High specific capacity composite cathode materials for lithium-sulfur batteries

Li与S完全反应生成Li₂S时,单质硫正极的理论比容量为1675 mA·h/g,比LiFePO₄,LiCoO₂等正极材料的比容量高很多.单质S价格低,无毒,是一种理想的正极材料,然而其导电性较低,循环比容量衰减较快,因此需要改善S正极材料的导电性来提高其电化学性能.本文综述了硫基复合正极材料的制备方法,结构与形貌,电化学性能.探讨了S与多孔碳,碳纳米管,石墨烯和聚吡咯等复合的正极材料的电化学性能,并对硫基正极材料的发展趋势进行了展望.     

Preparation and electrochemical performance of LiFePO4/S composite cathode materials

以提高磷酸铁锂体系动力电池的能量密度为目的,在LiFePO₄正极材料中加入少量S材料球磨制得LiFePO₄/S复合正极材料。使用X射线衍射（XRD）和扫描电子显微镜（SEM）表征了结构和形貌,并分别组装扣式电池和软包电池测试其电化学性能。结果表明,磷酸铁锂纳米颗粒致密均匀附着在硫材料表面,构成具有包覆性结构的复合材料。在不同比例的LiFePO₄/S复合材料中,硫的添加量为15%的LiFePO₄/S复合正极材料表现出最优异的电化学性能,0.1 C下的初始容量为251.5mA·h/g,循环100周之后容量保持率达94.9%。以该比例的复合材料为正极的0.5A·h软包电池,循环100周后容量保持率为86.7%。LiFePO₄作为一种极性载体,对多硫化物有一定的吸附能力,少量硫的加入可以在大幅度提高LiFePO₄材料放电容量的同时,维持优异的循环稳定性。LiFePO₄/S复合材料可为磷酸铁锂体系动力电池的发展提供新的思路。     

Characterization of Ni porous electrode covered by a thin film of LiMg0.05Co0.95O2

A porous electrode of nickel covered by a thin film of lithium cobaltite doped with magnesium (LiMg_0.05Co_0.95O₂) was prepared in order to protect nickel cathode against dissolution into the molten carbonate. A sol impregnation technique was used to deposit gel precursors on the porous surface of the substrate; the covered substrate was submitted to thermal treatments, which produced a lithium cobaltite layer. The cathode was characterized by the following measurements: biaxial bending test, SEM/EDX analysis, which demonstrated the uniformity of the lithium cobaltite layer and the presence of cobalt homogeneously distributed over the nickel particles, electrical conductivity.

To test the cathodic performance of the material under study a cell was assembled and tested in a 10 cm × 10 cm electrodes area plant. The cell performance during the time was studied carrying out polarization curves for many hours (more than 1000 h). To determine the influence of the cathodic gas composition on the electrode performance the atmosphere was changed maintaining alternatively at a constant value the partial pressure of CO₂ and O₂. In such a way the kinetic effect of the single gas was studied. By the technique of IR interruption the internal resistance of the cell was measured.     

A rechargeable lithium battery employing a porous thin film of Cu3+δMo6S7.9

Porous, thin films of copper molybdenum sulfides (Cu_3+δMo₆S_7.9), that have been prepared by the technique of painting and subsequent reaction with mixed H₂/H₂S gases at 500 °C, have been used as a cathode material for lithium secondary batteries. The test cell comprised: Li/2 M LiClO₄ in PC-THF (4:6)/Cu_3+δMo₆S_7.9 (porous, thin film). The discharge reaction proceeded via the intercalation of lithium ions into the structural interstices of the cathode material.

The first discharge curve of the cell showed that the porous film could incorporate up to 18 lithium ions per formula unit. The capacity of the thin film was four times higher than that previously reported for powder or pressed-pellet electrodes. The theoretical energy density was 675 W h kg⁻¹, i.e., higher than that of TiS₂ (455 W h kg⁻¹) which is one of the best materials for high-energy lithium batteries. From X-ray diffraction studies of the lithium incorporated in the thin film at each discharge step, it is suggested that there are four incorporation reactions of lithium ions into the cathode. Finally, cycling tests have been conducted at room temperature.     

