Mesocarbon microbeads MCMB

Apart from manifold structures, carbons can have various shapes, forms, and textures, including powders with different particle size distributions, foams, whiskers, foils, felts, papers, fibers [76, 77], spherical particles [76] such as mesocarbon microbeads (MCMB s) [78], etc. Comprehensive overviews are given, for example in [67, 71, 72], Further information on the synthesis and structures of carbonaceous materials can be found in [67, 70, 72, 75, 79]. Details of the surface composition and surface chemistry of carbons are reviewed in Chapter II, Sec. 8, and in Chapter III, Sec. 6, of this handbook. Some aspects of surface chemistry of lithiated carbons will also be discussed in Sec. 5.2.2.3. 

Mesocarbon microbeads (MCMB) particles, obtained from Osaka Gas Co., which are round graphite particles. They are also far from having a smooth morphology and have crevices on their surface. 

Activation is often conducted by processing with steam or chemical agents. Carbons activated by steam can be prepared from raw materials such as coal, peat, or lignite, which are carbonized and reacted with high-temperature water steam, in the process where fraction of carbon atoms are gasified, leaving beside porous structure. Chemically, carbon can also be activated with phosphoric acid. So-called mesocarbon microbeads (MCMBs) were produced from coal tar pitch in the Osaka... 

Liquid-phase carbonization Pitch, coal tar Cokes Mesocarbon microbeads (MCMB) Spherical particles... 

Attempts were made to discover the correlation between the crystalline structure of carbonaceous materials and their capability to reversibly intercalate lithium. This correlation has not been definitely established, but still, one can assume as a certain general principle that the optimum materials would contain an amorphous matrix with inclusions of a mesophase nuclei of graphite crystallites. Such materials are various cokes, pyrographite, and products of pyrolysis (carbonization) of various polymers. For practical purposes, the industry mastered some special materials providing high characteristics of negative electrodes in lithium ion batteries. The most popular material is manufactured by the Japanese company of Osaka Gas Co. under the name of mesocarbon microbeads, MCMB it represents the carbonization product of pitchy resins under a certain temperature regime. 

Another high-temperature approach for generating silicon/carbon composites is to deposit silicon particles on carbon or vice versa using CVD. Xie et al. [44] reported the deposition of silicon on mesocarbon microbeads (MCMB) by CVD of silane at 450°C and 500°C, but only a very small amount of silicon actually deposited on the MCMB. The material also demonstrated a very high (55%) irreversible loss. Vacuum deposition of nanometer-sized silicon particles on graphite surfaces has also been reported [45, 46]. The as-prepared anode showed an... 

F. 3 Voltage profiles in the first cycle of Li/mesocarbon microbead (MCMB) half cells with 1 M LiPFa in bi-solvent and tri-solvent electrolytes containing EC, PC, FEC (labeled as MFPC in the graph), and TFPC. Reproduced with permission [106]. Copyright 2010 Elsevier... 

In addition to the stabilizing effect of cathode particles on the electrolyte solutions at elevated temperatures, graphite-like carbon electrodes (anodes) were also foimd to reduce the thermal decomposition of bulk LiPFe electrolyte solutions. However, the reduction of bulk electrolyte decomposition coincided with reactions of the electrolyte with the anode. The surface of the carbon electrode was covered with the products of the electrolyte reduction, which formed a protective solid electrolyte interface (SEl) layer [35-37], The stabilizing effect of these anodes (e.g., based on lithiated mesocarbon microbeads, MCMB) on the electrolyte was proposed to relate to the degradation of the solid-electrolyte interphase (SEl) in LiPFe-based electrolytes at elevated temperatures [32,38], The loss of capacity and power from lithium-ion cells undergoing accelerated aging experiments has been attributed to the presence of thermal decomposition products of the electrolyte in the anode SEl [32],... 

Similar to the Si anode, serious electrochemical agglomeration occurs for nano-SnSb alloy. It is not good to achieve high reversible capacity and good cyclic performance since the SEl film is covered on the particles.In order to solve this problem, nano-SnSb ahoy was deposited on surface of mesocarbon microbead (MCMB] and hard carbon spherules (HCS], respectively as shown in Fig. 5.14. It was expected and confirmed that nanosized... 

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