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Zhang J.,CAS Shanghai Institute of Microsystem and Information Technology | Zhang J.,University of Chinese Academy of Sciences | Bao T.,Pylon Technologies Co. | Xie X.,CAS Shanghai Institute of Microsystem and Information Technology | Xia B.,CAS Shanghai Institute of Microsystem and Information Technology
Journal of Power Sources | Year: 2017

To enhance the electrochemical performance of SiO, a simple electroless plating and ultrasonication method is used to prepare SiO/Cu/expanded graphite(EG) composite. Electrochemical results show that the electrode has a reversible specific capacity of 836 mAh/g and the capacity retention ratio is 90.2% in the 100th cycle at 200 mA/g current density (25 °C). Moreover, real time stress measurements quantitatively show that EG effectively suppresses stress development in the electrodes, which results in good cycling performance. © 2017 Elsevier B.V.

Shi H.,Tianjin University of Technology | Wang X.,Tianjin Polytechnic University | Hou P.,Tianjin University of Technology | Zhou E.,Tianjin University of Technology | And 7 more authors.
Journal of Alloys and Compounds | Year: 2014

The comparative investigations between core-shell and non-core-shell structured layered materials with a same composition are seldom reported and extremely necessary. Li[Ni0.7Co0.1Mn0.2]O 2 is firstly redesigned into core-shell structured Li[(Ni 0.8Co0.1Mn0.1)0.7(Ni 0.45Co0.1Mn0.45)0.3]O2 and the detailed comparative investigations between them are performed in this work. In this core-shell structure, Li[Ni0.8Co0.1Mn 0.1]O2 with high capacity is encapsulated completely with Li[Ni0.45Co0.1Mn0.45]O2 as a stable layer. Transition metal hydroxide precursors were synthesized by coprecipitation method. The core-shell structure of hydroxide precursor as designed was identified by particle size analysis, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and derivative thermogravimetric analysis (DTG). The obtained core-shell precursor was calcined with stoichiometric Li2CO3 (nLi:nM = 1.05:1) at 850 C for 16 h to get lithiated oxide. XRD results showed that lithiated oxide can be indexed to a typical layered structure with a R-3m space group. EDS analysis from the cross-section of core-shell material particles revealed somewhat diffusion of cations in core-shell structure resulting in a concentration gradient layer, however, the core-shell structure of lithiated oxide was still remained. The electrochemical and differential scanning calorimetry (DSC) tests showed that core-shell structured Li[Ni0.7Co0.1Mn 0.2]O2 displayed remarkably improved cyclability and thermal stability compared with the non-core-shell structured one. These results can clarify the function of core-shell structure in core-shell structured layered materials by excluding the effects of composition variation. © 2013 Elsevier B.V. All rights reserved.

Hou P.,Tianjin University of Technology | Wang X.,Tianjin Polytechnic University | Song D.,Tianjin University of Technology | Shi X.,Tianjin University of Technology | And 3 more authors.
Electrochimica Acta | Year: 2014

LiNi1/3Co1/3Mn1/3O2 was redesigned into new core-shelled Li{[NiyCo1-2yMn y](1-x)}core{[Ni1/2Mn 1/2]x}shellO2 (0 ≤ x ≤; 0.3, 6y + 3x-6xy = 2) to improve its performances. Those core-shelled materials were successfully synthesized at 800 °C from core-shelled {[NiyCo 1-2yMny](1-x)}core{[Ni 1/2Mn1/2]x}shell(OH)2 precursors obtained via a co-precipitation route. Scanning Electron Microscope (SEM) shows that a morphology with good spherical secondary particles developed from needle-like primary particles was formed in the precursors and maintained well in the lithiated compounds even after the calcination at 800 °C. Energy Disperse X-ray Spectrum (EDS) on the surface of precursors particles, in combination with evidence of size increase from core to shell during co-precipitation process, supports the formation of the core-shell structure as designed in the precursors. This is certified by subsequent EDS experiments on the cross-section of single particle of the lithiated compounds, showing that the lithiated compounds approximately had a targeted core-shell structure of Li{[NiyCo1-2yMny](1-x)} core{[Ni1/2Mn1/2]x} shellO2. Nevertheless, it is hard to detect differences in XRD for those lithiated compounds. Electrochemical tests and Differential Scanning Calorimetry (DSC) experiments demonstrate the gradually improved cyclability at a severe charge-discharge condition (55 °C and charging to 4.5 V) and thermal stability of materials with increasing x value (thickness of shell). © 2014 Elsevier Ltd.

Hou P.,Tianjin University of Technology | Wang X.,Tianjin Polytechnic University | Wang D.,Tianjin University of Technology | Song D.,Tianjin University of Technology | And 4 more authors.
RSC Advances | Year: 2014

A novel core-concentration gradient-shelled LiNi0.5Co 0.2Mn0.3O2 was successfully synthesized for the first time by a simple method from core-shelled precursors [(Ni 0.6Co0.2Mn0.2)1/2(Ni 0.4Co0.2Mn0.4)1/2](OH)2 that were synthesized via a co-precipitation route. Particle size increase of hydroxide precursors from core to shell, in combination with subsequent investigations of Energy Disperse X-ray Spectrum (EDS) on precursors, supported the formation of a core-shelled structure. To obtain concentration gradient layer between core and shell, a high calcined temperature of 900 °C was selected as high temperature calcination gave rise to diffusion of cations in the core-shelled structure. Thus, the prepared precursor powders were then calcined with stoichiometric ratio lithium carbonate (Li/M = 1.05) at 900 °C in air, which resulted in core-concentration gradient-shelled (CCGS) LiNi 0.5Co0.2Mn0.3O2. The compositions of core and shell separately were LiNi0.60Co0.20Mn 0.20O2 and LiNi0.44Co0.20Mn 0.36O2, between which was a concentration gradient layer. X-ray diffraction (XRD) studies show that the prepared material was indexed to a typical layered structure with a R3m space group. Compared to LiNi 0.5Co0.2Mn0.3O2, the CCGS-LiNi 0.5Co0.2Mn0.3O2 presented remarkably improved cycling performance and thermal stability, which can be ascribed to LiNi0.44Co0.20Mn0.36O2 shell providing structural and thermal stability. This journal is © the Partner Organisations 2014.

