Ti_nO_2n–1/MXene Hierarchical Bifunctional Catalyst Anchored on Graphene Aerogel toward Flexible and High-Energy Li–S Batteries

Abstract

The development of lithium−sulfur (Li−S) batteries with high-energy density, flexibility, and safety is very appealing for emerging implantable devices, biomonitoring, and roll-up displays. Nevertheless, the poor cycling stability and flexibility of the existing sulfur cathodes, flammable liquid electrolytes, and extremely reactive lithium anodes raise serious battery performance degradation and safety issues. Herein, a metallic 1T MoS 2 and rich oxygen vacancies Ti n O 2n−1 /MXene hierarchical bifunctional catalyst (Mo−Ti/Mx) anchored on a reduced graphene oxide-cellulose nanofiber (GN) host (Mo−Ti/Mx−GN) was proposed to address the above challenges. By applying a directional freezing process, the hierarchical architecture of a flexible GN scaffold composed of waved multiarch morphology with long-range alignment is achieved. The synergetic effects of 1T MoS 2 and Ti n O 2n−1 /MXene are beneficial to suppress the shuttling behavior of lithium polysulfides (LiPSs), expedite the redox kinetics of sulfur species, and promote the electrocatalytic reduction of LiPSs to Li 2 S. The electrode demonstrates improved electrochemical properties with high sulfur-mass loading (8.4 mg s cm −2 ) and lean electrolyte (7.6 μL mg s −1 ) operation. We also explored the feasibility of producing pouch cells with such flexible electrodes, gel polymer electrolytes, and a robust lithium anode, which exhibited reversible energy storage and output, wide temperature adaptability, and good safety against rigorous strikes, implying the potential for practical applications.

Defect engineering of two-dimensional materials for advanced energy conversion and storage

“…Owing to its high natural abundance, low cost, and being environmentally benign, sulfur is an ideal cathode material to pair with the metal anode. [402][403][404][405] Compared to MIBs, the metal-sulfur batteries (MSBs) possess higher theoretical capacity (B1675 mA h g À1 ) and energy density (B2567 W h kg À1 for Li-S and B1274 W h kg À1 for Na-S), which can meet the large-scale demand, particularly for automotive electrification and grid storage applications. [406][407][408][409] During the discharge process, the metal ions from the anode will migrate to the cathode to react with the solid phase sulfur (S 8 ) and form various metal polysulfides (e.g., M 2 S 2 , M 2 S, and M 2 S x (x = 4-8)).…”

Enhanced Electrochemical Performance of Rare-Earth Metal-Ion-Doped Nanocrystalline Li4Ti5O12Electrodes in High-Power Li-Ion Batteries

“…Figure 8b presents the CV curves of the Li//Eu-LTO half-cell at varied scan rates from 0.05 to 10 mV s −1 in a voltage window from 1.0 to 2.5 V (Figure S4). The peak currents (I p ) and scan rates (ν) have a relationship expressed by eq 6 66 = I p (6) which can be rewritten as…”

Advanced Nanostructured Materials for Electrocatalysis in Lithium–Sulfur Batteries

“…In addition to TiO 2 , nano-Magnéli-phase titanium oxide (Ti n O 2n−1 ) also occupies an important position in the electrocatalysis of Li-S batteries. During the electrochemical reaction, Ti n O 2n−1 is capable of bonding or electrocatalysis with sulfur, which has a significant improvement on the battery performance [ 90 , 91 ]. In addition to common oxides, La 2 O 3 [ 92 ], WO 3 [ 93 ], CeO 2 [ 94 ], V 2 O 5 [ 95 ], and ZrO 2 [ 96 ] are also used in the field of electrocatalysis for Li-S batteries.…”