Lithium-Anode Protection in Lithium–Sulfur Batteries Chong Yan, Xue-Qiang Zhang, Jia-Qi Huang, Quanbing Liu, Qiang Zhang  Trends in Chemistry  DOI: 10.1016/j.trechm.2019.06.007 Copyright © 2019 Elsevier Inc. Terms and Conditions

Figure 1 The Configuration and Failure Mechanism of a Lithium–Sulfur (Li–S) Pouch Cell. (A) The internal components of a pouch cell are configured with folded units, including cathodes, anodes, a separator, and aluminum current collectors. (B) The depletion of liquid electrolytes and the powdering of lithium foil are the direct factors resulting in failure of pouch cells; the sulfur cathode incurs only slight damage and can work well when matched with fresh electrolyte and anode. Reprinted, with permission, from [47]. Trends in Chemistry DOI: (10.1016/j.trechm.2019.06.007) Copyright © 2019 Elsevier Inc. Terms and Conditions

Figure 2 A Brief Timeline Summarizing the Development of the Lithium–Sulfur (Li–S) Battery. The whole process was divided into three stages, mainly including: (i) how to cycle the Li–S battery (1970–2002); (ii) how to improve the cathode (2002–2014); and (iii) how to protect the anode (2014–present). In the first stage, the most important concept was finding desirable electrolytes. Liquid electrolytes (e.g., DOL, DME, TEGDME, DMSO) and polymer electrolytes (e.g., PEO, PVDF-HFP) were explored and are still used today. In the second stage, the appearance of nanostructured C/S and S-SPAN cathodes as well lithium nitrate enabled longer service life of coin Li–S batteries. In the third stage, the lithium-metal anode has become the bottleneck for long-cycle-life pouch cells; how to protect the anode is now the most important subject. See also [1,4–14,26–31,39,47,54,57,63,71,75,91]. Trends in Chemistry DOI: (10.1016/j.trechm.2019.06.007) Copyright © 2019 Elsevier Inc. Terms and Conditions

Figure 3 Molecular Simulations Revealing the Interactions of Li+ Ions with Solvating Molecules. (A) Ab initio molecular dynamics of the polysulfide species coordinated with dimethyl ether (DME) and 1,3-dioxolane (DOL). The distribution peak of DME (at ~0.16 nm) closer to the Li ion than the DOL molecule (at ~0.3 nm) confirms that the coordination of DME bidentate to the Li ion retains a relatively stable solvation structure. (B) Molecular simulations on the solvation structure of the Li ions with DOL and DME; the solvent−solute interactions are between the oxygen atoms from both solvents and the Li+ ions from the polysulfide species. Reprinted, with permission, from [55,56]. Trends in Chemistry DOI: (10.1016/j.trechm.2019.06.007) Copyright © 2019 Elsevier Inc. Terms and Conditions

Figure 4 The Sulfurized and Nitridized Artificial Solid Electrolyte Interphase (SEI) That Is Prepared via the Electrochemical Method. Li metal with a stable SEI can be transplanted into ether and ester electrolytes to efficiently cycle sulfur and LiNi0.5Co0.2Mn0.3O2 cathodes, respectively. Reprinted, with permission, from [63]. Trends in Chemistry DOI: (10.1016/j.trechm.2019.06.007) Copyright © 2019 Elsevier Inc. Terms and Conditions

Figure 5 X-Ray Photoelectron Spectroscopy (XPS) Spectra for a Pristine Sample and after Lithium-Metal Deposition (for Comparison). Unique interfacial structures and components can be reformed at the interface. Reprinted, with permission, from [82]. Trends in Chemistry DOI: (10.1016/j.trechm.2019.06.007) Copyright © 2019 Elsevier Inc. Terms and Conditions

Figure 6 Conductive Lithiophilic Micro/Nanostructured Framework Can Guide the Deposition of Li Due to Its Ag Particles and Interconnected Network. Such an electrode design renders dendrite-free morphology during repeated stripping/plating cycles and extraordinary electrochemical performance in Li–LiFePO4 and Li–S cells. Reprinted, with permission, from [92]. Trends in Chemistry DOI: (10.1016/j.trechm.2019.06.007) Copyright © 2019 Elsevier Inc. Terms and Conditions

Figure 7 A Schematic of a Lithium–Sulfur (Li–S) Battery Including a Prelithiated Graphite Framework Covering a Stable Solid Electrolyte Interphase (SEI) Layer to Maintain a Long Battery Lifespan. Reprinted, with permission, from [98]. DOL, 1,3-dioxolane; BTFE, bis(2,2,2-trifluoroethyl) ether. Trends in Chemistry DOI: (10.1016/j.trechm.2019.06.007) Copyright © 2019 Elsevier Inc. Terms and Conditions