Single-crystalline Ni-rich cathodes with high capacity have drawn much attention for mitigating cycling and safety crisis of their polycrystalline analogues. However, planar gliding and intragranular cracking tend to occur in single crystals with cycling, which undermine cathode integrity and therefore cause capacity degradation. Herein, we intensively investigate the origin and evolution of the gliding phenomenon in single-crystalline Ni-rich cathodes. Discrete or continuous gliding forms are revealed with new surface exposure including the gliding plane (003) and reconstructed (-108) under surface energy drive. It is also demonstrated that the gliding process is the in-plane migration of transition metal ions, and reducing oxygen vacancies will increase the migration energy barrier by which gliding and microcracking can be restrained. The designed cathode with less oxygen deficiency exhibits outstanding cycling performance with an 80.8% capacity retention after 1000 cycles in pouch cells. Our findings provide an insight into the relationship between defect control and chemomechanical properties of single-crystalline Ni-rich cathodes.
Chemical modification of electrode materials by heteroatom dopants is crucial for improving storage performance in rechargeable batteries. Electron configurations of different dopants significantly influence the chemical interactions inbetween and the chemical bonding with the host material, yet the underlying mechanism remains unclear. We revealed competitive doping chemistry of Group IIIA elements (boron and aluminum) taking nickel-rich cathode materials as a model. A notable difference between the atomic radii of B and Al accounts for different spatial configurations of the hybridized orbital in bonding with lattice oxygen. Density functional theory calculations reveal, Al is preferentially bonded to oxygen and vice versa, and shows a much lower diffusion barrier than BIII . In the case of Al-preoccupation, the bulk diffusion of BIII is hindered. In this way, a B-rich surface and Al-rich bulk is formed, which helps to synergistically stabilize the structural evolution and surface chemistry of the cathode.
High-nickel (Ni ≥ 90%) cathodes with high specific capacity hold great potential for next-generation lithium-ion batteries (LIBs). However, their practical application is restricted by the high interfacial reactivity under continuous air erosion and electrolyte assault. Herein, a stable high-nickel cathode is rationally designed via in situ induction of a dense amorphous Li2 CO3 on the particle surface by a preemptive atmosphere control. Among the residual lithium compounds, Li2 CO3 is the most thermodynamically stable one, so a dense Li2 CO3 coating layer can serve as a physical protection layer to isolate the cathode from contact with moist air. Furthermore, amorphous Li2 CO3 can be transformed into a robust F-rich cathode electrolyte interphase (CEI) during cycling, which reinforces the cathode's interfacial stability and improves the electrochemical performance. The assembled coin cell with this modified cathode delivers a high discharge capacity of 232.4 mAh g-1 with a superior initial Coulombic efficiency (CE) of 95.1%, and considerable capacity retention of 90.4% after 100 cycles. Furthermore, no slurry gelation occurs during the large-scale electrode fabrication process. This work opens a valuable perspective on the evolution of amorphous Li2 CO3 in LIBs and provides guidance on protecting unstable high-capacity cathodes for energy-storage devices.
Single-crystalline Ni-rich cathodes are promising candidates for the next-generation high-energy Li-ion batteries. However, they still suffer from poor rate capability and low specific capacity due to the severe kinetic hindrance at the nondilute state during Li+ intercalation. Herein, combining experiments with density functional theory (DFT) calculations, we demonstrate that this obstacle can be tackled by regulating the oxidation state of nickel via injecting high-valence foreign Ta5+ . The as-obtained single-crystalline LiNi0.8 Co0.1 Mn0.1 O2 delivers a high specific capacity (211.2â mAh g-1 at 0.1 C), high initial Coulombic efficiency (93.8 %), excellent rate capability (157â mAh g-1 at 4 C), and good durability (90.4 % after 100 cycles under 0.5 C). This work provides a strategy to mitigate the Li+ kinetic hindrance of the appealing single-crystalline Ni-rich cathodes and will inspire peers to conduct an intensive study.
Among the issues that restrict the power conversion efficiency (PCE) of quantum-dot-sensitized solar cells (QDSSCs), insufficient catalytic activity and stability of counter electrodes (CEs) are critical but challenging ones. The state-of-the-art Cu/Cu2S CEs still suffer from mechanical instability and uncertainty due to the reaction of copper and electrolyte. Herein, ITO@Cu2S core-shell nanowire arrays were developed to fabricate CEs for QDSSCs, which have no such issues in Cu/Cu2S CEs. These nanowire arrays exhibited small charge transfer resistance and sheet resistance, and provided more active catalytic sites and easy accessibility for electrolyte due to the three-dimensional structure upon use as CEs. More interestingly, it was found that the interface of ITO/Cu2S significantly affected the performance of ITO@Cu2S nanowire array CEs. By varying synthetic methods, a series of ITO@Cu2S nanowire arrays were prepared to investigate the influence of ITO/Cu2S interface on their performance. The results showed that ITO@Cu2S nanowire array CEs with a continuous Cu2S nanocrystal shell fabricated via an improved cation exchange route exhibited excellent and thickness-dependent performance. The PCE of corresponding QDSSCs increased by 11.6 and 16.5% compared to that with the discrete Cu2S nanocrystal and the classic Cu/Cu2S CE, respectively, indicating its promising potential as a new type of CE for QDSSCs.
