Electrochemical properties of niobium and phosphate doped spherical Li-rich spinel LiMn2O4 synthesized by ion implantation method

Spherical Li-rich lithium manganese oxide(LMO) spinel material was synthesized by an ion implanted method assisted by polyalcohol doped with Niobium and Phosphate simultaneously.The material was characterized by scanning electron microscopy,X-ray diffraction and BET specific surface area analysis.The electrochemical performances were investigated with galvanostatic techniques and cyclic voltammetry.The synthesis process was investigated with TG/DSC.The results show that the lithium ion can be immersed into the pore of manganese dioxide at a low temperature with the ion implanted method.The prepared materials have a higher discharge capacity and better crystallization than those prepared by solid phase method.The doped Nb can improve the capacity of the Li-rich LMO spinel and reinforce the crystal growth along(111) and(400) planes.The crystal grains show circular and smooth morphology,which makes the specific surface area greatly decreased.Phosphate-doped LMO spinel exhibits good high-rate capacity and structure stability.The prepared Li_(1.09)Mn_(1.87)Nb_(0.031)O_(3.99)(PO_4)_(0.021)delivers a discharge capacity of 119mAhg~(-1) at 0.2C(1C=148mAg~(-1)) and 112.8 mAhg~(-1) at 10 C,the discharge capacity retention reaches 98% at 1 ℃ after 50 cycles at 25 ℃ and 94% at 55 ℃.     

Sub-100 nm hollow SnO2@C nanoparticles as anode material for lithium ion batteries and significantly enhanced cycle performances

Rational designing and controlling of nanostructures is a key factor in realizing appropriate properties required for the high-performance energy fields. In the present study, hollow SnO₂@C nanoparticles (NPs) with a mean size of 50 nm have been synthesized in large-scale via a facile hydrothermal approach. The morphology and composition of as-obtained products were studied by various characterized techniques. As an anode material for lithium ion batteries (LIBs), the as-prepared hollow SnO₂@C NPs exhibit significant improvement in cycle performances. The discharge capacity of lithium battery is as high as 370 mAh g^-1, and the current density is 3910 mA g^-1(5 C) after 573 cycles. Furthermore, the capacity recovers up to 1100 mAh g^-1 at the rate performances in which the current density is recovered to 156.4 mA g^-1(0.2 C). Undoubtedly, sub-100 nm SnO₂@C NPs provide significant improvement to the electrochemical performance of LIBs as superior-anode nanomaterials, and this carbon coating strategy can pave the way for developing high-performance LIBs.     

Preparation of few-layer reduced graphene oxide-wrapped mesoporous Li4Ti5O12 spheres and its application as an anode material for lithium-ion batteries

A three-dimensional few-layer reduced graphene oxide-wrapped mesoporous Li₄Ti₅O₁₂ (m-LTO@FLRGO) electrode is produced using a simple solution fabrication process. When tested as an anode for Liion batteries, the m-LTO@FL-RGO composite exhibits excellent rate capability and superior cycle life. The capacity of m-LTO@FL-RGO reaches 165.4 mA h g^-1 after 100 cycles between 1 and 2.5 V at a rate of 1 C. Even at a rate of 30 C, a high discharge capacity of 115.1 mA h g^-1 is still obtained, which is three times higher than the pristine mesoporous Li₄Ti₅O₁₂ (m-LTO). The graphene nanosheets are incorporated into the m-LTO microspheres homogenously, which provide a high conductive network for electron transportation.     

Enhanced electrochemical performance and mechanism study of AgLi1/3Sn2/3O2 for lithium storage

AgLi_1/3Sn_2/3O₂ with delafossite structure is prepared by treating Li₂SnO₃ with molten AgNO₃ and it exhibits improved electrochemical performance compared to Li₂SnO₃.     

Controlling the morphology,size and phase of Nb2O5 crystals for high electrochemical performance

Herein, the nano-sized niobium pentoxide (Nb₂O₅) with different morphologies and phase structures are synthesized through a very simple thermal treatment method, including the pseudohexagonal Nb₂O₅ nanosheets and pseudohexagonal Nb₂O₅ nanoparticles, orthorhombic Nb₂O₅ nanoparticles. The synthesized pseudohexagonal Nb₂O₅ nanosheets and orthorhombic Nb₂O₅ nanoparticles exhibit better cycling and rate performance than the pseudohexagonal Nb₂O₅ nanoparticles due to the different morphologies and phase structures.     

