Hard carbon/lithium composite anode materials for Li-ion batteries

Hard carbon/lithium composite anode electrode is prepared to reduce the initial irreversible capacity of hard carbon, which hinders practical application of hard carbon in lithium ion batteries, by introducing lithium into hard carbon. Lithium foil effectively compensates the irreversible capacity of hard carbon in the first cycle. A full cell using LiCoO₂ cathode and the composite anode shows much higher initial coulombic efficiency than that of a cell using LiCoO₂ cathode and hard carbon anode. This paves the way to reduce the large initial irreversible capacity of hard carbon. Besides that, this composite anode enables conductive polymer/sulfur composite cathode to be used in Li-ion batteries with non-lithiated anode materials.     

Synthesis and electrochemical behaviour of tin oxide for use as anode in lithium rechargeable batteries

SnO₂ was synthesized by precipitation from an aqueous solution of SnCl₄ and NH₄OH, followed by a heat treatment. The product was characterized by XRD, SEM, FTIR spectroscopy, DSC and TG. The XRD patterns suggest the formation of phase-pure cassiterite form of SnO₂. SEM imaging indicates that the particles obtained are of sub-micron size with good morphology and size control (around ∼300 nm). Electrodes were fabricated by a slurry-coating procedure and the electrochemical performances of these electrodes were evaluated using galvanostatic cycling tests. The results suggest that the heat treated SnO₂ samples deliver higher capacities when cycled between 1.0 and 0.1 V vs. Li⁺/Li and showed coulombic efficiencies of more than 98% in the tenth cycle.     

Nanostructured Si/TiC composite anode for Li-ion batteries

Si/TiC nanocomposite anode was synthesized by a surface sol-gel method in combination with a following heat-treatment process. Through this process, nanosized Si was homogeneously distributed in a titanium carbide matrix. The electrochemically less active TiC working as a buffer matrix successfully prevented Si from cracking/crumbling during the charging/discharging process. The interspaces in the Si/TiC nanocomposite could offer convenient channels for Li ions to react with active Si. The Si/TiC composite exhibited a reversible charge/discharge capacity of about 1000 mAh g⁻¹ with average discharge capacity fading of 1.8 mAh g⁻¹ (0.18%) from 2nd to 100th cycle, indicating its excellent cyclability when used as anode materials for lithium-ion batteries.     

One-step synthesis of recoverable CuCo2S4 anode material for high-performance Li-ion batteries

A facile one-step hydrothermal method has been adopted to directly synthesize the CuCo₂S₄ material on the surface of Ni foam. Due to the relatively large specific surface area and wide pore size distribution, the CuCo₂S₄ material not only effectively increases the reactive area, but also accommodates more side reaction products to avoid the difficulty of mass transfer. When evaluated as anode for Li-ion batteries, the CuCo₂S₄ material exhibits excellent electrochemical performance including high discharge capacity, outstanding cyclic stability and good rate performance. At the current density of 200 mA·g⁻¹, the CuCo₂S₄ material shows an extremely high initial discharge capacity of 2510 mAh·g⁻¹, and the cycle numbers of the material even reach 83 times when the discharge capacity is reduced to 500 mAh·g⁻¹. Furthermore, the discharge capacity can reach 269 mAh·g⁻¹ at a current of 2000 mA·g⁻¹. More importantly, when the current density comes back to 200 mA·g⁻¹, the discharge capacity could be recovered to 1436 mAh·g⁻¹, suggesting an excellent capacity recovery characteristics.     

Composite anode material of silicon/graphite/carbon nanotubes for Li-ion batteries

A composite anode material of silicon/graphite/multi-walled carbon nanotubes (MWNTs) for Li-ion batteries was prepared by ball milling. This composite anode material showed a discharge capacity of 2274 mAh/g in the first cycle, and after 20 charge-discharge cycles, a reversible capacity of 584 mAh/g was retained, much higher than 218 mAh/g for silicon/graphite composite. It was observed that silicon particles were homogeneously embedded into the “lamellar structures” of flaked graphite particles, and the silicon/graphite composite particles were further wrapped by a MWNTs network. The improvement in the electrochemical properties of the composite anode material was mainly attributed to the excellent resiliency and good electric conductivity of the MWNTs network.     

