Lithium electrochemistry of NiSe2: A new kind of storage energy material

NiSe₂ thin film has been successfully fabricated by reactive pulsed laser deposition and was investigated for its electrochemistry with lithium for the first time. The reversible discharge capacities of NiSe₂/Li cells cycled between 1.0 V and 3.0 V were found in the range of 314.9–467.5 mA h g⁻¹ during the first 200 cycles. By using ex situ X-ray diffraction, transmission electron microscopy, and selected-area electron diffraction measurements, the intermediates of β-NiSe, and Ni₃Se₂ were identified during the reversible conversions of NiSe₂ into metal nickel and Li₂Se. Both cation (nickel) and anion (selenium) in NiSe₂ provide the redox active centers in its electrochemical reaction with lithium, indicating one of the features of its lithium electrochemistry. The high reversible capacity and good cycle ability of NiSe₂ electrode made it become a promising cathode material for future rechargeable lithium batteries.     

Nanocrystalline ZnMn2O4 as a novel lithium-storage material

Nanocrystalline ZnMn₂O₄ is prepared by a polymer-pyrolysis route and used as a novel anode for lithium ion batteries. XRD and HRTEM studies reveal that the products are highly phase-pure and 30–60 nm in size. Galvanostatic cycling of ZnMn₂O₄ electrode at 100 mA g⁻¹ (about 0.52 mA cm⁻²) between 0.01 and 3.0 V up to 50 cycles exhibits almost stable cycling performance between 10 and 50 cycles with only an average capacity fade of 0.20% per cycle and the electrode still maintains a capacity of 569 mAh g⁻¹ after 50 cycles.     

Electrochemical properties of polyaniline in p-toluene sulfonic acid solution

Polyaniline was deposited potentiodynamically on a stainless steel substrate in the presence of an inorganic acids (sulfuric acid). The electrochemical characterization of the electrode was carried out by means of cyclic voltammetry and electrochemical impedance spectroscopy in the organic acids (p-toluene sulfonic acid) solution. The results show that polyaniline has a high specific capacitance of 431.8 F g⁻¹ at 1 mV s⁻¹, high coulombic efficiency of 95.6% at 20 mV s⁻¹, and exhibits a high reversibility. This indicates the promising feasibility of the polyaniline used as an electrochemical capacitor material in the electrolyte of p-toluene sulfonic acid solution especially at high charge–discharge process.     

Preparation and electrochemical study of a new magnesium intercalation material Mg1.03Mn0.97SiO4

Orthorhombic magnesium manganese silicate (Mg_1.03Mn_0.97SiO₄) was prepared and evaluated as a new cathode material for rechargeable magnesium batteries. Although the electrochemical activity of the Mg_1.03Mn_0.97SiO₄ synthesized by high-temperature solid-state reaction is low, the magnesium storage capacity of nanosized Mg_1.03Mn_0.97SiO₄ prepared by modified sol–gel route and in situ carbon coating reaches 244 mAh g⁻¹. The capacity increase mechanism during charge/discharge cycling was also preliminary studied.     

Enhanced overcharge behavior and thermal stability of commercial LiCoO2 by coating with a novel material

Commercial LiCoO₂ has been modified with MnSiO₄ as a novel coating material. The structures, morphologies, overcharge behaviors and thermal stabilities of the pristine and MnSiO₄-coated LiCoO₂ materials were studied. The MnSiO₄-coated LiCoO₂ had initial discharge specific capacities of 181.1 and 232.2 mAh g⁻¹ within the potential ranges 2.75–4.5 and 2.75–4.7 V (vs. Li⁺/Li), respectively. It was found that the overcharge tolerance of the coated cathode was significantly better than that of the pristine LiCoO₂ under the same conditions – the discharge specific capacities of the coated cathode at upper charge cutoff voltages of 4.5 and 4.7 V were as high as 168.7 and 154.3 mAh g⁻¹, respectively, after 50 cycles. Moreover, DSC showed that the coated LiCoO₂ had a higher thermal stability than the pristine LiCoO₂.     

