Narrow Results

Carbon nano-coated LiNi_0.8Co_0.15Al_0.05O₂/C (LNCAO/C) cathode-active materials were prepared by a sol–gel method and investigated as the cathode material for lithium ion batteries. Electrochemical properties including the galvanostatic charge–discharge ability and cyclic voltammogram behavior were measured. Cyclic voltammetry (2.7–4.8 V) showed that the carbon nano-coating improved the "formation" of the LNCAO electrode, which was related to the increased electronic conductivity between the primary particles. The carbon nano-coated LNCAO/C exhibited good electrochemical performance at high C-rate. Also, the thermal stability at a highly oxidized state of the carbon nano-coated LNCAO was remarkably enhanced. The carbon nano-coating layer can serve as a physical and/or (electro-)chemical protection shell for the underlying LNCAO, which is attributed to an increase of the grain connectivity (physical part) and also to the protection of metal oxide from chemical reactions (chemical part).

The spinel LiMn₂O₄ powders were prepared by sol–gel technique using lithium acetate (Li(CH₃COO) · 2H₂O) and manganese acetate (Mn(CH₃COO)₂ · 4H₂O) as starting materials, citric acid as a chelating agent, and acrylamide as a gel formatting agent. In order to improve the electrochemical performance of lithium ion batteries and prevent structural disintegration from Mn dissolution generated by undesirable acid production, conductive agents were additionally coated on the surface of active material coated on pure aluminum foil as a current collector. Also, it was comparatively investigated using different conductive agents with different particle sizes as well as adopting the cells into the different thermal environments. The electrochemical performance of the Li/LiMn₂O₄ cells demonstrated that the spinel LiMn₂O₄ might be effectively shielded from acid, resulting in improved electrochemical capacity characteristics at room temperature as well as elevated temperature of 55°C.

LiFePO₄ nanocrystals were synthesized in various polyol media without any further post-heat treatment. The LiFePO₄ samples synthesized using three different polyol media namely, diethylene glycol (DEG), triethylene glycol (TEG), and tetraethylene glycol (TTEG), exhibited plate and rod-shaped structures with average sizes of 50–500 nm. The X-ray diffraction (XRD) patterns were indexed on the basis of an olivine structure (space group: Pnma). The samples prepared in DEG, TEG, and TTEG polyol media showed reversible capacities of 123, 155, and 166 mAh/g, respectively, at current density of 0.1 mA/cm² with no capacity fading and exhibited excellent capacity retention up to the 50th cycle. In particular, the samples showed excellent performances at high rates of 30 and 60 C with high capacity retention. It is assumed that the nanometer size materials (~50 nm) possessing a highly crystalline nature may generate improved performance at high rate current densities.

Singapore IBN's Urine-Powered Batteries for Biochip Devices.

International Study Suggests Possible Link Between Evolution and Cancer.

Scientists Discover Connection Between Fetal Stem Cells and Maternal Brain.

Submicron Li_0.8CoO₂ particles were prepared by sol–gel method, and then ball-mill grinding method was adopted to make nanosized Li_0.8CoO₂ powders. The two kinds of powders were then examined by X-ray diffraction (XRD), ICP (inductively coupled plasma), the multi-point BET (Brunauer, Emmett and Teller) and transmission electron micrographs (TEM). It appeared that the Li_0.8CoO₂ nanoparticles exhibited quite different electrochemical properties, such as higher open-circuit voltage and lower discharge capacity, compared to submicron Li_0.8CoO₂ particles.

