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

Grid-scale energy storage systems (ESSs) that can connect to sustainable energy resources have received great attention in an effort to satisfy ever-growing energy demands. Although recent advances in Li-ion battery (LIB) technology have increased the energy density to a level applicable to grid-scale ESSs, the high cost of Li and transition metals have led to a search for lower-cost battery system alternatives. Based on the abundance and accessibility of Na and its similar electrochemistry to the well-established LIB technology, Na-ion batteries (NIBs) have attracted significant attention as an ideal candidate for grid-scale ESSs. Since research on NIB chemistry resurged in 2010, various positive and negative electrode materials have been synthesized and evaluated for NIBs. Nonetheless, studies on NIB chemistry are still in their infancy compared with LIB technology, and further improvements are required in terms of energy, power density, and electrochemical stability for commercialization. Most recent progress on electrode materials for NIBs, including the discovery of new electrode materials and their Na storage mechanisms, is briefly reviewed. In addition, efforts to enhance the electrochemical properties of NIB electrode materials as well as the challenges and perspectives involving these materials are discussed.

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Recent Progress in Electrode Materials for Sodium-Ion Batteries

In this critical Review we focus on the evolution of the hybrid ion capacitor (HIC) from its early embodiments to its modern form, focusing on the key outstanding scientific and technological questions that necessitate further in-depth study. It may be argued that HICs began as aqueous systems, based on a Faradaic oxide positive electrode (e.g., Co3O4, RuOx) and an activated carbon ion-adsorption negative electrode. In these early embodiments HICs were meant to compete directly with electrical double layer capacitors (EDLCs), rather than with the much higher energy secondary batteries. The HIC design then evolved to be based on a wide voltage (∼4.2 V) carbonate-based battery electrolyte, using an insertion titanium oxide compound anode (Li4Ti5O12, LixTi5O12) versus a Li ion adsorption porous carbon cathode. The modern Na and Li architectures contain a diverse range of nanostructured materials in both electrodes, including TiO2, Li7Ti5O12, Li4Ti5O12, Na6LiTi5O12, Na2Ti3O7, graphene, hard carbon, soft carbo...

Review of Hybrid Ion Capacitors: From Aqueous to Lithium to Sodium.

Sodium-ion capacitors can potentially combine the virtues of high power capability of conventional electrochemical capacitors and high energy density of batteries. However, the lack of high-performance electrode materials has been the major challenge of sodium-based energy storage devices. In this work, we report a microwave-assisted synthesis of single-crystal-like anatase TiO2 mesocages anchored on graphene as a sodium storage material. The architecture of the nanocomposite results in pseudocapacitive charge storage behavior with fast kinetics, high reversibility, and negligible degradation to the micro/nanostructure. The nanocomposite delivers a high capacity of 268 mAh g–1 at 0.2 C, which remains 126 mAh g–1 at 10 C for over 18 000 cycles. Coupling with a carbon-based cathode, a full cell of sodium-ion capacitor successfully demonstrates a high energy density of 64.2 Wh kg–1 at 56.3 W kg–1 and 25.8 Wh kg–1 at 1357 W kg–1, as well as an ultralong lifespan of 10 000 cycles with over 90% of capacity rete...

Pseudocapacitive Sodium Storage in Mesoporous Single-Crystal-like TiO2–Graphene Nanocomposite Enables High-Performance Sodium-Ion Capacitors

The achievement of the superior rate capability and cycling stability is always the pursuit of sodium-ion batteries (SIBs). However, it is mainly restricted by the sluggish reaction kinetics and large volume change of SIBs during the discharge/charge process. This study reports a facile and scalable strategy to fabricate hierarchical architectures where TiO2 nanotube clusters are coated with the composites of ultrafine MoO2 nanoparticles embedded in carbon matrix (TiO2@MoO2-C), and demonstrates the superior electrochemical performance as the anode material for SIBs. The ultrafine MoO2 nanoparticles and the unique nanorod structure of TiO2@MoO2-C help to decrease the Na+ diffusion length and to accommodate the accompanying volume expansion. The good integration of MoO2 nanoparticles into carbon matrix and the cable core role of TiO2 nanotube clusters enable the rapid electron transfer during discharge/charge process. Benefiting from these structure merits, the as-made TiO2@MoO2-C can deliver an excellent cycling stability up to 10 000 cycles even at a high current density of 10 A g−1. Additionally, it exhibits superior rate capacities of 110 and 76 mA h g−1 at high current densities of 10 and 20 A g−1, respectively, which is mainly attributed to the high capacitance contribution.

Ultrafine MoO2-Carbon Microstructures Enable Ultralong-Life Power-Type Sodium Ion Storage by Enhanced Pseudocapacitance

Anatase TiO2 has been suggested as a potential sodium anode material, but the low electrical conductivity of TiO2 often limits the rate capability, resulting in poor electrochemical properties. To address this limitation, we propose graphene-wrapped anatase TiO2 nanofibers (rGO@TiO2 NFs) through an effective wrapping of reduced graphene oxide (rGO) sheets on electrospun TiO2 NFs. To provide strong electrostatic interaction between the graphene oxide (GO) sheets and the TiO2 NFs, poly(allylamine hydrochloride) (PAH) was used to induce a positively charged TiO2 surface by the immobilization of the -NH3+ group and to promote bonding with the negatively charged carboxylic acid (-COO−) and hydroxyl (-O−) groups on the GO. A sodium anode electrode using rGO@TiO2 NFs exhibited a significantly improved initial capacity of 217 mAh g−1, high capacity retention (85% after 200 cycles at 0.2C), and a high average Coulombic efficiency (99.7% from the second cycle to the 200th cycle), even at a 5C rate, compared to those of pristine TiO2 NFs. The improved electrochemical performances stem from highly conductive properties of the reduced GO which is effectively anchored to the TiO2 NFs.

Graphene-wrapped anatase TiO2 nanofibers as high rate and long cycling anode materials for sodium ion batteries = 그래핀 랩핑된 아나타제 타이타늄 옥사이드 나노섬유 합성 및 장수명/고효율 소듐 이차전지용 음극 물질 활용 연구

여열매

Papers

Graphene-wrapped anatase TiO2 nanofibers as high rate and long cycling anode materials for sodium ion batteries = 그래핀 랩핑된 아나타제 타이타늄 옥사이드 나노섬유 합성 및 장수명/고효율 소듐 이차전지용 음극 물질 활용 연구