Alkali metal ion batteries

Lithium is one of the most versatile alkali metals. From batteries to lubricants and catalysts to pharmaceuticals, lithium and its compounds find a wide variety of uses. Lithium stands out among the alkali metals for several reasons. It is the lightest alkali metal and the least-dense element that is solid at room temperature and atmospheric pressure. Lithium has the highest melting point of the alkali metals. Its ion (Li+) is the smallest ion in the family. Although less abundant that sodium or potassium, lithium is still relatively inexpensive to obtain. 

Addition of methanol to 2-methylene-1,3-dioxepane (28) leads to the corresponding seven-membered cyclic orthoacetate (156) (Equation (23)) <86TL1587>, and electrochemical reduction of 1,3-dioxepan-2-one (157) in an electrolyte containing alkali metal ions affords orthoester derivatives (158), useful for stabilizing /i-doped polyacetylene as the anode-active material of a battery (Equation (24)) <85JAP(K)60I2628I>. 

McMiUan, R. S. Worsfold, D. J. Murray, J. J. Davidson, I. J. Shu, Z. N., Electrolyte comprising ftuoro-ethylene carbonate and propylene carbonate, for alkali metal-ion secondary battery, US Patent 6,506,524 (National Research CouncU of Canada) 1998 (applied in 1996). 

PEO can coordinate alkali metal ions strongly and is used as a solid polymer electrolyte [20-22]. However, conventional PEO-Li salt complexes show conductivities of the order of 10 S/cm, which is not sufficient for battery, capacitor and fuel-cell applications. A high crystalline phase concentration limits the conductivity of PEO-based electrolytes. Apart from high crystallinity, PEO-based electrolytes suffer from low cation transport number (t ), ion-pair formation and inferior mechanical properties. Peter and co-workers [23] reported the modification of PEO with phenolic resin for improvement in mechanical properties and conductivity. 

Transport of alkali metal ions through the tunnels in Nasicons can be extremely rapid, particularly at elevated temperatures, although the electronic conductivities are low. For these reasons, these materials were originally proposed for use as solid ionic conductors (e.g., to replace 3" alumina in high temperature Na/S batteries). In spite of their low electronic conductivities, researchers recognized that Nasicon structures with redox-active transition metals and related three-dimensional framework compounds could function as electrode materials as early as the late 1980s [229-231] and numerous materials were investigated [232, 233]. In many cases, the electrochemical... 

A new perspective in polymer electrolytes was obtained in 1978 when Armand [70] suggested the use of PEO-alkali metal salt complexes for alkali metal rechargeable batteries. Poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) form ion complexes with, for instance, Nal, NaBF4, LiC104, LiCFsSOs, and others. Perhaps the most important advantage of such polymer electrolytes is the ability of the complex to form a good interface with solid electrodes, thereby permitting faster kinetics at the ion transfer between electrode and electrolyte. 

Recently a great deal of interest has been shown in polyacetylene films that can incorporate alkali metal ions reversibly at a cathode to form electronically conducting compounds of the form (CHNayXr- An all-polymer solid-state battery has been developed in which the electrolyte is a sodium iodide-polyethylene oxide and the electrodes are doped polyacetylenes ... 

It is now well established that in lithium batteries (including lithium-ion batteries) containing either liquid or polymer electrolytes, the anode is always covered by a passivating layer called the SEI. However, the chemical and electrochemical formation reactions and properties of this layer are as yet not well understood. In this section we discuss the electrode surface and SEI characterizations, film formation reactions (chemical and electrochemical), and other phenomena taking place at the lithium or lithium-alloy anode, and at the Li. C6 anode/electrolyte interface in both liquid and polymer-electrolyte batteries. We focus on the lithium anode but the theoretical considerations are common to all alkali-metal anodes. We address also the initial electrochemical formation steps of the SEI, the role of the solvated-electron rate constant in the selection of SEI-building materials (precursors), and the correlation between SEI properties and battery quality and performance. 

Intercalation of cations into a framework of titanium dioxide is a process of wide interest. This is due to the electrochromic properties associated with the process (a clear blue coloration results from the intercalation) and to the system s charge storage capabilities (facilitated by the reversibility of the process) and thus the potential application in rocking-chair batteries. We have studied alkali-metal intercalation and ion diffusion in the Ti02 anatase and spinel crystals by theoretical methods ranging from condensed-phase ab initio to semiempirical computations [65, 66]. Structure relaxation, electron-density distribution, electron transfer, diffusion paths and activation energies of the ion intercalation process were modeled. 

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