High capacity and excellent cyclability of vanadium (IV) oxide in lithium battery applications

A VO₂ · 0.43H₂O powder with a flaky particle morphology was synthesized via a hydrothermal reduction method. It was characterized by scanning electron microscopy, electron energy loss spectroscopy, and thermogravimetric analysis. As an electrode material for rechargeable lithium batteries, it was used both as a cathode versus lithium anode and as an anode versus LiCoO₂, LiFePO₄ or LiNi_0.5Mn_1.5O₄ cathode. The VO₂ · 0.43H₂O electrode exhibits an extraordinary superiority with high capacity (160 mAh g^?1), high energy efficiency (95%), excellent cyclability (142.5 mAh g^?1 after 500 cycles) and rate capability (100 mAh g^?1 at 10 C-rate).     

Fabrication and electrochemical properties of the Sn–Ni–P alloy rods array electrode for lithium-ion batteries

A new ternary Sn–Ni–P alloy rods array electrode for lithium-ion batteries is synthesized by electrodeposition with a Cu nanorods array structured foil as current collector. The Cu nanorods array foil is fabricated by heat treatment and electrochemical reduction of Cu(OH)₂ nanorods film, which is grown directly on Cu substrate through an oxidation method. The Sn–Ni–P alloy rods array electrode is mainly composed of pure Sn, Ni₃Sn₄ and Ni–P phases. The electrochemical experimental results illustrate that the Sn–Ni–P alloy rods array electrode has high reversible capacity and excellent coulombic efficiency, with an initial discharge capacity and charge capacity of 785.0 mAh g^?1 and 567.8 mAh g^?1, respectively. After the 100th discharge–charge cycling, capacity retention is 94.2% with a value of 534.8 mAh g^?1. The electrode also performs with an excellent rate capacity.     

Structural and electrochemical properties of a porous nanostructured SnO2 film electrode for lithium-ion batteries

A B₂O₃-doped SnO₂ thin film was prepared by a novel experimental procedure combining the electrodeposition and the hydrothermal treatment, and its structure and electrochemical properties were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, energy dispersive X-ray (EDX) spectroscopy and galvanostatic charge–discharge tests. It was found that the as-prepared modified SnO₂ film shows a porous network structure with large specific surface area and high crystallinity. The results of electrochemical tests showed that the modified SnO₂ electrode presents the largest reversible capacity of 676 mAh g^?1 at the fourth cycle, close to the theoretical capacity of SnO₂ (790 mAh g^?1); and it still delivers a reversible Li storage capacity of 524 mAh g^?1 after 50 cycles. The reasons that the modified SnO₂ film electrode shows excellent electrochemical properties were also discussed.     

Sol–gel preparation and electrochemical performances of LiFe1/3Mn1/3Co1/3PO4/C composites with core–shell nanostructure

LiFe_1/3Mn_1/3Co_1/3PO₄/C solid solution was prepared via a poly(ethylene glycol) assisted sol–gel method and exploited as cathode materials for lithium ion batteries. X-ray diffraction patterns indicate that LiFe_1/3Mn_1/3Co_1/3PO₄/C is crystallized in an orthorhombic structure. The scanning electron microscopy and transmission electron microscopy show that the particles are about 200 nm with a uniform carbon coating of about 8 nm in thickness to form a core–shell nanostructure. During charge–discharge cycles, LiFe_1/3Mn_1/3Co_1/3PO₄/C presented three plateaus corresponding to Fe³⁺/Fe²⁺, Mn³⁺/Mn²⁺ and Co³⁺/Co²⁺ redox couples, and a discharge capacity of 150.8 mAh g^?1 in the first cycle, remaining 121.2 mAh g^?1 after 30 cycles. Core–shell structure can optimize the performances of polyoxoanionic materials for lithium ion batteries.     

Fabrication and electrochemical performance of nickel ferrite nanoparticles as anode material in lithium ion batteries

Nano-sized nickel ferrite (NiFe₂O₄) was prepared by hydrothermal method at low temperature. The crystalline phase, morphology and specific surface area (BET) of the resultant samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and nitrogen physical adsorption, respectively. The particle sizes of the resulting NiFe₂O₄ samples were in the range of 5–15 nm. The electrochemical performance of NiFe₂O₄ nanoparticles as the anodic material in lithium ion batteries was tested. It was found that the first discharge capacity of the anode made from NiFe₂O₄ nanoparticles could reach a very high value of 1314 mAh g⁻¹, while the discharge capacity decreased to 790.8 mAh g⁻¹ and 709.0 mAh g⁻¹ at a current density of 0.2 mA cm⁻² after 2 and 3 cycles, respectively. The BET surface area is up to 111.4 m² g⁻¹. The reaction mechanism between lithium and nickel ferrite was also discussed based on the results of cycle voltammetry (CV) experiments.     

