As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium-sulfur (Li-S) batteries. In this paper, a mesoporous nitrogen-doped carbon (MPNC)-sulfur nanocomposite is reported as a novel cathode for advanced Li-S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verifi ed by X-ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC-sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm −2 with a high sulfur loading (4.2 mg S cm −2 ) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm −2 ) is demonstrated by using the novel cathode, which is crucial for the practical application of Li-S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon-sulfur composite cathodes for Li-S batteries.

Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries

Sodium-ion batteries (SIBs) are considered as promising alternatives to lithium-ion batteries owing to the abundant sodium resources. However, the limited energy density, moderate cycling life, and immature manufacture technology of SIBs are the major challenges hindering their practical application. Recently, numerous efforts are devoted to developing novel electrode materials with high specific capacities and long durability. In comparison with carbonaceous materials (e.g., hard carbon), partial Group IVA and VA elements, such as Sn, Sb, and P, possess high theoretical specific capacities for sodium storage based on the alloying reaction mechanism, demonstrating great potential for high-energy SIBs. In this review, the recent research progress of alloy-type anodes and their compounds for sodium storage is summarized. Specific efforts to enhance the electrochemical performance of the alloy-based anode materials are discussed, and the challenges and perspectives regarding these anode materials are proposed.

Alloy-Based Anode Materials toward Advanced Sodium-Ion Batteries

Due to massively growing demand arising from energy storage systems, sodium ion batteries (SIBs) have been recognized as the most attractive alternative to the current commercialized lithium ion batteries (LIBs) owing to the wide availability and accessibility of sodium. Unfortunately, the low energy density, inferior power density and poor cycle life are still the main issues for SIBs in the current drive to push the entire technology forward to meet the benchmark requirements for commercialization. Over the past few years, tremendous efforts have been devoted to improving the performance of SIBs, in terms of higher energy density and longer cycling lifespans, by optimizing the electrode structure or the electrolyte composition. In particular, among the established anode systems, those materials, such as metals/alloys, phosphorus/phosphides, and metal oxides/sulfides/selenides, that typically deliver high theoretical sodium-storage capacities have received growing interest and achieved significant progress. Although some review articles on electrodes for SIBs have been published already, many new reports on these anode materials are constantly emerging, with more promising electrochemical performance achieved via novel structural design, surface modification, electrochemical performance testing techniques, etc. So, we herein summarize the most recent developments on these high-performance anode materials for SIBs in this review. Furthermore, the different reaction mechanisms, the challenges associated with these materials, and effective approaches to enhance performance are discussed. The prospects for future high-energy anodes in SIBs are also discussed.

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Recent progress on sodium ion batteries: potential high-performance anodes

The reasonable design of electrode materials for rechargeable batteries plays an important role in promoting the development of renewable energy technology. With the in-depth understanding of the mechanisms underlying electrode reactions and the rapid development of advanced technology, the performance of batteries has significantly been optimized through the introduction of defect engineering on electrode materials. A large number of coordination unsaturated sites can be exposed by defect construction in electrode materials, which play a crucial role in electrochemical reactions. Herein, recent advances regarding defect engineering in electrode materials for rechargeable batteries are systematically summarized, with a special focus on the application of metal-ion batteries, lithium-sulfur batteries, and metal-air batteries. The defects can not only effectively promote ion diffusion and charge transfer but also provide more storage/adsorption/active sites for guest ions and intermediate species, thus improving the performance of batteries. Moreover, the existing challenges and future development prospects are forecast, and the electrode materials are further optimized through defect engineering to promote the development of the battery industry.

Defect Engineering on Electrode Materials for Rechargeable Batteries.

The goal of limiting global warming to 1.5 °C requires a drastic reduction in CO2 emissions across many sectors of the world economy. Batteries are vital to this endeavor, whether used in electric vehicles, to store renewable electricity, or in aviation. Present lithium-ion technologies are preparing the public for this inevitable change, but their maximum theoretical specific capacity presents a limitation. Their high cost is another concern for commercial viability. Metal-air batteries have the highest theoretical energy density of all possible secondary battery technologies and could yield step changes in energy storage, if their practical difficulties could be overcome. The scope of this review is to provide an objective, comprehensive, and authoritative assessment of the intensive work invested in nonaqueous rechargeable metal-air batteries over the past few years, which identified the key problems and guides directions to solve them. We focus primarily on the challenges and outlook for Li-O2 cells but include Na-O2, K-O2, and Mg-O2 cells for comparison. Our review highlights the interdisciplinary nature of this field that involves a combination of materials chemistry, electrochemistry, computation, microscopy, spectroscopy, and surface science. The mechanisms of O2 reduction and evolution are considered in the light of recent findings, along with developments in positive and negative electrodes, electrolytes, electrocatalysis on surfaces and in solution, and the degradative effect of singlet oxygen, which is typically formed in Li-O2 cells.

