A novel carbon-coated LiCoO2 as cathode material for lithium ion battery

Using a commercially available LiCoO₂ as starting material, a surface-modified cathode material was obtained by coating it with a nano layer of amorphous carbon. The carbon-coated LiCoO₂ was characterized by X-ray diffraction analysis, scanning electronic microscopy, transmission electronic microscopy, electrochemical impedance spectroscopy and measurement of charge/discharge behavior. Results show that the carbon-coated LiCoO₂ displays marked lower charge transfer resistance, higher lithium ion diffusion coefficient and much better rate capability than the original LiCoO₂. It also indicates promising application of lithium ion batteries in the areas requiring charge and discharge at high rate.     

A novel approach to massive preparation of LiV3O8 as a cathode material for lithium rechargeable battery

The layered cathode materials of LiV₃O₈ were successfully prepared for the lithium rechargeable battery via a wet-chemistry synthesis method. The as-synthesized materials were characterized by XRD (powder X-ray diffraction), SEM (scanning electron microscope) and galvanostatic charge-discharge test. The results indicate that this soft-synthesis technique offers reduced calcinations temperature, preferred surface morphology and better electrochemical performance. Among the thus-prepared materials, the material obtained at 350 °C demonstrates the first discharge capacity as high as 308 mAh g^-1 in the range of 4.0 ～1.7 V at a current rate of 30 mA g^-1 and remains at a stable discharge capacity of 250 mAh g^-1 within 30 cycles.     

A polythiophene derivative bearing TEMPO as a cathode material for rechargeable batteries

A polythiophene derivative bearing TEMPO radical was synthesized by oxidative chemical polymerization of its monomer. The polymer had a high spin density (2.05 × 10²¹ spins/g of polymer). CV studies of the polymer showed that the electrochemical redox reaction of the TEMPO radicals were completely reversible. We demonstrated, for the first time, construction and charge/discharge characteristics of an organic radical battery utilizing a TEMPO bearing polythiophene based cathode material. The battery had an initial specific discharge capacity of 79 A h/kg (87% of the theoretical capacity) and an average output voltage of 3.6 V. The specific energy capacity initially discharged was 268 W h/kg.     

新型反相限进材料及其性能

以溴代硅胶为引发剂,CuBr/2,2-联吡啶为催化体系,在改性硅胶上经二步表面引发原子转移自由基聚合(SIATRP)制备内表面接枝甲基丙烯酸十八烷基酯(C18)、外表面接枝甲基丙烯酸环氧丙酯(GMA)、水解得到表面含大量二醇基的新型反相限进材料。使用傅里叶变换红外光谱(FT-IR)、元素分析和热重分析(TGA)对其表征,采用静态吸附实验研究反相限进材料的吸附性能,其对磺胺二甲氧嘧啶和土霉素的最大吸附量分别为18.02和4.80mg/g。结合固相萃取(SPE)评价其对大分子蛋白质的排阻性能,以牛血清白蛋白(BSA)作为排阻大分子模型,排阻能力达90%。将其用于牛奶中土霉素的分离富集,经高效液相色谱(HPLC)检测,土霉素的平均加标回收率为89.19%,相对标准偏差为3.03%。有望将新型反相限进材料和HPLC或液相色谱-质谱(LC-MS)等分析系统结合应用于生物样品的处理和检测。     

Investigation of SOFC material properties for plant-level modeling

This article describes results of a recent study of SOFC (Solid Oxide Fuel Cell) material properties using a numerical tool. The created model was validated against experimental data collected for two different solid oxide fuel cells. With focus on ionic and electronic conductivities, temperature influence was investigated. Results are presented, compared with available data, and discussed. Model of a micro-CHP (Combined Heat and Power) unit based on a SOFC stack was used for evaluation of system performance with different cells. On-site generated bio-syngas was considered as a fuel fed for the unit. The overall system efficiency was analyzed using an Aspen HYSYS modeling environment. Properties of two generic electrolyte materials were implemented in the models for evaluation of a co-generative unit operation. Electrical and overall efficiencies of systems based on those cells were compared and differences were observed. Micro-scale power units with fuel cells are a promising technology for highly efficient distributed cogeneration. As it was concluded, selection of a proper cell is crucial to assure high system efficiency.      

Nickel tetrathiooxalate as a cathode material for potassium batteries

We report a nickel tetrathiooxalate (NiTTO) coordination polymer as a cathode material for potassium batteries. In a potential range of 1.3–3.6 V vs. K⁺/K, the specific capacity of the material is 209 mA h g^?1 at a current density of 0.1 A g^?1, which roughly corresponds to the two-electron reduction of polymer repeating units. The charge–discharge mechanisms of NiTTO in potassium cells were examined using operando Raman spectroscopy.     

