23 research outputs found
Crystallographic origin of cycle decay of the high-voltage LiNi\u3csub\u3e0.5\u3c/sub\u3eMn\u3csub\u3e1.5\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e spinel lithium-ion battery electrode
High-voltage spinel LiNi0.5Mn1.5O4 (LNMO) is considered a potential high-power-density positive electrode for lithium-ion batteries, however, it suffers from capacity decay after extended charge-discharge cycling, severely hindering commercial application. Capacity fade is thought to occur through the significant volume change of the LNMO electrode occurring on cycling, and in this work we use operando neutron powder diffraction to compare the structural evolution of the LNMO electrode in an as-assembled 18650-type battery containing a Li4Ti5O12 negative electrode with that in an identical battery following 1000 cycles at high-current. We reveal that the capacity reduction in the battery post cycling is directly proportional to the reduction in the maximum change of the LNMO lattice parameter during its evolution. This is correlated to a corresponding reduction in the MnO6 octahedral distortion in the spinel structure in the cycled battery. Further, we find that the rate of lattice evolution, which reflects the rate of lithium insertion and removal, is ∼9 and ∼10% slower in the cycled than in the as-assembled battery during the Ni2+/Ni3+ and Ni3+/Ni4+ transitions, respectively
The iNOS/Src/FAK axis is critical in Toll-like receptor-mediated cell motility in macrophages
AbstractThe Toll-like receptors (TLRs) play a pivotal role in innate immunity for the detection of highly conserved, pathogen-expressed molecules. Previously, we demonstrated that lipopolysaccharide (LPS, TLR4 ligand)-increased macrophage motility required the participation of Src and FAK, which was inducible nitric oxide synthase (iNOS)-dependent. To investigate whether this iNOS/Src/FAK pathway is a general mechanism for macrophages to mobilize in response to engagement of TLRs other than TLR4, peptidoglycan (PGN, TLR2 ligand), polyinosinic–polycytidylic acid (polyI:C, TLR3 ligand) and CpG-oligodeoxynucleotides (CpG, TLR9 ligand) were used to treat macrophages in this study. Like LPS stimulation, simultaneous increase of cell motility and Src (but not Fgr, Hck, and Lyn) was detected in RAW264.7, peritoneal macrophages, and bone marrow-derived macrophages exposed to PGN, polyI:C and CpG. Attenuation of Src suppressed PGN-, polyI:C-, and CpG-elicited movement and the level of FAK Pi-Tyr861, which could be reversed by the reintroduction of siRNA-resistant Src. Besides, knockdown of FAK reduced the mobility of macrophages stimulated with anyone of these TLR ligands. Remarkably, PGN-, polyI:C-, and CpG-induced Src expression, FAK Pi-Tyr861, and cell mobility were inhibited in macrophages devoid of iNOS, indicating the importance of iNOS. These findings corroborate that iNOS/Src/FAK axis occupies a central role in macrophage locomotion in response to engagement of TLRs
Human Neutrophil Peptides Mediate Endothelial-Monocyte Interaction, Foam Cell Formation, and Platelet Activation
Objective—Neutrophils are involved in the inflammatory responses during atherosclerosis. Human neutrophil peptides (HNPs) released from activated neutrophils exert immune modulating properties. We hypothesized that HNPs play an important role in neutrophil-mediated inflammatory cardiovascular responses in atherosclerosis. Methods and Results—We examined the role of HNPs in endothelial-leukocyte interaction, platelet activation, and foam cell formation in vitro and in vivo. We demonstrated that stimulation of human coronary artery endothelial cells with clinically relevant concentrations of HNPs resulted in monocyte adhesion and transmigration; induction of oxidative stress in human macrophages, which accelerates foam cell formation; and activation and aggregation of human platelets. The administration of superoxide dismutase or anti-CD36 antibody reduced foam cell formation and cholesterol efflux. Mice deficient in double genes of low-density lipoprotein receptor and low-density lipoprotein receptor–related protein (LRP), and mice deficient in a single gene of LRP8, the only LRP phenotype expressed in platelets, showed reduced leukocyte rolling and decreased platelet aggregation and thrombus formation in response to HNP stimulation. Conclusion—HNPs exert proatherosclerotic properties that appear to be mediated through LRP8 signaling pathways, suggesting an important role for HNPs in the development of inflammatory cardiovascular diseases
Human neutrophil peptides mediate endothelial-monocyte interaction, foam cell formation, and platelet activation
