所得样品的结构、形貌及电化学性能进行了表征. 结果表明, 900 ℃下烧结10 h后可获得晶粒细小均匀的层状Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂材料, 并具有良好的电化学性能, 在室温下以60 mA/g的电流充放电, 首次放电比容量可达到248.2 mAh/g, 循环50次后放电比容量为239.4 mAh/g, 容量保持率为96.45％. 测试了该材料的高低温循环性能.     

纳米Al2O3包覆富锂锰基正极材料Li1.2Ni0.13Co0.13Mn0.54O2的性能研究

采用纳米三氧化二铝(Al₂O₃)对富锂锰基正极材料Li_1.2Ni_0.13Co_0.13Mn_0.54O₂进行表面均匀包覆, 并考察了最优纳米Al₂O₃包覆量下材料的电化学性能. 扫描电子显微镜(SEM)和透射电子显微镜(TEM)显示了纳米Al₂O₃对富锂锰基正极材料表面均匀包覆, X射线衍射分析(XRD)结果表明包覆后富锂材料依然具有良好的层状结构. 恒流充/放电循环测试发现, 包覆后的Li_1.2Ni_0.13Co_0.13Mn_0.54O₂材料的首次放电比容量为249.7 mA·h/g, 循环100次后的容量保持率为89.5%, 与未包覆的Li_1.2Ni_0.13Co_0.13Mn_0.54O₂材料相比, 容量保持率提升约13%. 循环伏安(CV)和电化学阻抗(EIS)测试结果表明, 纳米Al₂O₃包覆可有效抑制材料极化, 降低界面阻抗和电荷转移阻抗, 进而提升富锂锰基正极材料的电化学性能.     

Modification of Li[Li0.13Ni0.2Mn0.47Co0.2]O2 cathode material by layered CeO2–C coating

Journal of Solid State Electrochemistry - Li[Li0.13Ni0.2Mn0.47Co0.2]O2 (LLNMC) cathode materials coated with CeO2 and pyrolytic carbon have been obtained by the consecutive thermal decomposition of...     

LiFePO4包覆的Li1.2Mn0.54Ni0.13Co0.13O2锂离子电池正极材料:增强的库伦效率和循环性能

In this work, we present a new design for a surface protective layer formed by a facile aqueous solution process in which a nano-architectured layer of LiFePO₄ is grown on a Li-rich cathode material, Li_1.2Mn_0.54Ni_0.13Co_0.13O₂. The coated samples are then calcined at 400 or 500℃ for 5 h. The sample after calcination at 400℃ demonstrates a high initial columbic efficiency of 91.9%, a large reversible capacity of 295.0 mAh·g^-1 at 0.1 C (1 C=300 mA·g^-1), and excellent cyclability with a capacity of 206.7 mAh·g^-1after 100 cycles at 1 C. Meanwhile, voltage fading of the coated sample is effectively suppressed by protection offered by a LiFePO₄ coating layer. These superior electrochemical performances are attributed to the coating layer, which not only protects the Li-rich cathode material from side reaction with the electrolyte and maintains the stability of the interface structure, but also provides excess reversible capacity.     

富锂正极材料Li1.2Mn0.54Co0.13Ni0.13NaxO2表面结构的电子显微分析

采用离子交换加固相烧结法制备出富锂锰基正极材料Li_1.2Mn_0.54Co_0.13Ni_0.13Na_xO₂,利用球差校正扫描透射电子显微镜（STEM）、X射线能谱（EDS）、电子能量损失谱（EELS）等分析手段对材料表面结构与成分展开表征。结果表明：镍（Ni）在样品表面存在选择性富集（垂直于锂扩散通道的表面,如（200）面）,倾向扩散进入锂离子层,并导致表面出现层状结构到岩盐相（rocksalt, Fm3m）结构转变;而钴（Co）在所观察的（001）、（200）表面均存在不同程度的富集,且集中在过渡金属层。进一步研究发现,表面钴（Co）富集不利于层状结构的稳定,时效后样品的（001）面观察到明显的表面重构,存在数量较多的过渡金属（TM）-锂（Li）反位缺陷与岩盐相结构区域。     

Parameters of Li2O2 · H2O crystallization from the LiOH-H2O2-H2O ternary system

The decomposition kinetics of peroxide products contained in the liquid phase of the LiOH-H₂O₂-H₂O ternary system were studied, and the applicability of the solubility method to studying this system was demonstrated for hydrogen peroxide concentrations in the liquid phase from 2 to 6 wt % and temperatures of 21–33°C. The stabilizing influence of solid Li₂O₂ · H₂O on hydrogen peroxide decomposition was demonstrated. The temperature and concentration boundaries of existence were determined for the Li₂O₂ · H₂O phase, whose identity was verified by chemical analysis and qualitative X-ray powder diffraction analysis.     

