Ni‐rich layered LiNixCoyMn1−x−yO2 (LNCM) with Ni content over >90% is considered as a promising lithium ion battery (LIB) cathode, attributed by its low cost and high practical capacity. However, ...Ni‐rich LNCM inevitably suffers rapid capacity fading at a high state of charge due to the mechanochemical breakdown; in particular, the microcrack formation has been regarded as one of the main culprits for Ni‐rich layered cathode failure. To address these issues, Ni‐rich layered cathodes with a textured microstructure are developed by phosphorous and boron doping. Attributed by the textured morphology, both phosphorous‐ and boron‐doped cathodes suppress microcrack formation and show enhanced cycle stability compared to the undoped cathode. However, there exists a meaningful capacity retention difference between the doped cathodes. By adapting the various analysis techniques, it is shown that the boron‐doped Ni‐rich layered cathode displays better cycle stability not only by its ability to suppress microcracks during cycling but also by its primary particle morphology that is reluctant to oxygen evolution. The present work reveals that not only restraint of particle cracks but also suppression of oxygen release by developing the oxygen stable facets is important for further improvements in state‐of‐the‐art Li ion battery Ni‐rich layered cathode materials.
Herein, the effect of boron doping on oxygen stability in LiNi0.92Co0.04Mn0.04O2 (LNCM) lithium ion battery cathodes is systematically investigated using various measurements. The boron‐doped LNCM produces the textured microstructure with more oxygen stabilized facets, thus not only aiding in restraining the particle cracks but also effectively suppressing the oxygen evolution to improve the cycle stability.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The anionic redox activity in lithium‐rich layered oxides has the potential to boost the energy density of lithium‐ion batteries. Although it is widely accepted that the anionic redox activity stems ...from the orphaned oxygen energy level, its regulation and structural stabilization, which are essential for practical employment, remain still elusive, requiring an improved fundamental understanding. Herein, the oxygen redox activity for a wide range of 3d transition‐metal‐based Li2TMO3 compounds is investigated and the intrinsic competition between the cationic and anionic redox reaction is unveiled. It is demonstrated that the energy level of the orphaned oxygen state (and, correspondingly, the activity) is delicately governed by the type and number of neighboring transition metals owing to the π‐type interactions between LiOLi and M t2g states. Based on these findings, a simple model that can be used to estimate the anionic redox activity of various lithium‐rich layered oxides is proposed. The model explains the recently reported significantly different oxygen redox voltages or inactivity in lithium‐rich materials despite the commonly observed LiOLi states with presumably unhybridized character. The discovery of hidden factors that rule the anionic redox in lithium‐rich cathode materials will aid in enabling controlled cumulative cationic and anionic redox reactions.
In lithium‐rich oxides, anionic redox activity is widely accepted to arise from orphaned oxygen energy states, however, the understanding required for practical use is still insufficient. In this work, it is demonstrated that the oxygen redox potential and activity are regulated by different π‐type interactions that are delicately governed by the relevant transition metal.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
NCM‐based lithium layered oxides (LiNi1–x–yCoxMnyO2) have become prevalent cathode materials in state‐of‐the‐art lithium‐ion batteries. Higher energy densities can be achieved in these materials by ...systematically increasing the nickel content; however, this approach commonly results in inferior cycle stability. The poor cycle retention of high‐nickel NCM cathodes is generally attributed to chemo‐mechanical degradation (e.g., intergranular microcracks), vulnerability to oxygen‐gas evolution, and the accompanying rocksalt phase formation via cation mixing. Herein, the feasibility of doping strategies is examined to mitigate these issues and effective dopants for high‐nickel NCM cathodes are theoretically identified through a stepwise pruning process based on density functional theory calculations. Specifically, a sequential three‐step screening process is conducted for 38 potential dopants to scrutinize their effectiveness in mitigating chemo‐mechanical lattice stress, oxygen evolution, and cation mixing at charged states. Using this process, promising dopant species are selected rationally and a silicon‐doped LiNi0.92Co0.04Mn0.04O2 cathode is synthesized, which exhibits suppressed lattice expansion/contraction, fewer intergranular microcracks, and reduced rocksalt formation on the surface compared with its undoped counterpart, leading to superior electrochemical performance. Moreover, a comprehensive map of dopants regarding their potential applicability is presented, providing rational guidance for an effective doping strategy for high‐nickel NCM cathodes.
