Lithium secondary battery

Details Lithium secondary battery Lithium secondary battery

1997-07-16

2001-08-07

Weiner, Laura (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S224000, C429S223000, C429S221000, C429S231500, C429S231600

Reexamination Certificate

active

06270924

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a lithium secondary battery, and more particularly, a lithium secondary battery comprising a cathode having a spinel-structured lithium-manganese complex oxide as the active material.
2. Description of the Related Art
Portable and cordless electronic appliances are becoming increasingly popular. As the power source for such electronic appliances, there is a great demand for small-sized and lightweight secondary batteries having a high energy-density. Lithium secondary batteries comprising a non-aqueous electrolytic solution have been put to practical use to meet such demands.
In general, a lithium secondary battery includes a cathode having a lithium-containing compound as the active material, an anode having a material capable of absorbing and desorbing lithium such as a carbon material or lithium metal as the active material, and a separator containing a non-aqueous electrolytic solution or a solid electrolyte. The lithium-containing compound for the active material of the cathode may include, for example, LiCoO
2
, LiNiO
2
and LiMn
2
O
4
which are now under study. Recently, attention is drawn to a spinel-structured lithium-manganese complex oxide, such as typically LiMn
2
O
4
, since the complex oxide may have a high oxidation-reduction potential and since the raw materials for the complex oxide are inexpensive and therefore a stable supply of the complex oxide is expected. In that situation, various lithium secondary batteries comprising the complex oxide as the cathode active material have been proposed.
For example, Japanese Patent Application Laid-Open No. 6-333562 discloses a lithium secondary battery comprising an LiMn
2
O
4
-type compound as the cathode active material, in which the compound is in the form of spherical particles having uniformly-roughened surfaces and having a particle size range of from 0.1 to 1.1 micrometer and a median diameter of from 0.5 to 0.6 micrometer. Japanese Patent Application Laid-Open No. 8-69790 discloses a lithium secondary battery comprising a lithium-manganese complex oxide as the cathode active material, in which the complex oxide has a specific surface area of from 0.05 to 5.0 m
2
/g.
However, the conventional lithium secondary batteries comprising such a spinel-structured lithium-manganese complex oxide as the active material are not yet satisfactory with respect to the battery capacity and the charge-discharge cycle characteristics.
Accordingly, the object of the present invention is to provide a lithium secondary battery having high capacity and excellent charge-discharge cycle characteristics.
SUMMARY OF THE INVENTION
The invention provides a lithium secondary battery of above mentioned kind, which is characterized in that the particles of said spinel-structured lithium-manganese complex oxide are hollow, spherical secondary particles formed by sintering of primary particles, and said secondary particles have a mean particle size of from about 1 to 5 micrometer and a specific surface area of from about 2 to 10 m
2
/g.
In the above lithium secondary battery, said spinel-structured, lithium-manganese complex oxide may be represented by a general formula of Li(Mn
2−x
Li
x
)O
4
where 0≦x<0.1, and the Mn may or may not be partially substituted by Cr, Ni, Fe, Co or Mg.
Since the lithium secondary battery employs spherical hollow particles of a spinel-structured lithium-manganese complex oxide as the cathode active material, and the particle size and the specific area are controlled in the above described manner, the non-aqueous electrolytic solution can well penetrate into the spherical hollow particles, while being prevented from being decomposed, and the contact area between the non-aqueous electrolytic solution and the particles is enlarged. Therefore, the degree of utilization of the cathode active material in the battery of the invention is improved. In addition, since the cathode active material comprises relatively large secondary particles formed through sintering of primary particles, it can be well shaped while having a suitably large specific surface area. Even if the amount of the binder added thereto is reduced, the material can still be shaped into a cathode having an increased energy density per the unit volume.
In the above lithium secondary battery, said spinel-structured, lithium-manganese complex oxide is preferably represented by the general formula of Li(Mn
2−x
Li
x
)O
4
where 0 <x<0.02.
When the spinel-structured lithium-manganese complex oxide for use in the invention is represented by a general formula Li(Mn
2−x
Li
x
)O
4
, it is preferable that x falls within the range of 0 to about 0.1, in order to obtain secondary batteries having higher energy efficiency and better charge-discharge cycle characteristics. More preferably, x in said general formula Li(Mn
2−x
Li
x
)O
4
falls within the range of greater than 0 and less than about 0.02, in order to obtain secondary batteries having much higher energy efficiency and much better charge-discharge cycle characteristics.
In addition, other spinel-structured lithium-magnesium complex oxides derived from those of Li(Mn
2−x
Li
x
)O
4
by substituting a part of the Mn site with any of Cr, Ni, Fe, Co and/or Mg are also employable in the present invention, while producing the same results.
The lithium secondary battery of the invention may comprise, as the active material for the anode, a material capable of absorbing and desorbing lithium such as a carbon material, or lithium metal or a lithium alloy. The non-aqueous electrolytic solution in the battery may be a solution as prepared by dissolving an electrolyte of a lithium salt, such as LiPF
6
, LiClO
4
, LiBF
4
or LiAsF
6
, in a mixed solvent comprising propylene carbonate or ethylene carbonate, and diethoxyethane or dimethoxyethane. As the separator for the battery, employable is a porous polypropylene film or non-woven fabric. In place of the separator impregnated with such a non-aqueous electrolytic solution, also employable is a solid electrolyte.


