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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. 

Abstract A stable lean‐electrolyte operating lithium–sulfur (Li–S) battery based on a cathode of Li₂S in situ electrocatalytically deposited from L₂S₈catholyte onto a support of metallic molybdenum disulfide (1T‐MoS₂) on carbon cloth (CC) is created. The 1T‐MoS₂significantly accelerates the conversion Li₂S₈catholyte to Li₂S, chemically adsorbs lithium polysulfide (LiPSs) from solution, and suppresses crossover of the LiPSs to the anode. These experimental findings are explained by density functional theory calculations that show that 1T‐MoS₂gives rise to strong adsorption of polysulfides on its surface and is electrocatalytic for the targeted reversible Li–S conversion reactions. The CC/1T‐MoS₂electrode in a Li–S battery delivers an initial capacity of 1238 mAh g⁻¹, with a low capacity fade of only 0.051% per cycle over 500 cycles at 0.5C. Even at a high sulfur loading (4.4 mg cm⁻²) and low electrolyte/S (E/S) ratio of 3.7 µL mg⁻¹, the battery achieves an initial reversible capacity of 1176 mA h g⁻¹at 0.5C, with 87% capacity retention after 160 cycles. The post 500 cycles Li metal opposing 1T‐MoS₂is substantially smoother than the Li opposing CC, with XPS supporting the role of 1T‐MoS₂in inhibiting LiPSs crossover.