Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1997-02-20
1999-11-16
Nuzzolillo, Maria
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
4292318, H01M 460
Patent
active
059854898
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a carbon for a lithium secondary batteries which is suitable as electrode material for rechargeable lithium secondary batteries; to a manufacturing method therefor, and to a lithium secondary battery.
BACKGROUND ART
As the starting material for a carbon for an electrode, carbonized plant and animal material such as lignite, brown coal, anthracite coal, coke, wood charcoal, coconut shell char; any kind of resin such as phenol resin, furan resin, vinylidene chloride copolymer, etc., which have been heated (dry-distilled) in an inert gas, and the like may be used.
Because carbonaceous materials are chemically inactive, they are used in a wide range of applications such as adsorption agents, catalysts, electrode materials, structural materials for use in machines, etc.; however, these applications are closely related to the structure of the carbon.
That carbon which is referred to as porous carbon has special effects due to the development of pores. For example, using the adsorption phenomena, there are mixture separation and refining actions. In addition, the carbon used in electrical double layer capacitors, the carbon used in lithium secondary batteries, and the like display electrochemical storage effects.
The structure of the carbonaceous material can take various forms depending on the starting material and the manufacturing method. Char and activated carbon obtained by activating char comprise microcrystalline carbon (crystallite), and carbon which takes on a chain structure. When the carbonaceous material is a nongraphitizing carbon, the crystallites take on a structure which is layered in a disorderly manner, and a wide range of pores, from micropores to macropores, are formed in the gaps between these crystallites.
The crystallites are layers of net planes of six membered carbon rings of several parallel layers, and graphite carbon which has a six membered carbon ring structure bonds using hybridized orbitals SP.sup.2. A net plane comprising six membered ring carbon is called a basal plane.
A graphitizing carbon develops crystallites by means of heating at a high temperature, and finally becomes graphite.
A nongraphitizing carbon and a graphitizing carbon which has not been completely graphitized usually contain unorganized carbon. Unorganized carbon refers to carbon other than graphite carbon which is chemically bonded to graphite carbon only; carbon which has a chain structure; carbon which is stuck around six membered ring carbon; carbon which is in the periphery (the prism plane) of six membered ring carbon; carbon which is held in cross-linked structures with other six membered carbon rings (crystallites), and the like. Unorganized carbon is bonded with oxygen atoms, hydrogen atoms, and the like in forms such as C--H, C--OH, C--OOH, and C.dbd.O; or is in the form of double bonded carbon (--C=C--).
Lithium secondary batteries which use porous carbonaceous material in the negative electrode are charged by means of the uptake (doping) of lithium ions by the carbonaceous material of the negative electrode and are discharged by the release (un-doping) of lithium ions. In this lithium secondary battery, the charging capacity is determined by the amount of lithium ions with which the carbonaceous material is doped and the discharging capacity is determined by the un-doping amount. The efficiency of the electrical charging and discharging is defined as the ratio of the charging capacity to the discharging capacity.
When using graphite as the above-mentioned carbonaceous material, the lithium ions are taken in between the layers of the net planes of the carbon. In this case, the opinion is that the theoretical maximum for the doping quantity is when there is one lithium ion for every six carbon atoms. However, there are reports that, when non-graphitizing carbonaceous material is used, charging capacities which exceed the above-mentioned theoretical maximum amount can be obtained.
To the present, various proposals have been made for manufacturing metho
REFERENCES:
patent: 5238760 (1993-08-01), Takahashi et al.
patent: 5658692 (1997-08-01), Ohsaki et al.
patent: 5756062 (1998-05-01), Greinke et al.
patent: 5772974 (1998-06-01), Ohashi et al.
Inui Takashi
Kigure Mitsuo
Nakamura Akihiro
Ohsaki Takushi
Taira Hiroshi
Nippon Sanso Corporation
Nuzzolillo Maria
O'Malley Jennifer
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