Negative electrodes properties

Whereas there had been a significant amount of work on the properties of lithium alloys in the research community for a number of years, this alternative did not receive much attention in the commercial world until about 1990, when Sony began producing batteries with lithium-carbon negative electrodes. Since then, there has been a large amount of work on the preparation, structure, and properties of various carbons in lithium cells. 

At the end of the 1990s in Japan, large-scale production of rechargeable lithium ion batteries was initiated. These contained lithium compounds intercalated into oxide materials (positive electrodes) as well as into graphitic materials (negative electrode). The development of these batteries initiated a further increase in investigations of the properties of different intercalation compounds and of the mechanism of intercalation and deintercalation processes. 

Anani A., Crouch-Baker S., Huggins RA. Kinetic and Thermodynamic Properties of Several Binary Lithium Alloy Negative Electrode Materials at Ambient Temperature. J. Electrochem. Soc. 1987 134 3098-101. 

In cathodic area, the Tafel slope in the presence of DDTC is bigger than that in the absence of DDTC, and the cathodic curves imder the conditions of different DDTC concentration are almost parallel and their Tafel slopes only change a little. These demonstrate that the chemisorption of DDTC on the surface of jamesonite electrode also inhibits the cathodic reaction, but the chemisorption amoimt of DDTC is a little and almost not affected by the DDTC concentration due to their negatively electric properties of DDTC anion and the electrode surface. This reveals that there is a little DDTC chemisorption on the mineral even if the potential is lower (i.e., negative potential). 

In lithium-based cells, the essential function of battery separator is to prevent electronic contact, while enabling ionic transport between the positive and negative electrodes. It should be usable on highspeed winding machines and possess good shutdown properties. The most commonly used separators for primary lithium batteries are microporous polypropylene membranes. Microporous polyethylene and laminates of polypropylene and polyethylene are widely used in lithium-ion batteries. These materials are chemically and electrochemically stable in secondary lithium batteries. 

Separators in lithium ion batteries must separate positive electrodes and negative electrodes to prevent short circuits, and must allow passage of electrolytes or ions. Porous films and nonwoven fabrics of resins are known separators. The lithium ion battery separators are also required to exhibit stable properties at high temperatures such as in charging, and therefore high heat resistance is desired (21). 

These requirements hold for the films at both the positive and negative electrode surfaces. Thus, these surface films frequently comprise quite complex mixtures of reaction products and their presence affects the kinetic properties of charge transfer across the interface. It is the deviation of surface film s properties from meeting this set of ideal requirements that is the single most important cause of cell failure in a large fraction of cases. When the decomposition reactions occur, a small amount of active material must also be irreversibly consumed. 

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