基于三维花状五氧化二铌及活性炭的锂离子混合电容器

锂离子混合电容器由于兼备锂离子电池和超级电容器的优势,即较高的能量密度和功率密度,而成为当前能量存储体系的研究热点。本工作合成了具有三维花状微纳结构的正交相五氧化二铌(T-Nb_2O_5),并将其与活性炭(AC)相匹配,设计出一种新型的T-Nb_2O_5/AC锂离子混合电容器。循环伏安和恒电流充放电的测试结果表明该锂离子混合电容器具有较好的电化学性能,如在碳酸酯类的有机电解液中,工作电压可达到3.0 V;在100 m A·g~(-1)的电流密度下,电容器的比能量和比功率密度可达到53.79 Wh·kg~(-1)和294 W·kg~(-1);在200 m A·g~(-1)的电流密度下,经过1000次充放电循环后,该电容器的比能量保持率为73%。由此可见,本工作开发的T-Nb_2O_5/AC锂离子混合电容器将在高功率的储能设备中有很好地应用前景。     

碳包覆CaSnO3纳米纤维作为高性能锂离子电池负极材料

采用静电纺丝技术制备出CaSnO3纳米纤维(CaSnO3 NFs)并作为模板,再经表面原位聚合酚醛树脂和碳化处理制得碳包覆CaSnO3纳米纤维(CaSnO3@C NFs)。使用X射线衍射、扫描电子显微镜、透射电子显微镜和X射线光电子能谱对材料的物相组成、形貌和微观结构进行了表征,通过循环伏安、恒电流充放电和交流阻抗谱研究了碳包覆及碳化温度对CaSnO3 NFs负极材料电化学性能的影响。结果显示,碳包覆改性使CaSnO3 NFs的电化学性能得到较大程度的提高,而且随着碳化温度的升高,CaSnO3@C NFs复合电极的比容量先增加后下降,600℃碳化获得的CaSnO3@C NFs?600复合材料具有最好的电化学性能。在0.1 A·g^-1的电流密度下,CaSnO3@C NFs?600电极的首圈放电比容量达到1102.2 mAh·g^-1,充放电循环100圈后比容量为548.8 mAh·g^-1,当电流密度提高到2 A·g^-1时,其比容量仍保持在333.5 mAh·g^-1。     

表面活性剂对氧化铝修饰富锂锰基正极材料的影响

采用氧化铝修饰改性富锂锰基正极材料,探讨了表面活性剂在修饰改性中的作用。利用扫描电子显微镜、X射线衍射仪、透射电子显微镜和电化学性能测试等方法对材料结构和电化学性能进行分析。实验结果表明,十二烷基三甲基溴化铵(DTAB)能使Al_2O_3纳米颗粒均匀包覆在富锂锰基正极材料表面,有效增强了复合材料结构的稳定性。在600 mA·g~(-1)电流密度下,该复合材料的初始放电容量为186mAh·g~(-1)。经过500次循环后,其可逆放电比容量仍高于132 mAh·g~(-1),初始容量保持率高达71%。此外,电压衰退也被有效抑制,复合材料表现出优异的综合电化学性能。     

纳米CoFe2O4/GNS负极制备及其电化学性能研究

采用溶剂热法一步合成纳米尺寸CoFe₂O₄/GNS复合材料（直径约为15 nm）,其颗粒尺寸均一,且均匀分散于石墨烯表面. 电化学测试结果表明,该复合物电极具有良好的循环和倍率性能,500 mA·g^-1电流密度下100周期循环比容量稳定在709 mAh·g^-1, 容量保持率高达95.8%;2 A·g^-1电流密度,其比容量仍高达482 mAh·g^-1.     