Quantum-dot-sensitized solar cell (QDSSC) has been considered as an alternative to new generation photovoltaics, but it still presents very low power conversion efficiency. Besides the continuous effort on improving photoanodes and electrolytes, the focused investigation on charge transfer at interfaces and the rational design for counter electrodes (CEs) are recently receiving much attention. Herein, core-shell nanowire arrays with tin-doped indium oxide (ITO) nanowire core and Cu2S nanocrystal shell (ITO@Cu2S) were dedicatedly designed and fabricated as new efficient CEs for QDSSCs in order to improve charge collection and transport and to avoid the intrinsic issue of copper dissolution in popular and most efficient Cu/Cu2S CEs. The high-quality tunnel junctions formed between n-type ITO nanowires and p-type Cu2S nanocrystals led to the considerable decrease in sheet resistance and charge transfer resistance and thus facilitated the electron transport during the operation of QDSSCs. The three-dimensional structure of nanowire arrays provided high surface area for more active catalytic sites and easy accessibility for an electrolyte. As a result, the power conversion efficiency of QDSSCs with the designed ITO@Cu2S CEs increased by 84.5 and 33.5% compared to that with planar Au and Cu2S CEs, respectively.
The tremendous future energy demand and environmental concerns prompt the lasting search for new materials for low-cost and high-efficiency solar cells. SnS, as a low-cost, earth-abundant, and environmentally friendly material with proper band gap and absorption coefficient, has received attention as a potential candidate for solar absorber, but it is still under-developed due to insufficient conversion efficiency. Fabricating SnS nanostructured films for solar cell design could be effective to boost photovoltaic performance and pave the way for applications in photovoltaics. Herein, a facile surfactant-free solution-based approach has been developed to prepare monolithic SnS nanostructured films directly on tin foil substrate. The morphologies of nanostructured films could be tuned from well-defined orthorhombic SnS nanobelt arrays to nanorods, nanosheets, or nanoflakes by simply changing the ratio of used solvents. The photoelectric response and electronic transportation properties of SnS nanobelts were investigated by fabricating single-nanobelt-based nanodevices. The SnS nanobelt exhibited a fast and reliable photoresponse even at illumination intensity as weak as 0.103 mW cm(-2). The measurements on SnS FET devices also indicated that the synthesized SnS nanobelts demonstrated a hole mobility as high as 12.33 cm(2) V(-1) s(-1). These results reveal that the reported approach for preparing monolithic SnS nanostructured films could be useful to further develop SnS as an alternative material for low-cost solar cells and electronic devices.
OBJECTIVE: To investigate the clinical feature, treatment and outcome of respiratory failure in patients with 2009 influenza A H1N1 infection in critically ill adults. METHODS: A prospective observational study of 18 patients with respiratory failure suffering from 2009 influenza A H1N1 infection admitted between November 22, 2009 and January 16, 2010. Their clinical data were analyzed. RESULTS: Respiratory failure occurred in 18 patients with confirmed (n=9) or probable (n=9) 2009 influenza A H1N1. Among the 18 patients 8 patients were male, 10 patients were female (7 were pregnant or postpartum). Eight patients had pre-existing medical conditions. Twelve patients were between 20 and 40 years of age, the mean age was 37.1 years. Three were obese with body mass index over 30 kg/m (2). The 28-day mortality was 33.3% (6/18) with 1 additional late death. The median duration from the onset of the illness to hospital admission was 4.1 days (1-5 days) and from the onset to first dose of oseltamivir was 5.5 days (2-12 days), from onset to mechanical ventilation initiation was 6.8 days (4-12 days). Seventeen patients had primary viral pneumonia and 1 patient had an asthma exacerbation and 3 patients experienced multiple organ dysfunction syndrome (MODS). Twelve patients received corticosteroids, 10 patients required vasopressors. All patients were mechanically ventilated, 1 patient underwent extracorporeal membrane oxygenation (ECMO). Patients who died had higher acute physiology and chronic health evaluation II score compared to survivors (29.2 + or - 7.3 vs. 18.6 + or - 6.4, P=0.02). All deceased patients received high-level ventilation settings [peak inspiratory pressure > or = 35 cm H(2)O (1 cm H(2)O=0.098 kPa) and positive end-expiratory pressure > or = 18 cm H(2)O] within the first 7 days of ventilation, and the hypoxemia [oxygenation index < or = 60 mm Hg (1 mm Hg=0.133 kPa)] lasted 24 hours. In contrast only 1 among survivors did (9.1% vs. 100.0%, P<0.01). Compared with survivors, acute kidney injury and barotrauma occurred more frequently in non-survivors (42.9% vs. 27.3%, 28.6% vs. 9.1%, both P<0.05). Whereas all deceased patients received vasopressors, only 4 survivors required vasopressor support (100.0% vs. 36.4%, P<0.05). CONCLUSION: Severe acute respiratory distress syndrome is the most common manifestation in critically ill patients with 2009 influenza A H1N1 infection in adult. Failure to obtain satisfactory oxygenation with high-level ventilation settings within the first 7-days, onset of acute kidney injury and barotrauma, and continuous need for vasopressors portend a poor prognosis.
Influenza A Virus, H1N1 Subtype , Influenza, Human/complications , Respiratory Insufficiency/therapy , Adult , Extracorporeal Membrane Oxygenation , Female , Humans , Male , Middle Aged , Pneumonia, Viral/etiology , Prognosis , Prospective Studies , Respiration, Artificial , Respiratory Distress Syndrome/etiology , Respiratory Insufficiency/virology , Young Adult
