Nanocomposite Engineering of a High-Capacity Partially Ordered Cathode for Li-Ion Batteries.

Understanding the local cation order in the crystal structure and its correlation with electrochemical performances has advanced the development of high-energy Mn-rich cathode materials for Li-ion batteries, notably Li- and Mn-rich layered cathodes (LMR, e.g., Li1.2 Ni0.13 Mn0.54 Co0.13 O2 ) that are considered as nanocomposite layered materials with C2/m Li2 MnO3 -type medium-range order (MRO). Moreover, the Li-transport rate in high-capacity Mn-based disordered rock-salt (DRX) cathodes (e.g., Li1.2 Mn0.4 Ti0.4 O2 ) is found to be influenced by the short-range order of cations, underlining the importance of engineering the local cation order in designing high-energy materials. Herein, the nanocomposite is revealed, with a heterogeneous nature (like MRO found in LMR) of ultrahigh-capacity partially ordered cathodes (e.g., Li1.68 Mn1.6 O3.7 F0.3 ) made of distinct domains of spinel-, DRX- and layered-like phases, contrary to conventional single-phase DRX cathodes. This multi-scale understanding of ordering informs engineering the nanocomposite material via Ti doping, altering the intra-particle characteristics to increase the content of the rock-salt phase and heterogeneity within a particle. This strategy markedly improves the reversibility of both Mn- and O-redox processes to enhance the cycling stability of the partially ordered DRX cathodes (nearly ≈30% improvement of capacity retention). This work sheds light on the importance of nanocomposite engineering to develop ultrahigh-performance, low-cost Li-ion cathode materials.

Extended Interfacial Stability through Simple Acid Rinsing in a Li-Rich Oxide Cathode Material.

Layered Li-rich Ni, Mn, Co (NMC) oxide cathodes in Li-ion batteries provide high specific capacities (>250 mAh/g) via O-redox at high voltages. However, associated high-voltage interfacial degradation processes require strategies for effective electrode surface passivation. Here, we show that an acidic surface treatment of a Li-rich NMC layered oxide cathode material leads to a substantial suppression of CO2 and O2 evolution, ∼90% and ∼100% respectively, during the first charge up to 4.8 V vs Li+/0. CO2 suppression is related to Li2CO3 removal as well as effective surface passivation against electrolyte degradation. This treatment does not result in any loss of discharge capacity and provides superior long-term cycling and rate performance in comparison to as-received, untreated materials. We also quantify the extent of lattice oxygen participation in charge compensation ("O-redox") during Li+ removal by a novel ex situ acid titration. Our results indicate that the peroxo-like species resulting from O-redox originate on the surface at least 300 mV earlier than the activation plateau region at around 4.5 V. X-ray photoelectron spectra and Mn L-edge X-ray absorption spectra of the cathode powders reveal a Li+ deficiency and a partial reduction of Mn ions on the surface of the acid-treated material. More interestingly, although the irreversible oxygen evolution is greatly suppressed through the surface treatment, O K-edge resonant inelastic X-ray scattering shows that the lattice O-redox behavior is largely sustained. The acidic treatment, therefore, only optimizes the surface of the Li-rich material and almost eliminates the irreversible gas evolution, leading to improved cycling and rate performance. This work therefore presents a simple yet effective approach to passivate cathode surfaces against interfacial instabilities during high-voltage battery operation.

Upregulation of Death Receptor 5 and Production of Reactive Oxygen Species Mediate Sensitization of PC-3 Prostate Cancer Cells to TRAIL Induced Apoptosis by Vitisin A.

BACKGROUND/AIMS: Although Vitisin A, derived from wine grapes, is known to have cytotoxic, anti-adipogenic, anti-inflammatory and antioxidant effects, the underlying antitumor mechanism has not been investigated in prostate cancer cells to date. In the present study, the apoptotic mechanism of Vitisin A plus TNF-related apoptosis-inducing ligand (TRAIL) in prostate cancer cells was elucidated. METHODS: The cytotoxicity of Vitisin A and/or TRAIL against PC-3, DU145 and LNCaP prostate cancer cells was measured by MTT colorimetric assay. Annexin V-FITC Apoptosis Detection kit was used to detect apoptotic cells by flow cytometry. Intracellular levels of ROS were measured by flow cytometry using 2070-diacetyl dichlorofluorescein (DCFDA). RESULTS: Combined treatment with Vitisin A and TRAIL enhanced cytotoxicity and also increased sub-G1 population in PC-3 cells better than DU145 or LNCap prostate cancer cells. Similarly, Annexin V and PI staining revealed that combination increased early and late apoptosis in PC-3 cells compared to untreated control. Consistently, combination attenuated the expression of pro-caspases 7/8, DcR1, Bcl-XL or Bcl-2 and activated caspase 3, FADD, DR5 and DR4 in PC-3 cells. Also, combination increased DR5 promoter activity compared to untreated control. Furthermore, combination increased the production of reactive oxygen species (ROS) and DR5 cell surface expression. The ROS inhibitor NAC and silencing of DR5 by siRNA transfection inhibited the ability of combination to induce PARP cleavage and generate ROS. CONCLUSION: These findings provide evidence that Vitisin A can be used in conjunction with TRAIL as a potent TRAIL sensitizer for synergistic apoptosis induction via upregulation of DR5 and production of ROS in prostate cancer cells.

High-energy cathode material for long-life and safe lithium batteries.

Layered lithium nickel-rich oxides, Li[Ni(1-x)M(x)]O(2) (M=metal), have attracted significant interest as the cathode material for rechargeable lithium batteries owing to their high capacity, excellent rate capability and low cost. However, their low thermal-abuse tolerance and poor cycle life, especially at elevated temperature, prohibit their use in practical batteries. Here, we report on a concentration-gradient cathode material for rechargeable lithium batteries based on a layered lithium nickel cobalt manganese oxide. In this material, each particle has a central bulk that is rich in Ni and a Mn-rich outer layer with decreasing Ni concentration and increasing Mn and Co concentrations as the surface is approached. The former provides high capacity, whereas the latter improves the thermal stability. A half cell using our concentration-gradient cathode material achieved a high capacity of 209 mA h g(-1) and retained 96% of this capacity after 50 charge-discharge cycles under an aggressive test profile (55 degrees C between 3.0 and 4.4 V). Our concentration-gradient material also showed superior performance in thermal-abuse tests compared with the bulk composition Li[Ni(0.8)Co(0.1)Mn(0.1)]O(2) used as reference. These results suggest that our cathode material could enable production of batteries that meet the demanding performance and safety requirements of plug-in hybrid electric vehicles.