NaOH浓度对Na0.44MnO2储钠性能的影响

我们通过球磨法及后续的高温焙烧合成出了短棒状的Na_0.44MnO₂,并研究了其作为碱性水溶液钠离子电池正极时,电解液NaOH浓度对其电化学性能的影响。结果表明,提高NaOH浓度有利于抑制嵌氢反应的发生并改善电极的循环性能和倍率性能,但同时也会造成析氧反应的提前触发,浓度过高时则又会降低其倍率性能。Na_0.44MnO₂在8 mol·L^?1 NaOH中表现出了最佳的电化学性能,0.5C(1C=121 mA·g^?1)的电流密度下,比容量达到79.2 mAh·g^?1,50C时,仍能释放出35.3 mAh·g^?1的比容量,在0.2–1.2 V(vs.NHE)的电压窗口内,500周后容量保持率64.3%。此外,我们也发现缩小电压窗口可以减少副反应、改善循环性能。Na_0.44MnO₂在浓碱电解液中也表现出了优异的耐过充能力。上述结果不仅表明通过优化电解液体系和测试条件可大大改善Na_0.44MnO₂的储钠性能,同时也证实了Na_0.44MnO₂作为一种水溶液钠离子电池正极材料,在大规模储能领域具有良好的应用前景。     

锂离子电池负极材料Li4Ti5O12的合成及性能研究

本文通过乙酸锂与二氧化钛反应,采用一步高温固相法在不同反应温度（750 °C/800 °C/850 °C）和反应气氛（氮气/空气）下合成Li₄Ti₅O₁₂材料. 通过热重分析、X射线衍射、扫描电子显微镜、循环伏安曲线和充放电曲线分析了Li₄Ti₅O₁₂的晶体结构,观察其微观形貌,并测试其电化学性能. 结果表明,800 °C氮气烧结得到的Li₄Ti₅O₁₂（L-800N）材料粒径较小,该材料在1.0C倍率下的首周期放电比容量达到170.7 mAh·g^-1,100周期循环后的容量保持率高达94.6%,即使是10C高倍率其首周期放电容量依然有143.0 mAh·g^-1,表现出了良好的倍率和循环寿命性能.     

纳米纤维素/MnO2自支撑锌离子电池正极的制备及其电化学性能研究

以羟基纳米纤维素为原料,利用其表面丰富的羟基还原KMnO 4,在纳米纤维表面原位生成MnO₂纳米颗粒,并与Super P混合,通过简单抽滤的方式获得CNF@MnO₂/Super P自支撑正极。结果表明:无粘结剂的CNF@MnO₂/Super P自支撑正极具有较高的循环稳定性,在0.5 A·g^-1的电流密度下,循环800圈后,容量仍能达到247 mAh·g^-1;均匀分布的纳米MnO₂与Super P能够有效缩短离子和电子扩散路径,大大降低材料的电阻,使正极具有良好的倍率性能,在2 A·g^-1的电流密度下,循环300圈之后,电池容量仍保持在175 mAh·g^-1,库仑效率~99%;利用该正极良好的延展性,制备了软包电池,并表现出了较高的循环稳定性和容量保持率,该工作为柔性无粘结剂的水系Zn-MnO₂二次电池的设计开发提供了新的研究思路。     

Synthesis and Visible-light Photocatalytic Performance of C-doped Nb2O5 with High Surface Area

C-doped Nb₂O₅ with abundant mesopores has been successfully synthesized through a facile solvothermal synthetic strategy followed by calcination treatment. The resulting C-doped Nb₂O₅ displayed the highest BET surface area(345 m²/g) and large mesopore size(ca. 4.2 nm), capable of offering more accessible active sites as well as faster mass transfer for catalysis. Besides, the doping of C(2.21%, molar fraction) at the O sites in Nb₂O₅ lattice greatly enhanced visible-light response by lowering the band gap, thereby making the material a photocatalyst under visible-light irradiation. Typically, the C-doped Nb₂O₅ exhibited a high H₂ evolution rate of ca. 39.10 μmol·g^-1·h^-1 and also degraded RhB dye completely after 30 min of visible light exposure, which turned out to be much better than Degussa P25 and pure Nb₂O₅ catalysts.     

