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1. Concentrated ternary ether electrolyte allows for stable cycling of a lithium metal battery with commercial mass loading high‐nickel NMC and thin anodes

   https://doi.org/10.1002/cey2.275  

   Yang, Jun; Li, Xing; Qu, Ke; Wang, Yixian; Shen, Kangqi; Jiang, Changhuan; Yu, Bo; Luo, Pan; Li, Zhuangzhi; Chen, Mingyang; et al (March 2023, Carbon Energy)

   Abstract A new concentrated ternary salt ether‐based electrolyte enables stable cycling of lithium metal battery (LMB) cells with high‐mass‐loading (13.8 mg cm⁻², 2.5 mAh cm⁻²) NMC622 (LiNi_0.6Co_0.2Mn_0.2O₂) cathodes and 50 μm Li anodes. Termed “CETHER‐3,” this electrolyte is based on LiTFSI, LiDFOB, and LiBF₄with 5 vol% fluorinated ethylene carbonate in 1,2‐dimethoxyethane. Commercial carbonate and state‐of‐the‐art binary salt ether electrolytes were also tested as baselines. With CETHER‐3, the electrochemical performance of the full‐cell battery is among the most favorably reported in terms of high‐voltage cycling stability. For example, LiNi_xMn_yCo_1–x–yO₂(NMC)‐Li metal cells retain 80% capacity at 430 cycles with a 4.4 V cut‐off and 83% capacity at 100 cycles with a 4.5 V cut‐off (charge at C/5, discharge at C/2). According to simulation by density functional theory and molecular dynamics, this favorable performance is an outcome of enhanced coordination between Li⁺and the solvent/salt molecules. Combining advanced microscopy (high‐resolution transmission electron microscopy, scanning electron microscopy) and surface science (X‐ray photoelectron spectroscopy, time‐of‐fight secondary ion mass spectroscopy, Fourier‐transform infrared spectroscopy, Raman spectroscopy), it is demonstrated that a thinner and more stable cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) are formed. The CEI is rich in lithium sulfide (Li₂SO₃), while the SEI is rich in Li₃N and LiF. During cycling, the CEI/SEI suppresses both the deleterious transformation of the cathode R‐3m layered near‐surface structure into disordered rock salt and the growth of lithium metal dendrites. 

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2. Understanding Cathode–Electrolyte Interphase Formation in Solid State Li‐Ion Batteries via 4D‐STEM

   https://doi.org/10.1002/aenm.202403904  

   Paranamana, Nikhila C; Werbrouck, Andreas; Datta, Amit K; He, Xiaoqing; Young, Matthias J (December 2024, Advanced Energy Materials)

   Abstract Interphase layers that form at contact points between the solid electrolyte (SE) and cathode active material in solid‐state lithium‐ion batteries (SS‐LIBs) increase cell impedance, but the mechanisms for this interphase formation are poorly understood. Here, we demonstrate a simple workflow to study cathode–electrolyte interphase (CEI) formation using 4D‐scanning transmission electron microscopy (4D‐STEM) that does not require SS‐LIB assembly. We show benefits of MoCl₅:EtOH as a chemical delithiating agent, and prepare chemically delithiated cathode LiNi_0.6Co_0.2Mn_0.2O₂(NMC) powder in contact with Li₁₀GeP₂S₁₂(LGPS) SE powder as a SS‐LIB CEI surrogate. We map the composition and structure of the CEI layers using 4D‐STEM, energy dispersive X‐ray spectroscopy (EDS), and electron pair distribution function analysis (ePDF). EDS indicates O migration from NMC into LGPS. ePDF analysis indicates sulfate and phosphate formation localized on the surface of LGPS, as well as Li₂O formation within the LGPS phase, and self‐decomposition of NMC. These results are consistent with an electrochemical self‐discharge mechanism for interphase formation arising from coupled redox reactions of sulfur oxidation in LGPS and transition metal reduction in NMC. This suggests that coatings which stop anion transport but allow Li⁺and e⁻transport may prevent interphase formation and reduce impedance in SS‐LIBs. 

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3. Stable metal anodes enabled by a labile organic molecule bonded to a reduced graphene oxide aerogel

   https://doi.org/10.1073/pnas.2001837117  

   Gao, Yue; Wang, Daiwei; Shin, Yun Kyung; Yan, Zhifei; Han, Zhuo; Wang, Ke; Hossain, Md Jamil; Shen, Shuling; AlZahrani, Atif; van Duin, Adri C.; et al (December 2020, Proceedings of the National Academy of Sciences)

   null (Ed.)

