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Zhang J.,Northeastern University China | Zhang J.,Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province | Luo S.,Northeastern University China | Luo S.,Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province | And 12 more authors.
Electrochimica Acta | Year: 2016

LiAlO2 composited LiMnPO4/C cathode material has been synthesized by in-situ growth hydrothermal method. The coexistence of minor LiAlO2 in LiMnPO4 plays an important role in electrochemical properties. The composite is characterized by XRD, SEM, HRTEM, Raman microprobe spectroscopy and their electrochemical properties are also studied. It shows that the LiAlO2 is composed of pure α-LiAlO2 phase with flaky-shaped nanoplates. LiAlO2 nanoplates porous structure is inherited from anodic aluminum oxide (AAO) structure and serves as substrates to grow LiMnPO4 nanocrystals, which provide a high surface area with a porous structure. The structure of LiMnPO4 is not affected by LiAlO2 nanoplates compositing. Among the investigated samples, the one with 6 wt.% LiAlO2 exhibits a higher specific discharge capacity of 142.8 mAh/g at 0.05C rate with a high capacity retention of 94.8% after 50 cycles. Electrochemical impedance spectroscopy (EIS) results show that the lithium diffusion constant (DLi +) for 6 wt.% content LiAlO2-LiMnPO4/C electrode is 2.07 × 10-14 cm2/s which is higher than the values for other contents LiAlO2-LiMnPO4/C electrode. The LiAlO2 is effective in suppressing the increase of the interfacial resistance between the electrode/electrolyte interface during charge-discharge cycling. © 2016 Elsevier Ltd. All rights reserved. Source


Wang Z.,Northeastern University China | Wang Z.,Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province | Luo S.,Northeastern University China | Luo S.,Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province | And 6 more authors.
Applied Surface Science | Year: 2016

Li-rich layered cathode Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is prepared via a co-precipitation followed with high-temperature calcination, and then successfully modified with nano-Li3PO4 by ball milling and annealing. The TEM and EDS reveal that Li3PO4 is homogeneously coated on the particle surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2. And the electrochemical performance of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is significantly improved by coating with lithium ion conductor Li3PO4. The Li3PO4-coated sample delivers a high initial discharge capacity of 284.7 mAhg-1 at 0.05 C, and retains 192.6 mAhg-1 after 100 cycles at 0.5 C, which is higher than that of the pristine sample (244 mAhg-1 at 0.05 C and 168.2 mAhg-1 after 100 cycles at 0.5 C). The electrochemical impedance spectroscopy (EIS) demonstrates that the resistance for Li/Li3PO4-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cell was reduced compared to Li/Li[Li0.2Mn0.54Ni0.13Co0.13]O2, which indicates the Li3PO4 coating layer with high ionic conductivity (6.6 × 10-8 S cm-1) facilitates the diffusion of lithium ions through the interface between electrode and electrolyte and accelerates the charge transfer process. What is more, the Li3PO4 coating layer can also act as a protection layer to protect the cathode material from encroachment of electrolyte. The two aspects account for the enhanced electrochemical performance of Li3PO4-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2. © 2016 Elsevier B.V. All rights reserved. Source


Wang Z.,Northeastern University China | Wang Z.,Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province | Luo S.,Northeastern University China | Luo S.,Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province | And 9 more authors.
RSC Advances | Year: 2016

The poor cycling stability resulting from large volume change is the major obstacle to the application of tin-based anode materials. In this paper, three-dimensional porous carbon nanosheet networks anchored with Cu6Sn5@carbon nanoparticles (10-35 nm) as a high-performance anode for lithium ion batteries are synthesized via a self-assembly NaCl template-assisted in situ chemical vapor deposition strategy. The composite exhibits superior rate capability (523, 443, 395, 327, 281, and 203 mA h g-1 at 0.2, 0.5, 1, 2, 5, and 10 A g-1, respectively) and excellent cycling stability (396.8 mA h g-1 at 1 A g-1 for the first cycle and maintains 92.3% after 200 cycles). The superior performance is attributed to the unique architecture: inactive metal copper serves as a "buffer matrix" and relaxes the large volume change of the tin; a uniform distribution of nano-sized Cu6Sn5 makes the inevitable stress/strain small, meanwhile it provides a short path for lithium ion diffusion; onion-like carbon shells not only prevent the Cu6Sn5 nanoparticles from agglomerating and growing but also offer mechanical support to accommodate the stress associated with the volume change of tin upon cycling, thus alleviating pulverization; 3D porous carbon nanosheet networks ensure the mechanical integrity and facilitate lithium ion diffusion as well as electron transportation. © 2016 The Royal Society of Chemistry. Source

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