Edge-rich MoS2 nanosheets for high performance self-supporting Li-S batteries

提高硫的电化学活性和抑制多硫离子的溶解是提高锂硫电池性能的关键问题。层状二维金属硫化物的边缘位点相对于平面位点具有更强的吸附多硫离子的能力。然而利用液相法控制合成具有丰富边缘位点的层状二维过渡金属硫化物材料仍是一个挑战。本文以碳布作为导电基体,设计生长了由小尺寸单层S-Mo-S单元通过层层自组装而成的MoS₂多晶纳米片（V-MoS₂/CC）。探究了该复合材料作为活性物质S载体时对锂硫电池倍率性能和循环稳定性的影响。垂直生长的MoS₂纳米片暴露较多的S-Mo-S层边缘活性位点,不仅可以使得随后负载的硫单质的尺寸保持在纳米级（5～10 nm）,而且对多硫化锂的催化转化及抑制溶解具有一定程度的促进作用。同时,基底材料碳布的存在使得电极材料无需添加导电剂和黏结剂且提高了整体导电性。使用V-MoS₂/CC@S复合材料组装而成的半电池,在1 C和2 C下循环400和800圈后比容量维持在857 mA·h/g和579 mA·h/g。     

三维石墨烯包覆的硫掺杂碳负载二硫化硒复合材料的制备及其储锂性能研究

二硫化硒（SeS₂）作为储锂的正极材料,具有硒和硫以外的独特优势。采用硫掺杂介孔碳（sulfur-doped mesoporous carbon, SMC）负载SeS₂,然后用三维石墨烯（three-dimensional grapheme, 3DG）对其进行包覆,制备了双重限定的SeS₂基正极结构。通过透射电子显微镜（transmission electron microscope, TEM）,扫描电子显微镜（scanning electron microscopy, SEM）以及X射线衍射（X-ray diffraction, XRD）对所制备的3DG-SMC-SeS₂纳米复合材料的形态和结构进行表征。结果显示,SeS₂均匀地分布在SMC基体的介孔通道中,3DG良好地包裹SMC-SeS₂复合材料。受益于SeS₂不可或缺的优势和独特设计的主体构架,3DG-SMC-SeS₂正极表现出极好的循环性能和优异的高倍率性能。这种新型SeS₂基正极材料为克服目前锂硫电池的主要瓶颈提供了一种可行的策略。     

Preparation of LiNi0.80Co0.15Al0.05O2 cathode material via Li-rich method

本文采用共沉淀法制备球形Ni_0.80Co_0.15Al_0.05(OH)_2.05前驱体,经预氧化后,采用富锂配比在氧气和空气气氛下烧结合成LiNi_0.80Co_0.15Al_0.05O₂正极材料.用X射线衍射,扫描电镜和恒电流充放电测试等方法对该材料的结构,形貌及电化学性能进行表征.结果表明:当锂配比为1.15时,氧气和空气中烧结合成的LiNi_0.80Co_0.15Al_0.05O₂正极材料的形貌,结构和电化学性能相当.富锂配比方法可在空气气氛下制备出电化学性能优异的LiNi_0.80Co_0.15Al_0.05O₂正极材料.0.1 C放电克比容量在200 mA·h/g以上,首次效率在87%左右;1 C放电克比容量在168 mA·h/g以上;800周循环容量保持率在80%以上.     

Porous nickel MCFC cathode coated by potentiostatically deposited cobalt oxide: II. Structural and morphological behavior in molten carbonate

Cobalt oxide was deposited on porous nickel by an electrodeposition technique as precursor of a novel MCFC cathode. The behavior of this cathode in molten (Li_0.52Na_0.48)₂CO₃ eutectics at 650 °C under an atmosphere of CO₂:air (30:70) was studied before and after 50 h of exposure by different techniques. Before the exposure, the deposit of cobalt corresponded to a Co₃O₄ thin layer of. This crystalline structure was identified by XRD and Raman spectroscopy. After its exposure in the eutectic melt a loss of cobalt was observed by XRD, Raman spectroscopy, XPS, EDS and ICP-AES. The change in the Co₃O₄ structure into lithium–cobalt–nickel oxide (LiCo_1−yNi_yO₂) was observed by Raman spectroscopy. The SEM micrographs for Co₃O₄-coated porous nickel showed different angular shapes with respect to porous Ni. The nickel solubility for the coated porous nickel, measured by ICP-AES, decreased with respect to uncoated nickel. The Co₃O₄-coated porous nickel cathode showed, after its immersion in the molten carbonate melt, a similar porosity but a higher pore size. LiCo_1−yNi_yO₂-coated NiO offers interesting features which combine the properties of nickel, lithium and cobalt in molten carbonate. This could be a promising novel MCFC cathode material.     

