Hierarchical Li electrochemistry using alloy-type anode for high-energy-density Li metal batteries.

Exploiting thin Li metal anode is essential for high-energy-density battery, but is severely plagued by the poor processability of Li, as well as the uncontrollable Li plating/stripping behaviors and Li/electrolyte interface. Herein, a thickness/capacity-adjustable thin alloy-type Li/LiZn@Cu anode is fabricated for high-energy-density Li metal batteries. The as-formed lithophilic LiZn alloy in Li/LiZn@Cu anode can effectively regulate Li plating/stripping and stabilize the Li/electrolyte interface to deliver the hierarchical Li electrochemistry. Upon charging, the Li/LiZn@Cu anode firstly acts as Li source for homogeneous Li extraction. At the end of charging, the de-alloy of LiZn nanostructures further supplements the Li extraction, actually playing the Li compensation role in battery cycling. While upon discharging, the LiZn alloy forms just at the beginning, thereby regulating the following Li homogeneous deposition. The reversibility of such an interesting process is undoubtedly verified from the electrochemistry and in-situ XRD characterization. This work sheds light on the facile fabrication of practical Li metal anodes and useful Li compensation materials for high-energy-density Li metal batteries.

Sustainable Anionic Redox by Inhibiting Li Cross-Layer Migration in Na-Based Layered Oxide Cathodes.

The irrational utilization of an anionic electron often accompanies structural degradation with an irreversible cation migration process upon cycling in sodium-layered oxide cathodes. Moreover, the insufficient understanding of the anionic redox involved cation migration makes the design strategies of high energy density electrodes even less effective. Herein, a P3-Na0.67Li0.2Fe0.2Mn0.6O2 (P3-NLFM) cathode is proposed with the in-plane disordered Li distribution after an in-depth remolding of the Li ribbon-ordered P3-Na0.6Li0.2Mn0.8O2 (P3-NLM) layered oxide. The disordered Li sublattice in the transition metal slab of P3-NLFM leads to the dispersed |O2p orbitals, the lowered charge transfer gap, and the suppressed phase transition at high voltages. Then the enhanced Mn-O interaction and electronic stability are disclosed by the crystal orbital Hamilton population (COHP) analysis at high voltage in P3-NLFM. Furthermore, ab initio molecular dynamics (AIMD) simulation suggests the order/disorder of the transition metal layer is highly correlated with the stability of the Li sublattice. The cross-layer migration and loss of Li in P3-NLM are suppressed in P3-NLFM to enable the high reversibility upon cycling. As a result, the P3-NLFM delivers a high capacity of 163 mAh g-1 without oxygen release and an enhanced capacity retention of 81.9% (vs 42.9% in P3-NLM) after 200 cycles, which constitutes a promising approach for sustainable oxygen redox in rechargeable batteries.

Revealing the aging process of solid electrolyte interphase on SiOx anode.

As one of the most promising alternatives to graphite negative electrodes, silicon oxide (SiOx) has been hindered by its fast capacity fading. Solid electrolyte interphase (SEI) aging on silicon SiOx has been recognized as the most critical yet least understood facet. Herein, leveraging 3D focused ion beam-scanning electron microscopy (FIB-SEM) tomographic imaging, we reveal an exceptionally characteristic SEI microstructure with an incompact inner region and a dense outer region, which overturns the prevailing belief that SEIs are homogeneous structure and reveals the SEI evolution process. Through combining nanoprobe and electron energy loss spectroscopy (EELS), it is also discovered that the electronic conductivity of thick SEI relies on the percolation network within composed of conductive agents (e.g., carbon black particles), which are embedded into the SEI upon its growth. Therefore, the free growth of SEI will gradually attenuate this electron percolation network, thereby causing capacity decay of SiOx. Based on these findings, a proof-of-concept strategy is adopted to mechanically restrict the SEI growth via applying a confining layer on top of the electrode. Through shedding light on the fundamental understanding of SEI aging for SiOx anodes, this work could potentially inspire viable improving strategies in the future.

