PDF Publication Title:
Text from PDF Page: 002
Introduction The world’s ever-growing energy demand has highlighted the role of energy storage systems more than ever. During the past few decades, lithium-ion batteries (LIBs) has been the gold standard technology both for mobile and grid level storage. Lithium-containing resources, e.g. mineral ore spodumene or mineral rich brine, are centered in three main countries: Aus- tralia, Chile, and Argentina.1–3 Such localized distribution of lithium (Li) accounts for more than 80% of the global reserves4 and creates an imbalance in supply and demand for growing large-scale applications. Prior to 2010, the cost of lithium metal accounted only for a very small fraction (< 2%) of total cost of LIBs. Emerging new technologies, such as electric vehicles and exponential production rise in small electronics, has disrupted the lithium metal market and led to a continuous increase on the market price of lithium metal. For instance, the price of Li2CO3, a well-known extraction resource for lithium metal, has tripled over the past 10 years.5 The high demand of Li resources and its increasing cost have triggered the exploration of alternatives or complementarities to Li-based battery technologies.6 Low cost per energy density, high safety, reliability, and sustainability are the key requirements for alternatives of lithium-ion batteries. Among different candidates, Na-ion bat- teries (NIBs) hold a great promise mainly due to the fact that, unlike Li, sodium (Na) is an earth abundant and cost-effective element. Moreover, Na+/Na redox couple possesses a reduction potential of − 2.73 V vs. standard hydrogen electrode (SHE) (compared to − 3.02 V vs. SHE for Li+/Li) making it a promis- ing candidate by enabling a similar operating voltage in NIBs compared to LIBs.5,7 Sodium has a higher molar mass (23 g mol−1 vs. 6.9 g mol−1 for Li+) and larger ionic radius (1.02 Å vs. 0.76 Å for Li+), leading to great differences in its chemical and electrochemical properties, compared to lithium.8 Higher chemical reactivity of sodium can cause faster solid electrolyte interphase (SEI) formation and a rapid electrolyte consump- tion.9–11 On the other hand, since sodium does not form an alloy with aluminum, even at reduced potentials, aluminum (Al) instead of copper (Cu) can be used as the current collector in NIBs. Al is more favorable due to its higher earth’s abun- dance and lower price compared to Cu (abundance in earth’s crust: 8.23% for Al and 0.0068% for Cu).12 Moreover, the charge density (q/r ratio) of Na+ is lower than Li+ in solid mate- rials and in certain cases the diffusion of Na+ in solid phases is much faster than Li+, thus allowing a fast-charging up to 500 °C current rate (58.5 A.g−1) as recorded by Yang et al.13 Despite the higher molar mass of Na, Na-containing materi- als exhibit a great diversity in their structures, especially in polyanions, where Na+-extracting voltages can be tuned easily through the so-called “inductive effect”, which can be used to design high-voltage materials and compensate the energy density loss due to the weight penalty.14–16 The attempt of employing the Na+ as the intercalating guest ion was first introduced in 1980 by G. Newman and L. Kle- mann from Exxon Research and Engineering Company.17 A reversible Na+ insertion/extraction using titanium sulfides (TiS2) as the host structure at ambient temperature was dem- onstrated with the cycling up to 16 cycles using sodium tri- ethyl (N-pyrrolyl) borate in 1,3-dioxolane as the electrolyte. Nevertheless, the (de)-sodiation of TiS2 occurred at rather low voltages (below 2.0 vs. Na+/Na)17 that it is not an ideal cathode for NIBs. In the same year, Delmas et al.18 published a summary study on the structural classification and proper- ties of AxMO2 layered oxides (where A stands for alkali metal and M stands for transition metals). In this study, the authors carefully investigated the crystal structures of several AxMO2 compositions, including A = Na, and classified them as O3, P2, and P3 types, depending on the Na crystallographic site and stacking sequence of MO2 slabs. This nomenclature is still widely used up to the present time. The transport properties such as the ionic mobility of the alkali ions based on the crys- tal chemistry were studied in continuation of their previous works on sodium oxides.19,20 Soon, the same team reported the electrochemical performance of NaxCoO2 (0.5 ≤ x ≤ 1) layered oxide with a promising performance and this was also con- sidered as the first layered oxide for the cathode in NIBs.21,22 Based on this pioneering work, several generations of layered oxides23 were developed including those with anionic redox activity.24–26 Besides layered oxides, polyanions are an important class of cathode materials for NIBs. Depending on the structure of the crystallized materials, polyanions can be classified as olivine,27 alluaudite,28,29 tavorite,30 Na3V2(PO4)2F3,31–33 or NA-Super-Ionic-CONductors34,35 (NASICON)-like struc- tures. Among them, NASICON-type materials have been widely developed as prospective cathodes for NIBs. This class of materials was discovered in 1976 by Goodenough et al.34,35 and its general chemical formula can be written as AnM2(XO4)3 (where A stands for alkali metal ions or vacancies, M stands for transition or main-group metals, and X stands for sulfur (S), phosphor (P), silicon (Si), or arsenic (As)). The structure possesses a robust tridimensional network due to the strong covalent bonds between XO4 tetrahedra and MO6 octahedra. Despite its early discovery, the electrochemical activity of NASICON in Na-based batteries had not been demonstrated till the mid-1980s with the pioneering work of Delmas et al.36 on NaTi2(PO4)3. Later, PBAs as another type of NIB cathode materials with the general formula of AxMy[M′(CN)6]z nG (where A stands for an alkali metal, M and M′ stands for tran- sition metals, and G stands for neutral molecules such as H2O) were developed.37–44 They were first introduced in the 1980s and 1990s, but their applications as cathode materials for NIBs using a non-aqueous electrolyte were demonstrated by Good- enough et al. in 2012.45,46 As this perspective discusses the future development of cathode materials for NIBs, they will be focused in more detail in later sections. The discoveries and developments in anode structures also catalyzed the improved performance of NIBs. Graphite has been historically known as a prevailing anode in LIBs and many early works in the field of NIBs attempted to employ graphite to this new technology.47–49 However, Na+ ions cannot be intercalated 2 MRS ENERGY & SUSTAINABILITY // VOLUME XX // www.mrs.org/energy-sustainability-journalPDF Image | cathode materials for sustainable sodium‐ion batteries
PDF Search Title:
cathode materials for sustainable sodium‐ion batteriesOriginal File Name Searched:
PerspectiveDesignOfCathodeMate.pdfDIY PDF Search: Google It | Yahoo | Bing
Salgenx Redox Flow Battery Technology: Salt water flow battery technology with low cost and great energy density that can be used for power storage and thermal storage. Let us de-risk your production using our license. Our aqueous flow battery is less cost than Tesla Megapack and available faster. Redox flow battery. No membrane needed like with Vanadium, or Bromine. Salgenx flow battery
| CONTACT TEL: 608-238-6001 Email: greg@salgenx.com | RSS | AMP |