Process for preparing spinel type lithium manganese...

Details Process for preparing spinel type lithium manganese... Process for preparing spinel type lithium manganese...

1999-10-25

2001-12-04

Bos, Steven (Department: 1754)

Chemistry of inorganic compounds

Oxygen or compound thereof

Metal containing

C423S600000, C429S224000

Reexamination Certificate

active

06325988

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a process for preparing a spinel type of lithium manganese complex oxide having an improved charging and discharging cycle characteristics at an elevated temperature (50° C. or more) and to a positive electrode active material for a lithium ion secondary battery which comprises the spinel type of lithium manganese complex oxide prepared by this process.
BACKGROUND ART
As electronic appliances have been rendered small and portable in recent years, there has been increased a demand for lithium secondary batteries having a light weight and a high energy density. Among them, a spinel type of LiMn
2
O
4
which may be utilized as a positive electrode active material for 4 V grade of lithium ion secondary batteries has been drawn attention for the use as the battery material for general use product such as automobile and the like since the raw material for manganese is abundant in resource and inexpensive.
Although spinel type of LiMn
2
O
4
is a material having relatively high battery capacity, it has a problem in cycle characteristics during charge and discharge, especially cycle characteristics under an elevated temperature (50° C. or more) or in the elution of Mn into an electrolyte.
In order to solve such a problem, there has been proposed substitution of a part of Mn present in the spinel LiMn
2
O
4
structure for other metal. MnO
6
octahedron wherein oxygen atoms are arranged in 6 directions is structually unstable because Mn located at the center of the structure has a large ionic radius so that clearance between oxygen atoms which are located at the outside of the octahedron becomes much. On the contrary, by substituting a part of Mn ion located at the center of the octahedron for an ion which is smaller than Mn, the structure is stabilized for the reason that the clearance between oxygen atoms becomes little so that a good packing is realized. Furthermore, it is expected that the reactivity of the other metal substituted product toward electrolyte is lowered so that the elution of Mn into the electrolyte becomes remarkably little.
As a process for preparing Mn complex oxides wherein a part of Mn is substituted for another metal, there is disclosed Al-substitution process (Japanese Laid-Open Patent Application Nos. Hei 4-289662, Hei 2-220358 etc.), B-substitution process (Japanese Laid-Open Patent Application No. Hei 8-195200), Fe- and Cr-substitution process (Japanese Laid-Open Patent Application No. Hei 9-245836) or the like. However, since each of these prior art processes is the so-called dry process wherein a water-insoluble Mn oxide or hydroxide and other metal component are mixed in a powdered form and subsequently heated, there has not yet been obtained complex oxide wherein metal to be substituted is uniformly doped with Mn. Therefore, there has not yet been obtained complex oxide which had eliminated sufficiently such fault of LiMn
2
O
4
as in the charging and discharging cycle characteristics, especially cycle characteristics at an elevated temperature (50° C. or more) or in the elution of Mn into an electrolyte.
Also, although Mn series of secondary batteries have been drawn attention as the electric source material for use in an electric automobile or notebook type of personal computer, they are often used under an environment of relatively higher temperature than the ordinary temperature, and therefore, the improvement in the charging and discharging cycle characteristics at an elevated temperature has been desired.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a process for preparing a spinel type of lithium manganese complex oxide which has the improved charging and discharging cycle characteristics under an environment of an elevated temperature (50° C. or more) by a means of substituting a part of Mn for the other metal and doping them uniformly as the solid solution, and further to provie a positive electrode active material for a lithium ion secondary battery which comprises the spinel type of lithium manganese complex oxide prepared by this process.
As a result of having studied ardently to achieve the above objects, the present inventors have found that the above objects may be achieved by spinel type of lithium manganese complex oxides which may be obtained by the process of the present invention and which may be represented by the general formula (I)
Li
x
Mn
(2−y)
M
y1
B
y2
O
4
  (I)
(wherein M is at least one metal selected from the group consisting of Al, Cr, Fe, Ni, Co, Ga and Mg, x is 0.9≦x≦1.1, y represents y=y
1
+y
2
, 0.002≦y≦0.5, 0≦y
1
<0.5, 0.002≦y
2
≦0.1) and which may also be represented by the general formula (Ia) where y
2
in the above general formula (I) is 0
Li
x
Mn
(2−y)
M
y
O
4
  (Ia)
(wherein each of M and x has the same significance as the above and y represents 0.002≦y≦0.5), and further found that by using as the positive electrode active material for a lithium ion secondary battery these spinel lithium manganese complex oxides wherein a part of Mn is substituted for at least one metal selected from the group consisting of Al, Cr, Fe, Ni, Co, Ga and Mg to result in a uniform doped product, the charging and discharging cycle characteristics under an environment of a relatively higher temperature (50° C. or more) than the ordinary temperature may be improved. The present invention is based on these findings.
That is, the present invention is a process for preparing a spinel type of lithium manganese complex oxide which may be represented by the general formula (I)
Li
x
Mn
(2−y)
M
y1
B
y2
O
4
  (I)
(wherein M is at least one metal selected from the group consisting of Al, Cr, Fe, Ni, Co, Ga and Mg, x is 0.9≦x≦1.1, y represents y=y
1+
y
2
, 0.002≦y≦0.5, 0≦y
1
<0.5, 0.002≦y
2
≦0.1) and which is characterized by the steps of:
suspending in an aqueous medium a manganese complex hydroxide which may be represented by the general formula (II)
Mn
2+
(1−a)
M
p+
a
(OH)
[2−(2−p)a−nz]
(A
n−
)
z
·m
H
2
O  (II)
(wherein M
p+
is at least one metal cation having p-valence (p=2~3) selected from the group consisting of Al
3+
, Cr
3+
, Fe
3+
, Ni
2+
, Co
2+
, Ga
3+
and Mg
2+
, A
n−
is an anion having n-valence (n=1~2) such as NO
3
−
, Cl
−
, Br
−
, CO
3
2−
, SO
4
2−
, CH
3
COO
−
or the like, a, z and m represent 0≦a≦0.25, 0.03<z<0.3 and 0<m, respectively)
adding an aqueous solution containing boric acid ion to the suspension,
adding further a water-soluble lithium compound in such an amount as to give the molar ratio of Li/(Mn+B)=0.45~0.55 [provided that the general formula (II) is limited to one where a=0] which indicates a molar ratio of lithium to the total metal content in the aqueous medium or the molar ratio of Li/(Mn+M+B)=0.45~0.55 which indicates a molar ratio of lithium to the total metal content in the aqueous medium to obtain a slurry,
spray- or freeze-drying the obtained slurry, and
heating the resultant residue at a temperature of 600 ~900° C., and a further process for preparing a spinel type of lithium manganese complex oxide which may be represented by the general formula (Ia) where y
2
in the above general formula (I) is 0
Li
x
Mn
(2−y)
M
y
O
4
  (Ia)
(wherein each of M and x has the same significance, and y represents 0.002≦y≦0.5) which is characterized by the steps of:
mixing a manganese complex hydroxide which may be represented by the general formula (IIa)
Mn
2+
(1−a)
M
p+
a
(OH)
[2−(2−p)a−nz]
(A
n−
)
z
·mH
2
O  (IIa)
(wherein M
p+
is at least one metal cation having p-valence (p=2~3) selected from the group consisting of Al
3+
, Cr
3+
, Fe
3+
, Ni
2+
, Co
2+
, Ga
3+
and Mg
2+
, A

Affiliated with

Also associated with

Rating

Process for preparing spinel type lithium manganese... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for preparing spinel type lithium manganese..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing spinel type lithium manganese... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2581726