采用新颖喷墨打印技术制备的薄膜LiCoO2电极及其电化学性能

采用喷墨打印技术制备了LiCoO2薄膜电极. 用X射线衍射、扫描电镜(SEM)、循环伏安和恒电流充放电试验对薄膜电极进行结构表征和电化学性能测试. SEM结果表明, 所制备的薄膜电极表面粒子分布均匀, 厚度约为1.27 μm. 经过轻微热处理(450 ℃, 30 min)的薄膜LiCoO2电极呈现出稳定的充放电循环性能. 当以20 μA/cm2进行充放电时, 第50次循环容量保持率约为首次放电容量(81 mA·h/g)的87%, 10次循环后的充放电过程的充放电效率均接近100％.     

石墨/LiCoO_2电池充放电过程电极活性材料结构演变研究

利用X射线衍射分析(XRD)详细地研究了石墨/LiCoO2体系18650型锂离子电池充放电过程中正负极活性材料的晶体结构和微结构的变化.结果发现,在电池充电过程中,锂嵌入石墨层中,优先进入碳原子六方网格面间的间隙位置,导致石墨的点阵参数a和c,以及微应变ε增加和堆垛无序度P的变化,电池充电至20%后负极中形成Li-C化合物;电池充电时,正极LiCoO2中处于(000)位的Li原子优先脱离晶体点阵,随着正极材料脱锂量的增大,其晶格参数a减小,c增大,微应变ε也随之增加.LiCoO2在整个充电和放电过程中均未发生相变.最后,讨论了锂离子电池的导电机制.发现,充电时,锂离子的迁移从负极-电解液界面开始;放电时,其迁移从正极-电解液界面开始;在充放电过程中,正负极活性材料的嵌脱锂都有一个从活性材料颗粒表面到内层的过程.电池的充放电过程不完全可逆.     

Preparation and Electrode Performance of Ferrihydrites For Rechargeable Lithium Batteries

Now LiCoO2 is the most widely used electrode material in commercial rechargeable lithium-based batteries; however, the toxicity of cobalt and the scarcity of cobalt sources, as well as the limited charge/discharge capacity（130-140 mA.h.g-1） of LiCoO2 electrode drive many efforts to develop various alternative electrode materials, including diverse transition metal oxides and their lithiated counterparts. Amongst them, iron oxides,     

Li2MnSiO4/CNTs复合正极材料的合成与电化学性能

采用水热辅助溶胶-凝胶工艺,通过原位复合的方法合成了锂离子电池用Li2MnSiO4/CNTs复合正极材料.分析了复合正极材料的形貌和组成特征,并对每摩尔分别复合5,10,20和30 g碳纳米管(CNTs)及未复合CNTs的样品进行了电化学性能测试.结果显示,所合成的Li2MnSiO4颗粒尺寸分布均匀,粒径在100 nm左右,易团聚.但随着CNTs复合量的增加,团聚现象逐渐改善.合成的Li2MnSiO4材料结晶度良好,属于正交晶系Pmn21空间群.电化学测试结果表明,每摩尔复合20 g CNTs的样品电化学性能最佳,在10 mA/g电流密度下,首周放电容量为150 mA.h/g,循环20周后仍保持在80 mA.h/g;CNTs的原位复合可提高Li2MnSiO4材料的导电性能,并改善其电化学性能.     

Controlled synthesis of nanocrystalline Li2MnSiO4 particles for high capacity cathode application in lithium-ion batteries

Monodispersed Li(2)MnSiO(4) nanoparticles are synthesized via a supercritical solvothermal method at 300 °C for 5 min reaction time. The as-synthesized nanoparticles are free from impurities and have 15-20 nm diameter. After coating with conductive polymer, a discharge capacity of 313 mA h g(-1) is obtained for the first time because of nearly 2Li(+) reaction.     