Synthesis and characterization of porous maghemite as an anode for Li-ion batteries

The synthesis of porous maghemite via a simple glycerol-mediated solution method was successfully accomplished. Thermal analysis, X-ray diffraction and Mössbauer spectroscopy results disclosed the formation of maghemite. The morphological and structural features of maghemite were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and nitrogen adsorption–desorption. The powder showed Brunauer–Emmett–Teller surface area of 285 m² g⁻¹ with micro-, meso- and macropores.The anode body was doctor bladed using primary powder with a binder and a conductive agent. Galvanostatic charge–discharge cycling of the porous maghemite exhibited a specific reversible capacity of approximately 1180 mAh g⁻¹ at 100 mA g⁻¹ current density, which was two times higher than that of common nanomaghemite with average particle size of 19 nm. The cell showed stability even at the high current charge–discharge rates of 3000 mA g⁻¹ and more than 94% retention. After multiple high current cycling regimes, the cell recovered to nearly full reversible capacity of ~1120 mAh g⁻¹ at 100 mA g⁻¹. The reason for this remarkable performance of the present anode was thought to be dependent upon the role of pores in increasing the surface area and resistance against volume changes during lithium insertion/extraction.     

Li2ZnTi3O8@α-Fe2O3 composite anode material for Li-ion batteries

Li₂ZnTi₃O₈@α-Fe₂O₃ composites have been successfully prepared by a facile hydrothermal process. Li₂ZnTi₃O₈/α-Fe₂O₃ composites show similar irregular spherical morphologies like Li₂ZnTi₃O₈ and relatively smaller particle sizes than pristine Li₂ZnTi₃O₈. Among all Li₂ZnTi₃O₈/α-Fe₂O₃ composites, Li₂ZnTi₃O₈/α-Fe₂O₃ composite (5 wt%) exhibits the best electrochemical properties. Li₂ZnTi₃O₈/α-Fe₂O₃ composite (5 wt%) delivers a reversible charge capacity of 184.8 mAh g^?1 even at 1000 mA g^?1 after 500 cycles, while pristine Li₂ZnTi₃O₈ only delivers a reversible charge capacity of 110.7 mAh g^?1. The strong covalent bonds between Li₂ZnTi₃O₈ and α-Fe₂O₃ will be formed, which is beneficial for the reduction of interfacial energy and thus helpful for the stabilization of the composite. Because of the special synergistic effect of the multi-phase interface, Li₂ZnTi₃O₈/α-Fe₂O₃ composites not only possess the advantages of single components but also show novel and attractive performances, such as the enhanced ionic conductivity, reduced interfacial charge transfer impedance, improved migration rate of lithium ions, and the enhancement of the rate performance and reversible capacity. The as-prepared Li₂ZnTi₃O₈/α-Fe₂O₃ composites reveal important potentials as anode materials for next-generation rechargeable Li-ion batteries, and this work also offers an effective strategy to design high performance lithium storage materials for advanced lithium-ion batteries.     

Advanced Sn/C composite anodes for lithium ion batteries

Metallic tin was deposited in fine particulate form on the surface of carbonaceous mesophase spherules (CMS) and in the pores of porous carbon by the decomposition and reduction of tin(II) 2-ethylhexanoate at 450 °C. The Sn/C composite powders obtained were used as anode materials for lithium ion cells. Electrochemical cycling tests of coin cells show that the dispersion of tin into the carbonaceous materials enhances the reversible capacity of the electrodes. The capacity retention at the 50th cycle is 91 % for Sn/CMS composite containing 22% tin, against 428 mAh g^–1 at the first cycle. With further increase in tin content, the capacity fade upon cycling is more rapid.     

Synthesis of nano Sb-encapsulated pyrolytic polyacrylonitrile composite for anode material in lithium secondary batteries

A novel process was proposed to synthesize nano Sb-encapsulated pyrolytic polyacrylonitrile composite for anode material in lithium secondary batteries. The preparation started with the dissolution of SbCl₃ and polyacrylonitrile (PAN) in dimethylformamide (DMF) solution, followed by the addition of KBH₄ to reduce Sb³⁺ in the solution. The Sb composite was obtained by pyrolysis of the Sb/PAN mixture that precipitated out when the DMF solution was added by plentiful water. The TEM analysis showed that about 100-200 nm Sb particles were embedded by the pyrolyzed PAN, which provided a conductive matrix to relieve the morphological change of Sb during electrochemical cycling. As-prepared composite presented good cycleability for lithium storage. The proposed process paves an effective way to prepare high performance alloy based composite anode materials for high performance lithium-ion batteries.     

Chemical reduction of nano-scale Cu2Sb powders as anode materials for Li-ion batteries

A novel process was attempted to prepare nano-scale Cu₂Sb alloy powders as anode materials for Li-ion batteries. The preparation started with chemical reduction of Cu₂Sb in an aqueous solution with sodium citrate as a complexing agent and KBH₄ as a reducer. The analysis of scanning electron microscopy and X-ray diffraction showed that as-prepared nano-scale Cu₂Sb powders presented tetragonal structure with particle size of 50-70 nm. Cycling between 0 and 1.2 V, the nano-scale Cu₂Sb alloy showed good cyclability with a stable specific capacity of 200 mAh g⁻¹ within 25 cycles.     