Li2O﹒2B2O3-H2O过饱和溶液20℃结晶动力学研究

盐水溶液中存在过饱和现象，硼酸盐溶液的过饱和即是一例．其中，镁础酸盐体系过饱和溶液在不同浓度和温度条件下的液固相关系曾有多次报道［‘－’］；给出过许多有益的结果，也探讨了镁硼酸盐的结晶反应机理并拟合出相应的结晶动力学方程．这些工作对认识盐水溶液过饱和现象有重要意义．为了更广泛地认识和了解不同棚酸盐水溶液中的过饱和现象，本文采用动力学方法，首先对Li20·2B203－HZO过饱和溶液结晶过程进行了研究．1实验初始反应溶液中Li。O／BZO。（摩尔比）为1／2，按此配比计算并称取需要量的Li0H·H。O（A．R．）、H。…     

3Li2O·B2O3-20%LiCl-H2O过饱和溶液20℃结晶动力学研究

配制3Li2O*B2O3-20%LiCl-H2O过饱和溶液在20±0.1℃恒温水槽中静置.采用结晶动力学方法研究过饱和溶液的结晶过程,此过饱和溶液结晶后析出Li2O*B2O3*4H2O一种固相,拟合给出结晶动力学方程,同时对结晶反应机理进行了探讨.     

Sb2O3掺杂Li4Ti5O12的电化学性能

采用Sb2O3掺杂改性Li4Ti5O12.用恒流充放电、循环伏安和交流阻抗技术对样品的电化学性能进行了测试.结果显示,当Ti:Sb＝4：1时,首次放电容量高达595.84mAhog-1,首次的库仑效率为45.7％,存在不可逆容量损失.提出了可能的反应机理,并用该机理解释了影响容量衰减的因素.经过20次充放电循环后,容量保持在249.57 mAhog-1.电化学阻抗谱表明,Sb的掺杂使得电化学反应阻抗减小了.     

Synthesis and study of lithium triuranate Li2U3O10 · 6H2O

Li₂U₃O₁₀ · 6H₂O crystal hydrate was synthesized by the reaction between synthetic schoepite UO₃ · 2.25H₂O and aqueous lithium nitrate solution under hydrothermal conditions at 200°C. The composition and structure of the obtained compound were established, and its dehydration and thermal decomposition were studied, by chemical analysis, X-ray diffraction, IR spectroscopy, and scanning calorimetry.     

甲烷氧化偶联制乙烯Li—ZrO2,Li—La2O3催化剂的研究

研究了添加Li的La_2O_3和ZrO_2两种催化剂对甲烷氧化偶联催化性能的影响,并用XRD,LRS和XPS等方法对催化剂进行了表征。结果表明,Li~+的加入提高了催化剂的C_2选择性,但两类催化剂上Li~+的添加作用机制不同。La_2O_2加入Li~+达40mol％时,样品可获得34.4％的甲烷转化率和60.4％的C_2选择性。Li~+在La_2O_3表面分散,表面O/(Li+La)比随Li~+添加量增加而下降。催化剂对C_2选择性的提高可能是因为Li~+覆盖了La_2O_3表面部分完全氧化中心所致。ZrO_2中添加Li~+有Li_2ZrO_3生成,75mol％Li-ZrO_2仅检测到Li_2ZrO_3晶相,该样品可得34％甲烷转化率和63％C_2选择性。样品的XRD及XPS研究表明,随Li~+加入量增加,表面Li/Zr比接近2:1,没有Li的富集,样品表面存在两种氧物种,其O_1s结合能分别为530.3和531.9eV。对75mol％Li—ZrO_2样品,后者占95％,该表面氧物种可能与C_2选择性提高有关。     