Advanced Composite Lithium Metal Anodes with 3D Frameworks: Preloading Strategies, Interfacial Optimization, and Perspectives.

Lithium (Li) metal is regarded as the most promising anode candidate for next-generation rechargeable storage systems due to its impeccable capacity and the lowest electrochemical potential. Nevertheless, the irregular dendritic Li, unstable interface, and infinite volume change, which are the intrinsic drawbacks rooted in Li metal, give a seriously negative effect on the practical commercialization for Li metal batteries. Among the numerous optimization strategies, designing a 3D framework with high specific surface area and sufficient space is a convincing way out to ameliorate the above issues. Due to the Li-free property of the 3D framework, a Li preloading process is necessary before the 3D framework that matches with the electrolyte and cathode. How to achieve homogeneous integration with Li and 3D framework is essential to determine the electrochemical performance of Li metal anode. Herein, this review overviews the recent general fabrication methods of 3D framework-based composite Li metal anode, including electrodeposition, molten Li infusion, and pressure-derived fabrication, with the focus on the underlying mechanism, design criteria, and interfacial optimization. These results can give specific perspectives for future Li metal batteries with thin thickness, low N/P ratio, lean electrolyte, and high energy density (>350 Wh Kg-1 ).

Slight compositional variation-induced structural disorder-to-order transition enables fast Na+ storage in layered transition metal oxides.

The omnipresent Na+/vacancy orderings change substantially with the composition that inevitably actuate the ionic diffusion in rechargeable batteries. Therefore, it may hold the key to the electrode design with high rate capability. Herein, the influence of Na+/vacancy ordering on Na+ mobility is demonstrated firstly through a comparative investigation in P2-Na2/3Ni1/3Mn2/3O2 and P2-Na2/3Ni0.3Mn0.7O2. The large zigzag Na+/vacancy intralayer ordering is found to accelerate Na+ migration in P2-type Na2/3Ni1/3Mn2/3O2. By theoretical simulations, it is revealed that the Na+ ordering enables the P2-type Na2/3Ni1/3Mn2/3O2 with higher diffusivities and lower activation energies of 200 meV with respect to the P3 one. The quantifying diffusional analysis further prove that the higher probability of the concerted Na+ ionic diffusion occurs in P2-type Na2/3Ni1/3Mn2/3O2 due to the appropriate ratio of high energy ordered Na ions (Naf) occupation. As a result, the interplay between the Na+/vacancy ordering and Na+ kinetic is well understood in P2-type layered cathodes.

Transition Metal d-band Center Tuning by Interfacial Engineering to Accelerate Polysulfides Conversion for Robust Lithium-Sulfur Batteries.

Although lithium-sulfur batteries (LSBs) promise high theoretical energy density and potential cost effectiveness, their applications are severely impeded by the shuttling and sluggish redox kinetics of lithium polysulfides (LiPSs). In this context, a Co9 S8 @MoS2 heterostructure is sophisticatedly designed as an efficient catalytic host to boost the sulfur reduction reaction/evolution reaction (SRR/SER) kinetics and suppresses the LiPSs shuttling in LSBs. The results indicate that the electronic structure is manipulated in the Co9 S8 @MoS2 heterostructure, where the built-in electric fields (BIEFs) within the heterointerfaces enable the sufficient adsorption sites to accelerate the ionic diffusion/charge transfer kinetics for LiPSs redox, thus enhancing the sulfur conversion. By tuning the electronic structure, the metal d-band of Co9 S8 @MoS2 heterostructure plays an important role in adsorbing and catalyzing the conversion of LiPSs, thus promoting the reaction kinetics of the corresponding LSBs. This work unlocks the potential of heterostructures as promising catalysts to the design of high-energy and stabilized LSBs.

Two Magnetic Orderings and a Spin-Flop Transition in Mixed Valence Compound Mn3O(SeO3)3.