Flexible free-standing graphene-silicon composite film for lithium-ion batteries

Flexible, free-standing, paper-like, graphene-silicon composite materials have been synthesized by a simple, one-step, in-situ filtration method. The Si nanoparticles are highly encapsulated in a graphene nanosheet matrix. The electrochemical results show that graphene-Si composite film has much higher discharge capacity beyond 100 cycles (708 mAh g^? 1) than that of the cell with pure graphene (304 mAh g^? 1). The graphene functions as a flexible mechanical support for strain release, offering an efficient electrically conducting channel, while the nanosized silicon provides the high capacity.     

Lithium insertion chemistry of some iron vanadates

Lithium insertion into various iron vanadates has been investigated. Fe₂V₄O₁₃ and Fe₄(V₂O₇)₃ · 3H₂O have discharge capacities approaching 200 mAh g⁻¹ above 2.0 V vs. Li⁺/Li. Although the potential profiles change significantly between the first and subsequent discharges, capacity retention is unexpectedly good. Other phases, structurally related to FeVO₄, containing copper and/or sodium ions were also studied. One of these, β-Cu₃Fe₄(VO₄)₆, reversibly consumes almost 10 moles of electrons per formula unit (ca. 240 mAh g⁻¹) between 3.6 and 2.0 V vs. Li⁺/Li, in a non-classical insertion process. It is proposed that both copper and vanadium are electrochemically active, whereas iron(III) reacts to form LiFe^IIIO₂. The capacity of the Cu₃Fe₄(VO₄)₆/Li system is nearly independent of cycling rate, stabilizing after a few cycles at 120–140 mAh g⁻¹. Iron vanadates exhibit better capacities than their phosphate analogues, whereas the latter display more constant discharge potentials.     

Polyol-mediated synthesis of ultrafine tin oxide nanoparticles for reversible Li-ion storage

A simple, cheap and versatile, polyol-mediated fabrication method has been extended to the synthesis of tin oxide nanoparticles on a large scale. Ultrafine SnO₂ nanoparticles with crystallite sizes of less than 5 nm were realized by refluxing SnCl₂ · 2H₂O in ethylene glycol at 195 °C for 4 h under vigorous stirring in air. The as-prepared SnO₂ nanoparticles exhibited enhanced Li-ion storage capability and cyclability, demonstrating a specific capacity of 400 mAh g⁻¹ beyond 100 cycles.     

Partially reduced SnO2 nanoparticles anchored on carbon nanofibers for high performance sodium-ion batteries

One-dimensional (1-D) carbon nanofibers anchored with partially reduced SnO₂ nanoparticles (SnO₂/Sn@C) were successfully synthesized through a simple electrospinning method followed by carbon coating and thermal reduction processes. The partially reduced Sn frameworks, combined with the carbon fibers, provide a more favorable mechanism for sodiation/desodiation than SnO₂. As a result, SnO₂/Sn@C exhibits a high reversible capacity (536 mAh g^− 1 after 50 cycles) and an excellent rate capability (396 mAh g^− 1 even at 2 C rate) when evaluated as an anode material for sodium-ion batteries (SIBs).     

Macroporous Co3O4 platelets with excellent rate capability as anodes for lithium ion batteries

This paper reports the microwave-assisted synthesis of Co₃O₄ nanomaterials with different morphologies including nanoparticles, rod-like nanoclusters and macroporous platelets. The new macroporous platelet-like Co₃O₄ morphology was found to be the best suitable for reversible lithium storage properties. It displayed superior cycling performances than nanoparticles and rod-like nanoclusters. More interestingly, excellent high rate capabilities (811 mAh g^?1 at 1780 mA g^?1 and 746 mAh g^?1 at 4450 mA g^?1) were observed for macroporous Co₃O₄ platelet. The good electrochemical performance could be attributed to the unique macroporous platelet structure of Co₃O₄ materials.     

Binder-free porous core–shell structured Ni/NiO configuration for application of high performance lithium ion batteries

An interwoven core–shell structured Ni/NiO anode for lithium ion batteries was created by a simple oxidation of Ni foam. As-prepared configuration has a high specific discharge capacity of 701 mAh g^?1 at the 2nd cycle. Its electrochemical performance at subsequent cycles shows good energy capacity of 646 mAh g^?1 at the 65th cycle as well as good rate capability. The porous core–shell structure not only buffers the volume change during cycling but also effectively increases the contact among anode, current collector and electrolyte. The small contact resistance between NiO and Ni facilitates enhanced intrinsic kinetics from conversion reaction.     

