Effect of the Molar Ratio of Li/Ti and Thermal Treatment on the Electrochemical Performance of Li4Ti5O12–rutile TiO2 Nanocomposite as Anode Materials

Zhen Yang,Xi-Ping Li,Jian Mao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.8

Li4Ti5O12–rutile TiO2 (LTO–RTO) dual-phase nanocomposite anode materials show excellent electrochemical performance. However, the effects of molar ratio of Li/Ti and thermal treatment on electrochemical properties of the LTO–RTO composite have been rarely reported. In this work, LTO–RTO nanocomposites were prepared by sol-hydrothermal method with different Li/ Ti molar ratios in raw materials and following calcinations at 600℃, 650℃ and 700℃ for the different holding time. The results indicate that with the decrease of Li/Ti molar ratio, the discharge capacity of the LTO–RTO nanocomposite increases at first and then decreases, and the optimal Li/Ti molar ratio is 4:4.77, which was obtained with calcination at 600℃ for 10 h. The effects of calcination temperature and holding time were further investigated. The result demonstrates that the thermal treatment has an obvious influence on the electrochemical performance due to the morphology change in the nanocomposite. The LTO–RTO nanocomposite calcinated at 650℃ for 2 h with a Li/Ti molar ratio of 4:4.77 in raw materials delivers excellent rate capability: the initial discharge capacity is 175.9, 176.3, 170.4, 167.5, 163.3 and 155.6 mA h g-1 at the rate of 0.5, 1, 3, 5, 10 and 20℃ (1 C = 175 mA h g-1), respectively.

Recent Developments in the Effects of Different Dopants on the Structure and Property of Lithium Titanate Material

Xi-Yang Li,Qian-Lin Chen,Min Yang,Ya-Nan Li,Jing-Bo Ma 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.3

The lithium titanium spinel Li4Ti5O12 has attracted more and more attention as anode materials applied in lithium ion batteries. Li4Ti5O12 material has been found to be able to intercalate lithium ions without deformation of the lattice. However, compared with graphite and other anode materials, the low conductivity of Li4Ti5O12 restricts its charging and discharging rate. Doping is deemed to be a businesslike method to enhance ionic and electronic conductivity of Li4Ti5O12. This paper reviews the effects of Li4Ti5O12 with different doping ions on different crystal lattice states. And it has been found by a summary that the doping objective of doping ions at Li4Ti5O12 is also different. Moreover, the applications of ion doping in different fields of Li4Ti5O12 are prospected.

White-Matter Hyperintensities and Lacunar Infarcts Are Associated with an Increased Risk of Alzheimer’s Disease in the Elderly in China

Shuai Ye,Shuyang Dong,Jun Tan,Le Chen,Hai Yang,Yang Chen,Zeyan Peng,Yingchao Huo,Juan Liu,Mingshan Tang,Yafei Li,Huadong Zhou,Yong Tao 대한신경과학회 2019 Journal of Clinical Neurology Vol.15 No.1

Background and Purpose This study investigated the contribution of white-matter hyperintensities (WMH) and lacunar infarcts (LI) to the risk of Alzheimer’s disease (AD) in an elderly cohort in China. Methods Older adults who were initially cognitively normal were examined with MRI at baseline, and followed for 5 years. WMH were classified as mild, moderate, or severe, and LI were classified into a few LI (1 to 3) or many LI (≥4). Cognitive function was assessed using the Mini Mental State Examination and the Activities of Daily Living scale. Results Among the 2,626 subjects, 357 developed AD by the end of the 5-year follow-up period. After adjusting for age and other potential confounders, having only WMH, having only LI, and having both WMH and LI were associated with an increased risk of developing AD compared with having neither WMH nor LI. Moderate and severe WMH were associated with an increased risk of developing AD compared with no WMH. Furthermore, patients with many LI had an increased risk of developing AD compared with no LI. Conclusions Having moderate or severe WMH and many LI were associated with an increased risk of developing AD, with this being particularly striking when both WMH and LI were present.

