Ti-substituted O3-type layered oxide cathode material with high-voltage stability for sodium-ion batteries.

O3-type layered transition metal oxides (NaxTMO2) have attracted extensive attention as a promising cathode material for sodium-ion batteries because of their high capacity. However, the irreversible phase transition especially cycled under high voltage remains a concerning challenge for NaxTMO2. Herein, a Ti-substituted NaNi0.5Co0.2Mn0.3O2 cathode with strongly suppressed phase transition and enhanced storage stability is investigated. The Ti substitution effectively inhibits the irreversible phase transition and alleviates the structural change even charged to 4.3 V during the repeated Na+ deintercalation process. After storing in air or water, the original O3 phase structure of the material is integrally maintained without the generation of impurity phase. As a result, the as-prepared material shows excellent long-term cycle stability and rate performance when charged to a high voltage of 4.3 V.

[Comparison of two screening scales used by 120 dispatchers for early identification of pre-hospital stroke patients and telephone guidance for treatment].

OBJECTIVE: To observe the effect of two different screening scales used by 120 dispatchers to early identify stroke patients and give telephone guidance for treatment. METHODS: From October 2018 to August 2019, 2 027 stroke and suspect stroke patients who called the Kaifeng 120 Emergency Center were enrolled. The differences in the final positive rate of stroke diagnosis and the incidence of adverse events were compared and analyzed in 1 020 cases using recognition of stroke in the emergency room (ROSIER) and 1 007 cases using facial drooping, arm weakness, speech difficulties and time (FAST) scale scores for telephone guidance. RESULTS: The positive rate of stroke identification in ROSIER score group was higher than that in FAST score group [31.4% (320/1 020) vs. 29.3% (295/1 007)], the false report rate was significantly lower than that in FAST score group [14.9% (152/1 020) vs. 18.8% (189/1 007), P < 0.05], the incidence of adverse events caused by vomiting, falling from bed and convulsions in ROSIER score group were lower than those in FAST score group [0.5% (1/208) vs. 2.2% (4/185), 0% (0/26) vs. 20.0% (2/10), 2.1% (1/48) vs. 10.3% (3/29)], however, the incidence of adverse events caused by falling out of bed was significantly lower (P < 0.05). The incidence of total adverse events in ROSIER score group was significantly lower than that in FAST score group [0.7% (2/305) vs. 3.8% (9/235), P < 0.05]. The time of FAST score group was shorter than that of ROSIER score group (minutes: 1.2±0.2 vs. 2.5±0.3), but the difference was not statistically significant (P > 0.05). CONCLUSIONS: Two different scales can be used to early identify stroke patients and provide timely pre-hospital guidance, thus reduce the incidence of adverse events. Although the ROSIER score takes longer time, the dispatchers guide the patients by phone which does not affect the dispatch time.

The Effects of Reversibility of H2-H3 Phase Transition on Ni-Rich Layered Oxide Cathode for High-Energy Lithium-Ion Batteries.

Although LiNi0.8Co0.1Mn0.1O2 is attracting increasing attention on account of its high specific capacity, the moderate cycle lifetime still hinders its large-scale commercialization applications. Herein, the Ti-doped LiNi0.8Co0.1Mn0.1O2 compounds are successfully synthesized. The Li(Ni0.8Co0.1Mn0.1)0.99Ti0.01O2 sample exhibits the best electrochemical performance. Under the voltage range of 2.7-4.3 V, it maintains a reversible capacity of 151.01 mAh·g-1 with the capacity retention of 83.98% after 200 cycles at 1 C. Electrochemical impedance spectroscopy (EIS) and differential capacity profiles during prolonged cycling demonstrate that the Ti doping could enhance both the abilities of electronic transition and Li ion diffusion. More importantly, Ti doping can also improve the reversibility of the H2-H3 phase transitions during charge-discharge cycles, thus improving the electrochemical performance of Ni-rich cathodes.

Porous Hollow Superlattice NiMn2O4/NiCo2O4 Mesocrystals as a Highly Reversible Anode Material for Lithium-Ion Batteries.

As a promising high-capacity anode material for Li-ion batteries, NiMn2O4 always suffers from the poor intrinsic conductivity and the architectural collapse originating from the volume expansion during cycle. Herein, a combined structure and architecture modulation is proposed to tackle concurrently the two handicaps, via a facile and well-controlled solvothermal approach to synthesize NiMn2O4/NiCo2O4 mesocrystals with superlattice structure and hollow multi-porous architecture. It is demonstrated that the obtained NiCo1.5Mn0.5O4 sample is made up of a new mixed-phase NiMn2O4/NiCo2O4 compound system, with a high charge capacity of 532.2 mAh g-1 with 90.4% capacity retention after 100 cycles at a current density of 1 A g-1. The enhanced electrochemical performance can be attributed to the synergistic effects of the superlattice structure and the hollow multi-porous architecture of the NiMn2O4/NiCo2O4 compound. The superlattice structure can improve ionic conductivity to enhance charge transport kinetics of the bulk material, while the hollow multi-porous architecture can provide enough void spaces to alleviate the architectural change during cycling, and shorten the lithium ions diffusion and electron-transportation distances.