PANI/MWCNT电极在硫酸锂溶液中电容性能

化学氧化法制备聚苯胺/多壁碳纳米管复合材料(PANI/MWCNT),扫描电镜(SEM)、XRD及IR表征样品结构及形貌,电化学方法测定复合电极循环伏安曲线、恒流充放电曲线及电极交流阻抗.结果表明,PANI/MWCNT电极在1mol/L的Li2SO4溶液中具有较好电容性能,在电流密度为5mA/cm2时,比电容为412F/g.PANI/MWCNT电极较PANI电极有更好的大电流放电能力,50mA/cm2下复合电极的比电容仍达318F/g,为5mA/cm2时该电极比电容的77.2%,而PANI电极的比电容仅为其5mA/cm2时的56.2%.交流阻抗证明碳纳米管降低复合电极的电阻,显著提高大电流放电能力.     

Enhanced electrochemical properties of LiFePO4 by Mo-substitution and graphitic carbon-coating via a facile and fast microwave-assisted solid-state reaction

A composite cathode material for lithium ion battery applications, Mo-doped LiFePO(4)/C, is obtained through a facile and fast microwave-assisted synthesis method. Rietveld analysis of LiFePO(4)-based structural models using synchrotron X-ray diffraction data shows that Mo-ions substitute onto the Fe sites and displace Fe-ions to the Li sites. Supervalent Mo(6+) doping can act to introduce Li ion vacancies due to the charge compensation effect and therefore facilitate lithium ion diffusion during charging/discharging. Transmission electron microscope images demonstrate that the pure and doped LiFePO(4) nanoparticles were uniformly covered by an approximately 5 nm thin layer of graphitic carbon. Amorphous carbon on the graphitic carbon-coated pure and doped LiFePO(4) particles forms a three-dimensional (3D) conductive carbon network, effectively improving the conductivity of these materials. The combined effects of Mo-doping and the 3D carbon network dramatically enhance the electrochemical performance of these LiFePO(4) cathodes. In particular, Mo-doped LiFePO(4)/C delivers a reversible capacity of 162 mA h g(-1) at a current of 0.5 C and shows enhanced capacity retention compared to that of undoped LiFePO(4)/C. Moreover, the electrode exhibits excellent rate capability, with an associated high discharge capacity and good electrochemical reversibility.     

锂钛复合氧化物锂离子电池负极材料的研究

采用 3种化学方法合成锂钛复合氧化物 .应用X -射线衍射分析对其结构进行表征以及电化学性能测试 ,结果表明 :由Li2 CO3、TiO2 高温合成的锂钛复合氧化物为尖晶石结构的Li4Ti5 O12 .Li4Ti5 O12 电极在 1 .5V左右有一放电平台 ,充放电可逆性良好 ,即充电电压平台与此接近 ,且电极的比容量较大 ,循环性能良好 .以 0 .30mA·cm- 2 充放电时 ,首次放电容量可达 30 0mAh·g- 1,可逆比容量为 1 0 0mAh·g- 1,经多次充放电循环后 ,其结构仍保持稳定性 .试验电池测试表明 ,Li4Ti5 O12 可选作Li4Ti5 O12 /LiCoO2 锂离子电池的负极材料 .     

Synthesis and Electrochemical properties of Phospho-olivine Type LiFexM(1-x)PO4(1 ≥x≥0) Compounds

Olivine-type LiFePO4 appears to be the best candidate for large size Lithium ion batteries compared with conventional cathode materials such as LiCoO2, LiNiO2 and LiMnO4 based on cost,environmental benign and safety. In addition, LiFePO4 has a large theoretical capacity of 170 mAhg-1, good cycle stability, and a flat discharge potential of 3.4V versus Li/Li+. However, its low ionic/electronic conductivity limits the electrochemical prosperities of this material, especially its rate capability. Many efforts have been devoted to increase and optimize the conductivity of LiFePO4 besides minimizing the particle size and making an intimate carbon coating around the particles, though it is not the way to change intrinsically the electrical conductivity of LiFePO4.In this research, LiFePO4 was synthesized by solid-state reaction. A discharge capacity of around 110mAhg-1 was achieved under a low current density of 17mAg-1 at room temperature. In order to compounds were prepared, respectively. As an example, LiFe0.9Ti0.1PO4 had the same XRD pattern as LiFePO4 but more developed crystalline intensity. The charge-discharge capacities of LiFe0.9Ti 0.1PO4 at the first cycle were 134mAhg-1 and 129 mAhg-1, respectively. The efficiency of charge-discharge was larger than 96%. A reversible capacity of 110 mAhg-1 was obtained after 20cycles and the capacity retention was over 85%. Moreover, the discharge voltage flat was maintained at 3.4V verse Li/Li+ after the first cycle. At even higher rates, it also exhibited good electrochemical performances.     

