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Annealing Effect of Mesoporous Tin-Phosphate Anodes on the Electrochemical Cycling
Cho, Jaephil 한양대학교 이학기술연구소 2008 이학기술논문지 Vol.12 No.-
The synthesis of structurally stable, hexagonal mesoporous tin phosphates was studied using a simple procedure with a polyoxyethylene-cetyl-ether surfactant as a structure-directing agent. The annealed mesoporous tin phosphate had a specific surface area of approximately 190 ㎡/g, and an average pore diameter of The mesoporous tin phosphates annealed at 400C, 500C, and 600C were cycled at a rate of 100 mA/g between 1.5 and 0 V with an initial charge capacity of ∼600 mAh/g. In particular, the 400C-annealed mesoporous anode showed a large initial charge capacity of 622 mAh/g, and an excellent capacity retention (∼90% up to 30 cycle) with the preserved mesoporous structure.
Cho, Yonghyun,Oh, Pilgun,Cho, Jaephil American Chemical Society 2013 Nano letters Vol.13 No.3
<P>A solid solution series of lithium nickel metal oxides, Li[Ni<SUB>1–<I>x</I></SUB>M<SUB><I>x</I></SUB>]O<SUB>2</SUB> (with M = Co, Mn, and Al) have been investigated intensively to enhance the inherent structural instability of LiNiO<SUB>2</SUB>. However, when a voltage range of Ni-based cathode materials was increased up to >4.5 V, phase transitions occurring above 4.3 V resulted in accelerated formation of the trigonal phase (<I>P</I>3̅<I>m</I>1) and NiO phases, leading to and pulverization of the cathode during cycling at 60 °C. In an attempt to overcome these problems, LiNi<SUB>0.62</SUB>Co<SUB>0.14</SUB>Mn<SUB>0.24</SUB>O<SUB>2</SUB> cathode material with pillar layers in which Ni<SUP>2+</SUP> ions were resided in Li slabs near the surface having a thickness of ∼10 nm was prepared using a polyvinylpyrrolidone (PVP) functionalized Mn precursor coating on Ni<SUB>0.7</SUB>Co<SUB>0.15</SUB>Mn<SUB>0.15</SUB>(OH)<SUB>2</SUB>. We confirmed the formation of a pillar layer via various analysis methods (XPS, HRTEM, and STEM). This material showed excellent structural stability due to a pillar layer, corresponding to 85% capacity retention between 3.0 and 4.5 V at 60 °C after 100 cycles. In addition, the amount of heat generation was decreased by 40%, compared to LiNi<SUB>0.70</SUB>Co<SUB>0.15</SUB>Mn<SUB>0.15</SUB>O<SUB>2</SUB>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-3/nl304558t/production/images/medium/nl-2012-04558t_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl304558t'>ACS Electronic Supporting Info</A></P>
Cho, Yong Jae,Kim, Han Sung,Im, Hyungsoon,Myung, Yoon,Jung, Gyeong Bok,Lee, Chi Woo,Park, Jeunghee,Park, Mi-Hee,Cho, Jaephil,Kang, Hong Seok American Chemical Society 2011 The Journal of Physical Chemistry Part C Vol. No.
<P>Nitrogen (N)-doped graphitic layers were deposited as shells on pregrown silicon nanowires by chemical vapor deposition. Graphite-like and pyridine-like structures were selectively chosen for 3 and 10% N doping, respectively. Increasing the thickness of the undoped graphitic layers from 20 to 50 nm led to an increase in the charge capacity of the lithium ion battery from 800 to 1040 mA h/g after 45 cycles. Graphite-like 3% N-doping in the 50 nm-thick shell increases the charge capacity by 21% (i.e., to 1260 mA h/g), while pyridine-like 10% N-doping in the 20 nm-thick shell increases it by 36% (i.e., to 1090 mA h/g). This suggests that both pyridine- and graphite-like structures can be effective for lithium intercalation. First principles calculations of the graphene sheets show that the large storage capacity of both N-doping structures comes from the formation of dangling bonds around the pyridine-like local motives upon lithium intercalation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-19/jp201485j/production/images/medium/jp-2011-01485j_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp201485j'>ACS Electronic Supporting Info</A></P>
Royal Society of Chemistry 2008 Journal of materials chemistry Vol.18 No.19
