Dynamic Intercalation–Conversion Site Supported Ultrathin 2D Mesoporous SnO₂/SnSe₂ Hybrid as Bifunctional Polysulfide Immobilizer and Lithium Regulator for Lithium–Sulfur Chemistry

Abstract

The practical application of lithium–sulfur batteries is impeded by the polysulfide shuttling and interfacial instability of the metallic lithium anode. In this work, a twinborn ultrathin two-dimensional graphene-based mesoporous SnO2/SnSe2 hybrid (denoted as G-mSnO2/SnSe2) is constructed as a polysulfide immobilizer and lithium regulator for Li–S chemistry. The as-designed G-mSnO2/SnSe2 hybrid possesses high conductivity, strong chemical affinity (SnO2), and a dynamic intercalation–conversion site (Li x SnSe2), inhibits shuttle behavior, provides rapid Li-intercalative transport kinetics, accelerates LiPS conversion, and decreases the decomposition energy barrier for Li2S, which is evidenced by the ex situ XAS spectra, in situ Raman, in situ XRD, and DFT calculations. Moreover, the mesoporous G-mSnO2/SnSe2 with lithiophilic characteristics enables homogeneous Li-ion deposition and inhibits Li dendrite growth. Therefore, Li–S batteries with a G-mSnO2/SnSe2 separator achieve a favorable electrochemical performance, including high sulfur utilization (1544 mAh g–1 at 0.2 C), high-rate capability (794 mAh g–1 at 8 C), and long cycle life (extremely low attenuation rate of 0.0144% each cycle at 5 C over 2000 cycles). Encouragingly, a 1.6 g S/Ah-level pouch cell realizes a high energy density of up to 359 Wh kg–1 under a lean E/S usage of 3.0 μL mg–1. This work sheds light on the design roadmap for tackling S-cathode and Li-anode challenges simultaneously toward long-durability Li–S chemistry.

Atomically Dispersed Fe–N4 and Ni–N4 Independent Sites Enable Bidirectional Sulfur Redox Electrocatalysis

“…A high areal capacity of around 7.5 mAh cm –2 was attained at 0.05 C with clear discharge plateaus (Figure h and Figure S26a). After cycling at 0.2 C for 50 cycles, the areal capacity of around 4.9 mAh cm –2 was maintained, which is higher than that of the commercial Li-ion batteries (4 mAh cm –2 ) . Two tandem coin cells can power the light-emitting diode and electric fan (Figure S26b and Figure h).…”

“…After cycling at 0.2 C for 50 cycles, the areal capacity of around 4.9 mAh cm −2 was maintained, which is higher than that of the commercial Li-ion batteries (4 mAh cm −2 ). 42 Two tandem coin cells can power the light-emitting diode and electric fan (Figure S26b and Figure 4h). With a lower N/P ratio around 3.8 (Figure S27), the Ni−Fe−NC/S cathode with 5 mg cm −2 areal sulfur loading retains a reversible capacity of 550 mAh g −1 after 60 cycles at 0.5 C under lean electrolyte condition (6 μL mg −1 ).…”

Understanding the Catalytic Kinetics of Polysulfide Redox Reactions on Transition Metal Compounds in Li–S Batteries

“…The active sites of transition metal catalysts usually have an affinity for polysulfides, which results in a large amount of Li 2 S accumulating and reducing the oxidation kinetics during charging. This can be remedied through, in addition to the common structure modulation, the construction of heterogeneous structures, which can also enhance the bidirectional redox kinetics of Li–S batteies. − In contrast to individual TMCs, the heterogeneous structures designed by interface engineering combine the advantages of different materials to create synergistic effects that result in good physicochemical properties. − Recently, an increasing number of researchers found that the heterostructures could accelerate charge transfer and promote the bidirectional sulfur reaction kinetics to significantly improve the electrochemical performance of Li–S batteries. − Table shows the electrochemical performance of heterostructures as the sulfur host/separator modifier in Li–S batteries.…”

CoSe2anchored vertical graphene/macroporous carbon nanofibers used as multifunctional interlayers for high-performance lithium–sulfur batteries

“…The two main challenges associated with Li-S batteries are the poor conductivity of elemental sulfur and nal Li 2 S/Li 2 S 2 components as well as the shuttle effect of soluble lithium polysuldes produced during the multi-step reduction, which inevitably leads to slow conversion kinetics and rapid capacity decay of the batteries. 8 In addition, Li-S batteries are plagued by the large volume change and uncontrolled growth of lithium dendrites. [9][10][11] These features prevent LSBs from being commercially applied.…”