   Metallic anodes (lithium, sodium, and zinc) are attractive for rechargeable battery technologies but are plagued by an unfavorable metal–electrolyte interface that leads to nonuniform metal deposition and an unstable solid–electrolyte interphase (SEI). Here we report the use of electrochemically labile molecules to regulate the electrochemical interface and guide even lithium deposition and a stable SEI. The molecule, benzenesulfonyl fluoride, was bonded to the surface of a reduced graphene oxide aerogel. During metal deposition, this labile molecule not only generates a metal-coordinating benzenesulfonate anion that guides homogeneous metal deposition but also contributes lithium fluoride to the SEI to improve Li surface passivation. Consequently, high-efficiency lithium deposition with a low nucleation overpotential was achieved at a high current density of 6.0 mA cm −2 . A Li|LiCoO 2 cell had a capacity retention of 85.3% after 400 cycles, and the cell also tolerated low-temperature (−10 °C) operation without additional capacity fading. This strategy was applied to sodium and zinc anodes as well. 

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4. Tailoring Ion Transport in Li _3‐3y Ho _1+y Cl _6‐x Br _x via Transition‐Metal Free Structural Planes and Charge Carrier Distribution

   https://doi.org/10.1002/advs.202409668  

   Ogbolu, Bright O; Poudel, Tej P; Dikella, Thilina_N_D D; Truong, Erica; Chen, Yudan; Hou, Dewen; Li, Tianyi; Liu, Yuzi; Gabriel, Eric; Xiong, Hui; et al (February 2025, Advanced Science)

   Abstract Localized atomistic disorder in halide‐based solid electrolytes (SEs) can be leveraged to boost Li⁺mobility. In this study, Li⁺transport in structurally modified Li₃HoCl₆, via Br⁻introduction and Li⁺deficiency, is explored. The optimized Li_3‐3yHo_1+yCl_6‐xBr_xachieves an ionic conductivity of 3.8 mS cm⁻¹at 25 °C, the highest reported for holmium halide materials.^6,7Li nuclear magnetic resonance and relaxometry investigations unveil enhanced ion dynamics with bromination, attaining a Li⁺motional rate neighboring 116 MHz. X‐ray diffraction analyses reveal mixed‐anion‐induced phase transitions with disproportionate octahedral expansions and distortions, creating Ho‐free planes with favorable energetics for Li⁺migration. Bond valence site energy analysis highlights preferred Li⁺transport pathways, particularly in structural planes devoid of Ho³⁺blocking effects. Molecular dynamics simulations corroborate enhanced Li⁺diffusion with Br⁻introduction into Li₃HoCl₆. Li‐Ho electrostatic repulsions in the (001) plane presumably drive Li⁺diffusion into the Ho‐free (002) layer, enabling rapid intraplanar Li⁺motion and exchange between the 2d and 4h sites. Li_3‐3yHo_1+yCl_6‐xBr_xalso demonstrates good battery cycling stability. These findings offer valuable insights into the intricate correlations between structure and ion transport and will help guide the design of high‐performance fast ion conductors for all‐solid‐state batteries. 

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5. Oxygen‐Induced Structural Disruption for Improved Li ⁺ Transport and Electrochemical Stability of Li ₃ PS ₄

   https://doi.org/10.1002/aenm.202302785  

   Deck, Michael J.; Chien, Po‐Hsiu; Poudel, Tej P.; Jin, Yongkang; Liu, Haoyu; Hu, Yan‐Yan (January 2024, Advanced Energy Materials)

   Abstract The performance of all‐solid‐state batteries (ASSBs) relies on the Li⁺transport and stability characteristics of solid electrolytes (SEs). Li₃PS₄is notable for its stability against lithium metal, yet its ionic conductivity remains a limiting factor. This study leverages local structural disorder via O substitution to achieve an ionic conductivity of 1.38 mS cm⁻¹with an activation energy of 0.34 eV for Li₃PS_4−xO_x(x = 0.31). Optimal O substitution transforms Li⁺transport from 2D to 3D pathways with increased ion mobility. Li₃PS_3.69O_0.31exhibits improvements in the critical current density and stability against Li metal and retains its electrochemical stability window compared with Li₃PS₄. The practical implementation of Li₃PS_3.69O_0.31in ASSBs half‐cells, particularly when coupled with TiS₂as the cathode active material, demonstrates substantially enhanced capacity and rate performance. This work elucidates the utility of introducing local structural disorder to ameliorate SE properties and highlights the benefits of strategically combining the inherent strengths of sulfides and oxides via creating oxysulfide SEs. 

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