Microstructure Evolution and Mechanical Properties of AA2099 Al–Li Alloy with Tailored Li‐Containing Precipitates in Uniaxial Compression at Medium Temperature

Li Hu,Mengdi Li,Weijiu Huang,Xusheng Yang,Fei Guo,Haipeng Dong 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.5

Microstructure characteristics and mechanical behavior of AA2099 Al–Li alloy with no pre-existing Li-containing precipitates(AA2099-1 sample), pre-existing δ′ precipitates (AA2099-2 sample), pre-existing T1phase (AA2099-3 sample) andpre-existing T2phase (AA2099-4 sample) are systematically investigated via isothermal uniaxial compression at 250 °C inthe present study. Experimental results demonstrate that at the onset of plastic deformation, dynamic precipitation of smallsizedT1phase occurs rapidly within AA2099-1 sample, while it will be hindered within AA2099-2 sample. The increasingplastic strain benefits to dynamic precipitation of small-sized T1phase in AA2099-2 sample. Consequently, AA2099-1 andAA2099-2 samples possess similar and intermediate mechanical behaviors. In terms of AA2099-3 sample, the existence oflarge-sized T1phase results in the maximum yielding stress. However, some regions within these large-sized T1precipitatesare suspected to be sheared by cross-slip, leading to the destruction of crystallographic structure and the formation of Almatrix intervals. This aspect is responsible for the gradual degradation in true stress-strain curve after peak stress. As forAA2099-4 sample, dynamic precipitation rarely happens during plastic deformation and the interaction between dislocationand the pre-existing T2phase belongs to Orowan looping, resulting in the minimal mechanical response. Besides,AA2099-1 sample possesses the average minimum deviation angle (MDA) of ~ 16.5° between the loading direction and the<110> crystal direction, whereas AA2099-4 sample owns the average MDA of ~ 7.5°. The difference in MDA is mainlyattributed to δ′ phase and T1phase, which will separately accelerate and postpone the rotation of orientation towards the<110> crystal direction.

CNT@Ni@Ni-Co silicate core-shell nanocomposite: a synergistic triple-coaxial catalyst for enhancing catalytic activity and controlling side products for Li-O₂ batteries

Li, Ziwei,Yang, Junghoon,Agyeman, Daniel Adjei,Park, Mihui,Tamakloe, Wilson,Yamauchi, Yusuke,Kang, Yong-Mook The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.22

<P>A great challenge in the application of carbon-based materials to Li-O2 batteries is to prevent the formation of carbonate-based side products, thereby extending the cycle life of Li-O2 batteries. Herein, for the first time, CNT@Ni@NiCo silicate core-shell nanocomposite is designed and used as a cathode catalyst in Li-O2 batteries. This nanocomposite shows a promising electrochemical performance with a discharge capacity of 10 046 mA h gcat<SUP>−1</SUP> and a low overpotential of 1.44 V at a current density of 200 mA gcat<SUP>−1</SUP>, and it can sustain for more than 50 cycles within the voltage range of 2-4.7 V. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) characterizations prove that the formation of Li2CO3 and other side products are prevented, likely due to the encapsulation of CNTs by NiCo silicates and Ni nanoparticles, which may help decompose the side products. Finally, the synergistic effects, which are contributed by the high electrical conductivity of CNTs, high surface area, the high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of NiCo silicate, and the simple decomposition of side products by Ni nanoparticles enable outstanding performance of the CNT@Ni@NiCo silicate core-shell nanocomposite as a cathode catalyst for Li-O2 batteries.</P>

Synthesis of full concentration gradient cathode studied by high energy X-ray diffraction

Li, Yan,Xu, Rui,Ren, Yang,Lu, Jun,Wu, Huiming,Wang, Lifen,Miller, Dean J.,Sun, Yang-Kook,Amine, Khalil,Chen, Zonghai Elsevier 2016 Nano energy Vol.19 No.-

