Acs Nano
One great challenge in the development of lithium ion batteries is to simultaneously achieve high power and large energy capacity at fast charge and discharge rates for several minutes to seconds. Here we show that nitrogen- or boron-doped graphene can be used as a promising anode for high-power and high-energy lithium ion batteries under high-rate charge and discharge conditions. The doped graphene shows a high reversible capacity of >1040 mAh g(-1) at a low rate of 50 mA g(-1). More importantly, it can be quickly charged and discharged in a very short time of 1 h to several tens of seconds together with high-rate capability and excellent long-term cyclability. For example, a very high capacity of similar to 199 and 235 mAh g(-1) was obtained for the N-doped graphene and B-doped graphene at 25 A g(-1) (about 30 s to full charge). We believe that the unique two-dimensional structure, disordered surface morphology, heteroatomic defects, better electrode/electrolyte wettability, increased intersheet distance, improved electrical conductivity, and thermal stability of the doped graphene are beneficial to rapid surface Li(+) absorption and ultrafast Li(+) diffusion and electron transport, and thus make the doped materials superior to those of pristine chemically derived graphene and other carbonaceous materials.
关键词:
doped graphene;anode;lithium ion batteries;high rate;nitrogen;boron;high-rate capability;electrochemical capacitors;carbon nanotubes;li;storage;electrodes;energy;performance;nanosheets;diffusion;films
Journal of Physical Chemistry C
The influence of carbonization procedures on poly(vinyl chloride) (PVC) coated natural graphite (NG) spheres as anode materials for lithium ion batteries was investigated in detail in this study. At first, thermogravimetry-mass spectrometry was utilized to analyze pyrolysis behaviors of PVC, and on the basis of the results three typical carbonization procedures consisting of different heating steps were determined to fabricate PVC-coated NG spheres. The structural parameters, morphologies, pore size distributions, and Brunauer-Emmett-Teller specific surface areas of these coated samples were systematically characterized by employing X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and N(2) adsorption/desorption isotherms. Electrochemical performance measurements indicated that all the coated samples display a significantly improved cyclability, rate capability, and initial Coulombic efficiency in comparison with the pristine NG spheres. The reasons for the performance improvement were further explored using electrochemical impedance spectroscopy. Moreover, the sample under the carbonization procedure involving isothermal heating steps at temperatures of 280, 450, and 900 degrees C is even better than the well-recognized mesocarbon microbeads in terms of reversible capacity and rate capability.
关键词:
electrochemical characteristics;secondary batteries;electrolyte;interface;surface modification;negative electrode;carbon material;performance;li;particles;capacity
材料科学技术（英文）
Micro-sized (1030.3 +/- 178.4 nm) and nano-sized (50.4 +/- 8.0 nm) Fe(3)O(4) particles have been fabricated through hydrogen thermal reduction of alpha-Fe(2)O(3) particles synthesized by means of a hydrothermal process. The morphology and microstructure of the micro-sized and the nano-sized Fe(3)O(4) particles were characterized by X-ray diffraction, field-emission gun scanning electron microscopy, transmission electron microscopy and high-resolution electron microscopy. The micro-sized Fe(3)O(4) particles exhibit porous structure, while the nano-sized Fe(3)O(4) particles are solid structure. Their electrochemical performance was also evaluated. The nano-sized solid Fe(3)O(4) particles exhibit gradual capacity fading with initial discharge capacity of 1083.1 mAhg(-1) and reversible capacity retention of 32.6% over 50 cycles. Interestingly, the micro-sized porous Fe(3)O(4) particles display very stable capacity-cycling behavior, with initial discharge capacity of 887.5 mAhg(-1) and charge capacity of 684.4 mAhg(-1) at the 50th cycle. Therefore, 77.1% of the reversible capacity can be maintained over 50 cycles. The micro-sized porous Fe(3)O(4) particles with facile synthesis, good cycling performance and high capacity retention are promising candidate as anode materials for high energy-density lithium-ion batteries.
关键词:
Lithium-ion battery;Fe(3)O(4);Porous structure;Anode materials;electrochemical properties;fe2o3-loaded carbon;electrode materials;negative-electrode;alpha-fe2o3;nanoparticles;nanofibers;hematite;li
Y.X. Chen L.H. He P.J. Shang Q.L. Tang Z.Q. Liu H.B. Liu L.P. Zhou
材料科学技术（英文）
Micro-sized (1030.3§178.4 nm) and nano-sized (50.4±8.0 nm) Fe3O4 particles have been fabricated through hydrogen thermal reduction of α-Fe2O3 particles synthesized by means of a hydrothermal process. The morphology and microstructure of the micro-sized and the nano-sized Fe3O4 particles were characterized by X-ray diffraction, field-emission gun scanning electron microscopy, transmission electron microscopy and high-resolution electron microscopy. The micro-sized Fe3O4 particles exhibit porous structure, while the nano-sized Fe3O4 particles are solid structure. Their electrochemical performance was also evaluated. The nano-sized solid Fe3O4 particles exhibit gradual capacity fading with initial discharge capacity of 1083.1 mAhg¡1 and reversible capacity retention of 32.6% over 50 cycles. Interestingly, the micro-sized porous Fe3O4 particles display very stable capacity-cycling behavior, with initial discharge capacity of 887.5 mAhg¡1 and charge capacity of 684.4 mAhg−1 at the 50th cycle. Therefore, 77.1% of the reversible capacity can be maintained over 50 cycles. The micro-sized porous Fe3O4 particles with facile synthesis, good cycling performance and high capacity retention are promising candidate as anode materials for high energy-density lithium-ion batteries.
关键词:
Lithium-ion battery
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null
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Y.X. Chen L.H. He P.J. Shang Q.L. Tang Z.Q. Liu H.B. Liu L.P. Zhou
材料科学技术（英文）
Micro-sized (1030.3§178.4 nm) and nano-sized (50.4±8.0 nm) Fe3O4 particles have been fabricated through hydrogen thermal reduction of α-Fe2O3 particles synthesized by means of a hydrothermal process. The morphology and microstructure of the micro-sized and the nano-sized Fe3O4 particles were characterized by X-ray diffraction, field-emission gun scanning electron microscopy, transmission electron microscopy and high-resolution electron microscopy. The micro-sized Fe3O4 particles exhibit porous structure, while the nano-sized Fe3O4 particles are solid structure. Their electrochemical performance was also evaluated. The nano-sized solid Fe3O4 particles exhibit gradual capacity fading with initial discharge capacity of 1083.1 mAhg¡1 and reversible capacity retention of 32.6% over 50 cycles. Interestingly, the micro-sized porous Fe3O4 particles display very stable capacity-cycling behavior, with initial discharge capacity of 887.5 mAhg¡1 and charge capacity of 684.4 mAhg−1 at the 50th cycle. Therefore, 77.1% of the reversible capacity can be maintained over 50 cycles. The micro-sized porous Fe3O4 particles with facile synthesis, good cycling performance and high capacity retention are promising candidate as anode materials for high energy-density lithium-ion batteries.
关键词:
Lithium-ion battery
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null
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