Thorn-Like Carbon Nanofibers Combined with Molybdenum Nitride Nanosheets as a Modified Separator Coating: An Efficient Chemical Anchor and Catalyst for Li–S Batteries

Abstract

Lithium–sulfur (Li–S) batteries have been regarded as one of the most promising candidates for the next-generation energy storage devices, attributed to their rather high theoretical energy density. However, affected by the shuttle effect and slow redox kinetics of lithium polysulfides (LiPSs), the application of the Li–S batteries is seriously hampered. Herein, novel thorn-like carbon nanofibers combined with molybdenum nitride nanosheets (denoted as MoN@CNFs) were well designed as a modified separator coating for Li–S batteries to restrain the shuttle effect and strengthen the redox kinetics of LiPSs. The conductive carbon nanofibers provided fast electronic transport, and the decorated MoN nanosheets possessed strong affinity to sulfur species, which could effectively anchor LiPSs, boost their redox reaction as an electrocatalyst,accelerate the reversible soluble/insoluble phase conversion process, and greatly increase the efficiency of active substance utilization. As a result, the Li–S batteries with the separators modified by MoN@CNFs exhibited outstanding rate performance, stable cycling capacity, and improved reaction kinetics, which delivered a high initial capacity of 1074 mA h g–1 at 0.2 C and sustained a capacity of 531 mA h g–1 after 500 cycles at 2 C, with only 0.055% capacity fade per cycle.

Molybdenum‐Based Catalytic Materials for Li–S Batteries: Strategies, Mechanisms, and Prospects

“…Using the MoN as a multifunctional coating to modify conventional Celgard separators, Li–S batteries can achieve impressive performance because the MoN nanosheets can chemically anchor polysulfides and distinctly improve the redox kinetics of LiPSs (Figure 9b). [ 78 ]…”

“…Using the MoN as a multifunctional coating to modify conventional Celgard separators, Li-S batteries can achieve impressive performance because the MoN nanosheets can chemically anchor polysulfides and distinctly improve the redox kinetics of LiPSs (Figure 9b). [78] The heterostructural mediators combining high conductivity and high polarity can accelerate the LiPSs conversion and regulate the deposition of solid Li 2 S/Li 2 S 2 . [79] Recently, MoN/Mo 2 Nbased heterostructures were reported for Li-S batteries, Cao et al designed the MoO 2 -Mo 2 N nanobelts as the multifunctional interlayer for Li-S batteries (Figure 9c).…”

WS2-TiO2 Heterostructure Catalyst for Boosting the Polysulfide Adsorption–Conversion in Lithium–Sulfur Batteries

“…Energy storage systems such as lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), , Mg-ion batteries (MIBs), lithium–sulfur (Li–S) batteries, and solid-state alkali-metal batteries , are regarded as the most promising power sources for portable devices and electric vehicle energy storage devices. , Li–S batteries have been widely studied because of their high theoretical energy density (2600 Wh kg –1 ). − However, their commercial application is limited by a low sulfur utilization (<80%) and limited lifespan (<500 cycles). There are mainly four reasons as follows: (i) the poor utilization of sulfur species due to the low conductivity of sulfur and its discharge product Li 2 S 2 /Li 2 S; , (ii) the loss of sulfur species and the corrosion of the Li metal anode caused by the “shuttling effect” of intermediate lithium polysulfides (LPSs); ,, (iii) the poor cycle stability and low Coulombic efficiency caused by the sluggish conversion kinetics of LPSs and the huge volume expansion (about 80%) of S 8 and Li 2 S 2 /Li 2 S; , and (iv) the loss of ion/electron transportation and active sulfur species caused by the depressed deposition and oxidation of the insoluble lithium sulfide (Li 2 S 2 /Li 2 S) on the cathode …”

“…8−10 However, their commercial application is limited by a low sulfur utilization (<80%) and limited lifespan (<500 cycles). There are mainly four reasons as follows: (i) the poor utilization of sulfur species due to the low conductivity of sulfur and its discharge product Li 2 S 2 /Li 2 S; 9,11 (ii) the loss of sulfur species and the corrosion of the Li metal anode caused by the "shuttling effect" of intermediate lithium polysulfides (LPSs); 9,12,13 (iii) the poor cycle stability and low Coulombic efficiency caused by the sluggish conversion kinetics of LPSs and the huge volume expansion (about 80%) of S 8 and Li 2 S 2 / Li 2 S; 14,15 and (iv) the loss of ion/electron transportation and active sulfur species caused by the depressed deposition and oxidation of the insoluble lithium sulfide (Li 2 S 2 /Li 2 S) on the cathode. 16 Therefore, choosing catalysts is considered as an effective way to solve the above problems.…”

Ultrafine Co-Species Interspersed g-C3N4 Nanosheets and Graphene as an Efficient Polysulfide Barrier to Enable High Performance Li-S Batteries

“…[ 22 , 23 ], metal nitrides (MoN, VN, etc. [ 18 , 24 ]), and metal nanoparticles (Fe, Co, Ni, etc.) [ 16 , 25 , 26 ], synergistically expediting the reaction kinetics of polysulfides in the redox process.…”