A mixed-valence manganese selenite, Mn3O(SeO3)3, was successfully synthesized using a conventional hydrothermal method. The three-dimensional framework of this compound is composed of an MnO6 octahedra and an SeO3 trigonal pyramid. The magnetic topological arrangement of manganese ions shows a three-dimensional framework formed by the intersection of octa-kagomé spin sublattices and staircase-kagomé spin sublattices. Susceptibility, magnetization and heat capacity measurements confirm that Mn3O(SeO3)3 exhibits two successive long-range antiferromagnetic orderings with TN1~4.5 K and TN2~45 K and a field-induced spin-flop transition at a critical field of 4.5 T at low temperature.

Design of Refining Slag Based on Structural Modifications Associated with the Boron Removal for SoG-Si.

Solar grade silicon (SoG-Si) is the core material of solar cells. The removal of boron (B) has always been a challenge in the preparation of high purity Si. Slag refining has always been considered as one of the effective methods to remove B, but the design of refined slag has been limited by the cognition of the relationship between slag structure and impurity removal, and can only rely on the apparent basicity and oxygen potential adjustment of slag based on a large number of conditional experiments. In order to clarify the B removal mechanism of slag refining from Si, nuclear magnetic resonance (NMR) and Raman vibrational spectroscopy were used to investigate in detail the behavior and state of B and aluminum (Al) in the SiO2-CaO-Al2O3-B2O3 slag. The role of the degree of B-Si cross linking on the B activity in slag was highlighted by comparing the partition ratio (LB) between slag and Si. Q2 structural unit of slag is an important site for capturing B. BO4 (1B, 3Si) species is the main form of connection between B and silicate networks, which determines the activity of B in the slag. The addition of Al2O3 into SiO2-CaO slag can change the relative fraction of Q2 and BO4 (1B, 3Si). Increasing Al2O3 content from 0 to about 20 wt% can lead to the overall increase of Q2 population, and a tendency to decrease first and then increase of BO4 (1B, 3Si) fraction under both basicity conditions (0.6 and 1.1). When Al2O3 content is less than 10 ± 1 wt%, the decrease of BO4 (1B, 3Si) population plays a major role in deteriorating the connectivity between B and aluminosilicate network, which leads to a higher activity of B. When the Al2O3 content is greater than 10 ± 1 wt%, B is incorporated into the silicate network more easily due to the formation of more Q2 and BO4 (1B, 3Si), which contributes to a rapid decline in activity of B in slag.

Constructing a Resilient Hierarchical Conductive Network to Promote Cycling Stability of SiOx Anode via Binder Design.

Despite exhibiting high specific capacities, Si-based anode materials suffer from poor cycle life as their volume change leads to the collapse of conductive network within the electrode. For this reason, the challenge lies in retaining the conductive network during electrochemical processes. Herein, to address this prominent issue, a cross-linked conductive binder (CCB) is designed for commercially available silicon oxides (SiOx ) anode to construct a resilient hierarchical conductive network from two aspects: on the one hand, exhibiting high electronic conductivity, CCB serves as an adaptive secondary conductive network in addition to the stiff primary conductive network (e.g., conductive carbon), facilitating faster interfacial charge transfer processes for SiOx in molecular level; on the other hand, the cross-linked structure of CCB shows resilient mechanical properties, which maintains the integrity of the primary conductive network by preventing electrode deformation during prolonged cycling. With the aid of CCB, untreated micro-sized SiOx anode material delivers an areal capacity of 2.1 mAh cm-2 after 250 cycles at 0.8 A g-1 . The binder design strategy, as well as, the relevant concepts proposed herein, provide a new perspective toward promoting the cycling stability of high-capacity Si-based anodes.

An Interface-Bridged Organic-Inorganic Layer that Suppresses Dendrite Formation and Side Reactions for Ultra-Long-Life Aqueous Zinc Metal Anodes.

