Metal oxide cathodes

It is so universally applied that it may be found in combination with metal oxide cathodes (e.g., HgO, AgO, NiOOH, Mn02), with catalytically active oxygen electrodes, and with inert cathodes using aqueous halide or ferricyanide solutions as active materials ("zinc-flow" or "redox" batteries). The cell (battery) sizes vary from small button cells for hearing aids or watches up to kilowatt-hour modules for electric vehicles (electrotraction). Primary and storage batteries exist in all categories except that of flow-batteries, where only storage types are found. Acidic, neutral, and alkaline electrolytes are used as well. The (simplified) half-cell reaction for the zinc electrode is the same in all electrolytes ... 

The air gas-diffusion electrode possesses two advantages over the metal-oxide cathode in the conventional primary batteries infinite charge... 

The cells shown in Figs. 28 and 29 all operate according to the same principles, which have been developed by Arup. The interior of the cell acts as the anode chamber, and a metal oxide cathode placed inside the cell in an alkaline electrolyte acts as the counter electrode. The hydrogen flux across the integrated membrane (coated with palladium on the internal surface) can be measured as the potential drop across a resistor placed between the membrane and the counter electrode. 

Figure 1. Schematic description of a (lithium ion) rocking-chair cell that employs graphitic carbon as anode and transition metal oxide as cathode. The undergoing electrochemical process is lithium ion deintercalation from the graphene structure of the anode and simultaneous intercalation into the layered structure of the metal oxide cathode. For the cell, this process is discharge, since the reaction is spontaneous.

Figure 51. Cathodic and anodic stability of LiBOB-based electrolytes on metal oxide cathode and graphitic anode materials Slow scan cyclic voltammetry of these electrode materials in LiBOB/EC/EMC electrolyte. The scan number and Coulombic efficiency (CE) for each scan are indicated in the graph. (Reproduced with permission from ref 155 (Eigure 2). Copyright 2002 The Electrochemical Society.)...

The early patent disclosures have claimed the application of a wide spectrum of gas-evolving ingredients and phosphorus-based organic molecules as flame retarding additives in the electrolytes. Pyrocarbonates and phosphate esters were typical examples of such compounds. The former have a strong tendency to release CO2, which hopefully could serve as both flame suppressant and SEI formation additive, while the latter represent the major candidates that have been well-known to the polymer material and fireproofing industries.The electrochemical properties of these flame retardants in lithium ion environments were not described in these disclosures, but a close correlation was established between the low flammability and low reactivity toward metallic lithium electrodes for some of these compounds. Further research published later confirmed that any reduction of flammability almost always leads to an improvement in thermal stability on a graphitic anode or metal oxide cathode. 

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... 

Historically, a Ca metal negative electrode was used with a fusible salt electrolyte (LiCl/KCl eutectic) and a metal oxide cathode, e.g., K2Cr207 (2.8— 3.3 V). Since the 1980s, Li alloy negatives have gained popularity and supplanted... 

Desilvestro, J., and Haas, O. 1990. Metal oxide cathode materials for electrochemical energy storage A review. Journal of the Electrochemical Society 137, 5C-22C. 

The feasibility of the gel electrolytes for lithium-ion batteries development has been tested by first examining their compatibility with appropriate electrode materials, i.e., the carbonaceous anode and the lithium metal oxide cathode. This has been carried out by examining the characteristics of the lithium intercalation-deintercalation processes in the electrode materials using cells based on the given polymer as the electrolyte and lithium metal as the counter electrode. 

W. Li, B. L. Lucht, J. Electrochem. Soc. 2006, 153, A1617-A1625. Lithium-ion batteries Thermal reactions of electrolyte with the surface of metal oxide cathode particles. 

M. Morita, O. Yamada, M. Ishikawa, J. Power Sources 1999, 81-82, 425-429. Charge and discharge performances of lithiated metal oxide cathodes in organic electrolyte solutions with different compositions. 

This section aims at demonstrating the importance and relevance of the surface chemistry developed on cathodes for Li-ion battery systems to their performance. The topics selected for discussion are the effect of nano-size, surface chemical aspects of lithiated transition metal oxide cathodes and a comparison with the surface chemistry of L1MPO4 olivine-type cathodes. 

Formation mechanism of SEI layers on cathodes in Li-ion batteries, their thermal and electrochemical stabihty, and their roles in affecting the cycle life and safety characteristics are well documented by many researchers [43 6]. Here we present some recent data on identifying the surface layer generation and their composition on transition metal oxide cathodes like spinel and layered materials by various spectroscopic techniques. The structural changes and the reaction at the surface during the first delithiation process in Li-rich layered material are explained. The effects of additives and coatings on electrode materials to their electrochemical performance are also discussed at the end. 

Xiao J, Chernova NA, Whittingham MS (2008) Layered mixed transition metal oxide cathodes with reduced cobalt content for lithium ion batteries. Chem Mater 20 7454—7464... 

Values estimated from DSC and ARC measurements of standard Li-ion electrolyte There is insufficient oxygen available inside a typical 18650 cell, even with a metal oxide cathode, to effect complete combustion of the solvent that would be present in the cell. However, if vented at high temperatures or vented in the presence of an ignition source, the solvent can bum outside the cell... 

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