Strategies to Improve the Performance of Li Metal Anode for Rechargeable Batteries

In Situ Engineering of Inorganic-Rich Solid Electrolyte Interphases via Anion Choice Enables Stable, Lithium Anodes

The discovery of liquid battery electrolytes that facilitate the formation of stable solid electrolyte interphases (SEIs) to mitigate dendrite formation is imperative to enable lithium anodes in next-generation energy-dense batteries. Compared to traditional electrolyte solvents, tetrahydrofuran (THF)-based electrolyte systems have demonstrated great success in enabling high-stability lithium anodes by encouraging the decomposition of anions (instead of organic solvent) and thus generating inorganic-rich SEIs. Herein, by employing a variety of different lithium salts (i.e., LiPF6, LiTFSI, LiFSI, and LiDFOB), it is demonstrated that electrolyte anions modulate the inorganic composition and resulting properties of the SEI. Through novel analytical time-of-flight secondary-ion mass spectrometry methods, such as hierarchical clustering of depth profiles and compositional analysis using integrated yields, the chemical composition and morphology of the SEIs generated from each electrolyte system are examined. Notably, the LiDFOB electrolyte provides an exceptionally stable system to enable lithium anodes, delivering >1500 cycles at a current density of 0.5 mAh g-1 and a capacity of 0.5 mAh g-1 in symmetrical cells. Furthermore, Li//LFP cells using this electrolyte demonstrate high-rate, reversible lithium storage, supplying 139 mAh g(LFP) -1 at C/2 (≈0.991 mAh cm-2 , @ 0.61 mA cm-2 ) with 87.5% capacity retention over 300 cycles (average Coulombic efficiency >99.86%).

Improving the Mg Sacrificial Anode in Tetrahydrofuran for Synthetic Electrochemistry by Tailoring Electrolyte Composition

Mg0 is commonly used as a sacrificial anode in reductive electrosynthesis. While numerous methodologies using a Mg sacrificial anode have been successfully developed, the optimization of the electrochemistry at the anode, i.e., Mg stripping, remains empirical. In practice, electrolytes and organic substrates often passivate the Mg electrode surface, which leads to high overall cell potential causing poor energy efficiency and limiting reaction scale-up. In this study, we seek to understand and manipulate the Mg metal interfaces for a more effective counter electrode in tetrahydrofuran. Our results suggest that the ionic interactions between the cation and the anion of a supporting electrolyte can influence the electrical double layer, which impacts the Mg stripping efficiency. We find halide salt additives can prevent passivation on the Mg electrode by influencing the composition of the solid electrolyte interphase. This study demonstrates that, by tailoring the electrolyte composition, we can modify the Mg stripping process and enable a streamlined optimization process for the development of new electrosynthetic methodologies.

Self-Healing Polymer Electrolytes for Next-Generation Lithium Batteries

The integration of polymer materials with self-healing features into advanced lithium batteries is a promising and attractive approach to mitigate degradation and, thus, improve the performance and reliability of batteries. Polymeric materials with an ability to autonomously repair themselves after damage may compensate for the mechanical rupture of an electrolyte, prevent the cracking and pulverization of electrodes or stabilize a solid electrolyte interface (SEI), thus prolonging the cycling lifetime of a battery while simultaneously tackling financial and safety issues. This paper comprehensively reviews various categories of self-healing polymer materials for application as electrolytes and adaptive coatings for electrodes in lithium-ion (LIBs) and lithium metal batteries (LMBs). We discuss the opportunities and current challenges in the development of self-healable polymeric materials for lithium batteries in terms of their synthesis, characterization and underlying self-healing mechanism, as well as performance, validation and optimization.

Constructing Bimetallic ZIF-Derived Zn,Co-Containing N-Doped Porous Carbon Nanocube as the Lithiophilic Host to Stabilize Li Metal Anodes in Li-O2 Batteries

Li metal, because of its ultrahigh theoretical capacity, has attracted extensive attention. However, uncontrollable dendritic Li formation and infinite electrode dimensional variation hinder application of Li anodes. Herein, Zn,Co bimetallic zeolitic imidazolate frameworks (ZIFs) were synthesized and further pyrolyzed to obtain Zn,Co-containing N-doped porous carbon nanocube (Zn/Co-N@PCN), which was further applied as lithiophilic host to construct the lithiated Zn/Co-N@PCN (Li-Zn/Co-N@PCN). Zn vapor produced many pores on the carbon framework during calcination process that could store enough Li and thus inhibit the huge electrode volume change. Additionally, there were abundant lithiophilic groups in Zn/Co-N@PCN, such as N- or Co/Zn-based species, which were beneficial to uniform Li deposition. Moreover, the stable and conductive carbon-based matrix could ensure superior and reproducible Li plating/stripping behavior in Zn/Co-N@PCN over cycling. As a result, the Li-Zn/Co-N@PCN anode showed a steady and high columbic efficiency of around 99.0 % for 600 cycles at 0.5 mA cm^-2 . The Li-Zn/Co-N@PCN-based Li-O₂ battery could continuously work beyond 200 cycles, superior to a cell with a Li-Cu anode. These results in this work provide a novel way for construction of the advanced Li-based anodes and the corresponding high-performance Li-O₂ batteries.

Uniform Deposition of Li-Metal Anodes Guided by 3D Current Collectors with In Situ Modification of the Lithiophilic Matrix

The lithium (Li)-metal anode is deemed as the "holy gray" of the next-generation Li-metal system because of its high theoretical specific capacity, minimal energy density, and lowest standard electrode potential. Nevertheless, its commercial application has been limited by the large volume variation during charge and discharge, the unstable interface between the Li metal and electrolyte, and uneven deposition of Li. Herein, we present a 3D host (Cu) with lithiophilic matrix (CuO and SnO₂) in situ modification via a facile ammonia oxidation method to serve as a current collector for the Li-metal anode. The 3D Cu host embellished by CuO and SnO₂ is abbreviated as 3D CSCC. By increasing interfacial activity, lowering the nucleation barrier, and accommodating changes in volume of the Li metal, the 3D CSCC electrode effectively demonstrates a homogeneous and dendrite-free deposition morphology with an excellent cycling performance up to 3000 h at a 1.0 mA cm^-2 current density. Additionally, the full cells paired with Li@3D CSCC anodes and LiCoO₂ cathodes show good capacity retention performance at 0.2 C.