Objective-: Neutrophils are involved in the inflammatory responses during atherosclerosis. Human neutrophil peptides (HNPs) released from activated neutrophils exert immune modulating properties. We hypothesized that HNPs play an important role in neutrophil-mediated inflammatory cardiovascular responses in atherosclerosis. Methods and results-: We examined the role of HNPs in endothelial-leukocyte interaction, platelet activation, and foam cell formation in vitro and in vivo. We demonstrated that stimulation of human coronary artery endothelial cells with clinically relevant concentrations of HNPs resulted in monocyte adhesion and transmigration; induction of oxidative stress in human macrophages, which accelerates foam cell formation; and activation and aggregation of human platelets. The administration of superoxide dismutase or anti-CD36 antibody reduced foam cell formation and cholesterol efflux. Mice deficient in double genes of low-density lipoprotein receptor and low-density lipoprotein receptor-related protein (LRP), and mice deficient in a single gene of LRP8, the only LRP phenotype expressed in platelets, showed reduced leukocyte rolling and decreased platelet aggregation and thrombus formation in response to HNP stimulation. Conclusion-: HNPs exert proatherosclerotic properties that appear to be mediated through LRP8 signaling pathways, suggesting an important role for HNPs in the development of inflammatory cardiovascular diseases. © 2011 American Heart Association. All rights reserved
Enhanced rate-capability and cycling-stability of 5 V SiO2- and polyimide-coated cation ordered LiNi0.5Mn1.5O4 lithium-ion battery positive electrodes
The ordered LiNi0.5Mn1.5O4 spinel exhibits great promise as a potential high-energy positive electrode for lithium-ion batteries due to its exceptionally high working potential of 4.7 V (vs. Li) and energy density of 640 Wh kg-1. The commercial application of this material at such voltages is unfortunately prevented by reaction phenomena including hydrofluoric acid attack and manganese dissolution, as well as the two-phase mechanism of Li insertion and extraction, with these limiting Li diffusivity and cycling stability. In this work, we demonstrate the improved performance of LiNi0.5Mn1.5O4 achieved by encapsulating the material in a thin layer of silica (SiO2) or polyimide using a simple wet-chemical method and organic solvents. The pristine and coated ordered LiNi0.5Mn1.5O4 spinel are both confirmed to have P4332 symmetry, with only a minor difference in their lattice parameter. The SiO2 coating is found to reduce capacity fade of ordered LiNi0.5Mn1.5O4 by 45 and 65% at 25 and 55 °C, respectively, with the improvement attributed to enhanced Li diffusivity alongside the suppression of the hydrofluoric acid attack. The polyimide coating is found to have a marginally negative effect on both capacity and rate performance of ordered LiNi0.5Mn1.5O4, with this being greatly offset by excellent thermal stability leading to high-temperature protection, with the material having the low capacity fade of 0.0585 mAh g-1 cycle-1 at 55 °C, which is comparable to that at 25 °C. While similar effects of these coatings are found for disordered LiNi0.5Mn1.5O4, the magnitude of enhancement to properties offered by these coatings is significantly lesser than those found here for the ordered LiNi0.5Mn1.5O4. A stabilizing effect of the coatings that mitigates against phase segregation occurring during the additional two-phase reaction in the ordered but not the disordered phase of the material may explain the greater benefit of the coatings to the ordered phase
Effect of AlF3-Coated Li4Ti5O12 on the Performance and Function of the LiNi0.5Mn1.5O4||Li4Ti5O12 Full Battery-An in-operando Neutron Powder Diffraction Study
The LiNi0.5Mn1.5O4||Li4Ti5O12(LMNO||LTO) battery possesses a relatively-high energy density and cycle performance, with further enhancement possible by application of an AlF3coating on the LTO electrode particles. We measure the performance enhancement to the LMNO||LTO battery achieved by a AlF3coating on the LTO particles through electrochemical testing and use in-operando neutron powder diffraction to study the changes to the evolution of the bulk crystal structure during battery cycling. We find that the AlF3coating along with parasitic Al doping slightly increases capacity and greatly increases rate capability of the LTO electrode, as well as significantly reducing capacity loss on cycling, facilitating a gradual increase in capacity during the first 50 cycles. Neutron powder diffraction reveals a structural response of the LTO and LNMO electrodes consistent with a greater availability of lithium in the battery containing AlF3-coated LTO. Further, the coating increases the rate of structural response of the LNMO electrode during charge, suggesting faster delithiation, and enhanced Li diffusion. This work demonstrates the importance of studying such battery performance effects within full configuration batteries
Effects of Fluorine and Chromium Doping on the Performance of Lithium-Rich Li<sub>1+<i>x</i></sub>MO<sub>2</sub> (M = Ni, Mn, Co) Positive Electrodes
Lithium-rich metal oxides Li<sub>1+<i>z</i></sub>MO<sub>2</sub> (M = Ni, Co Mn, etc.) are
promising positive electrode materials
for high-energy lithium-ion batteries, with capacities of 250–300
mAh·g<sup>–1</sup> that closely approach theoretical intercalation
limits. Unfortunately, these materials suffer severe capacity fade
on cycling, among other performance issues. While ion substitution
can improve the performance of many of these materials, the underlying
mechanisms of property modification are not completely understood.