ZIF-8 derived nano-SnO2@ZnO as anode for Zn/Ni secondary batteries

SnO₂@ZnO was synthesized by a new method involving the immobilization of Sn onto zeolitic imidazolate framework-8 (ZIF-8) followed by calcination. The synthesized nanoparticles were characterized as 20–30 nm spherical ZnO particles uniformly dotted with SnO₂. When SnO₂@ZnO were used as anode material for Zn/Ni batteries, the average specific capacity was approximately 600 mAh g^− 1 and remained stable after 150 cycles at a rate of 1 C.     

Sulfone-based electrolytes for high-voltage Li-ion batteries

Sulfone-based electrolytes have been investigated as electrolytes for lithium-ion cells using high-voltage positive electrodes, such as LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ spinels, and Li₄Ti₅O₁₂ spinel as negative electrode. In the presence of imide salt (LiTFSI) and ethyl methyl sulfone or tetramethyl sulfone (TMS) electrolytes, the Li₄Ti₅O₁₂/LiMn₂O₄ cell exhibited a specific capacity of 80 mAh g^?1 with an excellent capacity retention after 100 cycles. In a cell with high-voltage LiNi_0.5Mn_1.5O₄ positive electrode and 1 M LiPF₆ in TMS as electrolyte, the capacity reached 110 mAh g^?1 at the C/12 rate. When TMS was blended with ethyl methyl carbonate, the Li₄Ti₅O₁₂/LiNi_0.5Mn_1.5O₄ cell delivered an initial capacity of 80 mAh g^?1 and cycled fairly well for 1000 cycles under 2C rate. The exceptional electrochemical stability of the sulfone electrolytes and their compatibility with the Li₄Ti₅O₁₂ safer and stable anode were the main reason behind the outstanding electrochemical performance observed with high-potential spinel cathode materials. These electrolytes could be promising alternative electrolytes for high-energy density battery applications such as plug-in hybrid and electric vehicles that require a long cycle life.     

Electrochemical behavior of a micro-patterned Si anode/LiV3O8 secondary cell

Using a micro-patterned Si plate, a Li secondary cell was assembled and tested for its electrochemical properties. A micro-patterned Si plate was made by photolithography. This was followed by Pt coating and Li deposition. With a non-lithiated LiV₃O₈ cathode, a Li-deposited micro-patterned Si anode was assembled as a secondary cell. The cell exhibited an initial charge/discharge capacity of about 220 mAh g^? 1 at a current density of 0.1 C-rate and it continued for more than 100 cycles without failure. The morphologies of Li deposition/dissolution in the anode were observed via scanning electron microscopy (SEM). Dendrite behavior of the Li metal was not observed on the anode during the cyclic process.     

Microstructures and electrochemical hydrogen storage properties of novel Mg–Al–Ni amorphous composites

The amorphous Mg–Al–Ni composites were prepared by mechanical ball-milling of Mg₁₇Al₁₂ with x wt.% Ni (x = 0, 50, 100, 150, 200). The effects of Ni addition and ball-milling parameters on the electrochemical hydrogen storage properties and microstructures of the prepared composites have been investigated systematically. For the Mg₁₇Al₁₂ ball-milled without Ni powder, its particle size decreases but the crystal structure does not change even the ball-milling time extending to 120 h, and its discharge capacity is less than 15 mAh g^?1. The Ni addition is advantageous for the formation of Mg–Al–Ni amorphous structure and for the improvement of the electrochemical characteristics of the composites. With the Ni content x increasing, the composites exhibit higher degree of amorphorization. Moreover, the discharge capacity of the composite increases from 41.3 mAh g^?1 (x = 50) to 658.2 mAh g^?1 (x = 200) gradually, and the exchange current density I₀ increases from 67.1 mA g^?1 (x = 50) to 263.8 mA g^?1 (x = 200), which is consistent with the variation of high-rate dischargeability (HRD). The ball-milled Mg₁₇Al₁₂ + 200 wt.% Ni composite has the highest cycling discharge capacity in the first 50 cycles.     