<P><B>Abstract</B></P> <P>Nickel-rich metal oxides have been widely pursued as promising cathode materials for high energy-density lithium-ion batteries. Nickel-rich lithium transition metal oxides can deliver a high specific capacity during cycling, but can react with non-aqueous electrolytes. In this work, we have employed a full concentration gradient (FCG) design to provide a nickel-rich core to deliver high capacity and a manganese-rich outer layer to provide enhanced stability and cycle life. <I>In situ</I> high-energy X-ray diffraction was utilized to study the structural evolution of oxides during the solid-state synthesis of FCG lithium transition metal oxide with a nominal composition of LiNi<SUB>0.6</SUB>Mn<SUB>0.2</SUB>Co<SUB>0.2</SUB>O<SUB>2</SUB>. We found that both the pre-heating step and the sintering temperature were critical in controlling phase separation of the transition metal oxides and minimizing the content of Li<SUB>2</SUB>CO<SUB>3</SUB> and NiO, both of which deteriorate the electrochemical performance of the final material. The insights revealed in this work can also be utilized for the design of other nickel-rich high energy-density cathode materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Solid-state synthesis of FCG cathode is investigated by <I>in situ</I> XRD. </LI> <LI> Covariance analysis and Rietveld refinement are used to analyze the HEXRD data. </LI> <LI> Synthetic optimization of FCG cathode with excellent electrochemical performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Benefit from the covariance analysis and Rietveld refinement of <I>in situ</I> HEXRD data during the solid state synthesis, we can optimized the solid state synthesis conditions in a short time. And the full concentration gradient cathode composites (nickel-rich core and manganese-rich outer layer) with excellent electrochemical performance are obtained.</P> <P>[DISPLAY OMISSION]</P>

Nano/Microstructured Silicon-Graphite Composite Anode for High-Energy-Density Li-Ion Battery

Li, Peng,Hwang, Jang-Yeon,Sun, Yang-Kook American Chemical Society 2019 ACS NANO Vol.13 No.2

<P>With the ever-increasing demand for lithium-ion batteries (LIBs) with higher energy density, tremendous attention has been paid to design various silicon-active materials as alternative electrodes due to their high theoretical capacity (ca. 3579 mAh g<SUP>-1</SUP>). However, totally replacing the commercially utilized graphite with silicon is still insurmountable owing to bottlenecks such as low electrode loading and insufficient areal capacity. Thus, in this study, we turn back to enhanced graphite electrode through the cooperation of modified silicon via a facile and scalable blending process. The modified nano/microstructured silicon with boron doping and carbon nanotube wedging (B-Si/CNT) can provide improved stability (88.2% retention after 200 cycles at 2000 mA g<SUP>-1</SUP>) and high reversible capacity (∼2426 mAh g<SUP>-1</SUP>), whereas the graphite can act as a tough framework for high loading. Owing to the synergistic effect, the resultant B-Si/CNT-graphite composite (B-Si/CNT@G) shows a high areal capacity of 5.2 mAh cm<SUP>-2</SUP> and excellent cycle retention of 83.4% over 100 cycles, even with ultrahigh active mass loading of 11.2 mg cm<SUP>-2</SUP>,which could significantly surpass the commercially used graphite electrode. Notably, the composite also exhibits impressive application in Li-ion full battery using 2 mol % Al-doped full-concentration-gradient Li[Ni<SUB>0.76</SUB>Co<SUB>0.09</SUB>Mn<SUB>0.15</SUB>]O<SUB>2</SUB> (Al2-FCG76) as the cathode with excellent capacity retention of 82.5% even after 300 cycles and an outstanding energy density (8.0 mWh cm<SUP>-2</SUP>) based on the large mass loading of the cathode (12.0 mg cm<SUP>-2</SUP>).</P> [FIG OMISSION]</BR>

Formation and Inhibition of Metallic Lithium Microstructures in Lithium Batteries Driven by Chemical Crossover