Preparation and performance comparison of LiMn2O3.95Br0.05 and LiMn2O3.95Br0.05/SiO2 cathode materials for lithium-ion battery

LiMn₂O_3.95Br_0.05 and LiMn₂O_3.95Br_0.05/SiO₂ cathode composites for lithium-ion battery are prepared by solid-state reaction methods. The crystalline structures of the as-synthesized samples are investigated by X-ray diffraction and transmission electron microscope; at the same time, the electrochemical performances are tested by cyclic voltammetry and galvanostatic cycling. The results reveal that the sample of LiMn₂O_3.95Br_0.05/SiO₂ has more excellent electrochemical performance than the sample of LiMn₂O_3.95Br_0.05. It delivers an initial discharge capacity of 145.3 mA h g⁻¹ at ambient temperature, and 138.9 mA h g⁻¹ at the higher temperature of 55 °C with good capacity retention with the voltage range of 3.0–4.35 V (vs. Li) at a current density of 0.5 C; while the sample of LiMn₂O_3.95Br_0.05 only deliver initial discharge capacity 136.5 mA h g⁻¹ at ambient temperature, and 119.2 mA h g⁻¹ at 55 °C in the same conditions; in addition, the rate performance of LiMn₂O_3.95Br_0.05/SiO₂ is excellent too, so the SiO₂ layer has improved the electrochemical behaviors of LiMn₂O_3.95Br_0.05 availably.     

Solvent effect on the blue shifted weakly H-bound F3 CH…FCD3 complex

Solvent effect on the ν^c frequency of CH stretching vibration of the blue shifted F₃CH…FCD₃ complex has been studied in liquefied N₂, CO, Ar, Kr and Xe. In the case of Xe, the spectroscopic measurements have also been extended to the solid state. It was found that the ν^c position of the complex in the solutions studied lowers with respect to the value in the gas phase. In liquid Xe, characterized by the largest permittivity, this effect reaches its maximum value of −14.5 cm⁻¹. The ν^c frequency begins to grow again just below the freezing point of Xe, where a noticeable (15%) increase of the density of Xe occurs. The experimental results obtained for the liquid phase have been analyzed in the framework of the Onsager-like reaction field model and Polarizable Continuum Model (PCM) implemented into a standard Gaussian 98 Program.     

The phase transition behaviors of Li1−xMn0.5Fe0.5PO4 during lithium extraction studied by in situ X-ray absorption and diffraction techniques

How the structural changes take place in LiMn_yFe_1−yPO₄-type cathode materials during lithium extraction/insertion is an important issue, especially on if they go through the single-phase reaction (i.e., solid solution reaction) or the two-phase reaction regions. Here we report the studies on the phase transition behaviors of a carbon coated Li_1−xMn_0.5Fe_0.5PO₄ (CLi₁₋xMn_0.5Fe0_.5PO₄, 0.0  x  1.0) sample during the first charge using in situ X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques. The combination of in situ XAS and XRD results clearly identify two two-phase coexistence regions at two voltage plateaus of 3.6 (Fe²⁺/Fe³⁺) and 4.2 V (Mn²⁺/Mn³⁺) and a narrow intermediate region which proceeds via single-phase reaction in between two two-phase regions. In addition, simultaneous redox reactions of Fe²⁺/Fe³⁺ and Mn²⁺/Mn³⁺ in the narrow single-phase region are reported and discussed for the first time.     

Electronic structure theory investigation on the electrochemical properties of cyclohexanone derivatives as organic carbonyl-based cathode material for lithium-ion batteries