REFERENCES:
patent: 4567031 (1986-01-01), Riley
patent: 5081102 (1992-01-01), Gay et al.
patent: 5110696 (1992-05-01), Shokoohi et al.
patent: 5122505 (1992-06-01), Gusman et al.
patent: 5135732 (1992-08-01), Barboux et al.
patent: 5177055 (1993-01-01), Kinsman et al.
patent: 5264201 (1993-11-01), Dahn et al.
patent: 5370948 (1994-12-01), Hasegawa et al.
patent: 5449577 (1995-09-01), Dahn et al.
patent: 5490320 (1996-02-01), Hasegawa et al.
patent: 5496664 (1996-03-01), Sterr
patent: 5589300 (1996-12-01), Fauteux et al.
patent: 5599642 (1997-02-01), Toshiro et al.
patent: 5626635 (1997-05-01), Yamaura et al.
patent: 5629110 (1997-05-01), Kobayashi et al.
patent: 5648057 (1997-07-01), Ueda et al.
patent: 5683835 (1997-11-01), Bruce
patent: 5700442 (1997-12-01), Bloch et al.
patent: 5700597 (1997-12-01), Zhong et al.
patent: 5702679 (1997-12-01), Sheargold et al.
patent: 5702845 (1997-12-01), Kawakami et al.
patent: 5705296 (1998-01-01), Kamauchi et al.
patent: 5718877 (1998-02-01), Manev et al.
patent: 5742070 (1998-04-01), Hayashi et al.
patent: 5789115 (1998-08-01), Manev et al.
patent: 5792442 (1998-08-01), Manev et al.
patent: 5807646 (1998-09-01), Iwata et al.
patent: 0582448A1 (1994-02-01), None
patent: 0709906A1 (1996-05-01), None
patent: 7-006764 (1995-01-01), None
patent: 8-153513 (1996-06-01), None
patent: 8-321300 (1996-12-01), None
patent: WO94/25398 (1994-11-01), None
patent: 9534919 (1995-12-01), None
patent: 9612676 (1996-05-01), None
“Preparation of Spherical LiCoO2Powders by the Ultrasonic Spray Decomposition and Its Application to Cathode Active Material in Lithium Secondary Battery”; Takashi Ogihara, et al.;Journal of the Ceramic Society of Japan;International Edition; 101 (Oct. 1993); No. 10; pp. 1128-1132.
“Electrochemistry and Structural Chemistry of LiNiO2(R3) for 4 Volt Secondary Lithium Cells”; Tsutomu Ohzuku, et al.;J. Electrochem. Soc.;vol. 140, No. 7, Jul. 1993; pp. 1862-1870.

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