<P>VO<SUB><I>x</I></SUB>-coated LiMn<SUB>2</SUB>O<SUB>4</SUB> spinel nanorod clusters as a lithium battery cathode material are prepared by mixing OV(CH<SUB>3</SUB>H<SUB>7</SUB>)<SUB>3</SUB> dissolved in ethanol and LiMn<SUB>2</SUB>O<SUB>4</SUB> powder consisting of nanorod clusters and firing this mixture at 700 °C. In the coated spinel, the V atoms are distributed within ∼30 nm of the particle surface without showing any coating layer, indicating the possible formation of a solid solution (LiMn<SUB>2−<I>x</I></SUB>V<SUB><I>x</I></SUB>O<SUB>4</SUB>). The coated nanorod clusters exhibit a comparable rate capability to an uncoated counterpart, showing a discharge capacity of 117 mAh g<SUP>−1</SUP> at a rate of 7 C (= 1400 mA g<SUP>−1</SUP>), which corresponds to 89% of the capacity retention ratio at room temperature. Further, the coated cathode exhibits excellent structural stability in storage at 80 °C for 24h; a significantly decreased amount of Mn dissolution (60 ppm) is observed, in contrast to that of an uncoated counterpart (5000 ppm).</P> <P>Graphic Abstract</P><P>VO<SUB><I>x</I></SUB>-coated LiMn<SUB>2</SUB>O<SUB>4</SUB> spinel with an urchin-like nanostructure as a lithium battery cathode material is prepared by mixing OV(CH<SUB>3</SUB>H<SUB>7</SUB>)<SUB>3</SUB> dissolved in ethanol and LiMn<SUB>2</SUB>O<SUB>4</SUB> powder with an urchin-like morphology and firing this mixture at 700 °C. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b719177d'> </P>
Porous Si anode materials for lithium rechargeable batteries
Royal Society of Chemistry 2010 Journal of materials chemistry Vol.20 No.20
<P>Si anode materials for lithium rechargeable batteries have received much attention due to their high capacity. The Si itself can alloy with lithium up to Li<SUB>4.4</SUB>Si, corresponding to 4212 mAh/g (4.4Li + Si ↔ Li<SUB>4.4</SUB>Si). However, the large volume expansion of over 300% due to the formation of various Li<SUB><I>x</I></SUB>Si<SUB><I>y</I></SUB> phases generates enormous mechanical stress within the ionic character material, which becomes pulverized during the first few cycles and loses electrical integrity. Although such a drastic volume change cannot be removed completely, the degree of the volume change can be effectively reduced to utilize its application in anode materials. In this regard, when porous particles contain ordered pores, these pores act as a buffer layer for volume changes, demonstrating another means of controlling the volume expansion/contraction. In this review, recent developments in porous Si anodes, such as mesoporous nanowires, 3D porous particles, and nanotubes have been highlighted.</P> <P>Graphic Abstract</P><P>When porous particles contain ordered pores, these pores act as a buffer layer for volume changes, demonstrating another means of controlling the volume expansion/contraction. These porous particles demonstrate that the degree of the volume change can be effectively reduced to utilize its application in anode materials. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b923002e'> </P>
Hard templating synthesis of mesoporous and nanowire SnO<sub>2</sub> lithium battery anode materials
Kim, Hyesun,Cho, Jaephil Royal Society of Chemistry 2008 Journal of materials chemistry Vol.18 No.7
<P>Mesoporous and nanowire SnO<SUB>2</SUB> anode materials for lithium batteries were prepared using KIT-6 and SBA-15 SiO<SUB>2</SUB> templates, and their electrochemical properties were compared at different current rates. The as-prepared SnO<SUB>2</SUB> nanowires had a diameter of 6 nm and a length of >3 μm and Brunauer–Emmett–Teller (BET) surface area of 80 m<SUP>2</SUP> g<SUP>−1</SUP> while mesoporous SnO<SUB>2</SUB> showed a pore size of 3.8 nm and a BET surface area of 160 m<SUP>2</SUP> g<SUP>−1</SUP>. The charge capacities of these two anodes were similar to each other at 800 mAh g<SUP>−1</SUP>, but mesoporous SnO<SUB>2</SUB> showed much improved cycle life performance and rate capabilities because of its higher surface area than nanowire SnO<SUB>2</SUB>. Especially, the capacity retention of the mesoporous SnO<SUB>2</SUB> was 98%, compared with 31% for the SnO<SUB>2</SUB> nanowires at a 10 <I>C</I> rate (= 4000 mA g<SUP>−1</SUP>). The improved electrochemical performance of the mesoporous SnO<SUB>2</SUB> was related to the regular porosity which permitted thorough flooding of the electrolyte between the particles, and the mesopores which acted as a buffer zone during the volume contraction and expansion of Sn.</P> <P>Graphic Abstract</P><P>Mesoporous and nanowire SnO<SUB>2</SUB> prepared by KIT-6 and SBA-15 hard templates can lead to facile and reproducible nanowire and mesoporous SnO<SUB>2</SUB>, showing improved capacity retention and rate capabilities due to the quicker Li<SUP>+</SUP> ion diffusion. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b714904b'> </P>