Natural Lepidolite Enables Fast Polysulfide Redox for High‐Rate Lithium Sulfur Batteries

Abstract

ideally stores five times more energy per mass (1675 mAh g −1 ) than intercalationtype cathodes by multielectron reactions of sulfur, namely S 8 + 16 e − + 16 Li + ⇌ 8 Li 2 S, [8,9] and leads to extensive researches on Li-S batteries.Nevertheless, the development of Li-S batteries is plagued by three issues: (1) the sluggish electrical conductivities of sulfur (σ = 5 × 10 −30 S cm −1 ) and its end products (Li 2 S, σ = 1 × 10 −13 S cm −1 ) lead to slow conversion from soluble lithium polysulfides (LiPSs, namely Li 2 S x , 4 ≤ x ≤ 8) to solid Li 2 S 2 /Li 2 S; (2) the hydrophilic LiPS species are inclined to shuttle through porous separator and deposit at Li anode as Li 2 S which is difficult to be reused owing to the high activation energy [10][11][12][13] ; (3) the shuttling effect of polysulfides causes severe self-discharge, continuous energy loss and unsatisfactory energy density. [14][15][16] Reconstructing separators architecture is an effective strategy to ameliorate the aforementioned issues. [17][18][19] Carbon materials with a high specific surface area are introduced to the separator surface to physically block LiPS and accelerate its conversion due to the high conductivity (σ = 9 × 10 1 -5 × 10 3 S m −1 ), [20] but porous carbon shows limited capability to confine LiPS owing to the feeble van der Waals adsorption. [21,22] Polar compounds, such as metal compounds (MA, where M is metal, and A is oxygen, nitrogen, or sulfur), are promising materials to bond to LiPS through surface M-S or A-Li bonding, which prevents the shuttling effect and changes the reduction pathway of LiPS with decreased the redox energy barrier. [23,24] However, the strong A-Li bonding of ≈2 eV impedes Li + ion transport which delays the reaction kinetics of LiPSs. [25] In addition, most of them own complex design processes. [26] Recent studies show that the low cost and natural abundance lamellar clays own much lower Li-ion diffusion barrier (such as lithium-montmorillonite (0.15 eV), MA materials (ZnS (0.494 eV), MgO (0.45 eV), Al 2 O 3 (1.22 eV), and CeO 2 (0.66eV)), [27,28] which allows free lithium-ion diffusion in the sulfur cathode and gives rise to improved electrochemical performances of Li-S batteries. Unfortunately, these lamellar clays modified structures still show unsatisfactory rate performances for practical application. [29] Hence, it is necessary to further develop optimized lamellar clays structure for high-rate Li-S batteries.

Regulating the Molecular Interactions in Polymer Binder for High-Performance Lithium–Sulfur Batteries

“…Noteworthily, the battery can provide an ultrastable OCV for more than 3000 h with PNAVS, where the PNAGA and PVDF decreased at the very beginning, indicating the great advantage of PNAVS on LiPS adsorption, redox kinetics in Li–S batteries, and promising potential for future practical application and storage. This OCV stability for the battery with PNAVS has already surpassed most of the current reported batteries as shown in Figure b. − Dendrite formation is another issue for Li–S batteries. Asymmetrical Li/Cu semicells were employed to evaluate the Coulombic efficiency of different binders on lithium stripping/plating in Figure c.…”

CoS2@montmorillonite as an efficient separator coating for high-performance lithium–sulfur batteries

“…4b), suggesting a more rapid conversion of lithium polysulfides. 42 These electrochemical test results of the symmetrical cells amply proved the catalytic activity of the CoS 2 @montmorillonite composite for the LiPS redox process.…”

Multi-cavity carbon nanofiber film decorated with Co-Nx doped CNTs for lithium–sulfur batteries with high-areal-capacity

“…Since the battery was discharged to 1.7 V before the test, peaks at 373, 420, and 570 cm À1 were detected at the beginning of the charging process, which may correspond to S 6 2À + S 8 2À + Li 2 S, S 6 2À , and S 6 2À + Li 2 S 2 + LiS 3 $, respectively. 36,71 When the charging voltage was increased from 1.7 to 2.6 V, it was observed that the signal of S 6 2À was signicantly weakened. The CV curve showed that the oxidation reaction was over (Fig.…”