New materials based on a layered sodium titanate for dual electrochemical Na and Li intercalation systems

Abstract

The electrochemical properties of materials derived from NaTi 3 O 6 (OH)$2H 2 O have been investigated for the first time. The parent compound has a corrugated layered structure consisting of {Ti 6 O 14 } 4À units with hydrated sodium cations and protons in the interlayer spaces. Upon heating to 600 C, water is removed irreversibly, the interlayer distances become smaller, and connecting bonds between the octahedral layers form. It was found that this material can reversibly intercalate both lithium and sodium. The initial specific discharge capacities, as measured in half-cells, varied with the state of hydration and the nature of the counter electrode (Na or Li). The electrochemical potential showed a non-linear sloping dependence with degree of intercalation, indicative of a solid-solution mechanism of intercalation. The process was centered at a low average potential of about 0.3 V vs. Na or Li, the lowest ever reported for titanatebased Li hosts. The higher density and potential for higher rate capability of this compound, in comparison to carbonaceous materials with similar voltage and reversible capacities, make a compelling case for its development as an anode material, for both lithium and sodium ion batteries. Broader contextDespite the technological success of lithium ion batteries in small electronics applications, efforts continue to be directed at enabling them to break through the existing barriers to widespread adoption in applications such as electric drive vehicles. Recent attention has been diverted to sodium ion systems due to the attractive cost and abundance features of the raw materials. Finding and designing materials capable of reversibly storing large amounts of electrochemical energy is at the core of technological breakthroughs. While systems based on alloy or conversion reactions lead to huge storage capacities, materials that react with an alkali metal through intercalation reactions are ultimately favored because they require smaller atomic scale rearrangements in comparison, resulting in more durable devices. At the negative electrode, emphasis has been placed on carbonaceous materials. Ti-containing oxides are denser and have higher rate capability than graphite or hard carbons, but they typically show lower capacities and higher voltages of operation, both of which lower energy density. Herein we present results on a new layered titanate that is capable of reversibly intercalating both Li and Na at very low voltages and shows the potential for large storage capacities. Its properties provide insight into the frontiers of electrochemical ion intercalation as it applies to energy storage technologies.

Understanding sodium-ion diffusion in layered P2 and P3 oxides via experiments and first-principles calculations: a bridge between crystal structure and electrochemical performance

“…The superior rate capability and excellent cycling performances far surpass those of the P3 phase and even those of other sodium anode materials. [31][32][33][34] P2-Na 0.62 Ti 0.37 Cr 0.63 O 2 , with its usable discharge capacity, safe potential and outstanding rate capability and cycling performance, is a promising candidate for long-life and high-rate sodium-ion batteries. The crystal structures and the charge compensation mechanisms in the layered P2 and P3 structures are first confirmed by atomic-scale characterizations based on spherical aberration-corrected electron microscopy.…”

A tightly integrated sodium titanate-carbon composite as an anode material for rechargeable sodium ion batteries

“…Renewable energy storages as important energy storage devices for mobile, 9 electric vehicle and portable applications have been attracted a great deal of 10 awareness due to the environmental disruption and economic recession [1][2][3]. Cheaper, 11 safer and more environmentally benign energy storage technologies have been 12 considered as the most suitable candidate for the future renewable energy storages [4,13 5].…”

Monoclinic Sodium Iron Hexacyanoferrate Cathode and Non-Flammable Glyme-Based Electrolyte for Inexpensive Sodium-Ion Batteries

“…Despite such harsh demands, there have been a few promising NIB electrode materials reported which meet most of the above requirements for grid-storage batteries. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Among them, there is a class of cathodes belonging to the Prussian Blue Analogue (PBA) family which is very appealing due to its reliance on Fe and/or Mn as the redox active centers and possession of high sodium storage capacities (theoretical capacity limit as high as 170.8 mAh g −1 assuming two mole sodium storage per mole of material) at relatively high voltages. 23 The general formula for PBAs relevant for NIBs is Na x M 1 [M 2 (CN) 6 ] 1-y y .nH 2 O with 0 ≤ x ≤ 2 and 0 ≤ y < 1.…”