Phase-selective synthesis of nickel phosphide in high-boiling solvent for all-solid-state lithium secondary batteries

Nickel phosphide particles were synthesized by thermal decomposition of a nickel precursor in a mixed solution of trioctylphosphine and trioctylphosphine oxide. The crystal phase and morphology of samples prepared by changing the solvents, the amount of trioctylphosphine as a phosphorus source, the reaction temperature, and the nickel precursor were characterized using X-ray diffraction and transmission electron microscopy. Spherical Ni(5)P(4) particles with diameters of 500 nm were obtained using nickel acetylacetonate as a nickel precursor at 360 °C for 1 h in trioctylphosphine oxide. NiP(2) particles with diameters of 200-500 nm were obtained using nickel acetate tetrahydrate at 360 °C for 5 h in trioctylphosphine oxide. All-solid-state cells were fabricated using NiP(2) particles as an active material and 80Li(2)S·20P(2)S(5) (mol %) glass-ceramic as a solid electrolyte. The Li-In/80Li(2)S·20P(2)S(5)/NiP(2) cell exhibited an initial discharge capacity of 1100 mAh g(-1) at a current density of 0.13 mA cm(-2) and retained a discharge capacity of 750 mAh g(-1) after 10 cycles.     

AlN-Fe纳米复合薄膜:一种新型锂离子电池负极材料

采用脉冲激光沉积技术(PLD)制备了不同比例的Al N-Fe纳米复合薄膜(Al N和Fe摩尔比为3:1;2:1;1:1;1:2),首次研究了其作为锂离子电池负极材料的电化学行为。发现当Al N和Fe的比例为2:1时,复合薄膜具有最佳的电化学性能。在500 m A·g~(-1)电流密度下,Al N-Fe(2:1)经过100次循环充放电后容量仍能保持510 m Ah·g~(-1)。对其电化学反应机理研究发现,在放电过程中,Al N-Fe纳米复合薄膜中的Al N发生分解,Al N-Fe生成Li Al合金和Li_3N。纳米Fe颗粒的引入有效提高Al N的电化学活性;在充电过程中,部分Li_3N与Fe纳米颗粒反应生成了Fe_3N,其余部分Li_3N重新生成Al N。随后的充放电过程由Fe_3N、Al N和Al三者与Li的可逆反应共同参与,保证了Al N-Fe纳米复合薄膜优异的电化学性能。该研究为设计开发新型锂离子电池电极材料提供了一种新的思路。     

Carbon Nanotubes Act as Conductive Additives in the cathode of Lithium Ion Batteries

