First-principles investigation of V2CSe2 MXene as a potential anode material for non-lithium metal ion batteries

The electrochemical performances of the V₂CSe₂ MXene as anode materials for Na, K, Mg, Ca, and Al-ion batteries have been systematically investigated by the first-principles method. The adsorption energies of metal atoms show that Na, K, and Ca atoms can effectively adsorb on the V₂CSe₂, except for Mg and Al atoms. The large diffusion constants for Na, K, and Ca atoms calculated by the diffusion energy barriers (0.098 eV for Na, 0.066 eV for Ca, and 0.24 eV for Ca) indicate the high mobility on the V₂CSe₂ surface. Significantly, the maximum theoretical capacities of V₂CSe₂ reach up to 394.12 mA h/g for Na and Ca ions. Furthermore, the low average open-circuit voltage (OCV) (0.150 V for Na, 0.175 V for K, and 0.072 V for Ca) indicates the V₂CSe₂ is a suitable anode material. These results provide fundamental guidance for the V₂CSe₂ monolayer as anode materials of non-lithium metal-ion batteries.     

First-principles study of C3N nanoribbons as anode materials for Li-ion batteries

The potential of C₃N nanoribbons used as anode material for lithium-ion batteries has been systematically investigated through first-principles calculations. The results suggest that C₃N nanoribbons have excellent mechanical properties (stiffness ranging from 286.28 to 412.69 N m⁻¹) and good electronic conductivity (with a bandgap of 0-0.31 eV). Further studies reveal that the H-passivated C₃N nanoribbons have high Li insertion capacity (708.60 mA h g⁻¹) and significantly enhanced Li binding strength (0.21-2.11 eV) without the sacrifice of Li mobility. The high stiffness, superior cycle performance, good electronic conductivity, and excellent Li migration capability indicate the great potential of C₃N nanoribbons to be an anode material. The calculated results provide the valuable insights for the development of high-performance C₃N nanoribbons electrode materials in lithium-ion batteries.     

室温钠离子电池材料及器件研究进展

在众多电化学储能技术中,室温钠离子电池除具有能量密度高、循环寿命长的特点外,还具有其他电池体系所不具有的资源丰富和成本低廉的优势,是一种较理想的规模储能电池体系.中国科学院物理研究所自2011年以来致力于低成本、安全环保的钠离子电池技术的研发,在正、负极材料和电解质材料开发中取得了多项原创性的研究成果,并研制出Ah级钠离子软包电池.例如,首次发现Cu~(2+)/Cu~(3+)氧化还原电对高度可逆并设计了Na-Cu-Fe-Mn-O基低成本层状氧化物正极材料;首次通过简单的一步碳化法制备出性价比高的无烟煤基负极材料;首次将一种新型的钠盐NaFSI应用于碳酸酯非水电解质以大幅度提升电极材料的性能等.本文综述了物理所在钠离子电池材料及器件研究中所取得的重要进展和突破,期待经过进一步不懈地努力为实现钠离子电池的产业化做出重要贡献.     

Hierarchical hollow urchin-like structured MnO2 microsphere/carbon nanofiber composites as anode materials for Li-ion batteries

In this work, novel hollow urchin-like MnO₂ microspheres (u-MnO₂), consisting of a hollow core with nanotubes, are synthesized by a simple hydrothermal process. The morphology of the MnO₂ structures could be tuned from round particles to a hierarchical hollow urchin structure by controlling the hydrothermal reaction time, with no need for surfactant or templates. The nanostructures of the obtained u-MnO₂ are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The X-ray diffraction (XRD) pattern of the u-MnO₂ reveals a tetragonal structure of α-MnO₂. The carbon nanofibers (CNFs) are uniformly deposited on u-MnO₂ to improve the electrical conductivity and to utilize the hierarchical architecture of u-MnO₂. As the anode electrode of Li-ion batteries, the u-MnO₂/CNFs nanocomposites exhibit discharge capacity of 988 mAh·g⁻¹ after 100 cycles with a good rate capability. The superior electrochemical performances of the u-MnO₂/CNFs nanocomposites can be attributed to the hierarchical urchin-like structures and the superior electrical conductivity of the nanocomposites, which can facilitate fast electron and ion transport and accommodate a large volume change during charge/discharge.     

