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

With the advent of flexible electronics, flexible lithium-ion batteries have attracted great attention as a promising power source in the emerging field of flexible and wearable electronic devices such as roll-up displays, touch screens, conformable active radio-frequency identification tags, wearable sensors and implantable medical devices. In this review, we summarize the recent research progress of flexible lithium-ion batteries, with special emphasis on electrode material selectivity and battery structural design. We begin with a brief introduction of flexible lithium-ion batteries and the current development of flexible solid-state electrolytes for applications in this field. This is followed by a detailed overview of the recent progress on flexible electrode materials based on carbon nanotubes, graphene, carbon cloth, conductive paper (cellulose), textiles and some other low-dimensional nanostructured materials. Then recently proposed prototypes of flexible cable/wire type, transparent and stretchable lithium-ion batteries are highlighted. The latest advances in the exploration of other flexible battery systems such as lithium–sulfur, Zn–C (MnO2) and sodium-ion batteries, as well as related electrode materials are included. Finally, the prospects and challenges toward the practical uses of flexible lithium-ion batteries in electronic devices are discussed.

Progress in flexible lithium batteries and future prospects

Energy-storage technologies such as lithium-ion batteries and supercapacitors have become fundamental building blocks in modern society. Recently, the emerging direction toward the ever-growing market of flexible and wearable electronics has nourished progress in building multifunctional energy-storage systems that can be bent, folded, crumpled, and stretched while maintaining their electrochemical functions under deformation. Here, recent progress and well-developed strategies in research designed to accomplish flexible and stretchable lithium-ion batteries and supercapacitors are reviewed. The challenges of developing novel materials and configurations with tailored features, and in designing simple and large-scaled manufacturing methods that can be widely utilized are considered. Furthermore, the perspectives and opportunities for this emerging field of materials science and engineering are also discussed.

Flexible and Stretchable Energy Storage: Recent Advances and Future Perspectives

To meet the rapid development of flexible, portable, and wearable electronic devices, extensive efforts have been devoted to develop matchable energy storage and conversion systems as power sources, such as flexible lithium-ion batteries (LIBs), supercapacitors (SCs), solar cells, fuel cells, etc. Particularly, during recent years, exciting works have been done to explore more suitable and effective electrode/electrolyte materials as well as more preferable cell configuration and structural designs to develop flexible power sources with better electrochemical performance for integration into flexible electronics. An overview is given for these remarkable contributions made by the leading scientists in this important and promising research area. Some perspectives for the future and impacts of flexible energy storage and conversion systems are also proposed.

Advances and challenges for flexible energy storage and conversion devices and systems

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

Aligned carbon nanotube sheets provide an engineered scaffold for the deposition of a silicon active material for lithium ion battery anodes The sheets are low-density, allowing uniform deposition of silicon thin films while the alignment allows unconstrained volumetric expansion of the silicon, facilitating stable cycling performance The flat sheet morphology is desirable for battery construction

Aligned Carbon Nanotube‐Silicon Sheets: A Novel Nano‐architecture for Flexible Lithium Ion Battery Electrodes

Sodium resources are inexpensive and abundant, and hence, sodium-ion batteries are promising alternative to lithium-ion batteries. However, lower energy density and poor cycling stability of current sodium-ion batteries prevent their practical implementation for future smart power grid and stationary storage applications. Tin oxides (SnO2) can be potentially used as a high-capacity anode material for future sodium-ion batteries, and they have the advantages of high sodium storage capacity, high abundance, and low toxicity. However, SnO2-based anodes still cannot be used in practical sodium-ion batteries because they experience large volume changes during repetitive charge and discharge cycles. Such large volume changes lead to severe pulverization of the active material and loss of electrical contact between the SnO2 and carbon conductor, which in turn result in rapid capacity loss during cycling. Here, we introduce a new amorphous carbon-coated SnO2-electrodeposited porous carbon nanofiber (PCNF@SnO2@C) ...

Ozkan Yildiz

Papers

Aligned Carbon Nanotube‐Silicon Sheets: A Novel Nano‐architecture for Flexible Lithium Ion Battery Electrodes

Carbon-Confined SnO2-Electrodeposited Porous Carbon Nanofiber Composite as High-Capacity Sodium-Ion Battery Anode Material

Effect of CVD carbon coatings on Si@CNF composite as anode for lithium-ion batteries

Aligned carbon nanotube sheet high efficiency particulate air filters

Flexible binder-free silicon/silica/carbon nanofiber composites as anode for lithium–ion batteries