Sulfur cathode offers a high theoretical specific capacity of 1,675 mAh g À1 and a high specific energy of 2,600 Wh kg À1 when implemented in lithium-sulfur batteries (LSBs). Moreover, sulfur is the redundant by-product of the petroleum industry, ensuring the low cost of LSBs. These features make LSBs particularly competitive among next-generation energy storage systems. However, the sulfur cathode suffers from several challenges such as a large volume change, low electrical conductivity of sulfur, as well as the polysulfide shuttle effect, which result in low utilization and loss of cathode active materials. Insertion of membranes (or so-called interlayers) between the separator and cathode has been demonstrated as a promising approach to alleviate these issues. In this review, recent progress regarding the advanced interlayer systems are summarized. Specifically, we generalize the different types of interlayers, and the operating mechanisms and widespread availability of interlayers in LSBs are concluded. Furthermore, the scientific/technical challenges and perspective are presented.

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We report the effort in designing layered SnS nanocrystals decorated on nitrogen and sulfur dual-doped graphene aerogels (SnS@N,S-GA) as anode material of SIBs. The optimized mass loading of SnS along with the addition of nitrogen and sulfur on the surface of GAs results in enhanced electrochemical performance of SnS@N,S-GA composite. In particular, the introduction of nitrogen and sulfur heteroatoms could provide more active sites and good accessibility for Na ions. Moreover, the incorporation of the stable SnS crystal structure within the anode results in the superior discharge capacity of 527 mAh g under a current density of 20 mA g upon 50 cycles. It maintains 340 mAh g even the current density is increased to 800 mA g. Aiming to further systematically study mechanism of composite with improved SIB performance, we construct the corresponding models based on experimental data and conduct first-principles calculations. The calculated results indicate the sulfur atoms doped in GAs show a strong bridging effect with the SnS nanocrystals, contributing to build robust architecture for electrode. Simultaneously, heteroatom dual doping of GAs shows the imperative function for improved electrical conductivity. Herein, first-principles calculations present a theoretical explanation for outstanding cycling properties of SnS@N,S-GA composite.

The exploration of sodium ion batteries (SIBs) is a profound challenge due to the rich sodium abundance and limited supply of lithium on earth. Here, amorphous SnO2/graphene aerogel (a‐SnO2/GA) nanocomposites have been successfully synthesized via a hydrothermal method for use as anode materials in SIBs. The designed annealing process produces crystalline SnO2/graphene aerogel (c‐SnO2/GA) nanocomposites. For the first time, the significant effects of SnO2 crystallinity on sodium storage performance are studied in detail. Notably, a‐SnO2/GA is more effective than c‐SnO2/GA in overcoming electrode degradation from large volume changes associated with charge–discharge processes. Surprisingly, the amorphous SnO2 delivers a high specific capacity of 380.2 mAh g−1 after 100 cycles at a current density of 50 mA g−1, which is almost three times as much as for crystalline SnO2 (138.6 mAh g−1). The impressive electrochemical performance of amorphous SnO2 can be attributed to the intrinsic isotropic nature, the enhanced Na+ diffusion coefficient, and the strong interaction between amorphous SnO2 and GA. In addition, amorphous SnO2 particles with the smaller size better function to relieve the volume expansion/shrinkage. This study provides a significant research direction aiming to increase the electrochemical performance of the anode materials used in SIBs.

The short cycle life of lithium-sulfur batteries (LSBs) plagues its practical application. In this study, a uniform SnO/reduced graphene oxide (denoted as SnO/rGO) composite is successfully designed onto the commercial polypropylene separator for use of interlayer of LSBs to decrease the charge-transfer resistance and trap the soluble lithium polysulfides (LPSs). As a result, the assembled devices using the separator modified with the functional interlayer (SnO/rGO) exhibit improved cycle performance; for instance, over 200 cycles at 1C, the discharge capacity of the cells reaches 734 mAh g. The cells also display high rate capability, with the average discharge capacity of 541.9 mAh g at 5C. Additionally, the mechanism of anchoring behavior of the SnO/rGO interlayer was systematically investigated using density functional theory calculations. The results demonstrate that the improved performance is related to the ability of SnO/rGO to effectively absorb S cluster and LPS. The strong Li-O/Sn-S/O-S bonds and tight chemical adsorption between LPS and SnO mitigate the shuttle effect of LSBs. This study demonstrates that engineering the functional interlayer of metal oxide and carbon materials in LSBs may be an easy way to improve their rate capacity and cycling life.

The CoP nanoparticles hybridized with unique N-doping carbon matrices have been successfully designed employing ZIF-67 as the precursor via a facile two-step procedure. The CoP nanostructures are shielded with reduced graphene oxide (rGO) to enhance electrical conductivity and mitigate volume expansion/shrinkage during sodium storage. As anode materials for sodium-ion batteries (SIBs), the novel architectures of CoP@N-C@rGO exhibited excellent sodium storage performance with a high reversible capacity of 225 mA h g at 50 mA g after 100 cycles. Our study demonstrates the significant potential of CoP@N-C@rGO as anode materials for SIBs.

Development of alternative cathode materials is of highly desirable for sustainable and cost-efficient lithium-ion batteries (LIBs) in energy storage fields. In this study, for the first time, we report tunable nitrogen-doped graphene with active functional groups for cathode utilization of LIBs. When employed as cathode materials, the functionalized graphene frameworks with a nitrogen content of 9.26 at% retain a reversible capacity of 344 mAh g after 200 cycles at a current density of 50 mA g. More surprisingly, when conducted at a high current density of 1 A g, this cathode delivers a high reversible capacity of 146 mAh g after 1000 cycles. Our current research demonstrates the effective significance of nitrogen doping on enhancing cathode performance of functionalized graphene for LIBs.