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The electrochemical properties and performances of lithium-ion batteries are primarily governed by their constituent electrode materials, whose intrinsic thermodynamic and kinetic properties are understood as the determining factor. As a part of complementing the intrinsic material properties, the strategy of nanosizing has been widely applied to electrodes to improve battery performance. It has been revealed that this not only improves the kinetics of the electrode materials but is also capable of regulating their thermodynamic properties, taking advantage of nanoscale phenomena regarding the changes in redox potential, solid-state solubility of the intercalation compounds, and reaction paths. In addition, the nanosizing of materials has recently enabled the discovery of new energy storage mechanisms, through which unexplored classes of electrodes could be introduced. Herein, we review the nanoscale phenomena discovered or exploited in lithium-ion battery chemistry thus far and discuss their potential implications, providing opportunities to further unveil uncharted electrode materials and chemistries. Finally, we discuss the limitations of the nanoscale phenomena presently employed in battery applications and suggest strategies to overcome these limitations.
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A first-principles study was performed to elucidate the electrochemical properties of CaTi5O11, a recently discovered compound that is a crystallographic variant of TiO2(B) and that shows promise as an anode material for Li-ion batteries. The crystal structure of CaTi5O11 was further refined and two symmetrically distinct interstitial sites that can accommodate Li at positive voltage were identified. A statistical mechanics study relying on density functional theory (DFT) calculations predicted that interstitial Li in CaTi5O11 forms a solid solution with Li insertion resulting in a sloping voltage profile. Li diffusion within CaTi5O11 was found to be highly anisotropic with low barrier diffusion pathways forming one-dimensional channels parallel to the c axis.
RESUMO
OBJECTIVE: There is limited evidence regarding the effectiveness of left atrial appendage (LAA) closure during surgical ablation of atrial fibrillation (AF) in yielding superior clinical outcomes. This study aimed to evaluate the association of LAA closure versus preservation with the risk of adverse clinical outcomes among patients undergoing surgical ablation during cardiac surgery. METHODS: We evaluated 1640 patients (aged 58.8±11.5 years, 898 women) undergoing surgical ablation during cardiac surgery (including mitral valve (MV), n=1378; non-MV, n=262) between 2001 and 2018. Of these, 804 had LAA preserved, and the remaining 836 underwent LAA closure. Comparative risks of stroke and mortality between the two groups were evaluated after adjustments with inverse-probability-of-treatment weighting (IPTW). Longitudinal echocardiographic data (n=9674, 5.9/patient) on transmitral A-wave and E/A-wave ratio were analysed by random coefficient models. RESULTS: Adjustment with IPTW yielded patient cohorts well-balanced for baseline profiles. During a median follow-up of 43.5 months (IQR 19.0-87.3 months), stroke and death occurred in 87 and 249 patients, respectively. The adjusted risk of stroke (HR 0.85; 95% CI 0.52-1.39) and mortality (HR 0.80; 95% CI 0.61 to 1.05) did not differ significantly between the two groups. Echocardiographic data demonstrated higher transmitral A-wave velocity (group-year interaction, p=0.066) and lower E/A-wave ratio (group-year interaction, p=0.045) in the preservation group than in the closure group. CONCLUSIONS: LAA preservation during surgical AF ablation was not associated with an increased risk of stroke or mortality. Postoperative LA transport functions were more favourable with LAA preservation than with LAA closure.