Research Development on Sodium-Ion Batteries

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

Energy storage technology has received significant attention for portable electronic devices, electric vehicle propulsion, bulk electricity storage at power stations, and load leveling of renewable sources, such as solar energy and wind power. Lithium ion batteries have dominated most of the first two applications. For the last two cases, however, moving beyond lithium batteries to the element that lies below-sodium-is a sensible step that offers sustainability and cost-effectiveness. This requires an evaluation of the science underpinning these devices, including the discovery of new materials, their electrochemistry, and an increased understanding of ion mobility based on computational methods. The Review considers some of the current scientific issues underpinning sodium ion batteries.

The emerging chemistry of sodium ion batteries for electrochemical energy storage.

Mobile and stationary energy storage by rechargeable batteries is a topic of broad societal and economical relevance. Lithium-ion battery (LIB) technology is at the forefront of the development, but a massively growing market will likely put severe pressure on resources and supply chains. Recently, sodium-ion batteries (SIBs) have been reconsidered with the aim of providing a lower-cost alternative that is less susceptible to resource and supply risks. On paper, the replacement of lithium by sodium in a battery seems straightforward at first, but unpredictable surprises are often found in practice. What happens when replacing lithium by sodium in electrode reactions? This review provides a state-of-the art overview on the redox behavior of materials when used as electrodes in lithium-ion and sodium-ion batteries, respectively. Advantages and challenges related to the use of sodium instead of lithium are discussed.

From Lithium-Ion to Sodium-Ion Batteries: Advantages, Challenges, and Surprises.

The room temperature Na-ion secondary battery has been under focus lately due to its feasibility to compete against the already well-established Li-ion secondary battery. Although there are many obstacles to overcome before the Na-ion battery becomes commercially available, recent research discoveries corroborate that some of the cathode materials for the Na-ion battery have indeed indisputable advantages over its Li-ion counterparts. In this publication, a comprehensive review of layered oxides (NaTMO2, TM = Ti, V, Cr, Mn, Fe, Co, Ni, and a mixture of 2 or 3 elements) as a viable Na-ion battery cathode is presented. Single TM systems are well characterized not only for their electrochemical performance but also for their structural transitions during the cycle. Binary TM systems are investigated in order to address issues regarding low reversible capacity, capacity retention, operating voltage, and structural stability. As a consequence, some materials already have reached an energy density of 520 mW h g−1, which is comparable to that of LiFePO4. Furthermore, some ternary TM systems retained more than 72% of their capacity along with over 99.7% Coulombic efficiency for 275 cycles. The goal of this review is to present the development of Na layered oxide materials in the past as well as the state of the art today in order to emphasize the compatibility and durability of layered oxides as powerful candidates for Na-ion battery cathode materials.

A comprehensive review of sodium layered oxides: powerful cathodes for Na-ion batteries

Sodium-excess metal oxides Na2MO3 are appealing cathode materials for sodium-ion batteries. Here, the authors demonstrate that honeycomb-type cation ordering in Na2RuO3 triggers the oxygen redox reaction via frontier orbital reorganization, increasing the capacity by 1/3 compared with disordered Na2RuO3.

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Intermediate honeycomb ordering to trigger oxygen redox chemistry in layered battery electrode

Na-ion batteries have been the subjects of intensive studies for grid-scale energy storage recently. O3-type NaFeO2 is a promising candidate for the Na-ion cathode materials, though the irreversibility during Na-ion extraction/insertion seriously hinders its practical application. The present work demonstrates that partial replacement of Fe in O3-NaFeO2 with Ni leads to the significant improvement of the electrochemical properties. The 57Fe Mossbauer and X-ray absorption spectra show that O3-type NaFeO2–NaNiO2 solid solution forms hybridized frontier orbital of a Fe–O–Ni bond via ligand-to-metal charge transfer, which plays a dominant role in the charge–discharge process. The resulting O3-NaFe0.3Ni0.7O2 delivers an initial discharge capacity of 135 mA·h·g–1, most of which is in a high-voltage region of 2.5–3.8 V, with a high initial Coulombic efficiency of 93%, and shows enhanced cycle stability.

Role of Ligand-to-Metal Charge Transfer in O3-Type NaFeO2–NaNiO2 Solid Solution for Enhanced Electrochemical Properties

Phase pure sodium magnesium pyrophosphate Na1.82Mg1.09P2O7 was synthesized by a solid state reaction, and used as a model system to understand the Na+ dynamics in the related cathode materials Na2−xM1+x/2P2O7 (M = Fe, Mn, and Co). We found a three-dimensional framework structure formed by interconnecting Mg2O11 dimers with P2O7 pyrophosphate groups, where Na cages align along the [100] direction and are kinetically separated from each other. Diffuse distribution of Na was found inside the cage, and explained using a vacancy induced disorder model. Ionic conductivity is limited by inter-cage diffusion and measured to be 1.10 × 10−11 S cm−1 at room temperature with an activation energy of 0.77 eV. These features were further supported by bond-valence sum and lattice mechanics calculations.

Guandong Liu

Papers

Intermediate honeycomb ordering to trigger oxygen redox chemistry in layered battery electrode

Role of Ligand-to-Metal Charge Transfer in O3-Type NaFeO2–NaNiO2 Solid Solution for Enhanced Electrochemical Properties

Defect induced sodium disorder and ionic conduction mechanism in Na1.82Mg1.09P2O7