PVC disulfide (2SPVC) was synthesized by solution crosslink and its molecular structure was confirmed by infrared spectrum. 2SPVC's specific area is 36.1 m²·g^-1 tested by stand BET method, and granularity experiment gives out the particle size of d_0.5 = 11.3 μm. With SEM (Scanning Electron Microscope) experiment the surface morphology and particle shape of 2SPVC were observed. Cyclic voltammetry (scan rate: 0.5 mV·s^-1) shows that 2SPVC experience an obvious S–S redox reaction in charge-discharge process. When 2SPVC was used as cathode material for secondary lithium battery in a 1 mol·L^-1 solution of lithium bis(trifluoromethylsulfonyl) imide (Li(CF₃SO₂)₂N) in a 5:45:50 volume ratio mixture of o-xylene (oxy), diglyme (DG) and dimethoxymethane (DME) at 30°C, the first discharge capacity of 2SPVC is about 400.3 mAh·g^-1 which is very close to its theoretical value (410.5 mAh·g^-1) at a constant discharge current of 15 mA·g^-1. It can retain at about 346.1 mAh·g^-1 of discharge capacity after 30 charge-discharge cycles. So 2SPVC is a very promising cathode candidate for rechargeable lithium batteries.

Due to the high theoretical capacity of sulfur (1675mAh${\text{g}}^{-1})$, low cost and environmental friendliness, lithium-sulfur batteries have shown broad prospects in future energy conversion and storage systems. However, the shuttle effect and insulating properties of sulfur restrict its practical application. Herein, we report a facile approach to fabricate Al-TDC@S-PPy composite material as lithium-sulfur battery electrode. In this strategy, a topological porous Al-TDC ($\mathrm{\text{TDC}}=2$,5-thiophenedicarboxylate) with 8-connected clusters is reported, which can provide strong adsorption for dissolved intermediate polysulfides and alleviate volume expansion. Meanwhile, Polypyrrole, (PPy) as a conductive and flexible additive to expedite electron transport, improves electrical conductivity. Consequently, the Al-TDC@S-PPy composite cathode exhibits a higher initial specific capacity (1310.4mAh${\text{g}}^{-1}$ at 0.2C). The final reversible capacity is 411.0mAh${\text{g}}^{-1}$ after 200 cycles at 1 C. We can extend this strategy to other metal-organic frameworks (MOFs) and manufacture MOF/conductive polymer composite electrodes for high-performance lithium-sulfur batteries.

To fulfill the increasing energy demand, lithium-sulfur batteries (LIBs) are considered one of the most promising energy storage devices for the next generation because of their high specific capacity (1675mAhg${}^{-1})$ and high energy density (2600Whkg${}^{-1})$. However, the low conductivity of electrode materials, large volume expansion rate and shuttle effect, rapid decline of battery capacity and low cycle lifetime have restricted the commercialization of LIBs. In this paper, a type of silver-coated Co@NC porous carbon (ZIF-67 derivatives) is used as the principal material of the lithium-sulfur battery cathode (denoted Ag–Co@NC). These composites not only confine the active materials to the ordered pore structure composites but also inhibit the free migration of polysulfide and improve the redox reaction. Furthermore, uniformly modified silver nanoparticles are beneficial for enhancing the conductivity of Li₂S, thus exhibiting good rate performance and capacity and effectively improving the electrochemical performance of the material.

Rechargeable nonaqueous Li-O₂ batteries are considered as one of the most promising energy storage systems due to their super-high theoretical energy density. However, some technical obstacles, such as high overpotential and poor cycle stability, need to be overcome urgently, so that it is possible to make Li-O₂ batteries commercially viable. The key is to develop effective bifunctional cathode catalysts. Herein, Ni-doped TiO₂ (Ni-TiO${}_2)$ with microtubule structure was prepared by hydrothermal method and used as the cathode catalyst of Li-O₂ batteries. At a current density of 100mAg${}^{-1}$, Li-O₂ batteries with Ni-TiO₂ catalysts showed an initial discharge capacity of 5100mAh g${}^{-1}$ and can maintain 52 stable cycles at 100mAg${}^{-1}$ with a fixed capacity of 500mAhg${}^{-1}$. The microtubule structure composed of nanosheets not only facilitates the diffusion of O₂ and electrolyte, but also provides abundant catalytic sites for oxygen reduction reactions and oxygen evolution reactions (ORR/OER). In addition, the Ni doping into the structure of TiO₂ can significantly enhance the catalytic activity of ORR/OER, resulting in a reduced discharge/charge overpotential and enhanced discharge-specific capacity.