Although the doping strategy in high‐nickel NCM materials is a simple and effective method to improve the electrochemical performance, a dopant selection map revealing the unique properties of the dopant has not been presented yet. Here, a systematic stepwise pruning process combined with experimental validation is applied, and a dopant selection map is proposed, offering adequate guidance on doping strategies for high‐nickel NCM cathode materials.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Abstract
Sodium metal (Na) anodes are considered the most promising anode for high‐energy‐density sodium batteries because of their high capacity and low electrochemical potential. However, Na metal ...anode undergoes uncontrolled Na dendrite growth, and unstable solid electrolyte interphase layer (SEI) formation during cycling, leading to poor coulombic efficiency, and shorter lifespan. Herein, a series of Na‐ion conductive alloy‐type protective interface (Na‐In, Na‐Bi, Na‐Zn, Na‐Sn) is studied as an artificial SEI layer to address the issues. The hybrid Na‐ion conducting SEI components over the Na‐alloy can facilitate uniform Na deposition by regulating Na‐ion flux with low overpotential. Furthermore, density functional study reveals that the lower surface energy of protective alloys relative to bare Na is the key factor for facilitating facile ion diffusion across the interface. Na metal with interface layer facilitates a highly reversible Na plating/stripping for ≈790 h, higher than pristine Na metal (100 h). The hybrid self‐regulating protective layers exhibit a high mechanical flexibility to promote dendrite free Na plating even at high current density (5 mA cm
−2
), high capacity (10 mAh cm
−2
), and good performance with Na
3
V
2
(PO
4
)
3
cathode. The current study opens a new insight for designing dendrite Na metal anode for next generation energy storage devices.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The galvanostatic lithiation/sodiation voltage profiles of hard carbon anodes are simple, with a sloping drop followed by a plateau. However, a precise understanding of the corresponding redox sites ...and storage mechanisms is still elusive, which hinders further development in commercial applications. Here, a comprehensive comparison of the lithium‐ and sodium‐ion storage behaviors of hard carbon is conducted, yielding the following key findings: 1) the sloping voltage section is presented by the lithium‐ion intercalation in the graphitic lattices of hard carbons, whereas it mainly arises from the chemisorption of sodium ions on their inner surfaces constituting closed pores, even if the graphitic lattices are unoccupied; 2) the redox sites for the plateau capacities are the same as those for the closed pores regardless of the alkali ions; 3) the sodiation plateau capacities are mostly determined by the volume of the available closed pore, whereas the lithiation plateau capacities are primarily affected by the intercalation propensity; and 4) the intercalation preference and the plateau capacity have an inverse correlation. These findings from extensive characterizations and theoretical investigations provide a relatively clear elucidation of the electrochemical footprint of hard carbon anodes in relation to the redox mechanisms and storage sites for lithium and sodium ions, thereby providing a more rational design strategy for constructing better hard carbon anodes.
A comprehensive comparison of the lithium‐ and sodium‐ion storage behaviors of hard carbon is conducted, yielding the key findings: the sloping voltage section is presented by the lithium‐ion intercalation in the graphitic lattices of hard carbons, whereas it mainly arises from the chemisorption of sodium ions. The intercalation preference and the plateau capacity have an inverse correlation.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
To prevent potential hazards posed by fast-evolving drones, it is of importance to develop a radar system for drone detection. Frequency modulated continuous wave (FMCW) radars are widely used for ...that purpose. Heterodyne architectures are preferred for them to mitigate dc offset errors. Having said that, FMCW radars suffer from permanent leakage from the transmitter into the receiver. The leakage phase noise raises the total noise floor and limits the radar sensitivity. Here, we propose a stationary point concentration (SPC) technique in order to overcome the challenges. The SPC technique concentrates the leakage phase noise on a stationary point to alleviate the impact of the noise. The technique can be realized using digital signal processing without additional hardware. The results show that the proposed technique significantly lowers the noise floor.
