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A major challenge of lithium metal electrodes, in theory a suitable choice for rechargeable high energy density batteries, comprises non-homogeneous lithium deposition and the growth of reactive high surface area lithium, which eventually yields active material losses and safety risks. While it is hard to fully avoid inhomogeneous deposits, the achievable morphology of the occurring lithium deposits critically determines the long-term cycling behaviour of the cells. In this work, we focus on a combined scanning electron microscopy (SEM) and 7Li nuclear magnetic resonance spectroscopy (7Li-NMR) study to unravel the impact of the choice of conducting salts (LiPF6 and LiTFSI), solvents (EC : DEC, 3 : 7, DME : DOL, 1 : 1), as well as their respective concentrations (1 M, 3 M) on the electrodeposition process, demonstrating that lithium deposition morphologies may be controlled to a large extent by proper choice of cycling conditions and electrolyte constituents. In addition, the applicability of 7Li-NMR spectroscopy to assess the resulting morphology is discussed. It was found, that lithium deposition analysis based on the 7Li chemical shift and intensity should be used carefully, as various morphologies can lead to similar results. Still, our case study reveals that the combination of SEM and NMR data is rather advantageous and offers complementary insights that may provide pathways for the future design of tailored electrolytes. [ABSTRACT FROM AUTHOR]

PEO-based solid polymer electrolytes typically show limited capability for the suppression of Li metal dendrites, which is mainly attributed to their low mechanical strength. To tackle this issue, we improved the mechanical strength of a ternary solid polymer electrolyte (TSPE: PEO-LiTFSI-Pyr14TFSI) by integratingCelgard 2500 separator as a high modulus domain. The Celgard-reinforced TSPE (CgTSPE) presents a significantly higher elastic modulus (223MPa) than TSPE (0.2MPa) at 60°C, which in result leads tomore lithium anode utilization. Specifically, the Columbic efficiency of Li electrodeposition/dissolution during cycling in Li|CgTSPE|Cu cells (90%) is distinctly higher than in Li|TSPE|Cu (30%). Furthermore, the cycling of Li||Li symmetric cells with CgTSPE displays an improved cycling stability, due to the presence of Celgard, in which high surface area lithium (HSAL), e.g., dendrite formation is suppressed. Operando electrochemical dilatometry (ECD) analysis as well as post mortem surface analysis with SEM reveal the formation of "dead lithium" and cavities under an areal capacity utilization of 5 mAh/cm2. It is also suggested by the cycling behavior of the Li||Li cell with high areal capacity utilization that lithium surface treatment is required to completely eliminate the formation of "dead lithium" and of cavities. [ABSTRACT FROM AUTHOR]

Lithium-powder electrodes, prepared via paste casting method using lithium powder and polyisobutylene (PIB) as a binder, were investigated for their electrochemical properties in lithium-metal cells. The electrode paste casting method allows preserving the spherical shape of lithium-powder particles during processing to electrodes. However, these lithium-powder based electrodes suffer from poor active material utilization, as electronic isolation of lithium particles during the lithium electrodissolution process was observed to occur. In order to improve the lithium inter-particle contact as well as the contact with the current collector, a simple and effective chemical modification of the lithium-powder based electrodes was considered. Using a cementation reaction with ZnI2, the growth of a Li-Zn intermetallic ("alloy") between the lithium-powder particles and the surface of the lithium powder, lead to an increase of the active material utilization and overcame the side reactions due to lithium electrodissolution. Besides increasing the active material utilization, such simple chemical modification of the lithium-powder based electrodes improved the electrochemical performance resulting in more stable cycling behavior with low polarization and longer cycle life in both LiǁLi-symmetric and LiǁNMC 622 cells. [ABSTRACT FROM AUTHOR]

Without lithium ion batteries todays society is not imaginable. Mobile phones, notebooks, tablet PCs, photo cameras or handheld consoles, all these battery powered devices equipment have become essential for our daily lives. Only the high energy density, the proven reliability and the long life of the lithium ion battery (LIB) technology make it possible, to operate portable consumer electronics devices in that manner that we are used to. LIBs are also considered for application in electro mobility and for stationary storage of renewable energy. Here significant advances in R&D as well as in application have been made in the last years, and the expectations for the future of this technology are still growing. Can the LIB or an alternative battery system fulfill these expectations? Will there be a new 'super battery' chemistry? Are there new fields of research in battery chemistry and - technology for tomorrow and where?. These questions will be addressed by two articles on 'High energy density accumulators'. [ABSTRACT FROM AUTHOR]

The effect of mechanical surface modification on the performance of lithium (Li) metal foil electrodes is systematically investigated. The applied micro-needle surface treatment technique for Li metal has various advantages. 1) This economical and efficient technique is able to cover a wide range of surface area with a simple rolling process, which can be easily conducted. 2) This technique achieves improved rate capability and cycling stability, as well as a reduced interfacial resistance. The micro-needle treatment improves the rate capability by 20% (0.750 mAh at a rate of 7C) and increases the cycling stability by 200% (85% of the initial discharge capacity after 150 cycles) compared to untreated bare Li metal (0.626 mAh at a rate of 7C, 85% of the initial discharge capacity after only 70 cycles). 3) This technique efficiently suppresses Li formation of high surface area Li during the Li deposition process, as preferred sites for controlled Li plating are generated. [ABSTRACT FROM AUTHOR]