Lithiated nickel oxide films were thermally synthesized using Ni/Li/Ni films at various temperatures between 873 K and 1123 K. Structural and electrochemical properties of the synthesized films were investigated by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and galvanostatic charge–discharge half-cell tests between 4.5 V and 2.5 V. Lithiated nickel oxide films with the composition near stoichiometric LiNiO₂ could be obtained under annealing conditions (973–1073 K, 1 h). Surfaces of synthesized films consisted of some particles and became smoother with an increase in annealing temperature. Particles with the sharpest edge were formed at 1023 K. Cells with synthesized electrodes showed reversible Li ion transfer and clear voltage plateaus in charge–discharge curves that can confirm the phase transformation of LiNiO₂.

LiMn₂O₄ was prepared by a solid-state reaction, and for the first time its electrochemical behavior in the organic and aqueous electrolytes were compared. Since the host structure is the same, the intercalation and deintercalation behavior does not change, and the diffusion coefficient of Li⁺ ions are in the same range. However, due to much higher ionic conductivity of the aqueous electrolyte, its reversible redox behavior at high scan rate is much better than in the organic electrolyte. The reversible capacity in the aqueous electrolyte is 85 mAh ⋅ g^-1 at the current density of 50 mA ⋅ g^-1, and 22 mAh ⋅ g^-1 (26% of the normal capacity) when the current density is up to 10,000 mA ⋅ g^-1 (118 C). This shows that aqueous rechargeable lithium battery (ARLB) have very high-power density or excellent rate capability, and good cycling behavior.

New materials are of great importance for further development of lithium (Li) ion batteries. This paper reviews the latest development on core/shell structured nanocomposites. Due to different roles of the cores and the shells, the nanocomposites can be tailored to improve their electrochemical performance. Finally, further directions are pointed out.

Modified LiCoO₂ was prepared via a sol–gel method followed by a TiO₂ coating and characterized by X-ray diffraction analysis, transmission electronic microscopy and various measurements of charge/discharge behavior. Its cycling performance and rate capability were greatly improved compared to the original LiCoO₂. The initial capacity of the TiO₂-coated LiCoO₂ is 134 mAh g^-1 at the current density of 5000 mA g^-1. When the current density increases to 10,000 mA g^-1, the cathode displays an initial capacity of 128 mAh g^-1, much higher than that (<101 mAh g^-1) for the virginal LiCoO₂, and shows no evident capacity fading after 100 cycles.

Li₂FeSiO₄/C composites have been successfully prepared by a combination of solution route and high-temperature solid-state reaction processes. The morphology and crystalline structure were characterized using scanning electron microscope (SEM) and X-ray diffraction (XRD). Effects of calcination temperature on the electrochemical properties of Li₂FeSiO₄/C composite cathodes were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance measurements. The XRD patterns indicate that high-purity Li₂FeSiO₄ with well-developed crystallinity are obtained above 600°C. The primary particle size was increased by elevating the calcination temperature from 600°C to 750°C. The Li₂FeSiO₄/C composite synthesized at 650°C delivers the largest initial discharge capacity of 153.2 mAh g^-1 with a capacity retention of 93.5% after 30 cycles when tested at a current density of C/16 (1C = 166 mAh g^-1) between 1.5 and 4.8 V (vs. Li⁺/Li).

Polyanion LiVPO₄F has been recently recognized as a promising high energy cathode material for next generation rechargeable lithium batteries. With the aim of performance advancement in this paper, 3 at.% chromium are used to dope LiVPO₄F during carbothermal reduction synthesis. Rietveld refinement of X-ray diffraction pattern indicates that most of the chromium favors occupying the lithium site. Energy dispersive X-ray spectrum on selected area of the particle further demonstrates successful Cr doping into LiVPO₄F. Both the rate capability and cycling performance of LiVPO₄F are found noticeably improved possibly due to the stabilized crystalline structure and increased electric conductivity by Cr doping. The specific discharge capacities at C/24, C/5, 1 C and 8 C rates are 144.3, 135.1, 108.5 and 89.6 mA h g^-1, respectively. Moreover, it delivers a capacity of 128.7 mA h g^-1 at C/2 with the retention of 88.2% after 100 cycles.