Aqueous zinc (Zn) batteries (AZBs) are widely considered as a promising candidate for next-generation energy storage owing to their excellent safety features. However, the application of a Zn anode is hindered by severe dendrite formation and side reactions. Herein, an interfacial bridged organic-inorganic hybrid protection layer (Nafion-Zn-X) is developed by complexing inorganic Zn-X zeolite nanoparticles with Nafion, which shifts ion transport from channel transport in Nafion to a hopping mechanism in the organic-inorganic interface. This unique organic-inorganic structure is found to effectively suppress dendrite growth and side reactions of the Zn anode. Consequently, the Zn@Nafion-Zn-X composite anode delivers high coulombic efficiency (ca. 97 %), deep Zn plating/stripping (10 mAh cm-2 ), and long cycle life (over 10 000 cycles). By tackling the intrinsic chemical/electrochemical issues, the proposed strategy provides a versatile remedy for the limited cycle life of the Zn anode.

Hollow double-layer carbon nanocage confined Si nanoparticles for high performance lithium-ion batteries.

The huge volume variation and the unstable solid electrolyte interface (SEI) of Si (Si) during the lithiation and delithiation process severely obstruct its practical application as lithium-ion battery anodes. Here, we design and fabricate a hollow structure of double-layer hybrid carbon nanocage encapsulated Si nanoparticles to address these challenges. The double-layer hybrid carbon-Si nanoarchitecture is obtained by integrating electrostatic self-assembly, seed-induced growth and heterogeneous shrinkage. The internal layer of hollow N-doped carbon of the hybrid nanoarchitecture (Si@H-NC@GC) provides limited inner space for controlling volume changes of Si nanoparticles, while the outer graphite carbon layer facilitates the formation of a stable SEI. When evaluated as anode materials for LIBs, the Si@H-NC@GC nanoarchitecture exhibits greatly enhanced electrochemical performance compared with the bare Si, Si@NC and H-NC@GC electrodes. Notably, Si@H-NC@GC delivers a reversible capacity retention of 92.5% after 550 cycles at a high current density of 1 A g-1 and a high capacity of 1081 mA h g-1 after 500 cycles at 0.5 A g-1.

Discovery of space aromaticity in transition-metal monoxide crystal Nb3O3 enabled by octahedral Nb6 structural units.

An octahedral Nb6 structural unit with space aromaticity is identified for the first time in a transition-metal monoxide crystal Nb3O3 by ab initio calculations. The strong Nb-Nb metallic bonding facilitates the formation of stable octahedral Nb6 structural units and the release of delocalization energy. Moreover, the Nb atoms in continuously connected Nb6 structural units share their electrons with each other in a continuous space of framework, so that the electrons are uniformly distributed. The newly discovered aromaticity in the octahedral Nb6 structural units extends the range of aromatic compounds and broadens our vision in structural chemistry.

Unravelling H+ /Zn2+ Synergistic Intercalation in a Novel Phase of Manganese Oxide for High-Performance Aqueous Rechargeable Battery.

Aqueous Zn-MnO2 batteries using mild electrolyte show great potential in large-scale energy storage (LSES) application, due to high safety and low cost. However, structure collapse of manganese oxides upon cycling caused by the conversion mechanism (e.g., from tunnel to layer structures for α-, ß-, and γ-phases) is one of the most urgent issues plaguing its practical applications. Herein, to avoid the phase conversion issue and enhance battery performance, a structurally robust novel phase of manganese oxide MnO2 H0.16 (H2 O)0.27 (MON) nanosheet with thickness of ≈2.5 nm is designed and synthesized as a promising cathode material, in which a nanosheet structure combined with a novel H+ /Zn2+ synergistic intercalation mechanism is demonstrated and evidenced. Accordingly, a high-performance Zn/MON cell is achieved, showing a high energy density of ≈228.5 Wh kg-1 , impressive cyclability with capacity retention of 96% at 0.5 C after 300 cycles, as well as exhibiting rate performance of 115.1 mAh g-1 at current rate of 10 C. To the best current knowledge, this H+ /Zn2+ synergistic intercalation mechanism is first reported in an aqueous battery system, which opens a new opportunity for development of high-performance aqueous Zn ion batteries for LSES.

Multidimensional Integrated Chalcogenides Nanoarchitecture Achieves Highly Stable and Ultrafast Potassium-Ion Storage.