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Lithium-Oxygen Batteries and Related Systems: Potential, Status, and Future

Recent progress in rational design of anode materials for high-performance Na-ion batteries

Carbon-coated van der Waals stacked Sb2S3 nanorods (SSNR/C) are synthesized by facile hydrothermal growth as anodes for sodium ion batteries (SIBs). The sodiation kinetics and phase evolution behavior of the SSNR/C anode during the first and subsequent cycles are unraveled by coupling in situ transmission electron microscopy analysis with first-principles calculations. During the first sodiation process, Na+ ions intercalate into the Sb2S3 crystals with an ultrafast speed of 146 nm s−1. The resulting amorphous NaxSb2S3 intermediate phases undergo sequential conversion and alloying reactions to form crystalline Na2S, Na3Sb, and minor metallic Sb. Upon desodiation, Na+ ions extract from the nanocrystalline phases to leave behind the fully desodiated Sb2S3 in an amorphous state. Such unique phase evolution behavior gives rise to superb electrochemical performance and leads to an unexpectedly small volume expansion of ≈54%. The first-principles calculations reveal distinctive phase evolution arising from the synergy between the extremely low Na+ ion diffusion barrier of 190 meV and the sharply increased electronic conductivity upon the formation of amorphous NaxSb2S3 intermediate phases. These findings highlight an anomalous Na+ ion storage mechanism and shed new light on the development of high performance SIB anodes based on van der Waals crystals.

Unveiling the Unique Phase Transformation Behavior and Sodiation Kinetics of 1D van der Waals Sb2S3 Anodes for Sodium Ion Batteries

The increasing cost and limited availability of lithium have prompted the development of high-performance sodium-ion batteries (SIBs) as a potential alternative to lithium-ion batteries. However, it has been a critical challenge to develop high-performance anode materials capable of storing and transporting Na+ efficiently. Amongst the various options, MoS2 has significant advantages including low cost, and a high theoretical capacity of ∼670 mA h g−1. Nevertheless, MoS2 has several issues: its electronic conductivity is low and its structure deteriorates rapidly during charge/discharge cycles, leading to a poor electrochemical performance. Here, a dual-phase MoS2 (DP-MoS2) is synthesized by combining two distinct 1T (trigonal) and 2H (hexagonal) phases to solve these challenges. Compared to the conventional 2H-MoS2 counterpart, the DP-MoS2 phase material presents a highly reversible Na+ intercalation/extraction process aided by expanded interlayer spacing along with much higher electronic conductivity and Na ion affinity. Consequently, the DP-MoS2 electrode delivers a high cyclic stability with a reversible capacity of 300 mA h g−1 after 200 cycles at 0.5 A g−1 and an excellent rate capability of ∼220 mA h g−1 at 2 A g−1. The SIBs assembled with DP-MoS2 and Na3V2(PO4)3 as the negative and positive electrodes, respectively, have a specific capacity of 210 mA h g−1 (based on the mass of DP-MoS2) at 0.5 A g−1. This performance demonstrates that DP-MoS2 has a significant potential in commercial devices. This work offers a new approach to develop metal chalcogenides for electrochemical energy storage applications.

Jiang Cui

Papers

Recent progress in rational design of anode materials for high-performance Na-ion batteries

Unveiling the Unique Phase Transformation Behavior and Sodiation Kinetics of 1D van der Waals Sb2S3 Anodes for Sodium Ion Batteries

Dual-phase MoS2 as a high-performance sodium-ion battery anode

Dendrite-free lithium metal and sodium metal batteries

Revealing Pseudocapacitive Mechanisms of Metal Dichalcogenide SnS2/Graphene-CNT Aerogels for High-Energy Na Hybrid Capacitors