The development of sodium-ion batteries for large-scale applications requires the synthesis of electrode materials with high capacity, high initial Coulombic efficiency (ICE), high rate performance, long cycle life, and low cost. A rational design of freestanding anode materials is reported for sodium-ion batteries, consisting of molybdenum disulfide (MoS2) nanosheets aligned vertically on carbon paper derived from paper towel. The hierarchical structure enables sufficient electrode/electrolyte interaction and fast electron transportation. Meanwhile, the unique architecture can minimize the excessive interface between carbon and electrolyte, enabling high ICE. The as-prepared MoS2@carbon paper composites as freestanding electrodes for sodium-ion batteries can liberate the traditional electrode manufacturing procedure, thereby reducing the cost of sodium-ion batteries. The freestanding MoS2@carbon paper electrode exhibits a high reversible capacity, high ICE, good cycling performance, and excellent rate capability. By exploiting in situ Raman spectroscopy, the reversibility of the phase transition from 2H-MoS2 to 1T-MoS2 is observed during the sodium-ion intercalation/deintercalation process. This work is expected to inspire the development of advanced electrode materials for high-performance sodium-ion batteries.

MoS2 Nanosheets Vertically Aligned on Carbon Paper: A Freestanding Electrode for Highly Reversible Sodium Ion Batteries

Introduction Lithium-sulfur batteries are considered as a promising candidate for next-generation secondary batteries because of their high theoretical capacit y, safe operating voltage (2.15 V vs. Li/Li ), and low cost. Nevertheless, lithium-sulfur batteries suffer from capacity fading, which limits their widespread application, due to the insulating nature of sulfur and its reduced pro ducts and the dissolution of intermediate lithium polysul fides. To address these problems, carbon-based materials have been integrated with sulfur to enhance the conductivity and inhibit the polysulfide dissolutio n. Recently, graphene, a single-atom-thick carbon mate rial with superior electrical conductivity and mechanica l flexibility, has been successfully applied in lithi um-sulfur batteries. While graphene-sulfur composite cathodes  demonstrate promising electrochemical performance, their synthesis is usually complicated and challeng ing for large-scale application. On the other hand, the sol utionbased synthesis without heat treatment produces lar ge crystalline sulfur particles, resulting in low util ization of active materials and poor rate performance. Herein, we report hydroxylated graphene nanosheets as a substr ate to produce graphene-amorphous sulfur nanocomposites, exhibiting superior cyclability at high rates, by a facile in situ deposition method at room temperature.

Hydroxylated Graphene-Sulfur Nanocomposites for High-Rate Lithium-Sulfur Batteries

Heteroatom Doping: An Effective Way to Boost Sodium Ion Storage

Lithium-ion batteries, which have revolutionized portable electronics over the past three decades, were eventually recognized with the 2019 Nobel Prize in chemistry. As the energy density of current lithium-ion batteries is approaching its limit, developing new battery technologies beyond lithium-ion chemistry is significant for next-generation high energy storage. Lithium-sulfur (Li-S) batteries, which rely on the reversible redox reactions between lithium and sulfur, appears to be a promising energy storage system to take over from the conventional lithium-ion batteries for next-generation energy storage owing to their overwhelming energy density compared to the existing lithium-ion batteries today. Over the past 60 years, especially the past decade, significant academic and commercial progress has been made on Li-S batteries. From the concept of the sulfur cathode first proposed in the 1960s to the current commercial Li-S batteries used in unmanned aircraft, the story of Li-S batteries is full of breakthroughs and back tracing steps. Herein, the development and advancement of Li-S batteries in terms of sulfur-based composite cathode design, separator modification, binder improvement, electrolyte optimization, and lithium metal protection is summarized. An outlook on the future directions and prospects for Li-S batteries is also offered.

