Cathode Li-

Figure 50. Galvonostatic cycling of anode (Li/graphite) and cathode (Li/LiJV[n204) half-cells using 1.0 m LiPFe in FPMS/EMC 1 1 and 1 2 mixture solvents, respectively. i = 0.001 mA cm 2. (Reproduced with permission from ref 314 (Figure 8). Copyright 2002 The Electrochemical Society.)...

While XAS techniques focus on direct characterizations of the host electrode structure, nuclear magnetic resonance (NMR) spectroscopy is used to probe local chemical environments via the interactions of insertion cations that are NMR-active nuclei, for example lithium-6 or -7, within the insertion electrode. As with XAS, NMR techniques are element specific (and nuclear specific) and do not require any long-range structural order in the host material for analysis. Solid-state NMR methods are now routinely employed to characterize the various chemical components of Li ion batteries metal oxide cathodes, Li ion-conducting electrolytes, and carbonaceous anodes.Coupled to controlled electrochemical in-sertion/deinsertion of the NMR-active cations, the... 

At the anode, metallic lithium dissolves as lithium ion (Li+) and, at the cathode, Li+ diffuses into the crystal lattice of manganese dioxide. 

Cathode Li+ accepting material LiCo02, LiMn204, LiNiOj, Polyaniline, Polypyrrole... 

Therefore, in the cathode, Li+ ions engage in an electron-transfer reaction that decreases the chemical potential of lithium in relation to its value in the anode and calls for the compensating electron. Upon discharge, the cathode functions as an electron acceptor and the previous reaction (6) can be expressed alternatively as follows ... 

Abstract The synthesis and characterization of new lithium salts has been a core component of electrolyte research for the past three decades. Upon the commerciahzation of Li-ion batteries with a graphite anode, LiPF became the dominant salt for lithinm battery electrolytes. But the advent of new electrodes/ cell chemistries (e.g., Si alloy anodes, high-voltage cathodes, Li-air, Li-S), as well as the need for exceptional battery safety, higher/lower temperature operation, improved durabihty/longer lifetimes, etc., has resulted in the pressing need for new electrolyte formnladons. Lithium salts, either as a substitute for LiPF,5 or as an additive, are one central focus for this electrolyte transformation. 

The intercalation cathode Li MyXz (X = anion) should have a low lithium chemical potential, and the intercalation anode should have a high lithium chemical potential to maximize the cell voltage. This implies that the transition metal ion should have a high oxidation slate in the cathode and a low oxidation state in the anode. The chemical potential or redox energies of the cathode and anode could also be tuned by counter cations as illustrated by an increase in voltage on going from an oxide to a polyanion cathode with the same oxidation state for the transition metal ions. 

Thus, it is clear from the above that while at the anode, the Li/Li equilibrium common to most Li batteries is maintained, at the cathode, Li does not need to be accommodated, but rather, the counterion, C104 , readily and reversibly incorporated by a CP, is the charge carrier. This reduces effects of corrosion and other problems due to the highly reactive Li. (It is noted that there is one battery type which uses n-doped CPs (usually P(Ac)) where the de-doping of the CP corresponds to charging, but this is rare and impractical and so is not discussed further here.)... 

Let consider the electrochemical reaction in the high-voltage cathode Li tNiyMn2-> C>4 [31-35]. Using ultraviolet photoelectron spectroscopy, Gao et al. [34] studied the top of the valence band of LiNiyMn2 3,64 spinel structure for a series of samples with 0.0 < y < 0.5. A partial density of states attributed to Ni 3d electrons is located about 0.5-eV above that of the Mn 3d electrons. When y = 0, the voltage plateau of Li//LiMn204 is located at 4.1 V. As y increases, the capacity associated to the 4.1 V plateau decreases as l-2y Li per formula unit and a new plateau at 4.7 V appears. The capacity associated to the 4.7 V plateau increases as 2y Li per formula unit, so that the total capacity of the samples (the sum of the contributions from the 4.1 and 4.7 V plateau) is constant. This is taken as evidence that the oxidation state of Ni in these samples is +2, and therefore they can be written as Li+Niy" "Mnj 23,Mnj O [36]. 

The lithium metal-free sulphur battery concept was confirmed by using a lithiated silicon-carbon anode, an HCS-S (hard carbon spherules-sulphur composite) cathode (cfr. Figure 3.29) and a LiCFgSOgTEGDME liquid electrolyte (see Figure 3.31) [50]. The electrochemical process involves the transfer of lithium ions from the anode to the cathode Li Si-C -f S Lij.S + xSiC + HCS (HCS hard carbon spherules). The battery delivers a capacity of 500 mAh g g at an average voltage of 1.8 V (see Figure 3.31). 

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