EPR and optical absorption studies of Cu2+ doped bis (glycinato) Mg (II) monohydrate single crystals

Electron paramagnetic resonance (EPR) study of Cu²⁺ doped bis (glycinato) Mg (II) monohydrate single crystals is carried out at room temperature. Copper enters the lattice substitutionally and is trapped at two magnetically inequivalent sites. The observed spectra are fitted to a spin-Hamiltonian of rhombic symmetry with the following values of the parameters: Cu²⁺ (I), g_x = 2.1577 ± 0.0002, g_y = 2.2018 ± 0.0002, g_z = 2.3259 ± 0.0002, A_x = (87 ± 2) × 10^?4 cm^?1, A_y = (107 ± 2) × 10^?4 cm^?1, A_z = (141 ± 2) × 10^?4 cm^?1; Cu ²⁺ (II), g_x = 2.1108 ± 0.0002, g_y = 2.1622 ± 0.0002, g_z = 2.2971 ± 0.0002, A_x = (69 ± 2) × 10^?4 cm^?1, A_y = (117 ± 2) × 10^?4 cm^?1and A_z = (134 ± 2) × 10^?4 cm^?1. The ground state wave function of the Cu²⁺ ion in this lattice is evaluated to be predominantly |x² ? y². The g-factor anisotropy is also calculated and compared with the experimental value. With the help of the optical absorption study, the nature of bonding in the complex is discussed.     

Electrochemical performance of nanocomposite LiMnPO4/C cathode materials for lithium batteries

A LiMnPO₄/C composite cathode was prepared by a combination of spray pyrolysis and wet ball milling. The cathode showed stable performance at various cutoff voltages up to 4.9 V. The cutoff voltage increase up to 4.9 V allowed the achievement of a high discharge capacity in galvanostatic charge–discharge tests. The discharge capacities of 153 mAh g^?1 at 0.05 C and 149 mAh g^?1 at 0.1 C were achieved at room temperature; the trickle-mode discharge capacities at room temperature were 132, 120 and 91 mAh g^?1 at 0.1, 1 and 5 C discharge rates, respectively. The cell exhibited a good rate capability in the galvanostatic cycling up to 5 C discharge rates at both ambient temperature and 50 °C.     

Electrochemical properties of Li symmetric solid-state cell with NASICON-type solid electrolyte and electrodes

All-solid-state phosphate symmetric cells using Li₃V₂(PO₄)₃ for both the positive and negative electrodes with the phosphate Li_1.5Al_0.5Ge_1.5(PO₄)₃ as the solid electrolyte were proposed. Amorphous Li_1.5Al_0.5Ge_1.5(PO₄)₃ was added into the electrode to increase the interface area between the active materials and the electrolyte. Any other phases were not formed at the electrode/electrolyte interface even after hot pressing at 600 °C. The discharge capacity was 92 mAh g^? 1 at 22 µA cm^? 2 at 80 °C, and 38 mAh g^? 1 at 25 °C, respectively. Symmetric cell configuration leads to simplify the fabrication process for all-solid-state batteries and will reduce manufacturing costs.     

Hierarchically ordered porous nickel oxide array film with enhanced electrochemical properties for lithium ion batteries

Hierarchically ordered porous nickel oxide array film was prepared by electrodeposition through monolayer polystyrene spheres template. The as-prepared film had a highly porous structure of interconnected macrobowls array possessing nanopores. As anode material for lithium ion batteries, the porous array NiO film exhibited weaker polarization, higher coulombic efficiency and better cycling performance in comparison with the dense NiO film. After 50 cycles, the discharge capacity of porous array NiO film was 518 mAh g^? 1 at 1 C rate, higher than that of the dense NiO film (287 mAh g^? 1). The enhancement of the electrochemical properties was due to the unique hierarchical porous architecture, which provided fast ion/electron transfer and alleviated the structure degradation during the cycling process.     

Net-structured NiO–C nanocomposite as Li-intercalation electrode material

Net-structured NiO was prepared by urea-mediated homogeneous hydrolysis of Ni(CH₃COO)₂ under microwave radiation followed by a calcination at 500 °C. NiO–C nanocomposite was prepared by dispersing the as-prepared net-structured NiO in glucose solution and subsequent carbonization under hydrothermal conditions at 180 °C. The carbon in the composite was amorphous by the X-ray diffraction (XRD) analysis, and its content was 15.05 wt% calculated according to the energy dispersive X-ray spectroscopy (EDX) result. Transmission electron microscopy (TEM) image of the NiO–C nanocomposite showed that the NiO network was homogeneously filled by amorphous carbon. The reversible capacity of NiO–C nanocomposite after 40 cycles is 429 mAh g⁻¹, much higher than that of NiO (178 mAh g⁻¹). These improvements are attributed to the carbon, which can enhance the conductivity of NiO, suppress the aggregation of active particles, and increase their structure stability during cycling.