Sn-based glass–graphite-composite as a high capacity anode for lithium-ion batteries

Sn-based anode has been widely studied because of its high theoretical specific capacity. However, the capacity of Sn-based anode decreases sharply during the cycle, which hinders its application in commercial batteries. In this paper, Sn-based glass was successfully obtained by melt quenching method. Sn-based glass and graphite were combined by the ball milling method as anode materials. The Sn-based glass–graphite-composite anode can still maintain the capacity of 700 mA h g⁻¹ after 500 cycles at 500 mA g⁻¹, which is about 2.7 times that of the Sn glass anode (260 mA h g⁻¹) under the same test conditions. The addition of graphite can effectively inhibit the accumulation of Sn particles in the discharge process of Sn-based glass anode, which improves the capacity of Sn-based glass anode, and the addition of graphite can effectively reduce the resistance of Sn-based glass anode. Therefore, the Sn-based glass–graphite-composite anode has excellent Li⁺ ions storage properties.     

Synthesis and characterization of nanoflaky maghemite (γ-Fe2O3) as a versatile anode for Li-ion batteries

In this study, nanoflaky maghemite (γ-Fe₂O₃) was successfully prepared by heating of synthesized lepidocrocite (γ-FeO(OH)). Once maghemite obtained, the electrochemical performance of nanoflaky maghemite, as an anode for Li-ion batteries, was investigated. Synthesis of lepidocrocite was optimized by adjusting the heating time and ratio of ethylene glycol (EG) to water in solution. The results revealed that with equal ratio of EG to water, the obtained phase was crystalline lepidocrocite whereas in other ratios lepidocrocite was not the only emerged phase. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) results revealed that increasing heating time has no effect on morphology. This increment only led to the slight crystallite growth and agglomeration of precipitation. The optimized lepidocrocite were heated at 230?°C for 2?h to form maghemite, which was confirmed by using XRD. FESEM, high-resolution transmission electron microscopy, and nitrogen adsorption-desorption results disclosed that the particles have flaky morphology with thickness of less than 10?nm and surface area of 105?m² g^?1. Cyclic voltammetry results of anode body (prepared using nanoflaky maghemite) demonstrated reversible formation pathway of iron and lithium oxide through discharging and charging. Moreover, galvanostatic charge–discharge cycling showed a reversible capacity of about 480?mAh?g^?1 after 50 cycles at current density of 500?mA?g^?1. Good cyclability, and capacity retention of the anode is due to the nananometric size and flaky shape of the maghemite particles. These particles’ shape made it easier for them to expand and contract in thickness direction with minimized destructions imposed.     

Surface chemistry of intermetallic AlSb-anodes for Li-ion batteries

The solid electrolyte interphase (SEI) layer on AlSb electrodes has been studied in Li/AlSb cells containing a LiPF₆ EC/DEC electrolyte using X-ray photoelectron spectroscopy (XPS). Data were collected before SEI-formation, during formation, and after formation at 0.01 V versus Li⁰/Li⁺, and at full delithiation in cycled cells at 1.20 V. The thickness of the SEI layer increases during lithiation and decreases during delithiation. This dynamic behaviour occurs continuously on cycling the cells. The growth of the SEI layer can be attributed predominantly to the deposition of carbonaceous species below 0.50 V versus Li⁰/Li⁺; these species disappear almost completely during delithiation. The extra surface-layer formation is a consequence of the additional charge that is needed to lithiate the remaining Sb component of the micrometer-sized AlSb particles at low potentials as seen by synchrotron-based X-ray diffraction. Aluminium is not reactive to lithium alloying in this electrolyte. Relatively small amounts of LiF were detected in the AlSb SEI layers compared to that commonly found in the SEI layers on graphite electrodes.     

锂离子电池锡钴和锡钴碳负极材料的研究进展

综述了锂离子电池锡钴二元合金和锡钴碳三元复合材料的结构、电化学性能,反应机理及制备方法.改善锡基材料的循环性能主要有3个途径:元素多元化,减小颗粒粒度,无定形化.仅靠上述单一途径很难达到产业化对循环性能的要求,因此多种途径联合运用成为解决循环性能的研究趋势.     