锑基硫属化合物半导体及太阳电池

锑基硫属化合物是一类性质稳定、环境友好、元素含量丰富、带隙连续可调、光电性质优异的半导体材料,包括硒化锑（Sb₂Se₃）、硫化锑（Sb₂S₃）以及硒硫化锑[Sb₂(S,Se)₃]等。其中,Sb₂(S,Se)₃的带隙和太阳光谱的匹配度较高,比较适合作为太阳电池的光吸收层材料。以Sb₂(S,Se)₃为光吸收层的太阳电池取得了10% 的认证能量转换效率,显示了锑基硫属化合物太阳电池的巨大潜力。本文详细阐述了锑基硫属化合物的材料及光电特性、薄膜制备工艺及缺陷特性。结合近年来锑基硫属化合物太阳电池的研究进展,提出进一步提高锑基硫属化合物太阳电池性能的方向和策略。     

Synthesis of LiNi0.8Co0.2O2 cathode material through sintering in an air environment and electrochemical properties characterization

制备锂离子电池正极材料LiNi_0.8Co_0.2O₂通常需要在纯氧气气氛下进行烧结.本工作以硫酸镍,硫酸钴和氢氧化钠为原料,采用并流共沉淀法制备了高密度Ni_0.8Co_0.2(OH)₂前驱体,再采用高温固相反应法在空气中烧结制备了锂离子电池LiNi_0.8Co_0.2O₂正极材料.采用X射线衍射(XRD),扫描电镜(SEM),恒流充放电测试(ECT),循环伏安(CV)与比表面积(BET)测试等方法对目标样品进行了表征,详细考察了烧结条件对材料结构,微观形貌及电化学性能的影响.结果表明,锂/(钴+镍)摩尔比为1.13∶1时,在管式炉中和空气气氛下于第一段烧结温度700 ℃保温9 h,于第二段烧结温度750 ℃保温12 h,合成的材料比表面积适中(0.78 m²/g),具有规则的六边形α-NaFeO₂层状结构,晶粒分布均匀,电化学性能最优.在0.5 C充放电倍率下和2.7~4.3 V电压范围内,其首次放电比容量达到153.0 mA·h/g,循环20次后放电比容量仍为150.7 mA·h/g,容量保持率达到98.5%,显示了优异的循环稳定性能,可用做高能量密度动力电池正极材料.     

AC Impedance of Li(Ni1/3Co1/3Mn1/3)O2/graphite cell as UPS

以Li（Ni_1/3Co_1/3Mn_1/3）O₂/graphite动力电池为研究对象,在模拟备用电源工况下对动力电池进行交流阻抗测试。通过建立等效电路来研究欧姆阻抗R_s、电荷传递阻抗R_ct和扩散阻抗CPE_W随不同搁置时间、荷电状态（state of charge,SOC）的变化规律,研究Li（Ni_1/3Co_1/3Mn_1/3）O₂/graphite动力电池在备用电源工况下,容量和阻抗的变化趋势。结果表明：随着搁置时间的增加,电池容量衰减1.7%左右。随着搁置时间的增加,不同SOC下的欧姆阻抗R_s具有相同的变化趋势,电荷传递阻抗明显增加。随着SOC的降低,由双电层产生的电荷传递阻抗在逐渐增加。在SOC=0%时,扩散阻抗随搁置时间的增加而增加,在SOC=100%、50%的扩散阻抗有细微的增加。容量衰退和阻抗结果显示出Li（Ni_1/3Co_1/3Mn_1/3）O₂/graphite动力电池可以很好地在备用电源工况上使用。     

Lithium insertion into manganese dioxide electrode in MnO2/Zn aqueous battery: Part I. A preliminary study