Template-free synthesis of hierarchical NiO microtubes as high performance anode materials for Li-ion batteries

Hierarchical nanostructured NiO (h-NiO) microtubes were prepared by a simple wet-chemical synthesis without the use of template or surfactant, followed by the calcination of α-Ni(OH)₂ precursor. The structural characterization of the h-NiO microtubes were performed by scanning microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), the results of which indicated that the obtained h-NiO microtubes are covered by the nanosheet grown perpendicularly on the tube surface. The unique hierarchical nanostructure of h-NiO microtubes with high surface area and many voids facilitates the electrochemical reaction as well as the short ion and electron transport pathway. Therefore, as anode electrode of Li-ion batteries, the h-NiO microtubes deliver largely enhanced cycle capacity of 770 mAh·g⁻¹ at a current density of 0.5 C after 200 cycles with high columbic efficiency, compared to the NiO rods. These results suggest that the h-NiO microtubes can be a promising anode material for Li-ion batteries.     

Nanoporous silicon flakes as anode active material for lithium-ion batteries

Nanoporous-silicon (np-Si) flakes were prepared using a combination of an electrochemical etching process and an ultra-sonication treatment and the electrochemical properties were studied as an anode active material for rechargeable lithium-ion batteries (LIBs). This fabrication method is a simple, reproducible, and cost effective way to make high-performance Si-based anode active materials in LIBs. The anode based on np-Si flakes exhibited a higher performances (lower capacity fade rate, stability and excellent rate capability at high C-rate) than the anode based on Si nanowires. The excellent performance of the np-Si flake anode was attributed to the hollowness (nanoporous structure) of the anode active material, which allowed it to accommodate a large volume change during cycling.     

Synthesis of nanosized Si composite anode material for Li-ion batteries

A simple method was proposed to prepare nanosized Si composite anode materials for lithium-ion (Li-ion) batteries. The preparation started with the shock-type ball milling of silicon in liquid media of polyacrylonitrile (PAN)/dimethylformamide (DMF) solution, forming slurry where the nano-Si particles were uniformly dispersed, followed by the drying of the slurry to remove DMF. The nanosized Si composite anode material was obtained after the pyrolysis of the mixture at 300 °C where the pyrolyzed PAN provided a conductive matrix to relieve the morphological change of Si during cycling. As-prepared composite presented good cyclability for lithium storage. The proposed process paves an effective way to prepare high performance Si, Sn, Sb and their alloys based composite anode materials for Li-ion batteries.     

Synthesis and characterization of TiO2-coated magnetite clusters (nFe3O4@TiO2) as anode materials for Li-ion batteries

TiO₂-coated magnetite clusters (nFe₃O₄@TiO₂) were facilely prepared through the sol–gel reaction between Ti alkoxides (TEOT) and magnetite clusters (nFe₃O₄) with terminated alkoxy groups. The composite particles represented a core–shell nanostructure (nFe₃O₄@TiO₂) consisting of a Fe₃O₄ cluster core and a TiO₂ capsule layer. The capsule layer of nFe₃O₄@TiO₂ was increased with increasing amounts of TEOT (150, 300, 500 μl) in sol–gel reaction. The Fe₃O₄@TiO₂ (150 μl of TEOT) with a thin TiO₂ layer (ca. 10 nm) exhibited two kinds of cathodic (0.79 V and 1.61 V) and anodic (1.78 and 2.1 V) peaks attributed to the reduction and oxidation process by Fe₃O₄ core and TiO₂ layer, respectively. The thin nFe₃O₄@TiO₂ (150 μl of TEOT) exhibited the enhanced capacity retention by ca. 40% probably due to the buffering effect of TiO₂ capsule layer. However, the thick nFe₃O₄@TiO₂ (300–500 μl of TEOT) exhibited a rapid capacity fading due to the disintegrated core–shell nanostructure, i.e., unfavorable hetero-junction between TiO₂ matrix and magnetite clusters.     

Development and characterization of a novel silicon-based glassy composite as an anode material for Li-ion batteries

A novel silicon-based glassy composite anode material with high initial coulombic efficiency and long cycling performance for lithium-ion batteries was synthesized by a wet mechanochemical reduction method. The in situ formed Si particles with size of 5-10 nm were uniformly distributed in the glassy matrices formed by B₂O₃ and P₂O₅. The as-prepared composite electrode revealed an initial charge and discharge capacity of 432.7 and 514.4 mAh g^− 1, respectively, with an initial coulombic efficiency of 84%. After 100 cycles, the reversible capacity retention rate was still up to 97%, meaning a favorable cycling stability.     