Organic carbonyl-based compounds with redox-active site have recently gained full attention as organic cathode material in lithium-ion batteries (LIBs) owing to its high cyclability, low cost, high abundance, tunability of their chemical structure compared to traditionally used inorganic material. However, the utilization of organic carbonyl-based compounds in LIBs is limited to its poor charge capacity and dissolution of lower molecular weight species in electrolytes. In this study, we theoretically investigated five set of cyclohexanone derivatives (denoted as: H₁, H₂, H₃, H₄, and H₅) and influence of functional groups (-F and -NH₂) on their electrochemical properties using advanced level density functional theory (DFT) with the Perdew-Burke-Ernzenhof hybrid functional (PBE0) at 6-31+G(d,p) basis set. In line with the result gotten, the HOMO-LUMO results revealed that compound H₅ is the most reactive among the studied cyclohexanone derivatives exhibiting energy gap values of 0.552, 0.532, 0.772 eV for free optimized structures and structurally engineered structures with electron withdrawing group (EWG) and electron donating group (EDG) respectively. Also, results from electrochemical properties of the studied compounds lithiated with only one lithium atom displayed that compound H₂ exhibited interesting redox potential and energy density for all the studied structures in free optimized state (1108.28 W h kg^?1, 4.92 V vs Li/Li⁺), with EWG (648.22 W h kg^?1, 3.313 V Li/Li⁺), and with EDG (1002.4 W h kg^?1, 5.011 V vs Li/Li⁺). From our result, we can infer that compound H₂ and H₃ with corresponding redox potential, energy density and theoretical charge capacity value of 4.92 V vs Li/Li⁺, 1108.28 W h kg^?1, 225.26 mA h g^?1 and 5.168 V, 1041.61 W h kg^?1, 201.55 mA h g^?1 lithiated with only one lithium atom in free optimized state are the most suitable compounds to be employed as organic cathode material in lithium-ion batteries among all the investigated cyclohexanone derivatives.     

锂离子电池正极材料Li1.2Mn0.54-xNi0.13Co0.13ZrxO2的制备及电化学性能

为了改善富锂锰基正极材料Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ 的循环性能,采用燃烧法合成了正极材料Li_1.2Mn_0.54-xNi_0.13Co_0.13Zr_xO₂（x=0.00,0.01,0.02,0.03,0.06）. 通过X射线衍射（XRD）和扫描电镜（SEM）对其结构与形貌进行了表征,利用恒电流充放电测试,循环伏安（CV）及电化学交流阻抗谱（EIS）技术对其电化学性能进行测试. 结果表明,Li_1.2Mn_0.54-xNi_0.13Co_0.13Zr_xO₂（x=0.00,0.01,0.02,0.03,0.06）正极材料均具有α-NaFeO₂型层状结构;在室温,2.0-4.8 V电压范围,以0.1C和1.0C（充放电电流以1.0C=180 mA·g^-1计算）倍率充放电进行测试,样品Li_1.2Mn_0.52Ni_0.13Co_0.13Zr_0.02O₂的首次放电比容量分别为280.3 和206.4 mAh·g^-1. 其中,在1.0C倍率下,100次循环后容量保持率由原来的73.2%提高到88.9%;以5.0C倍率充放电进行测试,经50次循环后,掺杂正极材料的放电比容量为76.5 mAh·g^-1,而未掺杂材料仅有15.0 mAh·g^-1. 在50、25 和-10 ℃,2.0C倍率条件下,掺杂正极材料的电化学性能均得到有效改善,其中,在- 10℃ 经过50 次循环后正极材料Li_1.2Mn_0.52Ni_0.13Co_0.13Zr_0.02O₂比未掺杂的正极材料相比,其放电比容量提高了61.1%.     

Preparation and electrochemical performance of Li3V2(PO4)3/C cathode material by spray-drying and carbothermal method

Composite Li₃V₂(PO₄)₃/C cathode material can be synthesized by spray-drying and carbothermal method. The monoclinic-phase Li₃V₂(PO₄)₃/C was prepared with the process of double spray drying at 260 °C and subsequent heat treatment at 750 °C for 12 h. The results indicate that the Li₃V₂(PO₄)₃/C presents large reversible discharge capacity of 121.9 mA h g⁻¹ and charge capacity of 131.8 mA h g⁻¹ at the current density of C/5, good rate capability with 61.1 mA h g⁻¹ at 20C, and excellent capacity retention rate close to 100% at various current densities in the region of 3.0–4.3 V.     

Glass–ceramic Li2S–P2S5 electrolytes prepared by a single step ball billing process and their application for all-solid-state lithium–ion batteries

We report that glass–ceramic Li₂S–P₂S₅ electrolytes can be prepared by a single step ball milling (SSBM) process. Mechanical ball milling of the xLi₂S·(100 − x)P₂S₅ system at 55 °C produced crystalline glass–ceramic materials exhibiting high Li-ion conductivity over 10⁻³ S cm⁻¹ at room temperature with a wide electrochemical stability window of 5 V. Silicon nanoparticles were evaluated as anode material in a solid-state Li battery employing the glass–ceramic electrolyte produced by the SSBM process and showed outstanding cycling stability.     

