Lithiated graphitic carbons

The first lithiated graphitic carbons (lithium-graphite intercalation compounds, abbreviated as Li-GIC s),... 

The excess charge consumed in the first cycle is generally ascribed to SEI formation and corrosion-like reactions of Li C6[19, 66, 118-120]. Like metallic lithium and Li-rich Li alloys, lithiated graphites, and more generally lithiated carbons are thermodynamically unstable in all known electrolytes, and therefore the surfaces which are exposed to the electrolyte have to be kinetically protected by SEI films (see Chapter III, Sec.6). Neverthe-... 

Whereas the electrochemical decomposition of propylene carbonate (PC) on graphite electrodes at potentials between 1 and 0.8 V vs. Li/Li was already reported in 1970 [140], it took about four years to find out that this reaction is accompanied by a partially reversible electrochemical intercalation of solvated lithium ions, Li (solv)y, into the graphite host [64], In general, the intercalation of Li (and other alkali-metal) ions from electrolytes with organic donor solvents into fairly crystalline graphitic carbons quite often yields solvated (ternary) lithiated graphites, Li r(solv)yC 1 (Fig. 8) [7,24,26,65,66,141-146],... 

The issues that some cathode materials have with low conductivity associated with certain levels of lithiation have been demonstrated. Commercial anode materials, which are mainly graphitic carbons, do not have the same problems with conductivity variations as cathodes. However, there is still a need for conductive diluents in the anode. 

While PVDF stability at high voltages is undoubted, the question of the stability of fluorinated polymers at low voltages, as toward metallic lithium or lithiated graphite, is somehow questioned in the scientific community. The assumption is that fluorinated polymers can be attacked by lithium in a strong reductive environment, being reduced electronically to carbon and LiF. 

We have no evidence that lithiated graphite reacts with ethers in the same manner as Li metal. However, more reactive solvents, esters, alkyl carbonates. 

Hence, the discussion in sections 5c-e above is also relevant to carbon electrodes, and Schemes 3-5 also provide the reaction paths of esters, alkyl carbonates, salt anions, and contaminants on carbon electrodes polarized to low potentials, and on lithiated graphite as well. The only difference between lithiated graphite and lithium in terms of surface reactions in esters and alkyl carbonate solutions is that since the active surface of carbon electrodes per geometric area is much higher than that of Li electrodes, the impact of trace contaminants on the surface chemistry of carbon electrodes may be less pronounced. 

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