Potassium-ion batteries (KIBs) have come into the spotlight in large-scale energy storage systems because of cost-effective and abundant potassium resources. However, the poor rate performance and problematic cycle life of existing electrode materials are the main bottlenecks to future potential applications. Here, the first example of preparing 3D hierarchical nanoboxes multidimensionally assembled from interlayer-expanded nano-2D MoS2 @dot-like Co9 S8 embedded into a nitrogen and sulfur codoped porous carbon matrix (Co9 S8 /NSC@MoS2 @NSC) for greatly boosting the electrochemical properties of KIBs in terms of reversible capacity, rate capability, and cycling lifespan, is reported. Benefiting from the synergistic effects, Co9 S8 /NSC@MoS2 @NSC manifest a very high reversible capacity of 403 mAh g-1 at 100 mA g-1 after 100 cycles, an unprecedented rate capability of 141 mAh g-1 at 3000 mA g-1 over 800 cycles, and a negligible capacity decay of 0.02% cycle-1 , boosting promising applications in high-performance KIBs. Density functional theory calculations demonstrate that Co9 S8 /NSC@MoS2 @NSC nanoboxes have large adsorption energy and low diffusion barriers during K-ion storage reactions, implying fast K-ion diffusion capability. This work may enlighten the design and construction of advanced electrode materials combined with strong chemical bonding and integrated functional advantages for future large-scale stationary energy storage.

Discovering unusual structures from exception using big data and machine learning techniques.

Recently, machine learning (ML) has become a widely used technique in materials science study. Most work focuses on predicting the rule and overall trend by building a machine learning model. However, new insights are often learnt from exceptions against the overall trend. In this work, we demonstrate that how unusual structures are discovered from exceptions when machine learning is used to get the relationship between atomic and electronic structures based on big data from high-throughput calculation database. For example, after training an ML model for the relationship between atomic and electronic structures of crystals, we find AgO2F, an unusual structure with both Ag3+ and O22-, from structures whose band gap deviates much from the prediction made by our model. A further investigation on this structure might shed light into the research on anionic redox in transition metal oxides of Li-ion batteries.

Bioinspired, Spine-Like, Flexible, Rechargeable Lithium-Ion Batteries with High Energy Density.

The rapid development of flexible and wearable electronics proposes the persistent requirements of high-performance flexible batteries. Much progress has been achieved recently, but how to obtain remarkable flexibility and high energy density simultaneously remains a great challenge. Here, a facile and scalable approach to fabricate spine-like flexible lithium-ion batteries is reported. A thick, rigid segment to store energy through winding the electrodes corresponds to the vertebra of animals, while a thin, unwound, and flexible part acts as marrow to interconnect all vertebra-like stacks together, providing excellent flexibility for the whole battery. As the volume of the rigid electrode part is significantly larger than the flexible interconnection, the energy density of such a flexible battery can be over 85% of that in conventional packing. A nonoptimized flexible cell with an energy density of 242 Wh L-1 is demonstrated with packaging considered, which is 86.1% of a standard prismatic cell using the same components. The cell also successfully survives a harsh dynamic mechanical load test due to this rational bioinspired design. Mechanical simulation results uncover the underlying mechanism: the maximum strain in the reported design (≈0.08%) is markedly smaller than traditional stacked cells (≈1.1%). This new approach offers great promise for applications in flexible devices.

A CAD System for Hemorrhagic Stroke.

Computer-aided detection/diagnosis (CAD) is a key component of routine clinical practice, increasingly used for detection, interpretation, quantification and decision support. Despite a critical need, there is no clinically accepted CAD system for stroke yet. Here we introduce a CAD system for hemorrhagic stroke. This CAD system segments, quantifies, and displays hematoma in 2D/3D, and supports evacuation of hemorrhage by thrombolytic treatment monitoring progression and quantifying clot removal. It supports seven-step workflow: select patient, add a new study, process patient's scans, show segmentation results, plot hematoma volumes, show 3D synchronized time series hematomas, and generate report. The system architecture contains four components: library, tools, application with user interface, and hematoma segmentation algorithm. The tools include a contour editor, 3D surface modeler, 3D volume measure, histogramming, hematoma volume plot, and 3D synchronized time-series hematoma display. The CAD system has been designed and implemented in C++. It has also been employed in the CLEAR and MISTIE phase-III, multicenter clinical trials. This stroke CAD system is potentially useful in research and clinical applications, particularly for clinical trials.