Fabrication of mesoporous SiO2–C–Fe3O4/γ–Fe2O3 and SiO2–C–Fe magnetic composites

A synthetic method for the fabrication of silica-based mesoporous magnetic (Fe or iron oxide spinel) nanocomposites with enhanced adsorption and magnetic capabilities is presented. The successful in situ synthesis of magnetic nanoparticles is a consequence of the incorporation of a small amount of carbon into the pores of the silica, this step being essential for the generation of relatively large iron oxide magnetic nanocrystals (10 ± 3 nm) and for the formation of iron nanoparticles. These composites combine good magnetic properties (superparamagnetic behaviour in the case of SiO₂–C–Fe₃O₄/γ–Fe₂O₃ samples) with a large and accessible porosity made up of wide mesopores (>9 nm). In the present work, we have demonstrated the usefulness of this kind of composite for the adsorption of a globular protein (hemoglobin). The results obtained show that a significant amount of hemoglobin can be immobilized within the pores of these materials (up to 180 mg g⁻¹ for some of the samples). Moreover, we have proved that the composite loaded with hemoglobin can be easily manipulated by means of an external magnetic field.     

富锂层状正极材料Li_2Mn_(1-x)Ti_xO_3的合成及电化学性能

应用简单的高温固相烧结法合成了Ti掺杂改性的Li_2MnO_3材料。电子扫描显微镜、X射线衍射以及X射线光电子能谱分析表明Ti元素取代Mn离子掺入到Li_2MnO_3晶格中,且掺杂能有效地抑制一次颗粒的团聚。电化学阻抗和恒流充放电测试结果表明,在2.0~4.6 V的电压窗口下,掺杂改性的样品Li_2Mn_(0.97)Ti_(0.03)O_3的首圈放电比容量达到209 m Ah·g~(-1),库仑效率为99.5%,循环40圈后容量保持率为94%;当电流密度增大到400 m A·g~(-1)时,掺杂改性的样品仍然可以放出120 m Ah·g~(-1)比容量,远高于同等电流密度下未掺杂的Li_2MnO_3原粉的比容量(52 m Ah·g~(-1))。Ti掺杂可有效地改善Li_2MnO_3的循环稳定性和倍率性能,有利于促进该材料的商业化应用。     

富锂层状正极材料Li2Mn1-xTixO3的合成及电化学性能

应用简单的高温固相烧结法合成了Ti掺杂改性的Li₂MnO₃材料。电子扫描显微镜、X射线衍射以及X射线光电子能谱分析表明Ti元素取代Mn离子掺入到Li₂MnO₃晶格中,且掺杂能有效地抑制一次颗粒的团聚。电化学阻抗和恒流充放电测试结果表明,在2.0~4.6 V的电压窗口下,掺杂改性的样品Li₂Mn_0.9Ti_0.03O₃的首圈放电比容量达到209 mAh·g^-1,库仑效率为99.5%,循环40圈后容量保持率为94%;当电流密度增大到400 mA·g^-1时,掺杂改性的样品仍然可以放出120 mAh·g^-1比容量,远高于同等电流密度下未掺杂的Li₂MnO₃原粉的比容量（52 mAh·g^-1）。Ti掺杂可有效地改善Li₂MnO₃的循环稳定性和倍率性能,有利于促进该材料的商业化应用。     

RbAuUSe3, CsAuUSe3, RbAuUTe3, and CsAuUTe3: Syntheses and structure; magnetic properties of RbAuUSe3

The compounds RbAuUSe₃, CsAuUSe₃, and RbAuUTe₃ were synthesized at 1073 K from the reactions of U, Au, Q, and A₂Q₃ (A=Rb or Cs; Q=Se or Te). The compound CsAuUTe₃ was synthesized at 1173 K from the reaction of U, Au, Te, and CsCl as a flux. These isostructural compounds crystallize in the KCuZrS₃ structure type in space group Cmcm of the orthorhombic system. The structure consists of layers that contain nearly regular UQ₆ octahedra and distorted AuQ₄ tetrahedra. The infinite layers are separated by bicapped trigonal prismatic A cations. The magnetic behavior of RbAuUSe₃ deviates significantly from Curie–Weiss behavior at low temperatures. For T>200 K, the values of the Curie constant C and the Weiss constant θ_p are 1.82(9) emu K mol⁻¹ and −3.5(2)×10² K, respectively. The effective magnetic moment μ_eff is 3.81(9) μ_B. Formal oxidation states of A/Au/U/Q may be assigned as +1/+1/+4/−2, respectively.     

