The Role of "Hierarchical and Classified Prevention and Control Measures (HCPC)" Strategy for SARS-CoV-2 Delta Variant in Guangzhou: A Modeling Study.

BACKGROUND: The Delta variant of SARS-COV-2 has replaced previously circulating strains around the world in 2021. Sporadic outbreaks of the Delta variant in China have posed a concern about how to properly respond to the battle against evolving COVID-19. Here, we analyzed the "hierarchical and classified prevention and control (HCPC)" measures strategy deployed during the recent Guangzhou outbreak. METHODS: A modified susceptible-exposed-pre-symptomatic-infectious-recovered (SEPIR) model was developed and applied to study a range of different scenarios to evaluate the effectiveness of policy deployment. We simulated severe different scenarios to understand policy implementation and timing of implementation. Two outcomes were measured: magnitude of transmission and duration of transmission. The outcomes of scenario evaluations were presented relative to the reality case (i.e., 368 cases in 34 days) with 95% confidence interval (CI). RESULTS: Based on our simulation, the outbreak would become out of control with 7 million estimated infections under the assumption of the absence of any interventions than the 153 reported cases in reality in Guangzhou. The simulation on delayed implementation of interventions showed that the total case numbers would also increase by 166.67%-813.07% if the interventions were delayed by 3 days or 7 days. CONCLUSIONS: It may be concluded that timely and more precise interventions including mass testing and graded community management are effective measures for Delta variant containment in China.

Weakly solvated EC-free linear alkyl carbonate electrolytes for Ni-rich cathode in rechargeable lithium battery.

Ethylene carbonate (EC) in the electrolyte is not stable in cells operated at high voltage (≥4.4V) or with Li metal anode, which greatly reduce the energy density and lifetime of the rechargeable lithium battery. Herein, an EC-free linear alkyl carbonate-based electrolyte is developed, which enables the high-voltage (≥4.4V) and low-temperature (-30°C) application of Ni-rich cathode (LiNi0.8Mn0.1Co0.1O2, NCM811). The EC-free system, consisting of LiPF6 and LiNO3 in ternary linear alkyl carbonates, possesses low viscosity, weakly solvated structure, and high interfacial stability with both the Ni-rich cathode and the Li metal anode to avoid continuous electrode/electrolyte side reactions and metal dissolution from the cathode. As a result, the Li||NCM811 cell delivers remarkable capacity retention of 93 ± 0.5% at the voltage of 4.4V and 88 ± 0.6% at 4.5V over 100 cycles. This study provides very encouraging perspective to develop EC-free carbonate-based electrolyte for high-voltage and low-temperature application in high-energy-density rechargeable lithium batteries.

Facile Electroless Plating Method to Fabricate a Nickel-Phosphorus-Modified Copper Current Collector for a Lean Lithium-Metal Anode.

The compatibility of current collectors with reactive Li is key to inducing stable Li cycling and prolonged cycle life of lean Li-metal batteries. Herein, a thin and uniform layer of Ni-P complex was built on the surface of a Cu current collector (NiP@Cu) via an efficient, controllable, and cost-effective electroless plating method. The thickness, morphology, composition, and roughness of the Ni-P deposition were successfully regulated. Lithiophilicity of the current collector was greatly improved by Ni-P deposition, which effectively reduced the Li nucleation overpotential and suppressed the Li dendrite growth. In addition, NiP@Cu promoted an inorganic LiF/Li3P-rich solid electrolyte interphase to facilitate interfacial charge transfer and eliminate excessive side reactions between Li and the electrolyte. As a result, the Coulombic efficiency of half-cells remained above 98.5% for more than 400 cycles at 0.5 mA/cm2 and 98.2% for more than 250 cycles at 1 mA/cm2. Full cells with NiP@Cu also showed superior performance compared to those with bare Cu. This work proposes a promising surface modification method to develop a stable, dendrite-free, and cost-effective anode current collector for high-energy-density lean Li-metal batteries.