In this work we show enhanced performance of the Li<sub>1+z</sub>MO<sub>2</sub> electrode, consisting of Li<sub>2</sub>MnO<sub>3</sub> (with <i>C</i>2/<i>m</i> space group) and LiMO<sub>2</sub> (with <i>R</i>3̅<i>m</i> space group) phases, and establish
the effects of cationic and anionic substitution on the phase and
structure evolution underpinning performance changes. While the undoped
material has a high capacity of ∼270 mAh·g<sup>–1</sup>, only 79% of this remains after 200 cycles. Including ∼2%
Cr in the material, likely at the <i>R</i>3̅<i>m</i> metal (3<i>a</i>) site, improved cycle performance
by ∼13%, and including ∼5% F in the material, likely
at the <i>R</i>3̅<i>m</i> oxygen (6<i>c</i>) site, enhanced capacity by ∼4–5% at the
expense of a ∼12% decline in cycle performance. Moreover, Cr
doping enhances energy density retention by ∼13%, and F doping
suppresses this by 17%. We find that these changes arise by different
mechanisms. Both anionic and cationic substitution promote faster
Li diffusion, by 48% and 20%, respectively, as determined using cyclic
voltammetry and leading to better rate performance. Unlike anionic
substitution, cationic substitution enhances structural stability
at the expense of some capacity, by suppressing lattice distortion
during Li insertion and extraction. This work implicates strategic
cationic–anionic codoping for enhanced electrochemical performance
in lithium-rich layered metal-oxide phases
Enhanced Rate-Capability and Cycling-Stability of 5 V SiO<sub>2</sub>- and Polyimide-Coated Cation Ordered LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> Lithium-Ion Battery Positive Electrodes
The
ordered LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> spinel
exhibits great promise as a potential high-energy positive electrode
for lithium-ion batteries due to its exceptionally high working potential
of 4.7 V (vs. Li) and energy density of 640 Wh kg<sup>–1</sup>. The commercial application of this material at such voltages is
unfortunately prevented by reaction phenomena including hydrofluoric
acid attack and manganese dissolution, as well as the two-phase mechanism
of Li insertion and extraction, with these limiting Li diffusivity
and cycling stability. In this work, we demonstrate the improved performance
of LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> achieved by encapsulating
the material in a thin layer of silica (SiO<sub>2</sub>) or polyimide
using a simple wet-chemical method and organic solvents. The pristine
and coated ordered LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> spinel are both confirmed to have <i>P</i>4<sub>3</sub>32 symmetry, with only a minor difference in their lattice parameter.
The SiO<sub>2</sub> coating is found to reduce capacity fade of ordered
LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> by 45 and 65% at 25
and 55 °C, respectively, with the improvement attributed to enhanced
Li diffusivity alongside the suppression of the hydrofluoric acid
attack. The polyimide coating is found to have a marginally negative
effect on both capacity and rate performance of ordered LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub>, with this being greatly offset by
excellent thermal stability leading to high-temperature protection,
with the material having the low capacity fade of 0.0585 mAh g<sup>–1</sup> cycle<sup>–1</sup> at 55 °C, which is
comparable to that at 25 °C. While similar effects of these coatings
are found for disordered LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub>, the magnitude of enhancement to properties offered by these coatings
is significantly lesser than those found here for the ordered LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub>. A stabilizing effect of the
coatings that mitigates against phase segregation occurring during
the additional two-phase reaction in the ordered but not the disordered
phase of the material may explain the greater benefit of the coatings
to the ordered phase
Effect of AlF(3)-coated Li(4)Ti(5)O(12) on the performance and function of the LiNi(0.5)Mn(1.5)O(4)||Li(4)Ti(5)O(12) full battery—an in-operando neutron powder diffraction study
The LiNi₀.₅Mn₁.₅O₄ ||Li₄Ti₅O₁₂ (LMNO||LTO) battery possesses a relatively-high energy density and cycle performance, with further enhancement possible by application of an AlF3 coating on the LTO electrode particles. We measure the performance enhancement to the LMNO||LTO battery achieved by a AlF₃ coating on the LTO particles through electrochemical testing and use in-operando neutron powder diffraction to study the changes to the evolution of the bulk crystal structure during battery cycling. We find that the AlF₃ coating along with parasitic Al doping slightly increases capacity and greatly increases rate capability of the LTO electrode, as well as significantly reducing capacity loss on cycling, facilitating a gradual increase in capacity during the first 50 cycles. Neutron powder diffraction reveals a structural response of the LTO and LNMO electrodes consistent with a greater availability of lithium in the battery containing AlF₃-coated LTO. Further, the coating increases the rate of structural response of the LNMO electrode during charge, suggesting faster delithiation, and enhanced Li diffusion. This work demonstrates the importance of studying such battery performance effects within full configuration batteries.Gemeng Liang, Anoop Somanathan Pillai, Vanessa K. Peterson, Kuan-Yu Ko, Chia-Ming Chang, Cheng-Zhang Lu, Chia-Erh Liu, Shih-Chieh Liao, Jin-Ming Chen, Zaiping Guo, and Wei Kong Pan