Stabilizing Lithium-Sulfur Cells with Practical Loading and Cycling Conditions Using Li₂S₈-Containing Ethereal Electrolyte Solution

Abstract

We report on stabilization of Li–S cells cycled with an areal charge/discharge capacity of 2 mAh cm−2 at current densities of 1–2 mA cm−2 using ethereal LiTFSI/LiNO3/DOL/DME electrolyte solution containing 0.1M Li2S8. This electrolyte solution enables stable lithium metal stripping−plating both in symmetric Li∣Li and full Li–S cells with composite binder free sulfur impregnated activated carbon fibers cathodes. The addition of Li2S8 substantially extends cycling life of these cells due to the formation of smooth non-dendritic Li metal surface protected with an effective SEI enriched with Li sulfides, sulfites and sulfates species. Symmetric Li∣Li could be cycled stably for more than 1000 h at 1–2 mA cm−2 with Li2S8-containing electrolyte solutions. Full Li–S cells demonstrate more than 500 stable cycles (at least 3 times more than with Li2S8 free electrolyte solution) at a current density of 1 mA cm−2 and an areal capacity of 2 mAh cm−2. The most stable cycling results were achieved for the cells cycled with discharge cut off voltage of 1.9 V preventing the depletion of LiNO3. The use of electrolyte solutions containing liquid lithium poly-sulfides makes possible considerable decrease in the amount of the electrolyte solution and increases the energy density of the cells.

Uniform Deposition and Effective Confinement of Lithium in Three-Dimensional Interconnected Microchannels for Stable Lithium Metal Anodes

“…XPS depth profiling shown in Figure S14 and emergence of the Ti 2p peaks after sputtering indicate that the electrode surface is covered by a SEI layer. The XPS spectra (Figure S15) suggest that the SEI layer on top of the HTCNF-2 is composed of RCH 2 OLi, −(CH 2 CH 2 O) n –, ROCO 2 Li, LiF, Li–N, N–O, S–O, and so on, − in agreement with the STEM-EDS elemental maps in Figure g.…”

High-Coulombic-Efficiency Lithium Metal Anodes Enabled by Three-Dimensional Lithiophilic Nanostructures with Multiscale Porosity

“…In addition, the NiO/Ni/CC matrix gives rise to uniform Li depletion after 200th Li stripping (Figures S14 and S15) and maintains the original architecture of carbon fibers covered by 3D interlaced porous nanobranches. TEM images and XPS characterization show that the nanoparticles are covered by a continuous SEI layer composed of -(CH 2 CH 2 O) n -, RCH 2 OLi, ROCO 2 Li, Li–N, N–O, LiF, S–O, and so on. − These results prove that the superlithiophilic Li 2 O sites on the 3D framework and the multisacle pores promise a stable Li plating and stripping behavior at high current densities, alleviating formation of dead Li and limited volume expansion during the repeated cycling.…”

An Improved Cycling Performance of Different Types of Composite Sulfur-Carbon Cathodes with the Use of Lithium Polysulfides Containing Electrolyte Solutions

“…In our previous work we demonstrated enhanced cycling stability of composite S-carbon cathodes prepared with binder free activated microporous carbon cloth when the electrolyte solutions contained LPSs. 20 It is important to emphasize that that positive effect of LPS an additive is relevant when it presents in solutions a-priori, when Li is brought in contact with the electrolyte solutions at the first time. In such circumstances, the presence of LPS affects dominantly and positively the surface chemistry of the Li anodes (leading for the improved performance).…”

“…19 In our recent work we demonstrated the positive effect of the initial presence of Li 2 S 8 as an additive in standard electrolyte solutions (comprising DOL,DME, LiTFSI and LiNO 3 ) on the stability and cycling efficiency of both Li|Li symmetric and full Li-S cells cycled with practical cycling parameters (in terms of areal loading of electrodes, 100% DOD, high current densities and a minimal content of the electrolyte solution in the cells). 20 With the aim to exclude the effect of different components of composite sulfur cathodes on the obtained results we used model binder free composite S/carbon electrodes. The initial presence of LPS in solution as an additive was shown to allow decreasing the amount of the electrolyte solution in the cells, yet keeping their cycling performance.…”