Microbatteries are currently the best choice to power microelecronic devices. To maximize both energy density and power density of microbatteries within the areal footprint, the three-dimensional (3D) microbattery architectures have been proposed, comprising a 3D matrix of components (cathode, anode and electrolyte) arranged in either a periodic array or an aperiodic ensemble. As one of the key components, the cathode is vital to the electrochemical performance of microbatteries and the fabrication of 3D cathode is still challenging. This review describes recent advances in the development of 3D self-supported metal oxides as cathodes for lithium-ion microbatteries. Current technologies for the design and morphology control of 3D cathode fabricated using template, laser structuring and 3D printing are outlined along with different efforts to improve the energy and power densities.

Lithium and Mn rich solid solution materials Li[Li_0.26Ni_0.07Co_0.07Mn_0.56]O₂ were synthesized by a carbonate co-precipitation method and modified with a layer of graphene. The graphene-modified cathodes exhibit improved rate capability and cycling performance as compared to the bare cathodes. Electrochemical impedance spectroscopy (EIS) analyses reveal that the improved electrochemical performances are due to acceleration kinetics of lithium-ion diffusion and the charge transfer reaction of the graphene-modified cathodes.

Non-stoichiometric LiFe_1-xPO₄/C composites were synthesized by a simple sol–gel method. Different impurities were detected in the X-ray diffraction measurements with the change of Fe content. The effects of Fe-poor on the structure and electrochemical performance of LiFePO₄ were investigated. Compared with stoichiometric LiFePO₄/C, non-stoichiometric samples show better electrochemical performance because they have smaller impedance and faster lithium ion diffusion. Among these non-stoichiometric samples, LiFe_0.94PO₄/C cathode delivers the highest capacity of 149 mAh g^-1 at 0.2 C and 103 mAh g^-1 at 5 C and no capacity loss was found after 100 full cycles.

Lithium-sulfur batteries are considered as a promising candidate for the next-generation high energy density storage devices. However, they are still hindered by serious capacity decay on cycling caused by the dissolution of redox intermediates. Here, we designed a unique structure with polypyrrole (ppy) inserting into the graphene oxide (GO) sheet for accommodating sulfur. Such a sulfur host not only exhibits a good electronic and ionic conductivity, but also can suppress polysulfide dissolution effectively. With this advanced design, the composite cathode showed a high specific capacity of 548.4mA$\cdot$h$\cdot$g${}^{-1}$ at 5.0 C. A stable Coulombic efficiency of $\sim$99.5% and a capacity decay rate as low as 0.089% per cycle along with 300 cycles at 1.0 C were achieved for composite cathodes with 78wt.% of S. Besides, the interaction mechanism between PPy and lithium polysulfides (LPS) was investigated by density-functional theory (DFT), suggesting that only the polymerization of N atoms can bind strongly to Li ions of LPS rather than single N atoms. The 3D structure GO-PPy host with high conductivity and excellent trapping ability to LPS offered a viable strategy to design high-performance cathodes for Li–S batteries.

Aqueous zinc-ion batteries (ZIBs) as a new battery technology have received great attention due to the high energy and power density, low cost, high safety and environmental friendliness. However, their practical deployment has been restricted by some serious issues such as corrosion of zinc metal anode in aqueous electrolyte, undesired growth of zinc dendrites, and hydrogen evolution from the water splitting. Therefore, tremendous efforts have been devoted to mitigate these issues and significant progresses have been achieved. In this paper, we review some key recent progresses of aqueous ZIBs, focusing on materials engineering strategies that are able to address the major challenges. Moreover, we provide rational perspectives on the future development of ZIBs.