Hou P.,Tianjin University of Technology | Guo J.,Pylon Technologies Co. | Song D.,Tianjin University of Technology | Zhang J.,Pylon Technologies Co. | And 2 more authors.
Chemistry Letters | Year: 2012

LiNi1-x-yCoxMnyO2 can be redesigned to double-shelled structure, which does not change total composition compared with some reported coreshell materials. In this paper, the spherical double-shelled Li[(Ni0.8Co0.1Mn0.1) 2/7(Ni1/3Co1/3-Mn1/3) 3/14(Ni0.4Co0.2Mn0.4) 1/2]O2 with total composition of LiNi0.5Co0.2Mn0.3O2 was synthesized via a coprecipitation route for the first time. The double-shelled material displayed higher capacity, superior cycling performance, and thermal stability than the non-coreshell LiNi0.5Co0.2Mn 0.3O2 material. © 2012 The Chemical Society of Japan.

Hou P.,Tianjin University of Technology | Wang X.,Tianjin Polytechnic University | Song D.,Tianjin University of Technology | Shi X.,Tianjin University of Technology | And 3 more authors.
Journal of Power Sources | Year: 2014

LiNi0.5Co0.2Mn0.3O2 is redesigned into a new core-shelled Li[(Ni0.8Co0.1Mn 0.1)2/7]core[(Ni1/3Co 1/3Mn1/3)3/14]inner-shell[(Ni 0.4Co0.2Mn0.4)1/2] outer-shellO2, in which LiNi0.8Co 0.1Mn0.1O2 may deliver high capacity and LiNi0.4Co0.2Mn0.4O2 provides structural and thermal stability. To achieve such designed structure, double-shelled hydroxide precursors are firstly prepared via a co-precipitation route. Scanning electron microscope (SEM) shows that all precursors are of 6-10 μm spherical secondary particles developed from nanosheet-shaped primary particles. Energy disperse X-ray spectrum (EDS) on the surface of precursors, in combination with increase of particles size from core to shell during co-precipitation process, confirms the formation of core-shell structure as designed. The spherical morphology is preserved after lithiation at different temperatures from 800 °C to 900°C while the morphology of primary particles changes from nano-sized plate to micron-sized rectangular-like shapes. EDS surface composition analysis of lithiated compounds also strongly suggests the formation of core-shell structure; nevertheless, diffusion of transition metal ions between the core and shell occurs and becomes severe with increase of sintering temperature. Consequently, the double-shelled materials especially prepared at 850°C display the remarkably improved cycleability, rate capability, and thermal stability in contrast to normal one. The enhancement of those properties may be ascribed to structurally stable double shell components, especially outer shell. © 2014 Elsevier B.V. All rights reserved.

Cai Z.,Shanghai JiaoTong University | Liu Y.,Shanghai JiaoTong University | Zhao J.,Shanghai JiaoTong University | Li L.,Shanghai JiaoTong University | And 2 more authors.
Journal of Power Sources | Year: 2012

Tris(trimethylsilyl) borate (TMSB) used as new electrolyte additive to improve performance of LiFePO 4 based lithium-ion battery is investigated in this paper. The effects of the TMSB on the LiFePO 4 electrode are investigated via a combination of electrochemical impedance spectroscopy (EIS), cyclability, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). It is found that the LiFePO 4 battery with a composite LiPF 6-based electrolyte containing 1 wt% TMSB additive exhibits higher discharge retention and better cycling performance than the battery without TMSB additive at both 30 °C and 55 °C. SEM and XPS measurements show the changes of surface morphology and formation of solid electrolyte interface (SEI). EIS results indicate that the interfacial impedances of the batteries after cycled at 55 °C with the electrolyte containing TMSB additive are significantly smaller than the batteries without additive. The improved performances are ascribed to the enhancement of the thermal stability of the electrolyte and the modification of SEI component on the LiFePO 4 electrode. © 2011 Elsevier B.V. All rights reserved.

Liu Z.,Tianjin University | Wang Y.,Tianjin University | Zhang J.,Pylon Technologies Co. | Liu Z.,Pylon Technologies Co.
Applied Thermal Engineering | Year: 2014

Thermal management is crucial to maintain the performance of large battery packs in electric vehicles. To this end, we present herein a shortcut computational method to rapidly estimate the flow and temperature profiles in a parallel airflow-cooled large battery pack with wedge-shaped plenums for airflow distribution. The method couples a flow resistance network model with a transient heat transfer model to calculate the temperature distribution in a battery pack as influenced by the airflows within and among battery modules in the pack. The effects of the plate angle of the plenums, the minimal plenum width and the battery unit spacing on the airflow and temperature distributions are presented. Additionally, an example of collective parameter adjustment for acceptable temperature uniformity of a battery pack subjected to total volume constraint is given. © 2014 Elsevier Ltd. All rights reserved.

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