Olivine LiCoPO4 phase grown LiCoO2 cathode material for high density Li batteries

Olivine LiCoPO₄ phase grown LiCoO₂ cathode material was prepared by mixing precipitated Co₃(PO₄)₂ nanoparticles and LiCoO₂ powders in distilled water, followed by drying and annealing at 120 °C and 700 °C, respectively, for 5 h. As opposed to ZrO₂ or AlPO₄ coatings that showed a clearly distinguishable coating layer from the bulk materials, Co₃(PO₄)₂ nanoparticles were completely diffused into the surface of the LiCoO₂ and reacted with lithium of LiCoO₂. An olivine LiCoPO₄ phase was grown on the surface of the bulk LiCoO₂, with a thickness of ∼7 nm. The electrochemical properties of the LiCoPO₄ phase, grown in LiCoO₂, had excellent cycle life performance and higher working voltages at a 1C rate than the bare sample. More importantly, Li-ion cells, containing olivine LiCoPO₄, grown in LiCoO₂, showed only 10% swelling at 4.4 V, whereas those containing bare sample showed a 200% increase during storage at 90 °C for 5 h. In addition, nail penetration test results of the cell containing olivine LiCoPO₄, grown in LiCoO₂ at 4.4 V, did not exhibit thermal runaway with a cell surface temperature of ∼80 °C. However, the cell containing bare LiCoO₂ showed a burnt-off cell pouch with a temperature above 500 °C.     

Development of porous cathode powders for SOFC and influence of cathode structure on the oxygen electroreduction kinetics

Meso/macroporous La_1−xSr_xCoO_3−δ powder with the specific surface area higher than 140 m² g⁻¹ has been synthesized from the corresponding nitrates, using solution thermal decomposition method. These nanopowders have been used for preparation of SOFC cathodes, demonstrating lower oxygen electroreduction activation energy than that for less porous cathodes prepared from the powders synthesized using traditional solid state reaction method. To increase macroporosity of the cathodes the special pore forming agent has been added into the raw cathode paste. The very low total polarization resistance and activation energy values have been obtained for oxygen electroreduction, depending on the cathode porosity and potential applied.     

Activated graphene as a cathode material for Li-ion hybrid supercapacitors

Chemically activated graphene ('activated microwave expanded graphite oxide', a-MEGO) was used as a cathode material for Li-ion hybrid supercapacitors. The performance of a-MEGO was first verified with Li-ion electrolyte in a symmetrical supercapacitor cell. Hybrid supercapacitors were then constructed with a-MEGO as the cathode and with either graphite or Li(4)Ti(5)O(12) (LTO) for the anode materials. The results show that the activated graphene material works well in a symmetrical cell with the Li-ion electrolyte with specific capacitances as high as 182 F g(-1). In a full a-MEGO/graphite hybrid cell, specific capacitances as high as 266 F g(-1) for the active materials at operating potentials of 4 V yielded gravimetric energy densities for a packaged cell of 53.2 W h kg(-1).     

Zinc sulfide nanosheets as a novel solid‐phase extraction material for flavonoids

As a novel solid‐phase extraction material, zinc sulfide nanosheets were prepared by a simple method and were used to extract flavonoids. We used scanning electron microscopy to show its nanosheet morphology and energy dispersive X‐ray spectroscopy and powder X‐ray diffraction to confirm its chemical and phase compositions. Coupled to a high‐performance liquid chromatography, the zinc sulfide nanosheets were packed into a microcolumn and were used to extract four model flavonoids to examine their extraction ability. The parameters of sample loading and elution were investigated. Under optimized conditions, the analytical method for flavonoids was established. For the method, wide linearities from 1 to 250 μg/L and low limits of detection from 0.25 to 0.5 μg/L were obtained. The relative standard deviations for single column repeatability and column to column reproducibility were less than 7.7 and 10.4%, respectively. The established method was also used to analyze two real samples and the recoveries from 88.7 to 98.2% further proved the reliability of the method. Moreover, the zinc sulfide nanosheets have good stability and that in one column can be reused for more than 50 times. This work proves that the prepared zinc sulfide nanosheets are a good candidate as the flavonoids sorbent.     

Preparation and characterization of a novel form-stable phase change material for thermal energy storage

Journal of Thermal Analysis and Calorimetry - A series of novel polymeric form-stable phase change materials (FSPCMs) composed of poly(trimethylolpropane trimethacrylate-stearyl methacrylate) (PTS)...     