纳米MgO掺杂改善LiNi1/3Co1/3Mn1/3O2正极材料

将氢氧化物共沉淀法制备的(Ni_1/3Co_1/3Mn_1/3)（OH）₂在500℃热处理5 h得到具有尖晶石结构、纳米尺寸的氧化物M₃O₄(M=Ni_1/3Co_1/3Mn_1/3).将其与LiOH及不同量的纳米MgO混合均匀,并在850℃热处理24 h制备了Li(Ni_1/3Co_1/3Mn_1/3)_1/xMg_xO₂（x=0,0.01,0.02,0.03,0.04,0.05）正极村料.随着Mg掺杂量的增大,正极材料的晶胞参数增大;少量的Mg掺杂增大了锂离子的扩散系数,而过度掺杂却使锂离子扩散系数有所降低,其中Li(Ni_1/3Co_1/3Mn_1/3)_0.98Mg_0.02O₂的锂离子扩散系数最大,其脱出和嵌入扩散系数分别为D_Li-dein=29.20×10^-11cm²·S^-1和D_Li-in=4.760×10^-11cm²·s^-1;其以3C倍率充放电的平均放电比容量为139.3 mAh·g^-1,比未掺杂的原粉约高9.5 mAh·g^-1;另外其循环性能也得到了大幅度改善.     

Synthesis of carbon-coated Li4Ti5O12 and its electrochemical performance as anode material for lithium-ion battery

Carbon-coated Li_4Ti_5O_(12) sample was synthesized by a sol-gel method. The Li_4Ti_5O_(12) powders were obtained by calcinations of the gels at 750, 800, 850,900 ℃ at N_2 atmosphere. The structure, morphology and electrochemical properties of the materials were characterized by SEM, XRD and charge and discharge. The final product sintered at 850 ℃ demonstrates excellent performance with a specific capacity of 163.5 mAh/g after 100 cycles at 1C. Furthermore, the discharge specific capacity of the sample can retain 80 mAh/g at 10C.     

对苯二甲酸镁作为钠离子电池的有机负极材料

报道了对苯二甲酸镁作为钠离子电池负极材料的研究.以对苯二甲酸和氢氧化镁为原料,采用酸碱中和反应制备了含结晶水的对苯二甲酸镁(MgC8H4O4·2H2O),该材料对钠离子电池表现出了较好的电化学活性、优异的倍率性能以及良好的循环稳定性.在0.5C(1C=300 mA·g-1)倍率下循环50周以后,可逆容量由114mAh·g-1降至95 mAh·g-1,容量保持率高达83%;在2C的倍率下有高达90 mAh·g-1的可逆比容量.另外,在氮气气氛中,400℃进行后续热处理得到了不含结晶水的对苯二甲酸镁(MgC8H4O4),探讨了结晶水对其电化学性能的影响.结果表明,MgC8H4O4·2H2O的比容量、倍率性能以及循环稳定性都明显优于不含结晶水的对苯二甲酸镁.     

The fabrication of hollow magnetite microspheres with a nearly 100% morphological yield and their applications in lithium ion batteries

Hollow Fe_3O_4(H-Fe_3O_4) microspheres were fabricated through a facile one-step solvothermal synthesis,which was performed in an ethylene glycol(EG)–diethylene glycol(DEG) mixed solvent using polyethylene glycol(PEG) as the stabilizer. The addition of DEG increased the viscosity of the system,which caused the Fe_3O_4 primary crystal to aggregate slower and the morphological yield to approach nearly 100%. The as-prepared hollow Fe_3O_4 microspheres show promise for application in lithium ion battery anodes and showed a reversible specific capacity of 453.3 mAh g~(-1) after 50 cycles at 100 mA g~(-1).     

Freeze-drying-assisted Synthesis of Mesoporous CoMoO4 Nanosheets as Anode Electrode Material for Enhanced Lithium Batteries

A facile and green freeze-drying-assisted method was proposed to synthesize C0MoO4 mesoporous nano-sheets(MPNSs).The resulting product exhibits a Mgh specific capacity and good rate perfomance when evalimte an anode material for lithium-ion batteries(LIBs).The reversible specific capacity can be kept at 1105.2 mA·h·g^-1 after 100 cycles at a current density of 0.2 A/g.Even at the current densities of 1 and 4 A/gs the CoMoO4 MPNSs electrode can still retain the reversible capacities of 1148.7 and 540 mA·h·g^-1,respectively.Furthermore,the full cell(LiPePO4 catliode/CoMoO4 MPNSs anode)displays a stable discharge capacity of 146.7 mA·h·g^-1 at 0.1 C(1 C=170 mA/g)together with an initial coulombic efficiency of 98.2%.In addition,the CoMoO4 crystal structure is destroyed and reduced into Co^0 and Mo^0 in the first discharge process.In the subsequent cycles,the attractive Li storage properties come from the reversible conversions between Co/Co^2+and Mo/Mo^6+.The improved electroche-mical performance of CoMoO4 MPNSs is mainly attributed to their unique porous structures,which not only possess a good ion diffusion and electronic conduction pathway,but also provide many cavities to alleviate the volume changes during repeated cycling.This work offers a new perspective to the design of other porous electrode materials with a good energy storage performance.     

