State-of-the-art lithium (Li)-ion batteries are approaching their specific energy limits yet are challenged by the ever-increasing demand of today's energy storage and power applications, especially for electric vehicles. Li metal is considered an ultimate anode material for future high-energy rechargeable batteries when combined with existing or emerging high-capacity cathode materials. However, much current research focuses on the battery materials level, and there have been very few accounts of cell design principles. Here we discuss crucial conditions needed to achieve a specific energy higher than 350 Wh kg −1 , up to 500 Wh kg −1 , for rechargeable Li metal batteries using high-nickel-content lithium nickel manganese cobalt oxides as cathode materials. We also provide an analysis of key factors such as cathode loading, electrolyte amount and Li foil thickness that impact the cell-level cycle life. Furthermore, we identify several important strategies to reduce electrolyte-Li reaction, protect Li surfaces and stabilize anode architectures for long-cycling high-specific-energy cells.

Lithium (Li)-metal batteries have regained broad interest in the battery research community. Although many studies on Li anode have been published in recent years, it is difficult to evaluate and compare these advances for practical applications. A key challenge is a gap between materials and component properties and the achievable large-format cell-level performance. In this paper, we investigate the critical experimental parameters that determine the cycle number of coin cells to understand the performance variations reported in the literature. To define the range of cell parameters, we exemplify a representative Li-metal pouch cell with specific energy of 300 Wh/kg to provide an effective validation of electrode materials and accurate cell performance evaluations. Based on the pouch-cell-level requirements, we propose a set of coin-cell parameters and testing conditions to expedite the discovery of new materials and their full integration into realistic battery systems.

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Lithium metal has been considered an ideal anode for high-energy rechargeable Li batteries, although its nucleation and growth process remains mysterious, especially at the nanoscale. Here, cryogenic transmission electron microscopy was used to reveal the evolving nanostructure of Li metal deposits at various transient states in the nucleation and growth process, in which a disorder-order phase transition was observed as a function of current density and deposition time. The atomic interaction over wide spatial and temporal scales was depicted by reactive molecular dynamics simulations to assist in understanding the kinetics. Compared to crystalline Li, glassy Li outperforms in electrochemical reversibility, and it has a desired structure for high-energy rechargeable Li batteries. Our findings correlate the crystallinity of the nuclei with the subsequent growth of the nanostructure and morphology, and provide strategies to control and shape the mesostructure of Li metal to achieve high performance in rechargeable Li batteries.

A flow cell based, bench-scale electrochemical system for generation of synthesis-gas (syn-gas) is reported. Sensitivity to operating conditions such as CO 2 flow, current density, and elevated temperature are described. By increasing the temperature of the cell the kinetic overpotential for the reduction of CO 2 was lowered with the cathode voltage at 70 mA cm -2 decreased by 0.32 V and the overall cell voltage dropping by 1.57 V. This equates to an 18% increase in cell efficiency. By closely monitoring the products it was found that at room temperature and 70°C the primary products are CO and H 2 . By controlling the current density and the flow of CO 2 it was possible to control the H 2 :CO product ratio between 1:4 and 9:1. The reproducibility of performing experiments at elevated temperature and the ability to generate syn-gas for extended periods of time is also discussed.

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