Li3V2(PO4)3/C和Li2.5Na0.5V2(PO4)3/C的结构和电化学性能的比较研究

采用溶胶-凝胶法合成了锂离子正极材料Li3V2(PO4)3/C(LVP/C)及Li2.5Na0.5V2(PO4)3/C,并用XRD、循环伏安及交流阻抗等方法,研究了大量Na+掺杂对材料结构和电化学性能影响。结果表明,大量钠离子的掺杂会使LVP结构由单斜向菱方转变。掺杂化合物Li2.5Na0.5V2(PO4)3/C在0.5 C充电1 C放电时,首次放电容量为118 mAh.g-1,50次循环后容量保持率为92.4%,并发现与单斜LVP存在多个放电平台不同,Li2.5Na0.5V2(PO4)3/C仅在3.7 V处有一个放电平台。     

Synthesis and structure analysis of tetragonal Li7La3Zr2O12 with the garnet-related type structure

We have successfully synthesized a high-purity polycrystalline sample of tetragonal Li₇La₃Zr₂O₁₂. Single crystals have been also grown by a flux method. The single-crystal X-ray diffraction analysis verifies that tetragonal Li₇La₃Zr₂O₁₂ has the garnet-related type structure with a space group of I4₁/acd (no. 142). The lattice constants are a=13.134(4) Å and c=12.663(8) Å. The garnet-type framework structure is composed of two types of dodecahedral LaO₈ and octahedral ZrO₆. Li atoms occupy three crystallographic sites in the interstices of this framework structure, where Li(1), Li(2), and Li(3) atoms are located at the tetrahedral 8a site and the distorted octahedral 16f and 32g sites, respectively. The structure is also investigated by the Rietveld method with X-ray and neutron powder diffraction data. These diffraction patterns are identified as the tetragonal Li₇La₃Zr₂O₁₂ structure determined from the single-crystal data. The present tetragonal Li₇La₃Zr₂O₁₂ sample exhibits a bulk Li-ion conductivity of σ_b=1.63×10⁻⁶ S cm⁻¹ and grain-boundary Li-ion conductivity of σ_gb=5.59×10⁻⁷ S cm⁻¹ at 300 K. The activation energy is estimated to be E_a=0.54 eV in the temperature range of 300–560 K.     

The electronic gas-phase spectrum of B3 radical revisited

The gas-phase electronic spectrum of cyclic-B₃ (D_3h) radical has been remeasured in a supersonic molecular beam using a mass-selective resonant 2-color 2-photon technique, leading to a revision of previously reported spectroscopic constants. The species was prepared by ablation of a boron nitride rod in the presence of helium. Ab intio calculations on the geometries and vertical electronic excitation energies, as well as mass identification, indicate that the detected band, centered at 21848.77(2) cm⁻¹, is the origin of the cyclic-¹¹B₃ system. A spectral fit yields the rotational constants as B″ = 1.2246(45) and C″ = 0.62131(72) cm⁻¹ in the ground state, and B′ = 1.1914(44) and C′ = 0.61173(69) cm⁻¹ in the excited 2 ²E′ state.     

AlF3包覆对Li1.2Mn0.534Ni0.133Co0.133O2正极材料电化学性能的影响

通过共沉淀法制备锂离子电池富锂锰基正极材料Li1.2Mn0.534Ni0.133Co0.133O2,并对其进行AlF3包覆。实验结果表明,通过AlF3包覆,材料的电化学性能得到明显提高。在0.2C下,包覆前材料的首次放电比容量为253 mAh.g-1,首次充放电效率仅为88.8%。经过AlF3包覆,材料的首次放电比容量提高到294 mAh.g-1,首次充放电效率高达96.4%。同样,在1.0C下循环50次,未包覆材料的放电比容量由225 mAh.g-1降到185 mAh.g-1,容量保持率仅为82.2%。经过AlF3包覆,材料的放电比容量由230mAh.g-1仅降为222 mAh.g-1,容量保持率高达96.5%。