Safety issues caused by the metallic lithium inside a battery represent one of the main reasons for the lack of commercial availability of rechargeable lithium-metal batteries. The advantage of anodes based on coated lithium powder (CLiP), compared to plain lithium foil, include the suppression of dendrite formation, as the local current density during stripping/plating is reduced due to the higher surface area. Another performance and safety advantage of lithium powder is the precisely controlled mass loading of the lithium anode during electrode preparation, giving the opportunity to avoid Li excess in the cell. As an additional benefit, the coating makes electrode manufacturing safer and eases handling. Here, electrodes based on coated lithium powder electrodes (CLiP) are introduced for application in lithium-metal batteries. These electrodes are compared to lithium foil electrodes with respect to cycling stability, coulombic efficiency of lithium stripping/plating, overpotential, and morphology changes during cycling. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries are still characterized by the low intrinsic electronic conductivity of sulfur in both its charged state (S8) as well as discharged state (Li2S). Here, using ball milling, a well‐dispersed active material within the carbon network is achieved using carbon black Super C65 and synthetic graphite KS6 as conductive agents. Calendering these electrodes increases the electronic percolation path resulting in enhanced electrochemical performances and reaction kinetics. Using high‐speed and high‐impact preparation methods improves the quality and performances of the S8/C composite electrodes when compared with electrodes prepared using a simple mixing method (magnetic stirring). The scanning electron microscopy images indicate that KS6 is able to incase S8 particles, resulting in a homogeneous distribution of the active material that in turn enhances the accessibility of the active material by the electrolyte and electrons. Compared with the S8/Super C65 composite electrode, a discharge capacity of 703 mAh g−1 is delivered by the S8/KS6 composite electrode during the first cycle. After 30 cycles, the S8/KS6 composite electrode delivers 477 mAh g−1 compared to only 411 mAh g−1 for the S8/Super C65 composite electrode due to a continuous capacity fading. [ABSTRACT FROM AUTHOR]

Electrically rechargeable zinc-air batteries attract extensive research interests due to their potentially high energy density and low cost but suffer from chemical instability and poor electrochemical reversibility caused by the corrosive nature of the conventional alkaline electrolyte. Here we demonstrate a non-alkaline zinc acetate electrolyte for electrically rechargeable zinc-air batteries with long-term operation stability (>600 hours) in ambient air without any special cell engineering. The unique battery chemistry with reversible formation/decomposition of zinc hydroxyacetate dihydrate is systematically revealed using diversified electrochemical and analytical techniques. Furthermore, the carbon-based air cathode is modified towards a hydrophilic surface to increase the energy efficiency. This work provides new insight on effective electrolyte design to achieve long-term operation zinc-air batteries., (© 2022 Wiley-VCH GmbH.)

Li metal batteries (LMBs) containing cross-linked polymer electrolytes (PEs) are auspicious candidates for next-generation batteries. However, the wetting behavior of PEs on uneven Li metal surfaces has been neglected in most studies. Herein, it is shown that microscale defect sites with curved edges play an important role in a wettability-dependent electrodeposition. The wettability and the viscoelastic properties of PEs are correlated, and the impact of wettability on the nucleation and diffusion near the Li|PE interface is distinguished. It is found that the curvature of the edges is a key factor for the investigation of wetting phenomena. The appearance of microscale defects and phase separation are identified as main causes for erratic nucleation. It is emphasized that the implementation of stable and consistent long-term cycling performance of LMBs using PEs requires a deeper understanding of the "soft-solid"-solid contact between PEs and inherently rough Li metal surfaces., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

In many Mg-based battery systems, the reversibility of Mg deposition and dissolution is lowered by parasitic formation processes of the electrolyte. Therefore, high Coulombic efficiencies of Mg deposition and dissolution are only achieved after several "conditioning" cycles. As this phenomenon is especially reported for AlCl 3 -containing solutions, this study focuses on the "conditioning" mechanisms of MgCl 2 /AlCl 3 and MgHMDS 2 /AlCl 3 (HMDS = hexamethyldisilazide) in tetraethylene glycol dimethyl ether (TEGDME)-based electrolytes. Electrochemical (cyclic voltammetry) and spectroscopic investigations ( 27 Al nuclear magnetic resonance spectroscopy, Raman spectroscopy, inductively coupled plasma optical emission spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy) reveal that cationic AlCl 2 + species in TEGDME-based electrolytes with an AlCl 3 /MgCl 2 ratio higher than 1:1 corrode the Mg metal. According to a cementation reaction mechanism, the corrosion of Mg is accompanied with Al deposition. In effect, the consumption of Mg results in low Coulombic efficiencies of Mg deposition and dissolution during the electrolyte "conditioning". After understanding the mechanism of this process, we demonstrate that a careful adjustment of the stoichiometry in MgCl 2 /AlCl 3 and MgHMDS 2 /AlCl 3 in TEGDME formulations prevents Mg corrosion and results in "conditioning"-free, highly efficient Mg deposition and dissolution.