The layered compounds LiCoO2, LiNiO2 and spinel compound LiMn2O4 have served as very effective cathode active materials in lithium ion rechargeable batteries. Generally, their high conductive resistance easily results in a serious polarization and poor utilization of active materials.In order to make full use of the active materials and increase the capacity, the charge-discharge rate and the cycle life of lithium ion batteries, conductive additives are often added into the above cathode materials to form a conductive network. Carbon materials, such as carbon black, graphite powders and chemical vapor deposit carbon fibers have been widely used as conductive additives owing to their high electrical conductivity and chemical inertness. To effectively utilize the active materials, the contents of these carbon additives in the cathode often reach up to 10～20wt%. This leads to a great need for binder, for example, 10wt% or more. It follows therefore a considerable increase in volume of the lithium batteries and lower energy density because of the large amount of carbon additives and binder in the cathode.By substituting carbon nanotubes (CNTs) for carbon black, graphite powders or chemical vapor deposit carbon fibers, much conductive additives and binder are saved, and the cathode with only 3～5wt% of conductive additives CNTs shows excellent rate capacity. At the discharge rate 0.5C,2.0C and 3.0C, the LiCoO2 cathode with CNTs exhibits discharge capacity up to 134mAh/g, 126 and 120mAh/g, respectively. The explanation is given as follows. Firstly, their microstructure and graphitic crystallinity are very important for electron transport. CNTs employed in the experiments comprise an array of complete graphite sheets seamlessly wrapped into cylindrical tubes which are concentrically nested like the rings of a tree trunk. Thus, the process of -electrons transport occurs in graphite sheet in super-conjugative manner when they move from one end to the other end in CNTs. Apparently, the CNTs' microstructure does good to electron transport. On the other hand,being highly graphitic (concluded from XRD patterns), CNTs also displays high electron conductivity. Secondly, being smaller in diameter, CNTs possess much larger number of primary particles in unit mass than other carbon materials. Hence, it results in a lower percolation threshold in the case of CNTs. Finally, owing to their high surface energy, CNTs fallen into nano-materials tend to aggregate and then form firm webs effectively entrapping LiCoO2 particles during the preparation of the cathode to guarantee their close contact with the active materials.Accordingly, effective electron channels are provided to lessen the polarization loss.     

锂离子电池正极材料Li[Li_(0.167)Mn_(0.583)Ni_(0.25)]O_2的合成与性能研究

应用低热固相法制备镍锰复合正极材料Li[Li0.167Mn0.583Ni0.25]O2.XRD、FESEM和恒电流充放电测试表明,该材料结晶良好,可标定为α-NaFeO2型结构(空间群R3-m),颗粒粒径约为60~100 nm,粒度均匀细小.在2.5~4.4 V之间以0.5 C(100 mA/g)做充放电循环时,可逆比容量在120 mAh/g以上,循环性能非常稳定.如将截止电压升高到4.6 V,则比容量大大提高,最高可达234 mAh/g.上述充放电测试都出现了比容量随循环次数上升的现象.主要原因可归结为材料中Mn(Ⅳ)向Mn(Ⅲ)的转变,但在不同的电压范围内导致该转变的起因并不相同.     

新型锂离子电池正极材料Li0.86V0.8O2的水热合成及性质

采用两步反应制备了新型锂离子电池正极材料Li0.86V0.8O2. 该材料具有六方层状结构, 空间群为R3m. 研究了在水热条件下溶液的碱度对于钒酸锂盐形成的影响, 在低碱度的条件下, 前驱体V2O3和LiOH·H2O并未发生反应, 只有在碱度达到2.5 mol/L时, 才能形成单相的Li0.86V0.8O2材料. X射线光电子能谱分析发现, V2p的结合能位于516.4 和523.1 eV, 分别对应于四价钒离子的V2p3/2 和V2p1/2, 这说明在Li0.86V0.8O2中V离子主要价位为+4价. 在电流密度为7.4 mA/g的充放电中, Li0.86V0.8O2初始充电容量达到163 mA·h/g, 首次放电容量也能达到113 mA·h/g, 20次循环后放电容量仍然可以达到80 mA·h/g, 表现出较好的循环性能.     

多孔炭模板法制备Li4Ti5O12及其嵌锂行为

采用水合氧化钛溶胶为原料, 多孔炭为模板剂, 设计制备了一种新型准纳米晶锂钛复合氧化物, 并用SEM、XRD、恒流充放电及交流阻抗测试表征了材料的形貌、结构和电化学性能. 结果表明, 该氧化物晶粒尺寸约200 nm, 为典型的尖晶石Li4Ti5O12结构. 在0.5C(1C=0.2 mA·cm-2)电流条件下的首次嵌脱锂效率为99.8%, 嵌脱锂电位平坦, 可逆容量为117 mAh·g-1; 当电流从0.5C增至5C时, 其可逆嵌锂容量仍在100 mAh·g-1以上, 容量保持率大于86%, 倍率充放电性能优异. 交流阻抗测试结果表明, 模板剂多孔炭的应用使合成的尖晶石Li4Ti5O12具有更佳的导电性能, 且多孔特征明显.     