The discharge characteristics of manganese dioxide (γ-MnO₂ of electrolytic manganese dioxide (EMD) type) as a cathode material in a Zn–MnO₂ battery containing saturated aqueous LiOH electrolyte have been investigated. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) data on the discharged material indicate that lithium is intercalated into the host structure of EMD without the destruction of its core structure. The XPS data show that a layer of insoluble material, possibly Li₂CO₃, is deposited on the cathode, creating a barrier to H₂O, thus preventing the formation of Mn hydroxides, but allowing the migration of Li ions into the MnO₂ structure. The cell could be reversibly charged with 83% of voltaic efficiency at 0.5 mA/cm² current density to a 1.9 V cutoff voltage. The percentage utilization of the cathode material during discharge was 56%.     

A new way of obtaining LixNi1−xO cathodes for molten-carbonate fuel cells

An unsintered nickel plaque containing Li₂CO₃ and an organic binder were tested as a cathode in a molten-carbonate fuel cell. Organic burnout, nickel oxidation,lithium carbonate decomposition and Li_xNi_1−xO solid-solution formation occurred during the start-up of the cell. The in-cell test showed good performance after a short time of operation, and a limited performance decay after 3500 h.     

NiO–ScSZ and Ni0.9Mg0.1O–ScSZ-based anodes under internal dry reforming of simulated biogas mixtures

Solid oxide fuel cells (SOFCs) with NiO–ScSZ and Ni_0.9Mg_0.1O–ScSZ-based anodes were operated by directly feeding a fuel mixture of CH₄, CO₂ and N₂ (CH₄ to CO₂ ratio of 3:2). Stable operation under constant current load (200 mA cm⁻²) was achieved with a NiO–ScSZ type anode during 200 h operating hours at 900 °C. Less stable operation occurred with a Ni_0.9Mg_0.1O–ScSZ type anode. In the case of SOFC with Ni_0.9Mg_0.1O–ScSZ as the anode, the methane reforming activity was higher than that with NiO–ScSZ. This was explained by change in the microstructure promoting reforming reactions. However, the addition of MgO resulted in degradation of electrochemical performance due to increase in ohmic resistance of the anode material during operation.     

The influence of noble-metal-containing cathodes on the electrochemical performance of anode-supported SOFCs

In order to enhance the catalytic activity of the cathode for oxygen reduction and thus to increase the electrochemical performance of planar anode-supported solid oxide fuel cells, Pd, Ag, or Pt was added to the cathode. Four routes were used to add these noble metals: infiltration of the cathode with a Pd solution, deposition of Pt on the electrolyte surface, mixing of La_0.65Sr_0.30MnO₃ (LSM) and YSZ cathode powders with different metal precursors (Pt and Pd black, Pd on activated carbon, Ag powder, Ag₂O, Ag acetate, Ag citrate, Ag₂CO₃, colloidal Ag, AgNO₃), and synthesis of LSM powder with the addition of AgNO₃.

Between 750 and 900 °C no electrocatalytic effect occurred with respect to the presence of Pt, either added by deposition on the electrolyte or by mixing with cathode powders. Infiltration of the cathode with a Pd solution or mixing with Pd black did not result in a positive effect either. A catalytic effect was only found with Pd on activated carbon and in particular at lower temperatures.

Cells prepared with Ag powder and Ag₂O showed an improved electrochemical performance compared to Ag-free cells sintered at the same temperature (920 °C). However, in comparison to Ag-free cells sintered at the standard temperature (1100 °C) lower current densities were measured. This can be explained by a weak contact between electrolyte and cathode functional layer and an insufficiently sintered cathode. A detrimental effect was observed regarding the addition of the other Ag precursors. Thermal decomposition of these precursors resulted in the formation of large pores in the cathode.     