Moutan Cortex,
root, has long been used as a medicine for the treatment of inflammatory diseases. The aim of this study was to evaluate the modulative properties of Moutan Cortex water extract (CP) ...on endoplasmic reticulum (ER) stress-related macrophage activation via the calcium-CHOP pathway. RAW 264.7 mouse macrophages were activated by lipopolysaccharide (LPS), and the levels of various inflammatory mediators from RAW 264.7 were evaluated. The multiplex cytokine assay was used to investigate both cytokines and growth factors, and RT-PCR was used to investigate the expressions of inflammation-related genes, such as CHOP. Data represent the levels of NO and cytosolic calcium in LPS-stimulated RAW 264.7 were significantly inhibited by CP as well as hydrogen peroxide (
< 0.05). Minutely, NO production in LPS-stimulated RAW 264.7 incubated with CP at concentrations of 25, 50, 100, and 200 µg/mL for 24 h was 97.32 ± 1.55%, 95.86 ± 2.26%, 94.64 ± 1.83%, and 92.69 ± 2.31% of the control value (LPS only), respectively (
< 0.05). Calcium release in LPS-stimulated RAW 264.7 incubated with CP at concentrations of 25, 50, 100, and 200 µg/mL for 18 h was 95.78 ± 1.64%, 95.41 ± 1.14%, 94.54 ± 2.76%, and 90.89 ± 3.34% of the control value, respectively (
< 0.05). Hydrogen peroxide production in LPS-stimulated RAW 264.7 incubated with CP at concentrations of 25, 50, 100, and 200 µg/mL for 24 h was 79.15 ± 7.16%, 63.83 ± 4.03%, 46.27 ± 4.38%, and 40.66 ± 4.03% of the control value, respectively (
< 0.05). It is interesting that the production of IL-6, TNF-α, G-CSF, MIP-1α, MIP-2, and M-CSF in LPS-stimulated RAW 264.7 were significantly inhibited by CP (
< 0.05), while the production of LIX, LIF, RANTES, and MIP-1β showed a meaningful decrease. CP at concentrations of 25, 50, 100, and 200 µg/mL significantly reduced the transcription of
,
α,
,
,
,
,
,
,
,
,
, and
in LPS-stimulated RAW 264.7 (
< 0.05). CP at concentrations of 25, 50, and 100 µg/mL significantly reduced the phosphorylation of STAT3, p38 MAPK, and IκB-α in LPS-stimulated RAW 264.7 (
< 0.05). These results suggest that CP might modulate macrophage activation via LPS-induced calcium signaling and the ER stress-CHOP pathway.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Depression, one of the most costly and common mental disorders, is reported to be associated with lower quality of life (QoL) in several studies. Improved understanding of the associated factors with ...QoL is necessary to optimize long-term outcomes and reduce disability in patients with depression. Therefore, the aim of this study was to identify factors that are associated with lower QoL among patients with depression.
The study was based on the Korea National Health and Nutrition Examination Survey, a cross-sectional health examination, years 2008 to 2014. The final analyzed sample consisted of a total of 1,502 study subjects who had been diagnosed by clinicians as having depression. A multivariate logistic regression model was performed to exam the association between the clinical characteristics (age, sex, demographic and health-related characteristics) and QoL. Analysis of covariance was also used to analyze EQ-5D according to mental health.
Older age, lower level of education, lower income, worse subjective perception of health, unemployment, obesity and mental health struggles were found to be significantly associated with low QoL in depressive individuals after adjustment for multiple covariates.
This study has outlined grounding data in identifying patients who are at risk of QoL impairment. Policy makers should direct their interests to these individuals and provide appropriate management.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The realization of high performance Ni-rich layered cathodes remains a challenge because of the multiple degradation factors that concurrently operate during battery cycling. In particular, depletion ...of oxygen charge and consequent lattice-oxygen instability at deep charge state accelerate the subsequent chemomechanical degradation mechanisms. Among the proposed methodologies, doping has proven to be effective in enhancing the cathode cycle life by stabilizing the layered structure. Herein, we achieved the electrochemically stabilized Ni-rich LiNi
0.92
Co
0.04
Mn
0.04
O
2
through Zr doping, resulting in a 15% increase of the capacity retention after 100 cycles. In-depth investigations are conducted to unveil the effects of Zr doping on the layered cathode, and in particular, the critical role of Zr doping on the lattice oxygen stability is systematically studied. By combining state-of-the-art magnetometer characterization, X-ray analysis, and first-principles calculation, we reveal that Zr doping positively contributes the to lattice oxygen stability by alleviating the oxygen charge loss at deep charge, thereby improving the cathode electrochemical reversibility. Our findings provide an insight into the Zr doping mechanism and help to design Ni-rich layered oxides for future applications.
The suppression of oxygen oxidation is proposed as the critical origin of Zr doping on LiNi
0.92
Co
0.04
Mn
0.04
O
2
layered oxide LIB cathode material.
Lithium-rich layered oxides (LLOs) are considered promising cathode materials for lithium-ion batteries because of their high reversible capacity, which is attributed to the exploitation of the novel ...anionic redox in addition to the conventional cationic redox process. Transition metal (TM) migration, which is known to be the main cause of the voltage decay in LLOs, is now understood to also be the critical factor triggering anionic redox, although this origin is still under debate. A better understanding of the specific TM migration behavior and its effect during charge/discharge would thus enable further development of this class of materials. Herein, we demonstrate that the unique TM migration during charge/discharge significantly alters the lithium diffusion mechanism/kinetics of LLO cathodes. We present clear evidence of the much more sluggish lithium diffusion occurring during discharge (lithiation) than during charge (de-lithiation), which contrasts with the traditional lithium diffusion model based on simple topotactic lithium intercalation/deintercalation in the layered framework. The reversible but asymmetric TM migration in the structure, which originates from the non-equivalent local environments around the TM during the charge and discharge processes, is shown to affect the lithium mobility. This correlation between TM migration and lithium mobility led us to propose a new lithium diffusion model for layered structures and suggests the importance of considering TM migration in designing new LLO cathode materials.
We propose a new lithium diffusion model involving coupled lithium and transition metal migration, peculiarly occurring in a lithium-rich layered oxide.
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