Electrochemically activated MnO as a cathode material for sodium-ion batteries

Besides classical electrode materials pertaining to Li-ion batteries, recent interest has been devoted to pairs of active redox composites having a redox center and an intercalant source. Taking advantage of the NaPF₆ salt decomposition above 4.2 V, we extrapolate this concept to the electrochemical in situ preparation of F-based MnO composite electrodes for Na-ion batteries. Such electrodes exhibit a reversible discharge capacity of 145 mAh g^− 1 at room temperature. The amorphization of pristine MnO electrode after activation is attributed to the electrochemical grinding effect caused by substantial atomic migration and lattice strain build-up upon cycling.     

构建一维铜基配位聚合物作为锂离子电池正极材料

合成了一种新型的一维(1D)羰基配位聚合物[Cu (BGPD)(DMA)(H₂O)]·DMA (记为Cu-BD,H₂BGPD=N,N′-双(甘氨酰)均苯四甲酸二酰亚胺,DMA=二甲基乙酰胺),并考察了其用作锂离子电池正极材料的电化学性能。电化学测试结果表明,Cu-BD正极在50 mA·g^-1的电流密度下循环100圈后仍然保留50 mAh·g^-1的比容量,具有较好的循环稳定性。Cu-BD电极反应机理研究表明,BGPD^2-配体和Cu (Ⅱ)离子在充放电过程中都可能参与了电子转移过程。     

Low-temperature synthesis of a green material for lithium-ion batteries cathode

Abstract

Battery technology is an important anthropogenic source of the heavy metals which are highly threatening to human health. A category of rechargeable lithium batteries that is of great interest is the set of batteries where the cathode material is a lithium iron phosphate (LiFePO₄). LiFePO₄ is an environmentally friendly and safe lithium-ion battery cathode material, but it has a key limitation, and that is its extremely low-electronic conductivity, a problem that can be greatly overcome by zinc-doping LiFePO₄. For the first time to our knowledge, a low-temperature method, that is advantageous both economically and technologically, for the synthesis of a zinc-doped LiFePO₄ is presented. Since the method appears to be applicable for synthesizing various zinc-doped LiFePO₄ compounds with the general formula LiFe_1?x Zn _x PO₄ (0<x<1), it is very promising for the production of a green cathode material for lithium-ion batteries.     

构建一维铜基配位聚合物作为锂离子电池正极材料

合成了一种新型的一维(1D)羰基配位聚合物[Cu(BGPD)(DMA)(H₂O)]·DMA(记为Cu-BD,H₂BGPD=N,N''-双(甘氨酰)均苯四甲酸二酰亚胺,DMA=二甲基乙酰胺),并考察了其用作锂离子电池正极材料的电化学性能。电化学测试结果表明,Cu-BD正极在50 mA·g^-1的电流密度下循环100圈后仍然保留50 mAh·g^-1的比容量,具有较好的循环稳定性。Cu-BD电极反应机理研究表明,BGPD配体和Cu(II)离子在充放电过程中都可能参与了电子转移过程。     

A high-capacity cathode based on silicates material for advanced lithium batteries

Silicate materials have been proposed as alternative cathodes for Li-ion battery applications. A novel mixture of silicates, labelled Li₆MnSi₅, based on the molar ratio among the Li/Mn/Si precursors, with promising electrochemical properties as positive electrode material is synthesized through a solid-state reaction. The results indicate the proposed synthetic method as effective for preparation of nanostructured silicate powders with average particle diameter of 30 nm. Structural morphology of the samples was determined using X-ray powder diffraction (XRPD), XPS and FESEM analysis. A joint analysis by XRPD data and by density functional theory (DFT) identified LiHMn₄Si₅O₁₅, Li₂Mn₄Si₅O₁₅, Li₂Si₂O₅ and Li_0.125Mn_0.875SiO₄ as components of Li₆MnSi₅ mixture. The electrochemical performance of Li₆MnSi₅ was evaluated by charge/discharge testing at constant current mode. Li₆MnSi₅ discharge behaviour is characterized by high capacity value of 480 mA h g^?1, although such capacity fades gradually on cycling. Ex situ XPS studies carried out on the electrode in both full charged and discharged states pointed out that Li₂Si₂O₅ is decisive for achieving such high capacity. The discharge/charge plateau is most probably related to the change in the oxidation state of silicon at the surface of the silica material.     

A Fe-rich sodium iron orthophosphate as cathode material for rechargeable batteries

Phosphate compounds have been intensively investigated as cathode materials for sodium ion batteries. Here we report the synthesis and electrochemical performance of a novel iron-rich sodium iron orthophosphate. This new compound was synthesized by a conventional solid state reaction method, and was found to be electrochemically active, delivering a reversible capacity of 85 mAhg^− 1 at an average voltage of c.a. 3.0 V vs. Na/Na⁺. Besides, the desodiated phase can be (de)intercalated by lithium ions when assembled into a lithium cell. Our discovery will open up the scope of phosphate family and reveal the importance of off-stoichiometric compounds as cathode materials.