Energy production and storage technologies have attracted a great deal of attention for day-to-day applications. In recent decades, advances in lithium-ion battery (LIB) technology have improved living conditions around the globe. LIBs are used in most mobile electronic devices as well as in zero-emission electronic vehicles. However, there are increasing concerns regarding load leveling of renewable energy sources and the smart grid as well as the sustainability of lithium sources due to their limited availability and consequent expected price increase. Therefore, whether LIBs alone can satisfy the rising demand for small- and/or mid-to-large-format energy storage applications remains unclear. To mitigate these issues, recent research has focused on alternative energy storage systems. Sodium-ion batteries (SIBs) are considered as the best candidate power sources because sodium is widely available and exhibits similar chemistry to that of LIBs; therefore, SIBs are promising next-generation alternatives. Recently, sodiated layer transition metal oxides, phosphates and organic compounds have been introduced as cathode materials for SIBs. Simultaneously, recent developments have been facilitated by the use of select carbonaceous materials, transition metal oxides (or sulfides), and intermetallic and organic compounds as anodes for SIBs. Apart from electrode materials, suitable electrolytes, additives, and binders are equally important for the development of practical SIBs. Despite developments in electrode materials and other components, there remain several challenges, including cell design and electrode balancing, in the application of sodium ion cells. In this article, we summarize and discuss current research on materials and propose future directions for SIBs. This will provide important insights into scientific and practical issues in the development of SIBs.

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Sodium-ion batteries: present and future

We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

The ever-increasing demand of lithium-ion batteries (LIBs) caused by the rapid development of various electronics and electric vehicles will be hindered by the limited lithium resource. Thus sodium-ion batteries (SIBs) have been considered as a promising potential alternative for LIBs owing to the abundant sodium resource and similar electrochemical performances. In recent years, significant achievements regarding anode materials which restricted the development of SIBs in the past decades have been attained. Significantly, the sodium storage feasibility of carbon materials with abundant resource, low cost, nontoxicity and high safety has been confirmed, and extensive investigation have demonstrated that the carbonaceous materials can become promising electrode candidates for SIBs. In this review, the recent progress of the sodium storage performances of carbonaceous materials, including graphite, amorphous carbon, heteroatom-doped carbon, and biomass derived carbon, are presented and the related sodium storage mechanism is also summarized. Additionally, the critical issues, challenges and perspectives are provided to further understand the carbonaceous anode materials.

Carbon Anode Materials for Advanced Sodium-Ion Batteries

Endowing materials with specific functions that are not readily available is always of great importance, but extremely challenging. Co4 N, with its beneficial metallic characteristics, has been proved to be highly active for the oxidation of water, while it is notoriously poor for catalyzing the hydrogen evolution reaction (HER), because of its unfavorable d-band energy level. Herein, we successfully endow Co4 N with prominent HER catalytic capability by tailoring the positions of the d-band center through transition-metal doping. The V-doped Co4 N nanosheets display an overpotential of 37 mV at 10 mA cm-2 , which is substantially better than Co4 N and even close to the benchmark Pt/C catalysts. XANES, UPS, and DFT calculations consistently reveal the enhanced performance is attributed to the downshift of the d-band center, which helps facilitate the H desorption. This concept could provide valuable insights into the design of other catalysts for HER and beyond.

Tailoring the d-Band Centers Enables Co4N Nanosheets To Be Highly Active for Hydrogen Evolution Catalysis

Intricate hollow structures garner tremendous interest due to their aesthetic beauty, unique structural features, fascinating physicochemical properties, and widespread applications. Here, the recent advances in the controlled synthesis are discussed, as well as applications of intricate hollow structures with regard to energy storage and conversion. The synthetic strategies toward complex multishelled hollow structures are classified into six categories, including well-established hard- and soft-templating methods, as well as newly emerging approaches based on selective etching of “soft@hard” particles, Ostwald ripening, ion exchange, and thermally induced mass relocation. Strategies for constructing structures beyond multishelled hollow structures, such as bubble-within-bubble, tube-in-tube, and wire-in-tube structures, are also covered. Niche applications of intricate hollow structures in lithium-ion batteries, Li–S batteries, supercapacitors, Li–O2 batteries, dye-sensitized solar cells, photocatalysis, and fuel cells are discussed in detail. Some perspectives on the future research and development of intricate hollow structures are also provided.