Computational screening of electroactive indolequinone derivatives as high-performance active materials for aqueous redox flow batteries

The development of an organic-based aqueous redox flow battery (RFB) using quinone as an electroactive material has attracted great attention recently. This is because this battery is inexpensive, produces high energy density, and is environment friendly in stationary electrical energy storage applications. Herein, we investigate the redox potentials and solubilities of indole-5,6-quinone and indole-4,7-quinone derivatives in terms of the substituent effects of functional groups using theoretical calculations. Our results indicate that full-site substituted derivatives of indolequinone are more useful as active materials compared to single-site substituted derivatives. In particular, our calculations reveal that the substitution of –PO₃H₂ and –SO₃H functional groups with multiple polar bonds is very effective in increasing the activity of the aqueous RFB. As a strategy to overcome the limitation that the aqueous solubility is intrinsically low because they are organic molecules, we suggest the substitution of functional groups with multiple polar bonds to the backbones of active organic materials. Among 180 indolequinone derivatives, 17 candidates that meet the redox potential standards (≦ 0.2 V or ≧ 0.9 V) and eight candidates with solubility exceeding 2 mol/L are identified. Three indolequinone derivatives that satisfy both conditions are finally presented as promising electroactive candidates for an aqueous RFB.     

Pyrolysed pitch-polysilane blends for use as anode materials in lithium ion batteries II: the effect of oxygen

As previously reported, blends of pitch and polysilanes, (Me₂Si)_x(PhMeSi)_y, with various pitch/polysilane ratios were pyrolysed at 1000 °C [W. Xing, A.M. Wilson, G. Zank, J.R. Dahn, Solid State Ionics 93 (1997) 239]. Some of the pyrolysed mixtures demonstrated large reversible capacities for lithium insertion (600 mA h g⁻¹), small irreversible capacities (150–200 mA h g⁻¹) and small hysteresis between charge and discharge cycles. Here, we investigate the role of the oxygen in these materials. The magnitude of the irreversible capacity and hysteresis are correlated to the oxygen content. This suggests that these materials are disordered carbons containing nanodispersed silicon oxycarbide clusters and not nanodispersed silicon, as was previously suggested. This does not change our opinion that pyrolysed pitch-polysilane blends are good alternatives to carbons for anode materials in lithium ion batteries.     

锂离子电池硅基负极材料嵌锂行为的第一性原理研究

采用基于密度泛函理论的第一性原理平面波赝势方法,计算不同数量的锂离子引起的硅材料晶体结构的变化以及在嵌锂过程中形成Li_xSi(x=1、2、2.4、4.4)合金相的形成能与电子结构.采用LST/QST方法计算过渡态,模拟合金体相中的锂离子迁移过程.计算结果表明,随着嵌锂数量的增加,硅晶胞的体积在不断增大;Li_xSi合金相的形成能为负值,表明在嵌锂过程中锂离子和硅原子可以自发形成这些合金相,其中Li₇Si₃合金最容易形成;随着嵌锂量的增加,锂离子在费米能级处s轨道提供的电子数逐渐增加,锂硅合金在费米能级处的电子数量呈增大趋势,表明锂硅合金的导电性越来越优;常温下Li₂Si体相中很难直接形成锂离子空位,但锂离子空位的迁移过程很容易发生.     

Capacity improvement of mechanically and chemically treated Sri Lanka natural graphite as an anode material in Li-ion batteries

Sri Lanka natural graphite is found in various morphologies with different structural and physical characteristics. The most abundant morphology, the shiny–slippery–fibrous graphite found in Bogala mines (BSSI), has a very high purity of more than 98% and high crystallinity. Pure natural graphite as well as mechanically ball-milled and chemically oxidated in air or with (NH₄)₂S₂O₈ graphite has been evaluated as an anode material for Li-ion battery application, with a focus on improvement of the reversible capacity. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Facile synthesis of low-dimensional SnO2 nanostructures: An investigation of their performance and mechanism of action as anode materials for lithium-ion batteries

Owing to high-energy density of rechargeable lithium-ion batteries (LIBs), they have been investigated as an efficient electrochemical power sources for various energy applications. High theoretical capacities of tin oxide (SnO₂) anodes have led us a path to meet the ever-growing demands in the development of high-performance electrode materials for LIBs. In this paper, a facile approach is described for the synthesis of porous low-dimensional nanoparticles and nanorods of SnO₂ for application in LIBs with the help of Tween-80 as a surfactant. The SnO₂ samples synthesized at different reaction temperatures produced porous nanoparticles and nanorods with average diameters of ~7–10 nm and ~70–110 nm, respectively. The SnO₂ nanoparticle electrodes exhibit a high reversible charge capacity of 641.1 mAh/g at 200 mA/g after 50 cycles, and a capacity of 340 mAh/g even at a high current density of 1000 mA/g during the rate tests, whereas the porous nanorod electrodes delivers only 526.3 mAh/g at 200 mA/g after 50 cycles and 309.4 mAh/g at 1000 mA/g. It is believed that finer sized SnO₂ nanoparticles are much more favorable to trap more Li⁺ ion during electrochemical cycling, resulting in a large irreversible capacity. In contrast, rapid capacity fading was observed for the porous nanorods, which is the result of their pulverization resulting from repeated cycling.     

