Lithium negative insertion materials

To avoid the problems associated with lithium metal, lithium insertion materials (e.g., graphitic carbons) are being investigated as negative electrodes. With respect to lithium metal, the use of negative insertion materials improves the cycle life and safety of the battery but lowers the cell voltage, the theoretical specific capacity, and the charge transfer rate [104]. 

Beginning in the early 1980s [20, 21] metallic lithium was replaced by lithium insertion materials having a lower standard redox potential than the positive insertion electrode this resulted in a "Li-ion" or "rocking-chair" cell with both negative and positive electrodes capable of reversible lithium insertion (see recommended papers and review papers [7, 10, 22-28]). Various insertion materials have been proposed for the anode of rechargeable lithium batteries,... 

There are two main kinds of rechargeable battery based on lithium chemistry the lithium-metal and the lithium-ion battery. In both the positive electrode is a lithium insertion material the negative in the former is lithium metal and in the latter it is a lithium insertion host. The reason for the application in lithium batteries of insertion electrode materials, which are electronic and ionic conductive solid matrixes (inorganic and carbon-based), is that electrochemical insertion reactions are intrinsically simple and highly reversible. 

Research has also focused on the study of highly reversible negative lithium insertion materials. Transition metal oxides and chalcogenides, such as M0O2, WO2, and TiS2, if combined with a metal oxide positive electrode material yield cells with low OCV values (ca. 1.5-2 V) [111]. 

Higher OCV values can be attained with lithium alloys (Figure 16), which are under study as negative insertion electrode materials for their high specific capacity... 

Lithium insertion and extraction into/from the positive electrode material must occur at a higher potential and the same reactions on the negative electrode material must occur at the maximum negative potential. The difference between the lithium insertion and extraction potentials for the same material must be... 

Under discharge of the battery, deintercalation of lithium from the carbon material occurs on the negative electrode and lithium is inserted into the oxide on the positive electrode. Under charging, the processes are reversed. Thus, there is no lithium metal in the whole system and the discharge and charging processes are reduced to the... 

Although the two redox couples are not identical, as regards the electrolyte both redox reactions involve a supply or consumption of Li with the same stoichiometry. This applies to a Li-ion battery with two insertion materials or to a Li-polymer battery with Li as the negative electrode and an insertion material at the positive electrode. When a lithium battery is in operation, one must take into account simultaneously the migration and diffusion of the ions in the electrolyte, however, this makes no change in qualitative terms to what has just been illustrated. 

Figure 2.5 shows the evolution of the SOH of a lithium-ion device comprising two insertion materials (graphite for the negative electrode and mixed cobalt/nickel oxide for the positive electrode). Cycling was performed to a DOD of 75% for a C/5 charge/discharge current amplitude. 

Pure metals and metal compounds (metal oxides, intermetallic compounds) which are capable of forming alloys with lithium constitute another category of electrode materials versus the insertion materials seen previously. They are used for the negative electrode in lithium-ion batteries because their redox potential versus lithium is less than 2 V. They are cited in the following four sections ... 

Intercalate/insert This refers to a process of inserting a guest into a host, which usually has a layered structure. In this book, the guest is usually lithium, and the host is a positive or negative electrode material. 

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