Electrochemical thermal stability of the LiFePO4/LiNi0.8Co0.15Al0.05O2 blend cathode material for lithium ion batteries

为了改善LiNi_0.8Co_0.15Al_0.05O₂正极材料的电化学热稳定性能,加入LiFePO₄共混制成了LiFePO₄/LiNi_0.8Co_0.15Al_0.05O₂锂离子电池用混合正极材料。使用X射线衍射（XRD）和扫描电子显微镜（SEM）表征了结构和形貌,测试了电化学性能。结果显示,简单球磨的混合LiFePO₄/LiNi_0.8Co_0.15Al_0.05O₂正极材料中,纳米LiFePO₄粒子包覆在LiNi_0.8Co_0.15Al_0.05O₂粒子表面提高了混合正极材料在充放电过程中的电化学稳定性和结构稳定性。LiFePO₄/LiNi_0.8Co_0.15Al_0.05O₂混合正极材料在50 ℃下循环100周容量保持率为82.0%,明显地优于单一LiNi_0.8Co_0.15Al_0.05O₂材料的72.9%。     

The degradation analysis of lithium-ion storage battery with Li4Ti5O12 anode

钛酸锂作为储能电池负极材料,在长循环和安全性上有突出的表现。通过对室温1C和2C倍率下循环的三元+钴酸锂/钛酸锂储能电池拆解,结合SEM、FTIR、XRD和EIS等分析手段,发现造成容量衰减和阻抗增大的原因出现在正极,由于正极与电解液发生反应,在表面生成界面膜,并且循环过程中界面膜不稳定,进一步消耗活性锂离子导致。另外,对这款电池的产气分析发现,所产生气体的主要成分为CO2和C2H6,原因可能是在制备电池过程中严格控制水分以及在电解液添加剂方面做了改进。     

Synthesis of SnO2/C anode for lithium ion battery by a reflux-assisted hydrothermal method

以氯化亚锡(SnCl₂·2H₂O)及聚乙烯吡咯烷酮(polyvinylpyrrolidone,PVP)为原料,通过回流辅助水热法制备了SnO₂/C复合材料并将其用作锂离子电池负极材料.采用X射线衍射仪(XRD),扫描电子显微镜(SEM)和透射电子显微镜(TEM)分析材料的结构和形貌;用恒流充放电,交流阻抗(EIS)和循环伏安(CV)对复合材料作为锂离子电池负极材料的电化学性能进行表征.所制备的复合材料中,纳米SnO₂晶粒(5~10 nm)均匀分散在由PVP热解形成的无定形碳中.电化学性能测试表明,该复合材料100次循环后,可逆容量为591.7 mA·h/g,呈现较好的循环性能.优异的电化学性能主要归因于纳米SnO₂颗粒在无定形碳基体中均匀分散及无定形碳对锡颗粒体积变化的有效缓冲.     

Sm0.5Sr0.5CoO3 + Sm0.2Ce0.8O1.9 composite cathode for cermet supported thin Sm0.2Ce0.8O1.9 electrolyte SOFC operating below 600 °C

The cathode is a key component in low temperature solid oxide fuel cells. In this study, composite cathode, 75 wt.% Sm_0.5Sr_0.5CoO₃ (SSC) + 25 wt.% Sm_0.2Ce_0.8O_1.9 (SDC), was applied on the cermet supported thin SDC electrolyte cell which was fabricated by tape casting, screen-printing, and co-firing. Single cells with the composite cathodes sintered at different temperatures were tested from 400 to 650 °C. The best cell performance, 0.75 W cm⁻² peak power operating at 600 °C, was obtained from the 1050 °C sintered cathode. The measured thin SDC electrolyte resistance R_s was 0.128 Ω cm² and total electrode polarization R_p(a + c) was only 0.102 Ω cm² at 600 °C.     

Electrochemical characteristics and cycle performance of LiMn2O4/a-Si microbattery

A LiMn₂O₄ thin film and an amorphous Si (a-Si) thin film were prepared by radio-frequency (rf) magnetron sputtering. Each thin film was electrochemically evaluated by cyclic voltammetry (CV) and galvanostatic cycling. The rate of capacity fade on cycling was monitored as a function of the voltage window and current density. This was compared with the cycle performance of cathode and anode using two kinds of electrolyte, 1 M LiPF₆ in EC/DMC and PC, for 100 cycles. It was found that the discharge capacity of optimized LiMn₂O₄/a-Si full-cell reached 24 μAh/(cm²-μm) in the first cycle, and a reversible capacity of about 16 μAh/(cm² μm) was still maintained after 100 cycles. In a voltage window of 3.0–4.2 V, LiMn₂O₄/a-Si full-cell exhibits relatively stable cycle performance compared to a voltage window of 2.75–4.2 V.