Synthesis of passively prelithiated SiOx nanoparticles for Li-ion battery anode

A new concept of passive prelithiation to SiO_x nanoparticles is introduced and evaluated by investigating their nanostructures and electrochemical properties. Specifically, Li is incorporated into SiO_x nanoparticles during the nanoparticle synthesis. We obtain Si-Li-O-based nanoparticles, which we call SILIO; these are much larger than SiO_x particles and have totally different nanostructures. Due to nanostructures with various phase distributions, SILIO nanoparticles show enhanced electrochemical properties. The initial reversible capacity (IRC) and initial columbic efficiency (ICE) of SILIO nanoparticles are 946 to 1107 mAh/g and 72% to 77%, respectively, while SiO_x exhibits 1,064 mAh/g of IRC only with 41.5% of ICE. In addition, the stability of SILIO in the air is evaluated to guarantee no unstable phases such as Li₂O_x (x = 0–2) are present in SILIO. Through our findings, we suggest a new nanostructure model composed of crystalline Si, amorphous SiO_x, and lithium silicate.     

Structural,microstructural and electrochemical studies on LiMn2-x(GdAl)xO4 with spinel structure as cathode material for Li-ion batteries

Gd and Al co-doped LiMn_2-x(GdAl)_xO₄ (x?=?0, 0.01, 0.02, 0.03, 0.04 and 0.05) materials with spinel structure were synthesized by sol–gel method. Powder X-ray diffraction results confirm the formation of cubic spinel structure and average particle sizes are found to be between 80 and 110?nm from FE-SEM and TEM analysis. Decrease in peak potential difference as a function of doping in Cyclic Voltammetry results establishes enhancement in Li⁺ intercalation and de-intercalation. Electrochemical Impedance Spectroscopy (EIS) results showed that accumulation of charges on electrode has improved with doping over pristine samples. At a doping of x?=?0.02 charge transfer resistance values were found to be least. First cycle charge–discharge profiles for LiMn_1.96(GdAl)_0.02O₄ shows 139.2?mAh/g discharge capacity over other doped derivatives and pure LiMn₂O₄ (119.6?mAh/g) in aqueous Li₂SO₄ electrolyte. Doping of x?=?0.02 exhibit good cycling performance with only a total 4% capacity loss after 30 cycles.     

锂离子电池用增强型凝胶聚合物电解质

用相转移法制备无纺布增强型聚偏氟乙烯-六氟丙烯聚合物电解质,用扫描电子显微镜和循环伏安对所制聚合物膜性能进行表征,用充放电实验和交流阻抗测试聚合物电池的电化学性质。结果表明：无纺布增强后的聚合物电解质电化学稳定窗口超过5.0 V,室温离子电导率达到2.3 mS/cm,机械强度大幅度提高,以此制备的聚合物电池阻抗降低,充放电时界面阻抗稳定,循环性能得以提高。     

Development of gel-polymer electrolytes and nano-structured electrodes for Li-ion polymer batteries

A novel methacrylic gel-polymer membrane was synthesized by free radical photo polymerisation (UV-curing technique). The polymerisation was very easy, fast and reliable and the membrane shows good behaviour in terms of both conductivity and cyclability in Li cells. The anode materials were prepared by high energy ball milling obtaining nanocrystalline Ni–Sn alloys, while the hydrothermal processing in presence of a template was used to prepare nanostructured LiFePO₄/C as cathode material. Every component has been characterised separately from the structural and electrochemical point of view. The first experimental data on the performance of a complete Li-ion polymer cell assembled with the components studied are also presented. The results obtained demonstrate the overall satisfying, and some superior performances of the various single components and their feasibility as a complete system.     

Single source precursor-derived SiOC/TiOxCy as an anode component for Li-ion batteries

Amorphous silicon oxycarbides are known to be an effective anode material for lithium-ion batteries. Despite their exceptional properties and high charge capacities, however, their practical uses are limited by their significant first-cycle loss, considerable hysteresis, and low cyclic ability. Comparatively, SiOC/metal oxide materials have demonstrated increased rate capability and cyclic stability. This study utilized a liquid precursor-derived ceramic method to modify SiOC with titanium (IV) butoxide precursor to synthesize SiOC/TiO_xC_y. X-ray diffractograms confirmed the amorphous nature of SiOC/TiO_xC_y. The elemental composition and bonding properties were investigated using X-ray photoelectron spectroscopy, and electron microscopy was used to explore morphological features. In the first cycle, the reversible capacity of pyrolyzed SiOC/TiO_xC_y was 520 mAh g⁻¹, which then increased to 736 mAh g⁻¹ for the 1200°C annealed SiOC/TiO_xC_y due to the increased free carbon network and TiC conductive phases. The irreversible capacity of the first cycle was 568 mAh g⁻¹, which was lower than the annealed SiOC irreversible capacity of 695 mAh g⁻¹. Interestingly, the rate stability of the pyrolyzed SiOC/TiO_xC_y performed more stability than the annealed sample. Localized carbothermal reactions between amorphous SiOC/TiO_xC_y and free carbon at annealing temperatures resulted in loss of structure stability.