尖晶石型八面体结构锰酸锂的制备及其电化学性能

采用模板导向法和高温固相法制备尖晶石型八面体结构的LiMn₂O₄锂离子电池正极材料,研究了该材料的结构和电化学性能。 电化学性能研究表明,该电极材料具有良好的循环稳定性和倍率性能,在2.5~4.5 V电压范围,电流密度为100 mA/g时,首周充放电比容量分别为147和179 mA·h/g,循环50周后,其充放电比容量仍分别保持在180/181 mA·h/g。 优良的电化学性能可能归因于尖晶石LiMn₂O₄的形貌结构特征,该方法为制备锂离子电池正极材料提供了思路和依据。     

锂离子二次电池正极材料 Li~0~.~7~5Na~0~.~2~5MnO~1~.~9~2I~0~.~0~8化合物 的合成与表征

采用LiOH·H~2O为锂源,化学纯MnO~2(CMD)为锰源,NaI为添加剂,乙腈为非水介质,在常温常压下合成了锂离子二次电池正极材料Li~0~.~7~5Na~0~.~2~5MnO~1~.~9~2I~0~.~0~8化合物,并采用XRD,BET,TEM及电化学测试等手段对该化合物进行了表征。结果表明该化合物原料呈非晶态超细粉末,平均粒径在45～60nm之间,具有较大的比表面积(35～48m^2/g)。经260℃真空干燥后,样品转化为纳米晶态,以该化合物作正极材料与Li作对电极构成的锂电池,在1.5～4.3V之间和0.353mA/cm^2条件下恒流充放电,首次充放电比容量超过280(mA·h)/g。充放电效率大于95％。循环20次后,其充放电比容量仍大于260(mA·h)/g,是很有应用前景的锂离子二次电池正极材料。     

定向多壁碳纳米管电化学储氢研究

利用恒流充放电、循环伏安曲线(CV)和电化学阻抗技术(EIS)等方法对定向多壁碳纳米管(AMWCNTs)储氢的电化学行为及其储氢机制进行了探讨.研究表明,定向AMWCNTs-Cu电极有较高的电化学储氢性能,其储氢容量在1500mA/g的电流密度下可以达到1162mA·h/g.定向AMWCNTs的电化学储氢能力强与其空间结构有关,而铜粉的加入有利于提高碳纳米管的电催化反应表面积和电极电化学反应活性,有利于氢在碳纳米管中扩散,从而提高了碳纳米管电极材料的储氢量.     

Synthesis and enhanced electrochemical performance of Li(2)CoPO(4)F cathodes under high current cycling

Lithium cobalt fluorophosphate, Li(2)CoPO(4)F, is successfully synthesized by a solid state reaction under Ar flow at 700 °C. X-ray diffraction and scanning electron microscopic studies are utilized to analyze the structural and morphological features of the synthesized materials, respectively. The presence of fluorine is also supported by energy-dispersive X-ray spectroscopy. The electrochemical properties are evaluated by means of Li/Li(2)CoPO(4)F half-cell configurations in both potentiostatic and galvanostatic modes. The Li/Li(2)CoPO(4)F cell delivers an initial discharge capacity of 132 mA h g(-1) at a current density of 0.1 mA cm(-2) between 2.0 and 5.1 V at room temperature. Due to the higher operating potential of the Co(2+/3+) couple in the fluorophosphate matrix, this cell shows a capacity retention of only 53% after 20 cycles, still the material delivered 108 mA h g(-1) at a high current rate of 1 C. Cyclic voltammetric studies corroborate the insertion and extraction of Li(+) ions by a single phase reaction mechanism during cycling.     

A feasibility study on the use of Li(4)V(3)O(8) as a high capacity cathode material for lithium-ion batteries

Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate).