Facile synthesis of NiCo2O4 nanorod arrays on Cu conductive substrates as superior anode materials for high-rate Li-ion batteries

In this work, we report a mild and cost-effective solution method to directly grow Ni-substituted Co3O4 (ternary NiCo2O4) nanorod arrays on Cu substrates. Electrochemical impedance spectroscopy (EIS) measurements show that the values of the electrolyte resistance Re and charge-transfer resistance Rct of NiCo2O4 are 6.8 and 63.5 Ω, respectively, which are significantly lower than those of binary Co3O4 (10.4 and 122.4 Ω). This EIS characterization strongly confirms that the ternary NiCo2O4 anode has much higher electrical conductivity than that of the binary Co3O4 electrode materials, which should greatly enhance the lithium storage performances. Due to the well-aligned 1D nanorod microstructure and a higher electrical conductivity, these ternary NiCo2O4 nanorod arrays manifest high specific capacity, excellent cycling stability (a high reversible capacity of about 830 mA h g−1 was achieved after 30 cycles at 0.5 C) and high rate capability (787, 695, 512, 254, 127 mA h g−1 at 1 C, 2 C, 6 C 50 C and 110 C, respectively).

Effects of mechanical deformation on electric performance of rechargeable batteries embedded in load carrying composite structures

Integrating rechargeable battery cells with fibre reinforced polymer matrix composites is a promising technology to enable composite structures to concurrently carry load and store electric energy, thus significantly reducing weight at the system level. To develop a design criterion for structural battery composites, rechargeable lithium polymer battery cells were embedded into carbon fibre/epoxy matrix composite laminates, which were then subjected to tensile, flexural and compressive loading. The electric charging/discharging properties were measured at varying levels of applied loads. The results showed that degradation in battery performance, such as voltagea and energy storage capacity, correlated well with the applied strain under three different loading conditions. Under compressive loading, battery cells, due to their multilayer construction, were unable to prevent buckling of composite face sheets due to the low lateral stiffness, leading to lower compressive strength that sandwich panels with foam core.

Large-scale production of h-In2O3/carbon nanocomposites with enhanced lithium storage properties

h-In2O3/carbon nanocomposites were obtained via a facile ball milling process from a mixture of h-In2O3 nanoparticles and Super P carbon. Compared to pure h-In2O3 nanoparticles, the nanocomposites exhibited an initial discharge capacity of 1360 mAh g-1, a stable reversible capacity of 867 mAh g-1 after 100 cycles as well as a high coulombic efficiency of 99%. The superior lithium-ion battery performance can be attributed to the specific structure of h-In2O3 and the uniform and continuous nano-carbon coating layers. The nano-carbon coating could protect the inner active materials from fragmentation and increase the electronic conductivity. This study not only provides a promising electrode material for high-performance lithium-ion batteries, but also further demonstrates a straightforward, effective and environmental friendly process for synthesizing nanocomposites. © 2014 Elsevier Ltd.

Enhanced lithium storage in ZnFe2O4-C nanocomposite produced by a low-energy ball milling

Preparation of novel nanocomposite structure of ZnFe2O4-C is achieved by combining a sol-gel and a low energy ball milling method. The crucial feature of the composite's structure is that sol-gel synthesised ZnFe2O4 nanoparticles are dispersed and attached uniformly along the chains of Super P Li™ carbon black matrix by adopting a low energy ball milling. The composite ZnFe2O4-C electrodes are capable of delivering a very stable reversible capacity of 681 mAh g-1 (96% retention of the calculated theoretical capacity of ∼710 mAh g-1) at 0.1 C after 100 cycles with a remarkable Coulombic efficiency (82%) improvement in the first cycle. The rate capability of the composite is significantly improved and obtained capacity was as high as 702 at 0.1, 648 at 0.5, 582 at 1, 547 at 2 and 469 mAh g-1 at 4 C (2.85 A g-1), respectively. When cell is returned to 0.1 C, the capacity recovery was still ∼98%. Overall, the electrochemical performance (in terms of cycling stability, high rate capability, and capacity retention) is outstanding and much better than those of the related reported works. Therefore, our smart electrode design enables ZnFe2O4-C sample to be a high quality anode material for lithium-ion batteries.

Synthesis of LiFePO4@carbon nanotube core-shell nanowires with a high-energy efficient method for superior lithium ion battery cathodes

A high-energy efficient method is developed for the synthesis of LiFePO4@CNT core-shell nanowire structures. The method consists of two steps: liquid deposition approach to prepare FePO4@CNT core-shell nanowires and solvothermal lithiation to obtain the LiFePO4@CNT core-shell nanowires at a low temperature. The solution phase method can be easily scaled up for commercial application. The performance of the materials produced by this method is evaluated in Li ion batteries. The one-dimensional LiFePO4@CNT nanowires offer a stable and efficient backbone for electron transport. The LiFePO4@CNT core-shell nanowires exhibit a high capacity of 132.8 mAh g^-1 at a rate of 0.2C, as well as high rate capability (64.4 mAh g^-1 at 20C) for Li ion storage.

Gelled ionic liquid sodium ion conductors for sodium batteries

Owing to the unique properties of certain Ionic liquids (ILs) as safe and green solvents, as well as the potential of sodium as an alternative to lithium as charge carriers, we investigate gel sodium electrolytes as safe, low cost and high performance materials with sufficient mechanical properties for application in sodium battery technologies. We investigate the effect of formation of two types of gel electrolytes on the properties of IL electrolytes known to support Na/Na⁺ electrochemistry. The ionic conductivity is only slightly decreased by 0.0005 and 0.0002 S cm^-1 in the case of 0.3 and 0.5 M NaNTf2 systems respectively as the physical properties transition from liquid to gel. We observed facile plating and stripping of Na metal around 0 V vs. Na/Na⁺ through the cyclic voltammetry. A wide-temperature range of the gelled IL state, of more than 100 K around room temperature, is achieved in the case of 0.3 and 0.5 M NaNTf2. We conclude that the formation of a gel does not significantly affect the liquid-like ion dynamics in these materials, as further evidenced by DSC and FTIR analysis.

Understanding structure-function relationship in hybrid Co3O4-Fe2O3/C lithium-ion battery electrodes

A range of high-capacity Li-ion anode materials (conversion reactions with lithium) suffer from poor cycling stability and limited high-rate performance. These issues can be addressed through hybridization of multiple nanostructured components in an electrode. Using a Co3O4-Fe2O3/C system as an example, we demonstrate that the cycling stability and rate performance are improved in a hybrid electrode. The hybrid Co3O4-Fe2O3/C electrode exhibits long-term cycling stability (300 cycles) at a moderate current rate with a retained capacity of approximately 700 mAh g(-1). The reversible capacity of the Co3O4-Fe2O3/C electrode is still about 400 mAh g(-1) (above the theoretical capacity of graphite) at a high current rate of ca. 3 A g(-1), whereas Co3O4-Fe2O3, Fe2O3/C, and Co3O4/C electrodes (used as controls) are unable to operate as effectively under identical testing conditions. To understand the structure-function relationship in the hybrid electrode and the reasons for the enhanced cycling stability, we employed a combination of ex situ and in situ techniques. Our results indicate that the improvements in the hybrid electrode originate from the combination of sequential electrochemical activity of the transition metal oxides with an enhanced electronic conductivity provided by percolating carbon chains.

Self-assembled V2O5 interconnected microspheres produced in a fish-water electrolyte medium as a high-performance lithium-ion-battery cathode

Interconnected microspheres of V2O5 composed of ultra-long nanobelts are synthesized in an environmental friendly way by adopting a conventional anodization process combined with annealing. The synthesis process is simple and low-cost because it does not require any additional chemicals or reagents. Commercial fish-water is used as an electrolyte medium to anodize vanadium foil for the first time. Electron microscopy investigation reveals that each belt consists of numerous nanofibers with free space between them. Therefore, this novel nanostructure demonstrates many outstanding features during electrochemical operation. This structure prevents self-aggregation of active materials and fully utilizes the advantage of active materials by maintaining a large effective contact area between active materials, conductive additives, and electrolyte, which is a key challenge for most nanomaterials. The electrodes exhibit promising electrochemical performance with a stable discharge capacity of 227 mAh·g–1 at 1C after 200 cycles. The rate capability of the electrode is outstanding, and the obtained capacity is as high as 278 at 0.5C, 259 at 1C, 240 at 2C, 206 at 5C, and 166 mAh·g–1 at 10C. Overall, this novel structure could be one of the most favorable nanostructures of vanadium oxide-based cathodes for Li-ion batteries. [Figure not available: see fulltext.]

Synthesis of an indium oxide nanoparticle embedded graphene three-dimensional architecture for enhanced lithium-ion storage

Indium oxide nanoparticles were synthesised by using a facile and scalable strategy. The as-prepared nanoparticles (20-40 nm) were in situ and homogeneously distributed in a three-dimensional (3D) graphene architecture subsequently during the fabrication process. The obtained nanocomposite acts as a high capacity anode material for lithium-ion batteries and demonstrates good cycle stability. A drastically enhanced capacity of 750 mA h g^-1 in comparison with that of bare In2O3 nanoparticles can be maintained after 100 cycles, along with an improved high rate performance (210 mA h g^-1 at 1 A g^-1 and 120 mA h g^-1 at 2 A g^-1). The excellent performance is linked with the indium oxide nanoparticles and the unique 3D interconnected porous graphene structure. The highly conductive and porous 3D graphene structure greatly enhances the performance of lithium-ion batteries by protecting the nanoparticles from the electrolyte, stabilizing the nanoparticles during cycles and buffering the volume expansion upon lithium insertion.

Advanced N-doped mesoporous molybdenum disulfide nanosheets and the enhanced lithium-ion storage performance

With the increasing interest in two-dimensional van der Waals materials, molybdenum disulfide (MoS2) has emerged as a promising material for electronic and energy storage devices. It suffers from poor cycling stability and low rate capability when used as an anode in lithium ion batteries. Here, N-doped MoS2 nanosheets with 2-8 atomic layers, increased interlayer distance, mesoporous structure and high surface area synthesised by a simple sol-gel method show an enhanced lithium storage performance, delivering a high reversible capacity (998.0 mA h g-1, 50 mA g-1), high rate performance (610 mA h g-1, 2 A g-1), and excellent cycling stability. The excellent lithium storage performance of the MoS2 nanosheets might be due to the better electrical and ionic conductivity and improved lithium ion diffusion which are related to their structural characteristics and high concentration N doping. The possible mechanism of the improved performance is proposed and discussed.

N-doped pierced graphene microparticles as a highly active electrocatalyst for li-air batteries

In this work we report a novel scalable strategy to prepare a lithium-air battery electrode from 3D Ndoped pierced graphene microparticles (N-PGM) with highly active performance. This approach has combined the merits of spray drying technology and the hard template method. The pierced structured graphene microparticles were characterized physically and electrochemically. An x-ray
photoelectron spectrometer and Raman spectra have revealed that the novel structure possesses a higher N-doping level than conventional graphene without the pierced structure. A much higher BET surface area was also achieved for the N-PGMthan the conventional N-doped graphene microparticles (N-GM). Cyclic voltammetry indicated that the lithium-air battery with the N-PGM electrode has a better utilization for the graphene mass and a higher void volume for Li2O2 formation than that of theN-GMelectrode. N-PGMalso exhibits improved decomposition kinetics for Li oxide
species yielded in the cathodic reaction. Charge and discharge measurements showed that theN-PGM lithium-air battery achieved an improved specific capacity and an enhanced cycle performance than when anN-GMelectrode is used.

N7-(carboxymethyl)guanine-lithium crystalline complex: a bioinspired solid electrolyte

Electrochemical device with components having direct significance to biological life processes is a potent futuristic strategy for the realization of all-round green and sustainable development. We present here synthesis design, structural analysis and ion transport of a novel solid organic electrolyte (G7Li), a compound reminiscent of ion channels, derived from regioisomeric N7-guanine-carboxylate conjugate and Li-ions. G7Li, with it's in-built supply of Li(+)-ions, exhibited remarkably high lithium-ion transference number (= 0.75) and tunable room temperature ionic conductivity spanning three decades (≈10(-7) to 10(-3) Ω(-1) cm(-1)) as a function of moisture content. The ionic conductivity show a distinct reversible transition around 80-100 °C, from a dual Li(+) and H(+) (<100 °C) to a pure Li(+) conductor (>100 °C). Systematic studies reveal a transition from water-assisted Li-ion transport to Li hopping-like mechanism involving guanine-Li coordination. While as-synthesized G7Li has potential in humidity sensors, the anhydrous G7Li is attractive for rechargeable batteries.