Al掺杂的锂离子电池层状正极材料Li(Li0.17Ni0.17Al0.04Fe0.13Mn0.49)O2结构稳定性及氧离子氧化的理论研究

锂离子电池(LIB)正极材料比容量及结构稳定性的提高是提升电池整体性能的重要因素. 本工作选取层状无钴正极材料Li(Li_0.17Ni_0.17Al_0.04Fe_0.13Mn_0.49)O₂ (LNAFMO)为研究对象, 使用GGA (generalized gradient approximation)+U (Hubbard U value)方法研究了体系在充电时几何和电子结构变化、氧释放焓、脱锂形成能和脱锂电压. 研究结果表明, 充电时LNAFMO体系首先Ni氧化, 然后Fe氧化, 最后O氧化. 与未掺杂Al的Li(Li_0.17Ni_0.17Fe_0.17Mn_0.49)O₂ (LNFMO)体系不同的是, 除具有线性Li-O-Li和Fe-O-Li构型的氧离子更容易给出电子外, 具有线性Al-O-Li构型的氧离子也参与电荷补偿, 并且氧离子具有很强的活性, 这将避免参与氧化的氧离子过分集中, 有利于结构的稳定; Al的掺杂能进一步抑制氧的释放, 这将提升体系的结构稳定性和电池循环性能. 该研究为设计一种低经济成本、循环性良好、高能量密度的锂离子电池正极材料奠定了坚实的理论依据.     

The effects of Mo doping on 0.3Li[Li0.33Mn0.67]O2·0.7Li[Ni0.5Co0.2Mn0.3]O2 cathode material

Mo doped Li excess transition metal oxides formulated as 0.3Li[Li(0.33)Mn(0.67)]O(2)·0.7Li[Ni(0.5-x)Co(0.2)Mn(0.3-x)Mo(2x)]O(2) were synthesized using the co-precipitation process. The effects of the substitution of Ni and Mn with Mo were investigated for the density of the states, the structure, cycling stability, rate performance and thermal stability by tools such as first principle calculations, synchrotron X-ray diffraction, field-emission SEM, solid state (7)Li MAS nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), elemental mapping by scanning TEM (STEM), inductively coupled plasma atomic emission spectrometry (ICP-AES) and a differential scanning calorimeter (DSC). It was confirmed that high valence Mo(6+) doping of the Li-excess manganese-nickel-cobalt layered oxide in the transition metal enhanced the structural stability and electrochemical performance. This increase was due to strong Mo-O hybridization inducing weak Ni-O hybridization, which may reduce O(2) evolution, and metallic behavior resulting in a diminishing cell resistance.     

Structure and properties of glasses in the system Li2O–SnO–B2O3

Glasses in the system Li₂O–SnO–B₂O₃ system were prepared by a melt-quenching method. Thermal and viscous properties and local structure of these glasses were investigated. The SnO–B₂O₃ glasses exhibited relatively low glass-transition temperatures (T_g) around 350 °C and excellent thermal stability against crystallization. Viscosity measurements in the vicinity of T_g indicated that the glasses were considerably fragile compared to alkali borate glasses. Fraction of four-coordinated boron was maximized at the composition with 50 mol% SnO and that of nonbridging oxygen, which is not purely ionic in alkali borate systems but partially covalent, augmented with an increase in the SnO content. Correlation between glass properties and structure was discussed in the SnO–B₂O₃ binary system.     

Self-assembled Li4Ti5O12/TiO2/Li3PO4 for integrated Li–ion microbatteries

This work aims to maximize the number of active sites for energy storage per geometric area, by approaching the investigation to 3D design for microelectrode arrays. Self-organized Li₄Ti₅O₁₂/TiO₂/Li₃PO₄ composite nanoforest layer (LTL) is obtained from a layer of self organized TiO₂/Li₃PO₄ nanotubes. The electrochemical response of this thin film electrode prepared at 700 °C exhibited lithium insertion and de-insertion at 1.55 and 1.57 V respectively, which is the typical potential found for lithium titanates. The effects of lithium phosphate on lithium titanate are explored for the first time. By cycling between 2.7 and 0.75 V the LTL/LiFePO₄ full cell delivered 145 mA h g^− 1 at an average potential of 1.85 V leading to an energy density of 260 W h kg^− 1 at C/2. Raman spectroscopy revealed that the γ-Li₃PO₄/lithium titanate structure is preserved after prolonged cycling. This means that Li₃PO₄ plays an important role for enhancing the electronic conductivity and lithium ion diffusion.