As Li-ion battery costs decrease, energy density and thus driving range remains a roadblock for mass-market vehicle electrification. While Li-metal anodes help achieve Department of Energy targets of 500 Wh kg−1 (750 Wh l−1), Li Coulombic efficiencies fall below the 99.95+% required for 1,000+ cycles. Here we examine historical electrolyte developments underlying increased Coulombic efficiency and discuss emerging frameworks that support rational strategies to move beyond 99.9%. While multiple electrolytes reach 98–99% Coulombic efficiency over subsets of cycles, achieving >99.9% Coulombic efficiency consistently throughout cycling is an as yet unmet challenge. We analyse important interplays between electrolyte, solid electrolyte interphase composition, plating–stripping kinetics and Li morphology, many of which are only recently being quantified experimentally at the Li interface, and which collectively determine Coulombic efficiency. We also discuss forward-looking strategies that, if mastered, represent new opportunities to refine understanding and support new record values of Coulombic efficiency in the coming years. Irreversibility is one of the biggest obstacles in realizing practical Li-metal batteries. This Review surveys the trends in Coulombic efficiency (CE)—a reversibility indicator—reported for Li-metal batteries over the last five decades, abstracts key CE descriptors and analyses promising strategies to improve CE.

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Moving beyond 99.9% Coulombic efficiency for lithium anodes in liquid electrolytes

Electrolyte solutions design for lithium-sulfur batteries

Zinc dendrite growth and inhibition strategies

The rapid advance of mild aqueous zinc-ion batteries (ZIBs) is driving the development of the energy storage system market. But the thorny issues of Zn anodes, mainly including dendrite growth, hydrogen evolution, and corrosion, severely reduce the performance of ZIBs. To commercialize ZIBs, researchers must overcome formidable challenges. Research about mild aqueous ZIBs is still developing. Various technical and scientific obstacles to designing Zn anodes with high stripping efficiency and long cycling life have not been resolved. Moreover, the performance of Zn anodes is a complex scientific issue determined by various parameters, most of which are often ignored, failing to achieve the maximum performance of the cell. This review proposes a comprehensive overview of existing Zn anode issues and the corresponding strategies, frontiers, and development trends to deeply comprehend the essence and inner connection of degradation mechanism and performance. First, the formation mechanism of dendrite growth, hydrogen evolution, corrosion, and their influence on the anode are analyzed. Furthermore, various strategies for constructing stable Zn anodes are summarized and discussed in detail from multiple perspectives. These strategies are mainly divided into interface modification, structural anode, alloying anode, intercalation anode, liquid electrolyte, non-liquid electrolyte, separator design, and other strategies. Finally, research directions and prospects are put forward for Zn anodes. This contribution highlights the latest developments and provides new insights into the advanced Zn anode for future research. 

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Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives

https://link.springer.com/content/pdf/10.1007/s40820-021-00782-5.pdf

Due to an ultrahigh theoretical specific capacity of 3860 mAh g-1, lithium (Li) is regarded as the ultimate anode for high-energy-density batteries. However, the practical application of Li metal anode is hindered by safety concerns and low Coulombic efficiency both of which are resulted fromunavoidable dendrite growth during electrodeposition. This study focuses on a critical parameter for electrodeposition, the exchange current density, which has attracted only little attention in research on Li metal batteries. A phase-field model is presented to show the effect of exchange current density on electrodeposition behavior of Li. The results show that a uniform distribution of cathodic current density, hence uniform electrodeposition, on electrode is obtained with lower exchange current density. Furthermore, it is demonstrated that lower exchange current density contributes to form a larger critical radius of nucleation in the initial electrocrystallization that results in a dense deposition of Li, which is a foundation for improved Coulombic efficiency and dendrite-free morphology. The findings not only pave the way to practical rechargeable Li metal batteries but can also be translated to the design of stable metal anodes, e.g., for sodium (Na), magnesium (Mg), and zinc (Zn) batteries.

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Insight into the Critical Role of Exchange Current Density on Electrodeposition Behavior of Lithium Metal

Lithium/fluorinated carbon (Li/CFx) batteries have received widespread attention due to their high specific energy density. However, the development of Li/CFx primary batteries is seriously hampere...

Jun Ban

Papers

Insight into the Critical Role of Exchange Current Density on Electrodeposition Behavior of Lithium Metal

All-Temperature, High-Energy-Density Li/CFx Batteries Enabled by a Fluorinated Ether as a Cosolvent

Promoted rate and cycling capability of Li–S batteries enabled by targeted selection of co-solvent for the electrolyte