Population-based Stroke Atlas for outcome prediction: method and preliminary results for ischemic stroke from CT.

BACKGROUND AND PURPOSE: Knowledge of outcome prediction is important in stroke management. We propose a lesion size and location-driven method for stroke outcome prediction using a Population-based Stroke Atlas (PSA) linking neurological parameters with neuroimaging in population. The PSA aggregates data from previously treated patients and applies them to currently treated patients. The PSA parameter distribution in the infarct region of a treated patient enables prediction. We introduce a method for PSA calculation, quantify its performance, and use it to illustrate ischemic stroke outcome prediction of modified Rankin Scale (mRS) and Barthel Index (BI). METHODS: The preliminary PSA was constructed from 128 ischemic stroke cases calculated for 8 variants (various data aggregation schemes) and 3 case selection variables (infarct volume, NIHSS at admission, and NIHSS at day 7), each in 4 ranges. Outcome prediction for 9 parameters (mRS at 7th, and mRS and BI at 30th, 90th, 180th, 360th day) was studied using a leave-one-out approach, requiring 589,824 PSA maps to be analyzed. RESULTS: Outcomes predicted for different PSA variants are statistically equivalent, so the simplest and most efficient variant aiming at parameter averaging is employed. This variant allows the PSA to be pre-calculated before prediction. The PSA constrained by infarct volume and NIHSS reduces the average prediction error (absolute difference between the predicted and actual values) by a fraction of 0.796; the use of 3 patient-specific variables further lowers it by 0.538. The PSA-based prediction error for mild and severe outcomes (mRS  =  [2]-[5]) is (0.5-0.7). Prediction takes about 8 seconds. CONCLUSIONS: PSA-based prediction of individual and group mRS and BI scores over time is feasible, fast and simple, but its clinical usefulness requires further studies. The case selection operation improves PSA predictability. A multiplicity of PSAs can be computed independently for different datasets at various centers and easily merged, which enables building powerful PSAs over the community.

Characterization of intraventricular and intracerebral hematomas in non-contrast CT.

Characterization of hematomas is essential in scan reading, manual delineation, and designing automatic segmentation algorithms. Our purpose is to characterize the distribution of intraventricular (IVH) and intracerebral hematomas (ICH) in NCCT scans, study their relationship to gray matter (GM), and to introduce a new tool for quantitative hematoma delineation. We used 289 serial retrospective scans of 51 patients. Hematomas were manually delineated in a two-stage process. Hematoma contours generated in the first stage were quantified and enhanced in the second stage. Delineation was based on new quantitative rules and hematoma profiling, and assisted by a dedicated tool superimposing quantitative information on scans with 3D hematoma display. The tool provides: density maps (40-85HU), contrast maps (8/15HU), mean horizontal/vertical contrasts for hematoma contours, and hematoma contours below a specified mean contrast (8HU). White matter (WM) and GM were segmented automatically. IVH/ICH on serial NCCT is characterized by 59.0HU mean, 60.0HU median, 11.6HU standard deviation, 23.9HU mean contrast, -0.99HU/day slope, and -0.24 skewness (changing over time from negative to positive). Its 0.1(st)-99.9(th) percentile range corresponds to 25-88HU range. WM and GM are highly correlated (R (2)=0.88; p<10(-10)) whereas the GM-GS correlation is weak (R (2)=0.14; p<10(-10)). The intersection point of mean GM-hematoma density distributions is at 55.6±5.8HU with the corresponding GM/hematoma percentiles of 88(th)/40(th). Objective characterization of IVH/ICH and stating the rules quantitatively will aid raters to delineate hematomas more robustly and facilitate designing algorithms for automatic hematoma segmentation. Our two-stage process is general and potentially applicable to delineate other pathologies on various modalities more robustly and quantitatively.