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

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_(0.6)Co_(0.2)Mn_(0.2)O_(2))cathodes and 50μm Li anodes.Termed“CETHER-3,”this electrolyte is based on LiTFSI,LiDFOB,and LiBF4 with 5 vol%fluorinated ethylene carbonate in 1,2-dimethoxyethane.Commer-cial 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_(x)Mn_(y)Co_(1-x-y)O_(2)(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(Li_(2)SO_(3)),while the SEI is rich in Li_(3)N 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.

Efficient Catalytic Conversion of Polysulfides by Biomimetic Design of “Branch‑Leaf” Electrode for High‑Energy Sodium–Sulfur Batteries

Rechargeable room temperature sodium–sulfur(RT Na–S)batteries are seriously limited by low sulfur utilization and sluggish electrochemical reaction activity of polysulfide intermediates.Herein,a 3D“branch-leaf”biomimetic design proposed for high performance Na–S batteries,where the leaves constructed from Co nanoparticles on carbon nanofibers(CNF)are fully to expose the active sites of Co.The CNF network acts as conductive“branches”to ensure adequate electron and electrolyte supply for the Co leaves.As an effective electrocatalytic battery system,the 3D“branch-leaf”conductive network with abundant active sites and voids can effectively trap polysulfides and provide plentiful electron/ions pathways for electrochemical reaction.DFT calculation reveals that the Co nanoparticles can induce the formation of a unique Co–S–Na molecular layer on the Co surface,which can enable a fast reduction reaction of the polysulfides.Therefore,the prepared“branch-leaf”CNF-L@Co/S electrode exhibits a high initial specific capacity of 1201 mAh g^−1 at 0.1 C and superior rate performance.