NaTiSi2O6/C复合材料用于锂离子电池负极材料

The development of human society and the continuously emerging environmental problems call for cleaner energy resources. Lithium-ion batteries, since their commercialization in the early 1990s, have been an important power source of mobile phones, laptops as well as other portable electronic devices. Their advantages include environment-friendliness, light weight, and no memory effect compared with lead-acid or nickel-cadmium batteries. Electrode materials play an important role in the performance of lithium-ion batteries. The traditional commercial anode material, graphite, has a theoretical specific capacity of 372 mAh·g^-1 and working potential close to 0 V (vs Li⁺/Li), making it prone to the formation of lithium dendrite, which may cause short circuit especially when large current is applied. Another commercial anode material Li₄Ti₅O₁₂, which also undergoes an intercalation reaction during lithiation process, has a theoretical specific capacity of 175 mAh·g^-1 along with three lithium-ion intercalations per formula unit. This is relatively small, and it has a relatively high working potential of 1.55 V (vs Li⁺/Li), which reduces its output voltage and specific energy when assembled in full battery. To overcome the shortcomings mentioned above, it is essential to search for new anode materials that are low-cost, environment-friendly, and easy to synthesize. Silicate materials have gained widespread attention owing to their low cost and facile synthesis. Herein, we report for the first time a novel titanosilicate, NaTiSi₂O₆, synthesized by sol-gel and solid sintering. It is isostructural to pyroxene jadeite NaAlSi₂O₆, belonging to monoclinic crystal system with a space group of C2/c. By in situ pyrolysis and carbonization of glucose, nanosized NaTiSi₂O₆ mixed with carbon was successfully obtained with a specific surface area of 132 m²·g^-1, calculated according to the Brunauer–Emmett–Teller formula. The specific charge/discharge capacity in the first cycle at current density of 0.1 A·g^-1 is 266.6 mAh·g^-1 and 542.9 mAh·g^-1, respectively, with an initial coulombic efficiency of 49.1%. After 100 cycles, it retains a specific charge capacity of 224.1 mAh·g^-1, corresponding to a capacity retention rate of 84.1%. The average working potential of NaTiSi₂O₆ is 1.2–1.3 V (vs Li⁺/Li), slightly lower than that of Li₄Ti₅O₁₂. The reaction mechanism while charging and discharging was determined by in situ X-ray diffraction test as well as selected area electron diffraction. The results showed that NaTiSi₂O₆ undergoes an intercalation reaction during lithiation process, with two lithium-ion intercalations per formula unit. This makes NaTiSi₂O₆ a new member of the silicate anode material family, and may provide insights into the development of new silicate electrode materials in the future.     

三维介孔钴酸锌立方体的制备及其优异的储锂性能

采用简易、温和、实际耐用的水热方法制备了新型三维介孔立方体结构的钴酸锌纳米材料。每个钴酸锌立方体的边长大约在3-4μm之间,并由大量的纳米粒子和密集的孔隙所构成。通过氮吸附/脱附手段测试发现所制备的钴酸锌纳米材料具有较大的比表面积(41.4 m2?g~(-1))和介孔(6.32 nm)特性。使用钴酸锌纳米材料作为锂离子电池负极,金属锂作为正极组装锂电池并测试了材料的储锂性能。研究发现该电极材料在较高的电流密度下循环100周后,仍能呈现较高的可逆容量和超强的循环稳定性。这种优异的储锂性能主要归因于钴酸锌纳米材料的新型结构,这种介孔立方体结构能够加速锂离子的扩散,增加电极与电解液的接触面积并缓解锂离子嵌入/嵌出期间产生的体积膨胀。