Passivation lithiated carbons

Since this is a new field, little has been published on the LiXC6 /electrolyte interface. However, there is much similarity between the SEIs on lithium and on LixC6 electrodes. The mechanism of formation of the passivation film at the interface between lithiated carbon and a liquid or polymer electrolyte was studied by AC impedance [128, 142]. Two semicircles observed in AC-impedance spectra of LiAsF6/EC-2Me-THF electrolytes at 0.8 V vs. Li/Li+ [142] were attributed to the formation of a surface film during the first charge cycle. However, in the cases of LiC104 or LiBF4 /EC-PC-DME (di-... 

Kinetic stability of lithium and the lithiated carbons results from film formation which yields protective layers on lithium or on the surfaces of carbonaceous materials, able to conduct lithium ions and to prevent the electrolyte from continuously being reduced film formation at the Li/PC interphase by the reductive decomposition of PC or EC/DMC yielding alkyl-carbonates passivates lithium, in contrast to the situation with DEC where lithium is dissolved to form lithium ethylcarbonate [149]. EMC is superior to DMC as a single solvent, due to better surface film properties at the carbon electrode [151]. However, the quality of films can be increased further by using the mixed solvent EMC/EC, in contrast to the recently proposed solvent methyl propyl carbonate (MPC) which may be used as a single sol-... 

Surface Chemistry of Lithiated Carbons and Passivation Phenomena... 

The subject of surface films on electrodes in non-aqueous solutions is mostly important for the field of batteries. The performance of both Li and Li-ion batteries depends strongly on passivation phenomena that relate to surface film formation on both the anodes and the cathodes. Lithium and lithiated carbon anodes reduce all the solvents and salt anions in electrolyte solutions relevant to Li batteries. The products of these surface reactions always contain insoluble Li salts that precipitate on the electrodes as surface films. All charge transfer processes of Li, Li-C, and Li alloy anodes in Li batteries involve the critical step of Li-ion migration through the surface films. Thereby, the composition, structure, morphology, and electrical properties of surface films on Li, Li-C, and Li alloy electrodes were smdied very intensively over the years. In contrast, reversible magnesium electrodes can function only in surface film-free conditions. ... 

CO2 MF, BL, UaOe, LiAsFt, DMC Formation of surface films comprising UjCOj, good passivation of lithiated carbon electroes 65, 66... 

A mild heat generation continued from 130 C until a sharp exothermic peak appeared at 280°C for the samples (a) and (b) in Figure 5. As considered by von Sacken et al. [75], this mild heat generation is caused by a simple heterogeneous reaction between the electrolyte solvent and the lithiated carbon, where the reaction produces a passivating film on the carbon surface. In other words, the mild heat generation comes from the reaction of lithiated carbon with the electrolyte to form a new SET. The... 

Hence, due to the above-described passivation phenomena, aluminum current collectors are apparently stable in nonaqueous solutions, even at potentials above 5 V (Li/Li" ). In the case of cathodes for Li batteries where the active mass constitutes lithiated transition metal oxides, we discovered that there is a possibility for a variety of spontaneous reactions between LixMOy (M=Co, Ni, Mn, V, etc.) compounds and electrolyte solutions comprising alkyl carbonate solutions (strong electrophiles) and Li salts such as LiPFe, which form surface films. ... 

Cells with electrolyte formulations that contain alkyl carbonates, in particular EC, have been shown to offer low capacity fade, low irreversible capacity and high capacity. In EC containing electrolytes, the passivation film formed on the surface of Li-ion electrodes is formed with a minimum amount of lithium. This SEI has been shown to consist primarily of Li2(0C02(CH2)20C02)2, and related reaction products, including Li2C03 and LiOCHj, of the electrolyte solvent with either lithium or a lithiated species such as Li Cg. While solvents other than EC, typically esters or alkyl carbonates such as EMC or MFC, also form stable passivation films, most solvents do not. If an ester or alkyl carbonate is not used, graphite can be cycled in a solvent that does not form a stable passivation film if an additive, such as a crown ether or C02, is added to the electrolyte. 

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