Theoretical investigations of the effect of vacancies on the geometric and electronic structures of zinc sulfide

The effects of S-vacancy and Zn-vacancy on the geometric and electronic structures of zinc blende ZnS are investigated by the first-principles calculation of the plane wave ultrasoft pseudopotential method based on the density functional theory. The results demonstrate that both S-vacancy and Zn-vacancy decrease the cell volume and induce slight deformation of the perfect ZnS. Furthermore, this change of geometric structure caused by Zn-vacancy is more obvious than the one due to the S-vacancy. The formation energy of S-vacancy is higher than that of Zn-vacancy, indicating that Zn-vacancy is easier to form than S-vacancy in ZnS crystal. Electronic structure analysis shows that Zn-vacancy increases the band-gap of ZnS from 2.03 eV to 2.15 eV, while the S-vacancy has almost no effect on the band-gap of ZnS. Bond population analysis shows that Zn-vacancy increases covalence character of the Zn–S bonds around Zn-vacancy, while S-vacancy shows a relatively weak effect on the covalence character of Zn–S bonds.     

B掺杂的石墨烯作为钠离子电池负极材料的研究

采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯及缺陷石墨烯对钠原子的吸附行为.主要研究了三种石墨烯:本征石墨烯(P-graphene)、硼掺杂的石墨烯(Defect-Ⅰ)和硼掺杂的叽咯石墨烯(Defect-Ⅱ).结果表明,与P-graphene相比,Defect-Ⅰ和Defect-Ⅱ在吸附能、电荷密度、态密度和储钠量方面表现出很大的差异.Defect-Ⅰ和Defect-Ⅱ对钠原子的吸附能分别是-3.250 eV和-2.332 eV,约为P-graphene对钠原子吸附能的1.71倍和1.23倍.态密度计算结果表明,Defect-Ⅰ和Defect-Ⅱ中钠原子与硼原子发生轨道杂化,而P-graphene中不存在轨道杂化现象.Defect-Ⅰ和Defect-Ⅱ对钠原子的吸附量分别是9和8个,与P-graphene相比提高.因此,石墨烯中掺杂硼有望成为一种新型的储钠材料.     

The influence of nitrogen vacancies on the magnetic and electronic properties of ruthenium mononitride: First-principles study

We present FLAPW-GGA calculations of the magnetic and electronic properties of cubic RuN_x (x=1.0, 0.75 and 0.50). We find that RuN exhibits a ferromagnetic ground state and the local ruthenium magnetic moment abruptly decreases with nitrogen vacancies. The relative positions of t_2g and e_g states and the Ru 4d–N 2p hybridization in RuN_x are discussed. We have also found that the magnetic behavior for RuN_x vs. FeN_x as dependent on the nitrogen vacancies content displays an opposite trend.     

Structural and Electronic Properties of Li2Mg(NH)2 for Hydrogen Storage: First-principles Study

应用第一原理方法研究了储氢材料α-Li₂Mg(NH)₂和β-Li₂Mg(NH)₂两种构型的结构性质和电子性质．计算优化得到的晶胞参数和N-H键长符合实验得到的数据．通过Murnaghan状态方程得到了体积模量和零压力下的能量,计算结果表明α-Li₂Mg(NH)₂为基态构型．通过Mulliken布居分析说明α构型的N-Li/Mg的离子特性和N-H间的交互作用都弱于β构型．态密度分析结果表明,价带轨道主要由N原子的s轨道和p轨道占据,并与H原子的s轨道杂化．     

Synthesis and electrochemical properties of nanostructured Li2FeSiO4/C cathode material for Li-ion batteries

Nanostructured Li₂FeSiO₄/C was synthesized by high-energy ball-milling and the amorphous citrate-assisted techniques. Similar redox behaviour is observed for samples prepared by the amorphous citrate-assisted route followed by a 4 h heat treatment: 0.3 V polarization and more sloping behaviour was observed when cycling between 2.0 V and 3.7 V at 60 °C; lower capacity fade is also observed compared to Li₂FeSiO₄/C prepared by the solid-state reaction technique. A discharge capacity of 102 mA h g^− 1 is obtained for samples prepared by the high-energy ball-milling method, while capacities decrease from 95 to 77 mA h g^− 1 using the amorphous citrate method for heat-treatment times increasing successively from 4 h to 18 h.