Lithium ions, reactions

Lithium Nitride. Lithium nitride [26134-62-3], Li N, is prepared from the strongly exothermic direct reaction of lithium and nitrogen. The reaction proceeds to completion even when the temperature is kept below the melting point of lithium metal. The lithium ion is extremely mobile in the hexagonal lattice resulting in one of the highest known soHd ionic conductivities. Lithium nitride in combination with other compounds is used as a catalyst for the conversion of hexagonal boron nitride to the cubic form. The properties of lithium nitride have been extensively reviewed (66). 

The CF cathode reaction is beheved to be a heterogeneous process, initiated by the insertion of lithium ions between the CF planes. It is completed by the extmsion of LiF and the coUapse of the stmcture to carbon. 

The cathodic reaction is the reduction of iodine to form lithium iodide at the carbon collector sites as lithium ions diffuse to the reaction site. The anode reaction is lithium ion formation and diffusion through the thin lithium iodide electrolyte layer. If the anode is cormgated and coated with PVP prior to adding the cathode fluid, the impedance of the cell is lower and remains at a low level until late in the discharge. The cell eventually fails because of high resistance, even though the drain rate is low. 

The most important rechargeable lithium batteries are those using a soHd positive electrode within which the lithium ion is capable of intercalating. These intercalation, or insertion, electrodes function by allowing the interstitial introduction of the LE ion into a host lattice (16,17). The general reaction can be represented by the equation ... 

Good results are obtained with oxide-coated valve metals as anode materials. These electrically conducting ceramic coatings of p-conducting spinel-ferrite (e.g., cobalt, nickel and lithium ferrites) have very low consumption rates. Lithium ferrite has proved particularly effective because it possesses excellent adhesion on titanium and niobium [26]. In addition, doping the perovskite structure with monovalent lithium ions provides good electrical conductivity for anodic reactions. Anodes produced in this way are distributed under the trade name Lida [27]. The consumption rate in seawater is given as 10 g A ar and in fresh water is... 

Most other studies have indicated considerably more complex behavior. The rate data for reaction of 3-methyl-l-phenylbutanone with 5-butyllithium or n-butyllithium in cyclohexane can be fit to a mechanism involving product formation both through a complex of the ketone with alkyllithium aggregate and by reaction with dissociated alkyllithium. Evidence for the initial formation of a complex can be observed in the form of a shift in the carbonyl absorption band in the IR spectrum. Complex formation presumably involves a Lewis acid-Lewis base interaction between the carbonyl oxygen and lithium ions in the alkyllithium cluster. 

When lithium ions become sufficiently mobile due to heating, they migrate from the anode to the cathode with the reactions shown in Fig. 5.24 and produce open circuit voltages of about 2.5 V under ideal conditions. In... 

The disproportionation reaction destroys the layered structure and the two-dimensional pathways for lithium-ion transport. For >0.3, delithiated Li, AV02 has a defect rock salt structure without any well-defined pathways for lithium-ion diffusion. It is, therefore, not surprising that the kinetics of lithium-ion transport and overall electrochemical performance of Li, tV02 electrodes are significantly reduced by the transformation from a layered to a defect rock salt structure [76], This transformation is clearly evident from the... 

Some cations with an octahedral-site preference (such as Ni2+, Co3+, and Cr3+) are expected to occupy the 16d sites of the spinel with Mn, whereas cations with a strong tetrahedral-site preference (such as Zn2+) are expected to occupy the 8a sites and to dislodge corresponding lithium ions into the 16d sites. In cases where Mn is substituted by transition metal ions (such as Co, Ni, and Cr) that can partake in the electrochemical reaction, voltage plateaus between 4 and 5V have been observed [135, 136],... 

It is worthwhile to point out that lithium extraction from inverse spinels V[LiM]04, such as V[LiNi]04 and V[LiCo]04 takes place at high voltage, typically between 4 and 5V [153]. Lithium is extracted from the octahedral 16d sites of these spinels with a concomitant oxidation of the divalent nickel or cobalt ions. From a structural point of view, this can be readily understood because lithium must be dislodged from the 16d octahedral sites, which are of low-energy, into neighboring energetically unfavorable 8b tetrahedra, which share all four faces with 16d sites that are occupied by nickel or cobalt and by lithium. Lithium extraction reactions... 

The reactions of these insertion materials, except for LiMnO, [19, 20], consist of electron and lithium-ion insertion into, or extraction from, each matrix without the destruction of its core structure this is called a topotactic reaction. A series of LiCovNi, v02 (0 < y < 1)) and... 

The thermal behavior of Li, Ni02 in relation to safety is another key factor when in considering materials for lithium-ion batteries. LiNi02 is stable even when it is heated with an organic electrolyte. However, partially or fully oxidized LiNi02 is quite active toward organic electrolyte oxidation and this reaction is exothermic. 

As can be seen in Fig. 5, exothermic reactions observed even at room temperature for Li, A.Ni02, especially with x > 0.75, with an organic electrolyte may give some problems in designing high-volume lithium-ion batteries with LiNi02. In this section a possible haystack-type reaction,... 

The electroinsertion reaction of mobile lithium ions into a solid carbon host proceeds according to the general reaction scheme... 

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],... 

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. 

In general, lithium-ion batteries are assembled in the discharged state. That is, the cathode, for example LqCoC, is filly intercalated by lithium, while the anode (carbon) is completely empty (not charged by lithium). In the first charge the anode is polarized in the negative direction (electrons are inserted into the carbon) and lithium cations leave the cathode, enter the solution, and are inserted into the carbon anode. This first charge process is very complex. On the basis of many reports it is presented schematically [6, 74, 76] in Fig. 5. The reactions presented in Fig. 5 are also discussed in Sec. 6.2.1, 6.2.2 and 6.3.5. 

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