Li, Wangda,Kim, Un-Hyuck,Dolocan, Andrei,Sun, Yang-Kook,Manthiram, Arumugam American Chemical Society 2017 ACS NANO Vol.11 No.6

<P>The formation of metallic lithium microstructures in the form of dendrites or mosses at the surface of anode electrodes (e.g., lithium metal, graphite, and silicon) leads to rapid capacity fade and poses grave safety risks in rechargeable lithium batteries. We present here a direct, relative quantitative analysis of lithium deposition on graphite anodes in pouch cells under normal operating conditions, paired with a model cathode material, the layered nickel-rich oxide LiNi0.61Co0.12Mn0.27O2, over the course of 3000 charge discharge cycles. Secondary-ion mass spectrometry chemically dissects the solid electrolyte interphase (SEI) on extensively cycled graphite with virtually atomic depth resolution and reveals substantial growth of Li-metal deposits. With the absence of apparent kinetic (e.g., fast charging) or stoichiometric restraints (e.g., overcharge) during cycling, we show lithium deposition on graphite is triggered by certain transition-metal ions (manganese in particular) dissolved from the cathode in a disrupted SEI. This insidious effect is found to initiate at a very early stage of cell operation (<200 cycles) and can be effectively inhibited by substituting a small amount of aluminum (similar to 1 mol %) in the cathode, resulting in much reduced transition-metal dissolution and drastically improved cyclability. Our results may also be applicable to studying the unstable electrodeposition of lithium on other substrates, including Li metal.</P>

Superior lithium/potassium storage capability of nitrogen-rich porous carbon nanosheets derived from petroleum coke

Li, Peng,Hwang, Jang-Yeon,Park, Sang-Min,Sun, Yang-Kook The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.26

<P>Tremendous attention has been paid to carbon-based anodes for lithium-ion and potassium-ion batteries. Nevertheless, conferring high energy storage properties using carbon-based anodes is still challenging. In this work, petroleum coke-based nitrogen-doped porous carbon nanosheets (N-PCSs) were prepared using carbon nitride (g-C3N4) as both a template and nitrogen source and tested as advanced anode materials. The as-obtained N-PCSs constructed through an <I>in situ</I> solid-state approach possess both high capacity and excellent cycling stability. High capacities were obtained for Li-ion and K-ion batteries (407 mA h g<SUP>−1</SUP> after 500 cycles at 3720 mA g<SUP>−1</SUP> and 206 mA h g<SUP>−1</SUP> after 300 cycles at 1000 mA g<SUP>−1</SUP>, respectively); these are some of the best capacities for carbon-based electrode materials and could be ascribed to the unique microstructure of the anodes, <I>i.e.</I>, nanosheet morphology, developed porosity, ultrahigh nitrogen doping, and a high level of disorder. Meanwhile, this study represents a milestone for high-value utilization of petroleum coke and other kinds of heavy oil.</P>

A Mild Strategy to Strengthen Three Dimensional Graphene Aerogel for Supporting Sulfur as a Free‐standing Cathode in Lithium–Sulfur Batteries

Yinglin Yan,Haichao Qin,Yiqi Wei,Rong Yang,Yunhua Xu,Liping Chen,Qiaole Li,Mangmang Shi 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.5

Recently, three dimensional graphene aerogel (3DGA) supported sulfur microparticles was used as a cathode material for lithium?sulfur batteries, which was considered as one of the most promising next generation rechargeable batteries due to its ultra?high theoretical specific capacity (1675 mAh/g). However, the mechanical strength of 3DGA remains an issue for further application. Herein, a strengthened 3DGA (S3DGA) was achieved by soaking in a low concentration ammonia solution at a relative low temperature. Then the S3DGA loaded sulfur (S3DGA?S) was cut into a round piece and directly used as a cathode without additional binders or conductive additives in Li?S batteries. The mechanical strength, microstructure, and electrochemical properties were investigated by compare with a 3DGA prepared without strengthen. The S3DGA?S presented good mechanical strength, excellent capacity retention, and lower electrochemical impedance.