Intricate Hollow Structures: Controlled Synthesis and Applications in Energy Storage and Conversion

High utilization and loading of sulfur in cathodes holds the key in the realization of Li–S batteries We here synthesized a Co4N mesoporous sphere, which was made up of nanosheets, via an easy and convenient method This material presents high affinity, speedy trapping, and absorbing capacity for polysulfides and acts as a bifunctional catalysis for sulfur redox processes; therefore it is an ideal matrix for S active material With such a mesoporous sphere used as a sulfur host in Li–S batteries, extraordinary electrochemistry performance has been achieved With a sulfur content of 723 wt % in the composite, the Co4N@S delivered a high specific discharge capacity of 1659 mAh g–1 at 01 C, almost reaching its theoretic capacity Also, the battery exhibited a large reversible capacity of about 1100 mAh g–1 at 05 C and 1000 mAh g–1 at 1 C after 100 cycles At a high rate of 2 C and 5 C, after 300 cycles, the discharge capacity finally stabilized at 805 and 585 mAh g–1 Even at a 9488% sulfur content, the

Co4N Nanosheet Assembled Mesoporous Sphere as a Matrix for Ultrahigh Sulfur Content Lithium-Sulfur Batteries.

Sodium ion batteries (SIBs), based on earth-abundant and cost-effective elements, have attracted increasing attention. Carbon-based materials are still the most potential anode materials for SIBs. Because of insufficient interlayer spacing, graphite-based materials used currently in lithium ion batteries are not suitable for SIB anodes. Herein, combining macro-construction and micro-modification, we design and prepare novel SN-co-doped hollow carbon spheres (SN-HCSs) by a new method. The S and N play different roles during sodium ion storage. Due to the hierarchical porous structure and heteroatoms including S and N, the SN-HCS anode exhibits superior performance, especially with high rate capability (110 mA h g−1 at a current density of 10 A g−1) and excellent cyclic stability (cycle as long as 2000 cycles with only 0.0195 mA h g−1 specific capacity decay for each cycle).

Sulfur and nitrogen co-doped hollow carbon spheres for sodium-ion batteries with superior cyclic and rate performance

The polyanion Li7V15O36(CO3) is a nanosized molecular cluster (≈1 nm in size), that has the potential to form an open host framework with a higher surface-to-bulk ratio than conventional transition metal oxide electrode materials. Herein, practical rechargeable Na-ion batteries and symmetric Li-ion batteries are demonstrated based on the polyoxovanadate Li7V15O36(CO3). The vanadium centers in {V15O36(CO3)} do not all have the same VIV/V redox potentials, which permits symmetric devices to be created from this material that exhibit battery-like energy density and supercapacitor-like power density. An ultrahigh specific power of 51.5 kW kg−1 at 100 A g−1 and a specific energy of 125 W h kg−1 can be achieved, along with a long cycling life (>500 cycles). Moreover, electrochemical and theoretical studies reveal that {V15O36(CO3)} also allows the transport of large cations, like Na+, and that it can serve as the cathode material for rechargeable Na-ion batteries with a high specific capacity of 240 mA h g−1 and a specific energy of 390 W h kg−1 for the full Na-ion battery. Finally, the polyoxometalate material from these electrochemical energy storage devices can be easily extracted from spent electrodes by simple treatment with water, providing a potential route to recycling of the redox active material.

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Design and Performance of Rechargeable Sodium Ion Batteries, and Symmetrical Li-Ion Batteries with Supercapacitor-Like Power Density Based upon Polyoxovanadates

Hollow carbon sphere with open pore encapsulated MnO2 nanosheets as high-performance anode materials for lithium ion batteries

Lithium–sulfur (Li–S) batteries have been identified as the most promising options for energy storage because of their high theoretical capacity and environmental friendliness. However, low utilization of sulfur in the cathode and the shuttle effect, which leads to a poor cycle life, hinder the realization of Li–S batteries. Herein, we have designed a new type of rGO-supported TiN-nanoparticle (TiN/rGO) multifunction cover layer via an in situ synthesis method. The excellent blocking effect of lithium polysulfides and outstanding catalytic ability and superior electron conductivity of the TiN/rGO cover layer favor the development of a macro-chamber for S conversion reactions (MCSR) at a macroscopic scale. This macro-chamber, in which either pure sulfur powders or sulfur-based composites can be directly adopted as active materials, can significantly reduce the shuttle effect and increase sulfur utilization for lithium–sulfur batteries. When the S powder loading is as high as 8 mg cm−2, the battery continues to deliver outstanding electrochemical performance and cycling stability. Via this MCSR design, indispensable support materials for S and additives for electrolyte will no longer be needed in the current Li–S cells.

Jian-Chuan Ye

Papers

Co4N Nanosheet Assembled Mesoporous Sphere as a Matrix for Ultrahigh Sulfur Content Lithium-Sulfur Batteries.

Sulfur and nitrogen co-doped hollow carbon spheres for sodium-ion batteries with superior cyclic and rate performance

Design and Performance of Rechargeable Sodium Ion Batteries, and Symmetrical Li-Ion Batteries with Supercapacitor-Like Power Density Based upon Polyoxovanadates

Hollow carbon sphere with open pore encapsulated MnO2 nanosheets as high-performance anode materials for lithium ion batteries

In situ preparation of a macro-chamber for S conversion reactions in lithium–sulfur batteries