Lithium-ion inserted anodes

Table 2. Commercially available rechargeable coin-type cells with lithium-ion inserted anodes...

An Alternative to the Lithium-Metal Anode (Lithium-Ion Inserted Anodes)... 

Recently, lithium-ion inserted compounds have been investigated as new anodes. These compounds have the possibility of... 

Hahn, R., Ghicov,A,Tsuchiya, H.,Macak,]. M., Munoz,A G.,and Schmuki, P. [2007]. Lithium-ion insertion in anodic Ti02 nanotubes resulting in high electrochromic contrast. 5 International Conference on Porous Semiconductors — Science and Technology. Physica Status SolidiA —Applications and Materials Science., 204, pp. 1281-1285. 

Raman spectroscopy is sensitive to both the chemical and the stmctural variations of a material, liquid or solid/ As an in situ technique, Raman spectroscopy has been used to characterize the crystalline structural variation of graphite anodes and Li vPj and LiMn O cathodes in lithium ion batteries during lithium ion insertion and extraction. In the authors laboratory, Raman spectroscopy was used to extensively study the strong interactions between the components of polyacrylonitrile (PAN)-based electrolytes, the competition between the polymer and the solvent on association with the Li ions, the ion transport mechanisms of both salt-in-polymer and polymer-in-salt electrolytes. Based on the Raman spectroscopic study, Li ion insertion and extraction mechanisms in low-temperature pyrolytic carbon anode have also been proposed. " In many cases, Raman spectroscopy is used as compensation to the IR spectroscopy to give a complete understanding to the structure of a substance though there are as many cases that Raman spectroscopy is used independently. 

The work presented in this chapter involves the study of high capacity carbonaceous materials as anodes for lithium-ion battery applications. There are hundreds and thousands of carbonaceous materials commercially available. Lithium can be inserted reversibly within most of these carbons. In order to prepare high capacity carbons for hthium-ion batteries, one has to understand the physics and chemistry of this insertion. Good understanding will ultimately lead to carbonaceous materials with higher capacity and better performance. 

Chapter 11 reports the use of carbon materials in the fast growing consumer eleetronies applieation of lithium-ion batteries. The principles of operation of a lithium-ion battery and the mechanism of Li insertion are reviewed. The influence of the structure of carbon materials on anode performance is described. An extensive study of the behavior of various carbons as anodes in Li-ion batteries is reported. Carbons used in commereial Li-ion batteries are briefly reviewed. 

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. 

The Li-Ion system was developed to eliminate problems of lithium metal deposition. On charge, lithium metal electrodes deposit moss-like or dendrite-like metallic lithium on the surface of the metal anode. Once such metallic lithium is deposited, the battery is vulnerable to internal shorting, which may cause dangerous thermal run away. The use of carbonaceous material as the anode active material can completely prevent such dangerous phenomenon. Carbon materials can intercalate lithium into their structure (up to LiCe). The intercalation reaction is very reversible and the intercalated carbons have a potential about 50mV from the lithium metal potential. As a result, no lithium metal is found in the Li-Ion cell. The electrochemical reactions at the surface insert the lithium atoms formed at the electrode surface directly into the carbon anode matrix (Li insertion). There is no lithium metal, only lithium ions in the cell (this is the reason why Li-Ion batteries are named). Therefore, carbonaceous material is the key material for Li-Ion batteries. Carbonaceous anode materials are the key to their ever-increasing capacity. No other proposed anode material has proven to perform as well. The carbon materials have demonstrated lower initial irreversible capacities, higher cycle-ability and faster mobility of Li in the solid phase. 

Kumar TP, Ramesh R, Lin YY, Fey GTK (2004) Tin-filled carbon nanotubes as insertion anode materials for lithium-ion batteries. Electrochemistry Communications 6 520-525. 

The charging process implies the oxidation of the cathode polymer with the concurrent insertion of the C104 anions from the electrolyte and the deposition of lithium at the anode. In the discharging process the electroactive cathode material releases the anion and the lithium ions are stripped from the metal anode to restore the initial electrolyte concentration. Therefore, the electrochemical process involves the participation of the electrolyte salt to an extent which is defined by the doping level y. 

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