Advances in Lithium–Sulfur Batteries: From Academic Research to Commercial Viability

With the ever-increasing adaption of large-scale energy storage systems and electric devices, the energy storage capability of batteries and supercapacitors has faced increased demand and challenges. The electrodes of these devices have experienced radical change with the introduction of nano-scale materials. As new generation materials, heterostructure materials have attracted increasing attention due to their unique interfaces, robust architectures, and synergistic effects, and thus, the ability to enhance the energy/power outputs as well as the lifespan of batteries. In this review, the recent progress in heterostructure from energy storage fields is summarized. Specifically, the fundamental natures of heterostructures, including charge redistribution, built-in electric field, and associated energy storage mechanisms, are summarized and discussed in detail. Furthermore, various synthesis routes for heterostructures in energy storage fields are roundly reviewed, and their advantages and drawbacks are analyzed. The superiorities and current achievements of heterostructure materials in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), lithium-sulfur batteries (Li-S batteries), supercapacitors, and other energy storage devices are discussed. Finally, the authors conclude with the current challenges and perspectives of the heterostructure materials for the fields of energy storage.

Emerging of Heterostructure Materials in Energy Storage: A Review.

Tailored construction of advanced flexible supercapacitors (SCs) is of great importance to the development of high-performance wearable modern electronics. Herein, a facile combined wet chemical method to fabricate novel mesoporous vanadium nitride (VN) composite arrays coupled with poly(3,4-ethylenedioxythiophene) (PEDOT) as flexible electrodes for all-solid-state SCs is reported. The mesoporous VN nanosheets arrays prepared by the hydrothermal-nitridation method are composed of cross-linked nanoparticles of 10-50 nm. To enhance electrochemical stability, the VN is further coupled with electrodeposited PEDOT shell to form high-quality VN/PEDOT flexible arrays. Benefiting from high intrinsic reactivity and enhanced structural stability, the designed VN/PEDOT flexible arrays exhibit a high specific capacitance of 226.2 F g-1 at 1 A g-1 and an excellent cycle stability with 91.5% capacity retention after 5000 cycles at 10 A g-1 . In addition, high energy/power density (48.36 Wh kg-1 at 2 A g-1 and 4 kW kg-1 at 5 A g-1 ) and notable cycling life (91.6% retention over 10 000 cycles) are also achieved in the assembled asymmetric flexible supercapacitor cell with commercial nickel-cobalt-aluminum ternary oxides cathode and VN/PEDOT anode. This research opens up a way for construction of advanced hybrid organic-inorganic electrodes for flexible energy storage.

Coupling PEDOT on Mesoporous Vanadium Nitride Arrays for Advanced Flexible All‐Solid‐State Supercapacitors

Challenges and design strategies for high performance aqueous zinc ion batteries

Sulfur-impregnated disordered SnO2/carbon aerogel core–shell microspheres cathode for lithium-sulfur batteries

The development of advanced cathodes for lithium-ion batteries (LIBs) with high capacity and large energy density is of significant importance. Herein, we report a facile solvothermal-polymerization approach for the fabrication of self-supported VO2 arrays decorated with N-doped carbon (N–C@VO2). A thin N–C shell obtained from polymerized dopamine was uniformly coated on the solvothermal-synthesized VO2 skeleton, and self-supported composite arrays were formed. The lithium storage performance of the designed N–C@VO2 arrays was thoroughly studied. Due to the enhanced conductivity and more stable structure, the N–C@VO2 arrays exhibited much better reactivity and high-rate capability with a higher capacity (295 mA h g−1vs. 254 mA h g−1 at 1C) and an improved high-rate cycling life (95.3% vs. 91.5% after 500 cycles at 1C) as compared to the pure VO2 arrays. The synergistic effect between the array architecture and the N–C shell is responsible for the performance enhancement due to the accelerated reaction kinetics. Our research shows a new way to fabricate advanced high-capacity cathodes for application in electrochemical energy storage.

Xinqi Liang

Papers

Heteroatom Doping: An Effective Way to Boost Sodium Ion Storage

Coupling PEDOT on Mesoporous Vanadium Nitride Arrays for Advanced Flexible All‐Solid‐State Supercapacitors

Challenges and design strategies for high performance aqueous zinc ion batteries

Sulfur-impregnated disordered SnO2/carbon aerogel core–shell microspheres cathode for lithium-sulfur batteries

Self-supported VO2 arrays decorated with N-doped carbon as an advanced cathode for lithium-ion storage