Ambient temperature solid-state lithium

AMBIENT TEMPERATURE SOLID-STATE LITHIUM BATTERIES... 

Solid polymer and gel polymer electrolytes could be viewed as the special variation of the solution-type electrolyte. In the former, the solvents are polar macromolecules that dissolve salts, while, in the latter, only a small portion of high polymer is employed as the mechanical matrix, which is either soaked with or swollen by essentially the same liquid electrolytes. One exception exists molten salt (ionic liquid) electrolytes where no solvent is present and the dissociation of opposite ions is solely achieved by the thermal disintegration of the salt lattice (melting). Polymer electrolyte will be reviewed in section 8 ( Novel Electrolyte Systems ), although lithium ion technology based on gel polymer electrolytes has in fact entered the market and accounted for 4% of lithium ion cells manufactured in 2000. On the other hand, ionic liquid electrolytes will be omitted, due to both the limited literature concerning this topic and the fact that the application of ionic liquid electrolytes in lithium ion devices remains dubious. Since most of the ionic liquid systems are still in a supercooled state at ambient temperature, it is unlikely that the metastable liquid state could be maintained in an actual electrochemical device, wherein electrode materials would serve as effective nucleation sites for crystallization. 

Another type of lithium solid state cell which reached the quasi-commercial stage was developed in the mid-1980s by Eveready. This cell used a vitreous inorganic electrolyte formed by a mixture of Lil and Li8P4Oo,25S 13.75. This solid electrolyte had a reasonably high conductivity which allowed cell operation at ambient temperatures. A disadvantage was its high reactivity which imposed the use of severe fabrication controls (e.g. assembly in a strictly moisture-free environment). 

Only a few examples with organic positive electrodes are known. A representative one is the LiQ/PPy r.b. [541], An ambient-temperature, all-solid-state r.b. with a PPy positive electrode, a gelatinous PAN-based solid electrolyte, and lithium is described in [542]. The current densities are relatively high, at 0.1 mA/cm. ... 

The proline derived diamidobinaphthyl dilithium salt (S,S,S) 41, which is dimeric in the solid state and can be prepared via deprotonation of the corresponding tetraamine with nBuLi, represents the first example of a chiral main group metal based catalyst for asymmetric intramolecular hydroamination reactions of aminoalk enes [72]. The unique reactivity of (S,S,S) 41, which allowed reactions at or below ambient temperatures with product enantioselectivities of up to 85% ee (Scheme 11.12) [76], is believed to derive from the proximity of the two lithium... 

In the pure state n-butyl-, sec-butyl-, and iso-butyl lithiums are liquids at ambient temperatures, whereas methyl-, ethyl- and f-butyl lithiums are crystallinic solids. X-ray studies revealed that the crystals of methyl lithium are built of tetramers132, 135) a similar structure was deduced for /-butyl lithium128,133) whereas a layer structure, still built of tetrameric units, was proposed for ethyl lithium136). The inability of n-propyl-, n-butyl-, iso-butyl-, sec-butyl-, and amyl-lithium to crystallize seems to be caused by steric factors. 

In this case, we have an electrolyte identical to that which is present in lithium-polymer batteries, made of poly(ethylene oxide) (or PEO) in the presence of a lithium salt, solid at ambient temperature, and which needs to be heated above ambient temperature in order for the battery to work (T > 65°C for PEO). Thus, the electrolyte, in its molten state, exhibits sufficient ionic conductivity for the lithium ions to pass. This type of electrolyte can be used on its own (without a membrane) because it ensures physical separation of the positive and negative electrodes. This type of polymer electrolyte needs to be differentiated from gelled or plasticized electrolytes, wherein a polymer is mixed with a lithium salt but also with a solvent or a blend of organic solvents, and which function at ambient temperature. In the case of a Li-S battery, dry polymer membranes are often preferred because they present a genuine all solid state at ambient temperature, which helps limit the dissolution of the active material and therefore self-discharge. Similarly, in the molten state (viscous polymer), the diffusion of the species is slowed, and there is the hope of being able to contain the lithium polysulfides near to the positive electrode. In addition, this technology limits the formation of dendrites on the metal lithium... 

The incremental capacity of an insertion electrode material used in ambient temperature batteries can be estimated from voltage spectroscopy measurements which can help to the determination of phase diagram of the insertion compotmd [1], In the first section, we examine the various aspects of electrochemical lithium insertion into a number of electrode materials. The experimental techniques of solid-state electrochemistry are presented in the second section. Voltage spectroscopy and phase diagram during Li intercalation into cathode materials are investigated. Finally, the experimental determination of the diffusion coefficient of ions in solid materials is investigated. 

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